Enhancing electrochemical reversibility in lithium metal batteries through structural engineering of flexible composite current collectors

Lithium metal batteries (LMBs) offer high energy densities but face challenges including poor reversibility and Li dendrite growth. Herein, we evaluate two flexible composite current collectors composed of reduced graphene oxide and carbon nanotubes (rGO/CNT) to investigate how Li storage mechanisms influence electrochemical performance. By modulating the number of layers in rGO, the few-layered rGO/CNT collector (FL-CC) stores Li through a pure plating mechanism, whereas the multi-layered rGO/CNT collector (ML-CC) stores lithium via a hybrid intercalation/plating mechanism. The hybrid mechanism in ML-CC promotes reversible Li-ion storage, reduces active Li-ion loss, and suppresses dendrite formation. As a result, ML-CC achieves superior cycling stability compared to FL-CC in both LMBs and anode-free LMB tests paired with LiFePO₄ cathodes at a practical areal capacity of 4.5 mAh cm⁻². This study highlights the importance of structural design in current collectors and demonstrates that incorporating lithiatable materials can significantly enhance the electrochemical stability of anode-free LMBs.