Lithium ion battery electrolyte and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery electrolyte and a lithium ion battery. The lithium ion battery electrolyte comprises a lithium salt, an organic solvent and an additive, the organic solvent comprises an ether organic solvent; the additive comprises an o-benzoyl sulfonyl imide compound as shown in the following general formula (I): # imgabs0 # general formula (I). According to the lithium ion battery electrolyte, the o-benzoyl sulfonyl imide compound is added, and the ether organic solvent matched with the o-benzoyl sulfonyl imide compound is used, so that the impedance of a battery can be effectively reduced, lithium ion transmission kinetics at an interface can be effectively optimized, and a low-impedance, compact and stable N and S-rich SEI / CEI interface is formed; the generation of interface side reaction is inhibited, and the capacity and the cycling stability of the lithium ion battery under a high-rate condition are improved, so that the application range of the lithium ion battery is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular, to a lithium-ion battery electrolyte and a lithium-ion battery. Background Art

[0002] In recent years, with the development of science and technology and the influence of environmental protection policies, the wide application of lithium-ion batteries in passenger cars has become increasingly rapid. However, compared with traditional fuel vehicles, problems such as range anxiety and long charging time have become the main obstacles restricting the development of electric passenger cars. Therefore, the fast charging ability of the battery has become one of the key indicators in the actual evaluation of advanced batteries, and the demand for high specific energy and ultra-fast charging is becoming increasingly prominent in future high-end applications. However, conventional lithium-ion electrolytes will cause a large amount of rapid degradation of electrolyte components and distortion and rupture of the electrode material structure due to severe redox reactions under fast charging conditions, resulting in a decrease in the charge-discharge capacity of the battery, rapid capacity decay, poor rate performance, and a serious decline in cycle life. And improving the stability of the electrolyte and electrode material during fast charge and discharge through functional additives is undoubtedly a simple and efficient modification method.

[0003] Currently, the publicly reported electrolyte additives mainly include film-forming additives, interface adsorption and stabilization additives, acid and water removal additives, oxygen free radical scavenging additives, and flame retardant additives. These electrolyte additives can participate in constructing a more stable solid electrolyte interface (SEI) on the negative electrode and a solid electrolyte interface (CEI) on the positive electrode. For example, the patent with the publication number CN117895074A discloses a fast-charging and low-temperature electrolyte and a lithium-ion battery suitable for a 4.6V high-voltage cobalt acid lithium-ion battery. By adding a boron-containing lithium salt and a fluoroethylene carbonate additive to a mixed solution of carbonate and carboxylate, using the synergistic effect between multi-component additives, a uniform and stable electrode / electrolyte interface is formed on the electrode surface, which can effectively isolate the continuous contact between the electrode and the electrolyte and has the ability of rapid lithium ion transmission, improving the cycle stability and fast charging performance of the battery. However, the capacity and cycle stability of the battery are still poor under high-rate conditions and still cannot meet people's expectations for the charging speed. Summary of the Invention

[0004] The present invention provides a lithium-ion battery electrolyte and a lithium-ion battery to solve the problem of poor capacity and cycle stability under high-rate conditions when existing electrolyte additives are applied to lithium-ion batteries.

[0005] According to the first aspect of the present invention, the present invention provides a lithium-ion battery electrolyte, and the lithium-ion battery electrolyte includes a lithium salt, an organic solvent, and an additive; the organic solvent includes an ether-based organic solvent; the additive includes an o-benzoyl sulfimide compound, and the o-benzoyl sulfimide compound has a structure shown in the following general formula (I): General formula (I); In formula (I): R1 is selected from H, C 1-6 alkyl or lithium ion; R2 and R3 are each independently selected from H, a halogen atom, a cyano group, C 1-6 alkyl, C 1-6 alkoxy or nitro; or R2 and R3 together form a carbonyl or thiocarbonyl group; R4, R5, R6, R7 are each independently selected from H, a halogen atom, C 1-6 alkyl, C 1-6 alkoxy, halo C 1-6 alkyl, halo C 1-6 alkoxy, nitro, cyano, aldehyde group, carboxyl group or ester group.

