JP2019176040A - Manufacturing method of active carbon cellulose nanofiber - Google Patents

Manufacturing method of active carbon cellulose nanofiber Download PDF

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JP2019176040A
JP2019176040A JP2018063704A JP2018063704A JP2019176040A JP 2019176040 A JP2019176040 A JP 2019176040A JP 2018063704 A JP2018063704 A JP 2018063704A JP 2018063704 A JP2018063704 A JP 2018063704A JP 2019176040 A JP2019176040 A JP 2019176040A
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cellulose nanofiber
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freeze
water
butanol
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博之 脇坂
Hiroyuki Wakizaka
博之 脇坂
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Shiga Prefectural Government.
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13Energy storage using capacitors

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  • Battery Electrode And Active Subsutance (AREA)

Abstract

To provide a manufacturing method of active carbon cellulose nanofiber having sufficient conductivity, in which reduction in capacity incident to addition to an electrode material is less likely to occur, and which is usable suitably as an electrical conduction auxiliary.SOLUTION: A manufacturing method of active carbon cellulose nanofiber includes a freeze dry step of preparing a freeze dry solvent by adding a solvent, miscible with water, to a water dispersion cellulose nanofiber, and freeze drying freezing the cellulose nanofiber in a state dispersed into the freeze dry solvent, a heating step of carbonizing the freeze dried cellulose nanofiber obtained in the freeze dry step, and an activation step of activating the cellulose nanofiber carbonized in the heating step.SELECTED DRAWING: None

Description

本発明は、活性炭化セルロースナノファイバーの製造方法に関し、より詳しくは、導電助剤として好適に使用できる活性炭化セルロースナノファイバーの製造方法に関する。   The present invention relates to a method for producing activated carbonized cellulose nanofibers, and more particularly to a method for producing activated carbonized cellulose nanofibers that can be suitably used as a conductive additive.

従来、リチウムイオン電池や電気二重層キャパシタの電極には、活物質として、黒鉛や活性炭といった炭素材料が用いられている。そして、前記電極には、導電性を担保して内部抵抗を低減させるために、電極全体の10wt%程度の導電助剤が用いられている(例えば、特許文献1参照)。導電助剤としては、アセチレンブラックやケッチェンブラック等があげられるが、これらは粒子状であるため、前記炭素材料とは点接合となり、接合点が多くなることで内部抵抗の低減効果が十分に得られない場合があった。そこで、繊維由来の炭素を用いて、粒子間空隙を密に充填することが検討されている(例えば、特許文献2参照)。しかし、導電助剤は導電性の確保のためには必要であるものの、その添加によって、添加割合に応じて電池容量が低下してしまうため、導電性と電池容量との両立が困難であるという課題があった。   Conventionally, carbon materials such as graphite and activated carbon have been used as active materials for electrodes of lithium ion batteries and electric double layer capacitors. And in order to ensure electroconductivity and to reduce internal resistance, the said electrode uses the conductive support agent of about 10 wt% of the whole electrode (for example, refer patent document 1). Examples of the conductive assistant include acetylene black and ketjen black. However, since these are particulate, they are point-bonded to the carbon material, and the effect of reducing internal resistance is sufficiently obtained by increasing the number of joints. In some cases, it could not be obtained. Thus, it has been studied to densely fill the interparticle voids using fiber-derived carbon (see, for example, Patent Document 2). However, although the conductive auxiliary agent is necessary for ensuring conductivity, the addition of the conductive auxiliary agent decreases the battery capacity depending on the addition ratio, so that it is difficult to achieve both conductivity and battery capacity. There was a problem.

国際公開第2009/044856号International Publication No. 2009/044856 特開2018−26253号公報JP 2018-26253 A

本発明は上記課題を解決するものであり、導電性を十分に有するとともに、電極材料への添加にともなう容量の低下が起こりにくい、導電助剤として好適に使用できる活性炭化セルロースナノファイバーの製造方法を提供することを目的とする。   The present invention solves the above-mentioned problems, and has a sufficient conductivity and is less likely to cause a decrease in capacity due to addition to an electrode material. The method for producing activated carbonized cellulose nanofibers that can be suitably used as a conductive additive The purpose is to provide.

