Revealing the dynamic evolution of Li filaments within solid electrolytes by operando small-angle neutron scattering

Lithium dendrite (filaments) propagation in solid electrolytes (SEs) leading to short circuits is one of the biggest obstacles to the application of all-solid-state lithium metal batteries. Due to the lack of operando techniques that can provide high resolution, the insufficient knowledge of the lithium dendrite growth inside SEs makes it difficult to suppress the dendrite growth. To reveal the mechanism of the Li filament growth in SEs, we achieved real-time monitoring of the nanoscale Li filament growth by operando small-angle neutron scattering (SANS) in representative Li6.5La3Zr1.5Nb0.5O12 SEs. On continuous plating, the Li filament growth is not simply an accumulation of Li, but there is a dynamic evolution due to the competition between the Li filament growth and self-healing. With the aid of simulations and experiments, this dynamic competition was demonstrated to be highly dependent on temperature variation. The enhanced self-healing ability of Li at elevated temperatures plays a positive role in suppressing the Li filament growth. The heat therapy improved the cell's cycle life, which provided insight into suppressing the Li filament growth. Operando SANS with high Li sensitivity provides a platform for investigating Li filaments in SEs.