Metal Battery Anode: Rich in Electrons, Rich in Problems: A Critical Review from Industrial Perspectives

Metal-anode batteries promise energy densities beyond conventional Li-ion. However, despite decades of study and earlier discontinued commercialization efforts, they still lag Li-ion in efficiency, cycle life, and safety, leaving practical adoption uncertain. Key challenges stem from the metals' inherent reactivity, incomplete understanding of interphase formation and evolution, and nonstandard testing and reporting that can mask true failure modes and misses to present performance relevant to practical use. Encouragingly, progress in electrolyte development and understanding of interphases over the past decade has uncovered more shared behavior across different metals than previously assumed, alongside important metal-specific nuances. Thorough integration of these insights presents significant opportunities to deepen our knowledge and steer the field toward promising avenues for future advancements. This review unifies guiding principles for reactive monovalent (Li, Na) and multivalent (Mg, Ca) metal anodes across liquid and solid-state electrolyte designs, summarizes major advances and barriers, and flags frequent pitfalls to guide the research community.