Work

Metalloporphyrin‐Based Cathode for Rechargeable Magnesium‐Ion Batteries: Copper Leaching and Interphase Formation

Year: 2025

Type: article

Abstract: [5,15‐bis(ethynyl)‐10,20‐diphenylporphinato]copper(II) (CuDEPP) composite cathodes for rechargeable magnesium‐ion batteries have been investigated before, after, and during initial cycling (pristine, first charging, and consecutive discharging). The initial self‐conditioning is studied by scanning electron microscopy and spectroscopy‐based methods (energy‐dispersive X‐ray spectroscopy, total reflection X‐ray fluorescence spectrometry, and Raman spectroscopy) as well as time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and orbitrap SIMS (Orbi‐SIMS). This study shows that copper is released from the active material into the electrolyte solution during the initial cycling at potentials higher than 3.1 V versus Mg 2+ /Mg. The results point toward a transmetalation process transforming CuDEPP into [5,15‐bis(ethynyl)‐10,20‐diphenylporphinato]magnesium(II) (MgDEPP). Further, the self‐conditioning process via electro‐polymerization observed for monovalent ions appears to be absent in the investigated Mg‐based system, as the alkynyl group of the CuDEPP seems to remain unaltered during the initial charging and discharging steps. Additionally, cross‐sectional and laterally resolved ToF‐SIMS image analyses show an accumulation of inorganic fluorine‐rich copper and magnesium species at the electrode surface including the active material exposed to the electrolyte after cycling that might be a result of a passivation layer or the formation of a cathodic electrolyte interphase.

Source: ChemSusChem

DOI: 10.1002/cssc.202501463