[0006] Experimental findings of the present invention show that by using the o-benzoyl sulfimide compounds with specific structures of the present invention as additives for lithium-ion battery electrolytes, it is possible to effectively optimize the lithium-ion transport kinetics at the electrode / electrolyte interface, and preferentially decompose to form a low-impedance, uniform, dense and stable N, S-rich SEI / CEI interface, inhibit the occurrence of interfacial side reactions, reduce the direct contact between the solvent and the positive and negative electrodes, thereby reducing the further decomposition of the effective components in the electrolyte, the consumption of active lithium, and the further growth of lithium dendrites, as well as the lithium deposition on the surface of the negative electrode material and the degradation of the surface interface structure of the positive electrode material. Therefore, it can improve the capacity and cycle stability of the battery under high-rate conditions, has high practical application value, and enables lithium-ion batteries to be widely used in the fields of power batteries, drones, 3C electronic products, and power ships. Further, the lithium-ion battery electrolyte of the present invention uses an organic solvent including an ether-based organic solvent, which can improve the solubility of the o-benzoyl sulfimide compounds in the lithium-ion battery electrolyte, thereby enabling the o-benzoyl sulfimide compounds to fully exert their functions and better improve the capacity and cycle stability of the battery under high-rate conditions.

[0007] Further, R1 is selected from H or C 1-6 alkyl; R2 and R3 together form a carbonyl or thiocarbonyl group; R4, R5, R6, R7 are each independently selected from H or C 1-6 alkyl. Experimental findings of the present invention show that using the o-benzoyl sulfimide compounds with the above structural features can more effectively improve the capacity and cycle stability of the battery under high-rate conditions. Preferably, R1 is selected from H, R2 and R3 together form a carbonyl group, and R4, R5, R6, R7 are each independently selected from H.

[0008] Further, the dosage of the o-benzoyl sulfimide compound is 0.01% - 5% of the total mass of the lithium-ion battery electrolyte. The dosage of the o-benzoyl sulfimide compound in the lithium-ion battery electrolyte will affect the performance of the battery. If the dosage of the o-benzoyl sulfimide compound is too low, the improvement of the battery performance is not obvious. If the dosage of the o-benzoyl sulfimide compound is too high, due to the excessive decomposition of molecules, a loose SEI layer will be formed later, thus affecting the electrode interface transmission. The weight percentage of the o-benzoyl sulfimide compound in the total mass of the lithium-ion battery electrolyte is preferably 0.1% - 3.5%, and more preferably 0.5% - 1.0%.

[0009] Selecting a suitable type of ether organic solvent can better form a synergistic effect with the o-benzoyl sulfimide compound and better improve the application effect of the o-benzoyl sulfimide compound. Further, the ether organic solvent is selected from one or more of ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, and ethyl ether. In some specific embodiments, the ether organic solvent is selected from ethylene glycol dimethyl ether or triethylene glycol dimethyl ether, and preferably ethylene glycol dimethyl ether.

[0010] The dosage of the organic solvent has an important impact on the performance of the lithium-ion battery electrolyte, such as ionic conductivity, electrochemical stability, interfacial stability, low-temperature performance, and safety performance. An appropriate dosage of the organic solvent can balance these performance indicators, thereby achieving the best performance of the battery. Further, the dosage of the organic solvent is 10% - 50% of the total mass of the lithium-ion battery electrolyte. In some specific embodiments, the dosage of the organic solvent is 25% - 35% of the total mass of the lithium-ion battery electrolyte, and preferably 25% - 30%.

[0011] Preferably, a lithium-ion battery electrolyte is composed of the following components: 15 - 20 parts by weight of lithium bis(fluorosulfonyl)imide, 8 - 12 parts by volume of ethylene glycol dimethyl ether, 2 - 3 parts by weight of lithium nitrate, and 0.1 - 0.3 parts by weight of o-benzoyl sulfimide. It should be noted that in the present invention, the parts by volume are in milliliters, and the corresponding parts by weight are in grams, or the parts by volume are in liters, and the corresponding parts by weight are in kilograms.

[0012] Further, the organic solvent further includes an ester organic solvent, and the ester organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate, and ethyl butyrate; the ester organic solvent is a commonly used commercial organic solvent with a wide source and relatively low cost. Using the ester organic solvent as a part of the organic solvent can effectively reduce the cost of the lithium-ion battery electrolyte.

[0013] In some specific embodiments, the ester organic solvent is selected from two of dimethyl carbonate, diethyl carbonate, and ethylene carbonate.

[0014] In order to balance the cost and performance of the lithium-ion battery electrolyte, preferably, the volume ratio of the ether organic solvent to the ester organic solvent is (1.5 - 4):1.

