Electrolyte additive, electrolyte and battery

Abstract

The invention provides an electrolyte additive, an electrolyte and a battery. The electrolyte additive comprises an indolyl group, a carbonyl group, a fluorine atom, a siloxane group and a boron atom. Therefore, the silicon particles can be combined with the silicon particles to form a stable structure, a stable SEI film is formed, decomposition of an electrolyte is reduced, electronic conductivity is improved, and side reaction of the electrolyte is reduced, so that expansion of the silicon-carbon negative electrode is effectively inhibited, and the problems of low initial efficiency and poor cycle performance and high-temperature storage performance of the silicon-carbon negative electrode are solved; the cycle performance and the high-temperature storage performance of the battery are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to an electrolyte additive, an electrolyte and a battery. Background Art

[0002] Lithium-ion batteries are one of the main energy storage technologies in the field of new energy due to their high energy density, portability, strong designability and high safety. At present, the positive electrode of lithium-ion batteries is mainly composed of lithium iron phosphate and ternary materials (nickel, cobalt, manganese and aluminum), and the negative electrode is mainly composed of carbon materials (graphite, soft carbon and hard carbon, etc.). Silicon negative electrodes have a high theoretical specific capacity. After replacing traditional carbon material negative electrodes, it is expected to improve the mass and volume energy density of lithium-ion batteries.

[0003] Although the theoretical specific capacity (3579mAh / g) of silicon in the negative electrode of lithium-ion batteries is relatively high, however, silicon undergoes significant volume changes during the lithium insertion / delithiation process, which can cause cracking and pulverization of silicon particles, affecting the cycle life of the battery. In order to solve the problem of severe volume expansion of silicon, the prior art forms a silicon-carbon composite material, and utilizes the good conductivity and cycle stability of carbon materials as the substrate of silicon materials. For example, CN106935834A discloses a porous silicon negative electrode material coated with a composite carbon layer and a preparation method thereof, which is based on dealloyed porous silicon, and is coated with a composite carbon layer of graphene combined with high-density carbon or low-density carbon combined with high-density carbon, thereby achieving the first coating of loose carbon and the overall coating of external high-density carbon. The internal low-density carbon layer can improve the internal conductivity of the entire micron structure, and the external high-density carbon can well prevent the electrolyte from passing through the carbon layer into the interior of the micron particles. However, it is difficult to evenly disperse silicon particles in the carbon material. Therefore, the silicon-carbon negative electrode still has low kinetics and large volume expansion, which can cause the particles to pulverize and form inert lithium, making the silicon-carbon negative electrode difficult to apply.

[0004] Based on the above research, it is necessary to provide an electrolyte additive, which can inhibit the expansion and crushing of the silicon-carbon negative electrode during the charge and discharge process, and improve the initial effect and cycle stability of the silicon-carbon negative electrode. Summary of the invention

[0005] The object of the present invention is to provide an electrolyte additive, an electrolyte and a battery, and in particular to an electrolyte additive, an electrolyte and a battery matching a silicon-carbon negative electrode. The electrolyte additive adopts an electrolyte additive containing a specific group, which can combine with silicon particles to form a stable structure, form a stable SEI film, reduce the decomposition of the electrolyte, improve the electronic conductivity and reduce the occurrence of electrolyte side reactions, thereby effectively inhibiting the expansion of the silicon-carbon negative electrode, solving the problems of low initial efficiency, poor cycle performance and high-temperature storage performance of the silicon-carbon negative electrode, and improving the cycle performance and high-temperature storage performance of the battery.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an electrolyte additive, the structural formula of the electrolyte additive is shown in Formula 1):

[0008]

[0009] Wherein, R1 is independently selected from substituted or unsubstituted alkyl, R2 is selected from hydrogen, substituted or unsubstituted alkyl, R3 is selected from substituted or unsubstituted alkyl, and R4 is independently selected from substituted or unsubstituted alkyl.

[0010] The present invention adopts a specific electrolyte additive, which can specifically solve the problems of low initial efficiency, poor cycle and high-temperature storage of silicon-carbon negative electrodes, improve the mechanical stability, conductivity and cycle stability of silicon-carbon materials, reduce the decomposition of electrolytes, reduce the occurrence of side reactions in electrolytes, etc. The specific reasons are as follows: (1) The indole group in the electrolyte additive can be combined with silicon particles through chemical bonding to form a stable structure, thereby effectively alleviating the volume expansion problem of silicon particles during charging and discharging, enhancing the mechanical stability of silicon-carbon materials, and improving the conductivity and cycle stability of silicon-carbon materials.

