Practical Perspectives and Energy Density Criteria for Current Collector Engineering in Anode‐Free Li‐Metal Batteries

ABSTRACT This review provides a practical and in‐depth discussion of current collector engineering for Li‐metal batteries, emphasizing how the mass and volume introduced by modifications, together with the changes in Li inventory accompanying electrochemical processes, affect achievable energy metrics in realistic cell configurations. We compare major engineering approaches, including alloying and coating, crystallographic orientation control, and transitions from planar to three‐dimensional architectures, examining their impact on both initial energy density and long‐term retention. From these comparisons, we clarify key failure mechanisms and identify the stack‐level constraints that limit anode‐free Li‐metal batteries, including mass loading, volume occupation, electrolyte demand, and restricted Li inventory. To determine practical relevance, we introduce a quantitative energy density evaluation that benchmarks representative modification strategies against restricted Li inventory batteries. The analysis shows that although recent strategies enhance local plating and stripping behavior, they often reduce achievable energy density once realistic penalties related to volume, mass, and Li consumption are considered. These results establish clear criteria for identifying modifications that provide genuine practical benefit. Finally, we propose research directions that reduce geometric and material burdens while enhancing Li inventory retention, offering a perspective that supports the development of practical current collector designs for anode‐free Li‐metal batteries.