HIGH VISCOSITY LITHIUM CARBOXYMETHYLCELLULOSE AND MANUFACTURING PROCESSES FOR IT AND USES THEREOF

Abstract

Manufacturing process for a high viscosity lithium carboxymethylcellulose, wherein the lithium carboxymethylcellulose has a 1% viscosity of > 25000 mPa·s, characterized in that this process comprises the following steps: Mixing a cellulose, an aqueous solution of a polar solvent, and a sodium hydroxide solution in an ethanol solution; filling with nitrogen gas to create an inert atmosphere after vacuuming to remove air; carrying out an alkalization reaction under the inert atmosphere; subjecting a reaction product to etherification under normal pressure to obtain crude CMC-Na; acidifying the crude CMC-Na to obtain CMC-H; and adding the prepared CMC-H to a lithium salt ethanol solution to carry out a substitution reaction to obtain high-viscosity lithium carboxymethylcellulose; The amounts of cellulose, aqueous solution of the polar solvent, sodium hydroxide solution, and ethanol solution added in the alkalization reaction are 3 to 10 parts, 2 to 15 parts, 1 to 8 parts, and 5 to 25 parts, respectively, based on parts by weight; the aqueous solution of the polar solvent contains 20% to 85% methanol or isopropanol; the volume concentration of the ethanol solution is 70% to 95%; and the concentration of the sodium hydroxide solution is 25% to 50%. Specific steps of the alkalization reaction are as follows: Place the raw materials in the specified weight parts into a reactor, vacuum-seal for the first time to -10 to -25 kPa, then fill with nitrogen to 3 to 10 kPa, vacuum-seal a second time to -25 to -80 kPa, refill with nitrogen to 3 to 10 kPa, carry out the alkalization reaction; maintain a nitrogen gas pressure of 3 to 10 kPa during the reaction, and the duration of the alkalization reaction is 30 minutes; Specific steps of the etherification reaction are as follows: Addition of a product of the alkalization reaction to a monochloroacetic acid-ethanol solution to carry out an etherification reaction under normal pressure; a mass concentration of the monochloroacetic acid in the monochloroacetic acid-ethanol solution is 45% to 65%, a concentration of the ethanol in the monochloroacetic acid-ethanol solution is ≥93%, an amount of monochloroacetic acid-ethanol solution added is 2 to 10 parts by weight, and a duration of the etherification reaction is 30 to 80 min; The specific steps of the acidification reaction are as follows: Adding the crude CMC-Na to a sulfuric acid solution to carry out the acidification reaction in a normal pressure system; the concentration of the sulfuric acid solution is 10% to 40%, and the duration of the acidification is 60 to 180 min; the pH of the substitution reaction is 6.5 to 10.0 and the duration of the substitution reaction is 30 to 120 min.

Description

Technical field

[0001] The present application relates to a technical field for modifying natural polymer materials, in particular a high viscosity lithium carboxymethylcellulose and a manufacturing process for it and an application thereof. background

[0002] The rapid development of 3C products and new energy performance has led to higher demands on the energy density and electrochemical performance of lithium-ion batteries. There are two approaches to increasing energy density: one is the development of high-energy-density active materials, such as nickel-rich materials, silicon-carbon materials, and silicon oxide materials; the other is reducing the amount of additives applied in a slurry system, thereby decreasing the amount of active materials required. This can be achieved, for example, by using a highly conductive conductive agent, a high-viscosity adhesive, a dispersant with good dispersing properties, and similar additives.

[0003] Lithium carboxymethylcellulose is used in the production of a slurry for the negative electrode plate of a lithium-ion battery to stabilize the slurry, disperse active substances, and promote adhesion. However, lithium carboxymethylcellulose is a polymer material with poor conductivity, which can inhibit the electrochemical performance of the active substances when applied to them. Furthermore, the viscosity of existing lithium carboxymethylcellulose is limited, requiring a larger addition amount, typically 1.0% to 1.5%, which further increases production costs, while there is still considerable potential for improving the performance of carboxymethylcellulose.

[0004] The following publications are considered state of the art: CN 1 11 423 518 A, CN 1 13 614 946 A, US 2019 / 0 267 609 A1, CN 1 12 751 034 A, CN 1 12 724 266 A, CN 1 11 363 049 A, CN 1 05 330 751 A, US 2013 / 0 012 696 A1 and CN 1 12 072 110 A. Brief description

[0005] In light of this, the present application provides a high viscosity lithium carboxymethylcellulose which can reduce the amount of lithium carboxymethylcellulose required in the manufacture of a negative electrode plate of a lithium-ion battery and can increase the energy density and electrochemical performance of the lithium-ion battery.

