The invention relates to an electrochemical lithium accumulator comprising at least one first electrochemical cell and at least one second electrochemical cell separated from each other by a current-collecting substrate, which substrate supports on a first face, an electrode of said first electrochemical cell, and on its second face opposite to said first face, an electrode of opposite sign of said second electrochemical cell, each cell comprising a positive electrode and a negative electrode separated by an electrolyte, characterized inter alia in that said current-collecting substrate is in copper or in copper alloy.