para-Sexiphenylene as a model compound of poly(para-phenylene) during the electrochemical intercalation of lithium and sodium ions in ethylene carbonate-based electrolyte

The electrochemical intercalation of alkaline ions (Na+, Li+) into para-sexiphenylene (PSP) has been carried out in ethylene carbonate (EC) using MClO4 as the alkaline salt (M-Na or Li). Cyclic voltammetry and galvanostatic experiments reveal different behaviour for lithium and sodium. Intercalation of Na+ into PSP occurs with formation of successive stages of Na0.33(C6H4) and Na0.5(C6H4). After the first cycle, where the irreversible side reactions (such as the decomposition of the electrolyte, the reduction of the binder, etc.) occurred giving important capacity loss, the system exhibits a good reversibility. On the other hand, intercalation of Li+ into PSP is partially reversible whatever the cycle. A reversible capacity of 0.2 is reported in this case. The galvanostatic curves do not show any well-defined plateaux as in the case of the intercalation of Na+.