CN112928276A - Composite sulfur positive electrode material and preparation method and application thereof - Google Patents

Composite sulfur positive electrode material and preparation method and application thereof Download PDF

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CN112928276A
CN112928276A CN201911237894.5A CN201911237894A CN112928276A CN 112928276 A CN112928276 A CN 112928276A CN 201911237894 A CN201911237894 A CN 201911237894A CN 112928276 A CN112928276 A CN 112928276A
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sulfur
positive electrode
lithium
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陈剑
袁海峰
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Dalian Institute of Chemical Physics of CAS
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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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1399—Processes of manufacture of electrodes based on electro-active polymers
    • 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 composite sulfur anode material and a preparation method and application thereof. The layered metal phosphate is a cationic layered compound and has ion exchange, proton conduction, adsorption and catalysis performances. The used layered metal phosphate has good adsorption effect on polysulfide, and promotes the conversion reaction of polysulfide to lithium sulfide. The composite sulfur anode material consists of a sulfur-containing active substance and a sulfur anode reaction promoter, and the sulfur electrode comprises the composite sulfur anode material, a conductive agent, a binder and the like. When the sulfur electrode is applied to the positive electrode of the lithium-sulfur battery, the battery has higher capacity retention rate, cycle performance and rate performance. The lithium-sulfur battery developed by adopting the technology can be applied to the fields of large-scale energy storage, mobile and wireless electronic equipment, electric tools, hybrid power, electric vehicles and the like.

Description

Composite sulfur positive electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of new energy materials, and particularly relates to a composite sulfur positive electrode material and a preparation method and application thereof.
Background
With the progress and development of society, people increasingly consume fossil energy. In order to promote the revolution of energy structures, the development and utilization of new energy systems have been accelerated. Among them, lithium ion batteries are an important energy conversion technology, and play a significant role in the field of energy. However, limited by their low practical specific energy (<300Wh/kg), lithium ion batteries are not able to meet the demands of advanced portable devices and electric vehicles. Therefore, lithium sulfur batteries with high specific energy, low cost and environmental friendliness are one of the most promising technologies for next-generation energy storage systems. The theoretical specific capacity of sulfur is high (1675mAh/g), the theoretical energy density of the lithium-sulfur battery is high (2500Wh/kg), the natural resources are rich, the cost is low, and the lithium-sulfur battery is non-toxic and environment-friendly.
However, the commercialization of the battery is limited by the problem of poor cycle stability of the lithium-sulfur battery. The capacity fade of the cell during cycling is mainly due to the following reasons: (1) the sulfur and the discharge product thereof have poor conductivity, so that the utilization rate of active substances is reduced, and low specific discharge capacity and rate capability are caused; in addition, the slow dynamics is caused by poor conductivity, and larger polarization appears on a low-voltage platform, so that the actual energy density of the lithium-sulfur battery is reduced; (2) sulfur is used as a positive electrode material and has multi-step reactions in the discharging process of the battery, and the generated intermediate product lithium polysulfide is easily dissolved in organic electrolyte, so that the loss of the positive electrode sulfur is caused, a shuttle effect is generated, the charging and discharging efficiency is seriously reduced, the corrosion of the negative electrode of the battery is aggravated, the internal resistance is increased, the circulation stability is poor, and the coulombic efficiency is low; (3) in the battery cycle process, the sulfur positive electrode of the lithium-sulfur battery has serious volume expansion, which causes great change of the positive electrode area structure, and the volume expansion rate is as high as 80 percent; after many cycles, the integrity of the electrode is destroyed, causing reduced cycling stability and safety problems. Therefore, improving the cycle stability is an important issue in the development of lithium sulfur batteries.
