CN117175014A - Electrolyte and lithium ion battery - Google Patents
Electrolyte and lithium ion battery Download PDFInfo
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- CN117175014A CN117175014A CN202311366867.4A CN202311366867A CN117175014A CN 117175014 A CN117175014 A CN 117175014A CN 202311366867 A CN202311366867 A CN 202311366867A CN 117175014 A CN117175014 A CN 117175014A
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- additive
- electrolyte
- battery
- negative electrode
- lithium ion
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 90
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 48
- 239000000654 additive Substances 0.000 claims abstract description 126
- 230000000996 additive effect Effects 0.000 claims abstract description 115
- 125000004432 carbon atom Chemical group C* 0.000 claims abstract description 6
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 6
- 125000001183 hydrocarbyl group Chemical group 0.000 claims abstract description 5
- 229930195734 saturated hydrocarbon Natural products 0.000 claims abstract description 5
- 229930195735 unsaturated hydrocarbon Natural products 0.000 claims abstract description 5
- 239000007773 negative electrode material Substances 0.000 claims description 28
- 239000011230 binding agent Substances 0.000 claims description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 18
- 239000006183 anode active material Substances 0.000 claims description 16
- 229910052710 silicon Inorganic materials 0.000 claims description 13
- 229910003002 lithium salt Inorganic materials 0.000 claims description 12
- 159000000002 lithium salts Chemical class 0.000 claims description 12
- 239000002904 solvent Substances 0.000 claims description 10
- 239000000853 adhesive Substances 0.000 claims description 8
- 230000001070 adhesive effect Effects 0.000 claims description 8
- 229920001661 Chitosan Polymers 0.000 claims description 7
- 125000002057 carboxymethyl group Chemical group [H]OC(=O)C([H])([H])[*] 0.000 claims description 7
- 239000006258 conductive agent Substances 0.000 claims description 7
- 229910002804 graphite Inorganic materials 0.000 claims description 7
- 239000010439 graphite Substances 0.000 claims description 7
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 6
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-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
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 6
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 5
- 150000001875 compounds Chemical class 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 4
- 229920002125 Sokalan® Polymers 0.000 claims description 4
- 239000010405 anode material Substances 0.000 claims description 4
- 239000004584 polyacrylic acid Substances 0.000 claims description 4
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 4
- 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 3
- 229920002134 Carboxymethyl cellulose Polymers 0.000 claims description 3
- JGFBQFKZKSSODQ-UHFFFAOYSA-N Isothiocyanatocyclopropane Chemical compound S=C=NC1CC1 JGFBQFKZKSSODQ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052796 boron Inorganic materials 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
- 235000010948 carboxy methyl cellulose Nutrition 0.000 claims description 3
- 239000008112 carboxymethyl-cellulose Substances 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
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 claims description 3
- 239000002153 silicon-carbon composite material Substances 0.000 claims description 3
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 3
- 230000014759 maintenance of location Effects 0.000 abstract description 22
- 238000000034 method Methods 0.000 abstract description 22
- 230000008569 process Effects 0.000 abstract description 17
- ZXEYGQNXUCXTBK-UHFFFAOYSA-N 2-[2-fluoro-4-(trifluoromethyl)phenyl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane Chemical compound O1C(C)(C)C(C)(C)OB1C1=CC=C(C(F)(F)F)C=C1F ZXEYGQNXUCXTBK-UHFFFAOYSA-N 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 6
- 239000010410 layer Substances 0.000 description 19
- 239000000463 material Substances 0.000 description 13
- -1 propyl isocyanate compound Chemical group 0.000 description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
- 239000010703 silicon Substances 0.000 description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 9
- 229910052744 lithium Inorganic materials 0.000 description 9
- 239000007774 positive electrode material Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 6
- 230000002378 acidificating effect Effects 0.000 description 5
- 239000006227 byproduct Substances 0.000 description 5
- 238000000354 decomposition reaction Methods 0.000 description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 5
- 239000002033 PVDF binder Substances 0.000 description 4
- 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 4
- 229910021393 carbon nanotube Inorganic materials 0.000 description 4
- 239000002041 carbon nanotube Substances 0.000 description 4
- 239000013522 chelant Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 239000011888 foil Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 230000002035 prolonged effect Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- 239000006230 acetylene black Substances 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 3
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 3
