CN117038851A - Porous negative electrode and preparation method and application thereof - Google Patents
Porous negative electrode and preparation method and application thereof Download PDFInfo
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- CN117038851A CN117038851A CN202311306568.1A CN202311306568A CN117038851A CN 117038851 A CN117038851 A CN 117038851A CN 202311306568 A CN202311306568 A CN 202311306568A CN 117038851 A CN117038851 A CN 117038851A
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- active material
- negative electrode
- phosphide
- porous
- silicon
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- 238000002360 preparation method Methods 0.000 title abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 199
- 239000006183 anode active material Substances 0.000 claims abstract description 122
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 104
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 91
- 239000010439 graphite Substances 0.000 claims abstract description 91
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 85
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 85
- 239000010703 silicon Substances 0.000 claims abstract description 85
- 239000007773 negative electrode material Substances 0.000 claims abstract description 59
- 239000011888 foil Substances 0.000 claims abstract description 23
- 239000000126 substance Substances 0.000 claims abstract description 22
- 239000004020 conductor Substances 0.000 claims abstract description 14
- 229920000642 polymer Polymers 0.000 claims abstract description 14
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 27
- 229910052744 lithium Inorganic materials 0.000 claims description 27
- 239000010405 anode material Substances 0.000 claims description 22
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 21
- 229910052802 copper Inorganic materials 0.000 claims description 19
- 239000010949 copper Substances 0.000 claims description 19
- 238000003756 stirring Methods 0.000 claims description 16
- 238000002156 mixing Methods 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 13
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 238000003825 pressing Methods 0.000 claims description 11
- 239000002002 slurry Substances 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 11
- 229910001383 lithium hypophosphite Inorganic materials 0.000 claims description 10
- 229920001467 poly(styrenesulfonates) Polymers 0.000 claims description 10
- 239000004698 Polyethylene Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
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- -1 polyethylene Polymers 0.000 claims description 9
- 229920000573 polyethylene Polymers 0.000 claims description 9
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 239000011248 coating agent Substances 0.000 claims description 7
- 238000000576 coating method Methods 0.000 claims description 7
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- 229910001377 aluminum hypophosphite Inorganic materials 0.000 claims description 6
- GNTCPDPNMAMZFW-UHFFFAOYSA-N ferrous phosphide Chemical compound [Fe]=P#[Fe] GNTCPDPNMAMZFW-UHFFFAOYSA-N 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 6
- SEQVSYFEKVIYCP-UHFFFAOYSA-L magnesium hypophosphite Chemical compound [Mg+2].[O-]P=O.[O-]P=O SEQVSYFEKVIYCP-UHFFFAOYSA-L 0.000 claims description 6
- 229910001381 magnesium hypophosphite Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- CELVKTDHZONYFA-UHFFFAOYSA-N trilithium;phosphite Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])[O-] CELVKTDHZONYFA-UHFFFAOYSA-N 0.000 claims description 6
- VMFOHNMEJNFJAE-UHFFFAOYSA-N trimagnesium;diphosphite Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])[O-].[O-]P([O-])[O-] VMFOHNMEJNFJAE-UHFFFAOYSA-N 0.000 claims description 6
- 239000004642 Polyimide Substances 0.000 claims description 5
- 239000005543 nano-size silicon particle Substances 0.000 claims description 5
- 229920001721 polyimide Polymers 0.000 claims description 5
- 229960002796 polystyrene sulfonate Drugs 0.000 claims description 5
- 239000011970 polystyrene sulfonate Substances 0.000 claims description 5
- 229940006186 sodium polystyrene sulfonate Drugs 0.000 claims description 5
- RXBBZJPEEIUBJG-UHFFFAOYSA-N [O].[Si].[Li] Chemical compound [O].[Si].[Li] RXBBZJPEEIUBJG-UHFFFAOYSA-N 0.000 claims description 4
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 3
- QZRSKFCFTCPPOR-UHFFFAOYSA-N [O].[Mg].[Si] Chemical compound [O].[Mg].[Si] QZRSKFCFTCPPOR-UHFFFAOYSA-N 0.000 claims description 3
- 239000010426 asphalt Substances 0.000 claims description 3
- 239000012298 atmosphere Substances 0.000 claims description 3
- 239000010406 cathode material Substances 0.000 claims description 3
- 239000002006 petroleum coke Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 238000011065 in-situ storage Methods 0.000 abstract description 2
- 230000002035 prolonged effect Effects 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 92
- 230000000052 comparative effect Effects 0.000 description 27
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 12
- 229910001416 lithium ion Inorganic materials 0.000 description 12
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- ZVLDJSZFKQJMKD-UHFFFAOYSA-N [Li].[Si] Chemical compound [Li].[Si] ZVLDJSZFKQJMKD-UHFFFAOYSA-N 0.000 description 6
- 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 6
- 238000009792 diffusion process Methods 0.000 description 6
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- 239000008367 deionised water Substances 0.000 description 4
- 229910021641 deionized water Inorganic materials 0.000 description 4
- 238000005087 graphitization Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000007873 sieving Methods 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 3
- 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 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 229920002125 Sokalan® Polymers 0.000 description 2
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- 229920001495 poly(sodium acrylate) polymer Polymers 0.000 description 2
- 229920002401 polyacrylamide Polymers 0.000 description 2
- 239000004584 polyacrylic acid Substances 0.000 description 2
- 229920002239 polyacrylonitrile Polymers 0.000 description 2
- 230000000379 polymerizing effect Effects 0.000 description 2
- 239000000661 sodium alginate Substances 0.000 description 2
- 235000010413 sodium alginate Nutrition 0.000 description 2
- 229940005550 sodium alginate Drugs 0.000 description 2
- NNMHYFLPFNGQFZ-UHFFFAOYSA-M sodium polyacrylate Chemical compound [Na+].[O-]C(=O)C=C NNMHYFLPFNGQFZ-UHFFFAOYSA-M 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- SOXUFMZTHZXOGC-UHFFFAOYSA-N [Li].[Mn].[Co].[Ni] Chemical compound [Li].[Mn].[Co].[Ni] SOXUFMZTHZXOGC-UHFFFAOYSA-N 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
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Classifications
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- 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
