CN118136804A - Positive electrode material and preparation method and application thereof - Google Patents
Positive electrode material and preparation method and application thereof Download PDFInfo
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- CN118136804A CN118136804A CN202410234694.9A CN202410234694A CN118136804A CN 118136804 A CN118136804 A CN 118136804A CN 202410234694 A CN202410234694 A CN 202410234694A CN 118136804 A CN118136804 A CN 118136804A
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- positive electrode
- electrode material
- manganese dioxide
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- graphite alkyne
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 92
- 238000002360 preparation method Methods 0.000 title abstract description 41
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims abstract description 117
- -1 graphite alkyne Chemical class 0.000 claims abstract description 63
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 61
- 239000010439 graphite Substances 0.000 claims abstract description 61
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 claims abstract description 30
- 238000004519 manufacturing process Methods 0.000 claims abstract description 10
- 239000011246 composite particle Substances 0.000 claims description 30
- 238000000576 coating method Methods 0.000 claims description 23
- 239000011248 coating agent Substances 0.000 claims description 22
- 238000002156 mixing Methods 0.000 claims description 17
- 239000002245 particle Substances 0.000 claims description 15
- 238000000498 ball milling Methods 0.000 claims description 11
- 239000002131 composite material Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 239000002135 nanosheet Substances 0.000 claims description 9
- 239000010405 anode material Substances 0.000 claims description 7
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 abstract description 12
- 238000004090 dissolution Methods 0.000 abstract description 7
- 230000002195 synergetic effect Effects 0.000 abstract description 5
- 150000002500 ions Chemical class 0.000 abstract description 3
- 238000004146 energy storage Methods 0.000 abstract 1
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- 230000000052 comparative effect Effects 0.000 description 25
- 238000012360 testing method Methods 0.000 description 23
- 238000000034 method Methods 0.000 description 19
- 239000011572 manganese Substances 0.000 description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 14
- 230000000694 effects Effects 0.000 description 14
- 229910001437 manganese ion Inorganic materials 0.000 description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 9
- 229910017604 nitric acid Inorganic materials 0.000 description 9
- 238000001179 sorption measurement Methods 0.000 description 9
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 8
- 229910019142 PO4 Inorganic materials 0.000 description 8
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 8
- 239000003792 electrolyte Substances 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 239000000523 sample Substances 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 229910052744 lithium Inorganic materials 0.000 description 7
- 229910052748 manganese Inorganic materials 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 6
- 239000012286 potassium permanganate Substances 0.000 description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 5
- 239000011889 copper foil Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000006258 conductive agent Substances 0.000 description 4
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 3
- 239000006230 acetylene black Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 239000012792 core layer Substances 0.000 description 3
- 235000019441 ethanol Nutrition 0.000 description 3
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- 230000014759 maintenance of location Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 229920000767 polyaniline Polymers 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 2
- ZURRXKNELWBJHT-UHFFFAOYSA-N C1=CC=CC=C1.C#C.C#C.C#C.C#C.C#C.C#C Chemical compound C1=CC=CC=C1.C#C.C#C.C#C.C#C.C#C.C#C ZURRXKNELWBJHT-UHFFFAOYSA-N 0.000 description 2
- WAEMQWOKJMHJLA-UHFFFAOYSA-N Manganese(2+) Chemical compound [Mn+2] WAEMQWOKJMHJLA-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
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- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 150000004678 hydrides Chemical class 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 238000002386 leaching Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 2
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
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- 238000003860 storage Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229920000089 Cyclic olefin copolymer Polymers 0.000 description 1
- 229920002943 EPDM rubber Polymers 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910011980 LiFe0.4Mn0.6PO4 Inorganic materials 0.000 description 1
- 229910011990 LiFe0.5Mn0.5PO4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- KWYHDKDOAIKMQN-UHFFFAOYSA-N N,N,N',N'-tetramethylethylenediamine Chemical compound CN(C)CCN(C)C KWYHDKDOAIKMQN-UHFFFAOYSA-N 0.000 description 1
- 229920000459 Nitrile rubber Polymers 0.000 description 1
- AUBNQVSSTJZVMY-UHFFFAOYSA-M P(=O)([O-])(O)O.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.[Li+] Chemical compound P(=O)([O-])(O)O.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.[Li+] AUBNQVSSTJZVMY-UHFFFAOYSA-M 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920002334 Spandex Polymers 0.000 description 1
- 239000002174 Styrene-butadiene Substances 0.000 description 1
- NCZYUKGXRHBAHE-UHFFFAOYSA-K [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] Chemical compound [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] NCZYUKGXRHBAHE-UHFFFAOYSA-K 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 125000000304 alkynyl group Chemical group 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000004760 aramid Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 229920003235 aromatic polyamide Polymers 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000007771 core particle Substances 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 238000006880 cross-coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- DGTVXEHQMSJRPE-UHFFFAOYSA-M difluorophosphinate Chemical compound [O-]P(F)(F)=O DGTVXEHQMSJRPE-UHFFFAOYSA-M 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 229920001038 ethylene copolymer Polymers 0.000 description 1
- 239000005038 ethylene vinyl acetate Substances 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 229920001973 fluoroelastomer Polymers 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 1
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 description 1
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 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
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000011331 needle coke Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 238000011056 performance test Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 229920001200 poly(ethylene-vinyl acetate) Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920000346 polystyrene-polyisoprene block-polystyrene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920002689 polyvinyl acetate Polymers 0.000 description 1
- 239000011118 polyvinyl acetate Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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- 229920000468 styrene butadiene styrene block copolymer Polymers 0.000 description 1
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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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Electrochemistry (AREA)
- Nanotechnology (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Composite Materials (AREA)
- General Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application discloses a positive electrode material, a preparation method and application thereof, and belongs to the field of energy storage. According to the positive electrode material, the lithium iron manganese phosphate is used as an inner core, and at least one shell layer containing nano manganese dioxide and graphite alkyne is coated on the surface of the inner core, so that the manganese element dissolution degree of a product is obviously reduced when the product is applied to a secondary battery due to the synergistic effect of the nano manganese dioxide and the graphite alkyne, the gas yield at high temperature is low, and the ion conduction capability is strong; the secondary battery has excellent dynamic performance, low risk of high-temperature gas production, small volume expansion rate, high safety coefficient and excellent cycle performance.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a positive electrode material and a preparation method and application thereof.
