An electrolyte and a battery comprising the same

Abstract

The application provides an electrolyte and a battery comprising the electrolyte, the electrolyte comprising an organic solvent, a lithium salt and a functional additive. The first additive in the functional additive in the electrolyte is a sulfonyl fluoride compound containing an unsaturated bond, wherein the unsaturated double bond can undergo a polymerization reaction on the surface of a positive electrode to form a protective film, which can improve the oxidation resistance of a solid electrolyte film on the positive electrode side; the substitution of fluorine atoms can further improve the oxidation resistance of the solid electrolyte film on the positive electrode side; and the use of the first additive can improve the high-temperature cycle performance, high-temperature storage performance and safety performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrolyte and a battery comprising the same, and belongs to the technical field of lithium ion batteries. BACKGROUND

[0002] A lithium ion battery is a rechargeable battery that mainly relies on the movement of lithium ions between the positive and negative electrodes to work. During charging and discharging, Li + intercalate and deintercalate between two electrodes: when charging, Li + deintercalate from the positive electrode, intercalate into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; when discharging, the opposite is true. Due to the high specific energy, no memory effect, long cycle life, and small self-discharge of lithium ion batteries, they are widely used in digital, energy storage, electric vehicles, and other fields. With the improvement of people's living standards and the pursuit of a better life, the upgrading of battery application scenarios not only requires high energy density of batteries, but also requires different temperature ranges.

[0003] By increasing the limiting voltage of the positive electrode material, the energy density of the battery can be improved, but as the limiting voltage of the positive electrode material continues to increase, the gravimetric capacity of the electrode material gradually increases, and the high-temperature performance of the battery deteriorates seriously, and the long cycle life cannot be guaranteed. Especially at high voltage (> 4.5V), the structure of the positive electrode material will be destroyed during long-term cycle charging and discharging, and the release of active oxygen will further accelerate the oxidative decomposition of the electrolyte, and the protective film on the negative electrode surface will also be continuously damaged, eventually causing the battery capacity to decay seriously.

[0004] At the same time, there are often reports of lithium ion battery electronic equipment fires and explosions in society. While improving energy density and charging speed, ensuring that lithium batteries can also have safety performance is still a challenge we need to overcome. SUMMARY

[0005] In order to solve the problem of volume expansion of the positive electrode material and continuous oxidation of the electrolyte by the release of active oxygen in the existing lithium ion battery at high voltage, the purpose of the present application is to provide an electrolyte and a battery comprising the same, the use of which can improve the safety performance of the battery while ensuring high-temperature cycle performance and high-temperature storage performance.

[0006] The purpose of the present application is achieved by the following technical solution:

[0007] An electrolyte, comprising an organic solvent, a lithium salt, and a functional additive, wherein the functional additive comprises a first additive, and the first additive is a sulfonyl fluoride compound containing an unsaturated bond.

[0008] According to an embodiment of the present application, the unsaturated bond-containing sulfonyl fluoride compound includes an unsaturated double bond and a sulfonyl fluoride group (-SO2-F).

[0009] According to an embodiment of the present application, the unsaturated bond-containing sulfonyl fluoride compound is a fluorine-substituted unsaturated bond-containing sulfonyl fluoride compound including a fluorine-substituted unsaturated double bond (CF2=CF-) and a sulfonyl fluoride group (-SO2-F).

[0010] According to an embodiment of the present application, the first additive is selected from at least one of the compounds represented by Formula I:

[0011]

[0012] In Formula I, R4, R5, R6 are the same or different, and are each independently selected from hydrogen, halogen, substituted or unsubstituted alkyl; and if substituted, the substituent is halogen, alkyl;

[0013] R2, R3 are the same or different, and are each independently selected from O or S;

[0014] R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are the same or different, and are each independently selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; and if substituted, the substituent is halogen, alkyl.

[0015] According to an embodiment of the present application, R4, R5, R6 are the same or different, and are each independently selected from hydrogen, halogen, substituted or unsubstituted C 1-12 alkyl; and if substituted, the substituent is halogen, C 1-12 alkyl.

[0016] According to an embodiment of the present application, R4, R5, R6 are the same or different, and are each independently selected from hydrogen, halogen, substituted or unsubstituted C 1-6 alkyl; and if substituted, the substituent is halogen, C 1-6 alkyl.

[0017] According to an embodiment of the present application, R4, R5, R6 are the same or different, and are each independently selected from hydrogen, fluorine, substituted or unsubstituted C 1-3 alkyl; and if substituted, the substituent is fluorine, C 1-3 alkyl.

