CN116722221A - Electrolyte and lithium ion battery - Google Patents
Electrolyte and lithium ion battery Download PDFInfo
- Publication number
- CN116722221A CN116722221A CN202310924007.1A CN202310924007A CN116722221A CN 116722221 A CN116722221 A CN 116722221A CN 202310924007 A CN202310924007 A CN 202310924007A CN 116722221 A CN116722221 A CN 116722221A
- Authority
- CN
- China
- Prior art keywords
- electrolyte
- lithium
- additive
- positive electrode
- material layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 93
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 42
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 42
- 239000000654 additive Substances 0.000 claims abstract description 109
- 230000000996 additive effect Effects 0.000 claims abstract description 98
- 239000003960 organic solvent Substances 0.000 claims abstract description 46
- 125000004432 carbon atom Chemical group C* 0.000 claims abstract description 20
- -1 siloxanes Chemical class 0.000 claims abstract description 16
- 125000004093 cyano group Chemical group *C#N 0.000 claims abstract description 12
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 10
- 229930195734 saturated hydrocarbon Natural products 0.000 claims abstract description 10
- 229930195735 unsaturated hydrocarbon Natural products 0.000 claims abstract description 10
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 8
- 125000001153 fluoro group Chemical group F* 0.000 claims abstract description 8
- 125000003342 alkenyl group Chemical group 0.000 claims abstract description 5
- 125000003545 alkoxy group Chemical group 0.000 claims abstract description 5
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 5
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 4
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims abstract description 4
- 125000001183 hydrocarbyl group Chemical group 0.000 claims abstract 4
- 239000000463 material Substances 0.000 claims description 45
- 239000007774 positive electrode material Substances 0.000 claims description 44
- 229910052744 lithium Inorganic materials 0.000 claims description 31
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 30
- 239000011149 active material Substances 0.000 claims description 20
- 239000002904 solvent Substances 0.000 claims description 18
- 229910003002 lithium salt Inorganic materials 0.000 claims description 14
- 159000000002 lithium salts Chemical class 0.000 claims description 14
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 7
- 229910019142 PO4 Inorganic materials 0.000 claims description 6
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 6
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims description 6
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 claims description 6
- 239000010452 phosphate Substances 0.000 claims description 6
- 125000005287 vanadyl group Chemical group 0.000 claims description 6
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 5
- UHOPWFKONJYLCF-UHFFFAOYSA-N 2-(2-sulfanylethyl)isoindole-1,3-dione Chemical compound C1=CC=C2C(=O)N(CCS)C(=O)C2=C1 UHOPWFKONJYLCF-UHFFFAOYSA-N 0.000 claims description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 4
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 3
- JGFBQFKZKSSODQ-UHFFFAOYSA-N Isothiocyanatocyclopropane Chemical compound S=C=NC1CC1 JGFBQFKZKSSODQ-UHFFFAOYSA-N 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 3
- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 claims description 3
- ZMVMBTZRIMAUPN-UHFFFAOYSA-H [Na+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Na+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O ZMVMBTZRIMAUPN-UHFFFAOYSA-H 0.000 claims description 3
- PWLNAUNEAKQYLH-UHFFFAOYSA-N butyric acid octyl ester Natural products CCCCCCCCOC(=O)CCC PWLNAUNEAKQYLH-UHFFFAOYSA-N 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 claims description 3
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 3
- 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 description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 239000011572 manganese Substances 0.000 claims description 3
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 claims description 3
- 239000011734 sodium Substances 0.000 claims description 3
- 229910052708 sodium Inorganic materials 0.000 claims description 3
- AWRQDLAZGAQUNZ-UHFFFAOYSA-K sodium;iron(2+);phosphate Chemical compound [Na+].[Fe+2].[O-]P([O-])([O-])=O AWRQDLAZGAQUNZ-UHFFFAOYSA-K 0.000 claims description 3
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 3
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 3
- 150000004645 aluminates Chemical class 0.000 claims description 2
- LBSANEJBGMCTBH-UHFFFAOYSA-N manganate Chemical compound [O-][Mn]([O-])(=O)=O LBSANEJBGMCTBH-UHFFFAOYSA-N 0.000 claims description 2
- 238000003860 storage Methods 0.000 abstract description 39
- 229910052796 boron Inorganic materials 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 46
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 18
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- 239000011267 electrode slurry Substances 0.000 description 9
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- 239000002033 PVDF binder Substances 0.000 description 7
- 238000007600 charging Methods 0.000 description 7
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- 239000007773 negative electrode material Substances 0.000 description 6
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 3
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- 229920000178 Acrylic resin Polymers 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical group [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 229910013553 LiNO Inorganic materials 0.000 description 2
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- 239000010405 anode material Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- NVJBFARDFTXOTO-UHFFFAOYSA-N diethyl sulfite Chemical compound CCOS(=O)OCC NVJBFARDFTXOTO-UHFFFAOYSA-N 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- BDUPRNVPXOHWIL-UHFFFAOYSA-N dimethyl sulfite Chemical compound COS(=O)OC BDUPRNVPXOHWIL-UHFFFAOYSA-N 0.000 description 2
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- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 2
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 2
- 229910001486 lithium perchlorate Inorganic materials 0.000 description 2
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 2
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- 239000002184 metal Substances 0.000 description 2
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- MPQXHAGKBWFSNV-UHFFFAOYSA-N oxidophosphanium Chemical group [PH3]=O MPQXHAGKBWFSNV-UHFFFAOYSA-N 0.000 description 2
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- 150000003839 salts Chemical class 0.000 description 2
- 150000003384 small molecules Chemical class 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 229910001428 transition metal ion Inorganic materials 0.000 description 2
- 125000001889 triflyl group Chemical group FC(F)(F)S(*)(=O)=O 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- WDXYVJKNSMILOQ-UHFFFAOYSA-N 1,3,2-dioxathiolane 2-oxide Chemical compound O=S1OCCO1 WDXYVJKNSMILOQ-UHFFFAOYSA-N 0.000 description 1