[0006] To achieve the objective described above, the present application first provides a manufacturing process for a high viscosity lithium carboxymethylcellulose, wherein the lithium carboxymethylcellulose has a 1% viscosity of ≥ 25000 mPas, comprising the following steps: Mixing a cellulose, a crosslinking agent, and a sodium hydroxide solution in an ethanol solution; filling with nitrogen gas to create an inert atmosphere after vacuuming to remove air; carrying out an alkalization reaction under the inert atmosphere; subjecting a reaction product to etherification under normal pressure to obtain crude CMC-Na; acidifying the crude CMC-Na to obtain CMC-H; and adding the prepared CMC-H to a lithium salt ethanol solution to carry out a substitution reaction to obtain high-viscosity lithium carboxymethylcellulose.

[0007] Furthermore, the crosslinking agent is an aqueous solution of a polar solvent; moreover, the concentration of the crosslinking agent is 20% to 85%.

[0008] Furthermore, the volume concentration of the ethanol solution in the alkalization reaction is 70% to 95%.

[0009] Furthermore, the concentration of the sodium hydroxide solution is 25% to 50%.

[0010] Furthermore, raw materials are introduced into a reactor in the specified parts by weight; and the reactor is first vacuumed to -10 to -25 kPa, then filled with nitrogen to 3 to 10 kPa, a second time vacuumed to -25 to -80 kPa and again filled with nitrogen to 3 to 10 kPa to carry out an alkalization reaction.

[0011] Furthermore, the nitrogen gas pressure is maintained at 3 to 10 kPa during the reaction, and the alkalization reaction lasts for 30 minutes.

[0012] Furthermore, a product of the alkalization reaction of a monochloroacetic acid-ethanol solution is added to carry out an etherification reaction under normal pressure; moreover, a mass concentration of monochloroacetic acid in the monochloroacetic acid-ethanol solution is 45% to 65% and a concentration of ethanol in the monochloroacetic acid-ethanol solution is ≥93%.

[0013] Furthermore, the duration of the etherification reaction is 30 to 80 minutes.

[0014] Furthermore, the crude CMC-Na is added to a sulfuric acid solution to carry out the acidification reaction in a normal pressure system; moreover, a concentration of sulfuric acid solution of 10% to 40% is required.

[0015] Furthermore, the acidification reaction lasts between 60 and 180 minutes.

[0016] Furthermore, the lithium salt ethanol solution can be prepared by dissolving 0.5 to 3 parts of the lithium salt in 1 to 5 parts of the ethanol solution with a concentration of 65% to 95%, based on parts by weight.

[0017] Furthermore, the duration of the substitution reaction is 30 to 120 minutes.

[0018] Furthermore, the amount added of cellulose, crosslinking agent, sodium hydroxide solution, ethanol solution and monochloroacetic acid-ethanol solution is 3 to 10 parts, 2 to 15 parts, 1 to 8 parts, 5 to 25 parts and 2 to 10 parts respectively, based on parts by weight.

[0019] Secondly, the present application provides a high viscosity lithium carboxymethylcellulose produced by the manufacturing process previously described for high viscosity lithium carboxymethylcellulose.

[0020] Thirdly, the present application provides an application of high viscosity lithium carboxymethylcellulose in the manufacture of a negative electrode plate of a lithium-ion battery.

[0021] Specifically, this application includes the following steps: Add high-viscosity lithium carboxymethylcellulose to water, stir for 2 to 4 hours, add sodium ligninsulfonate, a single-walled carbon nanotube, and graphene while mixing, dissolve the high-viscosity lithium carboxymethylcellulose and sodium ligninsulfonate, then allow the solution to stand for 6 to 24 hours, mix graphite with conductive carbon black, then add the graphite and conductive carbon black to the solution, disperse for 1 to 3 hours at a rotational speed of 850 to 1500 rpm, reduce the rotational speed to 200 to 500 rpm after dispersal is complete, add styrene-butadiene latex and continue stirring for 0.5 to 1 hour to obtain a slurry;After adjusting the viscosity of the slurry to 3000 to 7000 mPa·s, the slurry is applied to a copper foil as a current collector for a negative electrode, dried, and rolled to obtain the negative electrode plate.

[0022] The following raw materials may be present in the following quantities, based on parts by weight:

[0023] Graphite 96 to 98 parts, conductive carbon black 1 to 2 parts, lithium carboxymethylcellulose 0.6 to 1 part, styrene butadiene latex 1 to 2 parts, sodium ligninsulfonate 0.1 to 0.5 parts, single-walled carbon nanotubes 0 to 0.5 parts, graphene 0 to 0.5 parts and water 20 to 70 parts.

