In LiFePO4's crystal structure, oxygen atoms are packed tightly in six directions. The po43-tetrahedron and FeO6 octahedron form the spatial framework of the crystal. Li and Fe occupy the octahedral gap, while P occupies the tetrahedral gap, in which Fe occupies the coangular position of the octahedron and Li occupies the coedge position of the octahedron. The FeO6 octahedron is connected to each other on the BC plane of the crystal, and the LiO6 octahedron along the B axis is connected to each other into a chain structure. One FeO6 octahedron is coarsed with two LiO6 octahedrons and one PO43-tetrahedron.
Due to the discontinuity of FeO6 cosided octahedron network, electronic conduction cannot be formed. At the same time, po43-tetrahedron limits the lattice volume change and affects the deintercalation and electron diffusion of Li+, resulting in extremely low electronic conductivity and ion diffusion efficiency of LiFePO4 cathode materials.
The LiFePO4 battery has a high theoretical specific capacity (about 170mAh/g) and a discharge platform of 3.4V. Li+ back and forth between the positive and negative poles to achieve charge and discharge, oxidation reaction occurs when charging, Li+ moved out from the positive electrode, by the electrolyte embedded in the negative electrode, iron from Fe2+ into Fe3+, oxidation reaction occurs.