Ultrafast Sintering and Dopant Effects in Garnet LLZO Solid Electrolytes

High-throughput, low-cost manufacturing, and optimization of solid electrolytes are necessary for the adoption of solid-state batteries. In this work, garnet-type Li7La3Zr2O12 (LLZO) with different aliovalent dopants, TaZr·, AlLi··, and GaLi··, have been ultrafast-sintered with different temperature ramping rates. The densification behavior, phases, their evolution, and surface chemistry of different LLZO have been investigated and linked to their electrochemical performances. It has been shown that LLZO with TaZr· dopant demonstrates the highest garnet phase purity and overall best electrochemical performances, and ultrafast sintering further improves densification, ionic conductivity, and electrochemical stability. On the other hand, LLZO doped with AlLi·· and GaLi·· are reaching higher cubic phase purities and ionic conductivities via conventional sintering, indicating undesirable dopant migration and segregation during the ultrafast sintering process. These findings provide insights into the manufacturing of solid electrolyte materials.