Reliable Sulfur Cathode Design for All‐Solid‐State Lithium Metal Batteries Based on Sulfide Electrolytes

Solid-state lithium-metal batteries using sulfide-based electrolytes show great promise due to their potentially high-energy-density and safety, but issues such as high insulation, large volume expansion, and poor interface contact hinder further improvement, especially on the cathode side. This review discusses the challenges and recent progress, aiming to provide guidance for the future development of sulfide-based solid-state lithium–sulfur batteries.

Abstract

Sulfide electrolytes are considered the most promising technique for all-solid-state lithium–sulfur batteries (ASLSBs) due to relatively high ionic conductivity and superior chemical compatibility with composite sulfur cathodes. However, sulfur cathodes based on sulfide electrolytes feature large volume expansion, unstable interfacial contact, and inherent insulating nature, which impedes the practical application of ASLSBs. Therefore, a systematic design of the cathode side of ASLSBs is crucial for ensuring a well-contacted, electrochemically stable cathode–electrolyte interface, and an effective ion-electron transfer network. Here, a comprehensive discussion of the latest strategies will be delivered, highlighting their effectiveness in improving the performances of the sulfur cathode in ASLSBs. First, the major challenges including slow oxidation kinetics and significant volume expansion of the sulfur cathode are dissected. Then, the focus is shifted to the degradation processes at the interface between the cathode and electrolyte. Subsequently, the improvement of ionic conductivity and stability of sulfide electrolytes by structural modulation is elaborated. Finally, based on the latest progress, we present a new perspective on constructing an efficient ion-electron transport network and a stable cathode-electrolyte interface, which offers insights and directions for achieving practical ASLSBs in the future.