Electrolyte and lithium ion battery

Abstract

The invention provides an electrolyte and a lithium ion battery. The electrolyte comprises the following components in percentage by mass: 10-15% of lithium salt, 80-87% of an organic solvent and 0.1-5% of an additive, wherein the additives comprise a first additive and a second additive; the first additive is selected from any one or more of # imgabs 0 # and # imgabs 1 #; and the structural formula of the second additive is as follows: # imgabs2. The first additive disclosed by the invention can generate a passive film with a compact structure and a stable structure on a negative electrode at a relatively low voltage. The second additive can generate a sulfur-containing SEI film with high mechanical strength under a specific voltage, thereby contributing to reducing impedance. Through the synergistic effect of the first additive and the second additive, the stability of the SEI membrane is higher, and the impedance is lower, so that the lithium ion battery can simultaneously give consideration to higher high-temperature cycling stability and higher low-temperature cycling stability.

Description

Technical Field

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

[0002] Since the beginning of the 21st century, as the demand for fossil energy has increased year by year, the consumption of non-renewable resources has been greatly accelerated, and the development of renewable energy has become a topic of global discussion. In this context, new energy electric vehicles have entered the historical stage and gradually replaced the current fuel vehicles.

[0003] However, a major disadvantage of new energy electric vehicles is that they perform poorly in high temperature environments. Temperature has a great impact on the charge and discharge performance of the battery. The electrode / electrolyte interface is regarded as the heart of the battery. The electrochemical reaction of lithium batteries at the electrode / electrolyte interface is related to the ambient temperature. At high temperatures, the active substances in the electrolyte accelerate degradation, and the activity of the active substances decreases, making the concentration difference of the electrolyte larger and the polarization stronger, which ultimately leads to a decrease in the battery capacity. More importantly, high temperatures can damage the negative electrode, causing lithium precipitation and the risk of short circuiting the battery.

[0004] In response to the dilemma of lithium-ion batteries in high-temperature environments, relevant work results have been reported. For example, a Chinese patent application with patent application publication number CN115882066A proposes a high-temperature lithium-ion battery electrolyte and a lithium-ion battery using the electrolyte. It improves the additives in the electrolyte to reduce the oxidative decomposition of the solvent and related side reactions, but does not solve its conductive performance, making its performance at high temperatures extremely limited. Summary of the invention

[0005] The main purpose of the present invention is to provide an electrolyte and a lithium ion battery to solve the problem in the prior art that it is difficult to simultaneously take into account high high temperature cycle stability and high low temperature cycle stability.

[0006] In order to achieve the above object, according to one aspect of the present invention, an electrolyte is provided, which comprises, by mass percentage, 10-15% of a lithium salt, 80-87% of an organic solvent and 0.1-5% of an additive; wherein the additive comprises a first additive and a second additive;

[0007] The first additive is selected from Any one or more of; the structural formula of the second additive is as follows:

[0008]

[0009] Furthermore, the mass ratio of the first additive to the second additive is 0.1 to 2:1.

[0010] Furthermore, the first additive is combination of The mass ratio is 0.2 to 1:1.

[0011] Furthermore, the first additive is combination of The mass ratio is 0.2 to 1:1, preferably 0.3 to 1:1.

[0012] Furthermore, the above-mentioned additives also include a third additive, and the third additive is selected from any one or more of trimethyl borate, lithium difluorooxalatoborate, vinylene carbonate, vinyl sulfate and fluoroethylene carbonate.

[0013] Furthermore, the third additive is a mixture of vinylene carbonate and fluoroethylene carbonate, and the mass ratio of vinylene carbonate to fluoroethylene carbonate is 1:6 to 3:1.

[0014] Furthermore, the ratio of the total mass of the first additive and the second additive to the mass of the third additive is 1:3 to 1:1.

[0015] Furthermore, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).

[0016] Furthermore, the organic solvent is selected from any one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

[0017] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a positive electrode sheet, a separator, an electrolyte and a negative electrode sheet, wherein the electrolyte is the electrolyte described above.

