A method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose

Abstract

This invention relates to the field of sodium carboxymethyl cellulose synthesis technology for lithium battery materials, specifically a method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose. The preparation steps include: S1. Preparation of modified montmorillonite; S2. Preparation of alkali cellulose; S3. Etherification of alkali cellulose; S4. Acidification reaction; S5. Secondary alkalization reaction; S6. Neutralization reaction; S7. Post-treatment. This invention, through the application and design of the preparation method, can improve the residual raw fiber in sodium carboxymethyl cellulose, overcoming the problems of poor uniformity and stability of cellulose produced by the traditional kneading method due to uneven heat and mass transfer during the process, as well as the problems of high insoluble content leading to easy filter clogging and frequent model switching due to uneven viscosity. It has the advantages of high product yield, fewer side reactions, less raw fiber residue, and high product stability.

Description

Technical Field

[0001] This invention relates to the field of sodium carboxymethyl cellulose synthesis technology for lithium battery materials, specifically a method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose. Background Technology

[0002] Currently, the binder in aqueous lithium-ion battery slurries is mainly sodium carboxymethyl cellulose used in combination with styrene-butadiene rubber latex. Sodium carboxymethyl cellulose, as an aqueous thickener, assists in binding the styrene-butadiene rubber latex, disperses the negative electrode active material and conductive agent, assists in binding 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] Referring to the publication number "CN114276461A" entitled "A sodium carboxymethyl cellulose and its preparation method and a battery negative electrode slurry and its preparation method", it can be seen that the technical effect of this application is that the prepared sodium carboxymethyl cellulose has the advantages of rapid dispersion and rapid release of viscosity, while having a low content of insoluble matter. In the process of preparing negative electrode slurry, the negative electrode slurry preparation time can be shortened by at least 50%, saving production costs. Moreover, the production process will not cause filter clogging, and no scratches will occur during the coating process. The coating surface density is relatively stable.

[0004] According to the publication number "CN12724266A" entitled "A method for preparing lithium carboxymethyl cellulose for lithium batteries", the technical effect of this application is to obtain lithium carboxymethyl cellulose hydrogen in one step, reduce the reaction between strong acid and sodium carboxymethyl cellulose, use lithium carbonate instead of lithium hydroxide, maximize the utilization efficiency of lithium salt, reduce waste, and reduce pollution.

[0005] According to the publication number "CN114685688A" entitled "A sodium carboxymethyl cellulose and its preparation method and application", the sodium carboxymethyl cellulose material prepared by alkalization and etherification under specific methods and conditions has the advantages of high degree of substitution (0.9-1.1), fast dissolution rate (1% concentration completely dissolved in 0.5-1.5h), high viscosity, and high purity.

[0006] The main production process of sodium carboxymethyl cellulose in the aforementioned patent is the kneading method. This method utilizes a pair of rotating blades in a kneader to rapidly and uniformly mix viscous materials through strong shearing, extrusion, kneading, and stirring. However, due to the short solid reaction time and low heat and mass transfer efficiency of the kneading method, the reaction is uneven, resulting in poor product stability, a high amount of residual raw fibers and gel particles, and the need for mechanical grinding to obtain powder. This easily leads to yellowing due to high-temperature aging, and even filter clogging during negative electrode slurry preparation due to the high content of insoluble matter. Furthermore, it can cause scratches and unstable coating density during lithium-ion battery coating, ultimately affecting cell performance and even battery safety. This makes it difficult to meet the high quality requirements of the lithium battery industry, which has stringent raw material requirements. Therefore, a new solution is needed to address these issues. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for synthesizing and preparing high-purity lithium battery grade sodium carboxymethyl cellulose.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose includes the following steps:

[0010] S1. Preparation of modified montmorillonite:

[0011] S11. Immerse 7-12 parts by weight of montmorillonite in a 0.5-1 mol / L hydrochloric acid solution for 0.5-1 h, then remove and dry.

[0012] S12. Mix the montmorillonite treated in step S11 with 23-30 parts of the modification solution and stir for 1.5-2 hours to obtain modified montmorillonite;

[0013] S2. Preparation of alkali cellulose: Take 12-15 parts of modified montmorillonite and 5-8 parts of lignocellulose, stir for 10-15 minutes, then add 1-3 parts of solid sodium hydroxide and 40-50 parts of 95% ethanol solution for a single alkalization reaction to obtain alkali cellulose.