Background
Secondary batteries, particularly lithium ion secondary batteries, exhibit different electrochemical performance characteristics depending on the type of positive electrode material. Compared with ternary positive electrode materials, the lithium iron phosphate positive electrode materials have the characteristics of low working voltage and high structural stability, and the prepared lithium iron phosphate lithium ion secondary battery is high in safety, however, the lithium iron phosphate positive electrode materials are high in capacity attenuation rate at low temperature (-20 ℃ and below), so that the application and development of the lithium iron phosphate positive electrode materials in a low-temperature environment are limited.
For this reason, lithium iron phosphate positive electrode materials have been used instead of pure lithium iron phosphate positive electrode materials, and the product can exhibit a higher capacity level at low temperatures. However, when the lithium iron manganese phosphate positive electrode material is applied to a lithium ion secondary battery, manganese ions are easily dissolved out due to the ginger-Taylor effect, and then SEI films formed on the pole pieces are damaged to be regenerated continuously, active lithium ions are continuously lost along with the battery circulation, the impedance of the pole pieces is increased, even gas is generated on the surface of a negative electrode, and finally the service life of the product is extremely fast attenuated, particularly in a high-temperature environment (more than 45 ℃), and the circulation performance and the safety of the lithium iron manganese phosphate positive electrode material are far lower than those of other commercial system materials.
Disclosure of Invention
The application aims to overcome the defects of the prior art and provide the anode material and the preparation method and application thereof. According to the positive electrode material disclosed by the application, the lithium iron manganese phosphate is taken as an inner core, and at least one shell layer containing nano manganese dioxide and graphite alkyne is coated on the surface of the inner core, so that manganese ions (or other impurity ions) dissolved out by the lithium iron manganese phosphate can be effectively selectively adsorbed due to the synergistic effect of the nano manganese dioxide and the graphite alkyne, the rapid deintercalation of the lithium ions is not influenced, and meanwhile, the conductivity of the whole material can be effectively improved, so that the internal resistance of the product is low when the product is applied to a lithium ion secondary battery, and the electrochemical performance is excellent in a high-temperature environment.
In order to achieve the above object, in a first aspect of the present application, there is provided a positive electrode material comprising composite particles including at least an inner core and a shell layer;
the inner core comprises lithium iron manganese phosphate;
The shell layer comprises nano manganese dioxide and graphite alkyne.
As an embodiment of the present application, the resistivity R of the positive electrode material satisfies: r is less than or equal to 900mΩ cm.
As an embodiment of the present application, the composite particles satisfy Ra: rb=1: (10-20), wherein Ranm is the average thickness of the shell layer, and Rbnm is the average diameter of the core.
As an embodiment of the present application, the Ra satisfies: ra is more than or equal to 10nm and less than or equal to 50nm; and/or, the Rb satisfies: ra is not less than 100nm and not more than 1000nm.
As an embodiment of the present application, the mass ratio of the nano manganese dioxide to the graphite alkyne is 1: (3-7).
In an embodiment of the present application, the particle diameter Dv 50 of the nano manganese dioxide is 1 to 15nm.
In the composite particles according to the embodiment of the present application, the mass ratio of the core layer to the shell layer is (95:5) to (89:11).
As an embodiment of the present application, the method for preparing the positive electrode material includes the steps of:
dispersing graphite alkyne and nano manganese dioxide in a disperse phase, centrifuging and drying to obtain a layered composite nano sheet;
And mixing, ball milling and coating the layered composite nano-sheet and lithium iron manganese phosphate to obtain the anode material.
