CN111211353A - Lithium ion battery electrolyte for high-voltage system - Google Patents
Lithium ion battery electrolyte for high-voltage system Download PDFInfo
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- CN111211353A CN111211353A CN202010013708.6A CN202010013708A CN111211353A CN 111211353 A CN111211353 A CN 111211353A CN 202010013708 A CN202010013708 A CN 202010013708A CN 111211353 A CN111211353 A CN 111211353A
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 85
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 71
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 71
- -1 trimethyl silane cyclic phosphate compound Chemical class 0.000 claims abstract description 42
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 26
- 239000010452 phosphate Substances 0.000 claims abstract description 26
- 239000000654 additive Substances 0.000 claims abstract description 18
- 229940094989 trimethylsilane Drugs 0.000 claims abstract description 18
- 230000000996 additive effect Effects 0.000 claims abstract description 16
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 12
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 12
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims abstract description 10
- 239000011356 non-aqueous organic solvent Substances 0.000 claims abstract description 10
- 150000001350 alkyl halides Chemical class 0.000 claims abstract description 8
- 125000003342 alkenyl group Chemical group 0.000 claims abstract description 6
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 6
- 125000004093 cyano group Chemical group *C#N 0.000 claims abstract description 6
- 125000005843 halogen group Chemical group 0.000 claims abstract description 6
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 6
- 150000001875 compounds Chemical class 0.000 claims description 39
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 11
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 11
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 3
- 125000004432 carbon atom Chemical group C* 0.000 claims description 3
- 229910052744 lithium Inorganic materials 0.000 claims description 3
- ZPFAVCIQZKRBGF-UHFFFAOYSA-N 1,3,2-dioxathiolane 2,2-dioxide Chemical compound O=S1(=O)OCCO1 ZPFAVCIQZKRBGF-UHFFFAOYSA-N 0.000 claims description 2
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 2
- 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 2
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 claims description 2
- BJWMSGRKJIOCNR-UHFFFAOYSA-N 4-ethenyl-1,3-dioxolan-2-one Chemical compound C=CC1COC(=O)O1 BJWMSGRKJIOCNR-UHFFFAOYSA-N 0.000 claims description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-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
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 2
- JGFBQFKZKSSODQ-UHFFFAOYSA-N Isothiocyanatocyclopropane Chemical compound S=C=NC1CC1 JGFBQFKZKSSODQ-UHFFFAOYSA-N 0.000 claims description 2
- RJUFJBKOKNCXHH-UHFFFAOYSA-N Methyl propionate Chemical compound CCC(=O)OC RJUFJBKOKNCXHH-UHFFFAOYSA-N 0.000 claims description 2
- PWLNAUNEAKQYLH-UHFFFAOYSA-N butyric acid octyl ester Natural products CCCCCCCCOC(=O)CCC PWLNAUNEAKQYLH-UHFFFAOYSA-N 0.000 claims description 2
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 150000005678 chain carbonates Chemical class 0.000 claims description 2
- 150000005676 cyclic carbonates Chemical class 0.000 claims description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 2
- CYEDOLFRAIXARV-UHFFFAOYSA-N ethyl propyl carbonate Chemical compound CCCOC(=O)OCC CYEDOLFRAIXARV-UHFFFAOYSA-N 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
- 229940017219 methyl propionate Drugs 0.000 claims description 2
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 claims description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims description 2
- 238000003860 storage Methods 0.000 abstract description 16
- 230000001681 protective effect Effects 0.000 abstract description 3
- 239000002131 composite material Substances 0.000 abstract description 2
- 239000013538 functional additive Substances 0.000 abstract description 2
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 17
- 230000014759 maintenance of location Effects 0.000 description 8
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- 229910013872 LiPF Inorganic materials 0.000 description 5
- 101150058243 Lipf gene Proteins 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 239000010405 anode material Substances 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000002000 Electrolyte additive Substances 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000011084 recovery Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910012265 LiPO2F2 Inorganic materials 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229920000620 organic polymer Polymers 0.000 description 2
- 238000006864 oxidative decomposition reaction Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- 229910001428 transition metal ion Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910012258 LiPO Inorganic materials 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 239000006183 anode active material Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004070 electrodeposition Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000004768 lowest unoccupied molecular orbital Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 125000000026 trimethylsilyl group Chemical group [H]C([H])([H])[Si]([*])(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- 238000003466 welding 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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
Abstract
The invention provides a lithium ion battery electrolyte for a high-voltage system, which comprises a non-aqueous organic solvent, electrolyte lithium salt and an additive; the additive comprises a trimethyl silane cyclic phosphate compound; wherein R1 is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide, and R2 is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide. The lithium ion battery electrolyte for the high-voltage system adopts lithium difluorophosphate and trimethylsilane cyclic phosphate compound as electrolyte composite functional additives, and a compact and stable protective film (CEI film) can be formed on the surface of the anode of the lithium ion battery through the synergistic effect of the trimethylsilane cyclic phosphate compound and the lithium difluorophosphate, so that the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery under high voltage are effectively improved.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a lithium ion battery electrolyte for a high-voltage system.
