CN115441057A - An electrolyte and a battery comprising the electrolyte - Google Patents

Abstract

The invention provides an electrolyte and a battery comprising the same. The first additive in the functional additives in the electrolyte is a sulfonyl fluoride compound containing unsaturated bonds, wherein the unsaturated bonds can generate polymerization reaction on the surface of the positive electrode to form a protective film, so that the oxidation resistance of the solid electrolyte film on the positive electrode side can be improved; substitution of fluorine atoms can also further improve the oxidation resistance of the positive electrode-side solid electrolyte membrane; the use of the first additive can improve the high-temperature cycle performance, the high-temperature storage performance, and the safety performance of the battery.

Description

An electrolyte and a battery comprising the electrolyte

technical field

The invention relates to an electrolytic solution and a battery comprising the electrolytic solution, belonging to the technical field of lithium ion batteries.

Background technique

A lithium-ion battery is a rechargeable battery that primarily relies on the movement of lithium ions between the positive and negative electrodes to function. During the charge and discharge process, Li ⁺ intercalates and deintercalates back and forth between the two electrodes: during charging, Li ⁺ deintercalates from the positive electrode, intercalates into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. Due to the advantages of high specific energy, no memory effect, long cycle life, and small self-discharge, lithium-ion batteries are widely used in digital, energy storage, electric vehicles and other fields. With the improvement of people's living standards and yearning for a better life, the upgrade of battery application scenarios not only puts forward requirements for battery energy density, but also puts forward requirements for different operating temperature ranges.

The energy density of the battery can be increased by increasing the limiting voltage of the positive electrode material, but with the continuous increase of the limiting voltage of the positive electrode material, the gram capacity of the electrode material gradually increases, the high temperature performance of the battery is seriously deteriorated, and the long cycle life cannot be guaranteed, especially at high temperature. Under the voltage (>4.5V), the structure of the positive electrode material will be destroyed during the long-term cycle charge and discharge process, and the release of active oxygen will further accelerate the oxidative decomposition of the electrolyte, and the protective film on the surface of the negative electrode will also be continuously damaged, eventually resulting in battery capacity. severe attenuation.

At the same time, news about the fire and explosion of lithium-ion battery electronic equipment is often reported in the society. While improving energy density and charging speed, it is still necessary for us to continue to overcome the safety performance of lithium-ion batteries.

Contents of the invention

In order to solve the problem of volume expansion of the positive electrode material in the existing high voltage lithium ion battery and the release of active oxygen to continuously oxidize the electrolyte, the purpose of the present invention is to provide an electrolyte and a battery comprising the electrolyte. The use of the electrolyte It can make the battery take into account the high-temperature cycle performance and high-temperature storage performance, and at the same time improve the safety performance of the battery.

The object of the invention is achieved through the following technical solutions:

An electrolytic solution, the electrolytic solution includes an organic solvent, a lithium salt and a functional additive, wherein the functional additive includes a first additive, and the first additive is a sulfonyl fluoride compound containing an unsaturated bond.

According to an embodiment of the present invention, the sulfonyl fluoride compound containing an unsaturated bond includes an unsaturated double bond and a sulfonyl fluoride group (-SO ₂ -F).

According to an embodiment of the present invention, the sulfonyl fluoride compound containing an unsaturated bond is a sulfonyl fluoride compound containing an unsaturated bond substituted by fluorine, and the sulfonyl fluoride compound containing an unsaturated bond substituted by fluorine includes Fluorine-substituted unsaturated double bond (CF ₂ =CF-) and sulfonyl fluoride (-SO ₂ -F).

According to an embodiment of the present invention, the first additive is selected from at least one of the compounds shown in formula I:

In formula I, R ₄ , R ₅ , and R ₆ are the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl;

R ₂ and R ₃ 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 the same or different, independently selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted ring Alkyl, substituted or unsubstituted aryl; if substituted, the substituent is halogen or alkyl.

