Preparation method of aminosulfonated cellulose salt and its application as a binder for lithium battery negative electrodes

Abstract

This invention relates to the field of lithium battery negative electrode adhesive preparation technology, specifically to a method for preparing aminosulfonated cellulose salt and its application as a lithium battery negative electrode adhesive. The preparation method includes the following steps: S1, adding sodium carboxymethyl cellulose to an ethanol-water solution and reacting with sulfuric acid to obtain a first product; S2, adding the first product to an ethanol-water solution containing modified nano-calcium carbonate and adding sodium aminosulfonate dropwise to obtain a reaction solution; S3, adding sulfuric acid dropwise to the reaction solution to obtain a second product; S4, adding the second product to an ethanol-water solution and reacting with an alkaline solution to obtain a third product; S5, drying and pulverizing the third product to obtain aminosulfonated cellulose salt. The aminosulfonated cellulose salt prepared by this invention, when applied to the adhesive of the lithium battery negative electrode, can effectively improve the overall flexibility of the material and extend the battery's lifespan.

Description

Technical Field

[0001] This invention relates to the field of lithium battery negative electrode adhesive preparation technology, specifically to the preparation method of aminosulfonated cellulose salt and its application as a lithium battery negative electrode adhesive. Background Technology

[0002] Currently, the binder in aqueous lithium-ion battery slurries is mainly sodium carboxymethyl cellulose used in combination with styrene-butadiene rubber (SBR) latex. Sodium carboxymethyl cellulose acts as an aqueous thickener, assisting in the binding of the SBR latex. It disperses the negative electrode active material and conductive agent, aids in the binding of the negative electrode active material and current collector, and thickens the slurry to prevent sedimentation, thus ensuring good fluidity of the negative electrode coating.

[0003] Existing carboxymethyl cellulose salts used as binders have the problem of low flexibility. When exposed to external forces, the lack of flexibility can easily cause the material to crack, thereby reducing the charge and discharge capacity of the battery and affecting its lifespan.

[0004] To address the issue of poor flexibility in existing carboxymethyl cellulose salts used as battery binders, those skilled in the art have proposed a method for preparing aminosulfonated cellulose salts with greater flexibility. The aminosulfonated cellulose salts prepared by this invention can maintain a good charge / discharge specific capacity of the battery even after being bent multiple times by external forces, thus extending the battery's service life. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing aminosulfonated cellulose salt and its application as a negative electrode binder for lithium batteries, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an aminosulfonated cellulose salt, the method comprising the following steps: S1. Add sodium carboxymethyl cellulose to an aqueous ethanol solution, then add sulfuric acid and stir until homogeneous. Adjust the pH to 1-2, heat to 40-50℃, react for 2-4 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the first product. S2. The modified nano-calcium carbonate is ultrasonically dispersed in an ethanol aqueous solution, and then the first product obtained in step S1 is added. The mixture is stirred and mixed evenly. Then, sodium aminosulfonate solution is added dropwise and the reaction is carried out for 1-3 hours to obtain the reaction solution. S3. Add sulfuric acid dropwise to the reaction solution obtained in step S2, react for 2-4 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the second product. S4. Add the second product obtained in step S3 to the ethanol aqueous solution, then add alkaline solution dropwise and stir evenly. Adjust the pH to 8-9, react for 1-3 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the third product. S5. The third product obtained in step S4 is dried at 90-100℃ for 5-8 hours, and then pulverized by air jet milling to finally obtain aminosulfonated cellulose salt. The modified nano-calcium carbonate is modified by the following method: Nano-calcium carbonate was ultrasonically dispersed in a deionized aqueous solution containing polyvinylpyrrolidone and citric acid, heated to 45-55℃, and reacted continuously for 2-4 hours. After filtration, the filtered product was washed with sufficient deionized water and then vacuum dried to constant weight to obtain modified nano-calcium carbonate.

[0007] Furthermore, in step S1, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, the mass ratio of sodium carboxymethyl cellulose to the aqueous ethanol solution in step S1 is 1:(6-8), and the concentration of sulfuric acid in step S1 is 10 wt%.

[0008] Furthermore, in step S2, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, and the mass ratio between the first product, the aqueous ethanol solution, and the modified nano-calcium carbonate in step S2 is 1:(12-15):(0.2-0.3).

[0009] Furthermore, in step S2, the concentration of the sodium aminosulfonate solution is 20-25 wt%, and the mass ratio between the sodium aminosulfonate solution and the first product in step S2 is (1-1.5):1.

