CN116190649A - MoO grows on mesoporous hollow carbon sphere surface in situ 2 Nanosheet composite material - Google Patents

MoO grows on mesoporous hollow carbon sphere surface in situ 2 Nanosheet composite material Download PDF

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CN116190649A
CN116190649A CN202211362331.0A CN202211362331A CN116190649A CN 116190649 A CN116190649 A CN 116190649A CN 202211362331 A CN202211362331 A CN 202211362331A CN 116190649 A CN116190649 A CN 116190649A
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sio
moo
sulfur
hmc
composite material
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胡晓琴
王光艳
苏峰
韩春
吴林韬
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Changzhi University
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • 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
    • 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
    • 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
    • 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
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses a mesoporous hollow carbon sphere surface in-situ growth MoO 2 Nanosheet composite material, siO (silicon dioxide) with core-shell structure 2 @SiO 2 RF loaded molybdenum-dopamine chelate nanosheets are carbonized and etched to remove SiO 2 After the template, moO grows on the surface of the obtained mesoporous hollow carbon sphere in situ 2 The composite material of the nano sheet has higher specific surface area and porous structure, is favorable for the permeation of electrolyte and sulfur, improves the conductivity of the material, simultaneously, the mesoporous shell and larger internal gap can provide enough sulfur storage space, and buffer the volume expansion of sulfur species in the charging and discharging process to ensure stable structure, in addition, the ultrathin MoO 2 NanosheetsCan expose more active sites, greatly improve the Li resistance 2 S x Is resistant to Li 2 S x Dissolution in the electrolyte effectively inhibits the shuttle effect. Thus, prepared HMC@MoO 2 S cathode at high sulfur loading (5.0 mg cm −2 ) Under the condition, the lithium sulfur battery shows excellent cycle stability.

Description

MoO grows on mesoporous hollow carbon sphere surface in situ 2 Nanosheet composite material
Technical Field
The invention belongs to the technical field of lithium-sulfur batteries, and particularly relates to a mesoporous hollow carbon sphere surface in-situ growth MoO 2 A nanosheet composite material.
Background
With the popularization of portable electronic devices and electric automobiles and the development of energy storage battery systems, the demand for high-energy long-service-life batteries is increasing, and lithium ion batteries cannot meet the development demands of novel commercial batteries. The theoretical energy density of the lithium-sulfur battery is as high as Wh.kg -1 And the sulfur simple substance has the outstanding advantages of abundant reserves, low cost, environmental friendliness and the like. Therefore, lithium sulfur batteries are considered as the most competitive next-generation secondary batteries. However, practical applications of lithium sulfur batteries still suffer from a number of technical challenges, wherein sulfur anodes suffer from the following problems: (1) Sulfur and lithium sulfide (Li) 2 S) poor conductivity, impeding the transport of electrons and ions, leading to slow reaction kinetics; (2) Sulfur (2.03 g cm) -3 ) And reduction product Li 2 S （1.66 g cm -3 ) The density of the electrode material is different, the volume fluctuation is up to 80% in the charge and discharge process, and the electrode material structure is damaged or even pulverized; (3) Reaction intermediate (Li) 2 S x X is more than or equal to 4 and less than or equal to 8) is easy to dissolve in electrolyte, li is in the charge and discharge process 2 S x Repetitive movement between positive and negative electrodes (so-called "shuttling effect"), in which part of Li 2 S x Formation of insoluble Li on the surface of lithium negative electrode 2 S 2 /Li 2 S, irreversible loss of sulfur, capacity attenuation of a battery and passivation of the surface of a lithium anode are caused; (4) The charge and discharge process of the lithium sulfur battery is a solid (S) -liquid (Li 2 S x ) -solid (Li) 2 S) the oxidation-reduction process carried out step by step involves complex disproportionation reaction and normalization reaction, and the reaction kinetics is slow, so that the overall performance of the battery is seriously affected.
