JP2020009847A - Active carbon for electric double layer capacitor, electric double layer capacitor, manufacturing methods thereof, and electrode for electric double layer capacitor - Google Patents

Abstract

To provide an active carbon for an electric double layer capacitor by using pruned branches of an apple tree which are a waste.SOLUTION: An active carbon for an electric double layer capacitor has a basic configuration as follows. The active carbon involves micro pores of 0.65 to 0.70 nm in pore diameter, which account for 24.9% of all of micro pores or more. As a raw material of the active carbon, a tree branch such as an apple tree pruned branch can be used suitably. Using, as a raw material, apple tree pruned branches, which are a waste in cultivation of apples, leads to the decrease in waste, and effective utilization of the waste. Particularly in the case of the active carbon for an electric double layer capacitor according to the invention, pellets arranged by using tree branches, especially apple tree pruned branches as a raw material can be used as a starting raw material.SELECTED DRAWING: None

Description

  The present invention particularly relates to activated carbon utilizing tree branches and its production technology, and more particularly to a new production technology of activated carbon for electric double layer capacitors.

  Activated carbon, which is a multifunctional material having a high specific surface area and a large number of pores, is produced mainly by using coconut husk, wood, or the like as a raw material by a two-stage treatment of carbonization and activation. The activation treatment includes (1) a gas activation method in which a gas or the like is injected in a process of heat-treating carbonaceous material obtained by carbonization, and (2) a chemical activation in which a starting material or a carbonized material is impregnated with zinc chloride or the like and then heat-treated. There are two laws. The former is a method of producing a fine porous carbonaceous adsorbent by contacting a carbonized raw material with steam, carbon dioxide, oxygen, other oxidizing gases, or the like at a high temperature. On the other hand, the latter is a method of impregnating the carbonaceous material by impregnating the raw material with zinc chloride etc. and firing it, dehydrating, lowering the carbonization temperature, and expressing the adsorption function, but the production process and production cost burden are more large.

  By the way, trace elements (metals and non-metallic elements) in wood are considered to promote the gasification reaction by catalytic action at the time of air activation, and when wood is carbonized, the effect of promoting the activation is considered. Can be expected. In particular, the branches contain about 7 to 10 times the amount of trace elements of the trunk, and a technique for producing a high specific surface area activated carbon using branches of weeping willow, zelkova, sakura, etc. as a raw material has been disclosed (the patents listed below). Reference 1).

  Now, in Aomori Prefecture, a world-wide apple production area, branches cut in apple orchard management (hereinafter referred to as "apple pruned branches") are produced in large quantities as waste materials, and their effective use is required. If activated carbon with excellent performance can be easily and simply manufactured without using the production process and production cost such as the chemical activation method using this, there are advantages in both the agricultural field and the manufacturing fields of activated carbon and adsorbents. is there. Based on this viewpoint, the inventor of the present application first utilized the apple pruned branch as a raw material, and obtained a large specific surface area, a fine pore volume, and a mesopore (diameter of 2 to 2) obtained by a simple process without using chemical activation. A method for producing activated carbon having many (50 nm pores) was invented and disclosed (Patent Document 1).

