Layered nickel-rich cathode material, LiNi_0.9Co_0.05Mn_0.05O₂, exhibits high specific capacity of approximately 220 mAh/g-oxide and shows attracted significant interest for use in plug-in hybrid electric vehicles owing to its high capacity and low cost. However, significant challenges remain to improve capacity retention during cycling and thermal-abuse tolerance of this material.

To improve the electrochemical performance and stability of this kind nickel-rich LiNi_xMn_yCo_zO₂ (NMC, x ≥ 0.6, x+y+z=1) cathode material for the usage in practical batteries, concentrated gradient cathode materials have been investigated. This family of materials shows the gradual decrease of nickel concentration and increase of manganese concentration from the center towards the outer layer of the particle [1-2].

Even though concentrated gradient cathode material is one of promising approaches to mitigate the capacity fade during cycling and thermal runaway of layered nickel-rich cathode materials, its working mechanism has not been fully understood yet. In this study, we explore two types of concentrated gradient cathode materials, core-shell and core-gradient, with nickel-rich LiNi_0.9Mn_0.05Co_0.05O₂ core and LiNi_0.33Mn_0.33Co_0.33O₂ surface composition which have LiNi_0.8Mn_0.1Co_0.1O₂ as overall composition. The precursors were synthesized using hydroxide co-precipitation method using a 20L batch reactor and then dried, mixed with lithium source and calcined. We report the characterized physical properties of the prepared core-shell and core-gradient materials. The detailed electrochemical performance comparison of the prepared materials with commercial NMC811 and NMC333 will be discussed.

Acknowledgement

Funding for this work from the Office of Vehicle Technologies of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, is gratefully acknowledged. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.

References

1. Y.-K. Sun, S.-T. Myung, M.H. Kim, J. Prakash and K. Amine, J. Am. Chem. Soc. 127(38), 13411 (2005).
2. U.-H. Kim, E.-J. Lee, C. S. Yoon, S.-T. Myung and Y.-K. Sun, Adv. Energy Mater. 6, 1601417 (2016)