Electrolyte and lithium ion battery

Abstract

The invention relates to the technical field of secondary batteries, in particular to an electrolyte and a lithium ion battery. The electrolyte comprises a solvent, a lithium salt, an additive and a polymerization initiator. Wherein the lithium salt is dissolved in the solvent; the additive comprises a polymerizable monomer additive; the polymerizable monomer additive is initiated and polymerized by the polymerization initiator at a temperature of more than 80 DEG C, so that the conductivity of the electrolyte is reduced from S1 to S2, S1 is more than or equal to 1 * 10 <-4 > S / cm, and S2 is less than or equal to 1 * 10 <-6 > S / cm. According to the invention, the polymerizable monomer additive and the polymerization initiator are added into the electrolyte, so that the electrolyte can be subjected to a polymerization reaction rapidly at a high temperature, and the thermal runaway phenomenon of the lithium ion battery is effectively prevented from continuing to diffuse.

Description

Technical Field

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

[0002] Lithium-ion batteries have become the preferred power source for electric vehicles, energy storage systems and other fields due to their high energy density, high voltage, and long cycle life. However, when lithium-ion batteries are used in high temperature environments, the chemical stability of the positive and negative electrode materials and electrolytes inside them will be affected. This is because the electrode materials in some lithium-ion batteries may undergo structural changes at high temperatures, causing the active materials in the materials to undergo violent redox reactions with the electrolyte. When the temperature exceeds a certain limit, the transition metal ions in the electrode materials may accelerate the decomposition of the electrolyte, eventually causing the lithium-ion battery to experience thermal runaway and spread to other lithium-ion batteries in the module.

[0003] In the prior art, lithium-ion battery modules are usually designed so that an aerogel with high porosity, low density, and low thermal conductivity can be added to the gaps between lithium-ion batteries in the module to prevent the thermal runaway of a single lithium-ion battery from spreading to other lithium-ion batteries. However, the better thermal insulation performance of aerogel will also reduce the heat dissipation efficiency of lithium-ion batteries, and the aerogel material is relatively hard, which will generate a large expansion force in the module in actual use. At the same time, the higher price of aerogel increases the manufacturing cost of lithium-ion batteries. Summary of the invention

[0004] In view of the above problems, the present invention provides an electrolyte which can rapidly reduce its own conductivity under high temperature conditions to cut off the electrochemical reaction inside the lithium-ion battery, thereby preventing the lithium-ion battery from continuing to heat up and avoiding the continuous spread of thermal runaway in the lithium-ion battery module.

[0005] The first aspect of the present invention provides an electrolyte, which includes a solvent, a lithium salt, an additive, and a polymerization initiator. The lithium salt is dissolved in the solvent; the additive includes a polymerizable monomer additive; the polymerizable monomer additive is initiated and polymerized by the polymerization initiator under a temperature greater than 80°C, so that the conductivity of the electrolyte decreases from S1 to S2, S1≥1×10 -4 S / cm, S2≤1×10 -6 S / cm.

[0006] Optionally, the polymerizable monomer additive is an unsaturated ester additive.

[0007] Optionally, the unsaturated ester additive is one or more of vinylene carbonate, acrylate, and methacrylate.

[0008] Optionally, the mass fraction of the polymerizable monomer additive in the electrolyte is 3%-8%.

[0009] Optionally, the polymerization initiator is a thermal polymerization initiator.

[0010] Optionally, the thermal initiator is a peroxide-based initiator.

[0011] Optionally, the peroxide initiator is one or more of cumene hydroperoxide, tert-butyl hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl perbenzoate.

[0012] Optionally, the polymerization initiator is added in an amount of 0.1% to 2% by weight of the polymerizable monomer additive.

[0013] Optionally, the solvent includes a carbonate solvent, and the carbonate solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

[0014] Optionally, the lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), and lithium bis(oxalatoborate).

[0015] A second aspect of the present invention provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and the above-mentioned electrolyte.

