Zeng Ao, Jiao Jianyue, Zhang Hong, Zhao Enyue, He Tao, Xu Zhenbang, Xiao Xiaoling
College of Materials Science and Optoelectronic Technology, Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.
ACS Appl Mater Interfaces. 2024 Feb 14;16(6):7119-7129. doi: 10.1021/acsami.3c16320. Epub 2024 Jan 31.
Manganese-based layered oxides are considered promising cathodes for sodium ion batteries due to their high capacity and low-cost manganese and sodium resources. Triggering the anionic redox reaction (ARR) can exceed the capacity limitation determined by conventional cationic redox. However, the unstable ARR charge compensation and Jahn-Teller distortion of Mn ions readily result in structural degradation and rapid capacity fade. Here, we report a P2-type NaLiMnCuO cathode that shows a capacity retention of 84.5% at 200 mA/g after 200 cycles. Combining X-ray diffraction and multi other characterizations, we reveal that the enhanced cycling stability is ascribed to a slow release of cationic redox activity which can well suppress the Jahn-Teller distortion and favor the ARR reversibility. Furthermore, density-functional theory calculations demonstrate that the inhibited interlayer migration and reduced band gap facilitate the stability and kinetic behavior of ARR. These findings provide a perspective for designing high-energy-density cathode materials with ARR activity.
基于锰的层状氧化物因其高容量以及低成本的锰和钠资源，被认为是钠离子电池很有前景的正极材料。触发阴离子氧化还原反应（ARR）可以突破由传统阳离子氧化还原所决定的容量限制。然而，不稳定的ARR电荷补偿以及锰离子的 Jahn-Teller 畸变很容易导致结构退化和快速的容量衰减。在此，我们报道了一种P2型NaLiMnCuO正极，在200 mA/g的电流密度下循环200次后容量保持率为84.5%。结合X射线衍射和其他多种表征，我们揭示出增强的循环稳定性归因于阳离子氧化还原活性的缓慢释放，这能够很好地抑制 Jahn-Teller 畸变并有利于ARR的可逆性。此外，密度泛函理论计算表明，层间迁移的抑制和带隙的减小促进了ARR的稳定性和动力学行为。这些发现为设计具有ARR活性的高能量密度正极材料提供了一个视角。
