Influence of Particle Size Distribution on the Performance of Ionic Liquid-based Electrochemical Double Layer Capacitors

Author(s)

Rennie, Anthony J. R. ^[1] ; Martins, Vitor L. ^{[1, 2]} ; Smith, Rachel M. ^[1] ; Hall, Peter J. ^[1]

Affiliation

^[1] Univ Sheffield, Chem & Biol Engn, Sir Robert Hadfield Bldg, Mappin St, Sheffield S1 3JD, S Yorkshire - England

^[2] Univ Sao Paulo, Inst Quim, CP 26077, BR-05513970 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: SCIENTIFIC REPORTS; v. 6, FEB 25 2016.
• Web of Science Citations: 13

Abstract

Electrochemical double layer capacitors (EDLCs) employing ionic liquid electrolytes are the subject of much research as they promise increased operating potentials, and hence energy densities, when compared with currently available devices. Herein we report on the influence of the particle size distribution of activated carbon material on the performance of ionic liquid based EDLCs. Mesoporous activated carbon was ball-milled for increasing durations and the resultant powders characterized physically (using laser diffraction, nitrogen sorption and SEM) and investigated electrochemically in the form of composite EDLC electrodes. A bi-modal particle size distribution was found for all materials demonstrating an increasing fraction of smaller particles with increased milling duration. In general, cell capacitance decreased with increased milling duration over a wide range of rates using CV and galvanostatic cycling. Reduced coulombic efficiency is observed at low rates (<25 mVs(-1)) and the efficiency decreases as the volume fraction of the smaller particles increases. Efficiency loss was attributed to side reactions, particularly electrolyte decomposition, arising from interactions with the smaller particles. The effect of reduced efficiency is confirmed by cycling for over 15,000 cycles, which has the important implication that diminished performance and reduced cycle life is caused by the presence of submicron-sized particles. (AU)

• FAPESP's process: 13/22748-7 - Development of High Performance Electrochemical Capacitors Based on Graphene and Ionic Liquids.
• Grantee: Vitor Leite Martins
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 14/14690-1 - Development and improvement of electrochemical capacitors containing ionic liquids as electrolytes
• Grantee: Vitor Leite Martins
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor