Insight on air-induced degradation mechanism of Li7P3S11 to design a chemical-stable solid electrolyte with high Li2S utilization in all-solid-state Li/S batteries

The ideal solid-state electrolyte must have exceptional chemical and electrochemical stability, high ionic conductivity, lower interfacial resistance and high active material utilization. Inspired by discovering new lithium thiophosphate superionic conductors for all-solid-state Li/S batteries (ASSLSBs), we designed and explored the local structure of Li6.95Zr0.05P2.9S10.8O0.1I0.4 (LZPSOI) solid-state electrolyte, which owns a high ionic conductivity of 3.01 mS cm−1 with improved air-stability at RT. The structure–property correlation behavior of the chemical stability of LZPSOI electrolyte was sequentially premeditated by a combination of ex-situ XRD, MAS-NMR, XPS and SEM. A mechanistically driven approach has been extensively evaluated that the chemical stability of Li7P3S11 could be enhanced via oxide doping, in which S2- was partly replaced by O2– in conductive structural units to yield POS33- and P2OS64- which was confirmed by XPS and 31P MAS-NMR. The ASSLSBs assembled with LZPSOI electrolyte exhibited a remarkable initial discharge capacity of 932 mAh g−1 and a coulombic efficiency of 99.2% under 0.064 mA cm−2 at RT, compared to Li7P3S11 counterpart. The exceptional cyclic performance was benefitted from higher electronic and ionic conductivities with LiI additive and additional reaction sites, which collectively enhanced the utilization of Li2S active material. This exploration gives birth to a potential contender as a solid-state electrolyte with high ionic conductivity and chemical stability to apply for next-generation ASSLSBs.