Grain Boundary Engineering in Ta-Doped Garnet-Type Electrolyte for Lithium Dendrite Suppression.

Solid-state lithium batteries (SSLBs) based on Ta-doped LiLaZrTaO (LLZTO) suffer from lithium dendrite growth, which hinders their practical application. Herein, first principles simulations indicate that the Ta element prefers to segregate along grain boundaries in the form of TaO precipitates due to a high energy difference induced by Ta doping. Grain boundary engineering is employed to regulate the distribution of the Ta element and enhance the density of LLZTO by introducing the LaO additive. The sufficient LaO additive reacts with the TaO precipitates, while the residual LaO nanoparticles fill up void defects, promoting the homogeneous distribution of the Ta element and improving the relative density to ∼98%. Critical current density of the symmetric Li battery reaches 2.12 mA·cm at room temperature with the solid-state electrolyte (LLZTO + 5 wt % LaO), which increases by 41% compared to pure LLZTO. SSLBs with the LiFePO cathode achieve a stable cycling performance with a discharge capacity of 138.6 mA·h·g after 400 cycles at 0.2 C. This work provides theoretical insights into the distribution of Ta-doped LLZTO and inhibits lithium dendrite growth through grain boundary engineering.