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

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, Li3PS4, is delved into via the introduction of LiBr. P-31 nuclear magnetic resonance (NMR)unveils the emergence of a glassy PS43- network interspersed with Br-. Li-6 NMR corroborates swift Li+ migration between PS43- 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 Li3PS4. 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 Li3PS4 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.