Papers by Keyword: High-Rate Performance

Abstract: CoO was usually added to the positive electrodes of MH/Ni batteries as the conductive agent. In this paper, well crystallized multi-walled carbon nanotubes (CNTs) with diameter about 10 nm were added to the positive electrodes of MH/Ni batteries together with CoO. During the process of transformation from CoO to CoOOH, a complex conductive network was created with CNTs as the frame. Because of the high conductivity and the excellent tension characteristics of CNTs, the charge-transfer capability of the electrode was improved and the integrality of the complex conductive network was enhanced. The electrochemical measurements indicated that the impedance of the electrode with CNT-CoO complex conductive agent was lessened compared to the electrode with simple CoO agent. Performance tests of the sealed batteries showed that the positive electrodes with CNT-CoO complex conductive agent exhibited higher discharge voltage, improved capacity, modified discharge stability and prolonged lifespan, especially at high current rates.

Abstract: Electrochemical properties of LiFePO4/carbon composites with various carbon materials were investigated to achieve high-rate charge and discharge properties. LiFePO4/carbon composites were synthesized by a pyrolysis of a LiFePO4 precursor solution added with porous graphite or particulate carbon powders. The LiFePO4/porous-graphite composite had a microstructure in which LiFePO4 particles existed on carbon surface and within pores. The LiFePO4/particulate-carbon composite had a microstructure in which each carbon particle was covered with LiFePO4 fine particles. The LiFePO4/porous-graphite and the LiFePO4/particulate-carbon composite electrodes showed high discharge capacities of 69 and 30 mAh g-1 at a high current density of 4000 mA g-1. The high electronic conductivity in the LiFePO4/porous-graphite composite contributed to achieving the large discharge capacity at the high current density.