PNNL

Abstract

High energy density nickel (Ni)-rich layered LiNixMnyCozO2 (NMC, x = 0.6) materials are promising cathodes for lithium-ion batteries. However, several technical challenges, such as fast capacity fading, are hampering their large scale application. Herein, we demonstrate that a Ni-rich cathode LiNi0.76Mn0.14Co0.10O2 (NMC76) calcined at an optimal temperature of 750~775oC exhibits a high discharge capacity (~215 mAh g-1 when charged to 4.5 V) and an excellent high rate capability. Even at a 10C rate, it still exhibits a capacity of more than 160 mAh g-1 and retains ca. 79% of its initial capacity after 200 cycles. The high performance of NMC76 is directly related to its optimized primary particle size (that constitute the spherical secondary particles of >10 m) and cation mixing. Higher calcination temperature (= 800 oC) leads to rapid increase of primary particle size, poor cycling stability, and inferior rate capability of NMC76 due to its severe micro strain and crack formation upon repeated lithium ion de/intercalations. Therefore, NMC76 calcined at 750~775oC is a very good candidate for the next generation of Li ion batteries.