A high rate Li-rich layered MNC cathode material for lithium-ion batteries

Abstract

We report a high rate Li-rich layered manganese nickel cobalt (MNC) oxide cathode material of the composition 0.5Li₂MnO₃·0.5LiMn_0.5Ni_0.35Co_0.15O₂, termed Li-rich MNC cathode material, with discharge capacities of 200, 250, and 290 mA h g⁻¹ at C, C/4 and C/20 rates, respectively, for Li-ion batteries. This high rate discharge performance combined with little capacity fade during long term cycling is unprecedented for this class of lithium ion (Li-ion) cathode materials. The exceptional electrochemistry of the Li-rich MNC in Li-ion cells is attributed to its open porous morphology and high electronic conductivity. The structure of the material investigated by means of X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Absorption Spectroscopy (XAS) combined with electrochemical data revealed that the porous morphology was effective in allowing electrolyte penetration through the particle grains in tandem with its high electronic conductivity to provide high Li⁺ transport for high rate discharge. Extended cycling behavior and structural phase transition of the new material were further examined through Field Emission Scanning Electron Microscopy (FESEM), XRD, XAS and HRTEM. The new Li-rich MNC cathode material could provide the next generation Li-ion batteries with specific energy exceeding 400 W h kg⁻¹ or energy density over 1000 W h l⁻¹.