In situ crystallization of high performing WO3-based electrochromic materials and the importance for durability and switching kinetics

Feng Lin; Jifang Cheng; Chaiwat Engtrakul; Anne C. Dillon; Dennis Nordlund; Rob G. Moore; Tsu-Chien Weng; S. K. R. Williams; Ryan M. Richards

doi:10.1039/C2JM32742B

In situcrystallization of high performing WO₃-based electrochromic materials and the importance for durability and switching kinetics†

Feng Lin,^ac Jifang Cheng,^b Chaiwat Engtrakul,^a Anne C. Dillon,^a Dennis Nordlund,^d Rob G. Moore,^d Tsu-Chien Weng,^d S. K. R. Williams^b and Ryan M. Richards*^bc

Author affiliations

* Corresponding authors

^a National Renewable Energy Laboratory, Golden, CO 80401, USA

^b Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
E-mail: rrichard@mines.edu
Tel: +1 (303)-273-3612

^c Materials Science Program, Colorado School of Mines, Golden, CO 80401, USA

^d SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA

Abstract

A chemical self-assembled synthesis was used to prepare disordered porous semicrystalline WO₃-based cathodic electrochromic films. The resulting films were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N₂ physisorption, Fourier transform infrared spectroscopy (FTIR) and near-edge X-ray absorption fine structure (NEXAFS). The electrochromic performance was evaluated in a Li-ion electrolyte (i.e., 1 M LiClO₄ dissolved in propylene carbonate) with cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL) and chronoamperometry (CA) techniques. It is demonstrated that the crystallinity of WO₃ thin films can be readily tuned with the variation of annealing temperatures and TiO₂ addition. The results demonstrated excellent stability and durability (i.e., 1500 GCPL cycles in 32 days) for WO₃ electrode annealed at 350 °C, ultrafast switching kinetics for WO₃–TiO₂ electrode (i.e., bleaching and coloration times are 5.5 s and 4.2 s, respectively) and excellent charge reversibility (%R ≈ 100%). Electrochemical, TEM and Raman spectroscopy studies suggest that a change in degree of crystallinity in WO₃ occurs during the extended durability test, which then influences the durability and switching kinetics.

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Article information

DOI: https://doi.org/10.1039/C2JM32742B
Article type: Paper
Submitted: 02 May 2012
Accepted: 29 Jun 2012
First published: 06 Jul 2012

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J. Mater. Chem., 2012,22, 16817-16823

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In situ crystallization of high performing WO₃-based electrochromic materials and the importance for durability and switching kinetics

F. Lin, J. Cheng, C. Engtrakul, A. C. Dillon, D. Nordlund, R. G. Moore, T. Weng, S. K. R. Williams and R. M. Richards, J. Mater. Chem., 2012, 22, 16817 DOI: 10.1039/C2JM32742B

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