Study Of First-principles Calculations And Super-exchange Effect In Olivine Lifepo₄ As Cathode Materials For Li-ion Batteries

LiFePO₄ is promising candidates of cathode materials for lithium ion batteries. The Fe-doping and Li-doping LiFePO₄ were prepared by high temperature solid-phase synthesization. A study on the synthesis method, structure and electrochemical performance of LiFePO₄ as cathode materials for lithium ion batteries had been carried out systemically and in detail through test measures such as XRD, SEM, and CV and so on in this dissertation. The test results showed the best doping contents in the samples.An ab initio method with pseudo potentials had been used to calculate the 0.25 doping content in the cathode material LiFePO₄ in Lithium batteries. The results showed that the band structure of doped was more complicated and dense than undoped LiFePO₄. There ware no significant changes in the total DOS. On the contrary, the changes had taken placed in the 3d orbit of the magnetic atoms at the Fermi level. The electron density distrutions of the nearest Fe atom were significantly influenced by the doping magnetic atoms.The first-principles calculations were also performed in the FePO₄. The calculated conclusions were revealed that there were differences in the band structure and electrons density between LiFePO₄ and FePO₄. Therefore, the basis had been prepared for the deep systemic structural analysis in LiFePO₄.