CN116632154A - Negative plate and lithium ion battery comprising same - Google Patents
Negative plate and lithium ion battery comprising same Download PDFInfo
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- CN116632154A CN116632154A CN202210125567.6A CN202210125567A CN116632154A CN 116632154 A CN116632154 A CN 116632154A CN 202210125567 A CN202210125567 A CN 202210125567A CN 116632154 A CN116632154 A CN 116632154A
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- Prior art keywords
- silicon oxide
- active material
- material layer
- negative electrode
- oxide particles
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 42
- 239000002245 particle Substances 0.000 claims abstract description 194
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 157
- 229910052814 silicon oxide Inorganic materials 0.000 claims abstract description 155
- 239000011149 active material Substances 0.000 claims abstract description 85
- 239000007773 negative electrode material Substances 0.000 claims abstract description 21
- 239000010410 layer Substances 0.000 claims description 103
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 30
- 229910052799 carbon Inorganic materials 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- 229910002804 graphite Inorganic materials 0.000 claims description 10
- 239000010439 graphite Substances 0.000 claims description 10
- 239000011247 coating layer Substances 0.000 claims description 8
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 abstract description 15
- 238000007600 charging Methods 0.000 abstract description 11
- 238000010277 constant-current charging Methods 0.000 abstract description 10
- 230000000052 comparative effect Effects 0.000 description 65
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 31
- 229910052744 lithium Inorganic materials 0.000 description 31
- 238000000498 ball milling Methods 0.000 description 16
- 239000011888 foil Substances 0.000 description 15
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 239000006256 anode slurry Substances 0.000 description 8
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- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 5
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 5
- 125000004122 cyclic group Chemical group 0.000 description 5
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- 238000003837 high-temperature calcination Methods 0.000 description 5
- 239000004698 Polyethylene Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 4
- 239000006183 anode active material Substances 0.000 description 4
- 239000010405 anode material Substances 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- 239000006258 conductive agent Substances 0.000 description 4
- 238000010280 constant potential charging Methods 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 4
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229920000573 polyethylene Polymers 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
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- 239000001301 oxygen Substances 0.000 description 3
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- 238000003756 stirring Methods 0.000 description 3
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 2
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- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001354 calcination Methods 0.000 description 2
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- 230000000694 effects Effects 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 230000014509 gene expression Effects 0.000 description 2
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- 150000002500 ions Chemical class 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 230000002427 irreversible effect Effects 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000002048 multi walled nanotube Substances 0.000 description 2
- 239000002985 plastic film Substances 0.000 description 2
- 229920006255 plastic film Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000011863 silicon-based powder Substances 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- UHOPWFKONJYLCF-UHFFFAOYSA-N 2-(2-sulfanylethyl)isoindole-1,3-dione Chemical compound C1=CC=C2C(=O)N(CCS)C(=O)C2=C1 UHOPWFKONJYLCF-UHFFFAOYSA-N 0.000 description 1
- RNMDNPCBIKJCQP-UHFFFAOYSA-N 5-nonyl-7-oxabicyclo[4.1.0]hepta-1,3,5-trien-2-ol Chemical compound C(CCCCCCCC)C1=C2C(=C(C=C1)O)O2 RNMDNPCBIKJCQP-UHFFFAOYSA-N 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229920002153 Hydroxypropyl cellulose Polymers 0.000 description 1
- 229910010238 LiAlCl 4 Inorganic materials 0.000 description 1
- 229910010090 LiAlO 4 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910012513 LiSbF 6 Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 206010042674 Swelling Diseases 0.000 description 1
- QXZUUHYBWMWJHK-UHFFFAOYSA-N [Co].[Ni] Chemical compound [Co].[Ni] QXZUUHYBWMWJHK-UHFFFAOYSA-N 0.000 description 1
- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
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- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- MZZUATUOLXMCEY-UHFFFAOYSA-N cobalt manganese Chemical compound [Mn].[Co] MZZUATUOLXMCEY-UHFFFAOYSA-N 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
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- 230000007423 decrease Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 229920005994 diacetyl cellulose Polymers 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 235000010977 hydroxypropyl cellulose Nutrition 0.000 description 1
- 239000001863 hydroxypropyl cellulose Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
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- 239000007924 injection Substances 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- ILXAVRFGLBYNEJ-UHFFFAOYSA-K lithium;manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[O-]P([O-])([O-])=O ILXAVRFGLBYNEJ-UHFFFAOYSA-K 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- ZAUUZASCMSWKGX-UHFFFAOYSA-N manganese nickel Chemical compound [Mn].[Ni] ZAUUZASCMSWKGX-UHFFFAOYSA-N 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920002620 polyvinyl fluoride Polymers 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910021384 soft carbon Inorganic materials 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
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- 239000010959 steel Substances 0.000 description 1
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- 229910052717 sulfur Inorganic materials 0.000 description 1
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- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
-
- 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
- H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Composite Materials (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a negative electrode plate and a lithium ion battery comprising the negative electrode plate, wherein the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises an active material layer A and an active material layer B, and the active material layer A is arranged between the current collector and the active material layer B; the active material layer a contains silicon oxide particles. The lithium ion battery provided by the invention has high constant current charging ratio and cycle capacity retention rate under the charging condition of 1.5-4.0 ℃.
Description
Technical Field
The invention relates to the field of energy storage, in particular to a negative plate and a lithium ion battery comprising the negative plate.
Background
In recent years, consumer demands for charging speed of electronic products and electric vehicles are increasing, and accordingly, demands for fast charging performance of lithium ion batteries as energy carriers are also increasing. According to the theory of porous electrodes, the lithium intercalation uniformity of active materials in the negative electrode sheet is related to the active materials used and the overall structure of the negative electrode sheet. Therefore, how to select a suitable anode active material and design a specific anode plate structure to solve the expansion and the cycle stability of the silicon anode, thereby realizing the fast charge performance of the lithium ion battery, and becoming a difficult problem to be solved in the field of anode material development and battery design.
Disclosure of Invention
In order to improve the technical problems, the invention provides a negative electrode sheet and a lithium ion battery comprising the negative electrode sheet.
In order to achieve the above purpose, the present invention is realized by the following technical scheme:
a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer including an active material layer a and an active material layer B, the active material layer a being provided between the current collector and the active material layer B;
the active material layer a contains silicon oxide particles that satisfy the following relation:
D i ≤35μm (III)，
d i ≤25μm (IV)，
0.45≤(ΣE j 2 )/(ΣD i 2 )≤0.75 (V)，
(ΣF k 2 )/(ΣD i 2 )≥0.37 (VI)，
wherein Σ represents summing the data, D i Represents the diameter of the circumcircle of any silicon oxide particle, d i Represents the inscribed circle diameter, E, of any silicon oxide particle j Representation D i Diameter of circumcircle of silicon oxide particles of 9 μm or more, F k Representation d i The diameter of the circumcircle of the silicon oxide particles of 4 μm or more, i, j, k represent the number of the silicon oxide particles.
According to the invention, the active material layer B is free of silicon oxide particles.
The research shows that the lithium intercalation potential of the silicon oxide particles is higher than that of graphite, and more sufficient lithium intercalation can be still realized when the polarization potential is smaller. Compared with the active material layer B, the polarization potential of the active material layer A is smaller, and silicon oxide particles are intensively arranged in the active material layer A, so that the non-uniformity of lithium intercalation of the whole pole piece can be effectively reduced.