The inventor of the present application completed the inventions [1] to [12] described below and applied for a patent for the purpose of controlling high moisture absorption performance of activated carbon having a large mesopore volume by a production process (Patent Document 2). Thus, the pore characteristics such as the mesopore volume can be controlled by the manufacturing method, and the moisture absorption performance can be adjusted and the moisture absorption performance can be imparted according to the application, thereby facilitating and expanding the product development.
[1] A method for producing activated carbon in which a carbonized material obtained by subjecting a carbonization raw material to carbonization is subjected to an activation treatment process to obtain activated carbon, and the yield of activated carbon obtained by adjusting the activation treatment conditions in the activation treatment process. A method for producing activated carbon, comprising adjusting the rate and thereby controlling the properties of the pores of the activated carbon.
[2] The characteristics of the pores are at least one of specific surface area, volume of micropores (pores having a diameter of 2 nm or less), volume of mesopores (pores having a diameter of 2 to 50 nm), and pore diameter distribution. The method for producing activated carbon according to [1].
[3] The activated carbon production method according to [1] or [2], wherein the activation treatment condition is an activation treatment time.
[4] The method for producing activated carbon according to [3], wherein the yield is lowered by extending the activation treatment time, thereby increasing the volume of the pores.
[5] The method for producing activated carbon according to [3], wherein the yield is reduced by lengthening the activation treatment time, thereby increasing the diameter of the pores.
[6] The method for producing activated carbon according to [5], wherein the pores are mesopores.
[7] The method for producing activated carbon according to [3], wherein the yield is reduced by lengthening the activation treatment time, thereby increasing the specific surface area.
[8] The method according to [3], wherein a relationship between the activation time or the yield and the pore characteristics is determined in advance, and desired pore characteristics are obtained by setting the activation time or the yield. Activated carbon production method.
[9] The method for producing activated carbon according to any one of [1] to [8], wherein the obtained activated carbon is in the form of pellets.
[10] The method for producing activated carbon according to any one of [1] to [9], wherein the carbonization raw material is a tree branch.
[11] The method for producing activated carbon according to any one of [1] to [9], wherein the carbonized raw material is apple pruned branches.
[12] The method for producing activated carbon according to any one of [1] to [11], further comprising a carbonization treatment step of obtaining the carbonized product from a pelletized carbonized raw material.

Patent No. 5935039, "Method for producing activated carbon" Japanese Patent Application No. 2017-040024, "Method for producing activated carbon" (not disclosed at the time of filing the present application)

  As described above, the inventor of the present application has mainly achieved results on activated carbon production technology utilizing tree branches. At the same time, based on these results, we are also conducting research on product development for each application, and we have been working on the most appropriate activated carbon production technology for electric double layer capacitors. The electric double layer is a phenomenon in which positive and negative charged particles form pairs at the interface and line up in layers as a result of charged particle movement when a potential is applied to a system in which charged particles can move relatively freely. An electric double-layer capacitor is a capacitor whose power storage amount is significantly increased by utilizing this. An electric double layer capacitor is configured to include a porous carbon electrode such as activated carbon and an electrolytic solution. The principle is that an electric double layer is formed at the interface between the pores of the activated carbon and the electrolytic solution, and charges are stored in the electric double layer. . It can be charged and discharged with a large current and has high stability at high temperatures in addition to long life.

  The problem to be solved by the present invention is to provide an activated carbon having characteristics suitable for use in an electric double layer capacitor and a method for producing the same, based on the prior art, and an electric double layer capacitor and a method for producing the same. , And an electrode for an electric double layer capacitor. Still another object of the present invention is to provide an activated carbon having characteristics suitable for an electric double layer capacitor using apple pruned branches as waste and a method for producing the same, and an electric double layer capacitor and a method for producing the same. , And an electrode for an electric double layer capacitor.

As a result of studying the above problems, the present inventor has found a means for solving the problems, and has completed the present invention. That is, the invention claimed in the present application as a means for solving the above-mentioned problem, or at least the disclosed invention is as follows.
[1] Activated carbon for an electric double layer capacitor, wherein micropores having a pore size of 0.65 nm or more and 0.70 nm or less are contained in a ratio of 24.9% or more of all the micropores.
[2] The activated carbon for electric double layer capacitors according to [1], wherein the raw material is a tree branch.
[3] The activated carbon for electric double layer capacitors according to [1] or [2], wherein the raw material is apple pruned branches.
[4] The electric double layer capacitor according to any one of [1] to [3], wherein the micropore distribution is adjusted using pellets made from tree branches or apple pruned branches as starting materials. Activated carbon.
[5] For an electric double layer capacitor, characterized by comprising a process of adjusting so that micropores having a pore size of 0.65 nm or more and 0.70 nm or less are included in a quantitative ratio of 24.9% or more of all micropores. Activated carbon production method.

