A carboxymethyl cellulose copolymer binder and its preparation method and application

Abstract

The present invention discloses a carboxymethyl cellulose copolymer binder and its preparation method and application. The structural formula of the carboxymethyl cellulose copolymer binder is shown in Formula I: #imgabs0# wherein R is one of CR1(COOH)-CR2(COOR3)-CR4(CN), CR1(COOH), COOR3, CR4(CN), CR2(COOR3), CR1(COOH)-CR4(CN), CR2(COOR3)-CR4(CN), CR1(COOH)-CR2(COOR3), R1 includes hydrogen or alkyl, R2 includes hydrogen or alkyl, R3 includes alkyl, and R4 includes hydrogen. The binder of the present invention has good wettability and dispersion performance for negative electrode slurry, is beneficial to the preparation of negative electrode sheets, has strong bonding force to negative electrode sheets, can improve the flexibility of the sheets, and has good processing performance under high shear rates. The cycle capacity retention rate and DCR after cycling of the battery prepared using the binder are better than those of the CMC+SBR system.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a carboxymethyl cellulose copolymer binder and a preparation method and application thereof. Background Art

[0002] Secondary batteries offer advantages such as high energy density, long cycle life, and zero pollution. With environmental and oil price concerns, they are increasingly being used in electric vehicles and energy storage. The cell structure of a secondary battery typically includes a positive electrode, a negative electrode, a separator, and an electrolyte. Taking lithium-ion batteries as an example, the negative electrode primarily consists of graphite, carbon black, a binder, and copper foil. Graphite is the active material, ensuring the insertion and extraction of lithium ions during the battery's charge and discharge processes; copper foil and carbon black provide pathways and channels for electron transmission. The binder ensures the integrity of the electrode. The binder is associated with the expansion, flexibility, and electrochemical performance of the negative electrode. Therefore, the quality of the binder has a certain impact on the battery's lifespan.

[0003] At present, the commonly used binders for negative electrodes include carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR) and acrylic polymers (PAA). Conventional negative electrode slurries use water as a solvent, but graphite is obviously stratified in water due to its hydrophobic properties, so CMC with specific anionic groups is required to effectively disperse the graphite. At the same time, the addition of SBR with a bonding effect can improve the problem of insufficient CMC bonding strength. However, SBR has a unique core-shell structure and there is a risk of demulsification under high shear. Reducing the shear rate will cause SBR to be unable to disperse effectively. During coating, SBR floats, resulting in low bonding strength of the pole piece. Reducing the stirring shear rate will also lead to reduced production capacity, affecting production progress. Therefore, it is crucial to develop a binder that simultaneously meets the dispersion properties of the negative electrode slurry, the bonding properties of the pole piece, and the processing performance under high shear.

[0004] CN108063258A uniformly mixes acrylic acid, deionized water, graphene-coated cobalt molybdate nanosheets, carboxymethyl cellulose, and a photoinitiator, then directly crosslinks the mixture with UV light via in-situ polymerization to produce a binder containing a polyacrylic acid-grafted carboxymethyl cellulose copolymer. This technique requires pretreatment of the cobalt molybdate nanosheets, requiring a long shelf life of 3 to 6 months. Furthermore, the binder is treated by uniformly mixing acrylic acid, carboxymethyl cellulose, and a photoinitiator to form a mixed solvent. Deionized water is then added to the mixed solvent to form a viscous solution, which is then irradiated with UV light to produce the binder containing the polyacrylic acid-grafted carboxymethyl cellulose copolymer. The initiator only crosslinks and cures the acrylic acid, preventing the grafting of the acrylic acid onto the carboxymethyl cellulose. Furthermore, the UV curing method consumes additional energy.

