High-density spherical nanocarbon clusters for pouch-type ionic liquid supercapacitors with high volumetric energy density and rate performance

Optimizing the volumetric energy density of carbon-based supercapacitors involves attaining a high working voltage window and volumetric capacitance while ensuring optimal rate performance. Ionic liquids and high-density porous carbons become emerging electrolytes and electrode materials due to their high decomposition voltage and large volumetric ion-accessible surface area, respectively. However, understanding the impact of ion diffusion pathways in porous carbon on capacitance performance proves challenging due to the diverse microstructures of carbon materials. This research presents customized spherical nanocarbon clusters functioning as the electrode material in pouch-type ionic liquid supercapacitors, aiming to enhance ion transport behavior within carbon electrodes by modifying the interlayer plane pathways into intercluster pore pathways. The obtained morphologies, close arrangements, and high densities of nanocarbon clusters shorten the ion transport pathway and facilitate ion accessibility for better rate capability and volumetric energy density. Using a relative green approach, we employed non-volatile EMIMBF4 ionic liquid as the electrolyte and a combination of carboxymethyl cellulose and styrene-butadiene rubber as aqueous binders for electrodes. This strategy resulted in remarkable specific areal capacitance of 0.091 F m−2, volumetric capacitance of 53 F cm−3 at 0.5 A g−1, and impressive volumetric energy densities of 22.73 Wh L−1 at 481.25 W L−1 and 12.79 Wh L−1 at 23020.85 W L−1. By using non-volatile EMIMBF4 ionic liquid as the green electrolyte, carboxymethyl cellulose combined with styrene-butadiene rubber as aqueous binders of electrodes, the outstanding specific areal capacitance of 0.091 F m−2 and volumetric capacitance of 53 F cm−3 are achieved at 0.5 A g−1 with outstanding volumetric energy densities of 22.73 and 12.79 Wh L−1 obtained at 481.25 and 23,020.85 W L−1, respectively.