CN114430027A - Positive electrode composite material, preparation method thereof and lithium ion battery - Google Patents
Positive electrode composite material, preparation method thereof and lithium ion battery Download PDFInfo
- Publication number
- CN114430027A CN114430027A CN202011171510.7A CN202011171510A CN114430027A CN 114430027 A CN114430027 A CN 114430027A CN 202011171510 A CN202011171510 A CN 202011171510A CN 114430027 A CN114430027 A CN 114430027A
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- positive electrode
- conductive agent
- composite material
- lithium iron
- manganese phosphate
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- 239000002131 composite material Substances 0.000 title claims abstract description 71
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 16
- 238000002360 preparation method Methods 0.000 title abstract description 10
- 239000000463 material Substances 0.000 claims abstract description 148
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 60
- 239000006258 conductive agent Substances 0.000 claims abstract description 58
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 43
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims abstract description 39
- 239000011247 coating layer Substances 0.000 claims abstract description 32
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000011572 manganese Substances 0.000 claims abstract description 26
- 239000013078 crystal Substances 0.000 claims abstract description 24
- 238000002441 X-ray diffraction Methods 0.000 claims abstract description 13
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 13
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- 229910052727 yttrium Inorganic materials 0.000 claims description 2
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- 238000007499 fusion processing Methods 0.000 claims 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract description 10
- 238000005056 compaction Methods 0.000 abstract description 7
- 238000001228 spectrum Methods 0.000 abstract description 6
- 230000000052 comparative effect Effects 0.000 description 19
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- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 6
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
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- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
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- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- 229910000616 Ferromanganese Inorganic materials 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
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- DALUDRGQOYMVLD-UHFFFAOYSA-N iron manganese Chemical compound [Mn].[Fe] DALUDRGQOYMVLD-UHFFFAOYSA-N 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 2
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- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
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- 229910013716 LiNi Inorganic materials 0.000 description 1
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- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 1
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- 238000010521 absorption reaction Methods 0.000 description 1
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
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- 235000010323 ascorbic acid Nutrition 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
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- 230000008859 change Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
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- 239000011258 core-shell material Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
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- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 229940071264 lithium citrate Drugs 0.000 description 1
- WJSIUCDMWSDDCE-UHFFFAOYSA-K lithium citrate (anhydrous) Chemical compound [Li+].[Li+].[Li+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O WJSIUCDMWSDDCE-UHFFFAOYSA-K 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
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- 150000003624 transition metals Chemical group 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Composite Materials (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application provides a positive electrode composite material, which comprises a lithium iron manganese phosphate material and a coating layer coated on the surface of the lithium iron manganese phosphate material, wherein the coating layer comprises a high-nickel ternary material, and the half-peak width of a (003) crystal plane diffraction peak in an XRD (X-ray diffraction) spectrum of the high-nickel ternary material is less than or equal to 0.09 degrees; the coating layer is also doped with a first conductive agent which is in a linear shape and/or a planar shape, the linear first conductive agent comprises at least one of carbon fibers and carbon nanotubes, and the planar first conductive agent comprises at least one of graphene and graphite micro-sheets. Through the arrangement of the high-nickel ternary material coating layer and the first conductive agent, the manganese dissolving phenomenon of the lithium iron manganese phosphate material is effectively improved, the structural stability is improved, and the conductivity is improved under the condition that the compaction density of the pole piece is not reduced. The application also provides a preparation method of the positive electrode composite material, a positive electrode plate and a lithium ion battery.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a positive electrode composite material, a preparation method thereof and a lithium ion battery.
Background
As an important component of lithium ion batteries, the selection of the positive electrode material directly affects the performance of the lithium ion battery. Lithium iron manganese phosphate (LMFP) is the mainstream positive electrode material of lithium ion batteries because of high potential, high safety and high cycle performance stability. However, in the actual preparation process of the battery, a certain amount of moisture inevitably exists in the electrolyte, and the moisture causes hydrolysis of lithium salts such as lithium hexafluorophosphate in the electrolyte to generate HF in the electrolyte, which accelerates elution of manganese element in LMFP (particularly, when the molar ratio of Mn to the sum of Mn and Fe is 65% or more), and further lowers the structural stability of LMFP and battery cycle performance.
