Air‐stable Li3.12P0.94Bi0.06S3.91I0.18 solid‐state electrolyte with high ionic conductivity and lithium anode compatibility toward high‐performance all‐solid‐state lithium metal batteries

Abstract Sulfide solid‐state electrolytes (SSEs) with superior ionic conductivity and processability are highly promising candidates for constructing all‐solid‐state lithium metal batteries (ASSLMBs). However, their practical applications are limited by their intrinsic air instability and serious interfacial incompatibility. Herein, a novel glass‐ceramic electrolyte Li 3.12 P 0.94 Bi 0.06 S 3.91 I 0.18 was synthesized by co‐doping Li 3 PS 4 with Bi and I for high‐performance ASSLMBs. Owing to the strong Bi‒S bonds that are thermodynamically stable to water, increased unit cell volume and Li + concentration caused by P 5+ substitution with Bi 3+ , and the in situ formed robust solid electrolyte interphase layer LiI at lithium surface, the as‐prepared Li 3.12 P 0.94 Bi 0.06 S 3.91 I 0.18 SSE achieved excellent air stability with a H 2 S concentration of only 0.205 cm 3 g −1 (after 300 min of air exposure), outperforming Li 3 PS 4 (0.632 cm 3 g −1 ) and the most reported sulfide SSEs, together with high ionic conductivity of 4.05 mS cm −1 . Furthermore, the Li 3.12 P 0.94 Bi 0.06 S 3.91 I 0.18 effectively improved lithium metal stability. With this SSE, an ultralong cyclability of 700 h at 0.1 mA cm −2 was realized in a lithium symmetrical cell. Moreover, the Li 3.12 P 0.94 Bi 0.06 S 3.91 I 0.18 ‐based ASSLMBs with LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode achieved ultrastable capacity retention rate of 95.8% after 300 cycles at 0.1 C. This work provides reliable strategy for designing advanced sulfide SSEs for commercial applications in ASSLMBs.