High structural stability of graphene coated nickel – rich cathode material in Li – ion battery

Abstract

The high energy density cathode material, nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (LNCM), has been extensively researched for its potential applications. Nevertheless, its structural instability, weak conductivity and unsafe properties greatly impede its further development. To address these issues, the method of surface coating by graphene and element doping by Mg atom for LNCM is proposed, and its structural and electrochemical properties, as well as the promoting mechanism are comprehensively studied. Such as, the structural and morphological features are investigated by X– ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) coupled with energy dispersive X – ray spectroscopy (EDX) and transmission electron microscopy (TEM). Characterization techniques depict the composites’ dimension, modified construction and components. Electrochemical performances are studied using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge – discharge test. The typical redox peaks of Ni2+/Ni4+ and Co3+/Co4+ are well-defined for LNCM@rGM, and its improved electrochemical performance compared to LNCM are demonstrated. Specifically, LNCM@rGM exhibits a higher capacity retention of 58%, maintaining a capacity of 123.3 mAh g−1 after the 200th cycle, from an initial value of 211.0 mAh g−1. Additionally, LNCM@rGM shows a higher rate capability of 80.2 mAh g−1 at 5 C, as well as improved Li+ diffusion and higher exchange current density. The findings indicate that the composite structure consisting of graphene coating and element doping shows improved electrochemical performance when exposed to an optimal heating temperature, resulting in enhanced structural stability, elevated ionic/electronic conductivity, and synergistic effects on the materials.