Graphene oxide as a filler to improve the performance of PAN-LiClO4 flexible solid polymer electrolyte

Abstract

Solid polymer electrolytes (SPEs) show structural flexibility and safety to meet the requirements of lithium battery applications. However, SPEs usually have a low ionic conductivity at room temperature. In this study, in order to improve the ionic conductivity, we add graphene oxide (GO) as a nano-filler into LiClO4-polyacrylonitrile (PAN) type SPEs with various weight percentages. The ionic conductivity of the composite SPE containing 1.0wt% GO has reached 4.0×10−4Scm−1 at 30°C, which is one order of magnitude higher than the bare one (2.2×10−5Scm−1 at 30°C). Meanwhile, the activation energy has reduced from 2.31 to 1.03eV and the tensile modulus has increased from 37 to 80MPa. This improvement is mainly ascribed to the functional groups (OH, COOH, CO, COC, et al.) in GO that can alleviate the polarity of “CN:”, which makes the polymer softer and facilitates the dissociation of LiClO4 in PAN matrix. Moreover, the LiFePO4 (LFP) cell with 1.0wt% GO-SPE as electrolyte shows a satisfactory average discharge capacity of 166mAhg−1 at 0.2C, which is better than the performance in the GO-free type cell (136mAhg−1).