A metallic lithium rechargeable electrochemical accumulator, including at least one lithium metal electrode and at least one polymeric electrolyte gel. The accumulator is capable of operating at temperatures from −20 to 60° C., essentially without formation of lithium dendrites on the whole surface of the metallic lithium electrode. The above is also wherein a particularly long life, even with intensive use at low temperature. The rechargeable accumulator can be produced by use of a production method with particular application of temperature control during the specific production stages. As a result of the extremely high electrochemical performance of said accumulator, in particular the remarkable stability thereof, the accumulator can be used in new application fields such as hybrid vehicles, electric vehicles and emergency supply systems such as those of the UPS type.