| 1. |
-
- 2019
-
Tidskriftsartikel (refereegranskat)
|
|
| 2. |
- Arvizu, Miguel, et al.
(författare)
-
Galvanostatic ion de-trapping rejuvenates oxide thin films
- 2015
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:48, s. 26387-26390
-
Tidskriftsartikel (refereegranskat)abstract
- Ion trapping under charge insertion-extraction is well-known to degrade the electrochemical performance of oxides. Galvano-static treatment was recently shown capable to rejuvenate the oxide, but the detailed mechanism remained uncertain. Here we report on amorphous electrochromic (EC) WO3 thin films prepared by sputtering and electrochemically cycled in a lithium-containing electrolyte under conditions leading to severe loss of charge exchange capacity and optical modulation span. Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li+ trapping associated with the degradation of the EC properties and, importantly, that Li+ detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance. Thus, ToF-ERDA provided direct and unambiguous evidence for Li+ detrapping.
|
|
| 3. |
- Baloukas, Bill, et al.
(författare)
-
Galvanostatic Rejuvenation of Electrochromic WO3 Thin Films : Ion Trapping and Detrapping Observed by Optical Measurements and by Time-of-Flight Secondary Ion Mass Spectrometry
- 2017
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:20, s. 16996-17002
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochromic (EC) smart windows are able to decrease our energy footprint while enhancing indoor comfort and convenience. However, the limited durability of these windows, as well as their cost, result in hampered market introduction. Here, we investigate thin films of the most widely studied EC material, WO3. Specifically, we combine optical measurements (using spectrophotometry in conjunction with variable-angle spectroscopic ellipsometry) with time-of-flight secondary ion mass spectrometry and atomic force microscopy. Data were taken on films in their as-deposited state, after immersion in a Li-ion-conducting electrolyte, after severe degradation by harsh voltammetric cycling and after galvanostatic rejuvenation to regain the original EC performance. Unambiguous evidence was found for the trapping and detrapping of Li ions in the films, along with a thickness increase or decrease during degradation and rejuvenation, respectively. It was discovered that (i) the trapped ions exhibited a depth gradient; (ii) following the rejuvenation procedure, a small fraction of the Li ions remained trapped in the film and gave rise to a weak short-wavelength residual absorption; and (iii) the surface roughness of the film was larger in the degraded state than in its virgin and rejuvenated states. These data provide important insights into the degradation mechanisms of EC devices and into means of achieving improved durability.
|
|
| 4. |
- Granqvist, Claes G., 1946-, et al.
(författare)
-
Advances in electrochromic device technology : Multiple roads towards superior durability
- 2019
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 357, s. 619-625
-
Tidskriftsartikel (refereegranskat)abstract
- Most electrochromic (EC) devices must have a service lifetime of many years, and this is particularly so for “smart windows” in buildings with good energy efficiency and indoor comfort. The central part of oxide-based EC devices contains thin films based on W oxide and Ni oxide together with an interposed electrolyte. Depending on operating conditions, these films may show degradation at a slower or faster pace, and means to prevent or reverse this phenomenon, or as a minimum allow reliable lifetime prediction, have been sought ever since the beginnings of EC technology. Here we survey recent endeavors related to EC films of W oxide and Ni oxide and show that (i) electrochemical pretreatment of films in a liquid electrolyte can significantly improve durability, (ii) electrochemical posttreatment in a liquid electrolyte can rejuvenate degraded films, (iii) mixed oxides can have better durability and optical performance than corresponding pure oxides, and (iv) lifetime prediction is possible.
|
|
| 5. |
- Granqvist, Claes Göran, 1946-, et al.
(författare)
-
Electrochromic materials and devices for energy efficiency and human comfort in buildings : A critical review
- 2018
-
Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 259, s. 1170-1182
-
Forskningsöversikt (refereegranskat)abstract
- Electrochromic (EC) materials can be integrated in thin-film devices and used for modulating optical transmittance. The technology has recently been implemented in large-area glazing (windows and glass facades) in order to create buildings which combine energy efficiency with good indoor comfort. This critical review describes the basics of EC technology, provides a case study related to EC foils for glass lamination, and discusses a number of future aspects. Ample literature references are given with the object of providing an easy entrance to the burgeoning research field of electrochromics.
|
|
| 6. |
- Ma, Wei-Juan, et al.
(författare)
-
Proteomic changes in articular cartilage of human endemic osteoarthritis in China.
