Preparation of poly(N-methylpyrrole) modified with pentathiepin rings and its application to positive active material for lithium secondary

Lithium secondary batteries with high energy density are key devices for portable electrical equipments. The specific capacity of metal oxide-based positive active materials is considerably lower than that of lithium metal. Organosulfur compounds, such as disulfide compounds are useful as a positive active material for lithium secondary cells. We prepared modified poly(N-methylpyrrole) (PMPy) with pentathiepin rings (S-PMPy) from PMPy and disulfur dichloride at room temperature. The S-PMPy electrode showed electrochemical responses in the organic electrolyte solution (mixture of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) (1:1, v/v) containing 1 mol dm−3 LiClO4). The maximum capacity of the test lithium secondary cell with the S-PMPy electrode was 14.8 A h kg−1 (per kilogram of S-PMPy) and the average capacity was 11.5 A h kg−1 (10 cycles) under the constant charge–discharge current condition at room temperature.