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Rechargeable lithium-ion batteries consisting of a nanostructured cathode of lithium transition metal oxides are known to provide excellent electrochemical performance: high energy storage capacity and fast charge–discharge kinetics due to a large surface area for Faradaic reaction and a short distance for mass and charge diffusion, as well as the added freedom for volume change that accompanies lithium-ion intercalation and discharge.1-4) However, the structural transformation of active materials and the instability of the electrode capacity caused by the dissolution of transition metals in electrolyte solutions can cause problems.5) A controlled conducting polymer nanocoating on the surface of transition metal oxides can be an alternative solution for unwanted phase transformation and dissolution. As long as the original crystalline structure and crystallinity of metal oxides are preserved during oxidative polymerization in an acidic medium containing metal oxides as oxidants, a controlled polymer coating can reduce the dissolution of a transition metal ion and can supply structural stability during charge-discharge cycles, thus improving the cycle life of the cell. In this talk, surface of the layered manganese oxide was uniformly nanocoated with polyaniline via the chemical oxidative polymerization of aniline in an acid medium, in which pristine metal oxide nanodisks acted as oxidants. Their electrochemical performance, charge-discharge capacity and cyclability, was measured to examine the effect of nanocoating on a metal oxide electrode.
References
1. Y. Wang, G. Cao, Adv. Mater.20, 2251 (2008).
2. X. Ji, K.T. Lee, L.F. Nazar, Nat. Mater. 8, 500 (2009).
3. M.G. Kim, J. Cho, Adv. Funct. Mater. 19, 1 (2009).
4. P.G. Bruce, B. Scrosati, J.-M. Tarascon, Angew. Chem. Int. Ed. 47, 2930 (2008).
5, W. Li, J.R. Dahn, J. Electrochem. Soc. 142, 1742 (1995).
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