[0015] Furthermore, the additive further includes one or more of lithium nitrate, lithium difluorooxalate borate, lithium bis(oxalato)borate, lithium difluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, fluoroethylene carbonate, vinylene carbonate, ethylene ethylenecarbonate, vinyl sulfate, propylene sulfite, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, and trifluoroethyl methyl carbonate. In some specific embodiments, the additive further includes lithium nitrate or lithium difluorooxalate borate. Preferably, the additive further includes lithium nitrate. More preferably, in the additive, the weight ratio of the phthalimide compound to lithium nitrate is (2 - 15):1.

[0016] Furthermore, the dosage of the additive is 0.1 - 15% of the total mass of the lithium-ion battery electrolyte. In some specific embodiments, the dosage of the additive is 9 - 12% of the total mass of the lithium-ion battery electrolyte.

[0017] Furthermore, the lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate. Selecting a suitable type of lithium salt can form a better synergistic effect with the organic solvent and additive in the lithium-ion battery electrolyte, thereby improving the overall performance of the lithium-ion battery electrolyte.

[0018] Preferably, calculated as lithium ions, the concentration of the lithium salt in the lithium-ion battery electrolyte is 0.01 - 5 mol / L. Preferably, the concentration of the lithium salt in the lithium-ion battery electrolyte is 0.05 - 2 mol / L. In some specific embodiments, the concentration of the lithium salt in the lithium-ion battery electrolyte is 1 mol / L.

[0019] Preferably, a lithium-ion battery electrolyte is composed of the following components: 15 - 20 parts by weight of lithium bis(fluorosulfonyl)imide, 6 - 8 parts by volume of ethylene glycol dimethyl ether, 1 - 2 parts by volume of ethylene carbonate, 1 - 2 parts by volume of dimethyl carbonate, 2 - 3 parts by weight of lithium nitrate, and 0.1 - 0.3 parts by weight of phthalimide.

[0020] According to the second aspect of the present invention, the present invention further provides a lithium-ion battery including the above lithium-ion battery electrolyte.

[0021] Further, in addition to the above-mentioned lithium-ion battery electrolyte, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

[0022] Further, the form of the lithium-ion battery is not limited and can be cylindrical, aluminum shell, plastic shell or soft package shell.

[0023] Further, the positive electrode is a lithium iron phosphate positive electrode material, lithium cobaltate or a ternary positive electrode material (LiMn 1-x- y Ni x Co y O2, where 0 < x < 1, 0 < y < 1, and x + y < 1), preferably a ternary positive electrode material.

[0024] Further, the negative electrode includes but is not limited to at least one of metallic lithium, carbon material or silicon-based material.

[0025] Further, the separator can be a separator commonly used in lithium-ion batteries, for example, it can be a Celgard 2325 separator.

[0026] The present application has the following beneficial effects: In a lithium-ion battery electrolyte of the present invention, by adding a phthalimide compound and simultaneously using an ether organic solvent adapted to the phthalimide compound, the impedance of the battery can be effectively reduced, the lithium ion transport kinetics at the interface can be effectively optimized, and a low-impedance, dense and stable SEI / CEI interface rich in N and S is preferentially formed by decomposition, reducing the direct contact between the solvent and the positive and negative electrodes, thereby reducing the further decomposition of the effective components in the electrolyte, the consumption of active lithium and the further growth of lithium dendrites, as well as the lithium deposition on the surface of the negative electrode material and the degradation of the surface interface structure of the positive electrode material. Description of the Drawings

[0027] Figure 1 It is a normal temperature cycle performance graph of an NCM811 / Li battery prepared from the lithium-ion battery electrolyte of Example 1 and Comparative Example 1 of the present invention.

[0028] Figure 2 It is a low temperature cycle performance graph of an NCM811 / Li battery prepared from the lithium-ion battery electrolyte of Example 1 of the present invention. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts belong to the scope of protection of the present invention.

[0030] Unless otherwise specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0031] The components used in the following examples and comparative examples are all of battery grade.

[0032] The preparation conditions for the lithium-ion battery electrolyte in the following examples and comparative examples are as follows: The operation is carried out in a glove box filled with argon with a purity of 99.999%. The moisture in the glove box is less than 0.1 ppm, and the temperature is room temperature. It should be noted that room temperature generally refers to 25 ± 5 °C.

[0033] Example 1 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of saccharin.

[0034] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of saccharin, and mix them thoroughly and stir evenly to obtain.

[0035] Example 2 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.94 g of saccharin.

[0036] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.94 g of saccharin, and mix them thoroughly and stir evenly to obtain.

[0037] Example 3 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of triethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of saccharin.

