In-situ preparation method of supercapacitor electrode

Abstract

The invention discloses a method for preparing a supercapacitor electrode in situ by adopting hydrothermal pretreatment and nitrogen protection heat treatment. According to the preparation method, glucose serves as a carbon source, soluble salt of metal and a soluble carbon source (glucose, fructose or cane sugar) form a solution, and the carbon and metal nano composite material is formed through a hydrothermal reaction. According to the composite material, polyvinyl alcohol is adopted as an additive, the surface of the foamed nickel is coated with the composite material, and the composite material is subjected to protective gas heat treatment and hydrogen peroxide surface oxidation treatment to prepare the supercapacitor electrode without the adhesive. The specific capacitance of the prepared supercapacitor can reach 600 F / g under the condition that the current density is 1 A / g.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor energy storage, and in particular to an in-situ preparation method of a supercapacitor electrode. Technical Background

[0002] Supercapacitors are a new type of energy storage device that has received much attention. Their energy storage density is higher than that of traditional capacitors, but lower than that of electrochemical cells. Compared with electrochemical cells, supercapacitors have more advantages in charging efficiency, discharge power and cycle life. These advantages make them a supplement to electrochemical cells in terms of application. In the usual supercapacitor electrode preparation process, an adhesive for the electrode material is used. The adhesive can bond the electrode material to the current collector to form a good contact and show a certain degree of flexibility and anti-bending properties. However, due to the process of uniform mixing of the adhesive with the electrode material and the bonding process of the electrode material to the current collector, a certain pressure always needs to be applied. In the process of applying pressure, the extrusion between the electrode active material particles will be caused, thereby reducing the specific surface area of ​​the electrode material. In addition, the adhesive particles may cause the contact ability between some active material particles to decrease, thereby increasing the device impedance. In order to solve the adverse effects of the adhesive, the present invention adopts in-situ preparation of the electrode without the need for an adhesive, so as to give full play to the surface storage charge of the electrode material.

[0003] Although patents CN115295317B and CN108492999A disclose a method for preparing in-situ grown electrode materials. However, the preparation process of this method is complicated and uses substances such as N,N-dimethylformamide (DMF) which have certain toxicity. CN105480962B discloses an in-situ preparation method, whose specific capacitance reaches 379 F / g (1 A / g) in a three-electrode system, but uses a freeze-drying process and polytetrafluoroethylene as an adhesive. The present invention does not use toxic and harmful solvents. Summary of the invention

[0004] The purpose of the present invention is to prepare a supercapacitor electrode with good performance by using a special process, and to develop a method for fixing the electrode active material on the nickel foam current collector without using a binder and mechanical pressure to realize the in-situ preparation of the supercapacitor electrode. The technical scheme adopted by the present invention is: mixing the metal solution and the carbon source solution under hydrothermal conditions to obtain nanocomposite particles, and then fixing them on the current collector through a high-temperature graphitization process, and then reoxidizing and heat treating to obtain the supercapacitor electrode.

[0005] Step 1: Take a certain amount of carbon source material (glucose, sucrose or fructose) and a soluble salt of a metal ion (such as nickel acetate, nickel nitrate, etc.) and dissolve them in deionized water.

[0006] Step 2, the solution of step 1 is placed in the bottom of a polytetrafluoroethylene-lined reactor, sealed, and kept hot for several hours under a certain temperature.

[0007] Step 3, preparing a water-soluble polymer solution: Take a water-soluble polymer (eg, polyvinyl alcohol) and heat and stir it in deionized water to fully dissolve it.

[0008] Step 4, the material obtained after the hydrothermal reaction in step 2 and the solution obtained in step 3 are fully stirred and mixed.

[0009] Step 5, heating, stirring and evaporating the aqueous solution obtained in step 4 to obtain a composite slurry with a certain solid content.

[0010] Step 6, evenly coating the composite slurry obtained in step 5 above on the cut and surface-treated nickel foam, and fully drying it at a certain temperature.

[0011] Step 7, the nickel foam with the coating slurry prepared in the above step 6 is heat treated under the protection of flowing nitrogen.

[0012] Step 8: Apply a protective layer on one side of the nickel foam that contacts the assembled electrode shell in step 7 to prevent oxidation of the nickel foam surface.

[0013] Step 9, the sample coated with the protective layer in the above step 8 is placed in hydrogen peroxide and soaked for a certain period of time.

[0014] Step 10: After the sample in step 9 is soaked in double cation water, it is heat treated for 1-3 hours in flowing nitrogen protection at about 300° C. to completely vaporize and remove the protective layer on the nickel foam.

[0015] Step 11, assemble the above samples into button cells using 40% NaOH solution as electrolyte solution, and perform electrochemical test, or perform three-electrode test in 40% NaOH solution. Implementation

[0016] To make the purpose, technical solution and advantages of the present invention clearer, the following will be described clearly and completely in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, but not all of them. Example

[0017] 1) Dissolve 2 g of glucose and 0.2 g of nickel acetate in 70 ml of deionized water.

[0018] 2) The above solution was placed in a 100 ml polytetrafluoroethylene-lined reactor, sealed, and subjected to hydrothermal reaction at 150°C for 20 hours.

[0019] 3) Take 0.02g of polyvinyl alcohol with an average molecular weight of 100,000 and heat and stir in 30ml of deionized water to fully dissolve.

