Energies

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10 pages, 1563 KiB

Open AccessArticle

Nitrogen-Doped and Carbon-Coated Activated Carbon as a Conductivity Additive-Free Electrode for Supercapacitors

by Su-Jin Jang, Jeong Han Lee, Seo Hui Kang, Yun Chan Kang and Kwang Chul Roh

Energies 2021, 14(22), 7629; https://doi.org/10.3390/en14227629 - 15 Nov 2021

Cited by 1 | Viewed by 1742

The development of supercapacitors with high volumetric capacitance and high-rate performance has been an important research topic. Activated carbon (AC), which is a widely used material for supercapacitor electrodes, has different surface structures, porosities, and electrochemical properties. However, the low conductivity of the [...] Read more.

The development of supercapacitors with high volumetric capacitance and high-rate performance has been an important research topic. Activated carbon (AC), which is a widely used material for supercapacitor electrodes, has different surface structures, porosities, and electrochemical properties. However, the low conductivity of the electrode material is a major problem for the efficient use of AC in supercapacitors. To tackle this challenge, we prepared conductive, additive-free electrodes for supercapacitors by a simple one-pot treatment of AC with melamine (nitrogen source), pitch, and sucrose (both carbon source). Nitrogen-doped and carbon-coated AC was successfully generated after high-temperature heat treatment. The AC was doped with approximately 0.5 at.% nitrogen, and coated with carbon leading to a decreased oxygen content. Thin carbon layers (~10 nm) were coated onto the outer surface of the AC, as shown in TEM images. The modification of the AC surface with a sucrose source is favorable, as it increases the electrical conductivity of AC up to 3.0 S cm⁻¹, which is 4.3 times higher than in unmodified AC. The electrochemical performance of the modified AC was evaluated by conducting agent-free electrode. Although the obtained samples had slightly reduced surface areas after the surface modification, they maintained a high specific surface area of 1700 m² g⁻¹. The supercapacitor delivered a specific capacitance of 70.4 F cc⁻¹ at 1 mA cm⁻¹ and achieved 89.8% capacitance retention even at a high current density of 50 mA cm⁻². Furthermore, the supercapacitor delivered a high energy density of 24.5 Wh kg⁻¹ at a power density of 4650 W kg⁻¹. This approach can be extended for a new strategy for conductivity additive-free electrodes in, e.g., supercapacitors, batteries, and fuel cells. Full article

(This article belongs to the Special Issue Supply of Materials for Energy Storage Devices)

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9 pages, 2420 KiB

Open AccessArticle

sp²–sp³ Hybrid Porous Carbon Materials Applied for Supercapacitors

by Ji Su Chae, Won-seop Kang and Kwang Chul Roh

Energies 2021, 14(19), 5990; https://doi.org/10.3390/en14195990 - 22 Sep 2021

Cited by 5 | Viewed by 2164

Abstract

Carbon materials have gained considerable attention in recent years due to their superior properties. Activated carbon has been used in supercapacitors due to its density and rapid adsorption capability. The sp²–sp³ hybrid porous carbon materials are synthesized using herringbone-type carbon [...] Read more.

Carbon materials have gained considerable attention in recent years due to their superior properties. Activated carbon has been used in supercapacitors due to its density and rapid adsorption capability. The sp²–sp³ hybrid porous carbon materials are synthesized using herringbone-type carbon nanofibers (CNFs) and carbonized spherical phenol resins, with KOH as the activating agent. The morphology of the hybrid porous carbon facilitates the formation of ribbon-like nanosheets from highly activated CNFs wrapped around spherical resin-based activated carbon. The etching and separation of the CNFs produce a thin ribbon-like nanosheet structure; these CNFs simultaneously form new bonds with activated carbon, forming the sp²–sp³ hybrid porous structure. The relatively poor electrical conductivity of amorphous carbon is improved by the 3D conductive network that interconnects the CNF and amorphous carbon without requiring additional conductive material. The composite electrode has high electron conductivity and a large surface area with a specific capacitance of 120 F g⁻¹. Thus, the strategy substantially simplifies the hybrid materials of sp²-hybridized CNFs and sp³-hybridized amorphous spherical carbon and significantly improves the comprehensive electrochemical performance of supercapacitors. The developed synthesis strategy provides important insights into the design and fabrication of carbon nanostructures that can be potentially applied as electrode materials for supercapacitors. Full article

(This article belongs to the Special Issue Supply of Materials for Energy Storage Devices)

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8 pages, 2010 KiB

Open AccessCommunication

Nano-Fe₃O₄/Carbon Nanotubes Composites by One-Pot Microwave Solvothermal Method for Supercapacitor Applications

by Sul Ki Park, Jagadeesh Sure, D. Sri Maha Vishnu, Seong Jun Jo, Woo Cheol Lee, Ibrahim A. Ahmad and Hyun-Kyung Kim

Energies 2021, 14(10), 2908; https://doi.org/10.3390/en14102908 - 18 May 2021

Cited by 17 | Viewed by 2784

Abstract

Carbon nanotubes (CNTs) are being increasingly studied as electrode materials for supercapacitors (SCs) due to their high electronic conductivity and chemical and mechanical stability. However, their energy density and specific capacitance have not reached the commercial stage due to their electrostatic charge storage [...] Read more.

Carbon nanotubes (CNTs) are being increasingly studied as electrode materials for supercapacitors (SCs) due to their high electronic conductivity and chemical and mechanical stability. However, their energy density and specific capacitance have not reached the commercial stage due to their electrostatic charge storage system via a non-faradic mechanism. Moreover, magnetite (Fe₃O₄) exhibits higher specific capacitance originating from its pseudocapacitive behaviour, while it has irreversible volume expansion during cycling. Therefore, a very interesting and facile strategy to arrive at better performance and stability is to integrate CNTs and Fe₃O₄. In this study, we demonstrate the microwave-solvothermal process for the synthesis of Fe₃O₄ nanoparticles uniformly grown on a CNT composite as an electrode for SCs. The synthesized Fe₃O₄/CNT composite delivers a reversible capacitance of 187.1 F/g at 1 A/g, superior rate capability by maintaining 61.6% of 10 A/g (vs. 1 A/g), and cycling stability of 80.2% after 1000 cycles at 1 A/g. Full article

(This article belongs to the Special Issue Supply of Materials for Energy Storage Devices)

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