Disclosure of Invention
In view of this, the present application provides a positive electrode composite material, in which a layer of high-nickel ternary material with high stability is coated on the surface of an LMFP material, and a linear and/or planar first conductive agent is doped in the coating layer, so that the occurrence of a manganese dissolution phenomenon of the LMFP material can be effectively improved, the structural stability of the LMFP material is improved, the conductivity of the LMFP material is improved, and further, the electrical performance of a lithium ion battery is improved.
In a first aspect, the application provides a positive electrode composite material, which is characterized by comprising a lithium iron manganese phosphate material and a coating layer coated on the surface of the lithium iron manganese phosphate material, wherein the coating layer comprises a high-nickel ternary material, and the half-peak width of a (003) peak in an XRD (X-ray diffraction) spectrum of the high-nickel ternary material is less than or equal to 0.09 degrees; the coating layer is further doped with a first conductive agent, the first conductive agent is linear and/or planar, the linear first conductive agent comprises at least one of carbon fibers and carbon nanotubes, and the planar first conductive agent comprises at least one of graphene and graphite micro-sheets.
In the application, a layer of high-nickel ternary material is coated on the surface of the LMFP material, so that the LMFP can be prevented from directly contacting with the electrolyte, the high-nickel ternary material absorbs moisture in the electrolyte, further the formation of HF in the electrolyte is inhibited, the structure of the LMFP material is stabilized, the manganese dissolution of the LMFP is reduced, the integral positive electrode composite material has higher structural stability, and the cycle performance of the composite material is improved; secondly, the high nickel ternary material is a single crystal material, the structural stability is high, and the existence of the LMFP can also slow down the phase transition of the high nickel ternary material from H2 to H3, so that the structural stability of the high nickel ternary material can be further improved. And the linear and/or planar first conductive agent is introduced into the coating layer, so that the conductivity of the coating layer can be improved, the positive electrode composite material is endowed with good rate performance, and the compacted density of a pole piece prepared from the positive electrode composite material is not reduced.
In a second aspect, the present application provides a method for preparing a positive electrode composite material, comprising:
dispersing a lithium iron manganese phosphate material, a high-nickel ternary material and a first conductive agent in a solvent to obtain a mixed material;
and (3) carrying out fusion treatment on the mixed materials in a mechanical fusion machine, and then drying to obtain the positive electrode composite material according to the first aspect of the application.
The preparation method of the cathode composite material is simple, strong in operability and suitable for large-scale production, and the cathode composite material with the excellent rate performance and cycle performance can be prepared.
In a third aspect, the present application provides a positive plate, the positive plate includes a current collector and a positive electrode material layer disposed on the current collector, the positive electrode material layer includes the positive electrode composite material of the first aspect of the present application, and a second conductive agent and a binder.
The positive plate provided by the third aspect of the application has low resistivity and high compaction density.
In a fourth aspect, the present application provides a lithium ion battery comprising the positive electrode sheet according to the third aspect of the present application.
The lithium ion battery provided by the fourth aspect of the present application has excellent structural stability and electrochemical properties, and is beneficial to wide application.
Drawings
Fig. 1 is a schematic structural diagram of a positive electrode composite material provided in an embodiment of the present application.
FIG. 2 shows LiNi, a high-nickel ternary material used in the examples of the present application083Co0.12Mn0.05X-ray diffraction (XRD) spectrum of (a).
Detailed Description
The technical solutions of the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.
Referring to fig. 1, an embodiment of the present application provides a positive electrode composite material, which has a core-shell structure and includes a lithium iron manganese phosphate material 10 (serving as a core) and a coating layer 20 coated on a surface of the lithium iron manganese phosphate material 10. The coating layer 20 comprises a high-nickel ternary material which is a single crystal material, and the half-peak width of the (003) peak in the XRD pattern is less than or equal to 0.09 degrees. The coating layer 20 is further doped with a first conductive agent 30, and the first conductive agent 30 is linear and/or planar, wherein the linear first conductive agent includes at least one of carbon fibers and carbon nanotubes, and the planar first conductive agent includes at least one of graphene and graphite micro-sheets.
