Electrochromism and electrochemical energy-storage share the same electrochemical principles of redox reaction that occurs when the charge is inserted or removed in the electrode. An electrochemical device that integrates electrochromic and electrochemical energy storage functions is defined as an electrochromic energy-storage device. Although single-function electrochromic devices and electrochemical energy-storage devices have been widely reported and commercialized, the research on electrochromic energy storage devices is still in the experimental stage. Such devices can change their transmittance in the visible or even infrared range while electrochemically storing energy, and can indicate the state of charge of the device with color change, providing a new application prospect for electrochemical devices. Electrochromic energy-storage devices mainly include electrochromic supercapacitors, electrochromic batteries, and photo-driven electrochromic smart windows. Electrochromic supercapacitors and electrochromic batteries are composed of positive and negative electrodes with materials having both electrochromic effects and charge storage properties, and photo-driven electrochromic smart windows include an additional photoelectric conversion component. These devices can be used in building energy-saving smart windows, static displays, smart sensors, etc. In addition, when fabricated on flexible substrates, these wearable electrochromic energy-storage devices have potential applications in smart apparel, implanted displays and electronic skins. In this review, we discuss the electrochromic energy-storage devices from the basic principles, research progress, application fields, and future research prospects.

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