In a second aspect of the present application, there is provided a secondary battery including the positive electrode material.
In a third aspect of the present application, there is provided an electric device including the secondary battery as a power supply source of the electric device.
The application has the beneficial effects that:
The application provides a positive electrode material and a preparation method and application thereof, wherein the positive electrode material takes lithium iron manganese phosphate as an inner core, and at least one shell layer containing nano manganese dioxide and graphite alkyne is coated on the surface of the positive electrode material; the secondary battery has excellent dynamic performance, low risk of high-temperature gas production, small volume expansion rate, high safety coefficient and excellent cycle performance.
Drawings
Fig. 1 is a graph comparing the results of XRD tests performed after 1500 charge-discharge cycles for the positive electrode material of example 1 of the present application (after the coating cycle) and the positive electrode material of the blank control (after the no coating cycle).
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the application, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
In the present application, the numerical ranges are referred to as continuous, and include the minimum and maximum values of the ranges, and each value between the minimum and maximum values, unless otherwise specified. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
In the present application, the specific dispersing and stirring treatment method is not particularly limited.
The reagents or apparatus used in the present application are conventional products commercially available without the manufacturer's knowledge.
The application is further illustrated by the following specific examples:
the embodiment of the application provides a positive electrode material, which comprises composite particles, wherein the composite particles at least comprise an inner core and a layer of shell;
the inner core comprises lithium iron manganese phosphate;
The shell layer comprises nano manganese dioxide and graphite alkyne.
One major drawback of lithium iron manganese phosphate positive electrode materials is that trivalent manganese is easily dissolved out when lithium is extracted and then disproportionation reaction is performed on the surface of a pole piece to generate divalent manganese ions, and the divalent manganese ions migrate to the surface of a negative electrode to further perform redox reaction, so that not only can SEI films be destroyed, but also negative electrode gas production phenomena can be caused, active lithium is finally continuously consumed and impedance is increased, and the phenomena are particularly severe in a high-temperature environment, so that the cyclicity of a battery is influenced, and the safety cannot be guaranteed. Therefore, the positive electrode material disclosed by the application has the advantages that by constructing composite particles with a core-shell structure, taking lithium iron manganese phosphate as a core, and coating at least one shell layer containing nano manganese dioxide and graphite alkyne on the outer layer, wherein the graphite alkyne is a carbon material with excellent selective ion adsorption performance, can effectively inhibit the dissolution of manganese ions, and has excellent conductivity and corrosion resistance; on the other hand, nano manganese dioxide has metal ion adsorptivity and corrosion resistance similar to those of graphite alkyne, and has a certain electrostatic adsorption effect on manganese ions based on negative charges carried by the nano manganese dioxide, so that the manganese ion adsorption degree of a shell layer is further improved. In the shell layer, the conjugated system of graphite alkyne and part of alkynyl with positive charges can be combined with nano manganese dioxide to form O-Mn-C bond, so that the structural stability of the shell layer is excellent, the bond also has an improvement effect on the active site of divalent manganese ion, the adsorption selectivity degree is higher, and when the product is applied to a secondary battery, excellent electrochemical performance and high-temperature stability can be realized.
In some embodiments, the positive electrode material has a resistivity R that satisfies: r is less than or equal to 900mΩ cm.
The resistivity of the positive electrode material has a certain relation with the conductivity, after the active composite particles are constructed by using the shell layer containing graphite alkyne, the positive electrode material has high conductivity, and the resistivity can be maintained within 900mΩ cm after test verification, so that the positive electrode material has good use effect.
Further, the positive electrode material has a resistivity R in a range of one or both of 900mΩ·cm, 800mΩ·cm, 700mΩ·cm, 600mΩ·cm, 500mΩ·cm, 400mΩ·cm, 300mΩ·cm, 200mΩ·cm, 100mΩ·cm, and 50mΩ·cm.
Specifically, the method for testing the resistivity R of the positive electrode material is a four-probe method, 5g of the material is taken, the test pressure point is 20kN, the sampling time is 10-20s, and 3 or more than 3 parallel samples are tested; the specific testing method is to put the material on a testing device by oil compacting or manual compacting so as to make the surface of the material flat. The manometer is adjusted to fix the test sample, ensuring good contact of the probe with the sample. Starting the testing device, introducing current into the sample to be tested through circuit connection, and recording voltage change. And calculating the resistance value of the sample according to ohm's law.
In some embodiments, the composite particles satisfy Ra: rb=1: (10-20), wherein Ranm is the average thickness of the shell layer, and Rbnm is the average diameter of the core.
In the composite particles of the positive electrode material, the thicknesses of the inner core and the shell layer are related to the energy density of the product and the dissolution inhibition phenomenon of manganese ions to a certain extent, and when the thicknesses of the inner core and the shell layer in the composite particles are set in the range, the obtained positive electrode material can keep higher reversible capacity when lithium is extracted, and meanwhile, the composite particles are excellent in cycle stability and high-temperature stability and good in comprehensive effect.