[0018] Applying the technical solution of the present application, the first additive and the second additive are added to the electrolyte of the present application, wherein the first additive can generate a dense and stable passivation film on the negative electrode at a lower voltage. The second additive can generate a sulfur-containing SEI film with high mechanical strength at a specific voltage, thereby helping to reduce impedance. The present application can make the SEI film more stable and have lower impedance through the synergistic effect of the first additive and the second additive, thereby improving the transmission efficiency of lithium ions. Specifically, on the one hand, the sulfonamide group in the second additive may react with the carboxylate ion, the decomposition product of the first additive, to form an ester compound, which helps the stability and compactness of the SEI film. On the other hand, the sulfur element contained in the second additive may react with the decomposition product of the first additive to form a sulfide or thioester compound, which helps to reduce the impedance of the SEI film and improve its mechanical strength. In addition, the second additive also helps to reduce the decomposition of the fluorine-containing additive in the electrolyte and modify the interface, thereby reducing the occurrence of side reactions between the interface of the electrolyte and the positive electrode material and the dissolution of metals in the positive electrode material, thereby helping to improve the cycle stability performance of lithium-ion batteries at high and low temperatures.

[0019] Moreover, under low voltage, the additive of the present application can form a stable SEI film on the surface of the positive electrode material more quickly than ethylene carbonate and vinylene carbonate, which helps to improve the stability of the interface between the electrolyte and the positive electrode material, and the formed SEI film exhibits a lower impedance, thereby helping to further improve the cycle stability of the lithium-ion battery at high temperatures. Therefore, adding the first additive and the second additive to the electrolyte of the present application helps to improve the stability of the electrolyte and the stability of the formed SEI film, so that the lithium-ion battery can simultaneously take into account higher high-temperature cycle stability and higher low-temperature cycle stability. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0021] As analyzed in the background technology of the present application, lithium-ion batteries in the prior art have the problem of difficulty in achieving both high high-temperature cycle stability and high low-temperature cycle stability. In order to solve this problem, the present application provides an electrolyte and a lithium-ion battery.

[0022] In a typical embodiment of the present application, an electrolyte is provided, which comprises, by mass percentage, 10-15% of a lithium salt, 80-87% of an organic solvent, and 0.1-5% of an additive; wherein the additive comprises a first additive and a second additive; the first additive is selected from Any one or more of; the structural formula of the second additive is as follows:

[0023]

[0024] The first additive and the second additive are added to the electrolyte of the present application, wherein the first additive can generate a dense and stable passivation film on the negative electrode at a lower voltage. The second additive can generate a sulfur-containing SEI film with high mechanical strength at a specific voltage, thereby helping to reduce impedance. The present application can make the SEI film more stable and less resistant through the synergistic effect of the first additive and the second additive, thereby improving the transmission efficiency of lithium ions. Specifically, on the one hand, the sulfonamide group in the second additive may react with the carboxylate ion of the decomposition product of the first additive to form an ester compound, which helps the stability and compactness of the SEI film. On the other hand, the sulfur element contained in the second additive may react with the decomposition product of the first additive to form a sulfide or thioester compound, which helps to reduce the impedance of the SEI film and improve its mechanical strength. In addition, the second additive also helps to reduce the decomposition of the fluorine-containing additive in the electrolyte and modify the interface, thereby reducing the occurrence of side reactions between the interface of the electrolyte and the positive electrode material and the dissolution of metals in the positive electrode material, thereby helping to improve the cycle stability performance of lithium-ion batteries at high and low temperatures.

[0025] Moreover, under low voltage, the additive of the present application can form a stable SEI film on the surface of the positive electrode material more quickly than ethylene carbonate and vinylene carbonate, which helps to improve the stability of the interface between the electrolyte and the positive electrode material, and the formed SEI film exhibits a lower impedance, thereby helping to further improve the cycle stability of the lithium-ion battery at high temperatures. Therefore, adding the first additive and the second additive to the electrolyte of the present application helps to improve the stability of the electrolyte and the stability of the formed SEI film, so that the lithium-ion battery can simultaneously take into account higher high-temperature cycle stability and higher low-temperature cycle stability.

[0026] In addition, the present application provides a second additive The preparation method is as follows:

[0027] In one embodiment of the present application, the mass ratio of the first additive to the second additive is 0.1-2:1.

[0028] It is preferred to control the mass ratio of the first additive to the second additive within the above range, which helps to fully exert the synergistic effect between the first additive and the second additive, thereby helping to improve the stability of the electrolyte at high temperature and the stability of the SEI film formed on the surface of the positive electrode material.

[0029] In addition, the mass ratio of the first additive to the second additive can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1. Of course, the mass ratio of the first additive to the second additive can be any point value within the range of 0.1 to 2:1. Preferably, the mass ratio of the first additive to the second additive can be any point value within the range of 0.5 to 2:1. Further, preferably, the mass ratio of the first additive to the second additive can be any point value within the range of 1 to 2:1, which will not be repeated here.