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
-
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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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
- H01M4/364—Composites as mixtures
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- 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
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- H01M4/366—Composites as layered products
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
-
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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
- H01M4/5805—Phosphides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- 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
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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
- H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
- H01M4/602—Polymers
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- 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
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative 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
Abstract
The invention relates to a porous negative electrode, a preparation method and application thereof. The porous negative electrode comprises an electrode foil and a porous negative electrode layer arranged on the surface of the electrode foil; the porous anode layer comprises a silicon anode active material and a graphite anode active material; the surface of the silicon anode active material is coated with a polymerized carbon layer phosphide; the surface of the graphite anode active material is coated with a polymerized carbon layer phosphide; the polymeric carbon layer phosphide comprises a carbon-coated phosphide. According to the invention, the polymer carbon layer phosphide is formed on the surfaces of the silicon negative electrode active material and the graphite negative electrode active material on the porous negative electrode in situ, so that the tight combination of the surfaces of the silicon negative electrode active material and the graphite negative electrode active material with the conductive material and the bonding substance is improved, the electron conduction of the silicon negative electrode active material and the graphite negative electrode active material is improved, the normal charge and discharge and the multiplying power performance of the electrode under high current density are optimized, and the service life of the battery is prolonged.
Description
Technical Field
The invention relates to the technical field of battery negative electrodes, in particular to a porous negative electrode, a preparation method and application thereof.
Background
After a steady development of over 20 years, the lithium ion battery still exhibits a higher energy capacity with graphite at the negative electrode and oxide or phosphate material at the positive electrode. However, in large-scale applications facing lithium ion batteries, especially, the longer charge time and lower energy density of lithium ion batteries make them unable to fully meet the application requirements of electric vehicles, and lithium ion batteries with high quality energy density are needed to develop silicon negative electrode materials with higher lithium storage capacity (> 4000 mAhg) -1 ) Become urgent.
However, the volume expansion of the silicon after lithium intercalation is up to 300%, so that pulverization and structural damage of the silicon anode active material are caused, the silicon anode active material is separated from the conductive agent and the adhesive, the conductivity of the electrode is reduced, normal charge and discharge and higher rate capability of the silicon anode under high current density cannot be ensured, the electrochemical performance is extremely fast in attenuation, and even the final battery is invalid.
Disclosure of Invention
In order to solve the technical problems, the invention provides a porous negative electrode, and a preparation method and application thereof. The invention provides a porous negative electrode, which improves the tight combination of the surfaces of a silicon negative electrode active material and a graphite negative electrode active material with a conductive material and a bonding substance by forming a polymerized carbon layer phosphide on the surfaces of the silicon negative electrode active material and the graphite negative electrode active material in situ, improves the electron conduction of the silicon negative electrode active material and the graphite negative electrode active material, optimizes the normal charge and discharge and the multiplying power performance of the electrode under high current density, and prolongs the service life of a battery.
The first object of the present invention is to provide a porous negative electrode, comprising an electrode foil and a porous negative electrode layer arranged on the surface of the electrode foil; the porous anode layer comprises a silicon anode active material and a graphite anode active material;
the surface of the silicon anode active material is coated with a polymerized carbon layer phosphide;
the surface of the graphite anode active material is coated with a polymerized carbon layer phosphide;
the polymeric carbon layer phosphide comprises a carbon-coated polymer.
In one embodiment of the invention, the porous anode layer meets the following conditions: t is less than or equal to 0.29 p -1）×1/lg（T si ）×T g ≤1.21；
Wherein T is si T is the mass percentage of the silicon anode active material to the porous anode layer g T is the mass percentage of the graphite anode active material to the porous anode layer p Is the porosity of the porous anode layer.
In one embodiment of the invention, the T p 19.2% -63%; the T is si 0.9% -55%; the T is g 44.5% -98%.
In one embodiment of the invention, one or more of the following conditions are met:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the polymer is selected from one or more of polyethylene, polymethyl methacrylate, sodium polystyrene sulfonate, lithium polystyrene sulfonate and polyimide;
the thickness of the polymeric carbon layer phosphide is 2-120nm;
the thickness of the porous anode layer is 45-320 mu m;
the thickness of the electrode foil is 3-50 mu m.
A second object of the present invention is to provide a method for preparing a porous negative electrode, comprising the steps of:
uniformly mixing a silicon anode active material coated with a polymeric carbon layer phosphide on the surface, a graphite anode active material coated with a polymeric carbon layer phosphide on the surface, a bonding substance and a conductive material, adding water and stirring to obtain anode substance slurry;
and coating the anode material slurry on one side or two sides of the electrode foil, drying and cold pressing to form a porous anode layer, and obtaining the porous anode electrode.
