US20180047520A1 - Fabrication of enhanced supercapacitors using atomic layer deposition of metal oxide on nanostructures - Google Patents
Fabrication of enhanced supercapacitors using atomic layer deposition of metal oxide on nanostructures Download PDFInfo
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- US20180047520A1 US20180047520A1 US15/727,052 US201715727052A US2018047520A1 US 20180047520 A1 US20180047520 A1 US 20180047520A1 US 201715727052 A US201715727052 A US 201715727052A US 2018047520 A1 US2018047520 A1 US 2018047520A1
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- 239000002086 nanomaterial Substances 0.000 title claims abstract description 26
- 238000004519 manufacturing process Methods 0.000 title description 10
- 229910044991 metal oxide Inorganic materials 0.000 title description 10
- 150000004706 metal oxides Chemical group 0.000 title description 10
- 238000000231 atomic layer deposition Methods 0.000 title description 7
- 229910052751 metal Inorganic materials 0.000 claims abstract description 73
- 239000002184 metal Substances 0.000 claims abstract description 73
- 230000008021 deposition Effects 0.000 claims abstract description 21
- 230000001590 oxidative effect Effects 0.000 claims abstract description 19
- 239000002243 precursor Substances 0.000 claims description 39
- 239000000463 material Substances 0.000 claims description 23
- DKPFZGUDAPQIHT-UHFFFAOYSA-N butyl acetate Chemical compound CCCCOC(C)=O DKPFZGUDAPQIHT-UHFFFAOYSA-N 0.000 claims description 10
- MGNZXYYWBUKAII-UHFFFAOYSA-N cyclohexa-1,3-diene Chemical compound C1CC=CC=C1 MGNZXYYWBUKAII-UHFFFAOYSA-N 0.000 claims description 10
- BZORFPDSXLZWJF-UHFFFAOYSA-N N,N-dimethyl-1,4-phenylenediamine Chemical compound CN(C)C1=CC=C(N)C=C1 BZORFPDSXLZWJF-UHFFFAOYSA-N 0.000 claims description 6
- -1 ethylcyclopentadienyl Chemical group 0.000 claims description 6
- WWRCMNKATXZARA-UHFFFAOYSA-N 1-Isopropyl-2-methylbenzene Chemical compound CC(C)C1=CC=CC=C1C WWRCMNKATXZARA-UHFFFAOYSA-N 0.000 claims description 5
- JFLCCNYEBDYEIR-UHFFFAOYSA-N CC(C)=CC(C)=C[Ru]C=C(C)C=C(C)C Chemical compound CC(C)=CC(C)=C[Ru]C=C(C)C=C(C)C JFLCCNYEBDYEIR-UHFFFAOYSA-N 0.000 claims description 5
- ZSWFCLXCOIISFI-UHFFFAOYSA-N endo-cyclopentadiene Natural products C1C=CC=C1 ZSWFCLXCOIISFI-UHFFFAOYSA-N 0.000 claims description 5
- 125000000058 cyclopentadienyl group Chemical group C1(=CC=CC1)* 0.000 claims description 4
- 238000000034 method Methods 0.000 abstract description 29
- 239000000203 mixture Substances 0.000 abstract description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 12
- 229910052707 ruthenium Inorganic materials 0.000 abstract description 11
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 abstract description 9
- 229910052742 iron Inorganic materials 0.000 abstract description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 abstract description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 abstract description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 abstract description 2
- 229910017052 cobalt Inorganic materials 0.000 abstract description 2
- 239000010941 cobalt Substances 0.000 abstract description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 abstract description 2
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 abstract description 2
- 229910052759 nickel Inorganic materials 0.000 abstract description 2
- 239000011135 tin Substances 0.000 abstract description 2
- 229910052718 tin Inorganic materials 0.000 abstract description 2
- 229910052719 titanium Inorganic materials 0.000 abstract description 2
- 239000010936 titanium Substances 0.000 abstract description 2
- 229910052720 vanadium Inorganic materials 0.000 abstract description 2
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 abstract description 2
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 178
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 80
- 239000010410 layer Substances 0.000 description 68
- 239000002041 carbon nanotube Substances 0.000 description 66
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 51
- 239000010408 film Substances 0.000 description 51
- 229910021393 carbon nanotube Inorganic materials 0.000 description 36
- 238000005259 measurement Methods 0.000 description 26
- 229910021426 porous silicon Inorganic materials 0.000 description 26
- 238000000151 deposition Methods 0.000 description 22
- 239000000758 substrate Substances 0.000 description 19
- 229910052760 oxygen Inorganic materials 0.000 description 17
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 16
- 239000001301 oxygen Substances 0.000 description 16
- 239000011248 coating agent Substances 0.000 description 15
- 238000000576 coating method Methods 0.000 description 15
- 238000006056 electrooxidation reaction Methods 0.000 description 15
- 238000007254 oxidation reaction Methods 0.000 description 15
- 238000002484 cyclic voltammetry Methods 0.000 description 14
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 13
- 230000003647 oxidation Effects 0.000 description 13
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 12
- 238000001878 scanning electron micrograph Methods 0.000 description 11
- 229910052710 silicon Inorganic materials 0.000 description 11
- 239000010703 silicon Substances 0.000 description 11
- 239000011148 porous material Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 230000002441 reversible effect Effects 0.000 description 7
- 230000007246 mechanism Effects 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 229910001868 water Inorganic materials 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000011651 chromium Substances 0.000 description 5
- 238000004146 energy storage Methods 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 238000006479 redox reaction Methods 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- 229910021607 Silver chloride Inorganic materials 0.000 description 4
- 238000003917 TEM image Methods 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 230000001351 cycling effect Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- SZVJSHCCFOBDDC-UHFFFAOYSA-N ferrosoferric oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 4
- 229910000480 nickel oxide Inorganic materials 0.000 description 4
- 230000006911 nucleation Effects 0.000 description 4
- 238000010899 nucleation Methods 0.000 description 4
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000012983 electrochemical energy storage Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 229910021389 graphene Inorganic materials 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 3
- 229910052750 molybdenum Inorganic materials 0.000 description 3
- 239000011733 molybdenum Substances 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 235000012431 wafers Nutrition 0.000 description 3
- 229910021503 Cobalt(II) hydroxide Inorganic materials 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910021627 Tin(IV) chloride Inorganic materials 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 239000002238 carbon nanotube film Substances 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- UBEWDCMIDFGDOO-UHFFFAOYSA-N cobalt(2+);cobalt(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[Co+2].[Co+3].[Co+3] UBEWDCMIDFGDOO-UHFFFAOYSA-N 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- VLTZUJBHIUUHIK-UHFFFAOYSA-N ethylcyclopentane;ruthenium Chemical compound [Ru].CC[C]1[CH][CH][CH][CH]1.CC[C]1[CH][CH][CH][CH]1 VLTZUJBHIUUHIK-UHFFFAOYSA-N 0.000 description 2
- 230000036571 hydration Effects 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 235000013980 iron oxide Nutrition 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 239000002048 multi walled nanotube Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 125000002524 organometallic group Chemical group 0.000 description 2
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 2
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 2
- 239000002491 polymer binding agent Substances 0.000 description 2
- 238000001205 potentiostatic coulometry Methods 0.000 description 2
- 238000002207 thermal evaporation Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 229910001887 tin oxide Inorganic materials 0.000 description 2
- HPGGPRDJHPYFRM-UHFFFAOYSA-J tin(iv) chloride Chemical compound Cl[Sn](Cl)(Cl)Cl HPGGPRDJHPYFRM-UHFFFAOYSA-J 0.000 description 2
- 241000252506 Characiformes Species 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- CZAYMIVAIKGLOR-UHFFFAOYSA-N [Ni].[Co]=O Chemical class [Ni].[Co]=O CZAYMIVAIKGLOR-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
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- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000000970 chrono-amperometry Methods 0.000 description 1
- ASKVAEGIVYSGNY-UHFFFAOYSA-L cobalt(ii) hydroxide Chemical compound [OH-].[OH-].[Co+2] ASKVAEGIVYSGNY-UHFFFAOYSA-L 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 1
- 238000005566 electron beam evaporation Methods 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- KTWOOEGAPBSYNW-UHFFFAOYSA-N ferrocene Chemical compound [Fe+2].C=1C=C[CH-]C=1.C=1C=C[CH-]C=1 KTWOOEGAPBSYNW-UHFFFAOYSA-N 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002073 nanorod Substances 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 239000002070 nanowire Substances 0.000 description 1
- BMGNSKKZFQMGDH-FDGPNNRMSA-L nickel(2+);(z)-4-oxopent-2-en-2-olate Chemical compound [Ni+2].C\C([O-])=C\C(C)=O.C\C([O-])=C\C(C)=O BMGNSKKZFQMGDH-FDGPNNRMSA-L 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 150000002843 nonmetals Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000767 polyaniline Polymers 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 229920000123 polythiophene Polymers 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical group [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000002109 single walled nanotube Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- MNWRORMXBIWXCI-UHFFFAOYSA-N tetrakis(dimethylamido)titanium Chemical compound CN(C)[Ti](N(C)C)(N(C)C)N(C)C MNWRORMXBIWXCI-UHFFFAOYSA-N 0.000 description 1
- 238000007736 thin film deposition technique Methods 0.000 description 1
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 1
- 229910009112 xH2O Inorganic materials 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/46—Metal oxides
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/26—Anodisation of refractory metals or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/66—Current collectors
- H01G11/70—Current collectors characterised by their structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/04—Hybrid capacitors
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Definitions
- Supercapacitors are electrochemical energy-storage devices that store charge by reversible adsorption of ions onto high-surface area, porous materials (known as “electric double layer capacitors”) or reversible surface reduction-oxidation (redox) reactions (known as “pseudo-capacitors”). With their high power density and long cycle stability, supercapacitors are well-suited to complement or replace batteries in a wide range of applications, including transportation, renewable energy, and portable electronics. High-performance supercapacitors are characterized by high specific capacitance, good stability over repeated cycling, and low series resistance.
