Preparation method of biomass-based high-performance capacitor carbon

Abstract

The invention discloses a biomass-based high-performance capacitor carbon preparation method, which comprises: S1, mixing a metal halide and an inorganic hydrogen bond donor, and carrying out heating stirring until a solution is clarified so as to obtain an inorganic eutectic solvent; s2, mixing the inorganic eutectic solvent and a biomass raw material for reaction; s3, filtering and washing the material obtained in the step S2 to obtain a mesoporous carbon material; s4, adding an activating agent into the mesoporous carbon material, and activating in high-temperature inert gas to obtain the biomass-based high-performance capacitor carbon. According to the method, the wood fiber biomass such as the lowest-value straw, the lowest-value bamboo and the lowest-value wood dust is directly used as raw materials, component separation does not need to be conducted on the wood fiber biomass, and high-value utilization of a large amount of low-value wood fiber biomass can be achieved. The method is simple in process and mild in condition, the use amount of the activating agent is reduced by at least 50% compared with that of a traditional method, and the product yield is high. The capacitor carbon prepared by the method has high specific area and high specific capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor carbon preparation, and in particular to a method for preparing biomass-based high-performance capacitor carbon. Background Art

[0002] The pores of porous carbon materials are primarily categorized into three types: micropores (less than 2 nanometers), mesopores (between 2 and 50 nanometers), and macropores (greater than 50 nanometers). Mesopores and micropores possess large internal surface areas and cavities, exhibiting significant interfacial coupling and quantum size effects, which effectively facilitate charge storage and transfer. In supercapacitors (SCs), increasing the number of mesopores and micropores can enhance rapid electrolyte ion transport, reduce transport resistance, and improve amplification performance, greatly facilitating efficient energy storage in the electrical double layer. However, traditional bio-based porous carbon materials typically have a low pore ratio. On the one hand, template methods struggle to form a well-developed pore structure when using bio-based materials. On the other hand, the complex structure of bio-based porous carbon materials leads to a complex carbonization mechanism. Lower temperatures result in underdeveloped pores in the generated biochar, while higher temperatures can lead to structural collapse and destruction, both of which reduce the material's specific surface area. To date, improving the performance of capacitive carbons by simply adjusting the carbonization temperature remains difficult. In order to improve the specific surface area, porosity and electrochemical performance of bio-based porous carbon materials, new methods need to be developed.

[0003] In recent years, the method of preparing high-performance capacitive carbon by chemical activation has become popular. Among them, the chemical activation method generally uses KOH and salts as activators for activation. Among them, potassium hydroxide activator (KOH) is a commonly used reagent for converting biomass into porous carbon. It can produce a large specific surface area without excessively increasing the temperature. However, the traditional activation method requires the use of a large amount of activator for carbon etching (the mass ratio of biomass to activator is usually 1 to 3 to 1 to 4), followed by neutralization and rinsing with a large amount of hydrochloric acid. Although this method helps to generate energy materials, it also leads to huge energy consumption and carbon emissions. Therefore, it is crucial to propose a method that can produce carbon with high capacitance (with a large ion-accessible specific surface area) while simultaneously improving the utilization efficiency of potassium hydroxide. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing biomass-based high-performance capacitor carbon, so as to at least achieve a low amount of activator (biomass: activator <1:2), so that the capacitor carbon has a high specific area and high specific capacity.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for preparing biomass-based high-performance capacitor carbon comprises the following steps:

[0007] S1: Mixing a metal halide and an inorganic hydrogen bond donor, heating and stirring until the solution is clear to obtain an inorganic deep eutectic solvent;

[0008] S2: mixing the inorganic deep eutectic solvent and the biomass raw material for reaction;

[0009] S3: filtering and washing the material obtained in step S2 to obtain a mesoporous carbon material;

[0010] S4: adding an activator to the mesoporous carbon material and activating the material in a high-temperature inert gas to obtain the biomass-based high-performance capacitor carbon.

[0011] Furthermore, the metal halide includes at least one of zinc chloride, aluminum chloride, tin chloride and lead chloride.

[0012] Furthermore, the inorganic hydrogen bond donor includes at least one of phosphoric acid, boric acid, and ammonium chloride.

