Sung Woo Oh

Double carbon coating of LiFePO4 as high rate electrode for rechargeable lithium batteries.

, and prom-ising electrochemical performance. This single-carbon-coating material was composed of micrometer-scale secondary parti-cles containing nanoscale carbon-coated primary particles; this morphology provided interconnected open pores that favor elec-trolyte absorption and signifi cantly reduce the diffusion path of the lithium ions. This feature, combined with the high tap density, resulted in electrodes having high volumetric energy density and rate capability. Here we report a double coating process that greatly improves the uniformity of the carbon coating on both the primary and secondary LiFePO

Nanoporous Structured LiFePO4 with Spherical Microscale Particles Having High Volumetric Capacity for Lithium Batteries

To overcome a major limitation of volumetric energy density, we prepared micrometer-sized LiFeP0 4 particles with a unique spongelike morphology and a high packing density. Each LiFePO 4 secondary particle (6 μm) consisted of nanoscale (200-300 nm) primary LiFeP0 4 particles coated with carbon and had nanoscale (100-200 nm) pores throughout. Compared with the nano-LiFePO 4 positive electrode material, this carbon-impregnated, spongelike, nanoporous material resulted in a similarly high rate capability plus a 2.5 times greater volumetric energy density.

The Effect of Morphological Properties on the Electrochemical Behavior of High Tap Density C – LiFePO4 Prepared via Coprecipitation

High-tap-density olivine C-LiFePO 4 , which is used as a positive electrode material in lithium-ion secondary batteries, was prepared via coprecipitation. The C-LiFePO 4 powders were prepared at various calcination temperatures between 650 and 850°C. The structural, electrochemical, and morphological properties, as well as the thermal stability of the prepared powders, were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and elemental analysis. Highly crystalline C-LiFePO 4 with a Pnma space group and a high tap density of 1.09 g cm -3 was obtained. Elemental analysis showed that the final product contained about 3 wt % carbon as a result of the carbon-coating process. SEM showed that the prepared materials consisted of secondary agglomerates with a 1-2 μm particle size, while the particle size of the primary particles was less than 100 nm. The C-LiFePΟ 4 materials prepared at 800°C exhibited an excellent rate capability of 150.8 mAh g -1 at the 0.1 C discharge rate and 106.7 mAh g -1 at the 10 C discharge rate.