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 description 1
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- OVAQODDUFGFVPR-UHFFFAOYSA-N lithium cobalt(2+) dioxido(dioxo)manganese Chemical compound [Li+].[Mn](=O)(=O)([O-])[O-].[Co+2] OVAQODDUFGFVPR-UHFFFAOYSA-N 0.000 description 1
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 description 1
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- 230000008961 swelling Effects 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 1
- LENZDBCJOHFCAS-UHFFFAOYSA-N tris Chemical compound OCC(N)(CO)CO LENZDBCJOHFCAS-UHFFFAOYSA-N 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
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- 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)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
Abstract
The application relates to an electrolyte and a lithium ion battery. The electrolyte comprises an additive A, an additive B and a silicon-substituted organic solvent; in the structural general formula of the additive A, X 1 、X 2 And X 3 Each independently selected from one of a fluorine atom, a cyano group, an isocyanate group, a hydrogen atom, a saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; r is R 1 And R is 2 Each independently selected from one of a fluorine atom, a phenyl group, a fluoroalkane group, a saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; in the structural general formula of the additive B, W 1 、W 2 And W is 3 Each independently selected from one of an alkyl group, an alkenyl group, an alkoxy group having 1 to 5 carbon atoms substituted with a cyano group or an isocyanate group; in the structural general formula of the silicon-substituted organic solvent, Y 1 、Y 2 、Y 3 And Y 4 Each independently selected from siloxanes having from 1 to 5 carbon atoms. The scheme provided by the application can improve the low-temperature discharge performance, the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery, and improve the comprehensive performance of the lithium ion battery.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery.
Background
The lithium ion battery has the advantages of high specific energy, good quick charge and quick discharge capability, small self discharge and the like, and is widely applied to energy storage power supply systems of hydraulic power, firepower, wind power, solar power stations and the like, and a plurality of fields of electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like.
When the lithium ion battery is fully charged, the positive electrode material is in a delithiated state, the valence state of transition metal ions is increased, the oxidizing property is enhanced, and the electrolyte is easier to oxidize; the negative electrode graphite is in a lithium intercalation state, has poor stability and is easy to react with electrolyte, so that the battery can be subjected to performance degradation during full charge storage, and the storage performance degradation is particularly remarkable under high temperature conditions. Meanwhile, the capacity of the lithium ion battery is lost to a certain extent after high-temperature storage, so that the cycle performance of the battery is deteriorated, and the service life of the battery is further influenced.
Therefore, how to improve the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery is a problem to be solved.
Disclosure of Invention
In order to solve or partially solve the problems in the related art, the application provides the electrolyte and the lithium ion battery, which can improve the low-temperature discharge performance, the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery and improve the comprehensive performance of the lithium ion battery.
The first aspect of the application provides an electrolyte comprising a solvent, an additive A and an additive B, wherein the solvent comprises a silicon-substituted organic solvent; the structural general formula of the additive A is shown as follows:
wherein X is 1 、X 2 And X 3 Each independently selected from fluorine atom, cyano group, isocyanate group, hydrogen atom, and havingOne of saturated or unsaturated hydrocarbon groups of 1 to 5 carbon atoms; r is R 1 And R is 2 Each independently selected from one of a fluorine atom, a phenyl group, a fluoroalkane group, a saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms;
the structural general formula of the additive B is shown as follows:
wherein W is 1 、W 2 And W is 3 Each independently selected from one of an alkyl group, an alkenyl group, an alkoxy group having 1 to 5 carbon atoms substituted with a cyano group or an isocyanate group;
the silicon-substituted organic solvent is selected from one or more of the compounds shown in the following structural general formulas:
wherein Y is 1 、Y 2 、Y 3 And Y 4 Each independently selected from siloxanes having from 1 to 5 carbon atoms.
In some embodiments of the application, the additive a is selected from at least one of the following structural formulas:
and/or the additive B is selected from at least one of the following structural formulas:
in some embodiments of the application, the silage organic solvent is selected from at least one of the following structural formulas:
in some embodiments of the application, the solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran.
In some embodiments of the application, the mass ratio of the additive A in the electrolyte is 0.01% -5%;
and/or the mass ratio of the additive B in the electrolyte is 0.01-5%;
and/or the mass ratio of the silicon-substituted organic solvent in the electrolyte is c%; wherein, c is more than or equal to 5% and less than or equal to 30%.
In some embodiments of the application, the electrolyte comprises a lithium salt, the concentration of the lithium salt in the electrolyte being between 0.5mol/L and 2mol/L; preferably 0.8mol/L to 2mol/L; more preferably 0.9mol/L to 1.3mol/L.
The second aspect of the application provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the electrolyte is the electrolyte of the first aspect of the application.
In some embodiments of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on a surface of the positive electrode current collector, the positive electrode material layer including a first material layer and a second material layer, the first material layer being disposed between the positive electrode current collector and the second material layer; the first material layer contains a first active material, preferably the first active material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium titanate; the second material layer comprises a second active material, preferably the second active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium vanadate, lithium manganate, lithium nickelate manganate, lithium-rich manganese base, lithium nickelate aluminate, lithium titanate.
In some embodiments of the application, the first material layer has a thickness D1 μm and the second material layer has a thickness D2 μm, the relationship between the positive electrode material layer and the electrolyte solution satisfying: c/(D1+D2) is more than or equal to 0.1 and less than or equal to 0.6.
