Giant dielectric ceramic of Li0.3Ti0.02Ni0.68O with abundant oxygen vacancies enabling high lithium-ion conductivity in composite solid-state electrolyte

The low ionic conductivity of composite solid-state electrolytes due to the lack of free Li-ions and Li dendrite growth induced by the low transference number seriously hinder their application. Herein, we find that the giant dielectric ceramic of Li 0.3 Ti 0.02 Ni 0.68 O (LTNO) with ultra-high dielectric constant can greatly promote the dissociation of Li salt to generate abundant movable Li-ions and realize a high room-temperature ionic conductivity (4.09 × 10 –4 S cm −1 ) as well as a low activation energy (0.16 eV). The oxygen vacancies on the surface of LTNO can effectively immobilize the anions to achieve a high Li transference number (0.61). Furthermore, the enhanced dielectric properties of the composite electrolyte induce homogenous Li plating/stripping to suppress the growth of Li dendrites. As a result, the Li||Li symmetric cells exhibit long lifespan of 2400 h and 1150 h at 0.1 mA cm −2 and 0.2 mA cm −2 , respectively. The Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 solid-state full cells show a high capacity retention of 83% after 430 cycles at 2C. This work highlights the critical role of high dielectric property and oxygen defects of fillers in composite solid-state electrolytes, and provides a demonstration for the application of giant dielectric materials in solid-state Li metal batteries.