LiNi_(0.5)Mn_(1.5)O_(3.975)F_(0.05) as novel 5 V cathode material

摘要

LiNi_(0.5)Mn_(1.5)O_4 obtained by sol-gel method often shows low capacity and 4 V discharge plateau due to the small amount of Mn~(3+) and impurity phases. In this study, fluorine-doped spinel with nominal composition of LiNi_(0.5)Mn_(1.5)O_(3.975)F_(0.05) was prepared using sol-gel technique and re-annealing in oxygen. XRD measurements reveal that fluorine doping can suppress the formation of NiO impurity. The electrochemical performance of LiNi_(0.5)Mn_(1.5)O_(3.975)F_(0.05) as cathode material for lithium-ion batteries was examined. Comparing with LiNi_(0.5)Mn_(1.5)O_4, fluorine doping enhances the initial capacity from about 130 mAhg~(-1) to over 140 mAh g~(-1) between 3.5 and 5.2 V and simultaneously reduces the voltage polarization. About 95% capacity is retained after 40 cycles. By followed re-annealing in oxygen, the 4 V plateau can be obviously restrained.