CNT-embedded LiMn0.8Fe0.2PO4/C microsphere cathode with high rate capability and cycling stability for lithium ion batteries

A solid solution of LiMn0.8Fe0.2PO4/Carbon composite has been successfully synthesized by introducing carbon nanotubes (CNT) into the microspheres with porous structure during the spray drying and calcination process. The micro-spherical CNT-embedded LiMn0.8Fe0.2PO4/C composite delivers the features of high voltage, high rate, and cycling stability, which are urgently needed for the development of commercial lithium ion batteries. Benefiting from the subtle porous structure with a moderate specific area, the micro-spherical LiMn0.8Fe0.2PO4/C samples without CNT material exhibits a high reversible capacity (162 mAh g−1 at 0.1 C) and good rate performance. CNT, embedded in the microspheres and entangling with the primary particles, can enhance an interconnected conducting network and optimize the electron transport pathways, resulting in improved lithium ion diffusion coefficient. Therefore, the increased rate capability and cycling performance are obtained. When charged and discharged at 20 C, the composite of LiMn0.8Fe0.2PO4/C microspheres with only 0.5 wt% CNT embedded, still exhibits an obviously higher capacity (128.7 mAh g−1) than those without CNT (120.8 mAh g−1). It also delivers a higher capacity retention of 91.6% up to 500 cycles at 5 C, showing excellent long-term cycle life. Tested in full batteries with Li4Ti5O12 as anode, the CNT-embedded LiMn0.8Fe0.2PO4/C microspheres have shown its promising potential in practice.