多元层状氧化物Nax[NiFeMn]O2介观晶体的设计合成及电化学性能研究

钠离子电池由于资源与成本等方面的明显优势，正成为新一代储能技术的发展热点，具有广阔的应用市场。其中，高性能正极材料的制备一直是钠离子电池研究领域的重点与难点问题。本项目针对目前多元层状氧化物正极材料结构稳定性较差、电子导电率较低等问题，提出物相调控、介观结构化和碳包覆改性是提升其电化学性能的有效途径。项目将以多元层状氧化物Nax[NiFeMn]O2介观晶体为研究对象，围绕电极材料物相、微观结构及碳包覆对电化学性能的影响规律等核心内容，开展离子液体体系中多元层状氧化物介观晶体及其功能化研究，阐明反应物配比、离子液体种类及反应温度等对产物物相组成、结构、形貌等影响，探索基于协同作用机制的多元正极材料Nax[NiFeMn]O2介观晶体对钠离子电池性能的影响，揭示电极材料各组分的作用及其介观结构化与充放电特性和循环性能的内在联系，为制备高性能的钠离子电池正极材料提供相应的理论基础和实验指导。

Sodium-ion batteries are now actively developed as a new generation of electric energy storage technology because of their advantages of resource abundance and low cost, thus have broad application in many areas. In particular, cathode materials with high capacity, high safety and long life have always been a key in the research field of sodium-ion batteries. However, the electrochemical performances of layered oxide cathode materials for sodium-ion batteries suffer from poor structural stability and low electronic conductivity. To address this issue, the aim of this project is to develop a facile route to fabricate sodium layered oxide Nax[NiFeMn]O2 mesocrystals as cathode materials with enhanced electrochemical performances. We will focus on the development of ionic liquid-assisted synthetic route to prepare Nax[NiFeMn]O2 mesocrystals with desired phase and carbon-coated modification, and systematically study their electrochemical performance for sodium-ion batteries. By rational design of ionic liquid precursor, we will investigate the effect of reactant ratio, temperature and ionic liquid on the formation of Nax[NiFeMn]O2 mesocrystals with desired phase and morphologies. By means of electrochemical analysis and structural characterization, we will reveal the role of each component of Nax[NiFeMn]O2 mesocrystals in the charge-discharge process, and investigate the impact of mesoscopic structured Nax[NiFeMn]O2 cathode materials based on synergistic effect for high-performance sodium-ion batteries. Furthermore, we will determine the optimal ratio of Na:Ni:Fe:Mn for Nax[NiFeMn]O2 mesocrystals with high capacity and well cycling performance. It is highly expected that these findings are useful for exploring an environment-friendly route for large-scale preparation of mesocrystal-type cathode materials with high capacity and long life for sodium-ion batteries.