Systematic Assessment of Coulombic Efficiency in Anode-Free and Lithium Metal Batteries

Driven by the demand for high-energy-density storage, Lithium metal batteries (LMBs) and anode-free Lithium metal batteries (AFLMBs) have attracted significant attention due to their high theoretical capacity and low reduction potential. However, achieving reproducible Coulombic Efficiency (CE) measurements remains a challenge due to inconsistencies in electrochemical protocols and experimental conditions. This study systematically evaluates and compares three CE measurement methodologies, identifying key factors that influence reproducibility and accuracy. Unlike previous studies, which often report CE values without considering their methodological limitations, the impact of electrolyte composition, electrolyte concentration, and electrode surface properties are highlighted on CE variations. Furthermore, this study demonstrates that a pre-cycling Li reservoir method effectively minimizes substrate effects, leading to the most sensitive measurements across various testing conditions. This work provides a standardized framework for CE evaluation in LMBs and AFLMBs, offering valuable insights for optimizing Li-free anode interfaces and accelerating the commercialization of high-performance LMBs.