The patent CN106981649B discloses a graphene hollow sphere-sulfur composite three-dimensional structure lithium-sulfur battery positive electrode material, the structure of graphene is modified through a pore-forming technology combining a template method and a spray drying technology, the graphene hollow sphere is prepared, the loading capacity of the positive electrode material sulfur is improved, and the volume expansion effect of the lithium-sulfur battery is relieved; but carbon material to polysulfideThe adsorption of substances is limited. Therefore, the long cycle performance is still not good; patent CN107240679B discloses a nitrogen-doped carbon nano conductive network/sulfur composite material and a preparation method thereof, wherein the carbon nano material is used as a framework to provide rich conductive networks and good mechanical toughness, the aromatic nitrile polymer has the characteristics of high nitrogen content doping and uniform nitrogen element distribution, the electrode material has a high specific surface area and a uniformly distributed pore structure, but the nitrogen-doped carbon nanotube has a weak adsorption force on polysulfide, so that the capacity retention rate of the battery is not high, and the cycle performance is still to be improved; patent CN108649194A discloses a method for preparing a sulfur positive electrode composite material by using graphene as a substrate and loading molybdenum disulfide as a carrier, wherein the graphene with a high specific surface can realize high loading of molybdenum disulfide and sulfur, and the molybdenum disulfide has a chemical adsorption effect on lithium polysulfide to relieve a shuttle effect of polysulfide and improve the cycling stability of a battery; but the cost of the graphene and the molybdenum disulfide is high, so that the graphene and the molybdenum disulfide are difficult to be applied to the field of large-scale energy storage; the zodiac helps soldiers (ACS Nano,2019,13,3608-3C2MXene Nanodets-dispersed Nanosheet for High-Energy-sensitivity Lithium-sulfurur Batteries) et al reported a Ti-based MXene3C2Tx(TxRepresenting surface functional groups) nanodot-dispersed Ti3C2TxThe nano sheet material carries sulfur, and polar sites on the surface of the material have an anchoring effect on polysulfide and promote the oxidation reduction of sulfur; jianghangqing (Angewandte Chemie 2018,130 (15)), Metal-Organic Frameworks for High Charge-Discharge Rates in Lithium-Sulfur Batteries and the like develop a composite material ppy-MOF of MOFs and conductive polymers (polypyrrole ppy), and the polarity and the porous advantages of the MOFs and the conductive characteristics of the conductive polymers are combined, so that the cycling stability of the battery is improved. However, the production cost of both MOF and MXENE is very high, limiting the large-scale application of the material.
The invention designs and prepares a sulfur anode by adopting layered metal phosphate as a sulfur anode reaction promoter. The layered metal phosphate is a cationic layered compound and has ion exchange, proton conduction, adsorption and catalysis performances. The used layered metal phosphate has good adsorption effect on polysulfide, and promotes the conversion reaction of polysulfide to lithium sulfide. The composite sulfur anode material consists of a sulfur-containing active substance and a sulfur anode reaction promoter, and the sulfur electrode comprises the composite sulfur anode material, a conductive agent, a binder and the like. The sulfur anode designed by adopting the layered metal phosphate as the anode reaction promoter can effectively improve the coulomb efficiency of the lithium-sulfur battery and improve the cycle performance of the lithium-sulfur battery. The lithium-sulfur battery developed by adopting the technology can be applied to the fields of large-scale energy storage, mobile and wireless electronic equipment, electric tools, hybrid power, electric vehicles and the like.
Disclosure of Invention
The invention provides a sulfur positive electrode reaction promoter, a composite sulfur positive electrode material thereof, a sulfur positive electrode and a preparation method thereof, aiming at solving the problem of poor battery cyclicity caused by dissolution loss of polysulfide of a sulfur positive electrode of a lithium sulfur battery. The sulfur anode reaction promoter is a layered metal phosphate, and the molecular general formula is as follows: m (HPO)4)2·H2O or M (PO)4)(H2PO4)·2H2O, wherein the metal cation is Ce4+Or Sn4+Or Pb4+Or Ge4+Or Mn4+Or Ni4+Or W4+Or Mo4+Or Hf4+One kind of (1); the composite sulfur positive electrode material consists of a sulfur-containing active substance and a sulfur positive electrode reaction promoter, wherein the sulfur positive electrode reaction promoter accounts for 0.5-60% by mass; the sulfur electrode comprises a composite sulfur positive electrode material, a conductive agent, a binder and the like, wherein the mass percentage of the composite sulfur positive electrode material is 20-90%, the mass percentage of the conductive agent is 3-40%, and the mass percentage of the binder is 3-40%.
