Influence of Ru substitution on Li-rich 0.55Li 2MnO 3·0.45LiNi 1/3Co 1/3Mn 1/3O 2 cathode for Li-ion batteries

Abstract

Li-rich cathode 0.55Li 2MnO 3·0.45LiNi 1/3Co 1/3Mn 1/3O 2 or written in a solid solution form Li(Li 0.20Mn 0.54Ni 0.13Co 0.13)O 2 doped with trace Ru is synthesized using a traditional co-precipitation method. The structural and morphological characterizations are carried out by employing inductively coupled plasma emission spectrometry (ICP), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Ru doping causes variation of lattice constants in both Li 2MnO 3 and LiNi 1/3Co 1/3Mn 1/3O 2 components according to the results of Rietveld refinement. Electrochemical measurement shows that Li(Li 0.19Mn 0.54Ni 0.13Co 0.12Ru 0.01)O 2 possesses the best performance, especially at high rate. A discharge capacity as high as 182 mAh g -1 at a current density of 500 mA g -1 (2 C) is achieved with a capacity fade of as low as 0.06% per cycle in the following 700 cycles. Such improvement is associated with the prominent appearance of spinel-like regions transferred from the original Li 2MnO 3 component in which Ru facilitates the phase transformation via enhancing the ability of Li diffusion in both Li 2MnO 3 and LiNi 1/3Co 1/3Mn 1/3O 2 components. The improvement in Li diffusion is also confirmed from the electrochemical impedance spectroscopy (EIS) analysis. © 2012 Elsevier Ltd.