A new concept hybrid electrochemical surpercapacitor:: Carbon/LiMn2O4 aqueous system

We present a new concept hybrid electrochemical surpercapacitor technology in which the activated carbon was used as a negative electrode and a lithium-ion intercalated compound LiMn2O4 as a positive electrode in a mild Li2SO4 aqueous electrolyte. The charge/ discharge process is associated with the transfer of Li-ion between two electrodes. The hybrid cell exhibits a sloping voltage profile from 0.8 to 1.8 V, and delivers an estimated specific energy of ca. 35 W h/kg based on the total weight of the active electrode materials. The cell exhibits excellent cycling performance with less than 5% capacity loss over 20,000 cycles at 10 degrees C charge/discharge rate. The new state-of-the-art hybrid aqueous supercapacitor technology overcomes the drawbacks of electrolyte depletion during charge process of conventional hybrid supercapcitors, and also solved the major problems of poor cycling life of lithium-ion battery electrode materials in aqueous electrolyte. (c) 2005 Elsevier B.V. All rights reserved.