Self-Assembly of Ultrahigh Porous Aramid/Poly(ether imide) Nanofibrillar Separators for Lithium-Metal Batteries

Nanoporous separators have been utilized to reduce the growth of Li dendrites for Li-metal batteries via delocalized distributions of Li ionic flux over the Li metal anode surfaces. However, the levels of the battery performances still require improvements for commercialization. Herein, we report the preparation of ultrahigh porous nanofibrillar separators with self-assembled aramid nanofibers (ANFs) with poly(ether imide) (PEI). 3-D nanoporous structures with high porosity of 95% are achieved via reprotonation-assisted self-assembly for the ANF/PEI nanofibrillar network structures. Such high porosity in the fibrillary nanostructures enables to increase ionic conductivity > 3 mS/cm. In addition, the ANF/PEI nanofibrillar separators show high Li-ion transference numbers > 0.8 that can be attributed to preferential adsorption of lithium salt on the nanofibrils and high Li ionic mobility. Combination of high Li-ion transports and delocalization of Li ionic flux via 3-D nanoporous structures enables to suppress the formation of Li dendrites on the Li-metal anodes. Li/Li symmetric cell and full-cell test results show highly stable cycle performances. Self-assembly assisted formation of the nanofibrillar network structures can be one of promising routes for the fabrications of advanced separators for energy storage devices.