高比能钒基双金属氧化物纳米材料储锂机理研究

Developing novel anode materials with high capacity, safety, and long cycling life is vital for improving the energy density of lithium ion batteries. Alloy-based materials, such as Sn, Sb, have long been recognized as promising candidates owing to their high capacities that are superior to the commercial graphite. However, the fast capacity fading upon charge/discharge are the main bottlenecks that hinder their practical applications. How to effectively accommodate the volumetric change or prevent the aggregations of pulverized particles has been a great focus. Constructing M/graphene (M=Sn, Sb…) nanocomposites are the most popular and effective methods to address this issue. But it is known that graphene is difficult to be synthesized and expensive. Recently, we have demonstrated the successful preparation of Co3V2O8 nanostructures and in detail studied the lithium-storage mechanism. An interesting surface-to-surface architecture that was generated upon the Li+ insertion and composed of CoO nanoparticles anchoring on amorphous VOx matrices showed the similar structure with M/C. The extracted VOx, which not only suppressed the volumetric changes but also significantly increased the ions/electrons transfer since the mixed valence of vanadium, played an important role in enhancing the battery performance. Therefore, designing new vanadium-based bi-metal oxides that contain the alloy-based materials may be a good solution to realize high-performance lithium-storage properties. However, there is a severe lack of the studies on the lithium-storage mechanism of these compounds. For reasons noted above, we propose this fundamental research.

发展高性能负极材料对于提高锂离子电池的能量密度至关重要。合金类材料如锡、锑等，具备远高于商品化石墨负极材料的质量、体积比容量，被认为是下一代理想的锂离子电池负极材料。然而，这些材料在嵌脱锂过程中巨大的体积变化，造成迅速的容量衰减严重限制其发展。如何能够有效缓冲体积变化或抑制粉化后材料的再团聚，成为当前研究的热点。通过构建与石墨烯复合材料是应用最为广泛的方法，但石墨烯合成困难且价格昂贵。此前，申请人在对钒酸钴的研究中发现，该材料在嵌锂后会自发地形成类似于合金类材料/石墨烯的复合纳米结构（氧化钴/氧化钒）。其中，氧化钒起到了类石墨烯的作用，其不仅能够有效地抑制纳米粒子的团聚，更是提高了材料的电导率，使材料表现出优异的储锂特性。因此，合成含合金类材料的钒基双金属氧化物，有望获得高性能锂离子电池负极材料。然而，目前有关此类钒基双金属氧化物的储锂机理尚不清晰。基于上述认识，我们提出本项目研究。

锂离子电池具有高能量密度，但也存在严重的成本和安全问题，因此开发低成本、高安全的新型储能电池具有十分重要的意义。本项目在完成钒氧化物作为锂离子电池电极材料的电化学性能与机理研究的基础上，拓展钒氧化物应用于水系锌离子电池正极材料，开展了一系列原创性研究工作。水系锌离子电池是一种兼具高容量、高安全和优异倍率特性的二次电池，由能够可逆嵌脱锌离子的正极材料、锌金属负极和中性或弱酸性水系电解液组成，被广泛认为在未来规模储能领域具有良好的应用前景。当前，水系锌离子电池的研究尚处于初期阶段，制约其发展的主要瓶颈是缺乏高性能的正极材料和锌负极的腐蚀与枝晶问题。针对于此，我们开展了以下研究内容：（1）系统研究了多种钒基正极材料的电化学储锌性能、储锌机理与性能衰退机制，阐明了电池反应过程中钒氧化物溶解和表面副产物的生成机制，提出了通过铝掺杂和构筑钒基双金属氧化物的改性策略，获得了若干具有良好电化学性能的新型正极材料；（2）在对钒氧化物/氧化石墨烯复合材料的储锌性能研究中发现，该复合材料除表现出传统的钒的氧化还原机理，同时钒氧化物表面以及氧化石墨烯表面的含氧基团均参与了氧化还原反应该材料，据此我们提出了一种新型的锌离子电池反应机制并命名为赝锌空反应，在此基础上设计制备了两种基于赝锌空反应机制的新型高容量正极材料；（3）开展了普鲁士蓝类似物作为水系锌离子电池正极材料的应用研究，提出了两种电解液优化策略，大幅提升了材料的电化学性能；（4）通过在水系锌离子电池电解液中引入新型添加剂，一定程度上解决电解液/锌负极界面的腐蚀与枝晶问题，较好地提升了水系锌离子电池的循环稳定性能。上述研究成果对发展高性能水系锌离子电池提供了很好的理论和实验基础，并以SCI论文的形式发表在包括Science China Materials, Energy & Environmental Science, ACS Nano, Advanced Energy Materials, Energy Storage Materials等在内的国内外高水平学术期刊。