Tuning of Ni, Mn, and Co (NMC) Content in 0.4(LiNi_xMn_yCo_zO₂)·0.4(Li₂MnO₃) toward Stable High-Capacity Lithium-Rich Cathode Materials

Li-rich cathode materials can offer a high specific capacity of ≥250 mA h g–1; however, the major issues are their structural instability, capacity degradation, and voltage decay upon prolonged cycling. Herein, we have shown that an increase in Ni content with a concomitant reduction in Mn and Co content in Li-rich cathode materials can help to alleviate structural and electrochemical instability to a considerable extent. In this regard, we have carried out a systematic investigation of tuning the Ni, Mn, and Co (NMC) content in the Li-rich phase, Li1.2(NixMnyCoz)O2 (where x + y + z = 0.8). In the composite notion, these Li-rich phases can also be written as 0.4(LiNixMnyCozO2)·0.4(Li2MnO3), where the layered oxide components LiNixMnyCozO2 (x + y + z = 1) are generally termed as NMC-333, NMC-442, NMC-532, NMC-622, and NMC-811, depending upon the concentration of metal constituents. The electrochemical studies reveal that the higher Ni-containing phase 0.4(LiNi0.8Mn0.1Co0.1O2)·0.4(Li2MnO3) or Li1.2Ni0.32Co0.04Mn0.44O2 shows the least voltage decay of about 0.4 V and a higher capacity retention of 85% after 100 cycles compared to those of the low Ni-containing composition 0.4(LiNi0.33Mn0.33Co0.33O2)·0.4(Li2MnO3) or Li1.2Ni0.13Co0.13Mn0.54O2, which shows a higher voltage decay of 1.0 V with a 69% capacity retention after 100 cycles at a 0.2 C rate.