Composite Sulfur Electrode for All-solid-state Lithium–sulfur Battery with Li₂S–GeS₂–P₂S₅-based Thio-LISICON Solid Electrolyte

Abstract

Composite sulfur electrodes are prepared by prolonged mechanical milling (≥300 min) for use in all-solid-state lithium-sulfur batteries, and their structure and electrochemical properties are investigated. These batteries exhibit a high initial discharge capacity (>1500 mAh g⁻¹). Sulfur, acetylene black, and the solid electrolyte Li_3.25Ge_0.25P_0.75S₄ are mixed by planetary ball milling to form composites that contain amorphous phases of the starting materials, as well as a byproduct with a novel structural unit arising from the reaction between sulfur and the solid electrolyte. Batteries with a composite electrode/Li_3.25Ge_0.25P_0.75S₄/Li–In anode configuration exhibit a high initial discharge capacity (>1100 mAh g⁻¹). However, the capacity fades during cycling (∼500 mAh g⁻¹ at the 30th cycle), possibly because of the increased resistance of the composite. Structural and compositional changes of the byproduct and the solid electrolyte itself during the battery reaction could contribute to the increase in resistance that cause the deterioration of cyclability.