CN117334909A - Composite positive electrode material, preparation method thereof, positive electrode plate and secondary battery - Google Patents
Composite positive electrode material, preparation method thereof, positive electrode plate and secondary battery Download PDFInfo
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- CN117334909A CN117334909A CN202311290437.9A CN202311290437A CN117334909A CN 117334909 A CN117334909 A CN 117334909A CN 202311290437 A CN202311290437 A CN 202311290437A CN 117334909 A CN117334909 A CN 117334909A
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 205
- 239000002131 composite material Substances 0.000 title claims abstract description 167
- 238000002360 preparation method Methods 0.000 title claims description 27
- 239000002245 particle Substances 0.000 claims abstract description 226
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 212
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 209
- 230000001502 supplementing effect Effects 0.000 claims abstract description 165
- 239000010410 layer Substances 0.000 claims abstract description 134
- 239000002344 surface layer Substances 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims description 116
- 239000011257 shell material Substances 0.000 claims description 109
- 239000011247 coating layer Substances 0.000 claims description 59
- 230000000087 stabilizing effect Effects 0.000 claims description 31
- 238000002156 mixing Methods 0.000 claims description 25
- 239000005022 packaging material Substances 0.000 claims description 22
- 238000005245 sintering Methods 0.000 claims description 20
- 230000008859 change Effects 0.000 claims description 17
- 239000003575 carbonaceous material Substances 0.000 claims description 15
- 239000002861 polymer material Substances 0.000 claims description 12
- 239000011149 active material Substances 0.000 claims description 11
- 229920001940 conductive polymer Polymers 0.000 claims description 6
- 239000002228 NASICON Substances 0.000 claims description 5
- 229910010293 ceramic material Inorganic materials 0.000 claims description 5
- 239000002223 garnet Substances 0.000 claims description 5
- 150000002736 metal compounds Chemical class 0.000 claims description 5
- 239000002227 LISICON Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000000034 method Methods 0.000 abstract description 30
- 230000008569 process Effects 0.000 abstract description 19
- 230000001351 cycling effect Effects 0.000 abstract description 3
- 239000011248 coating agent Substances 0.000 description 33
- 238000000576 coating method Methods 0.000 description 33
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 31
- 229910001416 lithium ion Inorganic materials 0.000 description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 19
- 230000008901 benefit Effects 0.000 description 17
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 16
- 239000002243 precursor Substances 0.000 description 16
- 238000005253 cladding Methods 0.000 description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 12
- 150000001875 compounds Chemical class 0.000 description 9
- 238000005538 encapsulation Methods 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 229920000620 organic polymer Polymers 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 7
- 229910052786 argon Inorganic materials 0.000 description 6
- 239000010406 cathode material Substances 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000010405 anode material Substances 0.000 description 5
- 230000003139 buffering effect Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000000605 extraction Methods 0.000 description 5
- 238000007086 side reaction Methods 0.000 description 5
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000006183 anode active material Substances 0.000 description 4
- 239000008187 granular material Substances 0.000 description 4
- 229910021389 graphene Inorganic materials 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 230000001965 increasing effect Effects 0.000 description 4
- 238000009830 intercalation Methods 0.000 description 4
- 239000011163 secondary particle Substances 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- SMZOGRDCAXLAAR-UHFFFAOYSA-N aluminium isopropoxide Chemical compound [Al+3].CC(C)[O-].CC(C)[O-].CC(C)[O-] SMZOGRDCAXLAAR-UHFFFAOYSA-N 0.000 description 3
- 229910003481 amorphous carbon Inorganic materials 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 description 3
- 239000002041 carbon nanotube Substances 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 238000009831 deintercalation Methods 0.000 description 3
- 230000002687 intercalation Effects 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229920001661 Chitosan Polymers 0.000 description 2
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- OHVGNSMTLSKTGN-BTVCFUMJSA-N [C].OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O Chemical compound [C].OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O OHVGNSMTLSKTGN-BTVCFUMJSA-N 0.000 description 2
- 239000004964 aerogel Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000006256 anode slurry Substances 0.000 description 2
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- 238000006138 lithiation reaction Methods 0.000 description 2
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
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- 239000011734 sodium Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 125000003184 C60 fullerene group Chemical group 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 101000856236 Clostridium acetobutylicum (strain ATCC 824 / DSM 792 / JCM 1419 / LMG 5710 / VKM B-1787) Butyrate-acetoacetate CoA-transferase subunit B Proteins 0.000 description 1
- 229910018871 CoO 2 Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910020719 Li0.33 La0.56 Inorganic materials 0.000 description 1
- 229910003055 Li0.33 La0.57 TiO3 Inorganic materials 0.000 description 1
- 229910021102 Li0.5La0.5TiO3 Inorganic materials 0.000 description 1
- 229910009274 Li1.4Al0.4Ti1.6 (PO4)3 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
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- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 229910006406 SnO 2 At Inorganic materials 0.000 description 1
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 125000006367 bivalent amino carbonyl group Chemical group [H]N([*:1])C([*:2])=O 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000011889 copper foil Substances 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
- 230000002708 enhancing effect Effects 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 239000001866 hydroxypropyl methyl cellulose Substances 0.000 description 1
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 description 1
- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 description 1
- UFVKGYZPFZQRLF-UHFFFAOYSA-N hydroxypropyl methyl cellulose Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC2C(C(O)C(OC3C(C(O)C(O)C(CO)O3)O)C(CO)O2)O)C(CO)O1 UFVKGYZPFZQRLF-UHFFFAOYSA-N 0.000 description 1
- 150000003949 imides Chemical group 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BDKWOJYFHXPPPT-UHFFFAOYSA-N lithium dioxido(dioxo)manganese nickel(2+) Chemical compound [Mn](=O)(=O)([O-])[O-].[Ni+2].[Li+] BDKWOJYFHXPPPT-UHFFFAOYSA-N 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 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
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-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
- 239000000203 mixture Substances 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012811 non-conductive material Substances 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 150000002927 oxygen compounds Chemical class 0.000 description 1
- 229920001197 polyacetylene Polymers 0.000 description 1
- 229920000767 polyaniline Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920000123 polythiophene Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 239000005033 polyvinylidene chloride Substances 0.000 description 1
- 229920002981 polyvinylidene 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
- 238000005096 rolling process Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000000661 sodium alginate Substances 0.000 description 1
- 235000010413 sodium alginate Nutrition 0.000 description 1
- 229940005550 sodium alginate Drugs 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
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- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
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- 229910052721 tungsten Inorganic materials 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 239000011800 void material Substances 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
Abstract
The composite positive electrode material comprises a core, lithium supplementing particles and a stable shell layer, wherein the core comprises a positive electrode active material; the lithium supplementing particles are distributed on the outer surface layer of the inner core; the stable shell layer is coated on the outer surface layers of the inner core and the lithium supplementing particles. Even though the volume of the lithium supplementing particles is reduced after lithium is removed in the first-circle charging process, the composite positive electrode material can maintain the total volume basically unchanged, so that the phenomenon that pits are easily formed on the surface of a positive electrode plate or gaps are easily formed inside the positive electrode plate after the lithium supplementing particles are simply mixed and compounded with the positive electrode active material for use is avoided, and the cycling stability of the composite positive electrode material can be ensured.
Description
Technical Field
The application relates to the technical field of secondary batteries, in particular to a composite positive electrode material and a preparation method thereof, a positive electrode plate and a secondary battery.