According to the invention, in the preparation process of the lithium-sulfur battery cathode material, the layered metal phosphate is added as an additive, so that polysulfide can be effectively adsorbed, and the coulombic efficiency and the capacity retention rate are improved.
The specific technical scheme of the invention is as follows:
a composite sulfur anode material is prepared fromThe sulfur anode reaction promoter consists of a sulfur-containing active substance and a sulfur anode reaction promoter, wherein the sulfur anode reaction promoter accounts for 0.5-60% by mass, and the sulfur anode reaction promoter is layered metal phosphate. The molecular general formula of the layered metal phosphate is as follows: m (HPO)4)2·H2O or M (PO)4)(H2PO4)·2H2O, wherein the metal cation M is Ti4+Or Ce4+Or Sn4+Or Pb4+Or Ge4+Or Mn4+Or Ni4+Or W4+Or Mo4+Or Hf4+One of (1) and (b).
The sulfur-containing active substance can be one or the combination of two or more of orthorhombic sulfur, monoclinic sulfur, elastic sulfur, vulcanized polyacrylonitrile, vulcanized polypyrrole, vulcanized polythiophene, vulcanized polyphenylene sulfide, vulcanized polyphenylacetylene, vulcanized polyaniline and vulcanized polyphenylene sulfide.
A sulfur electrode comprises a composite sulfur positive electrode material, a conductive agent, a binder and the like, wherein the mass percentage of the composite sulfur positive electrode material is 20-90%, the mass percentage of the conductive agent is 5-40%, and the mass percentage of the binder is 5-40%.
The preparation method of the layered metal phosphate can be a solid phase method, a coprecipitation method, a sol-gel method, a solvothermal method or the combined application of several methods.
The sulfur-containing active substance can be one or two or more of orthorhombic sulfur, monoclinic sulfur, elastic sulfur, vulcanized polyacrylonitrile, vulcanized polypyrrole, vulcanized polythiophene, vulcanized polyphenylene sulfide, vulcanized polyphenylacetylene, vulcanized polyaniline or vulcanized polyphenylene sulfide.
The conductive agent is one or two or more of acetylene BLACK, BLACK PEARLS 2000, ketjen BLACK, Super-P, carbon nano tube, carbon nano fiber, activated carbon and graphene.
In the synthetic method of the composite sulfur cathode material, when the sulfur-containing active substance is one or two or more of orthorhombic sulfur, monoclinic sulfur and elastic sulfur, the heat treatment process is carried out for 8-48 h at 150-200 ℃; when the sulfur-containing active substance is one or two or more of vulcanized polyacrylonitrile, vulcanized polypyrrole, vulcanized polythiophene, vulcanized polyphenylene sulfide, vulcanized polyphenylacetylene, vulcanized polyaniline or vulcanized polyphenylene sulfide, the heat treatment process is carried out at 280-400 ℃ for 3-36 h.
The preparation method of the composite sulfur anode comprises the steps of adding a composite sulfur anode material, a conductive agent and a binder into a solvent, and uniformly mixing by stirring or ball milling or sanding to prepare slurry; coating the slurry on the surface of one side or two sides of the positive current collector in a blade coating or spraying or coating mode, and drying to obtain the composite sulfur positive electrode; the electrode film has a thickness of 5 to 150 μm on one surface and a mass per unit area of 0.1 to 45mg/cm2。
Wherein the binder is a water-based binder or an oil-based binder; the oil system is polyvinylidene fluoride (PVDF); the water-based binder is one of LA132, sodium carboxymethyl cellulose, polytetrafluoroethylene, agar and starch; when the binder is an oil-based binder, the solvent is one or more of N-methyl pyrrolidone, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, diphenyl ether, hexamethylphosphoramidite and hexaethylphosphonite; when the binder is a water-based binder, the solvent is one or more of water, isopropanol and ethanol; the current collector is a metal foil or a carbon material; the metal foil comprises aluminum foil, aluminum mesh, iron foil and copper foil, and the carbon material is foam carbon, carbon paper, carbon cloth or carbon felt.
