Date of Award

5-1-2021

Thesis Type

phd

Document Type

Thesis (Restricted Access)

Divisions

science

Department

Faculty of Science

Institution

Universiti Malaya

Abstract

Gel polymer electrolytes (GPEs) based on poly(methyl methacrylate) (PMMA) are developed. Lithium-ions donor which are lithium bis(oxalato)borate (LiBOB) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) solvent was used in this work. Three GPE systems were prepared i.e. PMMA-LiBOB-TEGDME, PMMA-LiTFSI-TEGDME and PMMA-LiTFSI-TEGDMECalix[ 6]arene. Calix[6]arene as a trapping agent for anions is only added in 28.85wt.% PMMA–25wt.% LiTFSI–46.15wt.% TEGDME GPE (B4 sample) due to the highest electrolyte conductivity of (2.80±0.01) mS cm-1 obtained compared to 32.96wt.% PMMA–15wt.% LiBOB–52.04wt.% TEGDME GPE (A2 sample) of (1.69±0.09) mS cm-1. Addition of Calix[6]arene in B4 sample decreased the electrolyte conductivity. From Fourier-transform infrared (FTIR) studies, complexation between Li+ ions and functional groups of (C=O), (O-CH3) and (C-O-C) corresponding to PMMA and (C-O) corresponding to TEGDME have occurred. Addition of Calix[6]arene in B4 sample shows the occurrence of interaction between fluorine atom from CF3 group corresponding to TFSI¯ anion with H+ ion from OH group of calix[6]arene. Transference number measurement shows the electrolyte containing 0.5wt.% Calix[6]arene in B4 sample (now known as sample C1) gives highest lithium-ion transference number, Lit  of 0.51. Electrochemical window stability is most stable up to 5.5 V for sample A2. Sample C1 provides excellent stability at electrode-electrolyte interface and higher discharge capacity (1.40 mAh cm-2 or 0.53 mAh) along with discharge capacity retention of 35% after fifth cycles when applied in lithium-oxygen battery.

Note

Thesis (PhD) - Faculty of Science, Universiti Malaya, 2021.

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