A 2.3 V quasi-solid-state flexible supercapacitor of AC|PVA-Na2SO4//PVA-KOH|Zn@CFP with high specific energy

Activated carbon//zinc (AC//Zn) supercapacitors using alkaline electrolyte become promising as an energy storage device due to their impressive specific capacitance. However, it is limited by a narrow voltage window. In this work, a new type supercapacitor (AC|PVA-Na2SO4//PVA-KOH|Zn@CFP) was developed using a decoupled electrolyte system comprising Na2SO4-polyvinyl alcohol (PVA)//cation exchange membrane//KOH-PVA, AC as positive electrode and Zinc electrodeposited on the carbon fiber paper (Zn@CFP) as a negative electrode. Importantly, the operational cell voltage was successfully raised to 2.3 V. This design enables autonomous lighting a green light-emitting diode (LED) by a single device. The device delivers a specific capacity of 517.6C g−1 at 1 A g−1, corresponding to a specific energy of 186.9 Wh kg−1 at 1300 W kg−1, considering that the three-dimensional (3D) architecture of Zn@CFP offers a significantly enlarged surface area, thereby facilitating enhanced performance. The device also exhibited good stability, with a capacity retention of approximately 95.3 % after 1000 charge/discharge cycles. Furthermore, the PVA-based decoupled gel electrolyte offers excellent processability and remarkable flexibility. Remarkably, at an elevated temperature of 50 °C, the device showed an even higher specific energy of 238.8 Wh kg−1 at 1300 W kg−1. These findings underscore the substantial potential of the wide-voltage zinc-ion supercapacitor. Our strategy offers the device not only a high specific energy but also exceptional flexibility, rendering it highly promising for future applications in wearable electronic devices.