According to an embodiment of the present invention, R ₄ , R ₅ , and R ₆ are the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C _1-12 alkyl; if substituted, the substituent is halogen, C _1-12 alkyl.

According to an embodiment of the present invention, R ₄ , R ₅ , and R ₆ are the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted C _1-6 alkyl; if substituted, the substituent is halogen, C _1-6 alkyl.

According to an embodiment of the present invention, R ₄ , R ₅ , and R ₆ are the same or different, and are independently selected from hydrogen, fluorine, substituted or unsubstituted C _1-3 alkyl; if substituted, the substituent is fluorine, C _1-3 alkyl.

According to an embodiment of the present invention, R ₄ , R ₅ , and R ₆ are the same and selected from fluorine.

According to an embodiment of the present invention, R _2a , R _2b , R _2c , R _2d , R _3a , R _3b , R _3c , and R _3d are the same or different, and are independently 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 substituent is halogen, C _1-12 alkyl.

According to an embodiment of the present invention, R _2a , R _2b , R _2c , R _2d , R _3a , R _3b , R _3c , and R _3d are the same or different, and are independently 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 substituent is halogen, C _1-6 alkyl.

According to an embodiment of the present invention, R _2a , R _2b , R _2c , R _2d , R _3a , R _3b , R _3c , and R _3d are the same or different, and are independently 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 substituent is halogen, C _1-3 alkyl.

According to an embodiment of the present invention, the first additive can be prepared by methods known in the art, or can be purchased through commercial channels.

According to an embodiment of the present invention, the first additive is selected from at least one of the compounds represented by formula (1)-formula (9):

According to an embodiment of the present invention, the electrolyte solution further includes a second additive, and the second additive is at least one selected from polynitrile compounds.

According to an embodiment of the present invention, the polynitrile compound is selected from dinitrile compounds shown in formula II-1, trinitrile compounds shown in formula II-2 and tetranitrile compounds shown in formula II-3 At least one of:

Wherein, R ₂₁ is a group with at least 2 substitution positions and a carbon number of 1-10; R ₂₂ is a group with at least 3 substitution positions and a carbon number of 1-10; R ₂₃ is a group with at least 4 A group with 1-10 carbon atoms at each substitution position.

According to an embodiment of the present invention, the group with _{1-10 carbon atoms is selected from substituted or unsubstituted C 1-10 alkyl, substituted or unsubstituted C 1-10 alkoxy ,} substituted or unsubstituted C _2-10 alkenyl, substituted or unsubstituted C _1-10 alkyl-OC _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, the substituent is halogen, substituted or unsubstituted C _1-10 alkyl.

According to an embodiment of the present invention, the dinitrile compound represented by the formula II-1 is at least one selected from the following compounds: succinonitrile, glutaronitrile, adiponitrile, sebaconitrile, azelanitrile, Dicyanobenzene, terephthalonitrile, pyridine-3,4-dinitrile, 2,5-dicyanopyridine, 2,2,3,3-tetrafluorosuccinonitrile, tetrafluoroterephthalonitrile, 4 -Tetrahydrothiopyranylidene malononitrile, 3,3'-[1,2-ethanediylbis(oxyl)]bispropionitrile, fumaronitrile, ethylene glycol bispropionitrile ether and 1 , 4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile.

According to an embodiment of the present invention, the trinitrile compound represented by the formula II-2 is at least one selected from the following compounds: 1,3,6-hexanetrinitrile, 1,3,5-cyclohexane Trinitrile, 1,3,5-benzenetricyano, 1,2,3-propanetricarbonitrile, glycerol trinitrile.

