A cellulose-based porous carbon electrode material and a supercapacitor electrode prepared therefrom

Abstract

The present invention provides a cellulose-based porous carbon electrode material and a supercapacitor electrode prepared therefrom. The cellulose-based porous carbon electrode material is prepared by the following steps: Hydrazine hydrate, cellulose powder and nickel acetate hexahydrate are added to deionized water, ultrasonicated and uniformly mixed, and then the above mixture is transferred to the inner liner of a hydrothermal autoclave for hydrothermal reaction, filtered, washed and dried to obtain a cellulose-based carbon material; The cellulose-based carbon material is mixed with KOH, placed in a horizontal tubular furnace, and reacted under high temperature and in the presence of N2, and cooled to room temperature to obtain cellulose-based porous carbon; The cellulose-based porous carbon is stirred in an acid solution, washed to neutrality and dried to obtain the cellulose-based porous carbon electrode material. The cellulose-based porous carbon electrode material prepared by the present invention has the advantages of high specific surface area and cycle stability, as well as high specific capacitance and ideal pseudocapacitance.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation methods of biomass-based carbon materials, and particularly relates to a cellulose-based porous carbon electrode material and a supercapacitor electrode prepared therefrom. Background Art

[0002] Nowadays, with the consumption of non-renewable energy and the disadvantages of instability and intermittency of renewable energy, it is not easy to achieve "grid connection" for renewable energy power generation, resulting in a large number of phenomena of "abandoned wind" and "abandoned electricity". As a new type of energy storage device, supercapacitors have attracted wide attention due to their high energy density, power density, long cycle life, high specific capacitance, and good cycle stability. Among them, porous carbon is considered to be an excellent choice for preparing supercapacitor electrode materials with the most promising prospects.

[0003] When various carbon materials are made into supercapacitor electrode materials, biomass-based preparation of porous carbon materials has been widely used in supercapacitor electrode materials. CN106587055A discloses a biomass-based porous carbon material, its preparation method and application in supercapacitors. The biomass porous carbon obtained using rice straw as a precursor has a mass specific capacitance between 179 and 280 F / g; CN105788876A discloses a process for preparing biomass porous carbon, using ammonia gas and water vapor to carbonize and nitrogen-dope biomass. The maximum mass specific capacitance of the obtained activated carbon is 340 F / g. The preparation field of green biomass-based porous carbon supercapacitor electrode materials has received extensive attention from many researchers.

[0004] Limited by the limitations of biomass-based carbon materials themselves, the reported carbon materials prepared from biomass have defects such as low specific surface area, underdeveloped pore structure, and low specific capacitance. Therefore, it is urgent to find a new method for preparing carbon materials from biomass to obtain a high specific surface area, developed pore structure, and high specific capacitance.

[0005] Therefore, there is an urgent need to develop a preparation method for supercapacitor electrode materials that is simple, low-cost, controllable, and energy-saving. Summary of the Invention

[0006] To solve the above defects, the present invention provides a cellulose-based porous carbon electrode material and a supercapacitor electrode prepared therefrom. The cellulose-based porous carbon electrode material obtained by the present invention has advantages such as a high specific surface area and cycle stability, and also has a high specific capacitance and ideal pseudocapacitance.

[0007] In a first aspect, the present invention provides a method for preparing a cellulose-based porous carbon electrode material, which comprises the following steps: 1) Take hydrazine hydrate, cellulose powder and nickel acetate hexahydrate, add them into deionized water, sonicate to mix evenly, then transfer the above mixture to the inner liner of a hydrothermal reactor for hydrothermal reaction, filter, wash, and then dry to obtain a cellulose-based carbon material; 2) Mix the cellulose-based carbon material obtained in step 1) with KOH, then place it in a horizontal tubular furnace, and react under high temperature and in an atmosphere of N2 being introduced, cool to room temperature to obtain cellulose-based porous carbon; 3) Place the cellulose-based porous carbon obtained in step 2) in an acid solution and stir magnetically, wash it with deionized water and ethanol until neutral, and then dry to obtain a cellulose-based porous carbon electrode material.

