Temperature Effects on the Behavior of Lithium Iron Phosphate Electrodes

Resumo

The systematic study of the effect of temperature (in the range from −45 to +60°C) on the process of lithium extraction from LiFePO₄ and its insertion into FePO₄ is carried out. At a current of about C/1.5, with decreasing temperature, the capacity decreases, the polarization increases, the range of compositions corresponding to nonequilibrium solid solutions widens, and the slope of the linear section of the galvanostatic curves corresponding to the two-phase system increases. The decrease in the capacity with decreasing temperature is not described by the simple Arrhenius equation. It is assumed that the process on the lithium iron phosphate electrodes has a mixed diffusion-activation nature. The polarization of the anodic and cathodic processes increases with decreasing temperature in a complicated way, and the polarization of the anodic process exceeds that of the cathodic process appreciably.