WO2023273917A1 - Matériau d'électrode positive, son procédé de préparation et batterie au lithium-ion - Google Patents

Matériau d'électrode positive, son procédé de préparation et batterie au lithium-ion Download PDF

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WO2023273917A1
WO2023273917A1 PCT/CN2022/099358 CN2022099358W WO2023273917A1 WO 2023273917 A1 WO2023273917 A1 WO 2023273917A1 CN 2022099358 W CN2022099358 W CN 2022099358W WO 2023273917 A1 WO2023273917 A1 WO 2023273917A1
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positive electrode
lithium
electrode material
phosphate
vanadium
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PCT/CN2022/099358
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English (en)
Chinese (zh)
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何向明
王莉
胡乔
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清华大学
北京华睿新能动力科技发展有限公司
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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
    • H01M4/58—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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • 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

Definitions

  • the present application relates to the technical field of lithium-ion batteries, in particular to a positive electrode material, a preparation method thereof, and a lithium-ion battery.
  • lithium-ion batteries have been widely used in people's lives. Since Goodenough et al. proposed lithium cobalt oxide (LiCoO 2 ) as the cathode material for lithium-ion batteries in 1980, and after Sony commercialized lithium-ion batteries in 1990, many new cathode materials for lithium-ion batteries have emerged, such as lithium iron phosphate (LiFePO 4 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMnO 2 ), lithium vanadium phosphate (Li 3 V 2 (PO 4 ) 3 ), etc. Lithium iron phosphate has received great attention due to its wide source of raw materials, lower price and no environmental pollution, and has caused extensive research and rapid development.
  • LiFePO 4 has a lower voltage platform (3.4V, vs. Li/Li + ). Compared with LiFePO 4 , LiMnPO 4 is similar in structure to LiFePO 4 and also has the advantages of environmental friendliness and good compatibility with electrolytes. LiMnPO 4 4 has a high-voltage platform of 4.0V (vs. Li/Li + ), and its energy density can be increased by about 20%. However, the electronic conductivity and lithium ion conductivity of LiMnPO 4 are an order of magnitude lower than that of LiFePO 4 , and there is a ginger Taylor effect between LiMnPO 4 /MnPO 4 and Mn 2+ dissolved in the electrolyte during charge and discharge. However, the structure of LiMnPO 4 is destroyed, and it is difficult to obtain excellent cycle and rate performance.
  • lithium iron manganese phosphate At present, partial Fe 2+ substitution of LiMnPO 4 to form lithium iron manganese phosphate has become a mainstream method in the market.
  • This material has the advantages of high energy density and cycle stability.
  • the conductivity of lithium iron manganese phosphate is still low, which limits its reversible specific capacity at high current density, and it is difficult to meet the market demand.
  • a positive electrode material includes a matrix and graphene coated outside the matrix; the material of the matrix includes lithium iron manganese phosphate and lithium vanadium phosphate.
  • the lithium iron manganese phosphate is represented by the chemical formula LiMn 1-y Fe y PO 4 , where 0 ⁇ y ⁇ 0.9, and the lithium vanadium phosphate is represented by the chemical formula Li 3 V 2 (PO 4 ) 3 .
  • the chemical formula of the lithium iron manganese phosphate is LiMn 0.7 Fe 0.3 PO 4 .
  • the mass ratio of lithium vanadium phosphate to lithium iron manganese phosphate is x:(1-x), wherein 0 ⁇ x ⁇ 0.3.
  • the graphene content is 2wt% ⁇ 3wt%.
  • the graphene is in-situ grown on the surface of the substrate.
  • the positive electrode material is ellipsoidal particles with a particle size of 100nm-150nm.
  • a preparation method of the positive electrode material comprising the following steps:
  • the positive electrode material precursor is sintered in an inert atmosphere to obtain the positive electrode material.
  • the lithium source is at least one of lithium dihydrogen phosphate, lithium nitrate, lithium acetate, and lithium hydroxide.
  • the vanadium source is one or more of vanadium pentoxide, vanadium trioxide, vanadium dioxide and ammonium metavanadate.