- 2011
-
Ingår i: Proteomics. - : Wiley-VCH Verlagsgesellschaft. - 1615-9853 .- 1615-9861. ; 11:14, s. 2881-90
-
Tidskriftsartikel (refereegranskat)abstract
- Kashin-Beck disease (KBD) is a chronic endemic osteochondropathy with unclear pathogenesis. It is a degenerative disease similar to osteoarthritis, but with different manifestations of cartilage damage. The aim of this investigation was to show the protein changes in KBD cartilage and to identify the candidate proteins in order to understand the pathogenesis of the disease. Proteins were extracted from the media of primary cell cultures of KBD and normal chondrocytes, and separated by two-dimensional fluorescence difference gel electrophoresis (2-D DIGE). MALDI-TOF/TOF analysis revealed statistically significant differences in 27 proteins from KBD chondrocyte cultures, which consisted of 17 up-regulated and ten down-regulated proteins. The results were further validated by Western blot analysis. The proteins identified are mainly involved in cellular redox homeostasis and stress response (MnSOD, Hsp27, Peroxiredoxin-1, and Cofilin-1), glycolysis (PGK-1, PGM-1, α-enolase), and cell motility and cytoskeletal organization (Actin, Calponin-2, and Keratin). These KBD-associated proteins indicate that cytoskeletal remodeling, glycometabolism, and oxidative stress are abnormal in KBD articular cartilage.
|
|
| 7. |
|
|
| 8. |
- Niklasson, Gunnar A., Professor, 1953-, et al.
(författare)
-
Durability of electrochromic films : Aging kinetics and rejuvenation
- 2017
-
Ingår i: ECS Transactions. - : Electrochemical Society. ; , s. 1659-1669
-
Konferensbidrag (refereegranskat)abstract
- A major challenge for energy-efficient smart window technology is to ensure the durability of electrochromic (EC) devices over aservice life of more than 20 years. In this paper, we report recent results from a fundamental study of the aging kinetics of EC tungsten oxide and nickel oxide thin films and describe electrochemical rejuvenation mechanisms that are able to restore the films to their initial state. The aging kinetics displays an approximate power-law decrease of the charge capacity as a function of cycle number. This decay of charge capacity can be understood in terms of models built on so-called dispersive chemical kinetics. Tungsten oxide and nickel oxide EC films can be rejuvenated by applying a high electrochemical potential or a small constant current. Trapped ions in the bulk or at the surface of the films can be released by these procedures.
|
|
| 9. |
- Niklasson, Gunnar A., 1953-, et al.
(författare)
-
Electrochemical degradation and rejuvenation of electrochromic tungsten oxide thin films
- 2016
-
Konferensbidrag (refereegranskat)abstract
- Tungsten oxide is the most widely used cathodic electrochromic material for smart window applications. One of the main challenges for smart window technology is to ensure the durability of the electrochromic devices over a service life of more than 20 years. Hence, in order to facilitate large-scale practical application of electrochromic materials, their degradation under operating conditions must be better understood and preferably prevented. In this paper we address these issues by three different approaches. First we show that the electrochemical ageing of electrochromic tungsten oxide, under stressed conditions, can be described by stretched exponential kinetics. The goal of such accelerated ageing studies is eventually to be able to predict service life using this empirical relationship. Secondly, we report on a recently discovered rejuvenation processes for restoring aged coatings to their initial state. During severe ageing of the coatings, Li ions are trapped in the film, and subsequently these ions can be released by application of a high electrochemical potential for a few hours. We estimate activation energies for the release process from chronoamperometric measurements during rejuvenation. Thirdly we address the issue of the growth of a solid-electrolyte interface. Impedance spectroscopy measurements on tungsten oxide films were used to obtain the interfacial charge transfer resistance. After the films had been subjected to low potentials known to induce degradation, the charge transfer resistance in the usual operating range showed a marked increase. This is interpreted as a signature of the development of a solid-electrolyte interface. A similar increase of the charge transfer resistance has been observed in electrochromic devices subjected to accelerated aging at an elevated temperature of 80oC for a thousand cycles.
|
|
| 10. |
- Niklasson, Gunnar A., 1953-, et al.