[0016] Optionally, the positive electrode plate includes a positive electrode current collector and a positive electrode active material, and the positive electrode active material is lithium nickel cobalt manganese oxide; the negative electrode plate includes a negative electrode current collector and a negative electrode active material, and the negative electrode active material is graphite.

[0017] The electrolyte provided in some examples of the present invention can rapidly polymerize the polymerizable monomer additive by initiating the polymerization initiator at a high temperature greater than 80°C, thereby reducing the conductivity of the electrolyte, causing the lithium ions to be unable to migrate normally in the electrolyte, thereby cutting off the electrochemical reaction inside a single lithium-ion battery. The above method can not only quickly and effectively prevent the thermal runaway of a single lithium-ion battery from spreading to other lithium-ion batteries in the module, significantly improving the thermal safety performance of the lithium-ion battery module, but also significantly reducing the production cost of the lithium-ion battery module. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In this article, when it comes to numerical ranges, unless otherwise specified, the distribution of optional values ​​within the numerical range is considered continuous and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, as well as every value between the two numerical endpoints. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined.

[0020] The electrolyte provided in this embodiment includes a solvent, a lithium salt, an additive, and a polymerization initiator. Among them, the solvent includes a carbonate solvent, specifically one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The lithium salt is dissolved in the solvent, specifically one or more of lithium hexafluorophosphate (LiPF6), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium bisfluorosulfonyl imide (LiFSI), and lithium dioxalate borate (LiBOB). In order to balance the conductivity and viscosity of the electrolyte with each other, so as to take into account the capacity and charge and discharge performance of the lithium ion battery, in some embodiments of the present invention, preferably, the concentration range of the lithium salt in the electrolyte is 0.8mol / L-2mol / L, and more preferably, the concentration of the lithium salt in the electrolyte is 1mol / L.

[0021] Lithium-ion batteries are often used in electric vehicles, energy storage systems and other fields. Usually, multiple lithium-ion batteries are connected in series and parallel to form a lithium-ion battery module. During the use of lithium-ion batteries, accidental squeezing or puncture, voltage and current overload, high operating temperature and quality problems of the battery itself may cause the positive and negative electrode materials inside the lithium-ion battery to undergo violent decomposition reactions and violent oxidation reactions with the electrolyte, thereby generating high temperatures and releasing a large amount of gas, which may cause the lithium-ion battery to burn or explode. If thermal runaway continues to spread, it may also cause the temperature inside the lithium-ion battery module to rise sharply and lose control, causing serious consequences such as fire and explosion of the module.

[0022] In view of the above problems, in some embodiments of the present invention, some specific additives are added to the electrolyte, specifically polymerizable monomer additives and polymerization initiators. When high temperature occurs inside the lithium-ion battery, the polymerizable monomer additives can be rapidly polymerized to form a polymer network structure. By hindering the migration of lithium ions in the electrolyte to reduce the conductivity of the electrolyte, the electrochemical reaction inside the lithium-ion battery is cut off, and finally the purpose of preventing the further spread of thermal runaway in a single lithium-ion battery and a module is achieved. In some embodiments of the present invention, the selected polymerizable monomer additive is an unsaturated ester additive, which can form a polymer through free radical polymerization at high temperature, thereby preventing the further decomposition and reaction of the electrolyte, thereby avoiding the temperature inside the lithium-ion battery from continuing to rise and reducing the risk of thermal runaway spreading to other lithium-ion batteries in the module. Preferably, the unsaturated ester additive is vinylene carbonate (VC), acrylate (CH2=CHCOOR, R=(CH2) n CH3, n = 0-10), methacrylate (CH2 = C (CH3) COOR, R = (CH2) n CH3, n=0-10) or more thereof.

