Carboxymethyl cellulose grafted polyisoprene and lithiates thereof, preparation method and application

Abstract

The invention relates to carboxymethyl cellulose grafted polyisoprene and a lithiated compound thereof as well as a preparation method and application of the carboxymethyl cellulose grafted polyisoprene and the lithiated compound thereof. According to the method, one-pot continuous manufacturing is established, and three products, namely, the CMC (CMC-g-PiP) grafted and modified by the PiP, the CMC-g-PiP with improved hydrophilicity and the lithiated CMC-g-PiP, can be obtained in a segmented manner; the physical and chemical properties and application performance of the CMC are improved by grafting flexible groups, the problem of insufficient lithiation degree caused by reduction of water solubility of the CMC through hydrophobic modification is solved, hydrogen peroxide oxidation is performed after grafting and before lithiation, the hydrophilic-hydrophobic regulation gradient is reduced while the hydrophilicity of a grafted product is fine-tuned, and the CMC can be applied to the battery industry. Particularly, the preparation method has important significance in the aspects of improving the rheological property, thickening property and biocompatibility of the material.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification technology and relates to a carboxymethyl cellulose grafted polyisoprene, its lithiated product, preparation method, and application. The invention involves grafting flexible groups and simultaneously fine-tuning the hydrophilicity of the product in a one-pot process. This solves the problem of excessively large gradients in the hydrophilicity and hydrophobicity control of carboxymethyl cellulose grafted polyisoprene. Furthermore, the invention utilizes partial pre-lithiation to improve the physicochemical properties and application performance of CMC. This technology is applicable to the battery industry, particularly in improving the material's rheological properties, thickening properties, and biocompatibility. The innovative method of the invention can effectively enhance the functionality of CMC, thereby expanding its potential for application in flexible electrodes. Background Art

[0002] Carboxymethyl cellulose (CMC), an anionic natural polymer with excellent water solubility, film-forming properties, and biodegradability, is widely used in food additives, drug carriers, and battery binders. To address the issues of viscosity decay and rheological degradation that traditional CMC is prone to under high temperature, high salt, or strong shear conditions, the introduction of flexible molecular segments through graft copolymerization can effectively improve its molecular chain conformation and steric stability. This structural modification not only enhances the salting-out resistance and shear tolerance of CMC solutions but also imparts intelligent properties such as temperature responsiveness and self-healing, significantly expanding its application in the battery field.

[0003] With the advancement of polymer design and synthesis technologies, the moderate grafting of flexible segments can improve the dynamic viscoelastic modulus of CMC by 2-3 orders of magnitude while maintaining its original thickening properties, and the adjustable phase transition temperature range can be expanded to 40-90°C. However, existing free radical grafting methods are generally plagued by problems such as random grafting sites and numerous side reactions, while controlled polymerization techniques such as atom transfer radical polymerization (ATRP) face industrial bottlenecks such as catalyst residues and high costs. Therefore, the development of new grafting modification processes that combine atom economy and regioselectivity, particularly green catalytic systems that enable the targeted grafting of active groups, has become a core issue in enhancing the added value of CMC products. This study innovatively constructs a coordination activation mechanism between carboxymethyl cellulose and olefinic monomers. By performing hydrogen peroxide oxidation after grafting and before lithiation, the hydrophilicity of the grafted product is fine-tuned while reducing the hydrophilicity control gradient. To inhibit lithium dendrite growth, the oxidizing acid is neutralized with LiOH, achieving one-pot pre-lithiation. A model for the relationship between grafting density and the dynamic viscoelastic properties of materials has been established, providing theoretical support and technical solutions for the development of a new generation of intelligent bio-based functional materials. This environmentally friendly and process-stable modified CMC product demonstrates significant competitive advantages in strategic emerging fields such as binders for new energy batteries, and is expected to promote the industrialization and upgrading of bio-based materials in the context of carbon neutrality. Summary of the Invention

[0004] In light of this, the present invention addresses the issues of random grafting sites and numerous side reactions in existing free radical grafting methods, as well as the catalyst residues and high costs associated with controlled polymerization techniques such as atom transfer radical polymerization (ATRP). The present invention provides a carboxymethyl cellulose grafted polyisoprene, its lithiated product, preparation method, and application. This preparation method improves the physicochemical properties and application performance of CMC by grafting flexible groups. Furthermore, to address the issue of insufficient lithiation caused by hydrophobic modification that reduces CMC's water solubility, hydrogen peroxide oxidation is performed after grafting and before lithiation, fine-tuning the hydrophilicity of the grafted product while reducing the hydrophilicity-hydrophobicity gradient. This method has applications in the battery industry, particularly in improving the material's rheological properties, thickening properties, and biocompatibility. This innovative method effectively enhances the functionality of CMC, thereby expanding its potential for application in flexible electrodes.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing carboxymethyl cellulose grafted polyisoprene is characterized by selecting an ammonium cerium nitrate initiator solution to construct a homogeneous or acidic aqueous phase free radical initiation system with controllable microflocculation degree of carboxymethyl cellulose sodium (CMC-Na), and regulating the feed ratio of isoprene / CMC-Na / ammonium cerium nitrate and reaction conditions to obtain CMC-g-PiP grafted modified products with different grafting components.

