Enhanced rate performance of carbon-coated LiNi0.5Mn1.5O4 cathode material for lithium ion batteries

Conductive carbon has been coated on the surface of LiNi0.5Mn1.5O4 cathode material by the carbonization of sucrose for the purpose of improving the rate performance. The effect of carbon coating on the physical and electrochemical properties is discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), cycling and rate tests. Results demonstrate that the carbon coating can greatly enhance the discharge capacity, rate capability and cycling stability of the LiNi0.5Mn1.5O4 without degrading the spinel structure. The sample modified with 1 wt.% sucrose displays the best performance. A large capacity of 130 mAh g−1 at 1 C discharge rate with a high retention of 92% after 100 cycles and a stable 114 mAh g−1 at 5 C discharge rate can be delivered. The remarkably improved rate properties of the carbon-coated samples are due to the suppression of the solid electrolyte interfacial (SEI) layer development and faster kinetics of both the Li+ diffusion and the charge transfer reaction.

►The LiNi0.5Mn1.5O4 is modified with the carbon coating method. ► The coated carbon results in the increase of electronic conductivity. ► The electronic and ionic conductivities both contribute to the rate performance. ► The side reaction of active cathode material with electrolyte is reduced. ► The rate capability and rate cycling performance are remarkably enhanced.