Preparation process of lithium battery additive

Abstract

This invention relates to the field of lithium battery technology, and more particularly to a preparation process for a lithium battery additive. The process first prepares a Zn-MOF-74 catalyst through dissolution, crystallization, separation, and stepwise vacuum drying. Then, using γ-valerolactone as a solvent, propenyl-1,3-sulfonyl lactone undergoes an addition reaction with 4-aminophenylboronic acid under the action of the catalyst to generate an intermediate. This intermediate then undergoes a substitution reaction with ethyl bromoethyl, followed by recrystallization and vacuum drying to obtain a sulfonate-boron-oxygen heterocyclic synergistic additive. This additive utilizes the synergistic effect of the sulfonate group and the boron-oxygen heterocycle to improve the ionic conductivity of the electrolyte and inhibit its decomposition, significantly improving the room-temperature cycle life, wide-temperature-range discharge performance, and high-temperature storage stability of lithium batteries. The preparation process is controllable, the product has high purity, and it is suitable for various high-performance lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a preparation process for a lithium battery additive. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density and long cycle life, have been widely used in consumer electronics, new energy vehicles, and other fields. However, they still face many performance bottlenecks in practical applications. At low temperatures, the ionic conductivity of the electrolyte decreases, leading to a significant reduction in battery discharge capacity. At high temperatures, the electrolyte is prone to decomposition, causing increased internal resistance and poorer cycle stability, severely impacting battery safety and lifespan.

[0003] Traditional lithium battery additives are mostly single-function, such as only improving ionic conductivity or only inhibiting electrolyte decomposition, making it difficult to simultaneously meet multiple requirements such as wide temperature range adaptability, cycle stability, and safety. At the same time, the preparation process of some additives is complex, with a large number of by-products during the reaction, resulting in insufficient product purity, which further limits the improvement of battery performance and fails to meet the stringent requirements of high-end equipment for the comprehensive performance of lithium batteries. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a preparation process for lithium battery additives. By preparing a sulfonate-boron-oxygen heterocyclic synergistic additive, the problems of single function and numerous by-products of traditional lithium battery additives are solved. At the same time, it improves the performance defects of lithium batteries such as low-temperature discharge decay, high-temperature electrolyte decomposition, and short cycle life. Specifically, this is achieved through the following technical solution.

[0005] The present invention discloses a process for preparing a lithium battery additive, comprising the following steps: Step 1: Under inert gas protection, γ-valerolactone, propenyl-1,3-sulfonyl lactone and Zn-MOF-74 catalyst are mixed, heated and stirred, and 4-aminophenylboronic acid is added dropwise to react and generate a boron-oxyheterocyclic ester intermediate. Step 2: After cooling the reaction solution from Step 1, filter it to separate the filtrate and the solid catalyst; Step 3: React the filtrate obtained in Step 2 with ethyl bromoacetate to introduce sulfonate groups, resulting in a mixture of white needle-like crystals and liquid. Step 4: Filter, wash and recrystallize the white needle-like crystals obtained in Step 3 with the liquid mixture to obtain white flaky crystals; Step 5: Vacuum dry the white flaky crystals obtained in Step 4 to obtain a sulfonate-boron-oxygen heterocyclic synergistic additive.

[0006] Preferably, the preparation of the Zn-MOF-74 catalyst includes the following steps: S1: Dissolve zinc nitrate and 2,5-dihydroxyterephthalic acid in N,N-dimethylformamide to form a solution; S2: The solution is heated to react and a mixture is obtained; S3: The mixture is subjected to solid-liquid separation to obtain crude Zn-MOF-74, which is then washed with anhydrous ethanol and deionized water. S4: The washed Zn-MOF-74 product was vacuum dried to obtain the Zn-MOF-74 catalyst.

[0007] Preferably, in step S1, the molar ratio of N,N-dimethylformamide, zinc nitrate and 2,5-dihydroxyterephthalic acid is 60-70:0.9-1.1:0.9-1.1.

[0008] Preferably, in step S2, the heating reaction is carried out at a rate of 5°C / min from room temperature to 120°C and held at that temperature for 24 hours. In step S4, the vacuum drying includes drying at 55-70°C and -0.095-0.03 MPa for 4-6 hours, and then drying at 110-130°C and -0.098-0.03 MPa for 10-12 hours.