According to the invention, the thickness L of the active material layer A A Satisfies the L of 35 mu m or less A ≤60μm。
According to the invention, the thickness L of the active material layer B B Meets the requirement of L which is less than or equal to 20 mu m B ≤50μm。
When the thickness condition is satisfied, the uniformity of coating and the overall dynamics of the battery pole piece can be ensured. And when L A < 35 μm or L B When the particle size is less than 20 mu m, scraping and other phenomena easily occur during pole piece coating, and even distribution of active substances cannot be ensured; and when L A > 60 μm or L B When the electrode is more than 50 mu m, the ohmic resistance of the electrode plate is larger, the polarization is aggravated, and the lithium precipitation risk is increased.
According to the present invention, in the active material layer a, the blending amount of the silicon oxide particles satisfies the following relationship:
0.05≤(ΣF k 2 )/S≤0.47；
wherein Σ represents summing the data, F k Representation d i The diameter of the circumscribed circle of silicon oxide particles of 4 μm or more, k represents the number of the silicon oxide particles, and S represents the cross-sectional area of the active material layer a in the observation region.
According to the present invention, in the active material layer A, the specific surface area of the silicon oxide particles is smaller thanEqual to 1.2m 2 /g。
According to the invention, the mass ratio of the silicon oxide particles with respect to the active material layer a is about 5wt% to 25wt%.
According to the present invention, the silicon oxide particles contain Si element and O element, and the molar ratio x (mol/mol) of the O element to the Si element satisfies 0.7.ltoreq.x.ltoreq.1.4.
According to the present invention, at least a part of the surface of the silicon oxide particles contains a coating layer.
The invention also provides a silicon oxide particle for the negative electrode sheet, which at least comprises the following characteristics:
(1)D v max≤35；
(2)9.0≤D v 50≤13.0；
(3)BET≤1.2；
wherein:
D v max represents the maximum particle diameter of the silicon oxide particles in μm;
D v 50 represents the median particle diameter of the silicon oxide particles in μm;
BET represents the specific surface area of the silicon oxide particles in m 2 /g。
The invention also provides a lithium ion battery, which comprises the negative plate.
According to the invention, after the lithium ion battery is subjected to 1-5 charge-discharge cycles, the negative plate is irreversibly expanded, and the negative plate has the following characteristics:
(1) The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises an active material layer A and an active material layer B, and the active material layer A is arranged between the current collector and the active material layer B;
the active material layer A contains silicon oxide particles with a thickness L A Meet the requirement of 44 mu m less than or equal to L A ≤75μm；
The active material layer B contains no silicon oxide particles and has a thickness L B Satisfies the L of 21 mu m or less B ≤55μm。
(2) The silicon oxide particles satisfy the following relationship:
D i ’≤44μm，
d i ’≤32μm，
0.45≤(ΣE j ’ 2 )/(ΣD i ’ 2 )≤0.75，
(ΣF k ’ 2 )/(ΣD i ’ 2 )≥0.37，
0.06≤(ΣF k ’ 2 )/S’≤0.53，
wherein Σ represents summing the data, D i ' represents the diameter of the circumcircle of any silicon oxide particle, d i ' represents the inscribed circle diameter of any silicon oxide particle, E j ' represent D i The diameter of the circumcircle of the silicon oxide particles of' > 11.2 μm, F k ' represents d i The diameter of the circumcircle of the silicon oxide particles with the diameter of not less than 5.0 mu m is equal to or greater than the number of the silicon oxide particles, i, j and k are represented by numbers, and S' is represented by the cross-sectional area of the negative electrode plate in the observation area.
The beneficial effects of the invention are that
According to the theory of porous electrodes, when the electron conductance of the solid phase is far greater than the ion conductance of the liquid phase, the polarization of the negative plate approximates to that of the pure liquid phase. In an actual battery system, the solid-phase electronic conductivity K s > 0.1S/cm, liquid phase ion conductivity K l ＜0.01S/cm，K s Ratio K l More than an order of magnitude greater. Thus, the negative electrode sheet can be analyzed using a pure liquid phase polarization model, whereby a distribution formula of the polarization potential η can be obtained:
η(x)＝η 0 cosh[k·(x-L)]/cosh(kL)， (I)
wherein k= (ρ) l /Z) 1/2 ；η 0 For the polarization potential of the outer surface of the negative plate ρ l The positive electrode plate is the apparent specific resistance of electrolyte in the positive electrode plate, Z is the reaction impedance of the electrode in unit volume, and L is the thickness of the positive electrode plate active material layer; x is the distance along the thickness direction of the pole piece, and the outer surface of the active substance layer is x=0 μm and is in the current collector direction And in the positive direction.
From formula (I), at x ε [0, L]Within the range, η (x) monotonically decreases with x, and when x=0 μm, η (x) is the maximum value η 0 The method comprises the steps of carrying out a first treatment on the surface of the When x=l, η (x) is the minimum value of 0V. That is, the outer surface of the active material layer has the greatest polarization, while the inner surface in contact with the current collector has the least polarization. When the active material layer of the negative electrode plate is a uniform component, under the condition of high-rate current charging, the lithium is fully intercalated on the outer surface and the lithium is not fully intercalated on the inner surface, and the utilization rate of the whole electrode plate is lower. Therefore, reasonable component distribution design is carried out along the thickness direction of the pole piece, and the uniformity of lithium intercalation of the negative pole piece can be improved.
On the other hand, the volume change of the silicon oxide particles in the lithium intercalation and deintercalation cycle is large, the surface SEI film can be continuously damaged and repaired, and active lithium is continuously consumed. For micron-sized particles with smooth surfaces, the larger the specific surface area is, the larger the generated SEI film is, and the larger the damage and repair amount is, the faster the battery cycle capacity attenuation is. Therefore, on the premise of ensuring that the local strain does not cause the deformation of the pole piece, the particle size of the silicon oxide particles can be increased as much as possible, so that the specific surface area of the silicon oxide particles and the consumption of active lithium are reduced. However, merely increasing the particle size of the silicon oxide particles is insufficient to ensure a smaller specific surface area. Of all three-dimensional geometries, the sphere has the smallest specific surface area, whereas the silicon oxide particles are usually formed by bulk crushing, including various irregular shapes such as rods, flakes, polyhedrons, etc., which feature results in a larger specific surface area. Therefore, the shape of the silicon oxide particles is controlled, and the expansion of the silicon negative electrode can be relieved, so that the cycle performance of the negative electrode plate and the lithium ion battery can be further adjusted.
In view of this, the present invention provides a negative electrode sheet, and provides a lithium ion battery based on the negative electrode sheet, which has a high constant current charge ratio and cycle capacity retention rate under a charging condition of 1.5C to 4.0C.
Drawings
Fig. 1 is a schematic cross-sectional view of a negative electrode sheet of the present invention. Wherein 11 represents silicon oxide particles, 12 represents an active material layer, 13 represents a current collector, L A Represents the thickness of the active material layer A, L B The thickness of the active material layer B is shown.
FIG. 2 is a schematic illustration of the circumscribed circles and inscribed circles of silicon oxide particles in accordance with the present invention.
