Aqueous conductive polymer grafted binder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of binders, in particular to a water-based conductive polymer grafted binder as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, adjusting the pH value of a polyvinyl alcohol aqueous solution to 10-11, and adding an epichlorohydrin solution to carry out a ring-opening grafting reaction; s2, adjusting the pH value of the system to 5-6, raising the temperature to 50-90 DEG C, adding a compound A, and carrying out a pre-reaction; s3, adjusting the pH value of the system to 1-2, adding an initiator C and a monomer M, and continuously reacting in an ice-water bath for 8-12 hours; and S4, carrying out rotary evaporation on the product, transferring the product into a dialysis bag for dialysis, and then stirring and mixing the product with the component B to obtain the binder. According to the invention, the construction of a covalent cross-linked network and conductivity of the binder is realized, the mechanical property of the material can be remarkably improved, the pole piece cracking caused by volume expansion of a silicon negative electrode is relieved, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a water-based conductive polymer grafted adhesive, its preparation method, and its application. Background Technology

[0002] The most critical drawback of silicon as an anode material is its approximately 300% volume expansion during repeated lithium-ion insertion and extraction during battery charging and discharging. This leads to repeated formation of the solid electrolyte interphase (SEI) and electrode material breakage and pulverization, resulting in a sharp decline in battery cycle performance. Simultaneously, silicon's poor conductivity also affects related battery performance. Related research indicates that suitable binders can not only buffer the stress caused by silicon particle expansion but also improve electron transport between silicon and the current collector, achieving a more robust electrode structure. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a water-based conductive polymer grafted adhesive, its preparation method, and its application.

[0004] The present invention discloses a method for preparing a water-based conductive polymer grafted adhesive, comprising the following steps: S1. After adjusting the pH of the polyvinyl alcohol aqueous solution to 10-11 using an alkaline solution, epichlorohydrin solution is added to carry out the ring-opening grafting reaction; S2. After adjusting the pH of the system to 5-6, heat the system to 50-90℃ and add compound A to carry out a pre-reaction; S3. After cooling the system to room temperature, adjust the pH of the system to 1-2, add initiator C and monomer M, and continue the reaction in an ice-water bath for 8-12 hours; S4. After rotary evaporation, the product is transferred to a dialysis bag for dialysis, and then mixed with component B to carry out an esterification reaction to obtain a water-based conductive polymer grafted adhesive. A is one or more of o-toluidine, m-toluidine, p-toluidine, aniline, 2-aminopyrrole, 3-aminothiophene, and 3-aminocarbazole; Monomer M is one or more of pyrrole, thiophene, aniline, and carbazole; B is one or more of sodium alginate, polyacrylic acid, and carboxymethyl cellulose.

[0005] Further, in step S1, the concentration of the polyvinyl alcohol aqueous solution is 0.05 ~ 0.15 g / mL.

[0006] Furthermore, in step S1, the ring-opening grafting reaction is carried out at 50~100 °C, and the alkaline solution can be one of the aqueous solutions of NaOH, KOH, LiOH and ammonia.

[0007] Furthermore, in step S1, the mass ratio of epichlorohydrin to polyvinyl alcohol is 1:5 to 1:20.

[0008] Furthermore, in step S2, the molar ratio of compound A to epichlorohydrin in step S1 is 1:1 to 1:1.5.

[0009] Furthermore, the mass ratio of monomer M to polyvinyl alcohol is 1:1 to 1:5.

[0010] Furthermore, the mass ratio of component B to polyvinyl alcohol is 5:1 to 1:5.

[0011] Further, in step S3, the initiator C is one of potassium persulfate and ammonium persulfate, and its mass is 1 to 5% of the monomer M.

[0012] Furthermore, in step S4, the esterification reaction is carried out at a temperature of 80 ~ 120 °C.

[0013] A water-based conductive polymer grafted adhesive prepared by the preparation method described above.

[0014] A silicon anode is prepared using the above-mentioned water-based conductive polymer grafted binder as a binder.

[0015] A certain amount of silicon powder and conductive additives are weighed into an aqueous solution of a water-based conductive polymer grafted binder, stirred evenly, coated onto copper foil, and dried to obtain an electrode sheet for later use.

[0016] Further, the silicon powder has a particle size of 60-100 nm, more preferably 80 nm; the mass ratio of silicon powder, conductive additive and water-based conductive polymer grafted binder is 50-70:30-20:20-10, preferably 60-70:20:20-10, more preferably 60:20:20.

[0017] Further, the stirring time is 6 to 12 hours, preferably 7 to 10 hours, and more preferably 8 to 9 hours; the drying temperature is 60 to 120 degrees Celsius, preferably 70 to 110 degrees Celsius, and more preferably 80 to 100 degrees Celsius; and the drying time is 10 to 15 hours, preferably 12 hours.

