A negative electrode slurry and copper foil-graphite negative electrode for a battery

Abstract

The present invention discloses a negative electrode slurry for a battery, comprising the following raw materials: lithium carboxymethyl cellulose, water, graphite, conductive graphite powder, and SBR. The lithium carboxymethyl cellulose has the following structure: #imgabs0# wherein R2 is H or CH2COOLi, and m and n are natural numbers greater than 0. The negative electrode slurry of the battery of the present invention contains lithium carboxymethyl cellulose modified with a flexible chain, which overcomes the inherent rigidity of the cellulose structure and imparts a certain degree of flexibility to the product. In practical applications, the addition of lithium carboxymethyl cellulose can improve the flexibility and bendability of products prepared with the addition of lithium carboxymethyl cellulose, reducing application restrictions and expanding its scope of application.

Description

[0001] This application is a divisional application of the invention patent application with the application date of September 23, 2022, application number 2022111642656, and invention name “A kind of lithium carboxymethyl cellulose and its preparation method and application”. Technical Field

[0002] The present invention relates to the technical field of cellulose chemical modification, and in particular to a negative electrode slurry containing modified lithium carboxymethyl cellulose and a copper foil-graphite negative electrode prepared by using the negative electrode slurry. Background Art

[0003] Lithium carboxymethyl cellulose is a carboxymethylated derivative of cellulose, a water-soluble ionic cellulose ether obtained through chemical modification. Lithium carboxymethyl cellulose is used in lithium batteries because of its thickening, water-retention, emulsification, and dispersion properties in water. However, the carbon chain backbone of natural cellulose is a chair-shaped six-membered ring structure connected by β-1,4-glycosidic bonds. The cyclic main chain molecules of this structure cannot rotate freely, resulting in rigidity in products such as films. Even carboxymethyl modification cannot change this main chain structure. Therefore, colloids containing lithium carboxymethyl cellulose exhibit a certain degree of brittleness after dehydration, resulting in problems such as difficulty in bending, easy powder loss when bent, and easy breakage of the coating after folding.

[0004] In the preparation of battery graphite negative electrodes, a combination of lithium carboxymethyl cellulose and styrene-butadiene rubber (SBR) is often used as a binder. Although SBR is a soft binder, the added lithium carboxymethyl cellulose is inherently rigid. This can lead to powder shedding and cracking between the graphite layer and the base layer during the battery's folding and bending, especially for electrodes with relatively thick coatings or when a high proportion of lithium carboxymethyl cellulose is added. This can cause quality issues.

[0005] Chinese patent application CN 102206286A discloses a method for preparing lithium carboxymethyl cellulose for lithium batteries. This involves acidifying and washing sodium carboxymethyl cellulose to produce carboxymethyl cellulose hydrogen, which is then reacted with lithium hydroxide to produce lithium carboxymethyl cellulose. The lithium carboxymethyl cellulose prepared by this method retains the chair-type six-membered ring structure of cellulose connected by β-1,4-glycosidic bonds. However, when used at high concentrations or when the battery graphite coating is relatively thick, it is prone to powder shedding during folding and bending.

[0006] Chinese patent CN106336461B discloses another method for preparing lithium carboxymethyl cellulose. Cellulose is alkalized in lithium hydroxide and then etherified with chloroacetic acid to obtain lithium carboxymethyl cellulose. The lithium carboxymethyl cellulose prepared by this method also has a six-membered ring structure connected by glycosidic bonds. The resulting colloid is rigid after drying, which also limits its application in batteries.

[0007] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0008] In view of this, in order to overcome the defects of the prior art, the present invention provides a negative electrode slurry for a battery, which uses flexible chain-modified lithium carboxymethyl cellulose.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A negative electrode slurry for a battery comprises the following raw materials: lithium carboxymethyl cellulose, water, graphite, conductive graphite powder, and SBR; the lithium carboxymethyl cellulose has the following structure:

[0011]

[0012] Wherein, R2 is H or CH2COOLi, and m and n are natural numbers greater than 0.

[0013] According to some preferred embodiments of the present invention, the negative electrode slurry comprises the following raw material components, in parts by weight: 98.1 parts of deionized water, 1.3 parts of lithium carboxymethyl cellulose, 96.5 parts of graphite powder, 0.5 parts of superconducting graphite powder, and 3.6 parts of water-soluble SBR.

