Li-Na-Al-H体系的储锂性能及储锂机制

Metal hydrides have attracted considerable attention as novel anodes with high capacity for lithium-ion batteries. Among metal hydrides, complex alanates in Li-Na-Al-H system are considered to be one of the most promising anodes due to their high hydrogen content and proper thermodynamic stability. However, the development and applications of complex alanates anodes are blocked by poor cycling stability and small cycling capacity. In view of the above mentioned problems, in this project, the electrochemical lithium storage performances of complex alanates are systematically studied and the relation between lithium storage performances and material microstructures, such as phase structure and surface appearance, is investigated. On basis of experimental results, the key factors of cycling stability for lithium storage are discussed and the lithiation/delithiation mechanisms of complex alanates are proposed. Next, the influence of hydrogen storage performances on lithium storage performances of complex alanates is studied and the relationship between hydrogen storage performances and lithium storage performances is elucidated. Finally, the lithium storage performances of complex alanates are improved by the same strategy for enhancing the hydrogen storage performances. The results of this project not only propel the utilization of complex alanates anodes, but also provide a solid theoretical and technical support for the development of lithium storage properties of other metal hydrides.

金属氢化物是一种新型的锂离子电池高容量负极材料，其中Li-Na-Al-H体系的配位铝氢化物因高含氢量和适宜的热力学稳定性，被认为是最具应用前景的负极材料之一。但配位铝氢化物存在循环稳定性差和循环容量低等问题，制约了其发展和应用。针对这些问题，本项目拟首先系统地研究配位铝氢化物负极的储锂性能，获得组分和形貌等微观结构与储锂性能之间的关系，揭示影响循环储锂稳定性的关键因素，阐明配位铝氢化物的可逆储锂机制；其次，考察配位铝氢化物储氢性能对储锂性能的影响，揭示储氢与储锂性能间的内在关联，并根据储氢性能的调控手段来改善储锂性能。本项目的研究结果将推进配位铝氢化物这一类新型高能量密度负极材料的实际应用，也为其他金属氢化物的储锂性能改善提供理论基础与技术支持。

配位铝氢化物具有高比容量和低放电电压的优点，是一种极具应用潜力的锂电池负极材料。但配位铝氢化物的储锂机制不明，循环稳定性较差，制约了其在电池领域的发展。针对这些问题，项目制得了一系列Li-Na-Al-H体系的负极材料，表征了制得负极的组分、结构和储锂性能，阐明了配位铝氢化物基于转化反应的可逆储锂机制；表征了配位铝氢化物组分和结构在循环充放电过程中的演变，改善循环储锂稳定性，揭示了截止电位和电解质种类对铝氢化物循环储锂稳定性的影响规律；提出了一种金属氢化物/纳米碳复合电极材料的原位制备方法，制得了具有三维分级结构的铝氢化物与石墨烯复合电极，并与LiBH4固态电解质组成全固态氢化物电池，实现了铝氢化物的高稳定、高容量和高倍率的储锂。其中优化设计的LiNa2AlH6负极在1C条件下比容量可达900 mAh/g，循环500圈后仍有890 mAh/g；通过固相离子交换原位在铝氢化物表面形成过渡层，显著改善了铝氢化物负极的循环稳定性，制得的Li3AlH6/NaBH4/LiBH4复合负极在循环200圈后，仍能保持912 mAh/g的可逆充放电容量。通过本项目的研究，为推进氢化物这一类新型高能量密度负极材料的实用化提供坚实的理论基础与技术支持。