[0024] The present application has the following favorable effects: (1) The high viscosity lithium carboxymethylcellulose provided by the present application can, as an additive to a negative electrode plate, reduce the application quantity to 0.6%, or by 0.4% or more compared to the prior art of 1.0 to 1.5%, thereby saving production costs. (2) The high-viscosity lithium carboxymethylcellulose provided by the present application can also increase the energy density and the transfer rate of lithium ions in the battery, such that the DC resistance of the lithium battery during discharge at -30 °C is reduced by more or less than 18%. The capacity at a high rate can be increased by more or less than 15%, demonstrating that the lithium battery exhibits excellent electrochemical performance. (3) Furthermore, the use of the combination of sodium ligninsulfonate with high viscosity lithium carboxymethylcellulose can disperse the single-walled carbon nanotube and the graphene to increase the conductivity of the electrode plate, thereby increasing the dynamic performance of the battery. Detailed description of embodiments

[0025] A manufacturing process for a high viscosity lithium carboxymethylcellulose, wherein the lithium carboxymethylcellulose has a 1% viscosity of ≥ 25000 mPas, comprises the following steps: Mixing a cellulose, a crosslinking agent, and a sodium hydroxide solution in an ethanol solution; filling with nitrogen gas to create an inert atmosphere after vacuuming to remove air; carrying out an alkalization reaction under the inert atmosphere; subjecting a reaction product to etherification under normal pressure to obtain crude CMC-Na; acidifying the crude CMC-Na to obtain CMC-H; adding the prepared CMC-H to a lithium salt ethanol solution to carry out a substitution reaction to obtain high-viscosity lithium carboxymethylcellulose.

[0026] Furthermore, the crosslinking agent is an aqueous solution of methanol or isopropanol, wherein the concentration of methanol or isopropanol is 20% to 85%.

[0027] Furthermore, the volume concentration of the ethanol solution in the alkalization reaction is 70% to 95%.

[0028] Furthermore, the concentration of the sodium hydroxide solution is 25% to 50%.

[0029] Furthermore, raw materials are introduced into a reactor in the specified parts by weight; and the reactor is first vacuumed to -10 to -25 kPa, then filled with nitrogen to 3 to 10 kPa, a second time vacuumed to -25 to -80 kPa and again filled with nitrogen to 3 to 10 kPa to carry out an alkalization reaction.

[0030] One purpose of vacuuming is to remove air to prevent atmospheric oxygen from oxidizing the cellulose, which shortens the molecular chain and reduces viscosity. After vacuuming, filling with nitrogen creates an inert atmosphere to prevent air from re-entering the reactor. Repeated vacuuming-filling with nitrogen ensures the reactor is in an environment free of both air and oxygen. Finally, the entire alkalization reaction process requires maintaining a nitrogen gas pressure of 3 to 10 kPa, a slightly barotropic condition. The reactor is completely filled with this inert gas, and its purpose is to prevent air from entering and introducing oxygen.

[0031] Furthermore, the duration of the alkalization reaction is 30 minutes.

[0032] Furthermore, a product of the alkalization reaction of a monochloroacetic acid-ethanol solution is added to carry out an etherification reaction under normal pressure; moreover, a mass concentration of monochloroacetic acid in the monochloroacetic acid-ethanol solution is 45% to 65% and a concentration of ethanol in the monochloroacetic acid-ethanol solution is ≥93%.

[0033] Furthermore, the duration of the etherification reaction is 30 to 80 minutes.

[0034] Furthermore, after completion of the etherification reaction, a reaction product can be washed using an ethanol solution and purified by centrifugal separation; moreover, the volume concentration of the ethanol solution used during purification is 50 to 80% and the frequency of washing is 3 to 4 times.

[0035] Furthermore, the crude CMC-Na is added to a sulfuric acid solution to carry out an acidification reaction in a normal pressure system; moreover, a concentration of sulfuric acid solution of 10% to 40% is required.

[0036] Furthermore, the acidification reaction lasts between 60 and 180 minutes.

[0037] Furthermore, the lithium salt ethanol solution can be prepared by dissolving 0.5 to 3 parts of the lithium salt in 1 to 5 parts of the ethanol solution with a concentration of 65% to 95%, based on parts by weight; moreover, the lithium salt can be lithium acetate.

[0038] Furthermore, the lithium salt can also be lithium hydroxide or lithium carbonate. If lithium hydroxide or lithium carbonate is selected, water is added to 0.5 to 3 parts by weight of the lithium hydroxide or lithium carbonate until the lithium salt is dissolved. Once dissolved, the solution is mixed with 1 to 5 parts by weight of ethanol solution at a concentration of 65% to 95% to obtain the lithium salt-ethanol solution.

[0039] Furthermore, the duration of the substitution reaction is 30 to 120 minutes.

