Medium-entropy alloy modified Cu current collector for highly stable anode-free lithium metal batteries

Abstract Aiming at the core bottlenecks of anode-free lithium metal batteries (AFLMBs), including poor lithiophilicity of Cu current collectors, low reversibility of Li plating/stripping, and short cycle life caused by Li dendrite growth and dead Li accumulation, alloy-type interlayers, while an effective solution, suffer from critical inhomogeneous film formation via traditional preparation processes. In this work, room-temperature magnetron sputtering was adopted to construct a quaternary Al-Cu-In-Sn (ACIS) medium-entropy alloy (MEA) interlayer on Cu current collectors. Relying on the multi-element synergistic effect of MEA, the interlayer provides high-density uniform lithiophilic sites, reduces Li nucleation overpotential, induces LiF-rich solid electrolyte interphase (SEI) formation, precisely regulates Li deposition, and inhibits dendrite growth and interfacial side reactions. Electrochemical test results demonstrate that the modified Cu current collector achieves stable cycling for 250 cycles in Li-Cu half cells, the Li∥Li symmetric cells assembled with the MEA-modified electrode delivers stable cycling for over 2,000 h, the Li∥LFP full cells paired with a LiFePO 4 (LFP) cathode achieves a capacity retention of 98% after 250 cycles at 1 C rate, and the anode-free Cu∥LFP full cell exhibits stable cycling for 200 cycles. This work provides a novel strategy for the development of highly stable AFLMBs.