Electrolyte and application thereof

Abstract

The invention provides an electrolyte and application thereof. The electrolyte comprises fluoroethylene carbonate and a borate compound. When the electrolyte is used in the battery, the formation of a high-quality SEI film on the surface of a negative electrode is facilitated, and the side reaction of the silicon-based battery is effectively inhibited, so that the impedance of the battery is reduced, and the high-temperature cycle and high-temperature storage performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to an electrolyte and its application, belonging to the field of energy technology. Background Art

[0002] With the progress of technology and the diversification of energy demands, traditional energy is being consumed at an accelerating pace, and countries are accelerating their strategic deployments of new energy technologies. Among them, power batteries are emerging with the development of new energy vehicles, and energy storage batteries are also booming with the development of clean energy. Since 2017, the competition in the new energy vehicle industry has become increasingly fierce. Each power battery enterprise has been continuously researching and developing updated products to find a chemical power system that can better adapt to the market, so as to meet users' requirements for high specific energy and endurance, and to be able to comprehensively replace traditional energy-powered passenger cars and buses.

[0003] Lithium-ion batteries are one of the important products in new energy technology. Traditional lithium-ion batteries use graphite to prepare the negative electrode sheet, and the specific capacity of graphite is 372 mAh g -1 -1, which is already difficult to meet the requirements of higher specific energy for lithium-ion batteries. Therefore, researchers at home and abroad have gradually turned their attention to silicon negative electrode materials with high specific capacity. However, although silicon negative electrode materials can improve the energy density of the battery to a certain extent, during the cycling process of the battery, silicon negative electrode materials are prone to large volume expansion, which will cause the interfacial film between the negative electrode sheet and the electrolyte to be continuously damaged, resulting in continuous decomposition of the electrolyte and ultimately deteriorating the battery performance.

[0004] In order to solve the problem of battery performance deterioration caused by the damage of the interfacial film between the negative electrode sheet and the electrolyte during the cycling process of a battery containing silicon negative electrode materials, researchers have proposed that a stable interfacial film can be constructed on the surface of the negative electrode sheet by developing new electrolyte additives to reduce the negative effects brought about by the expansion of silicon negative electrode materials. For example, using fluoroethylene carbonate (FEC) as an electrolyte additive and adding it to the electrolyte to form a stable interfacial film on the surface of the negative electrode sheet, thereby effectively reducing the capacity loss caused by silicon negative electrode materials and reducing the interfacial impedance between the negative electrode sheet and the electrolyte. However, FEC will generate gas at high temperatures, which may cause battery failure or even explosion. Summary of the Invention

[0005] The present invention provides an electrolyte. When this electrolyte is used in a battery, it helps to form a high-quality SEI film on the negative electrode surface and effectively suppress the side reactions of silicon-based batteries, thereby reducing the battery impedance and improving the high-temperature cycling and high-temperature storage performance of the battery.

[0006] The present invention also provides a battery containing the above electrolyte, so this battery has relatively excellent electrochemical performance.

[0007] The present invention provides an electrolyte, which includes fluorinated ethylene carbonate and borate compounds.

[0008] The electrolyte as described above, wherein the structural formula of the borate compound is shown as any one of Formula 1 - Formula 4;

[0009]

[0010] In Formula 1 - Formula 4, R 1 , R 2 , R 3 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are each independently selected from substituted or unsubstituted C1 - C30 alkyl groups, substituted or unsubstituted C2 - C30 alkenyl groups, and substituted or unsubstituted C1 - C30 silyl groups;

[0011] In Formula 2, R 4 , R 5 are each independently selected from substituted or unsubstituted C1 - C30 alkyl groups, substituted or unsubstituted C2 - C30 alkenyl groups, and substituted or unsubstituted C1 - C30 silyl groups, and / or, R 4 , R 5 are connected to form a ring.

[0012] The electrolyte as described above, wherein the substituents of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are selected from at least one of substituted or unsubstituted C1 - C30 alkyl groups, substituted or unsubstituted C2 - C30 alkenyl groups, carbonyl groups, and halogens.

[0013] The electrolyte as described above, wherein the borate compound is selected from the compounds shown by the following structures;

[0014]

[0015]

[0016] The electrolyte as described above, wherein, based on the total mass of the electrolyte, the mass percentage content of the borate compound is 0.1%-2%.

[0017] The electrolyte as described above, wherein, based on the total mass of the electrolyte, the mass percentage content of fluoroethylene carbonate is 1%-15%.