本発明の活性炭化セルロースナノファイバーの製造方法は、
水分散セルロースナノファイバーに、水と混和する溶媒を添加して凍結乾燥溶媒を調製し、前記凍結乾燥溶媒に分散させた状態で前記セルロースナノファイバーを凍結乾燥する凍結乾燥工程と、
前記凍結乾燥工程で得られた凍結乾燥セルロースナノファイバーを炭化させるための加熱工程と、
前記加熱工程で炭化したセルロースナノファイバーを賦活させるための賦活工程とを含むことを特徴とする。
The method for producing the activated carbonized cellulose nanofiber of the present invention is as follows.
A lyophilization step of adding a solvent miscible with water to a water-dispersed cellulose nanofiber to prepare a lyophilized solvent, and lyophilizing the cellulose nanofiber in a state of being dispersed in the lyophilized solvent;
A heating step for carbonizing the freeze-dried cellulose nanofibers obtained in the freeze-drying step;
And an activation step for activating the cellulose nanofibers carbonized in the heating step.

本発明の活性炭化セルロースナノファイバーの製造方法において、前記水と混和する溶媒としてt−ブタノールを用い、前記凍結乾燥溶媒中のt−ブタノールの割合が、10wt%以上90wt%以下であることが好ましい。   In the method for producing activated carbonized cellulose nanofibers according to the present invention, t-butanol is preferably used as the solvent miscible with water, and the proportion of t-butanol in the lyophilized solvent is preferably 10 wt% or more and 90 wt% or less. .

本発明の活性炭化セルロースナノファイバーの製造方法において、前記賦活工程は、750℃以上1000℃以下の温度範囲で行うことが好ましい。   In the manufacturing method of the activated carbonized cellulose nanofiber of the present invention, the activation step is preferably performed in a temperature range of 750 ° C. or higher and 1000 ° C. or lower.

本発明によれば、導電性を十分に有するとともに、電極材料への添加にともなう容量の低下が起こりにくい、導電助剤として好適に使用できる活性炭化セルロースナノファイバーの製造方法を提供することができる。   ADVANTAGE OF THE INVENTION According to this invention, while having sufficient electroconductivity, the fall of the capacity | capacitance accompanying addition to an electrode material does not occur easily, The manufacturing method of the activated carbonized cellulose nanofiber which can be used conveniently as a conductive support agent can be provided. .

図1は、凍結乾燥時の溶媒を変更したときのセルロースナノファイバー凍結乾燥品の写真である。FIG. 1 is a photograph of a freeze-dried cellulose nanofiber when the solvent during lyophilization is changed. 図2は、炭化時の細孔形成のメカニズムを説明するイメージ図である。FIG. 2 is an image diagram for explaining the mechanism of pore formation during carbonization. 図3は、静電容量の測定結果を示す図である。FIG. 3 is a diagram illustrating a measurement result of capacitance. 図4は、活性炭化セルロースナノファイバーを導電助剤として用いた場合のコインセルの交流インピーダンスの測定結果を示す図である。FIG. 4 is a diagram showing the measurement results of the alternating current impedance of the coin cell when activated carbonized cellulose nanofibers are used as a conductive additive. 図5は、活性炭化セルロースナノファイバーを電極として用いた場合のコインセルの交流インピーダンスの測定結果を示す図である。FIG. 5 is a diagram showing a measurement result of the alternating current impedance of the coin cell when the activated carbonized cellulose nanofiber is used as an electrode.