According to an embodiment of the present invention, the tetranitrile compound represented by the formula II-3 is at least one selected from the following compounds: 1,1,3,3-propanetetracarbonitrile, 1,2,2,3 -Tetracyanopropane, 1,2,4,5-tetracyanobenzene, 2,3,5,6-pyrazinetetranitrile, 7,7,8,8-tetracyanobenzoquinodimethane, Tetracyanoethylene, 1,1,2,2,-tetra(ethoxycyano)ethane, 3-methyl-3-propyl-cyclopropane-1,1,2,2-tetracarbonitrile.

According to an embodiment of the present invention, the electrolyte solution further includes a third additive, and the third additive is at least one selected from fluorosulfonate imide salts.

According to an embodiment of the present invention, the third additive is selected from at least one of the compounds represented by formula III:

In formula III, R ₁ is selected from one of Li, Na, K, Rb, and Cs.

According to the embodiment of the present invention, the third additive can be prepared by methods known in the art, or can be purchased through commercial channels.

According to an embodiment of the present invention, the third additive is selected from at least one of the compounds represented by formula III-1 to formula III-5:

According to an embodiment of the present invention, the addition amount of the first additive is 0.1wt% to 5.0wt% of the total weight of the electrolyte solution, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt%, 3.8wt%, 4wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, or 5 wt%.

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

According to an embodiment of the present invention, the addition amount of the third additive is 1wt% to 5.0wt% of the total weight of the electrolyte, such as 1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt% , 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt% , 3.8wt%, 4wt%, 4.2wt%, 4.5wt%, 4.8wt% or 5wt%.

According to an embodiment of the present invention, the electrolyte solution further includes a fourth additive, and the fourth additive is selected from at least one of fluoroethylene carbonate and 1,3-propane sultone.

According to an embodiment of the present invention, the added amount of the fourth additive is 10wt%-15wt% of the total weight of the electrolyte, such as 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%.

According to an embodiment of the present invention, the lithium salt is selected from lithium hexafluorophosphate (LiPF ₆ ), lithium difluorophosphate (LiPO ₂ F ₂ ), lithium difluorooxalate borate (LiDFOB), lithium bistrifluoromethanesulfonimide, Lithium difluorobisoxalate phosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, bis(pentafluoroethylsulfonyl) ) lithium imide, lithium tris(trifluoromethylsulfonyl)methyl or lithium bis(trifluoromethylsulfonyl)imide, or two or more.

According to an embodiment of the present invention, the organic solvent is selected from carbonates and/or carboxylates, and the carbonates are selected from one or more of fluorinated or unsubstituted following solvents: ethylene carbonate (EC ), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate; the carboxylate is selected from one or more of fluorinated or unsubstituted following solvents : Propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, ethyl n-butyrate ester.

According to an embodiment of the present invention, the electrolyte is used in a lithium ion battery.

The present invention also provides a battery, which includes the above-mentioned electrolyte solution.

According to an embodiment of the present invention, the battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator.

According to an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder. agent.

According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both sides of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent and a binding agent. agent.

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

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

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

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

According to an embodiment of the present invention, the negative electrode active material is at least one selected from artificial graphite, natural graphite, mesocarbon microspheres, hard carbon, soft carbon, and silicon-based negative electrode active materials.

According to an embodiment of the present invention, the positive electrode active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganate, and lithium manganese iron phosphate; the chemical formula of the transition metal lithium oxide is Li _1+x Ni _y Co _z M _(1-yz) O ₂ , where, -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where, M One or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, Zr.

Beneficial effects of the present invention:

The invention provides an electrolytic solution and a battery comprising the electrolytic solution. The electrolytic solution includes an organic solvent, lithium salt and functional additives. The first additive in the electrolyte is a sulfonyl fluoride compound containing an unsaturated bond, wherein the unsaturated double bond can undergo polymerization reaction on the surface of the positive electrode to form a protective film, which can improve the oxidation resistance of the solid electrolyte membrane on the positive electrode side; The F-C-O structure or F-C-S-structure in the sulfonyl fluoride compounds containing unsaturated bonds can improve the oxidation resistance of the electrolyte, and the substitution of fluorine atoms can also further improve the oxidation resistance of the positive side solid electrolyte membrane; the said Sulfonyl fluoride compounds containing unsaturated bonds can form lithium alkyl sulfonate on the negative electrode side during the formation stage, which increases the ionic conductivity of the SEI membrane; under extreme conditions, the temperature of the battery can reach above 130°C, that is, the above-mentioned The polymerization reaction temperature of the sulfonyl fluoride compound containing unsaturated bonds, the sulfonyl fluoride compound monomer containing unsaturated bonds will undergo polymerization reaction to form a polymer, and the generated polymer will form a blocking layer on the surface of the electrode, so that The internal resistance of the battery increases rapidly, reducing the further reaction of the electrolyte, and significantly reducing and reducing the gas production and heat 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.

On the basis of the first additive, a polynitrile compound is introduced as the second additive. The cyano group in it can fully complex the transition metal ions in the positive electrode active material, and form a protective layer on the positive electrode side together with the first additive to prevent the positive electrode from The dissolution of transition metal ions in the active material improves the high-temperature cycle performance and high-temperature storage performance of the battery.

On the basis of the first additive, fluorosulfonate imide salt is introduced as the third additive, which can act on the positive electrode to form a protective layer and improve the high-temperature cycle performance and high-temperature storage performance of the battery.

On the basis of the first additive, the polynitrile compound as the second additive and the fluorosulfonate imide salt as the third additive are introduced, and the first additive, the second additive and the third additive act together and coat the positive electrode The interface surface forms a synergistic effect to jointly prevent the electrolyte from entering the positive electrode active material layer and corroding the positive electrode active material, so that the battery has excellent high-temperature cycle performance and high-temperature storage performance.

The fourth additive can participate in the formation of the SEI film at the initial stage of formation to protect the negative electrode, and at the same time it can continuously repair the damaged SEI film at the later stage of the cycle, thereby improving the electrochemical performance of the battery.

detailed description

The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following examples are only for illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies realized based on the above contents of the present invention are covered within the scope of protection intended by the present invention.

The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents and materials used in the following examples can be obtained from commercial sources unless otherwise specified.

In the description of the present invention, it should be noted that the terms "first", "second", "third", "fourth" and so on are only used for descriptive purposes, and do not indicate or imply relative importance.

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the implementation of the present invention. example, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

It can be understood that the lithium ion battery of the present invention includes a negative electrode sheet, an electrolyte solution, a positive electrode sheet, a separator and an outer package. Stack the positive electrode sheet, separator and negative electrode sheet to obtain the battery cell or stack the positive electrode sheet, separator film and negative electrode sheet, and then wind them to obtain the battery cell. The lithium ion battery of the present invention can be obtained by injecting the electrolyte.

Embodiment 1～18 and comparative example 1～7

The lithium-ion batteries of Examples 1-18 and Comparative Examples 1-7 were prepared through the following steps:

1) Preparation of positive electrode sheet

Mix positive electrode active materials lithium cobaltate (LiCoO ₂ ), polyvinylidene fluoride (PVDF), SP (super P) and carbon nanotubes (CNT) in a mass ratio of 96:2:1.5:0.5, and add N-formazan base pyrrolidone (NMP), stirring under the action of a vacuum mixer until the mixed system becomes a positive active slurry with uniform fluidity; the positive active slurry is evenly coated on both surfaces of the aluminum foil; the coated aluminum foil is dried, Then roll pressing and slitting to obtain the desired positive electrode sheet.

2) Negative sheet preparation

Negative electrode active materials artificial graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to the mass ratio of 94.5:2.5:1.5:1:0.5 Mix, add deionized water, and obtain the negative electrode active slurry under the action of a vacuum mixer; evenly coat the negative electrode active slurry on both surfaces of the copper foil; dry the coated copper foil at room temperature, and then transfer Dry in an oven at 80° C. for 10 hours, and then cold press and cut to obtain negative electrode sheets.