[0008] Preferably, in step 1), the mass ratio of the hydrazine hydrate, the cellulose powder and the nickel acetate hexahydrate is 0.28 - 0.46:3:0.40 - 0.50.

[0009] More preferably, in step 1), the mass ratio of the hydrazine hydrate, the cellulose powder and the nickel acetate hexahydrate is 0.60:3:0.45.

[0010] Preferably, in step 1), the temperature of the hydrothermal reaction is 180 - 220 °C.

[0011] More preferably, in step 1), the temperature of the hydrothermal reaction is 200 °C.

[0012] Preferably, in step 1), the time of the hydrothermal reaction is 2 - 4 h.

[0013] More preferably, in step 1), the time of the hydrothermal reaction is 3 h.

[0014] Preferably, in step 1), the temperature of the drying is 80 - 105 °C; the time of the drying is 8 - 12 h.

[0015] Preferably, in step 2), the mass ratio of the cellulose-based carbon material to the KOH is 1:(0.8 - 1.2).

[0016] Preferably, in step 2), the high temperature is 600 - 800 °C, and the time of the high temperature is 1 - 3 h.

[0017] More preferably, in step 2), the high temperature is 700 °C, and the time of the high temperature is 2 h.

[0018] Preferably, in step 2), the flow rate of the N2 is 180 - 220 mL·min -1 。

[0019] More preferably, in step 2), the flow rate of N2 is 200 mL·min -1 .

[0020] Preferably, in step 3), the acid solution is a hydrochloric acid solution; the mass concentration of the acid solution is 0.8 - 1.2 moL·L -1 .

[0021] More preferably, in step 3), the mass concentration of the acid solution is 1 moL·L -1 .

[0022] Preferably, in step 3), the drying temperature is 70 - 90 °C and the drying time is 20 - 28 h.

[0023] In a second aspect, the present invention provides a cellulose-based porous carbon electrode material obtained by the above-described preparation method.

[0024] In a third aspect, the present invention provides a method for preparing a supercapacitor electrode, comprising the following steps: uniformly mixing a conductive agent, a binder, and the above-described cellulose-based porous carbon electrode material in a mass ratio of 1:0.5 - 1.5:7 - 9, adding a solvent to reconcile it into a slurry state, then coating it on a current collector and drying, and compacting it under a pressure of 10 - 40 MPa to obtain a supercapacitor electrode.

[0025] Preferably, the conductive agent is acetylene black.

[0026] Preferably, the binder includes one or more of polytetrafluoroethylene, polyacrylamide, polybutadiene, polyvinylpyrrolidone, polyethylene oxide, fluororubber, and polyvinyl alcohol.

[0027] Preferably, the solvent includes one or more of alcohols, water, ethyl acetate, dimethyl carbonate, methyl propionate, and diethyl carbonate.

[0028] Preferably, the current collector is nickel foam and the area of the current collector is 0.8 - 1.2 cm 2 .

[0029] In a fourth aspect, the present invention provides a supercapacitor electrode obtained by the above-described preparation method.

[0030] In summary, the present invention provides a cellulose-based porous carbon electrode material and a supercapacitor electrode prepared therefrom. The beneficial effects of the present invention are:

[0031] The present invention prepares a cellulose-based porous carbon electrode material, which has rich raw material sources, low price, and is green and pollution-free. In the process of preparing the cellulose-based porous carbon electrode material, the nitrogen content is adjusted by regulating the amount of hydrazine hydrate, and the nitrogen doping and pore-forming steps are combined into one, which can greatly save the preparation time. Due to the molecular-level dispersion of hydrazine hydrate, a small amount of hydrazine hydrate can obtain a high nitrogen content and effectively reduce the cost, providing a new method for the industrial preparation of nitrogen-doped cellulose-based porous carbon supercapacitor electrode materials.

[0032] Furthermore, the cellulose-based porous carbon electrode material prepared by the present invention has a large specific surface area, an appropriate heteroatom doping amount, and a uniform honeycomb structure, which is beneficial to charge transfer, provides certain active sites for energy storage, and enables it to have good energy storage performance.

