基于π-π共轭作用的富勒烯复合材料构建隔膜防护层及其对锂负极枝晶的抑制机理研究

Metal lithium is an optimal anode material for high energy batteries. Effectively restraining the dendrite formed in charge/discharge process is a key issue in applying it as a practical anode and has become one of the hotspots in the related researches. It has been reported that the lithium dendrite could be well mitigated by interaction with non-lithium anions or modifying separator with 2D nanomaterials. Unfortunately, the long-time effectiveness and the mechanism are still not clear. Based on the design concept of above two methods and our preliminary works, we propose to fabricate a protection layer on the separator for inhibiting the lithium dendrite by the π-π interaction between fullerene and 2D nanomaterials. The protection layer combine both advantages of interaction with lithium dendrite from fullerene and impediment effectiveness from 2D nanomaterials. The fullerene in the composite possesses synergistic effect with 2D nanomaterials and the addition of the fullerene can great improve the Li+ conductivity to the protection layer. The corresponding mechanism and the relationship between the structure of protection layer and effectiveness of restraining the dendrite will be investigated based on the corresponding results. Firstly, a protection layer is fabricated on the surfaces of commercialized separator by the π-π interaction between fullerene molecules and 2D nanomaterials of graphene and MoS2; Secondly, the constituents, morphology and structure of protection layers are characterized, and then the effectiveness of restraining dendrite is checked by the assembled button cells and corresponding structure-activity relationship is summarized on the basis of above results. The interaction between fullerene and metal lithium and the mechanism model of restraining dendrite of protection layers are set up based on experimental results and theoretical calculation. The results from theory and experiments are compared and tested in order to get a proper theoretical model and a perfect protection layer, which can give advices for similar studies, enrich the knowledge of the formation and propagation of lithium dendrite and provide theoretical support for the application of metal lithium as an anode.

金属锂是高比能量锂电池的理想负极材料，有效抑制锂枝晶的生长是实用化过程中必须面对和解决的关键问题，已成为目前的研究热点之一。文献报道非锂正离子与锂枝晶间的作用和二维纳米材料的阻隔效应都能有效抑制枝晶的生长，但长期效果和作用机理尚不完全清楚。根据其设计理念和前期预研结果，本项目拟利用富勒烯和二维纳米材料的π-π共轭作用来构建隔膜的防护层：所构建的防护层拥有双重的抑制枝晶功能；富勒烯和二维材料之间具有协同增强效应；富勒烯的引入能够大大增加二维纳米材料防护层的锂离子传输性能。借助红外、拉曼、核磁、XPS等表征手段检测防护层的结构和组成，组装电池检验防护层对锂枝晶的抑制效果，研究防护层和抑制效果之间的构效关系，探索抑制枝晶的机理模型。相互对照并验证实验和理论的结果，获取恰当的理论模型以及性能优异的隔膜防护层，为同类研究提供借鉴，丰富锂枝晶的科学认识，为可充电锂负极的实际应用提供理论支撑。

金属锂是具有高比能量锂电池负极材料之一，而如何有效抑制锂枝晶的生长是其实用化过程中必须要解决的关键问题，锂枝晶生长的机理研究为金属负极材料的实用化提供理论指导。通过构建二维纳米复合材料来阻隔或有效抑制枝晶的生长是常用的手段之一，由此进一步探明其有效抑制枝晶生长的作用机理。首先，利用电化学诱导反应，制备出二维材料与聚合富勒烯的复合材料，将之应用于锂离子电池；然后根据其对锂枝晶抑制的效果，探索复合材料与抑制枝晶生长的构效关系，发现二维材料修饰后能够大幅度提高金属锂作为负极的电池的寿命；进而依据上述实验结果，结合理论模拟，发现均匀分布电场和高效锂离子传输通道为抑制锂枝晶的关键因素，从而证明了抑制锂枝晶的电场分布机理；最后，通过人为构建均匀的锂离子传输通道的新型隔膜，验证了抑制锂枝晶的机理模型。本课题研究中培养博士(联合)、硕士研究生7名，或授权国家发明专利2项，发表SCI论文7篇。相关成果可为同类研究提供借鉴，为锂负极的实际应用提供理论支撑。