In one embodiment of the present invention, the silicon negative electrode active material of the surface-coated polymeric carbon layer phosphide and the graphite negative electrode active material of the surface-coated polymeric carbon layer phosphide are prepared by the following methods:
and adding the polymer and phosphide into the mixture of the silicon anode active material and the graphite anode active material, uniformly mixing, and heating in an inert atmosphere to respectively obtain the silicon anode active material and the graphite anode active material containing the phosphide of the polymeric carbon layer.
In one embodiment of the invention, at least one or more of the following conditions are met:
the silicon negative electrode active material is selected from one or more of silicon-carbon negative electrode materials, carbon-coated nano silicon negative electrode materials, carbon-coated pre-lithium silicon-oxygen negative electrode materials and carbon-coated pre-magnesium silicon-oxygen negative electrode materials;
the graphite anode active material is selected from one or more of graphitized needle coke, graphitized asphalt tar and graphitized petroleum coke;
the heating temperature is 220-650 ℃, and the heating time is 30min-6h;
in one embodiment of the invention, at least one or more of the following conditions are met:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the polymer is selected from one or more of polyethylene, polymethyl methacrylate, sodium polystyrene sulfonate, lithium polystyrene sulfonate and polyimide;
the polymer accounts for 0.03-8wt% of the mass of the mixture, and the phosphide accounts for 0.01-3wt% of the mass of the mixture.
In one embodiment of the invention, one or more of the following conditions are met:
the mass ratio of the silicon anode active material coated with the polymeric carbon layer phosphide to the graphite anode active material coated with the polymeric carbon layer phosphide to the bonding substance to the conductive material is (0.9-55): (44.5-98): (0.2-6): (0.3-7);
the solid content of the cathode material slurry is 40% -70%;
the electrode foil is at least one selected from copper, nickel, titanium, nickel-plated copper, nickel-plated titanium, nickel-plated iron, nickel-plated aluminum, carbon-coated copper, carbon-coated nickel, carbon-coated iron and carbon-coated aluminum;
the drying temperature in the drying and cold pressing is 70-120 ℃;
the compacted density of the cold-pressed porous anode layer is 1.45-1.75g/cm 3 ；
The bonding substance is selected from polyacrylonitrile, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyacrylamide, polyacrylate, styrene butadiene rubber and sodium alginate.
The conductive material is selected from one or more of conductive carbon black, conductive copper powder, conductive silver powder, conductive nickel powder, conductive acetylene black, conductive graphene, conductive graphite, single-wall carbon nanotubes and multi-wall carbon nanotubes.
A third object of the present invention is to provide a secondary battery comprising the porous negative electrode, or the porous negative electrode obtained by the manufacturing method.
Compared with the prior art, the technical scheme of the invention has the following advantages:
(1) According to the invention, the surface of the silicon negative electrode active material and the graphite negative electrode active material is tightly combined with the conductive agent and the adhesive by polymerizing the phosphide of the carbon layer on the surface of the silicon negative electrode active material and the graphite negative electrode active material, so that the electrode conductivity of the porous negative electrode layer is facilitated. On the other hand, the surfaces of the silicon anode active material and the graphite anode active material are interconnected with a lamellar phosphide structure, so that the lithium ion diffusion capacity of the surfaces of the silicon anode active material and the graphite anode active material is closer, the polarization difference between the silicon anode active material and the graphite anode active material is reduced, the transmission path is optimized, the diffusion resistance of lithium ions is reduced, the electrochemical activity of the material is improved, the normal charge and discharge and the multiplying power performance of the porous anode electrode under high current density are improved, and the cycle life of the battery is prolonged.
(2) In the invention, the ratio (T) of the silicon anode active material on the porous anode layer is considered on the basis of the silicon anode active material and the phosphide of the polymerized carbon layer on the surface of the graphite anode active material si ) Duty ratio of graphite anode active material (T) g ) Within a certain range, the porosity (T) p ) When the water tank is fully filled with the water, the water tank is not more than 0.29 percent (T) p -1）×1/lg（T si ）×T g When the concentration of the electrolyte is less than or equal to 1.21, the electrolyte has better seepage capability in the porous anode electrode, is favorable for lithium ion diffusion, and has better tight combination condition of the surface of the silicon anode active material, the conductive agent and the adhesive.
Drawings
In order that the invention may be more readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, in which,
fig. 1 is a schematic view of a silicon anode active material and a graphite anode active material according to example 1 of the present invention.
Fig. 2 is a TEM image of the silicon anode active material obtained in example 1 of the present invention.
Fig. 3 is a TEM image of the graphite anode active material obtained in example 1 of the present invention, the surface layer being coated with a polymeric carbon layer phosphide.
Description of the specification reference numerals: 1. polymeric carbon layer phosphide; 2. a silicon negative electrode active material; 3. graphite negative electrode active material.
Detailed Description
In order to solve the technical problems pointed out in the background art, the invention provides a porous negative electrode, a preparation method and application thereof.
The invention is realized by the following scheme:
the invention provides a porous negative electrode, which comprises an electrode foil and a porous negative electrode layer arranged on the surface of the electrode foil; the porous anode layer comprises a silicon anode active material and a graphite anode active material;
the surface of the silicon anode active material is coated with a polymerized carbon layer phosphide;
the surface of the graphite anode active material is coated with a polymerized carbon layer phosphide;
the polymeric carbon layer phosphide comprises a carbon-coated polymer.