The sulfur electrode can be applied to a positive electrode of a lithium sulfur primary battery or a lithium sulfur secondary battery. Wherein the negative electrode of the lithium sulfur primary or secondary battery may be metallic lithium or a lithium alloy or pre-lithiated graphite or pre-lithiated carbon microspheres or pre-lithiated silicon-based material; the lithium alloy can be an alloy of lithium and one or two or more metals of Mg, Ca, Al, Si, Ge, Sn, Pb, In, Sb, Bi, Fe or Zn, and the mass content of lithium In the alloy is 10-90%.
Lithium sulfur batteries are used in the fields of mass energy storage, mobile and wireless electronics, electric tools, hybrid and electric vehicles, and the like.
The invention has the advantages that:
the layered metal phosphate synthesized by the method has the characteristics of stable structure, insolubility in water and organic solvents, larger specific surface area and surface charge density, and is a good adsorbent. Theoretical calculation shows that the layered metal phosphate has strong chemical adsorption on polysulfide and can play an anchoring role on lithium polysulfide. At the same time, the layered metal phosphate accelerates the long-chain lithium polysulfide to Li2S2And Li2Kinetics of the conversion reaction of S. Therefore, compared with the traditional carbon-sulfur composite material taking carbon as a carrier and an electrode thereof, the shuttle effect of lithium polysulfide is effectively relieved by adopting the metal phosphate, and the loss of active substances is reduced, so that the capacity retention rate of the battery is improved, and the battery has higher cycle stability. In addition, the cost of the raw materials for preparing the layered metal phosphate is low, the process is mature and simple, and the method is suitable for mass production and is very suitable for the technical field of large-scale energy storage.
In conclusion, the calculation results and the experimental research results show that the layered metal phosphate positive electrode reaction promoter has a strong chemical adsorption effect on lithium polysulfide, can accelerate the conversion of long-chain lithium polysulfide to lithium disulfide and lithium sulfide, and obviously inhibits the shuttle effect of the lithium polysulfide. When the lithium-sulfur battery positive electrode is applied to the positive electrode of the lithium-sulfur battery, the battery shows higher capacity retention rate, cycle performance and rate performance. The application of metal phosphate in the industrialization of lithium-sulfur batteries is verified.
Drawings
FIG. 1 is an XRD picture of tin hydrogen phosphate synthesized in example 1.
FIG. 2 is a transmission picture of tin hydrogen phosphate synthesized in example 1.
Fig. 3 is a comparison of cycle life of the lithium sulfur battery of example 1, charge and discharge rate: 1C, temperature: at 25 ℃.
Fig. 4 is a comparison of cycle life, charge and discharge rate of the lithium sulfur battery of the comparative example: 1C, temperature: at 25 ℃.
Fig. 5 is a comparison of the first-cycle charge-discharge curves at 0.1C rate for the lithium sulfur batteries of example 1 and comparative example.
Detailed Description
The following examples are presented to further illustrate the present invention and the present invention is not limited to the specific details of the following examples without departing from the spirit of the present invention.