[0007] Furthermore, inorganic acid was selected to regulate the degree of reaction flocculation and match the methanol extraction and ion precipitation system. The specific steps were as follows:

[0008] S1. Prepare carboxymethyl cellulose solution: Dissolve sodium carboxymethyl cellulose (CMC-Na) in water by stirring, control the concentration to be 1-2% by mass, and control the viscosity to be 900-1200 mPa·s;

[0009] S2. Preparation of free radical initiation system: dissolve the cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 1.0 mol / L inorganic acid to prepare an orange-yellow homogeneous or slightly flocculated cerium ammonium nitrate initiator solution. The flocculation degree in the system is adjusted by control The zeta potential of the suspension is controlled; wherein the concentration of ammonium cerium nitrate is in the range of 0.5 mol / L-1.5 mol / L, and the zeta potential is controlled in the range of -7.7 to -3.1;

[0010] S3. Preparation of carboxymethyl cellulose grafted with isoprene (CMC-g-PiP): Under an inert gas atmosphere, the ammonium cerium nitrate initiator solution prepared in step S2 was injected into the CMC-Na aqueous solution prepared above according to the molar ratio of ammonium cerium nitrate to the hydroxyl group on CMC-Na to form a mixed solution. After stirring evenly, isoprene was added according to the molar ratio of isoprene to the hydroxyl group on CMC-Na, wherein the molar ratio of the ammonium cerium nitrate initiator, the hydroxyl group of CMC-Na, and the isoprene monomer was 1:1:(0.5~1). The mixture was reacted at 0°C for 3-4 h, 200 mL of methanol was added, the mixture was centrifuged and washed with methanol three times, a large amount of methanol was removed by rotary evaporation, and N,N-dimethylformamide (DMF) was added and stirred at 30°C for 24 h to obtain a CMC-g-PiP grafted modified product.

[0011] Furthermore, in step S2, the inorganic acid is selected as a mixed acid of sulfuric acid and nitric acid, and the viscosity of the reaction system in step S3 is controlled by adjusting the ratio of the two acids, and the zeta potential of the particles represents the degree of flocculation of the material. When preparing the CMC-g-PiP product in step S3, the system viscosity related to the flocculation degree must be controlled in the range of 900 mPa·s to 1200 mPa·s, and the centrifugal acceleration must be greater than 3950 g; otherwise, the low degree of flocculation and the slow centrifugal force will result in the product being unable to settle by centrifugation.

[0012] The carboxymethyl cellulose grafted isoprene is prepared by the above-mentioned carboxymethyl cellulose grafted polyisoprene preparation method.

[0013] A method for preparing a carboxymethyl cellulose grafted polyisoprene lithium compound, characterized by comprising the following steps:

[0014] S4, isoprene grafted modified CMC (CMC-g-PiP); select ammonium cerium nitrate initiator solution to construct a homogeneous or micro-flocculation controlled acidic aqueous phase free radical initiation system of sodium carboxymethyl cellulose (CMC-Na), and adjust the isoprene / CMC-Na / ammonium cerium nitrate feed ratio and reaction conditions to obtain CMC-g-PiP grafted modified products with different grafting components;

[0015] S5, hydroxylation modification of CMC-g-PiP; adding an oxidant to the reaction system to initiate oxidation of the double bonds of the grafted PiP side chains into hydroxyl groups, regulating the micro-flocculation degree of the system to increase the probability of double bond oxidation, and obtaining a hydroxylation-modified CMC-g-PiP product with improved hydrophilicity;

[0016] S6. Lithiated CMC-g-PiP; Preparation of highly hydrophilic CMC-g-PiP in an acidic aqueous phase. After the reaction reaches a stable state, LiOH solution is added to obtain a lithiated CMC-g-PiP product.

[0017] Furthermore, inorganic acid was selected to regulate the degree of reaction flocculation and match the methanol extraction and ion precipitation system. The specific steps were as follows:

[0018] S7. Prepare a carboxymethyl cellulose solution: dissolve sodium carboxymethyl cellulose (CMC-Na) in water by stirring, controlling the concentration to be 1-2% by mass and the viscosity to be 900-1200 mPa·s;

[0019] S8. Prepare the free radical initiation system: dissolve the cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 1.0 mol / L inorganic acid to prepare an orange-yellow homogeneous or slightly flocculated cerium ammonium nitrate initiator solution. The flocculation degree in the system is adjusted by control The zeta potential of the suspension is controlled; wherein the concentration of ammonium cerium nitrate is in the range of 0.5 mol / L-1.5 mol / L, and the zeta potential is controlled in the range of -7.7 to -3.1;

[0020] S9. Preparation of carboxymethyl cellulose grafted with isoprene (CMC-g-PiP): Under an inert gas atmosphere, the ammonium cerium nitrate initiator solution prepared in step S8 was injected into the prepared CMC-Na aqueous solution according to the molar ratio of ammonium cerium nitrate to the hydroxyl group on CMC-Na to form a mixed solution. The solution was stirred evenly and then regulated to add isoprene according to the molar ratio of isoprene to the hydroxyl group on CMC-Na, wherein the molar ratio of the ammonium cerium nitrate initiator, the hydroxyl group on CMC-Na, and the isoprene monomer was 1:1:(0.5-1). The mixture was reacted at 0°C for 3-4 h, 200 mL of methanol was added, the mixture was centrifuged and washed with methanol three times, a large amount of methanol was removed by rotary evaporation, and N,N-dimethylformamide (DMF) was added and stirred at 30°C for 24 h to obtain a CMC-g-PiP grafted modified product.

