Method for preparing activated carbon material for supercapacitor

Abstract

To provide an activated carbon material for a supercapacitor.SOLUTION: Performing a first heat treatment under a pressure of 2atm to 3atm at 480 °C to 580 °C for more than 4 hours to obtain a soft carbon precursor having a quinoline-insoluble content of 78wt% to 98wt%, a toluene-insoluble content of 88wt% to 100wt%, and a mesophase structure content of more than 50vol%, mixing the soft carbon precursor with an active agent to obtain a mixture, performing a second heat treatment on the mixture to perform activation and carbonization reactions to obtain a composition containing activated carbon and residual active agent, removing the residual active agent in the composition to obtain an intermediate activated carbon material, and grinding and screening the intermediate activated carbon material and performing a third heat treatment to obtain an activated carbon material for a supercapacitor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing carbon materials, and more particularly to a method for producing activated carbon materials for supercapacitors. [Background technology]

[0002] Supercapacitors, also known as electric double-layer capacitors, are widely known in the industry as electrochemical capacitors with high energy density, and their capacity and performance lie between those of conventional electrolytic capacitors and storage batteries.

[0003] In addition, supercapacitors have become a key component in power supply systems due to their fast charging and discharging speed and long cycle life.

[0004] Currently, the most commonly used electrode material for supercapacitors is carbon, which can be produced by subjecting cheap heavy hydrocarbon oils sold at refineries to multiple manufacturing processes, thereby increasing the economic value of cheap heavy hydrocarbon oils.

[0005] Patent Document 1 discloses a method for producing coal pitch-based activated carbon including steps a to e in order.

[0006] In step a, the coal pitch is placed in a high-temperature oxidation furnace, and air is introduced from the bottom of the high-temperature oxidation furnace to oxidize the coal pitch for 2 to 5 hours to obtain an oxidized material.

[0007] In step b, the oxidized material is crushed, and then the oxidized material particles are selected using a sieve of 4 to 30 mesh.

[0008] In step c, the oxidized material particles are placed in a rotary carbonization furnace, and water vapor is introduced into the rotary carbonization furnace to carry out a carbonization reaction at 100°C to 450°C, thereby obtaining a carbonized material with a certain degree of strength.

[0009] In step d, the carbonized material is activated using a physical activation method. Specifically, the carbonized material is placed in a rotary activation furnace set at 650 to 800°C, and activation is performed for 1 to 5 hours while introducing an activation gas and controlling the oxygen concentration in the rotary activation furnace to 5 vol% or less, to obtain an activated material with a microporous structure.

[0010] In step e, the active material is crushed and sieved or ground and sieved to obtain granular or powdered activated charcoal.

[0011] The physical activation method used in Patent Document 1 can produce activated carbon for use as an electrode material in supercapacitors. However, because the physical activation method is used to activate the carbonized material, the resulting granular activated carbon has a specific surface area (hereinafter referred to as "BET") of only 971 m. 2 / g and the total pore volume is only 0.65 cm 3 / g, and powdered activated carbon has a BET of only 958m 2 / g, and the total pore volume is only 0.66 cm 3 / g.

[0012] Therefore, there is no significant contribution in terms of improving the specific capacity of the supercapacitor. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Chinese Patent Application Publication No. 117342554 Summary of the Invention [Problem to be solved by the invention]

[0014] In view of the above prior art, the development of a manufacturing method for activated carbon material that can increase the BET and total pore volume of the activated carbon material and improve the specific capacitance of supercapacitors is an issue in the related technical field.

[0015] The objective of the present invention is to provide a method for preparing activated carbon materials for supercapacitors that can increase the BET and total pore volume. [Means for solving the problem]

[0016] The present invention includes a step A of subjecting a heavy hydrocarbon oil to a first heat treatment at a pressure within a range of 2 atm to 3 atm to cause a coking reaction, thereby obtaining a soft carbon precursor having a quinoline insoluble component (hereinafter abbreviated as "QI") content within a range of 78 wt% to 98 wt% and a toluene insoluble component (hereinafter abbreviated as "TI") content within a range of 88 wt% to 100 wt%; Step B: mixing the soft carbon precursor with an activator to obtain a mixture; Step C: subjecting the mixture to a second heat treatment to cause an activation reaction and a carbonization reaction, thereby obtaining a composition containing activated carbon and residual activator; Step D: removing residual activator from the composition to obtain an intermediate activated carbon material; Step E of grinding and screening the intermediate activated carbon material; and step F of subjecting the ground and screened intermediate activated carbon material to a third heat treatment to obtain an activated carbon material for a supercapacitor; The present invention provides a method for producing an activated carbon material for a supercapacitor, wherein in step A, the ratio of a mesophase structure contained in the soft carbon precursor exceeds 50 vol%, the operating temperature of the coking reaction is within the range of 480°C to 580°C, and the operating time of the coking reaction is at least 4 hours. [Effects of the Invention]

[0017] In the method for producing an activated carbon material for supercapacitors of the present invention, the soft carbon precursor obtained in the first heat treatment in step A is mixed with an activator to obtain a mixture, the mixture is then subjected to a second heat treatment to obtain a composition containing activated carbon and residual activator, the residual activator is then removed from the composition to obtain an intermediate activated carbon material, and the intermediate activated carbon material is then ground, screened, and subjected to a third heat treatment to obtain an activated carbon material for supercapacitors, thereby improving the BET and total pore volume of the activated carbon material for supercapacitors. [Brief explanation of the drawings]