Detailed Description
[ negative electrode sheet and production thereof ]
As described above, the present invention provides a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer including an active material layer a and an active material layer B, the active material layer a being provided between the current collector and the active material layer B;
the active material layer a contains silicon oxide particles that satisfy the following relation:
D i ≤35μm (III)，
d i ≤25μm (IV)，
0.45≤(ΣE j 2 )/(ΣD i 2 )≤0.75 (V)，
(ΣF k 2 )/(ΣD i 2 )≥0.37 (VI)，
wherein Σ represents summing the data, D i Represents the diameter of the circumcircle of any silicon oxide particle, d i Represents the inscribed circle diameter, E, of any silicon oxide particle j Representation D i Diameter of circumcircle of silicon oxide particles of 9 μm or more, F k Representation d i The diameter of the circumcircle of silicon oxide particles of 4 μm or more, i, j, k denote the numbers of the silicon oxide particles, and S denotes the cross-sectional area of the active material layer A in the observation region.
In one embodiment, the thickness L of the active material layer A A Satisfies the L of 35 mu m or less A ≤60μm；
The active material layer B contains no silicon oxide particles and has a thickness L B Meets the requirement of L which is less than or equal to 20 mu m B ≤50μm。
The invention limits the particle size of the silicon oxide particles in the negative plate by the relations (III) and (IV). When the above condition is satisfiedThe particle size of the silicon oxide particles is moderate, and the volume change of the silicon oxide particles in the circulating process can not cause obvious deformation of the pole piece; when D is present i > 35 μm or d i When silicon oxide particles of > 25 μm, the absolute value of the volume change of these particles during cycling is large, which may lead to excessive local area stress and risk of swelling of the active material layer, and thus the electrical contact between the active material layer and the current collector is deteriorated, and the cycle capacity of the battery is further accelerated.
The present invention defines not only the particle size distribution but also the shape of the silicon oxide particles by the relationships (V) and (VI). Any cross section of the sphere is round, the diameters of the inscribed circle and the circumscribed circle of the cross section are equal, and for an irregular geometric body, the closer the inscribed circle and the circumscribed circle of the cross section are, the closer the shape is to the round. For example, when the circumscribed circle diameter is 1, the inscribed circle diameter of the equilateral triangle is 0.5, the inscribed circle diameter of the square is 0.71, the inscribed circle diameter of the regular hexagon is 0.87, and the inscribed circle diameter of the circle is 1. In view of this, the present inventors have unexpectedly found that, in the case where the circumscribed circle of the cross-sectional shape of the silicon oxide particles has a certain size, it is necessary to ensure that the inscribed circle diameter thereof is sufficiently large, and at this time, the overall shape of the silicon oxide particles is relatively close to a sphere, so that side reactions occurring on the surfaces of the silicon oxide particles can be effectively reduced. When the relational expressions (III) and (IV) are satisfied, the pole piece contains the proper proportion D i Not less than 9 μm and a sufficient proportion d i Silicon oxide particles of 4 μm or more, the specific surface area of the silicon oxide particles being 1.2m or less 2 Per gram (specific surface area of the silicon oxide conventionally used in the prior art is generally greater than 1.2m 2 /g), less side reactions; when (ΣE j 2 )/(ΣD i 2 ) When the particle diameter of the silicon oxide particles is less than 0.45, the overall particle diameter of the silicon oxide particles is smaller, the specific surface area is large, and the surface side reaction is more; when (ΣE j 2 )/(ΣD i 2 ) When the particle size of the silicon oxide particles is larger than 0.75, the uneven distribution of internal stress of the pole piece is easy to be aggravated, and the pole piece is deformed, so that the electric contact between the active material layer and the current collector is poor, and the cycle capacity attenuation of the battery is accelerated; when (Sigma F k 2 )/(ΣD i 2 ) When < 0.37, the overall shape of the silicon oxide particles deviates too far from spherical, for example, there are many rod-like or plate-like particles, and the specific surface area of the silicon oxide particles is generally greater than 1.2m 2 And/g, the side reaction is more.
In one embodiment, the amount of silicon oxide particles blended satisfies the following relationship: less than or equal to 0.05- k 2 ) S is less than or equal to 0.47, wherein, sigma, F k The definition of k and S is the same as above.
It was found that when the blending amount of the silicon oxide particles satisfies the above-described relational expression, the mass ratio of the silicon oxide particles with respect to the active material layer a is about 5wt% to 25wt%.
The research shows that when the mass ratio of the silicon oxide particles is about 5-25 wt%, the silicon oxide particles can be uniformly dispersed among the graphite particles, and the local bearing stress is smaller; when (Sigma F k 2 ) When S is less than 0.05, the content of silicon oxide particles is too low to ensure that the lithium ion battery has high energy density; when (Sigma F k 2 ) When S > 0.47, the content of the silicon oxide particles is too high, a particle aggregation area is easy to appear, local expansion is aggravated, the electric contact of the active substance is worsened, and the capacity of the battery is attenuated rapidly.
In the present invention, the above relation is a photograph of a cross section based on silicon oxide particles, which is a photograph of a cross section of a negative electrode sheet, and the cross section can be obtained by cutting perpendicularly to the surface of the negative electrode sheet using an ion milling apparatus and observing the cross section using a Scanning Electron Microscope (SEM) and an energy dispersive X-ray spectrometer (EDS). The length of the negative electrode sheet in the observation area is more than or equal to 150 mu m.
In the present invention, the circumscribed circle means a circle having a smallest diameter capable of completely containing silicon oxide particles therein. The inscribed circle represents a circle of the largest diameter that can be completely contained by the silicon oxide particles. The schematic diagram is shown in fig. 2.
In one embodiment, the molar ratio x of O element to Si element of the silicon oxide particles satisfies 0.7.ltoreq.x.ltoreq.1.4. Exemplary are 0.7, 0.8, 1.0, 1.2, 1.4 or any point in the range of values of the foregoing two-by-two compositions. When this relationship is satisfied, the silicon oxide particles have a higher gram capacity and a stable structure; when x is less than 0.7, the silicon oxide particles are embedded with lithium to form a few silicate inert matrixes, and the stability of a circulating structure is poor; when x is more than 1.4, the oxygen element content in the silicon oxide particles is too high, irreversible reaction is increased, the gram capacity of the material is reduced, and the aim of high energy density is not realized.
According to the present invention, at least a part of the surface of the silicon oxide particles (for example, the coating ratio is greater than 0 and equal to or less than 100%) of the active material layer a further includes a coating layer, specifically, a carbon coating layer. For example, the material in the carbon coating layer is selected from one or more of graphite, amorphous carbon, graphene and carbon nanotubes.
According to the present invention, the anode active material layer further includes other anode materials. For example, the other negative electrode material is one or more selected from graphite, hard carbon and soft carbon materials.
According to the present invention, the anode active material layer further includes a conductive agent. For example, the conductive agent is one or more selected from carbon black (Super P), acetylene black, ketjen black, carbon fiber, single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs).
Further, the anode active material layer further includes a binder. For example, the binder is one or more selected from carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyethylene, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polytetrafluoroethylene, polypropylene, polyacrylic acid, styrene Butadiene Rubber (SBR), and epoxy resin.
Further, the negative electrode current collector is one or more selected from copper foil, carbon coated copper foil and perforated copper foil.
