CN114552014A - Electrolyte and electrochemical device containing same - Google Patents
Electrolyte and electrochemical device containing same Download PDFInfo
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- CN114552014A CN114552014A CN202210181205.9A CN202210181205A CN114552014A CN 114552014 A CN114552014 A CN 114552014A CN 202210181205 A CN202210181205 A CN 202210181205A CN 114552014 A CN114552014 A CN 114552014A
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 53
- 239000000654 additive Substances 0.000 claims description 58
- 230000000996 additive effect Effects 0.000 claims description 56
- 125000004432 carbon atom Chemical group C* 0.000 claims description 9
- 229910052731 fluorine Inorganic materials 0.000 claims description 9
- 239000002131 composite material Substances 0.000 claims description 8
- 150000001875 compounds Chemical class 0.000 claims description 8
- -1 propylene sultone Chemical class 0.000 claims description 8
- 239000011737 fluorine Substances 0.000 claims description 7
- 125000001153 fluoro group Chemical group F* 0.000 claims description 7
- 239000003960 organic solvent Substances 0.000 claims description 7
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 6
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims description 5
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 claims description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 4
- OBNCKNCVKJNDBV-UHFFFAOYSA-N ethyl butyrate Chemical compound CCCC(=O)OCC OBNCKNCVKJNDBV-UHFFFAOYSA-N 0.000 claims description 4
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims description 4
- 229910003002 lithium salt Inorganic materials 0.000 claims description 4
- 159000000002 lithium salts Chemical class 0.000 claims description 4
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 3
- 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
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 3
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 2
- GWAOOGWHPITOEY-UHFFFAOYSA-N 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide Chemical compound O=S1(=O)CS(=O)(=O)OCO1 GWAOOGWHPITOEY-UHFFFAOYSA-N 0.000 claims description 2
- VTHRQKSLPFJQHN-UHFFFAOYSA-N 3-[2-(2-cyanoethoxy)ethoxy]propanenitrile Chemical compound N#CCCOCCOCCC#N VTHRQKSLPFJQHN-UHFFFAOYSA-N 0.000 claims description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 2
- 239000007983 Tris buffer Substances 0.000 claims description 2
- BTGRAWJCKBQKAO-UHFFFAOYSA-N adiponitrile Chemical compound N#CCCCCC#N BTGRAWJCKBQKAO-UHFFFAOYSA-N 0.000 claims description 2
- 125000003342 alkenyl group Chemical group 0.000 claims description 2
- 125000000217 alkyl group Chemical group 0.000 claims description 2
- VEWLDLAARDMXSB-UHFFFAOYSA-N ethenyl sulfate;hydron Chemical compound OS(=O)(=O)OC=C VEWLDLAARDMXSB-UHFFFAOYSA-N 0.000 claims description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 2
- VLKZOEOYAKHREP-UHFFFAOYSA-N hexane Substances CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 2
- 229910052744 lithium Inorganic materials 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 claims description 2
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims description 2
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 2
- WHULDTBQXVKIHX-UHFFFAOYSA-N propan-2-yl cyanate Chemical compound CC(C)OC#N WHULDTBQXVKIHX-UHFFFAOYSA-N 0.000 claims description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 2
- 125000004076 pyridyl group Chemical group 0.000 claims description 2
- IAHFWCOBPZCAEA-UHFFFAOYSA-N succinonitrile Chemical compound N#CCCC#N IAHFWCOBPZCAEA-UHFFFAOYSA-N 0.000 claims description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 22
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 22
- 238000007086 side reaction Methods 0.000 abstract description 5
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 239000007774 positive electrode material Substances 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 8
- 230000014759 maintenance of location Effects 0.000 description 6
- 125000000542 sulfonic acid group Chemical group 0.000 description 5
- 229910018557 Si O Inorganic materials 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000003487 electrochemical reaction Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910012820 LiCoO Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical group C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 229940021013 electrolyte solution Drugs 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003682 fluorination reaction Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000004770 highest occupied molecular orbital Methods 0.000 description 1
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000003071 parasitic effect Effects 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000004804 winding Methods 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
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0088—Composites
- H01M2300/0091—Composites in the form of mixtures
-
- 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
Abstract
The invention belongs to the technical field of electrochemical devices, and particularly relates to an electrolyte and an electrochemical device containing the same. The electrolyte has high voltage resistance, can reduce the occurrence of side reactions under high voltage, avoids the reaction with a positive electrode material, and improves the cycle life and the high-temperature storage performance of a lithium ion battery.
