Influence of ethylene oxide monomeric units on the bonding of poly (ethylene carbonate) (PEC) onto nickel-manganese-cobalt oxides

Polymers are very attractive materials in the field of all solid-state batteries not only because they act as binders, and even electrolytes if properly doped by salts, in electrodes but also because they can bring their unique ease of processing in large scale production by technologies such as extrusion. The issue of their adhesion, or at least wetting, onto materials such as metal oxides, is nevertheless of major importance since it plays a major role in charge transfer through interfaces. The present study shows the importance of the composition of polyethylene carbonate (PEC) that can be used as binder and solid electrolyte basis, on its bonding to NMC of the 622 type (LiNi0.6Mn0.2Co0.2O2) frequently used as insertion material in positive electrodes. Indeed, dynamic mechanical spectroscopy in the vicinity of the glass transition of the polymers reveals a significant bonding for one over three different PEC used in this study. The bonding was also clearly visible on images obtained by scanning electron microscopy and indirectly confirmed by rheological measurements. A deep analysis of the structure of the polymers by 1H NMR shows a significant difference in the content of ethylene oxide units. This difference was thought to be at the origin of the bonding.