(författare)
-
Electrochromic oxides: Electrochemical density of states, degradation kinetics and rejuvenation of degraded films
- 2015
-
Konferensbidrag (refereegranskat)abstract
- Electrochromic (EC) materials change their optical properties upon the application of a voltage signal. EC devices are of interest for energy efficient smart windows, as well as for a number of niche applications. An EC device can be viewed as a thin-film electrical battery whose charging state is manifested by optical absorption. The central part of the device comprises EC thin films based on amorphous tungsten oxide (WO3) and nano-crystalline nickel oxide (NiOx) joined by a layer of polymer electrolyte. This three-layer arrangement is positioned between transparent and electrically conducting thin films of indium tin oxide (In2O3:Sn; ITO) backed by polyester foils. Applying a voltage between the ITO films induces transport of ions between the WO3 and NiO films, together with charge compensating electron transport through the outer circuit. Insertion of ions and electrons in WO3 and extraction of them from NiO lead to enhanced optical absorption. In this paper we report novel developments regarding the electronic density of states (DOS), the ageing kinetics and the rejuvenation of aged EC materials. The optical absorption in EC oxides is due to electronic transitions between localized states close to the band edges. In order to model the optical absorption it is necessary to have a good understanding of the electronic DOS. We have found that it is possible to derive an effective DOS from electrochemical measurements, in particular from measurements of quasi-steady-state potential curves, during the ion/electron insertion process. The obtained “electrochemical DOS” exhibits good agreement with state-of-the-art density functional calculations of the DOS for a number of amorphous and nano-crystalline oxides. EC devices are prone to slowly degrade under repeated electrochemical cycling and a thorough understanding of the kinetics of this degradation is necessary in order to estimate the lifetime of smart window products. The ageing is often ascribed to irreversible incorporation of ions at the film surfaces or inside the film. We present results which show that the degradation displays dispersive kinetics and the chemical reaction behind the process can be modelled by using a rate constant with power-law time dependence. Results obtained for WO3 and NiO thin films show both similarities and differences. We have very recently found that rejuvenation of previously degraded WO3 films is possible. Films with heavily degraded charge capacity and optical switching were subjected to a galvanostatic treatment for a certain time. After subjecting the film to a small current for a number of hours, it regained its initial charge capacity and optical properties. The rejuvenation is ascribed to de-trapping of ions from deep traps, induced by a high electrochemical potential over the film. The optical absorption and switching as well as the durability of EC material are key issues for the successful commercial development of smart windows. The results presented here pave the way for an increased understanding of the optical switching as well as of the degradation kinetics. The possibility of rejuvenating degraded films is highly exciting, and further studies are necessary in order to develop this idea into a practical process.
|
|
| 11. |
|
|
| 12. |
- Wen, Rui-Tao, et al.
(författare)
-
Anodic Electrochromic Nickel Oxide Thin Films : Decay of Charge Density upon Extensive Electrochemical Cycling
- 2016
-
Ingår i: ChemElectroChem. - : Wiley-VCH Verlagsgesellschaft. - 2196-0216. ; 3:2, s. 266-275
-
Tidskriftsartikel (refereegranskat)abstract
- 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 4.4V 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.
|
|
| 13. |
- Wen, Rui-Tao, et al.
(författare)
-
Anodic Electrochromism for Energy-Efficient Windows : Cation/Anion-Based Surface Processes and Effects of Crystal Facets in Nickel Oxide Thin Films
- 2015
-
Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 25:22, s. 3359-3370
-
Tidskriftsartikel (refereegranskat)abstract
- Anodic electrochromic (EC) oxides are of major interest as counter electrodes for smart window applications owing to their unique optical properties upon charge insertion and extraction. However, performance optimization of such oxides has been hampered by limited understanding of their EC mechanism, particularly in Li+-conducting electrolytes. This paper reports on NiOx films with 1.16 x 1.32, prepared by sputter deposition. These films are immersed in an electrolyte of lithium perchlorate in propylene carbonate, and EC properties are studied by cyclic voltammetry and in situ optical transmittance measurements. The electrochromism is significantly enhanced at large values of x. It has been found that charge exchange in Ni oxide is mainly due to surface processes and involves both cations and anions from the electrolyte, which is different from the case of cathodic EC materials such as WO3. Whereas previous studies of Ni oxide have focused on cation intercalation, the cation/anion-based mechanism presented here offers a new paradigm for designing and developing EC devices such as smart windows for energy efficient buildings.
|
|
| 14. |
|
|
| 15. |
- Wen, Rui-Tao, et al.
