Interfacial electric field effects enhance the kinetics and stability of magnesium metal anodes for rechargeable magnesium batteries

Rechargeable magnesium batteries (RMBs) are considered promising candidates for next–generation energy storage systems due to their high theoretical capacity. However, the non–uniform deposition/stripping behavior of Mg metal hinders the practical application of RMBs. This study demonstrates that the designed interfacial electric field effect, driven by a copper phthalocyanine (CuPc) conductive interlayer, enhances the kinetics and stability of the Mg anode. In situ electrochemical impedance spectroscopy coupled with distribution of relaxation times analysis reveals that the highly delocalized electron cloud network of CuPc establishes a low-energy-barrier electron transport pathway, significantly reducing charge transfer resistance. Electrochemical characterization and density functional theory calculations indicate that the interfacial electric field effect effectively improves interfacial Mg 2+ diffusion by enhancing electron delocalization and reducing the Mg 2+ migration energy barrier. Furthermore, finite element simulations substantiate that the interfacial electric field imparts uniform interfacial charge distribution and homogeneous Mg deposition during plating/stripping processes. Consequently, the symmetric cell with CuPc@Mg achieves an ultra-long lifetime (1400 hours at 5 mA cm -2 ) and a high Coulombic efficiency (99.3%). Furthermore, the CuPc@Mg||Mo 6 S 8 cell achieves high capacity retention (92%). This work highlights the potential of metal phthalocyanines in stabilizing Mg anodes. The interfacial electric field effect at the CuPc-modified magnesium surface enables uniform Mg plating/stripping by homogenizing Mg 2+ flux and reducing the local charge density. This innovation enables exceptional cycling stability with minimal voltage hysteresis, demonstrating breakthrough durability for practical magnesium batteries. • Interfacial electric field effects enhance the kinetics and stability of magnesium metal anodes. • Identifying interfacial kinetic processes using in-situ EIS and DRT analysis. • The interfacial electric field is confirmed by finite element simulation to impart a uniform interfacial charge distribution and Mg flux.