[0009] Preferably, in step 1, the mass ratio of γ-valerolactone, propenyl-1,3-sulfonyl lactone and 4-aminophenylboronic acid is 90-110:7-9:6-8. The mass ratio of the propylene-1,3-sulfonyl lactone to the Zn-MOF-74 catalyst is 20:1 to 2.

[0010] Preferably, in step 1, the reaction conditions include: heating to 60-65°C before adding the catalyst, adding 4-aminophenylboronic acid dropwise over 1.2-1.5 hours, and then heating to 80-85°C and holding at that temperature for 8-10 hours after the addition is complete.

[0011] Preferably, in step 3, the molar ratio of the propenyl-1,3-sulfonyl lactone to ethyl bromoacetate is 1:1.1 to 1.3; The reaction conditions include: the temperature is 50-55℃ when adding ethyl bromoethyl, the addition time is 1-1.2 hours, the temperature is raised to 70-75℃ after the addition is completed and the reaction is maintained for 12-14 hours, and the stirring speed is maintained at 180-220 r / min during the reaction.

[0012] Preferably, in step 4, the recrystallization process uses an ethanol-water mixed solvent, wherein the volume ratio of ethanol to water is 3:1; The mass ratio of the ethanol-water mixed solvent to the mass of propylene-1,3-sulfonyl lactone in step 1 is 5-6:8.

[0013] Preferably, in step 4, the recrystallization process includes dissolving the crystals in an ethanol-water mixed solvent, heating to 70°C and stirring until completely dissolved, filtering while hot, and then allowing to stand at 0-5°C for 8 hours to crystallize.

[0014] Preferably, in step 5, the vacuum drying is carried out at 50°C and -0.098 MPa for 6 hours.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are: 1. The prepared sulfonate-boron-oxygen heterocyclic synergistic additive, through the synergistic effect of sulfonate groups and boron-oxygen heterocycles, not only improves the ionic conductivity of the electrolyte by means of sulfonate groups, but also inhibits electrolyte decomposition by means of boron-oxygen heterocycles, significantly improving the room temperature cycle life, wide temperature range discharge performance and high temperature storage stability of lithium batteries. After 500 cycles, the capacity retention rate is over 95%, the low temperature discharge retention rate at -20℃ is over 75%, and the performance degradation is slight after high temperature storage at 60℃.

[0016] 2. The catalyst preparation adopts stepwise vacuum drying and precise temperature control to ensure that the active sites of Zn-MOF-74 catalyst are fully activated. During the additive synthesis process, by controlling parameters such as reactant ratio, dropping rate, and reaction temperature, the generation of by-products is reduced and the purity of the product is improved. At the same time, the catalyst can be recycled and reused, reducing production costs.

[0017] 3. This additive is highly compatible with existing lithium battery electrolyte systems and can be added directly without adjusting the battery manufacturing process. The product has low water content and high purity, which can effectively reduce the internal resistance of the battery and reduce the risk of thermal runaway during battery use, thus ensuring the safe and stable operation of lithium batteries in different environments. Detailed Implementation

[0018] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0019] The present invention provides a process for preparing a lithium battery additive, the process comprising the following steps: Step 1: Add γ-valerol and propenyl-1,3-sulfonyl lactone to a four-necked flask, purge with nitrogen, heat to 60-65°C, add Zn-MOF-74 catalyst, stir for 10 minutes, and add 4-aminophenylboronic acid dropwise over 1.2-1.5 hours. After the addition is complete, heat to 80-85°C and maintain the temperature for 8-10 hours.

[0020] In the above process, the mass ratio of γ-valerolactone, propenyl-1,3-sulfonyl lactone, and 4-aminophenylboronic acid added is 90-110:7-9:6-8.

[0021] In the above process, Zn-MOF-74 catalyst is added in a ratio of propylene-1,3-sulfonyl lactone:Zn-MOF-74 catalyst = 20:1~2.

[0022] The aforementioned four-necked flask includes a mechanical stirrer, a thermometer, a dropping funnel, and a nitrogen protection device, which facilitates stirring, temperature monitoring, addition of 4-aminophenylboronic acid, and introduction of nitrogen during the reaction process.