[0013] Furthermore, in step S1, the molar ratio of the metal halide to the inorganic hydrogen bond donor is 1:0.1-10.

[0014] Preferably, the molar ratio of the metal halide to the hydrogen bond donor is 0.3:1.

[0015] Furthermore, in step S1, the temperature of the heating and stirring is 60-140°C.

[0016] Preferably, the temperature of the heating and stirring is 90°C.

[0017] Furthermore, in step S2, the biomass raw material is at least one of native biomass and biomass separation and decomposition products.

[0018] Furthermore, the primary biomass includes at least one of bamboo, straw and sawdust; and the biomass separation and decomposition products include at least one of glucose, cellulose and lignin.

[0019] Furthermore, in step S2, the solid-liquid ratio of the biomass raw material and the inorganic deep eutectic solvent is 1 g:1-30 mL.

[0020] Preferably, the solid-to-liquid ratio of the biomass raw material to the deep eutectic solvent is 1 g:5 mL.

[0021] Furthermore, in step S2, the reaction temperature of the mixed reaction is 100-400° C.; and the reaction time of the mixed reaction is 0.5-30 h.

[0022] Preferably, the reaction temperature is 300° C.; and the reaction time of the mixing reaction is 2 h.

[0023] Furthermore, in step S4, the activator includes at least one of potassium hydroxide, potassium carbonate or sodium carbonate.

[0024] Furthermore, in step S4, the amount of the activator added is 0.1 to 2 times the weight of the biomass raw material, which is approximately equivalent to 1 to 3 times the weight of the mesoporous carbon material obtained in step S3;

[0025] and / or, the temperature of the high-temperature inert gas is 700-900° C.;

[0026] And / or, the activation time is 0.5 to 30 hours.

[0027] Preferably, the temperature of the high-temperature inert gas is 800°C.

[0028] Preferably, the activation time is 1.5 h.

[0029] It is worth noting that in the present invention, IDES (inorganic deep eutectic solvent) composed of metal halides and hydrogen bond donors has a developed hydrogen bond network, which allows the biomass to swell at 10-30°C. At lower temperatures (100-400°C), IDES reacts when heated to generate fine metal salt templates inside the biomass, so that the obtained carbon material has a huge mesoporous volume.

[0030] The beneficial effects of the present invention are:

[0031] 1) The method of the present invention directly uses the lowest-value lignocellulosic biomass such as straw, bamboo and sawdust as raw materials, without the need to separate the components of the lignocellulosic biomass, and can achieve high-value utilization of bulk low-value lignocellulosic biomass.

[0032] 2) The method of the present invention has a simple process, mild conditions, reduces the amount of activator used by at least 50% compared with the traditional method, and has a high product yield.

[0033] 3) The capacitor carbon prepared by the method of the present invention has an ultra-high specific surface area (>3200m 2 / g) and ultra-high specific capacity (specific capacitance in alkaline aqueous solution>370F / g). BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a simplified process flow diagram of the present invention;

[0035] Figure 2 This is a scanning electron microscope image of the capacitor carbon in Example 1;

[0036] Figure 3The electron microscope scanning image and N2 adsorption-desorption curve of the capacitor carbon in Example 2;

[0037] Figure 4 This is the charge-discharge curve of the capacitive carbon material in Experimental Example 3 at 1 A / g in a three-electrode system. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0039] Example 1

[0040] Prepare a capacitor carbon, the specific method is as follows:

[0041] Zinc chloride powder and solid phosphoric acid were mixed in a 0.4:1 molar ratio (heated to melt), then stirred and heated at 90°C until the solution clarified to obtain IDES. 30g of biomass raw material straw powder and 100mL of IDES were added to a crucible, mixed, stirred evenly, and then heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature, filtered, and the solid matter was washed with acid and water to a constant pH. After drying, the activated precursor was obtained. The activated precursor was mixed with 5g of KOH and 2g of K2CO3 and heated to 800°C in an inert atmosphere for 2 hours to obtain capacitive carbon.

[0042] The obtained capacitor carbon material was subjected to SEM detection, as shown in FIG. Figure 1 shown.