[0040] Furthermore, the amounts added of cellulose, crosslinking agent, sodium hydroxide solution, ethanol solution and monochloroacetic acid-ethanol solution are 3 to 10 parts, 2 to 15 parts, 1 to 8 parts, 5 to 25 parts and 2 to 10 parts respectively, based on parts by weight.

[0041] Secondly, the present application provides a high viscosity lithium carboxymethylcellulose produced by the manufacturing process for high viscosity lithium carboxymethylcellulose described above.

[0042] Upon detection, the high viscosity lithium carboxymethylcellulose provided by the present application has the following physical and chemical properties: Degree of substitution: 0.6 to 1.0; 1% viscosity: >25000 mPa·s; pH value: 6.5 to 9.5; and Purity ≥99.7%.

[0043] The present application provides a method for applying high viscosity lithium carboxymethylcellulose in the manufacture of a negative electrode plate for a lithium-ion battery.

[0044] Specifically, this application includes the following steps: Add high-viscosity lithium carboxymethylcellulose to water and stir for 2 to 4 hours; add sodium ligninsulfonate, a single-walled carbon nanotube, and graphene while mixing; after dissolving the high-viscosity lithium carboxymethylcellulose and sodium ligninsulfonate, allow the solution to stand for 6 to 24 hours; after mixing graphite with a conductive carbon black, add the graphite and conductive carbon black to the solution; disperse for 1 to 3 hours at a rotational speed of 850 to 1500 rpm; reduce the rotational speed to 200 to 500 rpm after dispersal is complete and add a styrene-butadiene latex; continue stirring for 0.5 to 1 hour to obtain a slurry;After adjusting the viscosity of the slurry to 3000 to 7000 mPa·s, the slurry is applied to a copper foil as a current collector for a negative electrode, dried, and rolled to obtain the negative electrode plate.

[0045] Furthermore, the following raw materials may be included, based on parts by weight: Graphite 96 to 98 parts, conductive carbon black 1 to 2 parts, lithium carboxymethylcellulose 0.6 to 1 part, styrene butadiene latex 1 to 2 parts, sodium ligninsulfonate 0.1 to 0.5 parts, single-walled carbon nanotubes 0 to 0.5 parts, graphene 0 to 0.5 parts and water 20 to 70 parts.

[0046] Technical solutions in examples from the present application are subsequently described clearly and comprehensively. Obviously, the examples described are only a subset of the examples in the present application and are not all of them. Based on the examples in the present application, all other examples that a person skilled in the art in this field could obtain without performing any creative work fall within the scope of protection of the present application. Example 1

[0047] A high-viscosity lithium carboxymethylcellulose, wherein the lithium carboxymethylcellulose has a 1% viscosity of ≥ 25000 mPas, was prepared by the following steps: (1) Three parts by weight of a cellulose solution, two parts by weight of an aqueous methanol solution with a concentration of 20%, one part by weight of a sodium hydroxide solution with a concentration of 25%, and five parts by weight of an ethanol solution with a volume concentration of 70% were placed in a reactor; and the reactor was first vacuumed to -20 kPa, filled with nitrogen to 3 kPa, and a second time vacuumed to -25 kPa and filled with nitrogen to 3 kPa to carry out an alkalization reaction. A pressure of nitrogen gas was maintained at 3 kPa during the alkalization reaction, and the duration of the alkalization reaction was 30 minutes. (2) A product of the alkalization reaction was added to 2 parts by weight of a monochloroacetic acid-ethanol solution having a mass concentration of monochloroacetic acid of 45% and a concentration of ethanol of 93%, the pressure was increased to normal pressure to carry out an etherification reaction, the duration of the etherification reaction was 30 min and a product of the etherification reaction was washed three times using an ethanol with a concentration of 50% to obtain a crude CMC-Na. (3) The crude CMC-Na was added to 10% of a sulfuric acid solution, an acidification reaction was carried out under normal pressure to obtain CMC-H, and the duration of the acidification reaction was 60 min. (4) 0.5 parts by weight of lithium acetate were dissolved in 1 part by weight of an ethanol solution with a concentration of 65% to prepare a lithium salt ethanol solution, the CMC-H was added to the lithium salt ethanol solution to carry out a substitution reaction, the pH of the substitution reaction was adjusted to 6.5 and the duration of the substitution reaction was 30 min to obtain the high viscosity lithium carboxymethylcellulose.

