A Long‐Life Battery‐Type Electrochromic Window with Remarkable Energy Storage Ability

Abstract

Electrochromic (EC) windows with controllable transmittances according to ambient temperature and solar irradiation strength are highly desired for energy‐efficient buildings. However, traditional EC windows operate via consuming electrical energy to trigger the chromogenic reactions, with negligible energy storage ability. Herein, a facile battery‐type Prussian blue (PB, Fe4III[FeII(CN)6]3)/Zn EC window with excellent EC properties (transmittance modulation = 84.9% at 633 nm), remarkable energy storage ability (average output voltage = 1.24 V and areal capacity = 78.9 mAh m−2), fast switching time (tbleaching = 4.1 s and tcoloring = 4.6 s), as well as an ultralong cycling lifetime (7000 cycles with 60.7% capacity retention and 92.7% transmittance modulation retention) is reported, thanks to the rational electrode and electrolyte design. As an EC window, this device can effectively promote energy efficiency and occupational comfort of buildings by regulating visible light transmittance. As a battery, this device can work as backup power or a component of smart grids, making the buildings more sustainable and functional. The design concept of this bifunctional device is helpful to further the development of next‐generation EC windows.

Rechargeable Aqueous Zinc‐Ion Batteries with Mild Electrolytes: A Comprehensive Review

“…Very recently, our group developed a 0.9 M KCl + 0.1 M Zn(CH 3 COO) 2 dual-cation electrolyte to stable not only Fe-HCF cathode but also Zn anode, achieving an ultra-long lifetime of 7,000 cycles with capacity retention of 60.7 %. [113] Pay attention that the Fe-HCF was deposited on a transparent conducting FTO glass, resulting in a bi-functional device with excellent electrochromic and energy storage ability (Figure 8cf). This device represents an emerging class of versatile electrochromic batteries (or energy storage smart windows), which can effectively increase the energy efficiency of buildings by means of light and electric energy management.…”

“…[130,131] The rationally designed dual-cations electrolyte may even benefit the cycling stability of the ZIBs, because of the improved reaction kinetics and sometimes also the depression of Zn dendrite growth. [113,132] In dual-cation ZIBs, enough Zn + and foreign cations must to be pre-stored in the electrolyte to ensure the full use of the electrodes. This requirement may limit the energy density of batteries, if the solubility of cations' source salts is low.…”

“…[136] Taking this advantage into account, a ZnÀ Fe-HCF battery is designed with a Zn 2 + /K + dualcation electrolyte (i. e., 0.9 M KCl + 0.1 M Zn(CH 3 COO) 2 ). [113] Systematic analyses indicate that introducing K + into electrolyte benefits the reactions on both anode and cathode sides, resulting in an ultra-long cycling life of 7000 cycles. In addition, the couple of Zn and Fe-HCF enables the battery remarkable color-changing (i. e., electrochromic) ability.…”

“…If the electrodes have already been well isolated from each other by structure design, separators are eliminable, for example in some electrochromic batteries. [113,114,274] For solidstate batteries, the gel or solid-state electrolytes can be regarded as an integration of separators and electrolytes. [88] In this configuration, individual separators may also become unnecessary.…”

“…Photographs (c), galvanostatic charge discharge (GCD) curves (d), transmittance spectra (e), cycling stability (f) of a ZnÀ Fe-HCF battery in a 0.9 M KCl + 0.1 M Zn(CH 3 COO) 2 dual-cation electrolyte. Reproduced with permission from Ref [113]…”