Exploring dopant-enhanced ionic conductivity of AgCl-doped Li7P3S11 solid electrolytes: Integrating synchrotron Rietveld analysis, DFT, and ANN-based molecular dynamics approaches

Abstract

The effectiveness of dual-doping as a method of improving the conductivity of sulfide solid electrolytes (SEs) is not in doubt; however, the atomic-level mechanisms underpinning these enhancements remain elusive. In this study, we investigate the atomic mechanisms associated with the high ionic conductivity of the Li7P3S11 (LPS) SE and its response to Ag/Cl dual dopants. Synthesis and electrochemical characterizations show that the 0.2 M AgCl-doped LPS (Li6.8P3Ag0.1S10.9Cl0.1) exhibited an over 80% improvement in ionic conductivity compared with the undoped LPS. The atomic-level structures responsible for the enhanced conductivity were generated by a set of experiment and simulation techniques: synchrotron X-ray diffractometry, Rietveld refinement, density functional theory, and artificial neural network-based molecular dynamics simulations. This thorough characterization highlights the role of dual dopants in altering the structure and ionic conductivity. We found that the PS4 and P2S7 structural motifs of LPS undergo transformation into various PSx substructures. These changes in the substructures, in conjunction with the paddle-wheel effect, enable rapid Li migration. The dopant atoms serve to enhance the flexibility of PS4-P2S7 polyhedral frameworks, consequently enhancing the ionic conductivity. Our study elucidates a clear structure-conductivity relationship for the dual-doped LPS, providing a fundamental guideline for the development of sulfide SEs with superior conductivity.