Structure and phase regulation for in-situ reconstructed ZIFs derived (Co, Ni, Mn)-Se and research on high-performance hybrid-supercapacitors

Abstract

Exploiting the theoretical capacity of transition-metal selenide (TMSe) electrodes with improving stability is a challenge in hybrid supercapacitors (HSCs). An in-situ strategy of multidirectional recombination of reasonable/stable hierarchical structure and multiphase synergy is proposed to boost TMSe electrodes to a higher level. Herein, trimetallic layered double hydroxides (CoNiMn-LDH) are in-situ reconstructed with hollow CNFs (carbon–nitrogen frameworks), which can expose numerous active sites and facilitates rapid charge transport. After systematic selenization (time gradient), the valence-rich multiphase (Co, Ni, Mn)-Se@CNFs is regulated and the hierarchical structure is further optimized with reduction of layer spacing for rapid charge transfer and OH– adsorption. The multiphase coordinated electrode demonstrates a high capacity (334.7 mAh g−1, 1 A g−1, 6 M KOH) and superior rate capability (277.8 mAh g−1, 10 A g−1, 83.0%). Besides, the assembled HSC demonstrates a quite high energy density ((Co, Ni, Mn)-Se@CNFs//Activated carbon, 91.6 Wh kg−1 at 800 W kg−1). The ultra-high cycle retention rate (without attenuation, 16,000 cycles) illustrates the excellent stability, which is superior to the HSCs we know that use TMSes. The in-situ strategy with systematic research on structure/phase regulation provides effective ideas for the preparation and application of high-capacity electrodes and high-efficiency HSCs.