In the application, a layer of high-nickel ternary single crystal material is coated on the surface of the LMFP material, and therefore the coating layer can prevent the LMFP from directly contacting with the electrolyte, the high-nickel ternary single crystal material has better water absorbability, can absorb water in the electrolyte, inhibit the formation of HF in the electrolyte, stabilize the structure of the LMFP material, improve the problem of manganese dissolution of the LMFP material, enable the integral anode composite material to have higher structural stability, and improve the cycle performance of the anode composite material. Secondly, compared with the high nickel ternary material in the form of an aggregate, the high nickel ternary material in the form of a single crystal has higher structural stability, and a voltage synergistic effect exists between the high nickel ternary material and the LMFP material, so that the phase change of the high nickel ternary material from H2 to H3 can be slowed down by the existence of the LMFP, the structural stability of the high nickel ternary material can be further improved, and the high nickel ternary material has higher stability in the battery cycle process.
Wherein the structural general formula of the high-nickel ternary material is LiNixCoyMzWherein M is at least one of Mn, Al, Zr, Ti, Y, Sr and W, x is more than or equal to 0.70 and less than or equal to 0.98, and x is more than or equal to 0.70 and less than or equal to 0.98<y<1，0<z<1, and x + y + z is 1. Preferably, 0.80. ltoreq. x.ltoreq.0.90, more preferably 0.83. ltoreq. x.ltoreq.0.88. When the value of x is higher, the ternary material can be called as a high-nickel ternary single crystal material, has higher specific capacity and better rate performance, and is very easy to adsorb moisture due to high alkalinity. Preferably, y satisfies: y is more than or equal to 0.01 and less than or equal to 0.33, and z satisfies the following condition: z is more than or equal to 0.01 and less than or equal to 0.33.
In the application, the half-peak width of the (003) plane diffraction peak in the XRD spectrum of the high-nickel ternary material is less than or equal to 0.09 degrees (see figure 2). Wherein, the (003) plane diffraction peak corresponds to the distribution position of transition metals (Ni, Co and Mn). The lower half-peak width indicates that the high nickel ternary material has extremely high crystallinity, is a single crystal material and is not an aggregate. The single crystal type high nickel ternary material has high crystallization degree and high structural stability, can still maintain a stable structure after absorbing water, and has long cycle performance. The lithium iron manganese phosphate material 10 is coated by a single-crystal high-nickel ternary material, so that the obtained positive electrode composite material has good cycle performance.
Optionally, the high nickel ternary material has a particle size of 3.5-5.5 μm.
In the application, the lithium iron manganese phosphate material 10 may be an aggregate, may also be a single crystal-like material, and may also be a mixture of an aggregate and a single crystal-like material. The LMFP material in the single-crystal-like form is composed of one or a few (no more than 5) LMFP primary particles with few internal grain boundaries. The LMFP material in the form of an agglomerate is a secondary particle material formed by agglomeration of a plurality of primary particles of LMFP, with many internal grain boundaries.
Optionally, the ferromanganese molar ratio (Mn/Fe ratio) in the lithium iron manganese phosphate material 10 is in the range of 1.0-7.4. At this time, the battery made of the positive electrode composite material has a high discharge plateau.
Alternatively, the particle size D50 of the LMFP aggregate may be 10 to 15 μm, and the particle size D50 of the LMFP-like single crystal may be 1.2 to 2.5 μm. The LMFP aggregate has larger grain diameter, so that the grain diameter of the primary particles forming the LMFP aggregate is not too small, the specific surface area is not too large, and the LMFP aggregate has higher structural stability.
Optionally, the thickness of the coating layer 20 is 1/50-1/15 of the particle size D50 of the lithium iron manganese phosphate material 10. For example, when the lithium iron manganese phosphate material 10 is an aggregate, the thickness of the coating layer 20 may be 200 to 1000 nm; when the lithium iron manganese phosphate material 10 is a mono-like crystal, the thickness of the coating layer 20 may be 10 to 80 nm. The coating layer 20 has a suitable thickness, which not only can effectively coat the lithium iron manganese phosphate material 10, but also can prevent the ternary material and the lithium iron manganese phosphate material 10 from being separated into two phases, and the thickness can make the positive electrode composite material have good structural stability, higher ionic conductivity and electronic conductivity.
In one embodiment of the present application, the coating layer 20 completely coats the lithium iron manganese phosphate material 10 to avoid the dissolved manganese in the core as much as possible.
Optionally, the positive electrode composite material satisfies: l is1＝a×D50(ii) a Wherein L is1A length of the linear first conductive agent or a maximum lateral dimension of the planar first conductive agent, in μm; d50The particle size D50 of the lithium iron manganese phosphate material 10 is expressed in μm, wherein a is in a range of 2-3.