[0030] In one embodiment of the present application, the first additive is combination of The mass ratio is 0.2 to 1:1.

[0031] It is preferred to control the type of the first additive within the above range and control The mass ratio of is within the above range helps to form a denser and more uniform SEI film, thereby helping to further improve the stability of the electrolyte at high temperature and the stability of the formed SEI film.

[0032] also, The mass ratio can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1. Of course, The mass ratio can be any point value within the range of 0.2 to 1:1, preferably The mass ratio of can be any point value within the range of 0.5 to 1:1. Furthermore, it is preferred that The mass ratio can be any point value within the range of 0.8 to 1:1, which will not be described here.

[0033] In one embodiment of the present application, the first additive is and The mass ratio is 0.2 to 1:1, preferably 0.3 to 1:1.

[0034] It is preferred to control the type of the first additive within the above range and control The mass ratio of is within the above range, which helps the formation of the positive electrode CEI film and inhibits the dissolution of transition metals, thereby helping to further improve the stability of the electrolyte at high temperature and the stability of the formed SEI and CEI films.

[0035] also, The mass ratio can be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1. Of course, The mass ratio can be any point value within the range of 0.2 to 1:1, preferably The mass ratio of can be any point value within the range of 0.3 to 1:1. Furthermore, it is preferred that The mass ratio can be any point value within the range of 0.5 to 1:1, which will not be described in detail here.

[0036] In one embodiment of the present application, the above-mentioned additive also includes a third additive, and the third additive is selected from any one or more of trimethyl borate, lithium difluorooxalatoborate, vinylene carbonate, vinyl sulfate and fluoroethylene carbonate; preferably, the third additive is vinylene carbonate and fluoroethylene carbonate, and the mass ratio of vinylene carbonate to fluoroethylene carbonate is 1:6 to 3:1.

[0037] Adding a third additive to the additives, preferably controlling the type of the third additive within the above range, and preferably controlling the mass ratio of vinylene carbonate to fluoroethylene carbonate within the above range, helps to further improve the stability of the electrolyte at high temperatures.

[0038] In addition, the mass ratio of vinylene carbonate to fluoroethylene carbonate can be 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 3:2, 2:1, 5:2 or 3:1. Of course, the mass ratio of vinylene carbonate to fluoroethylene carbonate can be any point value within the range of 1:6 to 3:1. Preferably, the mass ratio of vinylene carbonate to fluoroethylene carbonate can be any point value within the range of 1:6 to 1:1. Further, preferably, the mass ratio of vinylene carbonate to fluoroethylene carbonate can be any point value within the range of 1:6 to 1:2, which will not be repeated here.

[0039] In one embodiment of the present application, the ratio of the total mass of the first additive and the second additive to the mass of the third additive is 1:3 to 1:1.

[0040] It is preferred to control the ratio of the total mass of the first additive and the second additive to the mass of the third additive within the above range, which helps to improve the synergistic coordination between the three, produce a good interface film at the positive and negative electrodes, and promote the long cycle of the battery, thereby helping to further improve the stability of the electrolyte at high temperature and the stability of the formed SEI film.

[0041] In addition, the ratio of the total mass of the first additive and the second additive to the mass of the third additive can be 1:3, 1:2.5, 1:2, 1:1.5 or 1:1. Of course, the ratio of the total mass of the first additive and the second additive to the mass of the third additive can be any point value within the range of 1:3 to 1:1. Preferably, the ratio of the total mass of the first additive and the second additive to the mass of the third additive can be any point value within the range of 1:2 to 1:1. Further, preferably, the ratio of the total mass of the first additive and the second additive to the mass of the third additive can be any point value within the range of 1:1.5 to 1:1, which will not be repeated here.

[0042] In order to further improve the lithium ion conductivity in the electrolyte, in one embodiment of the present application, the above-mentioned lithium salt is preferably selected from any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).

[0043] In order to further improve the solubility of lithium salt in the electrolyte and the stability of the electrolyte, in one embodiment of the present application, the organic solvent is preferably selected from any one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

[0044] In addition, the preparation method of the electrolyte of the present application includes: under an inert atmosphere, under the condition that the water content is less than 5 ppm and the oxygen content is less than 5 ppm, weighing a certain amount of organic solvent and lithium salt, and then adding additives and stirring until they are completely dissolved.

[0045] In another typical embodiment of the present application, a lithium-ion battery is provided, comprising a positive electrode sheet, a separator, an electrolyte and a negative electrode sheet, wherein the electrolyte is the aforementioned electrolyte.

