Nitrogen-doped carbon coated LiNi_0.6Co_0.2Mn_0.2O₂ cathode with enhanced electrochemical performance for Li-Ion batteries

LiNi_0.6Co_0.2Mn_0.2O₂ has attracted considerable attention as a high-performance cathode material for lithium ion batteries due to its relatively high specific capacity and low cost. However, structural instability and side reactions at the surface, which occur during the charge/discharge process, largely limit its performance. Here, we introduce a nanoscale nitrogen-doped carbon layer at the surface of the LiNi_0.6Co_0.2Mn_0.2O₂ particles by using simple mechanical activation and pyrolysis methods. Systematic characterization indicates that a nitrogen-doped carbon layer approximately 16 nm thick is uniformly coated on the LiNi_0.6Co_0.2Mn_0.2O₂ particles. It has been proved beneficial to stabilize the layered structure of the LiNi_0.6Co_0.2Mn_0.2O₂ with less cation disorder and residual lithium at the surface. The nitrogen-doped carbon-coated LiNi_0.6Co_0.2Mn_0.2O₂ exhibited a capacity retention of 92% after 100 cycles from 3.0 to 4.5 V at 1 C, and a discharge capacity of 156 mAh g⁻¹ at 5 C (78% of the capacity at 0.2 C), which is superior to the pristine LiNi_0.6Co_0.2Mn_0.2O₂ in this work and most other reported LiNi_0.6Co_0.2Mn_0.2O₂ cathodes. The improved electrochemical properties of the nitrogen-doped, carbon-coated cathode can be attributed to the higher degree of cation ordering, relieved side reactions between the cathode and electrolyte, and increased electronic conductivity.