In order to solve the above problems, researchers have focused on preparing sulfur anodes with unique structures and compositions to improve conductivity and suppress the shuttle effect. One of the most effective methods is to combine sulfur with high conductivity, high specific surface area carbon materials such as microporous/mesoporous porous carbon, hollow carbon spheres, carbon nanocages, carbon nanofibers, carbon nanotubes, graphene and hybrids thereof. However, the weakly polar carbon material is formed by physically confining Li 2 S x The limited ability to dissolve results in severe shuttling effects during charge/discharge, especially at high sulfur loadings. In recent years, with the increasing awareness of electrochemical processes of lithium sulfur batteries, researchers have proposed adsorption catalysis synergy strategies, polar metal compounds have been widely used as sulfur host materials or additives to host materials for lithium sulfur batteries, such as metal oxides (Bi 2 O 3 ，Mn 3 O 4 ) Metal sulfide (Sb 2 S 3 ，MoS 2 ) Metal carbide (Ti 3 C 2 ，Mo 2 C) And metal nitrides (TiN, VN), metal phosphides (CoP, moP) and heterostructures (TiO) 2 /TiN， CoS 2 /Fe 7 S8) equipolar metal compound is prepared through establishing chemical bond to Li 2 S x And the method has strong chemical adsorption effect, reduces the energy barrier of sulfur species conversion reaction, accelerates the redox reaction kinetics, effectively inhibits the shuttle effect, improves the utilization rate of sulfur, and realizes the high capacity and long cycle life of the lithium-sulfur battery. However, most polar metal compounds either have poor conductivity themselves, or have limited catalytic activity, or have insufficient specific surface area resulting in limited number of exposed catalytically active sites, failing to provide sufficient active sites to adsorb Li 2 S x And catalyzes its conversion. Therefore, the combination of the high catalytic activity metal compound with rich active sites and the high conductive carbon material with reasonable structure, the development of the multifunctional sulfur host material is an effective strategy for comprehensively improving the electrochemical performance of the lithium sulfur battery.
Disclosure of Invention
In order to solve the problem of the existence of the positive electrode material in the lithium sulfur batteryThe invention provides a method for growing ultrathin MoO on the surface of a mesoporous hollow carbon sphere (HMC) 2 Nanometer sheet (HMC@MoO) 2 ) A composite material.
The invention provides an in-situ growth ultrathin MoO on the surface of a mesoporous hollow carbon sphere 2 The nano sheet composite material and the method thereof comprise the following steps:
(1) Preparation of mesoporous hollow carbon sphere precursor SiO 2 @SiO 2 /RF；
(2) Adding dopamine hydrochloride into the ammonium molybdate solution, and uniformly stirring to obtain solution A; under vigorous stirring, siO obtained in the step (1) is reacted with 2 @SiO 2 Adding RF into ethanol to obtain solution B; slowly injecting the solution A into the solution B, centrifuging and drying to obtain HMC@MoO 2 A precursor;
(3) Calcining the precursor obtained in the step (2) for a period of time at a certain temperature in an argon atmosphere to obtain a product which is etched to remove SiO 2 The template is washed and dried in vacuum to obtain HMC@MoO 2 A composite material.
Preferably, in step (1), siO 2 @SiO 2 RF is prepared by the steps of: in ethanol and H 2 Adding NH into O mixed solvent 3 •H 2 O, adding tetrapropyl orthosilicate under stirring, stirring for 15 min to obtain milky colloidal solution, adding resorcinol and formaldehyde, stirring at room temperature for 24-h, centrifuging, washing, and drying to obtain SiO 2 @SiO 2 /RF。
Preferably, in the step (2), the mass ratio of the dopamine hydrochloride to the ammonium molybdate tetrahydrate is 1:1.
Preferably, in step (2), ammonium molybdate tetrahydrate is mixed with SiO 2 @SiO 2 The mass ratio of the RF is 11-33:500.
Preferably, in the step (3), the calcination is performed at 600-800 ℃ for 3-5 hours.
Preferably, in step (4), the SiO is etched away by using a 4M NaOH solution 2 And (5) a template.
The invention also provides a positive electrode material based on the composite material, which is prepared by mixing and grinding the composite material and sublimed sulfur uniformly according to the mass ratio of x to 100-x, wherein x=15-25, then placing the mixed powder into a high-pressure reaction kettle filled with Ar protection, and reacting at 155 ℃ for 12 h.