- FIG. 1 Conceptual illustration of ALD RuO x supercapacitor fabrication and energy storage mechanism.
- FIG. 2 Conceptual view of a forest of vertically-aligned CNTs is covered with a layer of RuO 2 .
- FIG. 3 Electron micrographs of RuO 2 coated carbon nanotubes.
- FIG. 4 Process and measurements of RuO 2 coated carbon nanotube films at different temperatures.
- FIG. 5 X-ray diffraction measurements of ALD RuO x -CNT electrodes.
- FIG. 6 SEM image of as-deposited ALD RuO x porous and planar Si supercapacitor electrode.
- FIG. 7 High-resolution XPS measurements of binding energies for ALD RuO x planar and CNT films.
- FIG. 8 Cyclic voltammetry and electrochemical impedance spectroscopy of ALD RuO 2 thermally and electrochemically oxidized electrodes.
- FIG. 9 Cyclic voltammetry measurements of ALD RuO x supercapacitors.
- FIG. 10 Cyclic voltammetry measurements of uncoated CNT and porous Si electrodes.
- FIG. 11 Change in specific capacitance of ALD RuO x supercapacitors with electrochemical oxidation.
- FIG. 12 Scan rate and life cycle performance testing of ALD RuO x supercapacitors.
- Supercapacitors are electrochemical energy storage devices with promising applications in many environmentally-friendly technologies—including renewable energy and electric vehicles—that require high power density and high cycle life energy storage.
- high performance supercapacitors employed high surface area electrodes coated with a thin film of active pseudocapacitive material, such as metal oxides or conductive polymers.
- active pseudocapacitive material such as metal oxides or conductive polymers.
- metal pseudocapacitive materials that store charge by a similar mechanism include ruthenium oxide (RuO x ), manganese oxide (MnO 2 ), vanadium oxide (V 2 O 5 ), mixed cobalt-nickel oxides (a-(Co+Ni)(OH) 2 .nH 2 O), cobalt oxide (Co 3 O 4 ), cobalt hydroxide (Co(OH) 2 ), nickel oxide (NiO), tin oxide (SnO 2 ), iron oxides (Fe 2 O 3 and Fe 3 O 4 ), and titanium dioxide (TiO 2 ).
- Non-metal pseudocapacitive materials include polyaniline, polypyrrole, and polythiophene.
- the coated “pseudocapacitive” electrodes store charge by reversible reduction-oxidation (redox) reactions.
- redox reversible reduction-oxidation
- the ruthenium oxide (RuO x ) reaction is one of the highest performing pseudocapacitive materials due to its fast, reversible redox reactions:
- RuO x supercapacitors intercalate positive ions (H + ) during charging; it is obligatory to have good proton and electron conductivity within the RuO x lattice for high supercapacitor performance.
- the supercapacitor performance depends on the hydroxyl content of the oxide, with hydrated, amorphous oxides often displaying better charge storage as a result of higher proton and more electrochemically active redox sites.
- fabrication methods must provide precise control of electrode structure and chemical composition as well as good uniformity over high surface areas.
- One supercapacitor fabrication method uses solution-based deposition, such as RuO x .
- RuO x supercapacitor fabrication method using solution-based deposition of ruthenium trichloride exhibited a lack of uniformity and control of the RuO x coating.
- Other fabrication methods include magnetic sputtering and electro-oxidation of Ru nanoparticles, and mixing of RuO 2 -xH 2 O particles with a polymer binding agent. These methods suffer from poor electronic conductivity (especially for polymer binding agents), low utilization of RuO x due to non-uniformly dispersed nanoparticles or films, and/or low proton conductivity due to poor hydration.
- a novel method was invented based on atomic layering deposition (ALD) to fabricate supercapacitors that had highly uniform, conformal coating of pseudocapacitive materials, which was applied to a diversity of surface compositions and structures.
- ALD atomic layering deposition
- Three such embodiments included planar, vertically-aligned carbon nanotubes (CNT) and porous silicon (Si) electrodes.
- CNT carbon nanotubes
- Si porous silicon
- a further embodiment was the use of post-ALD electrochemical oxidation to increase energy storage potential.
- This method is the first successful direct ALD coating of RuO 2 onto porous electrodes for supercapacitor applications, including CNTs and porous silicon one monolayer at a time. This method allows precise control over the RuO 2 layer thickness and composition without the use of binder molecules
- FIG. 1 a conceptual illustration of the general method for ALD supercapacitor fabrication process and charge storage mechanism of the hydrated coating is shown depicting a metal oxide, using RuO x as an example, onto porous structure.
- ALD is a highly versatile deposition process can be applied to any porous, high surface area, or high aspect ratio nanostructure, provided that the pores are accessible to the gas-phase precursors.
- FIG. 1 a a generic porous structure is coated with ALD RuO x by sequential pulsing of an organometallic ruthenium precursor and oxygen.
- FIG. 1 b the as-deposited ALD RuO x film is electrochemically oxidized to produce a hydrated pseudocapacitive layer with high proton conductivity.
- FIG. 1 a conceptual illustration of the general method for ALD supercapacitor fabrication process and charge storage mechanism of the hydrated coating is shown depicting a metal oxide, using RuO x as an example, onto porous structure.
- ALD is a highly versatile deposition process can be applied to
- the electrochemical energy storage mechanism of the hydrated ALD RuO x film is shown, which switches reversibly between oxide and hydroxide states through intercalation of hydrogen ions.
- the surface and near-surface charge storage mechanism of the RuO x layer enables rapid charging and discharging of the supercapacitor, while the high surface area, porous electrode structure increases power and energy density.
- FIG. 2 Another embodiment of different structure used is shown in FIG. 2 , where ALD metal oxide coated carbon nanotube (CNT) is illustrated during charging and discharging.
- CNT metal oxide coated carbon nanotube
- forest of vertically-aligned CNTs is covered with a layer of RuO 2 several nanometers thick deposited by ALD.
- the CNT provides a dynamic structure that can be varied and has exceptional high surface area, conductive, and flexible support for the active layer RuO 2 .
- the active RuO 2 layer absorbs protons from the electrolyte and electrons flow into the device from an external circuit as the RuO 2 layer is converted to Ru(OH) 2 by a surface redox reaction.
- Electrochemically oxidized ALD metal oxide supercapacitors prepared had exceptional high values of specific capacitance (644 F/g), power density (17 kW/kg), and energy density (4 Wh/kg). In view of prior methods, their supercapacitor performance was maintained over 10,000 charge-discharge cycles, and at ultra-high scan rates of up to 20 V/s.
- Example 1 Diverse Substrate Nanostructures for Supercapacitor Fabrication Using ALD
- metal oxide was successfully coated in a uniform, conformal application onto diverse porous electrodes composed of different nanostructures and different materials that previously were extremely difficult to fabricate.
- the porous materials was made from vertically aligned carbon nanotubes (CNT) while in the two other demonstrations planar and porous silicon was used as the starting electrode materials.
- CNT carbon nanotubes
- molybdenum- and oxide-coated silicon wafer a forest of vertically-aligned carbon nanotubes (CNT) grown on molybdenum- and oxide-coated silicon wafer.
- vertically aligned CNTs were synthesized by chemical vapor deposition on silicon substrates in a horizontal tube furnace as described by Jiang et al., Nano Lett. 13, 3524 (2013). Briefly, silicon substrates were cleaned in piranha solution, then coated with 100 nm thermal oxide and 50 nm molybdenum by electron beam evaporation. Iron and aluminum catalyst layers (10 nm and 5 nm, respectively) were then deposited by thermal evaporation. CNTs were grown at 720° C. and atmospheric pressure in a horizontal tube furnace in a mixture of 7:1 hydrogen-to-ethylene gas. A growth time of 10 minutes gave average CNT heights of 10 ⁇ m. Other CNT heights can also prepared by varying the growth times.