[0014] A method for preparing lithium carboxymethyl cellulose comprises the following steps:

[0015] Add cellulose and lithium hydroxide substances such as lithium hydroxide monohydrate or lithium hydroxide to an alcohol-containing aqueous solution, stir evenly, and react at 20-40°C for 2-4 hours;

[0016] Add diepoxy butadiene, continue to control the temperature at 20-40°C, and stir the reaction for 1-3 hours;

[0017] Add chloroacetic acid alcohol solution, raise the temperature to 40-75°C after addition, and react for 1-3 hours to obtain crude lithium carboxymethyl cellulose;

[0018] The crude lithium carboxymethyl cellulose is post-treated to obtain the lithium carboxymethyl cellulose.

[0019] Lithium hydroxide is added to cellulose to activate the cellulose, such as destroying the crystalline region of cellulose to fully expose the hydroxyl groups in the crystalline region, increasing the contact opportunities with small molecule reactants, and increasing the reactivity and uniformity of the cellulose in the later stage. Lithium hydroxide is also needed to provide the alkaline conditions thereafter. Diepoxy butadiene is used to flexibly modify the cellulose molecules. On the one hand, diepoxy butadiene has moderate reactivity, is relatively stable under neutral conditions, and is prone to nucleophilic substitution reactions under alkaline conditions. It can match the preparation process of lithium carboxymethyl cellulose, making the steps simple and the reaction controllable. On the other hand, diepoxy butadiene has a relatively small molecular weight. When preparing finished products of the same viscosity (the same viscosity can be approximately regarded as the same molecular weight), it can provide more embedding points, making the product more flexible.

[0020] According to some preferred embodiments of the present invention, when the lithium hydroxide substance is lithium hydroxide monohydrate, the mass ratio of the cellulose to lithium hydroxide monohydrate is 1:0.3-1.

[0021] According to some preferred embodiments of the present invention, the molecular weight of the cellulose is 2000-250000. If a cellulose with a higher molecular weight is used as the base reactant, the molecular weight of the final product will increase dramatically, resulting in an increase in insoluble matter in its aqueous solution, causing clogging of the battery slurry in the later stage and reducing battery production efficiency.

[0022] According to some preferred embodiments of the present invention, after cellulose and lithium hydroxide monohydrate are added to an alcoholic aqueous solution, the cellulose concentration in the system is 400-1000 g / L. If the cellulose concentration is too high, the cellulose absorption and extrusion effects in the kneader are poor, and the kneading resistance during the kneading process is significantly increased. If the cellulose concentration is too low, the reactant concentration is diluted, the reaction conversion rate is reduced, and the cost is increased.

[0023] According to some preferred embodiments of the present invention, the volume concentration of alcohol in the alcohol-containing aqueous solution is 50-98%.

[0024] According to some preferred embodiments of the present invention, the mass ratio of cellulose to diepoxy butadiene is 1:0.04 to 0.4. If the mass ratio of diepoxy butadiene to cellulose is too high, the reaction will continue, the molecular weight of the product will continue to increase, and ultimately the insoluble matter in the product aqueous solution will increase, affecting the production efficiency of the battery. If the mass ratio of diepoxy butadiene to cellulose is too low, the molecular weight of the generated product will be small, and the viscosity of its aqueous solution will be low. When preparing a battery slurry of the same viscosity, the amount of product used must be increased, which indirectly affects the energy density of the battery.

[0025] According to some preferred embodiments of the present invention, the mass ratio of cellulose to chloroacetic acid is 1:0.4 to 1. If the mass ratio of chloroacetic acid to cellulose is too low, the degree of hydroxyl substitution of the product after the reaction is too low, the water solubility of the product deteriorates, and a large amount of insoluble matter appears, affecting subsequent screen passing and coating. If the mass ratio of chloroacetic acid to cellulose is too high, the degree of hydroxyl substitution of the product is very high, which will reduce the adsorption of the product on the graphite surface, causing the graphite powder in the battery slurry to easily settle and stratify, affecting the uniformity of coating and the quality of the battery.

[0026] According to some preferred embodiments of the present invention, the mass fraction of the chloroacetic acid alcohol solution, that is, the mass proportion of chloroacetic acid in the alcohol solution, is 50-90%.

[0027] According to some preferred embodiments of the present invention, the alcoholic chloroacetic acid solution is added for 30-60 minutes. If the chloroacetic acid is added for too short a time, the reaction is uneven, resulting in a large amount of insoluble matter in the product aqueous solution. If the chloroacetic acid is added for too long, the reaction time is increased, thereby increasing production costs.

