基于盐湖锂资源可控制备层状过渡金属氧化物储钠正极材料的研究

To alleviate the problem of separating magnesium and lithium-containing inorganic salts rich in Qaidam Salt Lake, which is due to the high value of Mg/Li and the similar physicochemical properties between magnesium and lithium, this project aims to utilize the separate-coprecipitation method to selectively separate the Mg- and Li-containing inorganic salts, and also to explore the electrode nanomaterials for sodium-ion batteries (SIBs). In details, on the basis of our academic accumulation in utilizing layered double hydroxide (LDH) precursors to prepare diverse anode nanomaterials for lithium-ion batteries (LIBs) and SIBs, we will use the separate-coprecipitation method to design and prepare Mg and Li-containing LDHs to highly efficiently separate the Mg- and Li-containing inorganic salts, and thus prepare the LDH precursor-derived, lithium-doped layered transition metal oxides used as cycling-stable, high-capacity nanomaterials for SIBs. We will also explore the mechanism of sodium storage by using in-situ/semi-situ characterization techniques, and tune the electrochemical performances the L lithium-doped layered transition metal oxides as nanomaterials for SIBs in terms of nanostructure, cationic type and ratio of the LDH-precursors, on the basis of our designing concepts of heterojunction enhancement, crystallographic confinement, and multiple-component collaboration. This project is expected to provide a novel approach to the efficient separation and utilization of the magnesium/lithium-salt resources rich in Qaidam Salt Lake, and also a scientific reference for getting insight into the key scientific issues of nanomaterials for SIBs which are derived from lithium-containing LDH precursors.

针对柴达木盐湖因镁锂比高、性质相似而存在分离困难的问题，本课题拟采用分步共沉淀选择性分离法，实现盐湖镁、锂资源的有效分离，并开展锂资源作为钠离子电池关键材料的基础研究。即申请人基于在利用层状复合氢氧化物（简称LDHs）前驱体法制备纳米储锂、储钠材料研究方面积累，利用共沉淀选择性分离法，分步可控制备制备镁、锂基LDHs，以实现高效分离镁、锂资源；以锂基LDHs为前驱体，通过双活性组分增强、非活性组分网阱限域以及多组分协同储锂的设计理念，设计和构筑稳定、锂取代层状过渡金属氧化物的钠离子电池关键正极材料；借助于原位/半原位表征技术，揭示相关储钠机理，并进一步基于锂基LDHs前驱体精确调控钠离子电池正极材料的电化学性能。本课题旨在为盐湖锂资源的有效利用提供一种新途径，同时为基于LDHs前驱体的二次电池关键材料发展奠定良好的科学基础。

本项目以锂盐、镁盐制备出两种新型层状过渡金属氧化物钠离子电池正极材料（P2/P3-Na0.7Li0.06Mg0.06Ni0.22Mn0.67O2、P3-Na2/3Ni1/4Mg1/12Mn2/3O2）。这两种正极材料分别表现出优异的结构稳定性与容量保持率、优良的循环稳定性与高压特性；且与硬碳组装的钠离子全电池都显示出较高的能量密度。原位XRD和非原位XANES/EXAFS表征结果揭示了P2/P3-Na0.7Li0.06Mg0.06Ni0.22Mn0.67O2复合正极材料在高电压条件下保持P2/P3-OP4/P3高度可逆反应相变、且在整个氧化还原过程中仅发生Ni2+/Ni4+的氧化还原及Mn4+保持价态不变的储钠机制。进一步地，通过调控水滑石（LDHs）前驱体的金属阳离子的种类及比例，开展了层状过渡金属氧化物钠离子电池正极材料的制备与性能调控研究，并构建了LDHs前驱体法层状过渡金属氧化物钠离子电池正极材料及过渡金属氧化物钠离子电池负极材料的普适制备方法。这些研究结果有望为层状过渡金属氧化物正极材料的制备与调控提供一种特色途径，同时也为构筑高性能钠离子全电池及推进实用化奠定了科学和材料基础。