Browsing by Author "Iyapazham Vaigunda Suba, Prathap"

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    Aqueous Batteries for Large-Scale Energy Storage and Carbon Removal Applications
    (2024-08-08) Iyapazham Vaigunda Suba, Prathap; Thangadurai, Venkataraman; Karan, Kunal; Shi, Yujun; Shimizu, George; Roberts, Edward (Ted) PL; Kuss, Christian
    Aqueous batteries are safe and environmentally friendly energy storage devices, suitable for intermittent renewable energy sources and carbon removal applications. However, these batteries are hindered by the low operating potential which leads to limitation in energy density. In this thesis, aqueous battery chemistry concept is applied for two different applications such as: a redox-flow battery transformation to an all-gel battery and a seawater-battery for carbon removal application. Flexible, scalable, and low-cost energy storage solutions are required for the widespread use of renewable energy and the mitigation of climate change. In this regard, redox flow batteries are scalable due to their ability to decouple power and energy; however, the commercial applications of these batteries are limited by expensive ion-selective membranes. An auxiliary electrode (AE) mediated membrane-free redox battery concept was demonstrated and different AE materials were screened for their application in vanadium based redox battery. In an AE mediated membrane-free vanadium redox battery, the Coulombic efficiency of the system was limited to 36%. The low Coulombic efficiency observed in AE based battery was mitigated by using a gel-battery design approach in which Bi/BiOCl and V4+/V5+ redox couples were utilized in a gel-based architecture. The Bi/BiOCl conversion reaction based redox couple was demonstrated to work reversibly against traditional vanadium-based redox pair in an aqueous electrolyte. Redox active materials in this cell design are in the gel form, and a traditional membrane or a separator is not required. This proof-of-concept all-gel battery delivered 0.9 V with a volumetric energy density of 22.14 Wh L-1. For carbon removal applications, an aqueous battery with seawater electrolyte was studied. In this battery, iron phosphate (FePO4) electrode was utilized to manipulate ions in different seawater aliquots to generate sodium hydroxide, a base to use in ocean alkalinity enhancement. Electrochemical analysis, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) revealed that Na+ ions can be reversibly intercalated in FePO4. The alkalinity titration was used to determine the increase in alkalinity of seawater. The results indicated that a 16% increase in alkalinity was achieved in 15 ml of synthetic seawater over a period of 3.5 hours (one cycle) using the FePO4 electrode coupled with Pt electrode. A seawater electrolyte based battery with Ni(OH)2/NiOOH redox reaction in place of Pt electrode coupled with FePO4 electrode was studied. The battery delivered a potential of 0.6 V and the galvanostatic cycling experiments revealed that the battery can operate in seawater electrolyte for 50 cycles with 94% Coulombic efficiency.