  • the phosphorus source is at least one of ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid.
  • the first carbon source is a carbon-containing compound
  • the carbon-containing compound includes one or more of sugars, organic acids, organic acid esters, small molecule alcohols, and other carbon-containing polymer compounds.
  • the second carbon source is one or more of glucose, polyvinyl alcohol, polypropylene alcohol, and polybutenol.
  • the sintering temperature is 300° C. to 400° C.
  • the sintering time is 4 hours to 6 hours.
  • the sintering temperature is 650° C. to 800° C.
  • the sintering time is 8 hours to 16 hours.
  • a lithium ion battery the positive pole of which comprises the positive pole material.
  • FIG. 1 is an X-ray diffraction (XRD) diagram of the positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • FIG. 1 is an X-ray diffraction (XRD) diagram of the positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • FIG. 2A is a scanning electron microscope (SEM) image of the positive electrode material provided in Comparative Example 1.
  • SEM scanning electron microscope
  • 2B-2D are SEM images of the positive electrode materials provided in Examples 1-3.
  • FIG. 2E is an energy dispersive X-ray spectrum (EDS) element distribution diagram of the cathode material provided in Comparative Example 1.
  • EDS energy dispersive X-ray spectrum
  • FIG. 2F is an EDS element distribution diagram of the cathode material provided in Example 2.
  • Example 3 is a transmission electron microscope (TEM) image of the positive electrode materials provided in Example 2 and Comparative Example 1.
  • Fig. 4 is the first charge and discharge curve of the battery composed of positive electrode materials provided by Examples 1-3 and Comparative Example 1.
  • the curves in Fig. 4 are successively along the directions indicated by the arrows: x is 0, x is 0.05, x is 0.1, x is 0.3.
  • FIG. 5 is the cycle performance test curves of the batteries composed of positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • FIG. 5 is the cycle performance test curves of the batteries composed of positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • FIG. 6 is a rate performance test curve of batteries composed of positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • FIG. 6 is a rate performance test curve of batteries composed of positive electrode materials provided in Examples 1-3 and Comparative Example 1.
  • particle size refers to the size of the smallest mesh through which a particle can pass in the most favorable configuration.
  • An embodiment of the present application provides a positive electrode material, including a matrix, and graphene coated outside the matrix.
  • the materials of the matrix are mainly lithium iron manganese phosphate and lithium vanadium phosphate.
  • the positive electrode material provided in the embodiment of the present application uses lithium iron manganese phosphate and lithium vanadium phosphate as the matrix, and the matrix is coated with graphene.
  • the conductivity of electrons and the conductivity of ions in the process make the cathode material have more excellent high-rate performance and cycle stability under high voltage.
  • the particles of lithium iron manganese phosphate are basically ellipsoidal, and the particle size ranges from 100nm to 150nm. Lithium vanadium phosphate particles have irregular morphology. It can be understood that lithium iron manganese phosphate and lithium vanadium phosphate may also be spherical, rhombic or other shapes similar to ellipsoids. Using lithium iron manganese phosphate particles and lithium vanadium phosphate particles as substrates, wrinkled graphene is evenly coated on lithium iron manganese phosphate LiMn 0.7 Fe 0.3 PO 4 particles and lithium vanadium phosphate Li 3 V 2 (PO 4 ) 3 particles.
  • the mass ratio of lithium vanadium phosphate to lithium iron manganese phosphate is x:(1-x), wherein 0 ⁇ x ⁇ 0.3.
  • x can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3.
  • the content of graphene is any value between 2wt% and 3wt%, for example, it can also be 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%. wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%.
  • the embodiment of the present application also provides a method for preparing the above positive electrode material, comprising the following steps:
  • the lithium source may include, but is not limited to, at least one of lithium dihydrogen phosphate, lithium nitrate, lithium acetate, and lithium hydroxide, and in one embodiment, lithium acetate.
  • the vanadium source may include, but is not limited to, one or more of vanadium pentoxide, vanadium trioxide, vanadium dioxide and ammonium metavanadate, in one embodiment, ammonium metavanadate.