Background
Lithium ion secondary batteries are currently more common secondary batteries. SEI film can be generated in the first charging process of the lithium ion secondary battery, and a large amount of Li is consumed + So that Li + Is greatly reduced in capacity, and Li extracted from the negative electrode during the first discharge + Much smaller than Li deintercalated from positive electrode upon charging + Resulting in reduced coulombic efficiency, directly affecting the cycle life and energy density of the lithium battery. In order to solve the problem, a method for compensating lithium loss by adding lithium supplementing particles is commonly used at present, and meanwhile, overdischarge can be prevented, so that the safety performance of the lithium ion secondary battery is improved.
However, since the lithium supplementing particles are sacrificial lithium salts, lithium is removed and decomposed during primary charging, and the particle size is reduced or further pulverized, when the lithium supplementing particles are compounded with the positive electrode active material for use, pits are easily formed on the surface of the positive electrode sheet or gaps are easily formed in the positive electrode sheet after primary charging, and the stability of the overall structure of the positive electrode sheet is adversely affected, so that the cycle performance is deteriorated.
Disclosure of Invention
The purpose of the application is to provide a composite positive electrode material, a preparation method thereof, a positive electrode plate and a secondary battery, and the problem that gaps appear in the positive electrode plate after lithium supplementing particles are charged and adverse effects are caused on the overall structural stability of the positive electrode plate is solved.
In order to achieve the purpose of the application, the application provides the following technical scheme:
In a first aspect, the present application provides a composite positive electrode material comprising a core, lithium-compensating particles, and a stable shell layer, wherein the core comprises a positive electrode active material; the lithium supplementing particles are distributed on the outer surface layer of the inner core; the stable shell layer is coated on the outer surface layers of the inner core and the lithium supplementing particles.
The composite positive electrode material provided by the application has the core capable of circularly charging and discharging and the lithium supplementing particles with the lithium supplementing function, so that the composite positive electrode material provided by the application has higher initial efficiency and capacity and better cycle performance compared with the conventional core; and secondly, the outer surfaces of the inner core and the lithium supplementing particles are both coated with a stable shell layer, after lithium ions are released by the lithium supplementing particles, the stable shell layer can also keep self structural stability so as to prevent the stable shell layer from collapsing inwards after a cavity is formed between the lithium supplementing particles and the stable shell layer, so that even if the volume of the lithium supplementing particles is reduced after lithium is removed in the first-circle charging process, the composite positive electrode material can also maintain the total volume basically unchanged, and the phenomenon that pits are easily formed on the surface of a positive electrode plate or gaps are easily formed inside the positive electrode plate after the lithium supplementing particles and the inner core are simply mixed and compounded for use is avoided, thereby ensuring the cycling stability of the composite positive electrode material.
In one embodiment, the volume of the composite positive electrode material before lithium removal of the lithium supplementing particles is V1, the volume of the composite positive electrode material after lithium removal of the lithium supplementing particles is V2, and the volume of the lithium supplementing particles is V3, so that V1-V2 is more than or equal to 0 and less than V3.
In one embodiment, the composite positive electrode material further comprises a cavity formed between the delithiated lithium-compensating particles and the stable shell layer. The cavity generated in the stable shell layer can play a role in buffering stress generated by the lithium removal-lithium intercalation volume change of the positive electrode active material in the charge-discharge cycle process, so that the structural stability of the pole piece can be improved by the composite positive electrode material, and the cycle performance of the battery is improved.
In one embodiment, the composite positive electrode material further comprises a pre-coating layer, wherein the pre-coating layer is coated on the outer surface of the inner core, and the stable shell layer is coated on the outer surface of the pre-coating layer. Through setting up two-layer cladding (stable shell layer and precoat) at the surface of kernel, can make the cladding of kernel more complete, avoid the side reaction of composite positive electrode material and electrolyte better to and reduce phenomena such as water absorption.
In one embodiment, the lithium supplementing particles are distributed on the outer surface of the pre-coating layer, and the lithium supplementing particles are embedded in the stable shell layer, or the stable shell layer is partially coated on the outer surface of the pre-coating layer, and the other part is coated on the outer surface of the lithium supplementing particles.
In one embodiment, the material of the stable shell layer comprises one or more of a ceramic material, a polymer material, a carbon material, a perovskite type material, a NASICON type material, a garnet type material, an inverse perovskite type material, and a LISICON type material.
In one embodiment, the material of the pre-coat layer comprises one or more of a carbon material, a conductive polymer material, and a metal compound.
In one embodiment, the pre-coat material has a deformability greater than the deformability of the stabilizing shell material. The advantage of preparing the pre-coating layer by adopting the coating material with deformation capability is that the stress generated by the change of the lithium-inserting volume of the inner core can be absorbed by the pre-coating layer in advance in the charge-discharge cycle process, thereby realizing the buffer function, reducing the stress transferred to the stable shell layer, reducing the stress pressure of the packaging material, not only further enhancing the structural stability of the composite anode material, but also providing more possibility for the selection of the packaging material.
In one embodiment, the ratio of the thickness of the stabilizing shell layer to the thickness of the pre-coating layer is (0.1 to 50): 1.
In one embodiment, the mass ratio of the positive electrode active material to the lithium supplementing particles is (80-99): 1-20.
In one embodiment, the particle diameter D50 of the positive electrode active material is in the range of 1 μm to 50. Mu.m.
In one embodiment, the particle diameter D50 of the lithium supplementing particles is in the range of 0.1 μm to 10. Mu.m.
In one embodiment, the composite positive electrode material has a particle diameter D50 in the range of 1 μm to 100 μm.
In one embodiment, the volume change rate of the composite positive electrode material before and after delithiation of the lithium supplementing particles is 0.01% -3.0%.
In a second aspect, the present application provides a method for preparing a composite positive electrode material, including: mixing the positive electrode active material and lithium supplementing particles in proportion to obtain a first composite positive electrode material; mixing and sintering the first composite positive electrode material and the packaging material in proportion to obtain a second composite positive electrode material; the second composite positive electrode material comprises a core, the core comprises the positive electrode active material, the lithium supplementing particles are distributed on the outer surface layer of the core, and the packaging material forms a stable shell layer and is coated on the outer surfaces of the core and the lithium supplementing particles.
In a third aspect, the present application provides a positive electrode sheet, where the positive electrode sheet includes a current collector and an active material layer disposed on the current collector, where the active material layer includes the composite positive electrode material according to any one of the embodiments of the first aspect, or where the active material layer includes the composite positive electrode material obtained by the method for preparing a composite positive electrode material according to the second aspect.
In a fourth aspect, the present application provides a secondary battery, including the positive electrode sheet according to the third aspect, or including the composite positive electrode material according to any one of the embodiments of the first aspect, or including the composite positive electrode material obtained by the method for preparing the composite positive electrode material according to the second aspect.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic cross-sectional structure of a composite positive electrode material including a stabilizing shell layer according to one embodiment;
FIG. 2 is a schematic cross-sectional structure of a composite positive electrode material including a stabilizing shell layer and a cavity according to one embodiment;
FIG. 3 is a schematic cross-sectional structure of a composite positive electrode material including a stabilizing shell layer and a pre-coat layer according to one embodiment;
FIG. 4 is a schematic cross-sectional structure of another embodiment of a composite positive electrode material including a stabilizing shell layer and a pre-coat layer;
FIG. 5 is a schematic cross-sectional structure of a composite positive electrode material according to yet another embodiment including a stabilizing shell layer and a pre-coat layer;
FIG. 6 is a schematic cross-sectional structure of a composite positive electrode material according to one embodiment including a stabilizing shell layer, a pre-coat layer, and a cavity;
FIG. 7 is a flow chart of the preparation of a composite positive electrode material according to one embodiment;
fig. 8 is a flow chart of the preparation of a composite positive electrode material according to another embodiment.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When a component is considered to be "connected" to another component, it can be directly connected to the other component or intervening components may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description presented herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Some embodiments of the present application are described in detail below with reference to the accompanying drawings. The following embodiments and features of the embodiments may be combined with each other without conflict.
