Electrolyte additive, electrolyte and battery

Abstract

The application provides an electrolyte additive, an electrolyte and a battery, wherein the electrolyte additive comprises an indole group, a carbonyl group, a fluorine atom, a siloxane group and a boron atom, so that the electrolyte additive can combine with silicon particles to form a stable structure, form a stable SEI film, reduce decomposition of the electrolyte, improve electronic conductivity and reduce occurrence of electrolyte side reactions, thereby effectively inhibiting expansion of a silicon-carbon negative electrode, solving problems of low initial efficiency, poor cycle performance and poor high-temperature storage performance of the silicon-carbon negative electrode, and improving cycle performance and high-temperature storage performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to an electrolyte additive, an electrolyte, and a battery. Background Technology

[0002] Lithium-ion batteries are one of the main energy storage technologies in the new energy field due to their high energy density, portability, high design flexibility, and high safety. Currently, the positive electrode of lithium-ion batteries is mainly composed of lithium iron phosphate and ternary materials (nickel, cobalt, manganese, and aluminum), while 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 and, by replacing traditional carbon material negative electrodes, are expected to improve the mass and volumetric energy density of lithium-ion batteries.

[0003] Although silicon has a high theoretical specific capacity (3579 mAh / g) in lithium-ion battery anodes, it undergoes significant volume changes during lithium insertion / extraction, leading to silicon particle cracking and pulverization, thus affecting the battery's cycle life. To address the problem of severe silicon volume expansion, existing technologies utilize silicon-carbon composite materials, taking advantage of the excellent conductivity and cycle stability of carbon materials as a substrate for silicon. For example, CN106935834A discloses a porous silicon anode material with a composite carbon layer and its preparation method. Based on dealloyed porous silicon, a composite carbon layer is formed by combining graphene with high-density carbon or low-density carbon with high-density carbon. This achieves the initial coating of loose carbon and the overall coating of high-density carbon on the outside. The internal low-density carbon layer can improve the internal conductivity of the entire micron structure, while the external high-density carbon can effectively prevent the electrolyte from penetrating the carbon layer and entering the interior of the micron particles. However, it is difficult to achieve uniform dispersion of silicon particles in carbon materials. Therefore, silicon-carbon anodes still suffer from low kinetics and large volume expansion, leading to particle pulverization and the formation of inert lithium, making silicon-carbon anodes difficult to apply.

[0004] Based on the above research, there is a need to provide an electrolyte additive that can inhibit the expansion and fragmentation of silicon-carbon anodes during charging and discharging, thereby improving the initial efficiency and cycle stability of silicon-carbon anodes. Summary of the Invention

[0005] The purpose of this invention is to provide an electrolyte additive, an electrolyte, and a battery, particularly an electrolyte additive, an electrolyte, and a battery that are compatible with silicon-carbon anodes. The electrolyte additive, by employing an electrolyte additive containing specific groups, can combine with silicon particles to form a stable structure, form a stable SEI film, reduce electrolyte decomposition, improve electronic conductivity, and reduce the occurrence of electrolyte side reactions. This effectively suppresses the expansion of silicon-carbon anodes, solves the problems of low initial efficiency, poor cycle performance, and poor high-temperature storage performance of silicon-carbon anodes, and improves the cycle performance and high-temperature storage performance of the battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

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

[0008]

[0009] In this configuration, R1 is independently selected from substituted or unsubstituted alkyl groups, R2 is selected from hydrogen, substituted or unsubstituted alkyl groups, R3 is selected from substituted or unsubstituted alkyl groups, and R4 is independently selected from substituted or unsubstituted alkyl groups.

[0010] The present invention uses specific electrolyte additives to specifically solve problems such as low initial efficiency, poor cycle and high temperature storage of silicon-carbon anodes, improve the mechanical stability, conductivity and cycle stability of silicon-carbon materials, reduce electrolyte decomposition, and reduce the occurrence of side reactions in the electrolyte. The specific reasons are as follows: (1) The indole group in the electrolyte additive can combine 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 undergo polymerization on the surface of the silicon-carbon anode to form a polycarbonate polymer film, thereby preventing direct contact between the electrolyte and the anode and reducing the decomposition of the electrolyte.

[0012] (3) Since F has strong electron-withdrawing properties and there are fluorine atoms in the electrolyte additives, an electrolyte interface film (SEI film) rich in inorganic substances such as LiF will be formed during the charging and discharging process of the battery. The SEI film formed has high mechanical strength and stability, which can suppress the damage to the SEI structure caused by the volume expansion of the silicon-carbon anode during the charging and discharging process.

