A dual-function device with high coloring efficiency based on a highly stable electrochromic nanocomposite material

[Display omitted] •PB/MnO2 has abundant color variations (light yellow, blue, green, dark yellow).•PB/MnO2 has a large surface capacitance (25.34 mF/cm2).•PB/MnO2 shows excellent cycle stability.•Dual-function realizes fast response and high coloring efficiency. Inorganic electrochromic materials have attracted wide attention due to excellent safety and simple preparation process. However, its applications are limited by slow response time, monotonous color change, low coloring efficiency and poor stability. Although people have made great contributions to improve its performance, there is still a big challenge to get comprehensive improvement in the mentioned aspects. Here, we use Prussian blue (PB) with special crack structure as support, and composite manganese dioxide material (MnO2) on its surface to prepare a new electrochromic nanocomposite material PB/MnO2. PB/MnO2 materials can realize the superposition of different colors under the synergistic effect of the two materials. Meanwhile, MnO2 porous structure and PB crack structure provide the reaction of ion channels, and as a result of the existence of PB nanoparticles, enlarges the area of effective contact materials and the electrolyte, so as to shorten the response time of the reaction. Usually, the materials with porous and crack structures are poor in stability. Fortunately, the compactness of MnO2 pores makes up for this defect and even gives PB/MnO2 materials excellent cycle stability (99.62 % of the original surface capacitance after 1500 cycles). In addition, with PB/MnO2 material as an electrode, an electrochromic energy storage device can be prepared. The results show that the device can provide an open-circuit voltage up to 1.10 V, and can achieve obvious color change in a short time (response time is 2.98 s/3.62 s) under the action of applied voltage, and the coloring efficiency is as high as 2019.57 cm2/C, which is unprecedented in current research. This work provides a new opportunity to design next-generation safe and intelligent hybrid energy storage system for consumer electronics.