In some embodiments of the application, the sum of the masses of the first active material and the second active material is 80% to 99% of the total mass of the positive electrode material.
The technical scheme provided by the application can comprise the following beneficial effects:
the additive A, the additive B and the silicon-substituted organic solvent are used in a combined way, so that on one hand, the structural collapse and the crystal structure change of the positive electrode material can be restrained, meanwhile, the film can be formed on the surface of the positive electrode material to improve the oxidation resistance of the positive electrode material, the oxidative decomposition of electrolyte in the positive electrode is restrained, the high-temperature gas production phenomenon is reduced, and the high-temperature storage and high-temperature cycle performance of the battery are improved; on the other hand, the diffusion capability of lithium ions in the electrode active material can be improved, so that the low-temperature discharge performance of the lithium ion battery is improved, and the comprehensive performance of the lithium ion battery is improved.
By controlling the relation between the thickness of the positive electrode material layer and the silicon-substituted organic solvent in the electrolyte within a proper range, when the silicon-substituted organic solvent in the electrolyte is combined with the additive A and the additive B, the thermal shock resistance and the high-temperature storage performance of the battery can be further improved, meanwhile, the viscosity of the electrolyte is reduced, the migration capacity of lithium ions in the electrolyte solvent is improved, and the low-temperature discharge performance of the battery is improved.
Detailed Description
In order that the application may be readily understood, the application will be described in detail. Before the present application is described in detail, it is to be understood that this application is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Where a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the application. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the application, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the application.
Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Although any methods and materials equivalent to those described herein can also be used in the practice or testing of the present application, the preferred methods and materials are now described.
When the lithium ion battery is fully charged, the positive electrode material is in a delithiated state, the valence state of transition metal ions is increased, the oxidizing property is enhanced, and the electrolyte is easier to oxidize; the negative electrode graphite is in a lithium intercalation state, has poor stability and is easy to react with electrolyte, so that the battery can be subjected to performance degradation during full charge storage, and the storage performance degradation is particularly remarkable under high temperature conditions. Meanwhile, the capacity of the lithium ion battery is lost to a certain extent after high-temperature storage, so that the cycle performance of the battery is deteriorated, and the service life of the battery is further influenced.
According to the application, through the combined use of the additive A, the additive B and the silicon-substituted organic solvent, on one hand, the structural collapse and the crystal structure change of the positive electrode material can be restrained, and meanwhile, the film can be formed on the surface of the positive electrode material to improve the oxidation resistance of the positive electrode material, inhibit the oxidative decomposition of electrolyte in the positive electrode, reduce the high-temperature gas production phenomenon and improve the high-temperature storage and high-temperature cycle performance of the battery; on the other hand, the diffusion capability of lithium ions in the electrode active material can be improved, so that the low-temperature discharge performance of the lithium ion battery is improved, and the comprehensive performance of the lithium ion battery is improved.
The first aspect of the application provides an electrolyte, comprising a solvent, an additive A and an additive B, wherein the solvent comprises a silicon-substituted organic solvent; the structural general formula of the additive A is shown as follows:
wherein X is 1 、X 2 And X 3 Each independently selected from one of fluorine atom, cyano group, isocyanate group, hydrogen atom, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; r is R 1 And R is 2 Each independently selected from one of a fluorine atom, a phenyl group, a fluoroalkane group, a saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms;
the structural general formula of the additive B is shown as follows:
wherein W is 1 、W 2 And W is 3 Each independently selected from one of an alkyl group, an alkenyl group, an alkoxy group having 1 to 5 carbon atoms substituted with a cyano group or an isocyanate group;
the silicon-substituted organic solvent is selected from one or more of the compounds shown in the following structural general formulas:
wherein Y is 1 、Y 2 、Y 3 And Y 4 Each independently selected from siloxanes having from 1 to 5 carbon atoms.
According to the application, the additive A can effectively reduce the contact angle of the electrolyte on the isolating film, promote the wetting of the electrolyte on the isolating film, and further improve the cycle performance of the battery; meanwhile, boron atoms in the molecules can inhibit oxygen free radicals of the stable anode material and inhibit structural collapse and crystal structure change of the anode material, so that the high-temperature storage and high-temperature cycle performance of the battery are improved; the cyano functional group or the isocyanate functional group of the additive B can passivate the positive electrode active material to stabilize the positive electrode active material, and meanwhile, as the phosphine oxide functional group in the molecule can be synchronously attached to the surface of the positive electrode active material along with the cyano functional group, the oxidation resistance of the positive electrode active material is improved, so that the oxidative decomposition of electrolyte is effectively inhibited, and the high-temperature gas production phenomenon is inhibited; the Si-O bond in the silicon-substituted organic solvent has better thermal stability, can improve the thermal shock resistance and high-temperature storage performance of the battery, simultaneously reduce the viscosity of the electrolyte, improve the migration capacity of lithium ions in the electrolyte solvent, and improve the low-temperature discharge performance of the battery. When the electrolyte contains the additive A, the additive B and the silicon organic solvent, on one hand, the decomposition of the positive electrode active material and the electrolyte can be inhibited, the oxidation resistance of the surface film is improved while the formation of the positive electrode surface film is promoted, and the expansion of the thickness of the battery caused by high-temperature gas production of the electrolyte is inhibited, so that the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery are improved; on the other hand, the migration capability of lithium ions in the electrolyte can be improved, and the low-temperature discharge performance of the lithium ion battery is improved.
