A preparation method and device for supercapacitor carbon that improve activation efficiency and yield

Abstract

The present invention discloses a preparation method and device for supercapacitor carbon that improve the activation efficiency and yield. The method comprises the following steps: crushing and sieving raw carbon materials, then mixing them with a binder and rolling them to obtain raw carbon masses; using an activator as the core and the raw carbon masses as the shell to prepare core-shell structured raw carbon balls through a ball-making machine; adjusting the pore structure of the raw carbon balls through high-temperature activation, sequentially washing with water and pickling to remove impurities, and then performing high-temperature deoxidation to obtain supercapacitor carbon samples. The core-shell structured green ball carbon activation method provided by the present invention improves the reaction efficiency, and the yield is twice as high as that of the traditional activation method, reaching more than 70%; secondly, due to the same activation microenvironment of the core-shell structured raw carbon balls, the physical property parameters and electrochemical performance of the activated capacitor carbon are highly uniform; finally, the dosage of the activator is greatly reduced, solving the problem of equipment corrosion by alkaline activators.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing supercapacitor carbon, and particularly relates to a method and device for preparing supercapacitor carbon with improved activation efficiency and yield. Background Art

[0002] As a new type of power energy storage device, supercapacitors are widely used in circuit systems, rail transit, data storage and other fields due to their advantages such as high power density and long cycle life. The Ministry of Industry and Information Technology issued the "Action Plan for the Development of the Basic Electronic Components Industry (2021 - 2023)", focusing on promoting the application of supercapacitors in new energy vehicles and intelligent networked vehicles.

[0003] Supercapacitor carbon, as the core of supercapacitors, is widely used because of its easily available raw materials, adjustable pore structure and surface properties. At present, supercapacitor carbon mainly relies on imports, and there is still a significant gap between domestic supercapacitor carbon and imported products. The main problems are: the poor uniformity and stability of domestic supercapacitor carbon products, and the problems of serious corrosion and low impurity removal efficiency in large-scale preparation equipment. In addition, during large-scale activation, the different activation microenvironments also lead to non-uniform activation degrees of carbon materials, and there are large differences even within the same batch. In the preparation process of supercapacitor carbon, the activator at high temperature forms activation steam to etch the carbon material into a hierarchical porous structure. However, while etching the carbon material with steam, it will also strongly corrode the activation equipment. A large amount of Fe ions are mixed into the carbon material and are difficult to remove, which has a huge impact on the stability of the capacitor. The activation equipment cannot meet the demand for continuous production due to serious corrosion. Therefore, exploring an effective activation method, improving activation efficiency and yield, and reducing the corrosiveness of the activator to the equipment are the key points for large-scale preparation of supercapacitor carbon, and also the goals that the technical personnel in this field have been pursuing.

[0004] Chinese Patent "CN107892298A" discloses a method for activating capacitor carbon. This method is to mix the raw materials with strong alkali, use segmented heating, and introduce water vapor and carbon dioxide for activation at high temperature. However, water vapor will react with potassium vapor to produce microexplosions at high temperature, and the introduction of carbon dioxide will increase the dosage of the activator. In addition, the activation yield is difficult to guarantee. Chinese Patent "CN102849736A" activates capacitor carbon without inert gas protection, aiming to improve the yield of capacitor carbon. However, the alkali-carbon ratio in its activation process is as high as 4:1. The use of a large amount of alkaline activator will corrode the production equipment, and the activation uniformity is not involved. Therefore, how to reduce the dosage of the activator while ensuring uniform activation of carbon materials and reduce the problem of equipment corrosion is a difficult problem that needs to be solved urgently by the researchers in this field. Summary of the Invention

[0005] To solve the drawbacks and deficiencies of the prior art, the primary object of the present invention is to provide a method for preparing supercapacitor carbon with improved activation efficiency and productivity. The present invention adopts a core-shell structured carbon sphere activation method, with activator particles as the core and carbon masses as the shell. Core-shell structured carbon spheres are prepared through a pelletizer. During the high-temperature activation process, activator vapor slowly diffuses radially towards the carbon layer shell. During the diffusion process, the activator vapor fully activates the carbon particles to form pores, improving the reaction efficiency. The productivity is twice that of the traditional activation method, reaching over 70%. In addition, the independence and uniformity of each carbon sphere ensure the consistency of its activation microenvironment, and the physical properties and electrochemical performance of the activated capacitor carbon are highly uniform. Finally, the dosage of the activator is significantly reduced, solving the problem of equipment corrosion by alkaline activators.