[0014] S3. Etherification of alkali cellulose: Dissolve 7-15 parts of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent to obtain etherified alkali cellulose.

[0015] S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 7-15 parts of 98% sulfuric acid are added under stirring. The reaction is carried out for 1.5-4 hours, and the temperature is controlled at 30-45℃ to obtain the intermediate CMC-H.

[0016] S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 18-20 parts of 40% sodium hydroxide aqueous solution are added to obtain CMC-H after secondary alkalization. The reaction temperature range is 30-45℃ and the reaction time is 1.5-4h.

[0017] S6. Neutralization reaction: Glacial acetic acid was added to the CMC-H after secondary alkalization as a neutralizing agent to obtain a crude solution containing sodium carboxymethyl cellulose;

[0018] S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose.

[0019] Preferably, the modified solution in step S12 is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:4.

[0020] Preferably, the temperature range for the primary alkalization reaction in step S2 is 30-45°C.

[0021] Preferably, in step S3, the first etherification reaction takes 1-2.5 hours after the alkali cellulose and etherifying agent are mixed in step S2, with the temperature controlled at 40-60℃; the second etherification reaction takes 2.5-3 hours, with the temperature controlled at 60-85℃; the reaction formula for the first etherification reaction is:

[0022] ClCH2COOH + NaOH → ClCH2COONa + H2O; The reaction equation for the second etherification reaction is:

[0023] Cell-(OH) 3-x (O - Na + ) x +nCCH2COONa→Cell-(OH) 3-x (ONa) x-n (OCH2COO - Na + ) n +nNaCl.

[0024] Preferably, the reaction formula for the acidification reaction in step S4 is:

[0025] Cell-CH2COONa(CMC-Na)+HX→Cell-CH2COOH(CMC-H)+NaX.

[0026] Preferably, the reaction formula for the secondary alkalization reaction in step S5 is as follows:

[0027] Cell-CH2COOH(CMC-H)+NaOH→Cell-CH2COONa(CMC-Na)+H2O.

[0028] Preferably, the reaction formula for the neutralization reaction in step S6 is:

[0029] Cell-(OH) 3-x (ONa) x-n (OCH2COO-Na + ) n +(xn)CH3COOG→Cell-(OH) 3-n (OCH2COO-Na + ) n +(xn)CH3COONa,

[0030] Where x is a number less than or equal to 3, and n is the number of carboxymethyl groups that replace each glucose ring group in cellulose.

[0031] Preferably, in step S2, the temperature range for the primary alkalization reaction is 30-45℃, and the reaction time is 1.5-2h.

[0032] Preferably, in step S5, the temperature range for the secondary alkalization reaction is 30-45℃, and the reaction time is 1.5-4h.

[0033] Preferably, in step S6, the pH at the neutralization endpoint is 5-8, and the neutralization reaction temperature is 20-35℃.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. This invention, through the application design of the preparation method, can improve the residual raw fiber of sodium carboxymethyl cellulose. It overcomes the problems of poor uniformity and stability of cellulose produced by the traditional kneading method due to uneven heat and mass transfer during the process, as well as the problems of high content of insoluble matter that easily clogs the filter element and frequent model switching due to uneven viscosity. It can further process and purify raw materials and low-end sodium carboxymethyl cellulose raw materials to obtain battery-grade carboxymethyl cellulose products with uniform molecular weight distribution, good degree of substitution, stability, good flexibility, low raw fiber, low impurities, and high consistency of viscosity and purity.

[0036] 2. This invention provides better reaction conditions and precise process control. Combined with a unique formulation process, it effectively inhibits the activity of C2 and C3 short chains and reduces the number of substituent groups, while increasing the activity of C6 long chains and improving the substitution ratio of long-chain groups. This significantly improves the flexibility of existing CMC-Na products, resulting in products with higher elongation at break and greater flexibility. It also helps to improve cracking and curling during the coating process, leading to products with lower impurity content and better physical processing properties. This process offers advantages such as high product yield, fewer side reactions, less raw fiber residue, and high product stability.