[0043] Example 2

[0044] Prepare a capacitor carbon, the specific method is as follows:

[0045] Zinc chloride powder and 85wt% phosphoric acid solution were mixed in a molar ratio of 0.4:1, then stirred and heated at 90°C until the solution became clear. Heating and stirring were continued for 12 hours to remove excess water from the raw materials to obtain IDES. 40g of bamboo powder, a biomass raw material, was added to a crucible and mixed with 100mL of IDES. After stirring evenly, the mixture was heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature, filtered, and the solid matter was washed with acid and water to a constant pH. After drying, the activated precursor was obtained. The activated precursor was placed in a crucible, mixed with 5g of KOH, 1g of K2CO3, and 1g of Na2CO3, and carbonized at 800°C under a nitrogen atmosphere for 2 hours to obtain capacitor carbon.

[0046] Example 3

[0047] Prepare a capacitor carbon, the specific method is as follows:

[0048] Tin chloride powder, solid phosphoric acid, and boric acid powder were mixed (heated to melt) in a molar ratio of 0.6:1:0.2, then stirred and heated at 90°C until the solution clarified to obtain IDES. 20g of the biomass raw material bamboo powder was added to a crucible and mixed with 100mL of IDES. After stirring, the mixture was heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solid matter was then washed with acid and water to a constant pH, and dried to obtain an activated precursor. The dried activated precursor was placed in a crucible, mixed with 5g of KOH, 1g of K2CO3, and 1g of Na2CO3, and carbonized at 800°C under a nitrogen atmosphere for 2 hours to obtain capacitive carbon.

[0049] Comparative Example 1

[0050] A carbon material was prepared using biomass as raw material. Unlike Example 1, phosphoric acid was omitted and zinc chloride was used alone. The specific method was as follows: 30 g of the biomass raw material, sawdust, was mixed with 100 g of zinc chloride and reacted at 300°C for 2 h. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solids were then washed with acid and water until the pH was constant, and dried to obtain an activated precursor. The activated precursor was then mixed with 5 g of KOH and 2 g of K2CO3, heated to 800°C in an inert atmosphere, and activated for 2 h to obtain a capacitive carbon.

[0051] Comparative Example 2

[0052] A carbon material is prepared using biomass as raw material. The difference from Example 2 is that zinc chloride powder is not added and only phosphoric acid solution is used. The specific method is as follows: 40g of biomass raw material sawdust is added to a crucible and mixed with 100mL of 85%wt phosphoric acid. After stirring evenly, the mixture is heated at 300°C for 2h. After the reaction is completed, the obtained solid-liquid mixture is cooled to room temperature, filtered, and then the solid matter is washed with acid and water respectively until the pH is constant, and dried to obtain an activated precursor. The activated precursor is placed in a crucible, mixed with 5g KOH, 1g K2CO3 and 1g Na2CO3, and carbonized at 800°C in a nitrogen atmosphere for 2h to obtain capacitor carbon.

[0053] Comparative Example 3

[0054] Boric acid powder and 85wt% phosphoric acid solution are mixed in a molar ratio of 0.2:1, then stirred and heated at 90°C until the solution is clear, and continued to heat and stir for 12h to remove excess water from the raw materials to obtain a precursor solution. 40g of biomass raw material sawdust and 100mL of precursor solution are added to a crucible and mixed. After stirring evenly, the mixture is heated and reacted at 300°C for 2h. After the reaction is completed, the solid-liquid mixture is cooled to room temperature, filtered, and then the solid matter is washed with acid and water respectively until the pH is constant, and dried to obtain an activated precursor. The activated precursor is placed in a crucible, mixed with 5g KOH, 1g K2CO3 and 1g Na2CO3, and carbonized at 800°C in a nitrogen atmosphere for 2h to obtain capacitor carbon.

[0055] Comparative Example 4

[0056] A carbon material was prepared using biomass as raw material. Unlike Example 1, high-temperature activation was not performed. The specific method was as follows: zinc chloride powder and solid phosphoric acid were mixed (heated to melt) at a molar ratio of 0.4:1, then stirred and heated at 90°C until the solution clarified to obtain IDES. 30 g of the biomass raw material, straw powder, and 100 mL of IDES were added to a crucible, mixed, stirred, and then heated at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature, filtered, and the solids were washed with acid and water until the pH was constant. The carbon material was obtained after drying.

