柠檬酸体系粘结剂在锂离子电池硅负极中的结构调控与界面稳定多重作用协同机制研究

Silicon, due to its high theoretical capacity, is considered to be one of the most promising anode candidates for the next generation lithium-ion batteries. However, the commercial application of Si anode is hindered by the dramatic volume change during the lithiation/delithiation process. It induces the collapse of anode structure and continuous growth of solid electrolyte interface film(SEI) and consequently the rapid decay of the capacity, therefore considered to be the main failure reasons of the Si anode. To gain a high performance anode, besides the development of advanced Si materials, it is also critical to develop novel binders to effectively overcome the failure issues of Si electrode. This project focuses on the fundamental study of multi-functional binder citric acid (CA), which shows remarkable enhancement on the performance of Si anode. Firstly, this project investigates the interactions between CA molecules and Si particles to study the formation mechanism of the cross-linked CA layers on the Si surface. Based on this, the mechanisms of CA improvement on the dispersion morphology, mechanical properties as well as the Si-electrolyte interface stability are systematically studied to explore the synergistic effect of them. Therefore, the “chemical composition-microstructure-electrochemical behaviors” relationship will be clarified for CA-silicon electrode. Accordingly, a dual-binder will be designed by introducing long-chain molecules to construct a “scaffold” structure to promote the toughness and other properties. This project is of practical and theoretical significance in developing novel multi-functional binders for high performance silicon anode. By remitting the main failure issues deriving from volume change, the fundamental research on the multi-functional binders is important to offer useful experience.

锂离子电池硅负极因其高理论容量被认为是最有前景的下一代体系之一。然而循环过程中体积效应带来的结构破坏与SEI膜持续增厚等问题限制了其实际应用。除对活性材料进行设计外，开发能有效缓解硅失效问题的新型粘结剂对电极性能的全面提升尤为重要。基于小分子柠檬酸粘结剂显著的性能改善作用，本项目从柠檬酸通过表面键合形成包覆结构出发，系统深入的研究柠檬酸对电极中硅颗粒分散形态、力学性能以及界面电化学行为的影响规律。揭示该功能型粘结剂对硅电极主要失效问题的协同改善机制；阐明该体系中的“化学成分-微观结构-电化学性能”构效关系。在构效关系指导下，设计基于柠檬酸的复相粘结剂，通过引入长链分子搭建“脚手架”结构改善其短链的柔韧性，从而开发高性能硅电极。本项目将对多功能型粘结剂的全面深入理解提供理论指导与实践经验。对有类似体积效应电极体系的性能优化具有重要借鉴意义。

针对硅电极因为体积效应导致电池失效的瓶颈问题，本项目拟对以CA等小分子粘结剂在硅电极体系中的结构与界面作用机制展开系统深入探讨：①CA与硅颗粒通过化学键合作用搭建交联网络形成包覆结构，研究该包覆结构如何对硅颗粒的胶体化学分散性、电极材料力学粘结性、以及硅材料界面电化学行为等多方面协同作用提升电极性能；②基于CA多重协同改善机制，研究并设计基于CA的复相粘结剂，通过与长链分子搭建“脚手架”结构从而构筑“网络锚点”与“柔性锁链”效应，进一步综合提升电极材料性能；③研究柠檬酸系粘结剂应用于一体化硅@氧化石墨烯（Si@GO）高性能复合电极材料，解决硅纳米颗粒分散性差及与GO连接弱等问题，开发水系中绿色可控的制备工艺。本项目对以上机理问题的研究可望为硅电极粘结剂或柔性电池的开发提供理论指导与实践尝试，对硅电极瓶颈问题的解决具有较重要的学术价值和应用前景。