Surface modification of Li(Li0.17Ni0.2Co0.05Mn0.58)O2 with LiAlSiO4 fast ion conductor as cathode material for Li-ion batteries

Li-rich layered oxides are of great potential to promote the development of cathode materials for Li-ion batteries. In this work, the Li-rich layered Li(Li0.17Ni0.2Co0.05Mn0.58)O-2 (LNCMO) oxides are synthesized by a co-precipitation method followed by a solid-state reaction. Amorphous LiAlSiO4 (LAS) material is used to modify the LNCMO material via a sol-gel method. The structure and morphology of pristine and LAS-coated materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Infrared radiation (IR) and X-ray photoelectron spectroscopy (XPS) detection confirm the existence of LAS. All the peaks in XPS standing for Co2p, Ni2p and Mn2p move slightly to higher binding energy after coating with LAS, implying the activation of the cathode materials surface layer by LAS. The sample modified with optimized amount (2 wt.%) of LAS presents obviously improved initial coulombic efficiency, cyclic capacity, high rate performance and cycle stability. It can deliver high discharge capacity of 173.3 mAh g(-1) at 5 C rate with a capacity retention of 84.59% after 200 cycles which is much higher than that (147.6 mAh g(-1), 79.13% after 100 cycles) of the pristine material. The LAS-coated samples also present superior thermal stability proved by differential scanning calorimetry (DSC). The improvement of the electrochemical performance and thermal stability are attributed to the LAS amorphous coating films that can remarkably inhibit the change of the structure, activate the cathode and offer the fast Li-ion diffusion pathways. (C) 2015 Elsevier Ltd. All rights reserved.