Preparation method of conductive carboxymethyl cellulose derivative

Abstract

The invention discloses a preparation method of a conductive carboxymethyl cellulose derivative. The preparation method comprises the following steps: (1) preparing a carboxymethyl cellulose conductive matrix: carrying out grafting reaction on carboxymethyl cellulose and a compound with bifunctional groups; carrying out a first reaction in the presence of a first catalyst to obtain a carboxymethyl cellulose conductive substrate; and (2) linking a conductive base point: adjusting the system to be neutral, adding a conductive monomer and a second catalyst, and carrying out a second reaction to obtain the conductive carboxymethyl cellulose derivative, the conductive carboxymethyl cellulose derivative has the following structural formula: # imgabs0 #, in which n is more than or equal to 10 and less than or equal to 49, and n is an integer. According to the preparation method of the carboxymethyl cellulose derivative, the conductive monomer for forming the delocalized pi molecular orbit is grafted on the carboxymethyl cellulose salt, and the conductive monomer and the carboxymethyl cellulose salt are combined through chemical bonds, so that the carboxymethyl cellulose is provided with a conductive channel and low in resistivity, and the non-conductive performance of a CMC material is fundamentally improved.

Description

[0001] This application is a divisional application of the invention patent application with the application date of March 31, 2025, the application number of 2025103875874, and the invention title of "A Carboxymethyl Cellulose Derivative and Its Preparation Method and Application". Technical Field

[0002] The present invention relates to the technical fields of carboxymethyl cellulose and polymer chemical modification, and particularly relates to a preparation method of a carboxymethyl cellulose derivative with low resistivity suitable for electrode slurries. Background Art

[0003] Carboxymethyl cellulose materials (including sodium carboxymethyl cellulose and lithium carboxymethyl cellulose) are often used as auxiliary materials for preparing battery materials. They are mainly added to the negative electrode graphite slurries of lithium batteries. Their function is to keep the slurries stable for a period of time, so that the graphite powder in the slurries can be stably suspended and dispersed in the solution and does not settle and aggregate in a short time, so that the slurries have good processing and coating properties in the later stage.

[0004] However, as the battery preparation progresses, the water in the battery slurry coated on the copper foil surface evaporates, and the carboxymethyl cellulose finally also exists in the battery graphite negative electrode material in a solid state. And carboxymethyl cellulose is a natural poor conductor, and its presence has a negative effect on the electrical performance of the battery. As the addition amount of carboxymethyl cellulose increases, the internal resistance of the battery also increases, thereby reducing the electrical performance of the battery.

[0005] Regarding the above problem of "carboxymethyl cellulose is a poor conductor", there are also some publicly available solutions at present. For example, Patent CN111875792A proposes adding pyrrole and ammonium persulfate solution to dissolved carboxymethyl cellulose to obtain a conductive composite. However, the problems with this method are as follows: The conductive layer formed by this method is adsorbed on the surface of carboxymethyl cellulose, and the interaction force is weak. During the preparation process of the battery slurry, sodium carboxymethyl cellulose needs to be dissolved and then graphite is added and stirred continuously. The subsequent dissolution and stirring will affect the distribution of the conductive layer material adsorbed on the surface of CMC. Due to the dissolution of carboxymethyl cellulose, the centrifugal force during stirring, and its own lipophilicity, etc., the original conductive layer adsorbed on the surface of carboxymethyl cellulose will peel off from the carrier of carboxymethyl cellulose and gradually adsorb on the surface of graphite powder. The carboxymethyl cellulose in the dried battery electrode still exists in the form of no conductive layer, which will ultimately affect the conductivity of the battery negative electrode coating. The conductivity of the composite material tested simply (testing the conductivity of the material directly without dissolution) does not match the actual conductivity in the battery coating because the conductive layer on the surface of carboxymethyl cellulose after battery preparation will transfer, adsorb, and agglomerate due to the dissolution and precipitation of carboxymethyl cellulose, the centrifugal force during stirring, and its own polar attraction. After coating and drying, carboxymethyl cellulose still exists as a poor conductor in the battery negative electrode. The newly introduced conductive layer has little effect on reducing the poor conductor performance of carboxymethyl cellulose. Therefore, a relatively strong interaction force is needed to maintain the connection between the conductive layer and carboxymethyl cellulose.

