Lithium phosphate iron battery physics chemical properties.lithuim ion battery 18650

　　The expression of lithium -phosphate iron chemical molecular formula is: Limpo4, of which lithium is a positive price; central metal iron is a positive second price; the root of phosphate is a negative triple price. The octopus Feo6, while the phosphorus in the phosphoric acid root forms a tetraonal PO4 with phosphorus -centered sides with four oxygen atoms. The chain -shaped structure of the font, while the lithium ion occupies the octopus position composed of the space skeleton of the co -edge. In the lattice, the Feo6 is connected through the common angle of the BC side, and LiO6 forms the common edge of the B -axis direction. The chain, a FeO6 octopus and two LiO6 octopus and a PO4 tetraonae, while the PO4 tetraon is co -edged with a FeO6 octopus and two Li6 octopus. The symmetrical classification of crystalline studies belongs to the PMNB space group in the trapezine crystal system. The unit crystal constant is A = 6.008å, B = 10.334å, C = 4.693å, and the volume of the unit crystal is 291.4å3. Because the phosphate group in the structure has a stable effect on the framework of the entire material, the material itself has good thermal stability and circulation performance.

　　After the lithium ion is removed, FEPO4 is generated with a similar structure, but the space group is also PMNB, the unit lattice constant is A = 5.792å, B = 9.821å, C = 4.788å, the volume of the unit's lattice is 272.4å3, the lithium ion is removed out Later, the volume of the lattice is reduced, which is similar to the lithium oxide. The FEO6 octagonal conjunction in Limpo4 is separated by the oxygen atoms of PO43− tetraonal, which cannot form a continuous Feo6 network structure, which reduces electronic conduction. On the other hand, the oxygen atoms in the crystal are close to the most densely stacked ways in the six parties. Therefore, only a limited channel for lithium ions can be provided, which makes the migration rate of lithium ions in the structure very small at room temperature.

　　During the charging process, lithium ions and corresponding electrons are removed from the structure, and a new FEPO4 phase is formed in the structure, and a phase interface is formed. During the discharge process, lithium ions and corresponding electrons move into the structure, and form a new Limpo4 phase outside the FEPO4 phase. Therefore, for the particles of the orthopedic material of the spherical shape, whether it is moved in or off, lithium ions must go through a converter from the outside to the inside or from the inside to the outside. In the process of charging and discharge, the material has a decision step, that is, the two-phase interface of lixfeppo4 / li1-xfepo4. As the lithium continues to move in and the interface area decreases, after reaching the critical surface area, the generated FEPO4 electrons and ionic conductivity are low, which becomes two structures. Therefore, Limpo4 located in the center of the particle cannot be fully utilized, especially under the conditions of large current.

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