[0006] Another object of the present invention is to provide a device for integrally preparing supercapacitor carbon adapted to the above synthesis method.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A method for preparing supercapacitor carbon with improved activation efficiency and productivity, comprising the following steps:

[0009] Step 1: Crush and screen the carbon material, then mix it with a binder and roll it to obtain carbon masses;

[0010] Step 2: Use the activator as the core and the carbon masses as the shell to prepare core-shell structured carbon spheres;

[0011] Step 3: Adjust the pore structure of the carbon spheres through high-temperature activation, wash with water and acid to remove impurities in sequence, and then perform high-temperature deoxidation to obtain supercapacitor carbon samples.

[0012] The present invention prepares core-shell structured carbon spheres, with the activator as the core of the carbon spheres and the carbon material as the shell of the carbon spheres. Activation is carried out in the form of spherical carbon. At high temperature, the activator inside the spherical carbon will turn into activation vapor and diffuse radially towards the carbon layer. During the diffusion process, the activator vapor fully contacts the carbon layer and activates it to form pores.

[0013] Preferably, the carbon material in Step 1 is plant carbon with an ash content of less than 1%, such as coconut shell carbon, etc. The plant carbon can be purchased on the market.

[0014] Preferably, the carbon material in Step 1 is screened through a 200-300 mesh sieve after being crushed.

[0015] Preferably, the binder in Step 1 is at least one of starch, chitosan, and carboxymethyl cellulose.

[0016] Preferably, the binder in Step 1 accounts for 1-2 wt.% of the solid content of the carbon masses, and the carbon material accounts for 98-99 wt.% of the solid content of the carbon masses.

[0017] Preferably, the activator described in step 2 is at least one of KOH, K2CO3, and NaOH.

[0018] The activator is preferably at least one of KOH particles, K2CO3 particles, and NaOH particles.

[0019] Preferably, in step 3, the temperature of high-temperature activation is 750 - 850 °C, the mass ratio of the activator to the raw carbon mass is 1 - 2:1, nitrogen is used as the protective gas, and the gas flow rate is 2 - 5 mL / (cm 2 *min).

[0020] Preferably, in step 3, the pickling liquid is an organic acid with a concentration of 5 - 10 wt.%.

[0021] Preferably, the acid in step 3 is at least one of oxalic acid, acetic acid, and citric acid.

[0022] Preferably, in step 3, the deoxidation temperature is 700 - 800 °C.

[0023] The present invention provides supercapacitor carbon prepared by the above technical solution.

[0024] The present invention provides the use of the supercapacitor carbon prepared by the above technical solution for a supercapacitor, an energy storage device.

[0025] The present invention provides an integrated preparation device used in the above technical solution, including a crushing chamber, a vibrating screening chamber, a ball-making machine, an activation furnace, a washing device, an evaporator, and a drying and reduction chamber; wherein the crushing chamber, the vibrating screening chamber, the ball-making machine, the activation furnace, the washing device, and the drying and reduction chamber are connected in sequence, and both the ball-making machine and the washing device are connected to the evaporator;

[0026] The ball-making machine includes a slurry chamber, an activator storage chamber, and a ball-making chamber. The slurry chamber and the activator storage chamber are both connected to the ball-making chamber, and both the slurry chamber and the activator storage chamber are provided with fan blades; the washing device includes a water washing chamber and an acid pickling chamber; both the water washing chamber and the acid pickling chamber are provided with filter membranes.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The present invention uses ball carbon activation. During the activation process, the activator vapor diffuses radially towards the outer shell carbon layer. During the diffusion process, the activator vapor fully activates and pores the carbon, greatly improving the activation efficiency and yield.

[0029] (2) The present invention uses ball carbon activation. The independence and uniformity of each raw carbon ball ensure the consistency of its activation microenvironment, and the physical property parameters and electrochemical performance of the activated capacitor carbon are highly uniform.

[0030] (3) The present invention uses spherical carbon activation to prepare carbon spheres with a core-shell structure having an activator as the core and a carbon layer as the shell, which can not only reduce the dosage of the activator, but also reduce the contact area between the activator and the inner wall of the activation equipment, effectively inhibiting the corrosion of the strong alkaline activator to the production equipment.

[0031] (4) The present invention uses organic acids to replace inorganic acids for pretreating carbon materials, which can effectively remove magnetic metal ions while avoiding the residue of acid radical anions. At the same time, an electric current is introduced during the impurity removal process to deposit magnetic metal ions at the cathode, effectively reducing the acid dosage.