- planar and porous silicon (Si) wafers were used for deposition.
- substrate structure is linear, non-linear, planar or porous structures made of carbon, silicon, graphene, activated carbon, phosphorene, or like materials that may be coupled to the conductive substrate.
- the highly versatile deposition process was applied to any structures that are porous, high surface area, or high aspect ratio nanostructure, provided that the pores are accessible to the gas-phase precursors.
- Embodiments include carbon, silicon, phosphorene, or like materials are oriented substantially perpendicular such as nanotubes, single or multi-walled nanotubes, nanowires, nanorods, aggregated nanoparticles, fibers, ribbons, or other structures.
- Other embodiments include substrate scaffolds that are porous structures and made of carbon, silicon, phosphorene, or materials with similar properties.
- Example 2 ALD Layering of a Metal Oxide onto Carbon Nanotubes Structures
- CNT vertically-aligned, multi-walled carbon nanotubes
- FIG. 3 a provides a scanning electron microscope (SEM) image of vertically aligned CNTs coated with ALD RuO 2 .
- SEM scanning electron microscope
- a cross-sectional scanning electron microscope (SEM) image of the RuO 2 -coated CNTs found that the CNT forest is approximately 5 ⁇ m tall with large pore spaces available for the electrolyte to penetrate into the dense matrix of CNTs.
- a close-up SEM image FIG.
- FIG. 3 b The transmission electron microscope (TEM) image of a single CNT is shown in FIG. 3 c where the ALD coated CNT was approximately 20 nm thick and demonstrated good adhesion to the CNT surface.
- TEM transmission electron microscope
- ALD RuO x deposition was conducted in cycles using a Cambridge Fiji F200 Plasma ALD with bis(ethylcyclopentadienyl)ruthenium(II) (Ru(EtCp) 2 ) and oxygen (O 2 ) as precursors and argon carrier gas.
- ruthenium cyclopentadienyl (RuCp 2 ), Ru(od) 3 /n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II) (Ru(DMPD) 2 ), Ru(thd) 3 , Ru(EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene)Ru.
- Water or hydrogen peroxide may substitute as oxidizing reactants for oxygen gas.
- a cycle time included a pulse time for Ru(EtCp) 2 in an argon gas carrier for 1 to 5 seconds, waiting 1 to 10 seconds, purging 1 to 10 second with O 2 , and waiting 1 to 10 seconds.
- ALD reaction temperatures were varied from 270° C. to 400° C.
- the number of cycles for layering RuO 2 varied from 50 to 1000 cycles.
- percursors for ALD fabrication include titanium dioxide (TiO 2 ): tetrakis(dimethylamino)titanium (TMDAT) or titanium tetrakis isopropoxide (TTIP) with oxygen or water; tin oxide (SnO 2 ) and tin tetrachloride (SnCl 4 ) and water; cobalt oxide (Co 3 O 4 ): Co(thd) 2 and ozone; nickel oxide (NiO): Ni(acac) 2 and ozone; and iron oxide (Fe 2 O 3 , Fe 3 O 4 ):ferrocene (FeCp) 2 and oxygen.
- TiO 2 titanium dioxide
- TDAT titanium tetrakis(dimethylamino)titanium
- TTIP titanium tetrakis isopropoxide
- TTIP titanium tetrakis isopropoxide
- SnO 2 tin oxide
- SnCl 4
- ALD RuO 2 is deposited using ruthenium bis(ethylcyclopentadienyl) (Ru(EtCp) 2 ) and oxygen as precursors as illustrated in FIG. 4 a .
- the novel two step cycle process included pulsing with Ru(EtCp) 2 in [A], followed by oxidation using O 2 [B], to convert Ru(EtCp) 2 to RuO 2 deposition, ensuring that Ru underwent controlled oxidation. With multiple successive cycles, the RuO 2 layers were controllably “grown” to the desired thickness. From grazing-incidence x-ray photoelectron spectroscopy (GIXPS) analyses, it was found that a deposition temperature of 300 to 400° C. achieved good RuO 2 deposition.
- GIXPS grazing-incidence x-ray photoelectron spectroscopy
- FIG. 4 b showed the GIXPS spectrum for ALD RuO 2 deposited at 350° C. The results indicate a near-stoichiometric composition (65% O, 35% Ru) within the GIXPS measurement range (top 10 nm of the film).
- FIG. 4 c is a plot of the oxygen content of the ALD films measured by GIXPS as a function of deposition temperature. In the range of 300° C. to 400° C., higher deposition temperatures corresponded to increased oxygen content of the films. Materials characterization was done using a Siemens D5000 X-ray diffractometer (XRD), and a PHI 5400 X-ray photoelectron spectrometer (XPS) was used for glancing incident XPS (GIXPS) measurements.
- XRD Siemens D5000 X-ray diffractometer
- XPS PHI 5400 X-ray photoelectron spectrometer
- the ALD process for RuO 2 is believed to occur via the accumulation of subsurface oxygen in a depositing Ru films. It is believed that with respect to the ALD growth mechanisms for Ru vs. RuO 2 , several hundred deposition cycles of Ru are required before RuO 2 layers began to form. A certain thickness of Ru film is believed to be needed before there are enough defect sites to accumulate sufficient quantities of subsurface oxygen to form RuO 2 . In the present embodiments, XRD measurements of ALD-RuO 2 films deposited at temperatures ranging from 300° C. to 400° C. showed primarily Ru diffraction peaks. For supercapacitor applications, only a surface layer of RuO 2 is needed for charge storage. The presence of an underlying Ru layer with good electrical conductivity would be beneficial to supercapacitor performance.
- X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize ALD RuO x films on vertically-aligned CNT substrates. Similar to ALD RuO x films deposited on planar substrates, XRD measurements for ALD films on CNTs show predominantly Ru peaks ( FIG. 5 a ). High-resolution XPS measurements of the Ru3d peak for ALD RuO x -films on CNTs show a shift to higher binding energies compared to Ru metal at take-off angles of 15°, 30°, and 75°, indicating the presence of oxidized ruthenium ( FIG. 5 b ). High-resolution XPS measurements of the O 1s peak show the presence of RuO 2 (same as planar electrodes).
- Example 3 ALD Layering of a Metal Oxide onto Planar and Porous Silicon Structures
- RuO x is deposited over the entire depth of the pores (exceeding 127 ⁇ m), however nucleation is less uniform than on CNTs.
- ALD RuO x coating of planar supercapacitor electrodes is highly uniform and conformal, as expected.
- SEM images of ALD RuO x films deposited on porous Si is shown in FIG. 6 a - c .
- FIG. 6 a SEM image of as-deposited ALD RuO x porous Si supercapacitor electrode.
- ALD RuO x supercapacitors they were fabricated by depositing RuO x on a silicon substrate coated with 30 nm of chromium (Cr) and 70 nm gold (Au) by thermal evaporation. The chromium and gold layers were used to provide a better nucleation surface for ALD RuO x than pure silicon. The thickness of the ALD RuO x film was estimated from cross-sectional SEM images ( FIG. 6 d ). The mass of as-deposited ALD RuO x films was calculated using the density of Ru metal (12.45 g/cm 3 ), as XRD measurements indicate that the as-deposited films are predominantly Ru.
- the thickness of the film on planar silicon structure was readily adjusted depending on that desired, providing greater flexibility for its end use.
- the planar ALD RuO x film thickness were measured and estimated of average mass per cm 2 .
- Column A thin-film measurements of deposition are shown while in Column B those for thick-film are shown.
- FIG. 7 a - c showed XRD and XPS measurements of ALD films deposited on planar substrates that were similar to those for CNT electrodes shown elsewhere.
- XRD measurements of as-deposited ALD RuO x show a strong metallic ruthenium crystal structure (Ru(100)), suggesting that the films are not fully oxidized during the ALD process.
- ALD RuO x deposition The role of the oxygen precursor during ALD RuO x deposition is both to oxidatively decompose the organometallic ruthenium precursor and to oxidize the depositing Ru metal film.
- Previous studies suggest that in-situ ALD RuO x formation can be inhibited by low rates of subsurface oxygen absorption and slow reaction kinetics for Ru oxidation. In this process, increasing the ALD RuO x deposition temperature from 270° C. to 400° C. changed the dominant Ru crystal phase, but does not produce RuO 2 XRD peaks.
- XPS measurements provide qualitative characterization of a material's surface composition (approximately 1-10 nm film depth).
- XPS measurements of ALD RuO x films deposited on planar substrates reveal that the as-deposited films do have significant surface oxide character not detected by XRD.
