A method for deeply purifying activated carbon electrode materials for supercapacitors

Abstract

The present invention relates to the field of supercapacitor electrode materials, and discloses a method for deeply purifying activated carbon electrode materials for supercapacitors. The steps are as follows: preparing an acid solution containing NH4Cl; injecting the acid solution into an electrolytic cell, applying a voltage and passing an electric current for electrochemical assisted cleaning; the electrolytic cell includes a housing, a filter bag arranged inside the housing, and graphite electrodes arranged in the filter bag; activated carbon particles are filled between the filter bag and the graphite electrodes; the housing includes a stainless steel outer layer and a powder sintered metal layer arranged inside the stainless steel outer layer; the acid solution fills the gaps between the activated carbon particles and between the filter bag and the housing; taking out the activated carbon particles from the electrolytic cell, washing them to neutrality, and obtaining the deeply purified activated carbon electrode materials after drying and pulverization. The present invention adopts the electrochemical assisted cleaning method, which has a simple process, short cleaning time, simple equipment structure and high impurity removal rate.

Description

Technical Field

[0001] The present invention relates to the technical field of supercapacitor electrode materials, and particularly to a method for deeply purifying activated carbon electrode materials for supercapacitors. Background Art

[0002] Activated carbon electrode materials for supercapacitors need to have characteristics such as ultra-low metal impurity content, a small amount of surface functional groups, a high specific surface area (>1500 m 2 / g), and a porous structure (0.1 - 50 nm). Metal impurities in activated carbon not only increase the leakage current and equivalent resistance of the device, but also catalyze and initiate side reactions such as electrolyte decomposition, shortening the service life of supercapacitors.

[0003] In the prior art, the common methods for removing metal impurities in activated carbon for supercapacitors are dilute acid impregnation and gas-phase reaction. Dilute acid (such as dilute hydrochloric acid, dilute nitric acid, etc.) impregnation usually combines means such as bubbling, pressurization, and adding chelating agents to promote the penetration, diffusion of the cleaning solution into the porous structure, and the reaction and dissolution of impurities to improve the cleaning effect. For example, a method for preparing activated carbon for electrochemical energy storage devices disclosed in Patent CN103539119B. Since aqueous solutions are difficult to effectively penetrate, diffuse, wet micropores, fine tubes, complex irregular surfaces, high aspect ratio structures, and hydrophobic substrates, the cleaning process is long and repeated, and impurities inside the pore cavities are difficult to effectively remove, resulting in an unsatisfactory deep purification effect.

[0004] Gas-phase reactions usually use gases (such as Cl2-containing gases) for high-temperature treatment, which can quickly diffuse and fully contact with difficult-to-wet surfaces and pore structures, and remove some impurities by converting them into volatile compounds. However, since not all impurities can be converted into volatile compounds, the types of impurities that can be removed by gas-phase reactions are limited. Summary of the Invention

[0005] The present invention is to overcome the above problems existing in the activated carbon purification methods in the prior art, and provides a method for deeply purifying activated carbon electrode materials for supercapacitors. The method adopts an electrochemically assisted cleaning method, which has a simple process, short cleaning time, a simple equipment structure, and a high impurity removal rate.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for deeply purifying activated carbon electrode materials for supercapacitors, comprising the following steps:

[0008] (1) Prepare an acid solution containing NH4Cl;

[0009] (2) Inject the acid solution into the electrolytic cell, apply a voltage and pass an electric current for electrochemically assisted cleaning; the electrolytic cell includes a housing, a filter bag disposed within the housing, and a graphite electrode disposed within the filter bag; activated carbon particles are filled between the filter bag and the graphite electrode; the housing includes a stainless steel outer layer and a powder sintered metal layer disposed within the stainless steel outer layer; the acid solution fills the gaps between the activated carbon particles and between the filter bag and the housing.

[0010] (3) Take out the activated carbon particles from the electrolytic cell, wash them until neutral, dry and crush them to obtain a deeply purified activated carbon electrode material.