[0006] Another example is that Patent CN107663428A discloses a conductive composite water-based binder, its one-pot preparation method and application. It adds a double-bond grafted monomer and a conductive polymer monomer to a solution, and an initiator is added, and high molecular grafting and chemical polymerization of the conductive polymer occur simultaneously. Eventually, a two-component mixture of a water-soluble polymer with non-conductive branches and a conductive polymer composite material is formed. As a result, during the preparation of the slurry negative electrode later, after a large amount of stirring, the conductive polymer composite material with strong lipophilicity will gradually adsorb on the graphite, and the water-soluble polymer with non-conductive branches is dispersed in the system, and ultimately the resistance reduction of CMC is limited.

[0007] The disclosure of the above background technical content is only used to assist in understanding the inventive concept and technical solution of the present invention, and it does not necessarily belong to the prior art of this patent application. Without clear evidence showing that the above content was publicly available before the filing date of this patent application, the above background technology should not be used to evaluate the novelty and inventiveness 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 an improved preparation method of a conductive carboxymethyl cellulose derivative, and the prepared conductive carboxymethyl cellulose derivative has a continuous low resistivity.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing a carboxymethyl cellulose derivative, comprising the following steps:

[0011] Mix a carboxymethyl cellulose salt, a bifunctional compound, and a solvent;

[0012] Add a first catalyst to the system and carry out a first reaction to obtain a carboxymethyl cellulose conductive matrix;

[0013] Adjust the system to be neutral, add a conductive monomer and a second catalyst, and carry out a second reaction to obtain the carboxymethyl cellulose derivative;

[0014] The bifunctional compound has a first reactive group for connecting with the carboxymethyl cellulose salt and a second reactive group for connecting with the conductive monomer.

[0015] According to some preferred embodiments of the present invention, the mass ratio between the carboxymethyl cellulose salt, the bifunctional compound, and the first catalyst is 100:0.5 - 1:0.05 - 0.2.

[0016] According to some preferred embodiments of the present invention, the mass ratio between the carboxymethyl cellulose salt, the conductive monomer, and the second catalyst is 100:5 - 20:2 - 4.

[0017] According to some preferred embodiments of the present invention, the first reactive group is an epoxy group.

[0018] According to some preferred embodiments of the present invention, the epoxy group is an epoxyethane group.

[0019] According to some preferred embodiments of the present invention, the conductive monomer contains a conductive group capable of forming a delocalized π - orbital configuration.

[0020] According to some preferred embodiments of the present invention, the conductive group is a thiophene group.

[0021] According to some preferred embodiments of the present invention, the conductive monomer is a thiophene monomer.

[0022] According to some preferred embodiments of the present invention, the second reactive group is the same as the conductive group in the conductive monomer.

[0023] According to some preferred embodiments of the present invention, the bifunctional compound is 2 - ((thiophen - 2 - ylmethoxy)methyl)oxirane.

[0024] According to some preferred embodiments of the present invention, the second catalyst is one or more selected from ferric chloride, ammonium persulfate, potassium persulfate, sodium persulfate, iron p-toluenesulfonate, and preferably ammonium persulfate.

[0025] According to some preferred embodiments of the present invention, the first catalyst is a basic substance such as sodium hydroxide, and the adjustment system is made neutral by adding an acidic substance to the system.

[0026] According to some preferred embodiments of the present invention, the first catalyst is an acidic substance such as acetic acid or hydrochloric acid, and the adjustment system is made neutral by adding a basic substance to the system.

[0027] According to some preferred embodiments of the present invention, the carboxymethyl cellulose salt is sodium carboxymethyl cellulose and / or lithium carboxymethyl cellulose.

[0028] According to some preferred embodiments of the present invention, the first reaction is carried out at room temperature for 1 - 5 h.

[0029] According to some preferred embodiments of the present invention, the second reaction is carried out at 45 - 65 °C for 1 - 5 h.