  • the phosphorus source may include, but not limited to, one or more of vanadium pentoxide, vanadium trioxide, vanadium dioxide and ammonium metavanadate, in one embodiment, ammonium dihydrogen phosphate or diammonium hydrogen phosphate .
  • the first carbon source acts as a reducing agent to reduce pentavalent vanadium to trivalent vanadium.
  • the first carbon source may be selected from carbon-containing compounds, which may include, but not limited to, one or more of sugars, organic acids, organic acid esters, small molecule alcohols and other carbon-containing high molecular compounds.
  • Sugars can be selected from reducing carbons such as glucose and sucrose.
  • the range of the molar ratio of the lithium source, the vanadium source and the phosphorus source may be (2.9-3.3):2:(2.9-3.3). In some embodiments, the molar ratio of the lithium source, the vanadium source and the phosphorus source is 3:2:3.
  • the amount of the first carbon source can be any value between 5wt% and 20wt% of the total weight of the precursor of the lithium vanadium phosphate, for example, it can also be 6wt%, 7wt%, 8wt%, 9wt%, 10wt% , 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%.
  • the method of mixing the lithium source, the vanadium source, the phosphorus source and the first carbon source can be mechanical stirring or ball milling.
  • the ball milling equipment can be a stirring ball mill, a sand mill, a colloid mill, a jet pulverizer, an impact micropowder ball mill, an airflow spiral micropowder machine, an impact pulverizer or a rod mechanical pulverizer.
  • the material of ball mill jar and ball is stainless steel, corundum, zirconia or agate.
  • the rotational speed of ball milling and mixing may be 200r/min-500r/min, and the time of ball milling may be 0.5 hour-12 hours.
  • Ball milling can be done by dry ball milling or wet ball milling. In one embodiment, in order to make various raw materials mix more uniformly, wet ball milling may be used.
  • the solvent used in wet ball milling can be selected from organic or inorganic solvents, such as acetone or other low-polarity solvents. The selected solvent does not react with any of the raw materials but can provide an environment for the mutual reaction between the raw materials. In some embodiments, acetone is used, meeting both safety and cost requirements.
  • the sintering temperature for sintering the lithium vanadium phosphate precursor may be 300° C. to 400° C., and the sintering time may be 4 hours to 6 hours.
  • the inert atmosphere can be at least one of oxygen, nitrogen, nitrogen, and argon-hydrogen mixed gas. In one embodiment, the inert atmosphere is nitrogen.
  • lithium iron manganese phosphate can be obtained by commercially available or any known method for preparing lithium iron manganese phosphate, for example including but not limited to high temperature solid phase method, carbothermal reduction method and sol-gel method.
  • the raw material of lithium iron manganese phosphate used may contain other impurities besides lithium iron manganese phosphate.
  • Other impurities can be removed during the sintering in step S40.
  • the second carbon source generates graphene in situ under the catalysis of vanadium oxide in lithium vanadium phosphate calcined powder.
  • the second carbon source may be an organic carbon source, such as one or more of glucose, polyvinyl alcohol, polypropylene alcohol, and polybutenol.
  • the usage amount of the second carbon source may be 6wt%-10wt% of the total weight of the cathode material precursor.
  • the method of mixing the lithium vanadium phosphate calcined powder, the lithium iron manganese phosphate and the second carbon source can also be mechanical stirring or ball milling, the same as the above-mentioned lithium source, vanadium source, phosphorus source and the first carbon source.
  • the way of mixing is basically the same, and will not be repeated here.
  • the solvent used when performing wet ball milling on the calcined lithium vanadium phosphate powder, the precursor of lithium iron manganese phosphate, and the second carbon source, the solvent used may be absolute ethanol.
  • the sintering temperature for sintering the positive electrode precursor may be 650° C. to 800° C., and the sintering time may be 8 hours to 16 hours.
  • the inert atmosphere can be at least one of oxygen, nitrogen, nitrogen, and argon-hydrogen mixed gas. In one embodiment, the inert atmosphere is nitrogen.