[0011] (2) The presence of carbonyl groups in the electrolyte additives can cause a polymerization reaction on the surface of the silicon-carbon negative electrode to form a polycarbonate polymer film, thereby preventing direct contact between the electrolyte and the negative electrode and reducing the decomposition of the electrolyte.

[0012] (3) Due to the strong electron-withdrawing property of F and the presence of fluorine atoms in the electrolyte additive, an electrolyte interface film (SEI film) rich in inorganic substances such as LiF will be formed during the charge and discharge process of the battery. The formed SEI film has high mechanical strength and stability, which can inhibit the volume expansion of the silicon-carbon negative electrode during the charge and discharge process from damaging the SEI structure.

[0013] (4) The presence of siloxane in the electrolyte additive can increase the electronic conductivity of the silicon-carbon negative electrode material and reduce the resistance, thereby improving the charge and discharge rate and efficiency of the battery.

[0014] (5) The presence of B atoms in the electrolyte additive can form a stable borate film on the surface of the silicon-carbon negative electrode. The film has good flexibility and mechanical strength and can adapt to the volume change of the silicon-carbon negative electrode during the charging and discharging process, thereby maintaining the integrity of the SEI film. In addition, borates can also inhibit the decomposition of the electrolyte on the negative electrode surface and reduce the occurrence of side reactions.

[0015] In the present invention, R1 is independently selected from substituted or unsubstituted alkyl, for example, substituted or unsubstituted methyl, ethyl or isopropyl; R2 is selected from hydrogen, substituted or unsubstituted alkyl, for example, hydrogen, substituted or unsubstituted methyl, ethyl or isopropyl; R3 is selected from substituted or unsubstituted alkyl, for example, substituted or unsubstituted methyl, ethyl or isopropyl; R4 is independently selected from substituted or unsubstituted alkyl, for example, substituted or unsubstituted methyl, ethyl or isopropyl; among R1, R2, R3 and R4, in the substituted alkyl, the substituent may be halogen, etc.

[0016] Preferably, the electrolyte additive is:

[0017]

[0018] (CAS No.: 2334416-95-2).

[0019] In a second aspect, the present invention provides an electrolyte comprising a non-aqueous organic solvent, a lithium salt, a film-forming additive, and the electrolyte additive as described in the first aspect.

[0020] Preferably, in the electrolyte, the content of the electrolyte additive in the first aspect is 4wt%-10wt%, for example, it can be 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] The content of the electrolyte additive in the electrolyte of the present invention will affect its performance. The content of the electrolyte additive is preferably 4wt%-10wt% in the present invention, which can ensure that the performance is normal without deteriorating the battery performance and ensure the comprehensive performance of the battery.

[0022] Preferably, in the electrolyte, the content of the film-forming additive is 2wt%-6wt%, for example, it can be 2wt%, 3wt%, 4wt%, 5wt% or 6wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] A specific content of a film-forming additive is also added to the electrolyte of the present invention. The specific content of the film-forming additive cooperates with the electrolyte additive to further improve the performance of the battery.

[0024] Preferably, the film-forming additive comprises vinylene carbonate.

[0025] Preferably, the lithium salt includes any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide or lithium bis(trifluorosulfonyl)imide, or a combination of at least two thereof.

[0026] Preferably, in the electrolyte, the content of the lithium salt is 10wt%-15wt%, for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the non-aqueous organic solvent includes any one of ethylene carbonate, ethyl methyl carbonate, propylene carbonate or fluoroethylene carbonate, or a combination of at least two thereof.

[0028] Preferably, in the non-aqueous organic solvent, the mass ratio of ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate is (25-35):(50-60):(2-10):(5-15), for example, it can be 25:60:10:5, 30:55:5:15, 35:50:2:8 or 30:57:5:8, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] In a third aspect, the present invention provides a lithium ion battery, wherein the lithium ion battery comprises the electrolyte additive as described in the first aspect, or the electrolyte as described in the second aspect.

[0030] Preferably, the lithium-ion battery further comprises a positive electrode sheet, a negative electrode sheet and a separator.

[0031] Preferably, the negative electrode sheet comprises a silicon-carbon negative electrode material.

[0032] The electrolyte additive and electrolyte matching silicon-carbon negative electrode of the present invention are aimed at solving the problem that the silicon-carbon negative electrode is easy to expand.

[0033] Preferably, the positive electrode sheet comprises lithium iron manganese phosphate and / or a ternary positive electrode material.