[0018] According to embodiments of the present application, R4, R5, R6are the same and selected from fluorine.

[0019] According to embodiments of the present application, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are the same or different and independently of each other selected from hydrogen, halogen, substituted or unsubstituted C 1-12 alkyl, substituted or unsubstituted 3-12 membered cycloalkyl, substituted or unsubstituted C 6-12 aryl; if substituted, the substituents are halogen, C 1-12 alkyl.

[0020] According to embodiments of the present application, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are the same or different and independently of each other selected from hydrogen, halogen, substituted or unsubstituted C 1-6 alkyl, substituted or unsubstituted 3-8 membered cycloalkyl, substituted or unsubstituted C 6-10 aryl; if substituted, the substituents are halogen, C 1-6 alkyl.

[0021] According to embodiments of the present application, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are the same or different and independently of each other selected from hydrogen, halogen, substituted or unsubstituted C 1-3 alkyl, substituted or unsubstituted 3-6 membered cycloalkyl, substituted or unsubstituted C 6-8 aryl; if substituted, the substituents are halogen, C 1-3 alkyl.

[0022] According to embodiments of the present application, the first additive can be prepared by methods known in the art or can be purchased commercially.

[0023] According to embodiments of the present application, the first additive is selected from at least one of the compounds shown in formula (1) to formula (9):

[0024]

[0025]

[0026]

[0027] According to embodiments of the present application, the electrolyte further comprises a second additive selected from at least one of a polynitrile compound.

[0028] According to embodiments of the present application, the polynitrile compound is selected from at least one of a dinitrile compound of Formula II-1, a trinitrile compound of Formula II-2, and a tetranitrile compound of Formula II-3:

[0029]

[0030] wherein R 21 is a group of 1-10 carbon atoms having at least 2 substitution positions; R 22 is a group of 1-10 carbon atoms having at least 3 substitution positions; R 23 is a group of 1-10 carbon atoms having at least 4 substitution positions.

[0031] According to embodiments of the present application, the group of 1-10 carbon atoms is selected from substituted or unsubstituted C1- 10 alkyl, substituted or unsubstituted C 1-10 alkoxy, substituted or unsubstituted C 2-10 alkenyl, substituted or unsubstituted C 1-10 alkyl-O-C 1-10 alkyl, substituted or unsubstituted C 1-10 alkyl-C(O)-C 1-10 alkyl, substituted or unsubstituted C 4-10 heteroaryl, substituted or unsubstituted C 4-10 heterocyclyl, substituted or unsubstituted C 6-10 aryl, substituted with halogen, substituted or unsubstituted C 1-10 alkyl.

[0032] According to embodiments of the present application, the dinitrile compound of Formula II-1 is selected from at least one of succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, nonanedinitrile, dicyanobenzene, terephthalonitrile, pyridine-3,4-dinitrile, 2,5-dicyanopyridine, 2,2,3,3-tetrafluorosuccinonitrile, tetrafluoroterephthalonitrile, 4-tetrahydrothiopyran methylene malononitrile, 3,3'-[l,2-ethanediylbis(oxy)]dimalononitrile, fumaronitrile, ethyleneglycol bispropanenitrile ether, and 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile.

[0033] According to an embodiment of the present application, the trinitrile compound of formula II-2 is selected from at least one of 1,3,6-hexanetricarbonitrile, 1,3,5-cyclohexanetricarbonitrile, 1,3,5-benzene tricyanide, 1,2,3-propanetricarbonitrile, glycerol trinitrile.

[0034] According to an embodiment of the present application, the tetranitrile compound of formula II-3 is selected from at least one of 1,1,3,3-propanetetracarbonitrile, 1,2,2,3-tetracyanopropane, 1,2,4,5-tetracyanobenzene, 2,3,5,6-pyrazinetetracarbonitrile, 7,7,8,8-tetracyano-p-quinodimethane, tetracyanoethylene, 1,1,2,2,-tetrakis(ethoxycarbonyl)ethane, 3-methyl-3-propyl-cyclopropane-1,1,2,2-tetracarbonitrile.

[0035] According to an embodiment of the present application, the electrolyte further comprises a third additive selected from at least one of fluorosulfonic acid imide salt.

[0036] According to an embodiment of the present application, the third additive is selected from at least one of the compounds of formula III:

[0037]

[0038] In formula III, R1 is selected from one of Li, Na, K, Rb, Cs.