[0046] Since the lithium-ion battery contains the electrolyte of the present application, the lithium-ion battery can have both high high-temperature cycle stability and high low-temperature cycle stability.

[0047] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0048] Example 1

[0049] In an inert atmosphere glove box with a water content and an oxygen content both lower than 5 ppm, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were prepared into an organic solvent in a mass ratio of 30:60:10, lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide (3:1) were slowly added to the prepared organic solvent until dissolved, and then 4% additives of the total mass of the electrolyte were added, namely, vinylene carbonate (VC), the first additive Second additive (B&K Technology Co., Ltd.), among which, The mass ratio of the first additive to the second additive is 1:1, and the mass ratio of the first additive to the second additive is 1:1. After being fully stirred, the additive is completely dissolved to obtain a lithium-ion battery electrolyte. Lithium salt (lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide), organic solvent, vinyl carbonate (VC), Second additive The mass fractions are 12%, 84%, 2%, 0.5%, 0.5% and 1% respectively.

[0050] Preparation of cathode materials

[0051] Mix 92% NCM811, 3% conductive agent SP, 2% single-walled carbon nanotubes, and 3% binder PVDF in a mass ratio, add solvent N-methylpyrrolidone and stir to form a uniform slurry, apply it on a 12-micron thick aluminum foil, roll and cut it to obtain the positive electrode material

[0052] Preparation of negative electrode materials

[0053] 85% silicon carbon, 10% single-walled carbon nanotubes and 5% binder SBR in a mass ratio were mixed evenly, and deionized water was added as a solvent. The slurry was then coated on an 8-micron copper foil, dried, rolled and cut to obtain a negative electrode material.

[0054] Preparation of batteries

[0055] In a dry environment with a dew point controlled below -60°C, the positive electrode sheet, separator, and negative electrode sheet are stacked in order to ensure that the separator completely separates the positive electrode sheet from the negative electrode sheet, and the negative electrode completely covers the positive electrode. The battery cells are made by stacking the sheets, and then packaged in an aluminum-plastic film with glue ears after hot pressing. After baking until the moisture content is qualified, the prepared electrolyte is injected into the soft-pack battery cell, followed by sealing, formation, secondary sealing aging, and capacity separation to obtain a lithium-ion battery for testing.

[0056] Example 2

[0057] The difference from Example 1 is that the mass ratio of the first additive to the second additive is 0.1:1, and a lithium ion battery is finally obtained.

[0058] Example 3

[0059] The difference from Example 1 is that the mass ratio of the first additive to the second additive is 1:0.4, and a lithium ion battery is finally obtained.

[0060] Example 4

[0061] The difference from Example 1 is that The mass ratio is 0.2:1, and a lithium-ion battery is finally obtained.

[0062] Example 5

[0063] The difference from Example 1 is that The mass ratio is 0.1:1, and a lithium-ion battery is finally obtained.

[0064] Example 6

[0065] The difference from Example 1 is that combination of The mass ratio of is 1:1, and finally a lithium-ion battery is obtained.

[0066] Example 7

[0067] The difference from Example 6 is that The mass ratio of is 0.3:1, and finally a lithium-ion battery is obtained.

[0068] Example 8

[0069] The difference from Example 6 is that The mass ratio is 0.2:1, and a lithium-ion battery is finally obtained.

[0070] Example 9

[0071] The difference from Example 1 is that vinylene carbonate (VC), Second additive The mass fractions of are 3%, 0.25%, 0.25% and 0.5% of the total mass of the electrolyte respectively, and finally a lithium-ion battery is obtained.

[0072] Example 10

[0073] The difference from Example 1 is that vinylene carbonate (VC), Second additive The mass fractions of are 3.2%, 0.2%, 0.2% and 0.4% of the total mass of the electrolyte respectively, and finally a lithium-ion battery is obtained.

[0074] Embodiment 11

[0075] The difference from the embodiment is that the mass fraction of the third additive is 2% of the total mass of the electrolyte, the third additive is a mixture of vinylene carbonate and fluoroethylene carbonate, and the mass ratio of the two is 1:1, and a lithium ion battery is finally obtained.

[0076] Example 12

[0077] The difference from the embodiment is that the mass fraction of the third additive is 2% of the total mass of the electrolyte, the third additive is a mixture of vinylene carbonate and fluoroethylene carbonate, and the mass ratio of the two is 1:6, and a lithium ion battery is finally obtained.