In this specific embodiment, the porous anode layer meets the following conditions: t is less than or equal to 0.29 p -1）×1/lg（T si ）×T g Less than or equal to 1.21; further, it may be 0.32-1.21, 0.36-0.71, 0.42-0.58.
Wherein T is si T is the mass ratio of the silicon anode active material to the porous anode layer g T is the mass ratio of the graphite anode active material to the porous anode layer p Is the porosity of the porous anode layer.
In a specific embodiment, said T p 19.2% -63%, further, 32% -37%, 32% -63%, etc.; the T is si 0.9% -55%, further, may be 9% -55%, 9% -26.5%, etc.; the T is g 44.5% -98%.
In the invention, the anode materials are not in perfect contact and seamless, the slurry obtained by mixing is dried, water is removed, the pores are increased, the slurry is coated on the foil material or is in a porous structure, and the electrode plate containing the pores is obtained after cold pressing, so that the porous anode layer is formed.
The porosity of the porous anode layer also influences the transmission capacity of the silicon anode active material and the graphite anode active material to lithium ions. The internal clearance rate of the porous anode layer is smaller, the permeation flow path of the electrolyte in the porous anode layer is longer, the permeation resistance of the electrolyte to the internal silicon anode active material is increased, the transmission path of lithium ions is longer, the transmission rate is reduced, and the migration of lithium ions of the porous anode electrode and the diffusion on the silicon anode active material and the graphite anode active material are not facilitated. The porous material has high porosity, although the material with large volume change stress, such as the silicon anode active material in the porous anode layer, can be relieved, the porous material can enable the silicon anode active material and the graphite anode active material in the porous anode layer to occupy relatively low, so that the energy density of the battery is reduced; the bonding of the silicon anode active material, the graphite anode active material and the conductive substance, the porous anode layer and the electrode foil are also reduced, and the electron conductivity is reduced. In the present invention, therefore, the ratio (T) of the silicon anode active material on the porous anode layer is taken into consideration by polymerizing the phosphide of the carbon layer on the surface of the silicon anode active material, the graphite anode active material si ) Duty ratio of graphite anode active material (T) g ) Within a certain range, the porosity (T) p ) When the water tank is fully filled with the water, the water tank is not more than 0.29 percent (T) p -1）×1/lg（T si ) When the x Tg is less than or equal to 1.21, the electrolyte has better seepage capability on the porous anode electrode, is favorable for lithium ion diffusion, and has better tight combination condition of the surface of the silicon anode active material, the conductive agent and the adhesive.
In particular embodiments, one or more of the following conditions are met:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the polymer is selected from one or more of polyethylene, polymethyl methacrylate, sodium polystyrene sulfonate, lithium polystyrene sulfonate and polyimide;
the thickness of the polymeric carbon layer phosphide is 2-120nm; for example 2nm, 5nm, 8nm, 10nm, 12nm, 15nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm or any other value between 2 and 120 nm.
The thickness of the porous anode layer is 45-320 mu m;
the porous negative electrode has a thickness of 60-190 μm, for example, between 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm, 180 μm, 200 μm, or any other value between 60-190 μm.
The thickness of the electrode foil is 3-50 mu m. For example 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any other value between 3 and 50 μm.
The invention provides a preparation method of a porous negative electrode, which comprises the following steps:
uniformly mixing a silicon anode active material coated with a polymeric carbon layer phosphide on the surface, a graphite anode active material coated with a polymeric carbon layer phosphide on the surface, a bonding substance and a conductive material, adding water, stirring to adjust the solid content to 40-70%, stirring for 2-8h under vacuum, and filtering with a screen to control the fineness to be less than 120 mu m to obtain anode substance slurry;
coating the anode material slurry on one side or two sides of an electrode foil, drying, cold pressing and die cutting to form a porous anode layer, and obtaining the porous anode electrode.
In a specific embodiment, the silicon anode active material of the surface-coated polymeric carbon layer phosphide and the graphite anode active material of the surface-coated polymeric carbon layer phosphide are prepared by the following methods:
and adding the polymer and phosphide into the mixture of the silicon anode active material and the graphite anode active material, uniformly mixing, and heating in an inert atmosphere to respectively obtain the silicon anode active material and the graphite anode active material containing the phosphide of the polymeric carbon layer.
In particular embodiments, at least one or more of the following conditions are satisfied:
the silicon negative electrode active material is selected from one or more of silicon-carbon negative electrode materials, carbon-coated nano silicon negative electrode materials, carbon-coated pre-lithium silicon-oxygen negative electrode materials and carbon-coated pre-magnesium silicon-oxygen negative electrode materials;
the graphite anode active material is selected from one or more of graphitized needle coke, graphitized asphalt tar and graphitized petroleum coke;
in a specific embodiment, the silicon negative electrode active material has a particle size of 0.2 to 42 μm. For example 0.2 μm, 0.5 μm, 1.0 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 42 μm or any other value between 2 and 42 μm.
In specific embodiments, the graphite anode active material has a particle size of 1.5 to 85 μm, for example, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, or any other value between 2 and 55 μm.
In a specific embodiment, the heating temperature is 220-650 ℃ and the heating time is 30min-6h.
In a specific embodiment, the mass ratio of the silicon anode active material to the graphite anode active material is (0.9-55): (44.5-98).
