Dual-Conductivity Optimization Toward High-Rate and Ultralong Life All-Solid-State Lithium-Sulfur Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state lithium-sulfur batteries (ASSLSBs) offer high energy density but face challenges with sluggish reaction kinetics in sulfur cathodes.
• Poor ionic diffusion and electronic conduction limit the performance of traditional lithium sulfide cathodes, especially at high current densities.

Purpose of the Study:

• To engineer lithium sulfide to improve ionic diffusion and electronic conduction for enhanced reaction kinetics in ASSLSBs.
• To develop a novel cathode material for high-performance, safe, and high-energy-density solid-state batteries.

Main Methods:

• Electronic structure modulation of lithium sulfide through same-group element doping (selenium substitution).
• Synthesis and characterization of Li₂Se_0.2S_0.8 cathode material.
• Fabrication and testing of ASSLSB full cells with a silicon anode.

Main Results:

• Partial selenium substitution (Li₂Se_0.2S_0.8) created Se─S bonds, weakening sulfur's electronegativity and facilitating Li⁺ diffusion.
• The modified cathode exhibited a narrowed bandgap, enhancing electronic conduction.
• The Li₂Se_0.2S_0.8 cathode demonstrated excellent high-rate capability, retaining 97.5% capacity after 1000 cycles at 1 A g^-1.
• A full cell achieved a high energy density of 1324 Wh kg^-1.

Conclusions:

• Selenium doping is an effective strategy to concurrently enhance ionic and electronic transport in lithium sulfide cathodes.
• The developed Li₂Se_0.2S_0.8 cathode shows significant promise for high-energy and high-power ASSLSBs.
• This approach paves the way for practical, high-performance solid-state batteries.