[0078] Example 13

[0079] The difference from the embodiment is that the mass fraction of the third additive is 2% of the total mass of the electrolyte, the third additive is a mixture of vinylene carbonate and fluoroethylene carbonate, and the mass ratio of the two is 3:1, and a lithium ion battery is finally obtained.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the additive is the first additive (the mass ratio of the two is 1:1), vinylene carbonate (VC), wherein the first additive is 2% of the total mass of the electrolyte, vinylene carbonate (VC) is 2% of the total mass of the electrolyte, and the contents of the remaining components are the same as in Example 1, and finally a lithium ion battery is obtained.

[0082] Comparative Example 2

[0083] The difference from Example 1 is that the additive is the second additive and vinylene carbonate (VC), wherein the second additive is 2% of the total mass of the electrolyte, vinylene carbonate (VC) is 2% of the total mass of the electrolyte, and the contents of the remaining components are the same as in Example 1, and finally a lithium ion battery is obtained.

[0084] The lithium-ion batteries in the above examples and comparative examples were subjected to high temperature cycling (55°C), high temperature discharge (55°C), high temperature storage (55°C@14 days) and low temperature discharge (-20°C) tests. The results are shown in the following table.

[0085] Table 1

[0086]

[0087]

[0088] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0089] The first additive and the second additive are added to the electrolyte of the present application, wherein the first additive can generate a dense and stable passivation film on the negative electrode at a lower voltage. The second additive can generate a sulfur-containing SEI film with high mechanical strength at a specific voltage, thereby helping to reduce impedance. The present application can make the SEI film more stable and less resistant through the synergistic effect of the first additive and the second additive, thereby improving the transmission efficiency of lithium ions. Specifically, on the one hand, the sulfonamide group in the second additive may react with the carboxylate ion of the decomposition product of the first additive to form an ester compound, which helps the stability and compactness of the SEI film. On the other hand, the sulfur element contained in the second additive may react with the decomposition product of the first additive to form a sulfide or thioester compound, which helps to reduce the impedance of the SEI film and improve its mechanical strength. In addition, the second additive also helps to reduce the decomposition of the fluorine-containing additive in the electrolyte and modify the interface, thereby reducing the occurrence of side reactions between the interface of the electrolyte and the positive electrode material and the dissolution of metals in the positive electrode material, thereby helping to improve the cycle stability performance of lithium-ion batteries at high and low temperatures.

[0090] Moreover, under low voltage, the additive of the present application can form a stable SEI film on the surface of the positive electrode material more quickly than ethylene carbonate and vinylene carbonate, which helps to improve the stability of the interface between the electrolyte and the positive electrode material, and the formed SEI film exhibits a lower impedance, thereby helping to further improve the cycle stability of the lithium-ion battery at high temperatures. Therefore, adding the first additive and the second additive to the electrolyte of the present application helps to improve the stability of the electrolyte and the stability of the formed SEI film, so that the lithium-ion battery can simultaneously take into account higher high-temperature cycle stability and higher low-temperature cycle stability.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that: In terms of mass percentage, the electrolyte includes 10-15% of lithium salt, 80-87% of organic solvent and 0.1-5% of additives; Wherein, the additive comprises a first additive and a second additive; The first additive is selected from Any one or more of the following; The structural formula of the second additive is as follows:

2. The electrolyte according to claim 1, characterized in that The mass ratio of the first additive to the second additive is 0.1 to 2:

1.

3. The electrolyte according to claim 1 or 2, characterized in that The first additive is combination, and the and stated The mass ratio is 0.2 to 1:

1.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The first additive is combination, and the and stated The mass ratio is 0.2 to 1:1, preferably 0.3 to 1:

1.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The additives further include a third additive, and the third additive is selected from any one or more of trimethyl borate, lithium difluorooxalatoborate, vinylene carbonate, vinyl sulfate and fluoroethylene carbonate.

6. The electrolyte according to claim 5, characterized in that The third additive is a mixture of the vinylene carbonate and the fluoroethylene carbonate, and the mass ratio of the vinylene carbonate to the fluoroethylene carbonate is 1:6 to 3:

1.

7. The electrolyte according to claim 6, characterized in that The ratio of the total mass of the first additive and the second additive to the mass of the third additive is 1:3 to 1:

1.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide) and lithium bis(fluorosulfonyl imide).

9. The electrolyte according to any one of claims 1 to 8, characterized in that The organic solvent is selected from any one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dimethyl ether, diethyl ether, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate and ethyl butyrate.

10. A lithium ion battery comprising a positive electrode sheet, a separator, an electrolyte and a negative electrode sheet, characterized in that: The electrolyte is the electrolyte according to any one of claims 1 to 9.

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