(författare)
-
Cyclic voltammetry on sputter-deposited films of electrochromic Ni oxide : Power-law decay of the charge density exchange
- 2014
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:16, s. 163502-
-
Tidskriftsartikel (refereegranskat)abstract
- Ni-oxide-based thin films were produced by reactive direct-current magnetron sputtering and were characterized by X-ray diffraction and Rutherford backscattering spectroscopy. Intercalation of Li+ ions was accomplished by cyclic voltammetry (CV) in an electrolyte of LiClO4 in propylene carbonate, and electrochromism was documented by spectrophotometry. The charge density exchange, and hence the optical modulation span, decayed gradually upon repeated cycling. This phenomenon was accurately described by an empirical power law, which was valid for at least 10(4) cycles when the applied voltage was limited to 4.1V vs Li/Li+. Our results allow lifetime assessments for one of the essential components in an electrochromic device such as a "smart window" for energy-efficient buildings.
|
|
| 16. |
- Wen, Rui-Tao, et al.
(författare)
-
Degradation Dynamics for Electrochromic WO3 Films under Extended Charge Insertion and Extraction : Unveiling Physicochemical Mechanisms
- 2017
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:14, s. 12872-12877
-
Tidskriftsartikel (refereegranskat)abstract
- 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 WO3 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.
|
|
| 17. |
|
|
| 18. |
- Wen, Rui-Tao, et al.
(författare)
-
Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance
- 2016
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 163:2, s. E7-E13
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildings. However Ni oxide, typically being the anodic counter electrode in a W-oxide-based device, may suffer severe charge capacity degradation upon extended electrochemical cycling. It is therefore important to identify improved Ni-oxide-based thin films for electrochromics. Here we describe a new class of such films wherein an addition of a small amount of Ir to Ni oxide is found to provide strongly improved electrochemical cycling durability. Best properties were achieved with Ir/(Ir + Ni) = 7.6%, and such films displayed charge capacity and optical modulation that, remarkably, were still increasing after 10,000 cycles.
|
|
| 19. |
- Wen, Rui-Tao, et al.
(författare)
-
Electrochromic iridium oxide films : Compatibility with propionic acid, potassium hydroxide, and lithium perchlorate in propylene carbonate
- 2014
-
Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 120:Part A, s. 151-156
-
Tidskriftsartikel (refereegranskat)abstract
- Porous thin films of It oxide were prepared by reactive dc magnetron sputtering onto unheated substrates. The crystallite size was similar to 5 nm, and a small amount of unoxidized Ir was present. The electrochromic performance was studied by optical transmittance measurements and cyclic voltammetry applied to films in aqueous and non-aqueous electrolytes, specifically being 1 M propionic acid, 1 M potassium hydroxide (KOH), and 1 M lithium perchlorate in propylene carbonate (Li-PC). Cyclic voltammetry measurements indicated that the films had a fractal surface structure. Good electrochromism, with mid-luminous transmittance modulation between similar to 55 and similar to 90% in similar to 100-nm-thick films, was documented in all of the electrolytes.
|
|
| 20. |
- Wen, Rui-Tao, et al.
(författare)
-
Electrochromic nickel oxide films and their compatibility with potassium hydroxide and lithium perchlorate in propylene carbonate : Optical, electrochemical and stress-related properties
- 2014
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 565, s. 128-135
-
Tidskriftsartikel (refereegranskat)abstract
- Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure. Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for similar to 500-nm-thick films both in KOH and in Li-PC (similar to 70% and similar to 50% at 550 nm, respectively). In KOH, tensile and compressive stresses, due to the expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 and 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 and 4.7 V vs Li/Li+ in Li-PC yielded significant degradation after 1000 cycles.
|
|
| 21. |
- Wen, Rui-Tao, et al.
(författare)
-
Electrochromic performance of Ni oxide thin filmsintercalated with Li+ ions
- 2014
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 559, s. 012006-
-
Tidskriftsartikel (refereegranskat)abstract
- Porous Ni oxide thin films were deposited on unheated ITO/glass substrates by sputtering in argon-oxygen. The as-deposited thin films have a cubic NiO structure and still exhibit such a structure after 10,000 electrochemical cycles in 1 M LiClO4 in propylene carbonate in the range between 2.0 and 4.1 V vs Li/Li+. Electrochromic performance showed a rapid drop of charge density over the first hundreds of cycles and subsequently a very slow decrease. The charge density was 87% of the initial one after 1,000 cycles and 82% after 10,000 cycles, indicating an extremely slow decay after 1,000 cycles. Optical modulation was also slightly decreased after 10,000 cycles, which is due to the drop of charge density.