[0018] [Figure 1A] 1 is a polarizing microscope (hereinafter abbreviated as "PM") image of the soft carbon precursor obtained in step A of Comparative Example 1 (CE1). [Figure 1B] 1 is a PM image of the soft carbon precursor obtained in step A of Comparative Example 2 (CE2). [Figure 1C] 1 is a PM image of the soft carbon precursor obtained in step A of Example 1 (E1). [Figure 1D] 1 is a PM image of the soft carbon precursor obtained in step A of Example 2 (E2). [Figure 1E] 1 is a PM image of the soft carbon precursor obtained in step A of Example 3 (E3). [Figure 2] 1 is a graph showing the capacitance versus cycle of pouch cells made of activated carbon materials for supercapacitors obtained in Example 1a (E1a), Example 1g (E1g), Example 1i (E1i), and Example 3 (E3). [Figure 3] 3 is a graph of energy density versus power density obtained by compiling FIG. 2. [Figure 4] 1 is a graph of capacitance versus discharge current showing the capacity retention at low current density (0.5 A / g) and high current density (25 A / g) of the supercapacitors obtained in Example 1a (E1a), Example 1g (E1g), Example 1i (E1i), and Example 3 (E3). [Figure 5A] This is a graph showing the capacity retention rate versus cycle life, and is a graph showing the charge / discharge characteristics of a supercapacitor assembled using the activated carbon material of Example 1i (E1i) and a supercapacitor assembled using the activated carbon material currently used in the industry [Comparative Example 3 (CE3)] under a charge / discharge condition of 26A. [Figure 5B] 1 is a graph showing capacity retention versus cycle life, and is a graph showing the charge-discharge characteristics of the supercapacitor of Example 1i (E1i) and the supercapacitor of Comparative Example 3 (CE3) under a charge-discharge condition of 52A. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below.

[0020] An embodiment of the method for producing an activated carbon material for a supercapacitor of the present invention includes steps A to F.

[0021] In step A, a first heat treatment is performed on the heavy hydrocarbon oil at a pressure in the range of 2 atm to 3 atm to cause a coking reaction, and a soft carbon precursor having a quinoline-insoluble component content in the range of 78 wt% to 98 wt% and a toluene-insoluble component content in the range of 88 wt% to 100 wt% is obtained.

[0022] In step A, the ratio of the mesophase structure contained in the soft carbon precursor exceeds 50 vol%, the operating temperature of the coking reaction is within the range of 480°C to 580°C, and the operating time of the coking reaction is at least 4 hours.

[0023] More specifically, in step A, first, heavy hydrocarbon oil is transported to a reactor (not shown) and subjected to a first heat treatment for 4 hours or more at the above-mentioned operating temperature and pressure to decompose and condensation polymerize the heavy hydrocarbon oil in the reactor, thereby obtaining a soft carbon precursor.

[0024] In step B, the soft carbon precursor and an activator are mixed to obtain a mixture.

[0025] In some embodiments, in step B, the weight ratio of the soft carbon precursor to the activator is in the range of 0.125 to 0.25, that is, the weight ratio of the soft carbon precursor to the activator is in the range of 1:4 to 1:8.

[0026] In step B of this embodiment, the impregnation method is used, and potassium hydroxide (KOH) is used as the activator, but the activator is not limited to this.

[0027] Specifically, in step B, a mixed solution containing the soft carbon precursor, an activator, and water is placed in a thermostatic chamber of an ultrasonic oscillator (not shown) and subjected to ultrasonic vibration for 3 hours, and then the mixed solution is placed in a vacuum oven (not shown) and dried at 110°C for 6 hours to obtain a mixture.

[0028] In step C, the mixture is subjected to a second heat treatment to cause activation and carbonization reactions, resulting in a composition containing activated carbon and residual activator.

[0029] In step C of some embodiments, the second heat treatment is performed by increasing the temperature to a range of 700° C. to 900° C. at a rate of 1° C. / min to 10° C. / min in a nitrogen atmosphere.

[0030] In step D, the remaining activator in the composition is removed to obtain an intermediate activated carbon material (i.e., a semi-finished product of the activated carbon material for supercapacitors of the present invention).

[0031] In step D of this embodiment, the composition is subjected to an acid washing treatment, a water washing treatment, and a drying treatment, in that order.

[0032] Specifically, the pickling treatment involves introducing an aqueous solution containing hydrochloric acid (HCl) into the composition to neutralize any remaining KOH in the composition, producing potassium chloride (KCl) and obtaining a first aqueous solution containing the activated carbon. The water-washing treatment involves introducing deionized water into the first aqueous solution containing the activated carbon to remove KCl and HCl, obtaining a second aqueous solution containing the activated carbon, the pH of which is controlled to about 7. The drying treatment involves heating the second aqueous solution containing the activated carbon at a temperature of 100°C to 150°C for at least four hours to remove moisture and obtain an intermediate activated carbon material for step D.

[0033] In step D of this embodiment, the pickling treatment will be described using an aqueous solution containing hydrochloric acid (HCl) as an example, but is not limited to this.

[0034] In step E, the intermediate activated carbon material is ground and screened.

[0035] Specifically, after grinding the intermediate activated carbon material, intermediate activated carbon material having a particle size distribution D50 of 8 μm to 12 μm, a particle size distribution D10 of 2 μm to 6 μm, and a particle size distribution D90 of 14 μm to 20 μm is selected.