[0023] During the above steps, the 4-aminophenylboronic acid is added dropwise while stirring at a speed of 250–300 r / min. Nitrogen gas is also introduced during the dropwise addition of 4-aminophenylboronic acid at a flow rate of 50–70 mL / min.

[0024] During the reaction process described above, the double bond of propenyl-1,3-sulfonyl lactone undergoes an addition reaction with the amino group of 4-aminophenylboronic acid to generate a boron-containing heterocyclic ester intermediate.

[0025] In this process, γ-valerolactone is added in excess as a solvent to ensure complete dissolution of the reactants and maintain the stability of the reaction system, avoiding side reactions caused by excessively high local concentrations. The amounts of propenyl-1,3-sulfonyl lactone and 4-aminophenylboronic acid are added according to the stoichiometry of the chemical reaction. Nitrogen is an inert gas that can remove oxygen and moisture from the reaction system and prevent 4-aminophenylboronic acid from being oxidized. The slow dropwise addition of 4-aminophenylboronic acid can control the reaction rate and avoid the formation of byproducts due to excessively high instantaneous concentrations of reactants.

[0026] The preparation method of the Zn-MOF-74 catalyst in the above steps includes the following steps: S1: Add anhydrous DMF to a beaker, add zinc nitrate to the beaker, place it on a magnetic stirrer and stir for 10-15 minutes until the zinc nitrate is completely dissolved. Add 2,5-dihydroxyterephthalic acid and continue stirring for 30-40 minutes until the 2,5-dihydroxyterephthalic acid is completely dissolved, to obtain a pale yellow clear solution. The molar ratio of DMF, zinc nitrate, and 2,5-dihydroxyterephthalic acid is 60–70:0.9–1.1:0.9–1.1. In this ratio, DMF is used in excess as a solvent. On the one hand, this ensures that zinc nitrate and organic ligands are completely dissolved, avoiding solid residues that may affect subsequent reactions. On the other hand, excess DMF can maintain the stability of the reaction system and prevent premature precipitation of metal-organic framework materials, which could lead to structural inhomogeneity.

[0027] The magnetic stirrer operates at a speed of 280–320 r / min to accelerate the dissolution of zinc nitrate and 2,5-dihydroxyterephthalic acid, ensuring uniform dispersion of the two in DMF and preventing excessively high local concentrations that could lead to ligand polymerization and affect the pore size and structure of the MOF material.

[0028] S2: Transfer the pale yellow clear solution obtained in step S1 to a reaction vessel, raise the temperature from room temperature to 120°C at a rate of 5°C / min, and keep it at that temperature for 24 hours. After the reaction is completed, allow it to cool naturally to room temperature to obtain a mixed solution.

[0029] The above-described process of slow heating avoids sudden local temperature rises within the reactor, preventing rapid precipitation of MOF materials that could lead to disordered crystal structures and uneven pore sizes. It also reduces impurity phases caused by temperature fluctuations, ensuring product structural consistency. Furthermore, a reaction temperature of 120℃ facilitates the growth of Zn. 2+ It forms a stable MOF-74 structure with 2,5-dihydroxyterephthalic acid. A holding time of 24 hours can ensure that the reaction proceeds fully. Natural cooling to room temperature can reduce internal stress in the crystal, prevent crystal cracking or structural collapse, and ensure the structural integrity of Zn-MOF-74.

[0030] S3: Transfer the mixture obtained in step S2 to a centrifuge for solid-liquid separation. The resulting pale yellow granules are crude Zn-MOF-74. Wash the crude Zn-MOF-74 twice with anhydrous ethanol, and then wash it twice more with deionized water to obtain the Zn-MOF-74 product.

[0031] The volume of anhydrous ethanol used in each wash is the same as the volume of DMF added in step S1, and the volume of deionized water used in each wash is the same as the volume of DMF added in step S1.

[0032] The above steps, through centrifugation, initially separate the crude Zn-MOF-74 product from the liquid mixture. By repeatedly rinsing the crude Zn-MOF-74 product with anhydrous ethanol and deionized water, the residual DMF and unreacted organic ligands on the surface of the crude product can be effectively dissolved and removed, resulting in a Zn-MOF-74 product with higher purity, laying the foundation for subsequent activation.