Further, the composite particles satisfy Ra: rb=range values of one or any two of 1:10, 1:12, 1:15, 1:18, 1:20.
In some embodiments, the Ra satisfies: ra is more than or equal to 10nm and less than or equal to 50nm;
In some embodiments, the Rb satisfies: ra is not less than 100nm and not more than 1000nm.
Further, ra is a range value of one or any two of 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, and Rb is a range value of one or any two of 100nm, 200nm, 250nm, 350nm, 500nm, 750nm, 1000 nm.
Specifically, the testing method of Ra and Rb comprises the following steps: observing the thickness of a shell layer of a sample by using transmission electron microscope auxiliary element analysis (positioning carbon elements in graphite alkyne), randomly selecting at least 100 particles, calculating an average value as an Ra value of the composite particles, and testing the Rb by the following method: and (3) analyzing and searching the inner core by utilizing auxiliary elements (positioning lithium elements, phosphorus elements, iron elements and the like in the lithium manganese iron phosphate) of the high-resolution transmission electron microscope, measuring the thickness, selecting at least 100 composite particles, and calculating an average value as an Rb value of the composite particles.
In some embodiments, the ratio of the mass of the nano manganese dioxide to the mass of the graphite alkyne is 1: (3-7).
In the composite particles of the positive electrode material, nano manganese dioxide and graphite alkyne serving as shell active substances have a synergistic effect, and can jointly and selectively adsorb manganese elements dissolved out from lithium iron manganese phosphate in a core under the proportion and stably fix the manganese elements for a long time, and meanwhile, the conductivity of a product is greatly improved, so that the energy density and the conductivity of the material are balanced, and finally, longer cycle life and high-temperature stability are displayed.
Further, the mass ratio of the nano manganese dioxide to the graphite alkyne is in a range of values of one or any two of 1:3, 1:4, 1:5, 1:6, 1:7.
In some embodiments, the nano manganese dioxide has a particle size Dv 50 of 1 to 15nm.
When the size of the nano manganese dioxide is in the range, the nano manganese dioxide can be effectively embedded in graphite alkyne to form a high-stability combination body, and any angle (pi/pi) perpendicular to a horizontal axis in the combination body structure can rotate randomly, so that divalent manganese ions can be well chelated, and the cycle stability of a product is improved.
Further, the particle diameter Dv 50 of the nano manganese dioxide is one or any two of the range values of 1nm, 2nm, 5nm, 8nm, 10nm, 12nm and 15 nm.
Specifically, the method for testing the particle size Dv 50 of the nano manganese dioxide comprises the following steps: firstly, the thickness of a shell layer of a sample is assisted and positioned by using transmission electron microscope assisted element analysis, at least 100 composite particles are randomly selected, at least 50 nano manganese dioxide particles are randomly selected from the shell layers of each composite particle, and a statistical software is adopted to calculate the obtained test structure and obtain the particle size Dv 50.
In some embodiments, the mass ratio of core layer to shell layer in the composite particle is (95:5) - (89:11).
Further, in the composite particle, the mass ratio of the core layer to the shell layer is a range of values of one or any two of 95:5, 94:6, 93:7, 92:8, 91:9, 90:10, 89:11.
In some embodiments, the method of preparing the positive electrode material includes the steps of:
dispersing graphite alkyne and nano manganese dioxide in a disperse phase, centrifuging and drying to obtain a layered composite nano sheet;
And mixing, ball milling and coating the layered composite nano-sheet and lithium iron manganese phosphate to obtain the anode material.
The preparation method of the positive electrode material has simple operation steps, can implement industrialized mass production, is not limited to the method, and can be accepted by other commercialized conventional methods capable of preparing the same or similar technical effects.
Further, the disperse phase is a solution obtained by mixing water and absolute ethyl alcohol according to the mass ratio of (4:6) - (6:4).
In some embodiments, the method of preparing a graphite alkyne comprises the steps of:
Immersing the carbon cloth and copper foil treated by nitric acid into pyridine solution with the temperature of 70-90 ℃ for standing for 1.5-2.5 hours, then dropwise adding hexaacetylene benzene solution with the concentration of 0.5-0.8 mg/mL under the light-proof condition, heating to the temperature of 100-120 ℃ under the inert environment, standing for 20-25 hours for growing graphite alkyne, and finally washing, acid leaching, secondary washing and drying to obtain the graphite alkyne.
Further, the particle size Dv 50 of the graphite alkyne is 5-30 nm, and the porosity is 10% -30%.
The graphite alkyne in the composite particles can be prepared by adopting the acetylene cross-coupling method, the method has simple operation steps and high reaction yield, meanwhile, the graphite alkyne is not limited to be prepared by adopting the method, and other methods such as a solid phase method, a mechanical stripping method and the like are adopted, so long as the graphite alkyne with the same or similar quality can be obtained.
