Solid Catholyte with Regulated Interphase Redox for All-Solid-State Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium-sulfur batteries (ASSLSBs) are promising next-generation energy storage devices due to their potential for low cost, high safety, and high specific energy.
• Sulfide electrolytes offer high conductivity and low modulus for solid catholytes in ASSLSBs, but suffer from parasitic decomposition and interphase degradation, limiting cycle life.

Purpose of the Study:

• To stabilize ASSLSBs by regulating the interphase redox reversibility of sulfide catholytes.
• To introduce and validate a new sulfide electrolyte, Li6+xP1-xWxS5I (LPWSI), for improved interphase stability and cycling performance.

Main Methods:

• Formulation and characterization of a novel sulfide electrolyte, Li6+xP1-xWxS5I (LPWSI).
• Investigation of the interphase reaction mechanisms, focusing on the role of WS2 in regulating redox reversibility.
• Fabrication and electrochemical testing of ambient-temperature ASSLSBs using the LPWSI catholyte.

Main Results:

• The presence of mixed ionic-electronic conducting WS2 in the LPWSI electrolyte promotes a beneficial Li4P2S7-to-Li3PS4 reaction, preventing the accumulation of impeding P2S7 4- species.
• The LPWSI catholyte demonstrates enhanced interphase stability, leading to significantly improved cycling performance in ASSLSBs.
• ASSLSBs with LPWSI achieved stable cycling, retaining 92.2% of their initial capacity over 400 cycles at C/5, with an initial areal capacity of 1.95 mA h cm-2.
• The cells exhibited excellent high-rate stability, maintaining performance over 1000 cycles at 1C and 2C rates.

Conclusions:

• The strategy of regulating interphase redox reversibility by incorporating mixed ionic-electronic conducting materials like WS2 is effective in stabilizing sulfide catholytes.
• The developed LPWSI electrolyte offers a viable solution for enhancing the cycling life and performance of ambient-temperature ASSLSBs.
• This work provides new insights into the functioning of solid catholytes in composite cathodes and offers guidelines for designing advanced electrolytes for high-capacity conversion-based electrodes.