[0021] S10, select the flocculation system CMC-g-PiP product prepared in step S9, which can encapsulate and inhibit Ce 4+ To compete with the double bond oxidation, 30% H2O2 was added and reacted at room temperature for 4-6 h, and 1.0 mol / L LiOH solution was added to adjust the pH to neutral to obtain the hydroxylated modified CMC-g-PiP product with improved hydrophilicity;

[0022] S11, add 1.0 mol / L LiOH solution to the hydroxylated modified CMC-g-PiP prepared in step S10 to adjust the pH to neutral, and dialyze the product for 72 h to dialyze out Ce 4+ , and the lithiated CMC-g-PiP product was obtained.

[0023] Furthermore, in step S8, the inorganic acid is selected as a mixed acid of sulfuric acid and nitric acid, and the viscosity of the reaction system in step S9 is controlled by adjusting the ratio of the two acids, and the zeta potential of the particles represents the degree of flocculation of the material. When preparing the CMC-g-PiP product in step S9, the system viscosity related to the flocculation degree must be controlled in the range of 900 mPa·s to 1200 mPa·s, and the centrifugal acceleration must be greater than 3950 g; otherwise, the low degree of flocculation and the slow centrifugal force will result in the product being unable to undergo centrifugal sedimentation.

[0024] Furthermore, the CMC-g-PiP, hydroxylated-modified CMC-g-PiP, and lithiated CMC-g-PiP products obtained in steps S4, S5, and S6 can be dialyzed to neutrality instead of adding methanol for centrifugal precipitation. The dialysis treatment uses a dialysis bag with a molecular weight of 14,000 D.

[0025] The carboxymethyl cellulose grafted isoprene lithium compound is prepared by the above-mentioned method for preparing carboxymethyl cellulose grafted polyisoprene lithium compound.

[0026] Carboxymethyl cellulose grafted polyisoprene lithium compound is composited with carbon material and silicon material as battery electrode materials, and is used for electrode flexibility and coating flexibility modification. In addition to meeting the application requirements of electrode flexibility, it also has a lithium replenishment function; the carbon material is one of graphite, Super P, carbon nanotubes, and graphene; the silicon material is one of silicon oxide, silicon / carbon mixture, and silicon carbide.

[0027] The beneficial effects of the present invention are:

[0028] 1. In the preparation of carboxymethyl cellulose grafted with isoprene and its lithium compound disclosed in the present invention, the role of the inert gas is to remove the O2 contained in the deionized water and the reaction vessel. The dissolved CMC-Na solution should be repeatedly evacuated to a vacuum state, and a balloon should be used to detect whether the system has any air leaks to ensure that there is no O2 in the system to quench the reaction. The order of adding the acidic initiator and the isoprene monomer should be fixed. Due to the effect of ammonium cerium nitrate, sufficient time is required to generate free radicals on the carbon chain, and then sufficient reaction monomers are injected. Therefore, the addition interval between the two should be fixed. Because the ammonium cerium nitrate initiator solution contains Ce 4+Flocculation occurs. To prevent the high-valent cerium ions from causing difficulty in separating the flocculated product, pre-lithiation is used to partially replace the metal ions, reducing the degree of flocculation and allowing the precipitated product to be obtained through methanol treatment, ensuring the product can be separated and purified in a one-pot process. The boiling point of the isoprene monomer is 34°C. Therefore, considering the optimal reaction temperature of ammonium cerium nitrate and the reaction temperature of isoprene, the system temperature should be controlled below 10°C for low-temperature free radical-initiated grafting, with an ice-water bath at 0°C being the most preferred. The product obtained by free radical grafting decomposes at certain temperatures due to the influence of the monomer, so temperature control should be maintained during subsequent storage. Due to the properties of the free radical grafted product, it is not redispersible under direct oven drying conditions. Therefore, post-processing of the product requires redispersibility. Taking advantage of the boiling point difference between methanol and water, the product is spin-coated on a glass wall using a rotary evaporation method to remove most of the solvents, water and methanol. High-speed rotation accelerates solvent volatilization, minimizing phase separation or crystallization defects (such as polymer chain aggregation) caused by slow drying.

