The development of polymer electrolytes has long been the subject of research interest due to their potential applications not only in the area of rechargeable lithium batteries but also in other electrochemical devices. In the present study nanocomposite polymer electrolytes (NCPE’s) comprising poly(ethylene oxide), Ca3(PO4)2 and LiClO4/LiN(CF3SO2)2 in varying proportions are prepared by a hot press method. The nanosized calcium phosphate filler particles were synthesized using in situ deposition technique in the presence of poly ethylene oxide (PEO) as follows: Firstly, a complex of calcium chloride with PEO was prepared in desired proportions in methanol. An appropriate stoichiometric amount of trisodium phosphate, Na3(PO4) in distilled water was added to the above complex slowly without stirring. The whole mixture was allowed to digest at room temperature for 24h when both the chloride and phosphate ions diffused through the PEO and formed a white gel like precipitate, which was filtered, washed and dried.
The membranes were characterized by SEM, DSC, TG-DTA, ionic conductivity and transference number studies. The evolution of interfacial resistance as a function of time is followed with Li/NCPE/Li symmetric cells at 80°C under open- circuit conditions. This paper also describes FTIR spectroscopic studies of the interface between lithium metal and NCPE, which suggests that the surface chemistry of lithium electrodes in contact with NCPE is dominated by compounds with Li3PO4 bonding. The free volume (Vf) of the membranes is probed by positron annihilation lifetime spectroscopy at 30°C and the results support ionic conductivity data. The NCPE’s with LiClO4 exhibits higher ionic conductivity than that of NCPE with LiN(CF3SO2)2 (LiTFSI) as salt.
References
[1] A. Manuel Stephan, T. Prem Kumar, M.Anbu Kulandainathan, N. Angulakshmi
J. Phys. Chem. B 113 (2009)
[2] A. Manuel Stephan, Eur. Polym. J. 41 (2006) 21-42
