A novel air-stable Li₇Sb_0.05P_2.95S_10.5I_0.5 superionic conductor glass-ceramics electrolyte for all-solid-state lithium-sulfur batteries

The blend of air stability and high lithium-ion (Li⁺) conductivity is not a simplistic approach to attain for sulfide-based solid-state electrolytes (SSEs), which hinders the exploitation of high energy all-solid-state lithium-sulfur batteries (ASSLSBs). Herein we report a novel lithium superionic conductor of Li₇Sb_0.05P_2.95S_10.5I_0.5 as solid-state glass-ceramics electrolytes obtained by an annealing treatment in a solid-state reaction route. It systematically explores the impact of facile aliovalent dual doping into the newly synthesized solid electrolytes, which have influenced higher Li⁺ conductivity of 2.55 × 10⁻³ Scm⁻¹ at room temperature, and wide range of voltage stability vs. Li/Li⁺ up to 7 V. Except that, an activation barrier of Li₇Sb_0.05P_2.95S_10.5I_0.5 for Li⁺ migration drops expressively due to optimizing the dopant contents, and subsequently defects produced. The electrolyte also achieved significant air stability based on Hard and Soft Acid/Base (HSAB) theory. The intrinsic structural aspects of the air stability for Li₇P₃S₁₁ and Li₇Sb_0.05P_2.95S_10.5I_0.5 solid-state electrolytes are premeditated using a combination of ex-situ X-ray photoelectron spectroscopy, XRD as well as Raman spectroscopy and SEM. The Li₂S-VGCF-SSE composite cathode with Li₇Sb_0.05P_2.95S_10.5I_0.5 SSE exhibited a high initial discharge capacity of 622.3 mAhg⁻¹ at 0.060 mAcm⁻², and ASSLSB was retained over 683.3 mAh g⁻¹ after 15th cycle at room temperature, better than pristine Li₇P₃S₁₁ SSE-based cell. This research provides a novel concept on the design of air-stable and superionic conductor solid-state electrolytes for high-performance ASSLSBs.