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 150000003377 silicon compounds Chemical class 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000006256 anode slurry Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- QMCLWCCRKCPMGG-UHFFFAOYSA-N boric acid;propanedioic acid Chemical compound OB(O)O.OC(=O)CC(O)=O QMCLWCCRKCPMGG-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000002134 carbon nanofiber Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011267 electrode slurry Substances 0.000 description 2
- 125000002573 ethenylidene group Chemical group [*]=C=C([H])[H] 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000003273 ketjen black Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- PYLWMHQQBFSUBP-UHFFFAOYSA-N monofluorobenzene Chemical group FC1=CC=CC=C1 PYLWMHQQBFSUBP-UHFFFAOYSA-N 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 229920001228 polyisocyanate Polymers 0.000 description 2
- 239000005056 polyisocyanate Substances 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 229920001897 terpolymer Polymers 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- OQURWGJAWSLGQG-UHFFFAOYSA-N 1-isocyanatopropane Chemical group CCCN=C=O OQURWGJAWSLGQG-UHFFFAOYSA-N 0.000 description 1
- DSMUTQTWFHVVGQ-UHFFFAOYSA-N 4,5-difluoro-1,3-dioxolan-2-one Chemical compound FC1OC(=O)OC1F DSMUTQTWFHVVGQ-UHFFFAOYSA-N 0.000 description 1
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- 239000004135 Bone phosphate Substances 0.000 description 1
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910010238 LiAlCl 4 Inorganic materials 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910013467 LiNixCoyMnzO2 Inorganic materials 0.000 description 1
- 229910012513 LiSbF 6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229920006172 Tetrafluoroethylene propylene Polymers 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 239000011884 anode binding agent Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- WMNMARSCZZDKGQ-UHFFFAOYSA-N boric acid 2,2-difluoropropanedioic acid Chemical compound B(O)(O)O.FC(C(=O)O)(C(=O)O)F WMNMARSCZZDKGQ-UHFFFAOYSA-N 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- LEGITHRSIRNTQV-UHFFFAOYSA-N carbonic acid;3,3,3-trifluoroprop-1-ene Chemical compound OC(O)=O.FC(F)(F)C=C LEGITHRSIRNTQV-UHFFFAOYSA-N 0.000 description 1
- SVTMLGIQJHGGFK-UHFFFAOYSA-N carbonic acid;propa-1,2-diene Chemical compound C=C=C.OC(O)=O SVTMLGIQJHGGFK-UHFFFAOYSA-N 0.000 description 1
- 230000022131 cell cycle Effects 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 150000005676 cyclic carbonates Chemical group 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical group 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 101150004907 litaf gene Proteins 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004745 nonwoven fabric Substances 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 239000007858 starting material 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
- 125000004417 unsaturated alkyl group Chemical group 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application relates to an electrolyte and a lithium ion battery. The electrolyte comprises an additive A and an additive B, wherein the additive A is 2-fluoro-4-trifluoromethyl phenylboronic acid pinacol ester: r in the structural general formula of the additive B 1 、R 2 、R 3 Each independently selected from one of saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms. The scheme provided by the application can improve the high-temperature circulation capacity retention rate of the battery under the high-voltage condition, improve the volume expansion defect in the battery circulation process, improve the circulation performance of the battery, prolong the service life of the battery and improve the comprehensive performance of the 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
In recent years, with the popularization of portable electronic devices, development of electric tools and electric automobiles, lithium ion batteries as a new generation of energy have been widely paid attention, and it has been found that lithium ion batteries have advantages of high specific energy, high operating voltage, low self-discharge rate, small volume, light weight and the like, and thus can be widely applied to the fields of consumer electronics.
The energy density is a parameter for measuring the energy storage size of the lithium ion battery. In the field of power batteries, higher energy density becomes a key indicator of consumer attention due to the light weight of the whole vehicle and the requirement of longer cruising mileage. In order to increase the energy density of lithium ion batteries, a method of increasing the voltage value is generally employed. However, lithium ion batteries are very susceptible to oxidation during charge and discharge at high voltages, and as the number of cycles increases, battery capacity decreases, lifetime decreases, and battery cycle performance deteriorates particularly significantly at high temperatures.
Therefore, how to improve the cycle performance of lithium ion batteries under high voltage conditions is a current problem that needs 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 high-temperature cycle capacity retention rate of the battery under the high-voltage condition, improve the volume expansion defect in the battery cycle process, improve the cycle performance of the battery, prolong the service life of the battery and improve the comprehensive performance of the battery.
The first aspect of the application provides an electrolyte, wherein the structural formula of the additive A is shown as follows:
the structural general formula of the additive B is shown as follows:
wherein R is 1 、R 2 、R 3 Each independently selected from one of saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms.