[0036] More specifically, in step E of this embodiment, the ground intermediate activated carbon material is sorted using a cyclone type classifying device (manufacturer: NPK, model number: MDS-3) to select intermediate activated carbon material having a particle size distribution D50 of 8 μm to 10 μm, a particle size distribution D10 of 2 μm to 4 μm, and a particle size distribution D90 of 14 μm to 16 μm.

[0037] In step F, the ground and screened intermediate activated carbon material is subjected to a third heat treatment to obtain an activated carbon material for a supercapacitor.

[0038] In some embodiments, in step F, the third heat treatment is performed by increasing the temperature to less than 1000° C. in a nitrogen atmosphere at a temperature increase rate within a range of 1° C. / min to 10° C. / min.

[0039] In step F, the activated carbon material for supercapacitors has a plurality of micropores and a plurality of mesopores whose pore size is larger than that of the micropores, and the ratio of the total volume of the micropores to the total volume of the mesopores is within a range of 7.5 to 0.45.

[0040] The following comparative examples and specific examples are prepared according to the above-described embodiments to describe the specific preparation method of the present invention, the activated carbon material for a supercapacitor prepared by the method, the carbon electrode prepared using the activated carbon material, the supercapacitor assembled using the carbon electrode, and the electrical properties of the supercapacitor. [Example]

[0041] <Activated carbon material for supercapacitors> Comparative example 1 (CE1) The manufacturing method of Comparative Example 1 was in accordance with Example 5 disclosed in Taiwan Patent No. I656094 filed by the applicant of the present application.

[0042] To explain the manufacturing method of Comparative Example 1 in detail, a three-stage first heat treatment was performed on isotropic pitch at atmospheric pressure to obtain a soft carbon precursor of Comparative Example 1. In Comparative Example 1, the heating conditions for the first stage of the first heat treatment were heating from 30°C to 100°C at a temperature increase rate of 2°C / min and then maintaining at 100°C for 30 minutes, the heating conditions for the second stage of the first heat treatment were heating from 100°C to 200°C at a temperature increase rate of 2°C / min and then maintaining at 200°C for 30 minutes, and the heating conditions for the third stage of the first heat treatment were heating from 200°C to 430°C at a temperature increase rate of 2°C / min and then maintaining at 430°C for 1 hour.

[0043] Then, the soft carbon precursor of Comparative Example 1 and KOH were mixed by impregnation under the condition that the weight ratio of the soft carbon precursor to KOH was 1:4, thereby obtaining the mixture of Comparative Example 1.

[0044] Then, the mixture of Comparative Example 1 was heated from 30°C to 800°C at a temperature increase rate of 5°C / min and then maintained at 800°C for 1 hour, thereby carrying out a second heat treatment, thereby obtaining a composition containing the activated carbon of Comparative Example 1 and residual KOH.

[0045] Then, an aqueous solution containing HCl (concentration: 1 M) was introduced into the composition of Comparative Example 1, and neutralized with the residual KOH to produce KCl, thereby obtaining a first aqueous solution containing the activated carbon of Comparative Example 1. Deionized water was then introduced into the first aqueous solution containing the activated carbon of Comparative Example 1 to remove the KCl and residual HCl, thereby obtaining a second aqueous solution containing the activated carbon of Comparative Example 1, the pH of which was controlled to about 7. The water from the second aqueous solution containing the activated carbon of Comparative Example 1 was then removed at 100°C to 150°C, thereby obtaining an intermediate activated carbon material of Comparative Example 1.

[0046] Then, the intermediate activated carbon material of Comparative Example 1 was heated from 30°C to 700°C at a temperature increase rate of 10°C / min in an argon atmosphere and maintained at 700°C for 1 hour, thereby performing a third heat treatment to obtain the activated carbon material for supercapacitor of Comparative Example 1.

[0047] Comparative Example 2 (CE2) The manufacturing method of Comparative Example 2 is similar to that of Comparative Example 1, except for the first heat treatment, the amount of KOH used, the third heat treatment, and grinding and screening before the third heat treatment.

[0048] To explain the differences in detail, the heavy hydrocarbon oil was subjected to a first heat treatment at a pressure of 2 atm to 3 atm and an operating temperature of 450°C for at least 4 hours to cause a coking reaction, thereby obtaining a soft carbon precursor of Comparative Example 2.

[0049] Then, the soft carbon precursor of Comparative Example 2 and KOH were mixed by impregnation under the condition that the weight ratio of the soft carbon precursor to KOH was 1:6, thereby obtaining a mixture of Comparative Example 2.

[0050] The intermediate activated carbon material of Comparative Example 2 was ground and screened.

[0051] Then, the intermediate activated carbon material of Comparative Example 2 was heated from 30°C to 700°C at a temperature increase rate of 10°C / min in a nitrogen atmosphere and maintained at 700°C for 30 minutes, thereby performing a third heat treatment to obtain an activated carbon material for supercapacitors of Comparative Example 2.

[0052] <Example> Using the method for producing an activated carbon material for a supercapacitor according to the present invention, Specific Example 1a (E1a) to Specific Example 1i (E1i), Specific Example 2 (E2), and Specific Example 3 (E3) were produced. Specifically, they are similar to Comparative Example 2, and for the sake of brevity, the differences are summarized in Table 1. Furthermore, in the following measurements of only the soft carbon precursor, Specific Example 1a (E1a) to Specific Example 1i (E1i) will all be referred to as Specific Example 1 (E1) because the production conditions in Step A were the same. [Table 1]

[0053] <Evaluation of soft carbon precursors and activated carbon materials for supercapacitors> Measurement of quinoline insoluble fraction (QI value): The value of the quinoline-insoluble component was measured in accordance with ASTM D7280-06(2011) for each of the soft carbon precursors obtained by the manufacturing methods CE1, CE2, E1, E2, and E3.