The invention also provides a preparation method of the negative plate, which comprises the following steps:
mixing silicon oxide particles, other anode materials optionally contained, a conductive agent and a binder to obtain anode slurry A;
mixing other anode materials, a conductive agent and a binder which are optionally contained to obtain anode slurry B;
and coating the anode slurry A and the anode slurry B on the current collector in a layered mode, wherein the anode slurry A is arranged on an inner layer close to the current collector, the anode slurry B is arranged on an outer layer far away from the current collector, then drying and slicing, then drying, and finally rolling and slitting to obtain the anode sheet.
According to the present invention, the negative electrode slurry further contains a solvent. For example, the solvent is water.
According to the invention, the temperature of the drying is 70-90 ℃, and is exemplified by 70 ℃, 80 ℃ and 90 ℃.
According to the invention, the drying temperature is 90-110 ℃, and is exemplified by 90 ℃, 100 ℃ and 110 ℃; the drying time is 8-24 h, and is exemplified by 8h, 10h, 12h, 24h or any point value in the range of the numerical values of the two.
[ silicon oxide particles and production thereof ]
The present invention provides a silicon oxide particle for the above-described negative electrode sheet, the particle comprising at least the following features:
(1)D v max≤35；
(2)9.0≤D v 50≤13.0；
(3)BET≤1.2。
wherein:
D v max represents the maximum particle diameter of the silicon oxide particles in μm;
D v 50 represents the median particle diameter of the silicon oxide particles in μm;
BET represents the specific surface area of the silicon oxide particles in m 2 /g。
In some embodiments, the silicon oxide particles have a median particle diameter Dv50 that satisfies: dv50 is more than or equal to 9.0 and less than or equal to 11.0.
In some embodiments, the silicon oxide particles have a median particle diameter Dv50 that satisfies: dv50 is more than 11.0 and less than or equal to 13.0.
According to the present invention, the silicon oxide particles contain Si element and O element, and the molar ratio x (mol/mol) of the O element and Si element (O/Si) satisfies 0.7.ltoreq.x.ltoreq.1.4, and exemplified by 0.7, 1.0, 1.1, 1.2, 1.4 or any point value in the range of the numerical compositions of the foregoing two.
In some embodiments, the molar ratio x of O element and Si element of the silicon oxide particles satisfies: 1.0.ltoreq.x.ltoreq.1.4, illustratively 1.0, 1.1, 1.2, 1.4 or any point value within the range of values of the foregoing.
In some embodiments, the molar ratio x of O element and Si element of the silicon oxide particles satisfies: x is more than or equal to 0.7 and less than 1.0. Exemplary are 0.7, 0.8, 0.9, or any point in the range of the foregoing numerical compositions.
The invention also provides a preparation method of the silicon oxide particles, which comprises the following steps:
1) Silicon powder and silicon dioxide powder are mixed according to Si/SiO 2 Mixing the materials according to the molar ratio of 0.33-3.00 to obtain a mixture;
2) At 10 -6 ～10 -4 Reacting the mixture for 4 to 10 hours at the temperature of 1000 to 1200 ℃ under the pressure of MPa to generate gas;
3) Condensing the gas to obtain a solid;
4) Crushing the solid to obtain powder A;
5) Carrying out carbon coating treatment on the powder A to obtain powder B;
6) And (3) carrying out particle size classification treatment on the powder B to obtain the silicon oxide particles.
According to the invention, in step 1), the mixing may be carried out by means of a horizontal stirrer, a gas flow blender or a horizontal ball mill.
According to the invention, the comminution in step 4) comprises a primary comminution for grinding the solids into a powder and a secondary comminution for grinding off the corners of the powder particles to bring the particle shape towards a spherical shape. The primary pulverization may be performed by a horizontal ball mill, and the secondary pulverization may be performed by a vibratory ball mill. The container used for primary crushing and secondary crushing is made of stainless steel, and ball milling beads can be made of stainless steel or zirconia. In the primary crushing and the secondary crushing, the total filling volume of the solid to be crushed and the ball-milling beads is 25% -40% of that of the container. In the primary crushing, the diameter of ball-milling beads is 1-2 cm, the mass ratio of the solid to be crushed to the ball-milling beads is 0.05-0.15, the rotation frequency of a container is 200-300 rpm, and the ball-milling time is 8-12 h. In the secondary crushing, the diameter of ball-milling beads is 0.3-1 cm, the mass ratio of solid to be crushed to ball-milling beads is 0.3-0.5, the vibration frequency of a container is 400-800 rpm, and the ball-milling time is 5-8 h.
According to the invention, in step 5), the carbon coating method comprises chemical vapor deposition.
According to the present invention, the chemical vapor deposition method includes the steps of: and (3) carrying out high-temperature calcination treatment on the powder A in a carbon source gas atmosphere to prepare the powder B.
Preferably, the carbon source gas may be argon/acetylene (C 2 H 2 ) Is a mixed gas of (a) and (b). For example, acetylene (C 2 H 2 ) The ratio of (2) is 3 to 20%, and is exemplified by 3%, 5%, 8%, 10%, 15%, 20% or any point value in the range of the numerical compositions of the two.
According to the present invention, the mass ratio of the carbon source gas to the silicon oxide particles flowing per minute is 0.05% to 0.4%, and is exemplified by 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or any value in the range of the numerical values set forth above.
Preferably, the temperature of the high temperature calcination treatment is 600 to 800 ℃, and is exemplified by 600 ℃, 700 ℃, 800 ℃; the high-temperature calcination treatment time is 3-60 min, and is exemplified by 3min, 5min, 8min, 10min, 20min, 30min, 40min, 50min, and 60min. Further, the temperature rising rate of the high-temperature calcination treatment is 5-15 ℃/min, and is exemplified by 5 ℃/min, 10 ℃/min and 15 ℃/min.
Preferably, the high temperature calcination treatment is performed under an inert gas atmosphere. For example under nitrogen or argon atmosphere.
According to an exemplary embodiment of the present invention, the carbon-coated method includes the steps of:
i) Heating the powder A to 600-800 ℃ under the protection of argon;
ii) introducing C 2 H 2 3-20% of argon/acetylene mixed gas, and reacting for 3-60 min;
iii) And naturally cooling to room temperature under the protection of argon to obtain powder B.
According to the invention, in step 6), the purpose of the particle size classification treatment is to obtain D v max and D v 50 meets the aforementioned requirements, the method used comprising air classification.
[ lithium ion Battery ]
The invention also provides a lithium ion battery, which comprises the negative plate.
According to the invention, after the lithium ion battery is subjected to 1-5 charge-discharge cycles, the negative plate is irreversibly expanded, and the negative plate has the following characteristics:
(1) The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises an active material layer A and an active material layer B, and the active material layer A is arranged between the current collector and the active material layer B;
The active material layer A contains silicon oxide particles with a thickness L A Meet the requirement of 44 mu m less than or equal to L A ≤75μm；
The active material layer B contains no silicon oxide particles and has a thickness L B Satisfies the L of 21 mu m or less B ≤55μm。
(2) The silicon oxide particles satisfy the following relationship:
D i ’≤44μm，
d i ’≤32μm，
0.45≤(ΣE j ’ 2 )/(ΣD i ’ 2 )≤0.75，
(ΣF k ’ 2 )/(ΣD i ’ 2 )≥0.37，
0.06≤(ΣF k ’ 2 )/S’≤0.53。
wherein Σ represents summing the data, D i ' represents the diameter of the circumcircle of any silicon oxide particle, d i ' represents the inscribed circle diameter of any silicon oxide particle, E j ' represent D i The diameter of the circumcircle of the silicon oxide particles of' > 11.2 μm, F k ' represents d i The diameter of the circumscribed circle of the silicon oxide particles of equal to or greater than 5.0 μm, i, j, k denote the numbers of the silicon oxide particles, and S' denotes the cross-sectional area of the active material layer A in the observation region.