[0028] According to some preferred embodiments of the present invention, the alcohol in the alcohol-containing aqueous solution and the alcoholic solution of chloroacetic acid is one or more of ethanol, propanol, butanol, and isopropanol.

[0029] According to some preferred embodiments of the present invention, the post-processing step is to neutralize the crude lithium carboxymethyl cellulose with an acidic substance and then wash, dry and crush it.

[0030] According to some preferred embodiments of the present invention, the acidic substance is acetic acid and / or hydrochloric acid.

[0031] According to some preferred embodiments of the present invention, the washing is performed multiple times with an ethanol aqueous solution, preferably an ethanol aqueous solution with a mass concentration of 75%.

[0032] According to some preferred embodiments of the present invention, the drying condition is to maintain a constant temperature of 100-110° C. in a forced air oven for 2 hours.

[0033] The present invention also provides a method for preparing lithium carboxymethyl cellulose according to the above-described method for preparing lithium carboxymethyl cellulose, and the use of the lithium carboxymethyl cellulose in a lithium battery. Specifically, during the preparation of the battery's negative electrode slurry, the lithium carboxymethyl cellulose is added to prepare a lithium carboxymethyl cellulose aqueous solution, followed by the addition of graphite, conductive graphite powder, and SBR. The solution is stirred evenly and then coated on copper foil. The solution is then dried, extruded, and rolled to prepare the battery's negative electrode.

[0034] The basic principle of this invention is as follows: Di-epoxy butadiene reacts with the hydroxyl groups on cellulose under alkaline conditions through a nucleophilic substitution reaction, embedding a flexible chain connected by ether linkages between the low-molecular-weight cellulose segments. The resulting cellulose contains both rigid six-membered ring chains and flexible ether chains. This polymer structure, containing both rigid and flexible chains, exhibits high strength and flexibility. After further carboxymethylation, the resulting lithium carboxymethyl cellulose also exhibits these properties, improving its bending resistance and addressing the issues of coating breakage and powder shedding after bending.

[0035] The reaction principle of the present invention is shown in the following formula:

[0036]

[0037] Wherein, R1 is H or Li, R2 is H or CH2COOLi, and m and n are natural numbers greater than 0.

[0038] By adopting the above technical solution, the benefits of the present invention compared with the prior art are: the negative electrode slurry of the battery of the present invention contains flexible chain-modified lithium carboxymethyl cellulose, which overcomes the rigidity of the cellulose structure itself and makes the product have a certain flexibility; in practical applications, it can improve the flexibility and bendability of the product prepared by adding lithium carboxymethyl cellulose, reduce the conditions for its application, and expand its scope of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is a photo of a lithium battery negative electrode prepared using the lithium carboxymethyl cellulose of Example 2 of the present invention after being curled into a U shape;

[0041] Figure 2 This is a photo of a lithium battery negative electrode after U-shaped curling, prepared using commercially available lithium carboxymethyl cellulose. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0043] The present invention aims to provide a method for preparing lithium carboxymethyl cellulose modified with embedded flexible groups. By modifying the structure of the cellulose molecules into flexible chains, the rigidity of the cellulose structure itself is overcome, and the product has a certain degree of flexibility. This solves the problems of conventional lithium carboxymethyl cellulose, such as the rigidity generated by colloid dehydration and the easy powder loss and cracking of the coating after bending. To achieve this purpose, the preparation method of lithium carboxymethyl cellulose of the present invention comprises the following steps:

[0044] (1) Alkalization of cellulose

[0045] Cellulose with a molecular weight of 2,000-250,000 and lithium hydroxide monohydrate are added to an alcohol-containing aqueous solution at a mass ratio of 1:0.3-1. The cellulose concentration in the system is 400-1,000 g / L. After uniform stirring, the reaction is carried out for 2-4 hours at a temperature of 20-40°C. The volume concentration of the alcohol in the alcohol-containing aqueous solution is 50-98%.

[0046] (2) Grafting of cellulose

[0047] Add diepoxy butadiene, continue to control the temperature at 20-40°C, and stir the reaction for 1-3 hours. The mass ratio of cellulose to diepoxy butadiene is 1:0.04-0.4.