[0054] Measurement of toluene insoluble content (TI value): The value of the toluene-insoluble component was measured in accordance with ASTM D4312-95A (2010) for each of the soft carbon precursors obtained by the manufacturing methods CE1, CE2, E1, E2, and E3.

[0055] Measurement of mesophase structure Using a polarizing microscope (manufacturer: Nikon, model number: Eclipse LV100POL), images of each soft carbon precursor obtained by the manufacturing methods CE1, CE2, E1, E2, and E3 were taken, and PM images of each soft carbon precursor (Figure 1A to Figure 1E) were obtained.

[0056] Then, in accordance with the contents of ASTM D4616-95 (2013), each soft carbon precursor in Figures 1A to 1E was analyzed, and the ratio of mesophase structure in each soft carbon precursor obtained by the manufacturing methods CE1, CE2, E1, E2, and E3 was calculated.

[0057] Yield of activated carbon material for supercapacitor: The yield of activated carbon material for supercapacitor was calculated by Equation 1. Formula 1: (Wa / W) x 100% In the formula, Wa represents the weight of the activated carbon material for the supercapacitor, and W represents the weight of the isotropic pitch or soft carbon precursor.

[0058] BET Measurement: The BET was measured using an adsorption analyzer (manufacturer: Micromeritics Instrument Corp., USA, model number: ASAP 2020M) to measure the activated carbon materials for supercapacitors of each comparative example and each specific example, and the adsorption amount (V, cm) when nitrogen was at equilibrium pressure. 3 A graph of the relationship between the pressure (P / P) and the relative pressure (P / P0) was obtained.

[0059] Using the BET adsorption isotherm, Equation 2, a graph was created showing P / V (P0-P) versus P / P0, and the slope (C-1 / CVm) and intercept (1 / CVm) of the graph showing the relationship between each adsorption amount and relative pressure were obtained.

[0060]

number

[0061] In Equation 2, P represents the equilibrium pressure, P0 represents the saturated vapor pressure, C represents the BET constant, V represents the amount of adsorption at the equilibrium pressure, and V m represents the saturated adsorption amount in a single layer.

[0062] Then, the specific surface area (S BET ) was calculated.

[0063]

number

[0064] In Formula 3, N m represents the number of molecules of adsorbed gas, N represents Avogadro's constant, σ represents the adsorption cross section of the adsorbed gas molecule, and ν represents the molar volume of the adsorbed gas molecule.

[0065] In BET measurements, the relative pressure (P / P0) ranges from 0 to 1.

[0066] Mesopore BET and micropore BET measurements: The BET of mesopores and the BET of micropores were measured using the curves in the graph showing the relationship between each adsorption amount and relative pressure, in combination with an analytical model of heterogeneous surface-2-dimension non-localized density functional theory (hereinafter abbreviated as "HS-2D-NLDFT"), to calculate the BET of mesopores and the BET of micropores.

[0067] Total pore volume (unit: cm 3 / g) measurement: The total pore volume was measured using the above-mentioned adsorption analyzer to measure the activated carbon materials for supercapacitors of each comparative example and each specific example, and a graph of the relationship between the adsorption amount (V) and relative pressure (P / P0) of nitrogen adsorption and desorption when each gas is at equilibrium pressure was obtained.

[0068] The curves in each nitrogen adsorption / desorption relationship graph were combined with the analytical model of HS-2D-NLDFT to calculate the total pore volume of the activated carbon material for supercapacitors of each comparative example and each specific example.

[0069] Measurement of micropore distribution: The micropore distribution was measured using the nitrogen adsorption / desorption relationship graph described above, combined with the HS-2D-NLDFT analytical model, to calculate the micropore distribution of the activated carbon materials for supercapacitors of each comparative example and each specific example.

[0070] Mesopore distribution measurement: The mesopore distribution of the activated carbon materials for supercapacitors of each comparative example and each specific example was measured using the nitrogen adsorption / desorption relationship graph described above in combination with the HS-2D-NLDFT analytical model.

[0071] Micropore to mesopore ratio: The ratio of micropores to mesopores was calculated using the values ​​obtained by measuring the total pore volume of the activated carbon material for supercapacitors of each comparative example and each specific example, and the ratio of micropores therein was calculated using the following equation 4. Formula 4: (Vμ / Vtotal)×100%

[0072] In Equation 4, Vμ represents the total volume of micropores with a pore width of 2 nm or less, and Vtotal represents the total volume of pores. The mesopore ratio is calculated by subtracting the micropore ratio from 100%.

[0073] 1A to 1E are PM images of the soft carbon precursors obtained in step A of Comparative Examples 1 and 2 and Specific Examples 1 and 3, respectively.

[0074] 1A to 1E, the black parts are the same phase structure of each soft carbon precursor, and the non-black parts are the intermediate phase structure of each soft carbon precursor.

[0075] In accordance with ASTM D4616-95 (2013), the proportions of the mesophase structure of the soft carbon precursors CE1, CE2, E1, E2, and E3 calculated by analyzing the PM images of each soft carbon precursor were 78 vol%, 65 vol%, 52 vol%, 60 vol%, and 85 vol% (as shown in Table 2).

