@article{chagnot_abello_wang_dawlaty_rodriguez-lopez_zhang_augustyn_2024, title={Influence of Finite Diffusion on Cation Insertion-Coupled Electron Transfer Kinetics in Thin Film Electrodes}, volume={171}, ISSN={["1945-7111"]}, DOI={10.1149/1945-7111/ad1d98}, abstractNote={Materials that undergo ion-insertion coupled electron transfer are important for energy storage, energy conversion, and optoelectronics applications. Cyclic voltammetry is a powerful technique to understand electrochemical kinetics. However, the interpretation of the kinetic behavior of ion insertion electrodes with analytical solutions developed for ion blocking electrodes has led to confusion about their rate-limiting behavior. The purpose of this manuscript is to demonstrate that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained by well-established models for finite diffusion. To do this, we utilize an experimental and simulation approach to understand the kinetics of Li+ insertion-coupled electron transfer into a thin film material (Nb2O5). We demonstrate general trends for the peak current vs scan rate behavior, with the latter parameter elevated to an exponent between limiting values of 1 and 0.5, depending on the solid-state diffusion characteristics of the film (diffusion coefficient, film thickness) and the experiment timescale (scan rate). We also show that values < 0.5 are possible depending on the cathodic potential limit. Our results will be useful to fundamentally understand and guide the selection and design of intercalation materials for multiple applications.}, number={1}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Chagnot, Matthew and Abello, Sofia and Wang, Ruocun and Dawlaty, Jahan and Rodriguez-Lopez, Joaquin and Zhang, Chao and Augustyn, Veronica}, year={2024}, month={Jan} }
 @article{mitchell_wang_ko_long_augustyn_2022, title={Critical Role of Structural Water for Enhanced Li+ Insertion Kinetics in Crystalline Tungsten Oxides}, volume={169}, ISSN={["1945-7111"]}, DOI={10.1149/1945-7111/ac58c8}, abstractNote={Electrochemical ion insertion into transition metal oxides forms the foundation of several energy technologies. Transition metal oxides can exhibit sluggish ion transport and/or phase-transformation kinetics during ion insertion that can limit their performance at high rates (<10 min). In this study, we investigate the role of structural water in transition metal oxides during Li+ insertion using staircase potentiostatic electrochemical impedance spectroscopy (SPEIS) and electrochemical quartz crystal microbalance (EQCM) analysis of WO3·H2O and WO3 thin-film electrodes. Overall, the presence of structural water in WO3·H2O improves Li+ insertion kinetics compared to WO3 and leads to a less potential-dependent insertion process. Operando electrogravimetry and 3D Bode impedance analyses of nanostructured films reveal that the presence of structural water promotes charge accommodation without significant co-insertion of solvent, leading to our hypothesis that the electrochemically induced structural transitions of WO3 hinder the electrode response at faster timescales (<10 min). Designing layered materials with confined fluids that exhibit less structural transitions may lead to more versatile ion-insertion hosts for next-generation electrochemical technologies.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Mitchell, James B. and Wang, Ruocun and Ko, Jesse S. and Long, Jeffrey W. and Augustyn, Veronica}, year={2022}, month={Mar} }
 @article{wang_sun_brady_fleischmann_eldred_gao_wang_jiang_augustyn_2021, title={Fast Proton Insertion in Layered H2W2O7 via Selective Etching of an Aurivillius Phase}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202003335}, abstractNote={Abstract}, number={1}, journal={ADVANCED ENERGY MATERIALS}, author={Wang, Ruocun and Sun, Yangyunli and Brady, Alexander and Fleischmann, Simon and Eldred, Tim B. and Gao, Wenpei and Wang, Hsiu-Wen and Jiang, De-en and Augustyn, Veronica}, year={2021}, month={Jan} }
 @article{tsai_wang_boyd_augustyn_balke_2021, title={Probing local electrochemistry via mechanical cyclic voltammetry curves}, volume={81}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2020.105592}, abstractNote={Understanding the mechanical response of an electrode during electrochemical cycling and its correlation to the device electrochemical performance is crucial to improving the performance of insertion-type energy storage devices, electrochemical actuators, water purification, ion separation and neuromorphic computing applications. In this work, we visualized the electro-chemo-mechanical coupling behaviors during charge storage of anhydrous and hydrated WO3 electrodes via in situ atomic force microscopy (AFM) and developed the concept of mechanical cyclic voltammetry (mCV) curves. The relationship between electrochemical current and strain was investigated with simplified models and the results revealed that the proton insertion/deinsertion process could be described through potential-dependent electro-chemo-mechanical coupling coefficients which might indicate changes in insertion processes during electrode cycling. The mCV mapping results highlight the local heterogeneity and show that the charging processes varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations or chemical compositions with proper electrode designs.}, journal={NANO ENERGY}, author={Tsai, Wan-Yu and Wang, Ruocun and Boyd, Shelby and Augustyn, Veronica and Balke, Nina}, year={2021}, month={Mar} }
