Effects Of Polyacrylic Acid on the Suppression of Fe Deposition on Graphite for Lithium-Ion Batteries

In order to suppress the capacity fading of graphite negative-electrodes that is caused by the dissolution of LiFePO4 positive-electrode materials, the effects of the glue-like binder (polyacrylic acid) on the suppression of Fe deposition on the graphite electrodes were examined. The electrochemical properties of graphite electrodes using PAA as the binder were investigated by cycling test, cyclic voltammetry and electrochemical impedance spectroscopy in three kinds of different Fe content electrolyte solution. The graphite electrodes using PAA as the binder exhibit better cycle performance than those using PVDF as the binder in all electrolyte solution, and the reduction peaks occur at 1.8 V, which is corresponding to the Fe deposition process on the graphite electrodes, are remarkably weakened by using PAA as the binder. The growth rate of R-cell and R-ct, for graphite electrode after cycled in Fe-containing electrolyte are also significantly reduced. The SEM and XPS analysis show that the PAA binder can modify the surface film and block the electroreduction of iron ions on the graphite electrode. (C) 2013 The Electrochemical Society.