Electrolyte additives for lithium-ion batteries, their preparation methods and applications

Abstract

To provide an electrolyte additive for lithium ion batteries, and a preparation method and application thereof.SOLUTION: An electrolyte additive includes a mixture formed of an etching resist, a resist aid, a film-forming agent and a co-solvent. A molar ratio of the etching resist, the resist aid, the film-forming agent and the co-solvent is 1:(0.1-1):(20-50): (0.01-0.1). The electrolyte additive can protect electrode pieces and have a good corrosion inhibition effect, through the dual synergistic protection effect of a resist and film formation, so that the electrolyte additive can reduce the negative impact caused by corrosion and make up for the vacancy of such functional additives in the field of electrolyte. In addition, the electrolyte additive of the present invention is generally applicable to various types of conventional electrolyte systems, and the preparation process thereof is simple and easy, thus having broad application prospects.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application filed on May 24, 2023, bearing application number 202310595329.6, the entire contents of which are incorporated herein by reference.

[0002] Technical Field

[0003] The present invention relates to the technical field of lithium ion batteries, and in particular to an electrolyte additive for lithium ion batteries and its preparation method and application. [Background technology]

[0004] During the long-term use of lithium-ion batteries, electrolytes typically corrode battery components. To reduce electrolyte corrosion on the positive electrode current collector of lithium batteries, commonly used solutions include adjusting the electrolyte concentration, adding electrolyte additives, or changing the type of electrolyte solvent. However, these technical approaches are relatively complex and therefore unsuitable for industrial scale-up. For example, adjusting the electrolyte concentration can reduce the electrochemical performance of the battery. While adding additives and changing the electrolyte solvent composition can effectively inhibit corrosion, these methods are not universally applicable because they require the selection of additives or electrolyte types tailored to specific electrolyte components. Therefore, there is a clear technological threshold. Currently available electrolyte additives include overcharge protection agents, film-forming additives, flame retardants, and additives for improving low-temperature performance. However, there are few corrosion-preventing additives specifically designed to prevent electrode erosion. Because electrode erosion life has a significant impact on the cycle performance and charge-discharge performance of lithium batteries, the development of corrosion-preventing additives for lithium battery electrolytes is of great value and significance.

[0005] It is with this in mind that the present invention is particularly proposed. Summary of the Invention [Problem to be solved by the invention]

[0006] The first object of the present invention is to provide an electrolyte additive for lithium ion batteries. When applied to a conventional electrolyte system, the electrolyte additive of the present invention can provide good corrosion prevention and protective effect on the electrode pieces to prevent corrosion defects of the positive electrode current collector caused by the electrolyte, thereby filling the shortage of functional additives in the electrolyte field.

[0007] The second object of the present invention is to provide a method for preparing the lithium ion battery electrolyte additive, which can be achieved by simple mixing and filtration, is simple and easy to implement, and can be industrially produced.

[0008] The third object of the present invention is to provide a lithium ion battery, and the electrolyte additive of the present invention can protect the electrode pieces, thereby improving the battery's charge capacity and cycle performance. [Means for solving the problem]

[0009] In order to achieve the above object of the present invention, the following technical solutions are particularly used: An electrolyte additive for lithium ion batteries, comprising a mixture formed from an etching resist, a resist aid, a film forming agent, and a co-solvent, wherein the molar ratio of the etching resist, the resist aid, the film forming agent, and the co-solvent is 1:(0.1-1):(20-50):(0.01-0.1).

[0010] The method for preparing the electrolyte additive for lithium ion batteries includes: first, mixing an etching resist and a film-forming agent for the first time under an inert atmosphere; then, adding a co-solvent and a resist auxiliary agent in sequence; mixing for the second time; and then filtering to obtain the electrolyte additive.