Description
Technical Field
The invention belongs to the technical field of electrochemical devices, and particularly relates to an electrolyte and an electrochemical device containing the same.
Background
The lithium ion battery has the characteristics of high energy density, long cycle life, no pollution and the like, so that the lithium ion battery has wide application prospects in consumer electronic products, power automobile batteries and energy storage power supplies. With the rapid development of intelligent devices and the coming of the 5G era of new-generation mobile communication networks, the requirements of electric devices on the capacity of lithium ion batteries are continuously improved, and people expect the improvement of the energy density of the lithium ion batteries more and more. However, in a high-voltage lithium ion battery system, the cathode material is unstable in structure, has strong oxidizing property, is easy to generate electrochemical oxidation reaction with the electrolyte, and is repeatedly consumed by the electrolyte, and parasitic reaction is aggravated, so that the capacity of the lithium ion battery is rapidly attenuated or gas is generated, and therefore, the development of the electrolyte adaptive to the high-voltage anode material is an important research and development direction of the industry.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the electrolyte has high voltage resistance, can reduce the progress of side reactions under high voltage, avoids the reaction with a positive electrode material, and improves the cycle life and the high-temperature storage performance of the lithium ion battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
an electrolyte comprises an organic solvent, lithium salt and a composite additive, wherein the composite additive comprises a first additive and a second additive, the first additive is a compound with a chemical structural formula shown in a formula I, and the second additive is a compound with a chemical structural formula shown in a formula II:
wherein R1 in the formula I is at least one of substituted or unsubstituted phenyl with 6-9 carbon atoms or substituted or unsubstituted pyridyl with 5-9 carbon atoms, and R in the formula II10、R11、R12Each independently represents a hydrogen atom, a fluorine atom, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, or a substitution group having 2 to 5 carbon atomsOr at least one of an unsubstituted alkenyl group and a substituted or unsubstituted phenyl group having 6 to 8 carbon atoms.
Preferably, the first additive accounts for 0.1-8 wt% of the electrolyte. In some embodiments, the first additive is present in an amount of 0.1 wt%, 0.5 wt%, 1.1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt% of the electrolyte. Because of the fluorine substitution of the sulfonic acid group in the first additive, the other additives can preferentially carry out redox reaction to form an SEI film containing sulfur and fluorine structures, and the pyridine structure can also form a compact SEI film on the surface of the anode, so that the anode protection under high voltage is effectively improved.
Preferably, the second additive accounts for 0.1-5 wt% of the electrolyte. In some embodiments, the second additive is present in an amount of 0.1 wt%, 0.5 wt%, 1.1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt% of the electrolyte. The second additive can be physically adsorbed and can also form a film on the surfaces of the anode and the cathode through electrochemical reaction, so that the side reaction on the surface of the high-voltage anode material is inhibited, and the formed film structure is more stable because the second additive contains Si-O bonds with high bond energy, so that the anode material is protected, and the electrolyte is prevented from being subjected to oxidative decomposition on the surface of the high-voltage strong-oxidative cathode. When the fluorine is used for fluorination, the fluorine atoms contained in the fluorine can generate lithium fluoride, and the SEI film strength and the positive electrode interface protection are improved.
Preferably, the first additive comprises at least one of the following compounds:
preferably, the second additive comprises at least one of the following compounds:
preferably, the composite additive further comprises a third additive, and the third additive comprises two or more of vinylene carbonate, 1, 3-propane sultone, fluoroethylene carbonate, vinyl sulfate, succinonitrile, adiponitrile, 1,3, 6-hexane trinitrile, 1,2, 3-tris (2-cyanato) propane, propylene sultone, methylene methanedisulfonate, ethylene glycol bis (propionitrile) ether and fluorine-containing ether.
Preferably, the third additive accounts for 5-20 wt% of the electrolyte. In some embodiments, the third additive is present in an amount of 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, 10.5 wt%, 11 wt%, 11.5 wt%, 12 wt%, 12.5 wt%, 13 wt%, 13.5 wt%, 14 wt%, 15 wt%, 15.5 wt%, 16.5 wt%, 17 wt%, 17.5 wt%, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt% based on the mass of the electrolyte.
