Novel Prussian White@MnO₂-Based Inorganic Electrochromic Energy Storage Devices with Integrated Flexibility, Multicolor, and Long Life

Abstract

Flexible electrochromic devices have attracted considerable attention in recent years due to their great potential in smart multifunction electrochromic energy storage devices and wearable intelligent electronics. Herein, we present an inorganic flexible Li-based electrochromic energy storage device (EESD) by combining a Prussian white@MnO 2 -composited electrode (PWM) and sputtering-made WO 3 electrode. The synergistic effect of Prussian white and MnO 2 plays a positive role both in energy storage and electrochromic property of the EESD. Its energy level can be quantified by the transmittance spectrum and chrominance difference, and its charging−discharging process can be monitored in real time by optical modulation at special wavelength. Specifically, the EESD can endure a 10,000 times cyclic voltammetry cycle without obvious degradation at wide voltage windows (−2 to 2.5 V) and realize a high coloration efficiency (77.6 cm 2 /C) with 35% optical modulation at 510 nm. In terms of energy storage performance, the EESD demonstrates excellent volumetric energy/power density (1.25 W cm −3 /13.2 mWh cm −3 ) and remarkable stability with close to 98.3% capacitance retention and 99.4% coulombic efficiency after more than 4000 cycles. Its charging and discharging degree can be visualized in different spectral regions. There are 40% transmittance change for charging in the blue light region (450−480 nm) and 45% transmittance change for discharging in the red light region (620−750 nm). Based on its multicolor property, a quantitative indicator of charge state is achieved by the linear dependence of real-time chrominance change as stored or released charge. The ∼11 mC/cm 2 stored charge capacity can cause an ∼11 increase in chrominance difference ΔE value, while ∼7 mC/cm 2 discharge capacity can cause a ΔE value increase of ∼4. This work provides an efficient strategy to develop portable multicolor-integrated EESDs toward high performance and long stability.

Flexible Inorganic All-Solid-State Electrochromic Devices toward Visual Energy Storage and Two-Dimensional Color Tunability

“…With the cyclic process continuing, both the colored and bleached transmittance exhibited a rising trend, which means the partial electrode materials failed. Combined with the previous study, it is observed that it could be due to the poorer stability of MnO 2 compared with that of PB . For this inorganic flexible device, its mechanical flexibility combined with the electrochromic performance was also checked, as in Figure b–d.…”

“…Combined with the previous study, it is observed that it could be due to the poorer stability of MnO 2 compared with that of PB. 63 For this inorganic flexible device, its mechanical flexibility combined with the electrochromic performance was also checked, as in Figure 5b−d. The electrochemical process would be affected when the bending radius was lower than 3 cm (Figure 5b), but even under a small bending radius (1.5 cm), the capacity retention can still get up to ∼80%, which verified its good flexible function (Figure 5c).…”

High Electrochromic Performance of Perylene Bisimide/ZnO Hybrid Films: An Efficient, Energy-Saving, and Green Route

“…The CE is also an essential parameter for electrochromic materials, it can be calculated using the following equation normalC normalE ( λ ) = normalΔ A Q normald = log nobreak0em.25em⁡ T normalO normalX T normalr normale normald Q normald …”

“…The CE is also an essential parameter for electrochromic materials, it can be calculated using the following equation …”

Recent advances in electrochromic materials and devices for camouflage applications

“…53 This problem can be effectively solved by the introduction of structural colors and the preparation of composite materials. 54,55 The great advantage of organic EC materials compared to inorganic materials is that the color can be tuned by means of molecular structural design. [56][57][58] Of course, structural colors and color composites are also common means of color modulation in organic materials.…”