[0037] 3. In this invention, the modified montmorillonite undergoes acid treatment and mixing with the modification solution during preparation, resulting in improved activity and dispersibility. In the subsequent alkali cellulose preparation step, the modified montmorillonite, after mixing with lignocellulose, can be more uniformly dispersed in the reaction system, thereby promoting uniform heat and mass transfer and avoiding the reaction inhomogeneity problems caused by uneven heat and mass transfer in the traditional kneading method. The addition of modified montmorillonite provides a more active reaction environment for the preparation of alkali cellulose, helping to improve the efficiency and uniformity of the alkalization reaction, resulting in a more uniform structure of alkali cellulose and laying a good foundation for subsequent etherification reactions and other steps. Attached Figure Description

[0038] Figure 1 This is a process flow diagram for preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to the present invention;

[0039] Figure 2 This is a schematic diagram comparing the transmittance of the intermediate CMC-H before and after secondary alkalization obtained in Example 1 of the present invention.

[0040] Figure 3 This is a schematic diagram comparing samples of the intermediate CMC-H obtained in Example 1 of the present invention before and after secondary alkalization. Detailed Implementation

[0041] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] Please see Figure 1-3 The present invention provides a technical solution:

[0043] Example 1

[0044] A method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose:

[0045] S1. Preparation of modified montmorillonite:

[0046] S11. Immerse 7g of montmorillonite in a 0.5mol / L hydrochloric acid solution for 0.5h according to the mass ratio, then remove and dry it.

[0047] S12. Mix the montmorillonite treated in step S11 with 23g of the modification solution and stir for 1.5h to obtain modified montmorillonite. The modification solution is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:4.

[0048] S2. Preparation of alkali cellulose: 12g of modified montmorillonite and 5g of lignocellulose were mixed and stirred for 10min. Then, 1g of solid sodium hydroxide and 40ml of 95% ethanol solution were added to carry out a single alkalization reaction to obtain alkali cellulose. The temperature range of the single alkalization reaction was controlled at 30℃ and the reaction time was 1.5h.

[0049] S3. Etherification of alkali cellulose: Dissolve 7 ml of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent. Control the temperature at 40℃ for 1 hour and at 60℃ for 2.5 hours to obtain the etherified alkali cellulose.

[0050] S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 7 ml of 98% sulfuric acid is added under stirring. The reaction is carried out for 1.5 h, and the temperature is controlled at 30℃ to obtain intermediate CMC-H.

[0051] S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 18 ml of 40% sodium hydroxide aqueous solution is added to obtain CMC-H after secondary alkalization. The reaction temperature range is 30℃ and the reaction time is 1.5 h.

[0052] S6. Neutralization reaction: CMC-H after secondary alkalization was neutralized using glacial acetic acid as a neutralizing agent. The pH at the neutralization endpoint was 5, and the neutralization reaction temperature was 20℃, to obtain a crude solution containing sodium carboxymethyl cellulose.

[0053] S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose.

[0054] Example 2

[0055] A method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose:

[0056] S1. Preparation of modified montmorillonite:

[0057] S11 12g of montmorillonite was immersed in a 1mol / L hydrochloric acid solution for 1 hour, then removed and dried.

[0058] S12. Mix the montmorillonite treated in step S11 with 30g of the modification solution and stir for 2h to obtain modified montmorillonite. The modification solution is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:4.

[0059] S2. Preparation of alkali cellulose: 15g of modified montmorillonite and 8g of lignocellulose were mixed and stirred for 15min. Then, 3g of solid sodium hydroxide and 50ml of 95% ethanol solution were added to carry out a first alkalization reaction to obtain alkali cellulose. The temperature range of the first alkalization reaction was 45℃ and the reaction time was 2h.

[0060] S3. Etherification of alkali cellulose: Dissolve 15 ml of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent. Control the temperature at 60℃ for 2.5 h and at 85℃ for 3 h to finally obtain the etherified alkali cellulose.

[0061] S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 15 ml of 98% sulfuric acid is added under stirring. The reaction is carried out for 4 hours, and the temperature is controlled at 45℃ to obtain the intermediate CMC-H.

[0062] S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 20 ml of 40% sodium hydroxide aqueous solution is added to obtain CMC-H after secondary alkalization. The reaction temperature range is 45℃ and the reaction time is 4h.

[0063] S6. Neutralization reaction: CMC-H after secondary alkalization was neutralized using glacial acetic acid as a neutralizing agent. The pH at the neutralization endpoint was 8, and the neutralization reaction temperature was 35℃, resulting in a crude solution containing sodium carboxymethyl cellulose.