[0033] Furthermore, the cellulose-based porous carbon electrode material prepared by the present invention has an ultra-high specific capacitance of up to 415 F·g -1 at a current density of 0.5 A·g -1 . Making the cellulose-based porous carbon electrode material into a zinc-air battery can light up a diode. Description of the Drawings

[0034] Figure 1 Isothermal adsorption curve of the cellulose-based porous carbon electrode material prepared in Example 1.

[0035] Figure 2 Pore size distribution curve of the cellulose-based porous carbon electrode material prepared in Example 1.

[0036] Figure 3 SEM image of the cellulose-based porous carbon electrode material prepared in Example 1.

[0037] Figure 4 Cyclic voltammetry curves of the cellulose-based porous carbon electrode material prepared in Example 1 in a three-electrode system with 6 M potassium hydroxide as the electrolyte at different scan rates.

[0038] Figure 5 Galvanostatic charge-discharge curve of the cellulose-based porous carbon electrode material prepared in Example 1.

[0039] Figure 6 10,000-cycle charge-discharge and Coulomb efficiency diagram of the cellulose-based porous carbon electrode material prepared in Example 1. Detailed Embodiments

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0041] Example 1

[0042] Take 0.35 g of hydrazine hydrate, 3 g of cellulose powder, and 0.45 g of nickel acetate hexahydrate and add them to 120 mL of deionized water. Ultrasonic for 5 min and mix evenly. Then transfer the above mixture to the inner liner of a hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature and duration are 200 °C and 3 h respectively; filter and wash, and then dry at 80 - 105 °C for 8 - 12 h. Obtain cellulose-based carbon materials;

[0043] Mechanically mix the cellulose-based carbon materials and KOH at a mass ratio of 1, and then keep them at 700 °C in a horizontal tubular furnace for 2 h. The N2 flow rate is 200 mL·min -1 . Let it cool to room temperature to obtain cellulose-based porous carbon.

[0044] Magnetically stir the cellulose-based porous carbon in a 1 M acid solution for 24 h, and then wash it with deionized water and ethanol until neutral; then dry it in an oven at 80 °C for 24 h to obtain a cellulose-based porous carbon electrode material.

[0045] Uniformly mix acetylene black, polyacrylamide, and the cellulose-based porous carbon electrode material at a mass ratio of 1:1:8, add ethyl acetate to reconcile it into a slurry, and then coat it on a current collector and dry it. Compact it under a pressure of 30 MPa to obtain a supercapacitor electrode.

[0046] Test the cellulose-based porous carbon electrode material obtained in Example 1.

[0047] Figure 1 The isothermal adsorption curve of the cellulose-based porous carbon electrode material prepared for Example 1; it can be seen from the figure that the adsorption curve of the obtained cellulose-based porous carbon electrode material is a typical I / IV type adsorption curve, indicating the presence of micropores and mesopores, which is beneficial to charge transfer.

[0048] Figure 2 Pore size distribution curve of the cellulose-based porous carbon electrode material prepared in Example 1. It can be seen from the figure that the micropore distribution of the obtained cellulose-based porous carbon electrode material is mainly between 1.6 and 1.8 nm. The mesopores and macropores are also correspondingly evenly distributed, making the cellulose-based porous carbon electrode material have good electrochemical performance.

[0049] Figure 3 SEM image of the cellulose-based porous carbon electrode material prepared in Example 1, which has a very developed honeycomb structure.

[0050] Figure 4 Cyclic voltammogram curves of the cellulose-based porous carbon electrode material prepared in Example 1 at different scan rates. It can be seen from the figure that the CV curve is a slightly deformed rectangle, indicating that the overall capacitance is the result of the electric double layer capacitance and pseudocapacitance.

[0051] Figure 5 Galvanostatic charge-discharge curves of the cellulose-based porous carbon electrode material prepared in Example 1 at different current densities. 6M KOH was used as the electrolyte. At a current density of 0.5 A·g -1 the specific capacitance reached 415 F·g -1 .

