WO2023273917A1 - Positive electrode material and preparation method therefor, and lithium ion battery - Google Patents

Positive electrode material and preparation method therefor, and lithium ion battery 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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French (fr)
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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Publication of WO2023273917A1 publication Critical patent/WO2023273917A1/en

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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.

Abstract

The present application relates to a positive electrode material, comprising a matrix, and graphene coated on the outside of the matrix. The material of the matrix comprises lithium iron manganese phosphate and lithium vanadium phosphate. The present application also relates to a preparation method for the positive electrode material. The present application further relates to a lithium ion battery comprising the positive electrode material.

Description

正极材料及其制备方法和锂离子电池Positive electrode material, preparation method thereof and lithium ion battery
相关申请related application
本申请要求2021年06月30日申请的，申请号为202110738196.4，名称为“正极材料及其制备方法和锂离子电池”的中国专利申请的优先权，在此将其全文引入作为参考。This application claims the priority of the Chinese patent application filed on June 30, 2021 with the application number 202110738196.4 and titled "Positive Electrode Material and Its Preparation Method and Lithium-ion Battery", which is hereby incorporated by reference in its entirety.
技术领域technical field
本申请涉及锂离子电池技术领域，特别是涉及一种正极材料及其制备方法和锂离子电池。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.
背景技术Background technique
锂离子电池作为目前重要的新型绿色能源，已经广泛地应用到人们的生活当中。自从1980年Goodenough等提出了氧化钴锂(LiCoO 2)作为锂离子电池的正极材料，1990年Sony公司将锂离子电池进行商业化之后，涌现了很多新型的锂离子电池正极材料，比如磷酸铁锂(LiFePO 4)、镍酸锂(LiNiO 2)、锰酸锂(LiMnO 2)、磷酸钒锂(Li 3V 2(PO 4) 3)等。磷酸铁锂由于其原料来源广泛、价格更低廉且无环境污染受到了极大的关注并引起广泛地研究和迅速的发展。然而LiFePO 4的电压平台较低(3.4V，vs.Li/Li +)，相较于LiFePO 4，LiMnPO 4与LiFePO 4结构相似，同样具有环境友好、与电解液兼容性好等优点，且LiMnPO 4具有4.0V(vs.Li/Li +)的高电压平台，其能量密度可提高约20％。然而，LiMnPO 4的电子电导率和锂离子电导率相比于LiFePO 4低了一个量级，而且在充放电过程中LiMnPO 4/MnPO 4之间存在姜泰勒效应和Mn 2+溶解于电解液等问题，都使得LiMnPO 4结构被破坏，很难获得优异的循环和倍率性能。 As an important new type of green energy, 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. However, 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.
目前，对LiMnPO 4进行部分Fe 2+取代形成磷酸铁锰锂成为了市场上一种主流的方法，该材料兼具高能量密度和循环稳定的优点。然而，磷酸铁锰锂的电导率仍然较低，限制了其在大电流密度下的可逆比容量，难以满足市场的需求。 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. However, 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.
发明内容Contents of the invention
基于此，有必要提供一种正极材料及其制备方法和锂离子电池。Based on this, it is necessary to provide a positive electrode material, a preparation method thereof and a lithium ion battery.
一种正极材料，包括基体，以及包覆在所述基体外的石墨烯；所述基体的材料包括磷酸铁锰锂和磷酸钒锂。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.
在一实施例中，所述磷酸铁锰锂由化学式LiMn 1-yFe yPO 4表示，其中0<y≤0.9，所述磷酸钒锂由化学式Li 3V 2(PO 4) 3表示。 In one embodiment, 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 .
在一实施例中，所述磷酸铁锰锂的化学式为LiMn 0.7Fe 0.3PO 4。 In one embodiment, the chemical formula of the lithium iron manganese phosphate is LiMn 0.7 Fe 0.3 PO 4 .
在一实施例中，所述磷酸钒锂和磷酸铁锰锂的质量比为x:(1-x)，其中，0＜x≤0.3。In one embodiment, the mass ratio of lithium vanadium phosphate to lithium iron manganese phosphate is x:(1-x), wherein 0<x≤0.3.
在一实施例中，基于正极材料的总重量，所述石墨烯含量的2wt％～3wt％。In one embodiment, based on the total weight of the positive electrode material, the graphene content is 2wt%˜3wt%.
在一实施例中，所述石墨烯原位生成在所述基体表面。In one embodiment, the graphene is in-situ grown on the surface of the substrate.
在一实施例中，所述正极材料为类椭球形的颗粒，颗粒的尺寸为100nm～150nm。In one embodiment, the positive electrode material is ellipsoidal particles with a particle size of 100nm-150nm.
一种所述的正极材料的制备方法，包括以下步骤：A preparation method of the positive electrode material, comprising the following steps:
将锂源、钒源、磷源和第一碳源按照预定比例混合，得到所述磷酸钒锂的前驱体；mixing the lithium source, the vanadium source, the phosphorus source and the first carbon source according to a predetermined ratio to obtain the precursor of the lithium vanadium phosphate;
将所述磷酸钒锂的前驱体在惰性气氛下进行烧结处理，得到磷酸钒锂预烧粉；Sintering the precursor of the lithium vanadium phosphate under an inert atmosphere to obtain calcined powder of lithium vanadium phosphate;
将所述磷酸钒锂预烧粉、磷酸铁锰锂和第二碳源按照预定比例混合，得到正极材料前驱体；Mixing the lithium vanadium phosphate calcined powder, lithium iron manganese phosphate and a second carbon source according to a predetermined ratio to obtain a positive electrode material precursor;
将所述正极材料前驱体在惰性气氛下进行烧结处理，得到正极材料。The positive electrode material precursor is sintered in an inert atmosphere to obtain the positive electrode material.
