The present invention provides an electrochemical generator consisting of an anode, a cathode, and an electrolyte, wherein the anode and/or the cathode comprises a carbonaceous material obtained by a process comprising suspending a carbonaceous material containing carboxyl, amine and/or hydroxyl functions on its surface in a solution comprising at least one polymer and a solvent which dissolves the polymer, said polymer containing at least one carboxyl, amine and/or hydroxyl function, and treating the solution thus obtained under conditions promoting a dehydration reaction between at least one carboxyl function, and at least one amine and/or hydroxyl function, thereby grafting at least one said polymer onto said carbonaceous material by means of an ester or amide bond.