锂离子电池硅负极高离子导电性自修复粘结剂及性能研究

For improving the energy density of lithium-ion batteries (LIBs), silicon has been considered as the most promising anode materials for next-generation LIBs. Binder is a key factor to maintain the structure stability and good electrical contact of the silicon electrode. This project aims at the design and synthesis of ion-conductive self-healing binder based on supermolecule elastomer and ionic conductive macromolecule for silicon electrode. The Si/C anodes fabricated with the as-prepared binders are further applied to assemble high energy density LIBs with LiNi0.5Co0.2Mn0.3O2 (NCM) cathode. Modern physical/chemical characterizations, electrochemical measurements, and in-situ/ex-situ observation and characterization methods are utilized to investigate the relationship of chemical composition and molecular structure of the binders with the properties such as crystalline degree, Tg, as well as the mechanism of self-healing and self-healing efficiency. The compatibility of the ion-conductive self-healing binders with the Si/C anodes, the stability of electrode/electrolyte interface, the electrochemical reaction kinetics behavior of anode/cathode electrodes and energy storage performance of LIBs will be emphatically studied to reveal the mechanism of self-healing binders improving the electrochemical performance of Si/C anode. The Performance of the high-energy density lithium-ion batteries based on the pre-lithiated Si/C anode and the high voltage NCM cathode are further investigated. The research is believed to provide some theoretical and technical guidance for developing lithium-ion batteries with high energy density and long cycle life.

针对当前提升锂离子电池能量密度的迫切需求，硅负极被认为是最具发展前景的下一代锂离子电池负极材料，粘结剂是维持硅负极电极结构稳定和保持良好电连接性的关键因素。本项目拟基于超分子弹性体聚合物，将高分子离子导体引入，开展面向硅负极的高离子导电性自修复粘结剂的研究，并以高容量硅碳复合材料为负极，以高电压三元材料为正极，构建高比能锂离子电池。结合现代物理/化学表征技术，电化学测试技术并发展原位/非原位观测技术，阐明自修复粘结剂的分子组成和结构与其结晶度、玻璃化转变温度(Tg)等性质、自修复机理及自修复效率的作用规律。并对其与硅碳复合材料的兼容性、电极/电解液界面的稳定性、电化学反应动力学行为及储锂性能的影响进行重点研究，揭示自修复粘结剂对提升高比能硅碳负极电化学性能的作用机制。进而预锂化后与高电压三元正极材料进行匹配优化，为设计高比能及长寿命的锂离子动力电池奠定理论基础。

硅基负极具有高的理论比容量，但在电化学过程中巨大的体积膨胀严重影响了硅基负极的循环稳定性。本项目设计制备了多种三维结构粘结剂，包括聚多巴胺接枝的交联聚丙烯酰胺PDA-c-PAM、两性离子络合网状粘结剂PVA-Bet、基于氢键交联的网状粘结剂PEI-TA、基于氢键交联的CMC-LA133复合粘结剂，以及基于离子配位作用的CS-EDTA交联粘结剂。对各类粘结剂的组成进行了系统优化、机械及物理性能进行了系统研究。其次，高度交联的聚合物由于溶解性及可加工性变差，对电极制备带来了困难，提出并发展了简单的原位热交联方法及技术，利用线性聚合物之间的物理及化学相互作业，在硅基负极制备过程中将线性聚合物转变成三维交联的网络结构的聚合物，基于共价键与氢键等协同作用原位制备了三维网状粘结剂PAA-Dex、c-CMC-IDA150、c-PAA-PAM、c-PVA-CA。原位交联技术大大简化了基于三维粘结剂硅基负极的制备过程，对于三维粘结剂的工业应用具有现实的指导意义。3D 结构粘结剂有效提升了硅基材料的电化学性能，并对粘结剂的作用机制进行了揭示。另外，设计制备了多种高性能的新型硅碳复合材料，包括三明治夹层结构的高负载SiO/Gt结构负极、高度石墨化碳包覆多孔硅复合材料p-Si NSs@ C、管状石墨烯卷包覆硅纳米颗粒复合材料Si@rGO NSs、具有高密实三维导电骨架的B-SiOx@CNT@LBO复合材料。并将所设计制备的粘结剂或者硅碳复合材料用于构筑锂离子电池，对电池的储锂性能进行了系统表征及研究。