Transition Metals@MXenes electrocatalysts for high-performance Lithium–Sulfur batteries under lean electrolyte: A comprehensive review

Abstract

Lithium–sulfur batteries (LSBs) with various advantages including high energy density, low costs and environmental friendliness, have been considered as one of the most promising advanced rechargeable batteries. Although great achievements have been realized in recent years, these test conditions are generally carried out under excess electrolyte (electrolyte-to-sulfur (E/S) ratio > 10.0 µL mg⁻¹), significantly hindering practical energy density improvements of LSBs. The lean electrolyte is a key factor for improving the energy density of LSBs, yet several tough issues under lean electrolyte, such as shuttle effect, sluggish reaction kinetics and side reaction, seriously hinder the improvement of battery performances. Transition metals@MXenes have been considered as ideal electrocatalysts for regulating redox reaction of LSBs due to their metallic conductivity, large polar surface and abundant active sites. Nevertheless, a in-depth overview of transition metals@MXenes electrocatalysts for lean electrolyte LSBs is still lacking. This review aims to fill this gap by providing a detailed analysis of the mechanisms, challenges, and solutions associated with lean electrolyte LSBs. It focuses on the role of transition metals@MXenes in regulating redox reactions and improving lithium plating/stripping behaviors, particularly in high-concentration lithium polysulfide (LiPS) environments. The review also discusses the structure–activity relationship of these electrocatalysts, highlighting their potential to mitigate the shuttle effect and enhance reaction kinetics. Furthermore, the review presents the latest advancements in the application of transition metals@MXenes for high-performance lean electrolyte LSBs and proposes future research directions to advance their development in the energy storage field.