[0038] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of triethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of saccharin, and mix them thoroughly and stir evenly to obtain the product.

[0039] Example 4 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of saccharin.

[0040] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of saccharin, and mix them thoroughly and stir evenly to obtain the product.

[0041] Example 5 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether / ethylene carbonate / dimethyl carbonate (volume ratio = 6:2:2), 2.7 g of lithium nitrate, and 0.19 g of saccharin.

[0042] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether / ethylene carbonate / dimethyl carbonate, 2.7 g of lithium nitrate, and 0.19 g of saccharin, and mix them thoroughly and stir evenly to obtain the product.

[0043] Example 6 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether / ethylene carbonate / diethyl carbonate (volume ratio = 8:1:1), 2.7 g of lithium nitrate, and 0.19 g of saccharin.

[0044] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether / ethylene carbonate / diethyl carbonate, 2.7 g of lithium nitrate, and 0.19 g of saccharin, and mix them thoroughly and stir evenly to obtain the product.

[0045] Example 7 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of lithium saccharinate. The structural formula of lithium saccharinate is as follows: .

[0046] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.19 g of lithium o-benzenesulfonylimide, and mix them thoroughly and stir evenly to obtain the product.

[0047] Example 8 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.94 g of o-benzenesulfonylimide-based additive. The structural formula of the o-benzenesulfonylimide-based additive is as follows: 。

[0048] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.7 g of lithium nitrate, and 0.94 g of o-benzenesulfonylimide-based additive, and mix them thoroughly and stir evenly to obtain the product.

[0049] Example 9 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of lithium o-benzenesulfonylimide. The structural formula of lithium o-benzenesulfonylimide is the same as that in Example 7.

[0050] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of lithium o-benzenesulfonylimide, and mix them thoroughly and stir evenly to obtain the product.

[0051] Example 10 This example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of o-benzenesulfonylimide-based additive. The structural formula of the o-benzenesulfonylimide-based additive is the same as that in Example 8.

[0052] The preparation method is as follows: In a glove box filled with argon, take 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, 2.88 g of lithium difluoro(oxalato)borate, and 0.19 g of o-benzenesulfonylimide-based additive, and mix them thoroughly and stir evenly to obtain the product.

[0053] Comparative Example 1 This comparative example provides a lithium-ion battery electrolyte, which is composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, and 2.7 g of lithium nitrate.

[0054] The preparation method is as follows: in a glove box filled with argon, 18.7 g of lithium bis(fluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, and 2.7 g of lithium nitrate are mixed thoroughly and stirred evenly to obtain the product.

[0055] Comparative Example 2 This comparative example provides a lithium ion battery electrolyte, which consists of the following components: 18.7 g of lithium bis(trifluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether and 2.88 g of lithium difluorooxalatoborate.

[0056] The preparation method is as follows: in a glove box filled with argon, 18.7 g of lithium bis(trifluorosulfonyl)imide, 10 mL of ethylene glycol dimethyl ether, and 2.88 g of lithium difluorooxalatoborate are mixed thoroughly and stirred evenly to obtain the product.

[0057] Comparative Example 3 This comparative example provides a lithium-ion battery electrolyte composed of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide and 10 mL of ethylene glycol dimethyl ether.

[0058] The preparation method is as follows: in a glove box filled with argon, 18.7 g of lithium bis(fluorosulfonyl)imide and 10 mL of ethylene glycol dimethyl ether are mixed thoroughly and stirred evenly to obtain the product.

[0059] Comparative Example 4 This comparative example provides a lithium ion battery electrolyte, which consists of the following components: 18.7 g of lithium bis(fluorosulfonyl)imide, 8 mL of ethylene glycol dimethyl ether and 2 mL of ethylene carbonate / diethyl carbonate (volume ratio = 1:1).

[0060] The preparation method is as follows: in a glove box filled with argon, 18.7 g of lithium bis(fluorosulfonyl)imide and 8 mL of ethylene glycol dimethyl ether are mixed thoroughly, and after they are completely dissolved, 2 mL of ethylene carbonate / diethyl carbonate mixed solution is added and stirred evenly to obtain the product.