在一实施例中，所述锂源为磷酸二氢锂、硝酸锂、醋酸锂、氢氧化锂中的至少一种。In one embodiment, the lithium source is at least one of lithium dihydrogen phosphate, lithium nitrate, lithium acetate, and lithium hydroxide.
在一实施例中，所述钒源为五氧化二钒、三氧化二钒、二氧化钒和偏钒酸铵中一种或多种。In one embodiment, the vanadium source is one or more of vanadium pentoxide, vanadium trioxide, vanadium dioxide and ammonium metavanadate.
在一实施例中，所述磷源为磷酸铵、磷酸二氢铵、磷酸氢二铵、磷酸中的至少一种。In one embodiment, the phosphorus source is at least one of ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphoric acid.
在一实施例中，所述第一碳源为含碳化合物，所述含碳化合物包括糖类、有机酸、有机酸醋、小分子醇和其它含碳高分子化合物中的一种或多种。In one embodiment, the first carbon source is a carbon-containing compound, and the carbon-containing compound includes one or more of sugars, organic acids, organic acid esters, small molecule alcohols, and other carbon-containing polymer compounds.
在一实施例中，所述第二碳源为葡萄糖、聚乙烯醇、聚丙烯醇、聚丁烯醇中的一种或多种。In one embodiment, the second carbon source is one or more of glucose, polyvinyl alcohol, polypropylene alcohol, and polybutenol.
在一实施例中，对所述磷酸钒锂的前驱体进行烧结时，烧结温度为300℃～400℃，烧结时间为4小时～6小时。In one embodiment, when the precursor of lithium vanadium phosphate is sintered, the sintering temperature is 300° C. to 400° C., and the sintering time is 4 hours to 6 hours.
在一实施例中，对所述正极前驱体进行烧结时，烧结温度为650℃～800℃，烧结时间为8小时～16小时。In one embodiment, when the positive electrode precursor is sintered, the sintering temperature is 650° C. to 800° C., and the sintering time is 8 hours to 16 hours.
一种锂离子电池，其正极包括所述的正极材料。A lithium ion battery, the positive pole of which comprises the positive pole material.
附图说明Description of drawings
图1为实施例1～3和对比例1提供的正极材料的X射线衍射(XRD)图。FIG. 1 is an X-ray diffraction (XRD) diagram of the positive electrode materials provided in Examples 1-3 and Comparative Example 1. FIG.
图2A为对比例1提供的正极材料的扫描电镜(SEM)图。FIG. 2A is a scanning electron microscope (SEM) image of the positive electrode material provided in Comparative Example 1. FIG.
图2B～2D为实施例1～3提供的正极材料的SEM图。2B-2D are SEM images of the positive electrode materials provided in Examples 1-3.
图2E为对比例1提供的正极材料的能量散射X射线谱(EDS)元素分布图。FIG. 2E is an energy dispersive X-ray spectrum (EDS) element distribution diagram of the cathode material provided in Comparative Example 1. FIG.
图2F为实施例2提供的正极材料的EDS元素分布图。FIG. 2F is an EDS element distribution diagram of the cathode material provided in Example 2. FIG.
图3为实施例2和对比例1提供的正极材料的透射电镜(TEM)图。3 is a transmission electron microscope (TEM) image of the positive electrode materials provided in Example 2 and Comparative Example 1.
图4为实施例1～3和对比例1提供的正极材料组成的电池的首次充放电曲线，图4中曲线沿箭头所指示的方向依次是x为0,x为0.05,x为0.1，x为0.3。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.
图5为实施例1～3和对比例1提供的正极材料组成的电池的循环性能测试曲线。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.
图6为实施例1～3和对比例1提供的正极材料组成的电池的倍率性能测试曲线。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.
具体实施方式detailed description
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的较佳实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本申请的公开内容的理解更加透彻全面。In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Preferred embodiments of the application are shown in the accompanying drawings. However, the present application can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the application more thorough and comprehensive.
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the application are only for the purpose of describing specific embodiments, and are not intended to limit the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
术语“颗粒的尺寸”是指一个颗粒在最有利的姿态下能通过的最小筛孔的尺寸。The term "particle size" refers to the size of the smallest mesh through which a particle can pass in the most favorable configuration.
本申请实施例提供一种正极材料，包括基体，以及包覆在所述基体外的石墨烯。基体的材料主要为磷酸铁锰锂和磷酸钒锂。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.
本申请实施例提供的正极材料，以磷酸铁锰锂和磷酸钒锂为基体，基体外包覆石墨烯，磷酸铁锰锂、磷酸钒锂和石墨烯具有协同作用，有效提升正极材料在充放电过程中电子的传导率和离子的传导率，使正极材料具有更优异的大倍率性能和高电压下的循环稳定性。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.
磷酸铁锰锂的颗粒基本上为椭球形，颗粒的尺寸范围为100nm～150nm。磷酸钒锂颗粒为无规则形貌。可以理解的是，磷酸铁锰锂和磷酸钒锂也可以是球形、菱形或者其他类似椭球形的形状。以磷酸铁锰锂颗粒和磷酸钒锂颗粒为基体，褶皱的石墨烯均匀包覆在磷酸铁锰锂LiMn 0.7Fe 0.3PO 4颗粒和磷酸钒锂Li 3V 2(PO 4) 3颗粒上。 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.
