CN115548286A - Coated modified lithium iron phosphate composite material, and preparation method and application thereof - Google Patents
Coated modified lithium iron phosphate composite material, and preparation method and application thereof Download PDFInfo
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical class [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 79
- 239000002131 composite material Substances 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000007788 liquid Substances 0.000 claims abstract description 24
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000000843 powder Substances 0.000 claims abstract description 18
- 239000006185 dispersion Substances 0.000 claims abstract description 14
- 238000009210 therapy by ultrasound Methods 0.000 claims abstract description 13
- 238000004108 freeze drying Methods 0.000 claims abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 9
- 238000007710 freezing Methods 0.000 claims abstract description 7
- 230000008014 freezing Effects 0.000 claims abstract description 7
- 239000008367 deionised water Substances 0.000 claims abstract description 6
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 6
- 239000012298 atmosphere Substances 0.000 claims abstract description 5
- 230000001681 protective effect Effects 0.000 claims abstract description 5
- 238000001704 evaporation Methods 0.000 claims abstract description 3
- 238000001816 cooling Methods 0.000 claims description 25
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- 238000000137 annealing Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 7
- 239000000725 suspension Substances 0.000 claims description 7
- 239000010406 cathode material Substances 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 238000005303 weighing Methods 0.000 claims description 6
- 239000011261 inert gas Substances 0.000 claims description 5
- 239000007774 positive electrode material Substances 0.000 claims description 4
- 238000012935 Averaging Methods 0.000 claims description 2
- 238000013329 compounding Methods 0.000 claims description 2
- 239000007772 electrode material Substances 0.000 abstract description 12
- 238000009792 diffusion process Methods 0.000 abstract description 6
- 150000002500 ions Chemical class 0.000 abstract description 5
- 239000000463 material Substances 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 description 8
- 239000011259 mixed solution Substances 0.000 description 7
- 239000012300 argon atmosphere Substances 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- 238000004321 preservation Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000000527 sonication Methods 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- 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
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Abstract
The invention relates to the technical field of lithium ion battery materials, in particular to a coated modified lithium iron phosphate composite material, and a preparation method and application thereof. Adding a multilayer MXene turbid liquid into a deionized water beaker, and performing ultrasonic treatment under a protective atmosphere to obtain a uniformly dispersed few-layer MXene dispersion liquid; placing lithium iron phosphate into the less-layer MXene dispersion liquid, and performing ultrasonic treatment to obtain uniformly-mixed MXene/lithium iron phosphate dispersion liquid; and (3) putting the MXene/lithium iron phosphate solution into an evaporating dish, quickly freezing by using liquid nitrogen, and freeze-drying the sample in a freeze dryer to obtain the lithium iron phosphate powder uniformly coated with the MXene. The MXene-coated lithium iron phosphate effectively improves the electronic conductivity and the ion diffusion coefficient of the lithium iron phosphate, and the composite electrode material with high-rate charge and discharge performance is obtained.
Description
Technical Field
The invention relates to the technical field of lithium ion battery materials, in particular to a coated modified lithium iron phosphate composite material, and a preparation method and application thereof.
Background
The lithium ion battery mainly comprises a positive electrode material, a negative electrode material, electrolyte, a diaphragm and the like, wherein the positive electrode material is a main factor influencing the performance of the lithium ion battery, and the main positive electrode material at present comprises ternary materials of lithium cobaltate, lithium iron phosphate, lithium manganate and nickel cobalt manganese. The lithium iron phosphate has the advantages of excellent cycle performance, good thermal stability, rich resources, safety and the like, and has wide application and huge potential. The lithium iron phosphate is of an olivine structure, and oxygen atoms, iron atoms and phosphorus atoms are combined by strong covalent bonds, so that the structure of the lithium iron phosphate is more stable at high temperature, but the stable structure also increases the difficulty of lithium ion deintercalation, and the ion diffusion coefficient and the electronic conductivity are very low. At present, the rate capability of the material is improved by mostly adopting the material with better cladding and doping conductivity. MXene is a two-dimensional transition metal carbide or carbonitride with a graphene-like structure. Currently, MXene is mainly obtained by extracting weakly bonded A site elements (such as Al atoms) in the MAX phase through HF acid or a mixed solution of hydrochloric acid and fluoride. It has good conductivity and high ion diffusion coefficient. The MXene coated lithium iron phosphate can effectively improve the conductivity of the electrode and the diffusion speed of lithium ions, so that better rate performance is obtained.
Disclosure of Invention
In order to solve the technical problems, the invention provides an MXene-coated lithium iron phosphate composite electrode material and a preparation method thereof.
One of the objectives of the present invention is to provide an MXene-coated composite electrode material, which has a higher electronic conductivity and a faster ion diffusion rate as an electrode material of a lithium ion battery, so as to improve the rate capability, especially the high-current charge and discharge performance, of the lithium ion battery.