[0010] Furthermore, the sulfuric acid concentration in step S3 is 10 wt%, and the mass ratio between the sulfuric acid in step S3 and the modified nano-calcium carbonate in step S2 is (15-20):1.

[0011] Furthermore, in step S4, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, and the mass ratio between the second product, the aqueous ethanol solution, and the alkaline solution in step S4 is 1:(10-12).

[0012] Furthermore, in step S4, the alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 5 wt%.

[0013] Furthermore, the mass ratio between the nano-calcium carbonate and the deionized aqueous solution containing polyvinylpyrrolidone and citric acid is 1:(40-50), and the concentrations of polyvinylpyrrolidone and citric acid in the deionized aqueous solution containing polyvinylpyrrolidone and citric acid are 1-5wt% and 1-3wt%, respectively.

[0014] An aminosulfonated cellulose salt preparation method is used in the application of the prepared aminosulfonated cellulose salt in lithium battery negative electrode adhesive.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention prepares an aminosulfonated cellulose salt by reacting sodium carboxymethyl cellulose with sodium aminosulfonate. Compared with ordinary sodium carboxymethyl cellulose, the prepared negative electrode sheet has better flexibility and the charge-discharge specific capacity decreases less when it is bent by external force. 2. In the preparation process of this invention, modified nano-calcium carbonate is added. The nanoparticles are dispersed in the system and can form a micro-environment. They can combine with carboxymethyl cellulose and expose more active groups, which facilitates better reaction between carboxymethyl cellulose and sodium aminosulfonate. The reaction is more uniform and the quality of the prepared material is improved. After being modified by polyvinylpyrrolidone and citric acid, the nano-calcium carbonate can be better dispersed in the system. Attached Figure Description

[0016] Figure 1 This is a process flow diagram for preparing aminosulfonated cellulose salt according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1 The present invention provides: Example 1 A method for preparing an aminosulfonated cellulose salt, the method comprising the following steps: S1. Add 20g of sodium carboxymethyl cellulose to 140g of ethanol aqueous solution with an ethanol concentration of 92wt%. Then add 10wt% sulfuric acid and stir until homogeneous. Adjust the pH to 1.5, heat to 40-50℃, react for 2-4 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the first product. S2. 3.75g of modified nano-calcium carbonate was ultrasonically dispersed in 210g of ethanol aqueous solution with an ethanol concentration of 92wt%. Then, 15g of the first product obtained in step S1 was added and stirred until homogeneous. After that, 4.68g of sodium aminosulfonate solution with a concentration of 22wt% was added dropwise, and the reaction was carried out for 2 hours to obtain the reaction solution. In this step, carboxymethyl cellulose was modified by sodium aminosulfonate to form cellulose aminosulfonate, in which the added modified nano-calcium carbonate had space. S3. Add 60g of 10wt% sulfuric acid to the reaction solution obtained in step S2, react for 3h, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the second product; in this step, the modified nano-calcium carbonate in the reaction solution is removed by adding sulfuric acid. S4. Add 10g of the second product obtained in step S3 to 110g of ethanol aqueous solution with an ethanol concentration of 92wt%. Then add alkaline solution dropwise and stir until homogeneous. The alkaline solution is a 5wt% sodium hydroxide solution. Adjust the pH to 8.5 and react for 2 hours. Filter the product and wash it with sufficient anhydrous ethanol to obtain the third product. S5. The third product obtained in step S4 is dried at 95°C for 6 hours, and then pulverized by air jet milling to finally obtain sodium aminosulfonated cellulose. The above-mentioned modified nano-calcium carbonate was modified by the following method: 5g of nano-calcium carbonate was ultrasonically dispersed in 220g of a deionized aqueous solution containing polyvinylpyrrolidone and citric acid, with concentrations of 3wt% and 2wt% for polyvinylpyrrolidone and citric acid, respectively. The mixture was heated to 50℃ and reacted continuously for 3h. After filtration, the filtered product was washed with sufficient deionized water and then vacuum dried to constant weight to obtain modified nano-calcium carbonate.

