The effect of Ni oxidation state on the crystal structure and electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode material for highly reversible lithium storage

In this work, Ni-rich layered micron-sized LiNi0.8Co0.1Mn0.1O2 (SC-NCM) single crystals were prepared by wet ball-milling and molten-salt methods. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectrometry (XPS), the differences between SC-NCM and a commercial polycrystalline micron-sized NCM material (M-NCM) were compared. An extended sintering process for SC-NCM plays a role in decreasing cationic mixing accompanied by the ordered growth of single crystals. The SC-NCM sample presents homogeneous micron-sized crystals. The Ni3+ content in SC-NCM constitutes 90.45% of the total Ni content, while the Ni3+ in M-NCM constitutes only 68.49%. The existence of Ni2+ in ternary cathode materials is harmful to electrochemical stability and cyclic stability. The initial specific discharge capacity of SC-NCM (168 mAh g(-1)) is lower than that of M-NCM (187 mAh g(-1)); however, M-NCM shows a rapid decline in capacities and voltage plateaus from the 1st to 180th cycle. After 300 cycles at a 5 C rate, M-NCM remains only 42 mAh g(-1) with a capacity retention rate of only 25.6% in comparison with SC-NCM with a remaining capacity of 80.7 mAh g(-1) and a capacity retention of 62.0%. The effect of micron-sized single crystals on electrochemical properties during redox reactions is negative in terms of conductivity but positive in terms of structural stability. (C) 2021 Elsevier B.V. All rights

Automated summary

Ni-rich LiNi0.8Co0.1Mn0.1O2 single crystals prepared by wet ball-milling and molten-salt methods exhibit superior structural and electrochemical performance compared to traditional polycrystalline materials. The single crystal samples have higher Ni3+ content and better cyclic stability, with a significantly higher capacity retention rate after 300 cycles than polycrystalline samples.