  • the cathode material is obtained by cooling under an inert atmosphere after sintering.
  • the second carbon source generates wrinkled graphene in situ under the catalysis of vanadium oxide in lithium vanadium phosphate, which is coated on lithium iron phosphate and lithium vanadium phosphate particles. surface, thus forming a stable cathode material.
  • the embodiment of the present application also provides a lithium ion battery, including a positive electrode, a negative electrode, an electrolyte and the separator, and the positive electrode includes the positive electrode material. Except for the positive electrode material, other parts of the lithium ion battery of the present application can be prepared according to conventional methods known in the art. In some embodiments, the preparation method of the lithium-ion battery of the present application is specifically as follows.
  • the preparation method of the positive electrode may be: coating the positive electrode current collector with the positive electrode slurry containing the positive electrode material, the binder, the conductive agent and the solvent, and then drying and rolling the coated positive electrode current collector.
  • the positive electrode current collector material is not particularly limited, as long as it has conductivity and does not cause adverse chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon, nickel, titanium or carbon can be used.
  • stainless steel aluminum, nickel, titanium, fired carbon, or carbon, nickel, titanium or carbon
  • the positive electrode active material in the positive electrode sheet is the above positive electrode material.
  • the content of the positive electrode active material may be 80wt% to 99wt%, such as 90wt% to 99wt%. In the case where the amount of the positive electrode active material is 80 wt % or less, capacity may decrease due to decreased energy density.
  • the binder is an ingredient that helps the adhesion between the active material and the conductive agent and the adhesion with the current collector, wherein, based on the total weight of the solid components in the positive electrode slurry, the amount of the binder added is usually 1wt % to 30wt%.
  • binders may include, but are not limited to, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber and various copolymers, etc.
  • CMC carboxymethyl cellulose
  • binders may include, but are not limited to, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber and various copolymers, etc.
  • the conductive agent is a material that provides electrical conductivity without causing adverse chemical changes in the battery, wherein, based on the total weight of solid components in the positive electrode slurry, it may be added in an amount of 1 wt % to 20 wt %.
  • Examples of conductive agents may include, but are not limited to, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; graphite powder such as Natural graphite, artificial graphite or graphite; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorocarbon powders, aluminum powders, and nickel powders; conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers; conductive metals oxides such as titanium oxide; or polyphenylene derivatives.
  • carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black
  • graphite powder such as Natural graphite, artificial graphite or graphite
  • conductive fibers such as carbon fibers or metal fibers
  • conductive powders such as fluorocarbon powders, aluminum powders, and nickel powders
  • conductive whiskers such as zinc oxide whiskers and potassium titanate whiskers
  • the solvent may include water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) and alcohol, and may be used in an amount such that a desired viscosity is obtained when a positive active material and optionally a binder and a conductive agent are included.
  • NMP N-methyl-2-pyrrolidone
  • the content of the solvent may be such that the concentration of the solid component in the slurry including the positive active material and optionally the binder and the conductive agent is 10wt% to 60wt%, such as 20wt% to 50wt%.
  • the preparation method of the negative electrode may be: coating the negative electrode current collector with the negative electrode slurry containing the negative electrode active material, the binder, the conductive agent and the solvent, and then drying and rolling the coated negative electrode current collector.
  • the negative electrode current collector generally has a thickness of 3 ⁇ m to 500 ⁇ m.
  • the negative electrode current collector is not particularly limited as long as it has high conductivity and does not cause adverse chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon, nickel, titanium can be used Or a surface-treated copper or stainless steel in silver, etc., or aluminum-cadmium alloy, etc.
  • the negative electrode current collector may have various shapes such as a rod shape, a plate shape, a sheet shape, and a foil shape.
  • the negative electrode active material described in the present application can be any negative electrode active material known in the art, for example including but not limited to, metal lithium, graphite, natural graphite, artificial graphite, hard carbon, soft carbon, Li-Sn alloy, Li-Sn -O alloy, Sn, SnO, SnO 2 , tin-based composite material, lithiated TiO 2 with spinel structure, Li 4 Ti 5 O 12 , Li-Al alloy, silicon, Li-Si alloy, Li-Si-O One or more of alloys, silicon-based composite materials, and tin-silicon composite materials.
