Bon-Ryul Koo

Zinc‐ion hybrid supercapacitors (ZIHCs) are promising electrochemical energy storage system candidates owing to their eco‐friendliness, low‐cost, reliable safety, and high‐power density. Of particular note, ZIHCs are desirable alternatives to lithium‐ion batteries (LIBs) because they can overcome the disadvantages of LIBs, such as the explosion hazard and the complex manufacturing process. Nevertheless, the low specific capacity of ZIHCs caused by their limited active sites and poor cycling stability because of their low wettability and irreversible Zn dendrite formation at the electrode has hindered their commercial application. Herein, for the first time, the fabrication and interfacial engineering of ZIHCs using vanadium (IV) oxide sulfate (VOSO₄) as an additive chemistry agent is described, and the effect of the additive on the electrochemical performance is demonstrated. After the activation process, the resultant supercapacitor exhibits a zinc vanadium hydrate (ZVO) layer on both the anode and cathode. The electrochemical role of the ZVO layer on the electrodes are as follows: i) improved active sites for Zn‐ion intercalation at the cathode, ii) enhanced wettability between electrolyte and electrodes, and iii) buffer layer for the suppression of undesirable and irreversible Zn dendrites at the anode.

To improve the practical performance of Na-ion batteries, electrode structure engineering provides a new route to improve the electrochemical efficiency of the cathode active material. In this study, we suggest a new route of one-pot spray engineering to design Na_0.44MnO₂ cathodes to realize high-rate and cycle-stable Na-ion battery performance. This technique adjusts the electrode structure from a dense to an open sponge-like morphology during layer-by-layer deposition of the materials. The sponge-like cathode results in improved ion insertion and transport kinetics, thus accelerating the rate capability with increased capacity and high-rate cycling capability (100.1 mAh/g and 90.2% cycling retention after 100 cycles at 5 C). These results highlight the potential for design engineering of cathode structures to achieve high-rate and cycle-stable performance for Na-ion batteries.

Novel tunneled phosphorus (P)-doped WO₃ films developed using ignited red P are a valuable electrochromic material with stable fast-switching performances.

Mesoporous WO₃ films with oxygen vacancy defects fabricated via camphene show multifunctional electrochromic properties of ultrafast switching speeds and high coloration efficiency.