[0030] According to some preferred embodiments of the present invention, the step further includes post-treatment: the carboxymethyl cellulose derivative is successively washed with ethanol, dried at 110 °C - 130 °C for 1.5 - 2.5 h, and pulverized and then passed through a 60 - 100 mesh sieve to obtain the treated carboxymethyl cellulose derivative.

[0031] The present invention also provides a carboxymethyl cellulose derivative prepared by the above preparation method.

[0032] The carboxymethyl cellulose derivative provided by the present invention has the following structural formula:

[0033]

[0034] In the formula, 10 ≤ n ≤ 49, and n is an integer.

[0035] The present invention also provides an application of the carboxymethyl cellulose derivative as described above in electrode paste, battery electrode, or (lithium) battery.

[0036] The present invention also provides an electrode paste, which, by weight, comprises the following raw material components:

[0037]

[0038]

[0039] Wherein the CMC is the carboxymethyl cellulose derivative as described above.

[0040] The present invention also provides a method for preparing the above electrode paste, which comprises the following steps:

[0041] Mix and stir the above carboxymethyl cellulose derivative with deionized water. After the carboxymethyl cellulose derivative is fully dissolved, a CMC glue solution is obtained and reserved.

[0042] Mix the common graphite powder, conductive graphite powder and the above CMC glue solution, so that the dispersed graphite powder forms a dough-like shape that adheres to each other.

[0043] Add the above CMC glue solution again for mixing and dispersion. At this time, the mass of the added CMC glue solution is 0.8 - 1 times the mass of the CMC glue solution added last time.

[0044] Add deionized water and styrene-butadiene rubber (SBR), then defoam under vacuum and stir to obtain the electrode paste.

[0045] The present invention also provides a method for preparing an electrode, which comprises the following steps:

[0046] Coat the above electrode paste on a copper foil and heat for drying;

[0047] Cool to room temperature in a constant temperature and humidity space to obtain a (negative) electrode.

[0048] During testing, replace the above copper foil with a plastic film, and the resistivity of the graphite layer on the plastic film ≤ 0.75 Ω·cm.

[0049] The principle of the present invention is as follows: graft some conductive base points on the carboxymethyl cellulose salt through chemical bonds, and then add some conductive monomers that can form delocalized π molecular orbitals. Through a polymerization reaction, the conductive base points and the conductive monomers form conductive channels one by one. Since there is a covalent bond between the conductive monomers in the conductive layer and the carboxymethyl cellulose salt, during the subsequent dissolution and stirring processes, the conductive layer of the material will not undergo peeling and agglomeration phenomena. The carboxymethyl cellulose derivative prepared by the present invention is applied to the electrode paste, which can not only provide viscosity and a stable dispersed paste, but also the carboxymethyl cellulose after drying has its own conductive channels and low resistivity, so that it is no longer just a stumbling block that blocks the movement of electrons, and fundamentally improves the non-conductive performance of the CMC material.

[0050] In some embodiments of the present invention, the reaction principle is shown in the following formula:

[0051]

[0052] In the formula, 10 ≤ n ≤ 49, and n is an integer.

[0053] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows: In the preparation method of the carboxymethyl cellulose derivative of the present invention, a conductive monomer forming a delocalized π molecular orbital is grafted onto the carboxymethyl cellulose salt, and the two are chemically bonded, so that the carboxymethyl cellulose has its own conductive channels and low resistivity, fundamentally improving the non-conductive performance of the CMC material. Detailed implementation manners

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0055] In order to fundamentally solve the problem that "carboxymethyl cellulose is a poor conductor", the present invention provides a synthetic idea for reducing the resistance of carboxymethyl cellulose and its preparation method. The obtained carboxymethyl cellulose derivative has a grafted conductive polymer, and the conductive polymer is a conductive group having a delocalized π orbital; grafting means forming a covalent bond with the carboxymethyl cellulose salt through an active crosslinking group. The mass ratio of the carboxymethyl cellulose salt in the carboxymethyl cellulose derivative is greater than the mass ratio of the conductive polymer.

[0056] Among them, the mass of the conductive polymer is 2-20% of the mass of the carboxymethyl cellulose salt; the conductive group forming the delocalized π orbital is a thiophene group; the active crosslinking group is an epoxyethyl group.