According to the electrolyte disclosed by the application, the additive A is selected from 2-fluoro-4-trifluoromethyl phenylboronic acid pinacol ester, the additive B is selected from propyl isocyanate compounds, and the fluoro benzene ring, the boron-oxygen bond of the additive A and the unsaturated bond-NCO in the additive B are cooperatively matched, so that an SEI film with good stability and compactness can be formed on the surface of a negative electrode plate and a CEI film with good stability and compactness can be formed on the surface of a positive electrode plate at the same time, the volume expansion of a lithium ion battery in the circulation process is relieved, the high-temperature circulation performance of the lithium ion battery is improved, and the service life of the lithium ion battery is prolonged; meanwhile, the surface of the electrode has a good infiltration effect, so that the contact between the electrolyte and the positive pole piece and the contact between the electrolyte and the negative pole piece can be enhanced, and the lithium ion transmission is facilitated. The isocyanate group of the additive B can effectively complex the transition metal of the positive electrode, so that the structural stability of the positive electrode plate is maintained, and the capacity attenuation problem of the positive electrode material under high voltage is improved; meanwhile, the isocyanate groups can effectively capture acidic byproducts such as HF and the like generated by the decomposition of the electrolyte under the conditions of high voltage and high temperature, so that the negative influence caused by the decomposition failure of the electrolyte under the conditions of high voltage and high temperature is improved, the lithium ion battery can maintain good cycle capacity retention rate under the conditions of high voltage, and the cycle performance of the lithium ion battery is improved.
The benzene ring of the additive A is a fluorinated benzene ring, the bond energy of a fluorocarbon bond is stronger than that of a carbon-hydrogen bond, and the bond energy of a boron-oxygen bond is also stronger, so that the additive A with the fluorinated benzene ring and the boron-oxygen bond has better thermal stability and chemical stability in electrolyte, is favorable for forming an SEI film with better stability and better compactness on the surface of a negative electrode plate of a lithium ion battery, thereby relieving the volume expansion of the lithium ion battery in the circulation process, and particularly the volume expansion of the negative electrode plate prepared from Si material, so that the lithium ion battery has better high-temperature circulation performance. Meanwhile, as the impedance of the additive B is slightly larger, the additive A can improve the infiltration effect of the interface, thereby reducing the impedance of the interface and making up the defect of the additive B, so that the additive A and the additive B are combined for use, and the lithium ion battery can have good electrochemical performance.
Compared with linear or branched aliphatic polyisocyanates and aromatic polyisocyanates, the propyl isocyanate compound structure of the application can form CEI films with better chemical stability, structural stability and compactness on the surface of the positive electrode plate, is favorable for relieving the volume expansion of the lithium ion battery in the circulating process, and simultaneously has more stable structure after complexing with the positive electrode transition metal, and is favorable for maintaining the structural stability of the positive electrode plate, thereby improving the circulating capacity retention rate of the battery under the conditions of high voltage and high temperature, reducing the volume expansion rate of the battery after long-time circulation and prolonging the service life of the battery. In addition, when the side group of the additive B is selected to be saturated or unsaturated alkyl with 1-5 carbon atoms, the chain length of the side chain of the additive B can be controlled, so that the excessive chain length of the side group is prevented from increasing the viscosity of the electrolyte, the migration capacity of lithium ions in the electrolyte solvent is improved, the discharge performance of a battery is improved, and the combination of the propyl isocyanate compound and the additive A is adopted, so that the comprehensive performance of the battery is improved.
In some embodiments of the application, the additive B is selected from one of the following compounds:
the three compounds have high structural stability, and when the additive B adopts the compounds, the stability of the electrolyte under high-temperature conditions and high-voltage conditions can be improved, and the negative influence caused by the decomposition failure of the electrolyte can be reduced; meanwhile, the SEI film and the CEI film formed on the surface of the electrode have good thermal stability and chemical stability, so that the volume expansion of the lithium ion battery in the circulation process is relieved, the high-temperature circulation performance of the lithium ion battery is improved, and the service life of the lithium ion battery is prolonged.
In some embodiments of the application, the mass ratio of the additive A in the electrolyte is a percent, and a is more than or equal to 0.1 and less than or equal to 5; the mass ratio of the additive B in the electrolyte is b% and B is more than or equal to 0.1 and less than or equal to 5. When the content of the additive A and the additive B is too low, the additive A and the additive B cannot play a role in the electrolyte, and when the content of the additive A and the additive B is too high, the viscosity of the electrolyte can be increased, so that the movement of lithium ions in the electrolyte is subjected to larger resistance, the diffusion capacity is reduced, and the discharge rate performance of the lithium ion battery is influenced. The contents of the additive A and the additive B in the electrolyte are limited in the above range, so that the comprehensive performance of the battery can be effectively improved.
