One-step calcination reaction to synthesize Li2MnO3 coating layers for LiNi0.8Co0.1Mn0.1O2 to improve cycling performances under high-voltage for Li-ion batteries

Poor cycling performances restrict the large-scale application of Ni-rich LiNixCoyMnzO2 (x + y + z = 1, x >= 0.6) cathode materials, especially during high cut-off voltage cycling. Surface modification is proposed as a feasible method to improve the electrochemical performances for Ni-rich cathode materials. However, traditional coating method is defective for final products. Here, we propose an innovative strategy to synthesize coating layers on the surface of Ni-rich cathode materials by one-step calcination, for example, Li2MnO3 layer is coating on the surface of LiNi0.8Co0.1Mn0.1O2, and invest the optimum ratio of the coating layers to the materials. A diversity of characterization methods demonstrated the existence of Li2MnO3 on the surface of LiNi0.8Co0.1Mn0.1O2. The LiNi0.8Co0.1Mn0.1O2 with 5 % (mole ratio) Li2MnO3 coating layers exhibits much enhanced cycling performance when compared with the bare material. When charge-discharged at 1C (200 mA g-1) in the voltage range of 2.8-4.6 V, it delivers 169.6 mAh g-1 at the 100th cycling with capacity retention of 90.6%, whereas the bare material shows capacity retention of 81.1%. The enhanced electrochemical performance of the materials should be attributed to the Li2MnO3 coating layers, which not only protect the active cathode material from the electrolyte, but also suppress the phase transition of the materials from H2 to H3.