3) Preparation of electrolyte

In a glove box filled with argon (H ₂ O<0.1ppm, O ₂ <0.1ppm), mix EC/PC/DEC/PP according to the mass ratio of 10/10/20/60, and then quickly add Based on the fully dry lithium hexafluorophosphate (LiPF ₆ ) of 13wt% of the total mass of the electrolyte, after dissolving, add 8wt% of fluoroethylene carbonate and 4wt% of 1,3-propane sultone based on the total mass of the electrolyte, according to the table The additives shown in Table 1 and Table 3 were added to the first additive, the second additive (adiponitrile) and the third additive (the compound shown in formula III-1), and mixed uniformly to prepare the electrolyte solution.

4) Preparation of lithium ion battery

After the positive electrode sheet in step 1), the negative electrode sheet and the separator in step 2) are stacked in the order of the positive electrode sheet, separator and negative electrode sheet, and then wound to obtain the battery cell; the battery cell is placed in the outer packaging aluminum foil, The electrolyte solution in step 3) is injected into the outer packaging, and the lithium-ion battery is obtained through processes such as vacuum packaging, standing, forming, shaping, and sorting. The charging and discharging range of the battery of the present invention is 3.0-4.5V.

The composition of electrolyte additive in the lithium-ion battery of table 1 embodiment and comparative example

The first additive and content Second additive content Content of the third additive Example 1 Formula (1)/1wt% / / Example 2 Formula (2)/1wt% / / Example 3 Formula (3)/1wt% / / Example 4 Formula (4)/1wt% / / Example 5 Formula (5)/1wt% / / Example 6 Formula (6)/1wt% / / Example 7 Formula (7)/1wt% / / Example 8 Formula (8)/1wt% / / Example 9 Formula (9)/1wt% / / Comparative example 1 / / / Comparative example 2 / 3wt% / Comparative example 3 / 4wt% / Comparative example 4 / 5wt% / Comparative example 5 / / 1wt% Comparative example 6 / / 2wt% Comparative example 7 / / 3wt%

The lithium-ion battery that embodiment and comparative example obtain carry out following performance test respectively:

1) 45°C cycle performance test

Carry out the charge-discharge cycle for 1000 cycles at 45°C with a rate of 1C within the range of charge-discharge cut-off voltage. The discharge capacity of the first cycle of the test is counted as x1mAh, and the discharge capacity of the Nth cycle is counted as y1mAh; The capacity in the Nth week was divided by the capacity in the first week to obtain the cycle capacity retention rate R1=y1/x1 in the Nth week. The test results are shown in Table 2 and Table 4.

2) 85°C high temperature storage test

Charge the battery cell after capacity division to 4.5V with a current of 0.5C at room temperature, place the fully charged battery at 85°C for 6 hours, measure the thickness expansion rate by heat, and discharge it to 3.0V with a current of 0.5C after returning to room temperature. V, record the discharge capacity, the test results are shown in Table 2 and Table 4.

3) Safety performance test

Charge the cell at 0.5C to the upper limit cut-off voltage, and constant voltage to 0.05C; at an ambient temperature of 25°C±5°C, put the fully charged sample in a thermal shock test box, and then charge it at a rate of 15°C±2°C/min Raise the rate to 140°C±2°C, and keep this temperature for 42 minutes. After the test ends, observe whether the battery catches fire. The test results are shown in Table 2 and Table 4.

The performance test result of the lithium-ion battery of table 2 embodiment and comparative example

From the test results of Examples 1-9 and Comparative Example 1 in Table 2, it can be seen that the first additive can significantly improve the high-temperature cycle performance, high-temperature storage performance and safety performance of the battery, and contains the first additive substituted by F The improvement effect is more significant, but it is also related to the number of substituents, too many substituents may also have a certain degree of degradation. Moreover, both the second additive and the third additive can improve the high-temperature cycle performance and high-temperature storage performance of the battery, wherein the optimum amount of the second additive is 4wt%, and the optimum amount of the third additive is 2wt%; wherein the optimum amount of the second additive is 2wt%. When the dosage of the three additives is more than or equal to 2wt%, the safety performance is improved significantly.