Preferably, the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate and gamma-butyrolactone, and the mass percentage of the organic solvent to the electrolyte is 0.1-70 wt%. In some embodiments, the organic solvent is present in an amount of 0.1 wt%, 1.5 wt%, 8 wt%, 15 wt%, 20 wt%, 25 wt%, 27 wt%, 28 wt%, 32 wt%, 35 wt%, 36 wt%, 39 wt%, 40 wt%, 42 wt%, 43 wt%, 46 wt%, 48 wt%, 53 wt%, 54 wt%, 56 wt%, 68 wt%, 70 wt%, based on the mass of the electrolyte.
Preferably, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide and lithium difluorophosphate.
The second purpose of the invention is: aiming at the defects of the prior art, the electrochemical device is provided, and has high voltage resistance, good cyclicity and high-temperature storage performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
an electrochemical device comprises the electrolyte. The electrochemical device of the present invention includes, but is not limited to, primary batteries, secondary batteries, fuel cells, solar cells. Specifically, the electrochemical device comprises a positive plate, a negative plate, a diaphragm, a shell and the electrolyte, wherein the diaphragm separates the positive plate from the negative plate, and the positive plate, the negative plate, the diaphragm and the electrolyte are arranged and wrapped by the shell.
Compared with the prior art, the invention has the beneficial effects that: the electrolyte contains a composite additive, the composite additive comprises a first additive with a sulfonic acid group and a second additive of cyclic siloxane with a high-bond-energy Si-O bond, wherein the sulfonic acid group is substituted by fluorine, and the HOMO and LUMO of the sulfonic acid group are changed after the fluorine substitution, so that the sulfonic acid group is easy to react preferentially with other additives; the second additive forms a film on the surfaces of the positive electrode and the negative electrode through physical adsorption or electrochemical reaction, so that the side reaction on the surface of the high-voltage positive electrode material is inhibited, and the formed film structure is more stable due to the Si-O bond with high bond energy, so that the positive electrode material is maintained, and the electrolyte is prevented from being oxidized and dispersed on the surface of the high-voltage strong-oxidizing cathode. The first additive and the second additive are matched for use, so that the stability of the electrolyte under high voltage can be effectively improved, and the side reaction under high voltage is reduced, thereby improving the cycle life and the high-temperature storage performance of the lithium ion battery.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
Preparation of electrolyte: ethylene carbonate, propylene carbonate, diethyl carbonate and propyl propionate were mixed in the mass ratio EC: PC: DEC: PP 1: 1: 1: 2, and then, 14.5 wt% of lithium hexafluorophosphate (LiPF) based on the total weight of the electrolyte was slowly added to the mixed solution6) And finally, adding 0.5 wt% of first additive, 3.0 wt% of second additive and 7.0 wt% of third additive based on the total weight of the electrolyte, wherein the 7.0 wt% of third additive comprises 5 wt% of fluoroethylene carbonate (FEC) and 2.0 wt% of 1, 3-Propane Sultone (PS), and uniformly stirring to obtain the lithium ion battery electrolyte of example 1.
Preparing a soft package battery: the positive plate (active material LiCoO)2) The diaphragm and the negative plate (active material graphite) are sequentially stacked, the diaphragm is positioned between the positive plate and the negative plate, and the bare cell is obtained by winding; and (3) placing the bare cell into an aluminum plastic film outer package, injecting the prepared electrolyte into the dried battery, packaging, standing, forming, shaping and grading to finish 4.48V lithium ions.
Examples 1 to 6 and comparative examples 1 to 17.
Examples 1 to 6 and comparative examples 1 to 17 were the same as example 1 except that the electrolyte composition ratios of the respective components were added as shown in Table 1.
Table 1 compositions of the electrolyte solutions of examples 1 to 6 and comparative examples 1 to 17 were mixed.
The following tests were carried out on the lithium ion batteries of examples 1 to 6 and comparative examples 1 to 17, respectively:
(1) lithium ion battery cycle performance test
And (3) respectively placing the lithium ion battery in a thermostatic chamber of 25 ℃ and a thermostatic box of 45 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. The lithium ion battery reaching the constant temperature is charged with a constant current of 0.5C to a voltage of 4.48V, then charged with a constant voltage of 4.48V to a current of 0.05C, and then discharged with a constant current of 0.5C to a voltage of 3.0V, which is a charge-discharge cycle. Thus, the charge and discharge were repeated, and the capacity retention ratio of the lithium ion battery was calculated for 300 cycles, respectively.
