A Strategy for Polysulfides/Polyselenides Protection Based on Co9S8@SiO2/C Host in Na-SeS2 Batteries

Abstract

To obtain unbroken sulfides with delicate morphology from metal–organic frameworks (MOFs), a method for in situ growth of SiO2 protective layers on the surface of MOFs is proposed. This strategy can be successfully expanded to a variety of MOFs (ZIF-67, Cu-MOF, ZIF-8, and PBA). Importantly, room-temperature Na-SeS2 batteries with Co9S8@SiO2/C prepared from ZIF-67 as cathode host are assembled. Due to the hollow structure that can relieve the volume expansion and the co-adsorption of sodium polysulfides/sodium polyselenides by Co9S8@SiO2/C, the SeS2/Co9S8@SiO2/C cathode shows excellent rate performance and Coulombic efficiency. In addition, ex situ X-ray diffraction and in situ Raman results show that S8 and Se8 are generated after the discharge of SeS2, and Se8 is preferentially oxidized during charging.