A Functional Air-Stable Li_9.8GeP_1.7Sb_0.3S_11.8I_0.2 Superionic Conductor for High-Performance All-Solid-State Lithium...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Sulfide solid-state electrolytes (SSEs) offer high ionic conductivity but suffer from moisture sensitivity.
• This instability leads to decreased performance and increased processing complexity in solid-state batteries.
• Developing air-stable SSEs is crucial for advancing next-generation lithium-ion batteries.

Purpose of the Study:

• To design and synthesize a novel, air-stable solid-state electrolyte with enhanced ionic conductivity.
• To investigate the structural and chemical modifications responsible for improved stability.
• To evaluate the electrochemical performance of the new electrolyte in all-solid-state lithium-ion batteries.

Main Methods:

• Synthesis of Li_9.8GeP_1.7Sb_0.3S_11.8I_0.2 (LGPSSI) based on hard and soft acids and bases (HSAB) theory.
• Characterization using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS).
• Electrochemical testing of Li-ion conductivity, activation energy, and full cell performance (NCA//Li-In).

Main Results:

• LGPSSI exhibits a high Li⁺ conductivity of 6.6 mS cm^-1 and low activation energy (20.33 kJ mol^-1).
• The material shows superior air stability, with significantly reduced H₂S evolution compared to pristine LGPS.
• Full cells demonstrate high initial discharge capacity (209.1 mAh g^-1) and excellent cycling stability (92.64% retention over 100 cycles).

Conclusions:

• The strategic incorporation of Sb and I enhances the air stability and ionic conductivity of sulfide SSEs.
• LGPSSI represents a promising candidate for safe and high-performance all-solid-state lithium-ion batteries.
• The findings highlight the effectiveness of HSAB theory in designing stable and conductive solid electrolytes.