Immobilization of nanosized LiFePO4 spheres by 3D coralloid carbon structure with large pore volume and thin walls for high power lithium-ion batteries

A novel LiFePO4/C composite, including 85.4 wt% of spherical LiFePO4 nanocrystallites with the size of 22 nm is fabricated by using 3D coralloid nitrogen-containing carbon with large pore volume (4.68 cm(3) g(-1)) and thin walls (2-3 nm) as interpenetrating conductive framework. Based on the whole composite, the LiFePO4/C cathode material exhibits a stable and high reversible capacity of 144.6 mA h g(-1) at 0.1 C and 60.4 mA h g(-1) at 20 C (based on the weight of LiFePO4, it can deliver a high capacity of 155.8 mA h g(-1) at 0.1 C and 85.3 mA h g(-1) at 20 C). The cell retains 96.7% of its initial capacity at 10 C over 1000 cycles with an ultrahigh specific power of 5114 W kg(-1) and the coulombic efficiency is >99%. The excellent performance is ascribed to the facile lithium-ion diffusion within the LiFePO4 nanocrystallites and high conductivity through the 3D continuous network. This coralloid carbon not only provides sufficient space for LiFePO4 hosting to further assist in energy storage, but also acts as a rigid nano-confinement support that prevents agglomeration of LiFePO4 during calcinations, which might be extended for the fabrication of other nano-sized electrode materials. (C) 2012 Elsevier B.V. All rights reserved.