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Regulation of Oxygen Transport in Potassium-Oxygen Batteries Using Conducting Polymers

Gilmore, Paul
http://orcid.org/0000-0002-1323-1794
http://rave.ohiolink.edu/etdc/view?acc_num=osu1555588196317105

Abstract Details

2019, Doctor of Philosophy, Ohio State University, Mechanical Engineering.
Metal-oxygen batteries are an emerging class of energy storage devices that have some of the highest energy densities among secondary batteries. These batteries are unique because molecular oxygen is the active cathode material and is not stored in the cathode structure. During discharge, oxygen diffuses to an active cathode site, gets reduced on the surface on the cathode, and forms a metal oxide with the cation. The regulation of molecular oxygen concentration throughout the battery therefore becomes critical for battery performance. In particular, oxygen should be present in the cathode in sufficient concentrations but be prevented from diffusing to the anode. The process of oxygen diffusion to anode is known as oxygen crossover and poisons the anode surface, limiting the cycle life of the battery. The goal of this dissertation is to increase the cycle life of potassium-oxygen batteries by preventing molecular oxygen crossover and is achieved with conducting polymer membranes and functionally-graded cathode architectures. This work demonstrates that polypyrrole (PPy) electropolymerized on a porous membrane serves an effective oxygen barrier and increases cyclability. Dopant selection is found to have a strong influence on both ion transport properties and cycle stability in the DME-based electrolyte used for K-O2 batteries. PPy membranes doped with dodecylbenzenesulfonate (DBS-) increase the cycle life from 4 to 18 cycles by transporting K+ and blocking oxygen. However, electrochemical cycle stability of PPy(DBS) cathodes in DME is found to be poor. Bilayer bending studies are performed, and it is determined that the cycle stability depends on the mechanical boundary condition (free versus fixed). The free membrane has improved cycle stability compared to the fixed membrane, which is attributed to the higher cyclic compressive stresses in fixed membrane as estimated by a beam bending model. The presence of oxygen causes further degrades the cyclability via pulverization of the electrode by discharge products. Functionally-graded cathodes do not have a physical oxygen barrier but minimize oxygen crossover by consuming oxygen at the cathode-separator interface. Functionally-graded cathodes using PPy doped with hexafluorophosphate increase K-O2 battery cycle life from 4 to 100 cycles. PPy(PF6) is shown to have a high activity for oxygen reduction reaction and is therefore used as the inner layer of the cathode. An oxygen transport model is developed and used to estimate the oxygen crossover rate. Functionally-graded cathodes are demonstrated to be a scalable, low cost method for achieving long cycle life K-O2 batteries.
Vishnu Sundaresan (Advisor)
177 p.
Mechanical Engineering
functionally graded cathode, potassium-air battery, oxygen crossover model, mechanoelectrochemistry, cathode design, oxygen reduction reaction

Recommended Citations

Citations

  • Gilmore, P. (2019). Regulation of Oxygen Transport in Potassium-Oxygen Batteries Using Conducting Polymers [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555588196317105

    APA Style (7th edition)

  • Gilmore, Paul. Regulation of Oxygen Transport in Potassium-Oxygen Batteries Using Conducting Polymers. 2019. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1555588196317105.

    MLA Style (8th edition)

  • Gilmore, Paul. "Regulation of Oxygen Transport in Potassium-Oxygen Batteries Using Conducting Polymers." Doctoral dissertation, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555588196317105

    Chicago Manual of Style (17th edition)

osu1555588196317105
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© 2019, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.
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