Composite polymer electrolyte based on a new class of filler added to a PEGDME/LiClO4 model system has been investigated. “Ceramic super acids” used consist of grafted SO4 2− groups on Al2O3 particles surface obtained by calcinations route. Conductivity, DSC and FT-IR measurements performed on such composite electrolytes, when compared to the model PEGDME/LiClO4 electrolyte, showed only slight improvement of their inner characteristics. In contrary, Li/Li symmetric cells study, by means of impedance spectroscopy, has presented a spectacular decrease of the interfacial resistance compare to the model electrolyte. This result opens a new pathway of investigation to master the lithium metal/polymer electrolyte interface.