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The dual-site doping method combines three-fold benefits to enhance LiNi 0.9 Co 0.1 O 2 stability. [Display omitted] • A new Mg/Ta dual-site doping strategy was proposed for high-nickel LiNi 0.9 Co 0.1 O 2. • Mg2+ and Ta5+ ions reside in the 3a and 3b crystallographic sites respectively. • Mg2+ ions prevent Li+/Ni2+ anti-site exchange and inhibit detrimental phase transition. • Ta5+ ions expand layer spacing and induce LiTaO 3 surface coating and well-ordered structure. • The dual-site doping method combines three-fold benefits to enhance LiNi 0.9 Co 0.1 O 2 stability. 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+/Ni2+ 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 Mg2+ was doped in situ during the synthesis of cathode precursor, while Ta5+ ions were incorporated after the precursor synthesis. This novel synthesis approach leads to unique dual-site occupations of Mg2+ and Ta5+ in the 3a and 3b crystallographic sites respectively. The Mg2+ ions residing in 3a site can function as pillar ions by preventing the Li+/Ni2+ anti-site exchange and inhibiting layered to rock-salt phase transition. The Ta5+ 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. [ABSTRACT FROM AUTHOR]