- High-resolution XPS measurements of Ru 3d binding energies show a shift to higher energies, and hence higher oxidation states, compared to Ru metal.
- Ru—OH and surface adsorbed H 2 O Other forms of oxygen that may be present include Ru—OH and surface adsorbed H 2 O; these materials, however, have O 1s binding energies greater than 533 eV and are thus clearly distinguishable from RuO 2 given our high-resolution XPS measurement uncertainty of less than 0.2 eV.
- Ruthenium does not form a native oxide at room temperature, suggesting that the observed RuO 2 surface layer is formed during the ALD process.
- the ALD RuO 2 -coated CNTs When tested as a supercapacitor electrode, the ALD RuO 2 -coated CNTs demonstrated high capacitive energy storage capability. Cyclic voltammetry measurements of the ALD RuO 2 -coated CNT supercapacitor were compared to an uncoated (“bare”) CNT supercapacitor. A capacitive current of 10 mA/cm 2 at a scan rate of 100 mV/s corresponds to specific capacitance of 100 mF/cm 2 , which represents one of the best values in the literature.
- ESR equivalent series resistance
- ALD RuO 2 -coated CNTs performed as excellent high-performance supercapacitor electrodes.
- the device has low equivalent series resistance, rapid charge-discharge characteristics, and good stability over repeated cycling.
- the exceptionally high-performance of the ALD RuO 2 -coated CNTs can be attributed to: 1) excellent conformal coverage of the CNTs by the ALD RuO 2 coating, 2) a high-quality RuO 2 surface layer capable of fast, reversible redox reactions, and 3) high surface area of the dense, vertically-aligned CNT forest.
- as-deposited ALD films were electrochemically oxidized in 0.5 M H 2 SO 4 electrolyte at a constant potential of 1.3 V vs. Ag/AgCl for variable amounts of time, 3 min-120 min, which corresponds to the electrochemical oxidation potential of Ru.
- post-ALD thermal oxidation was conducted by heating as-deposited ALD RuO x electrodes to 600° C. in 70 sccm oxygen flow for 30 minutes.
- XRD measurements of electrochemically and thermally oxidized ALD RuO x planar films are shown in FIG. 5 a .
- both electrochemically and thermally oxidized films show evidence of RuO 2 crystal planes (RuO 2 (210) for the thermally oxidized film, and a mixture of RuO 2 (110)/RuO 2 (101) for the electrochemically oxidized film).
- the electrochemically oxidized sample shows greater amorphous structure than the thermally oxidized electrode, as seen by the broad peak of the XRD measurements.
- the amorphous character of the electrochemically oxidized RuO x film may be due in part to its hydrated structure, with incorporated water molecules distorting the polycrystalline structure.
- Specific capacitance values shown in FIG. 10 were calculated from CV measurements. Methods were used to estimate the mass of ALD RuO x -planar, porous Si, and CNT electrodes, specifically to calculate gravimetric specific capacitance, power, and energy density. Briefly, the mass of uncoated CNT electrodes was calculated from before and after mass measurements of CNT growth substrates. The mass of active porous Si electrode material from pore dimensions was estimated from SEM images. The mass of ALD RuO x films deposited on planar, porous Si, and CNT electrodes was estimated from thickness measurements of SEM and TEM images.
- thermal oxidation of ALD RuO x electrodes results in a decrease in supercapacitor performance under the conditions used.
- thermal oxidation the specific capacitance of planar and CNT electrodes dropped by 25% and 55% respectively compared to as-deposited ALD RuO x capacitance measurements.
- FIG. 11 The effect of increasing electrochemical oxidation time on the specific capacitance of planar, CNT, and porous Si ALD RuO x supercapacitors is shown in FIG. 11 .
- the capacitance of ALD RuO x -CNT electrodes increases steadily over 120 minutes of electrochemical oxidation ( FIG. 11 b ) while planar ALD 150 nm films start to delaminate after 5 minutes of oxidation ( FIG. 11 a ) and porous Si electrodes experience a decrease in capacitance after 3 minutes of oxidation ( FIG. 11 c ).
- Example 7 ALD Supercapacitors Scan Rate & Life Cycle Performance Testing
- ALD RuO x electrodes were tested over a range of CV scan rates to characterize supercapacitor performance at different charging speeds ( FIG. 12 a - c ).
- Planar, as-deposited ALD RuO x electrodes exhibited exceptional capacitance retention at high scan rates, maintaining the same specific capacitance at 10 mV/s and 20 V/s ( FIG. 6 a ).
- 20 V/s is one of the fastest scan rates reported in the literature for RuO x supercapacitors. As shown in FIG.
- life cycle performance testing results are shown for as-deposited and electrochemically oxidized ALD RuO x -CNT electrodes. Life cycle testing was conducted by repeated CV scans over the full supercapacitor operating range (0-1.0 V vs. RHE). Remarkably, the specific capacitance of as-deposited ALD RuO x -CNTs increased by 20% after 10,000 CV cycles. The improved performance improvement is likely due to the gradual, non-reversible electrochemical oxidation of as-deposited ALD RuO x during the CV. Similarly, planar ALD RuO x also had a capacitance increase with repeated cycling. Electrochemically oxidized ALD RuO x -CNTs tested over repeated charge-discharge cycles show a 19% decrease in specific capacitance.
- the present disclosure features a method to a fabricate high surface area, high performance supercapacitor.
- the method may include applying a metal layer to at least a portion of a nanostructure; after applying the metal layer, oxidizing the metal layer; applying a plurality of additional metal layers onto a previously oxidized metal layer; and after applying each additional metal layer, oxidizing the additional metal layer prior to applying a successive additional metal layer.
- the metal layers may include a composition comprising at least one metal, the at least one metal selected from the group consisting of ruthenium, titanium, manganese, vanadium, iron, tin, cobalt and nickel.
- each of the additional metal layers is applied using atomic layering deposition (ALD).
- ALD atomic layering deposition
- each of the additional metal layers may include a metal oxide or a metal precursor, and the step of applying the additional metal layers includes using ALD to pulse the metal layer.
- the ALD may be used to pulse the additional metal layers in a carrier gas at a temperature between 270° C. to 400° C.
- the pseudocapacitive metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od) 3 /n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd) 3 , (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene).
- the method may further include a step of electrochemically oxidizing at least one of the oxidized additional metal layers.
- the step of electrochemically oxidizing the at least one oxidized additional metal layers may include using an acidic electrolyte.
- the electrochemically oxidizing may be performed for 3 to 120 minutes at a constant potential (1.3 V versus Ag/AgCl) using controlled potential coulometry.
- the step of oxidizing the additional metal layers may include oxidizing the additional metal layers with oxygen, water, and hydrogen peroxide.
- the nanostructure may be selected from the group consisting of linear, non-linear, planar or porous nanostructures.
- the nanostructure may include a substrate composed of materials selected from the group consisting of carbon, silicon, graphene, activated carbon, and phosphorene.
- the nanostructure also optionally further include a conductive layer disposed on the substrate.
- the conductive layer may be selected from the group consisting of molybdenum, iron, aluminum, chromium and gold.
- the present disclosure features another method to a fabricate high surface area, high performance supercapacitor.
- the method includes using atomic layering deposition (ALD) to apply a metal precursor layer to a portion of a nanostructure; after applying the metal precursor layer, oxidizing the metal precursor layer; applying a plurality of additional metal precursor layers onto a previously oxidized metal precursor layer; and after applying each additional metal precursor layer, oxidizing the additional metal precursor layer prior to applying a successive additional metal precursor layer to form a layer of a pseudocapacitive material disposed about at least a portion of the nanostructure.
- ALD atomic layering deposition
- the method further includes the step of electrochemically oxidizing at least one of the oxidized additional metal precursor layers.
- the step of electrochemically oxidizing the at least one oxidized additional metal precursor layers may include using an acidic electrolyte.
- the electrochemically oxidizing may be performed for 3 to 120 minutes at a constant potential (1.3 V versus Ag/AgCl) using controlled potential coulometry.
- the metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od) 3 /n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd) 3 , (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene).
- the nanostructure may be selected from the group consisting of linear, non-linear, planar or porous nanostructures.
- the nanostructure may include a substrate composed of materials selected from the group consisting of carbon, silicon, graphene, activated carbon, and phosphorene.
- the nanostructure may optionally further include a conductive layer disposed on the substrate.
- the conductive layer may be selected from the group consisting of molybdenum, iron, aluminum, chromium and gold.
- the present disclosure features a high performance supercapacitor.
- the high performance supercapacitor may include a nanostructure; a first metal layer formed on at least a portion of the nanostructure, and at least one pseudocapacitive material layer formed over at least a portion of the first metal layer.
- the first metal layer may be formed on the at least a portion of the nanostructure by applying a metal precursor layer onto a nanostructure using atomic layering deposition (ALD) and thereafter oxidizing the metal precursor layer.