[0033] S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, and dry it for 4 to 6 hours at 55 to 70°C and -0.095 to -0.03 MPa, and then dry it for 10 to 12 hours at 110 to 130°C and -0.098 to -0.03 MPa. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0034] The Zn-MOF-74 product is spread to a thickness of less than or equal to 2 mm in the quartz boat to avoid accumulation that could lead to insufficient activation.

[0035] The purpose of using different drying temperatures under vacuum conditions in the above steps is to deeply remove residual DMF, ethanol and deionized water from the pores, thereby activating the catalytic active sites.

[0036] After drying, the catalyst is cooled to room temperature under vacuum to prevent moisture from the air from re-entering the Zn-MOF-74 channels during the cooling process, thus ensuring the dryness and activity of the catalyst.

[0037] Step 2: The reaction solution in step 1 was cooled to room temperature, filtered to separate solid and liquid, and the filtrate and solid catalyst were obtained. The solid catalyst was washed twice with γ-valerol and dried under vacuum at 100°C for 4 hours before use.

[0038] The collected filtrate is a γ-valerol solution containing boronoxane intermediates. The washed and dried solid catalyst can be reused multiple times.

[0039] This step separates the intermediate solution from the catalyst, while simultaneously recovering and activating the catalyst, thus reducing process costs. In this process, washing with γ-valerol can remove the intermediates and unreacted raw materials adsorbed on the catalyst surface without introducing new impurities.

[0040] Step 3: Transfer the filtrate from step 2 to a four-necked flask, stir and heat to 50-55°C, add ethyl bromoethyl dropwise to the solution over 1-1.2 hours. After the addition is complete, heat to 70-75°C and maintain the temperature for 12-14 hours. After the reaction is complete, allow it to cool naturally to room temperature and let it stand for 10-12 hours to obtain a mixture of white needle-like crystals and liquid.

[0041] In step 1, the molar ratio of propenyl-1,3-sulfonyl lactone to ethyl bromoacetate is 1:1.1 to 1.3. Excess ethyl bromoacetate ensures complete reaction of the amino group in the intermediate, introduces sulfonate groups, improves the ionic conductivity of the product, and avoids incomplete modification of the intermediate due to insufficient ethyl bromoacetate, which would affect the performance of the final product.

[0042] During the above reaction process, stirring is maintained at a speed of 180–220 r / min.

[0043] This step introduces sulfonate groups onto the borooxyheterocyclic ester intermediate via a substitution reaction, generating white needle-like crystals and laying the foundation for the sulfonate-boronoxyheterocyclic co-structure of the final product.

[0044] The introduced sulfonate group can improve the ionic conductivity of the product, and combined with the effect of boron-oxygen heterocycles in inhibiting the decomposition of lithium battery electrolyte, the two work synergistically to improve battery performance.

[0045] Step 4: After filtering the white needle-like crystal liquid mixture obtained in step 3, the solid was washed twice with γ-valerol and then transferred to a beaker. An ethanol-water mixture was added to the beaker, the temperature was raised to 70°C, and the mixture was stirred until the crystals were completely dissolved. After filtering while hot, the beaker was sealed and placed in a refrigerator at 0-5°C for 8 hours to obtain a white flaky crystal and liquid mixture.

[0046] The ethanol-water mixed solvent is prepared at a volume ratio of ethanol to water of 3:1.

[0047] The ratio of the mass of the ethanol-water mixed solvent prepared according to the above ratio to the mass of the propylene-1,3-sulfonyl lactone added in step 1 is 5 to 6:8.

[0048] In this process, trace impurities in the product are removed by recrystallization to obtain white flaky crystals with higher purity, thus avoiding the impact of impurities on the cycle performance and safety of lithium batteries.

[0049] In the above process, the crystals after filtration are washed multiple times with γ-valerol to remove impurities adsorbed on the crystal surface. The crystals are then heated to dissolve and filtered while hot to remove trace impurities that have not dissolved during the dissolution process, thus preventing impurities from precipitating with the crystals and affecting the purity of the final product. The crystals are then allowed to crystallize in a refrigerator, which enables rapid crystallization and collection of the product.

