Interfacial engineering of metal/semiconductor heterostructures for lithium metal batteries with low N/P ratio

Anode-free lithium metal batteries (AFLMBs) and LMB with low negative-to-positive (N/P) capacity ratio have attracted considerable interest in recent years due to their potential for high energy density. However, their practical application is hindered by severe lithium dendrite growth and an unstable solid electrolyte interphase (SEI), leading to rapid capacity degradation. Herein, we propose a TiN/Ag@Cu sandwich-structured electrode designed to extend cycle lifespan by introducing a metal/semiconductor heterointerface that regulates lithium-ion transport and nucleation behavior. The electrode architecture comprises a silver-plated copper underlayer (denoted as Ag@Cu) and a titanium nitride (TiN) top layer. The TiN layer serves as a fast Li + -screening channel, effectively blocking parasitic side reactions involving other ions and molecules, while the lithiophilic Ag@Cu alloy interlayer provides nucleation sites that guide uniform lithium deposition. This synergistic design enables homogeneous lithium plating, substantially enhancing cycling stability. With a limited amount of pre-deposited lithium, the sandwich-structured electrode enables symmetric Li/Li cells to operate stably for 1100 h. Moreover, Li/LiFePO₄ full cells with a low N/P ratio of 2 achieve a high capacity-retention of 92.3% after 250 cycles. The proposed multilayer architecture is amenable to continuous, large-scale fabrication via roll-to-roll magnetron sputtering, rendering it compatible with existing industrial production lines and offering a promising strategy to improve the cycling durability of anode-free batteries.