[0018] The electrolyte as described above, wherein, based on the total mass of the electrolyte, the mass percentage content of the borate compound is 0.1%-1%, and the mass percentage content of fluoroethylene carbonate is 5%-10%.

[0019] The electrolyte as described above, wherein the electrolyte further comprises a solvent, and based on the total mass of the electrolyte, the mass percentage content of the solvent is 10%-80%; and / or,

[0020] The electrolyte further comprises other additives, and based on the total mass of the electrolyte, the mass percentage content of the other additives is 0.5%-5%;

[0021] Wherein, the other additives are selected from at least one of vinylene carbonate, ethylene vinylene carbonate, ethylene sulfite, 1,3-propane sultone, 1,3-propene sulfonic acid lactone, ethylene sulfite, and tris(trimethylsilyl) borate.

[0022] The electrolyte as described above, wherein the electrolyte further comprises a lithium salt, and based on the total mass of the electrolyte, the mass percentage content of the lithium salt is 12%-18%.

[0023] The present invention provides a battery, which includes the electrolyte as described above.

[0024] The electrolyte composition of the present invention is simple. When this electrolyte is used in a battery, such as a secondary battery, it helps to form a denser and more stable SEI film on the negative electrode surface of the secondary battery to protect the electrode, and thus is beneficial to the improvement of the performance of the secondary battery;

[0025] For the battery of the present invention, since it includes the aforementioned electrolyte, a dense and stable SEI film is formed on the negative electrode surface to further avoid the contact damage between the electrode and the electrolyte. Therefore, the electrochemical device of the present invention has more excellent electrochemical performance, such as high-temperature cycling and high-temperature storage performance. Detailed embodiments

[0026] To make the objectives, 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 some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0027] The first aspect of the present invention provides an electrolyte, comprising fluoroethylene carbonate (FEC) and a borate compound.

[0028] When the electrolyte comprising fluoroethylene carbonate and a borate compound in the present invention is applied to a battery, it can significantly improve the electrochemical performance of the battery. The inventor analyzed this phenomenon and believes that the reason may be as follows: The boron atom in the borate compound is an electron-deficient atom, which can effectively complex the free fluoride ions generated by the decomposition of FEC in the electrolyte system, thereby cutting off the path of side reactions of FEC, and further effectively suppressing the generation of gas; at the same time, the borate in the borate compound can react with trace lithium salts in the electrolyte to generate components with low impedance to participate in the construction of the electrode / electrolyte interface film, reducing the diffusion energy barrier of lithium ions. Lithium ions can quickly complete insertion / extraction, reducing the generation of lithium dendrites and improving the cycle life of the lithium-ion battery. Moreover, the interface film with low impedance is conducive to the rapid insertion and extraction of lithium ions and can also improve the performance of the battery at low temperatures; it is worth mentioning that the boron atom is a common central atom, which can connect various effective groups in the electrolyte, further enhancing the film-forming effect of FEC, and thus improving the electrochemical performance of the battery.

[0029] In some embodiments of the present invention, the structural formula of the borate compound is as shown in any one of Formula 1 - Formula 4;

[0030]

[0031] In Formula 1 - Formula 4, R 1 , R 2 , R 3 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are each independently selected from a substituted or unsubstituted C1 - C30 alkyl group, a substituted or unsubstituted C2 - C30 alkenyl group, and a substituted or unsubstituted C1 - C30 silyl group;

[0032] In Formula 2, R 4 , R5 Each independently selected from substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C1-C30 silyl, and / or, R 4 and R 5 are connected to form a ring.

[0033] Specifically, in Formula 1-Formula 4, R 1 and R 2 and R 3 and R 6 and R 7 and R 8 and R 9 and R 10 and R 11 and R 12 and R 13 Each independently selected from substituted or unsubstituted C1-C30 alkyl (for example, it can be substituted linear alkyl, substituted branched alkyl, substituted cycloalkyl, unsubstituted linear alkyl, unsubstituted branched alkyl, unsubstituted cycloalkyl), substituted or unsubstituted C2-C30 alkenyl (for example, it can be substituted branched alkenyl, substituted linear alkenyl, substituted cycloalkenyl, unsubstituted linear alkenyl, unsubstituted branched alkenyl, unsubstituted cycloalkenyl), substituted or unsubstituted C1-C30 silyl (for example, it can be substituted linear silyl, substituted linear silyl, substituted cyclic silyl, unsubstituted branched silyl, unsubstituted linear silyl, unsubstituted cyclic silyl).