[0011] The present invention places activated carbon in an electrolytic cell and uses an electrochemically assisted cleaning method to deeply purify the activated carbon. In the electrolytic cell of the present invention, the positive electrode is the activated carbon particles, the negative electrode is the housing, and the filter bag plays a role similar to that of a diaphragm, wrapping the activated carbon and the graphite rod inside and isolating the positive and negative electrodes. The graphite electrode is similar to a current collector and plays a role in conducting electricity. The present invention uses a graphite electrode as the current collector, which has excellent electrical conductivity, is resistant to hydrochloric acid corrosion, is stable within the water decomposition voltage, and compared with general metal materials, even if it participates in the reaction, it will not introduce other metal ions. At the same time, the present invention provides a powder sintered metal layer as a lining inside the housing, and the powder sintered metal layer can increase the specific surface area of the inner wall of the housing, increase the over-current area, and enable the housing to better adsorb metal impurity cations.

[0012] The present invention adopts an electrochemically assisted cleaning method, which can promote the diffusion of the acid solution into the micropores and mesopores of the activated carbon and the migration of soluble impurity metal reactants; at the same time, NH4Cl is added to the acid solution in the present invention, and NH4 + can promote the displacement with metal impurity cations, and enable the cations to migrate and adsorb to the negative electrode metal powder sintered layer. Therefore, the purification method of the present invention has a simple process, a short cleaning time, a simple equipment structure and a high impurity removal rate.

[0013] Preferably, the mass concentration of NH4Cl in the acid solution in step (1) is 0.5 - 6.0%.

[0014] Preferably, the pH value of the acid solution in step (1) ≤ 3.

[0015] Preferably, the acid solution in step (1) is one of hydrochloric acid solution, sulfuric acid solution, acetic acid solution, formic acid solution, organic phosphonic acid solution, and citric acid solution.

[0016] Preferably, when injecting the acid solution in step (2), first inject the acid solution into the activated carbon particles and fully soak for 10 - 600 s, and then add the acid solution again until the gap between the filter bag and the outer shell is filled. Injecting part of the acid solution into the activated carbon particles for full soaking first and then adding the acid solution to the gap between the positive and negative electrodes is beneficial to reducing the pore bubbles between the activated carbon particles, thereby improving the purification effect.

[0017] Preferably, the voltage applied in step (2) ≤ 1.5 V, the current passed is between 20 μA and 1 A, and the time for electrochemically assisted cleaning is 1 - 1200 s.

[0018] Preferably, the filter bag material in the electrolytic cell is one of ZrO2, PTFE filter bag, PP filter bag, PE filter bag, and AGM. The filter bag in the present invention has good chemical and structural stability, good mechanical strength, a relatively high porosity and a uniform pore size distribution, which is beneficial to the free shuttle of ions, thereby being beneficial to improving the removal effect of impurities.

[0019] Preferably, the powder sintered metal layer in the outer shell of the electrolytic cell is one of a stainless steel layer, a nickel layer, and a Hastelloy layer.

[0020] Preferably, the top of the outer shell of the electrolytic cell is provided with a top cover, and the graphite electrode is connected to the top cover; a liquid injection port is provided on the top cover.

[0021] Preferably, in step (3), a vacuum drying method is adopted, the drying temperature is 90 - 150 °C, and the drying time is 2 - 8 h.

[0022] Therefore, the present invention has the following beneficial effects:

[0023] (1) By adopting the electrochemically assisted cleaning method, it can promote the diffusion of the acid cleaning solution deep into the micropores and mesopores of the activated carbon and the migration of soluble impurity metal reactants;

[0024] (2) Utilize NH4 + to promote the displacement with metal impurity cations, so that the cations migrate and adsorb to the negative electrode metal powder sintered layer, which is beneficial to further improving the removal rate of impurities;

[0025] (3) The purification method of the present invention has a simple process, short cleaning time, a simple equipment structure and a high impurity removal rate. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of the electrolytic cell of the present invention.

[0027] In the figure: 1 - outer shell, 2 - filter bag, 3 - graphite electrode, 4 - activated carbon particles, 5 - top cover. Detailed Embodiments

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art.

