High-temperature storage electrolyte additive of energy storage lithium ion battery, electrolyte and battery

Abstract

The invention provides an energy storage lithium ion battery high-temperature storage electrolyte additive, an electrolyte and a battery, and belongs to the technical field of lithium ion batteries, molecules of the electrolyte functional additive contain P = O groups, and oxygen atoms in the groups have high electronegativity and can generate complexation with transition metal ions. In the high-temperature storage process of the lithium ion battery, the complexing action can effectively inhibit the dissolution of transition metal ions and reduce a series of adverse effects caused by the dissolution of the transition metal ions, so that the self-discharge phenomenon of the battery during high-temperature storage is improved, and the high-temperature storage capacity retention rate is remarkably increased; and the performance of the battery in a high-temperature environment is improved fundamentally.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to an energy storage lithium-ion battery high-temperature storage electrolyte additive, an electrolyte, and a battery. Background Art

[0002] With the technological iteration of new energy vehicles, wearable electronic devices and portable mobile terminals, the stability standards of lithium-ion batteries under high-temperature conditions continue to improve. This demand drives the industry to accelerate the development of high-temperature resistant battery systems in order to meet the long-term operation requirements in high-voltage scenarios. Under high-temperature environments, the electrolyte system must simultaneously meet the dual indicators of thermal / electrochemical stability of the bulk material and electrode-electrolyte interface compatibility in order to achieve high-temperature steady-state operation of the electrochemical system. The current technical path mainly focuses on the optimization of three core elements: developing a new lithium salt system with high thermal stability, constructing a co-solvent system resistant to oxidative decomposition, and designing functional additives with interface passivation effects.

[0003] However, commercial lithium-ion battery electrolytes are generally composed of carbonate organic solvents and lithium hexafluorophosphate (LiPF6). Carbonate solvents are mainly composed of chain carbonates, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and fluoroethylene carbonate (4-Fluoro-1,3-dioxolan-2-one, FEC). Although EC in the electrolyte undergoes redox decomposition reactions on the surfaces of the ternary positive electrode and graphite negative electrode, forming an effective positive / negative electrode electrolyte interface film (Cathode Electrolyte Interface, CEI / Solid Electrolyte Interface, SEI), the film has poor stability at high temperatures. In addition, the hydrolysis and oxidation of carbonate solvents will generate products with active protons, which react with hexafluorophosphate (HFP) to form an effective cathode / negative electrode electrolyte interface film (CEI / SEI). ) to produce hydrogen fluoride (HF) and phosphorus pentafluoride (PF5) gas. Then, lithium carbonate (Li2CO3) on the positive electrode surface can react with HF to release carbon dioxide (CO2) and water (Hydrogen oxide, H2O), which will further react with LiFP6 and carbonate solvent. This cycle continues, and the HF produced will corrode the positive electrode interface, causing transition metal ions to dissolve during high-temperature storage, deteriorating the capacity retention rate.

[0004] The high temperature performance of commercial lithium-ion batteries is usually improved by the following methods: Optimize lithium salt: Add LiFSi, the thermal decomposition temperature of LiFSi exceeds 200℃, improving high-temperature storage performance and cycle performance.

[0005] Optimizing electrolyte solvents: EC-Free electrolyte design concept. EC-free electrolytes reduce gas production during high-temperature storage by inhibiting the release of lattice oxygen, significantly increasing the battery thermal runaway trigger temperature, thereby improving the battery's safety characteristics; EC-free electrolytes reduce interfacial side reactions and significantly improve the cycle stability of high-nickel materials.

[0006] Key additives: Adding water- and acid-removing additives, such as SN (succinonitrile) and HMDS (hexamethyldisilazane), to traditional electrolytes can effectively remove HF produced by the decomposition of FEC (fluoroethylene carbonate), protecting the positive electrode from HF corrosion and improving high-temperature storage performance.

