Balancing SEI Composition and Side Reactions via Porous Carbon Current Collectors for Anode-Free Lithium Metal Batteries

Anode-free lithium metal batteries (LMBs) have emerged as a promising next-generation secondary battery technology due to the ultrahigh energy density. However, the practical application is severely limited by irreversible Li plating/stripping behavior and an unstable solid electrolyte interphase (SEI) on the anode. Porous carbon coatings, which combine excellent electronic conductivity with tailorable pore structures, offer a viable approach to regulate Li deposition morphology and interfacial chemistry. Still, the systematic correlation between the structural parameters of carbon materials and cathode electrochemical behavior remains inadequately understood. In this study, porous conductive carbon coatings are constructed on Cu current collectors to systematically investigate the correlations among carbon structural parameters, SEI composition, and electrochemical performance. ECP600, EC300, and Super P with distinct specific surface areas and structural ordering were selected as model materials, and XRD, Raman, BET, and XPS were combined to elucidate how interlayer spacing, graphitization degree, and pore architecture regulate Li deposition modes and the inorganic/organic component ratio of the SEI. The results reveal that Super P, featuring a moderate specific surface area and a high graphitization degree, induces the formation of a thin SEI enriched in LiF/Li 2 O/Li 2 CO 3 , uniform in-pore confined deposition, and stable interfacial impedance, whereas the excessively high specific surface areas of ECP600 and EC300 lead to overly thick or compositionally unstable SEI layers, thereby amplifying polarization. This work proposes a carbon structure–centered interfacial engineering strategy, providing design guidelines for precise SEI regulation in anode-free LMBs.