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Anodic Electrochromic Nickel Oxide Thin Films: Decay of Charge Density upon Extensive Electrochemical Cycling
Author(s) -
Wen RuiTao,
Granqvist Claes G.,
Niklasson Gunnar A.
Publication year - 2016
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201500457
Subject(s) - electrochromism , materials science , diffusion , electrolyte , anode , electrochemistry , oxide , thin film , power density , ion , analytical chemistry (journal) , chemical physics , electrode , thermodynamics , nanotechnology , chemistry , power (physics) , metallurgy , physics , organic chemistry , chromatography
Electrochromic (EC) Ni oxide thin films are a critical component in the smart windows. However, long‐term decay of the EC performance in aprotic electrolytes is persistent and poorly understood, and it is difficult to assess lifetimes of EC devices. Here we report on charge density decline upon electrochemical cycling. The charge density decay was modeled with a power law or, alternatively, a stretched exponential; both models describe a rapid drop of charge density during the first hundreds of cycles and a subsequent slower decline. The decay is independent of film composition and applied potential range as long as the upper limit of the potential is ≤4.4 V vs. Li/Li + . Our decay models are interpreted in terms of dispersive chemical reaction kinetics and point at ion diffusion as the rate‐limiting step. Power‐law exponents are consistent with diffusion. The results provide a framework for evaluating EC durability of Ni‐oxide‐based thin films and may be important for assessing the durability of EC devices.