[0018] Polyvinyl alcohol (PVA), a highly flexible and water-soluble polymer, has abundant hydroxyl groups that provide grafting sites for conductive polymers on its side chains, while also enhancing interfacial adhesion through molecular chain entanglement. Furthermore, esterification of PVA with other polymers provides a supporting framework for the flexible segments of PVA, forming an interpenetrating network. This not only improves the mechanical toughness of the adhesive to buffer the volume expansion of silicon particles, but also enhances interfacial stability through chemical bonding.

[0019] The beneficial effects of the technical solution provided by this invention are: 1. This invention introduces conductive polymer chains into the binder through graft oxidative polymerization. Combined with the dynamic and static crosslinking of mechanically flexible PVA with other binder polymers, the covalent crosslinking network of the binder and the construction of conductivity are realized. This can significantly improve the mechanical properties of the material, which is beneficial to alleviating the electrode cracking caused by the volume expansion of silicon anodes and improving the cycle performance of the battery.

[0020] 2. The synthesis conditions of the water-based conductive polymer grafted adhesive preparation method provided by the present invention are simple, and the reaction solvent is environmentally friendly and non-toxic.

[0021] 3. The thermally initiated polymerization method used in the preparation method of the water-based conductive polymer grafted adhesive provided by the present invention has the advantages of being simple and efficient. Attached Figure Description

[0022] Figure 1 This is the synthesis route diagram for Example 1; Figure 2 Comparison of rate test results for lithium batteries prepared in Examples 1, 2, 3, and 4 and Control Examples 1 and 2 at current densities of 0.42 A / g, 0.84 A / g, 1.26 A / g, 2.1 A / g, 4.2 A / g, 8.4 A / g, and 0.42 A / g; Figure 3 The graph shows a comparison of the cycling results of the lithium batteries prepared in Example 1 and Control Example 1 at a current density of 2.1 A / g. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] Example 1 Take 0.5 g of polyvinyl alcohol (PVA) powder, add 4.5 mL of deionized water, and stir at 80 °C for 30 min until completely dissolved into a homogeneous, transparent, viscous solution. Then, slowly add 1 M sodium hydroxide (NaOH) solution to the solution to adjust the pH to 10-11. Add 0.1 g of epichlorohydrin (ECH) dropwise through a constant-pressure dropping funnel. Stir vigorously in an 80 °C oil bath for 2.5 h. Add dilute hydrochloric acid to adjust the pH to 5, raise the temperature to 90 °C, and slowly add 0.12 g of aniline monomer at this temperature, allowing for a pre-reaction of 2 h. After the system cools naturally to room temperature, further add dilute hydrochloric acid to adjust the pH to 1-2. Transfer the reaction system to an ice-water bath and maintain the temperature at 0-5 °C. Weigh 0.005 g of ammonium persulfate (APS) and 0.25 g of aniline separately, add them to 5 mL of deionized water, and mix thoroughly. Slowly add the mixture dropwise to the reaction solution while stirring vigorously, and then continue the reaction at low temperature for 8–12 h. After the reaction is complete, the product is rotary evaporated and transferred to a dialysis bag, and dialyzed with deionized water for 3–5 days. Dissolve a certain mass of sodium carboxymethyl cellulose powder in deionized water and mix it with the previously dialyzed solution at a solute-to-water ratio of 10:3. Heat and stir at 80 °C for 12 h to obtain a water-based conductive polymer grafted adhesive for later use.

[0025] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P and add them to 2 mL of aqueous solution containing 0.0400 g of water-based conductive polymer grafted binder. Stir thoroughly for 8 h to obtain a uniformly dispersed slurry. Then, use a coating machine to uniformly coat the slurry onto the surface of a 9 μm copper foil. Dry at 100 ℃ for 12 h and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0026] Example 2 Take 0.5 g of polyvinyl alcohol (PVA) powder, add 4.5 mL of deionized water, and stir at 80 °C for 30 min until completely dissolved into a homogeneous, transparent, viscous solution. Then, slowly add 1 M sodium hydroxide (NaOH) solution to the solution to adjust the pH to 10-11. Add 0.1 g of epichlorohydrin (ECH) dropwise through a constant-pressure dropping funnel. Stir vigorously in an 80 °C oil bath for 2.5 h. Add dilute hydrochloric acid to adjust the pH to 5, raise the temperature to 90 °C, and slowly add 0.1 g of 2-aminopyrrole monomer at this temperature, allowing for a pre-reaction of 2 h. After the system cools naturally to room temperature, further add dilute hydrochloric acid to adjust the pH to 1-2. Transfer the reaction system to an ice-water bath and maintain at 0-5 °C. Weigh 0.006 g of ammonium persulfate (APS) and 0.2 g of pyrrole separately, add them to 5 mL of deionized water and mix thoroughly. Slowly add the mixture dropwise to the reaction solution while stirring vigorously, and then continue the reaction at low temperature for 8–12 h. After the reaction is complete, the product is rotary evaporated and transferred to a dialysis bag, and dialyzed with deionized water for 3–5 days. Dissolve a certain mass of sodium carboxymethyl cellulose powder in deionized water and mix it with the previously dialyzed solution at a solute-to-water ratio of 3:1. Heat and stir at 80 °C for 12 h to obtain a water-based conductive polymer grafted adhesive for later use.