Background
The lithium ion battery is a secondary battery developed in the nineties of the last century, has the characteristics of long service life, high specific energy, safety, environmental protection and the like, and is a new-generation green and environment-friendly battery. In recent years, lithium ion power batteries have become a hot spot for research in new energy fields.
With the continuous development of the electric automobile market, the demand for improving the energy density of the lithium ion battery is increasingly urgent, and the improvement of the working voltage of the lithium ion battery is a method for effectively improving the energy density of the lithium ion battery. At present, the charge cut-off voltage of a general lithium ion battery is about 4.2V, and the requirement of higher charge cut-off voltage on the comprehensive performance of the lithium ion battery electrolyte is higher (especially when the anode material is a high-nickel ternary material). Therefore, the development of a functional electrolyte suitable for a high voltage system is an important basis for the development of a high specific energy battery.
In recent years, increasing the operating voltage of lithium ion batteries has become an indispensable option for increasing the energy density thereof. The lithium ion battery using the high-nickel ternary cathode material has the advantages of higher specific capacity, high energy density, environmental friendliness, low cost and the like, and has great application prospects in the fields of electric vehicles, large-scale energy storage devices and the like. However, under high pressure, the high nickel ternary positive electrode material has poor structural stability and is easy to generate negative phenomena such as transition metal ion dissolution, oxygen release and the like; at high voltage, the high-nickel anode ternary material is subjected to deep lithium removal, and at the moment, the anode material has very strong oxidizability, and if the anode material is in contact with an electrolyte, the electrolyte can be subjected to oxidative decomposition, and a large amount of byproducts are generated. The above phenomena all cause the performance of the lithium ion battery to be deteriorated. The above side effects are more serious when the lithium ion battery is in a high temperature environment; in addition, the electrolyte may be decomposed at high temperature to generate by-products such as HF, which corrodes the positive electrode active material to dissolve out the transition metal, thereby seriously deteriorating the performance of the lithium ion battery. Therefore, the high-voltage lithium ion battery has very high requirements on the comprehensive performance of the electrolyte, and the research and development of the functional electrolyte suitable for the high-voltage lithium ion battery are urgent.
Disclosure of Invention
In view of the above, the present invention is directed to provide an electrolyte for a lithium ion battery in a high voltage system, wherein an additive used in the electrolyte has excellent film forming characteristics, and can form a stable and dense passivation film on the surfaces of a positive electrode and a negative electrode at the same time to prevent the electrolyte from decomposing on the surfaces of the positive electrode and the negative electrode; the electrolyte additive can also absorb HF in the electrolyte to prevent the HF from corroding the positive active material. The electrolyte can obviously improve the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery under high voltage.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a lithium ion battery electrolyte for a high voltage system comprises a non-aqueous organic solvent, an electrolyte lithium salt and an additive;
the additive comprises a trimethyl silane cyclic phosphate compound;
the general formula of the trimethylsilane cyclic phosphate compound is as follows:
wherein R is1Is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide, R2Is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide.
Further, the trimethylsilyl cyclic phosphate compound is at least one of a compound (1-A), a compound (1-B), a compound (1-C), a compound (1-D), a compound (1-E) or a compound (1-F), and the chemical formulas of the compound (1-A), the compound (1-B), the compound (1-C), the compound (1-D), the compound (1-E) and the compound (1-F) are respectively as follows:
further, the carbon atom number of the alkyl halide is 1-10.
Further, the trimethyl silane cyclic phosphate compound accounts for 0.05-2% of the total mass of the lithium ion battery electrolyte; preferably, the trimethyl silane cyclic phosphate compound accounts for 0.5-1% of the total mass of the lithium ion battery electrolyte.