[0039] According to an embodiment of the present application, the third additive can be prepared by methods known in the art or can be purchased commercially.

[0040] According to an embodiment of the present application, the third additive is selected from at least one of the compounds of formula III-1 to III-5:

[0041]

[0042] According to embodiments of the present application, the first additive is added in an amount of 0.1 wt% to 5.0 wt% of the total weight of the electrolyte, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, or 5 wt%.

[0043] According to embodiments of the present application, the second additive is added in an amount of 1 wt% to 5.0 wt% of the total weight of the electrolyte, for example, 1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, or 5 wt%.

[0044] According to embodiments of the present application, the third additive is added in an amount of 1 wt% to 5.0 wt% of the total weight of the electrolyte, for example, 1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.3 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, or 5 wt%.

[0045] According to embodiments of the present application, the electrolyte further comprises a fourth additive selected from at least one of fluoroethylene carbonate and 1,3-propane sultone.

[0046] According to embodiments of the present application, the fourth additive is added in an amount of 10 wt% to 15 wt% of the total weight of the electrolyte, for example, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%.

[0047] According to an embodiment of the present application, the lithium salt is selected from one or more than two of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluoro oxalato borate (LiDFOB), lithium bis-trifluoromethylsulfonylimide, lithium difluorobisoxalate phosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methide or lithium bis(trifluoromethylsulfonyl)imide.

[0048] According to an embodiment of the present application, the organic solvent is selected from carbonates and / or carboxylic acid esters, the carbonates being selected from one or several of the following fluorinated or unsubstituted solvents: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate; the carboxylic acid esters being selected from one or several of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, ethyl n-butyrate.

[0049] According to an embodiment of the present application, the electrolyte is used in a lithium ion battery.

[0050] The present application also provides a battery comprising the electrolyte as described above.

[0051] According to an embodiment of the present application, the battery further comprises a positive electrode sheet comprising a positive electrode active material, a negative electrode sheet comprising a negative electrode active material, and a separator.

[0052] According to an embodiment of the present application, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, a conductive agent and a binder.

[0053] According to an embodiment of the present application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, a conductive agent and a binder.

[0054] According to an embodiment of the present application, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt% of positive electrode active material, 0.1-10 wt% of conductive agent, and 0.1-10 wt% of binder.

[0055] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt% of positive electrode active material, 0.2-5 wt% of conductive agent, and 0.2-5 wt% of binder.

[0056] According to an embodiment of the present application, the mass percentage of each component in the negative electrode active material layer is: 80-99.8wt% of negative electrode active material, 0.1-10wt% of conductive agent, and 0.1-10wt% of binder.

[0057] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6wt% of negative electrode active material, 0.2-5wt% of conductive agent, and 0.2-5wt% of binder.

[0058] According to an embodiment of the present application, the negative electrode active material is selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, and silicon-based negative electrode active material.

[0059] According to an embodiment of the present application, the positive electrode active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, and lithium iron manganese phosphate; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1, 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0060] The present application has the following advantages:

[0061] The present application provides an electrolyte and a battery comprising the electrolyte. The electrolyte comprises an organic solvent, a lithium salt, and a functional additive. The first additive in the electrolyte is a sulfonyl fluoride compound containing an unsaturated bond. The unsaturated double bond can undergo a polymerization reaction on the surface of the positive electrode to form a protective film, which can improve the oxidation resistance of the solid-state electrolyte film on the positive electrode side. The F-C-O structure or F-C-S structure in the sulfonyl fluoride compound containing an unsaturated bond can improve the oxidation resistance of the electrolyte. The substitution of fluorine atoms can further improve the oxidation resistance of the solid-state electrolyte film on the positive electrode side. The sulfonyl fluoride compound containing an unsaturated bond can form lithium alkyl sulfonate on the negative electrode side during the formation stage, which increases the ion conductivity of the SEI film. Under extreme working conditions, the temperature of the battery can reach more than 130℃, which is the polymerization temperature of the sulfonyl fluoride compound containing an unsaturated bond. The monomers of the sulfonyl fluoride compound containing an unsaturated bond will undergo a polymerization reaction to form a polymer, and the generated polymer forms a blocking layer on the surface of the electrode, thereby rapidly increasing the internal resistance of the battery, reducing the further reaction of the electrolyte, and significantly reducing and lowering the gas and heat generation of the battery. Therefore, the use of the first additive can improve the high-temperature cycle performance, high-temperature storage performance, and safety performance of the battery.