[0005] CN110028627A uses an ethylenically unsaturated monomer, an ethylenically unsaturated phosphate monomer, and carboxymethyl cellulose to undergo a cross-linking reaction under the action of an initiator to prepare a ternary copolymer adhesive. However, the addition of the ethylenically unsaturated monomer and the ethylenically unsaturated phosphate monomer has a limited effect on improving the bonding strength, and additional SBR (styrene-butadiene rubber) needs to be added to the slurry to assist in the bonding strength. Summary of the Invention

[0006] The primary purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art by providing a carboxymethyl cellulose copolymer binder. This binder exhibits excellent wettability and dispersion in negative electrode slurries, facilitating the preparation of negative electrode sheets. It also exhibits strong adhesion to negative electrode sheets, improving their flexibility, and exhibits shear resistance and excellent processing performance at high shear rates. Batteries prepared using this methyl cellulose copolymer binder exhibit superior cycle capacity retention and post-cycle DCR compared to a CMC+SBR system.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned carboxymethyl cellulose copolymer binder.

[0008] Another object of the present invention is to provide an application of the above-mentioned carboxymethyl cellulose copolymer binder.

[0009] The object of the present invention is achieved by the following technical solution: A carboxymethyl cellulose copolymer binder, whose structural formula is shown in Formula I:

[0010]

[0011] Wherein, R is one of CR1(COOH)-CR2(COOR3)-CR4(CN), CR1(COOH), COOR3, CR4(CN), CR2(COOR3), CR1(COOH)-CR4(CN), CR2(COOR3)-CR4(CN), CR1(COOH)-CR2(COOR3), R1 includes hydrogen or alkyl, R2 includes hydrogen or alkyl, R3 includes alkyl, and R4 includes hydrogen.

[0012] The preparation method of the above-mentioned carboxymethyl cellulose copolymer binder comprises the following steps: introducing sulfonic acid functional groups into the cellulose functional groups of sodium carboxymethyl cellulose by using a sulfonating agent, mixing and reacting a polymerization monomer, an initiator and the sodium carboxymethyl cellulose with the sulfonic acid functional groups introduced into the cellulose functional groups, cooling to room temperature, adjusting the pH to 7-9, and sieving to obtain the carboxymethyl cellulose copolymer binder.

[0013] The method for introducing sulfonic acid functional groups into the cellulose functional groups of sodium carboxymethyl cellulose comprises: dissolving sodium carboxymethyl cellulose in a solvent, adding a sulfonating agent dropwise, and reacting at 100-130° C. for 30-60 minutes.

[0014] The solvent includes deionized water, ethanol, isopropyl alcohol, NMP, toluene, acetone, etc.

[0015] The sulfonating agent includes at least one of sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfonic acid and aminosulfonic acid; preferably, the sulfonating agent is fuming sulfuric acid.

[0016] The polymerizable monomer includes at least one of acrylic acid, acrylic acid esters and acrylonitrile substances; preferably, the polymerizable monomer is a mixture of acrylic acid, acrylic acid esters and acrylonitrile substances.

[0017] Preferably, the acrylic acid esters include at least one of ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate and ethyl methacrylate.

[0018] Preferably, the acrylonitrile comprises at least one of acrylonitrile and methacrylonitrile.

[0019] The initiator includes at least one of sodium persulfate, tert-butyl hydroperoxide, sodium bisulfite, potassium persulfate, ammonium persulfate, vitamins, benzoyl peroxide, azobisisobutyronitrile, AIBA and AIBI; preferably, the initiator is sodium persulfate.

[0020] The reaction is stirred at 60-80° C. for 1-3 hours.

[0021] The normal temperature refers to 25-30°C.

[0022] Acetic acid is used to adjust the pH.

[0023] Preferably, the mass ratio of the sodium carboxymethyl cellulose, the polymerized monomer, the sulfonating agent, and the initiator is 50-60:20-60:1-2:0.2-0.5; more preferably, the mass ratio of the sodium carboxymethyl cellulose, the polymerized monomer, the sulfonating agent, and the initiator is 50:50:2:0.2.