- ALD atomic layering deposition
- the at least one pseudocapacitive material layer may be formed by applying an additional metal precursor layer onto a previously oxidized metal precursor layer and thereafter oxidizing the additional metal precursor layer prior to applying a successive additional metal precursor layer.
- the metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od) 3 /n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd) 3 , (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene).
- the additional metal precursor layers are applied and oxidized for 50 to 1000 cycles. Additionally (or alternatively), at least a portion of an outer surface of the at least one pseudocapacitive material layer may be electrochemically oxidized.
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Abstract
Description
- The present application is a divisional of U.S. patent application Ser. No. 14/602,104 filed Jan. 21, 2015 which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/930,917 filed Jan. 23, 2014, the entire content of each of which is fully incorporated herein by reference.
- Supercapacitors are electrochemical energy-storage devices that store charge by reversible adsorption of ions onto high-surface area, porous materials (known as “electric double layer capacitors”) or reversible surface reduction-oxidation (redox) reactions (known as “pseudo-capacitors”). With their high power density and long cycle stability, supercapacitors are well-suited to complement or replace batteries in a wide range of applications, including transportation, renewable energy, and portable electronics. High-performance supercapacitors are characterized by high specific capacitance, good stability over repeated cycling, and low series resistance.
- The present disclosure will be more fully understood by reference to the following drawings which are for illustrative purposes only.
-
FIG. 1 Conceptual illustration of ALD RuOx supercapacitor fabrication and energy storage mechanism. -
FIG. 2 Conceptual view of a forest of vertically-aligned CNTs is covered with a layer of RuO2. -
FIG. 3 Electron micrographs of RuO2 coated carbon nanotubes. -
FIG. 4 Process and measurements of RuO2 coated carbon nanotube films at different temperatures. -
FIG. 5 X-ray diffraction measurements of ALD RuOx-CNT electrodes. -
FIG. 6 SEM image of as-deposited ALD RuOx porous and planar Si supercapacitor electrode. -
FIG. 7 High-resolution XPS measurements of binding energies for ALD RuOx planar and CNT films. -
FIG. 8 Cyclic voltammetry and electrochemical impedance spectroscopy of ALD RuO2 thermally and electrochemically oxidized electrodes. -
FIG. 9 Cyclic voltammetry measurements of ALD RuOx supercapacitors. -
FIG. 10 Cyclic voltammetry measurements of uncoated CNT and porous Si electrodes. -
FIG. 11 Change in specific capacitance of ALD RuOx supercapacitors with electrochemical oxidation. -
FIG. 12 Scan rate and life cycle performance testing of ALD RuOx supercapacitors. - Supercapacitors are electrochemical energy storage devices with promising applications in many environmentally-friendly technologies—including renewable energy and electric vehicles—that require high power density and high cycle life energy storage.
- In the present embodiments, high performance supercapacitors employed high surface area electrodes coated with a thin film of active pseudocapacitive material, such as metal oxides or conductive polymers. Examples of metal pseudocapacitive materials that store charge by a similar mechanism include ruthenium oxide (RuOx), manganese oxide (MnO2), vanadium oxide (V2O5), mixed cobalt-nickel oxides (a-(Co+Ni)(OH)2.nH2O), cobalt oxide (Co3O4), cobalt hydroxide (Co(OH)2), nickel oxide (NiO), tin oxide (SnO2), iron oxides (Fe2O3 and Fe3O4), and titanium dioxide (TiO2). Non-metal pseudocapacitive materials include polyaniline, polypyrrole, and polythiophene.
- The coated “pseudocapacitive” electrodes store charge by reversible reduction-oxidation (redox) reactions. In one embodiment of a pseudocapacitive material reaction, the ruthenium oxide (RuOx) reaction is one of the highest performing pseudocapacitive materials due to its fast, reversible redox reactions:
- As shown above, RuOx supercapacitors intercalate positive ions (H+) during charging; it is obligatory to have good proton and electron conductivity within the RuOx lattice for high supercapacitor performance. In pseudocapacitive materials, the supercapacitor performance depends on the hydroxyl content of the oxide, with hydrated, amorphous oxides often displaying better charge storage as a result of higher proton and more electrochemically active redox sites.
- To achieve high specific capacitance, fabrication methods must provide precise control of electrode structure and chemical composition as well as good uniformity over high surface areas.
- One supercapacitor fabrication method uses solution-based deposition, such as RuOx. For example, RuOx supercapacitor fabrication method using solution-based deposition of ruthenium trichloride exhibited a lack of uniformity and control of the RuOx coating. Other fabrication methods include magnetic sputtering and electro-oxidation of Ru nanoparticles, and mixing of RuO2-xH2O particles with a polymer binding agent. These methods suffer from poor electronic conductivity (especially for polymer binding agents), low utilization of RuOx due to non-uniformly dispersed nanoparticles or films, and/or low proton conductivity due to poor hydration.
- According to one embodiment of the present disclosure, a novel method was invented based on atomic layering deposition (ALD) to fabricate supercapacitors that had highly uniform, conformal coating of pseudocapacitive materials, which was applied to a diversity of surface compositions and structures. Three such embodiments included planar, vertically-aligned carbon nanotubes (CNT) and porous silicon (Si) electrodes. A further embodiment was the use of post-ALD electrochemical oxidation to increase energy storage potential. This method is the first successful direct ALD coating of RuO2 onto porous electrodes for supercapacitor applications, including CNTs and porous silicon one monolayer at a time. This method allows precise control over the RuO2 layer thickness and composition without the use of binder molecules
- In
FIG. 1 , a conceptual illustration of the general method for ALD supercapacitor fabrication process and charge storage mechanism of the hydrated coating is shown depicting a metal oxide, using RuOx as an example, onto porous structure. ALD is a highly versatile deposition process can be applied to any porous, high surface area, or high aspect ratio nanostructure, provided that the pores are accessible to the gas-phase precursors. InFIG. 1a , a generic porous structure is coated with ALD RuOx by sequential pulsing of an organometallic ruthenium precursor and oxygen. InFIG. 1b , the as-deposited ALD RuOx film is electrochemically oxidized to produce a hydrated pseudocapacitive layer with high proton conductivity. InFIG. 1c , the electrochemical energy storage mechanism of the hydrated ALD RuOx film is shown, which switches reversibly between oxide and hydroxide states through intercalation of hydrogen ions. In the electrode design, the surface and near-surface charge storage mechanism of the RuOx layer enables rapid charging and discharging of the supercapacitor, while the high surface area, porous electrode structure increases power and energy density. - Another embodiment of different structure used is shown in
FIG. 2 , where ALD metal oxide coated carbon nanotube (CNT) is illustrated during charging and discharging. In the illustration, forest of vertically-aligned CNTs is covered with a layer of RuO2 several nanometers thick deposited by ALD. The CNT provides a dynamic structure that can be varied and has exceptional high surface area, conductive, and flexible support for the active layer RuO2. As the device charges, the active RuO2 layer absorbs protons from the electrolyte and electrons flow into the device from an external circuit as the RuO2 layer is converted to Ru(OH)2 by a surface redox reaction. When discharging, stored electrons flow out of the device to an external circuit and protons are released into the electrolyte as Ru(OH)2 is converted back to RuO2 in the reverse redox reaction. In this device, the high strength and mechanical flexibility of the CNT forest is important for relieving mechanical stresses in the RuO2 layer that arise from repeated cycling through redox states. - In some of the following embodiments to fabricate supercapacitors, a novel, high precision, thin-film deposition method using atomic layer deposition (ALD) and precursors is described that provides uniform, conformal coating of large surface area, diverse nanomaterials. In addition, further embodiments employed the use of post-ALD electrochemical oxidation to enhance energy storage potential. Electrochemically oxidized ALD metal oxide supercapacitors prepared had exceptional high values of specific capacitance (644 F/g), power density (17 kW/kg), and energy density (4 Wh/kg). In view of prior methods, their supercapacitor performance was maintained over 10,000 charge-discharge cycles, and at ultra-high scan rates of up to 20 V/s.
- In some of the following embodiments using atomic layer deposition, metal oxide was successfully coated in a uniform, conformal application onto diverse porous electrodes composed of different nanostructures and different materials that previously were extremely difficult to fabricate. In one demonstration the porous materials was made from vertically aligned carbon nanotubes (CNT) while in the two other demonstrations planar and porous silicon was used as the starting electrode materials.
