Effect of nano LiFePO4 coating on LiMn1.5Ni0.5O4 5V cathode for lithium ion batteries

C-LiFePO4 nanoparticles were used as surface coating for the LiMn1.5Ni0.5O4 spinel. However, it is impossible to prepare LiFePO4-coated LiMn1.5Ni0.5O4 by traditional sol-gel methods in Ar. Therefore, we used a new mechano-fusion dry process that provides a simple way to obtain surface coating for battery materials. Surface elemental analyses indicate that LiFePO4 nanoparticles were not simply mixed with the LiMn1.5Ni0.5O4, but successfully coated on its surface. This new composite was tested as a cathode for Li-ion batteries. LiMn1.5Ni0.5O4 showed better capacity retention after LiFePO4 coating, especially at high rate (>10C). After 100 cycles at 1C, the capacity declined from 105 to 65 mAh g(-1) for the bare LiMn1.5Ni0.5O4. In contrast, 82 mAh g(-1) of capacity was still obtained for the LiFePO4-coated LiMn1.5Ni0.5O4 with 75% of capacity retention after 140 cycles under 1C. The results suggest that the improved performance is due to the improvement of the surface conductivity due to the carbon coated LiFePO4 covering, end the protection against reactions of LiMn1.5Ni0.5O4 with the electrolyte. (C) 2011 Elsevier B.V. All rights reserved.