From starch to porous carbon nanosheets: Promising cathodes for high-performance aqueous Zn-ion hybrid supercapacitors

Aqueous Zn-ion hybrid supercapacitors (ZHSCs) have been regarded as an attractive candidate for energy storage devices on account of their combination features of both rechargeable batteries and supercapacitors. However, the slow ions diffusion dynamics and unsatisfied cycling stability is still a challenge. Herein, porous carbon nanosheets (PCNs) cathodes have been obtained through an effective one-step KNO3 assisted KOH activation strategy, whereas KOH acts as the activating reagent and KNO3 as the morphology adjusting engineer. Based on this experiment, the resulting ZHSCs exhibits the largest specific capacity of 149 mAh/g at 0.2 A/g, and it still delivers a capacity of 75 mAh/g at a large current density of 20.0 A/g with a good capacity retention of 50.3%. Moreover, it also displays excellent cycle performance (~91% specific capacity retained after 10,000 cycles at 10 A/g) and high energy-power densities characteristic (60 Wh/kg at a high power density of 15.976 kW/kg). These merits make the as-prepared PCNs cathodes hold potential for high-performance electrochemical energy storage devices. [Display omitted] •Porous carbon nanosheets have been obtained through one-step KNO3 assisted KOH activation strategy.•The introducing of KNO3 can control over the morphological and textural structures of the resulting carbons.•The resulting samples have large specific surface area and tunable micropore surface area.•Zn-ion hybrid supercapacitors with porous carbon nanosheets as the cathodes have been constructed.•The product with high surface area and moderate mesopore content exhibits excellent electrochemical performance.