在一些实施例中，所述磷酸钒锂和磷酸铁锰锂的质量比为x:(1-x)，其中，0＜x≤0.3。在一些实施例中，x可以取0.05、0.1、0.15、0.2、0.25、0.3。In some embodiments, the mass ratio of lithium vanadium phosphate to lithium iron manganese phosphate is x:(1-x), wherein 0<x≤0.3. In some embodiments, x can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3.
在一些实施例中，基于正极材料的总重量，石墨烯的含量为2wt％～3wt％之间的任意值，例如还可以为2.1wt％、2.2wt％、2.3wt％、2.4wt％、2.5wt％、2.6wt％、2.7wt％、2.8wt％、2.9wt％。In some embodiments, based on the total weight of the positive electrode material, 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%.
本申请实施例还提供一种上述正极材料的制备方法，包括以下步骤：The embodiment of the present application also provides a method for preparing the above positive electrode material, comprising the following steps:
S10，将锂源、钒源、磷源和第一碳源按照预定比例混合，得到所述磷酸钒锂的前驱 体；S10, mixing the lithium source, the vanadium source, the phosphorus source and the first carbon source according to a predetermined ratio to obtain the precursor of the lithium vanadium phosphate;
S20，将所述磷酸钒锂的前驱体在惰性气氛下进行烧结处理，得到磷酸钒锂预烧粉；S20, sintering the precursor of the lithium vanadium phosphate under an inert atmosphere to obtain calcined powder of lithium vanadium phosphate;
S30，将所述磷酸钒锂预烧粉、磷酸铁锰锂和第二碳源按照预定比例混合，得到正极材料前驱体；以及S30, mixing the lithium vanadium phosphate calcined powder, lithium iron manganese phosphate and a second carbon source according to a predetermined ratio to obtain a positive electrode material precursor; and
S40，将所述正极材料前驱体在惰性气氛下进行烧结处理，得到正极材料。S40, sintering the cathode material precursor under an inert atmosphere to obtain an anode material.
步骤S10中，所述锂源可以包括但不限于，磷酸二氢锂、硝酸锂、醋酸锂、氢氧化锂中的至少一种，在一实施例中为醋酸锂。In step S10, 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.
所述钒源可以包括但不限于，五氧化二钒、三氧化二钒、二氧化钒和偏钒酸铵中一种或多种，在一实施例中为偏钒酸铵。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.
所述磷源可以包括但不限于，五氧化二钒、三氧化二钒、二氧化钒和偏钒酸铵中一种或多种，在一实施例中为磷酸二氢铵或磷酸氢二铵。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 .
所述第一碳源起到还原剂的作用，将五价钒还原为三价钒。所述第一碳源可以选自含碳化合物，可以包括但不限于，糖类、有机酸、有机酸酯、小分子醇和其它含碳高分子化合物中的一种或多种。糖类可以选自葡萄糖、蔗糖等还原性碳。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.
所述锂源、钒源和磷源的摩尔比的范围可以为(2.9～3.3)：2：(2.9～3.3)。在一些实施例中，所述锂源、钒源和磷源的摩尔比为3:2:3。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.
所述第一碳源的用量可以为所述磷酸钒锂的前驱体总重量的5wt％～20wt％之间的任意值，例如还可以为6wt％、7wt％、8wt％、9wt％、10wt％、11wt％、12wt％、13wt％、14wt％、15wt％、16wt％、17wt％、18wt％、19wt％。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%.
将锂源、钒源、磷源和第一碳源进行混合的方法可以为机械搅拌或球磨。其中，球磨的设备可以为搅拌式球磨机、磨砂机、胶体磨机、气流粉碎机、冲击式微粉球磨机、气流蜗旋微粉机、冲击式粉碎机或者棒式机械粉碎机。球磨罐以及磨球材质为不锈钢、刚玉、氧化锆或玛瑙。球磨混合的转速可以为200r/min～500r/min，球磨的时间可以为0.5小时～12小时。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. Wherein, 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.
球磨可以采用干法球磨，也可以采用湿法球磨。在一实施例中，为了使各种原料能够混合的更为均匀，可以采用湿法球磨。湿法球磨时所采用的溶剂可以选自有机或无机溶剂，比如丙酮或者其他极性小的溶剂，所选用的溶剂不与其中任何一种原料反应但又能够提供原料之间相互反应的环境。在一些实施例中，采用丙酮，同时符合安全与成本的要求。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.
步骤S20中，对所述磷酸钒锂的前驱体进行烧结的烧结温度可以为300℃～400℃，烧结时间可以为4小时～6小时。In step S20 , 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.
惰性气氛可以为氧气、氮气、氮气、氩氢混合气中的至少一种。在一实施例中，惰性气氛为氮气。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.
步骤S30中，磷酸铁锰锂可以通过商购或已知的任意制备磷酸铁锰锂的方法获得，例如包括但不限于，高温固相法、碳热还原法和溶胶凝胶法等。In step S30, 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.
在一些实施例中，所用的磷酸铁锰锂原料除磷酸铁锰锂外可能还含有其它杂质。磷酸铁锰锂可以由化学式LiMn 1-yFe yPO 4表示，其中0<y≤0.9。在一实施例中，y＝0.3，磷酸铁锰锂化学式为LiMn 0.7Fe 0.3PO 4。其它杂质在步骤S40的烧结中可以除去。 In some embodiments, the raw material of lithium iron manganese phosphate used may contain other impurities besides lithium iron manganese phosphate. Lithium iron manganese phosphate can be represented by the chemical formula LiMn 1-y Fe y PO 4 , where 0<y≤0.9. In one embodiment, y=0.3, and the chemical formula of lithium iron manganese phosphate is LiMn 0.7 Fe 0.3 PO 4 . Other impurities can be removed during the sintering in step S40.