[6] The method for producing activated carbon for an electric double layer capacitor according to [5], wherein pellets made from tree branches are used as a starting material.
[7] The method for producing activated carbon for an electric double layer capacitor according to [5], wherein a pellet made from apple pruned branches is used as a starting material.
[8] In the process of activating the raw material activated carbon, various processing conditions such as the particle size, treatment amount (input amount), nitrogen gas circulation amount, steam circulation amount, set maximum attainment temperature, and activation treatment time of the carbide (before activation treatment) to be provided The method for producing activated carbon for an electric double layer capacitor according to any one of [5] to [7], wherein the activation treatment step specifies at least one of the conditions.
[9] It is necessary to preliminarily test an activation treatment time at which an optimum micropore distribution is obtained after fixing other conditions in the activation treatment process, and to manufacture using the activation treatment time specified thereby as a condition. The method for producing activated carbon for an electric double layer capacitor according to any one of [5] to [8].
[10] Activated carbon for an electric double layer capacitor according to any of [1] to [4], or electricity produced by the method for producing activated carbon for an electric double layer capacitor according to any of [5] to [9] An electrode for an electric double layer capacitor, characterized by using activated carbon for a double layer capacitor.
[11] Activated carbon for an electric double layer capacitor according to any one of [1] to [4], or electricity produced by the method for producing activated carbon for an electric double layer capacitor according to any of [5] to [9] An electric double layer capacitor characterized by using activated carbon for a double layer capacitor.
[12] The active carbon for an electric double layer capacitor according to any of [1] to [4], or the activated carbon for an electric double layer capacitor according to any of [5] to [9]. A method for manufacturing an electric double layer capacitor, comprising:

  The activated carbon for an electric double layer capacitor, the electric double layer capacitor, the method for producing the same, and the electrode for the electric double layer capacitor of the present invention are configured as described above. Activated carbon and an electrode for an electric double layer capacitor having excellent characteristics can be provided. In particular, new knowledge that the yield and specific surface area, micropore volume and mesopore volume show a high correlation shows that activated carbon or electric carbon having characteristics suitable for electric double layer capacitors by adjusting the micropore distribution. An electrode for a multilayer capacitor can be provided. Further, according to the present invention, it is possible to provide an activated carbon or an electrode for an electric double layer capacitor having characteristics suitable for an electric double layer capacitor by effectively utilizing apple pruned branches as waste, and to produce apple as a waste. It contributes to the reduction of waste amount of pruned branches and can be used effectively.

It is a graph which shows the relationship between the yield of activated carbon, and a bulk density. It is a graph which shows the relationship between the yield of activated carbon, and a specific surface area. It is a graph which shows the relationship between the yield of activated carbon, and micropore volume. It is a graph which shows the relationship between the yield of activated carbon, and mesopore volume. It is a graph which shows the micropore distribution of activated carbon for electric double layer capacitors. It is a graph which shows the mesopore distribution of the activated carbon for electric double layer capacitors. It is a graph which shows the relationship between time and capacitance. 5 is a graph showing a relationship between time and internal resistance. (FIGS. 1 to 8 are diagrams according to the first embodiment.) It is a graph which shows the micropore distribution per electrode. 5 is a graph showing the distribution of micropores per electrode from 0.5 to 0.9 nm. It is a graph which shows the mesopore distribution per electrode. It is a graph which shows the mesopore distribution per electrode of 1-10 nm. It is a graph which shows the micropore distribution per electrode. 5 is a graph showing the distribution of micropores per electrode from 0.5 to 0.9 nm. It is a graph which shows the mesopore distribution per electrode. It is a graph which shows the mesopore distribution per electrode of 1-10 nm. (FIGS. 9 to 16 are diagrams according to the second embodiment.)

Hereinafter, the present invention will be described in more detail.
First, the basic configuration of the activated carbon for an electric double layer capacitor according to the present invention is that micropores having a pore size of 0.65 nm or more and 0.70 nm or less are contained at a ratio of 24.9% or more of all the micropores. is there. Further, as a raw material of the activated carbon, a tree branch such as an apple pruned branch can be suitably used. When apple pruned branches, which are waste in apple cultivation, are used as raw materials, this leads to waste reduction and effective waste utilization. As will be described later in the examples, the activated carbon for an electric double layer capacitor of the present invention can use, in particular, pellets made from tree branches or apple pruned branches as starting materials. However, the activated carbon of the present invention is not limited thereto, and may be one using a conventionally known raw material or one using a commercially available activated carbon as a raw material.