Among them, the linear first conductive agent (carbon fiber, carbon nanotube, etc.) has a large aspect ratio and a long length, and the above-mentioned L is for the carbon nanotube1And may particularly refer to its tube length. The planar first conductive agent (graphene, graphite micro-flake, etc.) has a large lateral dimension, and its longitudinal dimension (i.e., thickness) is generally lower than its lateral dimension. The transverse dimension is the length, width or side length of the planar conductive agent, and the maximum value is taken. For example, when the planar conductive agent is a parallelogram, its lateral dimension is the maximum of its length and width, and when the planar conductive agent is an irregular shape, its lateral dimension is its maximum side length.
When the a is controlled within the range, the first conductive agent with certain flexibility can be relatively and completely coated among primary particles of the LMFP to form a proper continuous electron conduction path, and the conductive agent is not easy to agglomerate, so that the electron conductivity of the surface of the LMFP material is obviously improved, and the compaction density of a pole piece prepared from the positive pole composite material is not influenced.
Further optionally, when the LMFP is an agglomerate, the positive electrode composite material satisfies: l is1＝b×D50 1(ii) a Wherein L is1The meaning of is as defined above, but here L1In nm, D50 1Represents the particle size D50 in nm of the primary particles of the LMFP agglomerates; said D50 1The value range of b is 10-30 within the range of 100-300 nm. Wherein control D50 1In the range of 100-300nm, the LMFP aggregate has higher structural stability. And b is controlled within the range of 10-30, so that the first conductive agent 30 can be prevented from agglomerating in the coating layer 20, a proper electronic continuous conduction path can be formed, and the electronic conductivity of the surface of the cathode composite material is greatly improved.
Optionally, the mass of the first conductive agent 30 accounts for 0.2% -1.5% of the sum of the mass of the ternary single crystal material and the mass of the lithium iron manganese phosphate material 10. Preferably 0.5% to 0.8%. The addition amount of the first conductive agent 30 is small, but the electronic conductivity of the surface of the positive electrode composite material can be obviously improved, and the capacity exertion and the rate capability improvement of the material are facilitated; meanwhile, the first conductive agent has certain flexibility, and when a small amount of the first conductive agent is properly added, the tap density of the positive electrode composite material is basically not influenced, so that the compact density of a pole piece made of the positive electrode composite material is not reduced, and the energy density of the battery is not reduced.
Optionally, the ternary single crystal material accounts for 1% -10% of the sum of the mass of the ternary single crystal material and the lithium iron manganese phosphate material 10. Preferably 2 to 8 percent. The effective coating can be realized by proper mass ratio of the ternary single crystal material, the structural stability of the anode composite material is ensured, and the voltage platform of the anode composite material cannot be reduced.
Optionally, in the positive electrode composite material, the lithium iron manganese phosphate material accounts for 90-99 parts by weight, the ternary single crystal material accounts for 1-10 parts by weight, and the first conductive agent accounts for 0.2-1.5 parts by weight. Further, the weight part of the lithium iron manganese phosphate material can be 92-98 parts, the weight part of the ternary single crystal material can be 2-8 parts, and the weight part of the first conductive agent can be 0.5-0.8 part.
The lithium iron manganese phosphate material 10 serves as a main component of the core of the positive composite material, a higher voltage platform and energy density can be given to the positive composite material, the lithium iron manganese phosphate material is coated by a ternary single crystal material, the manganese dissolving phenomenon of the core can be effectively relieved, the structural stability of the positive composite material is greatly improved, the cycle performance is improved, the conductivity of the positive composite material can be improved by introducing a first conductive agent, and the multiplying power performance of the positive composite material is improved.
Optionally, in this embodiment of the application, before the lithium iron manganese phosphate material 10 is coated with the ternary single crystal material, the surface of the lithium iron manganese phosphate material 10 further has a carbon coating layer, so that the conductivity of the core is further improved.
Correspondingly, the application also provides a preparation method of the cathode composite material, and the cathode composite material is prepared. Wherein, the preparation method comprises the following steps:
s01, dispersing the lithium iron manganese phosphate material, the high-nickel ternary material and the first conductive agent in a solvent to obtain a mixed material;
and S02, fusing the mixed materials in a mechanical fusion machine, and drying to obtain the cathode composite material.
