Achieving rapid Li-ion insertion kinetics in TiO2 mesoporous nanotube arrays for bifunctional high-rate energy storage smart windows

Abstract

Smart electrochromic windows integrated with electrochemical energy storage capacity are receiving increasing interest for green buildings. However, the fabrication of bifunctional devices that demonstrate high-rate capability with stable and desirable optical modulation still remains a great challenge. Herein, a facile sacrificial template-accelerated hydrolysis approach is presented to prepare a designed lithium-ion insertion-type material layer on a fluorine-doped tin oxide substrate, with TiO₂ mesoporous nanotube array (MNTA) film as an example, with rapid Li-ion insertion kinetics and without sacrificing window transparency, to meet requirements. A bifunctional device is assembled to exhibit the optical-electrochemical superiority of MNTA nanostructures. The as-assembled bifunctional smart window exhibits strong electrochromic contrast and high-rate capability in the fast galvanostatic charge/discharge process. For instance, at 1 A g⁻¹, it completes the charge or discharge process within only 232 s and delivers a high, reversible and stable specific capacity of 60 mA h g⁻¹, accompanying obvious transmittance modulation in the visible spectrum, with a typical value of ca. 30.4% at 700 nm, and strong color changes between deep blue and transparency.