The promising P2-layered sodium manganese oxide (Na_2/3MnO₂) cathode often suffers from multiple structural transformations due to the Jahn–Teller distortion induced by Mn³⁺, hence the rapid capacity falloff. Other than many previous studies on partial substitution of Mn by low valence ions, here we have introduced vacancies into Mn sites in P2-Na_2/3MnO₂ (e.g., Na_2/3[□_1/6Mn_5/6]O₂, where □=vacancy) to oxidize Mn close to Mn⁴⁺. Combined experimental and theoretical studies reveal that such vacancy introduction overcomes the detrimental structural distortion due to irreversible phase transitions to O2 and OP4 and triggers oxygen redox activated by an orphaned O 2p state around Mn vacancies in addition to the conventional cationic redox. P2-Na_2/3[□_1/6Mn_5/6]O₂ shows smooth and continuous charge/discharge curves indicative of restrained phase transitions, leading to much superior cycling stability than the Jahn-Teller distorted pristine counterpart. This study demonstrates the critical role of transition-metal vacancies in triggering the anionic redox reaction and manipulating the phase transitions in P2-type layered cathodes.

由于 Mn ³⁺引起的 Jahn-Teller 畸变，有前景的 P2 层状钠锰氧化物 (Na _2/3 MnO ₂ ) 阴极经常遭受多次结构转变，因此容量迅速下降。除了之前许多关于用低价离子部分取代 Mn 的研究之外，我们在 P2-Na _2/3 MnO _{2 中的}Mn 位点引入了空位（例如，Na _2/3 [□ _1/6 Mn _5/6 ]O ₂ , 其中□=空位) 以氧化接近 Mn ^{4+ 的}Mn. 结合实验和理论研究表明，这种空位的引入克服了由于向 O2 和 OP4 的不可逆相变引起的有害结构畸变，并且除了常规的阳离子氧化还原外，还触发了由 Mn 空位周围的孤立 O 2p 状态激活的氧氧化还原。P2-Na _2/3 [□ _1/6 Mn _5/6 ]O ₂显示出平滑和连续的充电/放电曲线，表明相变受到限制，导致比Jahn-Teller 扭曲的原始对应物优越得多的循环稳定性。这项研究证明了过渡金属空位在触发阴离子氧化还原反应和操纵 P2 型层状阴极中的相变方面的关键作用。