The invention also provides an application of the positive electrode material based on the composite material in a lithium-sulfur battery.
Compared with the prior art, the invention has the following advantages: first, HMC@MoO 2 Has higher specific surface area and porous structure, is favorable for the permeation of electrolyte and sulfur, and improves the conductivity of the material. Second, the mesoporous shell and the larger internal void can provide sufficient sulfur storage space and buffer the volume expansion of sulfur species during charge and discharge to ensure structural stability. Third, ultra-thin MoO 2 The nano-sheet can expose more active sites, so that the Li resistance is greatly improved 2 S x Is resistant to Li 2 S x Dissolution in the electrolyte effectively inhibits the shuttle effect. Based on the combined action of the advantages, the prepared HMC@MoO 2 S cathode at high sulfur loading (5.0 mg cm −2 ) Under the condition, the lithium sulfur battery shows excellent cycle stability.
Drawings
FIG. 1 shows ultra-thin MoO grown on the surface of mesoporous hollow carbon spheres 2 Schematic of the synthesis of nanoplatelet composites.
FIG. 2 is a plot of HMC@MoO prepared in example 1 2 SEM images (a, b), TEM images (c), HRTEM images (d) of the composite material (the inset is an enlarged IFFT image), and HAADF images and EDS element map images (e).
FIG. 3 is a plot of HMC@MoO prepared in example 1 2 XRD spectra (a), N 2 Adsorption-desorption isotherms (b) and corresponding pore size distribution (c).
FIG. 4 is a mesoporous hollow carbon sphere doped MoO prepared in comparative example 1 2 SEM image of nanoparticle composites.
FIG. 5 is a plot of HMC@MoO prepared in example 2 2 -XRD spectrum (a) and TGA profile (b) of S.
FIG. 6 is a schematic diagram of HMC-S, HMC/p-MoO prepared according to the present invention 2 -S、HMC@MoO 2 -S、HMC@MoO 2 -S-1、HMC@MoO 2 Cycle performance at 0.1C for the S-2 positive electrode.
FIG. 7 is a plot of HMC@MoO prepared in example 5 2 S positive electrode with high area sulfur load of 5.0 mg cm −2 Cycle performance at 0.1C below.
FIG. 8 is a graph of HMC@MoO prepared according to the invention 2 -S has a schematic diagram of multiple functions.
Detailed Description
The invention is further elucidated below with reference to the drawings and the examples.
(1) Referring to FIG. 1, the HMC@MoO of the invention 2 The preparation process and the principle thereof are as follows:
in the first step, three small molecules of resorcinol, formaldehyde and tetrapropyl orthosilicate (TPOS) are used as reactants, and a one-pot surfactant-free synthesis method is adopted, so that the difference of reaction kinetics of resorcinol-formaldehyde (RF) polymerization and TPOS hydrolysis in an ethanol/water alkaline solution is utilized: (1) At the initial stage of the reaction, TPOS is hydrolyzed to generate SiO 2 Primary particles, the primary particles grow up and polymerize to form SiO 2 A core, (2) a late reaction stage of SiO 2 Co-condensation of primary particles with resorcinol-formaldehyde (RF) polymers on SiO 2 On the core, siO with core-shell structure is formed 2 @SiO 2 RF, i.e., HMC precursor. In this step, the first step of the present invention differs from the prior art in that in the prior art, siO is first prepared with the aid of a surfactant using tetraethyl orthosilicate (TEOS) 2 A ball. Then, at SiO 2 The surfaces of the balls are coated with polydopamine or phenolic resin. Finally, by carbonizing and etching SiO 2 And (5) template to obtain the hollow carbon sphere. The hollow carbon sphere obtained by the method has thinner and compact carbon shell and low specific surface area. When used as sulfur-carrying materials, sulfur tends to adhere to the surface thereof, and high sulfur loading is not achieved. The HMC precursor obtained by the invention is carbonized and etched to obtain the thick carbon shell hollow carbon sphere with high specific surface area and rich mesopores, and provides a guarantee for sulfur to melt, diffuse and infiltrate into the mesoporous carbon shell and realize high sulfur load.