The application provides a composite positive electrode material, please refer to fig. 1, including a core 10, lithium supplementing particles 20 and a stable shell layer a, wherein the core 10 includes a positive electrode active material, the lithium supplementing particles 20 are distributed on an outer surface layer of the core 10, and the stable shell layer a is coated on the outer surface layers of the core 10 and the lithium supplementing particles 20.
Specifically, the core 10 (positive electrode active material) is mainly composed of a lithium-containing compound, which is a core of the core 10 that provides lithium ions, and the structure of the lithium-containing compound is not particularly limited. Alternatively, the shape of the inner core 10 may be spherical or spheroid in structure or other irregular shape.
The positive electrode active material includes, but is not limited to, lithium iron phosphate, lithium manganese iron phosphate, ternary positive electrode active materials (such as NCM ternary or NCA ternary), binary positive electrode active materials, or lithium-rich positive electrode active materials. Alternatively, the lithium-rich positive electrode active material has a chemical formula of Li 2+x1 M y1 O z1 Wherein M is at least one element of W, ti, al, ni, fe, mn, co, cr, V, mo, nb, zr, cu, mg, K, -0.2.ltoreq.x1.ltoreq.0.2, y1 is more than 0 and less than 1, and z1 is more than 0 and less than 12. For example, the positive active material may be one or more of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium nickel cobalt aluminate, lithium nickel manganate, and lithium-rich layered oxygen compound.
The lithium supplementing particles 20 are mainly composed of a lithium-rich compound for supplementing lithium ions to the positive electrode active material, and the structure of the lithium supplementing particles 20 is not particularly limited. Alternatively, the shape of the lithium-compensating particles 20 may be spherical or spheroid in structure or other irregular shapes.
Alternatively, the lithium-rich compound has the formula Li x2 M y2 O z2 Wherein M is at least one of the transition metal elements such as Ti, V, cr, mn, fe, co, ni, cu, zr, nb, mo, ru, and X2 is more than or equal to 1 and less than or equal to 8, y2 is more than 0 and less than or equal to 0, and z2 is more than 0 and less than 7. Such as Li 2 NiO 2 、Li 2 MnO 2 、Li 5 FeO 4 、Li 2 CuO 2 、Li 2 CoO 2 、Li 6 MnO 4 、Li 6 CoO 4 、Li 6 ZnO 4 、Li 2 Ni k Cu (1-k) O 2 (0 < k < 1), etc. It should be noted that some of the above lithium-rich materials may be used directly as the core 10.
It will be appreciated that the addition of lithium compensating particles 20 to the surface of the positive electrode active material provides a "prelithiation" scheme to compensate for the loss of active lithium. The lithium supplementing particles 20 serve as a sacrificial agent in the first-round charging process, release all lithium ions as one time as much as possible, and are used for supplementing irreversible lithium ions consumed by forming an SEI film on the negative electrode, so that the abundance of lithium ions in a battery system is maintained, and the first effect and the overall electrochemical performance of the lithium battery are improved.
The stable shell layer A comprises an encapsulation material, which may comprise at least one of a ceramic material, a polymer material, a carbon material, a perovskite type material, a NASICON type material, a garnet type material, an inverse perovskite type material, and a LISICON type material. It should be explained that, in the packaging material provided in the present application, the structural stability is high, and the packaging material is not easy to collapse after forming the fixing structure.
Alternatively, the combination of the stabilizing shell a and the lithium-compensating particle 20 may be such that the stabilizing shell a is coated on the outer surface of the lithium-compensating particle 20 (as shown by the dotted line indicated by E in fig. 1), so that the stabilizing shell a is actually attached to the outer surface of the core 10. The advantage of this structure is that the lithium supplementing particles 20 are completely coated, so that water vapor in the external environment hardly attacks the lithium supplementing particles 20, thereby reducing side reactions occurring on the surfaces of the lithium supplementing particles 20. The lithium supplementing particles 20 and the core 10 of this structure have the advantage of being capable of being preserved for a long period of time.
Alternatively, the stabilizing shell layer a is disposed at a portion of the outer surface of the lithium-compensating particles 20 (as indicated by the broken line indicated by F in fig. 1), so that the lithium-compensating particles 20 are actually attached to the outer surface of the core 10. The benefit of this structure is that the lithium ion extraction rate in the lithium ion compensating particles 20 is increased to reduce the loss of lithium ions during extraction and to increase the first charge rate.
In the prior art, lithium supplementing particles are generally directly added into an active material layer of the positive electrode for use, so that pits are easy to appear on the surface of the positive electrode sheet or gaps appear in the positive electrode sheet after primary charging, the stability of the overall structure of the positive electrode sheet is adversely affected, and the cycle performance of the battery is further deteriorated. Therefore, in the embodiment of the application, the lithium supplementing particles are combined to the surface layer of the inner core formed by the positive electrode active material, so that the two particles are combined into a whole and then applied to the lithium battery. And the lithium ion is released from the lithium supplementing particles 20 in the first charge process of the battery assembled by the composite positive electrode material, so that the volume of the lithium supplementing particles 20 is reduced. Which may cause cavities or depressions to occur in the interior or exterior surface of the composite positive electrode material. Therefore, further, the stable shell layer A is arranged on the outer surface layers of the inner core 10 and the lithium supplementing particles 20, and the packaging material with higher structural stability is selected, so that the stable shell layer A cannot collapse in structure even if a cavity or a dent appears in the composite positive electrode material, and the structural stability of the composite positive electrode material is ensured.
It can be understood that the material (packaging material) selection criteria of the stable shell layer a provided in the present application are different from the coating material selection criteria commonly used in the existing lithium supplementing agent. In the prior art, the main purpose of the coating material is to improve the ion export or import capability and prevent the material from absorbing water. In this application, the shell layer a material to be stabilized is selected to ensure that the composite positive electrode material does not collapse inwards (i.e., the cavity formed by the reduced lithium supplementing particles 20) after the lithium supplementing particles 20 are removed from lithium, or the outer surface of the stabilizing shell layer a does not recess inwards.
In one embodiment, the volume of the composite positive electrode material before the consumption of the lithium supplementing particles 20 is V1, the volume of the composite positive electrode material after the consumption of the lithium supplementing particles 20 is V2, and the volume of the lithium supplementing particles 20 is V3, so that V1-V2 is more than or equal to 0 and less than V3. Wherein V1-V2 are actually the volume changes of the composite positive electrode material before and after the first charge.
Alternatively, in the case where the lithium supplementing particles 20 are coated with the stabilizing shell layer a, V1-V2 may approach 0 (or equal to 0), i.e., the stabilizing shell layer a outside the lithium supplementing particles 20 does not shrink inward (in the cavity), thereby making the volume of the composite positive electrode material vary within a very small range.
The composite positive electrode material provided by the application is provided with the inner core 10 capable of circularly charging and discharging and the lithium supplementing particles 20 with the lithium supplementing function, so that the composite positive electrode material provided by the application has higher initial efficiency and capacity and better cycle performance compared with the conventional inner core 10; secondly, the outer surfaces of the inner core 10 and the lithium supplementing particles 20 are both coated with a stable shell layer A, after lithium ions are released from the lithium supplementing particles 20, the stable shell layer A can also keep self-structural stability so as to avoid the phenomenon that after a cavity is formed between the lithium supplementing particles 20 and the stable shell layer A, the stable shell layer A collapses inwards, so that even if the volume of the lithium supplementing particles 20 is reduced after lithium is removed in the first charging process, the composite positive electrode material can maintain the total volume basically unchanged, and the phenomenon that pits are easily formed on the surface of a positive electrode sheet or gaps are easily formed inside the positive electrode sheet after the lithium supplementing particles 20 and the inner core 10 are simply mixed and compounded for use is avoided, thereby ensuring the cycling stability of the composite positive electrode material.