According to the invention, the lithium ion battery further comprises a positive plate.
According to the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on a surface of the positive electrode current collector. Preferably, the positive electrode active material layer includes a positive electrode material.
According to the invention, the current collector is one or more selected from aluminum foil, carbon-coated aluminum foil and perforated aluminum foil.
According to the invention, the positive electrode material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium iron silicate, lithium Cobalt Oxide (LCO), nickel cobalt manganese ternary material, nickel manganese/cobalt manganese/nickel cobalt binary material, lithium manganate and lithium-rich manganese-based material.
According to the invention, the lithium ion battery further comprises a separator. For example, the membrane is selected from one or more of polyethylene membrane or polypropylene membrane.
According to the invention, the lithium ion battery further comprises an electrolyte. Preferably, the electrolyte is a nonaqueous electrolyte, which includes a solvent and a lithium salt.
For example, the solvent is selected from one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), propyl Propionate (PP), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), 1,3 propane sulfonate lactone (PS), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC).
For example, the lithium salt is selected from LiPF 6 、LiBF 4 、LiSbF 6 、LiClO 4 、LiCF 3 SO 3 、LiAlO 4 、LiAlCl 4 、Li(CF 3 SO 2 ) 2 N, liBOB and LiDFOB.
According to the invention, the lithium ion battery further comprises an encapsulation shell. For example, the packaging shell is one or more selected from an aluminum plastic film, an aluminum shell and a steel shell.
In the present invention, as the median particle diameter Dv50 of the silicon oxide particles, a laser particle size test method can be employed. For example, measurements were made using a Malvern particle size tester, the test procedure being as follows: silicon oxide particles were dispersed in deionized water containing a dispersant (e.g., polyoxyethylene nonylphenol ether, content-0.03% wt.) to form a mixture, and the mixture was sonicated for 2 minutes and then placed into a Malvern particle size tester for testing.
For the specific surface area BET of the silicon oxide particles, a BET (Brunauer-Emmett-Teller) test method may be employed. For example, the measurement is performed using a TriStarII specific surface Analyzer.
For the molar ratio x of the O element to the Si element of the silicon oxide particles, an energy spectrum (EDS) analysis method may be employed. For example, the test is performed using an Oxford spectrometer.
The technical scheme of the invention will be further described in detail below with reference to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
Unless otherwise indicated, the starting materials and reagents used in the following examples were either commercially available or may be prepared by known methods.
In the following examples and comparative examples of the present invention, the electrical properties of the silicon oxide particles, the negative electrode sheet and the lithium ion battery were tested as follows:
1. the manufacturing and testing method of the button cell comprises the following steps:
mixing silicon oxide particles, sodium carboxymethylcellulose (CMC-Na), styrene-butadiene rubber (SBR), carbon black (Super P) and single-wall carbon tubes (SWCNTs) according to a mass ratio of 85:2:5.5:7:0.5, adding deionized water, and obtaining negative under the action of a vacuum stirrer The slurry is coated on copper foil, dried at 80 ℃ and sliced, and then transferred to a vacuum oven at 100 ℃ for drying for 12 hours. After rolling in a dry environment, compaction to about 1.4g/cm 3 A wafer having a diameter of about 1.2cm was then manufactured using a die press.
13wt% of a sufficiently dry lithium hexafluorophosphate (LiPF) was rapidly added to Ethylene Carbonate (EC) under an inert atmosphere 6 ) And 10wt% fluoroethylene carbonate (FEC), and stirring uniformly to obtain the desired electrolyte.
In a glove box, a metal lithium sheet is used as a counter electrode, a polyethylene diaphragm is used as a diaphragm, and an electrolyte is added to assemble the button cell.
The gram capacity and first efficiency of the negative electrode material were calculated using a blue electric (LAND) test system discharging to 0.005V at a current of 50mA/g, standing for 10min, and charging to 1.5V at 50 mA/g.
2. Full battery manufacturing and testing method
Silicon oxide particles, D v Graphite with the mass ratio of 50 of 15 mu m, sodium carboxymethylcellulose (CMC-Na), styrene Butadiene Rubber (SBR), carbon black (Super P) and single-walled carbon nanotubes (SWCNTs) are mixed according to the mass ratio of y (95-y): 1.5:2.5:0.85:0.15, deionized water is added, and the negative electrode slurry A is obtained under the action of a vacuum stirrer.
Will D v Graphite with the mass ratio of 50 of 15 mu m, sodium carboxymethylcellulose (CMC-Na), styrene Butadiene Rubber (SBR) and carbon black (Super P) are mixed according to the mass ratio of 96.4:1.3:1.7:0.6, deionized water is added, and negative electrode slurry B is obtained under the action of a vacuum stirrer.
Uniformly coating a copper foil with the thickness of 6 mu m with negative electrode slurry A, drying at 80 ℃, uniformly coating negative electrode slurry B, drying at 80 ℃, transferring to a vacuum oven at 100 ℃ for drying for 12 hours, and rolling and slitting to obtain the negative electrode plate.
Mixing Lithium Cobalt Oxide (LCO), polyvinylidene fluoride (PVDF) and carbon black (Super P) according to a mass ratio of 96:2:2, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until uniform anode slurry is formed. The positive electrode slurry was uniformly coated on an aluminum foil having a thickness of 12 μm. Coating the aboveBaking the good aluminum foil in a baking oven, and then transferring the baking oven into a baking oven with the temperature of 120 ℃ for drying for 8 hours, wherein the baking oven is 4.0g/cm 3 Rolling the pressed density of the anode plate, and then cutting the anode plate to obtain the required anode plate. The size of the positive plate is smaller than that of the negative plate, lithium precipitation at the edge of the negative plate is avoided, the first lithium removal capacity of the positive plate in unit area is 2% lower than that of the first lithium intercalation capacity of the negative plate, the negative plate is ensured to have enough lithium storage sites, and lithium precipitation of the negative plate is avoided.
Under inert atmosphere, the mass ratio of the components is EC: PC: PP: liPF (LiPF) 6 : FEC: and preparing a mixed solution of PS=13:13:50:15:5:4, and uniformly stirring to obtain the required electrolyte.
Polyethylene diaphragms 8 μm thick were chosen.
And (3) attaching a layer of lithium foil on the surface of the negative electrode plate by a rolling method to obtain a pre-lithiated negative electrode plate, so that the first efficiency of the pre-lithiated negative electrode plate in a button cell test is 91.5% -92.3%.