The second purpose of the invention is to provide a preparation method of the MXene-coated composite electrode material, the preparation method has simple process and good preparation effect, and MXene is uniformly distributed in lithium iron phosphate.
In order to achieve the technical purpose, the invention mixes the electrode material and MXene in the solvent uniformly, and prepares the MXene coated lithium iron phosphate composite electrode material by a freeze drying method.
Specifically, the technical scheme of the invention is as follows:
a preparation method of an MXene-coated lithium iron phosphate composite material comprises the following steps:
(1) Adding the multilayer MXene suspension into a deionized water beaker, and performing ultrasonic treatment under a protective atmosphere to obtain a uniformly dispersed few-layer MXene dispersion liquid;
(2) Placing lithium iron phosphate into the small-layer MXene dispersion liquid, and performing ultrasonic treatment to obtain an MXene/lithium iron phosphate dispersion liquid which is uniformly mixed;
(3) And (3) placing the MXene/lithium iron phosphate dispersion liquid into an evaporation dish, quickly freezing by using liquid nitrogen, and then placing the sample into a freeze dryer for freeze drying to obtain lithium iron phosphate powder uniformly coated with MXene.
(4) And annealing the powder to obtain the MXene/lithium iron phosphate composite anode material, wherein the composite material is provided with a conductive network opposite to points, the conductive network comprises lithium iron phosphate and MXene, and the lithium iron phosphate covers the surface of the MXene.
Preferably, in the step (1), the molecular formula of MXene is M b+1 X b Wherein, M atomic layers are in hexagonal close-packed packing, X atoms are filled in octahedral vacancies to form an MX layer, and M is selected from one or a mixture of more than two of Ti, zr, cr, mo, V and Ta; x is C or N; the MXene is selected from Ti 3 C 2 、Zr 3 C 2 、Ti 4 C 3 Or V 4 C 3 And determining the concentration of the multi-layer MXene suspension by repeatedly drawing a film, weighing and averaging, wherein the concentration is 4mg/ml. The protective atmosphere is one or two of nitrogen and argon which are mixed according to any proportion, the ultrasonic mode is water cooling ultrasonic, the water cooling temperature is 18-25 ℃, the ultrasonic power is 600W, and the ultrasonic time is 4-6 h.
Preferably, the lithium iron phosphate in the step (2) is commercial lithium iron phosphate, the particle size is 30-80 nm, the ultrasonic mode is water cooling ultrasonic, the water cooling temperature is 18-25 ℃, the ultrasonic power is 400W, and the ultrasonic time is 2h.
Preferably, the temperature of the freeze drying in the step (3) is-55 to-65 ℃, and the freeze drying is carried out for 24 hours.
Preferably, the annealing treatment in the step (4) is carried out in a high-temperature tube furnace, and the annealing process comprises the steps of heating to 400 ℃ at a speed of 1-2 ℃/min under the protection of inert gas argon, preserving heat for 2-4 h, then heating to 700-900 ℃ at a speed of 5 ℃/min, preserving heat for 2-4 h, and finally cooling to room temperature to obtain the MXene/lithium iron phosphate composite cathode material.
The invention also provides an MXene-coated lithium iron phosphate composite electrode material which comprises the following components: lithium iron phosphate and MXene, wherein the lithium iron phosphate accounts for 95-99%. MXene coats the lithium iron phosphate particles to realize the compounding on the nanometer size.
The beneficial effects of the invention are: (1) The MXene coated electrode material is prepared by adopting a freeze-drying method, and has the advantages of simple operation, good preparation effect and high production efficiency. (2) MXene and lithium iron phosphate particles are uniformly distributed in the solution after ultrasonic treatment. And (3) the quick freezing by liquid nitrogen avoids the stacking of MXene. (4) MXene can greatly reduce the contact area of the electrode material and the electrolyte and reduce the dissolution and self-discharge effects of the electrode material in the electrolyte. (5) The MXene coated lithium iron phosphate effectively improves the electronic conductivity and the ion diffusion coefficient of the lithium iron phosphate, and the composite electrode material with high-rate charge and discharge performance is obtained.
Drawings
In order to more clearly explain the technical solution of the present invention, the present invention will be described in detail by the accompanying drawings and examples.
Fig. 1 is a schematic diagram of a conductive network structure of an MXene-coated modified lithium iron phosphate composite material prepared in a first embodiment of the present invention.
Fig. 2 is a scanning electron microscope image of a pole piece prepared from the MXene-coated modified lithium iron phosphate composite material prepared in the first embodiment of the present invention.
Fig. 3 is a charge-discharge curve diagram of a pole piece prepared from the MXene-coated modified lithium iron phosphate composite material prepared in the first embodiment of the present invention under different multiplying powers.