[0064] S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose.

[0065] Example 3

[0066] A method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose:

[0067] S1. Preparation of modified montmorillonite:

[0068] S11. Immerse 9g of montmorillonite in a 0.7mol / L hydrochloric acid solution for 0.7h according to the mass ratio, then remove and dry it.

[0069] S12. Mix the montmorillonite treated in step S11 with 25g of the modification solution and stir for 1.5h to obtain modified montmorillonite. The modification solution is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:4.

[0070] S2. Preparation of alkali cellulose: 13g of modified montmorillonite and 6g of lignocellulose were mixed and stirred for 12min. Then, 2g of solid sodium hydroxide and 43ml of 95% ethanol solution were added to carry out a single alkalization reaction to obtain alkali cellulose. The temperature range of the single alkalization reaction was controlled at 35℃ and the reaction time was 1.5h.

[0071] S3. Etherification of alkali cellulose: Dissolve 10 ml of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent. Control the temperature at 50°C for 1.5 h and at 65°C for 2.5 h to finally obtain the etherified alkali cellulose.

[0072] S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 10 ml of 98% sulfuric acid is added under stirring. The reaction is carried out for 2 hours, and the temperature is controlled at 35℃ to obtain the intermediate CMC-H.

[0073] S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 19 ml of 40% sodium hydroxide aqueous solution is added to obtain CMC-H after secondary alkalization. The reaction temperature range is 35℃ and the reaction time is 2 h.

[0074] S6. Neutralization reaction: CMC-H after secondary alkalization was neutralized using glacial acetic acid as a neutralizing agent. The pH at the neutralization endpoint was 6, and the neutralization reaction temperature was 25℃, resulting in a crude solution containing sodium carboxymethyl cellulose.

[0075] S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose.

[0076] Example 4

[0077] A method for synthesizing high-purity lithium battery-grade sodium carboxymethyl cellulose:

[0078] S1. Preparation of modified montmorillonite:

[0079] S11: Immerse 11g of montmorillonite in a 0.9mol / L hydrochloric acid solution for 1 hour, then remove and dry it.

[0080] S12. Mix the montmorillonite treated in step S11 with 28g of the modification solution and stir for 2 hours to obtain modified montmorillonite. The modification solution is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:4.

[0081] S2. Preparation of alkali cellulose: 14g of modified montmorillonite and 7g of lignocellulose were mixed and stirred for 14min. Then, 2g of solid sodium hydroxide and 48ml of 95% ethanol solution were added to carry out a first alkalization reaction to obtain alkali cellulose. The temperature range of the first alkalization reaction was 40℃ and the reaction time was 2h.

[0082] S3. Etherification of alkali cellulose: Dissolve 14 ml of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent. Control the temperature at 55℃ for 2 hours and at 80℃ for 3 hours to finally obtain the etherified alkali cellulose.

[0083] S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 14 ml of 98% sulfuric acid is added under stirring. The reaction is carried out for 3 hours, and the temperature is controlled at 40℃ to obtain intermediate CMC-H.

[0084] S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 19 ml of 40% sodium hydroxide aqueous solution is added to obtain CMC-H after secondary alkalization. The reaction temperature range is 40℃ and the reaction time is 3h.

[0085] S6. Neutralization reaction: CMC-H after secondary alkalization was neutralized using glacial acetic acid as a neutralizing agent. The pH at the neutralization endpoint was 7, and the neutralization reaction temperature was 30℃, resulting in a crude solution containing sodium carboxymethyl cellulose.

[0086] S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose.

[0087] Performance testing:

[0088] Referring to national standard GB 1904-2005, the high-purity lithium battery-grade sodium carboxymethyl cellulose obtained in Examples 1-4 was prepared into a 1% CMC-Na aqueous solution. The viscosity was tested at 25°C, and the degree of substitution (DS) and purity were finally determined by titration and ash content determination. The final data are shown in Table 1 below:

[0089] Table 1

[0090] Viscosity (mPa·s) Substitutability purity(%) Example 1 1200 0.85 99.5 Example 2 1235 0.92 99.7 Example 3 1214 0.86 99.5 Example 4 1204 0.88 99.6

[0091] Viscosity is a crucial performance indicator for battery-grade sodium carboxymethyl cellulose (CMC), directly affecting its thickening and dispersing effects in lithium-ion battery slurries. As shown in Table 1, the high-purity lithium-ion battery-grade CMC obtained in this invention exhibits high viscosity, effectively preventing sedimentation of the negative electrode slurry and improving flowability and uniformity during coating. The corresponding degrees of substitution are all within the ideal range, indicating that the high-purity lithium-ion battery-grade CMC obtained in this invention possesses good solubility and stability. The data in Table 1 also show that the high-purity lithium-ion battery-grade CMC obtained in this invention has high purity and extremely low impurity content, meeting the high purity requirements for lithium-ion battery-grade CMC and contributing to improved electrochemical performance and safety of lithium-ion batteries.

