Surface nitridation of Li-rich layered Li(Li0.17Ni0.25Mn0.58)O2oxide as cathode material for lithium-ion battery

Abstract

A Li-rich layered Li(Li_0.17Ni_0.25Mn_0.58)O₂ oxide is prepared by a combination of co-precipitation and solid-state reaction. The surface nitridation is introduced into a Li-rich layered Li(Li_0.17Ni_0.25Mn_0.58)O₂ for the first time via heating at 400 °C in the ammonia atmosphere. The microstructure and morphology of the two samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is demonstrated that the nitrogen exists with a trace amount in the surface layer of the Li-rich layered Li(Li_0.17Ni_0.25Mn_0.58)O₂ oxide after the nitridation treatment. Electrochemical performances of the electrodes are measured by galvanostatic charge–discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). As expected, the discharge capacity, high-rate capability and cycle stability of the nitrided sample are improved dramatically as compared with the as-prepared sample, which is further confirmed by the high electrocatalytic activity and accelerated lithium diffusion process. Apparently, the existence of nitrogen in the surface layer is responsible for the improvement of the reaction kinetics and electrochemical performance of the nitrided sample.