Electrochemical and Thermal Studies of Poly (Ethyl Methacrylate) (PEMA)-Based Ion Conductor for EDLC Application

Yek, Siew Ching (2021) Electrochemical and Thermal Studies of Poly (Ethyl Methacrylate) (PEMA)-Based Ion Conductor for EDLC Application. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

The PEMA-LiTFSI polymer electrolytes had been prepared by solution casting method. The effect of adding different weight percent of the LiTFSI had been investigated. Incorporation of 50 wt. % LiTFSI elevates the ionic conductivity from (4.64 ± 0.01) × 10-11 S cm-1 to (1.22 ± 0.01) × 10-6 S cm-1. PEMA-LiTFSI polymer electrolytes obey Arrhenius theory in which charge carriers hop from one coordination site to another empty coordination site. The glass transition temperature (Tg) obtained from DSC demonstrates the crosslinking effect of Li+ with the oxygen of PEMA, where the Tg increases significantly from 73.43 ºC (PS 2) to 86.38 ºC (PS 3). Later, Tg value decreases marginally from 86.38 ºC to 81.11 ºC. The decrease in Tg is due to the ion aggregation that weakens the crosslinker effect of Li+. The doping of LiTFSI also improves the thermal stability of the polymer electrolyte from 331 ºC to 363 ºC. The remaining weight percent also improved from 1.58 % to 9.82 %. Moreover, structural information proposes that Li+ can interact with oxygen of carbonyl and ester groups. Linear Sweep Voltammetry shows that there has been an improvement of electrochemical stability window from 2.2 V to 3.2 V upon addition of 40 wt. % and 50 wt. % of LiTFSI. Transference number analysis affirmed ion is the major contributor to the ionic conductivity of the PEMA-LiTFSI polymer electrolyte system. PEMA-LiTFSI-based EDLC cell exhibits specific capacitance of 358.1 m F g-1. The energy density and power density of PEMA-LiTFSI-based EDLC cell are 22.2 mWh/kg and 14.0 W/kg respectively.