Developing W18O49 electrode material with excellent high-speed charging/discharging characteristics

Abstract:
We previously reported that the oxygen vacancies of tungsten oxide (WO3) play an important role in determining the charging/discharging rate of lithium ion secondary batteries (LIBs). We synthesized oxygen-deficient tungsten oxide (W18O49) powder from WO3 nanoparticles and succeeded in fabricating on electrode with high-speed charging/discharging characteristics. This material has superior electron conductivity and enables ultrafast charging/discharging by forming tunnels in crystal structures that serve as diffusion paths for Li ions. In this study, we evaluated the change in the crystal structure of W18O49 during charging/discharging in the voltage range of 1.4 – 2.4 V (vs Li/Li(exp +)). The volume expansion rate was 2.7% at 1.4 V, and it was revealed that the volume expansion and contraction were reversible. Furthermore, we fabricated a laminated trial power storage device and evaluated its charging/discharging characteristics. It was found to have a higher energy density and double the power density compared with an electric double-layer capacitor (EDLC), indicating that the trial power storage device has superior ultrafast charging/discharging characteristics.