Correlation of electrochemical and ab initio investigations of Iron poly-bipyridine coordination complexes for battery applications: impact of anionic environment and local geometries of the redox complexes on the electrochemical response

Although they exhibit a huge versatility, coordination complexes have been rarely investigated in the field of cathode material for battery. Despite their relative high molecular mass, according to the nature of the metallic center and the one of the ligand, the E° value and the electron transfer kinetics can be adjusted to reach performant material compatible with the electrolyte. Here, we propose to investigate FeII poly-bipyridine complexes in view to check the impact of the nature of the electrolyte as well as the influence of the distance between two redox centers when polymerized, on the electrochemical response in battery condition. To understand these changes, three lithium salts have been studied: LiClO4, LiPF6 and LiTFSI (TFSI = bistrifluoromethane sulfonimide). In order to mimic these impacts, monomer complexes (mono and binuclear) have been electrochemically studied, whereas thanks to ab initio calculations, their redox behavior have been correlated to the ligand environment of the metallic center. Finally, despite their expected low mass capacity, these polymeric coordination complexes have been involved in battery conditions