Enhanced Pseudocapacitive Performance of Symmetric Polypyrrole-MnO₂ Electrode and Polymer Gel Electrolyte

Herein, the nanostructured polypyrrole-coated MnO₂ nanofibers growth on carbon cloth (PPy-MnO₂-CC) to serve as the electrodes used in conjunction with a quasi-ionic liquid-based polymer gel electrolyte (urea-LiClO₄-PVA) for solid-state symmetric supercapacitors (SSCs). The resultant PPy-MnO₂-CC solid-state SSCs exhibited a high specific capacitance of 270 F/g at 1.0 A/g in a stable and wide potential window of 2.1 V with a high energy/power density (165.3 Wh/kg at 1.0 kW/kg and 21.0 kW/kg at 86.4 Wh/kg) along with great cycling stability (capacitance retention of 92.1% retention after 3000 cycles) and rate capability (141 F/g at 20 A/g), exceeding most of the previously reported SSCs. The outstanding performance of the studied 2.1 V PPy-MnO₂-CC flexible SSCs could be attributed to the nanostructured PPy-coated MnO₂ composite electrode and the urea-LiClO₄-PVA polymer gel electrolyte design. In addition, the PPy-MnO₂-CC solid-state SSCs could effectively retain their electrochemical performance at various bending angles, demonstrating their huge potential as power sources for flexible and lightweight electronic devices. This work offers an easy way to design and achieve light weight and high-performance SSCs with enhanced energy/power density.