离子液体聚合物固体电解质锂离子迁移机制研究

Solid-state electrolyte can fundamentally solve the hidden danger of leakage and flammability and improve the energy density as a replacement of the liquid electrolyte and separator of the traditional battery . It has become a promising candidate in next generation all-solid-state battery. All-solid-state batteries with polymer electrolytes attract intensive interests due to high safety characteristics, high energy density, wide operating temperature and long cycle life. There are some disadvantages of traditional polymer electrolytes, such as low conductivity, low lithium ion mobility and poor compatibility with high voltage cathode. In this study, poly(ionic liquid) with good ionic conductivity and mechanical strength will be synthesised as polymer electrolyte matrix. The polymer electrolytes with different compositions will be prepared by adding lithium salts and/or inorganic electrolyte particles into the poly(ionic liquid) matrix. The effects of the property and structure of poly(ionic liquid) on ionic conductivity and electrochemical properties will be explored through changing the types and structures of ionic liquid. And the transport mechanism of Li-ion in poly(ionic liquid) electrolyte will be putted forward. This project will provide a scientific basis for the design and preparation of polymer electrolytes, and provide a new idea for the development of all-solid-state batteries with high energy density and safety.

固体电解质取代传统锂电池中的电解液和隔膜，能从根本上解决电解液泄漏、易燃等安全隐患，并有助于提高锂电池的能量密度，成为发展下一代全固态电池的研究热点。全固态聚合物电解质电池具有安全性能好、能量密度高、工作温度区间广、循环寿命长等优点。针对传统聚合物电解质电导率低、锂离子迁移数低、与高电压正极相容性差的缺点，本项目拟合成兼备良好离子导电性与机械强度的离子液体聚合物作为聚合物电解质基体，在离子液体聚合物基体中加入锂盐和/或无机电解质颗粒，获得不同组成的离子液体聚合物电解质。通过改变离子液体阴阳离子的种类和结构，探索离子液体聚合物的性质及结构对离子电导率的影响，阐明对离子液体聚合物电解质电化学性能的影响规律，揭示锂离子在离子液体聚合物电解质中的传输机制。本项目的开展将为设计和制备聚合物电解质提供科学依据，并为高能量密度、高安全性的全固态电池的研制提供新思路。

锂离子电池作为一种高效的化学储能器件，已广泛应用于便携式电子设备。传统锂离子电池多采用可燃性聚合物隔膜和液体有机电解液，存在泄漏、易燃等安全隐患。而使用固体电解质取代传统电池中的电解液和隔膜，能从根本上解决这些安全问题，并有助于提高锂电池的能量密度，成为发展下一代全固态电池的研究热点。针对传统聚合物电解质电导率低、锂离子迁移数低、与高电压正极相容性差的缺点，本项目合成兼备良好离子导电性与机械强度的离子液体聚合物作为聚合物电解质基体，在离子液体聚合物基体中加入锂盐和/或无机电解质颗粒，获得不同组成的离子液体聚合物电解质。结果表明，聚合离子液体和纳米填料LLZTO可以有效改善界面相容性，得到的复合电解质的室温离子电导率为9.26×10-4 Scm-1，锂离子转移数为0.57，电化学窗口可达5.2 V，稳定的界面使锂对称电池在800 h内均匀电镀/剥离。使用LiFePO4为正极组装的固态电池100次循环后，0.5℃的容量保持率为94.1%，NCM811为正极的固态电池在0.1 C的室温放电容量为170 mAh g-1。使用该复合电解质组装的软包电池，在折叠、剪切等条件下仍能点亮LED灯。本项目的开展将为设计和制备聚合物电解质提供了新方法，并为高能量密度、高安全性的全固态电池的研制提供新思路。