A consecutive doping method for improvement of electrochemical properties of a commercial activated carbon for organic electric double-layer capacitors

양인찬,유지훈,권다혜,최달수,김명수,정지철 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

In this study, a commercial activated carbon (YP50f) for organic electric double-layer capacitors (EDLC) was improved by a consecutive doping method. The consecutive doping method is a doping method in which nitrogen-doping is used after oxygen-doping. Through this doping method, we successfully prepared a carbon material with high electrical conductivity as well as a large surface area. The surface area of the carbon material was mainly developed during the oxygen-doping process, whereas electrical conductivity was enhanced during the nitrogen-doping process. The consecutively doped carbon exhibited the higher capacitance properties than YP50f when used as an electrode material for organic EDLCs. Consequently, we improved the electrochemical properties of a commercial activated carbon for organic EDLCs by using a consecutive doping method. In addition, we concluded that the consecutive doping method is an effective method for preparing electrode carbon materials for organic EDLCs.

Converting cross-linked polyethylene waste into commercially available carbon materials for supercapacitors

양인찬,김성수,이성호,조세연 한국공업화학회 2022 한국공업화학회 연구논문 초록집 Vol.2022 No.-

Pore size-controlled carbon aerogels for EDLC electrodes in organic electrolytes

양인찬,Sang-Gil Kim,Soon Hyung Kwon,Jun Hyup Lee,Myung-Soo Kim,Ji Chul Jung 한국물리학회 2016 Current Applied Physics Vol.16 No.6

Pore size-controlled carbon aerogels (CA_X) are prepared from two starting materials: resorcinol and formaldehyde. Carbon aerogels with different pore sizes are successfully obtained by simply varying the polymerization time (X) in the polycondensation of resorcinol and formaldehyde. Pore sizes of the carbon aerogels monotonically increase with increasing polymerization time. The pore size of the carbon aerogel plays an important role in determining its electrochemical behavior (i.e., specific capacitance in EDLC) especially at high current density. A sufficiently large pore size in a carbon aerogel is required for easy transport of electrolyte ions, and these types of carbon aerogels provide excellent electrochemical performance as an EDLC electrode. CA_20, which was polymerized for the longest time, have the largest pore size and the largest pore volume. CA_20 exhibit the highest specific capacitance due to facile electrolyte ion transport. As a result, design of carbon aerogels with a sufficiently large pore size while maintaining a high specific surface area is very important for developing carbon aerogels for use in EDLC electrodes. In addition, we propose a schematic reaction pathway for the preparation of carbon aerogels in ambient conditions from resorcinol and formaldehyde using a base catalyst based on the characterization results.

Design of organic supercapacitors with high performances using pore size controlled active materials

양인찬,권다혜,유지훈,김명수,정지철 한국물리학회 2019 Current Applied Physics Vol.19 No.2

In this study, we thoroughly investigate the required properties of active materials for organic supercapacitors with high performances. In this regard, we synthesize carbon xerogels with different physical properties, including specific surface area and pore size. The carbon xerogels are prepared via the sol-gel reaction of resorcinol and formaldehyde under different gelation temperature conditions. Through Fourier-transform infrared, nitrogen adsorption–desorption, and scanning electron microscopy analysis, we can confirm that carbon xerogels with different physical properties can be successfully synthesized. We apply the prepared carbon xerogels to organic supercapacitor electrodes. As a result of electrochemical experiments, carbon xerogels with high surface area exhibit high electrochemical performances at low-rate charge−discharge processes. However, as the charge–discharge rate increases, carbon xerogels with low surface area and high conductivity exhibit higher performances. Therefore, the surface area of active materials is a key factor for supercapacitors with high performances at low-rate charge–discharge processes. However, the effects of conductivity can be more crucial as compared with those of surface area as the charge–discharge rates increase. In addition, we suggest that the physical properties of active materials should be differently optimized as the charge–discharge rate is employed.

유기계 슈퍼커패시터에서 도전재의 양이 전기화학적 특성에 미치는 영향

양인찬,이기훈,정지철,Yang, Inchan,Lee, Gihoon,Jung, Ji Chul 한국재료학회 2016 한국재료학회지 Vol.26 No.12