Alternatively, in step S01, the solvent may be one or more of N-methylpyrrolidone (NMP), Dimethylformamide (DMF), Dimethylsulfoxide (DMSO), acetone, anhydrous ethanol, isopropanol, and the like, but is not limited thereto.
Optionally, in step S02, the rotation speed of the mechanical fusion machine is 4000-7000r/min, preferably 4500-6500 r/min.
Optionally, the time of the fusion treatment is 10-30 min. Preferably 15-25 min.
Optionally, in step S02, the temperature of the drying treatment is 80 to 120 ℃, preferably 90 to 110 ℃, more preferably 95 to 105 ℃. The drying treatment time may be 0.5 to 2.5 hours, preferably 1 to 2 hours. The drying treatment is mainly used for removing the above solvent.
In an embodiment of the application, the lithium iron manganese phosphate material can be prepared by the following steps:
(1) mixing raw materials (a manganese source, an iron source, a phosphorus source, a lithium source and a carbon source) for synthesizing LMFP according to a certain mass ratio, adding water, and grinding by a wet method until the particle size of the materials is not more than 60 nm;
(2) spray drying the ground wet material to obtain dry powder;
(3) sintering the dried powder under the atmosphere of oxygen concentration less than 150 ppm;
(4) and (3) airflow crushing the sintered material, and screening and grading to obtain the LMFP material with the required median particle size D50.
Wherein, in the step (1), ferromanganese phosphate can be selected as a manganese source, an iron source and a phosphorus source at the same time. The lithium source may include at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate, and lithium acetate, but is not limited thereto. The carbon source includes at least one of glucose, sucrose, starch, fructose, citric acid, ascorbic acid, and polyethylene glycol, but is not limited thereto.
Optionally, in the step (1), the wet ball milling may include: grinding with 0.6-0.8mm grinding medium until the particle size of the material is below 50 μm, and grinding with 0.1-0.3mm grinding medium until the particle size of the material is below 60nm (such as 40-60nm, preferably 20-30 nm).
Alternatively, in the above step (2), the inlet temperature at the time of spray drying may be 150 to 200 ℃, preferably 160 to 180 ℃.
Optionally, in the step (3), the sintering process may include a first temperature-raising section, a first constant-temperature section, a second temperature-raising section, a second constant-temperature section, and a temperature-lowering section in sequence; wherein the first temperature rising section is heated from room temperature to a first constant temperature (such as 400 ℃), and the temperature rising time can be 2.5-3.5 h; the constant temperature time of the first constant temperature section is 3.5-5.5 h; the second temperature rising section is used for rising the temperature from the first constant temperature (such as 400 ℃) to the second constant temperature (such as 600-800 ℃), and the temperature rising time can be 2.5-4.0 h; the constant temperature time of the second constant temperature section can be 2.5-4.5 h; the temperature reduction section is used for reducing the temperature from the second constant temperature to about 50 ℃ for 5.5-7.5 h.
Optionally, in the step (4), the pressure of the airflow crushing can be 3-10MPa, and the time can be 2-3 h.
The difference of the preparation method for preparing the LMFP material in the form of the quasi-single crystal and the LMFP material in the form of the aggregate is that: the first constant temperature and the second constant temperature are different during sintering; the pressure at which the air stream breaks up is different. For example, in preparing the LMFP material in a mono-like form, the first constant temperature may be 450 ℃ and the second constant temperature may be 750 ℃; the pressure during the airflow crushing can be 5-8 MPa. When preparing the LMFP material in the form of agglomerates, the first constant temperature may be 400 ℃, and the second constant temperature may be 700 ℃; the pressure during the airflow crushing can be 3-5 MPa.
The preparation method of the cathode composite material is simple, strong in operability and suitable for large-scale production, and the cathode composite material with the excellent rate performance and cycle performance can be prepared.
Correspondingly, the embodiment of the application also provides a positive plate, which comprises a current collector and a positive material layer arranged on the current collector, wherein the positive material layer comprises the positive composite material, a second conductive agent and a binder.
The positive electrode material layer can be formed by coating and drying positive electrode slurry containing the positive electrode composite material, a second conductive agent, a binder and a solvent. When preparing the anode slurry, the binder and the solvent are mixed, the mixture is fully stirred, then the conductive agent is added, the anode composite material is added after stirring, and the mixture is sieved after stirring.