本発明の活性炭化セルロースナノファイバーの製造方法は、水分散セルロースナノファイバーに、水と混和する溶媒を添加して凍結乾燥溶媒を調製し、前記凍結乾燥溶媒に分散させた状態で前記セルロースナノファイバーを凍結乾燥する凍結乾燥工程と、前記凍結乾燥工程で得られた凍結乾燥セルロースナノファイバーを炭化させるための加熱工程と、前記加熱工程で炭化したセルロースナノファイバーを賦活させるための賦活工程とを含むことを特徴とする。以下各工程について具体的に述べる。   The method for producing activated carbonized cellulose nanofibers of the present invention comprises adding a solvent miscible with water to water-dispersed cellulose nanofibers to prepare a lyophilized solvent, and dispersing the cellulose nanofibers in the lyophilized solvent. A freeze-drying step for freeze-drying, a heating step for carbonizing the freeze-dried cellulose nanofibers obtained in the freeze-drying step, and an activation step for activating the cellulose nanofibers carbonized in the heating step It is characterized by that. Each step will be specifically described below.

[凍結乾燥工程]
市販のセルロースナノファイバー(水分散、ペースト)を、攪拌可能な粘度となるまで溶媒で希釈したセルロースナノファイバー分散体を調製する。前記溶媒としては、(A)水および(B)t−ブタノールを用いた。本実施例では、市販のセルロースナノファイバー10wt%の水分散ペーストを用い、これに前記溶媒900mLを徐々に添加して、攪拌可能な状態とした。このとき、希釈する溶媒として水を用いた場合は、分散媒は100%水である。また、希釈する溶媒としてt−ブタノールを用いた場合は、市販のセルロースナノファイバーの分散媒が水であるため、希釈後の分散媒は、90%t−ブタノール(水:t−ブタノール=1:9)となっている。
[Freeze drying process]
A cellulose nanofiber dispersion is prepared by diluting a commercially available cellulose nanofiber (water dispersion, paste) with a solvent until the viscosity becomes stirrable. As the solvent, (A) water and (B) t-butanol were used. In the present example, a commercially available cellulose nanofiber 10 wt% aqueous dispersion paste was used, and 900 mL of the solvent was gradually added thereto to allow stirring. At this time, when water is used as a solvent for dilution, the dispersion medium is 100% water. In addition, when t-butanol is used as a solvent for dilution, since the dispersion medium of the commercially available cellulose nanofiber is water, the dispersion medium after dilution is 90% t-butanol (water: t-butanol = 1: 9).

前記希釈されたセルロースナノファイバー分散体をナスフラスコに移し、液体窒素を用い−196℃で予備凍結後、常温雰囲気下で真空乾燥を行った。   The diluted cellulose nanofiber dispersion was transferred to a recovery flask, preliminarily frozen at −196 ° C. using liquid nitrogen, and then vacuum dried in a room temperature atmosphere.

[加熱工程(炭化)]
得られた乾燥セルロースナノファイバー試料を、800℃で炭化した。得られたセルロースナノファイバー炭化物の比表面積を、窒素ガス吸着法によって測定した。結果を表1に示す。表1には、凍結乾燥溶媒として水を用いたものと、市販の導電助剤(ライオン株式会社製 カーボンECP)の測定値も併せて記載した。
[Heating process (carbonization)]
The obtained dry cellulose nanofiber sample was carbonized at 800 ° C. The specific surface area of the obtained cellulose nanofiber carbide was measured by a nitrogen gas adsorption method. The results are shown in Table 1. Table 1 also shows the measured values of those using water as the lyophilization solvent and the commercially available conductive aid (carbon ECP manufactured by Lion Corporation).