[0007] Although the above methods can improve the high-temperature performance of the electrolyte under certain conditions, they all have certain limitations. The introduction of LiFSi into the electrolyte will lead to an increase in cost, and an excessively high LiFSi content will significantly deteriorate the safety performance of the battery; the conductivity of the electrolyte without an EC base is too low, which increases the internal resistance. The interface repairability of the electrolyte without an EC is poor, which deteriorates the normal temperature cycle; nitrile additives significantly improve the high-voltage stability of the electrolyte by complexing transition metal ions, self-oxidation film formation and removing water molecules, but the reduction stability is poor. Nitrile additives are incompatible with the graphite negative electrode, and the negative electrode interface is deteriorated during the cycle, resulting in too rapid an increase in DCR (Direct Current Resistance) during the cycle, causing the cycle to drop. Therefore, it is urgent to develop new additives to improve the comprehensive performance of the electrolyte at high temperatures. Summary of the Invention

[0008] In order to solve the problems existing in the prior art, the present invention provides an energy storage lithium-ion battery high-temperature storage electrolyte additive, an electrolyte, and a battery. The electrolyte functional additive can form a stable CEI film on the positive and negative electrodes of the lithium-ion battery, respectively, and reduce the dissolution of transition metal ions, thereby effectively reducing the interfacial side reactions of the lithium-ion battery under high-temperature working conditions, thereby improving the application performance of the lithium-ion battery under high-temperature conditions.

[0009] To achieve the above objectives, the present invention provides the following technical solution: an electrolyte additive for high-temperature storage of energy storage lithium-ion batteries, wherein the electrolyte functional additive contains a P=O group in its molecule, and its structural formula is as follows:

[0010] wherein R1 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy; R2 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy; R3 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, and substituted or unsubstituted ester.

[0011] Furthermore, in the structural formula of the electrolyte functional additive, R1 is independently selected from hydrogen, a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 4 to 6 carbon atoms, and a substituted or unsubstituted alkoxy group having 2 to 4 carbon atoms; R2 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted alkoxy having 2 to 4 carbon atoms; R3 is independently selected from hydrogen, a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 4 to 6 carbon atoms, and a substituted or unsubstituted ester group.

[0012] Furthermore, the electrolyte functional additive is selected from at least one of the following compounds:

[0013] Furthermore, the electrolyte functional additive is compounded with an electrolyte additive for use; the electrolyte additive includes fluoroethylene carbonate, vinylene carbonate, lithium difluorooxalatoborate, 1,3-propylene sultone and lithium difluorophosphate.

[0014] The present invention also provides an electrolyte, the raw materials of which include: an organic solvent, a lithium salt, an electrolyte functional additive and an electrolyte additive, wherein the electrolyte functional additive is the electrolyte functional additive mentioned above.

[0015] Furthermore, the concentration of the lithium salt in the electrolyte is 1.0 mol / L to 1.3 mol / L, and the lithium salt is at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0016] Furthermore, the mass percentage of the electrolyte functional additive in the electrolyte is 0.3% to 0.5%, the mass percentage of the electrolyte additive in the electrolyte is 4% to 9%, and the balance is the organic solvent.

[0017] Furthermore, the organic solvent is a mixed solvent of dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate.

[0018] Furthermore, the total volume of the organic solvent is 100%, which comprises, by volume percentage, 65% dimethyl carbonate, 20% ethylene carbonate and 15% ethyl methyl carbonate.

[0019] The present invention also provides a lithium-ion battery, which uses the above electrolyte. The capacity retention rate of the lithium-ion battery stored at 60° C. for 30 days is 92.5%-93.4%, and the capacity recovery rate is 97.4%-97.9%.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides an electrolyte additive for high-temperature storage of energy-storage lithium-ion batteries. The molecule contains a P=O group. The oxygen atom in this group has a high electronegativity and can form a complex with transition metal ions. During the high-temperature storage of lithium-ion batteries, this complexation effectively inhibits the dissolution of transition metal ions, reducing a series of adverse effects caused by the dissolution of transition metal ions. This can further improve the battery's self-discharge during high-temperature storage, significantly increase the high-temperature storage capacity retention rate, and fundamentally enhance the battery's performance in high-temperature environments.

[0021] The electrolyte provided by the present invention, prepared based on the aforementioned electrolyte functional additive, significantly improves the physicochemical properties of the electrolyte-positive electrode interface by introducing the electrolyte functional additive in addition to an organic solvent and a lithium salt. By forming a stable electrolyte interface film at both the positive and negative electrodes, this effectively reduces interfacial side reactions during high-temperature operation, creating a more stable environment for internal chemical reactions, ensuring the battery's normal operation in high-temperature environments, and improving the electrolyte's applicability and stability under these conditions.

