Cyclodextrin-Integrated PEO-Based Composite Solid Electrolytes for High-Rate and Ultrastable All-Solid-State Lithium Batteries

Poly(ethylene oxide) (PEO)-based composite solid electrolytes (CSEs) are considered as one of the most promising candidates for all-solid-state lithium batteries (ASSLBs). However, a key challenge for their further development is to solve the main issues of low ionic conductivity and poor mechanical strength, which can lead to insufficient capacity and stability. Herein, β-cyclodextrin (β-CD) is first demonstrated as a multifunctional filler that can form a continuous hydrogen bond network with the ether oxygen unit from the PEO matrix, thus improving the comprehensive performances of the PEO-based CSE. By relevant characterizations, it is demonstrated that β-CD is uniformly dispersed into the PEO substrate, inducing adequate dissociation of lithium salt and enhancing mechanical strength through hydrogen bond interactions. In a Li/Li symmetric battery, the β-CD-integrated PEO-based (PEO-LiTFSI-15% β-CD) CSE works well at a critical current density up to 1.0 mA cm-2 and retains stable lithium plating/stripping for more than 1000 h. Such reliable properties also enable its superior performance in LiFePO4-based ASSLBs, with specific capacities of 123.6 and 114.0 mA h g-1 as well as about 100 and 81.8% capacity retention over 300 and 700 cycles at 1 and 2 C (1 C = 170 mA g-1), respectively.