钠离子电池层状正极材料的层间距调控及动态嵌脱钠机理研究

Due to low-cost and high abundance of Na resource, Na-ion batteries have been regarded as one of the promising candidates for large-scale energy storage applications. However, owing to the large ionic radius of the Na+, Na-based layered materials have to bear metal slab gliding, complicated phase transition and large volume change during repeated charge and discharge. To tackle these problems, introducing a large radius cation into the structure of Na-based layered material is first proposed to construct stable layered structure for large ion diffusion via increasing interlayer spacing and expanding Na+ pathway. In this project, the influence of ionic radius on the interlayer spacing of the material will be systematically investigated, the relation between interlayer spacing and electrochemical properties, structural stability and transport kinetic will be meticulously explored, and the regulatory basis and rule of interlayer spacing will be clarified. In addition, the structure evolution process and ion transfer behavior during the dynamic Na+ insertion/extraction will be revealed. This project will provide new route for the structure and performance control of Na-based layered materials; offer reliable theoretical and experimental basis for developing advanced cathode materials for Na-ion batteries.

由于资源丰富和低成本的优势，钠离子电池被视为未来大规模储能应用的理想选择。然而由于Na+半径较大，电化学过程中Na+的迁移会造成钠离子电池层状正极材料金属层滑移、相结构转变和体积膨胀等问题。本项目首次提出采用大半径阳离子取代扩大钠层状正极材料层间距，拓宽Na+迁移通道，构建适合大离子嵌脱的稳定层状结构，从根源上解决材料的相变和形变难题。申请人将系统研究不同大半径阳离子取代对材料层间距的影响，深入探索层间距与材料电化学性能、体相结构变化、表面结构变化、离子扩散动力学之间的相关性，探明钠层状正极材料层间距调控依据和调控规律，揭示材料在动态嵌脱钠过程中的结构演变规律和离子迁移机制。本项目将为钠层状正极材料的结构和性能调控优化提供一种新思路和新途径，为开发先进性能的钠离子电池正极材料提供可靠的理论和实验依据。

为了拓宽层状结构材料的层间距和Na+扩散通道，我们设计和制备了一系列大半径阳离子掺杂的层状正极材料。包括Mg2+/Ti4+离子共掺杂的Na0.62Mn0.67Ni0.23Cu0.05Mg0.09-2yTiyO2材料、Cu/Mg/Zn/Al/Ti/Zr共掺杂的Na0.66Mn0.66Ni0.2Cu0.0176Mg0.0176Zn0.0176Al0.0176Ti0.0176Zr0.0176O2和Li/Cu/Mg/Zn/Al/Ti/Zr共掺杂的Na0.66Li0.1Mn0.635Ni0.2Cu0.176Mg0.0176Zn0.0176Al0.0176Ti0.0176Zr0.0176O2。XRD精修结果表明大半径阳离子掺杂确实会扩大层状材料的层间距。同步辐射原位XRD测试、电化学动力学测试和微结构表征结果显示，大的层间距有利于让层状材料具有更好的结构稳定性、热稳定性和快速的Na+动力学。因而，扩大层间距后，层状材料展现出了优异的大倍率性能和长循环性能。其中，制得的Na0.62Mn0.67Ni0.23Cu0.05Mg0.07Ti0.01O2在0.1C倍率下，首周放电容量148.2mAh·g-1，循环100周后，放电容量依然有132.9mAh·g-1，容量保持率89.6%。制得的Na0.66Mn0.66Ni0.2Cu0.0176Mg0.0176Zn0.0176Al0.0176Ti0.0176Zr0.0176O2材料也表现出优异的循环性能，1C倍率下，循环100周后，容量仍有112.7mAh·g-1，容量保持率85.5%。制得的Na0.66Li0.1Mn0.635Ni0.2Cu0.0176Mg0.0176Zn0.0176Al0.0176Ti0.0176Zr0.0176O2材料表现出卓越的高倍率性能，5C高倍率下，循环100周后，容量有101.8mAh·g-1，容量保持率94.5%。层间距调控这种独特的方法有利于为高功率和长寿命的电池提供高性能的正极材料。