Ion–polymer and ion–ion interaction in PEO‐based polymer electrolytes having complexing salt LiClO4 and/or ionic liquid, [BMIM][PF6]

Ion–polymer and ion–ion association in polymer electrolyte films of PEO complexed with salt LiClO4, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6) and (LiClO4 + BMIMPF6) have been studied by laser Raman spectroscopy. The cations (Li+ and/or BMIM+) of the dopant salt/IL are shown to complex with the ether oxygen of the polymer backbone (i.e. COC bond of PEO). The polymer–cation complexation results in the appearance of an additional peak at ∼1131 cm−1 apart from the COC stretching vibrations of PEO at ∼1062 and 1141 cm−1. This peak due to polymer–cation complexation is relatively strong for LiClO4 than BMIMPF6, indicating stronger interaction for the former. In the PEO:LiClO4 and PEO:BMIMPF6 spectra, Raman peaks at 937 and 747 cm−1, respectively related to Li+· ClO and BMIM+· PF ‘contact ion pairs’, have also been observed as a result of ion–ion association. In the polymer electrolyte PEO:LiClO4 + BMIMPF6 which contained two different anions, viz. ClO and PF, an interesting observation of the formation of ‘cross contact ion pairs’ viz. Li+· PF and BMIM+· ClO is also reported. Copyright © 2011 John Wiley & Sons, Ltd.

[1]  S. Chandra,et al.  Dielectric relaxation and conductivity studies on (PEO:LiClO4) polymer electrolyte with added ionic liquid [BMIM][PF6]: Evidence of ion–ion interaction , 2011 .

[2]  S. Chandra,et al.  Structural and transport studies on polymeric membranes of PEO containing ionic liquid, EMIM-TY: Evidence of complexation , 2011 .

[3]  Jianji Wang,et al.  Theoretical insights into PF6− and its alkali metal ion pairs: geometries and vibrational frequencies , 2005 .

[4]  R. Frech,et al.  Spectroscopic measurements of ionic association in solutions of LiPF6. , 2005, The journal of physical chemistry. B.

[5]  S. Dou,et al.  Nanoparticle-dispersed PEO polymer electrolytes for Li batteries , 2003 .

[6]  G. Silva,et al.  Micro-Raman study of poly(ethylene glycol) electrolytes near phase segregation compositions , 2001 .

[7]  Miho Fujita,et al.  Conductivity and Solvation of Li+ Ions of LiPF6 in Propylene Carbonate Solutions , 2000 .

[8]  Bruno Scrosati,et al.  Physical and chemical properties of nanocomposite polymer electrolytes , 1999 .

[9]  P. Jacobsson,et al.  Raman scattering investigations of PEO and PPO sulphonic acids , 1997 .

[10]  Chandra,et al.  Temperature dependence of positron-annihilation lifetime, free volume, conductivity, ionic mobility, and number of charge carriers in a polymer electrolyte polyethylene oxide complexed with NH4ClO4. , 1996, Physical review. B, Condensed matter.

[11]  R. Frech,et al.  Effect of Plasticizers on Ionic Association and Conductivity in the (PEO)9LiCF3SO3 System , 1996 .

[12]  L. M. Torell,et al.  Characterisation of poly(ethylene oxide) sulfonic acids , 1995 .

[13]  S. Chandra,et al.  Mixed-anion effect in polyethylene-oxide-based sodium-ion-conducting polymer electrolytes , 1994 .

[14]  J. R. Stevens,et al.  Ion pairing effects in poly(propylene glycol)–salt complexes as a function of molecular weight and temperature: A Raman scattering study using NaCF3SO3 and LiClO4 , 1991 .

[15]  S. Schantz.  On the ion association at low salt concentrations in polymer electrolytes; a Raman study of NaCF3SO3 and LiClO4 dissolved in poly(propylene oxide) , 1991 .

[16]  S. Mitra,et al.  Sol–gel derived, magnesium based ionically conducting composites , 2002 .

[17]  Chandra.  Experimental observation of large-size fractals in ion-conducting polymer electrolyte films. , 1994, Physical review. B, Condensed matter.

[18]  M. Ratner,et al.  Vibrational spectroscopy and structure of polymer electrolytes, poly(ethylene oxide) complexes of alkali metal salts , 1981 .