[0057] Comparative Example 5

[0058] A carbon material was prepared using biomass as a raw material. This material differs from Example 1 in that IDES was replaced with DES (choline chloride powder and lactic acid). The specific method is as follows: Using DES as a comparison, choline chloride powder and lactic acid were mixed in a 1:1 molar ratio and then heated at 90°C with stirring until the solution clarified. DES was obtained by adding 30g of the biomass raw material straw powder and 100ml of DES to a crucible, stirring evenly, and then heating at 300°C for 2 hours. After the reaction, the resulting solid-liquid mixture was cooled to room temperature and filtered. The solids were then washed with an acidic solution and then with water to a constant pH. The activated precursor was then dried to obtain a solid. The activated precursor was mixed with 5g of KOH and 2g of K2CO3 and heated to 800°C in an inert atmosphere for 2 hours to produce the capacitive carbon.

[0059] Experimental example

[0060] The specific surface area and pore volume of the carbon materials or capacitor carbon materials of Examples 1-3 and Comparative Examples 1-4 were detected by nitrogen adsorption-desorption method, and the specific capacitance was detected by a three-electrode system. Specifically, polyvinylidene fluoride (2 wt% dissolved in N-methylpyrrolidone), acetylene black, and the above-mentioned carbon material or capacitor carbon material were mixed in a ratio of 8:1:1 and evenly coated on graphite paper. The loading amount of the carbon material was 3-5 mg / cm 2 After being fully dried, the sample was used as the working electrode and tested in a 6M KOH solution. Graphite was used as the counter electrode and Hg / HgO was used as the reference electrode. The specific surface area, pore volume, and specific capacitance were calculated. A blank control was also set up. The results are shown in the following table:

[0061] Blank control

[0062] 30g of bamboo powder was mixed with 120g of KOH, heated in a nitrogen environment at 800℃ for 2h, then washed with 1M hydrochloric acid to remove KOH and impurities, and dried to obtain capacitor carbon.

[0063] The experimental results are shown in Table 1:

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from the above table, the specific capacitance of Example 1 is lower than that of Examples 2 and 3, which may be due to the different biomass raw materials. However, in general, the capacitive carbon obtained by pretreatment with IDES as a solvent and then activation has obvious specific surface area and performance improvements compared with the control group.

[0068] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A method for preparing biomass-based high-performance capacitor carbon, characterized in that: The following steps are involved: S1: Mixing a metal halide and an inorganic hydrogen bond donor, heating and stirring until the solution is clear to obtain an inorganic deep eutectic solvent; S2: mixing the inorganic deep eutectic solvent and the biomass raw material for reaction; S3: filtering and washing the material obtained in step S2 to obtain a mesoporous carbon material; S4: adding an activator to the mesoporous carbon material and activating the material in a high-temperature inert gas to obtain the biomass-based high-performance capacitor carbon.

2. The preparation method according to claim 1, wherein: The metal halide includes at least one of zinc chloride, aluminum chloride, tin chloride and lead chloride.

3. The preparation method according to claim 1, wherein: The inorganic hydrogen bond donor includes at least one of phosphoric acid, boric acid, and ammonium chloride.

4. The preparation method according to claim 1, wherein: In step S1, the molar ratio of the metal halide to the inorganic hydrogen bond donor is 1:0.1-10.

5. The preparation method according to claim 1, wherein: In step S2, the biomass raw material is at least one of primary biomass and biomass separation and decomposition products.

6. The preparation method according to claim 1, wherein: In step S2, the solid-liquid ratio of the biomass raw material to the inorganic deep eutectic solvent is 1:1 to 30.

7. The preparation method according to claim 1, wherein: In step S2, the reaction temperature of the mixing reaction is 100-400° C.; the reaction time of the mixing reaction is 0.5-30 h.

8. The preparation method according to claim 1, wherein: In step S4, the activator includes at least one of potassium hydroxide, potassium carbonate or sodium carbonate.

9. The preparation method according to claim 1, wherein: In step S4, the amount of the activator added is 0.1 to 2 times the weight of the biomass raw material; and / or, the temperature of the high-temperature inert gas is 700-900° C.; And / or, the activation time is 0.5 to 30 hours.

10. Capacitor carbon obtained by the preparation method according to any one of claims 1 to 9.

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