Preparation method of cross-linked self-repairing type composite electrode structure

Abstract

The invention discloses a preparation method of a cross-linked self-repairing type composite electrode structure, a composite binder integrating self-repairing and conductivity is designed, the composite electrode structure is constructed by cooperating with activated carbon, and the cross-linked self-repairing type composite electrode structure has the advantages that electrode pores can be dynamically repaired, an active material is inhibited from falling off, and the long-period high capacity retention rate of an electrode is realized.

Description

Technical Field

[0001] This invention relates to the field of electrode technology, and specifically to a method for preparing a cross-linked self-healing composite electrode structure. Background Technology

[0002] With the development of electric vehicles and portable electronic devices, the demand for high-quality energy storage devices is becoming increasingly urgent. Electrodes, as the core of energy storage devices, directly affect the performance of these devices. Current electrode materials generally lack self-healing pore capabilities and exhibit large capacity decay rates, requiring improvement. Summary of the Invention

[0003] To address at least one of the aforementioned technical deficiencies, the present invention provides the following technical solution: This invention discloses a method for preparing a cross-linked self-healing composite electrode structure, comprising the following steps: Step 1: Preparation of Adhesive At 60-70℃, guar gum base liquid is reacted with acrylic monomer, polyethylene glycol and initiator to form a prepolymer. The mass ratio of guar gum to acrylic monomer and polyethylene glycol is 1:1.4-2.8:0.3-0.8. The obtained prepolymer was reacted with a compound containing boric acid groups at 50-80℃, and the pH of the reaction product was adjusted to neutral to obtain an aqueous adhesive solution. Step 2: Preparation of composite conductive powder The reduced graphene oxide dispersion was mixed with activated carbon to form a slurry, and the slurry was then irradiated. The slurry was irradiated and then dried to obtain a composite conductive powder. Step 3: Electrode Preparation Activated carbon, composite conductive powder, binder and water are mixed in a mass ratio of 74-83:8-13:6-12:30-120 to obtain electrode slurry; The composite electrode is obtained by coating the electrode paste onto the current collector, drying, curing, and hot pressing.

[0004] Further, in step one, guar gum is mixed with water at a mass ratio of 1:30-100, heated to 75-95℃ and maintained for 1-2 hours to obtain a guar gum base solution. The guar gum base solution is then cooled to 45-65℃, and acrylic acid monomer, polyethylene glycol, and initiator are added to the guar gum base solution. The reaction is then carried out at a higher temperature for 3-6 hours to obtain a prepolymer. The preferred mass ratio of guar gum to initiator is 1:0.05-0.2.

[0005] Furthermore, in step one, a compound containing boric acid groups is added to the prepolymer and the pH value is adjusted to alkaline. The mass ratio of the compound containing boric acid groups to guar gum is 0.01-0.5:1.

[0006] Further, in step two, the activated carbon is activated by hydrogen peroxide treatment, and the reduced graphene oxide powder is mixed with water at a mass ratio of 1:3-8 and ultrasonically treated to form the reduced graphene oxide dispersion. When preparing the slurry, the reduced graphene oxide and the activated carbon are mixed at a mass ratio of 1:3-8, and the γ-ray irradiation treatment time is 15-90 min.

[0007] Furthermore, in step three, the current collector coated with electrode slurry is dried at a low temperature of 45-60℃, then cured at 85-105℃, and finally subjected to vacuum hot pressing at 110-140℃ and a vacuum degree of 1-30Pa to obtain the composite electrode.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention designs a composite binder that integrates self-healing and conductivity, and uses it in conjunction with activated carbon to construct a composite electrode structure. This structure has advantages such as dynamically repairing electrode pores, inhibiting active material shedding, and achieving high capacity retention over long periods.

[0009] The principle is as follows: This composite adhesive uses guar gum as a backbone and copolymerizes it with acrylic acid, introducing flexible segments (such as polyethylene glycol) to form a "rigid-flexible" network. Hydrogen bonds provide self-healing properties, while dynamic covalent bonds (such as borate ester bonds) impart reversible crosslinking capabilities. When pores become blocked due to stress or ion migration, the adhesive can release the pores through reversible bond breaking and recombination, while simultaneously inhibiting the shedding of active materials.

[0010] Reduced graphene oxide replaces PVDF as a conductive binder. Through high-energy ray irradiation, reduced graphene oxide can undergo partial deep reduction, crosslinking it with activated carbon. The two-dimensional structure of reduced graphene oxide builds conductive bridges between carbon particles, and it is firmly bonded to activated carbon particles through covalent bonds and strong π-π interactions, thus constructing a stable conductive-bonding integrated three-dimensional conductive network. Detailed Implementation

[0011] The present invention will be further described below with reference to specific embodiments.

