Lithium iron phosphate

Lithium iron phosphate (LFP) is an inorganic compound with the formula LiFePO4. It is a gray, red-grey, brown or black solid that is insoluble in water. The material has attracted attention as a component of lithium iron phosphate batteries, a type of Li-ion battery. This battery chemistry is targeted for use in power tools, electric vehicles, and solar energy installations. It is also used in OLPC XO education laptops. Lithium iron phosphate (LFP) is an inorganic compound with the formula LiFePO4. It is a gray, red-grey, brown or black solid that is insoluble in water. The material has attracted attention as a component of lithium iron phosphate batteries, a type of Li-ion battery. This battery chemistry is targeted for use in power tools, electric vehicles, and solar energy installations. It is also used in OLPC XO education laptops. Most lithium batteries (Li-ion) used in 3C (computer, communication, consumer electronics) products use cathodes made of other lithium compounds, such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and lithium nickel oxide (LiNiO2). The anodes are generally made of graphite. Lithium iron phosphate exists naturally in the form of the mineral triphylite, but this material has insufficient purity for use in batteries. With general chemical formula of LiMPO4, compounds in the LiFePO4 family adopt the olivine structure. M includes not only Fe but also Co, Mn and Ti. As the first commercial LiMPO4 was C/LiFePO4, the whole group of LiMPO4 is informally called “lithium iron phosphate” or “LiFePO4”. However, more than one olivine-type phase may be used as a battery's cathode material. Olivine compounds such as AyMPO4, Li1-xMFePO4, and LiFePO4-zM have the same crystal structures as LiMPO4 and may replace in a cathode. All may be referred to as “LFP”. Manganese, phosphate, iron, and lithium also form an olivine structure. This structure is a very useful contributor to the cathode of lithium rechargeable batteries. This is due to the olivine structure created when lithium is combined with manganese, iron, and phosphate (as described above). The olivine structures of lithium rechargeable batteries are significant, for they are affordable, stable, and can be safely stored as energy. LiFePO4 was identified as a cathode material for use in batteries in 1996 by Padhi et al. reversible extraction of lithium from LiFePO4 and insertion of lithium into FePO4 was demonstrated. Neutron diffraction confirmed that LFP was able to ensure the security of large input/output current of lithium batteries. The material can be produced by heating a variety of iron and lithium salts with phosphates or phosphoric acid. Many related routes have been described including those that use hydrothermal synthesis. In LiFePO4, lithium has a +1 charge, iron +2 charge balancing the -3 charge for phosphate. Upon removal of Li, the material converts to the ferric form FePO4. The iron atom and 6 oxygen atoms form an octahedral coordination sphere, described as FeO6, with the Fe ion at the center. The phosphate groups, PO4, are tetrahedral. The three-dimensional framework is formed by the FeO6 octahedra sharing O corners. Lithium ions reside within the octahedral channels in a zigzag manner. In crystallography, this structure is thought to belong to the Pmnb space group of the orthorhombic crystal system. The lattice constants are: a = 6.008 Å, b = 10.334 Å, and c = 4.693 Å. The volume of the unit cell is 291.4 Å3.