[0030] Overall embodiment:

[0031] A method for deep purification of activated carbon electrode materials for supercapacitors comprises the following steps:

[0032] (1) Prepare an acid solution containing NH4Cl;

[0033] (2) Injecting the acid solution into the electrolytic cell, applying voltage and passing current to perform electrochemical assisted cleaning; Figure 1 As shown in the figure, the electrolytic cell comprises a shell 1, a filter bag 2 arranged in the shell and a graphite electrode 3 arranged in the filter bag; activated carbon particles 4 are filled between the filter bag and the graphite electrode; a top cover 5 is provided on the top of the shell, the graphite electrode is connected to the top cover, and a liquid injection port is provided on the top cover; the shell comprises a stainless steel outer layer and a powder sintered metal layer arranged in the stainless steel outer layer; the acid solution fills the gaps between the activated carbon particles and between the filter bag and the shell;

[0034] (3) The activated carbon particles are removed from the electrolytic cell and washed to neutrality, dried, and then crushed to obtain deeply purified activated carbon electrode materials.

[0035] As a specific implementation, the mass concentration of NH4Cl in the acid solution of step (1) is 0.5~6.0%.

[0036] As a specific implementation, the pH value of the acid solution in step (1) is ≤3.

[0037] As a specific implementation, the acid solution in step (1) is one of hydrochloric acid solution, sulfuric acid solution, acetic acid solution, formic acid solution, organic phosphonic acid solution, and citric acid solution.

[0038] As a specific implementation method, when injecting the acid solution in step (2), the acid solution is first injected into the activated carbon particles, fully infiltrated for 10 to 600 seconds, and then the acid solution is added again to fill the gap between the filter bag and the shell.

[0039] As a specific implementation method, the voltage applied in step (2) is ≤1.5V, the current applied is between 20μA and 1A, and the time of electrochemical assisted cleaning is 1 to 1200s.

[0040] As a specific implementation, the filter bag material in the electrolytic cell is one of ZrO2, PTFE filter bag, PP filter bag, PE filter bag, and AGM.

[0041] As a specific implementation, the powder sintered metal layer in the outer shell of the electrolytic cell is one of a stainless steel layer, a nickel layer, and a Hastelloy layer.

[0042] Preferably, in step (3), a vacuum drying method is adopted, the drying temperature is 90 - 150 °C, and the drying time is 2 - 8 h.

[0043] Example 1:

[0044] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0045] (1) Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 0.5% and a pH value of 3;

[0046] (2) Fill the activated carbon particles to be treated (D50 ≤ 10 μm, D90 ≤ 20 μm, impurity content: Fe: 513 ppm; K: 2320 ppm; Na: 606 ppm; Mg: 139 ppm; Ca: 1209 ppm; Al: 337 ppm) between the filter bag and the graphite electrode of the electrolytic cell, then first inject the hydrochloric acid solution into the activated carbon particles, fully soak for 300 s, and then add the hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled; the outer shell in the electrolytic cell has a diameter of 150 mm and a height of 200 mm; the outer layer is stainless steel with a thickness of 4 mm, and the inner lining is a Hastelloy powder sintered layer with a thickness of 4 mm; the filter bag uses a ZrO2 powder sintered filter element with a thickness of 1 mm, the filter bag has a diameter of 100 mm and a height of 150 mm; the graphite electrode has a diameter of 10 mm and a height of 140 mm; the filling amount of the activated carbon particles is 60% of the volume of the filter bag;

[0047] (3) Apply a voltage of 1.5 V between the positive and negative electrodes of the electrolytic cell, and pass a current of 100 μA for electrochemical assisted cleaning; the cleaning time is 800 s;

[0048] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral;

[0049] (5) Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0050] Example 2:

[0051] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0052] (1) Prepare an acetic acid solution with a mass concentration of NH4Cl of 0.5% and a pH value of 3;

[0053] (2) Fill the activated carbon particles to be processed (D50≤10 μm, D90≤20 μm, impurity content: Fe: 513 ppm; K: 2320 ppm; Na: 606 ppm; Mg: 139 ppm; Ca: 1209 ppm; Al: 337 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject acetic acid solution into the activated carbon particles and soak them fully for 300 s. Then add acetic acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 150 mm and a height of 200 mm. The outer layer is made of stainless steel with a thickness of 6 mm, and the inner lining is a sintered Hastelloy powder layer with a thickness of 2 mm. The filter bag is a PTFE filter bag with a thickness of 1.5 mm, a diameter of 110 mm, and a height of 150 mm. The graphite electrode has a diameter of 11 mm and a height of 160 mm. The filling amount of the activated carbon particles is 80% of the volume of the filter bag.