[0023] In the polymerization reaction, monomer molecules are usually small molecules containing unsaturated bonds (such as carbon-carbon double bonds). They are reactive but require initiation to start polymerization. Therefore, in the embodiment of the present invention, after the unsaturated ester additive is added to the electrolyte, it is also necessary to add a substance that can initiate the monomer polymerization reaction, that is, a polymerization initiator. When the ambient temperature of the electrolyte is greater than 80°C, the polymerizable monomer additive is initiated and polymerized by the polymerization initiator, resulting in the obstruction of the movement of lithium ions between the positive and negative electrodes, thereby reducing the conductivity of the electrolyte from S1 to S2, where S1 ≥ 1×10 -4 S / cm, S2≤1×10 -6 S / cm, that is, the conductivity of the electrolyte ranges from 1×10 -4 S / cm, down to 1×10 -6 S / cm or less. At this point, the electrochemical reaction inside the lithium-ion battery is cut off, and the lithium-ion battery itself will not continue to heat up, effectively preventing the further development of thermal runaway.

[0024] In an embodiment of the present invention, the polymerization initiator is a free radical addition polymerization initiator. Under high temperature conditions, the free radical addition polymerization initiator can generate free radicals, which can attack the double bonds in the unsaturated ester monomers, causing them to open and start the polymerization process. In an embodiment of the present invention, the free radical addition polymerization initiator is preferably a thermal initiator, and commonly used thermal initiators include azo thermal initiators, peroxide thermal initiators, and inorganic persulfate thermal initiators. The thermal initiator in the embodiment of the present invention is further preferably a peroxide initiator. Peroxide initiators can decompose under relatively mild conditions to produce highly active free radicals. This highly active free radical allows the polymerization reaction to be carried out at a lower initiator concentration, reduces the residual amount of the polymerization initiator in the polymer product, and is conducive to improving the quality of the polymer product. At the same time, in order for the electrolyte to quickly prevent thermal runaway diffusion, the higher initiation efficiency of the peroxide initiator can enable the polymerization reaction to start in a shorter time and reach a certain degree of polymerization. In some embodiments of the present invention, preferably, the peroxide initiator is one or more of cumene hydroperoxide, tert-butyl hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl perbenzoate.

[0025] By testing the conductivity of the electrolyte in the embodiment of the present invention, it is found that when the content of the polymerizable monomer additive in the electrolyte is too high, the electrolyte conductivity under normal working temperature environment will be less than 1×10 -4 S / cm, at this time, lithium ions cannot migrate normally in the electrolyte, which in turn causes the lithium-ion battery to be unable to charge and discharge normally and affects its normal use. When the content of the polymerizable monomer additive in the electrolyte is too low, it will be difficult to effectively suppress the spread of thermal runaway. Therefore, in an embodiment of the present invention, in order to ensure that the electrolyte is at a normal operating temperature, the conductivity of the electrolyte is at a good level to maintain the normal charge and discharge performance of the lithium-ion battery; and when the electrolyte is in a high temperature environment greater than 80°C, a polymerization reaction can occur rapidly in the electrolyte to reduce the conductivity, and by cutting off the internal electrochemical reaction of the lithium-ion battery, the thermal runaway of the lithium-ion battery in the module is prevented from continuing to heat up and spread. Preferably, the mass fraction of the polymerizable monomer additive in the electrolyte is 3%-8%.

[0026] In the electrolyte, too much polymerization initiator residue may react chemically with other components in the electrolyte, affecting the stability of the electrolyte and the performance of the battery, and may also cause the polymerization reaction rate to be too fast at high temperature, causing the temperature of the reaction system to rise sharply; while if the amount of polymerization initiator added is too little, when the electrolyte is in a high temperature environment, it may not be able to effectively initiate the polymerization reaction, or the polymerization reaction rate may be too slow, resulting in the electrolyte being unable to quickly prevent the thermal runaway of a single lithium-ion battery from continuing to spread to other lithium-ion batteries in the module. Therefore, in the embodiment of the present invention, preferably, the polymerization initiator is 0.1%-2% of the polymerizable monomer additive by weight.

[0027] The second aspect of the present invention also provides a lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte in the above embodiment. During the battery charging and discharging process, lithium ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet, the separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and the electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet.

