(577c) Low Cobalt NCM811 with Cobalt Gradient for Improved Structural Stability and Electrochemical Performance

Synthesis of low cobalt content LiNi_1-x-yCo_xMn_yO₂(NCM)-based cathode materials for high performance Lithium-ion batteries (LIBs) is need of this hour.^[1] Among them, Nickle-rich layered oxide, NCM811 is regarded as the future of efficient cathode material for LIBs owing to its higher specific capacity and low cost. However, the commercialization of Ni-rich cathode material is hampered due to capacity fading from Li-Ni cation mixing and safety concerns related to the uncontrolled rise in temperature.^[2] Cobalt (III) in NCM811 reduces the surface energy of the material and cationic disorder and a controlled distribution of cobalt from core to surface of the particle can improve the structural robustness of the NCM811, which further ensures the improved cycling performance of the LIBs. ^[3]

In this work, we synthesized layered NCM811 with cobalt gradient from core to the surface. A series of precursors with varying concentration of cobalt were prepared using coprecipitation method. The precursors were mixed with LiOH·H₂O (the molar ratio of Li:Ni–Co–Mn = 1.05:1) and calcinated at optimized temperature for 10 hrs. to achieve the final active material (NCM811). The electrochemical performance of synthesized full concentration gradient material with cobalt gradient was further compared with the homogeneous NCM811 in terms of specific capacity, energy density and cycling performance.

References

1. Schmuch, R., Wagner, R., Hörpel, G. et al.Performance and cost of materials for lithium-based rechargeable automotive batteries. Nat Energy 3, 2018, Pages 267–278.
2. Longshan Li, Dingming Wang, Gaojie Xu, Qian Zhou, Jun Ma, Jianjun Zhang, Aobing Du, Zili Cui, Xinhong Zhou, Guanglei Cui, Recent progress on electrolyte functional additives for protection of nickel-rich layered oxide cathode materials, Journal of Energy Chemistry, Volume 65, 2022, Pages 280-292,
3. Zhenlei Huang, Jian Gao, Xiangming He, Jianjun Li, Changyin Jiang, Well-ordered spherical LiNi_xCo_(1−2x)Mn_xO₂ cathode materials synthesized from cobolt concentration-gradient precursors, Journal of Power Sources, Volume 202, 2012, Pages 284-290