P2-type Ni-Mn-based Na-layered cathodes suffer from severely large structural changes, such as the direct P2-O2 phase transition, occurring during charging to the high voltage region, resulting in the poor power-capability with large overpotential, as well as the diminished cycle-performance. In this study, through a combination of first-principles calculations and various experiments, we demonstrate that enhanced structural flexibility through Co-Al co-substitution provides smooth and continuous structural changes in the P2-type Ni-Mn-based Na-layered cathode without the direct phase transition, enabling the highly improved electrochemical performances. P2-type Na0.67[Ni0.35Co0.1Mn0.5Al0.05]O2 delivers a high discharge capacity of approximately ∼156.31 mAh g−1 and an energy density of ∼551.71 Wh kg−1 at 10 mA g−1, outperforming P2-type Na0.67[Ni0.35Mn0.65]O2. These performance differences are especially pronounced during fast charging/discharging process, highlighting the enhanced power-capability and Na+ diffusion kinetics due to improved structural flexibility. Moreover, smooth and continuous structural changes enable improved cycle performance, including reduced voltage decay during prolonged cycling, for P2-type Na0.67[Ni0.35Co0.1Mn0.5Al0.05]O2. These results highlight that introducing structural flexibility is one of the most efficient ways to enhance power-capability and fast-charging/discharging performance in P2-type Ni-Mn-based Na-layered cathodes, while also improving cyclability.

中文翻译：

---

增强 P2 型 Ni-Mn 基 Na 层阴极的结构灵活性，以实现高功率能力和快速充电/放电性能


P2 型 Ni-Mn 基 Na 层状阴极在充电到高压区时发生严重较大的结构变化，例如直接的 P2-O2 相变，导致功率能力差，过电位大，循环性能降低。在这项研究中，通过第一性原理计算和各种实验的结合，我们证明了通过 Co-Al 共取代增强结构柔韧性，可在 P2 型 Ni-Mn 基 Na 层状阴极中实现平滑和连续的结构变化，而无需直接相变，从而大大改善电化学性能。P2 型 Na0.67[Ni0.35Co0.1Mn0.5Al0.05]O2 在 10 mA g-1 时提供约 ∼156.31 mAh g-1 的高放电容量和 ∼551.71 Wh kg-1 的能量密度，优于 P2 型 Na0.67[Ni0.35Mn0.65]O2。这些性能差异在快速充电/放电过程中尤为明显，由于结构柔韧性的提高，突出了增强的功率能力和 Na+ 扩散动力学。此外，平滑和持续的结构变化可以提高 P2 型 Na0.67[Ni0.35Co0.1Mn0.5Al0.05]O2 的循环性能，包括减少长时间循环期间的电压衰减。这些结果强调，引入结构柔性是提高 P2 型 Ni-Mn 基 Na 层阴极的功率能力和快速充电/放电性能的最有效方法之一，同时还可以提高循环性。