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INVESTIGATION ON THE STRUCTURE-PROPERTY RELATIONSHIPS IN HIGHLY ION-CONDUCTIVE POLYMER ELECTROLYTE MEMBRANES FOR ALL-SOLID-STATE LITHIUM ION BATTERIES

Fu, Guopeng
http://rave.ohiolink.edu/etdc/view?acc_num=akron1508508844968127

Abstract Details

2017, Doctor of Philosophy, University of Akron, Polymer Engineering.
The present dissertation is focused on development of the highly ion-conductive polymer electrolyte membrane (PEM) for all-solid-state lithium ion batteries. The organic molecule urea was found to be good additives to enhance the ionic conductive PEM. However, it phase-separated from the electrolyte during the charging/discharging process and harm the performance of the batteries. In order to improve the ionic conductivity as well as stabilize the electrolyte, polyethylene glycol bis-carbamate (PEGBC) was synthesized via a condensation reaction between polyethylene glycol diamine and ethylene carbonate. The PEGBC and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) salt binary mixture exhibits an enhanced ionic conductivity by virtue of the complexation of the carbamate group and lithium ion. Subsequently, dimethacrylate groups were chemically attached to both ends of PEGBC to afford polyethylene glycol-bis-carbamate dimethacrylate (PEGBCDMA) precursor having crosslinking capability. The melt-mixed ternary mixtures consisting of PEGBCDMA, succinonitrile (SCN) plasticizer, and LiTFSI were completely miscible in a wide compositional range. Upon photo-crosslinking, the neat PEGBCDMA network was completely amorphous exhibiting higher tensile strength, modulus, and extensibility relative to polyethylene glycol diacrylate (PEGDA) counterpart. The succinonitrile-plasticized PEM network containing PEGBCDMA remained completely amorphous and transparent upon photo-crosslinking, showing superionic conductivity, improved thermal stability, and superior tensile properties with improved capacity retention during charge/discharge cycling as compared to the PEGDA-based PEM. By mixing PEGBCDMA, LiTFSI and ethylene carbonate, a flammable retardant and PEM can be fabricated. This transparent PEM is bendable and twistable, which makes it an ideal candidate for a flexible battery application. Moreover, the PEM also exhibits high ionic conductivity and large electrochemical stability windows. The PEM shows impressive performance in the coin-cell battery test. Over 80% of the initial capacity can be retained after 250 cycles in LiFePO4/PEM/graphite full cells. A proof-of-concept flexible all solid-state lithium ion battery has been built based on this PEM. The relationship between the ionic conductivity, glass transition temperature (Tg) and crosslink density has been studied in the branched copolymer system. PEGDA and monofunctional PEGMEA were copolymerized to afford PEGDA network attached with PEGMEA side chains. Attaching PEGMEA side branches to the PEGDA network backbone is to provide greater free volume afforded by lowering the Tg. The network flexibility is further manipulated by varying relative amounts of PEGMEA and PEGDA. Concurrently, the ionic conductivity of copolymer electrolyte membrane (co-PEM) consisting of LiTFSI salt and SCN plasticizer in the PEGMEA-co-PEGDA copolymer network is enhanced with increasing PEGMEA side branching. The relationship between the network Tg and ionic conductivity of the branched co-PEM has been analyzed in the context of Vogel-Tammann-Fulcher (VTF) equation. The plasticized branched co-PEM network exhibits room temperature ionic conductivity at a superionic conductor level of 10-3 S/cm as well as excellent capacity retention in charge/discharge cycling of Li4Ti5O12/co-PEM/Li and LiFePO4/co-PEM/Li half-cells.
Thein Kyu (Advisor)
Xiong Gong (Committee Chair)
Mark Soucek (Committee Member)
Steven Chuang (Committee Member)
Jiahua Zhu (Committee Member)
198 p.
Energy; Engineering; Polymer Chemistry; Polymers
lithium ion battery; solid polymer electrolyte; all-solid-state battery; flexible electronic

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Citations

  • Fu, G. (2017). INVESTIGATION ON THE STRUCTURE-PROPERTY RELATIONSHIPS IN HIGHLY ION-CONDUCTIVE POLYMER ELECTROLYTE MEMBRANES FOR ALL-SOLID-STATE LITHIUM ION BATTERIES [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1508508844968127

    APA Style (7th edition)

  • Fu, Guopeng. INVESTIGATION ON THE STRUCTURE-PROPERTY RELATIONSHIPS IN HIGHLY ION-CONDUCTIVE POLYMER ELECTROLYTE MEMBRANES FOR ALL-SOLID-STATE LITHIUM ION BATTERIES . 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1508508844968127.

    MLA Style (8th edition)

  • Fu, Guopeng. "INVESTIGATION ON THE STRUCTURE-PROPERTY RELATIONSHIPS IN HIGHLY ION-CONDUCTIVE POLYMER ELECTROLYTE MEMBRANES FOR ALL-SOLID-STATE LITHIUM ION BATTERIES ." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1508508844968127

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.