Tailored Redox-Active Catholytes Enabling High-Rate and High-Loading All-Solid-State Lithium-Sulfur Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium-sulfur batteries (ASSLSBs) offer high theoretical capacity but face challenges like slow kinetics and poor ionic conductivity.
• Volume changes during cycling and limited ionic percolation in composite cathodes hinder ASSLSB practical application.

Purpose of the Study:

• To develop novel solid electrolytes for ASSLSBs with improved ionic conductivity and electrochemical activity.
• To investigate the effect of iodine incorporation on the properties and performance of Li-Si-P-S solid electrolytes.

Main Methods:

• Synthesis of Li_10.5-xSi_1.5P_1.5S_12-xI_x solid electrolytes with varying iodine content (x = 0, 0.2, 0.4).
• Characterization of ionic conductivity, phase composition, and electrochemical behavior of the synthesized electrolytes.
• Fabrication and testing of ASSLSBs utilizing the novel electrolytes as catholytes.

Main Results:

• Solid electrolytes with high ionic conductivities (≥ 7 mS cm^-1) were achieved.
• Increased iodine content led to altered phase composition and reversible redox activity, enhancing sulfur conversion kinetics.
• ASSLSBs demonstrated high sulfur utilization (86% at C/2), excellent rate capability (1175 mAh g_sulfur^-1 at 5C), and record areal capacities (14 mAh cm^-2).

Conclusions:

• The developed redox-active catholytes significantly improve ASSLSB performance by enhancing ionic percolation and sulfur conversion kinetics.
• Iodine plays a crucial role in mediating redox activity and enabling high-performance ASSLSBs.
• These findings offer new strategies for designing advanced solid electrolytes for next-generation energy storage devices.