  The method for producing activated carbon for an electric double layer capacitor according to the present invention includes a process in which micropores having a pore diameter of 0.65 nm or more and 0.70 nm or less are adjusted so as to be contained in a ratio of 24.9% or more of all the micropores. Having a characteristic configuration. As a raw material used in the production method of the present invention, as described above, from the viewpoint of effective use of waste and reduction of production amount, pellets made from tree branches, particularly apple pruned branches, can be used as starting materials. Of course, the starting material is not limited to this. In particular, as will be described later in Examples, it is possible to produce an activated carbon having characteristics suitable for an electric double layer capacitor by subjecting a commercially available activated carbon to a treatment unique to the present invention.

  A specific method for adjusting the micropores can be performed by setting activation processing conditions in a predetermined activation processing step, as described later in Examples. That is, in the activation treatment of the raw material activated carbon, at least one of the processing conditions such as the particle size of the carbide to be provided (before activation), the treatment amount (input amount), the nitrogen gas circulation amount, the steam circulation amount, the set maximum reaching temperature, and the activation treatment time. By performing the activation process in which any one of the conditions is specified, the micropores having a pore diameter of 0.65 nm or more and 0.70 nm or less are adjusted so as to be included in a quantity ratio of 24.9% or more of all the micropores. Can be.

  For example, in the activation treatment of the raw material activated carbon, activation in which all of the particle size, treatment amount (input amount), nitrogen gas circulation amount, steam circulation amount, set maximum attainment temperature, and activation treatment time of the provided carbide (before activation) are specified The process may be a process, or, on the other hand, a process of specifying a nitrogen gas flow rate, a steam flow rate, a set maximum attainment temperature, and an activation time, a process of specifying a set pore attainment temperature and an activation time, and only the activation time. The process of specifying, and any other specific manner, is within the scope of the present invention.

  However, it is the target yield or yield in the activation treatment that determines the composition of the micropore distribution as the suitability as activated carbon for electric double layer capacitors. The target yield or the yield can be adjusted depending on the length of the activation treatment time. Therefore, an activation treatment time at which an optimum micropore distribution is obtained after fixing other conditions in the activation treatment process is tested in advance, and the activation treatment time specified thereby is used as a condition, and the electric double layer capacitor is used. Activated carbon may be produced.

  Note that the target yield (or yield) and activation treatment time at which characteristics suitable as activated carbon for electric double layer capacitors can be obtained depending on tree branches, apple pruned branches, commercially available activated carbon, and other raw materials used are not constant, but are not tested beforehand. This can be easily specified.

  It should be noted that the activated carbon for an electric double layer capacitor having any of the above-described structures, or the electric carbon configured using the activated carbon for an electric double layer capacitor manufactured by any of the above-described methods for producing an activated carbon for an electric double layer capacitor. The method for manufacturing an electrode for a multilayer capacitor, an electric double layer capacitor, and a method for manufacturing an electric double layer capacitor using activated carbon for an electric double layer capacitor having any of the above-described configurations is also within the scope of the present invention.

Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto. The description of the progress of the research leading to the completion of the present invention will be described as an example.
<Example 1>
Experimental Method 1.1 Preparation of Activated Carbon for Capacitor 1.1.1 Preparation of Pellet As a raw material, a pruned apple branch was chipped with a hammer crusher and sieved to 10 mm or less. Pelletization was performed using a pelletizer (EF-BS-150, manufactured by Earth Engineering Co., Ltd.) with a raw material supply of 100 kg / hour, a rotation speed of 60 times / minute, and a target diameter of 4 mm.

1.1.2 Preparation of activated carbon The pellets prepared in 1.1.1 were used as raw materials. In the carbonization treatment, 7400 g of pellets were charged into a kiln container using an activated carbon production experimental machine (manufactured by MET), and a maximum temperature of 850 ° C. and a holding time of 0.5 hour were passed while flowing 100 L / min of nitrogen gas. This was performed three times under the following conditions. The carbonization rate: Y _c (%) is obtained from the mass of the pellet after heating at 105 ° C. for 24 hours: W _t (%) and the mass of the carbonized product after heating at 105 ° C. for 24 hours: W _c (%). , Calculated from the following equation (1).
Y _c = W _c / W _t × 100 (1)

  In the activation treatment, the same amount of carbonized carbonized material (hereinafter, A1) was used for three times by using an activated carbon production experimental device (manufactured by MET) as in the case of carbonization, and 4200 g of the mixture was put into a kiln container, and 100 L of nitrogen gas was added. / Min and 12 mL / min of water vapor, and the maximum temperature reached 850 ° C. The target yield from A1 was adjusted to 80%, 70%, 50%, 40%, and 30% (hereinafter, A2, A3, A4, A5, and A6) by adjusting the activation time.

