Layered metal oxides have attracted widespread attention as cathodes for Na-ion batteries (NIBs) because of easy synthesis, high specific capacity, and high energy density. However, most reported layered oxides suffer from complex phase transitions upon a large amount of Na deintercalation. Here we report a P2-type Na_0.72[Li_0.24Mn_0.76]O₂, exhibiting exceptionally high initial charge capacity of ∼210 mAh/g (0.72 Na) based on a pure anionic redox reaction (ARR). Surprisingly, global P2 structure can be maintained with minimal volume change (1.35%) upon complete removal of Na⁺ ions. This is due to the reduced Coulombic repulsion associated with ARR and consequent suppression of the phase transition as observed in other P2 materials. Here we reveal for the first time that ARR has the functionality of stabilizing the structure, in addition to its role in increasing its already known capacity. This would pave the way for the further improvement of high-energy-density NIBs.

层状金属氧化物由于其易于合成，高比容量和高能量密度而作为钠离子电池（NIB）的阴极吸引了广泛的关注。然而，大多数报道的层状氧化物在大量的Na脱嵌时遭受复杂的相变。在这里，我们报道了一种P2型Na _0.72 [Li _0.24 Mn _0.76 ] O ₂，基于纯阴离子氧化还原反应（ARR），其初始充电容量极高，约为210 mAh / g（0.72 Na）。出乎意料的是，在完全去除Na ⁺后，可以维持最小的体积变化（1.35％）的整体P2结构离子。这是因为与其他P2材料一样，与ARR相关的库仑排斥力降低，并因此抑制了相变。在这里，我们首次揭示了ARR除了具有增加已知容量的作用之外，还具有稳定结构的功能。这将为进一步提高高能量密度的NIB铺平道路。