[0027] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P and add them to 2 mL of an aqueous solution containing 0.0400 g of the above-mentioned water-based conductive polymer grafted binder. Stir thoroughly for 8 h to obtain a uniformly dispersed slurry. Then, use a coating machine to uniformly coat the slurry onto the surface of a 9 μm copper foil. Dry at 120 ℃ for 12 h and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0028] Example 3 Take 0.5 g of polyvinyl alcohol (PVA) powder, add 4.5 mL of deionized water, and stir at 80 °C for 30 min until completely dissolved into a homogeneous, transparent, viscous solution. Then, slowly add 1 M sodium hydroxide (NaOH) solution to the solution to adjust the pH to 10-11. Add 0.05 g of epichlorohydrin (ECH) dropwise through a constant-pressure dropping funnel. Stir vigorously in an 80 °C oil bath for 2.5 h. Add dilute hydrochloric acid to adjust the pH to 5, raise the temperature to 90 °C, and slowly add 0.08 g of aniline monomer at this temperature, allowing for a pre-reaction of 2 h. After the system cools naturally to room temperature, further add dilute hydrochloric acid to adjust the pH to 1-2. Transfer the reaction system to an ice-water bath and maintain the temperature at 0-5 °C. Weigh 0.006 g of ammonium persulfate (APS) and 0.15 g of aniline into 5 mL of deionized water and mix thoroughly. Add the mixture slowly dropwise to the reaction solution while stirring vigorously, and continue the reaction at low temperature for 8–12 h. After the reaction is complete, the product is rotary evaporated and transferred to a dialysis bag, then dialyzed with deionized water for 3–5 days. Dissolve 0.2 g of polyacrylic acid powder in 9.8 mL of deionized water and mix it with the previously dialyzed solution at a solute-to-mass ratio of 10:3. Stir until homogeneous to obtain a water-based conductive polymer grafted adhesive for later use.

[0029] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P and add them to 2 mL of aqueous solution containing 0.0400 g of the above-mentioned water-based conductive polymer grafted binder. Stir thoroughly for 8 h to obtain a uniformly dispersed slurry. Then, use a coating machine to uniformly coat the slurry onto the surface of a 9 μm copper foil. Dry at 100 °C for 12 h and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0030] Example 4 Take 0.5 g of polyvinyl alcohol (PVA) powder, add 4.5 mL of deionized water, and stir at 80 °C for 30 min until completely dissolved into a homogeneous, transparent, viscous solution. Then, slowly add 1 M sodium hydroxide (NaOH) solution to the solution to adjust the pH to 10-11. Add 0.1 g of epichlorohydrin (ECH) dropwise through a constant-pressure dropping funnel. Stir vigorously in an 80 °C oil bath for 2.5 h. Add dilute hydrochloric acid to adjust the pH to 5, raise the temperature to 90 °C, and slowly add 0.12 g of aniline monomer at this temperature, allowing for a pre-reaction of 2 h. After the system cools naturally to room temperature, further add dilute hydrochloric acid to adjust the pH to 1-2. Transfer the reaction system to an ice-water bath and maintain the temperature at 0-5 °C. Weigh 0.005 g of ammonium persulfate (APS) and 0.25 g of aniline separately, add them to deionized water and mix thoroughly. Slowly add the mixture dropwise to the reaction solution while stirring vigorously, and then continue the reaction at low temperature for 8–12 h. After the reaction is complete, the product is rotary evaporated and transferred to a dialysis bag, and dialyzed with deionized water for 3–5 days. Dissolve 0.2 g of sodium alginate powder in 9.8 g of deionized water and mix it with the previously dialyzed solution at a solute-to-water ratio of 1:1. Stir thoroughly to obtain a water-based conductive polymer grafted adhesive for later use.

[0031] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P and add them to 2 mL of aqueous solution containing 0.0400 g of the above-mentioned water-based conductive polymer grafted binder. Stir thoroughly for 8 h to obtain a uniformly dispersed slurry. Then, use a coating machine to uniformly coat the slurry onto the surface of a 9 μm copper foil. Dry at 100 °C for 12 h and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0032] Comparative Example 1 Take 0.5 g of polyvinyl alcohol (PVA) powder, add 4.5 mL of deionized water, and stir at 80℃ for 30 min until completely dissolved into a uniform, transparent, viscous solution. Take 0.2 g of sodium carboxymethyl cellulose powder, dissolve it in 9.8 mL of deionized water, and mix it with the PVA solution at a solute-to-mass ratio of 10:3. Stir until homogeneous to obtain a water-based conductive polymer grafted adhesive for later use.

