Cosintering the Anode Active Material with Li 7 La 3 Zr 2 O 12 Solid Electrolyte for the All-Solid-State Battery: How to Predict the Interfacial Reaction at Elevated Temperatures

High Resolution Image Download MS PowerPoint Slide Cosintered-type all-solid-state batteries composed of Li 7 La 3 Zr 2 O 12 (LLZ) have garnered significant attention as next-generation batteries that offer both high energy density and long cycle life. However, achieving low-resistance interfaces through cosintering of electrode materials, particularly between the anode active material and LLZ, remains a big challenge due to the formation of reaction phases caused by interdiffusion during high-temperature sintering. In this study, we demonstrated the lithium concentration within the materials ( C Li: mol/cm 3 ) as a key factor for predicting the reactivity between the anode active material and LLZ during high-temperature sintering. Various kinds of anode active materials with different C Li values were mixed with LLZ, and the reactivity during sintering at 850 °C was carefully investigated. XRD results show that interfacial reaction proceeds between LLZ and low C Li materials due to the occurrence of Li loss in LLZ. Contrarily, Li 2 SnO 3, Li 2 TiO 3, and Li 3 SbO 4 in the high C Li group (larger than that of LLZ) achieve interaction suppression against the LLZ electrolyte during high-temperature sintering. However, lattice parameter characterization and TEM images reveal that interdiffusion and side reactions occurred at the interface layer in the composite LLZ/high C Li material. Densified composite LLZTBO–Li 2 SnO 3 (relative density ∼ 89%) and LLZTBO–Li 2 TiO 3 pellets (∼95%) were successfully obtained under 900 °C sintering for 15 h. Charge–discharge tests using the half-cell assembled with the cosintered composite anode and liquid electrolyte reveal the superior capacity of 550 mAh/g with nearly 92% Coulombic efficiency for the LLZTBO–Li 2 SnO 3 cosintered anode. The approach reported herein has the potential to rapidly screen possible cosintered electrodes for garnet-type solid-state electrolytes and achieve cosintered-type all-solid-state batteries with high energy density.