P2-type Na_0.67Ni_0.33Mn_0.67O₂, a typical layered transition metal oxide, has been extensively studied as future practical sodium ion batteries cathode due to the merit of high energy density. However, its inferior cyclability and poor rate capability have severely hindered its practical applications. Herein, a stable P2-Na_0.67Ni_0.23Mg_0.1Mn_0.67O₂ layered cathode with simultaneously achieving magnesium doping and hierarchical one-dimensional nanostructure composed of nanoplate subunits assembly is reported. In-situ X-ray diffraction measurement and diffusion kinetics analysis reveal that Mg ion doping restrains the P2-O2 phase transition and reduces the activation energy of interfacial charge transfer. In addition, the hierarchical nanostructure is shown to possess robust structure, which raises the capacity retention from 74.8% to 92.2% over 150 cycles when compared with its bulk counterpart. Owing to the combined advantages, this unique material exhibits extraordinary electrochemical performance with a high capacity retention of 90.9% over 1000 cycles at 5C in half cell. More importantly, the full cell could achieve the highest average operating voltage of 3.56 V and outstanding energy density of 249.9 Wh kg⁻¹ compared with previously reported state-of-the-art values based on layered oxide cathodes. This work may open up a new opportunity for developing high energy SIBs with practicability.

P 2型Na _0.67 Ni _0.33 Mn _0.67 O ₂（一种典型的层状过渡金属氧化物）由于具有高能量密度的优点，已作为未来实用的钠离子电池阴极进行了广泛的研究。然而，其差的循环性和差的速率能力严重阻碍了其实际应用。在此，稳定的P2-Na _0.67 Ni _0.23 Mg _0.1 Mn _0.67 O ₂报道了同时实现镁掺杂和由纳米板亚基组装组成的分层一维纳米结构的层状阴极。X射线原位测量和扩散动力学分析表明，Mg离子掺杂抑制了P2-O2相变并降低了界面电荷转移的活化能。另外，显示出分级的纳米结构具有坚固的结构，与大量本体相比，其在150个循环中的容量保持率从74.8％提高到92.2％。由于综合的优势，这种独特的材料具有出色的电化学性能，在半电池中在5C下经过1000次循环，其高容量保持率为90.9％。更重要的是，满电池可以达到最高的平均工作电压3。^-1与先前报告的基于分层氧化物阴极的最新值相比。这项工作可能为开发具有实用性的高能SIB开辟新的机会。