Functional Separators for Modulating Li‐Ion Flux Toward Uniform Li Deposition: A Review

Abstract Homogeneous Li‐ion flux is a significant precondition of uniform Li‐ion deposition in Li metal batteries (LMBs). Numerous methodologies have been presented for homogenizing Li‐ion flux before Li deposition based on the features of Li‐ion deposition. Separators that provide Li‐ion transfer channels and are directly exposed to Li metal anodes have attracted rising attention for their role in guiding regular Li‐ion distribution. More novel functional separators have been proposed aiming to achieve dendrite‐free deposition. Herein, the factors and strategies that regulate Li‐ion distribution through functional separators toward LMBs are concentrated on. The current mechanisms of Li‐ion flux regulation by functional separators are first highlighted, including physical properties, interactions with the electrolyte, and modification of the solid‐state electrolyte interphase. According to these mechanisms, functional separator strategies for regulating Li‐ion flux are divided into three methodologies, and typical examples are introduced. Finally, current limitations and suggestions for future functional separator studies are presented, aiming to inspire engaged researchers and newcomers to trigger more exciting works in this area.