[0029] 2. The method for preparing carboxymethyl cellulose grafted with isoprene and its lithiated product disclosed in the present invention controls the ratio of isomers in the addition polymerization by controlling the ratio of monomer to initiator, reaction time and other conditions, and the resulting products have different molecular weights and flexibility. By performing hydrogen peroxide oxidation after grafting and before lithiation, and then fine-tuning the hydrophilicity of the grafted product, the hydrophilicity control gradient is reduced. In order to inhibit the growth of lithium dendrites, the oxidizing acid is neutralized with LiOH to achieve one-pot pre-lithiation. This lithiation preparation method combines mild reaction conditions with a high degree of substitution. The prepared grafted product can be used as a softener to improve the flexibility and toughness of the coating, and can also be used as a softening finishing agent to better disperse the conductive filler evenly.

[0030] 3. The disclosed method for preparing carboxymethyl cellulose grafted with isoprene and its lithiated product can produce flexible electrode coatings with increased flexibility and more stable conductivity for lithium-ion batteries. This method utilizes main chain ring opening to form stable free radicals, effectively controlling molecular weight. This can be further tested using methods such as GPC and viscosity, further controlling the dispersibility of the graphite. This lithiated preparation method, followed by post-treatment and redispersion, effectively avoids the problem of traditional polymers agglomerating and being unable to redisperse. The centrifugal force generated by high-speed rotation causes the polymer solution to spread rapidly, forming a film of uniform thickness, resulting in a product with excellent water solubility.

[0031] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0033] Figure 1 Schematic diagram of the synthesis principle of the carboxymethyl cellulose grafted polyisoprene copolymer of the present invention;

[0034] Figure 2 (a) is a diagram showing the effect of yellow flocculent precipitation produced after grafting of carboxymethyl cellulose onto polyisoprene in Example 1 of the present invention. Figure 2 (b) Figure 2 (a) The effect of yellow flocculent precipitate on white flocculent precipitate after dialysis for 72 hours. Figure 2 (c) Figure 2 (a) The yellow flocculent precipitate is dissolved by adding H2SO4. Figure 2 (d) Figure 2 (c) The yellow flocculent precipitate becomes transparent after dissolution and dialysis for 72 hours;

[0035] Figure 3 (a) is the Raman spectrum of CMC before grafting. Figure 3 (b) is a Raman spectrum of carboxymethyl cellulose grafted with polyisoprene according to Example 1 of the present invention;

[0036] Figure 4 The XRD comparison diagram of CMC and the grafted product of the present invention, wherein the red represents the XRD diagram of CMC-g-PiP of Example 1, the blue represents the XRD diagram of CMC-g-PiP of Example 3, and the black represents the XRD diagram of CMC without grafting of polyisoprene;

[0037] Figure 5 Nyquist plots of graphite electrodes prepared from CMC and grafted products of the present invention, wherein orange represents the Nyquist plot of a graphite electrode prepared by CMC-g-PiP in Example 1, purple represents the Nyquist plot of a graphite electrode prepared by CMC-g-PiP in Example 2, green represents the Nyquist plot of a graphite electrode prepared by CMC-g-PiP in Example 3, and blue represents the Nyquist plot of a graphite electrode prepared by CMC without grafting polyisoprene;

[0038] Figure 6 The expansion rate of the graphite electrode made from CMC and the grafted product of the present invention;

[0039] Figure 7The peeling force curves of the graphite electrodes prepared by CMC and the grafted products of the present invention are shown in FIG. 1 , wherein the orange color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 1, the red color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 3, the blue color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 4, and the green color represents the peeling force curve of the graphite electrode prepared by CMC without grafting polyisoprene.

[0040] Figure 8 This is a comparison of the graphite electrode made of CMC and the grafted product of the present invention before and after folding. Figure 8 (a) is a comparison of the graphite electrode made of ungrafted polyisoprene before and after folding. Figure 8 (b) is a comparison of the graphite electrode made of CMC-g-PiP in Example 1 before and after folding. Figure 8 (c) is a comparison of the graphite electrode made of CMC-g-PiP in Example 2 before and after folding. Figure 8 (d) is a comparison of the graphite electrode made of CMC-g-PiP in Example 3 before and after folding. DETAILED DESCRIPTION

[0041] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] “Graft from” refers to the use of specific surface free radical initiation methods to carry out polymerization reactions on the solid surface to form hydrophilic polymer macromolecules. Figure 1The following is a schematic diagram of the synthesis principle of this carboxymethyl cellulose-grafted isoprene copolymer. Its main principle is to use ammonium cerium nitrate as an initiator under acidic conditions to generate free radicals on the carbon backbone of carboxymethyl cellulose (CMC), which is then grafted with isoprene. The specific preparation steps are as follows: S1. Under an inert gas atmosphere, CMC-Na is dissolved in deionized water to form a viscous, homogeneous solution. S2. Ammonium cerium nitrate is used as an initiator to generate free radicals on the carbon backbone of CMC, which then react with isoprene under a suitable acidic environment for grafting. The ratio of initiator to monomer is adjusted to ensure the optimal grafting rate and graft chain length. This invention utilizes a free radical graft-from method for grafting, effectively controlling the length of the hydrophobic long chains and optimizing their subsequent hydrophilic applications. Compared to conventional methods for grafting cellulose onto PiP, this method is carried out in an aqueous environment, eliminating the need for organic solvents, significantly reducing the risk of environmental pollution. Polymerization can be initiated directly in an acidic aqueous solution, eliminating the need for metal catalysts such as copper, thus avoiding metal residue contamination and improving the product's biocompatibility and environmental friendliness. Furthermore, due to the low boiling point of isoprene (34°C), experimental results indicate that the reaction is most stable at 0°C, which helps control the activity of free radical reactions and improve grafting efficiency. The resulting CMC-g-PiP material exhibits high flexibility, high viscosity, and good solubility, making it particularly suitable for flexible electrode materials. This method offers significant advantages, including a simple procedure, easily controllable conditions, a mild reaction, and adjustable grafting yield.

