Grid-scale energy storage is becoming a crucial component of the energy infrastructure as energy generation is rapidly evolving and involves intermittent renewable systems. A variety of thermal, mechanical, electrical, chemical, and electrochemical storage technologies are being considered. In this thesis, two important electrochemical systems are studied: redox flow batteries (RFBs) and solid oxide electrolyzer cells (SOECs). The new RFB involves novel linked chemicals that could enable a symmetric flow battery that utilizes a low-cost microporous separator rather than an expensive ion-selective membrane. Using new linked compounds addresses several issues with RFBs, namely capacity fade caused by crossover, as well as maintenance issues (rebalancing), and their high cost. Additive manufacturing was used to initially manufacture a flow cell which could demonstrate a linked compound, 4-phenothiazine 5,5-dioxide covalently linked via a propyl chain to 4-acetylpyridinum. The intention was to show that it could be cycled in a flow cell using inexpensive parts and materials. Viscosity, solubility, and other preliminary measurements were taken to aid in the selection of organic solvents and charge balancing electrolyte. Static, constant current, cyclic charge-discharge experiments were also performed in a commercial flow cell test fixture for the same compound. Electrochemical performance and stability were studied using solutions with identical concentrations of active species in two different organic solvents. The results showed that the specific linked system being studied could operate in a static cell without a membrane; however, it suffered from chemical decomposition. A variety of other compounds are possible which means the chemical stability can be improved. Experiments with flow were conducted to evaluate the impact that charging voltage, flow rate, and electrolyte recirculation have on electrochemical performance. A difference in the rate of the charging kinetics was observed. To improve coulombic efficiency, the charging flow rate was reduced while maintaining a faster discharging flow rate. An ideal charging voltage was observed. Electrochemical impedance spectroscopy was used to quantify and compare the internal losses associated with the cell separator and ion-selective membrane. As expected, the microporous separator displays significantly lower resistivity. A second important electrochemical system, solid oxide electrolyzers, was studied in this thesis. High temperature SOECs are an appealing hydrogen gas producing technology because they do not require an expensive catalyst; however, they suffer from premature electrode-electrolyte delamination. A multiphase, axisymmetric, microscale model was developed to identify the primary delamination mechanism. It was hypothesized that competition between two-phase and three-phase boundaries strains the lattice structure, leading to delamination. At high operating voltages, the reactions at the three-phase boundary dominated the two-phase reactions. This was thought to be driving delamination. The model was validated using experimental data that measured the overpotential and current density. The material composition of the electrode was altered by adding an additional thin, highly electronically conductive layer to enhance transport. This was studied both computationally and experimentally. The results from both experiments and computations indicated that the lattice oxygen at the surface was more evenly distributed. Using a bilayer electrode enhanced transport through the two-phase boundaries, reducing lattice structure expansion at the three-phase boundaries which could prevent delamination.
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