Synthesis of polyindole and its evaluation for Li-ion battery applications

This study is intended to develop a polyindole-based Li-polymer secondary battery system, which has a high electromotive force together with excellent cycle property and is capable of fast charging and discharging. The batteries include polyindole as the cathode and Li as the anode. LiBF4 was used as the electrolytic solution with about 3.0 V electromotive force. The battery achieves about 80–70 mAh/g at discharge current densities of 10–103 A/m2. As the theoretical capacity of polyindole is 84 mAh/g, its capacity occurrence rate is 95% at the discharge current density of 10 A/m2 with a very high reaction rate. In addition, a discharge capacity at discharge current density of 103 A/m2 maintains 87% of capacity relative to that at 10 A/m2. This indicates that this battery is excellent in fast charge and discharge properties. The cyclic life of the battery, which is measured at the current density of 10 A/m2 with the discharge depth 60% at 25, is about 30,000 times. This shows the battery system has very excellent cycle property. Summarily, this Li–polyindole battery system would be promising in future applications such as hybrid electric vehicle with the development of the battery system.