Lithium ion transport and ion–polymer interaction in PEO based polymer electrolyte plasticized with ionic liquid

• Published in: Solid state ionics Vol. 201; no. 1; pp. 73 - 80
• Main Authors: Kumar, Yogesh, Hashmi, S.A., Pandey, G.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 19-10-2011
• Subjects: Cations; Devices; Electrical conductivity; Electrolytes; Emittance; Ionic conductivity; Ionic liquid; Ionic liquids; Lithium; Polyethylene oxide; Raman spectroscopy; Solid-state NMR spectroscopy; Spectroscopy; Electrical conductivity; Solid-state NMR spectroscopy; Polyethylene oxide; Raman spectroscopy; Ionic liquid
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2011.08.010

The polyethylene oxide (PEO) based lithium ion conducting polymer electrolytes complexed with lithium trifluoromethanesulfonate (LiCF
3SO
3 or LiTf) plasticized with an ionic liquid 1-ethyl 3-methyl imidazolium trifluoromethanesulfonate (EMITf) have been reported. Morphological, spectroscopic, thermal and electrochemical investigations demonstrate promising characteristics of the polymer films, suitable as electrolyte in various energy storage/conversion devices. Significant structural changes have been observed in the polymer electrolyte due to the ionic liquid addition, investigated by X-ray diffraction (XRD) and optical microscopy. The ion-polymer interaction, particularly the interaction of imidazolium cation with PEO chains, has been evidenced by IR and Raman spectroscopic studies. The optimized composition of the polymer electrolyte i.e. PEO
25.LiTf
+
40
wt.% EMITf offer room temperature ionic conductivity of ~
3
×
10
−
4
S
cm
−
1
with wide electrochemical stability window and excellent thermal stability. The ‘σ versus 1/T’ curves show apparent Arrhenius behavior below and above melting temperature. The ionic conductivity has been observed due to Li
+ ions, as confirmed from
7Li-NMR studies, though the component ions of ionic liquid and anions also contribute significantly to the overall conductivity.
► Effect of ionic liquid addition on the PEO-based electrolyte properties is reported. ► PEO-LiCF
3SO
3-IL films are thermally and electrochemically stable electrolytes. ► FTIR and Raman studies confirm the ion-polymer, particularly EMI
+-PEO interaction. ► Material offers Li
+ and EMI
+ transport along with substantial contribution of anions.