Polyaniline‐vanadium oxide composite for Zn‐ion electrochromic devices and mechanistic investigation by in‐situ Raman spectroscopy

Abstract Vanadium oxide (VO X ) with tunable interlayer spacing and variable valence states of vanadium ions offers tremendous opportunities in aqueous electrochromic devices but is still challenging. Herein, a polyaniline (PANI)‐VO X composite material has been designed, increasing the conductivity and the structure stability. Owning to these virtues, the PANI‐VO X composite material achieves a high capacitance of 332 mAh·g –1 at 0.1 A·g –1 and a superior cycling performance (72% Δ T retention after 500 cycles). Importantly, in‐situ Raman spectroscopy has been utilized to reveal the rapid formation of Zn 3 (OH) 2 V 2 O 7 · n H 2 O and the reversible change of PANI‐VO X , which can further assist the development of aqueous electrochromic devices. This work highlights the understanding of the Zn 2+ electrochromic mechanism and sheds some light on organic–inorganic composite electrochromic materials.