Xia Yangyang, Xu Nuo, Du Lulu, Cheng Yu, Lei Shulai, Li Shujuan, Liao Xiaobin, Shi Wenchao, Xu Lin, Mai Liqiang
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China.
Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang 441053, China.
ACS Appl Mater Interfaces. 2020 May 20;12(20):22930-22938. doi: 10.1021/acsami.0c04387. Epub 2020 May 8.
Solid-state lithium batteries have attracted great attention owing to their potential advantages in safety and energy density. Among various solid electrolytes, solid polymer electrolyte is promising due to its good viscoelasticity, lightweight, and low-cost processing. However, key issues of solid polymer electrolyte include poor ionic conductivity and low Li transference number, which limit its practical application. Herein, a new-type of ultraviolet cross-linked composite solid electrolyte (C-CSE), composed of ZIF-based ionic conductor (named ZIL) and polymer, is designed with enhanced ion transport. The ZIL is composed of ZIF-8 and ionic liquid, which can provide C-CSE with fast ion transport paths. Moreover, the proper pore size of ZIF-8 can restrict the migration of embedded ionic liquid and thus construct a solid-liquid transport interface between polymer chains and ZIF-8, which could achieve fast ion transport. In addition, ultraviolet irradiation can decrease the crystallization of C-CSE and thus increase the amorphous region. Consequently, the C-CSE show excellent electrochemical performance including high ionic conductivity of 0.426 mS cm at 30 °C, high Li transference number of 0.67, and good Li|Li compatibility cycle over 1040 h. Experimental and computational results indicate that diffusion energy barrier of Li through ZIF-8 is smaller than that of polymer chains, which reveals a new Li transport mechanism between polymer chains and ZIL, from "chain-chain-chain" to "chain-ZIL-chain". This work demonstrates rational design of ion transport paths at the interface of solid electrolyte could facilitate the development of solid-state lithium batteries as a promising novel strategy.
固态锂电池因其在安全性和能量密度方面的潜在优势而备受关注。在各种固体电解质中，固体聚合物电解质因其良好的粘弹性、轻质和低成本加工而具有广阔前景。然而，固体聚合物电解质的关键问题包括离子电导率低和锂迁移数低，这限制了其实际应用。在此，一种由基于ZIF的离子导体（命名为ZIL）和聚合物组成的新型紫外交联复合固体电解质（C-CSE）被设计用于增强离子传输。ZIL由ZIF-8和离子液体组成，可为C-CSE提供快速离子传输路径。此外，ZIF-8合适的孔径可以限制嵌入离子液体的迁移，从而在聚合物链和ZIF-8之间构建固液传输界面，实现快速离子传输。此外，紫外线照射可以降低C-CSE的结晶度，从而增加非晶区。因此，C-CSE表现出优异的电化学性能，包括在30℃时0.426 mS cm的高离子电导率、0.67的高锂迁移数以及在1040 h以上良好的Li|Li兼容性循环。实验和计算结果表明，锂通过ZIF-8的扩散能垒小于聚合物链的扩散能垒，这揭示了聚合物链和ZIL之间一种新的锂传输机制，从“链-链-链”到“链-ZIL-链”。这项工作表明，在固体电解质界面合理设计离子传输路径可以作为一种有前景的新策略促进固态锂电池的发展。