[0043] Example 1

[0044] The method for preparing carboxymethyl cellulose grafted with isoprene and its lithiate by the grafting method comprises the following steps:

[0045] S1. Place 1.00 g of CMC-Na in a 250 mL four-necked oval-bottom flask and dissolve it in 100 mL of deionized water under nitrogen atmosphere with stirring for 60 min to obtain a viscous homogeneous solution for later use.

[0046] S2. Dissolve 0.33 g of cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 10 mL of 1.0 mol / L HNO3 to form an orange-yellow CAN solution until no crystals precipitate.

[0047] S3. After injecting the acidic initiator solution into the blend using a syringe for 10 minutes, the blend is formed by mixing the solutions prepared in steps S1 and S2. 1.02 g of monomer isoprene is added to the blend, and the mixture is uniformly stirred in an ice-water bath. After the temperature stabilizes, the mixture is stirred for 180 minutes to obtain a CMC-g-PiP grafted modified product.

[0048] S4. Add 30% H2O2 to the CMC-g-PiP graft-modified product prepared in step S3 and react at room temperature for 5 hours to obtain hydroxylated modified CMC-g-PiP with improved hydrophilicity.

[0049] S5. After the reaction is completed, 1.0 mol / L LiOH solution is added to the hydroxylated modified CMC-g-PiP prepared in step S4 to adjust the pH of the system to neutral to obtain a crude lithiated CMC-g-PiP product.

[0050] S6, dialyze the crude lithiated CMC-g-PiP product obtained in step S5 for 72 h to dialyze out Ce 4+ , and the purified carboxymethyl cellulose grafted isoprene lithium compound (CMC-g-PiP) was obtained.

[0051] Example 2

[0052] The method for preparing carboxymethyl cellulose grafted with isoprene and its lithiate by the grafting method comprises the following steps:

[0053] S1. Place 1.00 g of CMC-Na in a 250 mL four-necked oval-bottom flask and dissolve it in 100 mL of deionized water under nitrogen atmosphere with stirring for 60 min to obtain a viscous homogeneous solution for later use.

[0054] S2. Dissolve 0.33 g of cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 10 mL of 1.0 mol / L HNO3 to form an orange-yellow CAN solution until no crystals precipitate.

[0055] S3. After injecting the acidic initiator solution into the blend using a syringe for 10 minutes, the blend is formed by mixing the solutions prepared in steps S1 and S2. 1.53 g of monomer isoprene is added to the blend, and the mixture is uniformly stirred in an ice-water bath. After the temperature stabilizes, the mixture is stirred for 180 minutes to obtain a CMC-g-PiP grafted modified product.

[0056] S4. Add 30% H2O2 to the CMC-g-PiP graft-modified product prepared in step S3 and react at room temperature for 5 hours to obtain hydroxylated modified CMC-g-PiP with improved hydrophilicity.

[0057] S5. After the reaction is completed, 1.0 mol / L LiOH solution is added to the hydroxylated modified CMC-g-PiP prepared in step S4 to adjust the pH of the system to neutral to obtain a crude lithiated CMC-g-PiP product.

[0058] S6, dialyze the crude lithiated CMC-g-PiP product obtained in step S5 for 72 h to dialyze out Ce4+ , and the purified carboxymethyl cellulose grafted isoprene lithium compound (CMC-g-PiP) was obtained.

[0059] Example 3

[0060] The method for preparing carboxymethyl cellulose grafted with isoprene and its lithiate by the grafting method comprises the following steps:

[0061] S1. Place 1.00 g of CMC-Na in a 250 mL four-necked oval-bottom flask and dissolve it in 100 mL of deionized water under nitrogen atmosphere with stirring for 60 min to obtain a viscous homogeneous solution for later use.

[0062] S2. Dissolve 0.33 g of cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 10 mL of 1.0 mol / L HNO3 to form an orange-yellow CAN solution until no crystals precipitate.

[0063] S3. After injecting the acidic initiator solution into the blend using a syringe for 10 minutes, the blend is formed by mixing the solutions prepared in steps S1 and S2. 2.03 g of monomer isoprene is added to the blend, and the mixture is uniformly stirred in an ice-water bath. After the temperature stabilizes, the mixture is stirred for 180 minutes to obtain a CMC-g-PiP grafted modified product.

[0064] S4. Add 30% H2O2 to the CMC-g-PiP graft-modified product prepared in step S3 and react at room temperature for 5 hours to obtain hydroxylated modified CMC-g-PiP with improved hydrophilicity.

[0065] S5. After the reaction is completed, 1.0 mol / L LiOH solution is added to the hydroxylated modified CMC-g-PiP prepared in step S4 to adjust the pH of the system to neutral to obtain a crude lithiated CMC-g-PiP product.

[0066] S6. The crude lithiated CMC-g-PiP product prepared in step S5 was dialyzed for 72 h to remove Ce4+, thereby obtaining purified carboxymethyl cellulose grafted isoprene lithiate (CMC-g-PiP).

[0067] Example 4

[0068] The method for preparing carboxymethyl cellulose grafted with isoprene and its lithiate by the grafting method comprises the following steps:

[0069] S1. Place 1.00 g of CMC-Na in a 250 mL four-necked oval-bottom flask and dissolve it in 100 mL of deionized water under nitrogen atmosphere with stirring for 60 min to obtain a viscous homogeneous solution for later use.

[0070] S2. Dissolve 0.33 g of cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 10 mL of 1.0 mol / L HNO3 to form an orange-yellow CAN solution until no crystals precipitate.

[0071] S3. After injecting the acidic initiator solution into the blend using a syringe for 10 minutes, the blend is formed by mixing the solutions prepared in steps S1 and S2. 3.06 g of monomer isoprene is added to the blend, and the mixture is uniformly stirred in an ice-water bath. After the temperature stabilizes, the mixture is stirred for 180 minutes to obtain a CMC-g-PiP grafted modified product.

[0072] S4. Add 30% H2O2 to the CMC-g-PiP graft-modified product prepared in step S3 and react at room temperature for 5 hours to obtain hydroxylated modified CMC-g-PiP with improved hydrophilicity.

[0073] S5. After the reaction is completed, 1.0 mol / L LiOH solution is added to the hydroxylated modified CMC-g-PiP prepared in step S4 to adjust the pH of the system to neutral to obtain a crude lithiated CMC-g-PiP product.

[0074] S6, dialyze the crude lithiated CMC-g-PiP product obtained in step S5 for 72 h to dialyze out Ce 4+ , and the purified carboxymethyl cellulose grafted isoprene lithium compound (CMC-g-PiP) was obtained.

[0075] Figure 2 (a) is a diagram showing the yellow flocculent precipitate produced after grafting of carboxymethyl cellulose onto polyisoprene in Example 1. Figure 2 (b) Figure 2 (a) The effect of yellow flocculent precipitate on white flocculent precipitate after dialysis for 72 hours. Figure 2 (c) Figure 2 (a) The yellow flocculent precipitate is dissolved by adding H2SO4. Figure 2 (d) Figure 2 (c) The yellow flocculent precipitate becomes transparent after dissolution and dialysis for 72 hours;

[0076] Figure 3 (a) is the Raman spectrum of CMC before grafting. Figure 3 (b) is the Raman spectrum of carboxymethyl cellulose grafted with polyisoprene in Example 1. It can be seen that the chemical structure of the CMC material has changed, especially the appearance of a new Raman peak at 1666 cm⁻¹, which is due to the C=C structure of the grafted side chain introduced during the grafting process;

[0077] Figure 4The XRD comparison diagram of CMC and the grafted product, wherein the red color represents the XRD pattern of CMC-g-PiP of Example 1, the blue color represents the XRD pattern of CMC-g-PiP of Example 3, and the black color represents the XRD pattern of CMC without grafting of polyisoprene; Figure 5 Nyquist plots of graphite electrodes prepared by CMC and grafted products, where orange represents the Nyquist plot of graphite electrode prepared by CMC-g-PiP in Example 1, purple represents the Nyquist plot of graphite electrode prepared by CMC-g-PiP in Example 2, green represents the Nyquist plot of graphite electrode prepared by CMC-g-PiP in Example 3, and blue represents the Nyquist plot of graphite electrode prepared by CMC without grafting polyisoprene. It can be seen that the semicircle diameter of the CMC sample is the largest, indicating that its charge transfer resistance is the largest and the reaction kinetics is the slowest. With the increase of the isoprene ratio (from 1:0.5 to 1:1), the semicircle diameter gradually decreases, indicating that the charge transfer resistance decreases and the reaction kinetics accelerates.

[0078] Figure 6 The results show that the binder overswells in the electrolyte, significantly reducing its mechanical properties and making it difficult to maintain the stability of the electrode structure. This also results in a corresponding decrease in the battery's electrochemical performance. The 1:0.75 and 1:0.5 groups exhibited lower swelling rates of only 7.82% and 9.69%, respectively. This indicates that the binder can withstand the electrolyte environment well, interacting minimally with the electrolyte, while also exhibiting a certain degree of swelling, which facilitates ion transport within the binder.