In the present application, the pendant groups of additive a may be selected from saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms, i.e., the pendant groups of additive a may be selected from alkane, alkene, or alkyne groups. In some embodiments, when the pendant group of additive a is selected from saturated or unsaturated hydrocarbon groups having 1-5 carbon atoms, the chain length of the pendant chain of additive a is controlled so as to avoid an excessive pendant chain length increasing the viscosity of the electrolyte, improving the migration ability of lithium ions in the electrolyte solvent, and improving the low temperature discharge performance of the battery.
Similarly, when the side groups of additive B are alkyl, alkenyl, alkoxy groups having 1 to 5 carbon atoms substituted with cyano or isocyanate groups; or when the side group of the silicon-substituted organic solvent is siloxane with 1-5 carbon atoms, the chain length of the side group is not excessively long, so that the overall viscosity of the electrolyte system is reduced, and the low-temperature discharge performance of the battery is improved.
In some embodiments, additive a is selected from at least one of the following structural formulas:
in some embodiments, the additive B is selected from at least one of the following structural formulas:
in some embodiments, the silage solvent is selected from at least one of the following structural formulas:
in some embodiments, the solvent further comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran.
In some embodiments, the mass fraction of additive a in the electrolyte is 0.01% to 5%. For example, the content may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or the like, or any other value within the above range. When the additive amount of the additive a is within the above range, the cycle performance and the high-temperature storage performance of the battery can be improved; however, as the amount of additive increases, when the amount of additive a is too large, the interfacial resistance increases, deteriorating the battery cycle performance.
In some embodiments, the mass ratio of the additive B in the electrolyte is 0.01-5%; for example, the content may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or the like, or any other value within the above range. When the additive amount of the additive B is within the above range, the cycle performance and the high-temperature storage performance of the battery can be improved; however, as the amount of additive increases, when the amount of additive B is too large, the interfacial resistance increases, deteriorating the battery cycle performance.
In some embodiments, the mass ratio of the siliconized organic solvent in the electrolyte is c%; wherein, c is more than or equal to 5% and less than or equal to 30%. For example, c% may be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, or the like, or any other value within the above range. The silicon-substituted organic solvent in the range can effectively ensure the thermal stability of the electrolyte, reduce the oxidative decomposition of the electrolyte under the high-temperature condition, inhibit the volume expansion of the battery caused by the high-temperature gas production phenomenon, and improve the high-temperature cycle performance and the high-temperature storage performance of the battery; meanwhile, the overall dynamic performance of the electrolyte can be considered, the migration capacity of lithium ions in the electrolyte solvent can be improved, and the low-temperature discharge performance of the battery can be improved.
In some embodiments, the mass ratio between additive a, additive B, and the silage organic solvent is (0.1-3): (0.1-3): (1-15), preferably (1-3): (1-3): (5-15). For example, it may be 0.1:3:1, 1:1:5, 1:2:5, 1:3:5, 3:1:5, 2:1:5, 3:0.1:5, 1:1:15, 1:1:10, etc. ratios. The mass ratio of the additive A, the additive B and the silicon-substituted organic solvent in the electrolyte and the amount of the additive A, the additive B and the silicon-substituted organic solvent in the electrolyte are controlled, so that the synergistic effect of the additive A, the additive B and the silicon-substituted organic solvent can be fully exerted, and the high-temperature cycle performance, the high-temperature storage performance and the low-temperature discharge performance of the battery are improved.
In some embodiments, the mass ratio of additive A to additive B is (0.1-3): (0.1-3). For example, it may be 0.1:3, 1:1, 1:2, 1:3, 3:1, 2:1, 3:0.1, etc. The total addition amount of the additive A and the additive B in the electrolyte and the mass ratio of the additive A to the additive B are controlled within a proper range, so that the synergistic effect between the additive A and the additive B and the lithium supplementing additive can be effectively exerted, and the high-temperature cycle performance and the high-temperature storage performance of the battery are improved.
In some embodiments, the electrolyte comprises a lithium salt, the concentration of the lithium salt in the electrolyte being between 0.5mol/L and 2mol/L; preferably 0.8mol/L to 2mol/L; more preferably 0.9mol/L to 1.3mol/L. When the concentration of lithium salt in the electrolyte is too low, the conductivity of the electrolyte is low, and the multiplying power and the cycle performance of the whole battery system are affected; when the lithium salt concentration is too high, the electrolyte concentration is too high, which also affects the rate of the whole battery system.
In some embodiments, the lithium salt is selected from at least one of an organic electrolyte salt, an inorganic electrolyte salt. Example(s)Such as: lithium perchlorate (LiClO) may be selected 4 ) Lithium hexafluorophosphate (LiPF) 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium hexafluoroantimonate (LiSbF) 6 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium hexafluorotantalate (LiTaF) 6 ) Lithium tetrachloroaluminate (LiAlCl) 4 )、Li 2 B 10 Cl 10 、Li 2 B 10 F 10 The method comprises the steps of carrying out a first treatment on the surface of the Lithium trifluorosulfonyl LiCF 3 SO 3 Lithium difluoro (trifluoromethylsulfonyl) imide C 2 F 6 LiNO 4 S 2 Lithium bis (fluorosulfonyl) imide F 2 LiNO 4 S 2 Tris (trifluoromethylsulfonyl) methyllithium LiC (SO) 2 CF 3 ) 3 And lithium salts, the application is not limited herein. The lithium salt may also be selected from lithium salts of chelate orthoborates and chelate orthophosphates, for example: lithium dioxalate borate (LiB (C) 2 O 4 ) 2 ) Lithium bis malonate borate (LiB (O) 2 CCH 2 CO 2 ) 2 ) Lithium bis (difluoromalonic acid) borate (LiB (O) 2 CCF 2 CO 2 ) 2 ) Lithium (malonate) borate (LiB (C) 2 O 4 )(O 2 CCH 2 CO 2 ) Lithium (difluoro malonate) borate (LiB (C) 2 O 4 )(O 2 CCF 2 CO 2 ) Lithium phosphate tribasic (LiP (C) 2 O 4 ) 3 ) Lithium tris (difluoromalonic acid) phosphate (LiP (O) 2 CCF 2 CO 2 ) 3 ) Etc., the application is not limited thereto.
