Previous studies suggest that the formation of dendrites in lithium batteries can be explained by a model proposed by Chazalviel for dendritic growth during electrodeposition from a binary electrolyte. However, this model could only account for situations where the current densities are markedly higher than those in the usual operation conditions of lithium batteries. A model involving the development of concentration instabilities, due to nanoscale inhomogeneities at the electrode surface, has recently been proposed, which could extend the applicability of Chazalviel's model to the latter case. The aim of this study was to check the existence of such instabilities in symmetrical lithium/polymer electrolyte/lithium cells. We present our in situ observation technique permitting to map the ionic concentrations in the electrolyte and their evolution during cycling of a lithium/polymer cell. However, these experiments do not allow yet to follow the evolution of concentration maps at long times, due to the chemical/electrochemical production of impurities at the electrodes. (c) 2005 Published by Elsevier B.V.