[0076] [Table 2]

[0077] According to Table 2, the toluene-insoluble component values ​​(TI values) obtained by measuring the soft carbon precursors CE1, CE2, E1, E2, and E3 in accordance with ASTM D4312-95A(2010) were 45.0 wt%, 95.0 wt%, 89.9 wt%, 99.6 wt%, and 96.4 wt%, respectively. The quinoline-insoluble component values ​​(QI values) obtained by measuring the soft carbon precursors CE1, CE2, E1, E2, and E3 in accordance with ASTM D7280-06(2011) were 16.0 wt%, 78.1 wt%, 96.4 wt%, 97.4 wt%, and 88.8 wt%, respectively.

[0078] The mesophase structure ratio of the soft carbon precursor of CE1 reached 78 vol%, but the values ​​of the toluene-insoluble component and the quinoline-insoluble component were too low, so they were easily removed by KOH, resulting in a low yield of activated carbon material for supercapacitors.

[0079] According to the measurement results of E1a, E1b, E1c, E1d, and E1e in Table 3 below, the total pore volume of the activated carbon material for supercapacitors increases as the amount of activator used increases. Therefore, if the activated carbon material for supercapacitors E1a, E1b, E1c, E1d, and E1e are used to prepare electrodes and assemble them into a supercapacitor, it is advantageous to improve the power density of the supercapacitor.

[0080] [Table 3]

[0081] When activated carbon materials are applied to supercapacitors, the micropores in the activated carbon materials can support a large amount of adsorption area for electrolyte ions when an electric double layer is formed during the operation of the supercapacitor, thereby contributing to an increase in the specific capacitance of the supercapacitor and further improving the energy density.

[0082] Furthermore, the pore size of the mesopores in the activated carbon material is larger than the pore size of the micropores, and therefore the resistance to the electrolyte is small, which is advantageous in reducing the resistance to the transfer of electrolyte ions and charges.

[0083] Therefore, it can provide fast transfer of electrolyte ions and charges within the supercapacitor.

[0084] In particular, when applied to an environment where the current density is at least 100 A / g or more, the power density of the supercapacitor can be improved while maintaining a high specific capacitance.

[0085] Furthermore, according to Table 3, the ratio of the total volume of micropores to the total volume of mesopores of the activated carbon materials for supercapacitors E1a, E1b, E1c, E1d, E1e, E1f, E1g, E1h, E1i, E2 and E3 is calculated to be in the range of 6.14 to 0.49.

[0086] Therefore, when the activated carbon material for supercapacitor according to each embodiment of the present invention is applied to a supercapacitor, it can provide fast transfer of electrolyte ions and charges within the supercapacitor, and can maintain a high specific capacitance of the supercapacitor in a high current density environment.

[0087] Therefore, after the applicant completed the method for preparing the activated carbon material for supercapacitor of the present invention, the activated carbon materials for supercapacitor CE1, E1a, E1b, E1f, E1g, E1h, E1i and E3 were further used in accordance with the results of Table 3 to prepare electrode slurries and sets of carbon electrode sheets, respectively, and then multiple supercapacitors were assembled using each set of carbon electrode sheets.

[0088] In preparing the electrode slurry, the electrode slurry is divided into a first electrode slurry and a second electrode slurry, and a set of carbon electrode sheets is divided into a set of first carbon electrode sheets and a set of second carbon electrode sheets.

[0089] Specifically, the first electrode slurry was used to fabricate a first set of carbon electrode sheets, which were then used to assemble multiple supercapacitors for measurement, and the second electrode slurry was used to fabricate a second set of carbon electrode sheets, which were then used to assemble multiple pouch cells.

[0090] The capacitance of each pouch cell is about 1 F, which is larger than the capacitance of each supercapacitor used for measurement.

[0091] <Electrode slurry raw materials> The raw materials for the electrode slurry are listed below. Carboxymethyl cellulose powder (hereinafter abbreviated as "CMC powder") purchased from JSR Corporation and having the model number JSR-104A.

[0092] Conductive carbon black purchased from Timcal and having the trade name Super P.

[0093] Styrene-butadiene rubber (hereinafter abbreviated as "SBR") purchased from Nippon Paper Industries Co., Ltd. and having the model number MAC350HC.

[0094] Activated carbon materials for supercapacitors CE1, E1a, E1b, E1f, E1g, E1h, E1i and E3 (hereinafter abbreviated as "AC").

[0095] <Production of electrode slurry> The CMC powder was added to the first deionized water (volume: 12 ml) and homogenized at room temperature for 30 minutes using a homogenizer (manufacturer: IKA, Germany, model number: RW20) to completely dissolve the CMC powder in the first deionized water, resulting in a highly viscous and completely transparent first solution.

[0096] Super P was then added to the first solution and homogenized for 30 minutes, and AC was then added to the first solution and homogenized for approximately 150 minutes until the AC was completely dispersed in the first solution.

[0097] Finally, SBR was added to the first solution and homogenized for about 15 minutes to obtain a first electrode slurry.

[0098] The weight percentages (wt%) of CMC, SBR, Super P, and AC in the first electrode slurry are summarized in Table 4 below, and the weight of the dry powders (i.e., CMC, SBR, Super P, and AC) used to prepare the first electrode slurry was 0.2 g.

[0099] [Table 4]

[0100] The compounding ratio of CMC, SBR, Super P, and AC in the dry powder of the second electrode slurry was the same as that of the first electrode slurry, and the manufacturing method of the second electrode slurry was similar to that of the first electrode slurry, except that the weight of the dry powder used in the manufacturing of the second electrode slurry was 0.5 g and the following points were noted.

