Constructing\nHigh-Energy-Density Aqueous Supercapacitors\nwith Potassium Iodide-Doped Electrolytes by a Precharging Method

Abstract

Aqueous\nsupercapacitors (SCs) are safe and environmentally friendly\nwith a high power density while having low-voltage windows and a low\nenergy density. To address these challenges, poly­(vinyl alcohol) potassium\nborate (PVAPB) gel polymer electrolytes (GPEs), which have demonstrated\ngood electrochemical stability and wettability with electrodes, were\nprepared by in situ electrodeposition and then doped with potassium\niodide (KI). SCs based on commercial active carbon electrodes and\nKI-doped PVAPB GPEs could work stably at 1.6 V and achieve a specific\ncapacitance of 164.7 F g^–1 and an energy density\nof 14.38 Wh kg^–1 at a current density of 1 A g^–1, which are both significantly higher than for SCs\nwithout KI of 69.9 F g^–1 and 4.38 Wh kg^–1. Meanwhile, the SC prepared with KI-doped PVAPB GPEs has a high\nionic conductivity of 1.7 mS cm^–1 (more than 200%\nhigher than for the traditional organic electrolyte) with a power\ndensity of 3.55 kW kg^–1. Subsequently, we propose\na precharging method to further boost the capacitance and energy of\nSCs with KI-doped PVAPB GPEs, which could deliver an excellent specific\ncapacitance of 228.2 F g^–1 with an energy density\nof 17.3 Wh kg^–1 at 1 A g^–1. More\nimportantly, this precharging method works for the KI–KOH electrolyte\nsystem as well, which can effectively contribute to constructing high-energy-density\nSCs with KI-doped electrolytes.