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-Al2O3 nanocomposite electrolyte materials that incorporate various fractions of PAN, α-Al2O3 inorganic powders, propylene carbonate and ethylene carbonate as cosolvents, and LiClO4 were prepared. X-ray diffraction revealed that the gel nanocomposite electrolyte materials contained amorphous PAN in which was uniformly dispersed α-Al2O3. The gel PAN/α-Al2O3 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-Al2O3. The conductivity of the PAN/α-Al 2O3 nanocomposite films was inversely proportional to the size of the α-Al2O3 particles and directly proportional to (I) the amount of α-Al2O3 (up to 7 wt %), (II) the F value [LiClO4/CH2CH(CN) ratio], and (III) the amount of plasticizer (propylene carbonate/ethylene carbonate = 1: 1). Cyclic voltammetry revealed that adding α-Al2O3 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.