[0050] Step 5: The white flaky crystals obtained in step 4 were filtered and the liquid mixture was collected. The crystals were then transferred to a vacuum drying oven and dried at 50°C and -0.098 MPa for 6 hours to obtain the final product, a sulfonate-boron-oxygen heterocyclic synergistic additive.

[0051] In the above process, vacuum drying at 50°C avoids product decomposition caused by high temperature and quickly removes residual ethanol-water mixed solvent from the crystals, preventing solvent residue from affecting the electrochemical performance of the product. The final product is a pure sulfonate-boron-oxygen heterocyclic synergistic additive with low water content and high purity. It has the high ionic conductivity of sulfonate groups and the electrolyte stabilizing effect of boron-oxygen heterocycles, which can effectively improve the cycle life, rate performance and safety of lithium batteries.

[0052] To facilitate understanding of the present invention, the following embodiments and comparative examples are provided: Example 1 Phase 1: Catalyst Preparation S1: Add 20 mL of anhydrous DMF to a beaker, add 1.19 g of zinc nitrate to the beaker, place it on a magnetic stirrer and stir at 300 r / min for 12 minutes until the zinc nitrate is completely dissolved, add 0.72 g of 2,5-dihydroxyterephthalic acid, and continue stirring for 32 minutes until the 2,5-dihydroxyterephthalic acid is completely dissolved, to obtain a pale yellow clear solution; S2: Transfer the pale yellow clear solution obtained in step S1 to a reaction vessel, raise the temperature from room temperature to 120°C at a rate of 5°C / min, and keep it at that temperature for 24 hours. After the reaction is completed, allow it to cool naturally to room temperature to obtain a mixed solution.

[0053] S3: Transfer the mixture obtained in step S2 to a centrifuge for solid-liquid separation to obtain crude Zn-MOF-74 granules. Wash the crude Zn-MOF-74 twice with anhydrous ethanol and then wash it twice with deionized water to obtain the Zn-MOF-74 product.

[0054] S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, dry it for 6 hours at 60℃ and -0.095MPa, and then dry it for 12 hours at 120℃ and -0.098MPa. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0055] Phase 2: Preparation of sulfonate-boron-heterocyclic synergistic additives Step 1: Add 500 mL of γ-valerol and 40 g of propenyl-1,3-sulfonyl lactone to a four-necked flask. Purge with nitrogen gas at a flow rate of 50 mL / min. After heating to 62 °C, add 2 g of Zn-MOF-74 catalyst and stir at 250 r / min for 10 minutes. Then, add 35 g of 4-aminophenylboronic acid dropwise over 1.2 hours. After the addition is complete, heat to 80 °C and maintain the temperature for 8 hours.

[0056] Step 2: The reaction solution in step 1 was cooled to room temperature, filtered to separate solid and liquid, and the filtrate and solid catalyst were obtained. The solid catalyst was washed twice with 50 mL of γ-valerol and dried under vacuum at 100 °C for 4 hours before use.

[0057] Step 3: Transfer the filtrate from step 2 to a 1000 mL four-necked flask, stir at 200 r / min and heat to 50 °C, add 42 g of ethyl bromoacetate dropwise over 1 hour, and after the addition is complete, heat to 70 °C and keep the reaction at that temperature for 12 hours. After the reaction is complete, allow it to cool naturally to room temperature and let it stand for 10 hours to obtain a mixture of white needle-like crystals and liquid.

[0058] Step 4: After filtering the white needle-like crystal-liquid mixture obtained in step 3, the solid was washed twice with γ-valerolactone and then transferred to a beaker. 30 mL of an ethanol-water mixture prepared at a volume ratio of 3:1 was added to the beaker, the temperature was raised to 70°C, and the mixture was stirred until the crystals were completely dissolved. After filtering while hot, the beaker was sealed and placed in a 0°C refrigerator for 8 hours to obtain a white flaky crystal-liquid mixture.

