Optimized Lithium Ion Coordination via Chlorine Substitution to Enhance Ionic Conductivity of Garnet-Based Solid Electrolytes.

Garnet-type solid-state electrolytes attract abundant attentions due to the broad electrochemical window and remarkable thermal stability while their poor ionic conductivity obstructs their widespread application in all-solid-state batteries. Herein, the enhanced ionic conductivity of garnet-type solid electrolytes is achieved by partially substituting O 2- sites with Cl - anions, which effectively reduce Li + migration barriers while preserving the highly conductive cubic phase of garnet-type solid-state electrolytes. This substitution not only weakens the anchoring effect of anions on Li + to widen the size of Li + diffusion channel but also optimizes the occupancy of Li + at different sites, resulting in a substantial reduction of the Li + migration barrier and a notable improvement in ionic conductivity. Leveraging these advantageous properties, the developed Li 6.35 La 3 Zr 1.4 Ta 0.6 O 11.85 -Cl 0.15 (LLZTO-0.15Cl) electrolyte demonstrates high Li + conductivity of 4.21×10 -6  S cm -1 . When integrated with LiFePO 4 (LFP) cathode and metallic lithium anode, the LLZTO-0.15Cl electrolyte enables the solid-state battery to operate for more than 100 cycles with a high capacity retention of 76.61% and superior Coulombic efficiency of 99.48%. This work shows a new strategy for modulating anionic framework to enhance the conductivity of garnet-type solid-state electrolytes.