Novel flexible solid-state pseudo-parallel pseudocapacitor with manganese oxide active material synthesized using electrodeposition

Flexible and light-weight energy storage device is required for soft electronics. Novel flexible solid-state pseudo-parallel pseudocapacitor (SPP) with three electrodes is firstly proposed to achieve light-weight and excellent energy storage ability. SPP is assembled using only three electrodes without outer circuit. Active material of δ-MnO2 is fabricated on carbon cloth (CC) using electrodeposition with different currents. Highest specific capacitance of 9.41 F/cm2 is obtained for MnO2/CC electrode prepared using 30 mA, due to high surface area, large pore volume and suitable pore structure of nanosheet array. Normal-type pseudocapacitor (NP), two normal-type pseudocapacitor connected in parallel (NP in parallel), and two types of SPP are assembled using optimized MnO2/CC positive electrode and activated carbon negative electrode. The SPP composed of two positive electrodes and one negative electrode (PNP) shows best energy storage ability with energy density of 97.09 Wh/kg at power density of 0.65 W/kg, owing to more MnO2 pseudocapacitor electrode and better device configuration. However, worse charge/discharge stability is observed for PNP owing to lacking sufficient carbon material for providing stable electric double layer capacitor energy storage mechanism. This work greatly opens new blueprint for designing device configurations to achieve light-weight and efficient energy storage ability for flexible solid-state pseudocapacitors.