[0034] In Formula 2, R 4 and R 5 Each independently selected from substituted or unsubstituted C1-C30 alkyl (for example, it can be substituted linear alkyl, substituted branched alkyl, substituted cycloalkyl, unsubstituted linear alkyl, unsubstituted branched alkyl, unsubstituted cycloalkyl), substituted or unsubstituted C2-C30 alkenyl (for example, it can be substituted branched alkenyl, substituted linear alkenyl, substituted cycloalkenyl, unsubstituted linear alkenyl, unsubstituted branched alkenyl, unsubstituted cycloalkenyl), substituted or unsubstituted C1-C30 silyl (for example, it can be substituted linear silyl, substituted linear silyl, substituted cyclic silyl, unsubstituted branched silyl, unsubstituted linear silyl, unsubstituted cyclic silyl);

[0035] Or, R 4 and R 5 are directly connected to form a ring;

[0036] Or, R 4 and R 5 is a cyclic structure formed by connecting any two of the above groups.

[0037] The present invention has no specific requirements for R 1 and R 2, R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 The substituents of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are not particularly limited. 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 The substituents of R and R

[0038] can be substituents commonly used in the art. Exemplarily, the substituents can be at least one of substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C2-C30 alkenyl, carbonyl, halogen, substituted or unsubstituted C6-C60 aryl, amino, ester group, and cyano.

[0038] The inventors found in the research that when the borate compound has the above structure, the electrochemical performance of the battery can be further improved. In particular, when the borate compound contains a silyl group, the silyl group can further remove trace water in the electrolyte and further enhance the ability to cut off side reactions; further, when the borate compound has a silyl group including an unsaturated bond (for example, an unsaturated bond-substituted silyl group), the potential of the electrolyte to form a film can be improved; when the borate compound contains a Si-O bond, the high-temperature tolerance of the interface film can be further improved, ultimately enhancing the high-temperature performance of the battery.

[0039] When the borate compound contains an unsaturated bond (for example, contains substituted or unsubstituted alkenyl), the film-forming ability of the borate compound can be improved, enabling the borate compound to directly participate in the construction of the interface film. The central atom B of the borate compound can adhere to the electrode surface, better complex the free F ions in the electrolyte, reduce the attack of HF acid on the interface film and battery materials, and improve the electrochemical performance of the battery.

[0040] When the borate compound contains a fluoroalkyl group, the C-F bond in the fluoroalkyl group has excellent stability and is not easily converted into highly reactive fluoride ions in the electrolyte, thus avoiding side reactions caused by fluoride ions. At the same time, the fluoroalkyl group has very high stability and can be regarded as an excellent inert component. When the borate compound participates in the construction of the interface film, it can be embedded in the interface film, improving the inertness of the interface film, reducing the reaction sites of the interface film, and further enhancing the stability of the interface film.

[0041] Compared with Formula 1-3, the diboron structure of Formula 4 has dual central boron atoms, which has a better effect of adsorbing fluoride ions and further reduces the negative effects brought by fluoride ions. In addition, more functional functional groups can be carried on the diboron structure, which is beneficial to its participation in the construction of the interface film.

[0042] In some embodiments of the present invention, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 's substituents can be further selected to further improve the electrochemical performance of the electrolyte and the electrochemical performance of the battery. For example, the substituents of R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are selected from at least one of substituted or unsubstituted C1-C30 alkyl groups (for example, it can be a substituted straight-chain alkyl group, a substituted branched-chain alkyl group, a substituted cycloalkyl group, an unsubstituted straight-chain alkyl group, an unsubstituted branched-chain alkyl group, an unsubstituted cycloalkyl group), substituted or unsubstituted C2-C30 alkenyl groups (for example, it can be a substituted branched-chain alkenyl group, a substituted straight-chain alkenyl group, a substituted cycloalkenyl group, an unsubstituted straight-chain alkenyl group, an unsubstituted branched-chain alkenyl group, an unsubstituted cycloalkenyl group), carbonyl groups, and halogens (for example, F, Cl, Br, I).

[0043] Exemplarily, the borate compounds are selected from the compounds shown in the following structures;

[0044]

[0045]

[0046]

[0047]

[0048] It can be understood that the contents of borate compounds and fluoroethylene carbonate in the electrolyte will have a crucial impact on the performance of the electrolyte. Therefore, the present invention can further select the contents of borate compounds and fluoroethylene carbonate in the electrolyte in order to improve the comprehensive performance of the electrolyte. Exemplarily, based on the total mass of the electrolyte, the mass percentage content of borate compounds is 0.1%-2%; and / or, based on the total mass of the electrolyte, the mass percentage content of fluoroethylene carbonate is 1%-15%.