And stacking the prepared positive plate, the diaphragm and the negative plate in sequence, ensuring that the diaphragm is positioned between the positive plate and the negative plate to play a role in isolation, and then obtaining the bare cell without liquid injection by winding. And placing the bare cell in an aluminum plastic film shell, injecting the prepared electrolyte into the dried bare cell, and performing the procedures of vacuum packaging, standing, formation, shaping, sorting and the like to obtain the required lithium ion battery.
The test procedure for lithium ion batteries was as follows:
(1) The temperature was measured at 25℃using a blue electric (LAND) test system.
(2) Charging to 4.45V with 3.0C constant current to obtain constant current stage charging capacity Q C1 Constant voltage charging to 0.2C to obtain constant voltage segment capacity Q C2 Standing for 10min, discharging 1C to 3.0V to obtain initial capacity, and collecting the final product with Q C1 /(Q C1 +Q C2 ) For the initial constant current charge ratio, the product of the initial capacity and the discharge average voltage is taken as the energy of the battery.
The initial thickness of the battery was measured by constant current charging to 3.82V at 3.0C and constant voltage charging to 0.02C. The product of the initial thickness, the length and the width of the battery is taken as the initial volume of the battery, and the energy of the battery divided by the initial volume of the battery is taken as the energy density of the battery.
(3) Constant current charging is carried out at 3.0C to 4.45V, constant voltage charging is carried out at 0.2C, standing is carried out for 10min,1C discharging is carried out at 3.0V, standing is carried out for 10min, the charging and discharging steps are cycled for 500 weeks, and the 500 th week discharging capacity divided by the initial capacity is taken as the capacity retention rate.
(4) Charging to 4.45V with 3.0C constant current to obtain constant current stage charging capacity Q C3 Constant voltage charging to 0.2C to obtain constant voltage segment capacity Q C4 Standing for 10min, discharging 1C to 3.0V, and collecting the mixture with Q C3 /(Q C3 +Q C4 ) The final constant flow charge ratio.
Examples
1. Preparation of silicon oxide particles and physicochemical parameters
The following is an exemplary method for preparing silicon oxide particles:
1) Silicon powder and silicon dioxide powder are mixed according to Si/SiO 2 Mixing the materials according to the molar ratio of 0.33-3.00 to obtain a mixture;
2) At 2X 10 -5 Reacting the mixture for 6 hours under the pressure of MPa and the temperature of 1050 ℃ to generate gas;
3) Condensing the gas to obtain a solid;
4) Crushing the solid to obtain powder A;
5) Carrying out carbon coating treatment on the powder A to obtain powder B;
6) And (3) carrying out particle size classification treatment on the powder B to obtain the silicon oxide particles.
Wherein:
the pulverization of step 4) includes primary pulverization and secondary pulverization. In the primary crushing, the total filling volume of the material to be crushed and the ball-milling beads is 30 percent of that of the container, the diameter of the ball-milling beads is 1.5cm, the mass ratio of the material to be crushed to the ball-milling beads is 0.1, and the ball-milling time is 10 hours; in secondary crushing, the total filling volume of the material to be crushed and the ball-milling beads is 30 percent of that of the container, the diameter of the ball-milling beads is 0.5cm, the mass ratio of the material to be crushed to the ball-milling beads is 0.4, and the ball-milling time is 6 hours.
In step 5), acetylene (C) in the mixed gas 2 H 2 ) The ratio of (2) is5% by mass of the carbon source gas to the silicon oxide particles flowing through the reactor per minute was 0.2%, the calcination treatment temperature was 700℃and the calcination time was 15 minutes.
The preparation parameters of the examples and comparative examples are given in Table 1, including Si/SiO in step 1) 2 Molar ratio and vibration frequency of the ball mill in the secondary crushing in the step 4). The physicochemical parameters of the silicon oxide particles of the examples and comparative examples, including the O/Si molar ratio x and the maximum particle diameter D, are also shown in Table 1-1 v max, median particle diameter D v 50. Specific surface area BET, gram capacity of silicon oxide particles, and first effect.
Wherein, in the primary pulverization of examples 1 to 3 and comparative examples 1 to 5, the rotation frequency of the container was 250rpm; in the primary pulverization of comparative example 6, the rotation frequency of the container was 500rpm.
TABLE 1
The physical properties of the silicon oxide particles of examples 1 to 3 all satisfy the limitations of the present invention, wherein:
example 1 is a reference group; example 2 differs from example 1 in the molar O/Si ratio, example 1 being in the range of 1.0 to 1.4, example 2 being in the range of 0.7 to 1.0; example 3 differs from example 1 in the particle size, D of example 1 v 50 is in the range of 9.0 to 11.0 μm, D of example 3 v 50 is in the range of 11.0 to 13.0 μm.
The silicon oxide particles of comparative examples 1 to 6 do not fully satisfy the limitations of the present invention, and these features are indicated by bold italics in the table, in which: the O/Si molar ratio of comparative example 1 is greater than 1.4; the O/Si molar ratio of comparative example 2 was less than 0.7; in comparative example 3, in the secondary pulverization, the vibration frequency of the container was too low, the pulverizing effect was poor, and D of the silicon oxide particles v 50 is greater than 13.0 μm; in comparative examples 4 and 5, in the secondary pulverization, the vibration frequency of the container was too high, the pulverizing strength was too high, and D of the silicon oxide particles v 50 is less than 9.0 μm, and BET is greater than 1.2m due to the reduced particle size and increased specific surface area 2 /g; for a pair ofIn the case of the proportion 6, the rotation frequency of the vessel in the primary pulverization is increased, and the secondary pulverization step is omitted, in which the silicon oxide particles remain more angular, and BET is larger than 1.2m 2 /g。
As can be seen from table 1:
the molar ratio of O/Si of the silicon oxide particles of the example 1, the example 3 and the comparative examples 3 to 6 is 1.12, and the gram capacity and the initial effect are similar and are 1570 to 1610mAh/g and 74 to 75 percent respectively;
the molar ratios of O/Si in comparative example 1, example 2 and comparative example 2 were successively decreased to 1.55, 1.12, 0.91 and 0.66, respectively, and the corresponding gram capacities and initial effects were also successively increased, because the lower the oxygen content, the less irreversible reactions involving oxygen.
2. Preparation and physical parameters of negative plate
The preparation methods of the negative electrode sheets of examples 4 to 6 and comparative examples 7 to 14 are given below:
silicon oxide particles, D v Graphite with the mass ratio of 50 of 15 mu m, sodium carboxymethylcellulose (CMC-Na), styrene Butadiene Rubber (SBR), carbon black (Super P) and single-walled carbon nanotubes (SWCNTs) are mixed according to the mass ratio of y (95-y): 1.5:2.5:0.85:0.15, deionized water is added, and the negative electrode slurry A is obtained under the action of a vacuum stirrer.
Will D v Graphite with the mass ratio of 50 of 15 mu m, sodium carboxymethylcellulose (CMC-Na), styrene Butadiene Rubber (SBR) and carbon black (Super P) are mixed according to the mass ratio of 96.4:1.3:1.7:0.6, deionized water is added, and negative electrode slurry B is obtained under the action of a vacuum stirrer.
On a copper foil having a thickness of 6 μm, a concentration of 5mg/cm was used 2 Uniformly coating the surface density of the anode slurry A, drying at 80 ℃ and 4mg/cm 2 Is uniformly coated with a negative electrode slurry B, dried at 80 ℃ and then transferred to a vacuum oven at 100 ℃ for 12 hours to be dried at 1.6g/cm 3 Rolling, and then cutting to obtain the negative plate.
