Doctor of Philosophy, University of Akron, 2022, Polymer Engineering

To develop advanced sustainable technologies for the energy needs of society, solid-state lithium-ion batteries are considered safer and more reliable. In those aspects, solid polymer electrolytes have been considered as one of the promising candidates. The present dissertation focuses on the exploration of solid polymer electrolytes with high ionic conductivity, wider electrochemical stability window, enhanced stretchability, and ion storing capabilities of herein-developed polymer electrolyte membranes. Chapter III of the dissertation deals with elucidation on the effect of different plasticizers viz. succinonitrile (SCN), ethylene carbonate (EC), and polyethylene glycol dimethyl ether (PEGDME) on ionic conductivity, electrochemical stabilities, and stability of plasticized PEMs against the lithium metal anode. Succinonitrile plasticized PEMs demonstrated higher ionic conductivity (~ 10-3 S/cm) with higher electrochemical stability (~ 5 V). On the other hand, ethylene carbonate-based PEMs exhibited higher stability against lithium metal. Lastly, the addition of lithium bis(oxalate) borate (LiBOB) additive to PEMs which resulted in improvement of stability against the lithium metal is discussed. To improve the stretchability of the polymer electrolyte membranes (PEMs), PEG-b-PPG-b-PEG-DA block copolymer was synthesized by the esterification reaction. As a result of the high molecular weight of the block copolymer resulting in a loosely crosslinked copolymer network, the PEM consisting of PEG-b-PPG-b-PEG-DA/EC/LiTFSI exhibited increased stretchability (> 100 % elongation at break) along with ionic conductivity of superionic conductor level (~10-3 S/cm). Furthermore, thermal, and electrochemical stability of PEMs along with the satisfactory room temperature charge/discharge cycling performance of half-cells were discussed in detail in Chapter IV. The investigation of superionic, wider electrochemically stable, ion storing, supercapacitve nature of polyethylene g (open full item for complete abstract)

Committee: Thein Kyu (Advisor); Xiong Gong (Committee Chair); Jae-Won Choi (Committee Member); Steven Chuang (Committee Member); Ruel McKenzie (Committee Member) Subjects: Energy; Engineering; Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

Sustainable energy is becoming a crucial enabler to today's activities. Due to the increasing demand of electronics, smart technologies, and high-power requirements in applications such as electrical vehicles (EV), the development of consistent energy systems capable of generating, and/or storing energy is becoming more attractive. According to recent reports, the increase of shortage in conventional energy sources, such as fossil fuel, and the associated environmental concerns have motivated the energy industry to scout for energy alternatives from untapped resources, such as intermittent renewable wind, and solar energy. Another solution to mitigate the present challenge of energy scarcity manifest with the development of efficient energy supply via integrated energy storages “batteries”. The first part of this dissertation is dedicated to investigate the understudied mechanoelectrical phenomenon of ion polarization-based flexoelectricity in ion-containing polymers, viz. polymer electrolyte membranes (PEMs). Such materials operate under the principles of ion polarization/depolarization to derive electrical current and voltage in response to stress/deformation stimuli, best understood as the converse effect of electromechanical phenomenon reported for soft actuators based on ionic electroactive polymers. Under different bending modes (i.e. square-intermittent and sinusoidal-oscillatory bending), several factors influencing the mechanoelectrical response of PEMs were systematically studied including (1) the effect of side chain branching of host polymer matrix (i.e. employing various branching degrees of poly(ethylene glycol) networks), (2) role of ion characteristics, viz. cationic size and valency/charge, (3) dual effects of side-chain branching and multivalent counter ions, and (4) the impact polymer constituent functionality (i.e. ether vs. amine containing polymers). The measured flexoelectric coefficient based on ionic polarization was found to be as high as (open full item for complete abstract)

Committee: Thein Kyu PhD (Advisor); Xiong Gong PhD (Committee Chair); Steven Chuang PhD (Committee Member); Ruel McKenzie PhD (Committee Member); Celal Batur PhD (Committee Member) Subjects: Materials Science; Polymer Chemistry; Polymers

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Present dissertation outlines a study of the basic important physicochemical properties of photo-cured polymer electrolyte membranes (PEM) that can be enhanced and optimized in order to be implemented as electrolyte in solid-state Li-ion batteries. The studied properties include mechanical integrity, ionic conductivity, thermal and electrochemical stability, etc. This dissertation also introduces and characterizes a novel application of PEMs as energy harvesting materials, due to their capability to transform mechanical stimuli into an electrical signal and vice versa. Chapter I provides a brief overview of the general content of the dissertation. Chapter II presents the material that was taken as the basis for the study. It contains essential information related to the battery principles, operation, development and applications. In addition, it encompasses the description of electroactive polymers, which are in principle, equivalent to the discovered flexoelectric PEMs that are as well introduced in this work. Chapter III illustrates the materials, methods and calculations utilized to perform and analyze the data collected for the purpose of the study. Chapter IV describes an incorporation of mercaptopropyl methyl siloxane homopolymer (thiosiloxane) as a co-component to the matrix of the PEM, which in result enables enhancement of the polymer segmental motion and hence, the ionic conductivity. UV irradiation was applied to various thiosiloxane and poly(ethylene glycol) diacrylate (PEGDA) mixtures to get the `thio-ene' reaction between the thiol functionality and the double bonds of the PEGDA precursor, which formed a complete amorphous self-standing PEM. The thiosiloxane modified PEM film exhibits higher extension-at-break in comparison to the PEM containing only PEGDA such as PEGDA700/SCN/LiTFSI 20/40/40, FTIR and Raman spectroscopy techniques were employed to detect the thiol (SH) groups consumed after performing the so-called thiol-ene reaction. It was fou (open full item for complete abstract)