1.1.3 Activated carbon cleaning method Acid cleaning was performed using 2 g of activated carbon powdered with a planetary ball mill (MC-4A, manufactured by Ito Seisakusho) according to JIS H 1345, and 0.1 mol / L hydrochloric acid (Wako Pure). 17 mL of a reagent (manufactured by Yakuhin Kogyo Co., Ltd.) was placed in a 100 mL beaker, left for 1 hour, boiled for 2 minutes, washed with distilled water, and filtered. The activated carbon for capacitors obtained from A2 was B1, B3 from A3, B3 from A4, B4 from A5, and B5 from A6, which were used as activated carbon samples for electric double layer capacitors. The preparation of the sample from the activated carbon A1 and the capacitor test were not performed.
The carbonized products A2 to A6 prepared by adjusting the activation treatment time with the above target yields for the carbonized product A1 (yield 28.5%), and the activated carbon B1 to B5 for capacitors obtained by the acid washing treatment of A2 to A6. The relationships, and the actual yields of A1-A6 (shown in parentheses) are as follows.
A1-> No capacitor test (28.5%)
A2-> B1 (23.3%)
A3-> B2 (19.9%)
A4-> B3 (15.3%)
A5-> B4 (12.6%)
A6-> B5 (10.8%)

1.2 Evaluation of Basic Physical Properties Yield of each activated carbon: Y _Ca (%) is mass of A1 after heating at 105 ° C. for 24 hours: W _s (g), and activated carbon after heating at 105 ° C. for 24 hours. From the mass: W _c (g) of the following formula (2).
Y _Ca = W _c / W _s × 100 (2)

The diameter of the sample was measured using a caliper near the center of three randomly selected activated carbons. The bulk density: B _d (g / cm ³ ) is the mass of an empty measuring container: m ₀ (g), the mass of the measuring container filled with the sample: m ₁ (g), and the mass of the measuring container according to JIS Z 7302. The volume was calculated from the following formula (3) from V (cm ³ ), and the average was obtained from the results of three tests on the same sample.
B _d = (m ₁ −m ₀ ) / V × 1000 (3)

_Ash before and after washing: Y _Ash (%) was measured by placing 1 g of activated carbon in a magnetic dish and drying the sample after drying at 105 ° C. for 24 hours according to JIS K 1474: W _m (%) and a heating furnace (Isuzu Seisakusho Co., Ltd.). Ltd., ETP-26K) at 800 ° C., for 2 hours the sample after heating by _weight: from _W a (%), the following (4) calculated from the equation was determined from the average of three samples result.
Y _Ash = W _a / W _m × 100 (4)

1.3 Evaluation of Pore Structure The specific surface area, pore volume and distribution were calculated using a specific surface area / pore distribution measuring device (BELSORP-mini, manufactured by Bell Japan, Inc.). The sample was not pulverized, but was used in the form of pellets and activated carbon B1 to B5 powder for a capacitor. After degassing at 250 ° C. for 5 hours, a nitrogen adsorption / desorption isotherm at −196 ° C. was measured. (M ² / g), micropore volume: VtN (cm ³ / g) and micropore distribution were calculated by the MP method, and mesopore volume: ViN (cm ³ / g) and differential mesopore volume distribution were calculated by the BJH method. It was determined from the average of the sample results.

1.4 Production and Evaluation of Capacitors As a capacitor electrode material, polytetrafluoroethylene (hereinafter, PTFE) water dispersant as a binder, Ketjen black (hereinafter, KB) as a conductive material for B1 to B5, respectively, and a final ratio of 91 were used. : 3: 6, water was added and kneaded, and the mixture was transferred to a 150 ° C. drier to remove water. After cooling in a desiccator, a pressure of 3 t was applied, and the mixture was pulverized and sieved with a mesh of 75 μm to 250 μm to produce granulated powder. A certain amount of the granulated powder was collected and processed into an electrode having a thickness of 650 μm and a diameter of 12 mm by tableting.