[0061] Performance Testing The lithium-ion battery electrolytes prepared in the above embodiments and comparative examples were assembled into batteries and then the cycle performance was tested as follows: 0.8 Co 0.1 Mn 0.1Using O2 (NCM811) as the positive electrode, metallic lithium as the negative electrode, aluminum foil as the positive current collector, and a Celgard 2325 separator, a coin-type half-cell was assembled in a glove box and tested after standing for 24 hours. At a constant temperature of 25 °C, the battery was activated by performing 2 charge-discharge cycles between 3.0 V and 4.3 V at a rate of 0.1C. Subsequently, charge-discharge tests were carried out at rates of 0.2C, 0.5C, 1C, 2C, 3C, 4C, 5C, 10C, 15C, and 20C for 5 cycles each. The discharge capacities at different rates are shown in Table 1. Charge-discharge cycling tests were performed at a rate of 10C at 25 °C, and the test results are shown in Table 2.

[0062] Table 1. Discharge Capacities of NCM811 / Li Half-Cells Assembled in Examples and Comparative Examples at Different Rates

[0063] Table 2. Cycling Results of NCM811 / Li Half-Cells Assembled in Examples and Comparative Examples at 1C and 10C

[0064] Note: In Tables 1 and 2, a capacity of 0 means that without a suitable additive, the battery cannot cycle under high voltage or cannot complete the specified number of cycles due to overcharging.

[0065] From Tables 1 to 2 and Figures 1-2 it can be seen that whether it is the rate performance test or the long-cycle charge-discharge test at 1C or 20C, the capacity and cycle stability of the lithium-ion battery prepared with the lithium-ion battery electrolyte of the embodiments of the present invention are significantly better than those of the comparative examples, indicating that the lithium-ion battery electrolyte of the present invention can significantly improve the cycle stability of the lithium-ion battery and obtain excellent fast charge-discharge performance and cycle stability by introducing saccharin additives.

[0066] 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 for some of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium ion battery electrolyte, characterized in that: The lithium-ion battery electrolyte comprises a lithium salt, an organic solvent and an additive; the organic solvent comprises an ether organic solvent; the additive comprises an o-benzoylsulfonyl imide compound, and the o-benzoylsulfonyl imide compound has a structure shown in the following general formula (I): General formula (I); In formula (I): R1 is selected from H, C 1-6 Alkyl or lithium ion; R2 and R3 are each independently selected from H, a halogen atom, a cyano group, a C 1-6 Alkyl, C 1-6 Alkoxy or nitro; or R2 and R3 together form a carbonyl or thiocarbonyl; R4, R5, R6, R7 are each independently selected from H, halogen atoms, C 1-6 Alkyl, C 1-6 Alkoxy, halogenated C 1-6 Alkyl, halogenated C 1-6 Alkoxy, nitro, cyano, aldehyde, carboxyl or ester groups.

2. The lithium ion battery electrolyte according to claim 1, characterized in that: R1 is selected from H or C 1-6 alkyl; R2 and R3 together form a carbonyl or thiocarbonyl group; R4, R5, R6, R7 are each independently selected from H or C 1-6 alkyl.

3. The lithium ion battery electrolyte according to claim 1 or 2, characterized in that: The amount of the o-benzoylsulfonyl imide compound used is 0.01%-5%, preferably 0.1%-3.5%, of the total mass of the lithium ion battery electrolyte.

4. The lithium ion battery electrolyte according to any one of claims 1 to 3, characterized in that: The ether organic solvent is selected from one or more of ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran and diethyl ether.

5. The lithium ion battery electrolyte according to any one of claims 1 to 4, characterized in that: The amount of the organic solvent used is 10%-50% of the total mass of the lithium ion battery electrolyte.

6. The lithium ion battery electrolyte according to any one of claims 1 to 5, characterized in that: The organic solvent further comprises an ester organic solvent, and the ester organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate and ethyl butyrate; Preferably, the volume ratio of the ether organic solvent to the ester organic solvent is (1.5-4):

1.

7. The lithium ion battery electrolyte according to any one of claims 1 to 6, characterized in that: The additive also includes one or more of lithium nitrate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, fluoroethylene carbonate, vinylene carbonate, vinylethylene carbonate, vinyl sulfate, propylene sulfite, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate and trifluoroethylmethyl carbonate.

8. The lithium ion battery electrolyte according to any one of claims 1 to 7, characterized in that: The amount of the additive used is 0.1-15% of the total mass of the lithium ion battery electrolyte.

9. The lithium ion battery electrolyte according to any one of claims 1 to 8, characterized in that: The lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate and lithium perchlorate; Preferably, the concentration of the lithium salt in the lithium ion battery electrolyte is 0.01 to 5 mol / L, calculated as lithium ions.

10. A lithium ion battery, characterized in that: The invention comprises the lithium ion battery electrolyte according to any one of claims 1 to 9.

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