Committee: Thein Kyu Dr (Advisor); Mark Soucek Dr (Committee Member); Younjin Min Dr (Committee Chair); Steven Chuang Dr (Committee Member); Siamak Farhad Dr (Committee Member) Subjects: Chemistry; Energy; Plastics; Polymer Chemistry; Polymers; Solid State Physics

Doctor of Philosophy, University of Akron, 2017, Polymer Engineering

This research focused on the development of polymeric materials with enhanced electrochemical performance in Li-ion batteries (LIB) and reduction of rolling resistance in tire tread compounds. The first part of the thesis is devoted to separators and electrolytes used in Li-ion batteries. Specifically, the research focused on ionogel polymer electrolytes (IGPE) for high temperature LIB operation and composite solid polymer electrolytes (CSPE) for improvement of the mechanical properties of the existing solid polymer electrolyte technology. IGPEs were fabricated by incorporating the pores of thin film syndiotactic polystyrene (sPS) gels with ionic liquid (IL). The thermal and electrochemical performance of the ionogel membrane were compared with polyolefin based electrolyte-separator technology using Li+/ graphite half-cells at room temperature and at elevated temperatures (80-100 °C). sPS ionogels showed negligible shrinkage and stable electrochemical performance at 100 °C due to higher porosity and wettability of the polymer strands by the IL. The work further ventured into assessment of the state of IL molecules in the pores of sPS gel. The results revealed that the melting point of IL molecules was elevated due to confinement of the IL molecules in the sPS network. At room temperature, the non-bonded cation-cation through-space correlation was obtained for confined IL, while such correlation was absent in bulk IL. The information on ion aggregation and the effect of confinement can guide proper selection of polymer-IL pair for electrochemical membranes. The results of investigation on a composite solid polymer electrolyte (CSPE) membranes is presented in chapter VI. A photocurable plasticized solid polymer electrolyte formulation was incorporated in porous sPS gel with the aim of increasing the mechanical strength of the neat SPE. The all solid-state CSPE was characterized using TGA and DSC to assess their thermal stability. Mechanical strength of the composit (open full item for complete abstract)

Committee: Sadhan Jana Dr. (Advisor); Bryan Vogt Dr. (Committee Chair); Younjin Min Dr. (Committee Member); Toshikazu Miyoshi Dr. (Committee Member); George Chase Dr. (Committee Member) Subjects: Plastics; Polymer Chemistry; Polymers

Doctor of Philosophy, Case Western Reserve University, 2009, Chemical Engineering

Polymer electrolyte membrane fuel cells (PEMFCs) running on hydrogen hold great promise to provide a source of clean energy and reduce our dependence on foreign oil, but fuel cells must become more durable before they can be implemented. The effects of cationic contamination, the process of foreign cations replacing protons in the ionomer phase, reduce fuel cell durability.The purpose of this study was to experimentally determine and subsequently model the effects of cationic contamination on PEMFCs. This was accomplished using a three branched approach. The first branch included experiments evaluating the performance of fuel cell systems. The second branch consisted of theory based models to explain experimental observations by postulating the mechanisms of cationic contamination. The final branch used alternative fuel cell configurations to validate the mechanistic postulates. This study shows the drastic effects that cationic contamination can have on PEMFCs. These effects were quantified by contaminating PEMFCs to known amounts and then assessing fuel cell performance as a function of level of contamination. The maximum power that can be harnessed from contaminated cells decreases proportionally to the percentage of protons that are replaced. This decrease is due to a decrease in electrode kinetics, cell thermodynamics, and in the limiting current of the system. The transport of protons and contaminant ions was modeled to show why these limitations occur. When current is drawn in a contaminated system the cationic contaminants will accumulate at the cathode side of the membrane. This can decrease kinetics since fewer protons are available for reaction. This will also decrease the thermodynamic cell potential since a concentration gradient forms across the electrodes. Finally, the fuel cell limiting current will decrease because the fuel cell will become limited by the transport of protons to the cathode electrode. A nontraditional fuel cell configuration was emp (open full item for complete abstract)

Committee: Thomas Zawodzinski PhD (Advisor); Harihara Baskaran PhD (Advisor); Jesse Wainright PhD (Committee Member); Miklos Gratzl PhD (Committee Member) Subjects: Chemical Engineering; Engineering