[0024] Application of the above carboxymethyl cellulose copolymer binder in the preparation of batteries.

[0025] Preferably, the battery includes a lithium ion battery, a potassium ion battery, or a sodium ion battery.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention introduces sulfonic acid groups into the cellulose functional groups of sodium carboxymethyl cellulose to impart water-soluble surface activity to the product, increasing the affinity of cellulose. The polymerized monomer is then covalently grafted onto the hydroxyl groups of the carboxymethyl cellulose. The resulting carboxymethyl cellulose copolymer binder has good wettability and dispersion properties for the negative electrode slurry, facilitating the preparation of negative electrode sheets. It has strong adhesion to the negative electrode sheets, can improve the flexibility of the sheets, and is shear-resistant, with good processing performance at high shear rates. Batteries prepared using the methyl cellulose copolymer binder of the present invention exhibit better cycle capacity retention and post-cycle DCR than the CMC+SBR system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the infrared spectra of the carboxymethyl cellulose copolymer binder prepared in Example 1 and the carboxymethyl cellulose of Comparative Example 2. DETAILED DESCRIPTION

[0029] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a carboxymethyl cellulose copolymer binder, wherein the binder raw materials include: 50 parts by mass of carboxymethyl cellulose sodium, 10 parts by mass of acrylic acid, 15 parts by mass of methyl methacrylate, 10 parts by mass of butyl acrylate, 15 parts by mass of acrylonitrile, 2 parts by mass of fuming sulfuric acid, and 0.2 parts by mass of sodium persulfate.

[0032] Preparation method: First, dissolve sodium carboxymethyl cellulose in deionized water, then add fuming sulfuric acid solution dropwise. The mixture is reacted at 130°C for 40 minutes to introduce sulfonic acid groups onto the cellulose functional groups. Acrylic acid, methyl methacrylate, butyl acrylate, and acrylonitrile are then added to the sulfonated carboxymethyl cellulose solution. Sodium persulfate is then added and stirred at 80°C for 1 hour, allowing the acrylic acid, methyl methacrylate, butyl acrylate, and acrylonitrile to polymerize and covalently graft onto the hydroxyl groups of the carboxymethyl cellulose. The mixture is cooled to 25°C, the pH adjusted to 8 with acetic acid, and the mixture is sieved to obtain a carboxymethyl cellulose copolymer binder.

[0033] Carboxymethyl cellulose copolymer binder was subjected to infrared testing, and the results are shown in Figure 1 .Depend on Figure 1 The spectrum of carboxymethyl cellulose copolymer binder shows that at 3460 cm -1 There is a strong absorption peak due to -0H stretching vibration at 2950cm -1There is an absorption peak caused by CH stretching vibration at 1618cm, and the absorption peak intensity is significantly increased compared with CMC, which is mainly due to the increase of acrylic acid units; -1 The strongest peak in the spectrum is caused by the conjugated stretching vibration of ester, cyano and OCO in carboxylate; at 620 cm -1 The stretching vibration peak of the sulfonic acid group is the acyl group -SOH of sulfuric acid. Comprehensive infrared data analysis proves that the multi-polymerization has been successfully polymerized on the CMC side chain to prepare a carboxymethyl cellulose copolymer binder. The structural formula of the carboxymethyl cellulose copolymer binder is as follows:

[0034]

[0035] Example 2

[0036] This embodiment provides a carboxymethyl cellulose copolymer binder, wherein the binder raw materials include: 60 parts by mass of carboxymethyl cellulose sodium, 30 parts by mass of acrylic acid, 0.5 parts by mass of sodium persulfate, and 1 part by mass of fuming sulfuric acid.

