面向自保护电化学储能器件的温敏水凝胶电解质制备与应用研究

Thermal runaway is a serious problem to be solved urgently in electrochemical energy storage devices such as lithium-ion batteries and supercapacitors. One important method is to design effective thermal control systems to suppress the thermal runaway phenomenon. However, the existing thermal control systems usually have deficiencies in safety, device design, electrolyte conductivity and thermal control effects. Based on the good thermosensitive phase transition characteristics of poly(N-isopropylacrylamide) (PNIPAM), this project aims to develop thermosensitive hydrogel electrolyte systems with "intelligent reversible thermal control" to realize thermosensitive reversible interruption of ion migration in electrolytes, effectively solving the thermal runaway problem of electrochemical energy storage devices. In this study, we intends to develop synthesis systems of the thermosensitive hydrogel electrolytes with good performance by using the strategy of designing double-network-nanocomposite structure. We will investigate the preparation-structure-property relationship between reactant composition, preparation conditions and thermosensitive range, structural stability, mechanical strength and thermosensitive ionic conductivity of the hydrogel electrolytes. The mechanism of thermosensitive ionic conductivity of hydrogel electrolytes will be revealed at micro-nano scale. On this basis, self-protection lithium-ion battery and supercapacitor devices will be developed for electrochemical and thermosensitive self-protection performance investigation. And the thermosensitive self-protection performance of the electrochemical energy storage devices will be futher regulated through the composition and structure design of the electrolytes.

热失控现象是锂离子电池、超级电容器等电化学储能器件亟待解决的重大问题，设计合理有效的热控制系统是抑制热失控现象的重要手段。然而，目前报道的热控制方案在安全性、器件构造、电解质导电性能以及热控制作用效果等方面仍然存在不足。本项目基于聚N-异丙基丙烯酰胺（PNIPAM）的良好温敏相变特性，拟构建“智能可逆热控制”的温敏水凝胶电解质系统，实现电解质内部离子迁移的温敏式可逆阻断，有效解决电化学储能器件热失控问题。研究采用双网络-纳米复合结构的设计策略，发展高性能温敏水凝胶电解质的合成制备体系；系统研究反应物组分、制备条件与水凝胶电解质温敏区间、结构稳定性、力学强度、温敏离子传导行为等性能间的构效关系；并在微纳尺度下深入揭示电解质的温敏离子传导行为机制。在此基础上，发展自保护锂离子电池和超级电容器器件，考察其电化学性能和探究热响应自保护能力，并通过电解质组成、结构设计实现器件自保护性能调控。

随着现代生活和工业生产对电化学储能需求的日益增长，以超级电容器和锂离子电池为代表的电化学储能器件所面临热失控所致的安全性问题在近年来受到了越来越广泛的关注与重视。而从电解质角度出发，发展适用于电化学储能器件的温敏相变体系实现器件过热自保护，或开发新型高性能固态电解质替代传统易燃有机电解液均对高安全电化学储能器件的进一步发展具有重要意义。本项目创造性地基于β-环糊精/二苯胺/氯化锂/N,N-二甲基甲酰胺超分子体系的温敏凝胶化行为，成功开发了具有适宜热响应温度的自保护超级电容器器件；探明了物质组成与凝胶化温度的构效关系；系统考察了该器件温敏自保护响应速率并研究了不同温度对其自保护行为的影响规律；揭示了该超分子电解质体系实现器件温敏自保护性能的内在工作机制；实现了器件在70 °C临界温度之上界面阻抗跃升所致的快速过热自保护过程。此外，项目通过力学强化、富盐结构和无机锂离子导体掺杂协同作用，电荷均布调控以及阻燃综合设计等策略，设计制备了一系列高性能聚偏氟乙烯基锂离子电池三明治结构固态电解质膜；研究了固态电解质组成结构对离子电导率、电化学锂沉积行为、器件倍率和充放电循环性能的影响规律和作用机制；研究了低液量负载下电解质膜的阻燃特性和通过商用软包电池探究了电解质膜应对复杂应用环境的广泛适用性；实现了器件在室温下高于1000次的长周期高容量稳定充放电循环。本项目为高效智能自保护电化学储能器件提供了一种电解质新方案，为高性能电化学储能器件固态电解质的制备提供了新策略。研究成果对高安全电化学储能器件的设计具有一定指导意义。