In one embodiment, the material (encapsulation material) of the stabilized shell a includes, but is not limited to, at least one of a ceramic material, a polymer material, a carbon material, a perovskite type material, a NASICON type material, a garnet type material, an inverse perovskite type material, a LISICON type material.
Alternatively, the ceramic material may include Al 2 O 3 、SiO 2 Boehmite, si 3 N 4 One or more of SiC, boron nitride, zirconia, titania.
Alternatively, the polymeric material may include a polymer selected from the group consisting of 6 H 7 O 6 Na] n Organic polymer of structure [ C ] 6 H 7 O 2 (OH) 2 OCH 2 COONa] n Organic polymer of structure [ C ] 3 H 4 O 2 ]Organic polymer with n as structure, and [ C 3 H 3 O 2 Na] n Organic polymer of structure [ C ] 3 H 3 N] n Organic polymers of the structure containing- [ CH ] 2 -CF 2 ] n Organic polymers of the structure containing- [ NHCO ]]Organic polymers of structure containing imide rings- [ CO-N-CO ] in the main chain]-one or more of a structured organic polymer and polyvinylpyrrolidone.
Alternatively, the carbon material may include at least one of graphene, carbon nanotubes, amorphous carbon, graphite, carbon black.
Alternatively, the perovskite-type material may include Li 3x La 2/3-x TiO 3 (LLTO), in particular Li 0.5 La 0.5 TiO 3 、Li 0.33 La 0.57 TiO 3 、Li 0.29 La 0.57 TiO 3 、Li 0.33 Ba 0.25 La 0.39 TiO 3 、(Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O 3 、Li 0.5 La 0.5 Ti 0.95 Zr 0.05 O 3 At least one of the NASICON types such as but not limited to Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP), garnet type comprises Li 7 La 3 Zr 2 O 12 (LLZO)、Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 ，Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 At least one of (a)
In one embodiment, referring to fig. 1, a stabilizing shell layer a is coated on the outer surface of the lithium-compensating particles 20, so that a portion of the lithium-compensating particles 20 and the core 10 are relatively independent. Specifically, the preparation process of the structure may be that the encapsulating material and the lithium supplementing particles 20 are mixed first, so that the encapsulating material may be coated on the outer surface of the lithium supplementing particles 20 to form a mixed precursor. And then mixing the mixed precursor and the inner core 10, so that the mixed precursor and the inner core 10 are combined to form the stable shell layer A. The advantages of this structure are provided with reference to the above embodiments, and will not be described here.
In one embodiment, referring to fig. 1, an encapsulation material is bonded to the outer surface of the lithium-compensating particles 20 such that a portion of the lithium-compensating particles 20 are exposed and connected to the core 10. Specifically, the structure of the composite positive electrode material is shown in fig. 1. The preparation process of the structure can be that the inner core 10 and the lithium supplementing particles 20 are mixed firstly, so that the lithium supplementing particles 20 can be distributed on the outer surface of the inner core 10, and then the encapsulation materials are arranged on the outer surfaces of the inner core 10 and the lithium supplementing particles 20. So that the encapsulation material is bonded to the lithium supplementing particles 20 and the outer surface of the core 10 to form a stable shell layer a.
Alternatively, the structure may be prepared by mixing the encapsulating material, the lithium supplementing particles 20 and the core 10 at the same time, so that the encapsulating material, the lithium supplementing particles 20 and the core 10 are combined with each other.
The advantages of this structure are provided with reference to the above embodiments, and will not be described here. The preparation method of the structure has the advantages of fewer preparation process steps and lower preparation cost.
In one embodiment, referring to fig. 2, the composite positive electrode material further includes a cavity C formed between the lithium-removed lithium-supplementing particles and the stable shell layer a. Specifically, as shown in fig. 2, a cavity C may be formed in the stable shell layer a, and the cavity C may have a portion of the lithium supplementing particles 20 therein or may not have the lithium supplementing particles 20 therein. It can be appreciated that after the lithium-compensating particles 20 are de-lithiated during the first charge, the volume is reduced, the position occupied by the lithium-compensating particles 20 in the stable shell layer a is reduced, but the packaging material always maintains the original structure, i.e. forms the cavity C, while part of the unconsumed lithium-compensating particles 20 are still located in the cavity C.
The advantage of forming the cavity C in the stable shell layer A is that when the lithium supplementing particles 20 are subjected to lithium removal in the first-round charging process, the volume of the cavity C is reduced, the total volume of the particles which is basically unchanged is generated in the stable shell layer A, the phenomenon that pits are easily formed on the surface of a positive pole piece or gaps are formed in the positive pole piece after the lithium supplementing particles 20 are simply mixed and compounded with the inner core 10 for use is avoided, and meanwhile, the cavity C generated in the stable shell layer A can play a role of buffering stress generated by the lithium removal-lithium intercalation volume change of the inner core 10 in the charging and discharging cycle process, so that the structural stability of the pole piece can be improved, and the cycle performance of a battery can be improved by the composite positive pole material.
In another embodiment, the stabilizing shell a has cavities therein prior to delithiation of the lithium-compensating particles 20. After the positive electrode composite material is manufactured and molded, a cavity exists in the stable shell layer A. Optionally, the cavity may be filled with lithium supplementing particles 20; alternatively, the cavity may not be filled with lithium supplementing particles 20. The existence of the cavity can play a certain role in buffering the volume expansion of the composite positive electrode material.
In one embodiment, referring to fig. 3, the composite positive electrode material further includes a pre-coating layer B, wherein the pre-coating layer B coats the outer surface of the core 10, and the stabilizing shell layer a coats the outer surface of the pre-coating layer B.
Specifically, the pre-coating layer B is made of a pre-coating material. The precoating material is bonded to the outer surface of the core 10 and forms successive layers to provide a precoating layer B.
Alternatively, the preparation method of the composite positive electrode material with the structure may be that the pre-coating material and the core 10 are mixed first, and then the lithium supplementing particles 20 and the packaging material are mixed with the pre-coating material and the core 10, thereby obtaining the composite positive electrode material. The mixing manner of the lithium supplementing particles 20 and the encapsulating material with the core 10 having the pre-coating material can refer to the above embodiment, and will not be described herein.
Further, the pre-coat material has conductivity. Therefore, the pre-coat material may be a carbon material, a conductive polymer material, or a metal compound material. Of course, in other embodiments, the pre-cladding material may also be a non-conductive material, with the aim of further improving the tightness and uniformity of the cladding to the core.
Alternatively, the encapsulating material and the cladding material may be the same or different. It should be explained that the package material and the cladding material may have different structures in the case of the same elemental composition. For example, the encapsulation material may be graphene and the coating material may be amorphous carbon.
By providing the pre-coating layer B between the stable shell layer a and the inner core 10, and the pre-coating layer B also has conductivity, lithium ions in the inner core 10 can be extracted through the pre-coating layer B, and the ion extraction rate is improved.
In one embodiment, the material of the pre-coat layer B (pre-coat material) includes a carbon material, a conductive polymer material, and a metal compound.
Alternatively, the carbon material may include at least one of graphene, carbon nanotubes, amorphous carbon, graphite, carbon black.
Alternatively, the conductive polymer material may include at least one of polyacetylene, polypyrrole, polythiophene, polyaniline, and polyethylene dioxythiophene.
Alternatively, the metal compound may include In 2 O 3 、ZnO、SnO 2 At least one of them.
