Poly(ethylene oxide)-lithium difluoro(oxalato)borate new solid polymer electrolytes: ion–polymer interaction, structural, thermal, and ionic conductivity studies

Abstract

Solid polymer electrolytes based on high molecular weight poly(ethylene oxide) (PEO) complexed with lithium difluoro(oxalato)borate (LiDFOB) salt in various EO:Li molar ratios from 30:1 to 8:1 were prepared by using solution casting technique. Ion-polymer interaction, structural, thermal, and ionic conductivity studies have been reported by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), polarized optical microscopy (POM), differential scanning calorimeter (DSC), and impedance analysis. FTIR spectral studies suggested that the interaction of Li + cations with the ether oxygen of PEO, where a triple peak broad band centered at 1105 cm −1 , corresponds to C-O-C stretching and extreme deformation occurs. XRD, POM, and DSC indicated that the inclusion of LiDFOB salt could reduce the crystallinity of PEO. The melting temperature of PEO shifted to lower temperature side by the addition of LiDFOB. The glass transition temperature obtained for the system 10:1 was −38.2°C. An increase in the ionic conductivity from 3.95×10 −9 to 3.18× 10 −5 S/cm at room temperature (23°C) was obtained through the addition of LiDFOB to a high molecular weight PEO. In addition, the ionic conductivity of the polymer electrolyte films followed an Arrhenius relation, and the activation energy decreased with increasing LiDFOB concentration.

New solid polymer electrolytes (PEO20–LiTDI–SN) for lithium batteries: structural, thermal and ionic conductivity studies

“…DSC curves represented endothermic peaks due to the melting temperature (T m ) and glass transition temperature (T g ) of the solid polymer electrolytes. The glass transition temperature represents the amorphous phase, and melting temperature indicates the crystalline phase characteristics of PEO [23]. In the present work, T m of pure PEO was 72.6°C and corresponding heat enthalpy (DH m ) was 151.3 J/g.…”

“…Figure 5 shows the TGA curve of optimum conducting composition (OCC) PEO 20 -LiTDI-30 wt% of SN SPE film. The TGA curve of the OCC sample exhibited three regions; I, a plateau up to 260°C with a mass loss of *2.2 %, this weight loss was attributed to evaporation of superficial/ residual moisture in the samples [23], II, a small slope between 260 to 350°C with a mass loss of *10 %, and III, a large slope between 350 to 420°C with a mass loss of 72 %. This indicates its thermal stability up to *260°C and fast burning out at *350°C.…”

Review—On Order and Disorder in Polymer Electrolytes

“…53 The broadening and reduction in the intensity of the Bragg peaks with the addition of the salt to the polymer PEO confirmed the dissolution of salt in the polymer host and the increase in its amorphous nature. FTIR measurements proved the coordination of cations and the interaction of anions with the polar groups of the polymer host during the formation of the complex.…”

A Strategy to Make High Voltage LiCoO2Compatible with Polyethylene Oxide Electrolyte in All-Solid-State Lithium Ion Batteries

“…28 Moreover, the absorption peaks between 1000 cm −1 and 1200 cm −1 split obviously in the cycled LiCoO 2 /PEO-LiDFOB/Li cell, suggesting the weaken interaction between PEO and LiDFOB after battery cycling, which may be caused by the decomposition of LiDFOB. 29 On the contrary, the FTIR results of LiCoO 2 and PEO in the cycled PECA-coated LiCoO 2 /PEO-LiDFOB/Li cell showed no obvious differences from that of the pristine PEO electrolyte. It means that the PECA coating can effectively suppress the ring-opening reaction of DFOB − anion at high voltage and guarantee the strong interaction between PEO and LiDFOB.…”