[0048] (3) Cellulose etherification

[0049] Add the alcohol solution of chloroacetic acid for 30-60 minutes, then raise the temperature to 40-75°C and react for 1-3 hours to obtain crude lithium carboxymethyl cellulose.

[0050] The mass ratio of cellulose to chloroacetic acid is 1:0.4-1; the mass concentration of the chloroacetic acid alcohol solution is 50-90%.

[0051] (4) Post-processing

[0052] After the reaction is completed, the crude lithium carboxymethyl cellulose is neutralized with acetic acid or hydrochloric acid to neutrality, washed with 75% ethanol aqueous solution for 3 times, dried and powdered to obtain the finished lithium carboxymethyl cellulose.

[0053] The alcohol in the alcoholic aqueous solution and the alcoholic solution of chloroacetic acid is one or more of ethanol, propanol, butanol and isopropanol. The cellulose is wood pulp, bamboo pulp, cotton pulp and the like with a molecular weight of 2000-250000.

[0054] Example 1

[0055] Add 460 g of 90% ethanol aqueous solution, 120 g of water, 200 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a molecular weight of about 20,000 into the reactor, start stirring, control the temperature at 30° C. and react for 3 hours.

[0056] After completion, 40 g of diepoxy butadiene was added to the reactor and the temperature was raised to 30° C. for reaction for 2 h.

[0057] Then, 300 g of 75% chloroacetic acid alcohol solution was added, and the addition time was controlled to be about 30 minutes. After reacting at 40° C. for 1 hour, the temperature was raised to 70° C. and kept for reaction for 1 hour.

[0058] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral. The product was then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0059] Example 2

[0060] 500 g of 85% ethanol aqueous solution, 120 g of water, 200 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a molecular weight of about 20,000 were added to the reactor, stirring was started, the temperature was controlled at 30° C., and the reaction was carried out for 3 hours.

[0061] After completion, 50 g of diepoxy butadiene was added to the reactor and the temperature was raised to 40° C. for reaction for 2 h.

[0062] Then, 300 g of 75% chloroacetic acid alcohol solution was added, and the addition time was controlled to be about 50 min. After reacting at 40° C. for 1 h, the temperature was raised to 70° C. and kept for reaction for 1 h.

[0063] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral. The product was then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0064] Example 3

[0065] 460 g of 98% isopropyl alcohol aqueous solution, 120 g of water, 200 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a molecular weight of about 20,000 were added to the reactor, stirring was started, the temperature was controlled at 30° C., and the reaction was carried out for 2 h.

[0066] After completion, 40 g of diepoxy butadiene was added to the reactor and the temperature was raised to 30° C. for reaction for 2 h.

[0067] Then, 350 g of 75% chloroacetic acid alcohol solution was added, and the addition time was controlled to be about 50 minutes. After reacting at 40° C. for 1 hour, the temperature was raised to 70° C. and kept for reaction for 1 hour.

[0068] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral. The product was then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0069] Example 4

[0070] Add 460 g of 90% ethanol aqueous solution, 150 g of water, 250 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a molecular weight of about 20,000 into the reactor, start stirring, control the temperature at 40° C. and react for 4 hours.

[0071] After completion, 40 g of diepoxy butadiene was added to the reactor and the temperature was raised to 40° C. for reaction for 2 h.

[0072] Then, 300 g of 75% chloroacetic acid alcohol solution was added, and the addition time was controlled to be about 30 minutes. After reacting at 40° C. for 1 hour, the temperature was raised to 75° C. and kept for reaction for 2 hours.

[0073] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral. The product was then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0074] Example 5

[0075] Add 460 g of 98% isopropyl alcohol aqueous solution, 120 g of water, 200 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a molecular weight of about 20,000 into the reactor, start stirring, control the temperature at 20° C. and react for 2 h.

[0076] After completion, 30 g of diepoxy butadiene was added to the reactor and the temperature was raised to 30° C. for reaction for 2 h.

[0077] Then, 280 g of 80% chloroacetic acid alcohol solution was added, and the addition time was controlled to be about 30 minutes. After reacting at 40° C. for 1 hour, the temperature was raised to 60° C. and kept for reaction for 1 hour.

[0078] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral. The product was then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0079] Comparative Example 1

[0080] 460 g of 90% ethanol aqueous solution, 120 g of water, 200 g of lithium hydroxide monohydrate, and 300 g of wood pulp with a low molecular weight of about 20,000 were added to the reactor, and stirring was started and the mixture was reacted for 3 hours.