The second step, molybdic acid radical reacts with dopamine to form molybdenum-dopamine chelate nano-sheets,hydrophilic group (-NH) of molybdenum-dopamine chelate 2 ) With SiO 2 @SiO 2 The hydroxyl (-OH) on the surface of RF has hydrogen bonding effect, so that the molybdenum-dopamine chelate is uniformly distributed on SiO 2 @SiO 2 On RF ball to obtain HMC@MoO 2 A precursor.
Third step, HMC@MoO 2 The precursor is carbonized, and the molybdenum-dopamine chelate nanosheets are converted into ultrathin MoO 2 Nanoplatelets, siO 2 @SiO 2 Conversion of RF Complex to SiO 2 @SiO 2 C; siO removal 2 After the template, ultra-thin MoO grown on the surface of the mesoporous hollow carbon sphere is obtained 2 Nanosheet composite material (HMC@MoO) 2 ）。
(2) Referring to FIG. 8, the HMC@MoO of the invention 2 The principle of the multiple functions of S is:
firstly, the hollow mesoporous carbon provides enough space for the storage of sulfur and the volume expansion of sulfur species in the charging and discharging process; secondly, the mesoporous carbon shell is used as a first defense line, and Li is prevented by physical confinement 2 S x MoO on the surface of the carbon shell 2 Nanosheets as a second line of defense, capture of Li by chemisorption 2 S x Further prevent Li 2 S x Is dissolved in the solvent. Third, molybdenum-dopamine chelate-derived ultrathin MoO 2 The nano-sheet exposes more active sites and improves the Li resistance 2 S x Is effective in inhibiting Li 2 S x Is a shuttle effect of (c). Based on these advantages, HMC@MoO 2 The S positive electrode exhibits excellent long-term cycling stability at high sulfur loadings.
Example 1: ultra-thin MoO grown on surface of mesoporous hollow carbon sphere 2 Nanometer sheet (HMC@MoO) 2 ) Preparation of composite materials
The first step: at 80 ml ethanol/H 2 To O solvent (v/v=7:1) 3 ml NH was added 3 •H 2 O (25 wt%) was added with magnetic stirring to 3.46 ml tetrapropyl orthosilicate (TPOS). After 15 minutes, a milky white colloidal solution was obtained, then 0.4. 0.4 g resorcinol and 0.56. 0.56 ml formaldehyde (37 wt%) were added and stirred at room temperature for 24h. Centrifuging to collect precipitate, washing with water and ethanol, and drying at 50deg.C overnight to obtain mesoporous hollow carbon sphere HMC precursor (SiO 2 @SiO 2 /RF）。
And a second step of: first, 88 mg ammonium molybdate tetrahydrate ((NH) 4 ) 6 Mo 7 O 24 •4H 2 O) was dissolved in 15 mL deionized water and stirred for 5 min, then 88 mg dopamine hydrochloride was added and stirred for 30 min, the color of the solution turned reddish brown (noted as A solution). Secondly, adding 2 g of HMC precursor into 50 ml ethanol (marked as B solution) under intense stirring, slowly injecting the A solution into the B solution, stirring 1 h, obtaining a suspension with deep orange red color, centrifuging, collecting precipitate, and drying at 50 ℃ to obtain HMC@MoO 2 Precursor of the composite material.
And a third step of: HMC@MoO 2 The precursor is placed in a tube furnace, carbonized at 700 ℃ for 3 h in an argon atmosphere, and etched with 4M NaOH solution to remove SiO 2 Washing the template with water and ethanol, and vacuum drying to obtain ultra-thin MoO grown on the surface of the mesoporous hollow carbon sphere 2 Nanosheet composite material (HMC@MoO) 2 ）。
For the HMC@MoO obtained above 2 The composite material is characterized, and the morphology of the composite material is shown in figure 2. XRD spectra are shown in FIG. 3 (a), N 2 The adsorption-desorption isotherms are shown in fig. 3 (b), and the corresponding pore size distribution is shown in fig. 3 (c).