The composition of electrolyte additive in the lithium-ion battery of table 3 embodiment and comparative example

The first additive and content Second additive content Content of the third additive Example 10 Formula (7)/0.5wt% 4wt% / Example 11 Formula (7)/0.5wt% / 2wt% Example 12 Formula (7)/1wt% 4wt% / Example 13 Formula (7)/1wt% / 2wt% Example 14 Formula (7)/3wt% 4wt% / Example 15 Formula (7)/3wt% / 2wt% Example 16 Formula (7)/0.5wt% 4wt% 2wt% Example 17 Formula (7)/1wt% 4wt% 2wt% Example 18 Formula (7)/3wt% 4wt% 2wt%

The performance test result of the lithium-ion battery of table 4 embodiment and comparative example

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, high-temperature storage performance and safety performance of the battery can be significantly improved. It shows that there is a synergistic effect among the first additive, the second additive and the third additive.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-mentioned embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. an electrolytic solution, it is characterized in that, described electrolytic solution comprises organic solvent, lithium salt and functional additive, wherein, described functional additive comprises the first additive, and described first additive is the sulfonyl fluoride containing unsaturated bond class of compounds. 2. The electrolytic solution according to claim 1, wherein the sulfonyl fluoride compound containing unsaturated bonds is a sulfonyl fluoride compound containing fluorine-substituted unsaturated bonds, and the sulfonyl fluoride compound containing fluorine-substituted Sulfonyl fluoride compounds with saturated bonds include fluorine-substituted unsaturated double bonds (CF ₂ =CF-) and sulfonyl fluoride groups (-SO ₂ -F). 3. The electrolytic solution according to claim 1 or 2, wherein the first additive is selected from at least one of the compounds shown in formula I:

In formula I, R ₄ , R ₅ , and R ₆ are the same or different, and are independently selected from hydrogen, halogen, substituted or unsubstituted alkyl; if substituted, the substituent is halogen or alkyl; R ₂ and R ₃ 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 the same or different, independently selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted ring Alkyl, substituted or unsubstituted aryl; if substituted, the substituent is halogen or alkyl. 4. The electrolytic solution according to claim 1, characterized in that, the electrolytic solution further comprises a second additive, and the second additive is selected from at least one of polynitrile compounds. 5. electrolytic solution according to claim 4, is characterized in that, described polynitrile compound is selected from the dinitrile compound shown in formula II-1, the trinitrile compound shown in formula II-2 and formula II- At least one of the four nitrile compounds shown in 3:

Wherein, R ₂₁ is a group with at least 2 substitution positions and a carbon number of 1-10; R ₂₂ is a group with at least 3 substitution positions and a carbon number of 1-10; R ₂₃ is a group with at least 4 A group with 1-10 carbon atoms at each substitution position. 6. The electrolytic solution according to claim 1, characterized in that, the electrolytic solution further comprises a third additive, and the third additive is selected from at least one of fluorosulfonic acid imide salts. 7. The electrolytic solution according to claim 1 or 2, characterized in that, the added amount of the first additive is 0.1wt%-5.0wt% of the total weight of the electrolytic solution. 8. The electrolytic solution according to claim 4 or 5, characterized in that, the added amount of the second additive is 1wt%-5.0wt% of the total weight of the electrolytic solution. 9. The electrolytic solution according to claim 6, characterized in that, the added amount of the third additive is 1wt%-5.0wt% of the total weight of the electrolytic solution. 10. A battery, characterized in that the battery comprises the electrolyte solution according to any one of claims 1-9.