  • the content of the negative electrode active material may be 80wt% to 99wt%.
  • the binder, conductive agent and solvent in the negative electrode are calculated based on the total weight of the solid components in the negative electrode slurry, and their specific content, function and type are the same as those in the positive electrode.
  • the binder, conductive agent and solvent in are the same, and will not be repeated here.
  • suitable binders, conductive agents and solvents for the negative electrode can select suitable binders, conductive agents and solvents for the negative electrode according to actual needs.
  • the electrolytic solution may be one or more of gel electrolyte, solid electrolyte and electrolytic solution, and the electrolytic solution may include lithium salt and non-aqueous solvent.
  • the lithium salt may be selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) One or more of 3 , LiSiF 6 , LiBOB and lithium difluoroborate.
  • LiPF 6 is selected as a lithium salt because it can give high ion conductivity and improve cycle characteristics.
  • the non-aqueous solvent can be carbonate compound, carboxylate compound, ether compound, other organic solvent or their combination.
  • the carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof.
  • chain carbonate compounds may include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate ( EPC), methyl ethyl carbonate (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof .
  • fluorocarbonate compound may include, but are not limited to, fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1, 1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate , 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1, 1,2-trifluoroethylene carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-difluoro-1-methylethylene carbonate 1,1,2-trifluoro-2-methylethylene carbonate
  • Examples of the carboxylate compound may be methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, ⁇ -butyrolactone, decanolactone, valerolactone, Mevalonolactone, caprolactone, methyl formate, and combinations thereof.
  • ether compounds can be dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • organic solvents may be dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters, and combinations thereof.
  • a separator is used to separate the positive and negative electrodes.
  • the separator may be any of various separators typically used in conventional lithium ion batteries.
  • the separator may comprise a material having low resistance to ion migration of the electrolyte and good electrolyte retention, which may include, but is not limited to, a material selected from the group consisting of fiberglass, polyester, Teflon, polyethylene , polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof, each of which may be woven or nonwoven.
  • the membrane may have a pore size of about 0.01 ⁇ m to about 10 ⁇ m and a thickness of about 5 ⁇ m to about 300 ⁇ m.
  • LMFP is an abbreviation for lithium iron manganese phosphate
  • LVP is an abbreviation for lithium vanadium phosphate
  • Lithium acetate, ammonium metavanadate, and ammonium dihydrogen phosphate were mixed according to a molar ratio of 3:2:3, 15 wt% of citric acid was added, and zirconia balls were used as grinding balls.
  • the above materials were put into a ball mill jar, acetone was added and mixed for wet ball milling, and the slurry after wet ball milling was dried in an oven at 110° C. for 6 hours. Sintering at 400°C for 6 hours under the protection of N2 atmosphere with a heating rate of 3°C/min to obtain lithium vanadium phosphate calcined powder.
  • the positive electrode material After sintering, the positive electrode material is obtained, and the chemical formula of the matrix of the positive electrode material is obtained by phase analysis (XRD) is 0.95LiMn 0.7 Fe 0.3 PO 4 ⁇ 0.05Li 3 V 2 (PO 4 ) 3 (abbreviated as 0.95LMFP ⁇ 0.05LVP), its XRD pattern is shown in Figure 1.
  • XRD phase analysis
  • the chemical formula of the matrix of the cathode material prepared in Example 2 is 0.7LiMn 0.7 Fe 0.3 PO 4 0.3Li 3 V 2 (PO 4 ) 3 (abbreviated as 0.7LMFP 0.3LVP) through phase analysis (XRD), and its XRD The picture is shown in Figure 1.
  • LMFP lithium iron manganese phosphate
  • the XRD pattern of the positive electrode material is shown in FIG. 1 .
  • the crystal structure of the material was observed by XRD, and the morphology and particle size of the positive electrode material were observed by SEM, EDS elemental analysis and TEM.