[0062] The polycarbonitrile compound as the second additive can fully complex transition metal ions in the positive active material, and form a protective layer on the positive side together with the first additive, thereby preventing the transition metal ions in the positive active material from dissolving out, and improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0063] The fluorosulfonic acid imide salt as the third additive can act on the positive electrode to form a protective layer, thereby improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0064] The polycarbonitrile compound as the second additive and the fluorosulfonic acid imide salt as the third additive are introduced on the basis of the first additive, and through the combined action of the first additive, the second additive and the third additive and the coating on the surface of the positive electrode interface, a synergistic effect is formed to jointly prevent the electrolyte from entering the positive active material layer to corrode the positive active material, so that the battery has excellent high-temperature cycle performance and high-temperature storage performance.

[0065] The fourth additive can participate in the formation of the SEI film at the initial formation stage, play a role in protecting the negative electrode, and at the same time, can continuously repair the damaged SEI film at the later stage of the cycle, thereby improving the electrochemical performance of the battery. DETAILED DESCRIPTION

[0066] The application will be described in further detail below with reference to specific examples. It should be understood that the following examples are only illustrative and explanatory of the application, and should not be interpreted as limiting the scope of protection of the application. Any technology implemented based on the above description of the application is included in the scope of protection intended by the application.

[0067] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0068] In the description of the application, it should be noted that the terms "first", "second", "third", "fourth" and the like are only for descriptive purposes, and do not indicate or imply relative importance.

[0069] In order to make the objects, technical solutions and advantages of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0070] It can be understood that the lithium ion battery of the present application comprises a negative electrode sheet, an electrolyte, a positive electrode sheet, a separator and an outer package. The positive electrode sheet, the separator and the negative electrode sheet are stacked to obtain an electrode core or the positive electrode sheet, the separator and the negative electrode sheet are stacked and then wound to obtain an electrode core, the electrode core is placed in the outer package, and the electrolyte is injected into the outer package to obtain the lithium ion battery of the present application.

[0071] Examples 1-18 and Comparative Examples 1-7

[0072] The lithium ion batteries of Examples 1-18 and Comparative Examples 1-7 are prepared by the following steps:

[0073] 1) Preparation of a positive electrode sheet

[0074] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), SP (super P) and carbon nanotubes (CNT) are mixed in a mass ratio of 96:2:1.5:0.5, N-methyl pyrrolidone (NMP) is added, and stirring is performed under the action of a vacuum stirrer until the mixed system becomes a positive active slurry with uniform fluidity; the positive active slurry is uniformly coated on both surfaces of an aluminum foil; the coated aluminum foil is dried, then subjected to rolling and slitting to obtain the required positive electrode sheet.

[0075] 2) Preparation of a negative electrode sheet

[0076] Artificial graphite, sodium carboxymethyl cellulose (CMC-Na), butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) are mixed in a mass ratio of 94.5:2.5:1.5:1:0.5, deionized water is added, and a negative active slurry is obtained under the action of a vacuum stirrer; the negative active slurry is uniformly coated on both surfaces of a copper foil; the coated copper foil is air-dried at room temperature, then transferred to a 80°C oven for drying for 10h, and then subjected to cold pressing and slitting to obtain the negative electrode sheet.

[0077] 3) Preparation of an electrolyte

[0078] In an argon-filled glove box (H2O<0.1ppm, O2<0.1ppm), EC / PC / DEC / PP are mixed in a mass ratio of 10 / 10 / 20 / 60, then 13wt% of fully dried lithium hexafluorophosphate (LiPF6) based on the total mass of the electrolyte is quickly added, after dissolution, 8wt% of fluoroethylene carbonate and 4wt% of 1,3-propane sultone based on the total mass of the electrolyte are added, the first additive, the second additive (adiponitrile) and the third additive (the compound shown in formula III-1) are added according to Table 1 and Table 3, and the electrolyte is prepared after uniform mixing.

[0079] 4) Preparation of a lithium ion battery

[0080] The positive electrode sheet of step 1), the negative electrode sheet of step 2) and the separator film are stacked in the order of positive electrode sheet, separator film and negative electrode sheet, and then wound to obtain a battery cell; the battery cell is placed in an outer packaging aluminum foil, and the electrolyte of step 3) is injected into the outer packaging, and then the lithium ion battery is obtained through processes such as vacuum packaging, standing, formation, shaping, sorting and the like. The battery of the present application has a charge-discharge range of 3.0-4.5V.

