High electrochemical performance of nanocrystallized carbon-coated LiFePO 4 modified by tris(pentafluorophenyl) borane as a cathode material for lithium-ion batteries.

Tris(pentafluorophenyl) borane (C 18 BF 15 ) was first adopted as a boron source, which clearly demonstrated its modification effects. XPS and EDX mapping proved that boron can be successfully doped into a carbon layer. The high number of defects in the carbon induced by boron was demonstrated via Raman spectroscopy and thus, the electric conductivity of LiFePO 4 was greatly enhanced. The boron-doped composite possessed a higher specific discharge capacity and rate capability than the undoped sample. For instance, the reversible specific capacity for the boron-doped cathode reached 165.8 mA h g -1 at 0.5C, which was almost close to its theoretical capacity (166 mA h g -1 ). Even at a high rate of 5C, it still possessed a high specific capacity of 124.8 mA h g -1 . This provides for the possibility that boron-doped carbon-coated LiFePO 4 cathodes may deliver high energy and power density for rechargeable lithium-ion batteries.