铝离子电池正极材料的调控及其与Al3+或[AlxMy]n-之间的静电效应耦合关系研究

The aluminum ion battery is becoming the most promising next generation secondary battery because of its abundant reserves in the earth's crust, low cost, safe use of aluminium (Al) and shows important scientific research value and application prospect in energy storage. However, the further development of this battery has been districted by low specific capacity and low energy density of positive materials, which is mainly caused by the Al3+ or [AlxMy]n- insertion and extraction from the positive materials difficulties because of the large electrostatic effect between aluminum ion or poly aluminum anion and the cathode material, leading to low utilization rate of cathode material. Therefore, the project aims to explain the electrostatic coupling relationship between the ionic radius and charge density of charge transfer ion and positive material by controlling the composition of anion and cation in electrolyte, and study its influence on the electrochemical performance by adjusting the microstructure of the positive material in the form of pre-intercalation lithium or pre-oxidation. Based on above, we modify electrode material with halogen elements according to the theory of Hard-Soft-Acid-Base (HSAB), thus the halogen element occupying in the electrode material and the form and stability between it and Al3+ or [AlxMy]n- were investigated, and the basic scientific problems of electrostatic effect between the electrode materials and the Al3+ or [AlxMy]n- and the variation of energy barrier during charging and discharging were revealed, which will provide theoretical guarantee for industrial production of aluminum ion batteries.

铝离子电池由于铝在地壳中储量丰富、价格低廉且使用安全等特点被认为是最有潜力的下一代二次电池，在能源储存方面具有重要科研价值和应用前景。目前限制其发展至关重要的因素是铝离子电池的比容量和能量密度低，原因主要是铝离子或聚铝阴离子与正极材料间的静电效应大，引起Al3+或[AlxMy]n-嵌入脱出正极材料困难，造成正极材料利用率低。因此，本申请项目通过调控电解质中阴阳离子成分，解析传递电荷离子的离子半径和电荷密度与正极材料之间静电效应耦合关系，通过预嵌锂或预氧化对正极材料进行微观结构调控，研究其对电化学性能的影响规律。在此基础上，结合软硬酸碱理论对电极材料进行卤族元素改性处理，研究卤族元素在电极材料中的占位及与Al3+或[AlxMy]n-的结合形式和稳定性，揭示电极材料与Al3+或[AlxMy]n-之间的静电效应及充放电过程中能量垒的变化规律等基础科学问题，为铝离子电池工业化生产提供理论基础。

正极材料的研究与选取对铝离子电池电化学性能的提高具有重要影响，为改善铝离子电池能量密度低、电压平台低及放电比容量低等缺点，本项目从正极材料的研究与结构调控及其与嵌入离子之间的静电效应耦合关系出发，针对性地进行了各类正极材料制备并进行了微观结构调控。在石墨类电极材料中，采用预嵌锂扩大其层间距，降低了静电效应的影响。锂化石墨在500 mA g-1电流密度下经过500次循环后容量保持率为95.1%，极化更小，放电比容量明显高于普通石墨（68.3 mAh g-1vs 49.2mAh g-1）。在石墨正极的基础上改变了电解质的成分组成（PP14NTF2），揭示了其工作机理为电解质中的NTF2-阴离子和PP14+阳离子的嵌入脱出，对铝离子电池阴阳离子的调控具有指导意义。对于过渡金属氧化物，采取纳米化策略（纳米3D分层微球AlV3O9以及纳米球状棒状Co3O4）增大嵌入离子与材料的接触面积，有利于离子的传输，从而改善了电化学性能。在铝硒电池中，深入探究了其工作机理，揭示了Se的氧化中间产物不仅只有Se22+，实际还存在Se4+、Se2+、Se82+等其他氧化中间产物。为进一步提高电池电化学性能，引入具有碳类材料和过渡金属化合物双重特性的高电导率Mxenes材料Ti3C2Tx作为铝离子电池正极材料，经过Ag的修饰后，MXenes的结构并未发生改变，F-Ti3C2Tx@Ag复合材料表现出优异的循环性能，循环2000圈后，放电比容量仍保持150mAh g-1，并且Ag+的引入改变了材料中的活性Ti离子和官能团，从而降低了Al3+或[AlCl4]-在F-Ti3C2Tx@Ag层间嵌入脱出的能垒。此外，项目创新性地制备了不同3D形貌的正极材料（六边形片状CuSe@C复合材料、单晶SnSe、CoTe2多孔碳多面体复合材料）为铝离子电池正极材料的研究开辟了新道路。.项目顺利进行，取得了良好的预期成果：培养硕士生5名，博士生4名，本科生3名，发表SCI收录论文15篇，申请专利3项，并参与国际学术交流6次，国内学术交流3次。