Effects of ball-to-powder weight ratio on the performance of LiFePO4/C prepared by wet-milling assisted carbothermal reduction

Abstract

We prepared a LiFePO4/C composite using wet-milling assisted carbothermal reduction, and investigated how the ball-to-powder weight ratio affected the characteristics of the composite using X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle-size distribution measurements, and electrochemical performance testing. Four ball-to-powder weight ratios varying from 15:1 to 30:1 were compared. LiFePO4 surrounded by a network of carbon was obtained for all of the ball-to-powder weight ratios used. As the ball-to-powder weight ratio increased, the particles became more homogeneous, while the particle sizes of the slurries first decreased and then increased. The LiFePO4/C sample we prepared with a ball-to-powder weight ratio of 25:1 was mostly composed of ~50nm particles. Electrochemical tests indicated that the sample had a discharge capacity of 125mAhg−1 with no capacity loss after 100cycles at a 10C rate. This outstanding rate capability is mainly ascribed to the presence of nanoparticles with proper carbon structures and correspondingly reduced electrochemical polarization resistance.