The lithium salt in the electrolyte of the present application may be selected from any one, any two or a combination of more than any of the above. The lithium salt can be decomposed to generate small molecules in a battery system, so that the small molecules are deposited on an electrode interface to form a compact interface film, and the cycle performance and the high-temperature storage performance of the battery are improved.
In some embodiments, the electrolyte further includes a sulfur-containing additive, sulfur atoms of which may improve high temperature stability of the SEI film, thereby contributing to improvement of high temperature storage performance and high temperature cycle performance of the battery. In some embodiments of the present application, the sulfur-containing additive may be selected from at least one of sulfonate, sulfate, sulfite, and may be selected from at least one of 1, 3-Propane Sultone (PS), 1-propylene-1, 3-sultone (PST), vinyl sulfate (DTD), 4-methyl ethylene sulfate (PCS), ethylene sulfite (DTO), dimethyl sulfite (DMS), or diethyl sulfite (DES), for example.
In some embodiments, the electrolyte further comprises other additives. For example, negative electrode film-forming additives may be included; positive film forming additives may also be included; additives that can improve certain properties of the battery, such as additives that improve high temperature performance, additives that improve low temperature performance of the battery, additives that improve overcharge performance of the battery, may also be included. In some embodiments of the application, the other additives may include at least one of vinylene carbonate, vinylene carbonate derivatives, cyclic carbonates, chelate orthoborates, and chelate orthophosphate salts. For example, the other additive may be at least one of ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, and bis-fluoroethylene carbonate. When the other additives are combined with the additive A and the additive B in the electrolyte, the formation of the SEI film can be promoted, meanwhile, the organic components in the SEI film can be increased, and the toughness of the SEI film is increased by forming an organic and inorganic composite SEI film, so that the SEI film is prevented from being decomposed and broken, the damage to electrode materials caused by co-embedding of solvent molecules is avoided, the ionic conductivity can be enhanced, and the cycle performance and the service life of the whole battery system are further improved.
The second aspect of the application provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the electrolyte is the electrolyte of the first aspect of the application. In the process of charging and discharging the battery, active ions are inserted and separated back and forth between the positive pole piece and the negative pole piece, and the isolating film is arranged between the positive pole piece and the negative pole piece to play a role in isolation; the electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate.
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on a surface of the positive electrode current collector. The positive current collector may be a conventional metal foil or a composite current collector, for example, aluminum foil.
In some embodiments, the positive electrode material layer includes a first material layer and a second material layer, the first material layer being disposed between the positive electrode current collector and the second material layer. The first material layer and the second material layer are matched, so that the expansion stress of the electrode can be relieved in cooperation with electrolyte, collapse of the structure of the positive electrode material layer is restrained, exposure of positive electrode active substances is avoided, the electrode has good thermal stability, and the thermal shock resistance and high-temperature storage performance of the battery are improved; meanwhile, the continuous decomposition of the electrolyte can be effectively inhibited, so that the electrode plate has good safety performance and dynamic performance.
In some embodiments, the first material layer comprises a first active material, the second material layer comprises a second active material, and the positive active material of the positive material layer is comprised of the first active material and the second active material. In some embodiments of the present application, the first active material may be selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium titanate. In some embodiments of the present application, the second active material may be selected from at least one of lithium cobaltate, lithium iron phosphate, lithium vanadate, lithium manganate, lithium nickelate, lithium cobalt manganate, lithium-rich manganese base, lithium nickel cobalt aluminate, lithium titanate. The boron atom of the additive A can stabilize oxygen free radicals in lithium cobaltate, so that the structural collapse and the crystal structure change of the positive electrode material are inhibited, and the high-temperature storage and high-temperature cycle performance of the battery are improved; the cyano or isocyanate functional group of the additive B can form a complex with transition metal (such as lithium cobaltate) in the positive electrode active material, so that the transition metal on the surface of the positive electrode active material is stabilized, and simultaneously, the phosphine oxide functional group can be attached to the surface of the positive electrode active material, so that the oxidation resistance of the complex formed by the transition metal is improved, therefore, the oxidative decomposition of electrolyte under high temperature condition can be effectively inhibited, the thickness expansion of the battery caused by high temperature gas production phenomenon is inhibited, and therefore, the high temperature storage and high temperature cycle performance of the battery can be effectively improved through the combined use of the additive A and the additive B.
In some embodiments, the first material layer has a thickness of D1 μm and the second material layer has a thickness of D2 μm, the relationship between the positive electrode material layer and the electrolyte solution being: c/(D1+D2) is more than or equal to 0.1 and less than or equal to 0.6. According to the application, by limiting the relation between the mass ratio of the silicon-substituted organic solvent in the first material layer, the second material layer and the electrolyte, when the positive electrode material layer and the silicon-substituted organic solvent meet the relation, the positive electrode material layer and the silicon-substituted organic solvent can cooperate to relieve the expansion stress of the electrode, so that the collapse of the structure of the positive electrode material layer is further inhibited, the electrode has good thermal stability, and the high-temperature storage and cycle performance of the battery are further improved.
In some embodiments, the positive electrode active material comprises 80% to 99% of the positive electrode material by mass; that is, the sum of the masses of the first active material and the second active material accounts for 80% to 99% of the total mass of the cathode material. For example, 80%, 85%, 90%, 95%, 97%, 99% may be used.