凍結乾燥時の溶媒を、90wt% t−ブタノール(水:t−ブタノール=1:9)で調製することによって、市販の導電助剤(カーボンECP)と同等の比表面積であるセルロースナノファイバー炭化物が得られていることがわかる。このセルロースナノファイバー炭化物は、市販の導電助剤と同等レベルの比表面積であるので、同等レベルの静電容量を発現することができると考えられる。このように、凍結乾燥時の溶媒を、水とt−ブタノールとの混合組成とすることで、水のみの溶媒のものと比較して、炭化のみでも高比表面積が得られており、凍結乾燥時の溶媒を制御することによって、セルロースナノファイバー炭化物の比表面積制御ができる。   By preparing a solvent for lyophilization with 90 wt% t-butanol (water: t-butanol = 1: 9), a cellulose nanofiber carbide having a specific surface area equivalent to that of a commercially available conductive aid (carbon ECP) can be obtained. It turns out that it is obtained. Since this cellulose nanofiber carbide has a specific surface area equivalent to that of a commercially available conductive additive, it is considered that an equivalent level of capacitance can be expressed. Thus, by making the solvent at the time of freeze-drying a mixed composition of water and t-butanol, a high specific surface area is obtained even with carbonization alone, compared with that of a solvent with only water, and freeze-drying. By controlling the solvent at the time, the specific surface area of the cellulose nanofiber carbide can be controlled.

凍結乾燥時の溶媒は、乾燥時のセルロースナノファイバーの嵩密度に影響する。図1は、凍結乾燥時の溶媒を変更したときのセルロースナノファイバー凍結乾燥品の写真である。図中、左は溶媒が水、中央は溶媒が50%t−ブタノール(水:t−ブタノール=1:1)、右は溶媒が90%t−ブタノール(水:t−ブタノール=1:9)で、各々凍結乾燥を行ったセルロースナノファイバー凍結乾燥品である。t−ブタノールの比率が高い溶媒を使用することで、嵩高い凍結乾燥品が得られていることがわかる。   The solvent during lyophilization affects the bulk density of the cellulose nanofibers during drying. FIG. 1 is a photograph of a freeze-dried cellulose nanofiber when the solvent during lyophilization is changed. In the figure, the left is the solvent is water, the middle is the solvent 50% t-butanol (water: t-butanol = 1: 1), the right is the solvent 90% t-butanol (water: t-butanol = 1: 9). The cellulose nanofibers are freeze-dried and then freeze-dried. It can be seen that a bulky lyophilized product is obtained by using a solvent having a high ratio of t-butanol.

溶媒が水である場合、水素結合が強いため、乾燥時にセルロースナノファイバーの再凝集が起こりやすく、緻密構造となる。一方、t−ブタノールを添加した場合には、水による水素結合等の相互作用が緩和されるため、粗密構造となると考えられる。図2は、炭化時の細孔形成のメカニズムを説明するイメージ図である。嵩密度が小さい(空隙が大きい)場合、左図のようにセルロースナノファイバー間の隙間が大きく炭化時の分解ガスの発生(ガス化)が促進されるため、炭化物の細孔が効率的に形成されて、結果として比表面積が大きくなると考えられる。一方、嵩密度が大きい(空隙が小さい)場合、右図のようにセルロースナノファイバー間の隙間が小さく炭化時の分解ガスの発生(ガス化)が阻害されるため、比表面積は小さくなると考えられる。   When the solvent is water, the hydrogen bonding is strong, so that re-aggregation of cellulose nanofibers is likely to occur during drying, resulting in a dense structure. On the other hand, when t-butanol is added, the interaction such as hydrogen bonding due to water is alleviated, so it is considered that a dense structure is obtained. FIG. 2 is an image diagram for explaining the mechanism of pore formation during carbonization. When the bulk density is small (the void is large), the gap between the cellulose nanofibers is large as shown in the left figure, and the generation (gasification) of decomposition gas during carbonization is promoted. As a result, the specific surface area is considered to increase. On the other hand, when the bulk density is large (the gap is small), the gap between the cellulose nanofibers is small and the generation (gasification) of decomposition gas during carbonization is inhibited as shown in the right figure. .

