α‐Al2O3 improves the properties of gel polyacrylonitrile nanocomposite electrolytes used as electrolyte materials in rechargeable lithium batteries

Abstract In this investigation, a series of gel polyacrylonitrile (PAN)/α‐Al 2 O 3 nanocomposite electrolyte materials that incorporate various fractions of PAN, α‐Al 2 O 3 inorganic powders, propylene carbonate and ethylene carbonate as cosolvents, and LiClO 4 were prepared. X‐ray diffraction revealed that the gel nanocomposite electrolyte materials contained amorphous PAN in which was uniformly dispersed α‐Al 2 O 3 . The gel PAN/α‐Al 2 O 3 nanocomposite electrolytes had lower glass‐transition temperatures (as determined by dynamic mechanical analysis) and higher conductivity than a similar electrolyte prepared in the absence of α‐Al 2 O 3 . The conductivity of the PAN/α‐Al 2 O 3 nanocomposite films was inversely proportional to the size of the α‐Al 2 O 3 particles and directly proportional to (I) the amount of α‐Al 2 O 3 (up to 7 wt %), (II) the F value [LiClO 4 /CH 2 CH(CN) ratio], and (III) the amount of plasticizer (propylene carbonate/ethylene carbonate = 1 : 1). Cyclic voltammetry revealed that adding α‐Al 2 O 3 significantly increased the electrochemical stability of the composite electrolyte system. A rechargeable lithium battery prepared using this gel nanocomposite electrolyte system exhibited good cyclability and a stable capacity. The coulombic efficiency for the recharge/discharge process was approximately 75%, even after 100 cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011