[0022] The lithium-ion battery provided by the present invention, utilizing the aforementioned electrolyte, leverages the superior performance of the functional additives in the electrolyte to demonstrate exceptional performance advantages in high-temperature applications. This reduces interfacial side reactions at high temperatures, lowering the battery's internal resistance and improving its charge and discharge efficiency. Furthermore, it improves self-discharge and low capacity retention during high-temperature storage, extending the battery's service life in high-temperature environments and enhancing its safety and reliability under these conditions. This provides strong support for the application of lithium-ion batteries in high-temperature applications.

[0023] In summary, the electrolyte functional additive of the present invention improves the physicochemical properties of the interface between the electrolyte and the positive electrode, thereby protecting the battery interface and reducing side reactions, thereby effectively improving the problems of self-discharge and low capacity retention during high-temperature storage of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the transition metal content of the negative electrode plate of the lithium ion battery of the present invention after storage for 30 days. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] An embodiment of the present invention provides an electrolyte additive for high-temperature storage of energy storage lithium-ion batteries. The functional additive contains a P=O group in its molecule, wherein the oxygen atom has a high electronegativity and can complex with transition metal ions. This improves high-temperature storage self-discharge by inhibiting the dissolution of transition metal ions during high-temperature storage, thereby improving the high-temperature storage capacity retention rate. The general structural formula of the functional additive is:

[0027] wherein R1 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy, R2 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy, and R3 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted ester.

[0028] Further preferably, R1 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted alkoxy having 2 to 4 carbon atoms; R2 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted alkoxy having 2 to 4 carbon atoms; R3 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted ester group.

[0029] Further preferably, the electrolyte functional additive is selected from at least one of the following compounds:

[0030] The embodiment of the present invention also uses the above-mentioned electrolyte functional additive to prepare an electrolyte, and the raw materials of the electrolyte include: an organic solvent, a lithium salt, an electrolyte functional additive and an electrolyte additive, wherein the concentration of the lithium salt in the electrolyte is 1.0 mol / L~1.3 mol / L, the mass percentage of the functional additive in the electrolyte is 0.3%~0.5%, the mass percentage of the electrolyte additive in the electrolyte is 4%~9%, and the balance is an organic solvent.

[0031] Preferably, the lithium salt is at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0032] Preferably, the organic solvent is one or more of ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate; Further preferably, the organic solvent is a mixed solvent of dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate, the total volume of the organic solvent being 100%, which, by volume percentage, comprises: 65% dimethyl carbonate, 20% ethylene carbonate and 15% ethyl methyl carbonate.

[0033] Example 1 This embodiment provides an energy storage lithium-ion battery high-temperature storage electrolyte additive, the structural formula of which is shown in Formula I-1 (dibutylphosphine oxide):

[0034] Formula I-1 Among them, R1 replaces hydrogen, and R2 and R3 are respectively replaced by butyl groups.

[0035] The specific steps of preparing the electrolyte using the above electrolyte functional additive are as follows: Under an argon atmosphere, the total volume of the organic solvent is 100%, and the organic solvent is formed by mixing 65% of dimethyl carbonate, 20% of ethylene carbonate and 15% of ethyl methyl carbonate in terms of volume percentage.

[0036] Lithium hexafluorophosphate, the electrolyte functional additive, the electrolyte additive and the organic solvent are mixed and stirred at a temperature of 10° C. to obtain an electrolyte.

[0037] The electrolyte additives include fluoroethylene carbonate, vinylene carbonate, lithium difluorooxalatoborate, 1,3-propylene sultone and lithium difluorophosphate; The total mass of the electrolyte is 100%, of which the mass percentage of electrolyte functional additives is 0.3%, the mass percentage of fluoroethylene carbonate is 6%, the mass percentage of vinylene carbonate is 0.3%, the mass percentage of lithium difluorooxalatoborate is 0.5%, the mass percentage of lithium difluorophosphate is 0.8%, the mass percentage of 1,3-propylene sultone is 0.5%, and the balance is organic solvent.

[0038] The concentration of lithium hexafluorophosphate in the electrolyte is 1.2 mol / L.

[0039] Example 2 This embodiment provides an energy storage lithium-ion battery high-temperature storage electrolyte additive and an electrolyte, wherein the mass percentage of the functional additive is adjusted to 0.5%, and the rest is the same as in Example 1.

[0040] Example 3 This embodiment provides an energy storage lithium-ion battery high-temperature storage electrolyte additive and an electrolyte, wherein the mass percentage of the functional additive is adjusted to 0.4%, and the rest is the same as in Example 1.

