All-solid-state Li-S batteries with fast solid-solid sulfur reaction

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium-sulfur batteries (ASSLSBs) offer high energy, safety, and low cost for next-generation energy storage.
• Poor rate performance and short cycle life in ASSLSBs are attributed to sluggish solid-solid sulfur redox reactions (SSSRR) at three-phase boundaries.

Purpose of the Study:

• To address the limitations of ASSLSBs by enhancing the sluggish SSSRR.
• To develop a novel solid electrolyte that can act as a redox mediator to accelerate SSSRR.

Main Methods:

• Development of lithium thioborophosphate iodide (LBPSI) glass-phase solid electrolytes (GSEs).
• Utilizing the reversible redox of I-/I2/I3- within the solid electrolyte as a surficial redox mediator.
• Investigating the impact of the redox mediator on the density of active sites and reaction kinetics.

Main Results:

• The LBPSI GSE facilitated fast SSSRR, significantly increasing the density of active sites.
• ASSLSBs demonstrated ultrafast charging with a capacity of 1,497 mAh g−1sulfur at 2C and maintained 784 mAh g−1sulfur at 20C.
• Exceptional performance was observed at extreme rates (432 mAh g−1sulfur at 150C, 60°C) and cycle stability (80.2% retention over 25,000 cycles at 5C).

Conclusions:

• The developed LBPSI GSE effectively mediates SSSRR, overcoming previous limitations in ASSLSBs.
• This redox-mediated approach enables high-rate capability and superior cycling stability for ASSLSBs.
• The findings pave the way for advanced, high-energy, and safe ASSLSBs.