[0057] The preparation method of the carboxymethyl cellulose derivative for an electrode includes the following steps:

[0058] (1) Prepare the carboxymethyl cellulose conductive base point. Carboxymethyl cellulose reacts with a bifunctional compound. The first reaction group contained in the bifunctional compound is an epoxyethyl group; the second reaction group contained is a thiophene group capable of forming a delocalized π orbital form. The reaction is carried out under an acid or base catalyst to obtain a carboxymethyl cellulose conductive matrix.

[0059] (2) Link the conductive base points. Neutralize the above system, add a thiophene monomer and a catalyst, and carry out catalytic polymerization to obtain a crude product of the carboxymethyl cellulose derivative.

[0060] (3) The crude product after the above reaction is washed with ethanol multiple times, dried, and pulverized to obtain a purified carboxymethyl cellulose derivative.

[0061] Based on the above purpose and principle, the preparation method of the carboxymethyl cellulose derivative of the present invention specifically includes the following steps:

[0062] Step 1. Preparation of carboxymethyl cellulose conductive matrix

[0063] Mix the carboxymethyl cellulose salt, bifunctional compound and solvent; add a first catalyst to the system and carry out a first reaction to obtain the carboxymethyl cellulose conductive matrix. The mass ratio of the carboxymethyl cellulose salt, bifunctional compound and first catalyst is 100:0.5 - 1:0.05 - 0.2. The first reaction is carried out at room temperature (25 - 35°C) for 1 - 5 h.

[0064] The carboxymethyl cellulose salt is sodium carboxymethyl cellulose and / or lithium carboxymethyl cellulose, and the solvent is preferably ethanol. The first catalyst is a basic substance such as sodium hydroxide or an acidic substance such as acetic acid or hydrochloric acid, and preferably 48% sodium hydroxide aqueous solution.

[0065] The bifunctional compound has a first reactive group for connecting with the carboxymethyl cellulose salt and a second reactive group for connecting with the conductive monomer. The first reactive group is an epoxy group, preferably an ethylene oxide group. The second reactive group is a group that can form a delocalized π - orbital morphology after polymerization, preferably a thiophene group. More preferably, the bifunctional compound is 2 - ((thiophen - 2 - ylmethoxy)methyl)oxirane.

[0066] The reaction principle of Step 1 is shown in the following formula:

[0067]

[0068] Step 2. Preparation of crude carboxymethyl cellulose derivative

[0069] Adjust the system to be neutral, add the conductive monomer and a second catalyst, and carry out a second reaction to obtain the carboxymethyl cellulose derivative. The mass ratio of the carboxymethyl cellulose salt, conductive monomer and second catalyst is 100:5 - 20:2 - 4. The second reaction is carried out at 45 - 65°C for 1 - 5 h.

[0070] The conductive monomer contains a conductive group that can form a delocalized π - orbital morphology, preferably the same as the conductive group in the bifunctional compound, which is a thiophene monomer.

[0071] The second catalyst is one or more selected from ferric trichloride, ammonium persulfate, potassium persulfate, sodium persulfate, iron p - toluenesulfonate, and the addition amount is 10 - 50% of the mass of thiophene, preferably ammonium persulfate.

[0072] If the first catalyst is a basic substance, add an acidic substance to the system to adjust the system to be neutral; if the first catalyst is an acidic substance, add a basic substance to the system to adjust the system to be neutral.

[0073] The reaction principle of step 2 is shown below:

[0074]

[0075] Wherein, 10≤n≤49, and n is an integer.

[0076] Step 3: Post-processing

[0077] The crude carboxymethyl cellulose derivative is washed with ethanol, dried and crushed in sequence to obtain a treated and purified carboxymethyl cellulose derivative.

[0078] The carboxymethyl cellulose derivative prepared according to the above preparation method has the following structural formula:

[0079]

[0080] Wherein, 10≤n≤49, and n is an integer.

[0081] The present invention also provides a use of the above carboxymethyl cellulose derivative in an electrode slurry, a battery electrode or a (lithium) battery. For example, an electrode slurry comprises the following raw material components in parts by weight:

[0082]

[0083] The CMC is the above-mentioned carboxymethyl cellulose derivative.

