Universal Solution Synthesis of Sulfide Solid Electrolytes Using Alkahest for All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Sulfide solid electrolytes (SEs) offer potential for advanced all-solid-state batteries.
• Current wet-chemical preparation methods for SEs have limitations in precursor scope and composition.
• Existing techniques include suspension synthesis and solution processes with restricted compositional ranges.

Purpose of the Study:

• To develop a universal solution synthesis method for preparing a wider range of sulfide solid electrolytes.
• To investigate the solvent properties enabling the dissolution of diverse sulfide precursors.
• To demonstrate the efficacy of synthesized SEs in all-solid-state battery applications.

Main Methods:

• Developed a novel solution process utilizing a mixed solvent of 1,2-ethylenediamine (EDA) and 1,2-ethanedithiol (EDT).
• Dissolved various sulfide precursors, including Li2S, P2S5, Na2S, LiCl, GeS2, and SnS2, in the EDA-EDT solvent.
• Employed Raman spectroscopy and theoretical calculations to understand the solvent's interaction with GeS2.
• Fabricated and tested all-solid-state batteries using the synthesized SEs.

Main Results:

• The EDA-EDT solvent effectively dissolved a broad spectrum of sulfide precursors, overcoming previous limitations.
• Raman spectroscopy and calculations indicated strong nucleophilicity of thiolate anions in EDA-EDT, facilitating Ge-S bond dissociation.
• Synthesized Li10Ge2P12, Li6PS5Cl, and Na11Sn2PS12 exhibited high ionic conductivities (0.74, 1.3, and 0.10 mS cm−1 at 30 °C, respectively).
• Successful demonstration of these SEs in all-solid-state battery devices.

Conclusions:

• A universal solution synthesis approach has been established for sulfide solid electrolytes.
• The unique solvent system expands the compositional flexibility for SE development.
• The synthesized SEs show promising performance for next-generation all-solid-state batteries.