Department of Engineering Sciences, The Ångström Laboratory, Uppsala University , SE-75121 Uppsala, Sweden.
Materials Processing Center, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
ACS Appl Mater Interfaces. 2017 Apr 12;9(14):12872-12877. doi: 10.1021/acsami.7b01324. Epub 2017 Mar 30.
Degradation of electrochromic thin films under extended charge insertion and extraction is a technically important phenomenon for which no in-depth understanding is currently on hand. Here, we report on an explorative study of sputter-deposited WO films in a Li-ion-conducting electrolyte by use of cyclic voltammetry, in situ optical transmittance, and impedance spectroscopy. A cycling-dependent decrease of the charge capacity could be accurately modeled by a power-law function, and impedance spectroscopy gave evidence for anomalous diffusion as well as a higher charge-transfer resistance during deintercalation than during intercalation. Thus, a consistent conceptual picture emerged for the degradation dynamics; it includes the growth of an interfacial barrier layer and also embraces anomalous diffusion coupled with dispersive power-law chemical kinetics.
电致变色薄膜在长时间的充放电过程中的降解是一个技术上非常重要的现象，但目前我们对此并没有深入的了解。在这里，我们报告了一个关于在锂离子导电电解液中使用循环伏安法、原位光透射率和阻抗谱研究溅射沉积 WO 薄膜的探索性研究。通过幂律函数可以准确地模拟出与循环相关的电荷容量的下降，而阻抗谱则证明了在脱嵌过程中异常扩散以及电荷转移电阻比嵌入过程中更高。因此，一个一致的概念性画面出现了降解动力学；它包括界面阻挡层的生长，也包括异常扩散与弥散幂律化学动力学的耦合。