Comparative example 1: mesoporous hollow carbon sphere doped MoO 2 Nanoparticles (HMC/p-MoO) 2 ) Preparation of composite materials
The first step: as in example 1, a mesoporous hollow carbon sphere HMC precursor (SiO 2 @SiO 2 /RF）。
And a second step of: first, 88 mg ammonium molybdate tetrahydrate ((NH) 4 ) 6 Mo 7 O 24 •4H 2 O) was dissolved in 15 mL deionized water and stirred for 5 min (denoted as A solution). Secondly, adding 2 g of HMC precursor into 50 ml ethanol (marked as B solution) under intense stirring, slowly injecting the A solution into the B solution, stirring at 50 ℃ until the solvent is volatilized, and obtaining the mesoporous hollow carbon sphere doped MoO 2 Front of nanoparticle compositesAnd (3) a precursor.
And a third step of: doping mesoporous hollow carbon spheres with MoO 2 The precursor of the nano particles is placed in a tube furnace, carbonized at 700 ℃ for 3 h in an argon atmosphere, and etched with 4M NaOH solution to remove SiO 2 Washing the template with water and ethanol, and vacuum drying to obtain mesoporous hollow carbon sphere doped MoO 2 Nanoparticle composites (HMC/p-MoO) 2 ) The morphology is shown in figure 4.
Comparative example 2: preparation of mesoporous hollow carbon sphere-sulfur (HMC-S) composite material and application of composite material in lithium-sulfur battery
The first step: as in example 1, a mesoporous hollow carbon sphere HMC precursor ((SiO) was prepared 2 @SiO 2 /RF）。
And a second step of: placing HMC precursor into a tube furnace, carbonizing 3 h at 700 ℃ in argon atmosphere, and etching SiO with 4M NaOH solution 2 And washing the template with water and ethanol, and vacuum drying to obtain mesoporous hollow carbon spheres (HMC).
And a third step of: HMC material and sublimed sulfur in mass ratio 25:75, mixing and grinding uniformly. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. And cooling to room temperature to obtain the HMC-S composite material.
Fourth step: HMC-S, ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 were thoroughly mixed in an appropriate amount of N-methylpyridine Luo Wantong (NMP) to form a homogeneous slurry. The slurry was uniformly coated on a carbon-coated aluminum foil, and then dried overnight at 60 ℃ in a vacuum oven, and further cut into discs (d=1.2. 1.2 cm) to prepare a positive electrode, with an average sulfur loading of 1.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. In the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 6.
Comparative example 3: mesoporous hollow carbon sphere doped MoO 2 nanoparticle-Sulfur (HMC/p-MoO) 2 Preparation of S) composite materials and use thereof in lithium-sulfur batteries
The first step: HMC/p-MoO prepared in comparative example 1 2 The composite material and sublimed sulfur are mixed and ground uniformly according to the mass ratio of 25:75. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. Cooling to room temperature to obtain HMC/p-MoO 2 -S composite material.
And a second step of: HMC/p-MoO 2 The ketjen black and polyvinylidene fluoride (PVDF) are fully mixed in a proper amount of N-methyl pyridine Luo Wantong (NMP) according to the mass ratio of 8:1:1 to form uniform slurry. The slurry was uniformly coated on a carbon-coated aluminum foil, and then dried overnight at 60 ℃ in a vacuum oven, and further cut into discs (d=1.2. 1.2 cm) to prepare a positive electrode, with an average sulfur loading of 1.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. In the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 6.
Example 2: HMC@MoO 2 Preparation of S composite material and application thereof in lithium-sulfur battery
The first step: HMC@MoO prepared in example 1 2 The composite material and sublimed sulfur are mixed and ground uniformly according to the mass ratio of 25:75. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. Cooling to room temperature to obtain HMC@MoO 2 -S composite material. The XRD spectrum is shown in FIG. 5 (a), and the TGA curve is shown in FIG. 5 (b).
And a second step of: HMC@MoO 2 S, ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 were thoroughly mixed in an appropriate amount of N-methylpyridine Luo Wantong (NMP) to form a homogeneous slurry. The slurry is uniformly coated on a carbon-coated aluminum foil, and then dried in a vacuum oven at 60 ℃ overnight, and further cutThe wafer (d=1.2. 1.2 cm) was used as the positive electrode, and the average sulfur carrying capacity was 1.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. In the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 6.
