Mg/Ta dual-site doping of high-nickel layered cathode material LiNi0.9Co0.1O2 for extended cycling and thermal stability
Afei Li, Chengzhi Hu, Weijian Tang, Zhangxian Chen, Zeheng Yang, Jianhui Su, Xiaoqin Huang, Weixin Zhang
Abstract
Due to its high specific capacity and low cost, high-nickel layered oxide LiNi 0.9 Co 0.1 O 2 has found promising application as the cathode materials for lithium-ion batteries. However, the crystallographic instability induced by Li + /Ni 2+ anti-site exchange, the interfacial parasitic reactions and the microcracking caused by internal stress jointly contribute to the mechano-chemical failure of LiNi 0.9 Co 0.1 O 2 , leading to its fast capacity decay and high thermal stability concern. In this regard, a Mg/Ta dual-site doping strategy was proposed for LiNi 0.9 Co 0.1 O 2 , for which Mg 2+ was doped in situ during the synthesis of cathode precursor, while Ta 5+ ions were incorporated after the precursor synthesis. This novel synthesis approach leads to unique dual-site occupations of Mg 2+ and Ta 5+ in the 3a and 3b crystallographic sites respectively. The Mg 2+ ions residing in 3a site can function as pillar ions by preventing the Li + /Ni 2+ anti-site exchange and inhibiting layered to rock-salt phase transition. The Ta 5+ ions occupying 3b site not only leads to the expanded lithium layer spacing but also creates interfacial protection and well-ordered microstructure in LiNi 0.9 Co 0.1 O 2 . Consequently, the dual-site-doped LiNi 0.9 Co 0.1 O 2 outperforms the pristine and single-site-doped samples. For instance, its full cell shows a greatly enhanced cycling stability from 57.3 % to 90.5 % after 300 cycles at 1C/1C and well improved thermal stability from 205.2 °C to 225.6 °C, compared to the pristine sample. This Mg/Ta dual-site doping strategy provides a facile and practical way to improve the electrochemical and thermal performances of high-nickel layered cathode material LiNi 0.9 Co 0.1 O 2 .