In some embodiments, the positive electrode material may further include a binder, a conductive agent, or other optional auxiliary agents, and the specific types of the binder, the conductive agent, and the other optional auxiliary agents in the present application are not limited, and binders, conductive agents, or other optional auxiliary agents that can be used for the positive electrode material as known in the art may be used. In some embodiments, as an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), aqueous acrylic resin (water-basedacrylic resin), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, super P (SP), graphene, and carbon nanofibers.
In some embodiments, the preparation of the positive electrode sheet comprises the steps of:
(1) Mixing a first positive electrode active material, a conductive agent and a binder, adding a solvent, stirring and mixing to form a first positive electrode slurry, coating the first positive electrode slurry on a positive electrode current collector, and drying to form a first material layer which is used as a carrier of a second material layer;
(2) Mixing a second positive electrode active material, a conductive agent and a binder, adding a solvent, stirring and mixing to form second positive electrode slurry, and coating the second positive electrode slurry on the first material layer to form a second material layer; and the positive pole piece is obtained after the procedures of drying, cold pressing, cutting, slitting and the like.
In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode material on the negative electrode current collector. The negative electrode material includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.
The specific types of the negative electrode current collector, the negative electrode active material, the negative electrode binder and the negative electrode conductive agent of the present application are not limited, and any materials known in the art for negative electrode materials may be used without limitation.
In some specific embodiments, the negative electrode current collector may be selected from a metal foil or a composite current collector, for example, may be selected from copper foil, as examples; the negative electrode active material may be selected from graphite and/or silicon, such as natural graphite, artificial graphite, mesophase micro carbon spheres (abbreviated as MCMB), hard carbon, soft carbon, silicon-carbon composite, li-Sn alloy, li-Sn-O alloy, sn, snO, snO 2 Lithiated TiO of spinel structure 2 -Li 4 Ti 5 O 12 At least one of Li-Al alloy; the negative electrode binder may be at least one selected from styrene-butadiene rubber (SBR), aqueous acrylic resin (water-basedacrylic resin), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the negative electrode conductive agent may be at least one selected from conductive carbon black, acetylene black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and superconducting carbon.
In some embodiments, the separator of the present application may be arbitrarily selected from known porous structure separators having good chemical and mechanical stability. The material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
The battery disclosed by the embodiment of the application can be used for an electric device using the battery as a power supply or various energy storage systems using the battery as an energy storage element. The electric device includes, but is not limited to, a mobile phone, a tablet, a computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc., and is not limited herein.
In order that the application may be more readily understood, the application will be further described in detail with reference to the following examples, which are given by way of illustration only and are not limiting in scope of application. The starting materials or components used in the present application may be prepared by commercial or conventional methods unless specifically indicated.
Example 1: preparation of lithium ion batteries
(1) Preparation of electrolyte
Mixing ethylene carbonate EC, propylene carbonate PC, diethyl carbonate DEC and propyl propionate PP in a mass ratio of 1:1:1:1 as an organic solvent; adding additive A, additive B and fluoro-organic solvent with the mass percentage content shown in example 1 in table 1 into organic solvent, mixing uniformly, adding LiPF 6 Obtaining LiPF 6 An electrolyte with a concentration of 1.1 mol/L.
(2) Preparation of positive electrode plate
A first material layer: lithium iron phosphate (LiFePO) as a cathode active material 4 ) Mixing a conductive agent Carbon Nano Tube (CNT) and a binder polyvinylidene fluoride according to a mass ratio of 95:2:3, adding N-methyl pyrrolidone (NMP), stirring under the action of a vacuum stirrer until the system becomes uniform positive electrode slurry, uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil, and drying at 85 ℃ to form a first material layer which is used as a carrier of a second material layer.
And a second material layer: lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) Mixing a conductive agent Carbon Nano Tube (CNT) and a binder polyvinylidene fluoride according to a mass ratio of 95:2:3, adding N-methyl pyrrolidone (NMP), stirring under the action of a vacuum stirrer until the system becomes uniform positive electrode slurry, and uniformly coating the positive electrode slurry on the first material layer to form a second material layer; drying at 85 ℃, cold pressing, cutting and slitting, and drying for 4 hours under the vacuum condition at 85 ℃ to obtain the positive plate.
(3) Preparation of negative electrode plate
And fully stirring and mixing the anode active material graphite, the conductive agent acetylene black, the adhesive styrene-butadiene rubber and the thickener sodium carboxymethyl cellulose in a proper amount of deionized water solvent according to the mass ratio of 96:1.2:1.5:1.3, so that uniform anode slurry is formed. And coating the negative electrode slurry on a negative electrode current collector copper foil, drying, and cold pressing to obtain a negative electrode plate.
(4) Preparation of lithium ion batteries
The PE porous polymer film is used as a diaphragm.
And sequentially stacking the positive pole piece, the diaphragm and the negative pole piece, enabling the diaphragm to be positioned between the positive pole piece and the negative pole piece, playing an isolating role, and winding the stacked pole piece and the diaphragm to obtain the winding core. And (3) placing the coiled core in an aluminum-plastic film bag formed by punching, respectively injecting the prepared electrolyte into the baked and dried electric core, and performing the procedures of vacuum packaging, standing, formation and the like to prepare the lithium ion battery.
Examples 2 to 9 and comparative examples 1 to 7 were conducted in the same manner as in example 1 except that the additive A, additive B in the electrolyte and the type and content of the siliconized organic solvent in the electrolyte were different, and the specific differences are shown in Table 1.
TABLE 1
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Note that: "/" indicates that no additives were used.
