Lithium Iron Phosphate (LiFePO4) as High-Performance Cathode Material for Lithium Ion Batteries

As long as the energy consumption is intended to be more economical and more environment friendly, electrochemical energy production is under serious consideration as an alternative energy/power source. Among different energy/power storage devices, lithium-ion batteries (LIBs) are currently the best commercially available devices. However, there are safety issues to be investigated even when it is operating at room temperature since there have been various incidents reported. From that point of view, effective research has been going on to develop LIBs that are viable to operate safely at higher temperatures. In the search for better cathode materials for LIBs, researchers have been investigating a new class of iron-based compounds called polyanions such as (SO4)2−, (PO4)3,− or (AsO4)3−. Orthorhombic LiFePO4 (LFP), which has an ordered olivine structure, has attracted particular interest due to its high-power capability, non-toxicity, and thermal stability. This material has relatively high theoretical capacity of 170 mAhg−1 when compared with other cathode materials. The major drawbacks of the lithium iron phosphate (LFP) cathode include its relatively low average potential, weak electronic conductivity, poor rate capability, low Li+-ion diffusion coefficient, and low volumetric specific capacity. Hence, this chapter clearly emphasizes the role and progress of LFP as efficient cathode material for LIBs and their ways to overcome the existing drawbacks which include the optimization of their synthesis methods, controlling the diffusion rate, and modification strategies. The use of conventional electrolytes with LFP caused iron dissolution on the cathode surface, which catalyzed the electrolyte decomposition, which then contributed to the formation of thick obstructive solid electrolyte interphase (SEI) films. Use of electrolyte additives is one of the most effective methods to protect against LiFePO4 dissolution. The thermal stability of these materials can be accounted by the high Li+ ion diffusion rate and the electron transfer activity. Even at elevated temperatures up to 340 °C, charged LFP and electrolyte didn’t show any kind of chemical reactions, which makes this material thermally more feasible than other cathode materials like LiCoO2, LiNiO2, and LiMn2O4.