A novel coating strategy for graphene-modified Li1.2Mn0.54Ni0.13Co0.13O2 as cathode material for LIBs

In this study, reduced graphene oxide (RGO) coated Li1.2Mn0.54Co0.13Ni0.13O2 (RGO@LMNCO) materials with different amounts of RGO were synthesized using a facile hydrothermal method. The double electron layer on the graphene surface was opened by adding a certain amount of electrolyte（NaCl）to the solution to increase the activity of the graphene, thus contributing to the uniform dispersion of the nano-cathode material on the RGO and reducing the secondary agglomeration. The physical characterization and electrochemical test results confirmed that LMNCO material with 2 wt% RGO (2 wt%RGO@LMNCO) was most uniformly dispersed on RGO and exhibited the optimal overall electrochemical performance. The above result suggested that this strategy can be more conductive to exerting the superiority of RGO coating. RGO coating enhanced electronic and ionic conductivity while modifying the potential energy surface of LMNCO effectively and suppressing surface oxygen loss. Subsequently, it can be beneficial to avoid side reactions between the cathode material surface and the electrolyte. As a result, the surface stability of cathode materials was increased. The 2 wt%RGO@LMNCO electrode exhibited a maximum capacity of 308.7mAh g−1 at 0.2 C. With the increase of the charge/discharge current rate from 0.2 C to 10 C, it still reached 112.3mAh g−1. After 50 cycles at 0.2 C rate, the discharge capacity was decreased from 287.5 to 284.8 mAh·g−1, thus maintaining a capacity retention of 99.06%. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to analyze the synthesized sample. The main reason for enhanced electrochemical performance is that the RGO-LMNCO synthesized by the novel coating strategy, which can more effectively exert the modulation effect of graphene on the cathode material surface, exhibits better dispersion and uniform coating.