The above method was also adopted for comparative examples 15 and 16, except that: in comparative example 15, the areal density of the active material layer A was 8.5mg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the In comparative example 16, the active material layer B has an areal density of 8mg/cm 2 。
The active material layer of comparative example 17 is of uniform composition and is prepared as follows:
silicon oxide particles, D v Graphite with the mass ratio of 50 of 15 mu m, sodium carboxymethylcellulose (CMC-Na), styrene Butadiene Rubber (SBR), carbon black (Super P) and single-walled carbon nanotubes (SWCNTs) are mixed according to the mass ratio of 9.5:85.5:1.5:2.5:0.85:0.15, deionized water is added, and negative electrode slurry is obtained under the action of a vacuum stirrer.
On a copper foil having a thickness of 6 μm, 9mg/cm was used 2 Uniformly coated with a negative electrode slurry, dried at 80 ℃ and then transferred to a vacuum oven at 100 ℃ for 12 hours to obtain a product with a density of 1.6g/cm 3 Rolling, and then cutting to obtain the negative plate.
The preparation conditions of the negative electrode sheets of examples 4 to 6 and comparative examples 7 to 17, including the amounts of silicon oxide particles used and their blending amounts in the active material layer a, were given in table 2, wherein the blending amounts of the silicon oxide particles were obtained by the formula y/95. Table 2 also shows physical properties of the negative electrode sheet including the thickness L of the active material layer A A Thickness L of active material layer B B Diameter D of circumscribed circle i Maximum value of (d) inscribed circle diameter d i Maximum value of (ΣE) j 2 )/(ΣD i 2 )、(ΣF k 2 )/(ΣD i 2 )、(ΣF k 2 )/S。
TABLE 2
The negative electrode sheets of examples 4 to 6 all satisfy the limitations of the present invention, in which:
Example 4 is a reference group; example 5 differs from example 4 only in that: the silicon oxide particles used in the method have lower O/Si molar ratio; example 6 differs from example 4 in that: the silicon oxide particles used therein have a low secondary vibration frequency in synthesis, thus D v max and D v 50 is larger, and the particles with large particle diameterThe proportion of the components is also higher, and thus the corresponding (ΣE j 2 )/(ΣD i 2 ) Sum (ΣF) k 2 )/(ΣD i 2 ) Larger.
None of the negative plates of comparative examples 7-17 fully satisfies the limitations of the present invention (these features are indicated by bold italics in table 2), wherein: the silicon oxide particles used in comparative example 7 had an O/Si molar ratio of greater than 1.4; the silicon oxide particles used in comparative example 8 had an O/Si molar ratio of less than 0.7; d of negative electrode sheet in comparative example 9 i Maximum value is more than 35 mu m, d i Maximum value of more than 25 mu m, (ΣE) j 2 )/(ΣD i 2 ) Greater than 0.75, (ΣF) k 2 )/(ΣD i 2 ) Less than 0.37, and comparative analysis shows that the silicon oxide particles used in the negative electrode sheet have too low vibration frequency in the secondary pulverization process, and do not sufficiently grind off the corners of the particles, thus exhibiting a larger circumscribed circle diameter, while also causing (ΣF k 2 )/(ΣD i 2 ) The value is relatively reduced; the negative electrode sheet of comparative example 10 (ΣE j 2 )/(ΣD i 2 ) Less than 0.45, (ΣF) k 2 )/(ΣD i 2 ) The silicon oxide particles used in the negative plate have too high vibration frequency in the secondary crushing process, and the particle size is further refined, so that the related parameters of the circumscribed circle and the inscribed circle can not meet the requirements; negative electrode sheet of comparative example 11 (ΣE j 2 )/(ΣD i 2 )、(ΣF k 2 )/(ΣD i 2 ) This is because the silicon oxide particles used in the negative electrode sheet have a smaller particle diameter because the container vibration frequency is higher during the secondary pulverization than in comparative example 10; comparative example 12 (ΣF) k 2 )/(ΣD i 2 ) The silicon oxide particles used in the negative plate are thinned by primary crushing, the rotating frequency of the container is too high during crushing, and more edges and corners of the particles are reserved; comparative example 13 (ΣF) k 2 ) Too low a/S, too low an amount of silicon oxide particles to be blended; (ΣF of negative electrode sheet in comparative example 14 k 2 ) Too high/S, too much silicon oxide particles are blended; the thickness of the active material layer a in comparative example 15 was greater than 60 μm; the thickness of the active material layer B in comparative example 16 was greater than 50 μm; the thickness of the active material layer B in comparative example 17 was less than 20 μm.
3. Preparation and physical parameters of lithium ion battery
The lithium ion battery is obtained according to the preparation method.
Wherein, when preparing the pre-lithiated negative electrode sheet, a stripe lithium foil with a thickness of 5 μm is used, namely, the lithium foil segments and the blank segments are alternately and repeatedly distributed, and the widths of the lithium foil segments and the blank segments in each example and comparative example are as follows: examples 7, 9, comparative examples 20 to 23 and comparative example 28, the lithium foil segment width was 0.25cm, and the blank segment width was 0.75cm; example 8 and comparative example 27, lithium foil segment width 0.2cm, blank segment width 0.8cm; comparative example 18, lithium foil segment width 0.33cm, blank segment width 0.67cm; comparative example 19, lithium foil segment width 0.15cm, blank segment width 0.85cm; comparative example 24, no lithium supplementation; comparative example 25, lithium foil segment width 0.4cm, blank segment width 0.6cm; comparative example 26, lithium foil segment width 0.45cm, blank segment width 0.55cm.
And (5) carrying out charge and discharge cycles for 2 times according to the cycle system, and disassembling the battery to obtain the negative plate.
Table 3 shows physical properties of the negative electrode sheets after 2 cycles of the lithium ion batteries of examples 7 to 9 and comparative examples 18 to 28, including the thickness L of the active material layer A A Thickness L of', active material layer B B ' diameter D of circumcircle i Maximum value of' inscribed circle diameter d i ' maximum, (Σe) j ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 )/S。
TABLE 3 Table 3
The data shown in Table 3 are similar to those shown in Table 2, and will not be described again here.
4. Performance of lithium ion battery
Table 4 shows the energy densities, initial constant current charge ratios, capacity retention ratios, and final constant current charge ratios of the lithium ion batteries of examples 7 to 9 and comparative examples 18 to 28.
