Jahn-Teller distorted Mn(III) (t_2g³e_g¹) ions play a key role in the performance of manganese-based layered oxides. Here we show that there is an obvious relationship between the Jahn-Teller distortion of a trivalent manganese and the electrochemistry in a pair of Na isomer, namely orthorhombic and hexagonal P2-type Na_2/3Mn_0.9Ti_0.1O₂ having the same composition. It is found that more reversible phase transformations, higher working voltage and faster Na diffusion correlated with Jahn-Teller effect are found for distorted P′2-Na_2/3Mn_0.9Ti_0.1O₂ upon Na⁺ ions extraction/insertion. Such Jahn-Teller distorted Mn assisted Na migration enables that the orthorhombic Na_2/3Mn_0.9Ti_0.1O₂ delivers a high specific capacity of 204.0 mA h g⁻¹ with a 2.7 V average working voltage, reaching 550 Wh Kg⁻¹ with both better cycle stability (a capacity retention of 82.3% after 100 cycles) and enhanced rate capability (97.8 mA h g⁻¹ cycled at 10C) in Na cell in contrast with undistorted Na_2/3Mn_0.9Ti_0.1O₂. This strategy for understanding the Jahn-Teller effect of P2-type compounds at orbital energy level grasps new insight into designing high energy density positive electrode materials for Na-ion batteries.

Jahn-Teller变形的Mn（III）（t _2g ³ e _g ¹）离子在锰基层状氧化物的性能中起关键作用。在这里，我们表明三价锰的Jahn-Teller畸变与一对Na异构体，即具有相同组成的正交和六方P2-型Na _2/3 Mn _0.9 Ti _0.1 O ₂的电化学之间存在明显的关系。。可知更可逆相变，较高的工作电压和Jahn-Teller效应相关更快的Na扩散被发现为扭曲P'2钠_2/3的Mn _0.9的Ti _0.1 ø ₂时的Na⁺离子提取/插入。这种Jahn-Teller畸变的Mn辅助的Na迁移使斜方晶的Na _2/3 Mn _0.9 Ti _0.1 O ₂能够以2.7 V的平均工作电压提供204.0 mA h g ^-1的高比容量，两者均达到550 Wh Kg ^-1与未变形的Na _2/3 Mn _0.9 Ti _0.1 O ₂相比，Na电池具有更好的循环稳定性（在100次循环后容量保持率为82.3％）和增强的倍率能力（在10C循环下为97.8 mA hg ^-1）。。这种了解P2型化合物在轨道能级的Jahn-Teller效应的策略，为设计用于Na离子电池的高能量密度正极材料提供了新的见识。