The effect of electrochemical in situ surface pretreatment of copper current collector, for anode-free lithium-metal batteries with sulfolane-based localized high-concentration electrolyte is explored. The constant potential and constant current pretreatment procedures benefit the anode performance. The observed effect is associated with the synergistic influence of balanced inorganic–organic structure, enhanced viscoelastic properties, and homogeneous morphology of the layer on the micro/nanoscale.

This work explores the effect of in situ electrochemical pretreatment of copper current collectors (CuCC), acting as anodes in anode-free lithium-metal battery (AFLMB) with sulfolane-based localized high-concentration electrolyte. Two electrochemical pretreatment methods, not involving lithium overpotential deposition are in focus. These strategies are investigated in terms of passive layer growth, surface morphology evolution, composition of the formed interphases, and electrochemical performance for AFLMBs. The passive layers formed on CuCC (Cu–solid-electrolyte interphase [SEI]) are in situ characterized by means of electrochemical quartz crystal microbalance with damping monitoring, which indicates that the Cu–SEIs exhibit detectable viscoelastic properties. The morphological characterization of the modified CuCCs shows highly homogeneous Cu–SEI structure with low surface roughness. The composition and physical properties of the Cu–SEI layers are correlated with the electrochemical performance of the anodes. The observed positive effect of the procedures for SEI preformation is associated with the synergistic influence of balanced inorganic–organic composition, enhanced viscoelastic properties, and homogeneous morphology of the layer. The study demonstrates the positive impact of the designed pretreatments and provides an appropriate comparison between the proposed in situ approach and the state of the art.