[0054] (3) Apply a voltage of 1.2 V between the positive and negative electrodes of the electrolytic cell and pass a current of 1 mA for electrochemical assisted cleaning. The cleaning time is 200 s.

[0055] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral.

[0056] (5) Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0057] Example 3:

[0058] A method for deeply purifying an activated carbon electrode material for supercapacitors, the steps are as follows:

[0059] (1) Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 1.0% and a pH value of 2.

[0060] (2) Fill the activated carbon particles to be processed (D50≤8μm, D90≤15 μm, impurity content: Fe: 192 ppm; K: 2923 ppm; Na: 846 ppm; Mg: 68 ppm; Ca: 469 ppm; Al: 184 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject the hydrochloric acid solution into the activated carbon particles and soak them fully for 500 s. Then add the hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 200 mm and a height of 230 mm. The outer layer is made of stainless steel with a thickness of 5 mm, and the inner lining is a sintered stainless steel metal powder layer with a thickness of 3 mm. The filter bag is a ZrO2 powder sintered filter element with a thickness of 2 mm, a diameter of 150 mm, and a height of 180 mm. The graphite electrode has a diameter of 13 mm and a height of 200 mm. The filling amount of the activated carbon particles is 80% of the volume of the filter bag.

[0061] (3) Apply a voltage of 1.5 V between the positive and negative electrodes of the electrolytic cell, and pass a current of 100 μA for electrochemical-assisted cleaning; the cleaning time is 800 s;

[0062] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral;

[0063] (5) Vacuum-dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0064] Example 4:

[0065] A method for deeply purifying an activated carbon electrode material for supercapacitors, the steps are as follows:

[0066] (1) Prepare a formic acid solution with a mass concentration of NH4Cl of 1.0% and a pH value of 3;

[0067] (2) Fill the activated carbon particles to be treated (D50 ≤ 8 μm, D90 ≤ 15 μm, impurity content: Fe: 192 ppm; K: 2923 ppm; Na: 846 ppm; Mg: 68 ppm; Ca: 469 ppm; Al: 184 ppm) between the filter bag and the graphite electrode of the electrolytic cell, then first inject the formic acid solution into the activated carbon particles and soak them fully for 500 s, and then add the formic acid solution again until the gap between the filter bag and the outer shell is filled; the outer shell diameter of the electrolytic cell is 200 mm and the height is 230 mm; the outer layer is made of stainless steel with a thickness of 7 mm, and the inner lining is a stainless steel metal powder sintered layer with a thickness of 1 mm; the filter bag is a PP filter bag with a thickness of 2 mm, the filter bag diameter is 150 mm, and the height is 180 mm; the graphite electrode diameter is 13 mm and the height is 200 mm; the filling amount of the activated carbon particles is 30% of the filter bag volume;

[0068] (3) Apply a voltage of 1.2 V between the positive and negative electrodes of the electrolytic cell, and pass a current of 1 mA for electrochemical-assisted cleaning; the cleaning time is 200 s;

[0069] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral;

[0070] (5) Vacuum-dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0071] Example 5:

[0072] A method for deeply purifying an activated carbon electrode material for supercapacitors, the steps are as follows:

[0073] (1)Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 2.0% and a pH value of 3;

[0074] (2)Fill the activated carbon particles to be treated (D50 ≤ 6 μm, D90 ≤ 11 μm, impurity content: Fe: 99 ppm; K: 3154 ppm; Na: 915 ppm; Mg: 111 ppm; Ca: 376 ppm; Al: 115 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject the hydrochloric acid solution into the activated carbon particles and soak them fully for 600 s. Then, add the hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 600 mm and a height of 680 mm. The outer layer is made of stainless steel with a thickness of 2 mm, and the inner lining is a sintered layer of nickel metal powder with a thickness of 6 mm. The filter bag is made of a PE filter bag with a thickness of 0.5 mm, a diameter of 500 mm, and a height of 600 mm. The graphite electrode has a diameter of 100 mm and a height of 600 mm. The filling amount of the activated carbon particles is 100% of the volume of the filter bag;