[0011] A lithium ion battery comprising the electrolyte additive for lithium ion batteries or the electrolyte additive for lithium ion batteries prepared by the preparation method. [Effects of the Invention]

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] (1) The present invention uses a dual synergistic system of resist and film formation to significantly solve the problem of electrode corrosion in lithium batteries, especially the problem of aluminum positive electrodes. At the same time, in the case of bisfluorosulfonylimide-based lithium salts, the corrosive effect of these salts on aluminum electrode pieces is stronger than that of other electrolyte salts. Conventional film formers are difficult to completely solve the deficiencies in application performance caused by the corrosion problem. The present invention uses the dual chemical action of resist and film formation to reduce the electrode corrosion rate and improve the electrochemical performance of lithium batteries.

[0014] (2) The electrolyte additive of the present invention can provide a certain protective effect to various electrolyte solvents or electrolyte salt systems in the prior art, and has stronger universality compared with the conventional methods of using film-forming assistants in different systems. The use of the additive of the present invention can effectively lower the technical threshold and reduce the costs of production and application.

[0015] (3) The electrolyte additive of the present invention does not involve complex chemical reactions in the preparation process, and the process mainly achieves uniform dispersion through stirring. No by-products are produced in the process, which meets the requirements for green environmental protection and is suitable for large-scale industrial production. DETAILED DESCRIPTION OF THE INVENTION

[0016] The technical solutions of the present invention will be described clearly and completely below in conjunction with specific embodiments. However, those skilled in the art will understand that the examples described below are only some examples of the present invention, not all examples, and are used only to illustrate the present invention and should not be considered to limit the scope of the present invention. Based on the examples of the present invention, all other examples that a person skilled in the art can come up with without any creative effort fall within the scope of the present invention. Unless specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by manufacturers. Unless the manufacturers of the reagents or equipment used are specified, they are all conventional products available on the market.

[0017] In a first aspect, an embodiment of the present invention provides an electrolyte additive for a lithium ion battery, the electrolyte additive comprising a mixture formed of an etching resist, a resist aid, a film former, and a co-solvent, wherein the molar ratio of the etching resist, the resist aid, the film former, and the co-solvent is 1:(0.1-1):(20-50):(0.01-0.1).

[0018] The lithium-ion battery electrolyte additive in the present embodiment achieves a synergistic effect through the combination of the etching resist and film former components. Specifically, in lithium battery applications, the aldehyde groups in the etching resist molecules are strong polar groups, which can reduce the nucleation potential of lithium ions and thereby reduce the formation of lithium dendrites. At the same time, during the process of the film former and the electrode pieces forming the SEI film, the coordination between the aldehyde groups and the vacant aluminum orbitals can strengthen the adsorption between the SEI and the electrode pieces, thereby improving the overall stability of the SEI film. This film can provide good ion channels, effectively solving the corrosion problem of lithium battery electrode pieces, especially the corrosion of the aluminum positive electrode. Meanwhile, the active ingredient is prepared by combining the resist auxiliary and co-solvent, and the lithium-ion battery electrolyte additive is prepared by combining the above components contained therein. Based on the full utilization of each component's individual functions and the synergistic effect between the corresponding components, the lithium-ion battery electrolyte additive of the present application provides corrosion resistance.

[0019] In a preferred embodiment, the molar ratio of the etching resist, the resist auxiliary, the film forming agent, and the co-solvent is 1:(0.1-0.4):(30-40):(0.01-0.03).

[0020] In a preferred embodiment, the etching resist comprises at least one of lithium metaphosphate, lithium guanosine triphosphate, α,β-methylene adenosine 5'-triphosphate lithium salt, or (S)-ganciclovir-5'-triphosphate lithium salt. The etching resist has a chemical structure comprising a cyclic group and an aldehyde group. The aldehyde group is a polar group that can form a coordination interaction with the vacant orbital of aluminum and further strengthen the adsorption between the etching resist and the electrode plate, thereby improving the resist effect. At the same time, the etching resist is dissolved in an ester-based or sulfone-based electrolyte solvent and ionized to produce phosphate ions, which can form a good adsorption interaction with the aluminum electrode plate, providing excellent protection for the aluminum positive electrode.

