In Situ Probing and Synthetic Control of Cationic Ordering in Ni-Rich Layered Oxide Cathodes

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• 作者：Jianqing Zhao ; Wei Zhang ; Ashfia Huq ; Scott T. Misture ; Boliang Zhang ; Shengmin Guo ; Lijun Wu ; Yimei Zhu ; Zonghai Chen ; Khalil Amine ; Feng Pan ; Jianming Bai and Feng Wang
• 刊名：Advanced Energy Materials
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：7
• 期：3
• 全文大小：4186K
• ISSN：1614-6840

文摘

Ni-rich layered oxides (LiNi_1–xM_xO₂; M = Co, Mn, …) are appealing alternatives to conventional LiCoO₂ as cathodes in Li-ion batteries for automobile and other large-scale applications due to their high theoretical capacity and low cost. However, preparing stoichiometric LiNi_1–xM_xO₂ with ordered layer structure and high reversible capacity, has proven difficult due to cation mixing in octahedral sites. Herein, in situ studies of synthesis reactions and the associated structural ordering in preparing LiNiO₂ and the Co-substituted variant, LiNi_0.8Co_0.2O₂, are made, to gain insights into synthetic control of the structure and electrochemical properties of Ni-rich layered oxides. Results from this study indicate a direct transformation of the intermediate from the rock salt structure into hexagonal phase, and during the process, Co substitution facilities the nucleation of a Co-rich layered phase at low temperatures and subsequent growth and stabilization of solid solution Li(Ni, Co)O₂ upon further heat treatment. Optimal conditions are identified from the in situ studies and utilized to obtain stoichiometric LiNi_0.8Co_0.2O₂ that exhibits high capacity (up to 200 mA h g⁻¹ ) with excellent retention. The findings shed light on designing high performance Ni-rich layered oxide cathodes through synthetic control of the structural ordering in the materials.