[0041] Example 4 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery, wherein the structural formula of the electrolyte functional additive is shown in Formula I-2 (tributylphosphine oxide):

[0042] Formula I-2 wherein R1, R2, and R3 are each substituted with a butyl group; The mass percentage of the electrolyte functional additive in this embodiment is 0.5%, and the rest is the same as in Example 1.

[0043] Example 5 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery, wherein the structural formula of the electrolyte functional additive is shown in Formula I-3 (tripentylphosphine oxide):

[0044] Formula I-3 wherein R1, R2, and R3 are each substituted by a pentyl group; The mass percentage of the electrolyte functional additive in this embodiment is 0.5%, and the rest is the same as in Example 1.

[0045] Example 6 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery, wherein the structural formula of the electrolyte functional additive is shown in Formula I-4 (tricyclohexylphosphine oxide):

[0046] Formula I-4 wherein R1, R2, and R3 are each substituted by a cyclohexyl group; The mass percentage of the electrolyte functional additive in this embodiment is 0.5%, and the rest is the same as in Example 1.

[0047] Example 7 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery. The structural formula of the electrolyte functional additive is shown in Formula I-5 ([bis(2,2,2-trifluoroethoxy)phosphinyl]ethyl acetate):

[0048] Formula I-5 wherein R1 and R2 are substituted by substituted ethoxy groups, and R3 is substituted by substituted ester groups; The mass percentage of the electrolyte functional additive in this embodiment is 0.5%, and the rest is the same as in Example 1.

[0049] Example 8 This embodiment provides an energy storage lithium-ion battery high-temperature storage electrolyte additive and an electrolyte. The lithium salt is selected as lithium bis(fluorosulfonyl)imide. The concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 1 mol / L. The mass percentage of the electrolyte additive in the electrolyte is 4%. Other aspects are the same as those in Example 1.

[0050] Example 9 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery. The lithium salt is lithium bis(fluorosulfonyl)imide. The concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 1.2 mol / L. The mass percentage of the electrolyte additive in the electrolyte is 9%. Other aspects are the same as those in Example 1.

[0051] Example 10 This embodiment provides an electrolyte additive and an electrolyte for high-temperature storage of an energy storage lithium-ion battery. The lithium salt is lithium bis(fluorosulfonyl)imide. The concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 1.3 mol / L. The mass percentage of the electrolyte additive in the electrolyte is 7%. Other aspects are the same as those in Example 1.

[0052] Example 11 This embodiment provides an electrolyte additive and electrolyte for high-temperature storage of energy storage lithium-ion batteries. The lithium salts selected are lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The concentration of the lithium salt in the electrolyte is 1 mol / L. Other aspects are the same as those in Example 1.

[0053] Example 12 This embodiment provides an electrolyte additive and electrolyte for high-temperature storage of energy storage lithium-ion batteries. The lithium salts selected are lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The concentration of the lithium salt in the electrolyte is 1.1 mol / L. Other aspects are the same as those in Example 1.

[0054] Example 13 This embodiment provides an electrolyte additive and electrolyte for high-temperature storage of energy storage lithium-ion batteries. The lithium salts selected are lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The concentration of the lithium salt in the electrolyte is 1.2 mol / L. Other aspects are the same as those in Example 1.

[0055] Example 14 This embodiment provides an electrolyte additive and electrolyte for high-temperature storage of energy storage lithium-ion batteries. The lithium salts selected are lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide. The concentration of the lithium salt in the electrolyte is 1.3 mol / L. Other aspects are the same as those in Example 1.

[0056] Comparative Example 1 This comparative example 1 provides an electrolyte, which does not contain any electrolyte functional additives, and is otherwise the same as that of Example 1.

