PhD Dissertation Defense: Bret Marckx

Bret Marckx, Ph.D. Candidate

Advisor: Özgür Çapraz

Title: Elucidating Electro-Chemo-Mechanical Coupling of Electrodes in Aqueous Electrolytes for Zinc Batteries

Abstract:

The growing share of intermittent renewable sources such as solar and wind requires large-scale energy storage to balance supply and demand on the electrical grid. Aqueous zinc batteries are promising for this application because of their safety and low cost, yet they suffer from limited capacity retention and cycle life. Many of the processes responsible, including multi-ion insertion, interfacial salt formation, dissolution, and nonuniform metal deposition, deform the electrode. However, the chemo-mechanics of electrodes in aqueous electrolytes remain largely uncharacterized, and conventional techniques neither probe the mechanical state of the electrode nor distinguish bulk from interfacial processes. In this dissertation, we adapted operando techniques previously developed for alkali metal-ion batteries to aqueous multivalent systems: digital image correlation (DIC), which maps bulk strain across the electrode surface, and substrate-curvature measurements, which report the combined bulk and interfacial stress. We combined these with wide-field optical imaging, which tracks changes in electrode reflectance, and electrochemical quartz crystal microbalance with dissipation (EQCM-D), which resolves changes in film mass and viscoelastic properties.
In V2O5 cathodes, strain closely tracked the redox features and reflectance tracked the state of charge. Combined stress and strain measurements revealed that bulk and interfacial deformation evolve synchronously during discharge but asynchronously during charge, when interfacial stress relaxes through a non-faradaic, potential-governed process that depends on electrolyte anion chemistry. Interfacial stress was similarly decoupled from the redox reaction in poly(o-phenylenediamine), which EQCM-D showed stiffens roughly fourfold upon reduction.

Location: ENG 336

Agenda:

12:45 am EST - Welcome / Room Opens

1:00 pm EST - Presentation followed by questions from the audience. 

After the questions from the public, the meeting will be closed for the committee discussion.

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