  This electrode was adhered to the cap and the case of the capacitor cell using a conductive adhesive, followed by high-temperature vacuum drying. Thereafter, an electrolytic solution was injected into the electrodes in a glove box, a separator was inserted between the electrodes, a gasket was incorporated, and a case and a cap were caulked to produce a prototype electric double layer capacitor. As the electrolytic solution, a commercially available propylene carbonate solution of tetraethylammonium tetrafluoroborate was used.

  The capacitor was evaluated by measuring the capacitance, internal resistance, and leakage current characteristics of the coin cell at room temperature, and then putting the coin cell into a durability test at 85 ° C. and applying 1.8 V. The capacitor was taken out and discharged at predetermined time intervals. The above three characteristics were measured to evaluate the capacitor performance. The capacitance was measured by charging at a constant voltage of 1.8 V for 30 minutes, discharging at a constant current, and calculating from the voltage range of 1.4 V to 0.7 V using the relationship of q = CV. The internal resistance was measured using a commercially available LCR meter at a frequency of 1 kHz. The leakage current value was measured after performing constant voltage charging at 1.8 V for 30 minutes. In addition, as a comparative example, a commercially available activated carbon for electric double layer (YP-50F, manufactured by Kuraray Chemical Co., Ltd.) was prepared and evaluated by the same method.

In order to confirm the relationship between the performance of the electric double layer capacitor and the pore distribution, it is considered better to evaluate not per gram of activated carbon but per electrode. Then, from the value of the Y-axis of the micropore and mesopore distribution: Y, the mass ratio of activated carbon in the electrode of 91/100, and the density of the electrode: E _d (g / cm ³ ), the following equation (5) is used. The value of the Y-axis per electrode: _Yed was calculated.
Y _ed = Y × 91/100 × E _d (5)

2. Results and Discussion Table 1 shows the physical properties of the pellets and the activated carbon obtained therefrom. Ash content, specific surface area, micropore volume, and mesopore volume increased with decreasing yield. Table 2 shows the physical properties of the activated carbon for electric double layer capacitors. As is clear from the comparison with Table 1, the ash content was reduced by the acid washing. The average particle diameter of the obtained activated carbons B1 to B5 was smaller than that of Comparative Example YP-50F.

  FIGS. 1 to 4 graphically show the relationship between the yield of the activated carbon of this example and the bulk density, specific surface area, micropore volume, and mesopore volume. As shown in these figures, activated carbons (A1 to A6) tended to have lower bulk density and higher pore physical properties (micropore volume, mesopore volume) as yield decreased. Moreover, in comparison with YP-50F, the bulk density was high, and the specific surface area and the micropore volume were low. In addition, the mesopore volume of A3 was equivalent to that of the non-each example YP-50F.

  5 and 6 show the micropore distribution and the mesopore distribution of the activated carbon for an electric double layer capacitor of this example. In the micropore distribution, it was found that the peak shifted from 0.6 nm to larger pores as the yield became lower, that is, as B1, B2, B3, B4, and B5. Also, as the mesopore distribution decreases, that is, as B1, B2, B3, B4, and B5, the capacity of pores of larger sizes tends to increase as a whole. In the mesopores, B5 (10.8% yield) showed the highest capacity.

  Table 3 shows the capacitance and the internal resistance of the electric double layer capacitor. As a result of the test, in B3 (15.3% yield) and B4 (12.6% yield), the capacitance showed a value equal to or higher than that of Comparative Example YP-50F. In B1 (yield 23.3%), the capacitance was low.

  FIG. 7 shows the relationship between the test time and the capacitance of the electric double layer capacitor, and FIG. 8 shows the relationship between the test time and the internal resistance of the electric double layer capacitor. As shown in these, B3 (yield 15.3%) showed the same behavior as the capacitance and internal resistance of Comparative Example YP-50F.

  FIG. 9 shows the micropore distribution per electrode using each of the activated carbons B1 to B5, and FIG. 10 shows the micropore distribution per electrode of 0.5 to 0.9 nm in FIG. 9 in an enlarged manner. . Focusing on B3 (yield 15.3%) and B4 (12.6% yield), which have high capacitances in Table 3 above, among the micropore distributions, particularly, the micropores in the vicinity of 0.65 to 0.70 nm. It was found that the holes showed high electrode density and high capacitance.

