Ultrathin 3D Cu/Li Composite with Enhanced Li Utilization for High Energy Density Li‐Metal Battery Anodes

Abstract Li‐metal batteries (LMBs) are promising candidates for next‐generation energy storage devices because of their high energy densities. However, limitations of Li‐metal anodes (LMAs) such as dendrite formation hinder their practical application. This paper reports an ultrathin 3D Cu/Li composite anode (Li in 3DCu) with a thickness of <30 µm and moderate Li loading of 5 mA h cm⁻ 2 via electrochemical etching and electrodeposition, followed by thermal infiltration of Li. The lightweight composite anode achieves a specific capacity of 514 mA h g⁻¹ while effectively reducing current density and suppressing dendritic growth, thus enabling stable performance at high current densities. Novel insights regarding the Li infiltration mechanism are obtained via an integrated analysis of forces, interfacial chemistry, and thermodynamics, offering a comprehensive understanding for Li infiltration. Electrochemical characterization indicates that the proposed composite anode (Li in 3DCu) achieves a 335% improvement in cycle life compared to that when using a conventional anode with Li on a Cu foil in a Li@Cu||LFP cell. This study establishes a robust platform for lightweight high‐performance LMAs by combining structural innovations, maximizing Li utilization, and broadens the understanding of infiltration mechanisms to develop next‐generation LMBs.