For lithium-ion batteries of C/(spinel Li-Mn-O), the sever capacity loss occurs after storage of the battery at >50 degreesC. This is mainly due to degradation of the carbon which was induced by electroreduction of Mn(II) dissolved from the spinel; this step is followed by the irreversible electrochemical reaction at the graphite/(Mn deposits)/electrolyte interface. However, 2-vinylpyridine as an additive into the electrolyte was capable of suppressing this degradation of graphite anode, therefore, improved the battery performances. During the first charge, electropolymerization of 2-vinylpyridine from about 0.9 V vs Li/Li+ resulted in film formation of poly(2-vinylpyridine) on the anode surface. The polymer protected the graphite from dissolved Mn(II).