High Rate, Superior Capacity Retention LiMn_(2-2y)Li_yNi_yO_4 Spinel Cathodes for Lithium-Ion Batteries

摘要

LiMn_(2-2y)Li_yNi_yO_4 (0.05 <= y <= 0.1) cathodes synthesized by solid-state reactions at 800 deg C exhibit superior capacity retention and rate capability both at room temperature and 60 deg C compared to the LiMn_2O_4 cathodes. For example, the y = 0.05, 0.075, and 0.1 samples exhibit little capacity fades of, respectively, 3.2, 0.9, and 0.5 percent at room temperature and 7.4, 2.6, and 2.4 percent at 60 deg C in 50 cycles with initial capacities of around 90-115 mAh/g compared to around 40-50 percent fade for LiMn_2O_4. The y = 0.075 and 0.1 samples retain 98 percent of their capacity ongoing from C/10 to 4C rate with excellent cycling performance at 4C rate as well. The superior performances of these cathodes are attributed to the smaller lattice parameter differences between the two cubic phases formed during the discharge/charge process. The low cost and environmentally benign nature of these cathodes coupled with the high rate capability may make them attractive for electric vehicles despite slightly lower capacity values.