Synthesis of Porous Carbon Material with Suitable Graphitization Strength for High Electrochemical Capacitors

It is a long-lasting challenge to design and synthesize electric double-layered electrode materials with suitable graphitization strength, simultaneously working to achieve a high capacitance for electrochemical capacitors. In our work, starch-based porous carbons (SPCs) are obtained via carbonization and mature KOH chemical activation. The prepared materials have a superior specific capacitance of 397, 372, and 337 F g–1 corresponding to SPC-5, SPC-15, and SPC-25 (SPC-x, x represents the starch particle size), as well as a distinguished cycling stability of 97% capacity retention over 20 000 cycles in KOH electrolyte. In addition, in 6 M KOH electrolyte, SPC-5 exhibits a superior energy density of 22.59 W h kg–1 when the power density is 148 W kg–1. This is mainly due to its suitable graphitization strength and particle size. Biomass is used with different amylopectin content to control the degree of graphitization of carbon materials. The strategy demonstrates a way to fabricate a reasonable graphitized carbons derived from biomass with improved capacitance, which is critical for a broad range of devices for the field of energy storage.