[0033] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P in an aqueous solution containing 0.0400 g of the above polymer, stir thoroughly for 8 h to obtain a uniformly dispersed slurry, then coat the slurry uniformly onto the surface of a 9 μm copper foil using a coating machine, dry at 100℃ for 12 h, and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0034] Comparative Example 2 Dissolve 0.4000 g of sodium carboxymethyl cellulose in 20 mL of deionized water for later use.

[0035] The lithium-ion battery manufacturing method corresponding to this case is as follows: Take 0.1200 g of silicon powder and 0.0400 g of Super P in an aqueous solution containing 0.0400 g of the above polymer, stir thoroughly for 8 h to obtain a uniformly dispersed slurry, then coat the slurry uniformly onto the surface of a 9 μm copper foil using a coating machine, dry at 100℃ for 12 h, and finally cut into circular electrode sheets with a radius of 7.5 mm for later use.

[0036] Figure 1 This is the synthesis route diagram for Example 1.

[0037] Table 1 compares the tensile strength and electrode peeling performance of the adhesives used in Examples 1, 2, 3, 4 and Comparative Examples 1, 2.

[0038] Table 1

[0039] Figure 2 The graph shows a comparison of the rate test results of lithium batteries prepared in Examples 1, 2, 3, and 4, and Comparative Examples 1 and 2, at different current densities. It can be seen that Example 1 exhibits the best rate performance at high rates, and the other examples also demonstrate superior rate performance compared to the control examples.

[0040] Figure 3 This is a comparison graph showing the cycling results of the lithium batteries prepared in Example 1 and Comparative Example 1 at a current density of 2.1 A / g. Figure 3 It can be seen that the battery corresponding to Example 1 still has a discharge specific capacity of 1280 mAh / g after 300 cycles, and the capacity retention rate is 40.5%, which shows excellent cycle performance compared with Comparative Example 1.

[0041] For any points not covered above, existing technologies shall apply.

[0042] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing an aqueous conductive polymer grafted binder, characterized by, The method comprises the following steps: S1. After adjusting the pH of the polyvinyl alcohol aqueous solution to 10-11 using a basic solution, an epichlorohydrin solution is added to perform ring-opening grafting reaction; S2. After adjusting the pH of the system to 5-6, the temperature is increased to 50-90 ℃ and compound A is added to perform pre-reaction; S3. After cooling the system to room temperature, the pH of the system is adjusted to 1-2, initiator C and monomer M are added, and the reaction is continuously performed in an ice water bath for 8-12 h; S4. After the product is rotary evaporated, it is transferred to a dialysis bag for dialysis, and then mixed with component B to perform esterification reaction to obtain water-based conductive polymer grafted adhesive; A is one or more of o-toluidine, m-toluidine, p-toluidine, aniline, 2-aminopyrrole, 3-aminothiophene, and 3-aminocarbazole; Monomer M is one or more of pyrrole, thiophene, aniline, and carbazole; B is one or more of sodium alginate, polyacrylic acid, and carboxymethyl cellulose.

2. The production method according to claim 1, characterized by, In step S1, the concentration of the polyvinyl alcohol aqueous solution is 0.05-0.15 g / mL.

3. The production method according to claim 1, characterized by, In step S1, the ring-opening grafting reaction is performed at 50-100 ℃, and the basic solution can be one of NaOH, KOH, LiOH, and NH3·H2O aqueous solution.

4. The method of claim 1, wherein, In step S1, the mass ratio of epichlorohydrin to polyvinyl alcohol is 1:5-1:

20.

5. The preparation method according to claim 1, characterized in that, In step S2, the molar ratio of compound A to epichlorohydrin is 1:1.

5.

6. The method of claim 1, wherein, The mass ratio of monomer M to polyvinyl alcohol is 1:1-1:

5.

7. The preparation method according to claim 1, characterized in that, The mass ratio of component B to polyvinyl alcohol is 5:1-1:

5.

8. The method of claim 1, wherein, In step S3, the initiator C is one of potassium persulfate, ammonium persulfate, ferrous sulfate, and ferrous chloride; and in step S4, the temperature of the esterification reaction is 80-120 ℃.

9. A water-based conductive polymer grafted adhesive prepared by the preparation method of any one of claims 1-8.

10. A silicon negative electrode characterized by, The water-based conductive polymer grafted adhesive of claim 9 is used as an adhesive.

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