[0084] The method for preparing the electrode slurry comprises the following steps:

[0085] The carboxymethyl cellulose derivative is mixed with deionized water and stirred until the carboxymethyl cellulose derivative is fully dissolved to obtain CMC glue solution for later use.

[0086] Mix ordinary graphite powder, conductive graphite powder and the above CMC glue to make the dispersed graphite powder form a dough that sticks to each other.

[0087] Add the above CMC glue again to mix and disperse.

[0088] After adding deionized water and styrene-butadiene rubber (SBR), vacuum defoaming and stirring were performed to obtain electrode slurry.

[0089] The method for preparing an electrode comprises the following steps:

[0090] The electrode slurry is coated on the copper foil and heated and dried;

[0091] The (negative) electrode was obtained by cooling to room temperature in a constant temperature and humidity space.

[0092] During the test, replace the above-mentioned copper foil with a plastic film, and the resistivity of the graphite layer on the plastic film ≤ 0.75 Ω·cm.

[0093] Example 1

[0094] The preparation method of the carboxymethyl cellulose derivative in this example specifically includes the following steps:

[0095] Step 1: Add sodium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle, dropwise add 48% sodium hydroxide aqueous solution under stirring at room temperature, and continue stirring for 2 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of sodium carboxymethyl cellulose to 2-((thiophen-2-ylmethoxy)methyl)oxirane and 48% sodium hydroxide aqueous solution is 100:0.5:0.1.

[0096] Step 2: Add acid to neutralize in the above system, then add thiophene. After dispersing evenly, add ammonium persulfate, and stir and react at 50 °C for 3 h to obtain a low-resistance type carboxymethyl cellulose crude product. Among them, the mass ratio of sodium carboxymethyl cellulose, thiophene, and ammonium persulfate is 100:5:2.

[0097] Step 3: Wash the crude product with an ethanol aqueous solution multiple times to wash away unreacted monomers and catalysts, then dry, crush, and sieve for standby to obtain Product 1.

[0098] Example 2

[0099] The preparation method of the carboxymethyl cellulose derivative in this example specifically includes the following steps:

[0100] Step 1: Add lithium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle, dropwise add 48% sodium hydroxide aqueous solution under stirring at room temperature, and continue stirring for 5 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of lithium carboxymethyl cellulose to 2-((thiophen-2-ylmethoxy)methyl)oxirane and 48% sodium hydroxide is 100:0.5:0.2.

[0101] Step 2: Add acid to neutralize in the above system, then add thiophene. After dispersing evenly, add ammonium persulfate, and stir and react at 55 °C for 5 h to obtain a low-resistance type carboxymethyl cellulose crude product. Among them, the mass ratio of lithium carboxymethyl cellulose, thiophene, and ammonium persulfate is 100:10:2.

[0102] Step 3: Wash the crude product with an ethanol aqueous solution multiple times to wash away unreacted monomers and catalysts, then dry, crush, and sieve for standby to obtain Product 2.

[0103] Example 3

[0104] The preparation method of the carboxymethyl cellulose derivative in this embodiment specifically includes the following steps:

[0105] Step 1: Add sodium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle. Dropwise add acetic acid under stirring at room temperature and continue stirring for 3 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of sodium carboxymethyl cellulose to 2-((thiophen-2-ylmethoxy)methyl)oxirane and acetic acid is 100:1:0.1.

[0106] Step 2: Add an alkali to neutralize in the above system, then add thiophene. After dispersing evenly, add ferric trichloride and stir and react at 55 °C for 3 h to obtain a low-resistance type carboxymethyl cellulose crude product. Among them, the mass ratio of sodium carboxymethyl cellulose, thiophene, and ferric trichloride is 100:15:4.

[0107] Step 3: Wash the crude product with an ethanol aqueous solution multiple times to wash away unreacted monomers and catalysts, then dry, crush, and sieve for standby to obtain Product 3.