[0021] In a preferred embodiment, the resist aid comprises at least one of terephthalaldehyde, 6-(2-thienyl)-2-pyridylaldehyde, N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 2-pyrrole formaldehyde, 1-methyl-2-pyrrole formaldehyde, or 3-pyrrole formaldehyde. The resist aid is selected from polymers having a conjugated π-bond structure, which can improve the electrical conductivity of the electrolyte to a certain extent, thereby achieving the goal of improving electrochemical performance.

[0022] In a preferred embodiment, the film-forming agent comprises at least one of fluoroethylene carbonate and ethylene carbonate, which can form an SEI film between the film-forming agent and the aluminum pole piece, thereby achieving the purpose of protecting the pole piece.

[0023] In a preferred embodiment, the co-solvent comprises at least one of flumiclorac pentyl, perfluorotripropylamine, cinflumid, and teriflunomide. The solubility of the etching resist in the electrolyte is low, and adding a co-solvent can effectively improve the solubility of the etching resist. As the solubility improves, the above-mentioned technical effects also improve.

[0024] In a preferred embodiment, when two components are independently selected for the etching resist, resist aid, film former, or co-solvent, the molar ratio of the two components is 1:1. For example, when a two-component combination of lithium metaphosphate and lithium guanosine triphosphate is used for the etching resist, the molar ratio of lithium metaphosphate to lithium guanosine triphosphate is 1:1.

[0025] In a second aspect, an embodiment of the present invention provides a method for preparing an electrolyte additive for a lithium ion battery, the method including: firstly mixing an etching resist and a film-forming agent for a first time under an inert atmosphere, then sequentially adding a co-solvent and a resist auxiliary, mixing them for a second time, and then filtering to obtain the electrolyte additive.

[0026] In the embodiment of the present invention, the electrolyte additive is prepared without complex chemical reactions, and the process is mainly achieved by stirring to achieve uniform dispersion. No by-products are produced during the process, which meets the requirements of green environmental protection and is suitable for large-scale industrial production.

[0027] In a preferred embodiment, the duration of the first mixing is 1 hour to 3 hours, and the duration of the second mixing is 12 hours to 16 hours.

[0028] In a more preferred embodiment, both the first and second mixing are performed with mechanical agitation, and the duration of the first mixing includes, but is not limited to, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8, and 3 hours, and the duration of the second mixing includes, but is not limited to, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, and 16 hours.

[0029] In preferred embodiments, the inert atmosphere includes, but is not limited to, a nitrogen, helium, neon, or argon environment.

[0030] In a preferred embodiment, the pore size of the filtration net for filtration treatment is 150 mesh to 300 mesh, and in a more preferred embodiment, the pore size of the filtration net for filtration treatment is 200 mesh. In a preferred embodiment, the filtration treatment is carried out independently 2 to 4 times.

[0031] In a third aspect, embodiments of the present invention provide a lithium ion battery comprising the lithium ion battery electrolyte additive described above or obtained by the preparation method described above.

[0032] The lithium ion battery electrolyte additive has good corrosion resistance, and the electrolyte in the lithium ion battery provided by the present invention contains the lithium ion battery electrolyte additive, so the battery provided by the present invention also has good electrochemical performance, thereby improving the battery's power supply and cycle performance.

[0033] In a preferred embodiment, the amount of the electrolyte additive used is 0.5% to 1.5% of the total mass of the electrolyte in the lithium ion battery.

[0034] In a preferred embodiment, the positive electrode of the lithium ion battery is an aluminum current collector, and in another preferred embodiment, the lithium salt of the electrolyte in the lithium ion battery is a bisfluorosulfonylimide salt. [Example]

[0035] Example 1 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 15.6 parts terephthalaldehyde, and 4.9 parts flumiclorac pentyl.

