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

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_6.35La₃Zr_1.4Ta_0.6O_11.85-Cl_0.15 (LLZTO-0.15Cl) electrolyte demonstrates high Li⁺ conductivity of 4.21×10^-6 S cm^-1. When integrated with LiFePO₄ (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.