  FIG. 11 shows the mesopore distribution per electrode using each activated carbon B1 to B5, and FIG. 12 shows the mesopore distribution per electrode of 1 to 10 nm in FIG. 11 in an enlarged manner. Here, as in the evaluation of the micropore distribution, attention was paid to B3 (yield 15.3%) and B4 (yield 12.6%). No characteristic relationship with size could be found.

<Example 2>
1. Experimental Method 1.1 Preparation of Activated Carbon for Capacitor 1.1.1 Preparation of Activated Carbon Pellet-based activated carbon (3GG, C1 manufactured by Kuraray Chemical Co., Ltd.) was used as a raw material. The activation treatment was carried out using an activated carbon production experimental machine (manufactured by MET) at a maximum temperature of 850 ° C. while introducing 4200 g into a kiln vessel and flowing nitrogen gas 100 L / min and steam 12 mL / min. . The target yield from C1 was adjusted to 90%, 85%, 75%, and 65% (hereinafter, C2, C3, C4, and C5) by adjusting the activation time.

1.1.3 Activated carbon washing method The activated carbon was washed in the same manner as described in Example 1.
1.2 Evaluation of Basic Physical Properties Basic physical properties were evaluated in the same manner as described in Example 1.
1.3 Evaluation of pore structure The pore structure was evaluated in the same manner as described in Example 1.
1.4 Preparation and Evaluation of Capacitor A capacitor was prepared and evaluated in the same manner as described in Example 1.

2. Results and Discussion Table 4 shows the capacitance and the internal resistance of the electric double layer capacitor using the activated carbons C1 to C5. As a result of this test, as shown in the table, the capacitances of the capacitors using activated carbon of C1, C2 (target yield 90%), and C3 (target yield 85%) were compared with those of Comparative Example YP-50F. Equivalent values were shown.

  FIG. 13 is an enlarged view of the distribution of micropores per electrode, and FIG. 14 is an enlarged view of the distribution of micropores per electrode of 0.5 to 0.9 nm in FIG. As shown in these figures, focusing on the activated carbons C1, C2 (target yield: 90%) and C3 (target yield: 85%) having high capacitance, the same as the activated carbon derived from apple pruned branches in Example 1 In addition, it was found that the electrode density was high in the micropores around 0.65 to 0.70 nm. From this, it became clear that the micropores in the range increased the capacity of the capacitor regardless of the activated carbon raw material.

  FIG. 15 shows the mesopore distribution per electrode, and FIG. 16 shows the mesopore distribution per electrode of 1 to 10 nm in FIG. Again, as in the evaluation of the micropore distribution, attention was paid to each activated carbon of C1, C2 (target yield: 90%), and C3 (target yield: 85%). No characteristic relationship between volume and pore size could be found.

<Quantity ratio of specific micropore>
From the above test, it was examined how much micropores in the vicinity of 0.65 to 0.70 nm can be formed in all the micropores to determine that the activated carbon is suitable for an electric double layer capacitor.
In Table 3 shown in Example 1 above, the electrostatic capacitance of the electric double layer capacitor showed high values in YP-50F, B3, and B4. The values on the Y axis of B1 to B5 and YP-50F in FIG.
At a diameter of 0.6 nm, B1>B2>B3>YP-50F>B4> B5
At a diameter of 0.7 nm, YP-50F>B4>B3>B5>B2> B1
At a diameter of 0.8 nm, YP-50F>B4>B5>B3>B2> B1
It became.

On the other hand, in Table 4 according to Example 2, the capacitances of YP-50F, C1, C2, and C3 showed high values. The values of the Y axis of C1 to C5 and YP-50F in FIG.
At a diameter of 0.6 nm, C1>C2>C3>YP-50F>C4> C5
At a diameter of 0.7 nm, YP-50F>C1>C2>C3>C4> C5
At a diameter of 0.8 nm, YP-50F>C5>C4>C3>C1> C2
It became.

  Since the order of the capacitance of the electric double-layer capacitor in Tables 3 and 4 and the order of the values of the Y-axis having a diameter of 0.7 nm in FIGS. 10 and 14 match, the lower limit is at least B3 and C3. It is considered that if a predetermined amount of micropores of 0.64 nm or more, which is equal to or more than the above value, can be formed, activated carbon suitable for an electric double layer capacitor can be obtained. The value of 65 nm is a value confirmed in an actual test).