[0036] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 3700 parts of fluoroethylene carbonate, stirring for 2 hours, and then sequentially adding 15.6 parts of terephthalaldehyde and 4.9 parts of flumiclorac pentyl, and continuing to stir for 12 hours. After stirring is completed, the mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0037] Example 2 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of lithium metaphosphate, 4930 parts of fluoroethylene carbonate, 44 parts of 6-(2-thienyl)-2-pyridylaldehyde, and 10 parts of flumiclorac pentyl.

[0038] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 4930 parts of fluoroethylene carbonate, stirring for 2 hours, and then sequentially adding 44 parts of 6-(2-thienyl)-2-pyridylaldehyde and 10 parts of flumiclorac pentyl, and continuing to stir for 12 hours. After stirring is completed, the mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0039] Example 3 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of lithium metaphosphate, 3700 parts of fluoroethylene carbonate, 62.5 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, and 15 parts of flumiclorac pentyl.

[0040] The preparation method includes step 01: in an N2 atmosphere, weigh out 100 parts of lithium metaphosphate, add it to 3700 parts of fluoroethylene carbonate, and stir for 1 hour; then sequentially add 62.5 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde and 15 parts of flumiclorac pentyl; continue stirring for 14 hours; and after stirring, filter three times through a 200-mesh filter to obtain an electrolyte additive.

[0041] Example 4 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of α,β-methylene adenosine 5′-triphosphate lithium salt, 615 parts of fluoroethylene carbonate, 33 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, and 6 parts of perfluorotripropylamine.

[0042] The preparation method includes step 01 of weighing 100 parts of α,β-methylene adenosine 5'-triphosphate lithium salt in an Ar atmosphere, adding it to 615 parts of fluoroethylene carbonate, stirring for 3 hours, sequentially adding 33 parts of 2-pyrrole formaldehyde and 6 parts of perfluorotripropylamine, continuing to stir for 16 hours, and after stirring, filtering the mixture three times through a 200-mesh filter to obtain an electrolyte additive.

[0043] Example 5 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of α,β-methylene adenosine 5′-triphosphate lithium salt, 615 parts of fluoroethylene carbonate, 33 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, and 6 parts of perfluorotripropylamine.

[0044] The preparation method includes step 01 of weighing 100 parts of lithium guanosine triphosphate in an Ar atmosphere, adding it to 800 parts of fluoroethylene carbonate, stirring for 4 hours, sequentially adding 50 parts of 1-methyl-2-pyrrole formaldehyde and 12 parts of perfluorotripropylamine, continuing to stir for 16 hours, and after stirring, filtering the mixture three times through a 200-mesh filter to obtain an electrolyte additive.

[0045] Example 6 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, in parts by weight, of 100 parts lithium metaphosphate, 4320 parts fluoroethylene carbonate, 45 parts 2-pyrrole formaldehyde, and 10 parts perfluorotripropylamine.

[0046] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 4,320 parts of fluoroethylene carbonate, stirring for 3 hours, and then sequentially adding 45 parts of 2-pyrrole formaldehyde and 10 parts of perfluorotripropylamine, and continuing to stir for 16 hours. After stirring is completed, the resulting mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0047] Example 7 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 22 parts 2-pyrrole formaldehyde, 31 parts terephthalaldehyde, and 18 parts perfluorotripropylamine. The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 3,700 parts of fluoroethylene carbonate, stirring for 3 hours, and then sequentially adding 22 parts of 2-pyrrole formaldehyde, 31 parts of terephthalaldehyde, and 18 parts of perfluorotripropylamine, and continuing to stir for 16 hours. After stirring, the mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0048] Example 8 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 44 parts 6-(2-thienyl)-2-pyridylaldehyde, 25 parts 1-methyl-2-pyrrole formaldehyde, and 18 parts perfluorotripropylamine.

[0049] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 3,700 parts of fluoroethylene carbonate, stirring for 2 hours, and then sequentially adding 44 parts of 6-(2-thienyl)-2-pyridylaldehyde, 25 parts of 1-methyl-2-pyrrole formaldehyde, and 18 parts of perfluorotripropylamine, and continuing to stir for 16 hours. After stirring, the resulting mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0050] Example 9 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, in parts by weight, from 100 parts of (S)-ganciclovir-5′-triphosphate lithium salt, 600 parts of fluoroethylene carbonate, 44 parts of 6-(2-thienyl)-2-pyridylaldehyde, 42 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 22 parts of 3-pyrrole formaldehyde, and 18 parts of perfluorotripropylamine.