[0013] (4) The presence of siloxanes in electrolyte additives can increase the electronic conductivity of silicon-carbon anode materials and reduce 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 anode. This film has good flexibility and mechanical strength, and can adapt to the volume change of the silicon-carbon anode during charging and discharging, thereby maintaining the integrity of the SEI film. In addition, borate can also inhibit the decomposition of the electrolyte on the surface of the anode and reduce the occurrence of side reactions.

[0015] In this invention, R1 is independently selected from substituted or unsubstituted alkyl groups, such as substituted or unsubstituted methyl, ethyl, or isopropyl; R2 is selected from hydrogen, substituted or unsubstituted alkyl groups, such as hydrogen, substituted or unsubstituted methyl, ethyl, or isopropyl; R3 is selected from substituted or unsubstituted alkyl groups, such as substituted or unsubstituted methyl, ethyl, or isopropyl; R4 is independently selected from substituted or unsubstituted alkyl groups, such as substituted or unsubstituted methyl, ethyl, or isopropyl; among R1, R2, R3, and R4, the substituents in the substituted alkyl groups can be halogens, 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 an 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 range are also applicable.

[0021] The content of the electrolyte additive in the electrolyte affects its performance. The preferred content of the electrolyte additive in this invention is 4wt%-10wt%, which can ensure that the battery performance will not be deteriorated while ensuring its normal performance, thus guaranteeing the overall performance of the battery.

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

[0023] The electrolyte of the present invention also contains a specific amount of film-forming additives. The specific amount of film-forming additives, in combination with the electrolyte additives, further improves the performance of the battery.

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

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

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

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

[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. Other unlisted values ​​within the range are also applicable.

[0029] Thirdly, the present invention provides a lithium-ion battery comprising an electrolyte additive as described in the first aspect, or an electrolyte as described in the second aspect.

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

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

[0032] The electrolyte additive and electrolyte matching of the present invention are designed to solve the problem of easy expansion of silicon-carbon anode.

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

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

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

[0036] The electrolyte additive provided by this invention is an electrolyte additive that matches silicon-carbon anodes. Specifically, it uses substances containing specific groups that can combine with silicon particles to form a stable structure, form a stable SEI film, reduce electrolyte decomposition, improve electronic conductivity, and reduce the occurrence of electrolyte side reactions. This effectively suppresses the expansion of silicon-carbon anodes, solves the problems of low initial efficiency, poor cycle performance, and poor high-temperature storage performance of silicon-carbon anodes, and improves the cycle performance and high-temperature storage performance of batteries. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

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

[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 comprising 5 wt% electrolyte additives, 4 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0044] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0045] Example 2

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

[0047] This embodiment also provides an electrolyte comprising 7 wt% electrolyte additives, 4 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0049] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0050] Example 3

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

[0052] This embodiment also provides an electrolyte comprising 9 wt% electrolyte additives, 4 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0054] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0055] Example 4

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

[0057] This embodiment also provides an electrolyte comprising 7 wt% electrolyte additives, 2 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0059] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0060] Example 5

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

[0062] This embodiment also provides an electrolyte comprising 7 wt% electrolyte additives, 6 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0064] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0065] Example 6

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

[0067] This embodiment also provides an electrolyte comprising 5 wt% electrolyte additives, 2 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0069] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0070] Example 7

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

[0072] This embodiment also provides an electrolyte comprising 9 wt% electrolyte additives, 2 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0074] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0075] Example 8

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

[0077] This embodiment also provides an electrolyte comprising 5 wt% electrolyte additives, 6 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0079] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0080] Example 9

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

[0082] This embodiment also provides an electrolyte comprising 9 wt% electrolyte additives, 6 wt% vinylene carbonate, 12.5 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0084] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0085] Example 10

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

[0087] This embodiment also provides an electrolyte comprising 4 wt% electrolyte additives, 4 wt% vinylene carbonate, 15 wt% lithium hexafluorophosphate, and the balance non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0089] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[0090] Example 11

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

[0092] This embodiment also provides an electrolyte comprising 10 wt% electrolyte additives, 4 wt% vinylene carbonate, 10 wt% lithium hexafluorophosphate, and the balance being a non-aqueous solvent, wherein the non-aqueous solvent comprises ethylene 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 includes the following steps:

[0094] In an argon-filled glove box, ethylene carbonate, methyl ethyl carbonate, propylene carbonate, and fluoroethylene carbonate are mixed according to the formula. Then lithium hexafluorophosphate is added, followed by vinylene carbonate, and finally compound A is added. After stirring evenly, the electrolyte is obtained.

