导电、导离子、高粘弹性理想电极粘结剂的制备与性能研究

Optimization of the electrode is an important means to improve the performance of lithium batteries. Electrode can be regarded as a composite material mainly composed of active substance, conductive agent and binder. The electrode should have a spatial structure with connected electron and ion transfer channels. It should be able to buffer the volume change during the charge and discharge process and maintain the structure stable. To achieve this purpose, binder plays an important role, which was not realized until recent years. Studies reveal that the viscoelasticity, electron conductivity and ion conductivity of binders have obvious effects on the battery charge and discharge rate, cycle life and so on. However, most related studies are limited to the modification and complex of a few binders, or employment of other existing binders for electrodes. Few studies have analyzed the requirements from electrodes and prepare one binder molecule to satisfy all these requirements. Accordingly, based on the needs from electrode, an electrically conductive, ion-conducting, highly adhesive and elastic ideal electrode binder is proposed in the current proposal. The research will focus on the preparation and precise regulation of this multi-functional polymeric binder, the relationship between the polymer chain structure, phase morphology and functions, and the relationship between the binder and the battery performance. The research from the current proposal will have scientific significance on knowledge extension about the design and synthesis of multifunctional polymers, the relationship between their structure and properties. The improvement of electrode binder has important practical values on the performance improvement of lithium batteries and the development of high energy density batteries.

电极的优化是提升锂电池性能的重要手段。电极可视为一种复合材料，主要由活性物质、导电剂和粘结剂组成。电极应具备连通导电、导离子的空间结构，能够在往复充放电中缓冲体积变化、维持结构稳定，这其中粘结剂所起的关键作用在近些年被逐渐了解。研究发现电极粘结剂的粘弹性、导电、导离子能力对电池充放电速率、循环寿命等存在显著影响。但是，目前相关研究多局限在少数几种电极粘结剂的改性和复配，或将其它非电极粘结剂尝试用于电极，鲜有研究能分析电极各种需求，基于结构设计制备粘结剂分子来满足这些需求。因此，申请者分析电极需要，提出一导电、导离子、高粘结性、高弹性理想电极粘结剂，研究该多功能聚合物的制备和精确调控，其链结构、相形态与各功能间关系，粘结剂与电池性能间关系。该项研究对多功能聚合物的设计与合成、结构与性能间关系知识的扩展有重要的科学意义，电极粘结剂的技术进步对锂电池性能提升、高比容量电池研发有着重要的应用价值。

锂离子电池电极可视为一种复合材料，由活性物质、导电剂和粘结剂等组成。电极粘结剂的作用是将各活性组份、导电剂等无机颗粒粘结到金属集流体上得到一完整极片，并在往复充放电中缓冲体积变化、维持该结构稳定。因此，粘结剂性能对电池充放电速率、循环寿命等存在显著影响。在本项目中，研究者从分析电极需求出发，提出一导电、导离子、高粘结性、高弹性理想电极粘结剂。首先研究了该多功能电极粘结剂的制备和链结构的精确调控方法，通过程序控制半连续饥饿进料可逆加成断裂链转移乳液聚合制备了多嵌段共聚物，得到了导离子、导电子、高粘弹性多嵌段聚合物，实现了多功能粘结剂的制备及链结构的精确调控。该方法可针对不同电极材料及性能要求，灵活调节粘结剂的电解液溶胀能力、粘结官能团性质、粘结强度等。随后，系统研究并掌握了粘结剂链结构与其相形态、功能通道连通性、及最终材料导电、导离子性、粘弹性等各性能间关系。研究发现，嵌段结构可以解决粘结剂溶胀电解液能力与保持机械强度之间的矛盾，大幅提高电极粘结剂性能；而在各嵌段间引入梯度链序列结构，可显著提升相畴的连续性，对锂离子的传输速率有显著提升。针对传统锂离子电池正负极、高容量硅负极、硫正极、全固态电极、可拉伸电极等不同电极要求，设计制备了具有不同链结构的电极粘结剂，研究了粘结剂与电极结构及电极各项性能之间关系，通过粘结剂的设计显著提升了各种电极性能。特别是针对高比容量硅负极，将高弹性及对硅材料有强粘结力的丙烯酸引入粘结剂分子链中，制备了多功能硅负极粘结剂，使得到的硅负极循环寿命显著上升，初始比容量达4140 mAh/g，在100圈循环后，其比容量仍能保持在2200 mAh/g。该项目研究对多功能聚合物的设计与合成、结构与性能间关系知识的扩展有重要的科学意义，电极粘结剂的技术进步对锂电池性能提升、高比容量电池研发有着重要的应用价值。

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