Lithium Iron Phosphate - Improvement

Improvement

LFP has two shortcomings inhibiting market penetration: low conductivity and low lithium diffusion constant, both of which limit the rate at which batteries can be charged and discharged. Researchers all over the world are working on improving the conductivity of LiMPO₄. A123 is working around the problem of LFP’s extremely low conductivity (10-10 ~ 10-9 S/cm) by coating and replacing the material and converting the material into nano particles. Adding conducting particles in delithiated FePO₄ raises its electron conductivity. For example, adding conducting particles with good diffusion capability like graphite and carbon to LiMPO₄ powders significantly improves conductivity between particles, increases the efficiency of LiMPO₄ and raises its reversible capacity up to 95% of the theoretical values. LiMPO₄ shows good cycling performance even under the condition of as large charge/discharge current as 5C.

Besides, coating LFP with inorganic oxides can make LFP’s structure more stable and increase conductivity. Traditional LiCoO₂ with oxide coating shows improved cycling performance. This coating also inhibits dissolution of Co and slows the decay of LiCoO₂ capacity. Similarly, LiMPO₄ with inorganic coating, such as ZnO and ZrO₂, has a better cycling lifetime, larger capacity and better characteristics under the condition of a large discharge current. The addition of a conductive carbon in LiMPO₄ increases the efficiency of LiMPO₄, too. Mitsui Zosen Japan and Aleees reported that addition of other conducting metal particles, such as copper and silver, also increased LiMPO₄’s efficiency. LiMPO₄ with 1 wt. % of metal additives has a reversible capacity up to 140mAh/g and better characteristics under the condition of large discharge current.