  In addition, if the micropores having a pore diameter of 0.65 nm or more and 0.70 nm or less are contained in a quantitative ratio of 24.9% or more of all the micropores, the activated carbon for an electric double layer capacitor as the object of the present invention is sufficient. Properties can be obtained. Here, the basis for setting the quantity ratio to 24.9% or more is as follows.

  As the above-mentioned quantitative ratio, the percentage of 0.7 nm micropores in all the micropores shown in FIGS. 9 and 13 described above ((0.7 nm Y value) / (sum of all micropore Y values) × 100) is used. Calculated. It can be said that the higher this value is, the higher the capacitor capacity is. The percentages of B3, B4, C1, C2, C3, and YP-50F, each having a high capacitor capacity, were calculated and confirmed. As a result, the quantity ratio of B4 having the lowest capacitor capacity was 24.9%. That is, it was concluded that an electric double layer capacitor having sufficiently high performance as an activated carbon for an electric double layer capacitor, which is a subject of the present invention, can be obtained as long as it has this value or more.

According to the activated carbon for an electric double layer capacitor, the electric double layer capacitor, the method for producing the same, and the electrode for an electric double layer capacitor of the present invention, it is possible to produce activated carbon with high accuracy, so that the characteristics suitable for an electric double layer capacitor can be obtained. Activated carbon and an electrode for an electric double layer capacitor can be provided, and an electric double layer capacitor can be provided. In addition, the useful activated carbon, electrodes for electric double layer capacitors, and the like can be provided by effectively utilizing apple pruned branches as waste. Therefore, the invention is industrially highly applicable in the fields of capacitor production / utilization, agriculture, and all related fields.

Claims (12)

Activated carbon for an electric double layer capacitor, characterized in that micropores having a pore diameter of 0.65 nm or more and 0.70 nm or less are contained at a ratio of 24.9% or more of all micropores. The activated carbon for an electric double layer capacitor according to claim 1, wherein the raw material is a tree branch. The activated carbon for an electric double layer capacitor according to claim 1 or 2, wherein the raw material is apple pruned branches. The activated carbon for an electric double layer capacitor according to any one of claims 1 to 3, wherein a micropore distribution is adjusted using a pellet made of a tree branch or an apple pruned tree as a starting material. A method for producing activated carbon for an electric double layer capacitor, comprising a step of adjusting so that micropores having a pore diameter of 0.65 nm or more and 0.70 nm or less are contained in a quantity ratio of 24.9% or more of all micropores. . The method for producing activated carbon for an electric double layer capacitor according to claim 5, wherein a pellet made from a tree branch is used as a starting material. The method for producing activated carbon for an electric double layer capacitor according to claim 5, wherein a pellet made from apple pruned branches is used as a starting material. In the activation process of the raw material activated carbon, the particle size of the carbide to be provided (before the activation process), the throughput (input amount), the nitrogen gas flow rate, the steam flow rate, the set maximum attainment temperature, and the activation process time The method for producing activated carbon for an electric double layer capacitor according to any one of claims 5 to 7, wherein the activation process is performed by specifying at least one condition. It is characterized in that the activation process time at which the optimum micropore distribution is obtained after fixing other conditions in the activation process is tested in advance, and the activation process time specified thereby is used as a condition for production. The method for producing activated carbon for an electric double layer capacitor according to any one of claims 5 to 8. The activated carbon for an electric double layer capacitor according to any one of claims 1 to 4, or the activated carbon for an electric double layer capacitor manufactured by the method for producing an activated carbon for an electric double layer capacitor according to any one of claims 5 to 9 is used. An electrode for an electric double layer capacitor. The activated carbon for an electric double layer capacitor according to any one of claims 1 to 4, or the activated carbon for an electric double layer capacitor manufactured by the method for producing an activated carbon for an electric double layer capacitor according to any one of claims 5 to 9 is used. An electric double-layer capacitor. An activated carbon for electric double layer capacitors according to any one of claims 1 to 4, or an activated carbon for electric double layer capacitors according to any one of claims 5 to 9. Double layer capacitor manufacturing method.