[0059] Step 5: The white flaky crystals obtained in step 4 were filtered and the liquid mixture was collected. The crystals were then transferred to a vacuum drying oven and dried at 50°C and -0.098 MPa for 6 hours to obtain the final product, a sulfonate-boron-oxygen heterocyclic synergistic additive.

[0060] Example 2 This embodiment is based on Example 1, but the temperature of the catalyst vacuum drying in step S4 of the first stage is adjusted, specifically as follows: S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, dry it at 55℃ and -0.095MPa for 6 hours, and then dry it at 110℃ and -0.098MPa for 12 hours. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0061] The remaining steps are exactly the same as in Example 1.

[0062] Example 3 This embodiment is based on Example 1, but the vacuum degree of the catalyst vacuum drying in step S4 of the first stage is adjusted, specifically as follows: S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, dry it for 6 hours at 60℃ and -0.06MPa, and then dry it for 12 hours at 120℃ and -0.06MPa. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0063] The remaining steps are exactly the same as in Example 1.

[0064] Example 4 This embodiment is based on Example 1, but with adjustments made to the catalyst vacuum drying time in step S4 of the first stage. Specifically: S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, dry it at 60℃ and -0.095MPa for 4 hours, and then dry it at 120℃ and -0.098MPa for 10 hours. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0065] The remaining steps are exactly the same as in Example 1.

[0066] Example 5 This embodiment is based on Example 1, but with adjustments made to the amount of catalyst used in step 1 of the second stage, specifically: Step 1: Add 500 mL of γ-valerol and 40 g of propenyl-1,3-sulfonyl lactone to a four-necked flask. Purge with nitrogen gas at a flow rate of 50 mL / min. After heating to 62 °C, add 3 g of Zn-MOF-74 catalyst and stir at 250 r / min for 10 minutes. Then, add 35 g of 4-aminophenylboronic acid dropwise over 1.2 hours. After the addition is complete, heat to 80 °C and maintain the temperature for 8 hours.

[0067] The remaining steps are exactly the same as in Example 1.

[0068] Example 6 This embodiment is based on Example 1, but the dropping time of 4-aminophenylboronic acid in step 1 of the second stage is adjusted, specifically as follows: Step 1: Add 500 mL of γ-valerol and 40 g of propenyl-1,3-sulfonyl lactone to a four-necked flask. Purge with nitrogen gas at a flow rate of 50 mL / min. After heating to 62 °C, add 2 g of Zn-MOF-74 catalyst and stir at 250 r / min for 10 minutes. Then, add 35 g of 4-aminophenylboronic acid dropwise over 1.5 hours. After the addition is complete, heat to 80 °C and maintain the temperature for 8 hours.

[0069] The remaining steps are exactly the same as in Example 1.

[0070] Example 7 This embodiment is based on Example 1, but adjusts the amount of ethyl bromoacetate in step 3 of the second stage, specifically as follows: Step 3: Transfer the filtrate from step 2 to a 1000 mL four-necked flask, stir at 200 r / min and heat to 50 °C, add 38.5 g of ethyl bromoacetate dropwise to the solution over 1 hour. After the addition is complete, heat to 70 °C and maintain the temperature for 12 hours. After the reaction is complete, allow it to cool naturally to room temperature and let it stand for 10 hours to obtain a mixture of white needle-like crystals and liquid.

[0071] The remaining steps are exactly the same as in Example 1.

[0072] Example 8 This embodiment is based on Example 1, but the dropping time of ethyl bromoacetate in step 3 of the second stage is adjusted, specifically as follows: Step 3: Transfer the filtrate from step 2 to a 1000 mL four-necked flask, stir at 200 r / min and heat to 50 °C, add 42 g of ethyl bromoacetate dropwise over 1.2 hours. After the addition is complete, heat to 70 °C and maintain the temperature for 12 hours. After the reaction is complete, allow it to cool naturally to room temperature and let it stand for 10 hours to obtain a mixture of white needle-like crystals and liquid.

[0073] The remaining steps are exactly the same as in Example 1.

[0074] Comparative Example 1 This comparative example is based on Example 1, with adjustments made to the catalyst drying process in step 4 of the first stage, specifically: S4: Transfer the Zn-MOF-74 product obtained in step S3 to a quartz boat, place the quartz boat in a vacuum drying oven, and dry it at 100℃ and -0.095MPa for 15 hours. After drying, keep it under vacuum and cool it to room temperature to obtain a light yellow powdered Zn-MOF-74 catalyst.