Fig. 4 is a graph of cycle efficiency at 1C rate of a prepared pole piece of the MXene coated modified lithium iron phosphate composite prepared in the first example of the present invention.
As can be seen from the figure, the battery has higher specific discharge capacity under the 10C high-rate discharge working condition and better cycling stability under 1C.
Detailed Description
Hereinafter, the technical solution of the present invention will be described in detail according to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
Example 1:
(1) The multi-layer MXene suspension is subjected to film drawing and weighing to obtain the concentration of 4mg/ml, 15ml of the multi-layer MXene suspension is weighed and added into a beaker, 20ml of deionized water is added, water cooling and ultrasonic processing are carried out under the argon atmosphere, the water cooling temperature is 20 ℃, the ultrasonic power is 600W, and the small-layer MXene dispersion liquid which is uniformly dispersed is obtained after ultrasonic processing for 4 hours.
(2) Weighing 1g of lithium iron phosphate powder, adding the lithium iron phosphate powder into a beaker, carrying out water cooling ultrasonic treatment on the lithium iron phosphate powder with the particle size range of 30-80 nm under the argon atmosphere, wherein the water cooling temperature is 20 ℃, the ultrasonic power is 400W, and carrying out ultrasonic treatment for 2h to obtain a uniform mixed solution.
(3) And (3) quickly freezing the obtained mixed solution by using liquid nitrogen immediately, and then putting the sample into a freeze dryer for freeze drying at the temperature of-65 ℃ in a cold well for 24 hours to obtain the lithium iron phosphate powder uniformly coated with MXene.
(4) And (2) carrying out annealing treatment in a high-temperature tube furnace, wherein the annealing treatment process comprises the steps of heating to 400 ℃ at a speed of 2 ℃/min under the protection of inert gas argon, preserving heat for 3h, then heating to 800 ℃ at a speed of 5 ℃/min, preserving heat for 3h, and finally cooling to room temperature to obtain the MXene/lithium iron phosphate composite cathode material.
Example 2:
(1) The multi-layer MXene suspension is weighed by film drawing to obtain the concentration of 4mg/ml, 7.5ml of multi-layer MXene solution is weighed and added into a beaker, 20ml of deionized water is added, water cooling and ultrasonic processing are carried out under argon atmosphere, the water cooling temperature is 20 ℃, the ultrasonic power is 600W, and ultrasonic processing is carried out for 4 hours to obtain the uniformly dispersed small-layer MXene dispersion liquid.
(2) Weighing 1g of lithium iron phosphate powder, adding the lithium iron phosphate powder into a beaker, carrying out water cooling ultrasonic treatment on the lithium iron phosphate powder with the particle size range of 30-80 nm under the argon atmosphere, wherein the water cooling temperature is 20 ℃, the ultrasonic power is 400W, and carrying out ultrasonic treatment for 2h to obtain a uniform mixed solution.
(3) And (3) quickly freezing the obtained mixed solution by using liquid nitrogen immediately, and then putting the sample into a freeze dryer for freeze drying at the temperature of-65 ℃ in a cold well for 24 hours to obtain the lithium iron phosphate powder uniformly coated with MXene.
(4) And (2) carrying out annealing treatment in a high-temperature tube furnace, wherein the annealing treatment process comprises the steps of heating to 400 ℃ at a speed of 2 ℃/min under the protection of inert gas argon, carrying out heat preservation for 3h, then heating to 800 ℃ at a speed of 5 ℃/min, carrying out heat preservation for 3h, and finally cooling to room temperature to obtain the MXene/lithium iron phosphate composite cathode material.
Example 3:
(1) The multi-layer MXene suspension is weighed by film drawing to obtain the concentration of 4mg/ml, 7.5ml of multi-layer MXene liquid is weighed and added into a beaker, 20ml of deionized water is added, water cooling and ultrasonic processing are carried out under the argon atmosphere, the water cooling temperature is 20 ℃, the ultrasonic power is 600W, and the uniformly dispersed small-layer MXene dispersion liquid is obtained after ultrasonic processing for 6 hours.
(2) Weighing 1g of lithium iron phosphate powder, adding the lithium iron phosphate powder into a beaker, carrying out water cooling ultrasonic treatment on the lithium iron phosphate powder with the particle size range of 30-80 nm under the argon atmosphere, wherein the water cooling temperature is 20 ℃, the ultrasonic power is 400W, and carrying out ultrasonic treatment for 2h to obtain a uniform mixed solution.
(3) And (3) quickly freezing the obtained mixed solution by using liquid nitrogen immediately, and then putting the sample into a freeze dryer for freeze drying at the temperature of-65 ℃ in a cold well for 24 hours to obtain the lithium iron phosphate powder uniformly coated with MXene.