[0012] The materials are as follows: Guar Gum Powder, Guangdong Guangrao Liuhe Chemical Co., Ltd. Hydroxypropyl Guar Gum Acrylic acid monomer, octadecyl methacrylate, Hubei Fangde New Materials Co., Ltd. Polyethylene Glycol Jinan Shengfeng Industry & Trade Co., Ltd. PEG-4000 Benzylboronic acid, a compound containing boric acid groups, is produced by Shanghai Yuanye Biotechnology Co., Ltd. (S52293) Reduced graphene oxide (Shanghai Aladdin Biochemical Technology Co., Ltd.) R487603 Potassium persulfate initiator (HFD-528) - Jinan Huifengda Chemical Co., Ltd. The guar gum base solution is prepared as follows: by mass, 1 part of guar gum powder is mixed with 50 parts of deionized water at room temperature and stirred at a stirring speed of 600 rpm. The temperature is slowly raised to 85°C and stirred continuously at this temperature for 1 hour to form the guar gum base solution.

[0013] The activation treatment of activated carbon is as follows: Add activated carbon powder to a hydrogen peroxide solution (concentration of 40%) with a mass of 5 times its weight and treat for 30 minutes, then wash with deionized water until neutral and dry.

[0014] The preparation of the reduced graphene oxide dispersion is as follows: by mass, 1 part of reduced graphene oxide is mixed with 6 parts of deionized water and then exfoliated and dispersed into a uniform reduced graphene oxide dispersion by a cell disruption sonicator (power 600W, sonication time 1h).

[0015] Example 1 A method for preparing a cross-linked self-healing composite electrode structure includes the following steps: Step 1: Preparation of Adhesive At 50°C, guar gum base liquid was mixed with acrylic monomer and polyethylene glycol at a mass ratio of 1:1.8:0.6. Nitrogen gas was introduced, and initiator (potassium persulfate) was added at a mass ratio of 1:0.1. The mixture was heated to 60°C and reacted for 4 hours to form a prepolymer.

[0016] At 70°C and pH 8.5, the obtained prepolymer was reacted with a compound containing boric acid groups (phenylboronic acid, with a mass ratio of 0.2:1 to guar gum) for 4 hours. The pH of the reaction product was adjusted to neutral with dilute hydrochloric acid to obtain an aqueous solution of the adhesive. The adhesive was then dehydrated to obtain the adhesive.

[0017] Step 2: Preparation of composite conductive powder Reduced graphene oxide dispersion and activated carbon were mixed in a shear emulsifier (8000 rpm, 60 min) to form a slurry, wherein the mass ratio of reduced graphene oxide to activated carbon was 1:5. The slurry was then irradiated with gamma rays (60Co as the radiation source, dose rate 10 KGy / h, time 1.5h).

[0018] After irradiation, the product is filtered, washed, and dried to obtain a solid product. The solid product is then ground to form a composite conductive powder.

[0019] Step 3: Electrode Preparation Electrode slurry was prepared by mixing activated carbon, composite conductive powder, binder, and water in a mass ratio of 79:11:8:60. Specifically, the activated carbon and composite conductive powder were mixed evenly in a mixer, and then the prepared binder aqueous solution was added. An appropriate amount of deionized water was added to match the deionized water in the binder to achieve the above mass ratio. The mixture was then mixed evenly in a planetary mixer at 500 rpm and then stirred at 2100 rpm for 2 hours to obtain the desired electrode slurry.

[0020] Aluminum foil used in supercapacitors is used as the metal current collector. Its surface is subjected to plasma treatment (normal parameters are sufficient). The resulting electrode slurry is coated onto the current collector using an automatic coating machine. The wet electrode is then transferred to a drying oven and first slowly dried at 50°C to remove 60% of the water. Then it is cured at 90°C for 2 hours. Finally, it is vacuum hot-pressed at 120°C with a vacuum of 10 Pa for 4 hours. After cooling to room temperature, it is sliced ​​into the desired electrode shape.

[0021] Example 2 A method for preparing a cross-linked self-healing composite electrode structure differs from Example 1 in that: In the preparation of the adhesive in step one, guar gum is mixed with acrylic monomer and polyethylene glycol in a mass ratio of 1:2.2:0.7.

[0022] In step three, electrode preparation involves mixing activated carbon, composite conductive powder, binder aqueous solution, and water in a mass ratio of 80:13:7:35 to obtain an electrode slurry.