[0034] Preferably, the separator comprises a PE separator.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The electrolyte additive provided by the present invention is an electrolyte additive that matches the silicon-carbon negative electrode. Specifically, by adopting a substance containing a specific group, it can combine with silicon particles to form a stable structure, form a stable SEI film, reduce the decomposition of the electrolyte, improve the electronic conductivity, and reduce the occurrence of electrolyte side reactions, thereby effectively inhibiting the expansion of the silicon-carbon negative electrode, solving the problems of low initial efficiency, poor cycle performance and high-temperature storage performance of the silicon-carbon negative electrode, and improving the cycle performance and high-temperature storage performance of the battery. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] The structural formula of compound A described in Examples 1-14 is as follows:

[0039]

[0040] Example 1

[0041] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0042] This embodiment also provides an electrolyte, the electrolyte comprising 5wt% of an electrolyte additive, 4wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0043] The preparation method of the electrolyte comprises the following steps:

[0044] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0045] Example 2

[0046] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0047] This embodiment also provides an electrolyte, the electrolyte comprising 7wt% of an electrolyte additive, 4wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, the non-aqueous solvent comprising vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0048] The preparation method of the electrolyte comprises the following steps:

[0049] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0050] Example 3

[0051] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0052] This embodiment also provides an electrolyte, the electrolyte comprising 9wt% of an electrolyte additive, 4wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0053] The preparation method of the electrolyte comprises the following steps:

[0054] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0055] Example 4

[0056] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0057] This embodiment also provides an electrolyte, the electrolyte comprising 7wt% of an electrolyte additive, 2wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0058] The preparation method of the electrolyte comprises the following steps:

[0059] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0060] Example 5

[0061] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0062] This embodiment also provides an electrolyte, the electrolyte comprising 7wt% of an electrolyte additive, 6wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, the non-aqueous solvent comprising vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0063] The preparation method of the electrolyte comprises the following steps:

[0064] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0065] Example 6

[0066] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0067] This embodiment also provides an electrolyte, the electrolyte comprising 5wt% of an electrolyte additive, 2wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate, and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate, and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0068] The preparation method of the electrolyte comprises the following steps:

[0069] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0070] Example 7

[0071] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0072] This embodiment also provides an electrolyte, the electrolyte comprising 9wt% of an electrolyte additive, 2wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate, and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate, and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0073] The preparation method of the electrolyte comprises the following steps:

[0074] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0075] Example 8

[0076] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0077] This embodiment also provides an electrolyte, the electrolyte comprising 5wt% of an electrolyte additive, 6wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0078] The preparation method of the electrolyte comprises the following steps:

[0079] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0080] Example 9

[0081] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0082] This embodiment also provides an electrolyte, the electrolyte comprising 9wt% of an electrolyte additive, 6wt% of vinylene carbonate, 12.5wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, wherein the non-aqueous solvent comprises vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 30:57:5:8;

[0083] The preparation method of the electrolyte comprises the following steps:

[0084] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0085] Example 10

[0086] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0087] This embodiment also provides an electrolyte, the electrolyte comprising 4wt% of an electrolyte additive, 4wt% of vinylene carbonate, 15wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, the non-aqueous solvent comprising vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 35:50:10:5;

[0088] The preparation method of the electrolyte comprises the following steps:

[0089] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0090] Embodiment 11

[0091] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0092] This embodiment also provides an electrolyte, the electrolyte comprising 10wt% of an electrolyte additive, 4wt% of vinylene carbonate, 10wt% of lithium hexafluorophosphate and the remainder of a non-aqueous solvent, the non-aqueous solvent comprising vinyl carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate in a mass ratio of 25:60:2:15;

[0093] The preparation method of the electrolyte comprises the following steps:

[0094] In a glove box filled with argon, ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate are first mixed according to the formula, then lithium hexafluorophosphate is added, then vinylene carbonate is added, and finally compound A is added, and the electrolyte is obtained after stirring evenly.

[0095] Example 12

[0096] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0097] This embodiment also provides an electrolyte, which is the same as that of Embodiment 1 except that the content of the electrolyte additive is 2wt% and the content of the non-aqueous solvent is adaptively changed;

[0098] The preparation method of the electrolyte is the same as that of Example 1 except that the components are adaptively changed according to the formula amount.

[0099] Embodiment 13

[0100] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0101] This embodiment also provides an electrolyte, which is the same as that of Embodiment 1 except that the content of the electrolyte additive is 12wt% and the content of the non-aqueous solvent is adaptively changed;

[0102] The preparation method of the electrolyte is the same as that of Example 1 except that the components are adaptively changed according to the formula amount.

[0103] Embodiment 14

[0104] This embodiment provides an electrolyte additive, wherein the electrolyte additive is compound A;

[0105] This embodiment also provides an electrolyte, which is the same as that of embodiment 1 except that the content of the electrolyte additive is 7wt% and vinylene carbonate is not contained, and the content of the non-aqueous solvent is adaptively changed;

[0106] The preparation method of the electrolyte is the same as that of Example 1 except that the components are adaptively changed according to the formula amount.

