LiGaO2-mediated grain boundary engineering in Ta-doped Li7La3Zr2O12 solid electrolyte

Abstract

Solid-state lithium batteries (SSLBs) hold promise for next-generation energy storage due to their high safety and energy density. However, challenges such as poor interfacial contact, high interfacial impedance, and lithium dendrite growth limit the practical application of garnet-type Li₇La₃Zr₂O₁₂ (LLZO) and its derivatives (Ta-doped Li₇La₃Zr₂O₁₂, LLZTO). This study investigates the effects of incorporating LiGaO₂ (LGO) into LLZTO to enhance grain-boundary bonding, reduce activation energy, and suppress lithium dendrite growth. LiGaO₂ powder was synthesized via a solid-state reaction and mixed with LLZTO to form composite ceramics. Structural characterization using XRD and SEM confirmed that LGO stabilizes the cubic garnet structure of LLZTO without forming impurity phases. The LLZTO-1 wt% LGO composition, sintered at 1260 °C, exhibited superior performance with a room-temperature ionic conductivity of 0.951 mS cm⁻¹ and a relative density of 96.3%. Electrochemical impedance spectroscopy shows that the interfacial resistance decreases by ∼50% (from ∼30 Ω to ∼15 Ω). The hybrid full cell retains 99.3% capacity after 200 cycles at 0.8C, showcasing practical applicability. These results highlight the effectiveness of LGO-mediated grain boundary engineering in improving the electrochemical performance of LLZTO-based solid electrolytes, paving the way for their large-scale preparation and application in SSLBs.