2‑Mercaptobenzimidazole-Modified Copper Foil for Regulating Lithium Deposition in Anode-Free Lithium Batteries

Anode-free lithium batteries are limited by irreversible lithium loss and unstable lithium deposition on Cu current collectors. Herein, Cu foil was modified by a simple wet-chemical treatment using 2-mercaptobenzimidazole (MBI) to regulate the Cu/electrolyte interface. X-ray photoelectron spectroscopy suggests that MBI is anchored on the Cu surface through Cu-S and Cu-N interactions, while atomic force microscopy and Kelvin probe force microscopy show that the modification changes the surface roughness and surface potential of Cu foil. Electrochemical measurements show that MBI Cu exhibits a lower lithium nucleation overpotential (26.6 mV), a higher exchange current density (1.64 mA cm^-2), and reduced interfacial kinetic barriers compared with Bare Cu. In Li∥Cu half cells, MBI Cu also shows improved plating/stripping reversibility, slower impedance growth, and more compact lithium deposits. In anode-free Cu∥LiFePO₄ full cells, MBI Cu delivers an initial discharge capacity of 119.03 mAh g^-1 and retains 49.15% of its capacity after 100 cycles, whereas the Bare Cu counterpart retains 20.71% under the same conditions. These results suggest that MBI modification is a simple molecular approach for improving interfacial stability and regulating lithium deposition on Cu current collectors in anode-free lithium batteries.