Example 1:
a) hydro-thermal synthesis of tin hydrogen phosphate Sn (HPO)4)2·H2O: dissolving tin tetrachloride and concentrated phosphoric acid in a molar ratio of 1:2 in 60mL of deionized water, stirring for 0.5h, transferring the solution into a 100mL hydrothermal kettle, keeping the hydrothermal kettle in an oven at 180 ℃ for 18h, cooling to room temperature, centrifuging, washing with deionized water for multiple times, and transferring the solution into a vacuum oven at 80 ℃ to obtain a white tin hydrogen phosphate material.
b) Preparing anode slurry: and ball-milling and mixing the prepared tin hydrogen phosphate and orthogonal sulfur according to the mass ratio of 4:6, and then keeping the mixture in a tubular furnace at the constant temperature of 155 ℃ for 12 hours to obtain the anode composite material. Mixing the obtained positive electrode composite material, graphene and PVDF binder according to the mass ratio of 8:1:1, adding NMP solvent, stirring and grinding to prepare slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on an aluminum foil current collector, and performing vacuum drying at 55 ℃ for 12h to obtain a sulfur electrode, wherein the thickness of the electrode film is 150 mu m, and the area mass is 45mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE diaphragm and a metal lithium sheet and the prepared sulfur electrode as a positive electrode in a glove box with argon protection and water oxygen content of less than 1ppm, and a charge and discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 984mAh/g, and the capacity retention rate of the 800 circles is 55%.
Example 2:
a) coprecipitation method for synthesizing lead hydrogen phosphate Pb (HPO)4)2·H2O: dissolving 1.5g of lead acetate in 17mL of 2mol/L acetic acid solution, adding 32mL of 6mol/L phosphoric acid aqueous solution, stirring to find that white precipitate is generated, aging at 80 ℃ for 48h, then cooling to room temperature, centrifuging, washing with deionized water for multiple times, transferring to a vacuum oven at 60 ℃,white lead hydrogen phosphate material is obtained.
b) Preparing anode slurry: and ball-milling and mixing the prepared lead hydrogen phosphate and monoclinic sulfur according to the mass ratio of 0.5:99.5, and then keeping the mixture in a 150 ℃ tubular furnace for 48 hours at a constant temperature to obtain the anode composite material. Mixing the obtained positive electrode composite material, acetylene black and LA132 binder according to the mass ratio of 7:2:1, adding a mixed solvent of isopropanol and water in the volume ratio of 3:1, stirring and grinding to prepare slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on an iron foil current collector, and carrying out vacuum drying for 18h at 50 ℃ to obtain a sulfur electrode; the thickness of the electrode film is 65 μm, and the area mass is 16mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE diaphragm and pre-lithiated graphite and the prepared sulfur electrode as a positive electrode in a glove box with the protection of argon and the water oxygen content of less than 1ppm, and a charge and discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 1265mAh/g, and the capacity retention rate of the cycle 250 circles is 82%.
Example 3:
a) hydrothermal synthesis of germanium Hydrogen Phosphate (HPO)4)2·H2O: dissolving germanium dioxide and concentrated phosphoric acid in a molar ratio of 1:5 in 30mL of deionized water, stirring for 0.5h, transferring the mixture into a 50mL hydrothermal kettle, keeping the hydrothermal kettle in an oven at 125 ℃ for 96h, cooling to room temperature, centrifuging, washing with deionized water for multiple times, and transferring to a vacuum oven at 60 ℃ to obtain a white germanium hydrogen phosphate material.
b) Preparing anode slurry: and ball-milling and mixing the prepared germanium hydrogen phosphate and mixed sulfur (a mixture of elastic sulfur and orthogonal sulfur in a mass ratio of 1: 1) according to a mass ratio of 6:4, and keeping the mixture in a tubular furnace at a constant temperature of 200 ℃ for 48 hours to obtain the cathode composite material. And mixing the obtained positive electrode composite material, Super P and the sodium carboxymethylcellulose binder according to the mass ratio of 90:5:5, adding an aqueous solvent, stirring and grinding to prepare slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on a copper foil current collector, and vacuum drying at 60 ℃ for 8h to obtain a sulfur electrode, wherein the thickness of the electrode film is 80μ m, area mass 20mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE diaphragm and a pre-lithiated silicon-carbon composite material and the prepared sulfur electrode as a positive electrode in a glove box with the protection of argon and the water oxygen content of less than 1ppm, and a charge-discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 1126mAh/g, and the capacity retention rate of 200 circles of circulation is 83%.