所述第二碳源在磷酸钒锂预烧粉中钒氧化物的催化作用下，原位生成石墨烯。所述第二碳源可以为有机碳源，例如葡萄糖、聚乙烯醇、聚丙烯醇、聚丁烯醇中的一种或多种。所述第二碳源的使用量可以为正极材料前驱体总重量的6wt％～10wt％。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.
将所述磷酸钒锂预烧粉、所述磷酸铁锰锂和第二碳源进行混合的方式也可以为机械搅拌或球磨，同上述将锂源、钒源、磷源和第一碳源进行混合的方式基本相同，在此不再赘述。在一些实施例中，将所述磷酸钒锂预烧粉和所述磷酸铁锰锂的前驱体、第二碳源进行湿法球磨时，使用的溶剂可以为无水乙醇。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. In some embodiments, 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.
步骤S40中，对所述正极前驱体进行烧结的烧结温度可以为650℃～800℃，烧结时间可以为8小时～16小时。In step S40, 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.
惰性气氛可以为氧气、氮气、氮气、氩氢混合气中的至少一种。在一实施例中，惰性气氛为氮气。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.
在一些实施例中，烧结后在惰性气氛下进行冷却，得到所述正极材料。In some embodiments, the cathode material is obtained by cooling under an inert atmosphere after sintering.
需要说明的是，在步骤S40的高温烧结的过程中，第二碳源在磷酸钒锂中氧化钒的催化作用下，原位生成褶皱的石墨烯，包覆在磷酸铁锂和磷酸钒锂颗粒的表面，从而形成稳定的正极材料。It should be noted that during the high-temperature sintering process in step S40, 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.
本申请实施例还提供一种锂离子电池，包括正极、负极、电解质和所述的隔膜，所述正极包括所述正极材料。除所述正极材料外，本申请的锂离子电池的其他部分可以根据本领域已知的常规方法来制备。在一些实施例中，本申请的锂离子电池的制备方法具体如下所述。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.
(1)正极(1) Positive electrode
正极的制备方法可以为：用包含所述正极材料、粘合剂、导电剂和溶剂的正极浆料涂覆正极集流体，然后将涂覆的正极集流体干燥并辊压。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.
正极集流体物无特别限定，只要其具有导电性且不会在电池中引起不利的化学变化即 可，例如可以使用不锈钢、铝、镍、钛、烧制碳，或者用碳、镍、钛或银等中的一种表面处理过的铝或不锈钢。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. One of the surface treated aluminum or stainless steel among silver etc.
该正极片中正极活性材料为如上所述的正极材料。The positive electrode active material in the positive electrode sheet is the above positive electrode material.
基于正极浆料中固体组分的总重量，正极活性材料的含量可以为80wt％至99wt％，例如90wt％至99wt％。在正极活性材料的量为80wt％以下的情况下，由于能量密度降低，因此容量可能降低。Based on the total weight of solid components in the positive electrode slurry, 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.
粘合剂是有助于活性材料和导电剂之间的粘合以及与集流体的粘合的成分，其中，基于正极浆料中固体组分的总重量，粘合剂的添加量通常为1wt％至30wt％。粘合剂的实例可以包括但不限于，聚偏二氟乙烯、聚乙烯醇、羧甲基纤维素(CMC)、淀粉、羟丙基纤维素、再生纤维素、聚乙烯吡咯烷酮、四氟乙烯、聚乙烯、聚丙烯、乙烯-丙烯-二烯单体、苯乙烯-丁二烯橡胶、氟橡胶和各种共聚物等。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%. Examples of 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.
导电剂是提供导电性而不会在电池中引起不利的化学变化的材料，其中，基于正极浆料中固体组分的总重量，其添加量可以为1wt％～20wt％。导电剂的实例可以包括但不限于，碳粉，例如炭黑、乙炔黑、科琴黑、槽黑、炉黑、灯黑或热裂法碳黑；石墨粉，例如具有生长良好的晶体结构的天然石墨、人造石墨或石墨；导电纤维，例如碳纤维或金属纤维；导电粉末，例如氟碳粉末、铝粉末和镍粉末；导电晶须，例如氧化锌晶须和钛酸钾晶须；导电金属氧化物，例如氧化钛；或者聚亚苯基衍生物。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.
溶剂可以包括：水或有机溶剂，例如N-甲基-2-吡咯烷酮(NMP)和醇，并且其用量可以使得当包含正极活性材料以及可选的粘合剂和导电剂时获得期望的粘度。例如，溶剂的含量可使得包含正极活性材料以及可选的粘合剂和导电剂的浆料中的固体组分的浓度为10wt％至60wt％，例如20wt％至50wt％。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. For example, 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%.
(2)负极(2) Negative electrode
负极的制备方法可以为：用包含负极活性材料、粘合剂、导电剂和溶剂的负极浆料涂覆负极集流体，然后将涂覆的负极集流体干燥并辊压。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.
负极集流体通常具有3μm至500μm的厚度。负极集流体没有特别限制，只要其具有高导电性且不引起电池中不利的化学变化即可，例如，可以使用铜、不锈钢、铝、镍、钛、烧制碳，或者用碳、镍、钛或银等中的一种表面处理过的铜或不锈钢，或者铝-镉合金等。此外，与正极集流体类似，负极集流体可具有各种形状，如杆形、板形、片形和箔形。The negative electrode current collector generally has a thickness of 3 μm to 500 μm. 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. In addition, similar to the positive electrode current collector, the negative electrode current collector may have various shapes such as a rod shape, a plate shape, a sheet shape, and a foil shape.