[0081] Table 1 Composition of electrolyte additives in lithium ion batteries of examples and comparative examples

[0082] First additive and content Second additive content Third additive content Example 1 Formula (1) / 1 wt% / / Example 2 Formula (2) / 1 wt% / / Example 3 Formula (3) / 1 wt% / / Example 4 Formula (4) / 1 wt% / / Example 5 Formula (5) / 1 wt% / / Example 6 Formula (6) / 1 wt% / / Example 7 Formula (7) / 1 wt% / / Example 8 Formula (8) / 1 wt% / / Example 9 Formula (9) / 1 wt% / / Comparative Example 1 / / / Comparative Example 2 / 3 wt% / Comparative Example 3 / 4 wt% / Comparative Example 4 / 5 wt% / Comparative Example 5 / / 1 wt% Comparative Example 6 / / 2 wt% Comparative Example 7 / / 3 wt%

[0083] The lithium ion batteries obtained in the examples and comparative examples were respectively subjected to the following performance tests:

[0084] 1) 45℃ cycle performance test

[0085] The battery cell after being sized was subjected to charge-discharge cycling at 45℃ under a 1C rate within the charge-discharge cut-off voltage range for 1000 cycles, the discharge capacity of the first week was counted as x1 mAh, and the discharge capacity of the Nth cycle was counted as y1 mAh; the capacity of the Nth week was divided by the capacity of the first week to obtain the cycle capacity retention rate R1 of the Nth week = y1 / x1, and the test results are shown in Tables 2 and 4.

[0086] 2) 85℃ high-temperature storage test

[0087] The sized battery cell was charged to 4.5V at room temperature with a 0.5C current, the fully charged battery was placed in an 85℃ environment for 6 hours, the thickness expansion rate was measured, and after recovery to room temperature, the battery was discharged to 3.0V with a 0.5C current, and the discharge capacity was recorded, and the test results are shown in Tables 2 and 4.

[0088] 3) safety performance test

[0089] The battery cell was charged to the upper limit cut-off voltage at 0.5C, and then constant voltage was applied to 0.05C; at an ambient temperature of 25℃±5℃, the fully charged sample was placed in a thermal shock test chamber, then the temperature was raised to 140℃±2℃ at a rate of 15℃±2℃ / min, and after maintaining this temperature for 42min, the test was ended, and whether the battery caught fire was observed, and the test results are shown in Tables 2 and 4.

[0090] Table 2 Performance test results of lithium ion batteries of examples and comparative examples

[0091]

[0092] From the test results of examples 1-9 and comparative example 1 in table 2, it can be seen that the first additive can obviously improve the high-temperature cycle performance, high-temperature storage performance and safety performance of the battery, and the improvement effect of the first additive containing F substitution is more significant, but it is also related to the number of substituents, and too many substituents may also have certain deterioration. Moreover, the second additive and the third additive can both improve the high-temperature cycle performance and high-temperature storage performance of the battery, wherein the optimal amount of the second additive is 4wt%, and the optimal amount of the third additive is 2wt%; wherein the safety performance is significantly improved when the amount of the third additive is ≥2wt%.

[0093] Table 3 composition of electrolyte additives in lithium ion batteries of examples and comparative examples

[0094] First additive and content Second additive content Third additive content Example 10 Formula (7) / 0.5 wt% 4 wt% / Example 11 Formula (7) / 0.5 wt% / 2 wt% Example 12 Formula (7) / 1 wt% 4 wt% / Example 13 Formula (7) / 1 wt% / 2 wt% Example 14 Formula (7) / 3 wt% 4 wt% / Example 15 Formula (7) / 3 wt% / 2 wt% Example 16 Formula (7) / 0.5 wt% 4 wt% 2 wt% Example 17 Formula (7) / 1 wt% 4 wt% 2 wt% Example 18 Formula (7) / 3 wt% 4 wt% 2 wt%

[0095] Table 4 performance test results of lithium ion batteries of examples and comparative examples

[0096]

[0097] From the test results of examples 10-18 in table 4, it can be seen that when the first additive, the second additive and the third additive act together, the high-temperature cycle performance, the high-temperature storage performance and the safety performance of the battery can be significantly improved, which indicates that there is a synergistic effect between the first additive, the second additive and the third additive.