Wherein, the second conductive agent and the binder are conventional choices in the battery field. For example, the binder may be selected from one or more of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), Styrene Butadiene Rubber (SBR), Polyacrylonitrile (PAN), Polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethylcellulose (CMC), and sodium alginate. The PVDF may refer to a copolymer obtained by copolymerizing vinylidene fluoride and an olefin compound containing a polar group, where the polar group includes at least one of a carboxyl group, an epoxy group, a hydroxyl group, and a sulfonic group, and the presence of the polar group may enhance the peel strength between the positive electrode material layer and the current collector.
For example, the second conductive agent may include at least one of carbon nanotubes, carbon black and graphene, and preferably, the conductive agent includes three of carbon nanotubes, carbon black and graphene, and the conductive agent with three dimensions may provide better conductivity to the positive electrode material layer. Further, the mass ratio of the carbon nanotubes, the carbon black and the graphene may be 6: 5: 2.
the positive plate containing the positive electrode composite material has low resistivity and high compaction density. Optionally, the positive plate has a compacted density of 2.68g/cm3Above, preferably 2.75g/cm3The above.
The embodiment of the application also provides a lithium ion battery, and the lithium ion battery comprises the positive plate. The lithium ion battery comprises the positive plate, a negative plate, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are positioned between the positive plate and the negative plate. The lithium ion battery has excellent electrical properties such as high capacity, low probability of manganese dissolution, high cycle stability and the like.
The following further describes the examples of the present application in connection with a number of examples.
Example 1
A positive electrode composite material comprises an LMFP material and a coating layer coated on the surface of the LMFP material, wherein the coating layer comprises a ternary material NCX, and the half-peak width of a (003) crystal plane diffraction peak in an XRD (X-ray diffraction) spectrum of the ternary material is less than or equal to 0.09 degrees; the cladding layer is also doped with a first conductive agent. Wherein the parts by weight of LMFP, NCX and the first conductive agent are shown in Table 1, and L of the first conductive agent1Is a times the particle size of the D50 of the LMFP material, and the value of a is shown in table 1.
Positive electrode composites of other examples are provided, respectively, according to the parameters provided in table 1.
Preparing a positive plate: adding an organic solvent NMP and a binder PVDF into a stirrer according to a certain proportion, stirring for 1h, adding a conductive agent (specifically, a mixture of carbon tubes, carbon black and graphene in a mass ratio of 0.6: 0.5: 0.2), stirring for 30min, adding the positive electrode composite materials of the embodiments, stirring for 1.5h, and sieving to obtain the positive electrode slurry of the embodiments. Wherein, in the anode slurry, the mass ratio of the anode composite material to the conductive agent, the binder PVDF and the organic solvent NMP is 100: 2: 30.
The positive electrode slurry of each example was coated on both side surfaces of an aluminum foil, respectively, and after drying, a positive electrode material layer was formed on the aluminum foil to obtain an unpressurized positive electrode sheet, which was made to a size of 40 × 100mm, and then tabletted with a wild tableting machine to obtain a tabletted positive electrode sheet. The density of the two sides can be set to 400g/dm according to the density of the pole piece2) And the thickness after tabletting, calculating the compaction density of the pole piece, and testing the longitudinal resistivity of the pole piece, wherein the results are summarized in table 2.
The test mode of the longitudinal resistivity of the positive plate is as follows: the positive electrode slurry prepared in each example was applied to one surface of an aluminum foil to obtain a single-sided surface density of 200g/dm2The positive electrode sheet of (1); the positive electrode material layer was peeled off from the foil by means of an adhesive tape, cut into a circular sheet having a diameter of 1.5cm, and tested on a BER1300 sheet resistance meter to obtain the longitudinal resistivity of the sheet of each example. Wherein, the lower the longitudinal resistivity of the pole piece is, the stronger the conductivity of the pole piece is.
Preparing a battery: the positive electrode slurry according to each example was prepared to have an areal density of 2.0g/dm2The compacted density is 2.65g/cm3The single-sided positive electrode sheet of (1) is used to manufacture a 2025 button cell from each single-sided positive electrode sheet.