本実施形態では、凍結乾燥時の溶媒としてt−ブタノールを用いた場合を例示したが、本発明はこの溶媒に限定されるものではない。市販のセルロースナノファイバーは、一般には分散媒として水が用いられており、このようなセルロースナノファイバーを用いる場合、凍結乾燥時の溶媒として加える溶媒は、水と混和する溶媒であればt−ブタノールに限定されるものではなく、例えば、メチルアルコール、エチルアルコール、イソプロピルアルコール、テトラヒドロフラン、1,4−ジオキサン、アセトン、アセトニトリル等を用いることができる。   In this embodiment, although the case where t-butanol was used as a solvent at the time of freeze-drying was illustrated, this invention is not limited to this solvent. Commercially available cellulose nanofibers generally use water as a dispersion medium. When such cellulose nanofibers are used, the solvent added as a solvent during lyophilization is t-butanol as long as the solvent is miscible with water. For example, methyl alcohol, ethyl alcohol, isopropyl alcohol, tetrahydrofuran, 1,4-dioxane, acetone, acetonitrile and the like can be used.

[賦活工程(活性炭化)]
次に、前記加熱工程で炭化したセルロースナノファイバー(セルロースナノファイバー炭化物)を活性炭化(賦活)する。賦活は、温度750℃〜1000℃の範囲、好ましくは800℃〜950℃の範囲、より好ましくは900℃で行う。賦活工程を経ることで、活性炭化セルロースナノファイバーを得ることができる。賦活の触媒としては、ガスとしては、水(水蒸気)、炭酸ガス、空気(酸素)等が好ましく、薬品としては、水酸化カリウム、水酸化ナトリウム、りん酸および塩化亜鉛等を好ましく用いることができる。前記加熱工程(炭化)によって比表面積を大きくすることができたが、賦活によって、さらなる高比表面積化が可能である。
[Activation process (activated carbonization)]
Next, the active carbonization (activation) of the cellulose nanofiber (cellulose nanofiber carbide) carbonized in the heating step is performed. Activation is performed at a temperature in the range of 750 ° C. to 1000 ° C., preferably in the range of 800 ° C. to 950 ° C., more preferably 900 ° C. Active carbonized cellulose nanofibers can be obtained through the activation step. As an activation catalyst, water (water vapor), carbon dioxide gas, air (oxygen) or the like is preferable as the gas, and potassium hydroxide, sodium hydroxide, phosphoric acid, zinc chloride or the like can be preferably used as the chemical. . Although the specific surface area could be increased by the heating step (carbonization), it is possible to further increase the specific surface area by activation.

セルロースナノファイバーはアスペクト比が大きいことから、本発明により得られる活性炭化セルロースナノファイバーは、導電助剤として用いると、線接合による導電性の向上が期待できる。さらに、活性炭化していることによって、電荷の吸着サイトが増えるので、電気二重層キャパシタの容量向上も期待できる。なお、セルロースナノファイバーはバイオマス由来材料であることから、本発明による環境負荷低減や、持続可能社会への貢献も期待できる。   Since the cellulose nanofiber has a large aspect ratio, the activated carbonized cellulose nanofiber obtained according to the present invention can be expected to improve conductivity by wire bonding when used as a conductive auxiliary. Furthermore, since the activated carbon increases, the number of charge adsorption sites increases, so that the capacity of the electric double layer capacitor can be expected to be improved. In addition, since the cellulose nanofiber is a biomass-derived material, it can be expected to contribute to the reduction of environmental burden and sustainable society according to the present invention.

以下、本発明を実施例により具体的に説明する。   Hereinafter, the present invention will be specifically described by way of examples.

