Effect of nanostructured Al2O3 on poly(ethylene oxide)-based solid polymer electrolytes.

In this study, we investigated the effect of nanostructured Al₂O₃ particles on Li ion conducting, poly(ethylene oxide) (PEO)-based membranes prepared by electrospinning, solution casting and hot pressing. Pure PEO:LiBF₄ solid polymer electrolytes (SPEs) and also plasticizer containing membranes were investigated with various amounts of Al₂O₃. In a first step, the best-performing composition of pure PEO:LiBF₄ concerning the resulting ionic conductivity was identified and used as a standard for further experiments. In the following, the influence of the preparation method, the nature of the Al₂O₃, and the type of the plasticizer additives on the thermal and electrochemical properties for this standard composition were investigated. The Al₂O₃ composition was varied between 1 and 5 wt%. The ionic conductivity of bare electrospun PEO:LiBF₄ SPE standard material has been improved by a factor ten to 1.9 × 10⁻⁶ S cm⁻¹ at T = 293 K when 5 wt% of Al₂O₃ is added. For solution-casted PEO:LiBF₄ standard compositions 18:1 with an initial ionic conductivity of 6.7 × 10⁻⁸ S cm⁻¹, the addition of 2 wt% Al₂O₃ increased the performance to 1.4 × 10⁻⁷ S cm⁻¹, both at T = 293 K. If succinonitrile and Al₂O₃ was admixed to the solution casted standard material, the ionic conductivity was further increased to reach 5.5 × 10⁻⁵ S cm⁻¹ at T = 293 K. This material with a composition of 18:3:1 + 2 wt% Al₂O₃, outperforms the standard material by three orders of magnitude. [ABSTRACT FROM AUTHOR]