In some embodiments, the method of preparing nano manganese dioxide comprises the steps of:
mixing potassium permanganate, (NH 4)2S2O8) and nitric acid in water, heating to 100-180 ℃ and preserving heat for 15-20 h, cooling, separating solid from liquid, washing the obtained solid phase, and drying to obtain the nano manganese dioxide.
Further preferably, the mass ratio of the potassium permanganate to the (NH 4)2S2O8) to the nitric acid is (1.5-2.5): (3.5-4.5): (0.8-1.2).
The preparation method of the nano manganese dioxide can be replaced by other methods for obtaining nano manganese dioxide with the same or similar quality, and can also be obtained by directly purchasing commercial products according to actual needs.
In some embodiments, the lithium iron manganese phosphate has the formula LiFe xMn1-xPO4, where 0 < x.ltoreq.0.7.
The application also provides a secondary battery, which comprises a positive electrode plate and a negative electrode plate.
In some embodiments, the positive electrode sheet includes the positive electrode material of the present application, a conductive agent, and a binder.
In some embodiments, the conductive agent includes, but is not limited to, at least one of acetylene black, needle coke, carbon nanotubes, graphene.
In some embodiments, the binder includes, but is not limited to, at least one of polyethylene terephthalate, styrene-butadiene rubber, nitrile rubber, fluororubber, styrene-butadiene-styrene block copolymer or a hydride thereof, ethylene-propylene-diene terpolymer, styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or a hydride thereof, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-alpha-olefin copolymer, polyvinylidene fluoride, polytetrafluoroethylene.
In some embodiments, the negative electrode tab includes, but is not limited to, at least one of a carbon material, a silicon material.
In some embodiments, the secondary battery further comprises an electrolyte.
Further, the electrolyte includes an electrolyte and a solvent.
Further, the electrolyte includes at least one of lithium hexafluorophosphate (LiPF 6), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium tetrafluoroborate (LiBF 4), lithium perchlorate (LiClO 4), lithium difluorophosphate (LiDFPO 2), lithium tetrafluorooxalate phosphate (LiOTFP), lithium bis (oxalato) difluorophosphate (LiDFOP), lithium bis (oxalato) borate (LiBOB), lithium difluorooxalato borate (lidadiob).
Further, the solvent includes at least one of Ethylene Carbonate (EC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), propylene Carbonate (PC).
In some embodiments, the secondary battery further comprises a separator.
Further, the diaphragm comprises at least one of a polypropylene film, a polyethylene film, a polyvinylidene fluoride film, a spandex film and an aramid film.
The secondary battery provided by the application can adopt various sources or types of negative electrode plates, electrolyte and diaphragms to match the positive electrode plates prepared by the positive electrode materials based on actual needs, and the secondary battery is acceptable as long as the expected technical effect of the positive electrode materials is not affected, and is not limited to the embodiment of the application.
The application also provides an electric device which adopts the secondary battery as a power supply. The secondary battery has better cycle performance and lower gas production performance, so that the electric device has longer endurance, good structural stability at high temperature and better safety performance.
The application is further illustrated by the following specific examples, which are not to be construed as limiting the scope of the application as claimed:
Example 1
The preparation method of the positive electrode material comprises the following steps:
(1) Preparation of graphite alkyne: immersing carbon cloth (commercially available carbon cloth, subjected to nitric acid pretreatment, with the thickness of 0.3-0.5 mm and the surface density of about 180g/M 2) and copper foil subjected to nitric acid treatment into a pyridine solution with the concentration of 1mg/mL at 80 ℃ for standing for 2 hours, then dropwise adding a pyridine solution of 0.6mg/mL of hexaacetylene benzene under the condition of avoiding light, continuously standing for 4 hours, heating to 110 ℃ under the inert environment for 24 hours for growth of graphite alkyne, finally washing with dimethylformamide and acetone, leaching with a 0.5M sulfuric acid solution for 12 hours, washing with water and ethanol for the second time, and drying to obtain the graphite alkyne, wherein the particle size D v of the graphite alkyne is 22nm, and the porosity is about 20%.
(2) Preparation of nano manganese dioxide: mixing potassium permanganate, (NH 4)2S2O8) and nitric acid in water (mass ratio potassium permanganate, (NH 4)2S2O8: nitric acid: water=2:4:1:80), heating to 160 ℃, preserving heat for 18h, cooling, carrying out solid-liquid separation, washing the obtained solid phase with water and ethanol, and drying to obtain the nano manganese dioxide.
(3) Preparation of a positive electrode material:
(3.1) dispersing graphite alkyne and nano manganese dioxide in a solvent compounded by water and ethanol according to a mass ratio of 1:1, centrifuging, and drying to obtain a layered composite nano sheet;
And (3.2) mixing, ball-milling and coating the layered composite nano-sheet and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4 to obtain the anode material.
Examples 2 to 7
The difference between the positive electrode material and the preparation method and application thereof is that the layered composite nano-sheet and the lithium iron manganese phosphate are different in addition amount, so that the thicknesses of the inner core and the shell layer in the composite particles of the prepared positive electrode material are different.