In some embodiments of the application, the electrolyte has a mass ratio of additive A to additive B of (0.1-3) to (0.1-3). When the additive A and the additive B are combined, the mass ratio of the additive A to the additive B is required to be within a certain proportion range, and the additive A and the additive B can be mutually promoted within the range, so that the stability and compactness of the CEI film on the surface of the positive electrode plate and the SEI film on the surface of the negative electrode plate are obviously improved, the high-temperature cycle performance of the battery is effectively improved, the thickness expansion rate of the battery is reduced, and the comprehensive performance of the battery is improved.
In some embodiments of the application, the electrolyte further comprises a lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5mol/L to 2mol/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 of the application, the electrolyte further comprises a nonaqueous solvent selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran. The electrolyte solvent system formed by the two or more solvents has better properties than a single solvent, can overcome the defect of limited use temperature of the lithium ion battery, and can still keep good cycle performance when the lithium ion battery is applied under high temperature.
The second aspect of the application provides a lithium ion battery, comprising the electrolyte of the first aspect of the application; the lithium ion battery also comprises a negative electrode plate, wherein a negative electrode material in the negative electrode plate comprises a negative electrode active material, a binder and a conductive agent; wherein the negative electrode active material comprises Si, si-C composite and SiO X -a mixture of graphite and at least one of the C-complexes; the binder in the negative electrode material layer comprises at least one of carboxymethyl chitosan, polyacrylonitrile, polyacrylic acid and carboxymethyl cellulose.
The lithium ion battery adopts electrolyte composed of the additive A (2-fluoro-4-trifluoromethyl phenylboronic acid pinacol ester) and the additive B (propyl isocyanate compound), and fluoro benzene ring and boron oxygen bond in the additive A are beneficial to forming a passivation film SEI film with good stability and good mechanical property on the surface of a negative electrode plate; the unsaturated bond in the additive B can form a CEI film with good stability and mechanical property on the surface of the positive electrode plate, and can protect the structural stability of the positive electrode material, and the positive electrode and the negative electrode of the battery can keep good structural stability through the combined use of the additive A and the additive B, so that the battery cycle performance of the battery under the conditions of high voltage and high temperature is improved. Meanwhile, the isocyanate group of the additive B can decompose acidic byproducts such as HF and the like generated by the decomposition of the electrolyte under the conditions of high voltage and high temperature, so that the acidic byproducts are prevented from damaging the surface materials of the anode and the cathode, and the service life and the cycle performance of the battery are prolonged.
When silicon or a silicon compound is used as the anode active material, the specific capacity of the battery is improved, and when the silicon compound or the silicon and the silicon compound are used as the anode active material and the silicon is independently used as the anode active material, the volume expansion of the anode piece in the circulation process can be reduced. Meanwhile, si material in the negative electrode active material can form strong hydrogen bond action with carboxymethyl chitosan, polyacrylonitrile and the like in the binder, so that the thickness expansion rate in the circulation process is effectively improved.
In some embodiments of the present application, the mass ratio of Si in the anode active material is W 1 ％，1≤W 1 Less than or equal to 25, wherein the mass ratio of the adhesive in the anode material layer is W 2 ％，0.3％≤W 2 Less than or equal to 3 percent. The volume expansion of Si in the anode active material easily causes destruction of SEI, CEI film, and is unfavorable for maintaining stability of the cathode and anode structures when the Si content is too high, so that the Si content in the anode active material is limited within the above range,the specific capacity of the battery can be improved, and the thickness expansion of the battery can be kept in a controllable range, so that the comprehensive performance of the battery is improved. The content of the binder in the negative electrode material layer is limited in the range, so that the viscosity of the negative electrode slurry can be kept in a proper range, the negative electrode slurry is uniformly coated on the surface of the negative electrode current collector, the binder and other materials in the negative electrode material layer are uniformly distributed, the phenomenon that the pole piece is easy to crack can be avoided, and the negative electrode material has good structural stability.
In some embodiments of the present application, the relationship between the mass of Si in the anode active material and additive a in the electrolyte satisfies: a/W is more than or equal to 0.04 1 Less than or equal to 0.2. The additive A in the electrolyte participates in the formed SEI film, so that the mechanical property is better, the compactness is good, the volume expansion of silicon can be effectively relieved, and therefore, the volume expansion of a battery can be improved, but the high-content additive A in the electrolyte can increase the viscosity of the electrolyte, and the multiplying power performance of the battery is deteriorated, so that the problem of lithium precipitation occurs in the later period of circulation, and the circulation capacity retention rate of the battery is reduced, therefore, when the Si content in the anode active material and the content of the additive A in the electrolyte are limited in the above range, the circulation capacity retention rate of the battery can be effectively improved, the volume expansion of the battery is improved, and the comprehensive performance of the battery is improved.