[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 in Example 1 except that the content of electrolyte additives is 2wt% and the content of non-aqueous solvents is adaptable to changes.

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

[0099] Example 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 in Example 1 except that the content of electrolyte additives is 12wt% and the content of non-aqueous solvents is adaptable to changes.

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

[0103] Example 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 in Example 1 except that the content of electrolyte additives is 7 wt% and does not contain vinylene carbonate, and the content of non-aqueous solvents is adaptable to changes.

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

[0107] Comparative Example 1

[0108] This comparative example provides an electrolyte that is identical to that of Example 1, except that it does not contain electrolyte additives and the content of non-aqueous solvents is adaptable to changes.

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

[0110] The electrolytes injected into LiMn in the above embodiments and comparative examples 0.5 Fe 0.5 In a PO4-silicon-carbon system lithium-ion battery, electrochemical tests were then conducted, including the following procedures:

[0111] (1) Test of 30 days of storage at 60℃: The battery was charged to 4.5V at 25℃ with constant current and constant voltage at 1.0C, 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 with constant current and constant voltage at 1.0C and the initial thickness was measured. The battery was stored at 60℃±2℃ for 30 days in an open circuit. The battery was then taken out and the thermal thickness was tested. The cell was then charged and discharged at 1.0C and the remaining capacity and recovery capacity were tested. The thermal thickness change rate, capacity retention rate and capacity recovery rate were then calculated.

[0112] (2) 25℃, 1C charge-discharge cycle test: Charge and discharge at 1C at 25℃, 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] As can be seen from Table 1:

[0118] As can be seen from Examples 1-11 and Comparative Example 1, 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 silicon-carbon anodes during cycling. As can be seen from Examples 1-9 and Examples 12-13, the content of the electrolyte additive of the present invention is preferably in the range of 4-10 wt%, and more preferably 7 wt%. As can be seen from Examples 1, 6, 8 and 14, the electrolyte of the present invention preferably also contains film-forming additives, and the content of film-forming additives is preferably 2-6 wt%, and more preferably 4 wt%.

[0119] The above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection 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): ； Formula 1); In this context, R1 is independently selected from substituted or unsubstituted alkyl groups, R2 is selected from hydrogen, substituted or unsubstituted alkyl groups, R3 is selected from substituted or unsubstituted alkyl groups, and R4 is independently selected from substituted or unsubstituted alkyl groups. The electrolyte additive is matched to the silicon-carbon anode; The electrolyte additive is present in the electrolyte at a content of 4wt%-10wt%, and the electrolyte includes a film-forming additive, which includes vinylene carbonate.

2. The electrolyte additive according to claim 1, characterized in that, The electrolyte additive is: 。 3. An electrolyte, characterized in that, The electrolyte includes a non-aqueous organic solvent, a lithium salt, a film-forming additive, and an electrolyte additive as described in claim 1 or 2. The electrolyte contains 4wt%-10wt% of the electrolyte additive as described in claim 1 or 2. The film-forming additive includes vinylene carbonate.

4. The electrolyte according to claim 3, characterized in that, The content of the film-forming additive in the electrolyte is 2wt%-6wt%.

5. The electrolyte according to claim 3, characterized in that, The lithium salt includes any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium difluorophosphate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluorosulfonyl)imide.

6. The electrolyte according to claim 3, characterized in that, The content of lithium salt in the electrolyte is 10wt%-15wt%.

7. The electrolyte according to claim 3, characterized in that, The non-aqueous organic solvent includes any one or a combination of at least two of ethylene carbonate, ethyl methyl carbonate, propylene carbonate, or fluoroethylene carbonate.

8. The electrolyte according to claim 7, characterized in that, In the non-aqueous organic solvent, the mass ratio of ethylene carbonate, methyl ethyl carbonate, propylene carbonate and fluoroethylene carbonate is (25-35):(50-60):(2-10):(5-15).

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the electrolyte additive as described in claim 1 or 2, or the electrolyte as described in any one of claims 3-8; The lithium-ion battery also includes a positive electrode, a negative electrode, and a separator, wherein the negative electrode comprises a silicon-carbon negative electrode material.

10. The lithium-ion battery according to claim 9, characterized in that, The cathode material includes lithium manganese iron phosphate and / or ternary cathode materials.

11. The lithium-ion battery according to claim 9, characterized in that, The diaphragm includes a PE diaphragm.

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