[0032] (5) The specific surface area of the supercapacitor carbon prepared by the present invention is as high as 1700 - 2293 m 2 / g, and the pore size distribution is 0.5 - 4 nm. After fabricating a self-supporting electrode and assembling a button capacitor, under the condition of a current of 0.5 A / g, the specific capacitance of the device is as high as 52 F / g, and the performance is superior to that of commercial carbon (32 F / g) tested under the same conditions. After 10,000 cycles of long-term charge and discharge, the capacitance retention rate is as high as 98%. Description of the Drawings

[0033] Figure 1 It is the CV curve diagram of the supercapacitor carbon prepared in Example 3.

[0034] Figure 2 It is the galvanostatic charge and discharge curve diagram of the supercapacitor carbon prepared in Example 3 and commercial carbon 1.

[0035] Figure 3 It is the impedance comparison diagram of the supercapacitor carbon prepared in Example 3 and commercial carbon 1.

[0036] Figure 4 It is the long-cycle comparison diagram of the supercapacitor carbon prepared in Example 3 and commercial carbon 1.

[0037] Figure 5 It is the integrated equipment diagram for preparing supercapacitor carbon by the present invention, including a crushing chamber (1), a vibrating screening chamber (2), a slurry chamber (3), an activator storage chamber (4), a fan blade (5), a ball-making chamber (6), an activation furnace (7), a water washing chamber (8), an acid washing chamber (9), a filter membrane (10), an evaporator (11), a drying and reduction chamber (12), and a product tank (13).

[0038] Figure 6 It is the key equipment, the ball-making machine, for preparing supercapacitor carbon by the present invention.

[0039] Figure 7 It is the acid washing tank for preparing supercapacitor carbon by the present invention. Detailed Embodiments

[0040] The present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be directly purchased from the market. For process parameters not specifically noted, conventional techniques can be referred to.

[0041] The integrated preparation device used in the embodiments of the present invention is as Figure 5 shown, and includes a crushing chamber (1), a vibrating screening chamber (2), a ball-making machine, an activation furnace (7), a washing device, an evaporator (11), a drying and reduction chamber (12), and a product tank (13); among them, the crushing chamber (1), the vibrating screening chamber (2), the ball-making machine, the activation furnace (7), the washing device, the drying and reduction chamber (12), and the product tank (13) are connected in sequence;

[0042] The ball-making machine includes a slurry chamber (3), an activator storage chamber (4), and a ball-making chamber (6). The slurry chamber (3) and the activator storage chamber (4) are both connected to the ball-making chamber (6). The slurry chamber (3) is connected to the vibrating screening chamber (2), and the activator storage chamber (4) is connected to the evaporator (11). Blades (5) are provided in both the slurry chamber (3) and the activator storage chamber (4); the washing device includes a water washing chamber (8) and an acid washing chamber (9); filter membranes (10) are provided in both the water washing chamber (8) and the acid washing chamber (9), and the water washing chamber (8) is connected to the evaporator (11).

[0043] Example 1

[0044] A method for preparing supercapacitor carbon for energy storage applications is as Figure 5 shown, and includes the following steps:

[0045] Weigh 1 kg of coconut shell charcoal, crush it in the crushing chamber (1), and separate and screen out particles with a mesh size of 200 - 300 in the vibrating screening chamber (2), and then mix it with chitosan (1 wt.%) in the slurry chamber (3) and roll it into raw carbon pellets.

[0046] Transfer the raw carbon pellets to the ball-making chamber (6), and prepare raw carbon balls with a diameter of about 1 cm with the activator from the activator storage chamber (4) (the raw carbon balls have a core-shell structure, with activator particles as the inner core and raw carbon pellets as the outer shell), and control the mass ratio of NaOH to carbon in the raw carbon balls to be 1:1.

[0047] Transfer the raw carbon balls to the activation furnace (7) for activation, using nitrogen as the protective gas. During the activation process, maintain the gas flow rate in the furnace at 2 mL / (cm 2 *min). After activating at 750 °C for 2 h, first wash the preliminary product in the water washing chamber (8) to remove the excess alkali and conduct recovery treatment, then transfer the carbon to the acid washing chamber (9), remove magnetic metal ions with 5 wt.% oxalic acid. After the acid washing, transfer the carbon to the drying and reduction chamber (12) (vacuum furnace) for degassing and reduction. The reduction temperature is 700 °C. After reduction, seal and store the capacitor carbon.

