Hierarchical multiphase (Ni, Co)-Se with adjustable interlayer distance derived from reconstructed ZIF-L for enhanced hybrid-supercapacitors

Abstract

As attractive electrodes for hybrid-supercapacitors (HSCs), transition-metal selenides (TMSes) demonstrate ideal conductivity and abundant valence states for rapid charge. However, the traditional TMSes are restricted to accumulative or low-correlation active sites and the single phase. Herein, reasonable structures rich in synergistic active sites are solutions to manufacture high-efficiency electrodes. Regular hexagonal NiCo-LDH (layered double hydroxide) is reconstructed on hollow carbon–nitrogen frameworks (CNFs) and a stable hierarchical system is constructed. After systematic gradient selenization (time/temperature), the controllable interlayer spacing with phase transformation of LDH derivatives (multiphase selenides: M-(Ni, Co)-Se (Co9Se8, NiSe2)) is researched. It is found that the hydroxyl adsorption and conductivity can be enhanced due to the synergistic effect between the multiphase TMSes, which can significantly improve the capacity of the electrode. The optimal electrode M-(Ni, Co)-Se@CNFs/CC (carbon cloth) (378.9 mAh g−1, 1 A−1, 6 M KOH) is obtained after systematic research. Furthermore, the HSC (M-(Ni, Co)-Se@CNFs/CC//Activated carbon) exhibits ultrahigh energy density (96.6 Wh kg−1) and excellent stability (10,000 cycles, 133.6 %, 6 M KOH), which is superior to most similar work. The novel path of multiphase synergy is successfully realized through the multiphase system, which has reference significance in the high-efficiency HSC industry.