Lithium ion flux–controlling separator enabling longevous lithium metal anode

Lithium metal is an ideal anode material due to its high theoretical specific capacity and low standard electrode potential. However, its practical application is limited by the formation of Li dendrites during the repeated cycling. Localized lithium ion (Li⁺) concentration at specific sites has recently been identified as a major contributor to accelerated Li dendrite growth. Therefore, achieving a homogeneous Li⁺ flux is a promising strategy to regulate Li deposition behavior. Herein, a flux−controlling separator, incorporating a black TiO₂ (b–TiO₂) nanothin layer, is proposed to ensure uniform Li⁺ flux regulation. The formation of nanopores at grain boundaries and grain boundary triple junctions within the b–TiO₂ nanolayer, combined with the clogging of the original porous structure of polyethylene (PE) matrix, enables homogeneous Li⁺ flux through the separator by serving as a uniform ion transport channel. The uniform Li⁺ flux achieved with b–TiO₂/PE separator effectively suppresses the formation of Li dendrite, leading to enhanced electrochemical performance in both Li | Li symmetric cells and Li | LiFePO₄ full cells. Overall, this findings highlight the potential of b–TiO₂/PE separators to improve the durability of lithium metal anodes (LMAs), offering a promising approach for developing more reliable and efficient energy storage systems.