 @article{saeed_boyd_tsai_wang_balke_augustyn_2021, title={Understanding electrochemical cation insertion into prussian blue from electrode deformation and mass changes}, volume={57}, ISSN={["1364-548X"]}, url={https://doi.org/10.1039/D1CC01681D}, DOI={10.1039/d1cc01681d}, abstractNote={Alkali ion insertion into Prussian blue from aqueous electrolytes is characterized with operando AFM and EQCM, showing coupling of current with deformation and mass change rates.}, number={55}, journal={CHEMICAL COMMUNICATIONS}, publisher={Royal Society of Chemistry (RSC)}, author={Saeed, Saeed and Boyd, Shelby and Tsai, Wan-Yu and Wang, Ruocun and Balke, Nina and Augustyn, Veronica}, year={2021}, month={Jul}, pages={6744–6747} }
 @article{wang_boyd_bonnesen_augustyn_2020, title={Effect of water in a non-aqueous electrolyte on electrochemical Mg2+ insertion into WO3}, volume={477}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2020.229015}, abstractNote={Magnesium batteries are promising candidates for beyond lithium-ion batteries, but face several challenges including the need for solid state materials capable of reversible Mg2+ insertion. Of fundamental interest is the need to understand and improve the Mg2+ insertion kinetics of oxide-based cathode materials in non-aqueous electrolytes. The addition of water in non-aqueous electrolytes has been shown to improve the kinetics of Mg2+ insertion, but the mechanism and the effect of water concentration are still under debate. We investigate the systematic addition of water into a non-aqueous Mg electrolyte and its effect on Mg2+ insertion into WO3. We find that the addition of water leads to improvement in the Mg2+ insertion kinetics up to 6[H2O] : [Mg]2+. We utilize electrochemistry coupled to ex situ characterization to systematically explore four potential mechanisms for the electrochemical behavior: water co-insertion, proton (co)insertion, beneficial interphase formation, and water-enhanced surface diffusion. Based on these studies, we find that while proton co-insertion likely occurs, the dominant inserting species is Mg2+, and propose that the kinetic improvement upon water addition is due to enhanced surface diffusion of ions.}, journal={JOURNAL OF POWER SOURCES}, author={Wang, Ruocun and Boyd, Shelby and Bonnesen, Peter V and Augustyn, Veronica}, year={2020}, month={Nov} }
 @article{fleischmann_sun_osti_wang_mamontov_jiang_augustyn_2020, title={Interlayer Separation in Hydrogen Titanates Enables Electrochemical Proton Intercalation}, volume={8}, ISSN={["2050-7496"]}, DOI={10.1039/c9ta11098d}, abstractNote={Interlayer structural protons in H2Ti3O7 are identified as the key structural feature to enable electrochemical proton intercalation beyond the near-surface because they effectively reduce interconnections of the titanate layers.}, number={1}, journal={Journal of Materials Chemistry A}, author={Fleischmann, S. and Sun, Y. and Osti, N.C. and Wang, R. and Mamontov, E. and Jiang, D.E. and Augustyn, V.}, year={2020}, pages={412–421} }
 @misc{fleischmann_mitchell_wang_zhan_jiang_presser_augustyn_2020, title={Pseudocapacitance: From Fundamental Understanding to High Power Energy Storage Materials}, volume={120}, ISSN={["1520-6890"]}, DOI={10.1021/acs.chemrev.0c00170}, abstractNote={There is an urgent global need for electrochemical energy storage that includes materials that can provide simultaneous high power and high energy density. One strategy to achieve this goal is with pseudocapacitive materials that take advantage of reversible surface or near-surface Faradaic reactions to store charge. This allows them to surpass the capacity limitations of electrical double-layer capacitors and the mass transfer limitations of batteries. The past decade has seen tremendous growth in the understanding of pseudocapacitance as well as materials that exhibit this phenomenon. The purpose of this Review is to examine the fundamental development of the concept of pseudocapacitance and how it came to prominence in electrochemical energy storage as well as to describe new classes of materials whose electrochemical energy storage behavior can be described as pseudocapacitive.}, number={14}, journal={CHEMICAL REVIEWS}, author={Fleischmann, Simon and Mitchell, James B. and Wang, Ruocun and Zhan, Cheng and Jiang, De-en and Presser, Volker and Augustyn, Veronica}, year={2020}, month={Jul}, pages={6738–6782} }
 @article{wang_mitchell_gao_tsai_boyd_pharr_balke_augustyn_2018, title={Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition}, volume={12}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000436910200101&KeyUID=WOS:000436910200101}, DOI={10.1021/acsnano.8b02273}, abstractNote={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.}, number={6}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Wang, Ruocun and Mitchell, James B. and Gao, Qiang and Tsai, Wan-Yu and Boyd, Shelby and Pharr, Matt and Balke, Nina and Augustyn, Veronica}, year={2018}, month={Jun}, pages={6032–6039} }
 @article{daubert_wang_ovental_barton_rajagopalan_augustyn_parsons_2017, title={Intrinsic limitations of atomic layer deposition for pseudocapacitive metal oxides in porous electrochemical capacitor electrodes}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA02719B}, DOI={10.1039/c7ta02719b}, abstractNote={This work highlights the intrinsic capabilities and limitations of coating microporous materials using atomic layer deposition (ALD).}, number={25}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Daubert, James S. and Wang, Ruocun and Ovental, Jennifer S. and Barton, Heather F. and Rajagopalan, Ramakrishnan and Augustyn, Veronica and Parsons, Gregory N.}, year={2017}, month={Jul}, pages={13086–13097} }