Development of Poly (Vinyl Alcohol) (PVA)-Based Ion Conductors for Electrical Double Layer Capacitor (EDLC) Application

Tong, Zhi Xiang (2021) Development of Poly (Vinyl Alcohol) (PVA)-Based Ion Conductors for Electrical Double Layer Capacitor (EDLC) Application. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

A biodegradable poly (vinyl alcohol) (PVA)-LiTFSI polymer electrolytes had been fabricated via solution casting method. Effect upon addition of various ratio of salt into the polymer electrolyte has been evaluated thoroughly in this study. Upon the addition of 30 wt.% LiTFSI, the ionic conductivity at room temperature had increased from (5.27 ± 0.01) × 10-8 to (8.13 ± 0.01) × 10-7 S cm-1, where both the PVA 100% and PVA 70% electrolytes obey the Arrhenius theory. Successful complexation between PVA and LiTFSI was confirmed via fourier transform infrared studies. Differential scanning calorimetry (DSC) was used to determine glass transition temperature (Tg) of the electrolyte samples and it was found out that the Tg are demonstrating a decreasing trend as the weight percentage of LiTFSI salt added in the polymer increases, where it decreases from 69.58 °C to 57.01 °C. The decrease of Tg is due to softening of polymer backbone that caused by the plasticizing effect of the LiTFSI. Thermogravimetric analysis (TGA) has been done and it was found out that PVA polymer has 3 degradation stages where the first stage is the removal of water, second stage is the removal of OH side chain and third stage is the formation of aliphatic products. Besides, potential window of the electrolyte had been increased from 1.8 V to 3.5 V after addition of salt as observed in linear sweep voltammetry (LSV) study. The most conducting PVA electrolyte sample was further fabricated into EDLC cell by sandwiched the electrolyte with two carbon electrodes. Properties of the EDLC cell fabricated was further tested with galvanostatic charge-discharge (GCD), transference number and cyclic voltammetry (CV) studies to examine overall performance of the cell. It was found out that the resulting value in term of specific capacitance and cycle stability of the cell is low, indicating that this particular cell is yet to be further improve in the future.