[0101] Specifically, the CMC powder was added to the second deionized water (volume: 12 ml) and homogenized at room temperature for 40 minutes using a homogenizer to completely dissolve the CMC powder in the second deionized water, resulting in a highly viscous and completely transparent second solution.

[0102] Super P was then added to the second solution and homogenized for 40 minutes, and AC was then added to the second solution and homogenized for approximately 180 minutes until the AC was completely dispersed in the second solution.

[0103] Finally, SBR was added to the second solution and homogenized for about 30 minutes to obtain a second electrode slurry.

[0104] <Raw material for carbon electrode sheets> The raw material of the carbon electrode sheet is aluminum foil purchased from Nippon Capacitor Industrial Co., Ltd. and has the model number 30C054.

[0105] <Manufacturing carbon electrode sheets> The first electrode slurry was placed in a blade coater (manufacturer: Yasuda Seiki Seisakusho, model number: No. 542-AB-H) with a gap width set to 150 μm, and the first electrode slurry was uniformly applied to an aluminum foil serving as a first aluminum current collector to obtain a first electrode coating layer.

[0106] Then, the first electrode coating layer and the first aluminum current collector plate were placed in a vacuum oven (manufacturer: Taiwan DENGYNG INSTRUMENTS CO., LTD., model number: DOV-30) and heated at a temperature of 110°C for at least 4 hours to completely evaporate the water in the first electrode coating layer.

[0107] The dried first electrode coating layer and the first aluminum current collector plate were then placed in a rolling machine (roller, manufacturer: Taiwan UBIQ TECHNOLOGY CO., LTD., model number: RL-1500) and rolled at a rolling rate within a range of 30% to 40% to form a first carbon electrode layer with a thickness within a range of 40 μm to 50 μm on the first aluminum current collector plate, thereby forming a first carbon electrode from the first carbon electrode layer and the first aluminum current collector plate.

[0108] Finally, the first carbon electrode was cut into a plurality of first carbon electrode sheets to obtain a set of first carbon electrode sheets.

[0109] Each first carbon electrode sheet has an active area (1.0 cm x 1.0 cm in area) and a welding area protruding outward from the active area.

[0110] The fabrication of the second set of carbon electrode sheets is similar to that of the first set, except for the following.

[0111] The difference is that the gap width of the blade coater was set to 200 μm, and after the second electrode slurry was applied, heated, and rolled in order, a second carbon electrode layer with a thickness of approximately 80 μm was formed on the second aluminum current collector plate, thereby forming a second carbon electrode from the second carbon electrode layer and the second aluminum current collector plate.

[0112] Finally, the second carbon electrode was cut into a plurality of second carbon electrode sheets to obtain a set of second carbon electrode sheets.

[0113] Each second carbon electrode sheet has an active area (3.5 cm x 3.5 cm in area) and a welding area protruding outward from the active area.

[0114] <Supercapacitor raw materials> The raw materials for supercapacitors are listed below. Triethylmethylammonium tetrafluoroborate (hereinafter abbreviated as "TEMABF4") was purchased from Tokyo Chemical Industry Co., Ltd. and had the model number T2198.

[0115] Propylene carbonate (hereinafter abbreviated as "PC") was purchased from Sigma, USA, and had the model number 107913.

[0116] Acrylonitrile (hereinafter abbreviated as "AN") was purchased from Sigma, USA, and had the model number 605310.

[0117] The aluminum tab lead was purchased from UBIQ TECHNOLOGY CO., LTD. in Taiwan and was 0.1 mm thick, 3 mm wide, and 65 mm long.

[0118] The nickel tab lead was purchased from UBIQ TECHNOLOGY CO., LTD. in Taiwan and was 0.1 mm thick, 3 mm wide, and 65 mm long.

[0119] The separator used as the separator membrane for the supercapacitor was purchased from UNION CHEMICAL IND. CO., LTD. in Taiwan and had the model number TF40-30.

[0120] An aluminum laminated film (hereinafter referred to as "ALF") was purchased from UBIQ TECHNOLOGY CO., LTD., Taiwan, and had a thickness of 113 μm, a width of 480 mm, and a length of 10 m.

[0121] <Assembling the supercapacitor> Two first carbon electrode sheets are combined into a set, and each set is used as the first positive electrode sheet and the first negative electrode sheet of a supercapacitor for each measurement.

[0122] First, the carbon electrode layer on the welding area of ​​the first positive electrode sheet and the first negative electrode sheet of each set was wiped clean, and then an ultrasonic spot welding apparatus (manufacturer: SHENG-CING INSTRUMENTS CO., LTD., Taiwan, model number: MSK-800) was used to weld an aluminum tab lead to the welding area of ​​the first positive electrode sheet of each set, and a nickel tab lead to the welding area of ​​the first negative electrode sheet of each set. The surfaces opposite the welding areas of each aluminum tab lead and each nickel tab lead were covered with a plastic film.

[0123] Then, each pair of first positive electrode sheets and first negative electrode sheets was wound and wrapped while a plurality of first separator films having an appropriate size was placed between the working area of ​​the first positive electrode sheet and the working area of ​​the first negative electrode sheet of each pair.

[0124] Then, the first separator membranes wrapped around the first positive electrode sheet and the first negative electrode sheet of each set were placed in respective plastic bags and vacuum dried to again remove excess moisture from the first positive electrode sheet and the first negative electrode sheet.