In some embodiments of the application, the mass of the binder in the negative electrode material layer and the additive B in the electrolyte satisfy the following relationship: b/W is more than or equal to 0.5 2 And is less than or equal to 4. The silicon negative electrode has higher specific capacity than graphite, but has larger volume expansion coefficient in the circulation process, is easy to cause the exceeding of the thickness of the battery, the binder in the negative electrode material layer can form strong hydrogen bond with Si in the negative electrode active material to improve the volume expansion in the circulation process, but when the binder in the negative electrode material layer exists in a large amount, the electrolyte is catalyzed to decompose acidic byproducts to erode SEI (solid electrolyte interface) and CEI (electrolyte element interface) films at high voltage such as 4.55V to cause active lithium loss, thereby reducing the circulation capacity retention rate, and effectively improving the circulation capacity retention rate of the battery when the content of the binder in the negative electrode material layer and the content of the additive B in the electrolyte are limited in the proportion rangeThe thickness expansion of the battery is improved, the high-temperature cycle performance of the battery under high voltage is improved, and the volume expansion of the battery under high voltage is reduced.
The technical scheme provided by the application can comprise the following beneficial effects: through the combined use of the additive A and the additive B in the electrolyte, the high-temperature circulation capacity retention rate of the battery under the high-voltage condition can be effectively improved, the volume expansion defect in the battery circulation process is improved, the circulation performance of the battery is improved, the service life of the battery is prolonged, and the comprehensive performance of the battery is improved.
Further, through the combination of the additive A in the electrolyte and Si in the anode active material, the combination of the additive B in the electrolyte and the binder in the anode material layer and the material ratio of the Si material in the anode active material and the anode binder, the volume expansion of the battery in the circulation process can be effectively relieved, so that the battery can maintain good circulation capacity retention rate under the conditions of high voltage and high temperature, and the high-temperature circulation 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.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.
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. In the description of the present application, "plurality" means two or more unless specifically defined otherwise.
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.
Lithium ion batteries are extremely easy to oxidize in the charge and discharge process under the high-voltage condition, the capacity is reduced, the service life is shortened along with the increase of the cycle times, and the cycle performance of the battery is remarkably deteriorated under the high-temperature condition. According to the application, the additive A and the additive B are used in combination, so that the defect that the battery is easy to oxidize under high voltage is effectively overcome, and the cycle performance of the battery under high voltage is obviously improved.
The first aspect of the application provides an electrolyte, which comprises an additive A and an additive B, wherein the structural formula of the additive A is shown as follows:
the structural general formula of the additive B is shown as follows:
wherein R is 1 、R 2 、R 3 Each independently selected from one of saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms. R of additive B 1 、R 2 、R 3 May be selected from different saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms, respectively, or may be selected from the same qualified groups.
In some alternative embodiments, additive B is selected from one of the following compounds:
in the present application, when R of additive B 1 、R 2 、R 3 When the same groups meeting the conditions are selected, compared with three or two different groups, the structural stability is better, and the compactness and the stability of the CEI film on the surface of the positive electrode plate are improved.
In some alternative embodiments, the mass ratio of the additive A in the electrolyte is a%, 0.01.ltoreq.a.ltoreq.10, for example, 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 8% or 10%, etc., and any other value within the above range is also possible.
In some preferred embodiments, the mass ratio a% of additive A in the electrolyte is preferably 0.1.ltoreq.a.ltoreq.5.
In some alternative embodiments, the mass ratio of the additive B in the electrolyte is b%, and B is more than or equal to 0.01 and less than or equal to 10, for example, the mass ratio can be 0.01%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 8% or 10%, and the like, and any other value in the range can be adopted.
In some preferred embodiments, the mass ratio a% of additive A in the electrolyte is preferably 0.1.ltoreq.a.ltoreq.5.
In some alternative embodiments, the mass ratio of additive A to additive B in the electrolyte is (0.1-3): (0.1-3), and may be, for example, 0.1:0.1, 0.1:3, 1:1, 1:2, 1:3, 3:1, 2:1, 3:0.1, 3:3, etc., or any other value within the above range.
In some alternative embodiments, the electrolyte further comprises a lithium salt.
In some alternative embodiments, the concentration of lithium salt in the electrolyte is 0.5mol/L to 2mol/L, for example, 0.5mol/L, 0.8mol/L, 1mol/L, 1.5mol/L, or 2mol/L, etc., and any other value within the above range is also possible.
In some preferred embodiments, the concentration of lithium salt in the electrolyte is 0.9mol/L to 1.3mol/L.