[0048] Physical and chemical performance characteristics of the produced high-viscosity lithium carboxymethylcellulose were recorded, and the results are as follows: Degree of substitution: 0.65; 1% viscosity: 27580 mPa·s; pH value: 6.9; and Purity: 99.82%. Example 2

[0049] A high-viscosity lithium carboxymethylcellulose was produced by the following steps: (1) 10 parts by weight of a cellulose solution, 15 parts by weight of an aqueous isopropanol solution with a concentration of 85%, 8 parts by weight of a sodium hydroxide solution with a concentration of 50%, and 25 parts by weight of an ethanol solution with a concentration of 95% were placed in a reactor; and the reactor was first vacuumed to -20 kPa, filled with nitrogen to 10 kPa, and a second time vacuumed to -80 kPa and filled with nitrogen to 10 kPa to carry out an alkalization reaction. A pressure of nitrogen gas was maintained at 10 kPa during the alkalization reaction, and the duration of the alkalization reaction was 70 minutes. (2) A product of the alkalization reaction was added to 10 parts by weight of a monochloroacetic acid-ethanol solution having a mass concentration of monochloroacetic acid of 65% and a volume concentration of ethanol of 95%, the pressure was increased to normal pressure to carry out an etherification reaction, the duration of the etherification reaction was 80 min and a product of the etherification reaction was washed three times using an ethanol with a concentration of 50% to obtain a crude CMC-Na. (3) The crude CMC-Na was added to a 40% sulfuric acid solution, an acidification reaction was carried out under normal pressure to obtain a CMC-H, and the duration of the acidification reaction was 180 min. (4) A lithium salt ethanol solution was prepared by dissolving 3 parts by weight of lithium acetate in 5 parts by weight of an ethanol solution with a concentration of 95%, the CMC-H was added to the lithium salt ethanol solution to carry out a substitution reaction, the pH of the substitution reaction was adjusted to 9.5 and the duration of the substitution reaction was 120 min to obtain the high viscosity lithium carboxymethylcellulose.

[0050] Physical and chemical performance characteristics of the produced high-viscosity lithium carboxymethylcellulose were recorded, and the results are as follows: Degree of substitution: 0.70; 1% viscosity: 30180 mPa·s; pH value: 8.0; and Purity: 99.97%. Example 3

[0051] A high-viscosity lithium carboxymethylcellulose was produced by the following steps: (1) 5 parts by weight of cellulose, 7 parts by weight of an aqueous isopropanol solution with a concentration of 45%, 5 parts by weight of a sodium hydroxide solution with a concentration of 40%, and 15 parts by weight of an ethanol solution with a concentration of 80% were placed in a reactor; and the reactor was first vacuumed to -20 kPa, filled with nitrogen to 8 kPa, and a second time vacuumed to -50 kPa and filled with nitrogen to 8 kPa to carry out an alkalization reaction. The pressure of nitrogen gas during the alkalization reaction was maintained at 8 kPa, and the duration of the alkalization reaction was 50 minutes. (2) A product of the alkalization reaction was added to 6 parts by weight of a monochloroacetic acid-ethanol solution having a mass concentration of monochloroacetic acid of 50% and a volume concentration of ethanol of 93%, the pressure was increased to normal pressure to carry out an etherification reaction, the duration of the etherification reaction was 50 min and a product of the etherification reaction was washed three times using ethanol with a concentration of 50% to obtain a crude CMC-Na. (3) The crude CMC-Na was added to 20% of a sulfuric acid solution, an acidification reaction was carried out under normal pressure to obtain CMC-H, and the duration of the acidification reaction was 120 min. (4) A lithium salt ethanol solution was prepared by dissolving 2 parts by weight of lithium acetate in 4 parts by weight of an ethanol solution with a concentration of 75%, the CMC-H was added to the lithium salt ethanol solution to carry out a substitution reaction, the pH of the substitution reaction was adjusted to 8.0 and the duration of the substitution reaction was 90 min to obtain the high viscosity lithium carboxymethylcellulose.

[0052] Physical and chemical performance characteristics of the produced high-viscosity lithium carboxymethylcellulose were recorded, and the results are as follows: Degree of substitution: 0.69; 1% viscosity: 32905 mPa·s; pH value: 7.8; and Purity: 99.9%. Example 4

[0053] A manufacturing process for a negative electrode plate of a lithium-ion battery includes the following steps: (1) The following were weighed out, expressed in parts by weight: 96 parts of graphite, 1 part of conductive carbon black, 0.9 parts of high viscosity lithium carboxymethylcellulose produced in Example 3, 2 parts by weight of styrene-butadiene latex, 0.1 parts by weight of sodium ligninsulfonate and 20 parts by weight of deionized water. (2) The high viscosity lithium carboxymethylcellulose produced in Example 3 was mixed with the deionized water, the sodium ligninsulfonate was added during mixing, and the solution was left to stand for 12 hours after dissolving the high viscosity lithium carboxymethylcellulose and the sodium ligninsulfonate. (3) The solution in step (2) was added after uniform mixing of the graphite and the conductive carbon black and high-speed dispersion was carried out at 850 rpm for 3 hours. (4) After the high-speed dispersion was completed, the rotational speed was reduced to 200 rpm, the styrene-butadiene latex was added and stirring was continued for 1 hour to obtain a slurry. (5) The viscosity of the slurry was adjusted to 4986 mPa·s and the solids content of the slurry was 48.3%. (6) The slurry was applied to a copper foil as a current collector for a negative electrode, and drying and rolling were carried out to obtain the negative electrode plate. Example 5