[0051] The preparation method includes step 01: in a N2 atmosphere, weigh out 100 parts of (S)-ganciclovir-5'-triphosphate lithium salt, add it to 600 parts of fluoroethylene carbonate, and stir for 1 hour; then sequentially add 42 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 22 parts of 3-pyrroleformaldehyde, and 18 parts of perfluorotripropylamine; continue stirring for 15 hours; and after stirring, filter three times through a 200-mesh filter to obtain an electrolyte additive.

[0052] Example 10 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of lithium metaphosphate, 4320 parts of fluoroethylene carbonate, 42 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts of 1-methyl-2-pyrrole formaldehyde, and 5 parts of flumiclorac pentyl.

[0053] The preparation method includes step 01: in an N2 atmosphere, weigh out 100 parts of lithium metaphosphate, add it to 4,320 parts of fluoroethylene carbonate, and stir for 1 hour; then sequentially add 42 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts of 1-methyl-2-pyrrole formaldehyde, and 5 parts of flumiclorac pentyl; continue stirring for 16 hours; and after stirring, filter three times through a 200-mesh filter to obtain an electrolyte additive.

[0054] Example 11 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 44 parts N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts 1-methyl-2-pyrrole formaldehyde, and 7.2 parts synflumid.

[0055] The preparation method includes step 01: in an N2 atmosphere, weigh out 100 parts of lithium metaphosphate, add it to 3700 parts of fluoroethylene carbonate, and stir for 1 hour; then sequentially add 44 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts of 1-methyl-2-pyrrole formaldehyde, and 7.2 parts of synflumid; continue stirring for 16 hours; and after stirring, filter three times through a 200-mesh filter to obtain an electrolyte additive.

[0056] Example 12 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 44 parts N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts 1-methyl-2-pyrrole formaldehyde, and 9.4 parts teriflunomide.

[0057] The preparation method includes step 01: in an N2 atmosphere, weighing 100 parts of lithium metaphosphate and adding it to 3,700 parts of fluoroethylene carbonate, stirring for 1 hour, and then sequentially adding 44 parts of N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts of 1-methyl-2-pyrrole formaldehyde, and 9.4 parts of teriflunomide, and continuing to stir for 16 hours. After stirring is completed, the mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0058] Example 13 This example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, 44 parts N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 25 parts 1-methyl-2-pyrrole formaldehyde, and 9.4 parts teriflunomide.

[0059] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 3,600 parts of ethylene carbonate, stirring for 1 hour, and then sequentially adding 44 parts of 2-pyrrole formaldehyde and 9.8 parts of perfluorotripropylamine, and continuing to stir for 16 hours. After stirring is completed, the resulting mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0060] Comparison 1 This comparative example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts lithium metaphosphate, 3700 parts fluoroethylene carbonate, and 15.6 parts terephthalaldehyde.

[0061] The preparation method includes step 01: in a N2 atmosphere, weighing 100 parts of lithium metaphosphate, adding it to 3700 parts of fluoroethylene carbonate, stirring for 2 hours, adding 15.6 parts of terephthalaldehyde, continuing to stir for 12 hours, and after stirring, filtering the mixture three times through a 200-mesh filter to obtain an electrolyte additive.

[0062] Comparison 2 This comparative example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of lithium metaphosphate, 4930 parts of dimethyl carbonate, 44 parts of 6-(2-thienyl)-2-pyridylaldehyde, and 10 parts of flumiclorac pentyl.

