Engendering High Energy Density LiFePO 4 Electrodes with Morphological and Compositional Tuning.

Improving the energy density of Li-ion batteries is critical to meet the requirements of electric vehicles and energy storage systems. In this work, LiFePO 4 active material was combined with single-walled carbon nanotubes as the conductive additive to develop high-energy-density cathodes for rechargeable Li-ion batteries. The effect of the morphology of the active material particles on the cathodes' electrochemical characteristics was investigated. Although providing higher packing density of electrodes, spherical LiFePO 4 microparticles had poorer contact with an aluminum current collector and showed lower rate capability than plate-shaped LiFePO 4 nanoparticles. A carbon-coated current collector helped enhance the interfacial contact with spherical LiFePO 4 particles and was instrumental in combining high electrode packing density (1.8 g cm -3 ) with excellent rate capability (100 mAh g -1 at 10C). The weight percentages of carbon nanotubes and polyvinylidene fluoride binder in the electrodes were optimized for electrical conductivity, rate capability, adhesion strength, and cyclic stability. The electrodes that were formulated with 0.25 wt.% of carbon nanotubes and 1.75 wt.% of the binder demonstrated the best overall performance. The optimized electrode composition was used to formulate thick free-standing electrodes with high energy and power densities, achieving the areal capacity of 5.9 mAh cm -2 at 1C rate.