Examples 8 to 11
The positive electrode material, the preparation method and the application thereof only differ from example 6 in the mass ratio of the graphite alkyne to the nano manganese dioxide.
Examples 12 to 16
The positive electrode material, and the preparation method and application thereof, and the embodiment 1 only differ in that the preparation method of the nano manganese dioxide comprises the following steps: mixing potassium permanganate, (NH 4)2S2O8) and nitric acid in water (the mass ratio is potassium permanganate, (NH 4)2S2O8: nitric acid: water=2:4:1:80), heating to 120-160 ℃ and preserving heat for 18h.
Wherein the soak temperature in example 12 is 170 ℃, example 13 is 165 ℃, example 14 is 162 ℃, example 15 is 125 ℃, and example 16 is 120 ℃.
The particle sizes Dv 50 of the obtained nano manganese dioxide are different.
Example 17
The positive electrode material, and the preparation method and application thereof only differ from example 1 in that the lithium iron manganese phosphate is LiFe 0.5Mn0.5PO4.
Example 18
The positive electrode material, and the preparation method and application thereof only differ from example 1 in that the lithium iron manganese phosphate is LiFe 0.4Mn0.6PO4.
Example 19
The positive electrode material, and the preparation method and application thereof, and the embodiment 1 only differ in that the preparation method of the graphite alkyne comprises the following steps: immersing the copper foil into a flask of a mixed solution of acetone, pyridine and tetramethyl ethylenediamine in a volume ratio of 100:5:1; 10mg of hexaacetylenyl was dissolved with 50mL of acetone, then slowly added to the above mixed solution over 3 hours, and the mixture was then kept under argon atmosphere at 50℃for 12 hours. And after the reaction is finished, growing graphite diacetylene nano walls on the surface of the copper plate. And finally, sequentially washing the copper foil with heated acetone and DMF, removing unreacted monomers and oligomers, and drying under nitrogen to obtain the graphite alkyne. The particle size D v of the graphite alkyne is 18nm, the porosity is about 17%, and the mass ratio of the graphite alkyne to the nano manganese dioxide is different.
Comparative example 1
The positive electrode material, and the preparation method and application thereof, differ from example 1 only in that the preparation method of the positive electrode material comprises the following steps:
(1) Step (1) was performed as in example 1.
(2) Preparation of a positive electrode material:
and mixing graphite alkyne and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4, ball-milling and coating to obtain the anode material.
Comparative example 2
The positive electrode material, and the preparation method and application thereof, differ from example 1 only in that the preparation method of the positive electrode material comprises the following steps:
(1) Step (2) was performed as in example 1.
(3) Preparation of a positive electrode material:
And mixing, ball-milling and coating the nano manganese dioxide and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4 to obtain the anode material.
Comparative example 3
The positive electrode material, and the preparation method and application thereof, differ from example 1 only in that the preparation method of the positive electrode material comprises the following steps:
(1) Step (1) was performed as in example 1.
(2) Step (2) was performed as in example 2.
(3) Preparation of a positive electrode material:
(3.1) mixing graphite alkyne and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4, ball-milling and coating to obtain a mixture A;
And (3.2) mixing, ball milling and coating the nano manganese dioxide and the mixture A to obtain the positive electrode material, wherein two layers of shell layers exist in the composite particles of the positive electrode material, and any one layer of shell layer does not contain nano manganese dioxide and graphite alkyne at the same time.
Comparative example 4
The positive electrode material, and the preparation method and application thereof, differ from example 1 only in that the preparation method of the positive electrode material comprises the following steps:
(1) Step (1) was performed as in example 1.
(2) Step (2) was performed as in example 2.
(3) Preparation of a positive electrode material:
(3.1) mixing, ball-milling and coating nano manganese dioxide and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4 to obtain a mixture A;
And (3.2) mixing graphite alkyne and the mixture A, ball milling and coating to obtain the positive electrode material, wherein two layers of shell layers exist in the composite particles of the positive electrode material, and any one layer of shell layer does not contain nano manganese dioxide and graphite alkyne at the same time.
Comparative example 5
The only difference between the positive electrode material and the preparation method and application thereof is that in the preparation method of the positive electrode material, nano manganese dioxide is replaced by nano ferric oxide with the same mass and commercial purity of 99.5 percent and the grain diameter Dv 50 =10 nm.
Comparative example 6
The difference between the positive electrode material and the preparation method and application thereof is that in the preparation method of the positive electrode material, nano manganese dioxide is replaced by polyaniline particles with the same mass and the particle diameter D v 500 of 10 nm.
Comparative examples 7 to 8
The positive electrode material, and the preparation method and application thereof, differ from example 1 only in that the preparation method of the positive electrode material comprises the following steps:
and mixing, ball-milling and coating graphite with the commercial particle diameter D v of 25nm and about 20% of pores and lithium iron manganese phosphate LiFe 0.6Mn0.4PO4 to obtain the positive electrode material.
