Flexible electrochromic zinc ion battery based on Prussian blue prepared by MXene-assisted in situ growth

Abstract

Traditional electrodes for flexible/wearable electrochromic zinc ion batteries (EC-ZIBs) are typically prepared using electrodeposition or hydrothermal methods, which suffer from poor adhesion, leading to significant performance degradation during repeated bending. In this paper, a Prussian blue electrode with MXene (MPB electrode)-assisted in situ growth was prepared by the two-dimensional-material-assisted in situ growth (TAIG) method. The MPB electrode, achieved through simple immersion, features a nanoparticle shape with strong bonding to the flexible substrate. This nanoparticle-shaped PB does not clog the pores of the nylon fibers and grows inside the nylon fibers, which ultimately shortens the ion channels, allowing short ion diffusion pathways, fast electrochemical kinetics, favorable electrolyte penetration and improved specific capacity. In the fabrication of EC-ZIB devices, the MPB cathode exhibits a high specific capacity of 197.2 mAh g⁻¹ at 2 A g⁻¹ and retains 79.7% of its capacity even with a tenfold increase in current density. Additionally, the MPB electrode demonstrates excellent electrochromic performance (yellow, green and blue) within the range of 0.5 to 1.8 V, with rapid switching time of only 2.2 s for coloring and 2.0 s for bleaching. Therefore, the MPB electrodes fulfill the requirements for multifunctional devices, allowing easy monitoring of energy storage levels through color changes, and showing potential applications in smart camouflage, wearable displays and other fields, promoting the development of flexible smart energy storage devices.

Graphical Abstract