[0028] The positive electrode plate of the lithium-ion battery provided in the embodiment of the present invention includes a positive electrode current collector and a positive electrode active material. The positive electrode current collector is usually made of a material with good conductivity and mechanical strength, which is not limited here. The positive electrode active material includes lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2, LCO), lithium nickel cobalt manganese oxide (LiNi x Co y Mn z O2(x+y+z=1)) or a combination of at least two thereof. In other embodiments, the positive electrode active material may also be other materials, which are not specifically limited herein.

[0029] The negative electrode plate of the lithium-ion battery includes a negative electrode current collector and a negative electrode active material. The negative electrode current collector can be made of a material with good conductivity and mechanical strength, which is not limited here. The negative electrode active material may include any one of artificial graphite, natural graphite, soft carbon, hard carbon, a mixture of graphite and silicon oxide, a mixture of graphite and silicon, or a combination of at least two of them. In an embodiment of the present invention, preferably, the positive electrode active material is LiNi 0.6 Co 0.2 Mn 0.2 O2, the negative electrode active material is graphite.

[0030] The isolation membrane may be any conventional type in the art, for example, a porous membrane of polyethylene (PE) with a thickness of 12 μm may be selected as the isolation membrane.

[0031] The technical scheme of the present invention is described in detail below through specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0032] The electrolyte compositions of different groups of embodiments and comparative examples are specifically referred to Table 1.

[0033] Example 1

[0034] The solvent in the electrolyte is composed of ethylene carbonate (EC), dimethyl carbonate (DMC) and diethyl carbonate (DEC), and the ratio of each solvent is EC:DMC:DEC=1:1:1. The selected lithium salt is lithium hexafluorophosphate (LiPF6), and the concentration of LiPF6 in the electrolyte is 1 mol / L. The selected polymerizable monomer additive is ethyl acrylate, and the mass fraction of ethyl acrylate in the electrolyte is 3%. The selected polymerization initiator is cumene hydroperoxide, and the polymerization initiator is 0.1% of the polymerizable monomer additive by weight. In addition to the lithium salt, the polymerizable monomer additive and the polymerization initiator, the rest of the electrolyte is the above-mentioned mixed solvent.

[0035] Example 2

[0036] The system is the same as that in Example 1, but the mass fraction of ethyl acrylate in the electrolyte is 8%, and the rest is the same as that in Example 1.

[0037] Example 3

[0038] The system is the same as that in Example 1, but the mass fraction of ethyl acrylate in the electrolyte is 5%, and the rest is the same as that in Example 1.

[0039] Example 4

[0040] The system is the same as that in Example 1, except that the polymerizable monomer additive is ethyl methacrylate, and the mass fraction of ethyl methacrylate in the electrolyte is 5%. The rest is the same as that in Example 1.

[0041] Comparative Example 1

[0042] The system is the same as that in Example 1, but the mass fraction of ethyl acrylate in the electrolyte is 10%, and the rest is the same as that in Example 1.

[0043] Comparative Example 2

[0044] The system is the same as that in Example 1, but the mass fraction of ethyl acrylate in the electrolyte is 1%, and the rest is the same as that in Example 1.

[0045] Table 1. Electrolyte compositions of different groups of examples and comparative examples

[0046]

[0047] The electrolytes of Examples 1 to 4 and Comparative Examples 1 to 2 were respectively used in the preparation of lithium ion batteries.

[0048] In the embodiment of the present invention, the electrochemical device is a lithium ion battery, and the lithium ion battery is a primary lithium ion battery or a secondary lithium ion battery, comprising: a positive electrode sheet, a negative electrode sheet, a separator between the positive electrode and the negative electrode, and an electrolyte. The preparation method of the secondary lithium ion battery in the embodiment of the present invention is as follows:

[0049] (1) Preparation of positive electrode sheet

[0050] The positive electrode active material (LiNi 0.6 Co 0.2 Mn 0.2 O2), conductive agent carbon black (Super-P) and carbon nanotubes (CNT), and binder polyvinylidene fluoride (PVDF) are added into N-methylpyrrolidone (NMP) solvent system in a mass ratio of 97:1:1:1 and fully stirred and mixed to obtain positive electrode slurry, and the positive electrode slurry is evenly coated on cathode current collector aluminum foil with a thickness of 15 μm, and then the aluminum foil is dried and cold pressed to obtain the positive electrode sheet.