[0081] After completion, 300 g of 75% chloroacetic acid alcohol solution was added to the reactor, reacted at 40° C. for 2 h, then heated to 70° C. and kept warm for 1 h.

[0082] After completion, the temperature was lowered to below 40° C. and neutralized with acetic acid until neutral, and then washed with 75% alcohol, dried, and crushed to obtain the finished product of lithium carboxymethyl cellulose.

[0083] That is, the difference between this comparative example and Example 1 is that no diepoxybutadiene is added for modification during the preparation of lithium carboxymethyl cellulose.

[0084] Comparative Example 2

[0085] The difference between this comparative example and Example 1 is that this comparative example uses high molecular weight wood pulp with a molecular weight of about 600,000. During the reaction, due to the high molecular weight of cellulose, gelation occurs, making it difficult to continue the reaction.

[0086] Comparative Example 3

[0087] The difference between this comparative example and Example 1 is that the mass ratio of cellulose to diepoxy butadiene in this comparative example is 1:0.6. Since the ratio of diepoxy butadiene is too high, gelation occurs and the reaction is difficult to continue.

[0088] Comparative Example 4

[0089] This comparative example differs from Example 1 in that the mass ratio of cellulose to diepoxy butadiene in this comparative example is 1:0.01. Due to the low proportion of diepoxy butadiene, the obtained product has high hardness, poor toughness, and low elongation at break, resulting in insignificant improvement.

[0090] Comparative Example 5

[0091] The lithium carboxymethyl cellulose in this comparative example is a common commercial product produced by Chongqing Lihong Fine Chemical Co., Ltd., with a model batch number of CMC-LiBLCQ15-620090882.

[0092] Tests and Results

[0093] 1) The finished lithium carboxymethyl cellulose products from the examples and comparative examples were prepared into 0.3% aqueous solutions. 80.0 g of this aqueous solution was accurately weighed and poured into a Petri dish, dried at room temperature to obtain a transparent film. The film was then cut into strips measuring 6 x 1 cm in length and width. The tensile mechanical properties of the film strips were tested using a universal testing machine at a tensile speed of 500 mm / min. The test results are shown in the following table:

[0094] Table 1 Mechanical properties test results

[0095] Serial number Tensile breaking strength, N Elongation at break, % Example 1 20.9017 1.2 Example 2 28.7859 1.4 Example 3 22.4065 1.2 Example 4 23.6758 1.2 Example 5 19.8963 1.1 Comparative Example 1 16.4657 0.9 Comparative Example 4 16.9768 0.9 Comparative Example 5 16.8669 0.9

[0096] From the results in Table 1, it can be seen that compared with the comparative example, the tensile breaking force and elongation at break of the film prepared from the lithium carboxymethyl cellulose in the example are significantly improved, indicating that the mechanical properties of the film strip prepared in the example are enhanced.

[0097] 2) Testing the curling performance of lithium carboxymethyl cellulose in the examples and comparative examples when preparing battery copper foil-graphite negative electrode applications

[0098] The test method is as follows:

[0099] Add 98.1 g of deionized water, 1.3 g of lithium carboxymethyl cellulose obtained in the Examples or Comparative Examples, 96.5 g of graphite powder, 0.5 g of superconducting graphite powder, and 3.6 g of water-soluble SBR into a beaker;

[0100] After thorough stirring, place in a constant temperature water bath at 25°C for 4 hours to remove air bubbles;

[0101] Use a thin film preparation device to scrape out a slurry film on the copper foil with a thickness of 200 μm;

[0102] After drying in an oven, use a 5kg roller to roll the copper foil 10 times in the same direction, and then cut it into 10*10cm copper foil.

[0103] After curling the copper foil into a U-shape once, lay it flat and observe the cracking and shedding of the graphite layer on the surface of the copper foil.

[0104] The experimental results are as follows Figure 1 、 2 and as shown in Table 2.

[0105] Table 2 Results of U-shaped curling of battery copper foil-graphite negative electrode

[0106]

[0107]

[0108] Depend on Figure 1 、 Figure 2 As can be seen from the results in Table 2, after U-shaped curling, the lithium battery negative electrode film ( Figure 2 ) The graphite layer cracked and fell off; Figure 2 Due to the poor toughness of the coating, part of the graphite coating fell off the copper foil during the bending process, resulting in partial exposure of the copper foil, which is the light-colored part in the figure. The lithium carboxymethyl cellulose prepared in Example 2 was used to prepare the negative electrode film of the lithium battery ( Figure 1 ), although wrinkles were generated during the U-shaped curling process, the graphite layer did not crack or fall off.