In particular embodiments, at least one or more of the following conditions are satisfied:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the polymer is selected from one or more of polyethylene, polymethyl methacrylate, sodium polystyrene sulfonate, lithium polystyrene sulfonate and polyimide;
the polymer comprises 0.03wt% to 8wt%, for example 0.03wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 2.0wt%, 3.0wt%, 4.0wt%, 5.0wt%, 6.0wt%, 7.0wt%, 8.0wt% or any other value between 0.03 and 8wt% of the mass of the mixture.
The mass ratio of the phosphide to the mixture is 0.01-3 wt%; for example 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt% or any other value between 0.01 and 3wt%.
In particular embodiments, one or more of the following conditions are met:
the mass ratio of the silicon anode active material coated with the polymeric carbon layer phosphide to the graphite anode active material coated with the polymeric carbon layer phosphide to the bonding substance to the conductive material is (0.9-55): (44.5-98): (0.2-6): (0.3-7);
the solid content of the cathode material slurry is 40% -70%; for example 40%, 45%, 50%, 55%, 60%, 65%, 70% or any other value between 40% and 70%.
The electrode foil is at least one selected from copper, nickel, titanium, nickel-plated copper, nickel-plated titanium, nickel-plated iron, nickel-plated aluminum, carbon-coated copper, carbon-coated nickel, carbon-coated iron and carbon-coated aluminum;
the drying temperature in the drying and cold pressing is 70-120 ℃;
the compacted density of the cold-pressed porous anode layer is 1.45-1.75g/cm 3 ；
The bonding substance is selected from polyacrylonitrile, carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polyacrylamide, polyacrylate, styrene butadiene rubber and sodium alginate.
The conductive material is selected from one or more of conductive carbon black, conductive copper powder, conductive silver powder, conductive nickel powder, conductive acetylene black, conductive graphene, conductive graphite, single-wall carbon nanotubes and multi-wall carbon nanotubes.
The invention also provides a secondary battery comprising the porous negative electrode or the porous negative electrode obtained by the preparation method.
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to be limiting, so that those skilled in the art will better understand the invention and practice it.
Example 1
The embodiment provides a porous negative electrode and a preparation method thereof, wherein the specific preparation method is as follows:
step 1, a silicon anode active material containing a phosphide of a polymeric carbon layer, a graphite anode active material containing the phosphide of the polymeric carbon layer, a bonding substance (composed of lithium polyacrylate, sodium carboxymethyl cellulose and styrene-butadiene rubber according to a mass ratio of 3:1:1) and a conductive material (composed of conductive carbon black and single-walled carbon nanotubes according to a mass ratio of 9:1) according to a mass ratio of 9.5:85.5:3:2, mixing in a stirring tank, adding deionized water until the solid content is 50%, stirring for 6 hours under vacuum, and filtering with a screen to control the fineness to be less than 120 mu m to obtain a negative electrode substance;
step 2, coating the anode material of step 1 on both sides of a copper electrode foil with a thickness of 8 μm, drying at 105 ℃ and cold pressing to a compacted density of 1.6g/cm of a porous anode layer on a porous anode electrode 3 And the porosity is 32%, and die cutting is carried out, thus obtaining the porous negative electrode with the thickness of 130 mu m.
In step 1, the preparation methods of the silicon negative electrode active material containing the phosphide of the polymeric carbon layer and the graphite negative electrode active material containing the phosphide of the polymeric carbon layer are as follows:
s1, a carbon-coated pre-lithium silica anode material (YOB 166 silicon anode material) with the particle size of 2.7-18 mu m and a graphite anode material (BFC-Q graphite anode material) obtained by high-temperature graphitization of needle coke with the particle size of 3.6-26 mu m are mixed according to the mass ratio of 9.5:85.5 mixing and placing in a stirrer;
s2, adding polymethyl methacrylate and cuprous phosphide (the addition amounts are respectively 1% and 0.3% of the total mass of the carbon-coated pre-lithium silicon anode active material and the graphite anode active material) into the mixture of the carbon-coated pre-lithium silicon anode active material and the graphite anode active material obtained in the step S1, stirring, heating at 550 ℃ for 2 hours under argon atmosphere, cooling to room temperature, sieving to obtain a silicon anode active material containing a polymeric carbon layer phosphide and a graphite anode active material containing the polymeric carbon layer phosphide, and carrying out structural characterization on the obtained silicon anode active material and graphite anode active material with the surfaces coated with the polymeric carbon layer phosphide, wherein the results are shown in fig. 2 and 3.
Example 2
This embodiment is similar to embodiment 1, except that: the addition amount of the added polymethyl methacrylate and cuprous phosphide is 2% and 0.6% of the total mass of the silicon anode active material and the graphite anode active material respectively.
Example 3
This embodiment is similar to embodiment 1, except that: the addition amount of the added polymethyl methacrylate and cuprous phosphide is 3% and 0.9% of the total mass of the silicon anode active material and the graphite anode active material respectively.
Example 4
The embodiment provides a porous negative electrode and a preparation method thereof, wherein the specific preparation method is as follows:
step 1, a silicon anode active material/graphite anode active material containing polymeric carbon layer phosphide, a bonding substance (comprising lithium polyacrylate, sodium carboxymethylcellulose and styrene-butadiene rubber according to a mass ratio of 5:1:1), and a conductive material (comprising conductive carbon black and single-walled carbon nanotubes according to a mass ratio of 9:1) according to a mass ratio of 28.2:65.8:4:2, mixing in a stirring tank, adding deionized water until the solid content is 52%, stirring for 6 hours under vacuum, and filtering with a screen to control the fineness to be less than 120 mu m to obtain a negative electrode substance;
step 2, coating the anode material of step 1 on both sides of a copper electrode foil with a thickness of 8 μm, drying at 105 ℃ and cold pressing to a compacted density of 1.58g/cm of a porous anode layer on a porous anode electrode 3 And (3) the porosity is 37%, and the porous negative electrode with the thickness of 112 mu m is obtained through die cutting.