[0049] The inventors also found in the research that when, based on the total mass of the electrolyte, the mass percentage content of borate compounds is 0.1-1% and the mass percentage content of fluoroethylene carbonate is 5-10%, the borate compounds can better match with the fluoroethylene carbonate, further improving the comprehensive performance of the electrolyte, and thus improving the comprehensive performance of the battery.

[0050] In some embodiments of the present invention, the electrolyte further includes a solvent, and based on the total mass of the electrolyte, the mass percentage content of the solvent is 10-80%.

[0051] The present invention does not make any particular limitation on the solvent, and it can be a commonly used solvent in the art. Exemplarily, the solvent can be at least one of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluoroethylene carbonate, γ-butyrolactone, sulfolane, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate.

[0052] The electrolyte further includes other additives, and based on the total mass of the electrolyte, the mass percentage content of the other additives is 0.5-5%.

[0053] The present invention does not make any particular limitation on the other additives, and they can be commonly used electrolyte additives in the art. Exemplarily, the electrolyte additives can be at least one of vinylene carbonate (VC), ethylene vinyl carbonate (VEC), ethylene sulfite (DTD), 1,3-propane sultone (PS), 1,3-propene sulfonic acid lactone (PST), ethylene sulfite (ES), and tris(trimethylsilyl) borate (TMSB).

[0054] When the electrolyte further includes the solvent with the above-specified content and / or other additives with the above-specified content, the comprehensive performance of the electrolyte can be further improved, and thus the comprehensive performance of the battery can be improved.

[0055] In some embodiments of the present invention, the electrolyte further includes a lithium salt. Based on the total mass of the electrolyte, the mass percentage of the lithium salt is 12% - 18%. Further, the mass percentage of the lithium salt is greater than 12.5%.

[0056] The present invention does not particularly limit the lithium salt, and it can be a lithium salt commonly used in the art. Exemplarily, the lithium salt can be at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalato)borate, and lithium difluoro(oxalato)borate.

[0057] It can be understood that the lithium salt is an important component in the electrolyte. By further limiting the content of the lithium salt in the electrolyte, the present invention can give full play to the role of the lithium salt, improve the comprehensive performance of the electrolyte, and thus improve the comprehensive performance of the battery.

[0058] A second aspect of the present invention is a battery, which includes the electrolyte of the first aspect.

[0059] It can be understood that the battery of the present invention further includes a positive electrode plate, a negative electrode plate, a separator, and an outer package.

[0060] The present invention does not particularly limit the positive electrode plate, and it can be a positive electrode plate common in the art. In some embodiments, the positive electrode active material in the positive electrode plate can be at least one of lithium cobaltate, lithium iron phosphate, and ternary materials. Further, the molar percentage of Ni element or Mn element in the positive electrode active material is greater than 65%. The tap density of the positive electrode active layer of the positive electrode plate can be 1 - 5 g / cm 3 。

[0061] The present invention does not particularly limit the negative electrode plate, and it can be a negative electrode plate common in the art. In some embodiments, the negative electrode active material in the negative electrode plate can be selected from at least one of artificial graphite, natural graphite, lithium titanate, silicon, silicon-carbon, silicon-oxygen, and silicon metal compounds. Further, the negative electrode active material can be silicon-carbon and / or silicon-oxygen. The tap density of the negative electrode active layer of the negative electrode plate can be 1 - 4 g / cm 3 。

[0062] In the specific application process, a stable SEI film will be formed on the surface of the negative electrode by the electrolyte, and the electrolyte is not easy to generate gas at high temperature. Therefore, the battery including the electrolyte of the present invention can have excellent room-temperature cycle performance, high-temperature cycle performance, and high-temperature storage performance at the same time.

[0063] Hereinafter, the electrolyte of the present invention and its applications will be introduced in detail through specific examples.

