Electrochromic Nanocomposites with Endured Energy Storage Properties

Sustainable energies from transient and renewable energy reservoirs such as wind and solar are in urgent demand due to the ever increasing energy crisis arising from the limited reserves of fossil fuels. Given the intermittent nature of these renewable energy resources, reliable energy storage systems are critically needed to store and supply energy in a stable way.^1-5 Meanwhile, electrochromic materials for energy saving have attracted equivalent attention from both the academia and industry, for example, controllable light-reflective or light-transmissive devices for optical information and storage, glare-reduction systems for offices, smart windows for use in cars and buildings.^6-8 In this context, devices with integrated functions of energy storage and electrochromism are highly desirable from the point of view of sustainable development.⁹

Recently, electrically conductive polymers (CPs) have received intensive attention owing to their high pseudocapacitances arising from the rich redox reactions and the corresponding color switching, as well as their facile preparation, environmental stability, high electrical conductivity, and low cost, which make them promising candidates for both energy storage and electrochromic applications. However, structural degradation as a result of the swelling/shrinkage during the intercalation/deintercalation of counterions in the redox reactions remains a challenge for pure CPs thin films. Targeting to achieve stable conductive polymer nanocomposite thin films with desirable energy storage and electrochromic properties, polyaniline nanocomposite thin films incorporated with different nanofillers, i.e., tungsten oxide and graphite oxides have been prepared by in-situ electropolymerization of the monomers onto the nanofiller coated ITO glass. These nanocomposite thin films have demonstrated much more enhanced stability due to the interactions between the polymer matrix and the nanofillers, which help buffer the stress developed in the polymer matrix. Meanwhile, the nanocomposites exhibit multi-color electrochromism at different potentials, high color contrast, fast switching speed, and high energy efficiency while possessing significant energy storage properties in terms of high energy densities and power densities.

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