[0019] Example 2 A method for preparing an aminosulfonated cellulose salt, the method comprising the following steps: S1. Add 20g of sodium carboxymethyl cellulose to 120g of ethanol aqueous solution with an ethanol concentration of 90wt%. Then add 10wt% sulfuric acid and stir until homogeneous. Adjust the pH to 1, heat to 40℃, react for 2h, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the first product. S2. Disperse 3g of modified nano-calcium carbonate ultrasonically into 180g of ethanol aqueous solution with an ethanol concentration of 90wt%. Then add 15g of the first product obtained in step S1, stir and mix evenly, and then continue to add 3g of sodium aminosulfonate solution with a concentration of 20wt%. React for 1h to obtain the reaction solution. S3. Add 45g of 10wt% sulfuric acid to the reaction solution obtained in step S2, react for 2 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the second product. S4. Add 10g of the second product obtained in step S3 to 100g of ethanol aqueous solution with an ethanol concentration of 90wt%. Then add alkaline solution dropwise and stir until homogeneous. The alkaline solution is a 5wt% potassium hydroxide solution. Adjust the pH to 8 and react for 1 hour. Filter the product and wash it with sufficient anhydrous ethanol to obtain the third product. S5. The third product obtained in step S4 is dried at 90°C for 5 hours, and then pulverized by air jet milling to finally obtain potassium aminosulfonated cellulose. The above-mentioned modified nano-calcium carbonate was modified by the following method: 5g of nano-calcium carbonate was ultrasonically dispersed in 200g of a deionized aqueous solution containing polyvinylpyrrolidone and citric acid, with the concentrations of polyvinylpyrrolidone and citric acid being 1wt% and 1wt%, respectively. The mixture was heated to 45℃ and reacted continuously for 2h. After filtration, the filtered product was washed with sufficient deionized water and then vacuum dried to constant weight to obtain modified nano-calcium carbonate.

[0020] Example 3 A method for preparing an aminosulfonated cellulose salt, the method comprising the following steps: S1. Add 20g sodium carboxymethyl cellulose to 160g ethanol aqueous solution with an ethanol concentration of 95wt%. Then add 10wt% sulfuric acid and stir until homogeneous. Adjust the pH to 2, heat to 50℃, react for 4h, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the first product. S2. 4.5g of modified nano-calcium carbonate was ultrasonically dispersed into 225g of ethanol aqueous solution with an ethanol concentration of 95wt%. Then, 15g of the first product obtained in step S1 was added and stirred until homogeneous. After that, 6.75g of sodium aminosulfonate solution with a concentration of 25wt% was added dropwise and reacted for 3h to obtain the reaction solution. S3. Add 90g of 10wt% sulfuric acid to the reaction solution obtained in step S2, react for 4h, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the second product. S4. Add 10g of the second product obtained in step S3 to 120g of ethanol aqueous solution with an ethanol concentration of 95wt%. Then add alkaline solution dropwise and stir until homogeneous. The alkaline solution is a 5wt% sodium hydroxide solution. Adjust the pH to 9 and react for 3 hours. Filter the product and wash it with sufficient anhydrous ethanol to obtain the third product. S5. The third product obtained in step S4 is dried at 100°C for 8 hours, and then pulverized by air jet milling to finally obtain sodium aminosulfonated cellulose. The above-mentioned modified nano-calcium carbonate was modified by the following method: 5g of nano-calcium carbonate was ultrasonically dispersed in 250g of a deionized aqueous solution containing polyvinylpyrrolidone and citric acid, with concentrations of 5wt% and 3wt% for polyvinylpyrrolidone and citric acid, respectively. The mixture was heated to 55℃ and reacted continuously for 4 hours. After filtration, the filtered product was washed with sufficient deionized water and then vacuum dried to constant weight to obtain modified nano-calcium carbonate.

[0021] The average particle size of the nano-calcium carbonate used in this invention is controlled at 20-50 nm. In step S2, the modified nano-calcium carbonate is ultrasonically dispersed in an ethanol aqueous solution, and the nano-calcium carbonate is dispersed in a deionized aqueous solution containing polyvinylpyrrolidone and citric acid during the modification process. The ultrasonic dispersion frequency is 40 kHz.

[0022] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the modified nano-calcium carbonate added in step S2 is replaced with the same weight of unmodified nano-calcium carbonate, while the rest of the steps are exactly the same as in Example 1.

[0023] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the modified nano-calcium carbonate added in step S2 was completely removed, while the remaining steps are exactly the same as in Example 1.