In one embodiment, referring to fig. 4, the composite positive electrode material may include a pre-coating material, but the pre-coating material may not form the pre-coating layer B. I.e., the pre-coat material is bonded to the outer surface of the inner core 10 and also a portion of the inner core 10 is exposed. Therefore, the stabilizing shell A coats the outer surface of the exposed core 10, as well as the outer surface of the partially pre-coated material.
Alternatively, on the basis of the above embodiment, the composite positive electrode material may include a pre-coating material, and the pre-coating material may form the pre-coating layer B. I.e., the precoat layer B coats the outer surface of the core 10. Therefore, the stable shell layer A is coated on the outer surface of the pre-coating layer B. Through setting up two-layer cladding (stable shell layer A and precoating layer B) at the surface of kernel 10, can make the cladding of kernel 10 more complete, avoid the side reaction of composite positive electrode material and electrolyte better to and reduce phenomena such as water absorption.
In one embodiment, when the stable shell layer a is thicker and the particle size of the lithium-compensating particles 20 is smaller, the outer surface of the composite positive electrode material may be a smooth curved surface (i.e., spherical surface). The structure has the advantages that the smooth curved surface has smaller surface defects, so that the structural stability of the composite positive electrode material can be enhanced, and the corrosion of external water vapor is avoided.
In one embodiment, referring to fig. 5, when the stable shell layer a is thin and the particle size of the lithium-compensating particles 20 is large, the encapsulating material coated on the surface of the lithium-compensating particles 20 protrudes out and coats the encapsulating material on the surface of the pre-coating layer B or/and the core 10. The structure has the advantages that the specific surface area of the composite positive electrode material is increased through part of the protruded packaging material, so that the lithium removal-intercalation efficiency is improved.
In one embodiment, referring to fig. 3, the stabilizing shell layer a is partially coated on the outer surface of the pre-coating layer B, and the other portion is coated on the outer surface of the lithium-compensating particles 20. I.e. a portion of the lithium-compensating particles 20 is connected to the pre-coating layer B. Specifically, as shown in fig. 3, in the above embodiment, since the pre-coating layer B is previously formed on the outer surface of the core 10 and then the lithium supplementing particles 20 are mixed, part of the lithium supplementing particles 20 are directly connected to the pre-coating layer B.
The lithium supplementing particles 20 are jointly coated by the pre-coating layer B and the stable shell layer A, so that on one hand, the corrosion of external water vapor to the lithium supplementing particles 20 is reduced, the efficiency of lithium ion extraction in the lithium supplementing particles 20 can be improved through the conductive property of the coating material, and on the other hand, the total thickness of the stable shell layer A and the pre-coating layer B is reduced, and the size of the composite anode material is further reduced.
In one embodiment, the lithium supplementing particles 20 are distributed on the outer surface of the pre-coating layer B, and the lithium supplementing particles 20 are embedded in the stable shell layer a.
In one embodiment, referring to fig. 3, lithium supplementing particles 20 are distributed on the outer surface of the pre-coating layer B, and the lithium supplementing particles 20 are embedded in the pre-coating layer B. Specifically, as shown in fig. 3, the particles of the lithium supplementing particles 20 may be partially embedded in the pre-coating layer B. It will be appreciated that the lithium supplementing particles 20 are intercalated into the pre-coating layer B, taking into account the type of pre-coating material. For example, the pre-coating material is a carbon material, and the surface is a carbon material with holes, so that the lithium supplementing particles 20 can be embedded therein.
Alternatively, the precursor of the pre-coating material may be a polymer material, glucose, cellulose, resin, pitch, etc., and the precursor of the coating material may be mixed with the inner core 10 first, so that the precursor of the pre-coating material may coat the outer surface of the inner core 10. And then the lithium supplementing particles 20 are mixed therein, and the precursor of the pre-coating material is carbonized in a co-sintering manner, and concave is formed at the position where the lithium supplementing particles 20 are arranged, so that part of the position of the obtained pre-coating layer B (formed by the precursor of the pre-coating material) is intercalated by the lithium supplementing particles 20.
Alternatively, the precursor of the pre-coating material may also be a metal inorganic material with defects, and after the precursor of the pre-coating material coats the outer surface of the inner core 10, the resulting coating layer has defects. The lithium supplementing particles 20 are thus embedded in the coating material by the defect after the contact of the defect.
The benefit of inserting the lithium supplementing particles 20 into the pre-coating material by arranging part of the lithium supplementing particles is that the efficiency of lithium ion extraction in the lithium supplementing particles 20 is improved by utilizing the conductive property of the pre-coating material, and the total thickness of the stable shell layer A and the pre-coating layer B can be reduced by inserting the lithium supplementing particles 20, so that the size of the composite positive electrode material is further reduced.
In one embodiment, the material (pre-coat material) of the pre-coat layer B has a greater deformability than the material (encapsulation material) of the stabilizing shell layer a. Specifically, the pre-coating material may be an aerogel made of carbon material, or an aerogel made of conductive polymer material, or may be an elastomeric polymer material. That is, in the process of charging and discharging the inner core 10, the pre-coating material can generate corresponding change along with the volume change of the inner core 10, and plays a certain role in buffering the volume expansion of the positive electrode active material.
The preparation of the pre-coating layer B by adopting the coating material with deformation capability has the advantages that the stress generated by the change of the lithium removal-insertion volume of the inner core 10 in the charge-discharge cycle process can be absorbed by the pre-coating layer B in advance, so that the buffer function is realized, the stress transferred to the stable shell layer A is reduced, the stress pressure born by the packaging material is reduced, the structural stability of the composite anode material can be further enhanced, and more possibilities are provided for the selection of the packaging material.
In one embodiment, the cavity C may be formed at the contact of the stabilizing shell a and the pre-coat B. As shown in fig. 6, the lithium-compensating particles 20 are co-coated with the stabilizing shell a and the pre-coating layer B (or understood as the lithium-compensating particles 20 being embedded in the pre-coating layer B), so that after the lithium-compensating particles 20 are consumed, the cavity C appears at the contact of the stabilizing shell a and the pre-coating layer B.
In one embodiment, the ratio of the thickness of the stabilizing shell layer A to the thickness of the pre-coating layer B is (0.1 to 50): 1. Specifically, the thickness ratio of the stabilizing shell layer a to the pre-coat layer B may be, but is not limited to, 0.1:1, 0.5:1, 1:1, 2:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1. Optionally, the thickness ratio of the stable shell layer A and the pre-coating layer B is (1-50): 1, or (5-50): 1, or (20-50): 1, or (0.1-40): 1, or (0.1-30): 1, or (1-30): 1, or (5-40): 1.
The control of the thickness ratio of the stable shell layer A and the pre-coating layer B within the above range can ensure the content of the lithium supplementing particles 20, thereby ensuring the effect of 'pre-lithiation'; the particle size of the composite positive electrode material can be prevented from being too large, so that the composite positive electrode material is ensured to have higher specific surface area, and the charge and discharge efficiency is further ensured.
When the thickness of the stable shell layer a is smaller than the above ratio, the volume of the lithium compensating particles 20 is smaller, i.e., the lithium compensating particles 20 occupy less area, which results in insufficient lithium ions being provided in the first charging process, resulting in reduced coulombic efficiency, and directly affecting the cycle life and energy density of the lithium battery. When the thickness of the stable shell layer A is larger than the range of the ratio, the occupation ratio of the packaging material is larger, so that the energy density is not improved, and meanwhile, the particle size of the composite positive electrode material is too large, and the charge and discharge efficiency is affected.
In one embodiment, the thickness of the stabilized shell A is from 2nm to 2000nm. The effect of stabilizing the thickness range of the shell layer a can be referred to the above embodiment, and will not be described herein.