本申请所述负极活性材料可以为本领域已知的任意负极活性材料，例如包括但不限于，金属锂、石墨、天然石墨、人造石墨、硬碳、软碳、Li-Sn合金、Li-Sn-O合金、Sn、SnO、 SnO 2、锡基复合材料、尖晶石结构的锂化TiO 2、Li 4Ti 5O 12、Li-Al合金、硅、Li-Si合金、Li-Si-O合金、硅基复合材料、锡硅复合材料的一种或多种。 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.
基于负极浆料中固体组分的总重量，负极活性材料的含量可以为80wt％至99wt％。Based on the total weight of solid components in the negative electrode slurry, the content of the negative electrode active material may be 80wt% to 99wt%.
与正极中的粘合剂、导电剂和溶剂类似，负极中的粘合剂、导电剂和溶剂基于负极浆料中固体组分的总重量计算添加量，其具体的含量、作用和种类与正极中的粘合剂、导电剂和溶剂相同，在此不再赘述。本领域技术人员可以根据实际需求选择合适负极使用的粘合剂、导电剂和溶剂。Similar to the binder, conductive agent and solvent in the positive electrode, 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. Those skilled in the art can select suitable binders, conductive agents and solvents for the negative electrode according to actual needs.
(3)电解质(3) Electrolyte
所述电解液可以是凝胶电解质、固态电解质和电解液中的一种或多种，所述电解液可以包括锂盐和非水溶剂。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.
锂盐可以选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB和二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。 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. For example, LiPF 6 is selected as a lithium salt because it can give high ion conductivity and improve cycle characteristics.
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。The non-aqueous solvent can be carbonate compound, carboxylate compound, ether compound, other organic solvent or their combination.
碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。链状碳酸酯化合物的实例可以包括但不限于，碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。所述环状碳酸酯化合物的实例可以包括但不限于，碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及其组合。所述氟代碳酸酯化合物的实例可以包括但不限于，碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及其组合。The carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof. Examples of 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 . Examples of the 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.
羧酸酯化合物的实例可以为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯及其组合。Examples of the carboxylate compound may be methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolactone, valerolactone, Mevalonolactone, caprolactone, methyl formate, and combinations thereof.
醚化合物的实例可以为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及其组合。Examples of ether compounds can be dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
其它有机溶剂的实例可以为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及其组合。Examples of other 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.
(4)隔膜(4) Diaphragm
隔膜用于将正极和负极分开。该隔膜可以为在常规锂离子电池中典型地使用的各种隔膜中的任一种。例如，隔膜可包括具有低的对电解质的离子迁移的阻力和良好的电解质保持能力的材料，可包括但不限于选自如下的材料：玻璃纤维、聚酯、特氟隆(Teflon)、聚乙烯、聚丙烯、聚四氟乙烯(PTFE)、及其组合，其各自可为纺织的或非纺织的。该隔膜可具有约0.01μm～约10μm的孔尺寸和约5μm～约300μm的厚度。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. For example, 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 μm to about 10 μm and a thickness of about 5 μm to about 300 μm.
在下述实施例中，LMFP为磷酸铁锰锂的缩写，LVP为磷酸钒锂的缩写。In the following examples, LMFP is an abbreviation for lithium iron manganese phosphate, and LVP is an abbreviation for lithium vanadium phosphate.
实施例1Example 1
将醋酸锂、偏钒酸铵、磷酸二氢铵按照摩尔比为3:2:3混合，加入15wt％的柠檬酸，氧化锆球作为磨球。以上材料加入球磨罐中，加入丙酮混合进行湿法球磨，湿法球磨后的浆料在烘箱中110℃下干燥6小时。在N 2气氛保护下400℃烧结6小时，升温速率为3℃/min，获得磷酸钒锂预烧粉。 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.
将磷酸钒锂预烧粉和磷酸铁锰锂(主相为LiMn 0.7Fe 0.3PO 4，购自江苏合志新能源公司)按照质量比为0.05：0.95进行混合，即x＝0.05，加入8wt％聚乙烯醇(以磷酸钒锂预烧粉和磷酸铁锰锂的总重量计)进行研磨混合。混合均匀后再次放置于N 2保护气氛下，750℃烧结12小时，升温速率为3℃/min，烧结后获得正极材料，经物相分析(XRD)得到该正极材料的基体的化学式为0.95LiMn 0.7Fe 0.3PO 4·0.05Li 3V 2(PO 4) 3(简写为0.95LMFP·0.05LVP)，其XRD图如图1所示。 Lithium vanadium phosphate calcined powder and lithium iron manganese phosphate (the main phase is LiMn 0.7 Fe 0.3 PO 4 , purchased from Jiangsu Hezhi New Energy Company) were mixed according to the mass ratio of 0.05:0.95, that is, x=0.05, and 8 wt% poly Vinyl alcohol (based on the total weight of lithium vanadium phosphate calcined powder and lithium iron manganese phosphate) is ground and mixed. After mixing evenly, place it again under N2 protective atmosphere, sinter at 750°C for 12 hours, and the heating rate is 3°C/min. 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.
实施例2Example 2
实施例2的制备方法与实施例1的制备方法基本相同，不同之处在于：磷酸钒锂预烧粉和磷酸铁锰锂质量比为0.1:0.9，即x＝0.1。The preparation method of Example 2 is basically the same as that of Example 1, except that the mass ratio of lithium vanadium phosphate calcined powder to lithium iron manganese phosphate is 0.1:0.9, that is, x=0.1.