[実施例1]
賦活工程を次のとおり行い、BET比表面積、全細孔容積および平均細孔直径を測定した。凍結乾燥を行った乾燥セルロースナノファイバー試料を磁製皿に入れ、窒素気流中800℃まで昇温し、セルロースナノファイバー炭化物を得た。得られたセルロースナノファイバー炭化物を、所定量磁製皿に入れ、窒素気流中賦活温度(900℃)まで昇温した。900℃到達後、賦活ガスとして炭酸ガスを、N:CO=1:1の体積比となるように導入して賦活を行った。その後、冷却して活性炭化セルロースナノファイバーを回収した。活性炭の比表面積は、液体窒素温度(77K)における窒素の吸着等温線によるBET法によって得た。結果を表2に示す。
[Example 1]
The activation process was performed as follows, and the BET specific surface area, the total pore volume, and the average pore diameter were measured. The freeze-dried dried cellulose nanofiber sample was placed in a porcelain dish and heated to 800 ° C. in a nitrogen stream to obtain cellulose nanofiber carbide. The obtained cellulose nanofiber carbide was put in a predetermined amount of porcelain dish and heated to an activation temperature (900 ° C.) in a nitrogen stream. After reaching 900 ° C., activation was performed by introducing carbon dioxide gas as an activation gas so as to have a volume ratio of N 2 : CO 2 = 1: 1. Then, it cooled and collect | recovered activated carbonized nanofiber. The specific surface area of the activated carbon was obtained by a BET method using an adsorption isotherm of nitrogen at a liquid nitrogen temperature (77 K). The results are shown in Table 2.

表2に示すように、炭化のみの状態に比べて、活性炭化することで、比表面積が増加した。これにより容量向上に寄与可能である。そして、90%t−ブタノールを凍結乾燥溶媒とすると、水100%の場合と比べて、同程度のBET比表面積で平均細孔直径が大きくなっていることがわかる。これは、図2記載の炭化のメカニズムにおいて、炭化物の細孔が効率的に形成されるメカニズムと矛盾はないものである。   As shown in Table 2, the specific surface area was increased by active carbonization as compared with the state of carbonization alone. This can contribute to capacity improvement. When 90% t-butanol is used as the lyophilized solvent, it can be seen that the average pore diameter is increased with the same BET specific surface area as compared with the case of 100% water. This is consistent with the mechanism in which carbide pores are efficiently formed in the carbonization mechanism shown in FIG.

[実施例2]
得られた活性炭化セルロースナノファイバーの静電容量の測定を行った。静電容量の測定は、静電容量測定用コインセルを作製して行った。静電容量測定用コインセルは次のようにして作製した。
[Example 2]
The capacitance of the obtained activated carbonized cellulose nanofiber was measured. The capacitance was measured by producing a capacitance measuring coin cell. A coin cell for measuring capacitance was produced as follows.

活物質(株式会社クレハ製 BAC)、導電助剤(ライオン株式会社製 カーボンECP)およびバインダー(株式会社クレハ製 KFポリマーL9305)を、溶媒としてN−メチル−2−ピロリドン(NMP)を用いてスラリーとし、前記スラリーをアルミ箔(昭和電工株式会社製 SDX)に塗工してシートを得た。   Slurry using an active material (BAC manufactured by Kureha Co., Ltd.), a conductive additive (carbon ECP manufactured by Lion Co., Ltd.), and a binder (KF Polymer L9305 manufactured by Kureha Co., Ltd.) as a solvent using N-methyl-2-pyrrolidone (NMP). Then, the slurry was coated on an aluminum foil (SDX manufactured by Showa Denko KK) to obtain a sheet.

得られたシートを乾燥後、プレスして円形に打ち抜き、コインセルを作製した。作製したコインセルを用いて、電気化学測定(BioLogic SP−50)により、0V〜2.5Vで静電容量を測定した。結果を図3に示す。静電容量は、活性炭化セルロースナノファイバーの比表面積と正の相関がある。そして、活性炭化セルロースナノファイバーでの静電容量は、市販の導電助剤と比較して、最大で5%増加した。   The obtained sheet was dried and then pressed and punched into a circle to produce a coin cell. The capacitance was measured at 0 V to 2.5 V by electrochemical measurement (BioLogic SP-50) using the produced coin cell. The results are shown in FIG. The capacitance has a positive correlation with the specific surface area of the activated carbonized nanofiber. And the electrostatic capacitance in an activated carbonized cellulose nanofiber increased 5% at maximum compared with the commercially available conductive support agent.