[0064] Example 1

[0065] The battery of this example was prepared by a method including the following steps:

[0066] (1) Preparation of the positive electrode sheet

[0067] The positive electrode active material NCM811, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed at a mass ratio of 96.5:2:1.5, and N-methylpyrrolidone (NMP) was added. Stirring was carried out under the action of a vacuum mixer until the raw materials were mixed into a uniform and fluid positive electrode paste;

[0068] The positive electrode paste was uniformly coated on both surfaces of an aluminum foil with a thickness of 7 μm respectively. After baking in an oven with 5 different temperature gradients, it was then dried in an oven at 120 °C for 8 h, and then roll-pressed to control the compaction density of the positive electrode active layer to be 3.5 g / cm 3 , and the positive electrode sheet was obtained by slitting.

[0069] (2) Preparation of the negative electrode sheet

[0070] The negative electrode active material carbon-silicon material@graphite (the mass percentage content of the carbon-silicon material is 10%), the thickener sodium carboxymethyl cellulose (CMC-Na), the binder styrene-butadiene rubber, the conductive agent acetylene black, and the conductive agent single-walled carbon nanotube (SWCNT) were mixed at a mass ratio of 95.9:1:2:1:0.1, and deionized water was added. The negative electrode paste was obtained under the action of a vacuum mixer;

[0071] The negative electrode paste was uniformly coated on both surfaces of a copper foil with a thickness of 6 μm respectively, dried (temperature: 85 °C, time: 5 h), and roll-pressed to control the compaction density of the negative electrode active layer to be 1.65 g / cm 3 , and the negative electrode sheet was obtained by die-cutting.

[0072] (3) Preparation of the electrolyte

[0073] In a glove box filled with argon (moisture < 10 ppm, oxygen content < 1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC) were mixed evenly at a mass ratio of = 1.5:1.5:5:2 to obtain a mixed solution. Lithium salt, FEC, and borate compound that had been fully dried were quickly added to the mixed solution, as shown in Table 1 specifically.

[0074] (4) Preparation of the lithium-ion battery

[0075] After stacking the positive electrode sheet in step (1), the separator, and the negative electrode sheet in step (2) in sequence, winding is carried out to obtain a non-injected bare battery cell.

[0076] Place the bare battery cell in an outer packaging foil, inject the electrolyte in step (3) into the dried bare battery cell, and after processes such as vacuum packaging, standing, forming, shaping, and sorting, the required lithium-ion battery is obtained.

[0077] Among them, the separator is a coated polyethylene separator with a thickness of 8 μm.

[0078] Examples 2-52 and Comparative Examples 1-2

[0079] The composition of the electrolyte in Examples 2-52 is basically the same as that in Example 1, and the differences are shown in Table 1.

[0080] Replace the electrolyte in Example 1 with the electrolytes of Examples 2-52 and Comparative Examples 1-2 respectively to obtain the lithium-ion batteries of Examples 2-52 and Comparative Examples 1-2 respectively.

[0081] Table 1

[0082]

[0083]

[0084] In Table 1, the C compound is as follows:

[0085]

[0086] Performance test

[0087] Perform the following performance tests on the batteries in the examples and comparative examples respectively, and the test results are shown in Table 2;

[0088] 1) Room temperature cycle performance test

[0089] Charge the battery at a constant current of 1C to 4.2V at room temperature of 25°C, charge at a constant voltage of 4.2V until the cut-off current is 0.05C, and then discharge the battery at 1C to 2.75V. Repeat the charge and discharge 600 cycles, test and record the discharge capacity of the 600th cycle and divide it by the discharge capacity of the first cycle to obtain the capacity retention rate.

[0090] 2) High temperature cycle performance test

[0091] Charge the battery at a constant current of 1C to 4.2V at a high temperature of 45°C, charge at a constant voltage of 4.2V until the cut-off current is 0.05C, and then discharge the battery at 1C to 2.75V. Repeat the charge and discharge 200 cycles, test and record the discharge capacity of the 200th cycle and divide it by the discharge capacity of the first cycle to obtain the capacity retention rate.

[0092] 3) DCIR Test

[0093] Charge the formed battery to 4.2V at 1C at room temperature, let it stand for 5 min, then discharge it at 1C for 30 min, let it stand for 1 h, and then discharge it at 2C for 10 s to calculate the DCIR of the battery at 50% SOC.

