Dendrite-suppressing separator with high thermal stability modified by beaded-chain-like polyimide coating for a Li metal anode

Dendritic Li growth is the root hurdle against the implementation of a Li metal anode because it brings safety issues and unsatisfactory efficiency. In this work, a beaded-chain-like polyimide (PI) coating is designed on the commercial polyethylene (PE) separator to suppress the Li dendrite. Owing to the compactly stacking structure and high Li-ion absorption of the PI coating, the wettability of the prepared PI-PE separator is improved and a Li-ion-rich layer with uniform Li-ion transfer channels forms on the surface of the Li metal anode. Therefore, the planar Li deposition rather than dendrite growth has been achieved using this custom separator. The life spans of Cu||PI-PE||Li half-cells have been extended to 7 and 4 times longer than that of Cu||PE||Li half-cells at a current density of 1 mA/ cm² with deposition capacities of 0.5 and 1 mA h/cm², respectively. Besides suppressing Li dendrites, the multifunctional PI-PE separator also delivers a higher thermal stability to 120 °C than commercial PE and Al₂O₃-PE separators. This facile approach provides a feasible strategy to realize smooth lithium deposition, and the fundamental mechanism underlying the combination of pore structure and surface chemistry may lead to new approaches to tackle the dendritic problem of Li deposition.