Guo Chengran, Wang Jianqiang, Zhu Jiacheng, Wang Dongxiao, Yang Shiduo, Lyu Yingchun, Wang Xuefeng, Mao Huican, Zhu Chengjun, Xu Shuyin
Key Laboratory of Semiconductor Photovoltaic Technology and Energy Materials of Inner Mongolia, School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021, Inner Mongolia, P. R. China.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
ACS Appl Mater Interfaces. 2025 Aug 6;17(31):44440-44448. doi: 10.1021/acsami.5c08007. Epub 2025 Jul 28.
Tunnel-type NaMnO has emerged as a promising cathode material for sodium-ion batteries (SIBs) owing to its exceptional structural stability. However, its practical application is significantly constrained by the intrinsically limited movable sodium content in the pristine structure, yielding a modest initial charge capacity of merely 55 mAh g. While anionic redox reactions provide a viable pathway for capacity enhancement, which have been exclusively studied in layered oxides to date. In this work, we demonstrate the first successful implementation of highly reversible anionic redox activity in tunnel-type oxides through Ti-substituted NaMnTiO ( = 0.22, 0.33, 0.39). The optimized NaMnTiO cathode delivers an enhanced first charge capacity of 91.6 mAh g, featuring a stable plateau around 4.1 V, which is contributed by oxygen redox activity, as verified by soft X-ray absorption spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Combined with scanning transmission electron microscopy (STEM) images, it is revealed that oxygen oxidation occurs concomitantly with Na extraction from hexagonal channels. Remarkably, in situ X-ray diffraction and STEM characterizations indicate the exceptional structural integrity of the tunnel framework throughout electrochemical cycling, demonstrating its resilience against anionic redox-induced degradation. In addition, the final NaMnTiO|hard carbon full cells could deliver an impressive energy density of 190 Wh kg with good cycling stability and minimal voltage hysteresis. This work explores a fresh perspective for designing high-performance SIB cathodes through synergistic cationic-anionic redox chemistry in stable tunnel-type oxides.
隧道型NaMnO由于其出色的结构稳定性，已成为钠离子电池（SIBs）中一种很有前景的阴极材料。然而，其实际应用受到原始结构中固有可移动钠含量的显著限制，初始充电容量仅为55 mAh g，较为适中。虽然阴离子氧化还原反应为提高容量提供了一条可行途径，但迄今为止仅在层状氧化物中进行了专门研究。在这项工作中，我们通过Ti取代的NaMnTiO（ = 0.22、0.33、0.39）首次成功实现了隧道型氧化物中高度可逆的阴离子氧化还原活性。优化后的NaMnTiO阴极的首次充电容量提高到91.6 mAh g，在4.1 V左右具有稳定的平台，这是由氧氧化还原活性贡献的，软X射线吸收光谱、拉曼光谱和X射线光电子能谱证实了这一点。结合扫描透射电子显微镜（STEM）图像表明，氧氧化与从六边形通道中提取钠同时发生。值得注意的是，原位X射线衍射和STEM表征表明，在整个电化学循环过程中，隧道框架具有出色的结构完整性，证明了其对阴离子氧化还原诱导降解的耐受性。此外，最终的NaMnTiO|硬碳全电池可以提供令人印象深刻的190 Wh kg的能量密度，具有良好的循环稳定性和最小的电压滞后。这项工作通过在稳定的隧道型氧化物中协同阳离子-阴离子氧化还原化学，探索了设计高性能SIB阴极的新视角。