(4) And (2) carrying out annealing in a high-temperature tube furnace, wherein the annealing process comprises the steps of heating to 400 ℃ at a speed of 2 ℃/min under the protection of inert gas argon, carrying out heat preservation for 3h, then heating to 800 ℃ at a speed of 5 ℃/min, carrying out heat preservation for 3h, and finally cooling to room temperature to obtain the MXene/lithium iron phosphate composite cathode material.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, improvement, equivalent replacement, etc., which are made within the spirit and principle of the present application, should be included in the protection scope of the present application.
Comparative example 1:
preparing a lithium iron phosphate electrode by using conductive carbon black, and mixing the lithium iron phosphate powder: conductive carbon black: PVDF is mixed into slurry by an 8.
Table 1 shows comparative battery performance data between different embodiments of the present invention and the original lithium iron phosphate cathode material.
It can be seen from table 1 that example 1, in which the ratio of coated MXene is low, obtains better rate performance than the battery prepared in example 2, in which the specific gravity of coated MXene is high. Example 3, which has a long sonication time at the same coating ratio, has better rate performance than the battery prepared in example 1, which has a short sonication time. Under the same test condition, the electrochemical performance of the three examples is superior to that of the comparative example, which shows that the rate performance and the cycle performance of the MXene/lithium iron phosphate composite material are remarkably improved compared with the conventional lithium iron phosphate.
Claims (8)
1. A coated modified lithium iron phosphate composite material is characterized by comprising the following components in percentage by weight: the composite material comprises lithium iron phosphate and MXene, wherein the lithium iron phosphate accounts for 95% -99%, the MXene coats lithium iron phosphate particles to realize nano-size compounding, the composite material is provided with a point-to-point conductive network, the conductive network comprises the lithium iron phosphate and the MXene, and the lithium iron phosphate covers the surface of the MXene.
2. The coated modified lithium iron phosphate composite material of claim 1, wherein MXene is selected from Ti 3 C 2 、Zr 3 C 2 、Ti 4 C 3 Or V 4 C 3 。
3. The preparation method of the coated modified lithium iron phosphate composite material according to claim 1, comprising the following steps:
(1) Adding the multilayer MXene turbid liquid into a deionized water beaker, and performing ultrasonic treatment under a protective atmosphere to obtain a uniformly dispersed few-layer MXene dispersion liquid;
(2) Placing lithium iron phosphate into the less-layer MXene dispersion liquid, and performing ultrasonic treatment to obtain uniformly-mixed MXene/lithium iron phosphate dispersion liquid;
(3) Putting the MXene/lithium iron phosphate dispersion liquid into an evaporating dish, quickly freezing by using liquid nitrogen, and then putting a sample into a freeze dryer for freeze drying to obtain lithium iron phosphate powder uniformly coated by MXene;
(4) And annealing the powder to obtain the coated modified lithium iron phosphate composite material.
4. The method of claim 3, wherein in the step (1), the concentration of the multi-layer MXene suspension is determined by repeatedly extracting films, weighing and averaging, and is 4mg/ml; the protective atmosphere is one or two of nitrogen and argon which are mixed according to any proportion, the ultrasonic mode is water cooling ultrasonic, the water cooling temperature is 18-25 ℃, the ultrasonic power is 600W, and the ultrasonic time is 4-6 h.
5. The preparation method of the coated modified lithium iron phosphate composite material according to claim 3, wherein in the step (2), the particle size of the lithium iron phosphate is 30-80 nm, the ultrasonic mode is water cooling ultrasonic, the water cooling temperature is 18-25 ℃, the ultrasonic power is 400W, and the ultrasonic time is 2h.
6. The method for preparing a coated modified lithium iron phosphate composite material according to claim 3, wherein the freeze-drying temperature in step (3) is-55 ℃ to-65 ℃ and the freeze-drying time is 24 hours.
7. The preparation method of the coated modified lithium iron phosphate composite material according to claim 3, wherein in the step (4), the annealing treatment is performed in a high-temperature tube furnace, and the annealing process comprises raising the temperature to 400 ℃ at a rate of 1-2 ℃/min under the protection of inert gas argon, preserving the temperature for 2-4 h, then raising the temperature to 700-900 ℃ at a rate of 5 ℃/min, preserving the temperature for 2-4 h, and finally cooling to room temperature to obtain the MXene/lithium iron phosphate composite cathode material.
8. The use of the coated modified lithium iron phosphate composite material according to claim 1 for preparing a positive electrode material for a lithium ion battery.
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| CN116374986A (en) * | 2023-04-14 | 2023-07-04 | 河南佰利新能源材料有限公司 | Lithium iron phosphate positive electrode material, and preparation method and application thereof |
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