[0079] Figure 7 The peeling force curves of graphite electrodes prepared by CMC and grafted products are shown in Figure 1. The orange color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 1, the red color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 3, the blue color represents the peeling force curve of the graphite electrode prepared by CMC-g-PiP according to Example 4, and the green color represents the peeling force curve of the graphite electrode prepared by CMC without grafting polyisoprene. After the CMC was modified by grafting isoprene, the network structure was successfully used to increase the contact points between the CMC and the foil, so that a greater force was required to peel the electrode material from the foil.

[0080] Figure 8 Comparison of graphite electrodes made of CMC and grafted products before and after folding. Figure 8 (a) is a comparison of the graphite electrode made of ungrafted polyisoprene before and after folding. Figure 8 (b) is a comparison of the graphite electrode made of CMC-g-PiP in Example 1 before and after folding. Figure 8(c) is a comparison of the graphite electrode made of CMC-g-PiP in Example 2 before and after folding. Figure 8 (d) Comparison of the graphite electrode made from CMC-g-PiP in Example 3 before and after folding. Compared with the unmodified CMC, it can be found that when folded uniformly, the electrodes made from modified CMC did not show any powder loss.

[0081] The following table shows the results of partial lithiation degree of CMC and grafted products of the present invention

[0082]

[0083] The table shows the degree of lithiation (W) of CMC-g-PIP under different grafting conditions. Li ) and discharge specific capacity (DS). The table shows that different graft chain lengths have little effect on the degree of lithiation of the final lithiated product, with the lithiation degrees of the CMC-g-PiP prepared in Examples 1 to 3 all reaching 0.96%. Different graft chain lengths also have little effect on the discharge specific capacity of the final lithiated product, with the discharge specific capacities of the CMC-g-PiP prepared in Examples 1 to 3 reaching 0.324, 0.324, and 0.321, respectively.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing carboxymethyl cellulose grafted polyisoprene, characterized in that: Ammonium cerium nitrate initiator solution was selected to construct a homogeneous or micro-flocculation-controllable acidic aqueous phase free radical initiation system of sodium carboxymethyl cellulose (CMC-Na). The feed ratio of isoprene / CMC-Na / ammonium cerium nitrate and reaction conditions were adjusted to obtain CMC-g-PiP grafted modification products with different grafting components.

2. The method for preparing carboxymethyl cellulose grafted polyisoprene according to claim 1, wherein: Select inorganic acid to control the degree of reaction flocculation and match the methanol extraction and ion precipitation system. The specific steps are as follows: S1. Prepare carboxymethyl cellulose solution: Dissolve sodium carboxymethyl cellulose (CMC-Na) in water by stirring, control the concentration to be 1-2% by mass, and control the viscosity to be 900-1200 mPa·s; S2. Preparation of free radical initiation system: dissolve the cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 1.0 mol / L inorganic acid to prepare an orange-yellow homogeneous or slightly flocculated cerium ammonium nitrate initiator solution. The flocculation degree in the system is adjusted by control The zeta potential of the suspension is controlled; wherein the concentration of ammonium cerium nitrate is in the range of 0.5 mol / L-1.5 mol / L, and the zeta potential is controlled in the range of -7.7 to -3.1; S3. Preparation of carboxymethyl cellulose grafted with isoprene (CMC-g-PiP): Under an inert gas atmosphere, the ammonium cerium nitrate initiator solution prepared in step S2 was injected into the CMC-Na aqueous solution prepared above according to the molar ratio of ammonium cerium nitrate to the hydroxyl group on CMC-Na to form a mixed solution. After stirring evenly, isoprene was added according to the molar ratio of isoprene to the hydroxyl group on CMC-Na, wherein the molar ratio of the ammonium cerium nitrate initiator, the hydroxyl group of CMC-Na, and the isoprene monomer was 1:1:(0.5~1). The mixture was reacted at 0°C for 3-4 h, 200 mL of methanol was added, the mixture was centrifuged and washed with methanol three times, a large amount of methanol was removed by rotary evaporation, and N,N-dimethylformamide (DMF) was added and stirred at 30°C for 24 h to obtain a CMC-g-PiP grafted modified product.

3. The method for preparing carboxymethyl cellulose grafted polyisoprene as claimed in claim 2, wherein: In step S2, the inorganic acid is selected as a mixture of sulfuric acid and nitric acid. The ratio of sulfuric acid and nitric acid is adjusted to control the viscosity of the reaction system in step S3, and the zeta potential of the particles represents the degree of flocculation. When preparing the CMC-g-PiP product in step S3, the system viscosity related to the flocculation degree must be controlled in the range of 900 mPa·s to 1200 mPa·s, and the centrifugal acceleration must be greater than 3950 g.

4. Carboxymethyl cellulose grafted isoprene prepared by the method for preparing carboxymethyl cellulose grafted polyisoprene according to any one of claims 1 to 3.