[0048] Example 2

[0049] Weigh 1 kg of coconut shell charcoal, crush it, screen and select particles with a mesh size of 200 - 300, and then mix it with starch (2 wt.%) and roll it into a raw charcoal mass. Using activator K2CO3 as the core and the raw charcoal mass as the shell, prepare core - shell structured charcoal balls with a diameter of about 1.5 cm through a pelletizing machine; control the mass ratio of K2CO3 to charcoal in the charcoal balls to be 2:1. Activate the charcoal balls at 800 °C for 2 h, using nitrogen as the protective gas, and keep the gas flow rate in the furnace at 5 mL / (cm 2 *min) during the activation process. Then, wash the preliminary product with water first to remove the excess alkali and conduct a recovery treatment, and then wash it with 10 wt.% citric acid to remove magnetic metal ions. After the pickling is completed, transfer the charcoal to a vacuum furnace for degassing and reduction. The reduction temperature is 750 °C, and after reduction, seal and store the capacitive charcoal.

[0050] Example 3

[0051] Weigh 1 kg of coconut shell charcoal, crush it, screen and select particles with a mesh size of 200 - 300, and then mix it with carboxymethyl cellulose (1 wt.%) and roll it into a raw charcoal mass. Using activator KOH as the core and the raw charcoal mass as the shell, prepare core - shell structured charcoal balls with a diameter of about 1 cm through a pelletizing machine; control the mass ratio of KOH to charcoal in the charcoal balls to be 2:1. Activate the charcoal balls at 850 °C for 2 h, using nitrogen as the protective gas, and keep the gas flow rate in the furnace at 2 mL / (cm 2 *min) during the activation process. Then, wash the preliminary product with water first to remove the excess alkali and conduct a recovery treatment, and then wash it with a mixed acid of 5 wt.% acetic acid to remove magnetic metal ions. After the pickling is completed, transfer the charcoal to a vacuum furnace for degassing and reduction. The reduction temperature is 800 °C, and after reduction, seal and store the capacitive charcoal.

[0052] Comparative Example 1

[0053] Take 1 kg of coconut shell charcoal, crush it, screen and select particles with a mesh size of 200 - 300, control the mass ratio of NaOH to charcoal to be 1:1, and grind and mix the charcoal powder with activator NaOH evenly. Without pelletizing, transfer the whole to an activation furnace for activation, using nitrogen as the protective gas, and keep the gas flow rate in the furnace at 2 mL / (cm 2 *min) during the activation process. After activating at 750 °C for 2 h, wash the preliminary product with water first to remove the excess alkali and conduct a recovery treatment, and then wash it with 5 wt.% oxalic acid to remove magnetic metal ions. After the pickling is completed, transfer the charcoal to a vacuum furnace for degassing and reduction. The reduction temperature is 700 °C, and after reduction, seal and store the capacitive charcoal.

[0054] Comparative Example 2

[0055] Take 1 kg of coconut shell charcoal, crush it and screen out particles with a mesh size of 200 - 300. Control the mass ratio of K2CO3 to charcoal to be 2:1, and grind and mix the charcoal powder with the activator K2CO3 evenly. Without pelletizing, transfer the whole mixture to an activation furnace for activation, using nitrogen as the protective gas. During the activation process, maintain the gas flow rate in the furnace at 5 mL / (cm 2 *min). After activating at 800 °C for 2 h, first wash the preliminary product with water to remove the excess alkali and conduct a recovery treatment, then wash it with 10 wt.% citric acid to remove magnetic metal ions. After the pickling is completed, transfer the charcoal to a vacuum furnace for degassing and reduction. The reduction temperature is 750 °C. After reduction, seal and store the capacitor carbon.

[0056] Comparative Example 3

[0057] Take 1 kg of coconut shell charcoal, crush it and screen out particles with a mesh size of 200 - 300. Control the mass ratio of KOH to charcoal to be 2:1, and grind and mix the charcoal powder with the activator KOH evenly. Without pelletizing, transfer the whole mixture to an activation furnace for activation, using nitrogen as the protective gas. During the activation process, maintain the gas flow rate in the furnace at 2 mL / (cm 2 *min). After activating at 850 °C for 2 h, first wash the preliminary product with water to remove the excess alkali and conduct a recovery treatment, then wash it with 5 wt.% acetic acid to remove magnetic metal ions. After the pickling is completed, transfer the charcoal to a vacuum furnace for degassing and reduction. The reduction temperature is 800 °C. After reduction, seal and store the capacitor carbon.