Example 4:
a) hydrothermal synthesis of cerium hydrogen phosphate Ce (HPO)4)2·H2O: dissolving 0.001mol of cerium sulfate in 20mL of 0.5mol/L sulfuric acid solution under the heating condition of 60 ℃, adding 0.004mol of phosphoric acid solution, stirring for 1h, transferring the solution into a 50mL hydrothermal kettle, keeping the solution in a 100 ℃ oven for 6h, cooling to room temperature, centrifuging, washing with deionized water for multiple times, and transferring the solution into a 75 ℃ vacuum oven to obtain a white cerium hydrogen phosphate material.
b) Preparing anode slurry: and ball-milling and mixing the prepared cerium hydrogen phosphate and the elastic sulfur according to the mass ratio of 1:9, and then keeping the mixture at a constant temperature of 150 ℃ for 8 hours in a tubular furnace to obtain the anode composite material. The obtained positive electrode composite material, a composite conductive agent (acetylene black: BP2000: Super P ═ 1:1:1, mass ratio) and a polytetrafluoroethylene binder were mixed in a mass ratio of 2:4:4, and a mixed solvent of ethanol and water (2:1) was added to the mixture, followed by stirring and grinding to prepare a slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on a carbon paper current collector, and carrying out vacuum drying for 4h at 65 ℃ to obtain a sulfur electrode; the electrode film has a thickness of 5 μm and an area mass of 0.1mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE/PP diaphragm and a lithium boron alloy containing 10% of lithium and taking the prepared sulfur electrode as a positive electrode in a glove box with the protection of argon and the water oxygen content of less than 1ppm, and a charge and discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 1532mAh/g, and the capacity retention rate of the cycle 250 circles is 90%.
Example 5:
a) synthesis of phosphorus by sol-gel methodAcid hydrogen titanium Ti (HPO)4)2·H2O: adding 0.005mol of butyl titanate into 30mL of 0.6mol/L phosphoric acid aqueous solution dropwise, slowly stirring for 0.5h at 300rpm, standing for 15h at 50 ℃ to obtain gel, washing the gel with deionized water for multiple times, transferring to a vacuum oven at 120 ℃ for drying for 24h, and grinding to obtain the white titanium hydrogen phosphate material.
b) Preparing anode slurry: and ball-milling and mixing the prepared titanium hydrogen phosphate and the vulcanized polyacrylonitrile according to the mass ratio of 5:5, and then keeping the mixture in a tubular furnace at the constant temperature of 280 ℃ for 36 hours to obtain the anode composite material. Mixing the obtained positive electrode composite material, a composite conductive agent (the mass ratio of the carbon nano fiber to the carbon nano tube is 2:1) and a PVDF binder according to the mass ratio of 5:3:2, adding an N, N-dimethylformamide solvent, stirring and grinding to prepare slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on a carbon cloth current collector, and vacuum drying at 70 ℃ for 4h to obtain a sulfur electrode, wherein the thickness of the electrode film is 80 mu m, and the area mass is 25mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE/PP diaphragm and a lithium tin alloy with the lithium content of 90% and using the prepared sulfur electrode as a positive electrode in a glove box with the water oxygen content of less than 1ppm under the protection of argon, and a charge and discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 812mAh/g, and the capacity retention rate of the cycle 250 circles is 86%.
