CuS and Cu2S as Cathode Materials for Lithium Batteries: A Review

Nowadays, lithium‐ion batteries (LIBs) take a very important role for energy storage. LIBs are dominant in consumer electronics, and they have also entered the market of hybrid electric vehicles (HEVs), plug‐in HEVs, and pure EVs. However, state‐of‐the‐art LIBs are electrochemically intercalation‐based and are still limited in energy density and power rates. To address these challenges and others (e. g. safety issues and cost), conversion‐based copper sulfides (CuxS, 1≤x≤2) have been investigated as alternative cathodes for improved electrochemical performance, that is, higher energy density, better cycling stability, and enhanced rate capability. In this work, we summarize the recent research progress on CuxS to gain a better understanding of the material's electrochemical mechanisms and develop feasible strategies for improving its performance. Controversial decisions: A comprehensive summary on the crystal characteristics of CuS and Cu2S is presented as well as their electrochemistry and the strategies developed for their superior electrochemical performance. In comparison to the clear mechanism of Cu2S, there has some controversy on the mechanism of CuS. The long‐term cyclability and high rate capability of both CuS and Cu2S are desirable in many applications.