- In one embodiment of a structure on which a metal oxide is deposited was a forest of vertically-aligned carbon nanotubes (CNT) grown on molybdenum- and oxide-coated silicon wafer. In this embodiment, vertically aligned CNTs were synthesized by chemical vapor deposition on silicon substrates in a horizontal tube furnace as described by Jiang et al., Nano Lett. 13, 3524 (2013). Briefly, silicon substrates were cleaned in piranha solution, then coated with 100 nm thermal oxide and 50 nm molybdenum by electron beam evaporation. Iron and aluminum catalyst layers (10 nm and 5 nm, respectively) were then deposited by thermal evaporation. CNTs were grown at 720° C. and atmospheric pressure in a horizontal tube furnace in a mixture of 7:1 hydrogen-to-ethylene gas. A growth time of 10 minutes gave average CNT heights of 10 μm. Other CNT heights can also prepared by varying the growth times.
- In another embodiment, planar and porous silicon (Si) wafers were used for deposition.
- In yet other embodiments, substrate structure is linear, non-linear, planar or porous structures made of carbon, silicon, graphene, activated carbon, phosphorene, or like materials that may be coupled to the conductive substrate. The highly versatile deposition process was applied to any structures that are porous, high surface area, or high aspect ratio nanostructure, provided that the pores are accessible to the gas-phase precursors. Embodiments include carbon, silicon, phosphorene, or like materials are oriented substantially perpendicular such as nanotubes, single or multi-walled nanotubes, nanowires, nanorods, aggregated nanoparticles, fibers, ribbons, or other structures. Other embodiments include substrate scaffolds that are porous structures and made of carbon, silicon, phosphorene, or materials with similar properties.
- In this embodiment, vertically-aligned, multi-walled carbon nanotubes (CNT) were grown by chemical vapor deposition in a horizontal tube furnace with ethylene gas as the carbon-source. The CNTs were grown on a molybdenum- and oxide-coated silicon wafer, using aluminum and iron as catalyst layers.
- ALD RuOx films were deposited by atomic layering deposition (ALD) on planar, vertically-aligned CNT using bis(ethylcyclopentadienyl)ruthenium(II) (Ru(EtCp)2) as a RuOx precursor together with oxygen.
FIG. 3a provides a scanning electron microscope (SEM) image of vertically aligned CNTs coated with ALD RuO2. A cross-sectional scanning electron microscope (SEM) image of the RuO2-coated CNTs found that the CNT forest is approximately 5 μm tall with large pore spaces available for the electrolyte to penetrate into the dense matrix of CNTs. A close-up SEM image (FIG. 3b ) found that the CNTs were uniformly coated by the ALD process. The transmission electron microscope (TEM) image of a single CNT is shown inFIG. 3c where the ALD coated CNT was approximately 20 nm thick and demonstrated good adhesion to the CNT surface. In other (TEM) images of ALD RuOx-coated CNTs, it was shown that the as-deposited films are polycrystalline (FIG. 3d ) and highly conformal (FIG. 3e ). SEM images were taken using an FEI Nova NanoSEM 650 scanning electron microscope and TEM images with aTechnai 12 TEM. - The present methods developed using ALD with precursors and oxygen allowed for highly precise control over the RuO2 layer thickness and composition without the use of binder molecules. ALD RuOx deposition was conducted in cycles using a Cambridge Fiji F200 Plasma ALD with bis(ethylcyclopentadienyl)ruthenium(II) (Ru(EtCp)2) and oxygen (O2) as precursors and argon carrier gas. Other metal precurors, using ruthenium as an illustration, include ruthenium cyclopentadienyl (RuCp2), Ru(od)3/n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II) (Ru(DMPD)2), Ru(thd)3, Ru(EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene)Ru. Water or hydrogen peroxide may substitute as oxidizing reactants for oxygen gas.
- As an example, a cycle time included a pulse time for Ru(EtCp)2 in an argon gas carrier for 1 to 5 seconds, waiting 1 to 10 seconds, purging 1 to 10 second with O2, and waiting 1 to 10 seconds. ALD reaction temperatures were varied from 270° C. to 400° C. The number of cycles for layering RuO2 varied from 50 to 1000 cycles.
- Other embodiments of percursors for ALD fabrication include titanium dioxide (TiO2): tetrakis(dimethylamino)titanium (TMDAT) or titanium tetrakis isopropoxide (TTIP) with oxygen or water; tin oxide (SnO2) and tin tetrachloride (SnCl4) and water; cobalt oxide (Co3O4): Co(thd)2 and ozone; nickel oxide (NiO): Ni(acac)2 and ozone; and iron oxide (Fe2O3, Fe3O4):ferrocene (FeCp)2 and oxygen.
- In one embodied process, ALD RuO2 is deposited using ruthenium bis(ethylcyclopentadienyl) (Ru(EtCp)2) and oxygen as precursors as illustrated in
FIG. 4a . The novel two step cycle process included pulsing with Ru(EtCp)2 in [A], followed by oxidation using O2 [B], to convert Ru(EtCp)2 to RuO2 deposition, ensuring that Ru underwent controlled oxidation. With multiple successive cycles, the RuO2 layers were controllably “grown” to the desired thickness. From grazing-incidence x-ray photoelectron spectroscopy (GIXPS) analyses, it was found that a deposition temperature of 300 to 400° C. achieved good RuO2 deposition. - The composition of the ALD coating was investigated by GIXPS and XRD measurements.
FIG. 4b showed the GIXPS spectrum for ALD RuO2 deposited at 350° C. The results indicate a near-stoichiometric composition (65% O, 35% Ru) within the GIXPS measurement range (top 10 nm of the film).FIG. 4c is a plot of the oxygen content of the ALD films measured by GIXPS as a function of deposition temperature. In the range of 300° C. to 400° C., higher deposition temperatures corresponded to increased oxygen content of the films. Materials characterization was done using a Siemens D5000 X-ray diffractometer (XRD), and a PHI 5400 X-ray photoelectron spectrometer (XPS) was used for glancing incident XPS (GIXPS) measurements. - The ALD process for RuO2 is believed to occur via the accumulation of subsurface oxygen in a depositing Ru films. It is believed that with respect to the ALD growth mechanisms for Ru vs. RuO2, several hundred deposition cycles of Ru are required before RuO2 layers began to form. A certain thickness of Ru film is believed to be needed before there are enough defect sites to accumulate sufficient quantities of subsurface oxygen to form RuO2. In the present embodiments, XRD measurements of ALD-RuO2 films deposited at temperatures ranging from 300° C. to 400° C. showed primarily Ru diffraction peaks. For supercapacitor applications, only a surface layer of RuO2 is needed for charge storage. The presence of an underlying Ru layer with good electrical conductivity would be beneficial to supercapacitor performance.
- X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize ALD RuOx films on vertically-aligned CNT substrates. Similar to ALD RuOx films deposited on planar substrates, XRD measurements for ALD films on CNTs show predominantly Ru peaks (
FIG. 5a ). High-resolution XPS measurements of the Ru3d peak for ALD RuOx-films on CNTs show a shift to higher binding energies compared to Ru metal at take-off angles of 15°, 30°, and 75°, indicating the presence of oxidized ruthenium (FIG. 5b ). High-resolution XPS measurements of the O 1s peak show the presence of RuO2 (same as planar electrodes). - For porous Si electrodes, RuOx is deposited over the entire depth of the pores (exceeding 127 μm), however nucleation is less uniform than on CNTs. Previous studies of ALD RuOx have found that film nucleation efficiency depends on the substrate surface energy, with poorer nucleation expected on Si—H terminated surfaces like porous Si. ALD RuOx coating of planar supercapacitor electrodes is highly uniform and conformal, as expected. SEM images of ALD RuOx films deposited on porous Si is shown in
FIG. 6a-c . InFIG. 6a , SEM image of as-deposited ALD RuOx porous Si supercapacitor electrode. The lighter regions of the pores are areas coated with RuOx. In higher magnifications, SEM image of ALD RuOx conformally coating the bottom of a porous Si pore (FIG. 6b ). InFIG. 6c , SEM image showing the thickness of the ALD RuOx coating on the porous Si electrode (40 nm). - For planar ALD RuOx supercapacitors, they were fabricated by depositing RuOx on a silicon substrate coated with 30 nm of chromium (Cr) and 70 nm gold (Au) by thermal evaporation. The chromium and gold layers were used to provide a better nucleation surface for ALD RuOx than pure silicon. The thickness of the ALD RuOx film was estimated from cross-sectional SEM images (
FIG. 6d ). The mass of as-deposited ALD RuOx films was calculated using the density of Ru metal (12.45 g/cm3), as XRD measurements indicate that the as-deposited films are predominantly Ru. SEM images were taken using an FEI Nova NanoSEM 650 scanning electron microscope and TEM images with aTechnai 12 TEM. XRD measurements were conducted with a Siemens D5000 X-Ray Diffractometer (Cu Kα radiation) and XPS measurements with aPHI Quantum 2000 X-ray photoelectron spectrometer with pass energies of 11 eV (monochromated Alk 1486.6 eV x-ray source). The uncertainty in high-resolution XPS these measurements is less than 0.2 eV. - As illustrated in the table below, the thickness of the film on planar silicon structure was readily adjusted depending on that desired, providing greater flexibility for its end use. In these embodiments, the planar ALD RuOx film thickness were measured and estimated of average mass per cm2. In Column A, thin-film measurements of deposition are shown while in Column B those for thick-film are shown.
