Author links open overlay panelPeihua Yang, Peng Sun,https://doi.org/10.1016/j.mattod.2015.11.007Get rights and contentUnder a Creative Commons licenseopen accessEnergy storage devices with the smart function of changing color can be obtained by incorporating electrochromic materials into battery or sup. Author links open overlay panelPeihua Yang, Peng Sun,https://doi.org/10.1016/j.mattod.2015.11.007Get rights and contentUnder a Creative Commons licenseopen accessEnergy storage devices with the smart function of changing color can be obtained by incorporating electrochromic materials into battery or supercapacitor electrodes. In this review, we explain the working principles of supercapacitors, batteries, and electrochromic devices. In addition, we discuss the material candidates for electrochromic energy storages in detail. The challenges of the integrated electrochromic energy system for simultaneous realization of electrochromism and energy storage are specially highlighted.••Supercapacitors and batteries are considered two of the most promising energy storage technologies for electric vehicles and renewable energy systems,,,,,. During the charge insertion/extraction or chemical reduction/oxidation processes, some materials change their colors accordingly, which can be clearly observed when they. Supercapacitors and batteriesIn Li-ion batteries, one of the most important batteries, the insertion of Li+ that enables redox reactions in bulk electrode materials is diffusion-controlled and thus slow, leading to a high energy density but a long recharge time. Supercapacitors, or named as electrochemical capacitors, store electrical energy on the basis of two mechanisms: electrical double layer effect on material surface in electrical double layer capacitors (EDLCs) (Fig. 1a and b), and fast bidimensional redox reactions (Fig. 1c) or rapid tridimensional intercalation processes (Fig. 1d) in a very thin surface layer in pseudocapacitors. Based on the unique energy storage mechanisms, supercapacitors can be charged and discharged at a much higher rate than batteries.Electrochromic devicesElectrochromism, evocating the alteration of color by passing a current or applying a potential to special materials, has been greatly advanced over the past years, providing widespread applications in light-regulation and displays,. It is noteworthy that spectral change accompanying a redox reactio. Metal oxidesResearch and development on electrochromic materials and their applications has been continuing since the discovery of electrochromism,. Concerning electrochromic oxides, focuses on them show an explosive growth. There are two principally different kinds of electrochromic oxides: those referred to as “cathodic” color under ion insertion, and the “anodic” ones color under ion extraction. Applying a voltage in order to transport ions between the electrochromic films along one direction makes both of these films color, and transporting ions in the other direction makes both of them bleach; this can be referred to as “rocking chair” process from lithium battery technology.The most commonly used cathodic electrochromism oxides are mainly based on tungsten oxides,,,,,,,. The schematic reaction can be summarized as the equation below,(2)WO3+H++e−bleached↔HWO3coloredwhich is the case of proton insertion/extraction. Very recently, tungsten oxide for pseudocapacitor and electrochromic applications has drawn tremendous attention,,. For instance, Yang et al. designed multifunctional glass windows that combine energy storage and electrochromism using WO3 film electrodes which were obtained by facile thermal evaporation method (Fig. 5a–c). These WO3 fil. Electrochromic energy storage devices change their color while they store energy, which can be used in buildings and automobiles. Electrochromic devices and energy storage devices have many aspects in common, such as materials, chemical and structure requirements, physical and chemical operating mechanism. The charge and discharge properties of an.