Example 6:
a) coprecipitation-hydrothermal combined synthesis of titanium hydrogen phosphate Ti (PO)4)(H2PO4)·2H2O: firstly, 0.4mol of titanium tetrachloride is dissolved in 50mL of mixed solution of 2mol/L hydrochloric acid and 2mol/L phosphoric acid, stirred for 1h, filtered, washed with deionized water for multiple times to obtain precipitated Ti (HPO)4)2·H2O, and then adding the obtained Ti (HPO)4)2·H2Mixing O with 5mL of 10mol/L concentrated phosphoric acid, transferring the mixture into a 25mL hydrothermal kettle, keeping the mixture in an oven at 240 ℃ for 24 hours, cooling the mixture to room temperature, centrifuging the mixture, washing the mixture for multiple times by using deionized water, and transferring the mixture into a vacuum oven at 75 ℃ to obtain a product titanium hydrogen phosphate Ti (PO)4)(H2PO4)·2H2O。
b) Preparing anode slurry: and ball-milling and mixing the prepared titanium hydrogen phosphate and the vulcanized polyaniline according to the mass ratio of 6:4, and then keeping the mixture in a tubular furnace at the constant temperature of 400 ℃ for 3 hours to obtain the anode composite material. Mixing the obtained positive electrode composite material, Ketjen black and polytetrafluoroethylene binder according to the mass ratio of 6:2:2, adding a mixed solvent of water, ethanol and isopropanol with the volume ratio of 6:3:1, stirring and grinding to prepare slurry.
c) Preparation of a sulfur positive electrode: uniformly coating the slurry on a carbon felt current collector, and carrying out vacuum drying for 4h at 65 ℃ to obtain a sulfur electrode; the thickness of the electrode film is 75 μm, and the area mass is 20mg/cm2。
d) Assembling the battery: a battery is assembled by using a LiTFSI/DOL + DME electrolyte, a PP/PE/PP diaphragm and a lithium boron alloy containing 60% of lithium and taking the prepared sulfur electrode as a positive electrode in a glove box with the protection of argon and the water oxygen content of less than 1ppm, and a charge and discharge test is carried out. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a rate of 1C, the capacity of the first circle is 560mAh/g, and the capacity retention rate of the cycle 250 circles is 81%.
Comparative example:
a) preparing anode slurry: and carrying out ball milling on the graphene and the sulfur according to the mass ratio of 4:6, and then keeping the mixture in a tube furnace at the constant temperature of 155 ℃ for 12 hours to obtain the positive electrode composite material. Mixing the obtained positive electrode composite material, acetylene black and PVDF binder according to the mass ratio of 8:1:1, adding NMP solvent, stirring and grinding to prepare slurry.
b) Preparation of a sulfur positive electrode: and uniformly coating the slurry on an aluminum foil, and performing vacuum drying for 12 hours at the temperature of 55 ℃ to obtain the sulfur electrode.
1mol/L of LiTFSI/DOL + DME (1:1, volume ratio) electrolyte is adopted; the cell diaphragm Celgard2500 was used as a cell diaphragm, and the CR2016 type button cell was constructed using the electrode sheet prepared above as the positive electrode and the metal lithium sheet as the negative electrode in a glove box protected by argon gas and having a water oxygen content of 1ppm or less, and was subjected to charge and discharge tests. In a voltage range of 1.7-2.8V, when the battery is charged and discharged at a multiplying power of 1C, the capacity of the first circle is 798mAh/g, and the capacity retention rate of the cycle 250 circles is 55%.

Claims (10)

1. A composite sulfur positive electrode material characterized in that: the composite sulfur positive electrode material consists of a sulfur-containing active substance and a sulfur positive electrode reaction promoter, wherein the sulfur positive electrode reaction promoter accounts for 0.5-60% by mass, and is a layered metal phosphate.
2. The composite sulfur positive electrode material according to claim 1, characterized in that: the molecular general formula of the layered metal phosphate is as follows: m (HPO)4)2·H2O or M (PO)4)(H2PO4)·2H2O, wherein the metal cation M is Ti4+Or Ce4+Or Sn4+Or Pb4+Or Ge4+Or Mn4+Or Ni4+Or W4+Or Mo4+Or Hf4+One of (1) and (b).
