The invention relates to a bilayer polymer electrolyte for a lithium battery. The inventive electrolyte comprises N and P layers which are each formed by a solid solution of an Li salt in a polymer material, said Li salt being the same in both layers, whereby the concentration of polymer material is at least 60 % by weight and the concentration of lithium salt is between 5 and 25 % by weight. The polymer material from layer P contains a solvating polymer and a non-solvating polymer, the weight ratio between the two polymers being such that the solvating polymer forms a continuous network. The polymer material from layer N is formed by a solvating polymer and, optionally, a non-solvating polymer, the weight ratio between the two polymers being such that the solvating polymer forms a continuous network and the non-solvating polymer does not form a continuous network.