[0098] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An electrolyte, characterized by, The electrolyte comprises an organic solvent, a lithium salt, and a functional additive, wherein the functional additive comprises a first additive, the first additive being a sulfonyl fluoride compound containing an unsaturated bond; the first additive is selected from at least one of the compounds shown in formula I: In formula I, R4, R5, R6 are the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen, alkyl; R2, R3 are the same or different, and are independently selected from O or S; R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are identical or different and independently from each other selected from the group consisting of hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl; if substituted, the substituents are halogen, alkyl; The electrolyte further comprises a fourth additive, the fourth additive being selected from at least one of fluoroethylene carbonate and 1,3-propane sultone.

2. The electrolyte of claim 1, wherein, R4, R5, R6are the same or different, independently of one another, selected from the group consisting of hydrogen, halogen, substituted or unsubstituted C 1-12 alkyl; if substituted, the substituent is halogen, C 1-12 alkyl.

3. The electrolyte of claim 2, wherein, R4, R5, R6are the same or different, independently of one another, selected from the group consisting of hydrogen, halogen, substituted or unsubstituted C 1-6 alkyl; if substituted, the substituent is halogen, C 1-6 alkyl.

4. The electrolyte of claim 3, wherein, R4, R5, R6are the same or different and independently of each other selected from the group consisting of hydrogen, fluorine, substituted or unsubstituted C 1-3 alkyl; if substituted, the substituent is fluorine, C 1-3 alkyl.

5. The electrolyte of claim 4, wherein, R4, R5, R6 are the same, and are selected from fluorine.

6. The electrolyte of claim 1, wherein, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are the same or different, independently of each other, selected from hydrogen, halogen, substituted or unsubstituted C 1-12 alkyl, substituted or unsubstituted 3-12 membered cycloalkyl, substituted or unsubstituted C 6-12 aryl; if substituted, the substituents are halogen, C 1-12 alkyl.

7. The electrolyte of claim 6, wherein, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are identical or different and independently of each other selected from hydrogen, halogen, substituted or unsubstituted C 1-6 alkyl, substituted or unsubstituted 3-8 membered cycloalkyl, substituted or unsubstituted C 6-10 aryl; if substituted, the substituents are halogen, C 1-6 alkyl.

8. The electrolyte of claim 7, wherein, R 2a , R 2b , R 2c , R 2d , R 3a , R 3b , R 3c , R 3d are identical or different and independently of each other selected from hydrogen, halogen, substituted or unsubstituted C 1-3 alkyl, substituted or unsubstituted 3-6 membered cycloalkyl, substituted or unsubstituted C 6-8 aryl; if substituted, the substituents are halogen, C 1-3 alkyl.

9. The electrolyte of claim 1, wherein, The first additive is selected from at least one of the compounds shown in formula (1) to formula (9):

10. The electrolyte according to any one of claims 1 to 9, characterized in that, The electrolyte further comprises a second additive, the second additive being selected from at least one of polynitrile compounds.

11. The electrolyte of claim 10, wherein, The polynitrile compound is selected from at least one of the following: a di-nitrile compound shown in formula II-1, a tri-nitrile compound shown in formula II-2, and a tetra-nitrile compound shown in formula II-3: NC-R 21 - CN Formula II-1 wherein R 21 is a group having 1 to 10 carbon atoms having at least 2 substitution sites; R 22 is a group having 1 to 10 carbon atoms having at least 3 substitution sites; R 23 is a group having 1 to 10 carbon atoms having at least 4 substitution sites.

12. The electrolyte according to any one of claims 1 to 9, characterized in that, The electrolyte further comprises a third additive, the third additive being selected from at least one of fluorosulfonic acid imidazolide salts.

13. The electrolyte of claim 10, wherein, The electrolyte further comprises a third additive, the third additive being selected from at least one of fluorosulfonic acid imidazolide salts.

14. The electrolyte of claim 12, wherein, The third additive is selected from at least one of the compounds shown in formula III: In formula III, R1 is selected from one of Li, Na, K, Rb, and Cs.

15. The electrolyte according to any one of claims 1 to 9, characterized in that, The first additive is added in an amount of 0.1wt% to 5.0wt% of the total weight of the electrolyte.

16. The electrolyte of claim 10, wherein, The second additive is added in an amount of 1wt% to 5.0wt% of the total weight of the electrolyte.

17. The electrolyte of claim 12, wherein, The third additive is added in an amount of 1wt% to 5.0wt% of the total weight of the electrolyte.

18. The electrolyte according to any one of claims 1 to 9, characterized in that, The fourth additive is added in an amount of 10wt% to 15wt% of the total weight of the electrolyte.

19. A battery, characterized by The battery comprises the electrolyte according to any one of claims 1 to 18.

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