[0094] 4) High-temperature storage performance test

[0095] Charge the battery at a constant current of 1C to 4.2V at room temperature of 25°C, charge it at a constant voltage of 4.2V until the cut-off current is 0.05C, and then discharge the battery at a constant current of 0.5C. Record the discharge capacity as C 1 . At room temperature of 25°C, charge it at a constant current of 1C to 4.2V, charge it at a constant voltage of 4.42 until the cut-off current is 0.05C, measure the battery thickness, and record it as h1 (the battery thickness before storage at 60°C). Then transfer the battery to a high temperature of 60°C and let it stand for 7 days, measure the battery thickness again, and record it as h2 (the battery thickness after storage at 60°C for 7 days). Then discharge it at a constant current of 0.5C, and record the discharge capacity as C 2 , Capacity retention rate at 60°C = C 2 / C 1 *100%;

[0096] Use the method in 3) to test the DCIR of the battery after standing at 60°C for 7 days.

[0097] Table 2

[0098]

[0099]

[0100]

[0101] As can be seen from Table 2, the batteries in the embodiments of the present invention have more excellent room-temperature cycle performance, high-temperature cycle performance, high-temperature storage performance, and lower impedance;

[0102] Furthermore, it can be seen from Example 9 and Examples 47-48 that when the mass percentage content of the borate compound in the electrolyte is 0.1%-2%, the obtained batteries have more excellent comprehensive performance;

[0103] It can be seen from Examples 4-6 and Examples 7-8, Examples 9-12 and Examples 13-15, Examples 19, 21, 23 and Examples 20, 22, Examples 26-28 and Examples 29-30, Examples 31, 33 and Examples 32, 34, 35, Examples 36-38 and Examples 39-40, 44, Example 9 and Examples 45, 46 that when the mass percentage content of the borate compound in the electrolyte is 0.1-1% and the mass percentage content of fluoroethylene carbonate is 5-10%, the obtained battery has more excellent comprehensive performance;

[0104] It can be seen from Example 6 and Example 50, Example 11 and Example 51 that when other additives are further included in the electrolyte, the obtained battery has more excellent comprehensive performance.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte solution, characterized in that, it comprises fluorinated ethylene carbonate and a borate compound.

2. The electrolyte solution according to claim 1, characterized in that, the structural formula of the borate compound is as shown in any one of Formula 1 - Formula 4; In Formulas 1 to 4, R 1 , R 2 , R 3 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are each independently selected from substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C2-C30 alkenyl, and substituted or unsubstituted C1-C30 silyl; In Formula 2, R 4 , R 5 are each independently selected from substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C2-C30 alkenyl, substituted or unsubstituted C1-C30 silyl, and / or, R 4 , R 5 are connected to form a ring.

3. The electrolyte solution according to claim 1 or 2, characterized in that, R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 、R 8 、R 9 、R 10 、R 11 、R 12 、R 13 The substituents in are selected from at least one of substituted or unsubstituted C1-C30 alkyl, substituted or unsubstituted C2-C30 alkenyl, carbonyl, and halogen.

4. The electrolyte solution according to any one of claims 1 - 3, characterized in that, the borate compound is selected from the compounds shown in the following structures; 5. The electrolyte solution according to any one of claims 1 - 4, characterized in that, based on the total mass of the electrolyte solution, the mass percentage content of the borate compound is 0.1% - 2%.

6. The electrolyte solution according to any one of claims 1 - 5, characterized in that, based on the total mass of the electrolyte solution, the mass percentage content of the fluorinated ethylene carbonate is 1% - 15%.

7. The electrolyte solution according to claim 5 or 6, characterized in that, based on the total mass of the electrolyte solution, the mass percentage content of the borate compound is 0.1 - 1%, and the mass percentage content of the fluorinated ethylene carbonate is 5 - 10%.

8. The electrolyte solution according to any one of claims 1 - 7, characterized in that, the electrolyte solution further comprises a solvent, and based on the total mass of the electrolyte solution, the mass percentage content of the solvent is 10 - 80%; and / or, the electrolyte solution further comprises other additives, and based on the total mass of the electrolyte solution, the mass percentage content of the other additives is 0.5 - 5%; wherein, the solvent comprises at least one of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, fluorinated ethylene carbonate, γ - butyrolactone, sulfolane, methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate; the other additives are selected from at least one of vinylene carbonate, ethylene vinyl carbonate, ethylene sulfite, 1,3 - propanesultone, 1,3 - propene sulfonic acid lactone, ethylene sulfite, and tris(trimethylsilyl) borate.

9. The electrolyte solution according to any one of claims 1 - 8, characterized in that, the electrolyte solution further comprises a lithium salt, and based on the total mass of the electrolyte solution, the mass percentage content of the lithium salt is 12% - 18%.

10. A battery, characterized in that, it comprises the electrolyte solution according to any one of claims 1 - 9.

Images