Graphene@TiO2 co-modified LiNi0.6Co0.2Mn0.2O2 cathode materials with enhanced electrochemical performance under harsh conditions

Abstract

The electrochemical properties of LiNi0.6Co0.2Mn0.2O2, such as cycling stability, rate capacity and coulomb efficiency, are not fairly well at large rate, high cutoff voltage and elevated temperature. In this article, a uniform nanoscale graphene@TiO2 coating layer is skillfully formed on the surface of LiNi0.6Co0.2Mn0.2O2 via an artful sol-gel-based method. The rGO@TiO2 layer is evidenced by a series of detections, and the structures of the pristine and coated materials are investigated in detail. It indicates that the graphene@TiO2 layer with a thickness of ∼2 nm is uniformly covered on the LiNi0.6Co0.2Mn0.2O2 particles. The “synergistic effects” of graphene@TiO2 composite plays an important role in improving the comprehensive electrochemical performances of the cathode material. Compared with the pristine material, the graphene@TiO2 co-modified LiNi0.6Co0.2Mn0.2O2 shows enhanced electrochemical performances at large rate, elevated temperature, and high cutoff voltage. Particularly, it displays capacity retentions of 93.7% and 89.2% after 150 cycles at 1 C and 2 C, respectively, over 3.0–4.5 V. Even at high temperature of 55 °C and upper operating voltage of 4.5 V, the capacity retention of graphene@TiO2-coated sample increases almost 50% compared with the pristine sample after 150 cycles.