Impact of Disorder, Porosity, and Surface Chemistry of Salt Templated Carbons on Capacitance

Abstract

The necessity of tailoring the structure/texture of carbons to improve the performance of aqueous-based electrical double-layer capacitors (EDLCs) is emphasized. A green soft-salt templating approach allowed the preparation of a series of porous carbons for this target. The EDLCs operating in 1M Li2SO4 demonstrated a maximum capacitance of 244 F g−1 at 1.6 V (CsCl/KCl-T), long-term cycle life (288 h for LiCl/KCl-T), and a specific energy exceeding 10 Wh kg−1. The physicochemical properties of carbons have been correlated with capacitance, retention, and stability. The investigation by Raman spectroscopy revealed that carbons with the increased disorder, thus, higher ID/IG ratio, are in accord with enhanced capacitance. Active surface area (ASA) values, related to carbon defects, perfectly supported the Raman findings. Surface functionality, i.e., the phenol/ether and carboxyl groups are found to affect capacitance. The carbons showed a predominance of micropores, with a specific surface area (SSA) ranging from 2640 to 1453 m2 g−1. In sum, ID/IG, SSA, ASA, and volume of micropores are in linear proportion with capacitance at various regimes. However, the most ordered and less porous materials provided better lifespan performance. Therefore, a good compromise is required to satisfy both high capacitance and the long cycle life of EDLCs.