Further, the additive also comprises lithium difluorophosphate, and the percentage of the lithium difluorophosphate in the total mass of the lithium ion battery electrolyte is 0.8%.
Further, the non-aqueous organic solvent is at least one of a carbonate compound or a carboxylic ester compound with 1-4 carbon atoms; the carbonate compound comprises at least one of cyclic carbonate or chain carbonate; the non-aqueous organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, 1, 4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or propyl propionate; preferably, the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the ethylene carbonate to the ethyl methyl carbonate is 3: 7.
Further, the electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide or lithium bis (fluorooxalato) borate; preferably, the electrolyte lithium salt is lithium hexafluorophosphate; the percentage of the electrolyte lithium salt in the total mass of the lithium ion battery electrolyte is 10-20%; the concentration of the electrolyte lithium salt is 0.8-1.5 mol/L.
Further, the lithium ion battery electrolyte also comprises a negative electrode film-forming agent accounting for 0.1-4% of the total mass of the lithium ion battery electrolyte, wherein the negative electrode film-forming agent is at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, 1, 3-propane sultone or ethylene sulfate. The film-forming additive further improves high temperature cycle performance and high temperature storage performance.
The sum of the percentage contents of the non-aqueous organic solvent, the electrolyte lithium salt and the additive is equal to 100 percent.
A high voltage lithium ion battery comprises the lithium ion battery electrolyte for a high voltage system.
The upper limit cut-off voltage of the high-voltage lithium ion battery is greater than or equal to 4.3V.
The trimethylsilyl cyclic phosphate compound additive can perform oxidation reaction on the surface of the anode, so that a layer of complete organic polymer film with good protection effect can be formed on the surface of the anode, the trimethylsilyl groups in the compound can absorb HF in electrolyte to prevent the HF from corroding anode active materials, the trimethylsilyl cyclic phosphate compound can simultaneously protect the anode and the cathode of a battery, inhibit side reaction of the electrolyte on the interface of the anode and the cathode, and prevent anode and cathode materials from being damaged; lithium difluorophosphate has a lower LUMO orbital level than electrolyte solvent molecules (the main component is an organic non-aqueous solvent), and can perform a reduction reaction on the surface of a negative electrode to form an inorganic film (SEI film) with good protection effect and low resistance; lithium difluorophosphate can also form an inorganic passive film (CEI film) with low impedance and good stability on the surface of the positive electrode in an electrochemical deposition mode.
Compared with the prior art, the lithium ion battery electrolyte for the high-voltage system has the following advantages:
(1) the lithium ion battery electrolyte for the high-voltage system adopts lithium difluorophosphate and trimethylsilane cyclic phosphate compound as electrolyte composite functional additives, and a compact and stable protective film (CEI film) can be formed on the surface of the anode of the lithium ion battery through the synergistic effect generated by the trimethylsilane cyclic phosphate compound and the lithium difluorophosphate.
(2) The lithium ion battery electrolyte for the high-voltage system can inhibit the negative effects of phase change, dissolution of transition metal ions, oxygen release, oxidative decomposition of the electrolyte and gas generation of the high-nickel ternary positive electrode material; can also remove HF generated in the electrolyte, prevent HF from corroding positive active substances; under the high voltage of 4.3V, the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery prepared by using the electrolyte are obviously improved, so that the energy density of the lithium ion battery is favorably improved.
(3) The lithium ion battery electrolyte for the high-voltage system can improve the energy density of the battery and improve the cycle performance and the high-temperature storage performance of the battery.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
The present invention will be described in detail with reference to examples.
Example 1
A lithium ion battery electrolyte for high-voltage system is composed of 1% VC, 0.5% PS and 0.8% LiPO2F21% of compound (1-A), 12.7% of lithium hexafluorophosphate, 25.2% of EC, 58.8% of EMC.
A high voltage lithium ion battery comprises the lithium ion battery electrolyte for a high voltage system.
The preparation method of the lithium ion battery electrolyte for the high-voltage system comprises the following steps: in a glove box filled with argon (H)2O is less than 10ppm, Ar is more than 99.99 percent), Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) are mixed according to the mass ratio of EC to EMC being 3:7, and LiPF accounting for 12.7 percent of the total weight of the electrolyte is added6Then, 1% of VC based on the total weight of the electrolyte, 0.5% of PS based on the total weight of the electrolyte, and 0.8% of LiPF based on the total weight of the electrolyte were added, respectively2O2And (3) homogenizing 1% of trimethylsilyl cyclic phosphate compound additive compound (1-A) based on the total weight of the electrolyte to obtain the lithium ion battery electrolyte for the high-voltage system.
The preparation method of the high-voltage lithium ion battery comprises the following steps: the batteries are all soft package batteries, wherein the positive electrode is ternary nickel cobalt lithium manganate (NCM622), the negative electrode is graphite, the battery core capacity is 2.7Ah, and the cut-off voltage is 2.75V-4.3V. The preparation method comprises the steps of obtaining an electric core to be injected through homogenizing, coating, rolling, slitting, punching, laminating, welding, packaging and baking, injecting the prepared electrolyte into a dried battery, packaging, standing, forming and grading, and completing the preparation of the lithium ion soft package battery.
Example 2
The difference from example 1 was only that compound (1-B) was used as the trimethylsilyl cyclic phosphate compound.
Example 3
The difference from example 1 was only that compound (1-C) was used as the trimethylsilyl cyclic phosphate compound.
Example 4
The only difference from example 1 is that the compound (1-D) is used as the trimethylsilane cyclic phosphoric acid ester compound.
Example 5
The only difference from example 1 is that compound (1-E) is used as the trimethylsilyl cyclic phosphate compound.
Example 6
The only difference from example 1 is that the compound (1-F) is used as the trimethylsilane cyclic phosphoric acid ester compound.
Comparative example 1
A lithium ion battery electrolyte comprises 1% of VC, 0.5% of PS, 12.7% of lithium hexafluorophosphate, 25.2% of EC and 58.8% of EMC.
A lithium ion battery comprises the lithium ion battery electrolyte.
Comparative example 2
The only difference from comparative example 1 was that 1% of compound (1-A) was added.
Comparative example 3
The difference from comparative example 1 is only in that LiPO was added by 0.8%2F2。
Comparative example 4
And comparative example2 differ only in the addition of 0.8% LiPO2F2。
Comparative example 5
Differs from comparative example 3 only in that 0.5% of the compound (1-A) was added
Comparative example 6
The only difference from comparative example 3 was that compound (1-A) was added by 1.5%.
Comparative example 7
The only difference from comparative example 3 was that compound (1-A) was added by 2%.
The composition ratios of the components of the electrolyte additives of examples 1 to 6 and comparative examples 1 to 7 and the high temperature cycle and high temperature storage data thereof are shown in table 1.
High temperature cycling experiment: and at the temperature of 45 ℃, charging the divided battery cell to 4.3V at constant current and constant voltage according to 1C, stopping current at 0.05C, then discharging to 2.75V at constant current according to 1C, and circulating according to the above steps, and calculating the circulating capacity retention rate after charge-discharge circulation. The cell was cut off after cycling to capacity retention of less than 50% or 1000 weeks.
Capacity retention (%) - (discharge capacity at cycle end/first-cycle discharge capacity X100%)
High temperature storage experiment: the divided cells were subjected to two charge-discharge cycles at 25 ℃ and the discharge capacity before storage (C) was measured0) Charging the battery cell, storing at 55 deg.C for 7/14 days, performing two charge-discharge cycles, and measuring discharge capacity (C)1And C2) And finally, after the battery cell is fully charged, disassembling the battery cell, and observing the interface condition of the battery cell. (Charge-discharge cycle flow is the same as high-temperature cycle flow)
High temperature storage capacity retention rate ═ C1/C0X 100%, high temperature storage capacity recovery rate ═ C2/C0×100％
TABLE 1 composition ratios of components of electrolyte additives of examples 1-6 and comparative examples 1-7, and high temperature cycle and high temperature storage data thereof
As can be seen from a comparison of the electrical property test results of comparative examples 1 and 2, 1 and 3 in table 1: 0.8 percent of LiPF is added into the electrolyte2O2Or the trimethylsilane cyclic phosphate compound additive compound (1-A) can improve the cycle performance and the high-temperature storage performance of the battery cell.