Blank control group
The positive electrode material is lithium iron manganese phosphate LiFe 0.6Mn0.4PO4 in example 1.
The positive electrode materials prepared in each of the examples, comparative examples and blank were tested and characterized, and the parameters are shown in table 1.
TABLE 1
The positive electrode materials prepared in the above examples, comparative examples and blank comparative examples were respectively subjected to performance tests, and the specific methods are as follows:
(1) And (3) battery assembly:
(1.1) preparation of positive electrode plate: preparing slurry by dispersing the positive electrode materials prepared in each example, the comparative example and the blank comparative example, acetylene black serving as a conductive agent, PVP serving as a dispersing agent and polyvinylidene fluoride serving as a binder in NMP according to a mass ratio of 97.3:0.6:0.2:1.9, coating the slurry on two sides of an aluminum foil, and baking, rolling and cutting to obtain positive electrode plates (the surface density is 300g/1540.25mm 2);
(1.2) preparation of a negative electrode plate: mixing artificial graphite, a conductive agent acetylene black, a thickener CMC and a binder SBR according to a mass ratio of 96.4:0.8:1.5:1.3, dispersing in deionized water to prepare slurry, then coating the slurry on two sides of a copper foil, and baking, rolling and cutting to obtain a negative electrode plate (the surface density is 0.36g/1540.25mm 2);
(1.3) preparation of electrolyte: mixing EC and DMC according to a volume ratio of 1:1, and then adding lithium hexafluorophosphate into a glove box to prepare electrolyte with a concentration of 1 mol/L;
And (1.4) sequentially stacking the prepared positive electrode plate, the polyethylene diaphragm and the negative electrode plate, enabling the diaphragm to be positioned between the positive electrode plate and the negative electrode plate, winding, hot-pressing, shaping and welding the electrode lugs to obtain a bare cell, placing the bare cell in an outer packaging aluminum-plastic film, placing in an oven with the temperature of 85+/-10 ℃ for baking for 24 hours, injecting electrolyte into the dried cell, standing, forming and separating to obtain the lithium ion soft package battery.
(2) Testing of lithium ion soft package battery:
(1) Normal temperature DCR test: the secondary batteries 1C obtained in each of the examples, comparative examples and blank examples were charged to 4.3V at 25±2 ℃, discharged at 1C capacity for 30min, adjusted to 50% soc, and then charged for 10s again at 5C constant current pulse discharge for 10s, and the discharge dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current was calculated.
(2) And (3) testing normal temperature cycle performance: the secondary batteries obtained in each of the examples, comparative examples and blank examples were subjected to a charge-discharge cycle test at 25.+ -. 2 ℃ at a charge-discharge rate of 1C/1C in the range of 2.0 to 4.3V, and the number of cycles at which the battery capacity retention rate was 80% was recorded. 80 capacity retention (%) = specific discharge capacity per first week for last cycle number 100%.
(3) And (3) high-temperature storage and gas production test: the soft pack batteries obtained in the examples, the comparative examples and the blank comparative examples were charged to 4.3V at a constant current of 1C magnification at 25±2 ℃ and then charged at a constant voltage of 4.3V until the current was lower than 0.05C, so that they were in a full charge state of 4.3V. The volume of the fully charged battery before storage is tested and recorded as V 0; the fully charged battery was then placed in an oven at 60±2 ℃, after 60 days, the battery was removed, the stored volume was immediately tested and recorded as V 1, and the volume expansion (%) = (V 1-V0)/V0 x 100%) was calculated.
(4) And (3) high-temperature circulating gas production test: the soft package batteries obtained in the examples, the comparative examples and the blank comparative examples are subjected to charge-discharge cycle test at the temperature of 45+/-2 ℃ and the 1C/1C multiplying power in the range of 2.0-4.3V, wherein the volume of the battery in an open circuit voltage state before test cycle is V 2, and in the cycle process, the volume change is tested once every 100 times in the cycle; after cycling to 80% capacity retention, the cell was removed and immediately tested and the volume after cycling was recorded as V 3; if the gas production volume change rate in the circulating process is more than 100%, the test is immediately stopped and the circulating cycle number at the moment is recorded.
The test results are shown in Table 2.
TABLE 2
As can be seen from table 2:
1) The positive electrode material prepared by each embodiment of the application has good structural stability, the batteries of the embodiment 1 and the blank control group after being subjected to normal temperature circulation for 1500 times are disassembled, the positive electrode material in the pole piece is subjected to XRD test, and the result is shown in figure 1, the XRD spectrogram in the positive electrode material has newly added characteristic peaks (521) and (211) corresponding to the shell layer coating layer, and the dissolution condition of manganese ions after 1500 times of circulation is superior to that of the blank control group product, so that after the composite particle structure is constructed, the dissolution inhibition rate of manganese elements in lithium manganese phosphate in the inner core is high, and due to the effective design of the shell layer coating layer, the circulation stability at normal temperature is good, the high-temperature stability is excellent, the gas production risk is low, and the safety is high.