[0075] (3)Apply a voltage of 1.4 V between the positive and negative electrodes of the electrolytic cell and pass a current of 50 μA for electrochemical assisted cleaning; the cleaning time is 1000 s;

[0076] (4)Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral;

[0077] (5)Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0078] Example 6:

[0079] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0080] (1)Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 6.0% and a pH value of 1;

[0081] (2) Fill the activated carbon particles to be processed (D50≤6μm, D90≤11 μm, impurity content: Fe: 99 ppm; K: 3154 ppm; Na: 915 ppm; Mg: 111 ppm; Ca: 376 ppm; Al: 115 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject the hydrochloric acid solution into the activated carbon particles and soak them fully for 600 s. Then add the hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 500 mm and a height of 600 mm. The outer layer is made of stainless steel with a thickness of 6 mm, and the inner lining is a sintered layer of nickel metal powder with a thickness of 2 mm. The filter bag uses an AGM filter bag with a thickness of 5 mm, a diameter of 300 mm, and a height of 300 mm. The graphite electrode has a diameter of 80 mm and a height of 400 mm. The filling amount of the activated carbon particles is 20% of the volume of the filter bag.

[0082] (3) Apply a voltage of 1.0 V between the positive and negative electrodes of the electrolytic cell and pass a current of 50 μA for electrochemical assisted cleaning. The cleaning time is 1200 s.

[0083] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral.

[0084] (5) Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0085] Comparative Example 1 (without electrochemical assistance):

[0086] A method for purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0087] (1) Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 1.0% and a pH value of 3.

[0088] (2) Fill the activated carbon particles to be processed (D50≤10 μm, D90≤20 μm, impurity content: Fe: 513 ppm; K: 2320 ppm; Na: 606 ppm; Mg: 139 ppm; Ca: 1209 ppm; Al: 337 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject the hydrochloric acid solution into the activated carbon particles and soak them fully for 300 s. Then add the acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 150 mm and a height of 200 mm. The outer layer is made of stainless steel with a thickness of 4 mm, and the inner lining is a sintered layer of Hastelloy powder with a thickness of 4 mm. The filter bag uses a ZrO2 powder sintered filter element with a thickness of 1 mm, a diameter of 100 mm, and a height of 150 mm. The graphite electrode has a diameter of 10 mm and a height of 140 mm. The filling amount of the activated carbon particles is 60% of the volume of the filter bag.

[0089] (3) After 5 h, the activated carbon particles are taken out from the filter bag and washed with deionized water until neutral.

[0090] (4)The washed activated carbon particles are vacuum dried at 100 °C for 8 h and then crushed to obtain the deeply purified activated carbon electrode material.

[0091] Comparative Example 2 (without adding NH4Cl):

[0092] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0093] (1)Prepare a hydrochloric acid solution with a concentration of 0.001 mol / L and a pH value of 3.

[0094] (2)The activated carbon particles to be treated (D50≤10 μm, D90≤20 μm, impurity content: Fe: 513 ppm; K: 2320 ppm; Na: 606 ppm; Mg: 139 ppm; Ca: 1209 ppm; Al: 337 ppm) are filled between the filter bag and the graphite electrode of the electrolytic cell. Then, the hydrochloric acid solution is first injected into the activated carbon particles and fully infiltrated for 300 s. Then, the hydrochloric acid solution is added again until the gap between the filter bag and the outer shell is filled; the outer shell diameter of the electrolytic cell is 150 mm and the height is 200 mm; the outer layer is made of stainless steel with a thickness of 4 mm, and the inner lining is a Hastelloy powder sintered layer with a thickness of 4 mm; the filter bag uses a ZrO2 powder sintered filter element with a thickness of 1 mm, the filter bag diameter is 100 mm, and the height is 150 mm; the graphite electrode diameter is 10 mm and the height is 140 mm; the filling amount of the activated carbon particles is 60% of the filter bag volume;

[0095] (3)Apply a voltage of 1.5 V between the positive and negative electrodes of the electrolytic cell and pass a current of 100 μA for electrochemical assisted cleaning; the cleaning time is 800 s;

[0096] (4)The activated carbon particles are taken out from the filter bag and washed with deionized water until neutral.

