Li Jing-Chang, Xu Sheng, Tian Jiaming, Peng Bo, Sun Yu, Tang Jiayi, Liu Zhaoguo, Liu Yuankai, Zuo Daxian, Xu Chengrong, Rao Yuan, Deng Yu, Zhou Haoshen, Guo Shaohua
College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Collaborative Innovation Centre of Advanced Microstructures, Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing, 210093, P. R. China.
Lab of Power and Energy Storage Batteries, Shenzhen Research Institute of Nanjing University, Shenzhen, 518057, P. R. China.
ChemSusChem. 2025 Jan 14;18(2):e202401538. doi: 10.1002/cssc.202401538. Epub 2024 Oct 25.
Anionic redox chemistry has attracted increasing attention for the improvement in the reversible capacity and energy density of cathode materials in Li/Na-ion batteries. However, adverse electrochemical behaviors, such as voltage hysteresis and sluggish kinetics resulting from weak metal-ligand interactions, commonly occur with anionic redox reactions. Currently, the mechanistic investigation driving these issues still remains foggy. Here, we chemically designed NaFeTiS and NaFeTiO as model cathodes to explore the covalency effects on metal-ligand interactions during anionic redox process. NaFeTiS with strengthened covalent interaction of metal-ligand bonds exhibits smaller voltage hysteresis and faster kinetics than NaFeTiO during (de)sodiation process. Theoretical calculations suggest that Fe is the dominant redox-active center in NaFeTiS, whereas the redox-active center moves from Fe to O with the removal of Na in NaFeTiO. We attribute the above different redox behaviors between NaFeTiS and NaFeTiO to the charge transfer kinetics from ligand to metal. Moreover, the structural stability of NaFeTiS is enhanced by increasing the cation migration barriers through strong metal-ligand bonds during desodiation. These insights into the originality of metal-ligand interactions provide guidance for the design of high-capacity and structurally stable cathode materials for Li/Na-ion batteries.
阴离子氧化还原化学因其对锂/钠离子电池正极材料可逆容量和能量密度的提升作用而受到越来越多的关注。然而，诸如电压滞后以及由弱金属-配体相互作用导致的动力学迟缓等不利的电化学行为，在阴离子氧化还原反应中普遍存在。目前，引发这些问题的机理研究仍不明朗。在此，我们通过化学设计将NaFeTiS和NaFeTiO作为模型正极，以探究阴离子氧化还原过程中金属-配体相互作用的共价效应。在（脱）钠过程中，具有强化金属-配体键共价相互作用的NaFeTiS比NaFeTiO表现出更小的电压滞后和更快的动力学。理论计算表明，Fe是NaFeTiS中主要的氧化还原活性中心，而在NaFeTiO中随着Na的脱出，氧化还原活性中心从Fe转移至O。我们将NaFeTiS和NaFeTiO之间上述不同的氧化还原行为归因于从配体到金属的电荷转移动力学。此外，在脱钠过程中，通过强金属-配体键增加阳离子迁移势垒，增强了NaFeTiS的结构稳定性。这些对金属-配体相互作用本质的见解为锂/钠离子电池高容量和结构稳定正极材料的设计提供了指导。
