Improved reversibility of lithium deposition and stripping with high areal capacity under practical conditions through enhanced wettability of the polyolefin separator to highly concentrated electrolytes

Highly concentrated electrolytes (HCEs) have attracted great interest as electrolyte candidates for Li metal batteries because of their functionalities in improving the reversibility and cycling performance of the Li metal negative electrode. However, the poor wettability of conventional polyolefin separators toward HCEs with high viscosity remains a critical issue to be addressed. Although porous glass fiber filters are often used as separators for HCEs, Li dendrites easily penetrate the separator during repeated Li deposition/stripping under practical conditions, leading to an internal short circuit. Here, we report that the use of a meta-aramid-coated polyolefin separator improves the wettability with HCEs owing to its polar surface functional groups and enables stable and dendrite-free Li deposition/stripping with high coulombic efficiency of similar to 98% at practical areal capacity (2 mA h cm-2) for 100 cycles. A combined strategy utilizing HCEs and functional separators provides a promising possibility for the development of practical Li metal batteries. Highly concentrated electrolytes (HCEs) have attracted great interest as electrolyte candidates for Li metal batteries because of their functionalities in improving the reversibility and cycling performance of the Li metal negative electrode.