Electrochromic devices (ECDs) are actively switchable and transparent battery-like systems. They can modulate the transmission of visible and/or infrared light through the use of a low electrical stimulus, e.g. voltage or current.[1] ECDs only need a power supply during switching, so they can save up to 40% of the energy for buildings.[2] For the application of ECDs high performance electrolytes are required that are suitable for high-throughput and automized processing and exhibit high ionic conductivity, high transparency, as well as electrochemical, thermal and UV stability. Furthermore, the electrolyte components should be non-toxic and environmentally friendly. Gel polymer electrolytes (GPEs) combine the advantages of liquid and solid electrolytes because their properties can be tailored by adjusting the composition. [1,3] 

The goal of this research is to investigate the influence of crosslinker chain length on the mechanical stability of the resultant GPE, which is characterized by rheology, and on the temperature-dependent ionic conductivity, measured by electrical impedance spectroscopy. The simultaneous increase of mechanical stability and ionic conductivity is challenging. The viscosity of GPEs in non-cured state was successfully increased, e.g. from 2 to 6 Pa·s without compromising the ionic conductivity. The latter is higher than > 5·10^-4 S cm^-1 at room temperature (Fig. 1a). The GPEs developed are tested in exemplary ECDs containing a metal coordination polymer and Prussian blue as EC materials by measuring their optical properties and electrochemical stability. Finally, the GPEs will be used for automized assembly of ECDs in a robotic platform (Fig. 1b). Automized robotic platforms combined with artificial intelligence and machine learning can accelerate research and commercialization of ECDs by high-throughput experimentation in the future.

References

[1] Ah, C. S. et al., Solar Energy Materials and Solar Cells 2021, 221, 110883.

[2] Cannavale, A.; Ayr, U.; Fiorito, F.; Martellotta, F., Energies 2020, 13, 1449.

[3] Alesanco, Y.; Viñuales, A.; Rodriguez, J.; Tena-Zaera, R., Materials 2018, 11, 414.