嵌锂SnO2负极材料的纳米Sn粗化抑制与转化反应的可逆性

The application of high capacity SnO2 anodes has been constrained by the poor reversibility of the conversion reaction and their low initial Coulombic efficiency. In previous study the applicant has demonstrated that the reduced Sn/Li2O interfaces due to Sn coarsening is responsible for the poor reversibility of the initial conversion reaction in lithaited SnO2 anode. By creating high density grain boundaries of nano-sized SnO2, the coarsening of Sn could be suppressed, enabling high initial Coulombic efficiency in a SnO2 thin film anode. However, the reversibility of conversion reaction was gradually fading and leading to capacity decay during cycling. To solve this problem, in this project, the kinetics of Sn coarsening under different driving forces, as well as their influence on the interface reactivity of Sn/Li2O during lithiation-delithiation cycling of SnO2 will be studied. A novel strategy—adding transition metal (M) in SnO2-C composite to suppress the Sn coarsening and thus enhance the reversibility of conversion reaction, has been proposed. The roles of each component in the SnO2-M-C system for the enhancement of reversibility and cycleability of electrode will be elucidated. Moreover, the relationship between initial Coulombic efficiency, potential range and capacities, cycling stability of the SnO2-M-C composite anode in different kinds of batteries will be focused. As a result, we hope that it can bottom the development of the metal based anode materials for high capacity lithium ion batteries.

高容量SnO2基负极嵌锂转化反应的可逆性差和首次库仑效率低的问题严重制约其应用。申请人前期研究发现Sn粗化导致的Sn/Li2O界面减少是引起SnO2负极转化反应可逆性差的主要原因，并通过创制高密度晶界成功抑制了纳米Sn相长大，获得具有超高首次库仑效的SnO2薄膜负极。但是，循环中Sn/Li2O转化反应的可逆性会衰退并导致电极容量衰减。本项目针对这一问题，系统研究嵌锂SnO2负极循环过程中不同驱动力下Sn粗化的动力学特性及其对Sn/Li2O界面反应活性的影响规律；提出在SnO2-C复合物中添加过渡金属组元(M)抑制Sn粗化的新策略，阐明SnO2-M-C体系中各组元相对电极嵌锂-脱锂可逆性和稳定性的改善作用；考察该负极体系在不同体系电池应用中的首次库仑效率、电压范围与电池容量和循环稳定性的关系，为推动高容量金属基嵌锂负极材料的实际应用奠定科学依据和材料基础。

本项目主要针对高容量SnO2负极存在的首次嵌锂转化反应可逆性差和首次库仑效率低（<60%）的问题开展研究。 我们确定了单相SnO2薄膜和SnO2基多相复合负极中Sn/Li2O转化反应可逆性差的根本原因与重要影响因素，揭示了嵌锂SnO2负极循环过程中不同因素导致的Sn相粗化的动力学特性及其对Sn/Li2O界面反应活性的影响机制，深入阐明了SnO2-M-C多相复合体系中不同过渡金属添加物对电极嵌锂-脱锂可逆性和稳定性的改善作用以及各组元相之间交互作用和变化，掌握影响SnO2-M-C复合材料体系电极的首效的关键因素。在此基础上，通过等离子球磨技术，获得了一系列高首效（>80%）、高容量（>800 mAh/g）、长寿命（>1000次）、倍率性能优良的SnO2基负极材料体系及其高效宏量制备技术。相关研究成果在Energy Environ. Sci., Adv. Mater.，Nano Energy, J. Mater. Chem. A，Energy Storage Mater.等国内外知名学术期刊上发表论文27篇;申请发明专利12项，已获授权专利5项。在本项目执行过程中，等离子球磨材料制备技术、锡碳和硅碳电极材料的3个专利实施许可于企业，实现产业化；完成培养研究生5名；相关研究工作分别在中国材料大会、全国固态离子学会议、全国电化学会等重要会议上作分会邀请报告，研究成果受到了学术界同行的广泛关注。