[0108] Example 4

[0109] The preparation method of the carboxymethyl cellulose derivative in this embodiment specifically includes the following steps:

[0110] Step 1: Add sodium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle. Dropwise add hydrochloric acid under stirring at room temperature and continue stirring for 4 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of sodium carboxymethyl cellulose to 2-((thiophen-2-ylmethoxy)methyl)oxirane and hydrochloric acid is 100:1:0.1.

[0111] Step 2: Add an alkali to neutralize in the above system, then add thiophene. After dispersing evenly, add ferric trichloride and stir and react at 60 °C for 5 h to obtain a low-resistance type carboxymethyl cellulose crude product. Among them, the mass ratio of sodium carboxymethyl cellulose, thiophene, and ferric trichloride is 100:20:4.

[0112] Step 3: Wash the crude product with an ethanol aqueous solution multiple times to wash away unreacted monomers and catalysts, then dry, crush, and sieve for standby to obtain Product 4.

[0113] Comparative Example 1 does not contain active crosslinking groups

[0114] The preparation method of the carboxymethyl cellulose derivative in this comparative example specifically includes the following steps:

[0115] Step 1: Add sodium carboxymethyl cellulose, ethanol, and thiophene into a reaction kettle. After dispersing them evenly, add ammonium persulfate, and stir and react at 55 °C for 5 h to obtain a crude product. Among them, the mass ratio of sodium carboxymethyl cellulose, thiophene, and ammonium persulfate is 100:10:3.

[0116] Step 2: Wash the crude product with ethanol aqueous solution for multiple times to wash away the unreacted monomers and catalysts, then dry, crush, and sieve it for standby to obtain Product 5.

[0117] In Comparative Example 2, the addition amount of thiophene after crosslinking is small.

[0118] The preparation method of the carboxymethyl cellulose derivative in this comparative example specifically includes the following steps:

[0119] Step 1: Add sodium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle. While stirring at room temperature, dropwise add an aqueous sodium hydroxide solution and continue stirring for 2 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of sodium carboxymethyl cellulose, 2-((thiophen-2-ylmethoxy)methyl)oxirane, and 48% aqueous sodium hydroxide solution is 100:0.2:0.1.

[0120] Step 2: Add acid to neutralize the above system, then add thiophene. After dispersing them evenly, add ammonium persulfate, and stir and react at 55 °C for 4 h to obtain a low-resistance type carboxymethyl cellulose crude product. Among them, the mass ratio of carboxymethyl cellulose, thiophene, and ammonium persulfate is 100:1:0.3.

[0121] Step 3: Wash the crude product with ethanol aqueous solution for multiple times to wash away the unreacted monomers and catalysts, then dry, crush, and sieve it for standby to obtain Product 6.

[0122] In Comparative Example 3, the addition amount of thiophene after crosslinking is large.

[0123] The preparation method of the carboxymethyl cellulose derivative in this comparative example specifically includes the following steps:

[0124] Step 1: Add sodium carboxymethyl cellulose, ethanol, and 2-((thiophen-2-ylmethoxy)methyl)oxirane into a reaction kettle. While stirring at room temperature, dropwise add an aqueous sodium hydroxide solution and continue stirring for 2 h to obtain a carboxymethyl cellulose conductive matrix. Among them, the mass ratio of sodium carboxymethyl cellulose, 2-((thiophen-2-ylmethoxy)methyl)oxirane, and 48% aqueous sodium hydroxide solution is 100:1:0.1.

[0125] Step 2: Add acid to neutralize the above system, then add thiophene. After dispersing them evenly, add ammonium persulfate, and stir and react at 55 °C for 5 h to obtain a low-resistance type carboxymethyl cellulose crude product. The mass ratio of carboxymethyl cellulose, thiophene, and ammonium persulfate is 100:25:5.

[0126] Step 3: Wash the crude product with an ethanol aqueous solution multiple times to wash away the unreacted monomers and catalysts, then dry, crush, and screen it for later use to obtain Product 7.

[0127] Comparative Example 4 Ordinary CMC

[0128] This comparative example is ordinary commercially available CMC, purchased from Changshu Weiyi Technology Co., Ltd., with the model number BH90-III.

[0129] Example 5 Electrode Slurry, Electrode and Its Preparation Method

[0130] The electrode slurry of this example, by weight, includes the following raw material components:

[0131]

[0132] The CMC therein is the carboxymethyl cellulose derivative described above.