[0063] The preparation method includes step 01 of weighing 100 parts of lithium metaphosphate in a N2 atmosphere, adding it to 4930 parts of dimethyl carbonate, stirring for 2 hours, and then sequentially adding 44 parts of 6-(2-thienyl)-2-pyridylaldehyde and 10 parts of flumiclorac pentyl, and continuing to stir for 12 hours. After stirring is completed, the mixture is filtered three times through a 200-mesh filter to obtain an electrolyte additive.

[0064] Comparison 3 This comparative example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, by weight, from 100 parts of lithium metaphosphate, 4930 parts of dimethyl carbonate, 44 parts of 6-(2-thienyl)-2-pyridylaldehyde, and 10 parts of flumiclorac pentyl.

[0065] The preparation method includes step 01: in a N2 atmosphere, weigh out 100 parts of lithium metaphosphate, add it to 4930 parts of fluoroethylene carbonate, and stir for 2 hours, then add 10 parts of flumiclorac pentyl, and continue stirring for 12 hours; after stirring, filter the mixture three times through a 200-mesh filter to obtain an electrolyte additive.

[0066] Comparison 4 This comparative example provides an electrolyte additive for lithium ion batteries and a preparation method thereof. The lithium ion battery electrolyte additive comprises a mixture formed, in parts by weight, of 100 parts of α,β-methylene adenosine 5′-triphosphate lithium salt, 615 parts of fluoroethylene carbonate, and 33 parts of 2-pyrrole formaldehyde.

[0067] The preparation method includes step 01 of weighing 100 parts of α,β-methylene adenosine 5'-triphosphate lithium salt in an Ar atmosphere, adding it to 615 parts of fluoroethylene carbonate, stirring for 3 hours, adding 33 parts of 2-pyrrole formaldehyde, continuing to stir for 16 hours, and after stirring, filtering the mixture three times through a 200-mesh filter to obtain an electrolyte additive.

[0068] Test Example In these test examples, lithium batteries were manufactured using the corrosion inhibitors prepared in Examples 1 to 13 and Comparative Examples 1 to 5 as functional additive components, and their electrochemical performance was tested. The manufacturing and testing methods for lithium batteries were based on GB / T 42260-2022 "Test Method for Cycle Life in Electrochemical Performance Tests of Lithium Iron Phosphate" and GB / T 42161-2022 "Test Method for Initial Discharge Specific Capacity and Initial Charge / Discharge Efficiency in Electrochemical Performance Tests of Lithium Iron Phosphate."

[0069] Specific process: After pre-processing some materials, the steps of positive electrode production, negative electrode production, separator preparation, battery assembly, battery capacity screening, and battery testing are carried out sequentially to obtain final test data. Specifically, the lithium iron phosphate positive electrode material used was manufactured by Hubei Wanrun Co., Ltd., the graphite negative electrode was manufactured by Ningbo Shanshan Co., Ltd., and all other materials met the standard requirements. The lithium flakes were manufactured by Tianjin Zhongneng Co., Ltd., the conductive carbon material was conductive sp manufactured by Kejing Co., Ltd., and the electrolyte was a 1.0 mol / L LiPF6 solution (solvent: ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1), purchased from Guangdong Candlelight New Energy Technology Co., Ltd.

[0070] The test method for the initial discharge specific capacity and initial charge / discharge efficiency was to place the fabricated test battery in a thermostatic box, control the temperature at (23±2)°C, and leave it for 1-2 hours before testing it with an ion battery electrochemical performance tester. The charge / discharge procedure was to charge the battery at a constant current of 0.1C up to a charge limit voltage of 3.75V, then charge at a constant voltage with a constant voltage charge cutoff current of 0.05C, and discharge at a constant current of 0.1C down to a discharge end voltage of 2.0V.

[0071] The cycle life test conditions were to conduct a cycle life test on the test batteries after chemical formation and capacity screening using a lithium-ion battery electrochemical performance tester. The charge / discharge voltage limits were constant current / constant voltage charging up to a charge limit voltage of 3.6-3.7V, a constant charge cut-off current of 0.02C-0.05C, and a discharge end voltage of 2.0V-2.5V. The charge / discharge regime was 1C / 1C in accordance with GB / T18287, with the charge / discharge cycles performed at ambient temperatures of (23±2)°C and (55±2)°C, respectively.

