Synthesis of oxygen vacancies-enriched titanate nanostructures and their potassium storage properties study

The commonly adopted high-temperature calcination prior to electrode fabrication decreases the electrochemical activities of titanium-based layered oxides, a class of promising electrode materials with low cost and decent performance, through their microsctructure aggregations and interlayer spacing contractions. Here we present a low temperature method for generating abundant oxygen vacancies in K2Ti2O5 nanostructures (referred to as ov-KTO) as the electrode material to overcome this limitation. The rich vacancy in ov-KTO nanomaterial contributes increased interlayer spacing and heightened electrical conductivity compared to the bulk counterpart. It also causes a significance of redox Ti3+/Ti4+ reaction for ov-KTO in water-in-salt electrolyte. These advancements lead us to construct a high-performance ov-KTO//active carbon assembled aqueous hybrid supercapacitor. The device shows large working voltage window, impressive energy density, long lifespan and wide operation temperature, demonstrating its comparable with the aprotic-electrolyte supercapacitor in performance but being safer and more cost-effective.