Performance and characterization of lithium-manganese-oxide cathode material with large tunnel structure for lithium batteries

The synthesis, structure characterization and electrochemical performance of novel todorokite electrode materials (tunnel size: 3 X 3) for lithium batteries have been studied in this paper. It is shown by means of XRD that synthesized materials (e.g., Mg2+-containing sample) have todorokite structure. It is also found that the reversibility of the Li+ insertion process into the todorokite materials decreased after acid treatment due to removal of Mg2+ from the tunnel and the breakdown of the tunnel structure during the following intercalation/deintercalation cycles. The electrochemical impedance spectra (EIS) for todorokite electrode materials are measured and simulated. It was measured that the apparent diffusion coefficient (DLi+) of todorokite material is at a level between 10(-7) and 10(-10) cm(2)/s by use of potential-step electrochemical spectroscopy. (C) 1999 Elsevier Science S.A. All rights reserved.