[0133] The preparation method of the above electrode slurry includes the following steps:

[0134] 1. Add 492.5 g of deionized water to a beaker, slowly add 7.5 g of the carboxymethyl cellulose derivative prepared above under stirring, and continue stirring for 3 h until it is fully dissolved to obtain a CMC colloidal solution for later use.

[0135] 2. Add 300 g of ordinary graphite powder, 2.2 g of conductive graphite powder, and 137 g of the CMC colloidal solution to a 1 L mixing and dispersing device, and at the same time turn on the stirrer and the dispersing disk and stir for 1 h to form a dough-like state in which the dispersed graphite powder bodies are bonded to each other.

[0136] 3. Add another 112 g of the CMC colloidal solution and then stir and disperse for 2 h.

[0137] 4. Add 20 g of deionized water and 12.5 g of styrene-butadiene rubber (SBR), then carry out vacuum defoaming and stir for 1 h to obtain the electrode slurry.

[0138] The preparation method of the electrode of this example includes the following steps:

[0139] 1. Set the coating thickness of the coater to 70 microns.

[0140] 2. Turn on the vacuum pump to adsorb the copper foil, add the electrode slurry and carry out coating.

[0141] 3. After the coating is completed, cover the lid of the coater, turn on the heating and bake for 30 min.

[0142] 4. Place the electrode (including the graphite layer) prepared above in a room with constant temperature and humidity for 4 h, and then roll it 5 times in one direction with a 10 kg roller to compact it to obtain the battery (negative) electrode.

[0143] Test and Result Discussion

[0144] Prepare the carboxymethyl cellulose derivative product (CMC) in the above-mentioned examples or comparative examples into a conductive graphite layer respectively. The preparation steps are as follows:

[0145] 1. Set the coating thickness of the coater to 70 microns.

[0146] 2. Turn on the vacuum pump to adsorb the plastic film, add the electrode paste and carry out coating.

[0147] 3. After the coating is completed, cover the lid of the coater, turn on the heating and bake for 30 min for drying.

[0148] 4. Put the above-prepared plastic film (including the graphite layer) into a constant temperature and humidity room for 4 h, and then roll it 5 times in one direction with a 10 kg roller for compaction.

[0149] 5. Use the ST2258C four-probe tester to measure the resistivity of the graphite layer (linear four-probe, probe pitch 2.0 mm). The experimental results are as follows:

[0150] Table 1 Test Results of Products in Examples and Comparative Examples

[0151]

[0152] It can be seen from the data in the above table that:

[0153] 1. Compared with ordinary CMC, the CMC prepared by the examples can reduce the resistivity of the graphite layer. Its resistivity can be as low as 23.5%-28.7% of the resistivity of the negative electrode paste prepared with ordinary CMC.

[0154] 2. The test results of using the CMC product in Comparative Example 1 to prepare the negative electrode graphite layer are similar to the resistivity of ordinary CMC. The reason may be that for the CMC prepared in Comparative Example 1, after dissolution in the early stage, the conductive layer adsorbed on its surface lost its carrier, and due to the strong lipophilicity of the polymer formed in the later stage, it adsorbed on the surface of the graphite, losing its significance of reducing the resistivity of CMC.

[0155] 3. For the graphite negative electrode layer prepared with the CMC in Comparative Example 2, its resistivity is close to that of ordinary CMC. The reason may be that the amount of thiophene added is small, resulting in fewer conductive channels formed by the reaction, so the resistivity increases.

[0156] 4. The CMC of Comparative Example 3 was used to prepare the graphite negative electrode layer. Its resistivity was relatively low, but the conductive chains were lipophilic and not hydrophilic. Due to the increase in molecular weight, the molecular chains became longer, resulting in larger particles of insoluble matter, forming obvious insoluble matter. The insoluble matter was prone to form sharp points during the preparation process, affecting the product quality and the application of the product in the battery.