In some alternative embodiments, the lithium salt may be selected from one or more selected from organic electrolyte salts, inorganic electrolyte salts. For example LiPF 6 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiTaF 6 、LiAlCl 4 、Li 2 B 10 Cl 10 、Li 2 B 10 F 10 、LiClO 4 、LiCF 3 SO 3 Etc.; also, lithium salts of chelate orthoborates and chelate orthophosphates, such as lithium dioxaborate (LiB (C) 2 O 4 ) 2 ]Lithium bis malonate borate [ LiB (O) 2 CCH 2 CO 2 ) 2 ]Lithium bis (difluoromalonic) 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 ]And lithium tris (difluoromalonic acid) phosphate [ LiP (O) 2 CCF 2 CO 2 ) 3 ]。
The lithium salt in the electrolyte of the present application may be selected from any one or a combination of the above.
In some alternative embodiments, the electrolyte further comprises a non-aqueous solvent.
In some preferred embodiments, the nonaqueous solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, tetrahydrofuran.
In some alternative embodiments, the electrolyte may further include other additives, such as negative film-forming additives, positive film-forming additives, and additives that 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.
In some alternative embodiments, the negative electrode film-forming additive, i.e., other additives that can promote formation of an SEI film, include, but are not limited to, vinylene carbonate and its derivatives, ethylene carbonate derivatives having non-conjugated unsaturated bonds in their side chains, cyclic carbonates substituted with halogens, and salts of chelate orthoborates and chelate orthophosphates.
In some preferred embodiments, the other additives include one or more of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, and bis-fluoroethylene carbonate.
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 diaphragm 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 alternative embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer coated on a surface of the negative electrode current collector. 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.
In some alternative embodiments, the negative electrode material layer includes a negative electrode active material, a binder, and a conductive agent.
In some alternative embodiments, the negative active material comprises graphite.
In some preferred embodiments, the anode active material comprises Si, si-C composite, siO X Mixtures of graphite and at least one of the compounds-C, wherein SiO X X in the C complex is 1 or 2.
In some preferred embodiments, the mass ratio of Si in the anode active material is W 1 ％，1≤W 1 25, e.g., 1%, 5%, 10%, 15%, 20%, 25%, etc., may be any other value within the above range.
In some casesIn a preferred embodiment, the mass of Si in the anode active material and additive a in the electrolyte satisfy the relationship: a/W is more than or equal to 0.04 1 And.ltoreq.0.2, for example, 0.04, 0.08, 0.1, 0.12, 0.18, 0.2, etc., and any other value within the above-mentioned range may be used.
In some alternative embodiments, the binder in the negative electrode material layer is selected from at least one of carboxymethyl chitosan, polyacrylonitrile, polyacrylic acid, carboxymethyl cellulose.
In some preferred embodiments, the mass ratio of the binder in the anode material layer is W 2 ％，0.3％≤W 2 Less than or equal to 3%, for example, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 3%, etc., and any other value within the above range may be used.
In some preferred embodiments, the mass of the binder in the negative electrode material layer and the additive B in the electrolyte satisfy the relationship: b/W is more than or equal to 0.5 2 And 4. Ltoreq.4, for example, 0.5, 0.8, 1, 2, 3, 4, etc., and any other value within the above-mentioned range.
In some alternative embodiments, the conductive agent may be selected from one or more of conductive carbon black, acetylene black, ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and superconducting carbon, which the present application is not limited to.
In some alternative embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer coated 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 alternative embodiments, the positive electrode material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, ternary LiNixCoyMnzO 2 One or more of materials (wherein x+y+z=1, x+.y). The conductive agent includes, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Binders include, but are not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymers, vinylidene fluoride-hexafluoropropyleneAt least one of an alkene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylic ester resin.
In some alternative embodiments, the separator according to the present application may be arbitrarily selected from known porous structure separators having good chemical and mechanical stability. The material of the separator may be at least one selected from glass fiber, nonwoven 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 alternative 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.
A third aspect of the application provides an electrical device or various energy storage systems using a battery as an energy storage element. The electric device comprises, 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 and the like.
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
(1) Preparation of electrolyte
Mixing ethylene carbonate EC, diethyl carbonate DEC and propylene carbonate PC in a mass ratio of 1:1:1 as an organic solvent; adding additives with the mass percentage content shown in the example 1 in the table 1 into the organic solvent, mixing uniformly, adding the LiPF 6 Obtaining LiPF 6 An electrolyte with a concentration of 1.1 mol/L.
(2) Preparation of positive electrode plate
Lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) Conductive CNT (Carbon Nanotube), binder PVDF (polyvinylidene fluoride)And fully stirring and mixing the materials in an N-methyl pyrrolidone solvent according to the mass ratio of 97:1.5:1.5 to form uniform anode slurry. And (3) coating the slurry on an aluminum foil of a positive current collector, drying, and cold pressing to obtain a positive electrode plate.