[0092] Reference Appendix Figure 2 It can be seen that the present invention compares the transmittance of the intermediate CMC-H obtained in Example 1 before and after secondary alkalization, and through the attached... Figure 2 It can be observed that the intermediate CMC-H, which has undergone a secondary alkalization reaction, exhibits higher clarity and transmittance, as well as better uniformity and stability. (The text abruptly ends here.) Figure 3 The schematic diagrams of the intermediate CMC-H before and after the secondary alkalization show that the intermediate CMC-H after the secondary alkalization reaction is easily soluble, clear, has few insoluble substances, and no raw fiber residue.

[0093] 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 synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose, characterized in that, Includes the following steps: S1. Preparation of modified montmorillonite: S11. Immerse 7-12 parts by weight of montmorillonite in a 0.5-1 mol / L hydrochloric acid solution for 0.5-1 h, then remove and dry. S12. Mix the montmorillonite treated in step S11 with 23-30 parts of the modification solution and stir for 1.5-2 hours to obtain modified montmorillonite; S2. Preparation of alkali cellulose: Take 12-15 parts of modified montmorillonite and 5-8 parts of lignocellulose, stir for 10-15 minutes, then add 1-3 parts of solid sodium hydroxide and 40-50 parts of 95% ethanol solution for a single alkalization reaction to obtain alkali cellulose. S3. Etherification of alkali cellulose: Dissolve 7-15 parts of chloroacetic acid solution in 95% ethanol solution to prepare an etherifying agent. Mix the alkali cellulose obtained in step S2 with the etherifying agent to obtain etherified alkali cellulose. S4. Acidification reaction: Using 95% ethanol solution as the dispersion medium, the etherified alkali cellulose is dispersed in it, and 7-15 parts of 98% sulfuric acid are added under stirring. The reaction is carried out for 1.5-4 hours, and the temperature is controlled at 30-45℃ to obtain the intermediate CMC-H. S5. Secondary alkalization reaction: CMC-H is dispersed in 95% ethanol solution under normal pressure, and 18-20 parts of 40% sodium hydroxide aqueous solution are added to obtain CMC-H after secondary alkalization. The reaction temperature range is 30-45℃ and the reaction time is 1.5-4h. S6. Neutralization reaction: Glacial acetic acid was added to the CMC-H after secondary alkalization as a neutralizing agent to obtain a crude solution containing sodium carboxymethyl cellulose; S7. Post-processing: The crude solution containing sodium carboxymethyl cellulose is filtered and washed, dried, and then the lumps are crushed by air jet milling and sieved through a 300-mesh sieve to obtain high-purity lithium battery grade sodium carboxymethyl cellulose. The modified solution in step S12 is a mixture of ammonium dihydrogen phosphate and hexadecyltrimethylammonium bromide in a mass ratio of 3:

4.

2. The method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to claim 1, characterized in that, The controlled temperature range for the primary alkalization reaction in step S2 is 30-45℃.

3. The method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S3, the first etherification reaction takes 1-2.5 hours after the alkali cellulose obtained in step S2 is mixed with the etherifying agent, and the temperature is controlled at 40-60℃; the second etherification reaction takes 2.5-3 hours, and the temperature is controlled at 60-85℃.

4. The method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S2, the temperature range for the alkalization reaction is 30-45℃, and the reaction time is 1.5-2h.

5. The method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S5, the temperature range for the secondary alkalization reaction is 30-45℃, and the reaction time is 1.5-4h.

6. The method for synthesizing and preparing high-purity lithium battery-grade sodium carboxymethyl cellulose according to claim 1, characterized in that, In step S6, the pH at the neutralization endpoint is 5-8, and the neutralization reaction temperature is 20-35℃.

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