[0023] Example 3 A method for preparing a cross-linked self-healing composite electrode structure differs from Example 1 in that: In the preparation of the adhesive in step one, the mass ratio of guar gum to acrylic monomer and polyethylene glycol is 1:2.8:0.7.

[0024] In step three, electrode preparation involves mixing activated carbon, composite conductive powder, binder, and water in a mass ratio of 82:13:6:85 to obtain an electrode slurry.

[0025] Comparative Example 1 The difference from Example 1 is that in the preparation of the adhesive in step one, there is no polyethylene glycol, and the mass ratio of guar gum to acrylic monomer is 1:2.3.

[0026] Comparative Example 2 The difference from Example 1 is that in step two, when the activated carbon powder and the reduced graphene oxide dispersion are mixed, the shearing machine parameters are 4000 rpm for 60 min.

[0027] Comparative Example 3 The difference from Example 1 is that in the electrode preparation step three, the binder prepared in Example 1 is replaced with a traditional PVDF binder.

[0028] Comparative Example 4 The difference from Example 1 is that in the electrode preparation of step three, reduced graphene oxide is used instead of the composite conductive powder prepared in Example 1.

[0029] The performance of the electrodes prepared above was tested, as shown in Table 1.

[0030] Table 1 Electrode performance of each embodiment

[0031] The capacity retention rate is 20,000 cycles, and the self-healing efficiency refers to the crack repair rate.

[0032] As shown in Table 1, the electrodes formed by the process of this invention exhibit excellent performance in specific capacitance, internal resistance, capacity retention, and self-healing rate. In Comparative Example 1, the absence of polyethylene glycol significantly reduced the specific capacitance, capacity retention, and self-healing efficiency of the prepared electrodes. In Comparative Example 2, altered shear emulsification parameters significantly reduced the specific capacitance and capacity retention of the prepared electrodes. In Comparative Example 3, a change in the binder significantly reduced the specific capacitance and capacity retention of the prepared electrodes, and completely lost its self-healing function. In Comparative Example 4, the absence of composite conductive powder significantly reduced the specific capacitance of the prepared electrodes, and significantly increased the internal resistance.

[0033] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a cross-linked self-healing composite electrode structure, characterized in that, Includes the following steps: Step 1: Preparation of Adhesive At 60-70℃, guar gum base liquid is reacted with acrylic monomer, polyethylene glycol and initiator to form a prepolymer, wherein the mass ratio of guar gum to acrylic monomer and polyethylene glycol is 1:1.4-2.8:0.3-0.8; The obtained prepolymer was reacted with a compound containing boric acid groups at 50-80℃, and the pH of the reaction product was adjusted to neutral to obtain an aqueous adhesive solution. Step 2: Preparation of composite conductive powder The reduced graphene oxide dispersion was mixed with activated carbon to form a slurry, and the slurry was then irradiated. The slurry was irradiated and then dried to obtain a composite conductive powder. Step 3: Electrode Preparation Activated carbon, composite conductive powder, binder and water are mixed in a mass ratio of 74-83:8-13:6-12:30-120 to obtain electrode slurry; The electrode paste is coated onto the current collector, and then dried, cured, and hot-pressed to obtain the composite electrode.

2. The method for preparing a cross-linked self-healing composite electrode structure as described in claim 1, characterized in that: In step one, guar gum and water are mixed at a mass ratio of 1:30-100, heated to 75-95℃ and maintained for 1-2 hours to obtain guar gum base solution. The guar gum base solution is then cooled to 45-65℃, and acrylic monomer, polyethylene glycol and initiator are added to the guar gum base solution. The mixture is heated and reacted for 3-6 hours to obtain prepolymer.

3. The method for preparing a cross-linked self-healing composite electrode structure as described in claim 1, characterized in that: In step one, a compound containing boric acid groups is added to the prepolymer and the pH value is adjusted to alkaline. The mass ratio of the compound containing boric acid groups to guar gum is 0.01-0.5:

1.

4. The method for preparing a cross-linked self-healing composite electrode structure as described in claim 1, characterized in that: In step two, activated carbon is activated by hydrogen peroxide treatment, and reduced graphene oxide powder is mixed with water at a mass ratio of 1:3-8 and ultrasonically treated to form the reduced graphene oxide dispersion. During slurry preparation, the reduced graphene oxide and activated carbon are mixed at a mass ratio of 1:3-8.

5. The method for preparing a cross-linked self-healing composite electrode structure as described in claim 1, characterized in that: In step three, the current collector coated with electrode slurry is dried at a low temperature of 45-60℃, then cured at 85-105℃, and finally subjected to vacuum hot pressing at 110-140℃ and a vacuum degree of 1-30Pa to obtain the composite electrode.

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