[0052] Figure 6 Charge-discharge and Coulombic efficiency diagram of 10,000 cycles of the cellulose-based porous carbon electrode material prepared in Example 1. The capacitance retention rate of the sample after 10,000 cycles was 96.06% and the Coulombic efficiency was 100%.

[0053] Example 2

[0054] Take 0.28 g of hydrazine hydrate, 3 g of cellulose powder and 0.45 g of nickel acetate hexahydrate and add them to 120 mL of deionized water. Ultrasonic for 5 min and mix evenly. Then transfer the above mixture to the inner liner of the hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature and duration are 200 °C and 3 h respectively; filter and wash, and then dry at 80 - 105 °C for 8 - 12 h. Obtain the cellulose-based carbon material;

[0055] Mechanically mix the cellulose-based carbon material with KOH at a ratio of 1, and then keep it at 700 °C in a horizontal tubular furnace for 2 h, with a N2 flow rate of 200 mL·min -1 . Let it cool to room temperature to obtain the cellulose-based porous carbon.

[0056] Magnetically stir the cellulose-based porous carbon in 1M acid solution for 24 h, then wash it with deionized water and ethanol until neutral; then dry it in an oven at 80 °C for 24 h to obtain the cellulose-based porous carbon electrode material.

[0057] Mix acetylene black, polyacrylamide, and cellulose-based porous carbon electrode material evenly at a mass ratio of 1:1:8, add ethyl acetate to reconcile it into a slurry, then coat it on a current collector and dry it, and compact it under a pressure of 30 MPa to obtain a supercapacitor electrode.

[0058] Under a three-electrode system, the cellulose-based porous carbon electrode material uses 6 M KOH as the electrolyte, and at 0.5 A·g -1 the specific capacitance is relatively high at 305 A·g -1 .

[0059] Example 3

[0060] Take 0.45 g of hydrazine hydrate, 3 g of cellulose powder, and 0.45 g of nickel acetate hexahydrate and add them to 120 mL of deionized water. Ultrasonic for 5 min and mix evenly. Then transfer the above mixture to the inner liner of a hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature and duration are 200 °C and 3 h respectively; filter and wash, and then dry at 80 - 105 °C for 8 - 12 h. Obtain cellulose-based carbon material;

[0061] Mechanically mix the cellulose-based carbon material and KOH at a ratio of 1, then keep it at 700 °C in a horizontal tubular furnace for 2 h, and the N2 flow rate is 200 mL·min -1 . Let it cool to room temperature to obtain cellulose-based porous carbon.

[0062] Magnetically stir the cellulose-based porous carbon in 1 M acid solution for 24 h, then wash it with deionized water and ethanol until neutral; then dry it in an oven at 80 °C for 24 h to obtain cellulose-based porous carbon electrode material.

[0063] Mix acetylene black, polyacrylamide, and cellulose-based porous carbon electrode material evenly at a mass ratio of 1:1:8, add ethyl acetate to reconcile it into a slurry, then coat it on a current collector and dry it, and compact it under a pressure of 30 MPa to obtain a supercapacitor electrode.

[0064] Under a three-electrode system, the cellulose-based porous carbon electrode material uses 6 M KOH as the electrolyte, and at 0.5 A·g -1 the specific capacitance is relatively high at 319 A·g -1 .

[0065] Example 4

[0066] Take 0.35 g of hydrazine hydrate, 3 g of cellulose powder, and 0.45 g of nickel acetate hexahydrate and add them to 120 mL of deionized water. Ultrasonic for 5 min and mix evenly. Then transfer the above mixture to the inner liner of a hydrothermal reactor for hydrothermal reaction. The hydrothermal temperature and duration are 180 °C and 3 h respectively; filter and wash, and then dry at 80 - 105 °C for 8 - 12 h. Obtain cellulose-based carbon materials;

[0067] Mechanically mix the cellulose-based carbon materials and KOH at a ratio of 2, and then keep them at 700 °C in a horizontal tubular furnace for 2 h. The N2 flow rate is 200 mL·min -1 . Let it cool to room temperature to obtain cellulose-based porous carbon.

