A high-performance electrochromic battery based on complementary Prussian white/Li4Ti5O12 thin film electrodes

Abstract Electrochromic energy storage devices (EESDs) have a wide range of applications from static displays to building windows. However, it is a great challenge to assemble EESDs with both high performance of energy storage and electrochromism. In this work, we design a multifunctional EESD composed of a Li4Ti5O12 and a Prussian white. Li4Ti5O12 (E = 1.55 V vs Li/Li+) film with excellent lithium-ion storage performance is used as the anode, and Prussian white film (E = 3.2 V vs Li/Li+) as the cathode. Thanks to the complementary electrochromic behavior, the suitable redox voltage gap, and the intrinsic electrochemical stability of Li4Ti5O12 film and Prussian white film, the as-assembled EESD exhibits excellent electrochromic performances including broad optical modulation (55.3% at 529 nm), high coloration efficiency (170.1 cm2 C−1), and long-term cycling stability (retention of 95.8% of initial optical modulation after 1000 cycles). And the EESD shows high energy density of 127.2 mWh cm−2 and exceptionally high power density of 24 mW cm−2. This EESD with an output voltage of 1.5 V and Coulombic efficiency of 98.8% is promising for applications of electrochromic smart windows and static displays to significantly reduce their energy consumption.