LiFePO

LiFePO, commonly referred to in full as lithium iron phosphate (LiFePO4), is an inorganic compound used primarily as a cathode material in lithium-ion batteries. It belongs to the olivine family of phosphate minerals and features a one-dimensional lithium diffusion pathway within its crystalline structure.

In operation, lithium iron phosphate undergoes a two-phase redox reaction between LiFePO4 and FePO4. The material provides a relatively high safe operating voltage of about 3.2 to 3.3 volts versus Li/Li+. Its theoretical capacity is around 170 mAh per gram, with practical cell capacities typically in the 160–170 mAh/g range. The olivine structure confers excellent thermal and chemical stability, contributing to favorable safety characteristics and long cycle life.

Synthesis and processing methods for LiFePO4 include solid-state reactions, hydrothermal and sol-gel approaches. Because pristine LiFePO4 is electronically insulating, it is commonly combined with conductive carbon coatings or doped with other elements to improve electrical conductivity and rate performance. Controlling particle size and surface area also helps enhance kinetics for fast charging and discharging.

Applications and performance: LiFePO4 is widely used as a cathode material in lithium-ion batteries for electric vehicles, power tools, and stationary energy storage. It offers good cycle life, robust safety performance, and a relatively low cost due to the abundance of iron and phosphate. However, its energy density is typically lower than that of cobalt- or nickel-containing cathodes, and diffusion along the one-dimensional channels can limit high-rate capability if not mitigated by materials engineering.

Environmental and economic aspects: LiFePO4 is environmentally benign and relatively inexpensive compared to many other cathode chemistries, contributing to its popularity in applications prioritizing safety and longevity.