[0057] Performance testing: Graphite was used as the negative electrode active material, and graphite, conductive agent acetylene black, binder CMC, and SBR were prepared into a negative electrode slurry in a mass ratio of 94.4:1.5:2.4:1.7. The negative electrode slurry was coated on a copper foil current collector and vacuum dried to prepare a negative electrode plate. NCM811 (a high nickel ternary positive electrode material with a molar ratio of nickel, cobalt, and manganese of 8:1:1) was used as the positive electrode active material, and the positive electrode active material, conductive agent acetylene black, and binder PVDF were prepared into a positive electrode slurry in a mass ratio of 96.5:2.2:1.3. The positive electrode slurry was coated on an aluminum foil current collector and vacuum dried to prepare a positive electrode plate. The electrolytes prepared in Examples 1 to 7 and Comparative Example 1 were respectively used with the above-mentioned positive electrode plate, negative electrode plate, and separator to assemble 18650 batteries. The capacity retention rate and capacity recovery rate data of the batteries after storage at 60°C for 30 days are shown in Table 1: Table 1 shows the capacity retention rate and capacity recovery rate data of the battery stored at 60℃ (30d)

[0058] Combine Figure 1As can be seen from the data in Table 1, compared with Comparative Example 1, the phosphine oxide compounds will complex with the transition metal ions (Ni / Co / Mn) dissolved from the positive electrode ternary material, reducing its damage to the negative electrode interface film. The content of dibutylphosphine oxide in Example 2 and Example 3 is increased compared with Example 1, and the effect of inhibiting the transition metal ions (Ni / Co / Mn) is increased, so the capacity retention rate is increased; Example 4 has one more butyl group than Example 2, which may be because the oxidation stability of Example 4 at high temperature (about 4.4V) is better than that of Example 2 (about 4.3V), so the capacity retention rate is higher. The inhibitory effect of Example 2, Example 5, and Example 6 on the dissolution of transition metal ions (Ni / Co / Mn) is not much different, so the capacity retention rate is not much different. Example 7 contains not only P=O groups, but also F atoms. F atoms will capture hydrogen ions to inhibit the hydrolysis of lithium hexafluorophosphate, reduce HF corrosion on the positive electrode surface, and better inhibit the dissolution of transition metal ions (Ni / Co / Mn). Therefore, the capacity retention rate is improved most significantly.

Claims

1. An energy storage lithium ion battery high temperature storage electrolyte additive, characterized in that: The molecules of the electrolyte functional additives contain a P=O group, and the structural formula is as follows: wherein R1 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy; R2 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy; R3 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, and substituted or unsubstituted ester.

2. The high-temperature storage electrolyte additive for energy storage lithium-ion batteries according to claim 1, characterized in that: In the structural formula of the electrolyte functional additive: R1 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted alkoxy having 2 to 4 carbon atoms; R2 is independently selected from hydrogen, substituted or unsubstituted alkyl having 1 to 8 carbon atoms, cycloalkyl having 4 to 6 carbon atoms, and substituted or unsubstituted alkoxy having 2 to 4 carbon atoms; R3 is independently selected from hydrogen, a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 4 to 6 carbon atoms, and a substituted or unsubstituted ester group.

3. The high-temperature storage electrolyte additive for energy storage lithium-ion batteries according to claim 1, characterized in that: The electrolyte functional additive is selected from at least one of the following compounds:

4. The high-temperature storage electrolyte additive for energy storage lithium-ion batteries according to claim 1, characterized in that: The electrolyte functional additive is compounded with an electrolyte additive for use; the electrolyte additive comprises fluoroethylene carbonate, vinylene carbonate, lithium difluorooxalatoborate, 1,3-propylene sultone and lithium difluorophosphate.

5. An electrolyte, characterized in that The raw materials include: an organic solvent, a lithium salt, an electrolyte functional additive and an electrolyte additive, wherein the electrolyte functional additive is the electrolyte functional additive according to any one of claims 1 to 4.

6. An electrolyte according to claim 5, characterized in that: The concentration of the lithium salt in the electrolyte is 1.0 mol / L to 1.3 mol / L, and the lithium salt is at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

7. An electrolyte according to claim 5, characterized in that: The mass percentage of the electrolyte functional additive in the electrolyte is 0.3% to 0.5%, the mass percentage of the electrolyte additive in the electrolyte is 4% to 9%, and the balance is organic solvent.

8. An electrolyte according to claim 5, characterized in that: The organic solvent is a mixed solvent of dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate.

9. An electrolyte according to claim 5, characterized in that: The total volume of the organic solvent is 100%, which comprises, by volume percentage, 65% of dimethyl carbonate, 20% of ethylene carbonate and 15% of ethyl methyl carbonate.

10. A lithium ion battery, characterized in that: The lithium-ion battery uses the electrolyte according to any one of claims 6 to 8, and the capacity retention rate of the lithium-ion battery stored at 60° C. for 30 days is 92.5% to 93.4%, and the capacity recovery rate is 97.4% to 97.9%.

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