Example 3: HMC@MoO 2 Preparation of S-1 composite material and application thereof in lithium-sulfur battery
The first step: as in example 1, a mesoporous hollow carbon sphere HMC precursor (SiO 2 @SiO 2 /RF). And a second step of: first, 44 mg ammonium molybdate tetrahydrate ((NH) 4 ) 6 Mo 7 O 24 •4H 2 O) was dissolved in 15 mL deionized water and stirred for 5 min, then 44 mg dopamine hydrochloride was added and stirred for 30 min, the color of the solution turned reddish brown (noted as A solution). Secondly, adding 2 g of HMC precursor into 50 ml ethanol (marked as B solution) under intense stirring, slowly injecting the A solution into the B solution, stirring 1 h, obtaining a suspension with deep orange red color, centrifuging, collecting precipitate, and drying at 50 ℃ to obtain HMC@MoO 2 Precursor of the composite material.
And a third step of: HMC@MoO 2 The precursor is placed in a tube furnace, carbonized at 700 ℃ for 3 h in an argon atmosphere, and etched with 4M NaOH solution to remove SiO 2 Washing the template with water and ethanol, and vacuum drying to obtain ultra-thin MoO grown on the surface of the mesoporous hollow carbon sphere 2 Nanosheet composite material (HMC@MoO) 2 ）。
Fourth step: HMC@MoO 2 The mass ratio of the composite material to the sublimated sulfur is 25:75, mixing and grinding uniformly. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. Cooling to room temperature to obtain HMC@MoO 2 -S composite material.
Fifth step: HMC@MoO 2 -S, ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, inAppropriate amounts of N-methylpyridine Luo Wantong (NMP) were thoroughly mixed to form a homogeneous slurry. The slurry was uniformly coated on a carbon-coated aluminum foil, and then dried overnight at 60 ℃ in a vacuum oven, and further cut into discs (d=1.2. 1.2 cm) to prepare a positive electrode, with an average sulfur loading of 1.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. In the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 6.
Example 4: HMC@MoO 2 Preparation of S-2 composite material and application thereof in lithium-sulfur battery
The first step: as in example 1, a mesoporous hollow carbon sphere HMC precursor (SiO 2 @SiO 2 /RF). And a second step of: first, 132 mg ammonium molybdate tetrahydrate ((NH) 4 ) 6 Mo 7 O 24 •4H 2 O) was dissolved in 15 mL deionized water and stirred for 5 min, then 132 mg dopamine hydrochloride was added and stirred for 30 min, the color of the solution turned reddish brown (noted as A solution). Secondly, adding 2 g of HMC precursor into 50 ml ethanol (marked as B solution) under intense stirring, slowly injecting the A solution into the B solution, stirring 1 h, obtaining a suspension with deep orange red color, centrifuging, collecting precipitate, and drying at 50 ℃ to obtain HMC@MoO 2 Precursor of the composite material.
And a third step of: HMC@MoO 2 The precursor is placed in a tube furnace, carbonized at 700 ℃ for 3 h in an argon atmosphere, and etched with 4M NaOH solution to remove SiO 2 Washing the template with water and ethanol, and vacuum drying to obtain ultra-thin MoO grown on the surface of the mesoporous hollow carbon sphere 2 Nanosheet composite material (HMC@MoO) 2 ）。
Fourth step: HMC@MoO 2 The mass ratio of the composite material to the sublimated sulfur is 25:75, mixing and grinding uniformly. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. Cooled to the roomAfter the temperature is reached, the HMC@MoO is obtained 2 -S composite material.
Fifth step: HMC@MoO 2 S, ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 were thoroughly mixed in an appropriate amount of N-methylpyridine Luo Wantong (NMP) to form a homogeneous slurry. The slurry was uniformly coated on a carbon-coated aluminum foil, and then dried overnight at 60 ℃ in a vacuum oven, and further cut into discs (d=1.2. 1.2 cm) to prepare a positive electrode, with an average sulfur loading of 1.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. In the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 6.