[0051] (2) Preparation of negative electrode sheet

[0052] The negative electrode active material graphite, conductive agent carbon black (Super-P), dispersant sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber (SBR) are fully stirred and mixed in a deionized water solvent system in a mass ratio of 96:1:1.4:1.6 to obtain a negative electrode slurry, and the negative electrode slurry is evenly coated on an anode current collector copper foil with a thickness of 10 μm, and then the copper foil is dried and cold pressed to obtain a negative electrode sheet.

[0053] (3) Preparation of diaphragm

[0054] Polyethylene (PE) having a thickness of 12 μm was used as the separator.

[0055] (4) Preparation of electrolyte

[0056] First, the solvents are mixed and stirred, then the lithium salt is added to the mixed solvent under stirring conditions, and stirring is continued until the lithium salt is completely dissolved, and finally the additives and polymerization initiator are added to the solution and stirred evenly.

[0057] The types of solvents, lithium salts, additives, and polymerization initiators selected in the electrolytes of Examples 1-4 of the present invention and Comparative Examples 1-2 and the mass fractions based on the total weight of the electrolytes are all based on the settings in Table 1. The above components are mixed to obtain an electrolyte. The electrolytes in different embodiments and comparative examples are prepared in the same manner except that the component ratios are specified in the table.

[0058] (5) Preparation of secondary lithium-ion batteries

[0059] The negative electrode sheet, the separator, and the positive electrode sheet are stacked in order and packed into a packaging bag to obtain a dry battery cell. The electrolytes in Table 1 are respectively injected into the dry battery cells of different components, and after the processes of infiltration, formation, aging, capacity, etc., the finished lithium-ion battery is packaged.

[0060] The conductivity test was performed on the electrolytes of Examples 1-4 and Comparative Examples 1-2 that were not polymerized at room temperature and after being polymerized at high temperature. The capacity retention rate of the lithium-ion batteries assembled from the above-mentioned electrolytes that were not polymerized at room temperature was tested for 25°C 1C / 2C charge-discharge cycles. The test results are shown in Table 2. The test method is as follows:

[0061] (1) Capacity retention test of normal temperature cycle at 25°C

[0062] At 25°C, charge the battery at 1C constant current to 4.25V, then charge at 4.25V constant voltage until the current is less than 0.05C, leave it for 10 minutes, and then discharge it at 2C constant current to 2.5V. Test the discharge capacity of the battery at this time, which is the discharge capacity of the first cycle; the battery is cycled multiple times under the above conditions, and the capacity retention rate of the battery after 400 cycles is calculated. The capacity retention rate after the cycle is calculated according to the following formula:

[0063] Capacity retention rate (%) = (discharge capacity corresponding to 400 cycles / discharge capacity of the first cycle) × 100%.

[0064] (2) Conductivity test of unpolymerized electrolyte at 25°C:

[0065] Take out the electrolytes of different components that have not been heated and polymerized, use stainless steel as an inert electrode, immerse the calibrated electrode in the electrolyte to be tested, and use an electrochemical workstation to test the AC impedance. The conductivity = thickness / (impedance*area).

[0066] (3) Conductivity test of the polymer electrolyte after heating to 130°C and maintaining for 10 minutes:

[0067] The electrolytes of different components after high-temperature polymerization were taken out, stainless steel was used as an inert electrode, the calibrated electrodes were immersed in the electrolyte to be tested, and the AC impedance was tested using an electrochemical workstation. The conductivity = thickness / (impedance*area).

[0068] The test results are shown in Table 2.