[0037] Preparation method: First, dissolve sodium carboxymethyl cellulose in deionized water, add fuming sulfuric acid solution dropwise, and react at 100°C for 60 minutes to introduce sulfonic acid functional groups onto the cellulose functional groups. Then, add acrylic acid and sodium persulfate to the sulfonated carboxymethyl cellulose solution and stir at 60°C for 3 hours to graft the acrylic acid onto the carboxymethyl cellulose hydroxyl groups. Cool to 30°C, adjust the pH to 7 with acetic acid, and sieve to obtain a carboxymethyl cellulose copolymer binder. The structural formula of the carboxymethyl cellulose copolymer binder is as follows:

[0038]

[0039] Example 3

[0040] This embodiment provides a carboxymethyl cellulose copolymer binder, wherein the binder raw materials include: 50 parts by mass of carboxymethyl cellulose sodium, 20 parts by mass of methyl methacrylate, 20 parts by mass of butyl acrylate, 8 parts by mass of acrylonitrile, 2 parts by mass of sulfur trioxide, and 0.2 parts by mass of sodium persulfate.

[0041] Preparation method: First, dissolve sodium carboxymethyl cellulose in deionized water, add fuming sulfuric acid solution dropwise, and react at 130°C for 40 minutes to introduce sulfonic acid functional groups on the cellulose functional groups. Then, add methyl methacrylate, butyl acrylate, and acrylonitrile to the sulfonated carboxymethyl cellulose solution, and add sodium persulfate. Stir and react at 80°C for 1 hour to polymerize and covalently graft methyl methacrylate, butyl acrylate, and acrylonitrile on the hydroxyl groups of the carboxymethyl cellulose. Cool to 25°C, adjust the pH to 9 with acetic acid, and sieve to obtain a carboxymethyl cellulose copolymer binder. The structural formula of the carboxymethyl cellulose copolymer binder is as follows:

[0042]

[0043] Example 4

[0044] This embodiment provides a carboxymethyl cellulose copolymer binder, wherein the binder raw materials include: 50 parts by mass of carboxymethyl cellulose sodium, 20 parts by mass of acrylic acid, 15 parts by mass of methyl methacrylate, 15 parts by mass of butyl acrylate, 2 parts by mass of fuming sulfuric acid, and 0.2 parts by mass of tert-butyl hydroperoxide.

[0045] Preparation method: First, dissolve sodium carboxymethyl cellulose in deionized water, add fuming sulfuric acid solution dropwise, and react at 130°C for 40 minutes to introduce sulfonic acid functional groups on the cellulose functional groups. Then, add acrylic acid, methyl methacrylate, and butyl acrylate to the sulfonated carboxymethyl cellulose solution, and add sodium persulfate. Stir and react at 80°C for 1 hour to allow acrylic acid, methyl methacrylate, and butyl acrylate to polymerize and covalently graft onto the hydroxyl groups of the carboxymethyl cellulose. Cool to 25°C, adjust the pH to 8 with acetic acid, and sieve to obtain a carboxymethyl cellulose copolymer binder. The structural formula of the carboxymethyl cellulose copolymer binder is as follows:

[0046]

[0047] Comparative Example 1

[0048] This embodiment provides a carboxymethyl cellulose copolymer binder, wherein the binder raw materials include: 50 parts by mass of carboxymethyl cellulose sodium, 10 parts by mass of acrylic acid, 15 parts by mass of methyl methacrylate, 10 parts by mass of butyl acrylate, 15 parts by mass of acrylonitrile, and 0.2 parts by mass of sodium persulfate.

[0049] Preparation method: First, dissolve sodium carboxymethyl cellulose in deionized water. Add acrylic acid, methyl methacrylate, butyl acrylate, and acrylonitrile to the carboxymethyl cellulose solution, and then add sodium persulfate. Stir and react at 80°C for 1 hour to allow acrylic acid, methyl methacrylate, butyl acrylate, and acrylonitrile to polymerize and covalently graft onto the hydroxyl groups of the carboxymethyl cellulose. Cool to 25°C, adjust the pH to 8 with acetic acid, and sieve to obtain a carboxymethyl cellulose copolymer binder. The structural formula of the carboxymethyl cellulose copolymer binder is as follows:

[0050]

[0051] Effect testing

[0052] Negative electrode glue and slurry performance test

[0053] Glue viscosity test: The binders obtained in Examples 1-4 and the comparative example were dissolved in secondary deionized water at a mass ratio of 1:9. After dissolution and after standing for 48 hours, the viscosity of the glue was tested using a rotational viscometer at 25°C.