In step 1, the preparation method of the silicon negative electrode active material/graphite negative electrode active material containing the polymeric carbon layer phosphide comprises the following steps:
s1, graphitizing a carbon-coated nano silicon negative electrode material (YOB 166 silicon negative electrode material) with the particle size of 3-22 mu m and needle coke with the particle size of 3.6-26 mu m at high temperature to obtain a graphite negative electrode material (BFC-Q graphite negative electrode material) with the mass ratio of 28.2:65.8 mixing and placing in a stirrer;
s2, adding polyethylene and lithium hypophosphite (the addition amounts are respectively 1% and 0.3% of the total mass of the silicon anode active material and the graphite anode active material) into the mixture of the carbon-coated pre-lithium silicon anode active material and the graphite anode active material obtained in the step S1, stirring, heating at 500 ℃ for 4 hours under argon atmosphere, cooling to room temperature, and sieving to obtain the silicon anode active material containing the phosphide of the polymeric carbon layer and the graphite anode active material containing the phosphide of the polymeric carbon layer.
Example 5
This embodiment is similar to embodiment 4, except that: polyethylene and lithium hypophosphite are added, and the addition amounts are 2% and 0.6% of the total mass of the silicon negative electrode active material and the graphite negative electrode active material respectively.
Example 6
This embodiment is similar to embodiment 4, except that: polyethylene and lithium hypophosphite are added, and the addition amounts are 3% and 0.9% of the total mass of the silicon negative electrode active material and the graphite negative electrode active material respectively.
Example 7
The embodiment provides a porous negative electrode and a preparation method thereof, wherein the specific preparation method is as follows:
step 1, a silicon anode active material containing a phosphide of a polymeric carbon layer, a graphite anode active material containing the phosphide of the polymeric carbon layer, a bonding substance (composed of lithium polyacrylate, sodium carboxymethyl cellulose and styrene-butadiene rubber according to a mass ratio of 3:1:1) and a conductive material (composed of conductive carbon black and single-walled carbon nanotubes according to a mass ratio of 9:1) according to a mass ratio of 7.5:88.5:2.5:1.5, mixing in a stirring tank, adding deionized water until the solid content is 48%, stirring for 6 hours under vacuum, and filtering with a screen to control the fineness to be less than 120 mu m to obtain a negative electrode substance;
step 2, coating the anode material of step 1 on both sides of a copper electrode foil with a thickness of 8 μm, drying at 105 ℃ and cold pressing to a compacted density of 1.46g of a porous anode layer on a porous anode electrode/cm 3 And the porosity is 63%, and die cutting is carried out, thus obtaining the porous negative electrode with the thickness of 130 mu m.
In step 1, the preparation methods of the silicon negative electrode active material containing the phosphide of the polymeric carbon layer and the graphite negative electrode active material containing the phosphide of the polymeric carbon layer are as follows:
s1, a carbon-coated pre-lithium silica anode material (YOB 166 silicon anode material) with the particle size of 2.7-18 mu m and a graphite anode material (BFC-Q graphite anode material) obtained by high-temperature graphitization of needle coke with the particle size of 3.6-26 mu m are mixed according to the mass ratio of 7.5:88.5 mixing and placing in a stirrer;
s2, adding polymethyl methacrylate and cuprous phosphide (the addition amounts are respectively 1% and 0.3% of the total mass of the carbon-coated pre-lithium silicon anode active material and the graphite anode active material) into the mixture of the carbon-coated pre-lithium silicon anode active material and the graphite anode active material obtained in the step S1, stirring, heating at 550 ℃ for 2 hours under argon atmosphere, cooling to room temperature, and sieving to obtain the silicon anode active material containing the polymeric carbon layer phosphide and the graphite anode active material containing the polymeric carbon layer phosphide.
Example 8
The embodiment provides a porous negative electrode and a preparation method thereof, wherein the specific preparation method is as follows:
step 1, a silicon anode active material/graphite anode active material containing polymeric carbon layer phosphide, a bonding substance (comprising lithium polyacrylate, sodium carboxymethylcellulose and styrene-butadiene rubber according to a mass ratio of 5:1:1), and a conductive material (comprising conductive carbon black and single-walled carbon nanotubes according to a mass ratio of 9:1) according to a mass ratio of 55:39:4:2, mixing in a stirring tank, adding deionized water until the solid content is 51%, stirring for 6 hours under vacuum, and filtering with a screen to control the fineness to be less than 120 mu m to obtain a negative electrode substance;
step 2, coating the anode material of step 1 on both sides of a copper electrode foil with a thickness of 8 μm, drying at 105 ℃ and cold pressing to a compacted density of 1.71g/cm of a porous anode layer on a porous anode electrode 3 And (3) the porosity is 19%, and the porous anode electrode with the thickness of 86 μm is obtained through die cutting.
