Transition metal phosphides: new generation cathode host/separator modifier for Li–S batteries

Abstract

Owing to their promising applications including, aircrafts, military field, and submarines, lithium–sulfur (Li–S) batteries with high energy density (2500 W h kg−1) are emerging as the next-generation energy storage system with low cost to replace lithium-ion batteries. Nevertheless, the road to commercialization is mainly hindered by low coulombic efficiency, poor cycling, and rate capabilities, which are mainly due to the so-called polysulfide (PS) shuttle, sluggish electrochemical reactions, etc. One of the most effective and direct strategies among different optimization methods is to rationally design the cathode host of Li–S batteries. Transition metal phosphides (TMPs) feature relatively good electrical performance, mild synthesis, adequate chemical adsorption strength and exceptional catalytic capability for PS, which make them a cathode host/separator modifier for the new generation of Li–S batteries. In this review, the electrochemical reaction mechanisms of Li–S batteries and major roadblocks to commercial applications are firstly described. Following that, we summarize the synthesis strategy of TMPs and systematically review the recent progress on TMPs in Li–S batteries, where light is shed on the specific roles of TMPs as Li–S battery cathodes and separator modifiers, and briefly on the synthesis. In future research on Li–S batteries, the review provides insight into the challenges of TMPs and directions for further development.