In one embodiment, the thickness of the precoat layer B is 2nm to 1000nm. As can be appreciated, the thickness of the pre-coat layer B ensures the specific capacity of the composite positive electrode material and the electronically conductive environment. When the thickness of the pre-coating layer B is smaller than the above range, it is unfavorable to construct a good electron conductive environment; when the thickness of the pre-coating layer B is greater than the above range, since the pre-coating layer B does not contribute lithium ions, the overall gram-capacity of the composite cathode material may be reduced.
In one embodiment, the mass ratio of the core 10 to the lithium-compensating particles 20 is (80-99): 1-20. Specifically, the mass ratio of the core 10 and the lithium-compensating particles 20 may be, but is not limited to, 80:1, 90:1, 99:1, 80:5, 90:5, 99:5, 80:10, 90:10, 99:10, 80:20, 90:20, 99:20. Optionally, the mass ratio of the core 10 to the lithium supplementing particles 20 is (90-99): (1-20), or (80-99): (5-20), or (80-99): (10-20), or (80-99): (1-10), or (90-99): (1-5), or (90-99): (10-20).
The mass ratio of the core 10 to the lithium supplementing particles 20 is controlled within the above range, so that not only the content of the lithium supplementing particles 20 can be ensured, thereby ensuring the effect of 'pre-lithiation', but also the excessive use of the lithium supplementing particles 20 can be avoided, resulting in energy surplus and resource waste.
When the mass ratio of the core 10 is greater than the above range or the mass ratio of the lithium supplementing particles 20 is less than the above range, the content of the lithium supplementing particles 20 in the composite positive electrode material is low, which results in insufficient lithium ions being provided in the first charging process, resulting in reduced coulombic efficiency, and directly affecting the cycle life and energy density of the lithium battery. When the mass ratio of the core 10 is smaller than the above range or the mass ratio of the lithium supplementing particles 20 is larger than the above range, the content of the lithium supplementing particles 20 in the composite positive electrode material is large, resulting in surplus energy and waste of resources.
In one embodiment, the particle size D50 of the inner core 10 is in the range of 1 μm to 50. Mu.m. Specifically, the particle diameter D50 of the core 10 may be, but is not limited to, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm. Alternatively, the particle diameter D50 of the core 10 is 1 μm to 40 μm, or 5 μm to 50 μm, or 10 μm to 30 μm.
When the particle size of the core 10 is larger than the above range, the overall particle size of the composite positive electrode material is larger, which is not beneficial to improving the energy density and the deintercalation efficiency of lithium ions; when the particle diameter of the core 10 is smaller than the above range, the difficulty in preparation increases, and the particles form relatively serious agglomerates.
In one embodiment, the particle diameter D50 of the lithium supplementing particles 20 is in the range of 0.1 μm to 10. Mu.m. Specifically, the particle diameter D50 of the lithium supplementing particles 20 may be, but is not limited to, 0.1 μm, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm. Alternatively, the particle diameter D50 of the lithium supplementing particles 20 is 0.1 μm to 5 μm, or 0.1 μm to 3 μm, or 1 μm to 10 μm, or 5 μm to 10 μm.
When the particle size of the lithium supplementing particles 20 is larger than the above range, the thickness of the stable shell layer a is excessively large, and the overall particle size of the composite positive electrode material is large, which is not beneficial to improving the energy density and the deintercalation efficiency of lithium ions; when the particle diameter of the lithium supplementing particles 20 is smaller than the above range, the difficulty of preparation increases, and the particles form relatively serious agglomerates.
In one embodiment, the composite positive electrode material has a particle diameter D50 in the range of 1 μm to 100. Mu.m. Specifically, the particle diameter D50 of the composite positive electrode material may be, but is not limited to, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 60 μm, 80 μm, 100 μm. Alternatively, the particle diameter D50 of the composite positive electrode material is 1 μm to 80 μm, or 1 μm to 50 μm, or 10 μm to 80 μm, or 20 μm to 50 μm.
When the particle size of the composite positive electrode material is larger than the above range, the energy density and the deintercalation efficiency of lithium ions are not improved; when the particle diameter of the composite positive electrode material is smaller than the above range, the difficulty of preparation increases, and particles form relatively serious agglomeration, and the difficulty of preparation of the core 10 and the lithium supplementing particles 20 increases accordingly.
In one embodiment, the composite positive electrode material has a volume change rate of less than 3.0% before and after delithiation of the lithium-compensating particles 20. Specifically, the volume change rate of the composite positive electrode material before and after delithiation of the lithium supplementing particles 20 may be, but is not limited to, 0.01%, 0.1%, 0.5%, 1%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 3%. Optionally, the volume change rate of the composite positive electrode material before and after lithium removal of the lithium supplementing particles 20 is 0.01% -2.0%, or 0.01% -1.0%, or 0.1% -1%, or 0.5% -2.0%, or 0.5% -1.5%. It can be appreciated that in this embodiment, the composite positive electrode material can maintain a substantially constant total volume even if the volume of the lithium-compensating particles is reduced after lithium removal during the first charge cycle.
According to the embodiment of the application, the stable shell layer is arranged on the outer surface layer of the inner core and the lithium supplementing particles, after the lithium supplementing material is subjected to lithium removal, a cavity is formed between the lithium supplementing particles and the stable shell layer, on one hand, the stable shell layer can improve the overall structural stability of the composite positive electrode material, the composite positive electrode material cannot collapse from outside to inside, and on the other hand, the cavity can also play a role in buffering stress generated by lithium removal-lithium intercalation volume change of the positive electrode active material in the charge-discharge cycle process, so that the structural stability of the pole piece can be improved.
In an embodiment, the present application further provides a method for preparing the composite positive electrode material, please refer to fig. 7, which is specifically used for preparing the composite positive electrode material in the above embodiment. The preparation method comprises the following steps:
and S10, mixing the positive electrode active material and the lithium supplementing particles in proportion to obtain a first composite positive electrode material.
And S20, mixing and sintering the first composite positive electrode material and the packaging material in proportion to obtain a second composite positive electrode material.
The second composite positive electrode material comprises a core, the core comprises a positive electrode active material, lithium supplementing particles are distributed on the outer surface layer of the core, and the packaging material forms a stable shell layer and is coated on the outer surfaces of the core and the lithium supplementing particles.
Optionally, in step S10, the positive electrode active material and the lithium supplementing particles are mixed in proportion and sintered, or may be mixed by ball milling without sintering.
Alternatively, in step S10, the structural formulas of the positive electrode active material and the lithium supplementing particles may be referred to the above-described embodiments.
Alternatively, in step S10, the mixing ratio of the positive electrode active material and the lithium supplementing particles may be referred to the above embodiment.
Alternatively, in step S20, the kind of the encapsulation material may be referred to the above-described embodiment.
Alternatively, in step S20, the method of bonding the encapsulating material and the first composite positive electrode material may employ a solid phase method, a liquid phase method, a sol-gel method, CVD, ALD, or the like.
In another embodiment, the method for preparing the composite positive electrode material includes the steps of:
and S10', mixing and sintering the packaging material and the lithium supplementing particles in proportion to obtain a mixed precursor.
And S20', mixing and sintering the mixed precursor and the positive electrode active material in proportion to obtain the composite positive electrode material.
In another embodiment, the method for preparing the composite positive electrode material includes the steps of:
and S10', mixing and sintering the packaging material, the lithium supplementing particles and the positive electrode active material in proportion to obtain the composite positive electrode material.
In an embodiment, the present application further provides a method for preparing the composite positive electrode material, please refer to fig. 8, and the composite positive electrode material includes a pre-coating material. The preparation method comprises the following steps:
s00, mixing and sintering the positive electrode active material and the pre-coating material or the precursor thereof in proportion to obtain the first composite positive electrode material.