[0054] Film swelling test: The adhesives obtained in Examples 1-4 and the comparative example were dissolved in secondary deionized water at a mass ratio of 1:9. The dissolved adhesive solution was placed in an oven for drying to prepare adhesive films. The films were then cut into strips measuring 50 mm x 20 mm in length and width and weighed. An electrolyte solution (ethylene carbonate (EC): dimethyl carbonate (DMC): propylene carbonate (PC) = 1:1:1 (mass ratio)) was prepared. Adhesive films prepared with the adhesives obtained in Examples 1-4 and the comparative example were placed in the electrolyte solution. After 48 hours, the films were removed and weighed. The weight difference before and after the treatment was compared to calculate the weight gain.

[0055] Slurry performance test: Graphite, conductive agent SP, binders obtained in Examples 1-4 and Comparative Examples were added into a stirring tank at a weight ratio of 95:2:3 and kneaded to prepare a negative electrode slurry, which was then subjected to the following tests.

[0056] Maximum shear rate of slurry: The maximum shear rate of the negative electrode slurry was tested using a rheometer, and the maximum shear rate when the slurry changed from a non-Newtonian fluid to a Newtonian fluid was recorded.

[0057] Slurry solid content: The solid content of the negative electrode slurries prepared with the binders obtained in Examples 1-4 and the comparative example was tested using a rapid drying method. 4 g of the slurry sample was baked at 150°C for 1 hour. The difference in mass before and after drying was compared to calculate the solid content.

[0058] Slurry viscosity: The slurry viscosity was tested using a rotational viscometer. 100 g of the negative electrode slurry prepared with the binder of Examples 1-4 and the comparative example was taken and the viscosity of the slurry was tested using a 64# rotor at a speed of 30 rpm and an ambient temperature of 25°C.

[0059] Slurry fineness: Use a scraper fineness meter to test the fineness of the negative electrode slurry. Refer to the GB1724-89 test method, conduct three parallel tests, and take the arithmetic mean of the two similar results.

[0060] Comparative Example 2: CMC and SBR were used to prepare conventional negative electrode glue and negative electrode slurry. CMC was first dissolved in secondary deionized water to prepare a negative electrode glue; graphite, conductive agent SP, and negative electrode glue were added to a stirring tank in a weight ratio of graphite, conductive agent SP, and CMC of 95:2:1.5, and kneaded and stirred. Then 1.5 parts by weight of SBR was added and stirred at a low speed to prepare a negative electrode slurry.

[0061] The test data is shown in Table 1.

[0062] Table 1 Properties of glue and slurry

[0063]

[0064]

[0065] From the performance data of the glue and slurry, it can be seen that the glue of Comparative Examples 1 and 2 has poor stability, large viscosity rebound, and the glue film is easy to swell. In addition, the fineness and viscosity of the negative electrode slurry are high, and the performance of the slurry is poor. The large rebound of the glue viscosity, the high viscosity and fineness of the slurry will make the slurry difficult to coat and roll in the subsequent preparation of the electrode sheet, while the glue of the embodiment has good wettability and dispersion performance of the negative electrode slurry, which is beneficial to the preparation of the negative electrode sheet. The binder obtained by using acrylic acid, acrylate, and acrylonitrile as polymerization monomers in Example 1 is the best in glue and slurry performance. At the same time, compared with the maximum shear rate in the actual stirring process, the binder of the embodiment is shear-resistant, and the fineness and viscosity of the slurry after high-speed dispersion are significantly better than those of the conventional CMC and SBR slurries in Comparative Example 2. Example 2 uses acrylic acid as a polymerization monomer. Acrylic acid can improve the dispersion performance of the slurry. The slurry has a higher solid content and lower viscosity. Example 3 uses methyl methacrylate, butyl acrylate, and acrylonitrile as polymerization monomers. Due to the lack of acrylic acid to provide dispersion performance, the viscosity and fineness of the slurry are greater than those of Examples 1 and 2.

