Efficient electrochemical energy storage designed by second alcoholic fermentation of rice

Supercapacitors can deliver energy quickly, offering extraordinary potential for efficient electrochemical energy storage (EES) systems. Specifically, carbon-based supercapacitors have reliable operational stability and outstanding cycle lifespans. However, designing low-cost and high-energy-density carbon electrode materials using a simple method remains an enormous challenge. Here, we design a porous carbon material JKPC-4-700 derived from a second alcoholic fermentation rice by tuning the pore sizes using a simple approach. The main pore sizes of JKPC-4-700 are 0.57 and 1.22 nm, in good agreement with the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) ionic liquid. The specific surface area of JKPC-4-700 reaches 2662 m2 g−1, which enables JKPC-4-700 a specific capacity of 465 F g−1 (at 1.0 A g−1 in 6 M KOH). The symmetric capacitors based on JKPC-4-700 deliver an excellent energy density of 117 Wh kg−1 (at a power-density of 900 W kg−1). Our research offers a new strategy for developing high-energy-density, low-cost, and functional carbon materials for efficient EES systems.