Electrodeposited non-stoichiometric tungstic acid for electrochromic applications: film growth modes, crystal structure, redox behavior and stability

Pugolovkin, Leonid V.; Cherstiouk, Olga V.; Plyasova, L. M.; Molina, I. Yu.; Kardash, T. Yu.; Стонкус, О. А.; Yatsenko, D. A.; Каичев, В. В.; Tsirlina, Galina A.

doi:10.1016/j.apsusc.2016.04.168

Cited by 10 publications

(6 citation statements)

References 23 publications

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“…The W 4f core scans of both materials show well-defined peaks at 37.9 and 35.8 eV, corresponding to W 4f 5/2 and W 4f 7/2 , respectively. The positions of these peaks are correlated to W in the +6 oxidation state in WO 3 , consistent with previous results. , In the O 1s region, the O–W binding energies are similar in WO 3 ·2H 2 O and WO 3 (∼530.7 eV), but WO 3 ·2H 2 O exhibits an additional peak around 533 eV that is attributed to O–H and consistent with the hydrated nature of the material.…”

Section: Results and Discussionsupporting

confidence: 90%

Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide

et al. 2017

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The kinetics of energy storage in transition metal oxides are usually limited by solid-state diffusion, and the strategy most often utilized to improve their rate capability is to reduce ion diffusion distances by utilizing nanostructured materials. Here, another strategy for improving the kinetics of layered transition metal oxides by the presence of structural water is proposed. To investigate this strategy, the electrochemical energy storage behavior of a model hydrated layered oxide, WO3·2H2O, is compared with that of anhydrous WO3 in an acidic electrolyte. It is found that the presence of structural water leads to a transition from battery-like behavior in the anhydrous WO3 to ideally pseudocapacitive behavior in WO3·2H2O. As a result, WO3·2H2O exhibits significantly improved capacity retention and energy efficiency for proton storage over WO3 at sweep rates as fast as 200 mV s–1, corresponding to charge/discharge times of just a few seconds. Importantly, the energy storage of WO3·2H2O at such rates is nearly 100% efficient, unlike in the case of anhydrous WO3. Pseudocapacitance in WO3·2H2O allows for high-mass loading electrodes (>3 mg cm–2) and high areal capacitances (>0.25 F cm–2 at 200 mV s–1) with simple slurry-cast electrodes. These results demonstrate a new approach for developing pseudocapacitance in layered transition metal oxides for high-power energy storage, as well as the importance of energy efficiency as a metric of performance of pseudocapacitive materials.

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Section: Results and Discussionsupporting

confidence: 90%

Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide

et al. 2017

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“…also observed the merging of these peaks with chemical intercalation of protons into WO 3 ·2H 2 O. Prior reports indicate that the phase transition is likely due to a structural transformation toward a more symmetric crystal structure via increasing orthogonality of WO 5 (OH 2 ) octahedra − due to the storage of protons in the octahedral tungsten oxide layer. , The distortion of WO 3 ·2H 2 O due to proton intercalation is therefore only two-dimensional, whereas the distortion of WO 3 is three-dimensional. This difference in structural distortion between the WO 3 structure and WO 3 ·2H 2 O may contribute to the more irreversible electrochemical intercalation kinetics in the former, resulting in the previously reported transition from battery to pseudocapacitive behavior via structural water …”

Section: Results and Discussionmentioning

confidence: 99%

Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition

et al. 2018

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The presence of structural water in tungsten oxides leads to a transition in the energy storage mechanism from battery-type intercalation (limited by solid state diffusion) to pseudocapacitance (limited by surface kinetics). Here, we demonstrate that these electrochemical mechanisms are linked to the mechanical response of the materials during intercalation of protons and present a pathway to utilize the mechanical coupling for local studies of electrochemistry. Operando atomic force microscopy dilatometry is used to measure the deformation of redox-active energy storage materials and to link the local nanoscale deformation to the electrochemical redox process. This technique reveals that the local mechanical deformation of the hydrated tungsten oxide is smaller and more gradual than the anhydrous oxide and occurs without hysteresis during the intercalation and deintercalation processes. The ability of layered materials with confined structural water to minimize mechanical deformation likely contributes to their fast energy storage kinetics.

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“…To probe electrochemical proton intercalation into WO 3 · n H 2 O under extremely short time scales (seconds to subseconds), we electrodeposited WO 3 · n H 2 O and WO 3 thin film electrodes (∼300 nm) and performed cyclic voltammetry with sweep rates ( v ) from 100 to 2000 mV s –1 (time scales ranging from 9 s to 500 ms) in a sulfuric acid electrolyte. The high-rate electrochemical behavior of all three phases at 2 V s –1 (∼500 ms charge/discharge) is shown in Figure d.…”

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confidence: 99%

Confined Interlayer Water Promotes Structural Stability for High-Rate Electrochemical Proton Intercalation in Tungsten Oxide Hydrates

et al. 2019

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There is widespread interest in determining the structural features of redox-active electrochemical energy storage materials that enable simultaneous high power and high energy density. Here, we present the discovery that confined interlayer water in crystalline tungsten oxide hydrates, WO3·nH2O, enables highly reversible proton intercalation at subsecond time scales. By comparing the structural transformation kinetics and confined water dynamics of the hydrates with anhydrous WO3, we determine that the rapid electrochemical proton intercalation is due to the ability of the confined water layers to isolate structural transformations to two dimensions while stabilizing the structure along the third dimension. As a result, these water layers provide both structural flexibility and stability to accommodate intercalation-driven bonding changes. This provides an alternative explanation for the fast energy storage kinetics of materials that incorporate structural water and provides a new strategy for enabling high power and high energy density with redox-active layered materials containing confined fluids.

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Electrodeposited non-stoichiometric tungstic acid for electrochromic applications: film growth modes, crystal structure, redox behavior and stability

Cited by 10 publications

References 23 publications

Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide

Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide

Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition

Confined Interlayer Water Promotes Structural Stability for High-Rate Electrochemical Proton Intercalation in Tungsten Oxide Hydrates

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