O3-type layered oxide cathode material for sodium-ion batteries (SIBs) has attracted much attention as one of the most viable candidates due to its high specific capacity and mature synthesis process, while the moisture sensitivity and harmful phase transformation lead to poor processing properties and unsatisfactory life-span, hindering its large-scale and commercial application. Herein, single crystallization strategy is adopted to enhance air stability and processing performance, and surface structure reconstruction for single crystalline cathode material O3-NaNi1/3Fe1/3Mn1/3O2 by ammonium tetraborate pretreatment is employed to further remove residual alkali and improve sodium ions diffusion dynamics and suppress heterogeneous phase transformation, achieving superior structure stability. Surface residual alkali is in-situ converted into a protective coating layer of Na2B4O7 and meanwhile partial B atoms enter into the interstitial site of sub-surface or near surface, which accelerates sodium ions transport as well as enhances TM-O bonding and hybridization of surface O (2p)-Fe (3d-t2g) orbital, inhibits TMO6 slabs gliding and strengthens structure on the surface and near surface. Additionally, the formed boron-rich surface exhibits high stability, effectively alleviating structural degradation from surface to bulk and enhancing air stability. Benefiting from the reconstructed surface structure, the modified single crystalline oxides (NFM@B) exhibit distinguished processing performance and electrochemical properties.

中文翻译：

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表面结构重构抑制空气稳定单晶 O3 型氧化钠的异相转变


钠离子电池 （SIBs） 用 O3 型层状氧化物正极材料因其高比容量和成熟的合成工艺而成为最可行的候选材料之一，而湿敏性和有害相变导致加工性能差和寿命不理想，阻碍了其大规模和商业应用。本文采用单结晶策略来提高空气稳定性和加工性能，采用四硼酸铵预处理对单晶正极材料 O3-NaNi1/3Fe1/3Mn1/3O2 进行表面结构重构，以进一步去除残余碱，改善钠离子扩散动力学，抑制非均相相变，实现优异的结构稳定性。表面残余碱原位转化为 Na2B4O7 的保护涂层，同时部分 B 原子进入亚表面或近表面的间隙位点，加速钠离子传输，增强 TM-O 键合和表面 O （2p）-Fe （3d-t2g） 轨道的杂化，抑制 TMO6 板基滑动并增强表面和近表面的结构。此外，形成的富硼表面表现出高稳定性，有效缓解了从表面到本体的结构降解，增强了空气稳定性。得益于重构的表面结构，改性的单晶氧化物 （NFM@B） 表现出优异的加工性能和电化学性能。