In step 1, the preparation method of the silicon negative electrode active material/graphite negative electrode active material containing the polymeric carbon layer phosphide comprises the following steps:
s1, graphitizing a carbon-coated nano silicon negative electrode material (YOB 166 silicon negative electrode material) with the particle size of 3-22 mu m and needle coke with the particle size of 3.6-26 mu m at high temperature to obtain a graphite negative electrode material (BFC-Q graphite negative electrode material) with the mass ratio of 55:39 mixing and placing in a stirrer;
s2, adding polyethylene and lithium hypophosphite (the addition amounts are respectively 1% and 0.3% of the total mass of the silicon anode active material and the graphite anode active material) into the mixture of the carbon-coated pre-lithium silicon anode material and the graphite anode material obtained in the step S1, stirring, heating at 500 ℃ for 4 hours under argon atmosphere, cooling to room temperature, and sieving to obtain the silicon anode active material containing the phosphide of the polymeric carbon layer and the graphite anode active material containing the phosphide of the polymeric carbon layer.
Comparative example 1
This comparative example is similar to example 1, except that: the surface of the graphite anode material obtained by high-temperature graphitization of the carbon-coated pre-lithium silica anode material and the needle coke is free of polymeric carbon layer phosphide.
Comparative example 2
This comparative example is similar to example 1, except that: in step 2, the porous anode layer on the porous anode electrode had a solid density of 1.32g/cm 3 And the porosity was 66%, and the thickness of the porous anode electrode was 183 μm.
Comparative example 3
This comparative example is similar to example 3, except that: in step 2, the porous anode layer on the porous anode electrode has a solid density of 1.78 g/cm 3 The porosity was 17%, and the thickness of the porous negative electrode was 98. Mu.m.
Comparative example 4
This comparative example is similar to example 8, except that: in step 2, the porous anode layer on the porous anode electrode had a solid density of 1.75g/cm 3 The porosity was 16%, and the thickness of the porous negative electrode was 98. Mu.m.
Performance test:
(1) The porous negative electrode, separator and positive electrode of the above examples and comparative examples (containing 97.5wt% of lithium nickel cobalt manganese oxideLiNi 0.81 Co 0.11 Mn 0.09 O 2 Positive electrode active material) layer is laminated, coiled, ultrasonically welded with a negative electrode tab and a positive electrode tab, a diaphragm is fixed by rubberizing to obtain a bare cell, the bare cell is put into an aluminum plastic film with a side surface heat-sealed, and is dried at 105 ℃ to remove water and injected with 1.2mol/L LiPF 6 Electrolyte (preparing solvent of electrolyte by ethylene carbonate, propylene carbonate and methyl acetate according to volume ratio of 1:1:1), adding 6wt% ethylene carbonate, 3wt% fluoroethylene carbonate and then adding LiPF 6 Until the concentration is 1.2 mol/L), heat-sealing the top of the aluminum plastic film to obtain 10 secondary batteries of 3.2 Ah.
(2) Calculation of T of examples and comparative examples p 、T si 、T g 、（T p -1）×1/lg（T si ）×T g ，
(3) And (3) formation: the secondary batteries of the examples and the comparative examples are connected with a charging and discharging cabinet at a temperature of 45 ℃ and a humidity of less than 20% under a clamping force of 3000N, the charging and discharging cabinet is charged at 0.1C to 3.5V, the charging at 0.5V to 4.25V, and the secondary batteries are stood for 24 hours, so that the formation is completed.
(4) Multiplying power test: the secondary batteries of the examples and the comparative examples are respectively 3, the anode and the cathode of the secondary batteries are connected into a charging and discharging cabinet under the conditions of a clamping force of 3000N, a temperature of 25 ℃ and a humidity of less than 20%, 1.5C of each secondary battery of the examples and the comparative examples is charged to 4.25V,1.5C of each secondary battery is discharged to 2.5V, and the charging and the discharging are circularly carried out for 10 times; the secondary batteries of the examples and comparative examples were each charged at 2.0C to 4.25V and discharged at 2.0C to 2.5V, and the charge and discharge were cycled 10 times; the secondary batteries of examples and comparative examples were each charged at 2.5C to 4.25V and discharged at 2.5C to 2.5V, and the charge and discharge were cycled 10 times. The batteries were disassembled, and the interface conditions of the negative electrode of the secondary batteries of each example and comparative example were observed, and the interface lithium precipitation conditions under high-current charge and discharge were determined (determination was made by calculating the white area ratio, wherein the white area ratio was 0% for non-precipitation lithium, the white area ratio was 1-5% for slight precipitation lithium, the white area ratio was 5-10%, the local precipitation lithium, the white area ratio was 10-20%, and the white area ratio was 20 >% for severe precipitation lithium).
(5) And (3) cyclic test: the secondary batteries of the examples and comparative examples were 1 each, and the positive and negative electrodes of the secondary batteries were connected to a charging and discharging cabinet at a clamping force of 3000N, a temperature of 25℃and a humidity of < 20%, 1C was discharged to 2.8V, initial discharge capacities were recorded, 1C was charged to 4.25V, and 1C was discharged to 2.8V, and the charging and discharging were circulated. The number of cycles corresponding to the capacity decay of the secondary battery to 80% of the initial discharge capacity was recorded.