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
- Wen, Rui-Tao
(författare)
-
Electrochromism in Metal Oxide Thin Films : Towards long-term durability and materials rejuvenation
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electrochromic thin films can effectively regulate the visible and infrared light passing through a window, demonstrating great potential to save energy and offer a comfortable indoor environment in buildings. However, long-term durability is a big issue and the physics behind this is far from clear. This dissertation work concerns two important parts of an electrochromic window: the anodic and cathodic layers. In particular, work focusing on the anodic side develop a new Ni oxide based layers and uncover degradation dynamics in Ni oxide thin films; and work focusing on the cathodic side addresses materials rejuvenation with the aim to eliminate degradation.In the first part of this dissertation work, iridium oxide is found to be compatible with acids, bases and Li+-containing electrolytes, and an anodic layer with very superior long-term durability was developed by incorporating of small amount (7.6 at. %) of Ir into Ni oxide. This film demonstrated sustained cycle-dependent growth of charge density and electrochromic modulation even after 10,000 CV cycles. The (111) and (100) crystal facets in Ni oxide are found to possess different abilities to absorb cation and/or anion, which yields different degrees of coloration and this is very significant for the electrochromic properties. The degradation of charge capacity in Ni oxide has an inevitable rapid decay in the first hundreds of cycles, subsequently combined with a more gradual decay, which is independent of applied potential and film composition. The consistent phenomenon can be very well modeled by power-law or stretched exponential decay; however the two models are indistinguishable in the current stage. Interestingly, in both models, the power-law exponent is 0.2 ≤ p ≤ 0.8, with most of the values around 0.5, in line with normal or anomalous diffusion models.The second part of dissertation work deals with cathodic WO3 and TiO2. WO3 suffers from ion trapping induced degradation of charge capacity and optical modulation upon electrochemical cycling. This speculation is strongly supported by direct evidence from Time-of-Flight Elastic Recoil Detection Analysis (ToF-ERDA). Most importantly, this ion trapping induced degradation can be eliminated by a galvanostatic de-trapping process. Significant ion-trapping takes place when x exceeds ~0.65 in LixWO3. The trapped ions are stable in the host structure, meaning that the ions cannot de-trap without external stimuli. The similar work done on TiO2 significantly complements and extends the work on the recuperation of WO3; the difference is that the trapped ions in host TiO2 seem to be less stable compared with the trapped ions in WO3. Overall, this dissertation presents a refined conceptual framework for developing superior electrochromic windows in energy efficient buildings.
|
|
| 26. |
- Wen, Rui-Tao, et al.
(författare)
-
Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films
- 2015
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 14, s. 996-1001
-
Tidskriftsartikel (refereegranskat)abstract
- There is keen interest in the use of amorphous WO3 thin films as cathodic electrodes in transmittance-modulating electrochromic devices1–4. However, these films suer from ion-trapping-induced degradation of optical modulation and reversibility on extended LiC-ion exchange. Here,we demonstrate that ion-trapping-induced degradation, which is commonly believed to be irreversible, can be successfully eliminatedby constant-current-driven de-trapping; that is, WO3 films can be rejuvenated and regain their initial highly reversible electrochromic performance. Pronounced ion trapping occurs when x exceeds 0.65 in LixWO3 during ion insertion. We find two main kinds of Li+-ion-trapping site (intermediate and deep) in WO3, where the intermediate ones are most prevalent. Li+ ions can be completely removed from intermediate traps but are irreversibly bound in deep traps. Our results provide a general framework for developing and designing superior electrochromic materials and devices.
|
|
| 27. |
- Wen, Rui-Tao, et al.
(författare)
-
Eliminating Electrochromic Degradation in Amorphous TiO2 through Li-Ion Detrapping
- 2016
-
Ingår i: ACS Applied Materials and Interfaces. - ACS : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:9, s. 5777-5782
-
Tidskriftsartikel (refereegranskat)abstract
- The quest for superior and low-cost electroehromic (EC) thin films, for applications in smart windows, remains strong because of their large importance for energy-efficient buildings. Although the development of new EC materials for improved devices is important, diminishing or reversing degradation is another key issue, and electrical rejuvenation of degraded EC materials can offer new opportunities. Here we demonstrate that cathodically coloring EC thin films of TiO2, which normally suffer from ion-trapping-induced degradation of charge capacity and optical modulation upon extensive electrochemical cycling, can recover their initial EC performance by a rejuvenation procedure involving Li+ ion detrapping. Thus, the initial performance can be regained, and refreshed TiO2 films exhibit the same degradation features as as-deposited films upon prolonged electrochemical cycling. The rejuvenation was carried out by using either galvanostatic or potentiostatic treatments. Our study may open avenues to explore the recovery not only of EC materials and devices based on those but also for other ion-exchange-based devices.
|
|
| 28. |
|
|
| 29. |
- Wen, Rui-Tao, et al.