[0109] The preparation method of the flexible lithium carboxymethyl cellulose of the present invention is to modify the structure of the cellulose molecule into a flexible chain to form a structure that is both rigid and flexible, and then carboxymethylate it to form lithium carboxymethyl cellulose of a certain molecular weight. Compared with commercially available lithium carboxymethyl cellulose, the lithium carboxymethyl cellulose prepared by the present invention can be used in products to make the products have a certain flexibility. In practical applications, the flexibility and bendability of the products prepared by adding lithium carboxymethyl cellulose can be improved, the conditions for its application are reduced, and its scope of use is expanded. It can be used as a binder for lithium batteries. The modified molecules contain functional monomers such as carboxyl and hydroxyl groups and flexibly rotatable carbon chains, which give the product a certain flexibility and overcome the rigidity of the cellulose structure itself. The modified lithium carboxymethyl cellulose prepared by the present invention not only has the original thickening, dispersing, bonding, and lithium supplementing functions, but also has a better effect of preventing powder loss and cracking between the graphite layer and the metal surface during the folding process of the battery coating.

[0110] The equipment and raw materials used in the above-mentioned embodiments can be purchased from the market or are commonly used in this area. The methods in the above-mentioned embodiments, unless otherwise specified, are conventional methods in this area. The raw materials not specifically specified in the embodiments are all commercially available. Operations without special mention of temperature are carried out at room temperature. The operating methods and conditions not specifically specified can adopt the well-known or conventional means and conditions in this area. The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in this article.

[0111] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A negative electrode slurry for a battery, characterized in that: The raw materials include lithium carboxymethyl cellulose, water, graphite, conductive graphite powder and SBR; the lithium carboxymethyl cellulose has the following structure: ； Wherein, R2 is H or CH2COOLi, and R2 is not all H, and m and n are natural numbers greater than 0; The lithium carboxymethyl cellulose is prepared by the following steps: Add cellulose and lithium hydroxide to an alcohol-containing aqueous solution, stir evenly, and react at 20-40°C for 2-4 hours; Add diepoxy butadiene, continue to control the temperature at 20-40°C, and stir the reaction for 1-3 hours; Add chloroacetic acid alcohol solution, raise the temperature to 40-75°C after addition, and react for 1-3 hours to obtain crude lithium carboxymethyl cellulose; post-treating the crude lithium carboxymethyl cellulose to obtain the lithium carboxymethyl cellulose; The molecular weight of the cellulose is 2000-250000; the mass ratio of the cellulose to diepoxy butadiene is 1:0.04-0.

4.

2. The negative electrode slurry according to claim 1, wherein The negative electrode slurry comprises the following raw material components in parts by weight: 98.1 parts of deionized water, 1.3 parts of lithium carboxymethyl cellulose, 96.5 parts of graphite powder, 0.5 parts of superconducting graphite powder, and 3.6 parts of water-soluble SBR.

3. The negative electrode slurry according to claim 1, characterized in that Prepared by the following steps: Lithium carboxymethyl cellulose is dissolved in water to prepare a lithium carboxymethyl cellulose aqueous solution, and then graphite, conductive graphite powder and SBR are added and stirred evenly to obtain the negative electrode slurry.

4. The negative electrode slurry according to claim 3, characterized in that The step further includes: after stirring evenly, placing the mixture in a constant temperature water tank at 25° C. for 4 hours to eliminate bubbles in the negative electrode slurry.

5. The negative electrode slurry according to claim 1, characterized in that The lithium hydroxide substance is lithium hydroxide monohydrate or lithium hydroxide; when the lithium hydroxide substance is lithium hydroxide monohydrate, the mass ratio of the cellulose to the lithium hydroxide monohydrate is 1:0.3~1.

6. The negative electrode slurry according to claim 1, characterized in that The post-treatment is to neutralize the crude lithium carboxymethyl cellulose with an acidic substance, and then wash, dry and crush it.

7. A copper foil-graphite negative electrode for a battery, characterized in that: The negative electrode is prepared by the following method: coating the negative electrode slurry according to any one of claims 1 to 6 on a copper foil, and then drying, extruding, and curling the copper foil to obtain the negative electrode of the battery.

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