基于锡（锗、锑）-石墨层间化合物的钠离子电池负极研究

Graphite is used in most of the commercial lithium ion batteries as an anode material due to its low cost, friendly environment and excellent electrochemical performance. However, the result is unsatisfying when used in sodium ion batteries (NIBs). Graphite can reversibly intercalate lithium by forming a series of binary graphite intercalation compounds (b-GIC), but cannot intercalate sodium to form b-GICs under moderate conditions, which is assumed to be the result of an unfavorable mismatch between the graphite layer spacing and the size of the Na ion. Therefore, change the sodium ions embedded mode (such as intercalate solvated sodium ions to form ternary GICs) or amplification the layer spacing of graphite becomes the key of graphite used effectively as an anode material for sodium ion batteries. As the metal atoms can be inserted into the graphite by forming a series of graphite intercalation compounds, this project would use tin (germanium, antimony), which have higher sodium storage capacity than graphite, as insert to synthesize a series of Sn (Ge, Sb) - graphite intercalation compounds, achieving the modified of graphite without harming its sodium storage capacity. Through the microstructure characterization of the material system （layer spacing, electron density, etc), the structure change of graphite materials after inserting Sn (Ge, Sb) is in-depth understood. Based on the electrochemical performance of material system in sodium ion battery, investigate the relationship between the microstructure and electrochemical properties of graphite intercalation compounds. This work will provide theoretical as well as experimental basis into developing metal-graphite intercalation compounds with superior properties in the sodium ion battery.

石墨材料因成本低廉、环境友好、嵌锂性能优异等优点在锂离子电池领域得以广泛应用。然当其应用于钠离子电池时却未得到期许的结果，这是因为Na+半径（比Li+半径大）与石墨层间距不匹配，在温和条件下，Na+不能在石墨层中进行二元可逆脱嵌。因此改变Na+的嵌入方式（如将其溶剂化后进行三元共嵌）或者扩增石墨层间距成为石墨应用于钠离子电池的关键所在。本项目从金属原子可以插入石墨层形成石墨层间化合物这一性质入手，选用储钠容量远超石墨材料的金属单质作为插入物，制备锡（锗、锑）-石墨层间化合物体系，在不损害石墨储钠容量的基础上对其进行改性。通过对材料体系的微观结构（层间距、电子密度等）表征，揭示内插金属对石墨材料微观性质的影响规律。并基于材料体系在钠离子电池中的电化学表现，探讨了石墨层间化合物的微观结构与宏观电化学性能间的关系，为金属-石墨层间化合物材料在钠离子电池负极中的应用提供了必要的理论与实验依据。

锂/钠离子电池因具有便携、安全、高能量密度等优点而备受关注，其性能很大程度上取决于电极材料，尤其是正极材料。项目主要围绕镍、锰氧化物，开展可控制备与电化学性能研究。延续了共沉淀（水热法）与高温固相相结合的制备方法，实现了形貌-结构的可控制备，获得了电化学性能优异的正负极材料。开发出了具有高放电平台的微米级层状材料Na0.5Ni0.25Mn0.75O2体系，放电平台可达3.8 V vs. Na+/Na；并在此基础上研究了通过包覆AlF3、Al2O3等金属氧、氟化物来改善其电化学性能，研究结果表明均匀包覆在材料表面的AlF3层，更能有效的提升微米级Na0.5Ni0.25Mn0.75O2的倍率循环性能。此外，设计和制备了一维纳米棒结构的LiNi0.5Mn0.5O2及碳包覆的Na3V2(PO4)2F3@C纳米材料，通过独特的一维或碳包覆纳米结构，实现了锂、钠离子电池的高倍率放电目标；Cr2(MoO4)3和Ti0.9Fe1.1O3的制备探索为新型负极材料的研究提供了思路。项目执行期间，发表相关SCI论文6篇，培养了7名本科生。