[0069] Table 2. Lithium ion battery performance test results of Examples 1-4 and Comparative Examples 1-2

[0070]

[0071] Analyzing the above data, we can draw the following conclusions:

[0072] (1) By comparing Examples 1-3, it can be seen that when the mass fraction of the polymerizable monomer additive in the electrolyte is 3%-8%, as the mass fraction of the polymerizable monomer additive in the electrolyte gradually increases, the conductivity and capacity retention rate of the electrolyte gradually decrease, indicating that the addition of the polymerizable monomer additive will cause a certain deterioration in the charge and discharge performance and service life of the lithium-ion battery. However, the conductivity of the electrolyte before polymerization is still greater than 1×10 -4 S / cm, and the conductivity of the electrolyte after polymerization is less than 1×10 -6 S / cm, indicating that before the high-temperature polymerization of the above-mentioned components, the conductivity of the electrolyte can meet the normal charge and discharge performance of the lithium-ion battery; when the electrolyte undergoes polymerization reaction under high temperature environment, its conductivity decreases and it is unable to continue to maintain the electrochemical reaction inside the above electrolyte. At this time, the thermal runaway of a single lithium-ion battery is effectively prevented.

[0073] (2) By comparing Examples 1-3 with Comparative Example 1, it can be seen that when the mass fraction of the polymerizable monomer additive in the electrolyte is greater than 8%, the conductivity of the electrolyte before polymerization is less than 1×10 -4 S / cm, and in the capacity retention test, the lithium-ion battery showed poor cycle performance. The above shows that when the content of polymerizable monomer additives in the electrolyte is too high, it will change the physical properties of the electrolyte such as viscosity and dielectric constant, thereby interfering with the transmission of lithium ions and affecting the charge and discharge performance of the battery; at the same time, too much polymerizable monomer additives will also destroy the original component ratio in the electrolyte and affect the service life of the lithium-ion battery.

[0074] (3) By comparing Examples 1-3 with Comparative Example 2, it can be seen that when the mass fraction of the polymerizable monomer additive in the electrolyte is less than 3%, the conductivity of the electrolyte after polymerization will be greater than 1×10 -6 S / cm, indicating that when the polymerizable monomer additive in the electrolyte polymerizes due to abnormally high temperature in a single lithium-ion battery in the module, it is not enough to significantly reduce the conductivity of the electrolyte. This will lead to poor blocking effect on abnormal electrochemical reactions in the electrolyte.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that: include: Solvents; a lithium salt, dissolved in the solvent; additives, the additives comprising polymerizable monomer additives; and The polymerizable monomer additive is initiated and polymerized by the polymerization initiator at a temperature greater than 80° C., thereby reducing the conductivity of the electrolyte from S1 to S2, S1 ≥ 1×10 -4 S / cm, S2≤1×10 -6 S / cm.

2. The electrolyte according to claim 1, characterized in that The polymerizable monomer additive is an unsaturated ester additive.

3. The electrolyte according to claim 2, characterized in that The unsaturated ester additive is one or more of vinylene carbonate, acrylate, and methacrylate.

4. The electrolyte according to claim 3, characterized in that The mass fraction of the polymerizable monomer additive in the electrolyte is 3%-8%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The polymerization initiator is a thermal initiator.

6. The electrolyte according to claim 5, characterized in that The thermal initiator is a peroxide initiator.

7. The electrolyte according to claim 6, characterized in that The peroxide initiator is one or more of cumene hydroperoxide, tert-butyl hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, and tert-butyl perbenzoate.

8. The electrolyte according to claim 5, characterized in that The amount of the polymerization initiator added is 0.1% to 2% by weight of the polymerizable monomer additive.

9. The electrolyte according to claim 1, characterized in that The solvent includes a carbonate solvent, and the carbonate solvent is one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

10. The electrolyte according to claim 1, characterized in that The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), and lithium bis(oxalatoborate).

11. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte according to any one of claims 1 to 10.

12. The lithium ion battery according to claim 11, characterized in that The positive electrode plate comprises a positive electrode current collector and a positive electrode active material, wherein the positive electrode active material is lithium nickel cobalt manganese oxide; The negative electrode plate comprises a negative electrode current collector and a negative electrode active material, and the negative electrode active material is graphite.

Images