[0020] 4) Add fully dissolved polyvinyl alcohol aqueous solution to the mixture after the hydrothermal reaction and stir and mix thoroughly.

[0021] 5) Add the polyvinyl alcohol aqueous solution to the slurry, heat and stir, and evaporate until it becomes a composite slurry of about 15 ml.

[0022] 6) The composite slurry prepared above is evenly coated on the cut, surface-treated and weighed nickel foam, and then fully dried at 100°C.

[0023] 7) The dried nickel foam with the coating slurry is heat treated at 700° C. for 1 h under nitrogen protection.

[0024] 8) Apply a protective layer on one side of the nickel foam contact assembly electrode shell to prevent oxidation of the nickel foam surface.

[0025] 9) The samples coated with the protective layer are placed in about 5wt% hydrogen peroxide and soaked for 2 hours.

[0026] 10) After the sample was soaked in double cation water, it was heat treated for 3 hours in flowing nitrogen protection at 300°C to completely vaporize and remove the protective layer on the nickel foam.

[0027] 11) The above samples were assembled into button batteries using 40% NaOH solution as the electrolyte solution and electrochemical tests were performed.

[0028] The supercapacitor prepared in this example has a specific capacitance of 600 F / g at a current density of 1 A / g. Example

[0029] 1) Dissolve 3 g of glucose and 0.2 g of cobalt nitrate in 70 ml of deionized water.

[0030] 2) The above solution was placed in a 100 ml polytetrafluoroethylene-lined reactor, sealed, and kept hydrothermally reacted at 130°C for 6 hours.

[0031] 3) Take 0.03g of polyvinyl alcohol with an average molecular weight of 100,000 and heat and stir in 30ml of deionized water to fully dissolve.

[0032] 4) Add fully dissolved polyvinyl alcohol aqueous solution to the mixture after the hydrothermal reaction and stir and mix thoroughly.

[0033] 5) Add the polyvinyl alcohol aqueous solution to the slurry, heat and stir, and evaporate until it becomes a composite slurry of about 15 ml.

[0034] 6) The composite slurry prepared above is evenly coated on the cut, surface-treated and weighed nickel foam, and then fully dried at 100°C.

[0035] 7) The dried nickel foam with the coating slurry is heat treated at 750° C. for 1 h under nitrogen protection.

[0036] 8) Apply a protective layer on one side of the nickel foam contact assembly electrode shell to prevent oxidation of the nickel foam surface.

[0037] 9) The sample coated with the protective layer is placed in about 10wt% hydrogen peroxide and soaked for 2 hours.

[0038] 10) After the sample was soaked in double cation water, it was heat treated for 3 hours in flowing nitrogen protection at 350°C to completely vaporize and remove the protective layer on the nickel foam.

[0039] 11) The above samples were assembled into button batteries using 40% NaOH solution as the electrolyte solution and electrochemical tests were performed.

[0040] The supercapacitor prepared in this example has a specific capacitance of 580 F / g at a current density of 1 A / g.

Claims

1. A method for in-situ preparation of supercapacitor electrodes based on a hydrothermal method and a water-based resin treatment combined with a flowing nitrogen protection heat treatment, characterized in that The method comprises the following steps: Step 1: dissolve a certain amount of carbon source material and soluble salt of metal ions in deionized water. Carbon sources include glucose, sucrose and fructose. Soluble salts of metal ions include nickel acetate, nickel nitrate, cobalt nitrate and cobalt acetate, as well as other soluble nickel and cobalt salts. The mass concentration of the aqueous solution of the carbon source is 1-20%; Step 2, the solution of step 1 is placed in a polytetrafluoroethylene-lined reactor bottom, sealed, and subjected to hydrothermal reaction at 120-190° C. for 1-20 hours; Step 3, preparing a water-soluble polymer solution: the polymer soluble in the aqueous solution is heated and stirred in deionized water to fully dissolve. The soluble substances used include polyvinyl alcohol, water-soluble acrylic resin, polyethylene glycol and other water-soluble polymers. The content of the water-soluble resin used is 0.1-5% of the sum of the mass of the carbon source material and the aqueous solution ions; Step 4, fully stirring and mixing the material obtained after the hydrothermal reaction in step 2 and the solution obtained in step 3; Step 5, heating and stirring the aqueous solution obtained in step 4, and evaporating the mixture to obtain a composite slurry with a high solid content. The composite slurry has a solid content of 5-20% by weight; Step 6, evenly coating the composite slurry obtained in step 5 above on the cut and surface-treated nickel foam, and fully drying at 50-20° C.; Step 7, the nickel foam coated with the slurry prepared in the above step 6 is heat treated at 600-900° C. for 0.5-10 h under the protection of flowing nitrogen; Step 8, coating a protective layer on one side of the contact assembly electrode shell of the nickel foam in the above step 7 to prevent oxidation on the surface of the nickel foam. The protective layer material is a homemade water-insoluble organic substance that can protect and isolate the surface of the nickel foam from oxidation; Step 9, the sample coated with the protective layer in the above step 8 is placed in hydrogen peroxide and soaked for 1-10 hours; Step 10: After the sample in step 9 is soaked in double cation water, it is heat treated for 1-3 hours in flowing nitrogen protection at about 150-400° C. to completely vaporize and remove the protective layer on the nickel foam.