2) According to the data of examples 1 to 7, the mass ratio of the inner core to the shell layer in the composite particles of the positive electrode material is different, the thickness ratio of the inner core to the shell layer is also different, and the electrochemical properties of the product are also different.
3) According to the data of examples 7 and examples 8 to 11, as the ratio of nano manganese dioxide to graphite alkyne in the shell layer is changed and is in a proper range, the chimeric effect of the nano manganese dioxide and graphite alkyne is optimal, the synergistic effect of the nano manganese dioxide and graphite alkyne can be fully exerted, the dissolved manganese element is adsorbed and fixed through multiple adsorption, the conductivity of the product is effectively improved, and the energy density is ensured.
4) According to examples 7 and examples 12 to 16, it can be seen that when a nano manganese dioxide compound graphite alkyne of a proper size is selected, it can be effectively and physically inlaid in gaps of the graphite alkyne and strengthen the fixing degree through chemical bonds, and then the graphite alkyne is assisted by chemical bonds and charge effects to adsorb manganese element more preferably, so that the finally prepared product has excellent performance.
5) As can be seen from the data of example 1 and comparative example 1 and the blank control example, compared with the blank control example, the coating of the inner core by graphite alkyne alone can inhibit the dissolution of manganese element to a certain extent, but the effect is not obvious and is far less than the improvement effect of the positive electrode material.
6) Similarly, as can be seen from the data of example 1, comparative example 2 and blank comparative example, nano manganese dioxide is difficult to effectively compound with core particles to realize coating without the load of graphite alkyne, and meanwhile, when the nano manganese dioxide is used alone, no obvious adsorption effect is caused on manganese elements dissolved in lithium iron manganese phosphate, and even the product performance is poorer due to manganese dissolution of the nano manganese dioxide.
7) According to the data of example 1, comparative example 3 and comparative example 4, it can be seen that if graphite alkyne and nano manganese dioxide are coated and modified by adopting a sequential coating process, the two modified materials cannot be effectively combined and are not in a shell layer, so that the cycle performance of the lithium iron manganese phosphate cannot be improved, and even the attenuation of the cycle performance is aggravated, and the main reason is that the single nano manganese dioxide has a certain manganese element dissolved out, and the negative influence caused by the single nano manganese dioxide cannot be restrained by coating in a composite mode.
8) According to the data of comparative examples 5 and 6, when the nano manganese dioxide is replaced by the traditional ferric oxide or polyaniline, the nano manganese dioxide does not have manganese adsorption per se and can not effectively improve the adsorption effect of graphite alkyne, so that the nano manganese dioxide and the polyaniline have no synergistic effect; the latter, although having some improvement in the conductivity of the product, also has no adsorption effect, so that the performance of the replaced product is inferior to that of the product of each example.
9) According to comparative examples 7 and 8, it can be seen that the electrochemical performance of the conventional graphite coating on lithium manganese iron phosphate is improved to a certain extent, but the conventional graphite coating still has no great difference from the blank product in a high-temperature environment, and the energy density of the conventional graphite coating is reduced due to the excessive graphite, so that the comprehensive performance, particularly the cycle performance and the safety performance at high temperature, are far inferior to those of the product of each embodiment of the application.
Claims (10)
1. The positive electrode material is characterized by comprising composite particles, wherein the composite particles at least comprise an inner core and a layer of shell;
the inner core comprises lithium iron manganese phosphate;
The shell layer comprises nano manganese dioxide and graphite alkyne.
2. The positive electrode material according to claim 1, wherein the resistivity R of the positive electrode material satisfies: r is less than or equal to 900mΩ cm.
3. The positive electrode material according to claim 1, wherein the composite particles satisfy Ra: rb=1: (10-20), wherein Ra nm is the average thickness of the shell layer and Rb nm is the average diameter of the core.
4. The positive electrode material of claim 3, wherein Ra satisfies: ra is more than or equal to 10nm and less than or equal to 50nm; and/or, the Rb satisfies: ra is not less than 100nm and not more than 1000nm.
5. The positive electrode material according to claim 1, wherein the mass ratio of the nano manganese dioxide to the graphite alkyne is 1: (3-7).
6. The positive electrode material according to claim 1, wherein the nano manganese dioxide has a particle diameter Dv 50 of 1 to 15nm.
7. The positive electrode material according to claim 1, wherein the mass ratio of the core to the shell in the composite particles is (95:5) to (89:11).
8. The method for producing a positive electrode material according to any one of claims 1 to 7, comprising the steps of:
dispersing graphite alkyne and nano manganese dioxide in a disperse phase, centrifuging and drying to obtain a layered composite nano sheet;
and mixing, ball milling and coating the layered composite nano-sheet and lithium iron manganese phosphate to obtain the anode material.
9. A secondary battery comprising the positive electrode material according to any one of claims 1 to 7.
10. An electric device comprising the secondary battery according to claim 9 as a power supply source of the electric device.
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