基于PEO/Li7La3Zr2O12三维复合结构的电极/电解质一体化固态锂硫电池的构筑及性能研究

The solid state lithium-sulfur batteries have been becoming the hotspot and key point in the field of rechargeable batteries, due to its high energy density and high safety. However, the low ionic and electronic conductivity of sulfur, poor electrode/electrolyte interface compatibility are still the challenges for its practical application. To solve these issues, an electrode/electrolyte integrated solid state Li-S batteries based on three dimensional (3D) conductive network has been proposed. By the “electrospinning-carbon coating” method, the 3D free-standing Li7La3Zr2O12 (LLZO)/C fiber membrane is constructed to form the fast ion/electron transport network. In order to improve the microscopic-interface compatibility of sulfur/conductive network interface and macroscopic-interface compatibility of cathode/electrolyte interface, the flexible PEO/LLZO hybrid electrolyte, the 3D free-standing LLZO@C/S film electrode and lithium metal anode are incorporated into an integrated solid-state Li-S cell. Meanwhile, combined with a variety of characterization techniques, the relationships between the microstructure and ionic/electronic conductivity of electrode are demonstrated. The method to regulate the interfacial compatibility in integrated solid state Li-S cells is developed and the lithium storage mechanism and kinetics model of sulfur cathode in integrated solid state Li-S cells is further revealed. This project not only achieve the solid-state lithium sulfur batteries with high specific energy density and long cycle life, but also play an important role in guiding the development of other type solid state Li-ion batteries.

固态锂硫电池因具有高能量密度、高安全性等优点已成为储能电池技术研究的热点和重点，但仍面临硫正极电子电导和离子电导较低、正极与固态电解质之间的界面兼容性较差等挑战。针对这些关键问题，申请人拟提出并构筑一种具有三维结构导电网络的一体化固态锂硫电池，通过“静电纺丝-离子液体原位包碳”方法制备自支撑三维Li7La3Zr2O12（LLZO）/C纳米纤维薄膜，以形成离子/电子快速协同传输网络；将柔性PEO/LLZO电解质与自支撑三维LLZO@C/S薄膜电极和锂负极复合成一体化固态锂硫电池，以改善硫/导电网络微观界面与硫正极/电解质宏观界面的多尺度界面兼容性。同时，结合多种表征技术，阐明电极微结构与离子/电子传输之间的构效关系；发展电极/电解质界面兼容特性的调控方法；明晰固态硫正极的储能机理和电极动力学模型。本项目的实施可望获得高比能、长寿命的固态锂硫电池，同时也为其他类型固态锂电池的研发提供新思路。

固态锂硫电池因为其高能量密度、高安全性和高循环稳定性而在储能电池技术领域备受关注，但是其发展一直受到硫正极中电子和离子电导率低、正极与固态电解质之间界面兼容性差等关键问题的制约。为此，本项目拟设计构筑一种具有三维导电网络结构的一体化固态锂硫电池。通过静电纺丝制备自支撑Li7La3Zr2O12（LLZO）纤维薄膜，再通过离子液体原位碳化包覆形成离子/电子协同快速传输网络。研究发现造成LLZO前驱体纤维直径差异主要在于前驱液进样速率，而适合煅烧LLZO纤维薄膜的温度和时间分别为750 ℃和2小时。将柔性PEO/LLZO电解质与自支撑三维LLZO@C/S薄膜电极和锂负极复合成一体化固态锂硫电池。所组装电池能稳定循环110次以上，容量衰减率仅为5%。但电池的可逆容量仅有约500 mAh g-1，且在116次循环后因锂枝晶而短路。为了提升固态锂硫电池的可逆容量，本项目开发了两种硫转化反应催化剂——缺陷型普鲁士蓝和MXene负载过渡金属纳米颗粒。为了解决锂负极/电解质界面兼容性较差带来的锂枝晶问题，本项目开发了离子液体界面润湿剂，并优化了其添加量和探究了离子液体阳离子对界面化学的影响。本项目阐明一体化电池中电极微结构与离子/电子传输之间的构效关系；揭示电池中固态硫正极的储能机理和电极动力学模型；发展一体化电池中电极/电解质界面兼容特性的调控方法。本项目的实施对构建高比能固态锂硫电池体系有理论指导意义，也会为其他类型固态锂电池的开发应用提供重要的参考价值。

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