Ultrahigh-performance hybrid supercapacitors based on sodium sulfate template-derived electrodes with surface modulation

Exploring efficient and durable electrode materials is crucial for the mature application of high-performance hybrid supercapacitors. Herein, the Fe3O4/Fe nanoparticles with surface phosphate ions modulation (P-Fe3O4/Fe) are successfully deposited on the two-dimensional carbon nanosheets (CNS) through a solid-state sodium sulfate template-directed two-step calcination strategy. Benefiting from the synergistic effect of each component and the unique two-dimensional architecture, the prepared P-Fe3O4/Fe/CNS delivers excellent energy storage features with splendid specific capacitance (427.4 F g−1 at 1 A g−1) and outstanding cycling stability at 15 A g−1 (90.8% retention after 10,000 cycles). Following, phosphate functionalized Co9S8/CoS (P-Co9S8/CoS) nanoparticles anchored on CNS are also fabricated by the same synthesis route, which deliver a maximum specific capacity of 544.6 C g−1 at 1 A g−1 and long cyclic retention of 91.6% after 10,000 cycles at 15 A g−1. By coupling with P-Fe3O4/Fe/CNS and P-Co9S8/CoS/CNS electrodes, the assembled P-Co9S8/CoS/CNS//P-Fe3O4/Fe/CNS hybrid supercapacitor depicts an admirable energy density of 73.4 Wh kg−1 at 1041.7 W kg−1 in alkaline electrolyte and ultralong cycling stability up to 20,000 cycles with only 10.5% capacitance decay. Furthermore, the red light-emitting diode (LED) can be successfully operated for up to 45 min by the series connection of the two devices. This work proposes an efficient strategy to construct ultrahigh-performance hybrid supercapacitors with advanced sodium sulfate template-derived electrodes by phosphate functionalization.