-
A B Average film thickness 36.7 nm 151.2 nm Number of film thickness 10 10 measurements Standard deviation 3.7 nm 16.2 nm Average film mass 0.046 mg/cm2 0.19 mg/cm2 - Following ALD RuOx deposition, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were performed to determine the composition of our ALD films.
FIG. 7a-c showed XRD and XPS measurements of ALD films deposited on planar substrates that were similar to those for CNT electrodes shown elsewhere. XRD measurements of as-deposited ALD RuOx (FIG. 5a ) show a strong metallic ruthenium crystal structure (Ru(100)), suggesting that the films are not fully oxidized during the ALD process. The role of the oxygen precursor during ALD RuOx deposition is both to oxidatively decompose the organometallic ruthenium precursor and to oxidize the depositing Ru metal film. Previous studies suggest that in-situ ALD RuOx formation can be inhibited by low rates of subsurface oxygen absorption and slow reaction kinetics for Ru oxidation. In this process, increasing the ALD RuOx deposition temperature from 270° C. to 400° C. changed the dominant Ru crystal phase, but does not produce RuO2 XRD peaks. - XPS measurements provide qualitative characterization of a material's surface composition (approximately 1-10 nm film depth). XPS measurements of ALD RuOx films deposited on planar substrates reveal that the as-deposited films do have significant surface oxide character not detected by XRD. High-resolution XPS measurements of Ru 3d binding energies (
FIG. 7a ) show a shift to higher energies, and hence higher oxidation states, compared to Ru metal. For the O 1s peak, we measured a binding energy of 530 eV for our as-deposited ALD RuOx films (FIG. 7b ), consistent with previously reported results for RuO2. Other forms of oxygen that may be present include Ru—OH and surface adsorbed H2O; these materials, however, have O 1s binding energies greater than 533 eV and are thus clearly distinguishable from RuO2 given our high-resolution XPS measurement uncertainty of less than 0.2 eV. Ruthenium does not form a native oxide at room temperature, suggesting that the observed RuO2 surface layer is formed during the ALD process. - When tested as a supercapacitor electrode, the ALD RuO2-coated CNTs demonstrated high capacitive energy storage capability. Cyclic voltammetry measurements of the ALD RuO2-coated CNT supercapacitor were compared to an uncoated (“bare”) CNT supercapacitor. A capacitive current of 10 mA/cm2 at a scan rate of 100 mV/s corresponds to specific capacitance of 100 mF/cm2, which represents one of the best values in the literature. Measurements for cyclic voltammetry (CV) were conducted using a three-electrode test set-up, Ag/AgCl reference and Pt counter electrode and
Gamry Reference 600 potentiostat, in 0.5 M H2SO4 aqueous electrolyte at 100 mV/s scan rate (though it should be appreciated that other acidic electrolytes may work such as, but not limited to, nitric acid (HNO3), hydrochloric acid (HCl), or the like may also and/or alternatively be used). The supercapacitor performance of the ALD RuO2-CNTs is approximately fifty times that of the uncoated CNTs (FIG. 8a ). The Nyquist plot inFIG. 8b shows that the device has an equivalent series resistance (ESR) of 7Ω, one of the lowest reported values. This low ESR value can be attributed to the conformal nature of the ALD coating which minimizes contact resistance between the active RuO2 layer and the CNTs. In addition, rapid charge-discharge characteristics have been demonstrated and remained stable over time, as shown inFIG. 8b . It is expected that these results can be further improved upon by optimizing the stoichiometry and thickness of the RuO2 coating. With the ALD fabrication method, these properties can be controlled with angstrom-level precision to achieve exceptionally high-performance supercapacitor devices. - Repeating chronoamperometry was used to measure the device response to a step-change in applied potential. The ALD-RuO2 coated CNTs display rapid charge-discharge characteristics that remain remarkably stable over time.
- These results demonstrated that ALD RuO2-coated CNTs performed as excellent high-performance supercapacitor electrodes. In addition to high specific capacitance, the device has low equivalent series resistance, rapid charge-discharge characteristics, and good stability over repeated cycling. The exceptionally high-performance of the ALD RuO2-coated CNTs can be attributed to: 1) excellent conformal coverage of the CNTs by the ALD RuO2 coating, 2) a high-quality RuO2 surface layer capable of fast, reversible redox reactions, and 3) high surface area of the dense, vertically-aligned CNT forest.
- To further enhance the supercapacitor performance of our ALD RuOx electrodes, as-deposited ALD films were electrochemically oxidized in 0.5 M H2SO4 electrolyte at a constant potential of 1.3 V vs. Ag/AgCl for variable amounts of time, 3 min-120 min, which corresponds to the electrochemical oxidation potential of Ru. For comparison, post-ALD thermal oxidation was conducted by heating as-deposited ALD RuOx electrodes to 600° C. in 70 sccm oxygen flow for 30 minutes. XRD measurements of electrochemically and thermally oxidized ALD RuOx planar films are shown in
FIG. 5a . In contrast to as-deposited ALD films, both electrochemically and thermally oxidized films show evidence of RuO2 crystal planes (RuO2(210) for the thermally oxidized film, and a mixture of RuO2(110)/RuO2(101) for the electrochemically oxidized film). The electrochemically oxidized sample shows greater amorphous structure than the thermally oxidized electrode, as seen by the broad peak of the XRD measurements. The amorphous character of the electrochemically oxidized RuOx film may be due in part to its hydrated structure, with incorporated water molecules distorting the polycrystalline structure. - To determine the specific capacitance of thermally and electrochemically oxidized ALD RuOx supercapacitors, cyclic voltammetry (CV) measurements were performed using the three-electrode test set-up as previously described. A comparison of as-deposited (“ALD RuOx”), thermally oxidized (“Thermal ox.”), and electrochemically oxidized (“Electrochem ox.”, with oxidation time) supercapacitors showed that electrochemical oxidation improved capacitance, while thermal oxidation decreases charge-storage ability compared to as-deposited ALD electrodes (
FIG. 9 ). CV measurements for 40 nm and 150 nm thickness planar electrodes were compared to uncoated CNT (FIG. 10a ) and uncoated porous Si (FIG. 10b ) electrodes. - Specific capacitance values shown in
FIG. 10 were calculated from CV measurements. Methods were used to estimate the mass of ALD RuOx-planar, porous Si, and CNT electrodes, specifically to calculate gravimetric specific capacitance, power, and energy density. Briefly, the mass of uncoated CNT electrodes was calculated from before and after mass measurements of CNT growth substrates. The mass of active porous Si electrode material from pore dimensions was estimated from SEM images. The mass of ALD RuOx films deposited on planar, porous Si, and CNT electrodes was estimated from thickness measurements of SEM and TEM images. In calculating RuOx mass, the density of Ru (12.45 g/cm3) for as-deposited ALD RuOx films and the density of RuO2 (6.97 g/cm3) for electrochemically oxidized films (based on evidence of film composition from XRD measurements) were used. - CV measurements of ALD RuOx on planar, CNT, and porous Si substrates (
FIG. 9a-d ) show that the as-deposited ALD RuOx films are highly capacitive. The shape of the CV curves for as-deposited ALD RuOx electrodes is characteristic of RuO2 supercapacitors reported. In this work, the highest values of specific capacitance are obtained with vertically aligned CNT electrodes due to their highly porous structure and large double layer capacitance. There was a two-order of magnitude an increase in specific capacitance for vertically aligned CNT electrodes with the ALD RuOx coating, from 3.4 F/g for uncoated CNTs (FIG. 10a ) to 363 F/g for as-deposited ALD RuOx-CNTs (404 F per gram of RuOx). For porous Si electrodes, specific capacitance increases nearly 5000× with the ALD RuOx coating, from 0.39 mF/g for uncoated porous Si (FIG. 10b ) to 1.88 F/g for ALD RuOx-porous Si. This is the highest value of gravimetric specific capacitance reported for porous Si-based electrodes, which traditionally have received little consideration for supercapacitor applications due to their low intrinsic capacitance compared to carbon-based materials. - With post-ALD electrochemical oxidation, there was an increase in the specific capacitance of ALD RuOx-coated planar, CNT, and porous Si electrodes (
FIG. 9 ). The increased capacitance was found in the conversion of as-deposited, mixed metal-oxide ALD films to hydrated amorphous RuOx, as confirmed by XRD measurements. After electrochemical oxidation, the specific capacitance of our ALD RuOx-CNT supercapacitors reaches a maximum value of 644 F/g of RuOx (578 F/g including the mass of CNTs). For comparison, the theoretical capacitance of RuO2 is 1450 F/g and the highest values reported in the literature range from 900 F/g-950 F/g. Optimization of supercapacitor electrode geometry, including both surface area and pore size, is critical to attaining high supercapacitor performance. In these embodiments, the ALD RuOx-CNT electrodes achieved nearly 70% of the maximum RuO2 capacitance reported to-date even without optimization of supercapacitor electrode geometry. - In contrast to electrochemical oxidation, thermal oxidation of ALD RuOx electrodes results in a decrease in supercapacitor performance under the conditions used. With thermal oxidation, the specific capacitance of planar and CNT electrodes dropped by 25% and 55% respectively compared to as-deposited ALD RuOx capacitance measurements.