(3) Preparation of negative electrode plate
And fully stirring and mixing the anode active material graphite and the conductive agent acetylene black in a proper amount of deionized water solvent according to the mass ratio of 96:1.2:1.5:1.3 of the binder sodium carboxymethyl cellulose to form uniform anode slurry. And (3) coating the slurry on a copper foil of a negative current collector, 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 13 and comparative examples 1 to 5 were carried out in the same manner as in example 1, except that the parameters of additive A and additive B in the electrolyte were different, and the specific differences are shown in Table 1.
Cell performance test: 45 ℃ cycle test
The testing method comprises the following steps: and (3) charging the lithium ion battery to 4.55V at a constant current and a constant voltage of 1C in a constant temperature box with the temperature of 45+/-2 ℃, cutting off the current by 0.05C, and 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 thickness expansion rate and the capacity retention rate after 800 cycles of the battery were calculated, 5 batteries each, and the test results are shown in table 1.
Thickness expansion (%) = (full cell thickness corresponding to number of cycles-full cell thickness of initial first week)/full cell thickness of initial first week 100%.
Capacity retention (%) = discharge capacity for cycle number (mAh)/discharge capacity for the third cycle (mAh) x 100%.
TABLE 1
/>
Note that: "/" indicates that no additives were used.
As is apparent from comparison of the data of comparative example 1 and example 1, when the additive a (2-fluoro-4-trifluoromethylphenyl boronic acid pinacol ester) and the additive B (propyl isocyanate compound) according to the present application are simultaneously added to the electrolyte, the thickness expansion rate of the battery is reduced from 18.5% to 8.4%, and the cycle capacity retention rate is increased from 57.3% to 70.2%, and it is apparent that the high temperature cycle performance of the lithium ion battery at a high voltage of 4.55V is improved by simultaneously adding the additive a (2-fluoro-4-trifluoromethylphenyl boronic acid pinacol ester) and the additive B propyl isocyanate compound to the electrolyte.
As can be seen from the comparison of the data of comparative examples 2-5 and examples 1-3, the thickness expansion rate of the battery is only about 8.4% and the cycle capacity retention rate is about 70.5% after the additive A (2-fluoro-4-trifluoromethylphenylboronic acid pinacol ester) and the additive B (propyl isocyanate compound) are adopted; by using the additive A or additive B of the present application alone or in combination with the additive B of the present application, the thickness expansion ratio was slightly decreased as compared with that of comparative example 1, and the cycle volume retention ratio was slightly increased, but both the thickness expansion ratio and the cycle volume retention ratio were still far inferior to those of example 1. The additive A (2-fluoro-4-trifluoromethyl phenylboronic acid pinacol ester) and the additive B (propyl isocyanate compound) are added into the electrolyte, and the additive A and the additive B are used together to synergistically increase the high-temperature cycle performance of the lithium ion battery at a high voltage of 4.55V, so that the thickness expansion condition is greatly improved.
As can be seen from the comparison of the data in examples 4-13, the content of the additive A (2-fluoro-4-trifluoromethylphenyl boronic acid pinacol ester) or the additive B (propyl isocyanate compound) in the electrolyte needs to reach a certain range when the additive A or the additive B is combined, so that the high-temperature cycle performance of the battery at a high voltage of 4.55V can be obviously improved, and the thickness expansion rate of the battery is reduced. Further, when the mass ratio of the additive a to the additive B is within a certain ratio range, it is preferable that (a: B) = (0.1-3): (0.1-3), the high-temperature cycle capacity retention rate of the battery is further increased, and the thickness expansion rate is further decreased.
Examples 14 to 26
A lithium ion battery was fabricated by the same fabrication method as in example 1, except that the negative electrode active material was a mixture of graphite and Si, and the mass of Si in the negative electrode active material and the composition and mass of the binder in the negative electrode material layer were adjusted, and specific parameter adjustment conditions can be seen in table 2.
Examples 14-26 were subjected to 45℃cycle test, and specific test methods can be found in example 1, 45℃cycle test methods, and test results are found in Table 2.
