A hydrogel-assisting surface-confined corrosion strategy toward self-supported amorphous NiFe-layered double hydroxides enabling high-performance hybrid solid-state supercapacitors

Abstract

Layered double hydroxides (LDHs) are promising energy materials for supercapacitors. It is demonstrated that the integrated performance of the amorphous LDHs is superior to that of crystalline materials. However, it is still a great obstacle to producing amorphous LDHs. Herein, a simple and facile strategy is proposed to synthesize the self-supported amorphous NiFe-LDHs using a surface-confined method. The corrosion process takes place in a cost-effective hydrogel at ambient temperature and pressure, which can synchronously change the chemical structure and morphology of the NiFe-LDHs. This method is also proved to be effective in fabricating S-doped amorphous NiFe-LDHs. The as-prepared products show excellent electrochemical performance in the charge-discharge process with fast kinetics, low impedance, good stability, and significant capacity, which is superior to most reported crystalline electrode materials. Moreover, the assembled hybrid solid-state supercapacitor devices display excellent capacitive performance including high energy density, superb rate capability and outstanding long-term cycling stability. This work offers a new sight into economically synthesizing amorphous mixed-metal compositions for high-performance supercapacitors.