[0066] Negative electrode and battery performance test

[0067] Negative electrode and lithium-ion battery preparation

[0068] 1. The negative electrode slurries of Examples 1-4 and Comparative Examples 1 and 2 were extruded and coated to prepare negative electrode sheets. The negative electrode surface density was 75 g / m 2 , compacted 1.6gcc.

[0069] 2. Add lithium iron phosphate, PVDF, and conductive agent SP into a mixing tank at a weight ratio of 96.0:2.0:2.0 5 to obtain a uniformly distributed positive electrode slurry, which is then coated and rolled to obtain a positive electrode sheet. The positive electrode surface density is 200g / m 2 , compacted 2.45gcc.

[0070] 3. Assemble the prepared negative electrode sheet, positive electrode sheet, polyethylene separator and electrolyte into a lithium-ion battery according to conventional methods.

[0071] The negative electrode sheets of the embodiment and the comparative example were subjected to performance tests:

[0072] Pole flexibility test: Fold the pole piece several times to observe whether there are micro cracks on the surface, and record the number of folds until micro cracks appear.

[0073] Pole peeling force test: Cut the negative electrode into strips with a length and width of 2000mm*24mm, and evenly stick a 3M tape with a width of 24mm on the negative electrode. Use a universal tensile testing machine to perform a 180° tensile peeling test at a peeling speed of 20mm / min.

[0074] Pole sheet resistance test: Peel the negative electrode sheet from the surface of the negative copper foil with insulating tape, use a four-probe tester to test the electrode sheet resistivity, and use a penetration resistance tester to test the electrode sheet penetration resistance.

[0075] The test results are shown in Table 2.

[0076] Table 2 Negative electrode performance

[0077]

[0078] The data from Examples 1, 2, 3, and 4, as well as Comparative Examples 1 and 2, show that the addition of acrylic acid and sulfonic acid groups to the binder improves the dispersion of the negative electrode slurry. This is reflected in the electrical performance data, where both the through-hole resistance and resistivity of the electrode sheet are superior to those of other groups. Furthermore, the addition of acrylonitrile improves the flexibility of the electrode sheet, allowing light transmission only after multiple folds, meeting actual production requirements. The addition of ester functional groups effectively improves the peel strength of the electrode sheet, ensuring its integrity.

[0079] Performance test of the batteries of the embodiment and comparative example

[0080] Formation: Place for 5 minutes, charge with 0.02C constant current for 180min, then charge with 0.1C constant current for 180min, and charge with 0.2C constant current for 180min.

[0081] Capacity division: let it sit for 5 minutes, charge to 3.65V with 1 / 3C constant current, constant voltage to 0.05C at 3.65V, let it sit for 5 minutes, discharge to 2.0V with 1 / 3C constant current, let it sit for 5 minutes, discharge to 2.0V with 0.1C constant current, let it sit for 5 minutes, discharge to 2.0V with 0.05C constant current, let it sit for 5 minutes, charge to 2.0V with 1 / 3C constant current for 60 minutes. Cycle 1000: charge the battery to 3.65V with 1C current, then constant voltage to 0.05C current, let it sit for 5 minutes, then discharge the battery to 2.0V with 1C constant current, let it sit for 10 minutes, repeat the above charge and discharge steps to 1000 cycles.