5. A method for preparing carboxymethyl cellulose grafted polyisoprene lithium compound, characterized in that: The following steps are involved: S4, isoprene grafted modified CMC (CMC-g-PiP); select ammonium cerium nitrate initiator solution to construct a homogeneous or micro-flocculation controlled acidic aqueous phase free radical initiation system of sodium carboxymethyl cellulose (CMC-Na), and adjust the isoprene / CMC-Na / ammonium cerium nitrate feed ratio and reaction conditions to obtain CMC-g-PiP grafted modified products with different grafting components; S5, hydroxylation modification of CMC-g-PiP; adding an oxidant to the reaction system to initiate oxidation of the double bonds of the grafted PiP side chains into hydroxyl groups, regulating the micro-flocculation degree of the system to increase the probability of double bond oxidation, and obtaining a hydroxylation-modified CMC-g-PiP product with improved hydrophilicity; S6. Lithiated CMC-g-PiP; Preparation of highly hydrophilic CMC-g-PiP in an acidic aqueous phase. After the reaction reaches a stable state, LiOH solution is added to obtain a lithiated CMC-g-PiP product.

6. The method for preparing the carboxymethyl cellulose grafted polyisoprene lithium compound according to claim 5, wherein: Select inorganic acid to control the degree of reaction flocculation and match the methanol extraction and ion precipitation system. The specific steps are as follows: S7. Prepare a carboxymethyl cellulose solution: dissolve sodium carboxymethyl cellulose (CMC-Na) in water by stirring, controlling the concentration to be 1-2% by mass and the viscosity to be 900-1200 mPa·s; S8. Prepare the free radical initiation system: dissolve the cerium ammonium nitrate ([NH4]2[Ce(NO3)6]) in 1.0 mol / L inorganic acid to prepare an orange-yellow homogeneous or slightly flocculated cerium ammonium nitrate initiator solution. The flocculation degree in the system is adjusted by control The zeta potential of the suspension is controlled; wherein the concentration of ammonium cerium nitrate is in the range of 0.5 mol / L-1.5 mol / L, and the zeta potential is controlled in the range of -7.7 to -3.1; S9. Preparation of carboxymethyl cellulose grafted with isoprene (CMC-g-PiP): Under an inert gas atmosphere, the ammonium cerium nitrate initiator solution prepared in step S8 was injected into the prepared CMC-Na aqueous solution according to the molar ratio of ammonium cerium nitrate to the hydroxyl group on CMC-Na to form a mixed solution. The solution was stirred evenly and then regulated to add isoprene according to the molar ratio of isoprene to the hydroxyl group on CMC-Na, wherein the molar ratio of the ammonium cerium nitrate initiator, the hydroxyl group on CMC-Na, and the isoprene monomer was 1:1:(0.5-1). The mixture was reacted at 0°C for 3-4 h, 200 mL of methanol was added, the mixture was centrifuged and washed with methanol three times, a large amount of methanol was removed by rotary evaporation, and N,N-dimethylformamide (DMF) was added and stirred at 30°C for 24 h to obtain a CMC-g-PiP grafted modified product. S10, select the flocculation system CMC-g-PiP product prepared in step S9, which can encapsulate and inhibit Ce 4+ To compete with the double bond oxidation, 30% H2O2 was added and reacted at room temperature for 4-6 h, and 1.0 mol / L LiOH solution was added to adjust the pH to neutral to obtain the hydroxylated modified CMC-g-PiP product with improved hydrophilicity; S11, add 1.0 mol / L LiOH solution to the hydroxylated modified CMC-g-PiP prepared in step S10 to adjust the pH to neutral, and dialyze the product for 72 h to dialyze out Ce 4+ , and the lithiated CMC-g-PiP product was obtained.

7. The method for preparing the carboxymethyl cellulose grafted polyisoprene lithium compound according to claim 6, wherein: In step S8, the inorganic acid is selected as a mixture of sulfuric acid and nitric acid. The ratio of sulfuric acid and nitric acid is adjusted to control the viscosity of the reaction system in step S9, and the zeta potential of the particles represents the degree of flocculation. When preparing the CMC-g-PiP product in step S9, the system viscosity related to the flocculation degree must be controlled in the range of 900 mPa·s to 1200 mPa·s, and the centrifugal acceleration must be greater than 3950 g.

8. The method for preparing the carboxymethyl cellulose grafted polyisoprene lithium compound according to claim 7, wherein: The CMC-g-PiP, hydroxylated-modified CMC-g-PiP, and lithiated CMC-g-PiP products obtained in steps S4, S5, and S6 can be dialyzed to neutrality instead of adding methanol for centrifugal precipitation. The dialysis treatment uses a dialysis bag with a molecular weight of 14,000 Da.

9. Carboxymethyl cellulose grafted isoprene lithiate prepared by the method for preparing carboxymethyl cellulose grafted polyisoprene lithiate according to any one of claims 5 to 8.

10. The use of the carboxymethyl cellulose grafted polyisoprene lithium compound according to claim 9, wherein: Carboxymethyl cellulose grafted polyisoprene lithium compound is composited with carbon material and silicon material as battery electrode materials, and is used for electrode flexibility and coating flexibility modification. In addition to meeting the application requirements of electrode flexibility, it also has a lithium replenishment function; the carbon material is one of graphite, Super P, carbon nanotubes, and graphene; the silicon material is one of silicon oxide, silicon / carbon mixture, and silicon carbide.

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