Grain Boundary Engineering\nin Ta-Doped Garnet-Type\nElectrolyte for Lithium Dendrite Suppression

Abstract

Solid-state lithium batteries (SSLBs) based on Ta-doped\nLi_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) suffer from lithium dendrite growth, which hinders\ntheir\npractical application. Herein, first principles simulations indicate\nthat the Ta element prefers to segregate along grain boundaries in\nthe form of Ta₂O₅ precipitates due to a high\nenergy difference induced by Ta doping. Grain boundary engineering\nis employed to regulate the distribution of the Ta element and enhance\nthe density of LLZTO by introducing the La₂O₃ additive. The sufficient La₂O₃ additive reacts\nwith the Ta₂O₅ precipitates, while the residual\nLa₂O₃ nanoparticles fill up void defects, promoting\nthe homogeneous distribution of the Ta element and improving the relative\ndensity to ∼98%. Critical current density of the symmetric\nLi battery reaches 2.12 mA·cm^–2 at room temperature\nwith the solid-state electrolyte (LLZTO + 5 wt % La₂O₃), which increases by 41% compared to pure LLZTO. SSLBs with\nthe LiFePO₄ cathode achieve a stable cycling performance\nwith a discharge capacity of 138.6 mA·h·g^–1 after 400 cycles at 0.2 C. This work provides theoretical insights\ninto the distribution of Ta-doped LLZTO and inhibits lithium dendrite\ngrowth through grain boundary engineering.