[0054] A manufacturing process for a negative electrode plate of a lithium-ion battery includes the following steps: (1) The following were weighed out, expressed in parts by weight: 98 parts by weight of graphite, 2 parts by weight of conductive carbon black, 0.5 parts by weight of a single-walled carbon nanotube, 1 part of the high viscosity lithium carboxymethylcellulose produced in Example 3, 1 part by weight of styrene-butadiene latex, 0.5 parts of sodium ligninsulfonate and 70 parts of deionized water. (2) The high viscosity lithium carboxymethylcellulose produced in Example 3 was mixed with the deionized water, the sodium ligninsulfonate and single-walled carbon nanotubes were added during mixing, and the solution was left to stand for 8 hours after dissolving the high viscosity lithium carboxymethylcellulose and the sodium ligninsulfonate. (3) The solution in step (2) was added after uniform mixing of the graphite and the conductive carbon black and high-speed dispersion was carried out at 1500 rpm for 1 hour. (4) After the high-speed dispersion was completed, the rotational speed was reduced to 500 rpm, the styrene-butadiene latex was added and stirring was continued for 0.5 hours to obtain a slurry. (5) The viscosity of the slurry was adjusted to 4830 mPa·s and the solids content of the slurry was 48.0%. (6) The slurry was applied to a copper foil as a current collector for a negative electrode, and drying and rolling were carried out to obtain the negative electrode plate. Example 6

[0055] A manufacturing process for a negative electrode plate of a lithium-ion battery includes the following steps: (1) The following were weighed out, expressed in parts by weight: 96 parts of graphite, 0.5 parts of conductive carbon black, 0.5 parts of graphene, 0.6 parts of high viscosity lithium carboxymethylcellulose produced in Example 3, 2 parts by weight of styrene-butadiene latex, 0.4 parts of sodium ligninsulfonate and 50 parts of deionized water. (2) The high viscosity lithium carboxymethylcellulose produced in Example 3 was mixed with the deionized water, the sodium ligninsulfonate and the graphene were added during mixing, and the solution was left to stand for 12 hours after dissolving the high viscosity lithium carboxymethylcellulose and the sodium ligninsulfonate. (3) The solution in step (2) was added after uniform mixing of the graphite and the conductive carbon black, and high-speed dispersion was carried out at 1000 rpm for 2 hours. (4) After the high-speed dispersion was completed, the rotational speed was reduced to 300 rpm, the styrene-butadiene latex was added and stirring was continued for 0.5 hours to obtain a slurry. (5) The viscosity of the slurry was adjusted to 4880 mPa·s and the solids content of the slurry was 48.73%. (6) The slurry was applied to a copper foil as a current collector for a negative electrode, and drying and rolling were carried out to obtain the negative electrode plate. Comparative example

[0056] A manufacturing process for a negative electrode plate of a lithium-ion battery includes the following steps: (1) The following were weighed out, expressed in parts by weight: 95.5 parts of graphite, 1 part of conductive carbon black, 1.5 parts of commercially available lithium carboxymethylcellulose, 2 parts by weight of styrene-butadiene latex, and 50 parts of deionized water. The degree of substitution for the commercially available lithium carboxymethylcellulose was 0.68, the viscosity of 1% was 4950 mPa·s, and the pH was 7.6. (2) A lithium carboxymethylcellulose was mixed with deionized water and the solution was left to stand for 12 hours after dissolving the lithium carboxymethylcellulose. (3) The solution in step (2) was added after uniform mixing of the graphite and the conductive carbon black and high-speed dispersion was carried out at 850 rpm for 3 hours. (4) After the high-speed dispersion was completed, the rotational speed was reduced to 200 rpm, the styrene-butadiene latex was added and stirring was continued for 1 hour to obtain a slurry. (5) The viscosity of the slurry was adjusted to 4770 mPa·s and the solids content of the slurry was 47.9%. (6) The slurry was applied to a copper foil as a current collector for a negative electrode, and drying and rolling were carried out to obtain the negative electrode plate.

