Towards understanding the rate capability of layered transition metal oxides LiNi_yMn_yCo_1-2yO₂

This work attempts to understand the rate capability of layered transition metal oxides LiNi_yMn_yCo_1-2yO₂ (0.33 ≤ y ≤ 0.5). The rate capability of LiNi_yMn_yCo _1-2yO₂ 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 Li_xNi _yMn_yCo_1-2yO₂ 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 Li_xNi_yMn _yCo_1-2yO₂ investigated by GITT and PITT experiments are calculated to be around 10^-10 cm² s ^-1, lower than that of Li_xCoO₂. The electronic conductivity of Li_xNi_yMn_yCo _1-2yO₂ is inferior compared to Li_xCoO ₂ at same temperature and delithiation stage. However, the Li _xNi_yMn_yCo_1-2yO₂ 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.