Engineering extreme high energy density lithium metal batteries (>500Wh kg-1) for electrification of society

Lithium Metal Batteries (LMBs) are considered among the most promising candidates for next-generation, ultra high energy density batteries; yet they suffer from intrinsic failure mechanisms that impede their large-scale, real-world deployment. At the core of this challenge is the lithium metal itself, acting as a double-edged sword that enables unprecedented energy densities yet severely limits cycling lifespan. LMBs also suffer from dendrite growth, unstable solid electrolyte interface, volume fluctuation and poor Coulombic efficiency. This review article addresses this paradox by discussing the practical requirements for LMBs to exceed the 500 Wh kg -1 energy density threshold, by bridging chemistry and storage mechanism with advanced engineering and scalable cell-to-pack design. The review systematically evaluates recent optimization strategies across all battery components to address the fundamental stability and performance bottlenecks. For anode development, the article examines cutting-edge approaches including anode-free and lithium-alloy configurations. The article also analyzes the evolution of advanced electrolytes designed to stabilize the lithium interface, encompassing liquid, solid-state, and hybrid systems. For cathode materials, a diverse array of high-capacity cathode chemistries is explored, ranging from conventional oxides and olivines to next-generation conversion materials such as sulfur, oxygen, halides, organics, selenium, and tellurium. Overall, this work provides a holistic roadmap for integrating and scaling-up the material and system-level advancements to realize commercially viable, safe and cost-friendly, >500 Wh kg -1 LMBs.