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

Abstract

Hierarchical nest-like TiO 2 -nitrogen-doped-carbon hybrid structures (TiO 2 /NC-HN) have been synthesized through the supramolecular assembly assisted one-pot strategy, which exhibits impressive electrochemical performance for both sodium and potassium ion storage derived from the synergist effect of hierarchical morphology, highly porous structure, strongly coupled interface and the possible oxygen vacancy in TiO 2 . More importantly, the potassium-ion hybrid capacitors based on TiO 2 /NC-HN anode could deliver a decent energy density of 108.6 Wh kg −1 and a record cycling life up to 30,000 cycles at the rate of 2.5 A g −1 based on the total mass of anode and cathode. • Nest-like TiO 2 -nitrogen-doped-carbon hybrid structures have been synthesized. • Supramolecular assembly assisted one-pot strategy was employed. • Synergistic effect of hierarchical morphology, porous structure, coupled interface. • KIHCs based on TiO 2 /NC-HN deliver a decent energy density and a record cycling life. 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.