Influence of lithium content on high rate cycleability of layered Li1+xNi0.30Co0.30Mn0.40O2 cathodes for high power lithium-ion batteries

Layered Li_1+xNi_0.30Co_0.30Mn_0.40O₂ (x = 0, 0.05, 0.10, 0.15) materials have been synthesized using citric acid assisted sol-gel method. The materials with excess lithium showed distinct differences in the structure and the charge and discharge characteristics. The rate capability tests were performed and compared on Li_1+xNi_0.30Co_0.30Mn_0.40O₂ (x = 0, 0.05, 0.10, 0.15) cathode materials. Among these materials, Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ cathode demonstrated higher discharge capacity than that of the other cathodes. Upon extended cycling at 1C and 8C, Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ showed better capacity retention when compared to other materials with different lithium content. Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ exhibited 93 and 90% capacity retention where as Li_1.05Ni_0.30Co_0.30Mn_0.40O₂, Li_1.15Ni_0.30Co_0.30Mn_0.40O₂, and Li_1.00Ni_0.30Co_0.30Mn_0.40O₂ exhibited only 84, 71, and 63% (at 1C), and 79, 66 and 40% (at 10C) capacity retention, respectively, after 40 cycles. The enhanced high rate cycleability of Li_1.10Ni_0.30Co_0.30Mn_0.40O₂ cathode is attributed to the improved structural stability due to the formation of appropriate amount of Li₂MnO₃-like domains in the transition metal layer and decreased Li/Ni disorder (i.e., Ni content in the Li layer).