Battery testing and analysis
(1) And (3) cycle test at 45 ℃:
the testing method comprises the following steps: charging the lithium ion battery to 4.45V at a constant current and constant voltage of 1C in a constant temperature box at 45+/-2 ℃, stopping the current at 0.05C, then discharging the lithium ion battery to 3V at 1C, and carrying out charge and discharge cycles for a plurality of times according to the conditions. The capacity retention after 300 and 500 battery cycles, respectively, was calculated for each group of 5 batteries.
The calculation formula is as follows: capacity retention (%) = corresponding cycle number discharge capacity (mAh)/discharge capacity for the third cycle (mAh) 100%
The capacity retention after each group of 5 cells cycled through different cycles is averaged and reported in tables 2 and 3.
(2) High temperature storage test at 60 ℃):
and (3) carrying out 1C/0.5C charge and discharge after the lithium ion battery is kept stand for 2 hours at 25+/-2 ℃, wherein the charge and discharge voltage is 3.0V-4.45V, and the discharge capacity is the first discharge capacity, and then fully charging the battery. Placing the battery at 60 ℃ for storage, and calculating the remaining capacity retention rate of the battery after storage, wherein the calculation formula is as follows: remaining capacity retention (%) = (remaining discharge capacity on the nth day)/(first cycle discharge capacity) ×100%; and calculating the thickness expansion rate of the stored battery, wherein the calculation formula is as follows: the thickness swelling ratio (%) = (the thickness of the battery after the storage on the nth day)/(the initial thickness of the battery) ×100%. The calculation results are recorded in tables 2 and 3.
(3) Low temperature discharge performance test:
discharging the battery with the capacity of 0.2C to 3.0V at the temperature of 25 ℃ and standing for 5min; charging to 4.45V at 0.2C, changing to 4.45V constant voltage charging when the voltage of the battery cell reaches 4.45V until the charging current is less than or equal to the given cutoff current of 0.05C, and standing for 5min; transferring the fully charged core into a high-low temperature box, setting the temperature to-20 ℃, and standing for 120min after the temperature of the box reaches; then discharging at 0.2C to a final voltage of 3.0V, and standing for 5min; then the temperature of the high-low temperature box is adjusted to 25+/-3 ℃, and the box is left for 60 minutes after the temperature of the box is reached; charging the battery to 4.45V at 0.2C, and changing the battery to 4.45V constant voltage charging when the voltage of the battery cell reaches 4.45V until the charging current is less than or equal to the given cutoff current of 0.05C; standing for 5min; the capacity retention rate of low-temperature discharge at-20 ℃ is calculated to be 3.0V. The calculation results are recorded in tables 2 and 3.
The calculation formula is as follows: -20 ℃ discharge 3.0V capacity retention (%) = (-20 ℃ discharge to 3.0V discharge capacity/25 ℃ discharge to 3.0V discharge capacity) ×100%.
TABLE 2
As can be seen from the data of tables 1 and 2, the low-temperature discharge performance is not significantly changed but the high-temperature cycle performance and the high-temperature storage are improved after the additives a and B are separately added in the comparative examples 2 and 3, respectively, as compared with the comparative example 1; the low-temperature discharge performance is improved after the silicon-substituted organic solvent is added in the comparative example 4, but the high-temperature storage performance is not changed obviously.
From the comparison of comparative example 5 and comparative example 2, it is known that, when the addition amount of additive a or additive B is large, the low-temperature discharge performance and the high-temperature cycle performance are deteriorated; it is presumed that this is because an excessive amount of the additive will increase the interface resistance, deteriorating the low-temperature discharge performance of the battery. From a comparison of comparative example 7 and comparative example 4, it is understood that the high-temperature cycle performance is deteriorated when an excessive amount of the silicon-substituted organic solvent is added.
As can be seen from the comparison of comparative examples 2, 3 and 8, the addition of additive a and additive B to the electrolyte simultaneously did not significantly change the low-temperature discharge performance, the high-temperature cycle performance and the high-temperature storage performance; as is clear from the comparison of comparative examples 2 and 9 and the comparison of comparative examples 3 and 10, when the additive a and the silicon-substituted organic solvent or the additive B and the silicon-substituted organic solvent are added simultaneously to the electrolyte, the low-temperature discharge performance is improved but the high-temperature cycle performance and the high-temperature storage performance are deteriorated at the same time; from the comparison of comparative examples 4 and 9 and the comparison of examples 4 and 10, it is understood that when the additive a and the silicon-substituted organic solvent or the additive B and the silicon-substituted organic solvent are added simultaneously to the electrolyte, the high-temperature cycle performance and the high-temperature storage performance are not significantly changed, but the low-temperature discharge performance is deteriorated.
TABLE 3 Table 3
According to comparison of comparative examples 11 to 16 and examples 1 and examples 10 to 13, when the additive A, the additive B and the silicon-substituted organic solvent are added simultaneously, the capacity retention rate of the battery at-20 ℃ for discharging 3.0V is above 69%, the capacity retention rate at 45 ℃ for 500 weeks is above 77%, and the thermal state thickness expansion rate at 60 ℃ for 30 days is below 7.9%; the low-temperature discharge performance, the high-temperature cycle performance and the high-temperature storage performance of the battery are obviously improved.
As is evident from the comparison of examples 1 to 3, the additive A was added in an increasing amount, the capacity retention rate of the battery at-20℃discharge 3.0V was slightly decreased, the capacity retention rate was increased by 500 weeks at 45℃cycle, and the thermal state thickness expansion rate was decreased by 30 days at 60℃storage, i.e., the high temperature cycle performance and the high temperature storage performance of the battery were further improved.
As is evident from comparison of examples 1, 4 and 5, the additive B was added in an increasing amount, the battery was slightly decreased in capacity retention rate of 3.0V at-20℃discharge, increased in capacity retention rate at 500 weeks at 45℃cycle, and decreased in thermal state thickness expansion rate at 60℃for 30 days, i.e., the high-temperature cycle performance and high-temperature storage performance of the battery were further improved.
