P2型Na-Cu-M-O（M = Mn, Ni, Co, Fe）钠离子电池正极材料的结构调控与储能机制

Sodium-ion battery (SIB) is an alternative low-cost energy storage device that has the potential to complement or even partially replace lithium-ion battery (LIB) in the future. It relies on earth-abundant sodium as the mean to store and release energy. However, SIBs face challenges of low specific energy, short cycling life, and insufficient specific power, owing to the heavy mass and large radius of Na+ ions. As an important component of SIBs, cathode materials have a significant effect on the SIB electrochemical performance. Major efforts have been devoted to the search for high performance cathode materials with high specific capacity, high voltage, high energy and power density, long cycling life and safety. Layered NaxAO2 compound where A is a transition metal is a potential candidate as cathode material for sodium-ion battery. It has similar structure as common cathode materials in LIB. But the drawbacks of the materials such as poor cycling performance and rate capability limit their practical application. In this proposal, we described a copper substituted P2-type Na-Cu-M-O (M = Mn, Ni, Co, Fe) layered oxides which contain both Cu and also one or more than one transition metal M in the structure based on our previous work. The inclusion of copper atoms in the lattice most importantly improves the cycle performance (capacity retention) of the material and stabilizes the structure of the material by suppressing phase transitions during the sodiation and de-sodiation processes and also Cu-substitution raises the voltage of the electrode and improves the rate performance of the material by increasing the kinetics of sodium transport in the material. We want to control the structure of P2-type Na-Cu-M-O layered oxides through changing the mole ratios of Na:Cu:M, the kinds of M and crystallization process, in order to investigate the effect of Cu-substitution on the crystal microstructure and the improved electrochemical performance. The aim of this proposal is to investigate the relationship between the microstructure and the electrochemical performance and to develop excellent P2-type Na-Cu-M-O cathode materials for SIB through Cu-substitution.

钠离子电池由于资源丰富、分布广泛和价格低廉已成为能源存储领域的热点。正极材料对电池性能的提高起到关键性作用，开发高比容量、高工作电压、结构稳定且安全的正极材料非常重要。层状材料NaxAO2 (A为过渡金属)是比较有潜力的正极材料，但循环和倍率性能差等缺点限制其实际应用。本项目在前期工作的基础上，利用具有高氧化还原电位的Cu元素取代制备P2型Na-Cu-M-O (M = Mn, Ni, Co, Fe) 层状氧化物，拟通过调节Na:Cu:M摩尔比例和结晶过程等参数实现P2型氧化物的结构调控，研究Cu元素取代对P2型正极材料循环性能和倍率性能的提升的本质。通过分析Cu元素取代对Na+脱嵌过程中相变及动力学特征的影响分析晶体微观结构和各组分协同效应与电化学性能之间的构效关系，理解Cu元素取代对储能机制的影响。本项目旨在通过Cu元素调控P2型层状材料，制备出性能优良的钠离子电池正极材料以推动其应用。

随着传统化石能源的日益枯竭以及环境污染日益加剧，稳定利用新能源尤为重要，其中，电化学储能扮演了重要角色。由于钠源储存量大且分布广泛而使钠离子电池具有价格优势，近年来受到密切关注。但由于钠离子半径大而导致的体积效应和受限的动力学特征，需要开发合适的钠离子电池电极材料。正极材料对电池性能的提高起到关键性作用，开发高比容量、高工作电压、结构稳定且安全的正.极材料非常重要。本研究以二氧化锰微球模板为前驱体，通过高温煅烧掺杂化学计量比当量的Cu、Ni、F元素，最终得到P2型Na-Mn-M-O层状氧化物。正离子掺杂和负离子掺杂都可以影响材料晶胞参数、元素的氧化还原态，从而影响材料所包含元素的电化学活性。进而可以调控材料的比容量、循环性能和稳定性。为了推动正极材料的实际应用，此外还研究了P2型材料在全电池中的性能影响因素，发现负极材料对全电池的开发也至关重要，因此，发展了结构导向模板的合成策略，利用金属有机框架化合物模板或者溶剂热，得到了碳基多组分硫族化合物体系的构筑。在介观尺度上实现硫族化合物的电子结构和晶体结构的调控，发挥各组分之间的协同效应和界面效应以显著改善硫族化合物钠离子电池负极材料的电化学性能。通过预钠化处理，可以显著改善P2型正极材料的全电池性能。本研究可以为钠离子电池电极材料的开发及实际应用提供借鉴。