A Ni-MOF derived graphene oxide combined Ni3S2–Ni/C composite and its use in the separator coating for lithium sulfur batteries

Abstract

Lithium–sulfur batteries (LSBs) are widely regarded as reliable novel secondary batteries due to their low price and high capacity. Nevertheless, the notorious “shuttle effect” limits the commercialization of LSBs. In order to solve this problem, we fabricated a Ni₃S₂–Ni/C composite through carbonization, vulcanization and hydrothermal reactions by using a Ni-MOF precursor and applied it as a separator modification layer to enhance the electrochemical properties of LSBs. To further increase the conductivity of the material, a small amount of GO was added during the experiment. The prepared material was also used as separator modified coating material to optimize the electrochemical performance of LSBs. The as prepared Ni₃S₂–Ni/C(GO) composite shows good conductivity and has a superior porous structure and abundant active sites. Lithium polysulfides (LPs) can be physically confined and chemically adsorbed, what is more, the Ni and Ni₃S₂ active sites enable fast conversion of LPs which further optimizes the rate performance. From the cycle performance measurement, the initial discharge specific capacity of the Ni₃S₂–Ni/C(GO) modified separator battery is found to be 1263.4, 1181.5, 1090.6, and 840.3 mA h g⁻¹ at 0.05, 0.1, 0.3 and 0.5C, respectively. After 400 charge/discharge cycles at 0.5C, the capacity remains at 483.6mA h g⁻¹ with a capacity retention ratio of 57.56%.