Opportunities of liquid metals and liquid metal cations for Li-metal batteries

Uncontrolled Li dendrite growth is a severe issue which limits practical application of Li-metal batteries (LMBs) and anode-free lithium metal batteries (AFLMBs). Li dendrite growth causes "dead Li", electrolyte decomposition, anode volume change, and low coulombic efficiency. This perspective briefly discusses the implementation of liquid metals (Na, K, Rb, Cs, and Ga) and their eutectic alloys and liquid metal cations (Na+, K+, Rb+, Cs+, and Ga2+) in developing dendrite-free liquid metal-reinforced LMBs and AFLMBs. The fundamental unique properties of liquid metals and liquid metal cations, challenges, and corresponding resolving strategies are discussed in detail. Two principal Li dendrite suppression mechanisms, including liquid metal coating onto Li-metal or Cu current collector and self-healing electrostatic shielding effects (SHES) using liquid metal cations as electrolyte additives, are clarified in detail. Finally, the summary and future outlooks are given for future investigations in this field to establish stable and dendrite-free liquid metal-reinforced LMBs and AFLMBs. This perspective suggests future research directions to promote practical liquid metal LMBs.