TABLE 4 Table 4
As can be seen from table 4, the negative electrodes of examples 4 to 6 and the lithium ion batteries of corresponding examples 7 to 9 satisfy the features set forth in the present invention, the battery energy density is greater than 700Wh/L, the initial constant current charge ratio is greater than 60%, the cyclic capacity retention ratio is greater than 80%, and the final constant current charge ratio is greater than 30%; the lithium ion batteries of comparative example 7 and comparative example 18 used silicon oxide particles with an excessively high O/Si molar ratio, and a battery energy density of less than 700Wh/L; the negative electrode sheet of comparative example 8 and the lithium ion battery of comparative example 19 used silicon oxide particles having an O/Si molar ratio too low, a cycle capacity retention ratio of less than 80%, and a final constant current charge ratio of less than 30%; d of negative electrode sheet of comparative example 9 i 、d i 、(ΣE j 2 )/(ΣD i 2 )、(ΣF k 2 )/(ΣD i 2 ) And the lithium ion battery of comparative example 20D i ’、d i ’、(ΣE j ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 )/(ΣD i ’ 2 ) The limitation of the invention is not satisfied, the retention rate of the circulating capacity is less than 80%, and the final constant-current charging ratio is less than 30%; negative electrode sheet of comparative example 10 (ΣE j 2 )/(ΣD i 2 )、(ΣF k 2 )/(ΣD i 2 ) And the lithium ion battery of comparative example 21 (Σe j ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 )/(ΣD i ’ 2 ) The limitation of the invention is not satisfied, the retention rate of the circulating capacity is less than 80%, and the final constant-current charging ratio is less than 30%; negative electrode sheet of comparative example 11 (ΣE j 2 )/(ΣD i 2 )、(ΣF k 2 )/(ΣD i 2 )、(ΣF k 2 ) S and the lithium ion battery of comparative example 22 (ΣE j ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 )/(ΣD i ’ 2 )、(ΣF k ’ 2 ) S does not meet the limit of the invention, the retention rate of the circulating capacity is less than 80%, and the final constant-current charging ratio is less than 30%; negative electrode sheet of comparative example 12 (ΣF k 2 )/(ΣD i 2 ) And the lithium ion battery of comparative example 23 (Σf k ’ 2 )/(ΣD i ’ 2 ) The limitation of the invention is not satisfied, the retention rate of the circulating capacity is less than 80%, and the final constant-current charging ratio is less than 30%; negative electrode sheet of comparative example 13 (ΣF k 2 ) S and the lithium ion battery of comparative example 24 (ΣF k ’ 2 ) The S is not satisfied with the limitation of the invention, the energy density of the battery is lower than 700Wh/L, the initial constant current charging ratio is lower than 60%, the cyclic capacity retention rate is lower than 80%, and the final constant current charging ratio is lower than 30%; negative electrode sheet of comparative example 14 (ΣF k 2 ) S and the lithium ion battery of comparative example 25 (ΣF k ’ 2 ) S does not satisfy the limitation of the invention, the retention rate of the circulating capacity is less than 80%, and the final constant-current charging ratio is less than 30%; l of negative plate of comparative example 15 A And L of lithium ion Battery of comparative example 26 A ' not satisfying the limitation of the present invention, the initial constant-current charge ratio is less than 60%, the cyclic capacity retention rate is less than 80%, and the final constant-current charge ratio is less than 30%; l of negative plate of comparative example 16 B And L of lithium ion Battery of comparative example 27 B ' not satisfying the limitation of the present invention, the initial constant-current charge ratio is less than 60%, the cyclic capacity retention rate is less than 80%, and the final constant-current charge ratio is less than 30%; the silicon oxide particles of the negative plates of comparative example 17 and comparative example 28 were uniformly distributed in the active material layer, and did not satisfy the limitation of the present invention, the battery energy density was lower than 700Wh/L, the initial constant current charge ratio was less than 60%, the cyclic capacity retention ratio was less than 80%, and the final constant current charge ratio was less than 30%.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A negative electrode sheet, characterized in that the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being provided on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising an active material layer a and an active material layer B, the active material layer a being provided between the current collector and the active material layer B;
The active material layer a contains silicon oxide particles that satisfy the following relation:
D i ≤35μm (III)，
d i ≤25μm (IV)，
0.45≤(ΣE j 2 )/(ΣD i 2 )≤0.75 (V)，
(ΣF k 2 )/(ΣD i 2 )≥0.37 (VI)，
wherein Σ represents summing the data, D i Represents the diameter of the circumcircle of any silicon oxide particle, d i Represents the inscribed circle diameter, E, of any silicon oxide particle j Representation D i Diameter of circumcircle of silicon oxide particles of 9 μm or more, F k Representation d i The diameter of the circumcircle of the silicon oxide particles of 4 μm or more, i, j, k represent the number of the silicon oxide particles.
2. The negative electrode sheet according to claim 1, wherein the thickness L of the active material layer a A Satisfies the L of 35 mu m or less A ≤60μm；
And/or the active material layer B is free of silicon oxide particles;
and/or the thickness L of the active material layer B B Meets the requirement of L which is less than or equal to 20 mu m B ≤50μm。
3. The negative electrode sheet according to claim 1, wherein the blending amount of the silicon oxide particles in the active material layer a satisfies the following relationship:
0.05≤(ΣF k 2 )/S≤0.47；
wherein Σ represents summing the data, F k Representation d i The diameter of the circumscribed circle of silicon oxide particles of 4 μm or more, k represents the number of the silicon oxide particles, and S represents the cross-sectional area of the active material layer a in the observation region.
4. The negative electrode sheet according to any one of claims 1 to 3, wherein in the active material layer a, a specific surface area of silicon oxide particles is 1.2m or less 2 /g。
5. The negative electrode sheet according to any one of claims 1 to 4, wherein the mass ratio of the silicon oxide particles with respect to the active material layer a is about 5wt% to 25wt%.
6. The negative electrode sheet according to any one of claims 1 to 5, wherein the silicon oxide particles contain Si element and O element, and a molar ratio x (mol/mol) of the O element to the Si element satisfies 0.7.ltoreq.x.ltoreq.1.4.
7. The negative electrode sheet according to any one of claims 1 to 6, wherein at least a part of the surface of the silicon oxide particles contains a coating layer.
8. The negative electrode sheet according to claim 7, wherein the coating layer is selected from a carbon coating layer, and the material in the carbon coating layer is selected from one or more of graphite, amorphous carbon, graphene, and carbon nanotubes.
9. A lithium ion battery comprising the negative electrode sheet of any one of claims 1-8.
10. The lithium ion battery of claim 9, wherein the negative electrode sheet has the following characteristics after 1 to 5 charge-discharge cycles of the lithium ion battery:
(1) The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises an active material layer A and an active material layer B, and the active material layer A is arranged between the current collector and the active material layer B;
The active material layer A contains silicon oxide particles with a thickness L A Meet the requirement of 44 mu m less than or equal to L A ≤75μm；
The active material layer B contains no silicon oxide particles and has a thickness L B Satisfies the L of 21 mu m or less B ≤55μm；
(2) The silicon oxide particles satisfy the following relationship:
D i ’≤44μm，
d i ’≤32μm，
0.45≤(ΣE j ’ 2 )/(ΣD i ’ 2 )≤0.75，
(ΣF k ’ 2 )/(ΣD i ’ 2 )≥0.37，
0.06≤(ΣF k ’ 2 )/S’≤0.53，
wherein Σ represents summing the data, D i ' represents the diameter of the circumcircle of any silicon oxide particle, d i ' represents the inscribed circle diameter of any silicon oxide particle, E j ' represent D i The diameter of the circumcircle of the silicon oxide particles of' > 11.2 μm, F k ' represents d i The diameter of the circumscribed circle of the silicon oxide particles of equal to or greater than 5.0 μm, i, j, k denote the numbers of the silicon oxide particles, and S' denotes the cross-sectional area of the active material layer A in the observation region.
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