Mass Production of LiFeP /C Powders by Large Type Spray Pyrolysis Apparatus and Its Application to Cathode for Lithium Ion Battery

Spherical LiFeP /C powders were successfully produced at a rate of 100？g/h using a large type spray pyrolysis apparatus. Organic compounds such as citric acid and sucrose were used as carbon sources. Scanning electron microscopy observation showed that they had a spherical morphology with nonaggregation. X-ray diffraction analysis revealed that the olivine phase was obtained by heating at under argon (95%)/hydrogen (5%) atmosphere. The chemical composition of LiFeP /C powders was in good agreement with that of the starting solution. Electrochemical measurement revealed that the use of citric acid was most effective in ensuring a high rechargeable capacity and cycle stability. The rechargeable capacity of the LiFeP /C cathode obtained using citric acid was 155？mAh/g at a discharge rate of 1？C. Because of the good discharge capacity of the LiFeP /C cathode, it exhibited excellent cycle stability after 100 cycles at each discharge rate. Moreover, this high cycle stability of the LiFeP /C cathode was maintained even at . 1. Introduction Recently, olivine-type LiFePO4 has been considered as a suitable cathode material for lithium-ion batteries used in EVs (electric vehicles), HEVs (hybrid electric vehicles), and power supplies used for load leveling in wind power generation and solar power generation. [1, 2]. Olivine-type LiFePO4 exhibits a relatively high theoretical capacity of 170？mAh/g and a stable cycle performance at high temperatures. However, in the past, the low electrical conductivity of LiFePO4 prevented its application as a cathode material for the lithium-ion battery. Therefore, conductive materials such as carbon and metals were added to LiFePO4 in order to enhance its electrical conductivity [3–6]. Yang et al. reported the electrochemical properties of LiFePO4/C cathode materials prepared by spray pyrolysis [7]. The advantages of spray pyrolysis [8, 9] are as follows: (1) spherical and homogeneous oxide powders can be directly prepared, and the synthesis time is much shorter than that required for a solid-state reaction and the sol-gel method and (2) carbon or metal ions are directly doped to the particles in one step. We have synthesized various types of lithium oxide powders such as LiNiO2, LiMn2O4, and LiNi1/3Mn2/3O4 for the development of the lithium-ion battery by spray pyrolysis [10–12]. We found that by using the materials prepared by spray pyrolysis as cathode materials for the lithium-ion battery, the rechargeable capacity and cycle life of the battery were improved. It has been found clear that a LiFePO4/C cathode produced by spray