TABLE 1T of examples, comparative examples p 、T si 、T g 、（T p -1）×1/lg（T si ）×T g
TABLE 2 lithium precipitation case for examples, comparative examples
Table 3 cycle numbers of examples, comparative examples
Compared with the embodiment, the carbon-coated pre-lithium silicon oxygen anode material of the comparative example 1 and the non-polymerized carbon layer phosphide on the surface of the graphite anode material obtained by high-temperature graphitization of the needle coke begin to precipitate lithium at 1.5C, and the lithium precipitation of the embodiment 1-8 begins at 2.5C, so that the circulation condition of the comparative example 1 is poor, and the surface non-polymerized carbon layer phosphide is beneficial to improving the high-current charge and discharge of the secondary battery and improving the circulation performance; although T of comparative examples 2 to 4 si 、T g Designed in a reasonable range (T) si 0.9-55%; t (T) g 44.5-98%) of the porous anode layer of comparative example 2, the porous anode layer of comparative example 3, the porous anode layer of comparative example 4, and the T of comparative examples 2, 3, and 4, respectively, were 66%, 17%, and 16% p The porosity is not in a reasonable range, lithium still is separated out under the charge and discharge of 2.0 ℃ and is unfavorable for lithium ion diffusion, and the circulation condition is poorIn a word, the porosity of the porous anode layer is set in a reasonable range, and all three are required to be simultaneously in the range specified by the invention, so that the high-current charge and discharge of the secondary battery are improved, and the cycle performance of the battery is improved.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.
Claims (10)
1. The porous negative electrode is characterized by comprising an electrode foil and a porous negative electrode layer arranged on the surface of the electrode foil; the porous anode layer comprises a silicon anode active material and a graphite anode active material;
the surface of the silicon anode active material is coated with a polymerized carbon layer phosphide;
the surface of the graphite anode active material is coated with a polymerized carbon layer phosphide;
the polymeric carbon layer phosphide comprises a carbon-coated phosphide.
2. The porous negative electrode according to claim 1, wherein the porous negative electrode layer meets the following conditions: t is less than or equal to 0.29 p -1）×1/lg（T si ）×T g ≤1.21；
Wherein T is si T is the mass percentage of the silicon anode active material to the porous anode layer g T is the mass percentage of the graphite anode active material to the porous anode layer p Is the porosity of the porous anode layer.
3. The porous negative electrode according to claim 2, wherein the T p 19.2% -63%; the T is si 0.9% -55%; the T is g 44.5% -98%.
4. The porous negative electrode according to claim 1, wherein one or more of the following conditions are satisfied:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the thickness of the polymeric carbon layer phosphide is 2-120nm;
the thickness of the porous anode layer is 45-320 mu m;
the thickness of the electrode foil is 3-50 mu m.
5. A method for preparing a porous negative electrode, comprising the steps of:
uniformly mixing a silicon anode active material coated with a polymeric carbon layer phosphide on the surface, a graphite anode active material coated with a polymeric carbon layer phosphide on the surface, a bonding substance and a conductive material, adding water and stirring to obtain anode substance slurry;
and coating the anode material slurry on one side or two sides of the electrode foil, drying and cold pressing to form a porous anode layer, and obtaining the porous anode electrode.
6. The method according to claim 5, wherein the silicon negative electrode active material of the surface-coated polymeric carbon layer phosphide and the graphite negative electrode active material of the surface-coated polymeric carbon layer phosphide are prepared by the following methods:
and adding the polymer and phosphide into the mixture of the silicon anode active material and the graphite anode active material, uniformly mixing, and heating in an inert atmosphere to respectively obtain the silicon anode active material and the graphite anode active material containing the phosphide of the polymeric carbon layer.
7. The method of claim 6, wherein at least one or more of the following conditions are satisfied:
the silicon negative electrode active material is selected from one or more of silicon-carbon negative electrode materials, carbon-coated nano silicon negative electrode materials, carbon-coated pre-lithium silicon-oxygen negative electrode materials and carbon-coated pre-magnesium silicon-oxygen negative electrode materials;
the graphite anode active material is selected from one or more of graphitized needle coke, graphitized asphalt tar and graphitized petroleum coke;
the heating temperature is 220-650 ℃, and the heating time is 30min-6h.
8. The method of claim 6, wherein at least one or more of the following conditions are satisfied:
the phosphide is selected from one or more of cuprous phosphide, ferrous phosphide, aluminum hypophosphite, magnesium hypophosphite, copper hypophosphite, lithium hypophosphite, magnesium phosphite and lithium phosphite;
the polymer is selected from one or more of polyethylene, polymethyl methacrylate, sodium polystyrene sulfonate, lithium polystyrene sulfonate and polyimide;
the polymer accounts for 0.03-8wt% of the mass of the mixture, and the phosphide accounts for 0.01-3wt% of the mass of the mixture.
9. The method of claim 5, wherein one or more of the following conditions are satisfied:
the mass ratio of the silicon anode active material coated with the polymeric carbon layer phosphide to the graphite anode active material coated with the polymeric carbon layer phosphide to the bonding substance to the conductive material is (0.9-55): (44.5-98): (0.2-6): (0.3-7);
the solid content of the cathode material slurry is 40% -70%;
the electrode foil is at least one selected from copper, nickel, titanium, nickel-plated copper, nickel-plated titanium, nickel-plated iron, nickel-plated aluminum, carbon-coated copper, carbon-coated nickel, carbon-coated iron and carbon-coated aluminum;
the drying temperature in the drying and cold pressing is 70-120 ℃;
the compacted density of the cold-pressed porous anode layer is 1.45-1.75g/cm 3 。
10. A secondary battery comprising the porous negative electrode according to any one of claims 1 to 4, or the porous negative electrode obtained by the production method according to any one of claims 5 to 9.
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