  • Fig. 2A is the SEM image of lithium iron manganese phosphate (LiMn 0.7 Fe 0.3 PO 4 ) of Comparative Example 1
  • Fig. 2B is the SEM image of the positive electrode material of Example 1
  • Fig. 2C is The SEM image of the positive electrode material of Example 2
  • Figure 2D is the SEM image of the positive electrode material of Example 3
  • Figure 2E is the positive electrode material of Comparative Example 1, that is, the EDS element distribution of lithium iron manganese phosphate (LiMn 0.7 Fe 0.3 PO 4 )
  • Figure 2F is the EDS elemental distribution diagram of the cathode material of Example 2.
  • the EDS elemental analysis of the positive electrode material of Comparative Example 1 shows that there is no V element therein.
  • FIG. 2F by performing EDS elemental analysis on the positive electrode material of Example 2, it can be seen that there is V element therein.
  • the particle size of the positive electrode materials prepared in Examples 1-3 is 100nm-150nm, LiMn 0.7 Fe 0.3 PO 4 and Li 3 V 2 (PO 4 ) can be clearly distinguished in the figure 3
  • Two kinds of particles, the particles are ellipsoidal.
  • the positive electrode material of Example 2 ( Figures 3d-3f) appeared transparent wrinkled sp 2 type carbon (ie, graphite ene), and two distinct lattice fringes (Fig. 3f) can be observed in the positive electrode material of Example 2, and the interplanar spacings of 0.427nm and 0.214nm correspond to the (011) crystal plane of LMFP and the crystal plane of LVP, respectively. (400) crystal plane.
  • the battery type is a button cell, model CR2032.
  • the electrolyte is 1mol/L lithium hexafluorophosphate as the solute
  • the solvent is a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate with a mass ratio of 1:1:1
  • 1% VC is added as a film-forming additive.
  • the isolation membrane is celgard2400 polypropylene porous film.
  • Preparation of positive electrode sheet mix the positive electrode material provided in Example 1, conductive agent C45, and binder polyvinylidene fluoride at a mass ratio of 8:1:1, wherein polyvinylidene fluoride is dissolved in N-methylpyrrolidone, and the mass The fraction is 5%, mixed evenly, coated on aluminum foil with a thickness of 200 ⁇ m, and vacuum-dried at 60°C for 6 hours to make an electrode sheet with a diameter of ⁇ 12mm.
  • the loading capacity of the active material of the electrode sheet is about 1.5-2.5 mg.
  • the negative electrode is made of pure lithium metal. Cell assembly was performed in a glove box under argon protection.
  • Test voltage range 2.2-4.5V.
  • Table 1A-Table 1B are the ratio test results of Examples 1-3 and Comparative Example 1.
  • the batteries made of the cathode materials provided in Examples 1-3 have significantly improved high-rate performance and better cycle stability.
  • Example 3 has a certain loss in reversible specific capacity, which is due to the theoretical specific capacity of Li 3 V 2 (PO 4 ) 3 being 133mAh g -1 in the voltage range of 2.2-4.5V , lower than that of LiMn 0.7 Fe 0.3 PO 4 (160mAh g -1 ), but it can still be found that the cycle stability and large rate capability of 0.7LiMn 0.7 Fe 0.3 PO 4 ⁇ 0.3Li 3 V 2 (PO 4 ) 3 are greatly improved big boost.

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Abstract

La présente invention concerne un matériau d'électrode positive, comprenant une matrice et du graphène revêtu sur l'extérieur de la matrice. Le matériau de la matrice comprend du phosphate de lithium-fer-manganèse et du phosphate de lithium-vanadium. La présente invention concerne également un procédé de préparation du matériau d'électrode positive. La présente invention concerne en outre une batterie au lithium-ion comprenant le matériau d'électrode positive.
PCT/CN2022/099358 2021-06-30 2022-06-17 Matériau d'électrode positive, son procédé de préparation et batterie au lithium-ion WO2023273917A1 (fr)

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