The P2-structured sodium transition metal oxides suffer from an irreversible phase transition to OP4, which results in the -1.3 Å shrinking of lattice c and locks the following electrochemical cycles between OP4 and P2’, seriously aggravating the cracking of cathode materials. Therefore, strategies to suppress the phase transition from P2 to OP4 are currently pursued to alleviate the destructively volumetric changes. Here, the DFT calculations reveal that the transition to OP4 phase is not driven by thermodynamical mechanism but is induced by structural defects. To verify this prediction, an in-situ formed NiF₂ layer via electrolyte additives is coated on the P2-structured Na_0.67Ni_0.1Co_0.1Mn_0.8O₂ during initial charging, which mitigates the generation of structural defects from the side reaction of electrolyte with active sites of cathode particles. The sample protected with NiF₂ layer presents a continuous, moderate and reversible structural evolution, free from phase P2’. Therefore, the coated sample delivers 230.1 mAh/g at 0.1C and retains 83.4% capacity at 0.5C after 150 cycles, significantly higher than the values, 174.5 mAh/g and 63.4%, respectively, of the pristine materials. This work demonstrates the severe phase transition in P2-type cathode can be effectively alleviated by a simple surface modification.

P2结构的钠过渡金属氧化物发生向OP4的不可逆相变，导致晶格c收缩-1.3Å ，并锁定OP4和P2'之间的后续电化学循环，严重加剧正极材料的开裂。因此，目前正在寻求抑制从 P2 到 OP4 的相变的策略，以减轻破坏性的体积变化。在这里，DFT 计算表明向 OP4 相的转变不是由热力学机制驱动的，而是由结构缺陷引起的。为了验证这一预测，将通过电解质添加剂原位形成的 NiF ₂层涂覆在 P2 结构的 Na _0.67 Ni _0.1 Co _0.1上Mn _0.8 O ₂在初始充电期间，这减轻了电解质与正极颗粒活性位点的副反应产生的结构缺陷。_{用NiF 2}层保护的样品呈现连续、适度和可逆的结构演化，没有相P2'。因此，涂层样品在 0.1C 下提供 230.1 mAh/g，并在 150 次循环后在 0.5C 下保持 83.4% 的容量，显着高于原始材料的值，分别为 174.5 mAh/g 和 63.4%。这项工作证明了 P2 型正极的严重相变可以通过简单的表面改性得到有效缓解。