In this paper we report a polymer lithium cell using a PVdF-based, gel-type electrolyte formed in-situ during cell assembly. The gel electrolyte formation is monitored prior to cell assembly by electro-chemical impedance spectroscopy and by Raman spectroscopy in order to determine the characteristics of the lithium salt diffusion into the gel-membrane. The results show an efficient gel formation and a fast lithium salt diffusion, this finally resulting in an optimized behaviour in a lithium cell using a high voltage spinel-type cathode. We believe that the results here reported may contribute to the enhancement of the safety of lithium batteries. (C) 2013 Elsevier B.V. All rights reserved.