[0057] The negative electrode plates of the lithium-ion battery produced in Examples 4 to 6 and the comparison example were each fitted with a positive electrode plate of a lithium iron phosphate system and wound to form 500 mAh batteries. The electrochemical performance was tested, and results of the performance tests are shown in Tables 1 to 5. Table 1 Results for tests of initial efficiency in examples 4 to 6 and comparison example Initial discharge capacity (mAh) Initial efficiency (%) Example 4 437 87,4 436 87,2 439 87,8 Example 5 438 87,6 440 88,0 435,5 87,1 Example 6 442,5 88,5 440,5 88,1 442 88,4 Comparative example 428,5 85,7 426,5 85,3 428 85, 6 Table 2 Results for tests of normal temperature DCR in examples 4 to 6 and comparison example DCR(mΩ) 5C DC 30s at 25°C Charge states 70% SOC 50% SOC 30% SOC Example 4 173,51 167,42 172, 96 174,25 166, 87 173, 12 174,69 167, 03 172,76 Example 5 168,86 160,02 165,83 167,43 159,46 166,41 169,23 159,20 165,79 Example 6 160,72 153,48 158, 65 162,38 154,25 159,06 161,59 154,10 159,24 Comparative example 191, 53 185,12 189,26 192,28 186,26 188, 62 190,89 184,91 188, 79 Table 3 Results for tests of low-temperature DCR in examples 4 to 6 and comparison example DCR (mΩ) 5C DC 30s at -30°C Charge states 70% SOC 50% SOC 30% SOC Example 4 177,08 174,35 176, 83 177,43 173, 84 176,28 178, 65 174,12 177,51 Example 5 173,70 170,56 172,43 173, 12 169, 68 172,71 173,56 169,75 171,76 Example 6 168,29 165,43 167,05 168, 46 165,70 167,28 168, 93 164, 97 166, 68 Comparative example 203,06 199,20 201,68 203,19 198,49 201,26 203,36 199,87 201,09 Table 4 Results for tests of high-temperature and low-temperature performance in examples 4 to 6 and comparison example High-temperature and low-temperature performance at 1°C Temperature (°C) -25 -20 0 25 50 Example 4 71,9% 75,3% 90,5% 100% 100, 8% 71,2% 74,9% 90,5% 100% 100,5% 72,4% 75,8% 91,2% 100% 100,3% Example 5 73,1% 76,8% 92,3% 100% 101,2% 72,9% 76,1% 91,9% 100% 100,9% 72,5% 75,7% 91,5% 100% 101,0% Example 6 71,0% 74,3% 90,3% 100% 100,4% 72,6% 75,4% 91,7% 100% 101,7% 71,3% 74,8% 91,0% 100% 100,3% Comparative example 68,7% 72,5% 88,1% 100% 100,3% 68,0% 72,7% 88, 6% 100% 100, 8% 67,9% 72,2% 88, 0% 100% 100,1% Table 5 Results for tests of rate performance in examples 4 to 6 and comparison example Charging capability at various rates at 0.33C rate 0,33C 0, 5C 1C 2C 3C Example 4 100% 92,3% 77,3% 65,3% 53,8% 100% 92,7% 78, 0% 65,7% 54, 0% 100% 93,1% 76,1% 65,1% 53,2% Example 5 100% 93,5% 77, 6% 66,4% 55,7% 100% 92, 6% 77,5% 65,9% 55,0% 100% 93, 0% 78,3% 66, 9% 55,6% Example 6 100% 93,7% 77,8% 66,3% 55,4% 100% 94, 0% 78,1% 67,2% 55,7% 100% 93,1% 77,3% 66, 6% 55,1% Comparative example 100% 90, 0% 72,5% 58,2% 43,2% 100% 89,7% 72,9% 58,7% 43,8% 100% 91, 6% 71, 6% 58, 6% 44%

[0058] Table 1 shows that using the combination of high viscosity lithium carboxymethylcellulose with sodium ligninsulfonate as a dispersant and thickening agent in the negative electrode slurry system can reduce the amount added by 0.5% and increase the amount of active substances added, thereby increasing the capacity and initial efficiency of the battery.

[0059] Tables 2 to 5 show that the combination of high-viscosity lithium carboxymethylcellulose with sodium ligninsulfonate can disperse the single-walled carbon nanotube and graphene. Furthermore, the combination of conductive carbon black with the single-walled carbon nanotube or graphene combines short-range electrical conductivity with long-range electrical conductivity, which can increase the conductivity of the electrode plate and thus improve the battery's dynamic performance. Normal-temperature DCRs are reduced by 9% to 16%, low-temperature DCRs by 13% to 17%, high-temperature and low-temperature capacity retention rates are increased by approximately 3%, and high-rate (3C) capacity retention rates can be increased by 10% to 12%.

[0060] Various examples in this patent specification are described consecutively, with each example highlighting the description of the difference to other examples, and the same or identical parts may be mutually referenced between different examples.

