A high-performance asymmetric supercapacitor-based (CuCo)Se2/GA cathode and FeSe2/GA anode with enhanced kinetics matching

The performance of asymmetric supercapacitors (ASCs) is limited by the poorly matched electrochemical kinetics of available electrode materials, which generally results in reduced energy density and inadequate voltage utilization. Herein, a porous conductive graphene aerogel (GA) scaffold was decorated with copper cobalt selenide ((CuCo)Se2) or iron selenide (FeSe2) to construct positive and negative electrodes, respectively. The (CuCo)Se2/GA and FeSe2/GA electrodes exhibited high specific capacitances of 672 and 940 F g−1, respectively, at 1 A g−1. The capacitance contributions from the Co3+/Co2+ and Fe3+/Fe2+ redox couple for the positive and negative electrodes were determined to elucidate the energy storage mechanism. Furthermore, the kinetics study of the two electrodes was performed, revealing b values ranging between 0.7 and 1 at various scan rates and demonstrating that the surface-controlled processes played the dominant role, leading to fast charge storage capability for both electrodes. Fabrication of an ASC device with a configuration of (CuCo)Se2/GA//FeSe2/GA resulted in a voltage of 1.6 V, a high energy density of 39 W h kg−1, and a power density of 702 W kg−1. The excellent electrochemical performances of the (CuCo)Se2/GA and FeSe2/GA electrodes demonstrate their potential applications in energy storage devices.