Effect of the addition of hydrophobic clay on the electrochemical property of polyacrylonitrile/LiClO4 polymer electrolytes for lithium battery

In this study, an organoclay, ALA–MMT, was prepared by the ionic exchange reaction of montmorillonite (MMT) with 12-aminododecanoic acid (ALA). ALA–MMT was then used as a filler to prepare a series of composite polymer electrolytes based on polyacrylonitrile (PAN) and LiClO4. The effect of the addition of ALA–MMT on the properties of the composite polymer electrolytes (CPEs) was investigated by XRD, FT-IR, DSC, tensile strength, AC impedance, and cyclic voltammetry measurements. It was found that the ALA–MMT particles were well dispersed in the CPEs. Owing to the incorporation of ALA–MMT, a higher fraction of the free anions was obtained, indicating that the lithium salt dissolved in the PAN matrix more effectively for the CPE than in the PAN/LiClO4 polymer electrolyte. Moreover, the glass-transition temperature was reduced, benefiting the ion transport. The best ionic conductivity at room temperature was obtained from the CPE with 7 wt% of the modified clay and 0.6 M LiClO4 per PAN repeat unit (CPE-7) and was more than seven times higher than that from the corresponding PAN/LiClO4 polymer electrolyte (CPE-0). The mechanical property and the cation transference number, t+, of CPE-7 are largely increased compared to that of CPE-0. Besides, the CPEs were electrochemically stabilized up to 4.75 V and the corresponding cell exhibited excellent electrochemical stability and cyclability over the potential range between 0 V and 4.0 V vs. Li/Li+.