[0075] The remaining steps are exactly the same as in Example 1.

[0076] Comparative Example 2 This comparative example is based on Example 1, with the first stage removed and the catalyst no longer added in step 1 of the second stage. Specifically: Step 1: Add 500 mL of γ-valerol and 40 g of propenyl-1,3-sulfonyl lactone to a four-necked flask. Purge with nitrogen gas at a flow rate of 50 mL / min. Heat to 62 °C and stir at 250 r / min for 10 minutes. Add 35 g of 4-aminophenylboronic acid dropwise over 1.2 hours. After the addition is complete, heat to 80 °C and maintain the temperature for 8 hours.

[0077] The remaining steps are exactly the same as in Example 1.

[0078] Comparative Example 3 Propylene-1,3-sulfonyl lactone was used as an additive for lithium batteries.

[0079] Comparative Example 4 Lithium dioxaborate was used as an additive for lithium batteries.

[0080] The lithium battery additives from the above examples and comparative examples were used to prepare electrolytes at a concentration of 1.5%. The solvent of the electrolyte was a mixture of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7. Lithium hexafluorophosphate at a concentration of 1.0 mol / L was added to the electrolyte.

[0081] The above electrolyte is filled into an aluminum-plastic film pouch cell to prepare an aluminum-plastic film pouch cell battery, and the positive electrode material of the battery is LiNi. 0.6 Co 0.2 Mn 0.2 O2, the negative electrode material is a silicon-carbon composite material with a silicon content of 10%.

[0082] Batteries prepared in different embodiments and comparative examples were subjected to room temperature cycle life tests, wide temperature range discharge performance tests, AC impedance tests, and high temperature storage performance tests. The test data are as follows:

[0083] Based on the comparative analysis of the above data, it can be seen that the sulfonate boron oxide heterocyclic synergistic additive provided by the present invention exhibits strong comprehensive performance.

[0084] Examples 1, 5, 6, and 8 all exhibited excellent performance in key indicators such as room temperature cycle life, wide temperature range discharge performance, AC impedance, and high temperature storage performance. After 500 cycles, the capacity retention rate generally exceeded 95%, the low-temperature discharge retention rate at -20°C was higher than 75%, and the internal resistance was lower than 22.5mΩ. These data are significantly better than all comparative examples, fully demonstrating that the synergistic additive prepared by precise processes can effectively improve the overall performance of lithium batteries.

[0085] Specifically, in each embodiment, the catalyst preparation and synthesis process parameters of Example 1 were in the optimal range. The performance of Example 5 was slightly improved due to the increase in catalyst dosage, indicating that a more complete reaction helps to improve product purity. Examples 6 and 8 achieved performance comparable to the baseline by extending the reactant addition time, indicating that a stable reaction process is beneficial to reducing by-products.

[0086] Conversely, in Examples 2, 3, and 4, slight deficiencies in catalyst drying conditions (temperature, vacuum, or time) resulted in incomplete catalyst activation and a slight decline in performance. In Example 7, the reduced amount of ethyl bromoacetate prevented the complete introduction of sulfonate groups, weakening the synergistic effect and leading to the most significant performance decline. This highlights the importance of precise control of reactant ratios.

[0087] In the comparative examples, Comparative Example 1, due to the excessively high catalyst drying temperature, damaged the catalyst pore structure, resulting in a significant deterioration in indicators such as cycle life. Comparative Example 2, which carried out the reaction without a catalyst, found it difficult to effectively conduct the key addition reaction, and its performance was the worst among all samples. Comparative Examples 3 and 4, which used single components or traditional additives respectively, had better performance than Comparative Examples 1 and 2, but were still systematically inferior to the embodiments of the present invention. This strongly demonstrates that the high ionic conductivity provided by the sulfonate group and the interfacial stability provided by the boron-oxygen heterocycle have a synergistic effect that is far superior to any single-function traditional solution.