[0157] The carboxymethyl cellulose derivative for electrodes of the present invention includes carboxymethyl cellulose and a conductive polymer grafted on the carboxymethyl cellulose. The conductive groups are connected by chemical bonds to form multiple branched chains of CMC. The conductive polymer contains groups that form delocalized π-orbitals, preferably thiophene groups; the mass ratio of carboxymethyl cellulose in the derivative is greater than that of the conductive polymer. The preparation method is a two-step synthesis method, specifically including the following steps: 1. Prepare the carboxymethyl cellulose conductive base points. Covalently graft the conductive base points at different positions on the carboxymethyl cellulose chain through grafting chemical reactions; 2. Link the conductive base points through the polymerization reaction of monomers. Add monomers and catalysts to extend or link the conductive points, so as to achieve the purpose of conductivity. The carboxymethyl cellulose derivative prepared by this method, in addition to retaining the dispersion, water retention, thickening and other properties of the original carboxymethyl cellulose, the resistivity of the graphite layer of the battery negative electrode prepared by it is significantly reduced.

[0158] The equipment and raw materials used in the above embodiments can all be purchased from the market or are commonly used in the art. The methods in the above embodiments are all conventional methods in the art unless otherwise specified. The raw materials not specifically mentioned in the embodiments are obtained through commercial purchase. Operations without specifically mentioning the temperature are carried out at room temperature. The operation methods and conditions not specifically mentioned can adopt the well-known or conventional means and conditions in the art. In the ranges disclosed in this article, the endpoints and any values are not limited to the exact 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, between the endpoint values of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0159] The above embodiments are only for illustrating the technical concept and characteristics of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A preparation method of a conductive carboxymethyl cellulose derivative, characterized in that, It includes the following steps: (1) Prepare a carboxymethyl cellulose conductive matrix Carboxymethyl cellulose undergoes a graft reaction with a bifunctional compound; under a first catalyst, a first reaction is carried out to obtain a carboxymethyl cellulose conductive matrix; (2) Link conductive base points Adjust the system to be neutral, add a conductive monomer and a second catalyst, and carry out a second reaction to obtain the conductive carboxymethyl cellulose derivative; The conductive carboxymethyl cellulose derivative has the following structural formula: In the formula, 10 ≤ n ≤ 49, and n is an integer.

2. The preparation method according to claim 1, wherein, The bifunctional compound has a first reaction group for connecting with carboxymethyl cellulose salt and a second reaction group for connecting with a conductive monomer.

3. The preparation method according to claim 2, wherein The first reaction group is an epoxy group.

4. The preparation method according to claim 3, wherein The epoxy group is an ethylene oxide group.

5. The preparation method according to claim 2, characterized in that, The second reaction group is a group that can form a delocalized π orbital form after polymerization.

6. The preparation method according to claim 2, characterized in that, The second reaction group is a thiophene group.

7. The preparation method according to claim 2, characterized in that, The conductive group in the conductive monomer is the same as the second reaction group.

8. The preparation method according to claim 1, characterized in that, The bifunctional compound is 2-((thiophen-2-ylmethoxy)methyl)oxirane.

9. The preparation method according to claim 1, wherein The mass ratio among the carboxymethyl cellulose salt, the bifunctional compound and the first catalyst is 100:0.5 - 1:0.05 - 0.2; and / or, The mass ratio among the carboxymethyl cellulose salt, the conductive monomer and the second catalyst is 100:5 - 20:2 - 4.

10. The preparation method according to claim 1, characterized in that, The first catalyst is an alkaline substance, and adjusting the system to be neutral means adding an acidic substance to the system; or, The first catalyst is an acidic substance, and adjusting the system to be neutral means adding an alkaline substance to the system.

11. The preparation method according to claim 1, characterized in that, The first reaction is carried out at room temperature for 1 - 5 h; and / or, the second reaction is carried out at 45 - 65 °C for 1 - 5 h.

12. The preparation method according to claim 1, wherein The step also includes (3) post-treatment: washing, drying and pulverizing the carboxymethyl cellulose derivative in sequence to obtain the treated carboxymethyl cellulose derivative.

13. The preparation method according to claim 12, characterized in that, The drying is carried out at 110 °C - 130 °C for 1.5 - 2.5 h; and / or, after pulverizing, it passes through a 60 - 100 mesh sieve.

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