Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors

Polypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Here a two-prong strategy is demonstrated to stabilize PPy film by growing it on a functionalized partial-exfoliated graphite (FEG) substrate and doping it with -naphthalene sulfonate anions (NS-). The PPy electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between -0.8 and 0 V versus saturated calomel electrode for 10 000 cycles. Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retains 97% of capacitance after 10 000 cycles, which is the best value reported for PPy-based supercapacitors. The exceptional stability of PPy electrode can be attributed to two factors: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and 2) the presence of immobile NS- dopants suppresses the counterion drain effect during charge-discharge cycling.