3. The composite sulfur positive electrode material according to claim 1, characterized in that: the sulfur-containing active substance can be one or the combination of two or more of orthorhombic sulfur, monoclinic sulfur, elastic sulfur, vulcanized polyacrylonitrile, vulcanized polypyrrole, vulcanized polythiophene, vulcanized polyphenylene sulfide, vulcanized polyphenylacetylene, vulcanized polyaniline and vulcanized polyphenylene sulfide.
4. The composite sulfur positive electrode material according to claim 1, characterized in that: the layered metal phosphate is prepared by a solid phase method, a precipitation method, a gel method or a solvothermal method, or a combination of the methods.
5. A method for producing the composite sulfur positive electrode material as defined in any one of claims 1 to 4, characterized in that: when the sulfur-containing active substance is one or two or more of orthorhombic sulfur, monoclinic sulfur and elastic sulfur in combined application, the heat treatment process is carried out for 8-48 h at the temperature of 150-200 ℃; when the sulfur-containing active substance is one or two or more of vulcanized polyacrylonitrile, vulcanized polypyrrole, vulcanized polythiophene, vulcanized polyphenylene sulfide, vulcanized polyphenylacetylene, vulcanized polyaniline or vulcanized polyphenylene sulfide, the heat treatment process is carried out at 280-400 ℃ for 3-36 h.
6. A composite sulfur electrode comprising the composite sulfur positive electrode material according to any one of claims 1 to 4, characterized in that: the sulfur electrode comprises a composite sulfur positive electrode material, a conductive agent and a binder, wherein the mass percentage of the composite sulfur positive electrode material is 20-90%, the mass percentage of the conductive agent is 5-40%, and the mass percentage of the binder is 5-40%; the electrode film has a thickness of 5 to 150 μm on one surface and a mass per unit area of 0.1 to 45mg/cm2；
The conductive agent is one or two or more of acetylene BLACK, BLACK PEARLS 2000, ketjen BLACK, Super-P, carbon nano tube, carbon nano fiber, activated carbon and graphene; the binder is a water-based binder or an oil-based binder;
the oil-based binder is polyvinylidene fluoride (PVDF); the water-based binder is one of LA132, sodium carboxymethylcellulose, polytetrafluoroethylene, agar and starch.
7. A method of synthesis of a composite sulphur electrode according to claim 6, wherein: adding the composite sulfur positive electrode material, the conductive agent and the binder into a solvent, and uniformly mixing by stirring or ball milling or sanding to prepare slurry; coating the slurry on the surface of one side or two sides of the positive current collector in a blade coating or spraying or coating mode, and drying to obtain the composite sulfur positive electrode;
the adopted current collector is a metal foil or a carbon material; the metal foil comprises aluminum foil, iron foil and copper foil, and the carbon material is foam carbon, carbon paper, carbon cloth or carbon felt.
8. The method for synthesizing a composite sulfur electrode according to claim 7, wherein: when the binder is an oil-based binder, the solvent is one or more of N-methyl pyrrolidone, N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, diphenyl ether, hexamethylphosphoramidite and hexaethylphosphonite; when the binder is an aqueous binder, the solvent is one or more of water, isopropanol and ethanol.
9. A lithium sulfur battery based on the composite sulfur electrode of claim 6, wherein: the negative electrode of the lithium sulfur battery may be metallic lithium or a lithium alloy or pre-lithiated graphite or pre-lithiated carbon microspheres or pre-lithiated silicon-based materials; the lithium alloy can be an alloy of lithium and one or two or more of Mg, Ca, B, Al, Si, Ge, Sn, Pb, In, Sb, Bi, Fe and Zn, and the mass content of lithium In the alloy is 10-90%.
10. Use of a lithium-sulphur cell according to claim 9, wherein: lithium sulfur batteries are used in the fields of mass energy storage, mobile and wireless electronics, electric tools, hybrid and electric vehicles, and the like.
CN201911237894.5A 2019-12-06 2019-12-06 Composite sulfur positive electrode material and preparation method and application thereof Pending CN112928276A (en)

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