Effects of Cl doping on the structural and electrochemical properties of high voltage LiMn_(1.5)Ni_(0.5)O_4 cathode materials for Li-ion batteries

摘要

LiMn_(1.5)Ni_(0.5)O_4 and LiMn_(1.5)Ni_(0.5)O_(3.9)Cl_(0.1) are prepared by a solution-based process to investigate the influences of Cl doping on the structural and electrochemical properties of high voltage LiMn_(1.5)Ni_(0.5)O_4 cathode materials for Li-ion batteries. LiMn_(1.5)Ni_(0.5)O_(3.9)Cl_(0.1) features an improved cyclic performance at 30 °C and 55 °C compared with LiMn_(1.5)Ni_(0.5)O_4, which originates from the enhanced structural stability by formation of strong Mn-Cl and Ni-Cl bonds revealed by XPS analysis. The improvement in the rate capability of LiMn_(1.5)Ni_(0.5)O_(3.9)Cl_(0.1) is attributed to the facilitated Li-ion diffusion in the lattice, due primarily to the larger ionic radius of Cl than that of 0. From the GITT analysis, it is revealed that the Li-ion diffusivity of LiMn_(1.5)Ni_(0.5)O_(3.9)Cl_(0.1) is improved about 2 times compared with that of LiMn_(1.5)Ni_(0.5)O_4. The improved Li-ion diffusivity in the lattice is assigned to the increase in the lattice constant of LiMn_(1.5)Ni_(0.5)O_(3.9)Cl_(0.1) compared with that of LiMn_(1.5)Ni_(0.5)O_4 by the doping of Cl.