Improving Electrochemical Performance of High Ni Layered Materials by Adding High Valence Elements

Compared to the LiCoO₂, a high Ni layered material has been spotlighted in terms of price and capacity.[1,2] However, such a high Ni layered material suffers from poor cycle stability that can be severely affected by the cracks caused by a large volume change during the charge/discharge process because created cracks easily provide a new surface and side reactions such as the decomposition of electrolytes easily occurs especially in the surface.[3] To suppress this capacity fading, several approaches such as coating process and a doping strategy have been in progress.[4,5] Typically, a high valence metal doping significantly affects the Li/Ni disordering because the doping of high valence metal causes the reduction of Ni³⁺ to Ni ²⁺ and the increased amount of Ni²⁺ easily induces the replacement of Li+ ions in Li layer resulting in the increase in the degree of the cation-disordering. The increase in the cation disordering can improve the structural stability of the layered oxides, especially at the end of charge state while the kinetic of the Li can be decreased due to blocking of the Li channel in Li layer. [7]<br/>In this study, we simultaneously changed both bulk and surface properties of the high nickel cathode material by adding a high valence metal. To understand the improved electrochemical properties, bulk properties and surface properties of the doped material have been separately investigated with respect to the effects such as the kinetic of multiple phase transformation and polarization on the improved electrochemical performance. Furthermore, we will discuss about the meaning of these findings and understandings and the way to implement these things for further improving electrochemical performance.<br/><br/>Reference<br/>1. Kim, Youngjin, Won Mo Seong, and Arumugam Manthiram. "Cobalt-free, high-nickel layered oxide cathodes for lithium-ion batteries: Progress, challenges, and perspectives." <i>Energy Storage Materials</i> 34 (2021): 250-259.<br/>2. Li, Wangda, Evan M. Erickson, and Arumugam Manthiram. "High-nickel layered oxide cathodes for lithium-based automotive batteries." <i>Nature Energy</i> 5.1 (2020): 26-34.<br/>3. Ryu, Hoon-Hee, et al. "Capacity fading of Ni-rich Li [Ni x Co y Mn1–x–y] O2 (0.6≤ x≤ 0.95) cathodes for high-energy-density lithium-ion batteries: bulk or surface degradation?." <i>Chemistry of materials</i> 30.3 (2018): 1155-1163.<br/>4. Kim, Un-Hyuck, et al. "Heuristic solution for achieving long-term cycle stability for Ni-rich layered cathodes at full depth of discharge." <i>Nature energy</i> 5.11 (2020): 860-869.<br/>5. Yoon, Moonsu, et al. "Reactive boride infusion stabilizes Ni-rich cathodes for lithium-ion batteries." <i>Nature Energy</i> 6.4 (2021): 362-371.<br/>6. Sun, H. Hohyun, et al. "Transition metal-doped Ni-rich layered cathode materials for durable Li-ion batteries." <i>Nature communications</i> 12.1 (2021): 6552.<br/>7. Wei, Yi, et al. "Kinetics tuning of Li-ion diffusion in layered Li (Ni x Mn y Co z) O2." <i>Journal of the American Chemical Society</i> 137.26 (2015): 8364-8367.