And S10, mixing and sintering the first composite positive electrode material and the lithium supplementing particles in proportion to obtain a second composite positive electrode material.
And S20, mixing and sintering the second composite positive electrode material and the packaging material in proportion to obtain a third composite positive electrode material.
The third composite positive electrode material comprises a pre-coating material combined on the outer surface of the positive electrode active material and a mixed precursor combined on the outer surface of the pre-coating material, wherein the mixed precursor comprises lithium supplementing particles and an encapsulating material.
Optionally, in step S00, the precursor of the pre-coat material includes one or more of a polymeric material, glucose, cellulose, resin, pitch, and the like.
Optionally, in step S00, when the pre-cladding material is a carbon material, step S10 may further include a sintering process. Wherein the sintering temperature is 350-800 ℃, the sintering time is 1-15 h, and the sintering environment can be at least one of nitrogen, argon, helium and neon.
In one embodiment, the present application further provides a positive electrode sheet comprising a current collector and an active material layer disposed on the current collector, the active material layer comprising the composite positive electrode material of any one of the above embodiments.
In one embodiment, the positive electrode plate comprises a positive electrode current collector, the positive electrode current collector is provided with a positive electrode active layer, the positive electrode active layer comprises a composite positive electrode material, a conductive agent, a binder and other components, the materials are not particularly limited, and suitable materials can be selected according to practical application requirements. The positive electrode current collector includes, but is not limited to, any one of copper foil and aluminum foil. The conductive agent comprises one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nano tube, and the content of the conductive agent in the positive electrode active layer is 3-5 wt%. The binder comprises one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, and the content of the binder in the positive electrode active layer is 2-4wt%.
In one embodiment, the present application also provides a secondary battery comprising a negative electrode tab, a separator, and the positive electrode tab described above. The positive electrode plate comprises the composite positive electrode material.
The technical scheme of the invention is described in detail by specific examples.
Example 1
The embodiment provides a composite positive electrode material and a preparation method thereof, wherein the composite positive electrode material comprises a core, lithium supplementing particles and a stable shell layer, the core comprises a positive electrode active material (lithium iron phosphate), and the lithium supplementing particles comprise a lithium-rich compound (Li) 5 FeO 4 ) The stabilizing shell comprises an encapsulating material (alumina).
The preparation method of the composite positive electrode material comprises the following steps:
(1) Combining lithium iron phosphate positive electrode active material with Li 5 FeO 4 Uniformly mixing the lithium supplementing particles according to the mass ratio of 95:5 to obtain the lithium with externally distributed particles 5 FeO 4 And (3) secondary particles of positive electrode active material of the lithium supplementing particles.
(2) And uniformly mixing the secondary particles of the positive electrode active material with aluminum isopropoxide (aluminum source) according to the mass ratio of 90:10, and sintering for 6 hours at 500 ℃ under the argon cladding atmosphere to obtain the composite positive electrode material.
Example 2
The embodiment provides a composite positive electrode material and a preparation method thereof, wherein the composite positive electrode material comprises a core, lithium supplementing particles, a pre-coating layer and a stable shell layer, the core comprises a positive electrode active material (lithium iron phosphate), and the lithium supplementing particles comprise a lithium-rich compound (Li) 5 FeO 4 ) The pre-coating layer is a carbon layer, the stable shell layer comprises an encapsulating material (alumina), and the lithium supplementing particles are embedded into the stable shell layer.
The preparation method of the composite positive electrode material comprises the following steps:
(1) And uniformly mixing the lithium iron phosphate anode active material with a glucose carbon source according to the mass ratio of 90:10, and sintering for 10 hours at 600 ℃ under the protection of argon to obtain the carbon-coated lithium iron phosphate anode active material.
(2) Combining carbon-coated lithium iron phosphate positive electrode active material with Li 5 FeO 4 Uniformly mixing the lithium supplementing particles according to the mass ratio of 95:5 to obtain the lithium with externally distributed particles 5 FeO 4 And (3) secondary particles of positive electrode active material of the lithium supplementing particles.
(3) And uniformly mixing the secondary particles of the positive electrode active material with aluminum isopropoxide (aluminum source) according to the mass ratio of 90:10, and sintering for 6 hours at 500 ℃ under the argon cladding atmosphere to obtain the composite positive electrode material.
Example 3
The embodiment provides a composite positive electrode material and a preparation method thereof, wherein the composite positive electrode material comprises a core, lithium supplementing particles, a pre-coating layer and a stable shell layer, the core comprises a positive electrode active material (lithium iron phosphate), and the lithium supplementing particles comprise a lithium-rich compound (Li) 5 FeO 4 ) The pre-coating layer is a carbon layer, the stable shell layer comprises a packaging material (aluminum oxide), the lithium supplementing particles are distributed on the outer surface of the pre-coating layer, part of the stable shell layer is coated on the outer surface of the pre-coating layer, and the other part of the stable shell layer is coated on the outer surface of the lithium supplementing particles.
The preparation method of the composite positive electrode material comprises the following steps:
(1) And uniformly mixing the lithium iron phosphate anode active material with a glucose carbon source according to the mass ratio of 90:10, and sintering for 10 hours at 600 ℃ under the protection of argon to obtain the carbon-coated lithium iron phosphate anode active material.
(2) Combining carbon-coated lithium iron phosphate positive electrode active material with Li 5 FeO 4 And uniformly mixing lithium supplementing particles and aluminum isopropoxide (aluminum source) according to the mass ratio of 95:5:10, and sintering for 6 hours at 500 ℃ under an argon cladding atmosphere to obtain the composite anode material.
Example 4
Unlike example 2, the encapsulating material used for the stable shell layer in example 4 was Li 7 LV 3 Zr 2 O 12 。
Example 5
Unlike example 2, the precoat layer of example 5 uses the material In 2 O 3 。
Example 6
Unlike example 2, the mass ratio of the positive electrode active material and the lithium supplementing particles was 90:10.
Comparative example 1
This comparative example provides a composite positive electrode material, which differs from example 1 in that: the composite positive electrode material only comprises a positive electrode active material inner core and lithium supplementing particles, wherein the lithium supplementing particles are distributed on the outer surface layer of the inner core, the positive electrode active material comprises lithium iron phosphate, and the lithium supplementing particles comprise lithium-rich compounds (Li 5 FeO 4 ) Wherein lithium iron phosphate: li (Li) 5 FeO 4 The mass ratio of (2) is 95:5.
Comparative example 2
This comparative example provides a positive electrode material that is lithium iron phosphate and lithium supplementing particles (Li 5 FeO 4 ) Wherein lithium iron phosphate: li (Li) 5 FeO 4 The mass ratio of (2) is 95:5.
The composite cathode materials provided in examples 1-6 above, and the cathode materials provided in comparative examples 1-2 were assembled into a cathode and a lithium ion battery, respectively, according to the following methods:
mixing the composite anode material, SP and PVDF according to the mass ratio of 90:4:6 to homogenate anode slurry, coating the anode slurry on the surface of an aluminum foil, vacuum drying overnight at 110 ℃, and rolling to obtain an anode sheet;
a negative electrode, namely a lithium sheet;
electrolyte, mixing ethylene carbonate and ethylmethyl carbonate in a volume ratio of 3:7, and adding LiPF 6 Electrolyte is formed, liPF 6 The concentration of (2) is 1mol/L;
a separator, namely a polypropylene microporous separator;
and (3) assembling the lithium ion battery, namely assembling the button type lithium ion whole battery in an inert atmosphere glove box according to the assembling sequence of the graphite negative electrode plate, the diaphragm, the electrolyte and the positive electrode plate.
