O3-type layered oxides are considered promising cathode materials for next-generation high-energy-density sodium-ion batteries (SIBs). However, they face challenges, such as low rate capacity and poor cycling stability, which arise from structural deformation, sluggish Na⁺ diffusion kinetics, and interfacial side reactions. Herein, a synergistic substitution strategy for transitional and interstitial sites was adopted to improve the structure stability and Na⁺ diffusion kinetics of the O3-type NaNi_0.2Fe_0.4Mn_0.4O₂. Simulation results indicate that Co³⁺/B³⁺ codoping effectively lowers the Na⁺ migration energy barrier. In addition, the synergistic effect of Co³⁺/B³⁺ codoping provides ultralow lattice strain during repeated Na⁺ deintercalation/intercalation. In situ characterization verified that the complex phase transformation during charge and discharge was suppressed, thereby significantly improving the structural stability. At 1 and 3 C, the capacity retention of the modified O3–Na(Ni_0.2Fe_0.4Mn_0.4)_0.96Co_0.04B_0.02O₂ (NFMCB) improved from 29.6% and 1.7% to 86.7% and 88.6% after 200 cycles, respectively. Even at 10 C, it could still produce 107.2 mAh·g^–1. Furthermore, full cells assembled with this material and commercial hard carbon exhibit a high energy density of 316.2 Wh·kg^–1 and a capacity retention of 80.8% after 200 cycles at 1 C. It is expected that this strategy will facilitate the commercialization of O3-type layered oxides.

中文翻译：

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锚定过渡/间隙位点对提高 O3 型层状氧化钠结构和电化学稳定性的协同作用


O3 型层状氧化物被认为是下一代高能量密度钠离子电池 （SIB） 的有前途的正极材料。然而，它们面临着结构变形、Na⁺ 扩散动力学缓慢和界面副反应引起的挑战，例如低速率容量和不良循环稳定性。在此，采用了过渡位点和间隙位点的协同取代策略，以提高 O3 型 NaNi_0.2Fe_0.4Mn_0.4O₂ 的结构稳定性和 Na⁺ 扩散动力学。仿真结果表明，Co³⁺/B³⁺ 共掺杂有效降低了 Na⁺ 迁移能垒。此外，Co³⁺/B³⁺ 共掺杂的协同效应在重复的 Na⁺ 脱嵌/插层过程中提供了超低的晶格应变。原位表征验证了充电和放电过程中的复杂相变受到抑制，从而显著提高了结构稳定性。在 1 和 3 C 下，改性 O3–Na（Ni_0.2Fe_{0.4 Mn 0.4}）_0.96Co_0.04B_0.02O₂ （NFMCB） 的容量保持率在 200 次循环后分别从 29.6% 和 1.7% 提高到 86.7% 和 88.6%。即使在 10 C 下，它仍然可以产生 107.2 mAh·g^–1。此外，用这种材料和商用硬碳组装的全电池在 1 C 下循环 200 次后表现出 316.2 Wh·kg^–1 的高能量密度和 80.8% 的容量保持率。预计该策略将促进 O3 型层状氧化物的商业化。