TABLE 2
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As is clear from the comparison of the data of examples 13 to 18, as the silicon content in the negative electrode sheet increases, the high-temperature cycle capacity retention rate and the cycle thickness expansion rate of the battery gradually deteriorate while the other components are unchanged; the SEI film formed by the additive A has better mechanical property and can relieve the volume expansion of silicon, but the electrolyte is increased by the excessive content of the additive AViscosity, rate performance of the battery is deteriorated to cause lithium precipitation at a later stage of cycle to reduce a cycle capacity retention rate, so that the overall performance of the battery is optimal when the content of the additive a and silicon is within a certain ratio range. For example, examples 13-14, when the additive A content was unchanged, the silicon content was reduced from 10% to 5%, and no significant improvement was observed in the thickness expansion and the cyclic capacity retention; examples 17 to 18, in which the silicon content was 20% to 25%, the deterioration of the cell performance was remarkable, indicating that the protection of additive A was insufficient, and thus 0.05.ltoreq.a/W 1 When the total performance of the battery is less than or equal to 0.1, the comprehensive performance of the battery is optimal.
The adhesive such as carboxymethyl chitosan and polyacrylonitrile can form strong hydrogen bonding with Si, so that the thickness expansion rate in the circulation process can be effectively improved, but when the adhesive exists in a large amount, the electrolyte can be catalyzed to decompose acidic byproducts at high voltage of 4.55V to erode SEI and CEI films, so that active lithium is lost, and the circulation capacity retention rate is reduced. The isocyanate group in the additive B can effectively capture HF, so that the negative influence of the decomposition failure of the adhesive under high voltage can be improved, and the comprehensive performance of the battery is better when the content of the additive B and the content of the adhesive are in a certain proportion range. As is evident from the comparison of the data of examples 19 to 23, when the content of the binder was reduced from 0.5% to 0.3% without changing other components, the performance of the battery was remarkably deteriorated, indicating that the amount of the binder carboxymethyl chitosan was too small, the bonding strength to the negative electrode material layer was insufficient, and thus the performance of the battery was remarkably deteriorated; as the content of the binder increases, the cell cycle thickness expansion rate and capacity retention rate are improved, and when the binder content is too high, the improvement in the thickness expansion rate is not noticeable, but rather the high-temperature cycle performance is deteriorated, so that when 0.833.ltoreq.b/W 2 When the total performance of the battery is less than or equal to 2, the comprehensive performance of the battery is optimal. From the comparison of the data in examples 24-26, it is clear that the performance rules are consistent when the adhesive is replaced by polyacrylonitrile, polyacrylic acid group, sodium carboxymethyl cellulose by carboxymethyl chitosan.
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 is characterized by comprising an additive A and an additive B, wherein the structural formula of the additive A is shown as follows:
the structural general formula of the additive B is shown as follows:
wherein R is 1 、R 2 、R 3 Each independently selected from one of saturated or unsaturated hydrocarbon groups having 1 to 5 carbon atoms.
2. The electrolyte of claim 1, wherein: the additive B is selected from one of the following compounds:
3. the electrolyte of claim 1, wherein: the mass ratio of the additive A in the electrolyte is a percent, and a is more than or equal to 0.1 and less than or equal to 5; the mass ratio of the additive B in the electrolyte is b% and B is more than or equal to 0.1 and less than or equal to 5.
4. The electrolyte according to any one of claims 1 to 3, wherein: in the electrolyte, the mass ratio of the additive A to the additive B is (0.1-3) to (0.1-3).
5. The electrolyte according to any one of claims 1 to 3, wherein: the electrolyte also comprises lithium salt, and the concentration of the lithium salt in the electrolyte is 0.5 mol/L-2 mol/L.
6. The electrolyte according to any one of claims 1 to 3, wherein: the electrolyte also comprises a nonaqueous solvent, wherein the nonaqueous solvent is selected from two or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate and tetrahydrofuran.
7. A lithium ion battery comprising the electrolyte of any one of claims 1 to 6; the lithium ion battery also comprises a negative electrode plate, wherein a negative electrode material in the negative electrode plate comprises a negative electrode active material, a binder and a conductive agent; wherein the negative electrode active material comprises Si, si-C composite and SiO X -a mixture of graphite and at least one of the C-complexes; the binder in the negative electrode material layer comprises at least one of carboxymethyl chitosan, polyacrylonitrile, polyacrylic acid and carboxymethyl cellulose.
8. The lithium ion battery of claim 7, wherein: the mass ratio of Si in the anode active material is W 1 ％，1≤W 1 Less than or equal to 25, wherein the mass ratio of the adhesive in the anode material layer is W 2 ％，0.3％≤W 2 ≤3％。
9. The lithium ion battery of claim 8, wherein: the relation between the mass of Si in the anode active material and the additive A in the electrolyte is as follows: a/W is more than or equal to 0.04 1 ≤0.2。
10. The lithium ion battery of claim 8, wherein: the relation between the mass of the adhesive in the negative electrode material layer and the additive B in the electrolyte is as follows: b/W is more than or equal to 0.5 2 ≤4。
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