[0058] Performance Test

[0059] Evaluate the electrochemical performance of 1 - 3, Comparative Examples 1 - 3, and commercial supercapacitor carbons 1 and 2. Use the ASAP - 2460 specific surface area and pore size distribution analyzer of American Micro Company to characterize the pore structure of the prepared carbon materials. The pore structure data are shown in Table 1. There is no obvious difference in BET and total pore volume between the supercapacitor carbon prepared by ball - activated carbon in this invention and the supercapacitor carbon prepared by non - pelletized activation. However, the yield of the supercapacitor carbon prepared by pelletized activation is twice that of the supercapacitor carbon prepared by grinding and mixing activation. From the results, it can be seen that pelletized activation can greatly improve the yield without affecting the activation mechanism. Yield calculation formula:

[0060] Yield = M2 / M1 * 100%

[0061] M2 is the weighed mass of the supercapacitor carbon after deoxidation

[0062] M1 is the mass of the raw charcoal material after grinding and sieving

[0063] Table 1 Comparison of specific surface area / pore volume / Fe content and yield of different samples

[0064]

[0065]

[0066] Samples from Example 3 and commercial supercapacitor carbon 1 were selected to fabricate self-supporting electrode sheets for assembling button cells to test their electrochemical performance. A CH Instrument CHI 760E was used to perform cyclic voltammetry tests and impedance tests on the button capacitors, and a Wuhan Blue Electric channel was used to perform constant current charge-discharge tests and long cycle tests on the button capacitors. The test results are as Figures 1-4 shown:

[0067] Figure 1 The CV curve of the supercapacitor carbon prepared in Example 3: The CV test results show a rectangular structure, indicating that the supercapacitor carbon produced by activating spherical carbon with a core-shell structure has obvious electric double layer behavior.

[0068] Figure 2 The constant current charge-discharge curves of the supercapacitor carbon prepared in Example 3 and commercial carbon 1: The GCD test results show an isosceles triangle shape, indicating that no redox reaction occurs during the charge-discharge process, further verifying electric double layer energy storage; and under the same test conditions (current density of 0.25 A / g), the discharge time of Example 3 is longer than that of commercial carbon 1, indicating that the specific mass capacitance of Example 3 is larger than that of commercial carbon 1.

[0069] Figure 3 The impedance comparison chart of the supercapacitor carbon prepared in Example 3 and commercial carbon 1: In the EIS test, the charge transfer impedance of Example 3 is larger than that of commercial carbon 1, indicating a smaller self-discharge effect, and the curve slope is very large in the low-frequency region, indicating that the diffusion resistance of electrolyte ions in the supercapacitor carbon is very small.

[0070] Figure 4 The long cycle comparison chart of the supercapacitor carbon prepared in Example 3 and commercial carbon 1: In the long cycle test comparison, the capacitance retention rate of Example 3 after 10,000 cycles (current density of 0.25 A / g) is 98%, which is greater than 95% of commercial carbon 1, indicating that the supercapacitor carbon prepared in Example 3 has better cycle stability.

[0071] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing supercapacitor carbon with improved activation efficiency and yield, characterized in that, It includes the following steps: Step 1: Crush and screen the raw carbon material, and then mix it with a binder and roll it to obtain raw carbon pellets; Step 2: Use the activator as the core and the raw carbon pellets as the shell to prepare core-shell structured raw carbon spheres; Step 3: Adjust the pore structure of the raw carbon spheres by high-temperature activation, wash with water and pickle to remove impurities in sequence, and then perform high-temperature deoxidation to obtain supercapacitor carbon samples; In Step 3, the temperature of the high-temperature activation is 750 - 850 °C, and the mass ratio of the activator to the raw carbon pellets is 1 - 2:1; the pickling liquid is an organic acid with a concentration of 5 - 10 wt.%, and the organic acid is at least one of oxalic acid, acetic acid, and citric acid.

2. The preparation method of supercapacitor carbon for improving the activation efficiency and yield according to claim 1, characterized in that, The raw carbon material described in Step 1 is plant carbon with an ash content of less than 1%; In Step 1, the crushed raw carbon material is screened through a 200 - 300 mesh sieve.

3. The preparation method of supercapacitor carbon for improving the activation efficiency and yield according to claim 1, characterized in that, The binder in Step 1 is at least one of starch, chitosan, and carboxymethyl cellulose; The binder in Step 1 accounts for 1 - 2 wt.% of the solid content of the raw carbon pellets, and the raw carbon material accounts for 98 - 99 wt.% of the solid content of the raw carbon pellets.

4. A method for preparing supercapacitor carbon with improved activation efficiency and yield according to claim 1, characterized in that The activator described in Step 2 is at least one of KOH, K2CO3, and NaOH.

5. The preparation method of supercapacitor carbon for improving activation efficiency and yield according to claim 1, characterized in that, In step 3, nitrogen is used as the protective gas, and the gas flow rate is 2 - 5 mL / (cm 2 *min).

6. The preparation method of supercapacitor carbon for improving the activation efficiency and yield according to claim 1, characterized in that, The deoxidation temperature in Step 3 is 700 - 800 °C.

7. A supercapacitor carbon prepared by the method according to any one of claims 1 - 6.

Images