The positive electrode slurry according to each example was prepared to have an areal density of 4.0g/dm2The compacted density is 2.65g/cm3The double-sided positive plate; further, an areal density of 2.1g/dm is provided2The compacted density of the powder is 1.60g/cm3The double-sided negative plate; the diaphragm adopts PP membrane, assembles 053450 full cell.
The trigger temperature of thermal runaway of each button cell was tested, the cycle performance of each full cell and the amount of Mn dissolved in the negative electrode during the cycle were tested, and the results are summarized in table 2.
The method for testing the trigger temperature of the thermal runaway of the anode material comprises the following steps: the button cell corresponding to each embodiment is fully charged to enable the positive plate to be in a complete lithium removal state, then the button cell is disassembled, the positive plate is taken out, the positive material on the positive plate and the electrolyte are mixed according to a certain mass ratio and then placed in a high-temperature crucible, the temperature is raised at a certain temperature raising speed (3 ℃/min), and a thermogram of the battery is tested by a Differential Scanning Calorimeter (DSC) to observe the trigger temperature of the positive material due to thermal runaway.
The method for testing the capacity retention rate of the resin at 45 ℃ for 2000 weeks comprises the following steps: at 45 ℃, the full cell corresponding to each example is charged by a constant current of 1C to a voltage of 4.1V, and the cutoff current is 0.05C; and then discharging at constant current under 1C until the voltage is 2.5V, and after the charge-discharge cycle is carried out for 2000 weeks, calculating the ratio of the discharge capacity of the 2000 th circle of the battery to the discharge capacity of the first circle of the battery, and taking the ratio as the capacity retention rate of the 2000 weeks of the battery cycle.
The method for testing the Mn dissolving amount of the negative electrode comprises the following steps: the full cell corresponding to each example was charged at 45 ℃ at a constant current of 1C to a voltage of 4.1V and an off current of 0.05C; then discharging at constant current under 1C to voltage of 2.5V, after the charge-discharge cycle is carried out for 2000 weeks, disassembling the battery, taking out the negative electrode material of the negative electrode plate, and testing the content of Mn dissolved out from the negative electrode material; wherein the content of Mn is measured using an inductively coupled plasma-emission spectrometer (ICP).
In addition, in order to highlight the beneficial effects of the technical scheme of the application, the positive electrode composite materials of comparative examples 1-5 are also provided, the parameters of the positive electrode composite materials are summarized in table 1 (except comparative example 5), and the performances of the pole piece and the battery prepared from the positive electrode composite materials are summarized in table 2. Wherein, the half-peak widths of the (003) plane diffraction peaks in the XRD spectrums of the ternary materials used in the examples and the comparative examples in the table 1 are all less than or equal to 0.09 degrees; the half-peak width of the diffraction peak of the (003) plane in the XRD pattern of the ternary material used in the comparative example 5 is more than 0.09 degrees, and the ternary material is an aggregate material. Wherein, in examples 1-5, 9-10 and comparative examples 1, 3-5, the structural formula of the ternary material NCX is LiNi0.83Co0.12Mn0.05O2The formula of the ternary material NCX in examples 6 to 8 is LiNi0.88Co0.09Mn0.03O2The formula of the ternary material NCX in comparative example 2 is LiNi0.55Co0.15Mn0.30O2。
TABLE 1 parameters of positive electrode composite materials in examples and comparative examples
TABLE 2 PERFORMANCE PARAMETERS OF POSITIVE-ELECTRODE SHEETS AND BATTERIES OF EXAMPLES AND COMPARATIVE EXAMPLES
As can be seen from table 2, from comparison between comparative example 1 and example 1, when only LMFP was used as the positive electrode active material (comparative example 1), the content of Mn eluted from the negative electrode material after 2000 cycles of the battery was extremely high, and the capacity retention rate of the battery was also extremely low. In the embodiments 1 to 10, after the LMFP is coated with the high-nickel ternary material NCX and the specific first conductive agent is introduced into the coating layer, the performances of the obtained battery can be improved, and the positive plate has good conductivity and high compaction density. As is clear from comparison between comparative example 5 and example 1, if the ternary material used is not a single crystal material (comparative example 2), the stability of the high nickel ternary material based on the form of agglomerates is poor, the Mn content eluted in the negative electrode material increases, the capacity retention rate of the battery greatly decreases, and the DSC trigger temperature of the positive electrode composite material also decreases. In addition, as is clear from comparison between comparative example 2 and example 4, when the ternary material used is a low nickel ternary material (comparative example 2), the low nickel ternary material has a lower basicity than the high nickel ternary material, and therefore has a weak water absorption ability, and has a weak effect of suppressing HF in the electrolyte solution, and further has a high Mn content eluted from the negative electrode material.