[0072] The test data for each of the above are shown in Table 1 below (wherein the amount used represents the percentage of the additive prepared in the examples or comparative examples relative to the total mass of the electrolyte).

[0073] [Table 1]

[0074] Under the condition that an appropriate amount of corrosion-preventing additive is used, the electrochemical performance of the lithium battery improves as the amount of additive used increases. At the same time, under the appropriate amount of additive, the additive prepared in the examples can achieve the effect of targeting the corrosion of the electrode pieces by the electrolyte and improving performance.

[0075] In Comparative Examples 1 and 4, no cosolvent was added. When the cosolvent was insufficient, the solubility of the active ingredient was significantly reduced, making it difficult to achieve good erosion prevention. In Comparative Example 2, dimethyl carbonate was used instead of fluoroethylene carbonate. Dimethyl carbonate has good solubility in other materials, but the F atom in the molecular structure of fluoroethylene carbonate reduces / passivates the electrode surface under high potential conditions due to its electron absorption effect, forming a stable SEI film. However, dimethyl carbonate does not have this function, so the overall effect is much less than that of the Examples. In Comparative Example 3, no resist aid was added. The combined effect between the etching resist and the resist aid is crucial for erosion prevention. Therefore, when the etching resist is insufficient, the overall effect is significantly less than that of the Examples.

[0076] Although the present invention has been described using specific embodiments, it should be noted that the above embodiments are only used to describe the technical solutions of the present invention, and are not intended to limit them. Those skilled in the art should understand that, without departing from the spirit and scope of the present invention, they can modify the technical solutions described in the above embodiments or equivalently replace some or all of the technical features therein, and these modifications or replacements will not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention. Therefore, the appended claims are intended to include all such replacements and modifications belonging to the present invention.

Claims

1. A mixture formed from an etching resist, a resist auxiliary, a film-forming agent, and a co-solvent, wherein the molar ratio of the etching resist, the resist auxiliary, the film-forming agent, and the co-solvent is 1:(0.1-1):(20-50):(0.01-0.1); The etching resist is a compound containing lithium metaphosphate, lithium guanosine triphosphate, α at least one of β-methylene adenosine 5'-triphosphate lithium salt and (S)-ganciclovir-5'-triphosphate lithium salt, the resist aid is at least one of terephthalaldehyde, 6-(2-thienyl)-2-pyridylaldehyde, N-methyl-N-(2-hydroxyethyl)-4-aminobenzaldehyde, 2-pyrrole formaldehyde, 1-methyl-2-pyrrole formaldehyde, and 3-pyrrole formaldehyde; the film-forming agent is at least one of fluoroethylene carbonate or ethylene carbonate; The electrolyte additive for lithium ion batteries is characterized in that the cosolvent is at least one of flumiclorac pentyl, perfluorotripropylamine, cinflumid, and teriflunomide.

2. 2. The electrolyte additive for lithium ion batteries according to claim 1, wherein the molar ratio of the etching resist, the resist aid, the film forming agent, and the co-solvent is 1:(0.1-0.4):(30-40):(0.01-0.03).

3. A method for preparing the lithium ion battery electrolyte additive according to claim 1 or 2, First, the etching resist and the film forming agent are mixed together for the first time under an inert atmosphere; Then, adding a co-solvent and a resist aid in sequence, mixing for a second time, and then filtering to obtain the electrolyte additive.

4. 4. The method for preparing an electrolyte additive for a lithium ion battery according to claim 3, wherein the duration of the first mixing is 1 hour to 3 hours, and the duration of the second mixing is 12 hours to 16 hours.

5. 4. The method for preparing an electrolyte additive for a lithium ion battery according to claim 3, wherein the pore size of the filtration screen is 150 mesh to 300 mesh.

6. A lithium ion battery comprising the electrolyte additive for lithium ion batteries according to claim 1 or 2.

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