[0082] Cyclic DCR: rest for 5 minutes, 1 / 3C constant current discharge for 90 minutes, rest for 60 minutes, 1C constant current discharge for 30 seconds, rest for 5 minutes, 1C constant current charge to 3.65V, 3.65V constant voltage to 0.05C, rest for 5 minutes, 1C constant current discharge to 2.0V, rest for 10 minutes.

[0083] The test results are shown in Table 3.

[0084] Table 3 Electrical performance test results

[0085]

[0086] Comparison of Examples 1-4 with Comparative Examples 1 and 2 demonstrates that the multi-component copolymerized carboxymethyl cellulose binder of the present invention exhibits superior cycling capacity retention and post-cycling DCR growth compared to conventional CMC+SBR systems. The capacity retention of Example 1 after 1000 cycles was 96.39%, 5.61% higher than the 90.78% achieved by the CMC+SBR system in Comparative Example 2. The DCR after 1000 cycles was 1.37 mΩ lower than that of Comparative Example 2.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A carboxymethyl cellulose copolymer binder, characterized in that Its structural formula is shown in Formula I: Wherein, R is one of CR1(COOH)-CR2(COOR3)-CR4(CN), CR1(COOH), COOR3, CR4(CN), CR2(COOR3), CR1(COOH)-CR4(CN), CR2(COOR3)-CR4(CN), CR1(COOH)-CR2(COOR3), R1 includes hydrogen or alkyl, R2 includes hydrogen or alkyl, R3 includes alkyl, and R4 includes hydrogen.

2. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 1, wherein The following steps are involved: introducing sulfonic acid functional groups into the cellulose functional groups of sodium carboxymethyl cellulose by using a sulfonating agent, mixing a polymerization monomer, an initiator and the sodium carboxymethyl cellulose with the sulfonic acid functional groups introduced into the cellulose functional groups and reacting the mixture, cooling the mixture to room temperature, adjusting the pH to 7-9, and sieving the mixture to obtain a carboxymethyl cellulose copolymer binder; The polymerizable monomer includes at least one of acrylic acid, acrylic esters and acrylonitrile substances.

3. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 2, wherein: Include at least one of the following: The sulfonating agent includes at least one of sulfuric acid, oleum, sulfur trioxide, chlorosulfonic acid and aminosulfonic acid; The initiator includes at least one of sodium persulfate, tert-butyl hydroperoxide, sodium bisulfite, potassium persulfate, ammonium persulfate, vitamins, benzoyl peroxide, azobisisobutyronitrile, AIBA and AIBI.

4. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 3, wherein: Include at least one of the following: The sulfonating agent is fuming sulfuric acid; The polymerization monomer is a mixture of acrylic acid, acrylic acid esters and acrylonitrile substances; The initiator is sodium persulfate.

5. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 3 or 4, characterized in that: Include at least one of the following: The acrylic acid esters include at least one of ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate and ethyl methacrylate; The acrylonitrile includes at least one of acrylonitrile and methacrylonitrile.

6. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 2, wherein: The method for introducing sulfonic acid functional groups into the cellulose functional groups of sodium carboxymethyl cellulose comprises: dissolving sodium carboxymethyl cellulose in a solvent, adding a sulfonating agent dropwise, and reacting at 100-130° C. for 30-60 minutes.

7. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 2, wherein: The mass ratio of the sodium carboxymethyl cellulose, the polymerization monomer, the sulfonating agent and the initiator is 50-60:20-60:1-2:0.2-0.

5.

8. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 7, wherein: The mass ratio of the sodium carboxymethyl cellulose, the polymerization monomer, the sulfonating agent, and the initiator is 50:50:2:0.

2.

9. The method for preparing the carboxymethyl cellulose copolymer binder according to claim 2, wherein: Include at least one of the following: The reaction is stirred at 60-80°C for 1-3 hours; Acetic acid is used to adjust the pH.

10. Use of the carboxymethyl cellulose copolymer binder according to claim 1 in the preparation of batteries.

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