As can be seen from comparison of comparative examples 3 to 4 with example 1, when the coating layer in the positive electrode composite material does not contain a conductive agent, the conductivity of the positive electrode composite material is slightly poor, the resistivity of the positive electrode sheet is high (comparative example 3), the polarization phenomenon of the battery is severe, the capacity loss of the battery due to polarization is large, and the cycle performance is deteriorated; when the conductive agent contained in the coating layer in the positive electrode composite material is not in a linear and/or planar form (for example, graphite in a granular form, comparative example 4), although the resistivity of the positive electrode sheet in comparative example 4 is lowered as compared with comparative example 3, the compaction density of the obtained positive electrode sheet is lower than that of the positive electrode sheet in example 1.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (12)
1. The positive electrode composite material is characterized by comprising a lithium iron manganese phosphate material and a coating layer coated on the surface of the lithium iron manganese phosphate material, wherein the coating layer comprises a high-nickel ternary material, and the half-peak width of a (003) crystal plane diffraction peak in an XRD (X-ray diffraction) pattern of the high-nickel ternary material is less than or equal to 0.09 degrees; the coating layer is further doped with a first conductive agent, the first conductive agent is linear and/or planar, the linear first conductive agent comprises at least one of carbon fibers and carbon nanotubes, and the planar first conductive agent comprises at least one of graphene and graphite micro-sheets.
2. The positive electrode composite material according to claim 1, wherein the coating layer has a thickness of 1/50 to 1/15 of the particle size D50 of the lithium iron manganese phosphate material.
3. The positive electrode composite material according to claim 2, wherein the lithium iron manganese phosphate material is an aggregate and/or a single crystal-like material, wherein the particle size D50 of the aggregate is 10 to 15 μm, and the particle size D50 of the single crystal-like material is 1.2 to 2.5 μm.
4. The positive electrode composite material according to claim 3, wherein when the lithium iron manganese phosphate material is an aggregate, the coating layer has a thickness of 200 to 1000 nm; when the lithium iron manganese phosphate material is a monocrystal-like material, the thickness of the coating layer is 10-80 nm.
5. The positive electrode composite material according to claim 1, wherein the positive electrode composite material satisfies: l is1＝a×D50；
Wherein, L is1A length of the linear first conductive agent or a maximum lateral dimension of the planar first conductive agent, and the unit is μm; said D50The unit of the particle size D50 of the lithium iron manganese phosphate material is μm; the value range of the a is 2-3.
6. The positive electrode composite material according to claim 1, wherein the high-nickel ternary material accounts for 1% -10% of the sum of the mass of the high-nickel ternary material and the mass of the lithium iron manganese phosphate material.
7. The positive electrode composite material according to claim 1, wherein the mass of the first conductive agent is 0.2 to 1.5% of the sum of the mass of the high-nickel ternary material and the mass of the lithium iron manganese phosphate material.
8. The positive electrode composite material according to any one of claims 1 to 7, wherein the high nickel ternary material has a general structural formula of LiNixCoyMzWherein M is at least one of Mn, Al, Zr, Ti, Y, Sr and W, x is more than or equal to 0.70 and less than or equal to 0.98, and x is more than or equal to 0.70 and less than or equal to 0.98<y<1，0<z<1, and x + y + z is 1.
9. A method for preparing the positive electrode composite material as defined in any one of claims 1 to 8, comprising:
dispersing a lithium iron manganese phosphate material, a high-nickel ternary material and a first conductive agent in a solvent to obtain a mixed material;
and carrying out fusion treatment on the mixed materials in a mechanical fusion machine, and drying to obtain the cathode composite material.
10. The method according to claim 9, wherein the rotation speed of the mechanical fusion machine is 4000 to 7000r/min, and the time of the fusion process is 10 to 30 min.
11. A positive electrode sheet comprising a current collector and a positive electrode material layer disposed on the current collector, the positive electrode material layer comprising the positive electrode composite material according to any one of claims 1 to 8, and a second conductive agent and a binder.
12. A lithium ion battery, characterized in that it comprises the positive electrode sheet according to claim 11.
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