Example 5: at high sulfur loading (5.0 mg cm −2 ) Under the condition of HMC@MoO 2 Preparation of S-2 composite material and application thereof in lithium-sulfur battery
The first step: HMC@MoO prepared in example 1 2 The composite material and sublimed sulfur are mixed and ground uniformly according to the mass ratio of 15:85. The mixed powder was then placed in an autoclave filled with Ar protection and reacted at 155 ℃ for 12 h. Cooling to room temperature to obtain HMC@MoO 2 -S composite material.
And a second step of: HMC@MoO 2 S, ketjen black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1 were thoroughly mixed in an appropriate amount of N-methylpyridine Luo Wantong (NMP) to form a homogeneous slurry. The slurry is uniformly coated on a carbon-coated aluminum foil by a fractional coating method, and then dried overnight at 60 ℃ in a vacuum oven, and further cut into wafers (d=1.2 cm) to prepare a positive electrode, wherein the average sulfur carrying capacity is 5.0 mg cm −2 . The Celgard 2400 film is used as a diaphragm, the lithium foil is used as a cathode, and the electrolyte is prepared from 1M LiTFSI and 1 wt% LiNO 3 With DOL/DME (v/v=1:1) solvent, the ratio of electrolyte to sulfur (E/S μl mg −1 ) 20. CR2032 coin cell was assembled in an argon filled glove box. At the position ofIn the voltage range of 1.7-2.8V, 0.1C (1C =1675 mAh g) −1 ) Constant current charge and discharge tests were performed on a new wire battery test system, the results of which are shown in fig. 7.
From the test results of the above examples and comparative examples, it is known that: when HMC is used as sulfur-carrying material, because HMC has higher specific surface area and abundant mesoporous gaps, after sulfur is uniformly compounded with HMC, the conductivity of the carbon-sulfur positive electrode is greatly enhanced, and therefore, in comparative example 2, the initial discharge specific capacity of the HMC-S positive electrode can reach 1182.9 mA h/g under the current density of 0.1C. However, after 100 cycles, the discharge capacity rapidly decreased to 631.7 mA h/g, with an average decay rate of 0.44% per cycle (based on the second discharge capacity). This is because: (1) Weak polarity HMC carbon material pair Li 2 S x Is weak in adsorption; (2) Mesoporous carbon shell vs Li 2 S x Is limited in its physical confinement. Leading to Li 2 S x The active substance sulfur is irreversibly lost when dissolved in the electrolyte, and the capacity is rapidly attenuated. Introducing a small amount of MoO 2 After nanomaterial, due to MoO 2 Has stronger Li adsorption 2 S x And the ability to catalyze their interconversion, thus, in comparative example 3, HMC/p-MoO at a current density of 0.1C 2 The specific capacity of the first discharge of the S positive electrode can reach 1169.7 mA h/g, and after 100 cycles, the discharge capacity is attenuated to 746.4 mA h/g, and the average attenuation rate of each cycle is 0.33% (based on the second discharge capacity). To make MoO 2 Exposing more active sites as much as possible, improving the resistance to Li 2 S x Is effective in slowing down Li 2 S x Is a shuttle effect of (c). Thus, the mesoporous hollow carbon sphere (HMC) surface is prepared to grow ultrathin MoO 2 The composite of nanoplatelets and used for sulfur-bearing materials, exhibits more excellent cycling stability in the examples. However, a small amount of MoO 2 The nanoplatelets have limited active sites for hmc@moo in example 3 2 S-1 positive electrode, average decay rate per cycle of 0.32% (based on second discharge capacity), excess MoO 2 The nanoplatelets are easily stacked, for hmc@moo in example 4 2 -S-2 positive electrode, per cycleThe average decay rate of (a) was 0.25% (based on the second discharge capacity). Further, for the optimized HMC@MoO of example 2 2 The positive electrode S, the first discharge specific capacity is up to 1316.3 mA h/g, after 100 cycles, the discharge capacity still has 946.4 mA h/g, and the average attenuation rate of each cycle is only 0.22% (based on the second discharge capacity). In particular, for example 5, HMC@MoO 2 -S cathode at 5.0 mg cm −2 Under the condition of high area sulfur loading, the initial area capacity of 0.1 to C is 4.48 mAh cm -2 The capacity of the material after 500 times of circulation is kept to be 3.32 mAh cm -2 。
Furthermore, HMC@MoO 2 The raw materials used by the composite material only relate to 5 small molecular compounds, are low in cost and easy to obtain, have simple and easy to operate synthesis steps, do not need expensive equipment, are suitable for large-scale production, and are expected to be applied to actual production of lithium-sulfur batteries.

