Li-growth and SEI engineering for anode-free Li-metal rechargeable batteries: A review of current advances

Li-metal battery systems are attractive for next-generation high-energy batteries due to their high theoretical specific capacity and Li-metal's low redox potential. Anode-free Li-metal batteries (AFLBs) have a higher energy density than conventional Li-metal batteries because the anode material is absent in the pristine state. An additional advantage is that the battery production costs are relatively low due to simplified anode coating processing, which makes AFLBs favorable for large-scale industrial production. Despite these advantages, commercializing AFLBs remains challenging because of the high reactivity of Li-metal and dendrite-growth issues at the anode side. The chemical and physical properties of solid-electrolyte interphase (SEI) formed at Li-metal anodes determine the Li-ion transport kinetics, Li-metal deposition behavior, and overall cycling performance. The key to resolving these issues is to grow a homogeneous Li-metal and design a stable SEI. Many approaches, such as electrolyte optimization and artificial layers design, have been developed to guide a uniform Li-metal growth and form a stable SEI, facilitating rapid Li-ion transport and suppressing Li-dendrite growth and other undesirable side reactions. An overview of these discoveries and developments in Li-growth and SEI engineering and insights into the intrinsic mechanisms of battery performance, presented in this review, is, therefore, of great interest to the battery research community.