Oxygen-Vacancies Enhanced Fast Potassium Storage in Layered Titanate Nanostructures

The electrochemical activities of titanium-based layered oxides, a class of promising electrode materials with low cost and decent performance, can be optimized by modulating their microsctructures and interlayer spacings. However, these advantages are often traded off by the commonly adopted high-temperature calcination prior to electrode fabrication. To overcome this limitation, we present a novel method for generating abundant oxygen vacancies in K2Ti2O5 nanostructures (referred to as ov-KTO). Compared to the bulk counterpart, the ov-KTO nanomaterial exhibits increased interlayer spacing and heightened electrical conductivity. Furthermore, its enhanced electrochemical activity leads to a significance of redox Ti3+/Ti4+ reaction in water-in-salt electrolyte. This advancement leads us to construct a high-performance ov-KTO//active carbon assembled aqueous hybrid supercapacitor. The large working voltage window, impressive energy density, long lifespan and wide operation temperature demonstrate the device is comparable with the aprotic-electrolyte supercapacitor in performance but being safer and more cost-effective.