Claims (10)

1. Ultra-thin MoO grown on mesoporous hollow carbon sphere surface in situ 2 The preparation method of the nano-sheet composite material is characterized by comprising the following steps:
(1) Preparation of mesoporous hollow carbon sphere precursor SiO 2 @SiO 2 /RF；
(2) Adding dopamine hydrochloride into the ammonium molybdate solution, and uniformly stirring to obtain solution A; under vigorous stirring, siO obtained in the step (1) is reacted with 2 @SiO 2 Adding RF into ethanol to obtain solution B; slowly injecting the solution A into the solution B, centrifuging and drying to obtain HMC@MoO 2 A precursor;
(3) Calcining the precursor obtained in the step (2) for a period of time at a certain temperature in an argon atmosphere to obtain a product which is etched to remove SiO 2 The template is washed and dried in vacuum to obtain HMC@MoO 2 A composite material.
2. The method of claim 1, wherein in step (1), siO 2 @SiO 2 RF is prepared by the steps of: in ethanol and H 2 Adding ammonia water into the O mixed solvent, adding tetrapropyl orthosilicate under stirring, stirring for a period of time, and adding m-phenylene diamineStirring phenol and formaldehyde at room temperature over 24 and h, centrifuging, washing and drying to obtain SiO 2 @SiO 2 /RF。
3. The method according to claim 2, wherein in step (1), after stirring for 15 minutes, a milky colloidal solution is obtained, and resorcinol and formaldehyde are added.
4. The method of claim 1, wherein in step (2), the mass ratio of dopamine hydrochloride to ammonium molybdate tetrahydrate is 1:1.
5. The method of claim 1, wherein in step (2), ammonium molybdate tetrahydrate is mixed with SiO 2 @SiO 2 The mass ratio of the RF is 11-33:500.
6. The method of claim 1, wherein in step (3), calcination is performed at 600 to 800 ℃ for 3 to 5 hours.
7. The method of claim 1, wherein in step (4), the SiO is etched away using a 4M NaOH solution 2 And (5) a template.
8. A composite material prepared by the method of any one of claims 1-7.
9. The positive electrode material of the lithium-sulfur battery is characterized in that the composite material prepared by the method of any one of claims 1-7 is mixed with sublimed sulfur according to a mass ratio x of 100-x and is uniformly ground, wherein x=15-25, then the mixed powder is placed in a high-pressure reaction kettle filled with Ar protection, and the reaction is carried out at 155 ℃ for 12 h, so that the positive electrode material is obtained.
10. The high-sulfur-loading lithium-sulfur battery positive electrode material is characterized in that the composite material prepared by the method of any one of claims 1-7 is mixed with sublimed sulfur according to a mass ratio of 15:85 and is uniformly ground, then the mixed powder is placed in a high-pressure reaction kettle which is fully filled with Ar protection, and the reaction is carried out at 155 ℃ for 12 h, so that the high-sulfur-loading lithium-sulfur battery positive electrode material is obtained.
CN202211362331.0A 2022-11-02 2022-11-02 MoO grows on mesoporous hollow carbon sphere surface in situ 2 Nanosheet composite material Pending CN116190649A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117219759A (en) * 2023-11-09 2023-12-12 蜂巢能源科技股份有限公司 Silicon-based anode material with core-shell structure and preparation method and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117219759A (en) * 2023-11-09 2023-12-12 蜂巢能源科技股份有限公司 Silicon-based anode material with core-shell structure and preparation method and application thereof
CN117219759B (en) * 2023-11-09 2024-01-23 蜂巢能源科技股份有限公司 Silicon-based anode material with core-shell structure and preparation method and application thereof

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