经物相分析(XRD)得到实施例2制备的正极材料的基体的化学式为0.9LiMn 0.7Fe 0.3PO 4·0.1Li 3V 2(PO 4) 3(简写为0.9LMFP·0.1LVP)，其XRD图如图1所示。 Obtain the chemical formula of the substrate of the cathode material prepared in Example 2 by phase analysis (XRD) be 0.9LiMn 0.7 Fe 0.3 PO 4 0.1Li 3 V 2 (PO 4 ) 3 (abbreviated as 0.9LMFP 0.1LVP), its XRD The picture is shown in Figure 1.
实施例3Example 3
实施例2的制备方法与实施例1的制备方法基本相同，不同之处在于：磷酸钒锂预烧粉和磷酸铁锰锂质量比为0.3:0.7，即x＝0.3。The preparation method of Example 2 is basically the same as that of Example 1, except that the mass ratio of lithium vanadium phosphate calcined powder to lithium iron manganese phosphate is 0.3:0.7, that is, x=0.3.
经物相分析(XRD)得到实施例2制备的正极材料的基体的化学式为0.7LiMn 0.7Fe 0.3PO 4·0.3Li 3V 2(PO 4) 3(简写为0.7LMFP·0.3LVP)，其XRD图如图1所示。 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.
对比例1Comparative example 1
正极材料仅为购买的磷酸铁锰锂(LiMn 0.7Fe 0.3PO 4，简写为LMFP)，即x＝0，正极材 料的XRD图如图1所示。 The positive electrode material is only purchased lithium iron manganese phosphate (LiMn 0.7 Fe 0.3 PO 4 , abbreviated as LMFP), that is, x=0. The XRD pattern of the positive electrode material is shown in FIG. 1 .
结构表征Structure Characterization
采用XRD观察材料的晶体结构，采用SEM、EDS元素分析和TEM观察正极材料的形貌以及颗粒粒径。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.
正极材料物相分析(XRD)Phase analysis of cathode materials (XRD)
由图1可以看出，实施例1～3制备的正极材料，LiMn 0.7Fe 0.3PO 4和Li 3V 2(PO 4) 3两相共存，没有明显的峰位偏移和其它杂峰产生，说明制备的正极材料无明显晶向杂质存在，而且随着添加的磷酸钒锂预烧粉比例的增加，Li 3V 2(PO 4) 3的峰强占比也变高，表明正极材料中Li 3V 2(PO 4) 3含量也增多。 It can be seen from Figure 1 that for the positive electrode materials prepared in Examples 1-3, the two phases of LiMn 0.7 Fe 0.3 PO 4 and Li 3 V 2 (PO 4 ) 3 coexist, and there is no obvious peak shift and other miscellaneous peaks. It shows that there is no obvious crystalline impurity in the prepared positive electrode material, and with the increase of the proportion of the added calcined lithium vanadium phosphate powder, the proportion of the peak intensity of Li 3 V 2 (PO 4 ) 3 also becomes higher, indicating that the Li 3 V 2 (PO 4 ) 3 in the positive electrode material V 2 (PO 4 ) 3 content also increased.
正极材料形貌分析(SEM&EDS&TEM)Morphology analysis of cathode materials (SEM&EDS&TEM)
参见附图2和附图3，其中，图2A为对比例1的磷酸铁锰锂(LiMn 0.7Fe 0.3PO 4)的SEM图，图2B为实施例1的正极材料的SEM图，图2C为实施例2的正极材料的SEM图，图2D为实施例3的正极材料的SEM图，图2E为对比例1的正极材料，即磷酸铁锰锂(LiMn 0.7Fe 0.3PO 4)的EDS元素分布图，图2F为实施例2的正极材料的EDS元素分布图。 Referring to accompanying drawing 2 and accompanying drawing 3, among them, 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, and 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.
如图2E所示，通过对对比例1的正极材料进行EDS元素分析可知其中无V元素。如图2F所示，通过对实施例2的正极材料进行EDS元素分析可知其中有V元素。As shown in FIG. 2E , the EDS elemental analysis of the positive electrode material of Comparative Example 1 shows that there is no V element therein. As shown in 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.
图3(a)～(c)为对比例1的正极材料，即磷酸铁锰锂(LiMn 0.7Fe 0.3PO 4)的不同分辨率的高分辨率透射电镜(HR-TEM)图，图3(d)～(f)为实施例2的正极材料的不同分辨率的HR-TEM图。 Figure 3(a)-(c) are the high-resolution transmission electron microscope (HR-TEM) images of different resolutions of the positive electrode material of Comparative Example 1, that is, lithium iron manganese phosphate (LiMn 0.7 Fe 0.3 PO 4 ), and Figure 3 ( d) to (f) are HR-TEM images of different resolutions of the cathode material of Example 2.
从图2和图3中可以看出，实施例1～3制备的正极材料的颗粒尺寸大小为100nm～150nm，图中能明显区分出LiMn 0.7Fe 0.3PO 4和Li 3V 2(PO 4) 3两种颗粒，颗粒为椭球形。相比较于对比例1的磷酸铁锰锂(LiMn 0.7Fe 0.3PO 4)(图3a～3c)，实施例2的正极材料(图3d-3f)中出现透明褶皱的sp 2型碳(即石墨烯)，且实施例2的正极材料中可以观察到有着明显区别的两种晶格条纹(图3f)，其晶面间距0.427nm和0.214nm分别对应于LMFP的(011)晶面和LVP的(400)晶面。 It can be seen from Figure 2 and Figure 3 that 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. Compared with the lithium iron manganese phosphate (LiMn 0.7 Fe 0.3 PO 4 ) of Comparative Example 1 (Figures 3a-3c), 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.
