Novel zinc-iodine hybrid supercapacitors with a redox iodide ion electrolyte and B, N dual-doped carbon electrode exhibit boosted energy density

With the development of modern society, energy storage has gradually become a crucial issue for portable devices and electric vehicles. Recently, zinc-ion hybrid supercapacitors (ZHSs), a new type of energy storage devices, have received significant attention mainly because zinc possesses many advantages such as natural abundance, low cost, non-toxicity and high safety. However, the limited energy density of the currently reported ZHSs should be further improved to achieve their large-scale applications. Herein, we designed novel zinc-iodine hybrid supercapacitors (Z-IHS) by introducing a redox iodide ion into the ZnSO₄ electrolyte to improve the energy density and employing B, N dual-doped porous carbon microtubes (BN-CMTs) as a cathode to facilitate the faradaic reaction on the electrode surface by changing the electronic structure and density state of carbon. The BN-CMT-based Z-IHS exhibits the amazingly high capacity of 416.6 mA h g^-1, a high energy density (472.6 W h kg^-1) at the power density of 1600 W kg^-1 in the voltage range of 0.2-1.8 V and excellent cycling stability with the capacity retention of 99.1% over 10 000 cycles at 10 A g^-1. The strategy proposed in this study should provide a new insight into the exploration of high energy-density storage devices.