また、活性炭化セルロースナノファイバーを導電助剤として用いた場合の静電容量は、炭化前のセルロースナノファイバーの試料調製手法によって異なっている。すなわち、凍結乾燥処理時の溶媒(凍結乾燥溶媒)が水の場合と比べて、t−ブタノールの場合の静電容量が大きくなった。これは、凍結乾燥条件(溶媒種類)により、セルロースナノファイバー炭化物の比表面積や嵩密度が異なることに起因するものと考えられる。比表面積が同程度の活性炭化セルロースナノファイバーであっても、前記条件の違いによって、セルロースナノファイバー上の細孔形成能の効率性が異なり、t−ブタノールを用いた場合の方が広径化(平均細孔直径大)が進む。その結果、電荷吸着サイトが多くなり、容量が向上する。   Moreover, the electrostatic capacitance at the time of using activated carbonized nanofiber as a conductive additive differs depending on the sample preparation method of cellulose nanofiber before carbonization. That is, the electrostatic capacity in the case of t-butanol was larger than that in the case where the solvent (freeze-drying solvent) during the lyophilization treatment was water. This is considered due to the fact that the specific surface area and bulk density of the cellulose nanofiber carbide differ depending on the freeze-drying conditions (solvent type). Even with activated carbonized cellulose nanofibers with the same specific surface area, the efficiency of pore-forming ability on cellulose nanofibers varies depending on the above conditions, and the diameter is larger when t-butanol is used. (Average pore diameter is large). As a result, the number of charge adsorption sites increases and the capacity is improved.

[実施例3]
得られた活性炭化セルロースナノファイバーの交流インピーダンスの測定を行った。交流インピーダンスの測定は、静電容量測定用コインセルを用い、電気化学測定装置(ソーラートロン社1287)で周波数20kHz〜0.1Hz、振幅10mVの条件で行った。結果を図4に示す。Cole−Cole plotで、内部抵抗に相当する半円(図中二点鎖線で囲んだ部分)の大きさに注目すると、従来の導電助剤と比較して、活性炭化セルロースナノファイバーの半円は小さく、内部抵抗が低いことがわかった。
[Example 3]
The AC impedance of the obtained activated carbonized nanofiber was measured. The measurement of AC impedance was performed using a capacitance measuring coin cell under the conditions of a frequency of 20 kHz to 0.1 Hz and an amplitude of 10 mV with an electrochemical measuring device (Solartron 1287). The results are shown in FIG. Focusing on the size of the semicircle corresponding to the internal resistance in the Cole-Cole plot (portion surrounded by a two-dot chain line in the figure), the semicircle of the activated carbonized cellulose nanofiber is It was small and the internal resistance was low.