电池制备：Cell preparation:
电池类型为纽扣电池，型号为CR2032。The battery type is a button cell, model CR2032.
电解液为1mol/L六氟磷酸锂为溶质，溶剂为质量比为1：1：1的碳酸乙烯酯，碳酸甲乙酯，碳酸二甲酯混合而成，并加入1％VC作为成膜添加剂。隔离膜为celgard2400聚丙烯多孔薄膜。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, and 1% VC is added as a film-forming additive. The isolation membrane is celgard2400 polypropylene porous film.
正极片制备：将实施例1提供的正极材料，导电剂C45，粘合剂聚偏氟乙烯按照质量比为8：1：1混合，其中聚偏氟乙烯溶解于N-甲基吡咯烷酮中，质量分数为5％，混合均匀后涂覆在铝箔上，厚度为200μm，60℃真空干燥6小时后，制成直径为Φ12mm的电极片。电极片活性物质负载量为1.5-2.5mg左右。负极片选用纯金属锂片。氩气保护下的手套箱中进行电池组装。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 μm, and vacuum-dried at 60°C for 6 hours to make an electrode sheet with a diameter of Φ12mm. 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.
相应的，以实施例2～3以及对比例1中提供的材料为正极材料，按照相同的方式制备获得电池。Correspondingly, using the materials provided in Examples 2-3 and Comparative Example 1 as positive electrode materials, a battery was prepared in the same manner.
电化学性能测试Electrochemical performance test
测试电压区间：2.2-4.5V。Test voltage range: 2.2-4.5V.
测试电流：1C＝160mA/g。Test current: 1C=160mA/g.
电池测试温度：室温25±2℃。Battery test temperature: room temperature 25±2°C.
参见附图4～6，实施例1～3以及对比例1的电池性能测试结果。Referring to accompanying drawings 4-6, the battery performance test results of Examples 1-3 and Comparative Example 1.
表1A-表1B为实施例1～3以及对比例1的倍率测试结果。Table 1A-Table 1B are the ratio test results of Examples 1-3 and Comparative Example 1.
表1ATable 1A
Figure PCTCN2022099358-appb-000001
Figure PCTCN2022099358-appb-000001
表1BTable 1B
Figure PCTCN2022099358-appb-000002
Figure PCTCN2022099358-appb-000002
相比于对比例1提供的LiMn 0.7Fe 0.3PO 4，实施例1～3提供的正极材料制成的电池，大倍率性能提升明显，循环稳定性更佳。 Compared with the LiMn 0.7 Fe 0.3 PO 4 provided in 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.
另外，从图4可以看出，相比于纯相的LiMn 0.7Fe 0.3PO 4，实施例1～3的曲线出现3.59V和3.68V的新平台，对应于Li 3V 2(PO 4) 3中V的+3/+4可逆变价，而且随着磷酸钒锂预烧粉比例的增加，3.59V和3.68V的平台容量贡献变多，电池的倍率性能提升越多，这是由于随着LVP比例的增多，碳的形态进一步向sp 2型转变。但是实施例3相比于实施例2，可逆比容量出现了一定的损失，这是由于在2.2-4.5V电压区间内，Li 3V 2(PO 4) 3的理论比容量为133mAh g -1，低于LiMn 0.7Fe 0.3PO 4(160mAh g -1)，但仍然可以发现， 0.7LiMn 0.7Fe 0.3PO 4·0.3Li 3V 2(PO 4) 3的循环稳定性和大倍率性能得到了很大的提升。 In addition, it can be seen from Fig. 4 that compared with the pure phase LiMn 0.7 Fe 0.3 PO 4 , the curves of Examples 1-3 show new plateaus of 3.59V and 3.68V, corresponding to Li 3 V 2 (PO 4 ) 3 The +3/+4 reversible price of medium V, and with the increase of the proportion of lithium vanadium phosphate calcined powder, the contribution of the platform capacity of 3.59V and 3.68V increases, and the higher the rate performance of the battery is, this is due to the With the increase of the proportion of LVP, the form of carbon further changes to sp 2 type. However, compared with Example 2, 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.
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.
以上所述实施例仅表达了本申请的几种实施例，其描述较为具体和详细，但并不能因此而理解为对申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of protection of the patent application should be based on the appended claims.

Claims (14)

  1. 一种正极材料，其特征在于，包括：A positive electrode material, characterized in that it comprises:
    基体；及substrate; and
    包覆在所述基体外的石墨烯，Graphene coated outside the matrix,
    其中，所述基体的材料包括磷酸铁锰锂和磷酸钒锂。Wherein, the material of the matrix includes lithium iron manganese phosphate and lithium vanadium phosphate.
  2. 根据权利要求1所述的正极材料，其特征在于，所述磷酸铁锰锂由化学式LiMn 1-yFe yPO 4表示，其中0<y≤0.9，所述磷酸钒锂由化学式Li 3V 2(PO 4) 3表示。 The positive electrode material according to claim 1, wherein the lithium iron manganese phosphate is represented by the chemical formula LiMn 1-y Fe y PO 4 , wherein 0<y≤0.9, and the lithium vanadium phosphate is represented by the chemical formula Li 3 V 2 (PO 4 ) 3 means.