As can be seen from a comparison of the results of the electrical property tests of comparative examples 1-7 in Table 1: when the content of the trimethylsilane cyclic phosphate compound additive compound (1-A) is not less than 0.1 percent of the total mass of the electrolyte, an effective organic polymer protective film is more easily formed on the surface of the anode of the battery, and the cycle performance and the high-temperature storage performance of the lithium ion battery can be improved; but when the content thereof is more than 2% of the total mass of the electrolyte, it may cause a decrease in battery performance (possibly due to excessive addition of additives to cause excessive internal resistance of the cell). Therefore, the compound (1-A) is preferably contained in an amount of 0.1% to 2% by mass of the total mass of the electrolyte, and more preferably in an amount of 0.5% to 1.5% by mass of the total mass of the electrolyte when used in a power battery.
As can be seen from a comparison of the electrical property test results of examples 1-6 in Table 1: at a cut-off voltage of 4.3V, 0.8% LiPF based on the mass of the electrolyte was contained2O2The battery cell used together with the electrolyte containing 1% of A1, 1% of VC and 0.5% of PS in percentage by mass has better high-temperature circulation capacity retention rate than the battery cell containing other trimethylsilane cyclic phosphate compound additives, and has excellent capacity retention rate and capacity recovery rate during high-temperature storage, and the interface is kept well.
From the above results, it is apparent that at a high voltage, the electrolyte composition containing 1% by mass of an additive of a trimethylsilyl cyclic phosphate ester compound and 0.8% by mass of LiPF based on the electrolyte2O2When used together, can effectively improve the high-temperature storage performance and the high-temperature cycle performance of the battery core, thereby being beneficial to improving the performance of the lithium ion batteryEnergy density. Among them, the trimethylsilyl cyclic phosphate ester compound 1-A had the best experimental effect.
When the high-temperature cycle is carried out for 1000 times, the capacity retention rate of the battery cell can reach over 85 percent; after being stored for 7-14 days at high temperature, the cell interface still keeps good, and the cell interface has good capacity retention rate and capacity recovery rate. The results show that the non-aqueous electrolyte remarkably improves the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery under the high-voltage condition, and is beneficial to improving the energy density of the lithium ion battery.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (9)
1. A lithium ion battery electrolyte for a high voltage system, characterized in that: comprises a non-aqueous organic solvent, an electrolyte lithium salt and an additive;
the additive comprises a trimethyl silane cyclic phosphate compound;
the general formula of the trimethylsilane cyclic phosphate compound is as follows:
wherein R is1Is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide, R2Is at least one of a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, a cyano group or an alkyl halide.
2. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the trimethylsilyl cyclic phosphate compound is at least one of a compound (1-A), a compound (1-B), a compound (1-C), a compound (1-D), a compound (1-E) or a compound (1-F), and the chemical formulas of the compound (1-A), the compound (1-B), the compound (1-C), the compound (1-D), the compound (1-E) and the compound (1-F) are respectively as follows:
3. the lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the carbon atom number of the alkyl halide is 1-10.
4. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the trimethyl silane cyclic phosphate compound accounts for 0.05-2% of the total mass of the lithium ion battery electrolyte; preferably, the trimethyl silane cyclic phosphate compound accounts for 0.5-1% of the total mass of the lithium ion battery electrolyte.
5. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the additive also comprises lithium difluorophosphate, and the percentage of the lithium difluorophosphate in the total mass of the lithium ion battery electrolyte is 0.8%.
6. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the non-aqueous organic solvent is at least one of a carbonate compound or a carboxylic ester compound with 1-4 carbon atoms; the carbonate compound comprises at least one of cyclic carbonate or chain carbonate; the non-aqueous organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl ethyl carbonate, 1, 4-butyrolactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or propyl propionate; preferably, the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate, and the mass ratio of the ethylene carbonate to the ethyl methyl carbonate is 3: 7.
7. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide or lithium bis (fluorooxalato) borate; preferably, the electrolyte lithium salt is lithium hexafluorophosphate; the percentage of the electrolyte lithium salt in the total mass of the lithium ion battery electrolyte is 10-20%; the concentration of the electrolyte lithium salt is 0.8-1.5 mol/L.
8. The lithium ion battery electrolyte for high voltage systems according to claim 1, characterized in that: the lithium ion battery electrolyte also comprises a negative electrode film-forming agent accounting for 0.1-4% of the total mass of the lithium ion battery electrolyte, wherein the negative electrode film-forming agent is at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, 1, 3-propane sultone or ethylene sulfate.
9. A high voltage lithium ion battery, characterized by: a lithium ion battery electrolyte for high voltage systems comprising any of claims 1 to 8.
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