LiFePO4-Carbon Nanofiber Composite Cathodes for Li-ion Batteries

LiFePO₄ offers interesting possibilities as a cathode material for Li-ion batteries because of its steady operating voltage, excellent structural stability, nontoxicity, and inexpensive source materials. However, its poor electronic conductivity is a major challenge for commercialization. Although different techniques have been developed to address this problem, we approach this challenge by incorporating carbon nanofibers (CNFs) as conductive additives in the LiFePO₄ cathode material. CNFs have high electrical conductivity and high aspect ratio. The effect of adding different percentages of CNFs to LiFePO₄ cathodes was investigated using scanning electron microscopy (SEM), four-point probe, and electrochemical measurements. Electrochemical testing showed the LiFePO₄ with few percents CNFs added to the composite cathode exhibited excellent rate capability performance at 20C and higher cycling capacity with less fading over 200 cycles at 5C. This improved performance is attributed to the increase in electronic percolation pathways created by adding CNFs.