Towards understanding the rate capability of layered transition metal oxides LiNiyMnyCo1−2yO2

This work attempts to understand the rate capability of layered transition metal oxides LiNiyMnyCo1−2yO2 (0.33 ≤ y ≤ 0.5). The rate capability of LiNiyMnyCo1−2yO2 increase with increasing Co in the compounds and with increasing amount of carbon additives in the electrodes. The lithium diffusion coefficients and electronic conductivities of LixNiyMnyCo1−2yO2 are investigated and compared. The 333 compound has higher diffusivity and electronic conductivity and thus better rate performance than 550. Chemical diffusion coefficients for both delithiation and lithiation of LixNiyMnyCo1−2yO2 investigated by GITT and PITT experiments are calculated to be around 10−10 cm2 s−1, lower than that of LixCoO2. The electronic conductivity of LixNiyMnyCo1−2yO2 is inferior compared to LixCoO2 at same temperature and delithiation stage. However, the LixNiyMnyCo1−2yO2 are able to deliver 55%–80% of theoretical capacity at 5 C with good electronic wiring in the composite electrode that make them very promising candidates for electric propulsion in terms of rate capability.