[0024] Battery fabrication: The positive electrode, negative electrode, and separator are wound into a core, which is then sealed with an aluminum-plastic film. The core is dried under vacuum for 24 hours to remove moisture, then injected with electrolyte and allowed to stand for 12 hours. After formation and capacity testing, a small square soft-pack lithium-ion battery is obtained. The positive electrode uses a lithium cobalt oxide system, and the electrolyte is a carbonate solution containing LiPF6. The preparation method of the negative electrode is as follows: Graphite, carbon black, styrene-butadiene rubber, and aminosulfonated cellulose salt (a total of 6 groups were set up, of which 5 groups were prepared by Examples 1-3 and Comparative Examples 1-2 respectively, and the control group directly used sodium carboxymethyl cellulose) were added to deionized water and stirred until uniform. The mass ratio between graphite, carbon black, styrene-butadiene rubber, and aminosulfonated cellulose salt was 40:2:1:1:50. The mixture was coated on the current collector to obtain the negative electrode sheet of the lithium-ion battery.

[0025] The negative electrode was folded five times, and the discharge specific capacity before and after folding was tested. The test results are shown in Table 1 below: Table 1: Charge-discharge specific capacity before and after folding of aminosulfonated cellulose salts prepared in Examples 1-3 and Comparative Examples 1-2 As can be seen from the data in Table 1 above, before and after folding, the charge-discharge specific capacity of the negative electrode sheets composed of aminosulfonated cellulose salt prepared in Comparative Example 1 and Comparative Example 2 is significantly reduced after folding compared to before folding, with the control group showing the most significant reduction. The aminosulfonated cellulose prepared in this invention can effectively improve flexibility and maintain a high charge-discharge specific capacity.

[0026] The aminosulfonated cellulose salt prepared by this invention has a high viscosity effect and can be applied to the negative electrode of lithium battery.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an aminosulfonated cellulose salt, characterized in that, The preparation method includes the following steps: S1. Add sodium carboxymethyl cellulose to an aqueous ethanol solution, then add sulfuric acid and stir until homogeneous. Adjust the pH to 1-2, heat to 40-50℃, react for 2-4 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the first product. S2. The modified nano-calcium carbonate is ultrasonically dispersed in an ethanol aqueous solution, and then the first product obtained in step S1 is added. The mixture is stirred and mixed evenly. Then, sodium aminosulfonate solution is added dropwise and the reaction is carried out for 1-3 hours to obtain the reaction solution. S3. Add sulfuric acid dropwise to the reaction solution obtained in step S2, react for 2-4 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the second product. S4. Add the second product obtained in step S3 to the ethanol aqueous solution, then add alkaline solution dropwise and stir evenly. Adjust the pH to 8-9, react for 1-3 hours, filter the product, and wash the product with sufficient anhydrous ethanol to obtain the third product. S5. The third product obtained in step S4 is dried at 90-100℃ for 5-8 hours, and then pulverized by air jet milling to finally obtain aminosulfonated cellulose salt. The modified nano-calcium carbonate is modified by the following method: Nano-calcium carbonate was ultrasonically dispersed in a deionized aqueous solution containing polyvinylpyrrolidone and citric acid, heated to 45-55℃, and reacted continuously for 2-4 hours. After filtration, the filtered product was washed with sufficient deionized water and then vacuum dried to constant weight to obtain modified nano-calcium carbonate.

2. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, In step S1, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, the mass ratio of sodium carboxymethyl cellulose to aqueous ethanol solution in step S1 is 1:(6-8), and the concentration of sulfuric acid in step S1 is 10 wt%.

3. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, In step S2, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, and the mass ratio between the first product, the aqueous ethanol solution, and the modified nano-calcium carbonate in step S2 is 1:(12-15):(0.2-0.3).

4. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, In step S2, the concentration of sodium aminosulfonate solution is 20-25 wt%, and the mass ratio of sodium aminosulfonate solution to the first product in step S2 is (1-1.5):

1.

5. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, The sulfuric acid concentration in step S3 is 10 wt%, and the mass ratio between sulfuric acid in step S3 and modified nano-calcium carbonate in step S2 is (15-20):

1.

6. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, In step S4, the concentration of ethanol in the aqueous ethanol solution is 90-95 wt%, and the mass ratio of the second product, the aqueous ethanol solution, and the alkaline solution in step S4 is 1:(10-12).

7. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, In step S4, the alkaline solution is either a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkaline solution is 5 wt%.

8. The method for preparing aminosulfonated cellulose salt according to claim 1, characterized in that, The mass ratio between the nano-calcium carbonate and the deionized aqueous solution containing polyvinylpyrrolidone and citric acid is 1:(40-50), and the concentrations of polyvinylpyrrolidone and citric acid in the deionized aqueous solution are 1-5wt% and 1-3wt%, respectively.

9. The application of the aminosulfonated cellulose salt prepared by the method according to any one of claims 1-8 in the negative electrode adhesive of lithium battery.

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