Recently, the demand of Li-ion secondary battery is increasing with the growth of the mobile electronic products industries such as communication devices, cellular phone, notebook, and so on. In this situation, the mobile batteries play the very important role.
Lithium cobalt oxide secondary battery is first developed at SONY in 1991. But it has problems such as high cost, thermal instability and so on, despite of its good performance. Thus the research for finding new cathode material that can replace the $LiCoO_2$ is proceeded actively. At present, the possible candidate material is $LiFePO_4$ that is low-priced, thermally stable and environmentally benign because of using Fe, not Co. But its synthesis method is so difficult due to unstable $Fe^{2+}$ ions.
In this study, $LiFePO_4$ powder is synthesized in hydrogen reduction atmosphere by solid state reaction in order to suppress the oxidation of $Fe^{2+}$ ions. Synthesized powder is measured by SEM, XRD for microstructure, and by particle size analysis for diffusion- limited current dependency with respect to the calcination temperature.
In the case of $LiFePO_4$, because the obstacle of the commercialization is the low conductivity of the $Li^+$ ions and the electrons, in order to enhance the conductivity, we synthesized powder by carbon mixing & post heat treatment and analyzed the electrochemical properties.
