Recent advances in separator engineering for effective dendrite suppression of Li-metal anodes

Lithium dendrites cause battery failures and safety hazards in liquid-electrolyte lithium-based batteries. To address this problem, each component of the battery, such as cathode, anode, electrolyte and separator, should be well matched and engineered for the integrated battery system. The separator plays an increasingly important role owing to its gradual transformation from an inert to an active component in the battery, especially for resolving Li dendrite issues in Li-metal batteries. Armed with advanced nanotechnology solutions, separator engineering presents a formidable strategy to suppress dendrite growth dynamics by modifying the electrolyte chemistry, regulating/trapping unwanted ionic species and redirecting dendrite growth direction. This review summarizes recent advances in separator engineering for effective dendrite suppression of Li-metal anodes. We first introduce the challenges that the Li-metal anode faces and the irreplaceable role of separators in the battery system. The characterization parameters and design principles of separators are also discussed. Then, the mainstream techniques for separator functionalization and their impacts on dendrite suppression are scrutinized and highlighted. Lastly, the conclusion is drawn and the future outlook for separator engineering is presented.