[0088] In summary, the data analysis shows that precise control of the preparation process is a prerequisite for obtaining high-performance additives. The sulfonate boron-oxygen heterocyclic synergistic molecular structure created in this invention has successfully achieved a performance breakthrough, providing an effective solution for improving the cycle life, rate performance, and wide temperature range adaptability of lithium batteries.

[0089] The embodiments described above are not exhaustive, nor do they limit the invention to any specific embodiments. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A preparation process for a lithium battery additive, characterized in that, Includes the following steps: Step 1: Under inert gas protection, γ-valerolactone, propenyl-1,3-sulfonyl lactone and Zn-MOF-74 catalyst are mixed, heated and stirred, and 4-aminophenylboronic acid is added dropwise to react and generate a boron-oxyheterocyclic ester intermediate. Step 2: After cooling the reaction solution from Step 1, filter it to separate the filtrate and the solid catalyst; Step 3: React the filtrate obtained in Step 2 with ethyl bromoacetate to introduce sulfonate groups, resulting in a mixture of white needle-like crystals and liquid. Step 4: Filter, wash and recrystallize the white needle-like crystals obtained in Step 3 with the liquid mixture to obtain white flaky crystals; Step 5: Vacuum dry the white flaky crystals obtained in Step 4 to obtain a sulfonate-boron-oxygen heterocyclic synergistic additive.

2. The preparation process of the lithium battery additive according to claim 1, characterized in that, The preparation of the Zn-MOF-74 catalyst includes the following steps: S1: Dissolve zinc nitrate and 2,5-dihydroxyterephthalic acid in N,N-dimethylformamide to form a solution; S2: The solution is heated to react and a mixture is obtained; S3: The mixture is subjected to solid-liquid separation to obtain crude Zn-MOF-74, which is then washed with anhydrous ethanol and deionized water. S4: The washed Zn-MOF-74 product was vacuum dried to obtain the Zn-MOF-74 catalyst.

3. The preparation process of the lithium battery additive according to claim 2, characterized in that, In step S1, the molar ratio of N,N-dimethylformamide, zinc nitrate, and 2,5-dihydroxyterephthalic acid is 60–70. 0.9～1.1：0.9～1.1。 4. The preparation process of the lithium battery additive according to claim 2, characterized in that, In step S2, the heating reaction is carried out at a rate of 5°C / min from room temperature to 120°C and held at that temperature for 24 hours. In step S4, the vacuum drying includes drying at 55-70°C and -0.095-0.03 MPa for 4-6 hours, and then drying at 110-130°C and -0.098-0.03 MPa for 10-12 hours.

5. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 1, the mass ratio of γ-valerolactone, propenyl-1,3-sulfonyl lactone and 4-aminophenylboronic acid is 90-110:7-9:6-8. The mass ratio of the propylene-1,3-sulfonyl lactone to the Zn-MOF-74 catalyst is 20:1 to 2.

6. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 1, the reaction conditions include: heating to 60-65°C before adding the catalyst, adding 4-aminophenylboronic acid dropwise over 1.2-1.5 hours, and then heating to 80-85°C and holding at that temperature for 8-10 hours after the addition is complete.

7. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 3, the molar ratio of propenyl-1,3-sulfonyl lactone to ethyl bromoacetate is 1:1.1 to 1.3; The reaction conditions include: the temperature is 50-55℃ when adding ethyl bromoethyl, the addition time is 1-1.2 hours, the temperature is raised to 70-75℃ after the addition is completed and the reaction is maintained for 12-14 hours, and the stirring speed is maintained at 180-220 r / min during the reaction.

8. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 4, the recrystallization process uses an ethanol-water mixed solvent, wherein the volume ratio of ethanol to water is 3:1; The mass ratio of the ethanol-water mixed solvent to the mass of propylene-1,3-sulfonyl lactone in step 1 is 5-6:

8.

9. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 4, the recrystallization process includes dissolving the crystals in an ethanol-water mixed solvent, heating to 70°C and stirring until completely dissolved, filtering while hot, and then allowing to stand at 0-5°C for 8 hours to crystallize.

10. The preparation process of the lithium battery additive according to claim 1, characterized in that, In step 5, the vacuum drying is carried out at 50°C and -0.098 MPa for 6 hours.

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