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Role of Ionic Liquid in Electroactive Polymer Electrolyte Membrane for Energy Harvesting and Storage

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2020, Master of Science, University of Akron, Polymer Engineering.
The present thesis focuses on elucidation on the role of ionic liquid in polymer electrolyte membranes for energy harvesting and storage. Recently, research interest on ionic liquid-in-salt has gained considerably due to its high thermal stability and ionic conductivity, which has potential as a replacement for the facile organic solvent electrolyte in lithium ion battery. The status of emerging lithium ion batteries has been reviewed in Chapter I, followed by Materials and Methods including physical and electrochemical characterizations in Chapter II and Chapter III. In Chapter IV, the polymer electrolyte membrane (PEM) containing liquid polyether sulfide (PES, Thiokol) was fabricated via thiol-ene click reaction with poly (ethylene glycol) diacrylate (PEGDA) with the aid of a photo-initiator under UV light for photocuring. The so-called solid polymer electrolyte membrane thus formed is an isotropic, completely amorphous, transparent, and flexible solid-state membrane. The ionic conductivity of (PES-co-PEGDA/HMIMTFSI) was determined by AC impedance as a function of thiol (SH) content which served as flexible side chains. The ionic liquid (HMIMTFSI) can dissociate Li ions from its salt and also plasticize the PEM network. As a result, the increasing amount of Thiokol and HMIMTFSI can both sevred as the ionizers to enhance the ionic conductivity. The flexoelectric coefficients (μ) of various PEMs-(TK-co-PEGDA/HMITFSI) were determined under intermittent square wave and dynamic oscillatory bending modes by using Dynamic Mechanical Analyzer (DMA) combined with Solartron Potentiostat/Galvanostat. The present PEM (TK-co-PEGDA/HMIMTFSI) exhibited larger flexoelectric coefficient than those of conventional insulating materials such as ferroelectric ceramics and bent-core nematic liquid crystals. Last not least, the efficiency of mechano-electrical energy conversion the PEM (TK-co-PEGDA/HMITFSI) is discussed. Chapter V addresses the mutual solubility of ionic liquid (IL) (e.g., hexyl methyl imidazolium (HMIMTFSI)) in lithium bis-trifluoromethane sulfonyl imide (LiTFSI) salt, which has been a challenging issue. To alleviate the immiscibility issues, binary and ternary phase diagrams of PEGDA, HMITFSI, and LiTFSI mixtures were established by means of differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The binary phase diagrams of LiTFSI/HMIMTFSI and PEGDA/HMIMTFSI mixtures both showed a typical eutectic phase diagram with a wide isotropic region bound by liquidus and solidus lines. Subsequently, the ternary phase diagram of PEGDA/HMIMTFSI/LiTFSI was established. In Chapeter VI, guided by a wide isotropic region, the PEM thus fabricated was completely amorphous and exhibited high ionic conductivity close to the superionic level of 10-3 S cm-1. These PEMs (PEGDA/ HMIMTFSI/ LiTFSI) were assembled into half-cells (LiTFSI/PEM/Li) to determine the electrochemical performance by means of linear sweep voltammetry and galvanometric cyclic voltammograms. The PEMs appeared stable up to 5.55V in the linear sweep and charge/discharge cycling for 50 cycles tested. Potential applications of the above IL containing PEM in energy storage system such as all solid-state lithium ion battery have been discussed.
Thein Kyu (Advisor)
Xing Gong (Committee Member)
Kevin Cavicchi (Committee Member)
105 p.

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Citations

  • Chen, P. (2020). Role of Ionic Liquid in Electroactive Polymer Electrolyte Membrane for Energy Harvesting and Storage [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590688110146547

    APA Style (7th edition)

  • Chen, PoYun. Role of Ionic Liquid in Electroactive Polymer Electrolyte Membrane for Energy Harvesting and Storage. 2020. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1590688110146547.

    MLA Style (8th edition)

  • Chen, PoYun. "Role of Ionic Liquid in Electroactive Polymer Electrolyte Membrane for Energy Harvesting and Storage." Master's thesis, University of Akron, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1590688110146547

    Chicago Manual of Style (17th edition)