The Role of Interphase Engineering for the Development of Stable Anode-Free Batteries.

Anode-free batteries (AFBs) are emerging as a safer and more energy-dense option for next-generation energy storage. Their simple design, lower material costs, and compatibility with current lithium-ion battery (LIB) manufacturing processes make them a potential game-changer. Unlike traditional LIBs, AFBs-often referred to as "Li-free" or "anode-less"-use a bare current collector (CC) as the negative electrode, which theoretically enables significantly higher energy density. However, challenges remain, including low Coulombic efficiency (CE) (often < 90%), quick capacity loss due to dendritic lithium (Li) growth, and formation of "dead" Li. This review overviews surface engineering techniques for CCs aimed at overcoming these challenges. The focus is on coatings that encourage homogeneous Li deposition, reduce nucleation overpotentials, curb dendrite formation, and stabilize the chemistry at the interface. Various coating methods are critically assessed, including inorganic, polymeric, and carbon-based layers. With mechanistic understanding and comparative analysis, this review highlights engineered surface modifications as a key enabler of uniform Li deposition and prolong cycle life. This review bridges the gap between materials science, focusing on surface chemistry, morphology, and interface design with electrochemical engineering principles such as cell design, ion transport, and interfacial kinetics, thereby guiding the development of next-generation AFBs.