A team of researchers from Harbin Institute of Technology and Southern University of Science and Technology have developed a flexible electrochromic bifunctional energy storage device. This flexible device can display its energy state through color changes and serve as an energy provider for various portable electronic devices.

The team used a flexible silver nanowire network electrode as a collector, and coated the network with a polymeric mixture of two ionomers, called PEDOT:PSS, to improve its electrochromic stability. In addition, Co(OH)2 nanosheets were deposited on the silver nanowire network to further increase the energy density of the device.

First author He Zhang explained, “In our work, we used silver nanowires to replace the conventional ITO material, and PEDOT:PSS can solve the electrochemical instability problem of silver nanowires.” The results obtained showed excellent stability against mechanical deformation, and stable areal capacitance during 1000 bending cycles.

The team has studied a flexible device based on a silver nanowire electrode, but it can also be generalized to other materials such as copper nanowires and carbon nanotube gratings. The findings could have a broad impact on the future development of smart windows for energy-efficient buildings.