In this study, we intensively investigated the effect of conductive additive amount on electrochemical performance of organic supercapacitors. For this purpose, we assembled coin-type organic supercapacitor cells with a variation of conductive additive(carbon black) amount; carbon aerogel and polyvinylidene fluoride were employed as active material and binder, respectively. Carbon aerogel, which is a highly mesoporous and ultralight material, was prepared via pyrolysis of resorcinol-formaldehyde gels synthesized from polycondensation of two starting materials using sodium carbonate as the base catalyst. Successful formation of carbon aerogel was well confirmed by Fourier-transform infrared spectroscopy and $N_2$ adsorption-desorption analysis. Electrochemical performances of the assembled organic supercapacitor cells were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements. Amount of conductive additive was found to strongly affect the charge transfer resistance of the supercapacitor electrodes, leading to a different optimal amount of conductive additive in organic supercapacitor electrodes depending on the applied charge-discharge rate. A high-rate charge-discharge process required a relatively high amount of conductive additive. Through this work, we came to conclude that determining the optimal amount of conductive additive in developing an efficient organic supercapacitor should include a significant consideration of supercapacitor end use, especially the rate employed for the charge-discharge process.

Fabrication of Activated Carbon Fibers from Polyacrylonitrile-Derived Carbon Fibers: Investigating CO2 Adsorption Capability in Relation to Surface Area

김성건,이수진,양인찬,김두원,최달수 한국복합재료학회 2023 Composites research Vol.36 No.6

Activated carbon fibers (ACFs) are fibrous form of activated carbon (AC) with higher mechanical strength and flexibility, which make them suitable for building modules for applications including directional gas flow such as air and gas purification. Similarly, ACFs are anticipated to excel in the efficient capture of CO2. However, due to the difficulties in fabricating monofilament carbon fibers at a laboratory scale, most of the studies regarding ACFs for CO2 capture have relied on electrospun carbon fibers. In this study, we fabricated monofilament carbon fibers from PAN-based monofilament precursors by stabilization and carbonization. Then, ACFs were successfully prepared by chemical activation using KOH. Different weight ratios ranging from 1:1 to 1:4 were employed in the fabrication of ACFs, and the samples were designated as ACF-1 to ACF-4, respectively. As a function of KOH ratio, increase in surface area could be observed. However, the CO2 adsorption trend did not follow the surface area trend, and the ACF-3 with second largest surface area exhibited the heighted CO2 adsorption capacity. To understand the phenomena, nitrogen content and ultramicropore distribution, which are important factors determining CO2 adsorption capacity, were considered. As a result, while nitrogen content could not explain the phenomena, ultramicropore distribution could provide a reasoning that the excessive etching led ACF-4 to develop micropore structure with a broader distribution, resulting in high surface area yet deteriorated CO2 adsorption.

Effects of Molecular Weight of Polyvinylidene Fluoride Binder on Electrochemical Performances of Organic Electric Double-Layer Capacitors

Jihoon Yoo(유지훈),Inchan Yang(양인찬),Myung-Soo Kim(김명수),Ji Chul Jung(정지철) 한국고분자학회 2019 폴리머 Vol.43 No.6

본 논문에서는 바인더가 유기계 전기이중층 커패시터(EDLCs)의 전기화학적 성질에 미치는 영향을 조사하기 위하여 플루오르화 폴리비닐리덴(polyvinylidene fluoride, PVDF) 바인더의 분자량을 다르게 하여 EDLC를 조립한 후 다양한 전기화학적 특성 분석을 실시하였다. 특성 분석 결과, 낮은 분자량의 PVDF를 사용하여 조립된 EDLC는 높은 분자량의 PVDF를 사용하여 조립된 EDLC보다 낮은 저항 및 높은 용량 특성을 나타냈으나 충-방전이 진행되는 동안 활물질과 도전재 사이의 구조가 높은 분자량의 PVDF를 사용하여 조립된 EDLC에 비해 느슨해져 결과적으로 낮은 수명을 나타내었다. 따라서 높은 성능을 갖는 EDLC를 제조하기 위해서는 적절한 바인더 분자량이 요구된다. Herein, we assembled electric double-layer capacitor (EDLCs) electrodes with polyvinylidene fluoride (PVDF) as the binder. The effect of the molecular weight of PVDF on the electrochemical properties of the EDLCs were investigated by various characterization tools. The EDLCs assembled using PVDF with low molecular weight showed relatively good capacitance compared to those assembled using PVDF with high molecular weight owing to their low resistance. However, in long-term durability experiments, EDLCs assembled using PVDF with high molecular weights showed higher durability than EDLCs assembled using PVDF with low molecular weights. To investigate the underlying reasons, field emission-scanning electron microscopy (FE-SEM) was applied. Although all prepared EDLC electrodes showed tightly packed morphologies before charge–discharge process was conducted, morphologies of electrodes using low molecular weight PVDF were gradually loosed as charge–discharge process was conducted. As a result, an appropriate binder molecular weight is required to prepare EDLC with high performances.