Addressing Lithium Deficiency in Anode-Free Lithium Metal Batteries: Design Principles and Supplementation Strategies.

Anode-free lithium metal batteries (AFLMBs) are now considered as a promising next-generation energy storage system due to their exceptional energy density and compatibility with existing lithium-ion battery manufacturing infrastructure. However, their practical deployment is hindered by severe capacity degradation, primarily caused by the irreversible consumption of lithium. This perspective explores how lithium supplementation and recovery strategies can address these challenges by shifting focus from conventional structural engineering to chemical compensation mechanisms. Recent advances are systematically categorized into three main approaches: cathode overlithiation, cathode additives, and electrolyte-based supplementation. For each strategy, the underlying mechanisms, representative materials, and electrochemical performance are critically evaluated. Particular attention is given to lithium storage capacity, decomposition potential, electrochemical compatibility, and byproduct management. The interdependence between lithium compensation methods and electrode/electrolyte design is also examined to clarify their cooperative or competing roles within full-cell configurations. In addition, strategies for recovering inactive lithium, including dead lithium reactivation and solid electrolyte interphase reconstruction, are discussed as complementary pathways. By comparing the advantages and limitations of these approaches, this perspective highlights key material design principles and provides practical insights for advancing AFLMB systems with high-energy density and extended cycling stability.