[実施例4]
得られた活性炭化セルロースナノファイバーを活物質として用い、導電助剤を用いずに電気二重層キャパシタ電極を作製した。電極は、活物質およびバインダー(株式会社クレハ製 KFポリマーL9305)を、溶媒としてN−メチル−2−ピロリドン(NMP)を用いてスラリーとし、前記スラリーをアルミ箔(昭和電工株式会社製 SDX)上に塗工してシート化した。または、活物質およびバインダー(ダイキン工業株式会社製 ポリフロン F−104)を混練してシート化した。得られたシートを乾燥後、プレスして円形に打ち抜き電極を作製後、コインセル化した。また、比較として、市販の電気二重層キャパシタ用活性炭(株式会社クレハ製 BAC)、および導電助剤(株式会社ライオン製 カーボンECP)によるスラリー塗工品、シート成形品を準備し、コインセル化した。用いた活物質(活性炭)の物性値を表3に示す。
[Example 4]
The obtained activated carbonized cellulose nanofiber was used as an active material, and an electric double layer capacitor electrode was produced without using a conductive additive. The electrode is made of an active material and a binder (KF polymer L9305 manufactured by Kureha Co., Ltd.) as a slurry using N-methyl-2-pyrrolidone (NMP) as a solvent, and the slurry is on an aluminum foil (SDX manufactured by Showa Denko KK). Was coated into a sheet. Alternatively, the active material and a binder (polyflon F-104 manufactured by Daikin Industries, Ltd.) were kneaded to form a sheet. The obtained sheet was dried, pressed, punched out into a circular shape, and made into a coin cell. For comparison, a slurry coated product and a sheet molded product using commercially available activated carbon for electric double layer capacitors (BAC manufactured by Kureha Co., Ltd.) and a conductive additive (Carbon ECP manufactured by Lion Co., Ltd.) were prepared and converted into coin cells. Table 3 shows the physical property values of the used active material (activated carbon).

作製したコインセルを用いて、実施例2および実施例3と同様に、静電容量測定および交流インピーダンス測定を行った。結果を表4および図5に示す。   Using the manufactured coin cell, the capacitance measurement and the AC impedance measurement were performed in the same manner as in Example 2 and Example 3. The results are shown in Table 4 and FIG.

交流インピーダンス測定の結果、Cole−Cole plotでの内部抵抗に相当する半円(図中二点鎖線で囲んだ部分)の大きさはほぼ同じであり、内部抵抗が同等であることがわかった。活性炭化セルロースナノファイバーは、導電助剤なしで従来と同等の抵抗値で電極化をすることが可能であることがわかる。
As a result of AC impedance measurement, it was found that the size of the semicircle corresponding to the internal resistance in Cole-Cole plot (portion surrounded by a two-dot chain line in the figure) was almost the same, and the internal resistance was equivalent. It can be seen that the activated carbonized cellulose nanofiber can be made into an electrode with a resistance value equivalent to the conventional one without a conductive auxiliary.

Claims (3)

水分散セルロースナノファイバーに、水と混和する溶媒を添加して凍結乾燥溶媒を調製し、前記凍結乾燥溶媒に分散させた状態で前記セルロースナノファイバーを凍結乾燥する凍結乾燥工程と、
前記凍結乾燥工程で得られた凍結乾燥セルロースナノファイバーを炭化させるための加熱工程と、
前記加熱工程で炭化したセルロースナノファイバーを賦活させるための賦活工程とを含むことを特徴とする活性炭化セルロースナノファイバーの製造方法。
A lyophilization step of adding a solvent miscible with water to a water-dispersed cellulose nanofiber to prepare a lyophilized solvent, and lyophilizing the cellulose nanofiber in a state of being dispersed in the lyophilized solvent;
A heating step for carbonizing the freeze-dried cellulose nanofibers obtained in the freeze-drying step;
And an activation step for activating the cellulose nanofibers carbonized in the heating step.
前記水と混和する溶媒としてt−ブタノールを用い、前記凍結乾燥溶媒中のt−ブタノールの割合が、10wt%以上90wt%以下である、請求項1記載の活性炭化セルロースナノファイバーの製造方法。 The method for producing activated carbonized cellulose nanofibers according to claim 1, wherein t-butanol is used as the solvent miscible with water, and the proportion of t-butanol in the lyophilized solvent is 10 wt% or more and 90 wt% or less. 前記賦活工程は、750℃以上1000℃以下の温度範囲で行う、請求項1または2記載の活性炭化セルロースナノファイバーの製造方法。 The said activation process is a manufacturing method of the activated carbonized cellulose nanofiber of Claim 1 or 2 performed in the temperature range of 750 degreeC or more and 1000 degrees C or less.
JP2018063704A 2018-03-29 2018-03-29 Manufacturing method of active carbon cellulose nanofiber Pending JP2019176040A (en)

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