MOF-71 derived layered Co-CoP/C for advanced Li-S batteries

Abstract

The commercialization of lithium-sulfur (Li-S) batteries is severely plagued by the shuttle effect and sluggish kinetic conversion of polysulfides. Herein, the layered cobalt phosphide CoP/C nanoparticle derived from MOF-71 by two-step heat treatment was synthesized to act as sulfur host in Li-S batteries. The physical characterization results indicate that Co-CoP/C has a specific surface area of 113 m2 g−1, with more micropores and mesopores, which is beneficial to the transmission of ions and electrons. MOF-derived polar metal phosphide Co-CoP/C has shown layered porous structure, which can provide more the active site to adsorb more polysulfides, furthermore, the cobalt phosphide can promote catalytic conversion of polysulfides. Thus the lithium-sulfur battery assembled with Co-CoP/C@S as the positive electrode showed excellent electrochemical performance: tested at a rate of 0.2 C, the initial discharge specific capacity of the battery reached 1441.9 mAh g−1. Additionally, the long-cycle stability performance test was performed at a rate of 0.5 C, and the battery still maintained a reversible specific capacity above 600 mAh g−1 after 300 cycles of charge and discharge.