Selenium sulfide cathode with copper foam interlayer for promising magnesium electrochemistry

Magnesium (Mg) metal anode pairing with Sulfur (S) cathode has been regarded as a promising contender for next-generation battery technology holding the characteristics of safety in use, low cost and high energy density. However, the sluggish kinetic and the inferior reversibility of Mg-S electrochemical reaction are two main challenges impeding the development of practical Mg-S batteries. Herein, SeS2 is proposed as a superior cathode for Mg batteries based on the complementary features of S (high specific capacity) and Se (high electronic conductivity). In this designed Mg-SeS2 battery with a Cu foam interlayer between cathode and separator, SeS2 compositing with ordered mesoporous carbon (SeS2/CMK3) exhibits impressive electrochemical performance. Various characterizations towards the electrochemical evolution on cathode side reveal that Cu foam interlayer not only acts as the trapping layer by the rapid chemical immobilization of polysulfide (polyselenide) species on Cu foam, but also serves as a "promoter" to propel the overall charge-discharge kinetics by the reversible displacement reaction between copper sulfide (copper selenide) and Mg2+. Benefiting from the unique advantages of SeS2/CMK3 and the rationally designed Cu interlayer, this novel Mg-SeS2 system demonstrates a feasible strategy to exploit the rechargeable Mg batteries with low cost, high areal capacity and large current capability.