Nitrogen-doped carbon coated LiNi0.6Co0.2Mn0.2O2 cathode with enhanced electrochemical performance for Li-Ion batteries

Abstract

LiNi0.6Co0.2Mn0.2O2 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 LiNi0.6Co0.2Mn0.2O2 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 LiNi0.6Co0.2Mn0.2O2 particles. It has been proved beneficial to stabilize the layered structure of the LiNi0.6Co0.2Mn0.2O2 with less cation disorder and residual lithium at the surface. The nitrogen-doped carbon-coated LiNi0.6Co0.2Mn0.2O2 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 LiNi0.6Co0.2Mn0.2O2 in this work and most other reported LiNi0.6Co0.2Mn0.2O2 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.