MOF derived cobalt-nickel bimetallic phosphide (CoNiP) modified separator to enhance the polysulfide adsorption-catalysis for superior lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) have aroused great research interest due to their high theoretical capacity and high energy density. To further develop lithium-sulfur batteries, it has become more and more important to put more efforts in promoting the adsorption and rapid catalytic conversion of lithium polysulfides (LiPSs). Herein, Ni/Co bimetallic phosphides were encapsulated into nitrogen-doped dual carbon conductive network (NiCoP@NC) by annealing and phosphorizing Ni-ZIF-67 precursor at high temperature. Due to their numerous co-adsorption/catalytic sites and high conductivity of carbon skeleton, the encapsulated Ni/Co phosphides particles could significantly enhance the anchoring and catalytic conversion of LiPSs and provide ultrafast channels for Li+ transport. When used as a modified separator for LSBs, the cells displayed superior performance with an initial capacity of 1083.4 m Ah g−1 at 0.5 C and outstanding cycle stability with a capacity decay rate of only 0.09% per cycle for 300 cycles. Besides, even at high sulfur loading (3.2 mg cm−2), they still present satisfactory performance. Therefore, this study presents a novel strategy on how to use MOF derived bimetallic phosphides with chemical adsorption and catalytic conversion of polysulfides for high-power advanced lithium-sulfur batteries.