- The effect of increasing electrochemical oxidation time on the specific capacitance of planar, CNT, and porous Si ALD RuOx supercapacitors is shown in
FIG. 11 . The capacitance of ALD RuOx-CNT electrodes increases steadily over 120 minutes of electrochemical oxidation (FIG. 11b ) whileplanar ALD 150 nm films start to delaminate after 5 minutes of oxidation (FIG. 11a ) and porous Si electrodes experience a decrease in capacitance after 3 minutes of oxidation (FIG. 11c ). These results are due to each electrode's ability to accommodate stresses in the ALD RuOx film arising from simultaneous oxidation and hydration processes. TEM images of ALD RuOx-coated CNTs before and after 9 minutes of electrochemical oxidation show a 35% increase in RuOx thickness. For porous Si electrodes, a substantial degradation of both the ALD RuOx film and porous Si substrate after 18 minutes of electrochemical oxidation was found. In contrast, vertically aligned CNTs have a high degree of mechanical flexibility that can accommodate substantial increases in RuOx coating thickness without visible degradation. - ALD RuOx electrodes were tested over a range of CV scan rates to characterize supercapacitor performance at different charging speeds (
FIG. 12a-c ). Planar, as-deposited ALD RuOx electrodes exhibited exceptional capacitance retention at high scan rates, maintaining the same specific capacitance at 10 mV/s and 20 V/s (FIG. 6a ). To our knowledge, 20 V/s is one of the fastest scan rates reported in the literature for RuOx supercapacitors. As shown inFIG. 12c , increasing the oxidation time of ALD RuOx-CNT electrodes from 18 minutes to 120 minutes enabled the supercapacitors to maintain 20% of their 10 mV/s specific capacitance value at a scan rate of 2 V/s. This enhanced performance at higher scan rates is thought to result from improved proton conductivity and hence faster redox reactions in the electrochemically oxidized ALD RuOx films. - In
FIG. 12d , life cycle performance testing results are shown for as-deposited and electrochemically oxidized ALD RuOx-CNT electrodes. Life cycle testing was conducted by repeated CV scans over the full supercapacitor operating range (0-1.0 V vs. RHE). Remarkably, the specific capacitance of as-deposited ALD RuOx-CNTs increased by 20% after 10,000 CV cycles. The improved performance improvement is likely due to the gradual, non-reversible electrochemical oxidation of as-deposited ALD RuOx during the CV. Similarly, planar ALD RuOx also had a capacitance increase with repeated cycling. Electrochemically oxidized ALD RuOx-CNTs tested over repeated charge-discharge cycles show a 19% decrease in specific capacitance. - According to one aspect, the present disclosure features a method to a fabricate high surface area, high performance supercapacitor. The method may include applying a metal layer to at least a portion of a nanostructure; after applying the metal layer, oxidizing the metal layer; applying a plurality of additional metal layers onto a previously oxidized metal layer; and after applying each additional metal layer, oxidizing the additional metal layer prior to applying a successive additional metal layer. The metal layers may include a composition comprising at least one metal, the at least one metal selected from the group consisting of ruthenium, titanium, manganese, vanadium, iron, tin, cobalt and nickel.
- Optionally, each of the additional metal layers is applied using atomic layering deposition (ALD). For example, each of the additional metal layers may include a metal oxide or a metal precursor, and the step of applying the additional metal layers includes using ALD to pulse the metal layer. The ALD may be used to pulse the additional metal layers in a carrier gas at a temperature between 270° C. to 400° C. The pseudocapacitive metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od)3/n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd)3, (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene).
- Optionally, the method may further include a step of electrochemically oxidizing at least one of the oxidized additional metal layers. For example, the step of electrochemically oxidizing the at least one oxidized additional metal layers may include using an acidic electrolyte. The electrochemically oxidizing may be performed for 3 to 120 minutes at a constant potential (1.3 V versus Ag/AgCl) using controlled potential coulometry.
- The step of oxidizing the additional metal layers may include oxidizing the additional metal layers with oxygen, water, and hydrogen peroxide. The nanostructure may be selected from the group consisting of linear, non-linear, planar or porous nanostructures. For example, the nanostructure may include a substrate composed of materials selected from the group consisting of carbon, silicon, graphene, activated carbon, and phosphorene. The nanostructure also optionally further include a conductive layer disposed on the substrate. The conductive layer may be selected from the group consisting of molybdenum, iron, aluminum, chromium and gold.
- According to another aspect, the present disclosure features another method to a fabricate high surface area, high performance supercapacitor. The method includes using atomic layering deposition (ALD) to apply a metal precursor layer to a portion of a nanostructure; after applying the metal precursor layer, oxidizing the metal precursor layer; applying a plurality of additional metal precursor layers onto a previously oxidized metal precursor layer; and after applying each additional metal precursor layer, oxidizing the additional metal precursor layer prior to applying a successive additional metal precursor layer to form a layer of a pseudocapacitive material disposed about at least a portion of the nanostructure.
- Optionally, the method further includes the step of electrochemically oxidizing at least one of the oxidized additional metal precursor layers. For example, the step of electrochemically oxidizing the at least one oxidized additional metal precursor layers may include using an acidic electrolyte. The electrochemically oxidizing may be performed for 3 to 120 minutes at a constant potential (1.3 V versus Ag/AgCl) using controlled potential coulometry.
- The metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od)3/n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd)3, (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene).
- Optionally, the nanostructure may be selected from the group consisting of linear, non-linear, planar or porous nanostructures. For example, the nanostructure may include a substrate composed of materials selected from the group consisting of carbon, silicon, graphene, activated carbon, and phosphorene. The nanostructure may optionally further include a conductive layer disposed on the substrate. The conductive layer may be selected from the group consisting of molybdenum, iron, aluminum, chromium and gold.
- According to yet another aspect, the present disclosure features a high performance supercapacitor. The high performance supercapacitor may include a nanostructure; a first metal layer formed on at least a portion of the nanostructure, and at least one pseudocapacitive material layer formed over at least a portion of the first metal layer. The first metal layer may be formed on the at least a portion of the nanostructure by applying a metal precursor layer onto a nanostructure using atomic layering deposition (ALD) and thereafter oxidizing the metal precursor layer. The at least one pseudocapacitive material layer may be formed by applying an additional metal precursor layer onto a previously oxidized metal precursor layer and thereafter oxidizing the additional metal precursor layer prior to applying a successive additional metal precursor layer.
- Optionally, the metal precursor layer may be selected from the group consisting of bis(ethylcyclopentadienyl), cyclopentadienyl, (od)3/n-butylacetate solution, bis(2,4-dimethylpentadienyl)ruthenium(II), (thd)3, (EtCp)(DMPD), and (isopropylmethylbenzene)(cyclohexadiene). According to one embodiment, the additional metal precursor layers are applied and oxidized for 50 to 1000 cycles. Additionally (or alternatively), at least a portion of an outer surface of the at least one pseudocapacitive material layer may be electrochemically oxidized.
- Further aspects of the present disclosure will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon.
- While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
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US9847351B2 (en) | 2016-01-26 | 2017-12-19 | United Microelectronics Corp. | Semiconductor device and method for fabricating the same |
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2015
- 2015-01-21 AU AU2015209438A patent/AU2015209438A1/en not_active Abandoned
- 2015-01-21 WO PCT/US2015/012290 patent/WO2015112628A1/en active Application Filing
- 2015-01-21 CA CA2937819A patent/CA2937819A1/en not_active Abandoned
- 2015-01-21 US US14/602,104 patent/US9805880B2/en active Active
- 2015-01-21 EP EP15740256.1A patent/EP3097574A4/en not_active Withdrawn
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AU2015209438A1 (en) | 2016-08-11 |
WO2015112628A1 (en) | 2015-07-30 |
CA2937819A1 (en) | 2015-07-30 |
EP3097574A4 (en) | 2017-12-27 |
US9805880B2 (en) | 2017-10-31 |
US20150303001A1 (en) | 2015-10-22 |
EP3097574A1 (en) | 2016-11-30 |
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