Insight into the Microstructure and Ionic Conductivity of Cold Sintered NASICON Solid Electrolyte for Solid-State Batteries.

LiAlTi(PO) (LATP) is a popular solid electrolyte used in solid-state lithium batteries due to its high ionic conductivity. Traditionally, the densification of LATP is achieved by a high-temperature sintering process (about 1000 °C). Herein, we report the compaction of LATP by a newly developed cold sintering process and post-annealing. LATP pellets are first densified at 120 °C and then annealed at 650 °C, yielding an ionic conductivity of 8.04 × 10 S cm at room temperature and a relative density of 93% with a low activation energy of 0.37 eV. High-resolution transmission electron microscopy of the cold sintered pellets is investigated as well, showing that the particles are interconnected with some nanoprecipitates at the grain boundaries. Such nanocrystalline-enriched grain boundaries are beneficial for lithium-ion transportation, which leads to higher ionic conductivity of the cold sintered sample. This new sintering process can direct new horizons for development of all solid-state batteries due to its simplicity.