[0061] The above description of the disclosed examples enables a person skilled in the art to implement or use the present application. Various modifications made to these examples will be obvious to a person skilled in the art, and a general principle defined here can be implemented in other examples without departing from the essence and scope of the present application. Therefore, the present application is not limited to these examples shown here, but rather confirms the broadest scope in accordance with the principle and the novel features disclosed herein.

Claims

[1] Manufacturing process for a high viscosity lithium carboxymethylcellulose, wherein the lithium carboxymethylcellulose has a 1% viscosity of > 25000 mPa·s, characterized by that this procedure includes the following steps: Mixing a cellulose, an aqueous solution of a polar solvent, and a sodium hydroxide solution in an ethanol solution; filling with nitrogen gas to create an inert atmosphere after vacuuming to remove air; carrying out an alkalization reaction under the inert atmosphere; subjecting a reaction product to etherification under normal pressure to obtain crude CMC-Na; acidifying the crude CMC-Na to obtain CMC-H; and adding the prepared CMC-H to a lithium salt ethanol solution to carry out a substitution reaction to obtain high-viscosity lithium carboxymethylcellulose; The amounts of cellulose, aqueous solution of the polar solvent, sodium hydroxide solution, and ethanol solution added in the alkalization reaction are 3 to 10 parts, 2 to 15 parts, 1 to 8 parts, and 5 to 25 parts, respectively, based on parts by weight; the aqueous solution of the polar solvent contains 20% to 85% methanol or isopropanol; the volume concentration of the ethanol solution is 70% to 95%; and the concentration of the sodium hydroxide solution is 25% to 50%. Specific steps of the alkalization reaction are as follows: Place the raw materials in the specified weight parts into a reactor, vacuum-seal for the first time to -10 to -25 kPa, then fill with nitrogen to 3 to 10 kPa, vacuum-seal a second time to -25 to -80 kPa, refill with nitrogen to 3 to 10 kPa, carry out the alkalization reaction; maintain a nitrogen gas pressure of 3 to 10 kPa during the reaction, and the duration of the alkalization reaction is 30 minutes; Specific steps of the etherification reaction are as follows: Addition of a product of the alkalization reaction to a monochloroacetic acid-ethanol solution to carry out an etherification reaction under normal pressure; a mass concentration of the monochloroacetic acid in the monochloroacetic acid-ethanol solution is 45% to 65%, a concentration of the ethanol in the monochloroacetic acid-ethanol solution is ≥93%, an amount of monochloroacetic acid-ethanol solution added is 2 to 10 parts by weight, and a duration of the etherification reaction is 30 to 80 min; The specific steps of the acidification reaction are as follows: Adding the crude CMC-Na to a sulfuric acid solution to carry out the acidification reaction in a normal pressure system; the concentration of the sulfuric acid solution is 10% to 40%, and the duration of the acidification is 60 to 180 min; the pH of the substitution reaction is 6.5 to 10.0 and the duration of the substitution reaction is 30 to 120 min. [2] High viscosity lithium carboxymethylcellulose produced by the manufacturing process for high viscosity lithium carboxymethylcellulose according to claim 1. [3] Application of the high viscosity lithium carboxymethylcellulose according to claim 2 in the manufacture of a negative electrode plate, characterized by that this application includes the following steps: Add high-viscosity lithium carboxymethylcellulose to water and stir for 2 to 4 hours; add sodium ligninsulfonate, a single-walled carbon nanotube, and graphene while mixing the high-viscosity lithium carboxymethylcellulose; dissolve the sodium ligninsulfonate; then allow the solution to stand for 6 to 24 hours; mix graphite with conductive carbon black; then add the graphite and conductive carbon black to the solution; disperse for 1 to 3 hours at a rotational speed of 850 to 1500 rpm; reduce the rotational speed to 200 to 500 rpm after dispersal is complete; add styrene-butadiene latex and continue stirring for 0.5 to 1 hour to obtain a slurry;After adjusting the viscosity of the slurry to 3000 to 7000 mPa·s, the slurry is applied to a copper foil as a current collector for a negative electrode, dried, and rolled to obtain the negative electrode plate. [4] Use of high viscosity lithium carboxymethylcellulose in the manufacture of the negative electrode plate according to claim 3, characterized by , that the proportions of different raw materials for the production of the negative electrode plate are as follows: Graphite 96 to 98 parts, conductive carbon black 1 to 2 parts, lithium carboxymethylcellulose 0.6 to 1 part, styrene butadiene latex 1 to 2 parts, sodium ligninsulfonate 0.1 to 0.5 parts, single-walled carbon nanotubes 0 to 0.5 parts, graphene 0 to 0.5 parts and water 20 to 70 parts.