[0097] (5)The washed activated carbon particles are vacuum dried at 100 °C for 8 h and then crushed to obtain the deeply purified activated carbon electrode material.

[0098] Comparative Example 3 (excessive NH4Cl added):

[0099] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0100] (1)Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 10.0% and a pH value of 1.

[0101] (2) Fill the activated carbon particles to be processed (D50≤6μm, D90≤11 μm, impurity content: Fe: 99 ppm; K: 3154 ppm; Na: 915 ppm; Mg: 111 ppm; Ca: 376 ppm; Al: 115 ppm) between the filter bag and the graphite electrode in the electrolytic cell. Then, first inject the hydrochloric acid solution into the activated carbon particles and soak them fully for 600 s. Then add the hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 150 mm and a height of 200 mm. The outer layer is made of stainless steel with a thickness of 4 mm, and the inner lining is a sintered nickel metal powder layer with a thickness of 4 mm. The filter bag is an AGM filter bag with a thickness of 5 mm, a diameter of 300 mm, and a height of 300 mm. The graphite electrode has a diameter of 80 mm and a height of 400 mm. The filling amount of the activated carbon particles is 20% of the volume of the filter bag.

[0102] (3) Apply a voltage of 1.0 V between the positive and negative electrodes of the electrolytic cell and pass a current of 50 μA for electrochemical assisted cleaning. The cleaning time is 1200 s.

[0103] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral.

[0104] (5) Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain the deeply purified activated carbon electrode material.

[0105] Comparative Example 4 (using a metal electrode instead of a graphite electrode):

[0106] The difference between Comparative Example 3 and Example 6 is that a platinum electrode is used instead of the graphite electrode in Example 6, and the rest are the same as in Example 6.

[0107] Comparative Example 5 (without an inner lining in the outer shell):

[0108] The difference between Comparative Example 4 and Example 6 is that there is no sintered stainless steel powder layer in the outer shell, and the rest are the same as in Example 6.

[0109] Comparative Example 6 (not soaking the activated carbon with the acid solution first):

[0110] A method for deeply purifying an activated carbon electrode material for a supercapacitor, the steps are as follows:

[0111] (1) Prepare a hydrochloric acid solution with a mass concentration of NH4Cl of 6.0% and a pH value of 1.

[0112] (2) Fill the activated carbon particles to be processed (D50 ≤ 6 μm, D90 ≤ 11 μm, impurity content: Fe: 99 ppm; K: 3154 ppm; Na: 915 ppm; Mg: 111 ppm; Ca: 376 ppm; Al: 115 ppm) between the filter bag and the graphite electrode of the electrolytic cell. Then, first inject hydrochloric acid solution into the activated carbon particles, and then add hydrochloric acid solution again until the gap between the filter bag and the outer shell is filled. The outer shell in the electrolytic cell has a diameter of 500 mm and a height of 600 mm. The outer layer is made of stainless steel with a thickness of 2 mm, and the inner lining is a sintered nickel metal powder layer with a thickness of 3 mm. The filter bag uses an AGM filter bag with a thickness of 5 mm, a diameter of 300 mm, and a height of 300 mm. The graphite electrode has a diameter of 80 mm and a height of 400 mm. The filling amount of the activated carbon particles is 20% of the volume of the filter bag.

[0113] (3) Apply a voltage of 1.0 V between the positive and negative electrodes of the electrolytic cell, and pass a current of 50 μA for electrochemical assisted cleaning. The cleaning time is 1200 s.

[0114] (4) Take out the activated carbon particles from the filter bag and wash them with deionized water until neutral.

[0115] (5) Vacuum dry the washed activated carbon particles at 100 °C for 8 h and then crush them to obtain a deeply purified activated carbon electrode material.

[0116] Test the impurity content in the purified activated carbon in the above examples and comparative examples, and the results are shown in Table 1.

[0117] Table 1: Purification conditions and test results of impurity content

[0118]

[0119] As can be seen from Table 1, the method of the present invention can effectively remove impurities in activated carbon in Examples 1-6, and the purified activated carbon meets the usage requirements of electrode materials in supercapacitors.