[0107] Comparative Example 1

[0108] This comparative example provides an electrolyte, which is the same as Example 1 except that the electrolyte does not contain electrolyte additives and the content of the non-aqueous solvent is adaptively changed;

[0109] The preparation method of the electrolyte is the same as that of Example 1 except that the components are adaptively changed according to the formula amount.

[0110] The electrolytes of the above embodiments and comparative examples are injected with LiMn 0.5 Fe 0.5 PO4-silicon-carbon system lithium-ion battery, and then electrochemical testing is carried out. The testing process includes:

[0111] (1) Test of storage at 60℃ for 30 days: The battery was charged to 4.5V at 1.0C constant current and constant voltage at 25℃, left to stand for 5 minutes, and then discharged to 2.5V at 0.1C. The discharged capacity was recorded as the initial capacity. The battery was then charged to 4.5V at 1.0C constant current and constant voltage, and the initial thickness was measured. The battery was stored at 60℃±2℃ for 30 days in an open circuit. The battery was removed and the hot thickness was tested. The battery was then charged and discharged at 1.0C to test the remaining capacity and recovery capacity. The thermal thickness change rate, capacity retention rate, and capacity recovery rate were calculated.

[0112] (2) 25°C, 1C charge-discharge cycle test: Charge and discharge at 1C at 25°C with a voltage range of 2.5-4.5V, and calculate the capacity retention rate.

[0113] The test results are shown in Table 1 below:

[0114] Table 1

[0115]

[0116]

[0117] From Table 1 we can see that:

[0118] It can be seen from Examples 1-11 and Comparative Example 1 that the addition of the electrolyte additive of the present invention can improve the high temperature storage performance and cycle performance of the battery, indicating that the electrolyte additive can specifically solve the problems of easy expansion and poor high temperature storage of the silicon-carbon negative electrode during the cycle; it can be seen from Examples 1-9 and Examples 12-13 that the content of the electrolyte additive of the present invention is preferably in the range of 4-10wt%, and more preferably 7wt%; it can be seen from Examples 1, 6, 8 and 14 that the electrolyte of the present invention preferably also contains a film-forming additive, and the content of the film-forming additive is preferably 2-6wt%, and more preferably 4wt%.

[0119] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. An electrolyte additive, characterized in that: The structural formula of the electrolyte additive is shown in Formula 1): Wherein, R1 is independently selected from substituted or unsubstituted alkyl, R2 is selected from hydrogen, substituted or unsubstituted alkyl, R3 is selected from substituted or unsubstituted alkyl, and R4 is independently selected from substituted or unsubstituted alkyl.

2. The electrolyte additive according to claim 1, characterized in that: The electrolyte additive is 3. An electrolyte, characterized in that: The electrolyte comprises a non-aqueous organic solvent, a lithium salt, a film-forming additive and the electrolyte additive according to claim 1 or 2.

4. The electrolyte according to claim 3, characterized in that In the electrolyte, the content of the electrolyte additive as claimed in claim 1 or 2 is 4wt%-10wt%.

5. The electrolyte according to claim 3 or 4, characterized in that In the electrolyte, the content of the film-forming additive is 2wt%-6wt%; Preferably, the film-forming additive comprises vinylene carbonate.

6. The electrolyte according to any one of claims 3 to 5, characterized in that: The lithium salt includes any one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide or lithium bis(trifluorosulfonyl)imide, or a combination of at least two thereof; Preferably, in the electrolyte, the content of the lithium salt is 10wt%-15wt%.

7. The electrolyte according to any one of claims 3 to 6, characterized in that: The non-aqueous organic solvent includes any one of ethylene carbonate, ethyl methyl carbonate, propylene carbonate or fluoroethylene carbonate, or a combination of at least two thereof; Preferably, in the non-aqueous organic solvent, the mass ratio of ethylene carbonate, ethyl methyl carbonate, propylene carbonate and fluoroethylene carbonate is (25-35):(50-60):(2-10):(5-15).

8. A lithium ion battery, characterized in that: The lithium-ion battery comprises the electrolyte additive according to claim 1 or 2, or the electrolyte according to any one of claims 3-7.

9. The lithium-ion battery according to claim 8, characterized in that: The lithium-ion battery further comprises a positive electrode sheet, a negative electrode sheet and a separator.

10. The lithium ion battery according to claim 8 or 9, characterized in that: The negative electrode sheet includes a silicon-carbon negative electrode material; Preferably, the positive electrode sheet comprises lithium iron manganese phosphate and / or a ternary positive electrode material; Preferably, the separator comprises a PE separator.

Images