[0125] Then, each plastic bag containing each set of the first positive electrode sheet, the first negative electrode sheet, and the first separator film was placed in a glove box with an argon atmosphere, and a first electrolyte solution (containing TEMABF and PC, with a TEMABF concentration of 1 M) was dropped into each plastic bag to completely permeate the first positive electrode sheet, the first negative electrode sheet, and the first separator film.

[0126] Finally, a vacuum packaging machine (manufacturer: Taiwan SHENG-CING INSTRUMENTS CO., LTD., model number: MSK-115A-S) was used to seal the opening of each plastic bag so that each aluminum tab lead and each nickel tab lead was reliably exposed outside the plastic bag, and the plastic film on each aluminum tab lead and each nickel tab lead was sealed inside the plastic bag so that it was aligned with the opening of the plastic bag, thereby obtaining each supercapacitor for measurement.

[0127] The assembly of the pouch cell is similar to that of the measurement supercapacitor, except for the following points.

[0128] The difference is that two second carbon electrode sheets are used as a pair to serve as the second positive electrode sheet and the second negative electrode sheet of each pouch cell.

[0129] In more detail, two aluminum laminate films of the same size were stacked together as a pair, and then a vacuum packaging machine was used to seal three sides of each pair of aluminum laminate films to obtain a flexible packaging bag with one opening.

[0130] The second separator film wrapped around the second positive electrode sheet and the second negative electrode sheet of each set was placed in a soft packaging bag and vacuum dried to again remove excess moisture from the second positive electrode sheet and the second negative electrode sheet of each set.

[0131] Then, each flexible packaging bag containing each set of second positive electrode sheet, second negative electrode sheet, and second separator film was placed in a glove box with an argon atmosphere, and a second electrolyte solution (containing TEMABF and AN, with a TEMABF concentration of 1 M) was dropped into each flexible packaging bag to completely permeate the second positive electrode sheet, second negative electrode sheet, and second separator film.

[0132] Finally, the opening of each flexible packaging bag was sealed using a vacuum packaging machine to obtain each pouch cell.

[0133] In addition, based on the results of Table 3, the supercapacitor E1f and the supercapacitor of Comparative Example 3 (CE3) were assembled at a supercapacitor assembly factory using the activated carbon material for the supercapacitor E1f and activated carbon material purchased from Kuraray (model number: YP-50F).

[0134] <Capacitor performance test> Measurement of gravimetric capacitance (unit: F / g) The gravimetric capacitance was measured using a cell test system (manufacturer: Solartron Analytical, UK, model number: Model 1470e) for measuring supercapacitors and pouch cells for CE1, CE3, E1a, E1b, E1f, E1g, E1h, E1i, and E3.

[0135] First, the first positive electrode sheet and the first negative electrode sheet of each supercapacitor for measurement and the second positive electrode sheet and the second negative electrode sheet of each pouch cell were activated by cyclic voltammetry (hereinafter abbreviated as "CV").

[0136] The scan rate of the cyclic voltammetry was 50 mV / s, and the scan voltage of the cyclic voltammetry was 0V to 2.7V.

[0137] Then, each supercapacitor for measurement and each pouch cell were charged at a current density of 2 A / g.

[0138] Then, constant current discharge measurements were performed on the supercapacitors CE1, E1a, E1b, E1g, and E1h for measurement at current densities of 2A / g and 100A / g and voltages ranging from 0V to 2.7V, and the pouches E3, E1a, E1g, and E1i were measured at current densities of 0.5A / g, 5A / g, 10A / g, 12.5A / g, 15A / g, 20A / g, and 25A / g and voltages ranging from 0V to 2.7V. Five constant current charge / discharge measurements were performed on each cell, and one constant current charge / discharge measurement was performed on each of the pouch cells E3, E1a, E1g, and E1i at current densities of 0.5 A / g, 1.0 A / g, 2.5 A / g, 5 A / g, 7.0 A / g, 10 A / g, 12.5 A / g, 15 A / g, 17.5 A / g, 20 A / g, 22.5 A / g, and 25 A / g and voltages ranging from 0 V to 2.7 V.

[0139] Finally, the gravimetric capacitance of each measurement supercapacitor and each pouch cell was calculated using the following formula 5. Formula 5: Weight specific capacity = 4×I×td / (M×△V)

[0140] In Equation 5, I represents the discharge rate, td represents the discharge time (seconds), M represents the weight of the carbon electrode layer in the electrode sheet of each supercapacitor used for measurement, and ΔV represents the potential difference after subtracting the internal resistance drop (hereinafter referred to as “IR drop”).

[0141] Capacity retention rate (unit: %) measurement: The capacity retention rate was calculated by (capacitance at a current density of 25 A / g) / (capacitance at a current density of 0.5 A / g)×100%.

[0142] According to the results shown in Table 5, the corresponding gravimetric capacitances of the supercapacitors for measurement of E1a, E1b, E1g and E1h of the present invention under the measurement condition of 2 A / g are 154 F / g, 156 F / g, 147 F / g and 153 F / g, respectively, which are all lower than the gravimetric capacitance of CE1 (160 F / g).

[0143] However, the corresponding gravimetric capacitances under the measurement conditions of high current density (100 A / g) for the supercapacitors E1a, E1b, E1g and E1h of the present invention are 130 F / g, 130 F / g, 121 F / g and 117 F / g, respectively, which are all higher than the gravimetric capacitance of CE1 (110 F / g).

[0144] Therefore, the supercapacitors for measuring E1a, E1b, E1g and E1h of the present invention have superior power densities to the supercapacitor for measuring CE1 under the use condition of a large current density (100 A / g).

