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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 glycol diacrylate-co-trimethylolpropane tris(3-mercaptopropionate) based polymer electrolytes were discussed in chapter V. The SCN plasticized co-network exhibited excellent electrochemical stability up to 5 V. The in-situ lithiation revealed the ion-storing capabilities of the present co-network by forming complexations of lithium ions with functional groups such as thiols (-SH) and ether oxygen. The pseudocapacitive to electric double-layer capacitor (EDLC) behavior was further demonstrated by means of cyclic voltammetry in the voltage range of 0.01 V to 2.5 V. |
