Rational design of hollow WO3/PEDOT/WO3 hybrid nanospheres with superior electrochromic energy storage performance

Abstract

In this research, we report on the fabrication of hollow WO₃/PEDOT/WO₃ nanospheres through template-assisted magnetron sputtering combined with one-pot sequential electrochemical deposition. The PEDOT layer creates an efficient conductive network that facilitates electron transport, while the unique hollow nanosphere architecture and the low crystallinity WO₃ layers provide short diffusion lengths and numerous binding sites for small ions, respectively. The sandwiched hybrid structure enhances the protection of the intermediate conductive PEDOT layer and provides an improved synergistic effect, leading to better electrochromic and energy storage performance. The electrochromic performance of the hollow WO₃/PEDOT/WO₃ nanospheres is exceptional, exhibiting a significant optical modulation in both the visible and near-infrared regions (96.4 % at 633 nm, 91.5 % at 1500 nm). Additionally, these nanospheres demonstrate rapid response times for coloring (3.0 s) and bleaching (5.6 s), while maintaining excellent cycling stability (with only an 11.4 % decrease in optical modulation after undergoing 6000 cycles). Moreover, their coloration efficiency is decent (115.6 cm²C^-1) when operated at low potentials for coloration/bleaching (−1.0/1.0V). The nanospheres also demonstrate high areal capacitance of 47.5 mF cm⁻², superior rate capability, and good cyclic stability. The aforementioned properties render it a promising candidate for high efficiency electrochromic energy storage applications.