[0068] Magnetically stir the cellulose-based porous carbon in 1 M acid solution for 24 h, and then wash it with deionized water and ethanol until neutral; then dry it in an oven at 80 °C for 24 h to obtain cellulose-based porous carbon electrode materials.

[0069] Uniformly mix acetylene black, polyacrylamide, and cellulose-based porous carbon electrode materials in a mass ratio of 1:1:8, add ethyl acetate to reconcile it into a slurry state, and then coat it on a current collector and dry it. Compact it under a pressure of 30 MPa to obtain a supercapacitor electrode.

[0070] Under a three-electrode system, use 6 M KOH as the electrolyte for the cellulose-based porous carbon electrode materials. At 0.5 A·g -1 The specific capacitance is relatively high at 342 A·g -1 .

[0071] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a cellulose-based porous carbon electrode material, characterized in that: It includes the following steps: 1) Hydrazine hydrate, cellulose powder and nickel acetate hexahydrate are added to deionized water, ultrasonicated and uniformly mixed. Then the above mixture is transferred to the inner liner of a hydrothermal autoclave for hydrothermal reaction, filtered, washed and then dried to obtain a cellulose-based carbon material; In step 1), the mass ratio of the hydrazine hydrate, the cellulose powder and the nickel acetate hexahydrate is 0.28 - 0.46:3:0.40 - 0.50; the temperature of the hydrothermal reaction is 180 - 220 °C; the time of the hydrothermal reaction is 2 - 4 h; the temperature of the drying is 80 - 105 °C; the time of the drying is 8 - 12 h; 2) The cellulose-based carbon material obtained in step 1) is mixed with KOH, then placed in a horizontal tubular furnace and reacted under high temperature and the condition of introducing N2, and cooled to room temperature to obtain cellulose-based porous carbon; In step 2), the mass ratio of the cellulose-based carbon material to the KOH is 1:(0.8 - 1.2); the high temperature is 600 - 800 °C, the time of the high temperature is 1 - 3 h; the flow rate of the N2 is 180 - 220 mL·min -1 ; 3) The cellulose-based porous carbon obtained in step 2) is magnetically stirred in an acid solution, washed with deionized water and ethanol until neutral, and then dried to obtain a cellulose-based porous carbon electrode material.

2. The preparation method of the cellulose-based porous carbon electrode material according to claim 1, wherein: In step 3), the acid solution is a hydrochloric acid solution; the mass concentration of the acid solution is 0.8 to 1.2 moL·L -1 ; In step 3), the temperature of the drying is 70 - 90 °C, and the time of the drying is 20 - 28 h.

3. A cellulose-based porous carbon electrode material obtained by the preparation method according to any one of claims 1 to 2.

4. A method for preparing a supercapacitor electrode, characterized in that, It includes the following steps: The conductive agent, the binder and the cellulose-based porous carbon electrode material according to claim 3 are uniformly mixed according to a mass ratio of 1:0.5 - 1.5:7 - 9, a solvent is added to reconcile it into a slurry state, and then it is coated on a current collector and dried, and compacted under a pressure of 10 - 40 MPa to obtain a supercapacitor electrode.

5. The preparation method of the supercapacitor electrode according to claim 4, characterized in that, The conductive agent is acetylene black; The binder includes one or more of polytetrafluoroethylene, polyacrylamide, polybutadiene, polyvinylpyrrolidone, polyethylene oxide, fluororubber and polyvinyl alcohol.

6. The preparation method of the supercapacitor electrode according to claim 4, characterized in that, The solvent includes one or more of alcohols, water, ethyl acetate, dimethyl carbonate, methyl propionate and diethyl carbonate.

7. The preparation method of the supercapacitor electrode according to claim 4, characterized in that, The current collector is nickel foam, and the area of the current collector is 0.8 to 1.2 cm 2 .

8. A supercapacitor electrode obtained by the preparation method according to any one of claims 4 to 7.

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