多壳层结构锡基负极材料的可控构筑及储钠行为研究

Sodium-ion batteries have become a hot topic in the past couple of years due to its tremendous storage in crust and ocean, low price and the similarity of both Li and Na insertion chemistries. Especially in the large-scale energy storage system and future smart grid, it is more important to develop and improve sodium ion batteries. To address current critical challenge in Tin-based anodes applied in sodium-ion batteries, the design and preparation of Sn metal and its compounds (e.g. SnO2、SnS2、SnP3) with multi-shelled structure will be proposed in this project on the basis of ours experiences in lithium ion batteries. Actually, it could be expected that electrochemical activity could be improved by these nanoparticles and the available specific surface, and the volume change and stress during discharge-charge process could be buffered which is the key point limiting their application of these materials. Moreover, the transfer rate of electrolyte ions could be accelerated due to the hollow structure and rate capacity could be increased. More importantly, the structure could be maintained by the different shells, thereby the stability cycle and life-span could be enhanced. The energy density as well as the power density, conductivity and lifespan would be discussed systematically. Above all, a novel, facile and universal method for fabricating non oxides microspheres with multi-shelled structure will be proposed, which shall make a significant and immediate impact on the development of energy storage research. This research project aims to understand the fundamental materials and device characteristics including the relationship between the structure and sodium storage, electrochemical reaction mechanism on the electrode interface and the behaviour of mass and charge transfer.

由于钠元素的储量优势和与锂相似的电化学特性，钠离子电池成为关注的热点，特别是在大规模储能和智能电网领域，发展钠离子电池技术具有重要的战略意义。本项目借鉴锂离子电池材料的经验，以钠离子电池应用需求为导向，针对电极材料体积膨胀和钠离子传输问题，构筑锡金属及其化合物（包括SnO2、SnS2、SnP3等）多壳层结构，利用中空结构缓冲体积变化，仅依靠活性材料、通过不同壳层的自我支撑来保持电极结构的稳定，解决电极充放电过程中粉化、容量衰减的问题，提高电极的稳定性；利用壳层中的空隙和孔道设计，促进钠离子传输，提高倍率性能；通过壳层中的纳米粒子及多个壳层，增加比表面积和单位体积内的电化学活性位点，提高其可逆容量；开发非氧化物材料多壳层结构的可控制备方法，研究电极与储钠性能的构效关系，揭示电极界面化学反应机理、物质传输特征等基础科学问题及关键影响因素，为同类材料的研究提供支持，推动钠电池的发展。

在中空多壳层结构（HoMS）锂离子电池材料研究基础上，针对目前钠离子电池存在的循环稳定性和钠离子扩散的问题，基于次序模板法，结合外场调控和表面技术，实现了锡基HoMS电极材料的可控合成，在一定温度下通过还原、硫化、磷化等方法成功制备了具有HoMS结构的硫化物、磷化物及其复合材料，包括SnO2 HoMS、SnS2/SnO2 HoMS、SnO2 @PPy HoMS、SnO2 @PDA HoMS、Sn/C HoMS、Sn@C HoMS以及CoP HoMS、NiS HoMS、NiS2 HoMS、Ni3S2 HoMS和Fe2(MoO4)3 HoMS等，建立了多种非氧化物材料HoMS的可控制备方法，极大丰富了中空多壳层结构电极材料的多样性。以Fe2(MoO4)3 HoMS材料为代表，将其作为钠离子电池正极材料应用，表现出优异的电池性能，尤其是五壳层Fe2(MoO4)3空心球比容量达到99.0mAh/g、2.2C电流密度下循环100次，仍然能够保持85.6mAh/g的容量、即使电流密度增加到10C，比容量仍然保持了67.4mAh/g，从而证明了HoMS材料作为钠离子电池材料具有很好的发展前景和应用潜力。系统研究了HoMS结构和组成对储钠性能的增强作用，研究成果表明：中空多壳层微纳结构，能够有效缓冲电极材料体积变化和充放电过程的应力应变，保持其循环稳定性；通过增大材料有效的比表面积，能够提高材料的反应活性，大大提高电池的储钠能力；通过多壳层中空结构和孔道，能够有效改善物质和电荷传输，提高倍率性能。通过系统研究结构与性质的构效关系，获得了高性能、长期稳定钠离子电池电极材料的制备规律，为电极材料的研发提供了启示。