(författare)
-
Ion Trapping and Detrapping in Amorphous Tungsten Oxide Thin Films Observed by Real-Time Electro-Optical Monitoring
- 2016
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 28:13, s. 4670-4676
-
Tidskriftsartikel (refereegranskat)abstract
- Several technologies for energy saving and storage rely on ion exchange between electrodes and electrolytes. In amorphous electrode materials, a detailed knowledge of Li-ion intercalation is hampered by limited information about the structure and transport properties of the materials. Amorphous tungsten oxide is the most studied electrochromic material and suffers from ion trapping-induced degradation of charge capacity and optical modulation span upon extensive electrochemical cycling. In this paper, we investigate trapping and detrapping processes in connection with performance degradation and specifically use real-time electro-optical monitoring to identify different trap energy ranges pertinent to the ion-intercalated system. Evidence of three kinds of traps that degrade electrochromic tungsten oxide during ion intercalation is presented: (i) shallow traps that erode the colored state, (ii) deep traps that lower the bleached-state transmittance, and (iii) irreversible traps. Importantly, Li-ion detrapping from shallow and deep traps takes place by different processes: continuous Li-ion extraction is possible from shallow traps, whereas a certain release time must be exceeded for detrapping from deep traps. Our notions for ion trapping and detrapping, presented here, may serve as a starting point for discussing ion intercalation in various amorphous materials of interest for energy-related applications.
|
|
| 30. |
- Wen, Rui-Tao, et al.
(författare)
-
Progress in Electrochromics: Towards Long-Term Durability and Materials Rejuvenation for Oxide-Based Thin Films
- 2015
-
Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862 .- 1938-6737. ; , s. 9-16
-
Konferensbidrag (refereegranskat)abstract
- Most electrochromic devices, such as “smart windows” for energy efficient glazings, must be durable enough for many years of service life. Typical constructions use films based on thin films of W oxide and Nioxide, and this paper summarizes progress on durability-related issues for these materials. For W oxide, we describe recent and unexpected progress on galvanostatic rejuvenation of aged W oxide films, and we also discuss the beneficial effects of Ti addition. For Ni oxide, we report how charge exchange declination during extended voltammetric cycling can be modeled in terms of a power law and also demonstrate how modest additions of Ir can dramatically extend the cycling durability.
|
|
| 31. |
- Wen, Rui-Tao, et al.
(författare)
-
Strongly Improved Electrochemical Cycling Durability by Adding Iridium to Electrochromic Nickel Oxide Films
- 2015
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:18, s. 9319-9322
-
Tidskriftsartikel (refereegranskat)abstract
- Anodically colored nickel oxide (NiO) thin films :are of much interest as counter electrodes in tungsten oxide based electrochromic devices such as "smart windows" for energy-efficient buildings. However, NiO films are prone to Suffering severe charge density degradation upon prolonged electrochemical cycling, which can lead to insufficient device lifetime. Therefore, a means to improve the durability of NiO-based films is an important challenge at present. Here we report that the incorporation of a modest amount of iridium into NiO films [Ir/(Ir + Ni) = 7.6 atom %] leads to remarkable durability, exceeding 10000 cycles in a lithium-conducting, electrolyte, along with significantly improved optical modulation during extended cycling. Structure characterization showed that the face-centered-cubic-type NiO structure remained after iridium addition. Moreover, the crystallinity of these films was enhanced upon electrochemical cycling.
|
|
| 32. |
- Wen, Rui-Tao, et al.
(författare)
-
Sustainable rejuvenation of electrochromic WO3 films
- 2015
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:51, s. 28100-28104
-
Forskningsöversikt (refereegranskat)abstract
- Devices relying on ion transport normally suffer from a decline of their long-term performance due to irreversible ion accumulation in the host material, and this effect may severely curtail the operational lifetime of the device. In this work, we demonstrate that degraded electrochromic WO3 films can sustainably regain their initial performance through galvanostatic de-trapping of Li+ ions. The rejuvenated films displayed degradation features similar to those of the as-prepared films, thus indicating that the de-trapping process is effectively reversible so that long-term performance degradation can be successfully avoided. De-trapping did not occur in the absence of an electric current.
|
|