[0120] In Comparative Example 1, electrochemical assisted cleaning is not used, and only pickling is carried out. The impurity content in the purified activated carbon is significantly increased compared with that in the examples, and it cannot meet the usage requirements in supercapacitors.

[0121] In Comparative Example 2, NH4 is not added to the acid solution + , which is not conducive to promoting the displacement with metal impurity cations, and the cations cannot effectively migrate and adsorb to the negative electrode sintered nickel metal powder layer. The impurity content in the treated activated carbon is also increased compared with that in the examples.

[0122] In Comparative Example 3, the added NH4 +Excessive amounts will cause the temperature to rise too quickly, generate bubbles, affect the uniformity and integrity of the reaction, and thus affect the reaction effect and product purity.

[0123] In Comparative Example 4, a metal electrode was used instead of the graphite electrode in the present invention. It will participate in the reaction during the cleaning process, thus introducing new metal impurities into the activated carbon, not meeting the impurity removal requirements. Moreover, the removal effect of platinum electrodes on other metal impurities is also significantly reduced compared with that of graphite electrodes.

[0124] In the electrolytic cell housing of Comparative Example 5, a powder-sintered metal layer is not provided. The specific surface area of the inner wall of the housing decreases, the current-carrying area decreases, and it is difficult for the housing to effectively adsorb metal impurity cations. The impurity removal effect is also reduced compared with that in the examples.

[0125] In Comparative Example 6, the activated carbon particles were not infiltrated with an acid solution first. The number of pore bubbles between the activated carbon particles increased, and the impurity content after purification increased compared with that in the examples.

[0126] The above content is a further detailed description of the technical solution of the present invention in combination with specific preferred embodiments. It should not be construed as a limitation on the scope of the present invention that can be implemented. For those of ordinary skill in the art to which the present invention pertains, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the scope of patent protection determined by the claims submitted for the present invention.

Claims

1. A method for preparing an activated carbon electrode material for a deep purification supercapacitor, characterized in that It includes the following steps: (1) Prepare an acidic solution containing NH4Cl; (2) Inject the acidic solution into an electrolytic cell, apply a voltage and pass an electric current for electrochemically assisted cleaning; the electrolytic cell includes a housing, a filter bag disposed inside the housing, and a graphite electrode disposed in the filter bag; Activated carbon particles are filled between the filter bag and the graphite electrode; the housing includes a stainless steel outer layer and a powder sintered metal layer disposed inside the stainless steel outer layer; the acidic solution fills the gaps between the activated carbon particles and between the filter bag and the housing; (3) Take out the activated carbon particles from the electrolytic cell, wash them until neutral, dry and crush them to obtain a deeply purified activated carbon electrode material.

2. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, characterized in that, The mass concentration of NH4Cl in the acidic solution in step (1) is 0.5 - 6.0%.

3. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1 or 2, characterized in that, The pH value of the acidic solution in step (1) ≤ 3.

4. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 3, characterized in that, The acidic solution in step (1) is one of hydrochloric acid solution, sulfuric acid solution, acetic acid solution, formic acid solution, organic phosphonic acid solution, citric acid solution.

5. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, wherein When injecting the acidic solution in step (2), first inject the acidic solution into the activated carbon particles, fully soak for 10 - 600 s, and then add the acidic solution again until the gap between the filter bag and the housing is filled.

6. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, characterized in that, The voltage applied in step (2) ≤ 1.5 V, the current passed is between 20 μA and 1 A, and the time for electrochemically assisted cleaning is 1 - 1200 s.

7. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, characterized in that, The filter bag material in the electrolytic cell is one of ZrO2, PTFE filter bag, PP filter bag, PE filter bag, AGM.

8. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, characterized in that, The powder sintered metal layer in the housing of the electrolytic cell is one of stainless steel layer, nickel layer, Hastelloy layer.

9. The method for preparing the activated carbon electrode material for deep purification supercapacitor according to claim 1, characterized in that, The top of the housing of the electrolytic cell is provided with a top cover, the graphite electrode is connected to the top cover; a liquid injection port is provided on the top cover.

10. The method for preparing an activated carbon electrode material for a deep purification supercapacitor according to claim 1, characterized in that, In step (3), a vacuum drying method is adopted, the drying temperature is 90 - 150 °C, and the drying time is 2 - 8 h.

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