[0145] [Table 5]

[0146] Referring to the graph of capacitance vs. cycles in FIG. 2 , the present invention performed five constant-current charge-discharge measurements on pouch cells E3, E1a, E1g, and E1i at current densities of 0.5 A / g, 5 A / g, 10 A / g, 12.5 A / g, 15 A / g, 20 A / g, and 25 A / g, respectively, and the capacitance gradually decreased. However, when the pouch cells were again subjected to constant-current charge-discharge measurements at a current density of 0.5 A / g, the capacitances of the pouch cells E3, E1a, E1g, and E1i of the present invention after two constant-current charge-discharge measurements at a current density of 0.5 A / g were close to the capacitances after one constant-current charge-discharge measurement at a current density of 0.5 A / g.

[0147] Therefore, the pouch cells E3, E1a, E1g and E1i of the present invention have excellent capacity retention rates.

[0148] Referring to FIG. 3, which is a graph of energy density versus power density obtained by compiling FIG. 2, the pouch cells E3, E1a, E1g, and E1i of the present invention have higher power and energy densities than the energy or power densities of each conventional supercapacitor (i.e., the gray areas in FIG. 3).

[0149] Furthermore, as shown in FIG. 4, the pouch cells E3, E1a, E1g, and E1i of the present invention all maintain a capacity retention rate of 93.0% or more after constant current charge / discharge measurement at a current density of 0.5 A / g to 25 A / g.

[0150] Furthermore, as shown in FIG. 5A, the E1f supercapacitor and the CE3 supercapacitor of the present invention all have cycle lives of nearly 18,000 cycles under the conditions of a charge / discharge rate of 100C (charging / discharging is completed in 36 seconds) and a charge / discharge current of 26A. The curves of both supercapacitors are similar in trend, and the capacity retention rates are all maintained at 80% or more.

[0151] As shown in FIG. 5B, the E1f supercapacitor and the CE3 supercapacitor of the present invention all have cycle lives of nearly 40,000 cycles under the conditions of a charge / discharge rate of 200C (charging / discharging is completed in 18 seconds) and a charge / discharge current of 52A. The curves of both supercapacitors are similar in trend, and the capacity retention rates are all maintained at around 80%.

[0152] That is, when the activated carbon material for supercapacitors produced by the production method of the present invention is made into a carbon electrode sheet and assembled into a supercapacitor, its charge / discharge characteristics are close to those of the activated carbon material (CE3) currently used in the industry. Therefore, the production method of the present invention can increase the economic value of cheap heavy hydrocarbon oils.

[0153] According to the above, the method for producing an activated carbon material for a supercapacitor of the present invention not only increases the economic value of cheap heavy hydrocarbon oils, but also has a high BET and total pore volume of the produced activated carbon material. Furthermore, after being fabricated into a carbon electrode sheet and assembled into a supercapacitor, the supercapacitor also has a high energy density, a high power density, and an excellent capacity retention rate, thereby certainly achieving the object of the present invention.

[0154] The above-described embodiments are illustrative for explaining the principles and effects of the present invention, and are not intended to limit the present invention. Those skilled in the art may make slight changes or modifications to the above-described embodiments without departing from the spirit and scope of the present invention. Therefore, all changes and modifications made by those skilled in the art without departing from the gist of the present invention should be considered to fall within the scope of protection of the present invention. [Industrial Applicability]

[0155] The method for producing an activated carbon material of the present invention is particularly suitable for producing an activated carbon material for a supercapacitor.

Claims

1. a step A of subjecting a heavy hydrocarbon oil to a first heat treatment at a pressure within a range of 2 atm to 3 atm to cause a coking reaction, thereby obtaining a soft carbon precursor having a quinoline-insoluble component content within a range of 78 wt % to 98 wt % and a toluene-insoluble component content within a range of 88 wt % to 100 wt %; Step B: mixing the soft carbon precursor with an activator to obtain a mixture; Step C: subjecting the mixture to a second heat treatment to cause an activation reaction and a carbonization reaction, thereby obtaining a composition containing activated carbon and a residual activator; Step D: removing residual activator from the composition to obtain an intermediate activated carbon material; Step E of grinding and screening the intermediate activated carbon material; and step F of subjecting the ground and screened intermediate activated carbon material to a third heat treatment to obtain an activated carbon material for a supercapacitor. In the step A, the ratio of the mesophase structure contained in the soft carbon precursor is more than 50 vol%, the operating temperature of the coking reaction is in the range of 480°C to 580°C, and the operating time of the coking reaction is at least 4 hours.

2. 2. The method for producing an activated carbon material for a supercapacitor according to claim 1, wherein in step B, the weight ratio of the soft carbon precursor to the activator is in the range of 0.125 to 0.

25.

3. 2. The method for producing an activated carbon material for a supercapacitor according to claim 1, wherein in step C, the second heat treatment is performed in a nitrogen atmosphere at a temperature rising rate of 1°C / min to 10°C / min to a temperature range of 700°C to 900°C.

4. 2. The method for producing an activated carbon material for a supercapacitor according to claim 1, wherein in step F, the third heat treatment is performed in a nitrogen atmosphere at a temperature increase rate of 1°C / min to 10°C / min to a temperature less than 1000°C.

5. In the step F, the activated carbon material for a supercapacitor has a plurality of micropores and a plurality of mesopores having a pore size larger than the micropores, 2. The method for producing an activated carbon material for a supercapacitor according to claim 1, wherein the ratio of the total volume of the micropores to the total volume of the mesopores is in the range of 7.5 to 0.45.

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