基于化学偶联和氢键诱导的自修复硅负极粘结剂的设计与性能研究

Silicon is a promising anode material for the next generation energy storage system owing to its extremely high theoretical capacity. However, practical application of silicon anodes is seriously hindered by its fast capacity fading as a result of huge volume changes during the charge/discharge process. Non-functional polymer binders widely used in the state-of-the-art lithium-ion battery cannot maintain the integrity of silicon anode upon cycling due to their poor interaction, leading to fast capacity fading and low Coulombic efficiency. Here, we propose that a novel functional silyl-terminated poly(urethane-urea) binder for silicon anode to address the issues mentioned above. The silyl group (-Si(OEt)3) can chemically bond silicon particles to form Si-O-Si bond through its hydrolysis and condensation. This “coupling effect” can significantly improve the compatibility of inorganic particles with polymer binder, enabling a robust silicon electrode. In addition, this hybrid polymer exhibits good self-healing ability thanks to the strong hydrogen bonding of poly(urethane-urea) moieties in the binder. These characteristics facilitate the structural stability of silicon anode upon large volume changes in cycling. The structure, morphology, and electrochemical performance of silicon anode with self-healing binder will be systematically investigated through multiple characterization techniques, such as SEM, TEM, XPS, and EIS. Moreover, the structure-performance relationship will be further discussed based on the aforementioned experimental analysis to clarify the mechanism of the silyl-terminated poly(urethane-urea) binder. The rationally designed structure, exceptional electrochemical performance together with the clarified electrochemical mechanism will be greatly helpful for the design and fabrication of novel high-performance-electrodes with large volume change during cycling.

作为一种高比容电池材料，硅负极潜力巨大，但脱嵌锂过程中巨大的体积变化造成的极片结构破坏问题严重制约着该材料的大规模应用。传统的非功能聚合物粘结剂与无机硅颗粒界面相容性差且结合力弱，难以维持电极结构稳定性，易导致容量的快速衰减。本项目拟基于“化学偶联”和“氢键诱导”策略设计一种具有高粘合力和自修复功能的端硅氧烷基聚氨酯脲粘结剂。该粘结剂的硅氧烷端基易与硅发生化学偶联，将显著增强二者的界面结合力；聚氨酯脲主链在氢键作用下可促进电极结构的动态自修复，实现硅负极的结构完整性。通过调控缩合聚合和封端反应条件，可改变粘结剂的化学组成和分子量，实现粘结剂功能的最优设计。通过本项目的研究，揭示粘结剂的化学组成、分子结构以及分子量等对硅负极结构稳定性、离子及电子传导以及固体-电解液界面层的影响，阐明粘结剂结构与电化学性能之间的内在关系，为高比容负极用粘结剂的开发提供理论和实验指导。

作为一种高比容电池材料，硅负极潜力巨大，但脱嵌锂过程中巨大的体积变化造成的极片结构破坏问题严重制约着该材料的大规模应用。传统的非功能聚合物粘结剂与无机硅颗粒界面相容性差且结合力弱，难以维持电极结构稳定性，易导致容量的快速衰减。本项目基于“化学偶联”和“氢键诱导”策略设计一种具有高粘合力和自修复功能的端硅氧烷基聚氨酯脲粘结剂。该粘结剂的硅氧烷端基易与硅发生化学偶联，显著增强二者的界面结合力；聚氨酯脲主链在氢键作用下促进电极结构的动态自修复，实现硅负极的结构完整性。.在此基础上，进一步探究超分子相互作用在粘合剂分子设计中的作用，制备了逐级应力耗散型粘合剂和离子交联型力学增强粘合剂，阐明粘结剂结构与电化学性能之间的内在关系，为高比容负极用粘结剂的开发提供理论指导。通过对分子内部氢键键能的调控，构建了连续氢键（−2.88至−10.04 kcal mol−1）耗能体系，解决了传统粘合剂因能量耗散不充分而导致结构破坏的问题，极大地改善了高比容Si基负极的结构稳定性和循环寿命。基于逐级应力耗散型粘合剂所制备的2 Ah软包电池，在1 C下连续循环700周电池容量保持率可高达80.2%，使其在实际应用中更具发展潜力。.

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