As can be seen from comparison of examples 1, 6 and 7, the addition amount of the silicon-substituted organic solvent is continuously increased, the capacity retention rate of the battery is increased by discharging at-20 ℃ for 3.0V, the capacity retention rate is increased by cycling at 45 ℃ for 500 weeks, and the thermal state thickness expansion rate is not obviously changed after the battery is stored at 60 ℃ for 30 days, namely the low-temperature discharge performance and the high-temperature cycling performance of the battery are further improved.
Therefore, the low-temperature discharge performance, the high-temperature cycle performance and the high-temperature storage performance of the battery can be effectively improved through the synergistic cooperation of the additive A, the additive B and the silicon-substituted organic solvent.
To illustrate the importance of the relationship between the electrolyte and the positive electrode material layer mentioned in the present application, the present application prepared examples 1a to 1h based on the lithium ion production method in example 1 and additive a, additive B and a siliconized organic solvent added to the electrolyte of example 1, and tested the low-temperature discharge performance and high-temperature cycle performance of the battery. The specific differences between examples 1a-1h are shown in Table 4.
TABLE 4 Table 4
As can be seen from the comparison of examples 1a to 1h in Table 4, when the silicon-substituted organic solvent and the positive electrode material layer in the electrolyte satisfy the condition of 0.1.ltoreq.c/(D1+D2). Ltoreq.0.6, the wetting effect of the silicon-substituted organic solvent on the positive electrode sheet is good, and the low-temperature discharge performance and the high-temperature cycle performance are good. As c/(d1+d2) increases, if the content of the siliconized organic solvent in the electrolyte is too high without changing the thickness of the positive electrode material layer, the low-temperature discharge performance is further improved, but the high-temperature cycle performance is also deteriorated to some extent. Therefore, when the mass ratio of the silicon organic solvent in the electrolyte is 5-30%, c/(D1+D2) is more than or equal to 0.1 and less than or equal to 0.6, the low-temperature discharge performance and the high-temperature cycle performance of the battery are optimal.
It should be noted that the above-described embodiments are only for explaining the present application and do not constitute any limitation of the present application. The application has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the application as defined in the appended claims, and the application may be modified without departing from the scope and spirit of the application. Although the application is described herein with reference to particular means, materials and embodiments, the application is not intended to be limited to the particulars disclosed herein, as the application extends to all other means and applications having the same function.
Claims (10)
1. An electrolyte, characterized in that: comprises a solvent, an additive A and an additive B, wherein the solvent comprises a silicon-substituted organic solvent; the structural general formula of the additive A is shown as follows:
wherein X is 1 、X 2 And X 3 Each independently selected from one of fluorine atom, cyano group, isocyanate group, hydrogen atom, saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms; r is R 1 And R is 2 Each independently selected from one of a fluorine atom, a phenyl group, a fluoroalkane group, a saturated or unsaturated hydrocarbon group having 1 to 5 carbon atoms;
the structural general formula of the additive B is shown as follows:
wherein W is 1 、W 2 And W is 3 Each independently selected from one of an alkyl group, an alkenyl group, an alkoxy group having 1 to 5 carbon atoms substituted with a cyano group or an isocyanate group;
the silicon-substituted organic solvent is selected from one or more of the compounds shown in the following structural general formulas:
wherein Y is 1 、Y 2 、Y 3 、Y 4 Each independently selected from siloxanes having from 1 to 5 carbon atoms.
2. The electrolyte of claim 1, wherein: the additive A is selected from at least one of the following structural formulas:
and/or the additive B is selected from at least one of the following structural formulas:
3. the electrolyte of claim 1, wherein: the silicon-substituted organic solvent is selected from at least one of the following structural formulas:
4. the electrolyte of claim 1, wherein: the solvent also comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran.
5. The electrolyte according to any one of claims 1 to 4, wherein: the mass ratio of the additive A in the electrolyte is 0.01% -5%;
and/or the mass ratio of the additive B in the electrolyte is 0.01-5%;
and/or the mass ratio of the silicon-substituted organic solvent in the electrolyte is c%; wherein, c is more than or equal to 5% and less than or equal to 30%.
6. The electrolyte according to any one of claims 1 to 4, wherein: the electrolyte comprises lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5 mol/L-2 mol/L; preferably 0.8mol/L to 2mol/L; more preferably 0.9mol/L to 1.3mol/L.
7. The utility model provides a lithium ion battery, includes positive pole piece, negative pole piece, diaphragm and electrolyte, its characterized in that: the electrolyte according to any one of claims 1 to 6.
8. The lithium ion battery of claim 7, wherein: the positive electrode plate comprises a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises a first material layer and a second material layer, and the first material layer is arranged between the positive electrode current collector and the second material layer; the first material layer contains a first active material, preferably the first active material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium titanate; the second material layer comprises a second active material, preferably the second active material comprises at least one of lithium cobaltate, lithium iron phosphate, lithium vanadate, lithium manganate, lithium nickelate manganate, lithium-rich manganese base, lithium nickelate aluminate, lithium titanate.
9. The lithium ion battery of claim 8, wherein: the thickness of the first material layer is D1 mu m, the thickness of the second material layer is D2 mu m, and the relationship between the positive electrode material layer and the electrolyte meets the following conditions: c/(D1+D2) is more than or equal to 0.1 and less than or equal to 0.6.
10. The lithium ion battery according to claim 8 or 9, wherein: the sum of the mass of the first active material and the second active material accounts for 80-99% of the total mass of the positive electrode material.
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