Authors: Fábio A. S. Leite^1,2, Piotr Wierzchowiec¹, Laura Maggini², Antoine Stopin², Carlos Pinheiro¹, Davide Bonifazi²

¹ Ynvisible Gmbh, Engesserstraße 4A, 79108 Freiburg im Breisgau, Germany

² University of Vienna, Faculty of Chemistry, Institute of Organic Chemistry, Währinger Straße 38, 1090 Vienna, Austria

Abstract

Transition from traditional liquid electrolytes to solid polymer electrolytes (SPE) gained thrust due to increased safety, flexibility, mechanical durability, and adhesion to electrodes. Yet the required ionic conductivity of 10^-3 S/cm for commercial applications has not been achieved.(1)   In addition to their use in batteries, electrochemically gated transistors and dye sensitized solar cells application, electrolytes are also required in electrochromic devices (ECDs) often employed in smart windows and labels.(2) For effective commercialization, electrolytes must be compatible with industrial manufacturing processes, facilitate overprinting of functional inks, and operate over a wide range of temperature (- 40 ºC to 80 ºC).

 In this contribution we are presenting a hybrid printable solid polymer electrolyte composed of i) PVDF, a high dielectric constant polymer , to improve the ionic conductivity, and ii) cross-linked acrylate monomers to provide mechanical rigidity after printing. Lithium perchlorate was selected for its high ionic conductivity and highly delocalized charge anion. This two-polymer system possesses a thixotropic shear thinning behaviour with a viscosity of 0.1 Pa.s above shear rates of 100 s^-1. Using electrical impedance spectroscopy, we obtained a bulk ionic conductivity of 2.01 x 10^-3 S/cm at room temperature. Additionally, electrolyte thin films obtained are robust and flexible and could be recycled and reused by re-laminating the film on a new device.

Finally, the electrolyte was implemented in a reversible PEDOT:PSS based ECD. We observed fast-switching times (5s to achieved 75% of Δ%T) with an optical contrast of ΔT = 30 %. In literature these values were observed in ECDs with gel electrolyte with higher solvent content. (3)

References

(1) Bocharova, V.; Sokolov, A. P. Perspectives for Polymer Electrolytes: A View from Fundamentals of Ionic Conductivity. Macromolecules 2020, 53 (11), 4141–4157. 

(2) Lee, M.; Son, M.; Chun, D. man; Lee, C. S. Evaluation of Electrochromic Device Influenced by Various Formulation of Solid Polymer Electrolyte. International Journal of Precision Engineering and Manufacturing 2021, 22 (1), 189–199. 

(3) Assis, L. M. N.; Andrade, J. R.; Santos, L. H. E.; Motheo, A. J.; Hajduk, B.; Łapkowski, M.; Pawlicka, A. Spectroscopic and Microscopic Study of Prussian Blue Film for Electrochromic Device Application. Electrochimica Acta 2015, 175, 176–183.