Transforming Li3PS4 Via Halide Incorporation: a Path to Improved Ionic Conductivity and Stability in All‐Solid‐State Batteries

Abstract To enhance Li + transport in all‐solid‐state batteries (ASSBs), harnessing localized nanoscale disorder can be instrumental, especially in sulfide‐based solid electrolytes (SEs). In this investigation, the transformation of the model SE, Li 3 PS 4 , is delved into via the introduction of LiBr. 31 P nuclear magnetic resonance (NMR)unveils the emergence of a glassy PS 4 3− network interspersed with Br − . 6 Li NMR corroborates swift Li + migration between PS 4 3− and Br − , with increased Li + mobility indicated by NMR relaxation measurements. A more than fourfold enhancement in ionic conductivity is observed upon LiBr incorporation into Li 3 PS 4 . Moreover, a notable decrease in activation energy underscores the pivotal role of Br − incorporation within the anionic lattice, effectively reducing the energy barrier for ion conduction and transitioning Li + transport dimensionality from 2D to 3D. The compatibility of Li 3 PS 4 with Li metal is improved through LiBr incorporation, alongside an increase in critical current density from 0.34 to 0.50 mA cm −2 , while preserving the electrochemical stability window. ASSBs with 3Li 3 PS 4 :LiBr as the SE showcase robust high‐rate and long‐term cycling performance. These findings collectively indicate the potential of lithium halide incorporation as a promising avenue to enhance the ionic conductivity and stability of SEs.