Nest-like TiO2-nitrogen-doped-carbon hybrid nanostructures as superior host for potassium-ion hybrid capacitors

Energy storage devices beyond lithium, including sodium/potassium ion batteries and hybrid capacities have recently attracted increasing attention due to their particular merit of cost-effectiveness. Currently, there is a common challenging issue in these devices, which is the rapid capacity fading of anodes due to the much larger ionic radius and sluggish kinetics of Na + /K + intercalation. Herein, we presented the formation of hierarchical nest-like TiO 2 -nitrogen-doped carbon hybrid nanostructures (denoted as TiO 2 /NC-HN) through the supramolecular assembly directed one-pot strategy, which exhibits outstanding electrochemical performance for both sodium and potassium ion storage with largely improved specific capacity and cycling stability. Specifically, it can deliver a high specific capacity of 382.5 and 323.1 mAh g −1 at the rate of 100 mA g −1 for Na + and K + storage, respectively, and can also maintain ultra-stable cycling capability under high rates. More importantly, the potassium ion hybrid capacitors based on TiO 2 /NC-HN anode can deliver a high energy/power density of 108.6 Wh kg −1 95 W kg −1 and exhibit superior cycling stability up to 30,000 cycles at the rate of 2.5 A g −1 . This work could not only provide a low-cost strategy for advanced hybrid nanostructures, but also benefit the development of energy storage devices based on earth-abundant sodium/potassium.