  3. 根据权利要求1或2所述的正极材料，其特征在于，所述磷酸铁锰锂的化学式为LiMn 0.7Fe 0.3PO 4。 The positive electrode material according to claim 1 or 2, characterized in that the chemical formula of the lithium iron manganese phosphate is LiMn 0.7 Fe 0.3 PO 4 .
  4. 根据权利要求1～3任一项所述的正极材料，其特征在于，所述磷酸钒锂和磷酸铁锰锂的质量比为x:(1-x)，其中，0＜x≤0.3。The positive electrode material according to any one of claims 1 to 3, wherein the mass ratio of the lithium vanadium phosphate to lithium iron manganese phosphate is x:(1-x), wherein 0<x≤0.3.
  5. 根据权利要求1～4任一项所述的正极材料，其特征在于，基于正极材料的总重量，所述石墨烯含量为2wt％～3wt％。The positive electrode material according to any one of claims 1-4, characterized in that, based on the total weight of the positive electrode material, the graphene content is 2wt%-3wt%.
  6. 根据权利要求1～5任一项所述的正极材料，其特征在于，所述石墨烯原位生成在所述基体表面。The positive electrode material according to any one of claims 1 to 5, characterized in that the graphene is formed in situ on the surface of the substrate.
  7. 根据权利要求1～6任一项所述的正极材料，其特征在于，所述正极材料为类椭球形的颗粒，颗粒的尺寸为100nm～150nm。The positive electrode material according to any one of claims 1 to 6, characterized in that the positive electrode material is ellipsoidal particles with a size of 100 nm to 150 nm.
  8. 一种如权利要求1～7任一项所述的正极材料的制备方法，其特征在于，包括以下步骤：A method for preparing a positive electrode material according to any one of claims 1 to 7, characterized in that it comprises the following steps:
    将锂源、钒源、磷源和第一碳源按照预定比例混合，得到所述磷酸钒锂的前驱体；mixing the lithium source, the vanadium source, the phosphorus source and the first carbon source according to a predetermined ratio to obtain the precursor of the lithium vanadium phosphate;
    将所述磷酸钒锂的前驱体在惰性气氛下进行烧结处理，得到磷酸钒锂预烧粉；Sintering the precursor of the lithium vanadium phosphate under an inert atmosphere to obtain calcined powder of lithium vanadium phosphate;
    将所述磷酸钒锂预烧粉、磷酸铁锰锂和第二碳源按照预定比例混合，得到正极材料前驱体；Mixing the lithium vanadium phosphate calcined powder, lithium iron manganese phosphate and a second carbon source according to a predetermined ratio to obtain a positive electrode material precursor;
    将所述正极材料前驱体在惰性气氛下进行烧结处理，得到正极材料。The positive electrode material precursor is sintered in an inert atmosphere to obtain the positive electrode material.
  9. 根据权利要求8所述的正极材料的制备方法，其特征在于，所述锂源为磷酸二氢锂、硝酸锂、醋酸锂、氢氧化锂中的至少一种，所述钒源为五氧化二钒、三氧化二钒、二氧化钒和偏钒酸铵中一种或多种，所述磷源为磷酸铵、磷酸二氢铵、磷酸氢二铵、磷酸中的至少一种。The method for preparing positive electrode materials according to claim 8, wherein the lithium source is at least one of lithium dihydrogen phosphate, lithium nitrate, lithium acetate, and lithium hydroxide, and the vanadium source is dihydrogen pentoxide One or more of vanadium, vanadium trioxide, vanadium dioxide and ammonium metavanadate, and the phosphorus source is at least one of ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphoric acid.
  10. 根据权利要求8或9所述的正极材料的制备方法，其特征在于，所述第一碳源为含碳化合物，所述含碳化合物包括糖类、有机酸、有机酸醋、小分子醇和其它含碳高分子 化合物中的一种或多种。The preparation method of positive electrode material according to claim 8 or 9, characterized in that, the first carbon source is a carbon-containing compound, and the carbon-containing compound includes sugars, organic acids, organic acid esters, small molecule alcohols and other One or more of carbon-containing polymer compounds.
  11. 根据权利要求8～10任一项所述的正极材料的制备方法，其特征在于，所述第二碳源为葡萄糖、聚乙烯醇、聚丙烯醇、聚丁烯醇中的一种或多种。The method for preparing positive electrode materials according to any one of claims 8 to 10, wherein the second carbon source is one or more of glucose, polyvinyl alcohol, polypropylene alcohol, and polybutenol .
  12. 根据权利要求8～11任一项所述的正极材料的制备方法，其特征在于，对所述磷酸钒锂的前驱体进行烧结时，烧结温度为300℃～400℃，烧结时间为4小时～6小时。The method for preparing positive electrode materials according to any one of claims 8 to 11, characterized in that, when the precursor of lithium vanadium phosphate is sintered, the sintering temperature is 300° C. to 400° C., and the sintering time is 4 hours to 4 hours. 6 hours.
  13. 根据权利要求8～12任一项所述的正极材料的制备方法，其特征在于，对所述正极前驱体进行烧结时，烧结温度为650℃～800℃，烧结时间为8小时～16小时。The method for preparing a positive electrode material according to any one of claims 8 to 12, characterized in that, when the positive electrode precursor is sintered, the sintering temperature is 650° C. to 800° C., and the sintering time is 8 hours to 16 hours.
  14. 一种锂离子电池，其特征在于，包括正极，所述正极包括权利要求1～7任一项所述的正极材料。A lithium ion battery, characterized in that it comprises a positive electrode, and the positive electrode comprises the positive electrode material according to any one of claims 1-7.
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