Each lithium ion battery assembled in the above lithium ion battery example was subjected to electrochemical performance test under the following conditions:
charging and discharging at 0.1C multiplying power, and voltage range is 2.5-4.3V.
The test of the volume change rate of the composite positive electrode material is characterized by adopting SEM, and the thickness of an active material layer of the original positive electrode plate is recorded as d 0 The thickness of the active material layer of the positive plate after the first charge and discharge is recorded as d 1 Volume change rate= (d 0 -d 1 )/d 0 ×100％。
The test results of the above composite positive electrode material and lithium ion battery are shown in table 1 below.
TABLE 1 Performance test results
As can be seen from the test results of examples 1-6 and comparative examples 1-2 in Table 1, the battery provided in examples 1-6 has a first-cycle charge specific capacity of more than 161mAh/g, a discharge specific capacity of more than 156mAh/g, and a capacity retention rate after 100 cycles is significantly higher than those of comparative examples 1 and 2, which indicates that the stable shell layer of the composite positive electrode material provided by the application has a good protection effect on the composite positive electrode material, and can reduce the conditions of water absorption deterioration and side reaction with electrolyte of the composite positive electrode material.
Meanwhile, the volume change rate of the composite positive electrodes of the embodiments 1-6 is relatively low (less than 0.5%), which indicates that the pole piece structure is stable, and the pole piece is also the reason that the capacity retention rate of the embodiments 1-6 is high; and in comparative examples 1 and 2, after the first charge and discharge are completed, the volume is reduced due to the delithiation of the lithium supplementing material, the change rate exceeds 4%, the pole piece structure is unstable, and the capacity retention rate is reduced.
As can be seen from the test results of example 1, example 2 and example 3 in table 1, the provision of the pre-coating layer (carbon layer) between the stable shell layer and the core can further improve the electrochemical performance of the battery and reduce the expansion rate of the composite cathode material. The precoat layer has better conductivity, so that the lithium ion transmission effect can be improved, and the conditions of water absorption and deterioration and side reaction with electrolyte of the composite positive electrode material can be further reduced.
From the test results of example 2 and example 3 in table 1, it can be seen that the specific structure formed by the lithium supplementing particles and the stable shell layer has less influence on the performance of the battery. And since the one-step process is reduced in example 3, the production efficiency in actual production can be improved and the cost can be reduced by adopting the preparation method of example 3.
From the test results of example 2 and example 4 in table 1, it can be seen that the encapsulation materials used for the stable shell layer may have a variety, and the selected materials have less influence on the battery performance and the performance of the composite cathode material. The scheme provided by the application has the advantages of improving the battery performance and universality, so that the scheme provided by the application has extremely high commercial value.
As can be seen from the test results of example 2 and example 5 in table 1, the material of the pre-coating layer may not be limited to the carbon material, other materials may be selected, and the replacement material has less influence on the battery performance and the performance of the composite cathode material.
As can be seen from the test results of example 2 and example 6 in table 1, the battery capacity can be increased by increasing the content of the lithium supplementing particles, and the volume change rate of the composite positive electrode material is lower under the scheme provided in the present application.
In summary, compared with the conventional positive electrode material and the lithium supplementing material which are simply mixed for use, the composite positive electrode material provided by the application has higher initial efficiency and capacity and better cycle performance. The application provides a composite positive electrode material surface cladding has stable shell layer, after the lithium ion is released to the benefit lithium granule, stable shell layer can also keep self stable in structure to avoid forming the cavity back between benefit lithium granule and stable shell layer, so the benefit lithium granule even the volume reduces after first round charging process delithiation, composite positive electrode material also can maintain basic unchangeable total volume, the phenomenon that pit appears or the inside void appears in the positive plate after the first time charging when having avoided benefit lithium granule and kernel simple mixed compound use on the positive plate surface, thereby can ensure composite positive electrode material's circulation stability.
In the description of the embodiments of the present application, it should be noted that, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like refer to the orientation or positional relationship described based on the drawings, which are merely for convenience of description and simplification of the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.
The foregoing disclosure is only a preferred embodiment of the present application, and it is not intended to limit the scope of the claims, and one of ordinary skill in the art will understand that all or part of the processes for implementing the embodiments described above may be performed with equivalent changes in the claims of the present application and still fall within the scope of the present application.
Claims (11)
1. A composite positive electrode material, comprising:
a core including a positive electrode active material;
lithium supplementing particles distributed on the outer surface layer of the inner core;
and the stable shell layer is coated on the outer surface layers of the inner core and the lithium supplementing particles.
2. The composite positive electrode material according to claim 1, wherein the volume of the composite positive electrode material before delithiation of the lithium supplementing particles is V1, the volume of the composite positive electrode material after delithiation of the lithium supplementing particles is V2, and the volume of the lithium supplementing particles is V3, and the requirement that V1-V2 is more than or equal to 0 and less than V3 is satisfied.
3. The composite positive electrode material of claim 1, further comprising a cavity formed between the lithium-compensating particles after delithiation and the stabilizing shell layer.
4. The composite positive electrode material according to claim 1, further comprising a pre-coating layer, wherein the pre-coating layer is coated on the outer surface of the inner core, and wherein the stabilizing shell layer is coated on the outer surface of the pre-coating layer.
5. The composite positive electrode material according to claim 4, wherein the lithium supplementing particles are distributed on the outer surface of the pre-coating layer, and the lithium supplementing particles are embedded in the stable shell layer, or the stable shell layer is partially coated on the outer surface of the pre-coating layer, and the other part is coated on the outer surface of the lithium supplementing particles.
6. The composite positive electrode material according to claim 4, wherein the material of the stable shell layer comprises one or more of a ceramic material, a polymer material, a carbon material, a perovskite type material, a NASICON type material, a garnet type material, an inverse perovskite type material, a LISICON type material; and/or the material of the pre-coating layer comprises one or more of a carbon material, a conductive polymer material and a metal compound.
7. The composite positive electrode material according to claim 4, wherein the pre-coat material has a deformability greater than that of the stable shell material; and/or the ratio of the thickness of the stabilizing shell layer to the pre-coating layer is 1: (0.1-50).
8. The composite positive electrode material according to any one of claims 1 to 7, wherein,
the mass ratio of the positive electrode active material to the lithium supplementing particles is (80-99) to (1-20);
And/or the particle diameter D50 of the positive electrode active material is in the range of 1 μm to 50 μm;
and/or the particle diameter D50 of the lithium supplementing particles ranges from 0.1 mu m to 10 mu m;
and/or the particle diameter D50 of the composite positive electrode material is in the range of 1-100 mu m;
and/or the volume change rate of the composite positive electrode material before and after lithium removal of the lithium supplementing particles is less than 3.0%.
9. The preparation method of the composite positive electrode material is characterized by comprising the following steps:
mixing the positive electrode active material and lithium supplementing particles in proportion to obtain a first composite positive electrode material;
mixing and sintering the first composite positive electrode material and the packaging material in proportion to obtain a second composite positive electrode material;
the second composite positive electrode material comprises a core, the core comprises the positive electrode active material, the lithium supplementing particles are distributed on the outer surface layer of the core, and the packaging material forms a stable shell layer and is coated on the outer surfaces of the core and the lithium supplementing particles.
10. A positive electrode sheet, characterized in that the positive electrode sheet comprises a current collector and an active material layer provided on the current collector, the active material layer comprising the composite positive electrode material according to any one of claims 1 to 8, or the active material layer comprising the composite positive electrode material obtained by the method for producing a composite positive electrode material according to claim 9.
11. A secondary battery comprising the positive electrode sheet according to claim 10, or comprising the composite positive electrode material according to any one of claims 1 to 8, or comprising the composite positive electrode material obtained by the method for producing a composite positive electrode material according to claim 9.
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