(2) High temperature storage volume expansion test
The lithium ion battery is charged to 4.48V at a constant current of 0.5C, and then charged at a constant voltage until the current is 0.05C, until the battery is in a full charge state. The thickness of the lithium ion battery in the fully charged state was tested for THK 1. The fully charged cells were stored in a 60 ℃ high temperature oven 14D and cell thickness THK2 was tested. The swelling ratio of the lithium ion battery was calculated as follows: the swelling ratio is (THK2-THK1)/THK 1.
The results of the performance tests on the lithium ion batteries of examples 1 to 6 and comparative examples 1 to 17 are shown in Table 2
Table 2 lithium ion battery and electrolyte performance test results.
From table 2 above, it can be seen that:
compared with the embodiment 1-6 and the comparative example 15, the additive used in the electrolyte can solve the problem of high-temperature storage expansion and avoid serious gas expansion of the battery.
Compared with examples 1-6 and comparative examples 16-17, when the conventional additive (i.e., only the third additive) is used in the electrolyte, the expansion rate can be reduced, but the expansion rate is still large, and the cycle retention rate at normal temperature (25 ℃) and high temperature (45 ℃) is low.
Compared with the embodiment 1 and the comparative examples 1 to 14, when the first additive and the second additive are used together, compared with the single additive, the improvement effect is more obvious, the cycle retention rate at normal temperature (25 ℃) and high temperature (45 ℃) can be effectively improved, and the expansion rate is kept low.
From comparison of examples 1 to 4, when the first additive is represented by formula I-1 in a mass part of 1 wt% and the second additive is represented by formula II-1 in a mass part of 1 wt% in the electrolyte (i.e., example 3), the electrolyte has a high cycle retention rate at normal temperature (25 ℃) and high temperature (45 ℃) and a low expansion rate.
From comparison of examples 3 and 5, when the content of FEC in the third additive in the electrolyte is increased to 7.0%, the cycle retention rates at normal temperature (25 ℃) and high temperature (45 ℃) are effectively improved.
From comparison between examples 5 and 6, the electrolyte is a complex mixed system, different systems are used to achieve different promotion effects, and when the first additive in the electrolyte is represented by formula I-1, the promotion effect on the cycle retention rate at normal temperature (25 ℃) and high temperature (45 ℃) is better than that when the first additive is represented by formula I-6.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. The electrolyte is characterized by comprising an organic solvent, a lithium salt and a composite additive, wherein the composite additive comprises a first additive and a second additive, the first additive is a compound with a chemical structural formula shown in a formula I, and the second additive is a compound with a chemical structural formula shown in a formula II:
wherein R1 in the formula I is at least one of substituted or unsubstituted phenyl with 6-9 carbon atoms or substituted or unsubstituted pyridyl with 5-9 carbon atoms, and R in the formula II10、R11、R12Each of which isIndependently at least one of a hydrogen atom, a fluorine atom, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, and a substituted or unsubstituted phenyl group having 6 to 8 carbon atoms.
2. The electrolyte according to claim 1, wherein the first additive accounts for 0.1-8 wt% of the electrolyte.
3. The electrolyte according to claim 1, wherein the second additive accounts for 0.1-5 wt% of the electrolyte.
4. The electrolyte of claim 1, wherein the first additive comprises at least one of the following compounds:
5. the electrolyte of claim 1, wherein the second additive comprises at least one of the following compounds:
6. the electrolyte of claim 1, wherein the composite additive further comprises a third additive, and the third additive comprises a mixture of two or more of vinylene carbonate, 1, 3-propane sultone, fluoroethylene carbonate, vinyl sulfate, succinonitrile, adiponitrile, 1,3, 6-hexane trinitrile, 1,2, 3-tris (2-cyanato) propane, propylene sultone, methylene methanedisulfonate, ethylene glycol bis (propionitrile) ether, and fluorine-containing ether.
7. The electrolyte according to claim 6, wherein the third additive accounts for 5-20 wt% of the electrolyte.
8. The electrolyte according to claim 1, wherein the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate and gamma-butyrolactone, and the mass percentage of the organic solvent in the electrolyte is 0.1-70 wt%.
9. The electrolyte of claim 1, wherein the lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (fluorosulfonyl) imide, and lithium difluorophosphate.
10. An electrochemical device comprising the electrolyte of any one of claims 1 to 9.
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