Abstract The layered-transition-metal oxides NaxMO2 (M = Mn, Co, V, etc.) has been widely recognized as a sodium-storage electrode material for Faradaic deionization. However, the relatively low desalination capacity caused by the poor conductivity makes it still inadequate for the high performing requirements. Herein, Zn-doped NaxCoO2 has been developed for the enhanced capacitive deionization (CDI) properties. The partial Co3+ substituted by Zn2+ can induce the appearance of electronic holes and effectively improve the electrical conductivity, which consequently is beneficial to the enhancement of the desalination performance. Compared with the pristine material, the capacity retention of Na0.71Co0.99Zn0.01O2 improved from 88.6% to 98.3% over 50 cycles, indicating that the inactive Zn2+ ions can also prevent the irreversible interlayer-gliding from alleviating the structure destruction. Additionally, in situ Raman was employed for the first time to investigate the mechanism, demonstrating that Na+ ions were reversibly inserted/extracted into/out of interlayers, along with c-axis length decreased and expanded back completely.

中文翻译：

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原子取代基对提高Zn掺杂NaxCoO2脱盐性能的影响

摘要 层状过渡金属氧化物 NaxMO2（M = Mn、Co、V 等）已被广泛认为是用于法拉第去离子的储钠电极材料。然而，由于导电性差导致的相对较低的脱盐能力使其仍然不足以满足高性能要求。在此，Zn 掺杂的 NaxCoO2 已被开发用于增强电容去离子 (CDI) 特性。部分Co3+被Zn2+取代可以诱导电子空穴的出现，有效提高电导率，从而有利于提高脱盐性能。与原始材料相比，Na0.71Co0.99Zn0.01O2 的容量保持率在 50 次循环后从 88.6% 提高到 98.3%，表明非活性的 Zn2+ 离子也可以防止不可逆的层间滑移减轻结构破坏。此外，首次采用原位拉曼来研究其机理，证明 Na+ 离子可逆地插入/提取到/离开夹层，同时 c 轴长度减少并完全向后扩展。