Enhancing high rate performance and cyclability of LiFePO4 cathode materials for lithium ion batteries by boron doping

Abstract

The application of olivine-type LiFePO4 as cathode material for lithium-ion batteries is hampered by its low electronic conductivity and slow lithium-ion diffusion coefficient. To settle these problems, many efforts focus on cation substitution on Li or Fe-site. Here, we fabricated boron doped LiFePO4 on P-site, LiFeP1−xBxO4-δ/C (x = 0, 0.01, 0.02, 0.04), via a normal solvothermal routine. In this work, the proper amounts adding of B can refine crystal size, improve dispersity, decrease charge transfer resistance, increase electronic conductivity, enhance the mobility of lithium ions, so as to modify its cycling and rate capability. For this reason, the LiFeP0.98B0.02O4-δ/C shows the excellent electrochemical performance among all investigated samples, which delivers the first discharge capacity of 138 mAh g−1 at 2 C with no evident capacity fading after 300 cycles. Even at 10C, it still reveals a high discharge capacity of 110 mAh g−1. It is also found that the excessive doping of B could lead to oxygen defects in the material, resulting in the decrease of active lithium and unfavorable electrochemical property. Our work not only states the significance of B doping with different contents, but also provides a promising opportunity to design of cathode materials with superior performance.