Metal Organic Framework Nanorod Doped Solid Polymer Electrolyte with Decreased Crystallinity for High‐Performance All‐Solid‐State Lithium Batteries

Poly(ethylene oxide) (PEO), an important solid polymer electrolyte (SPE) for solid‐state lithium batteries, suffers from low ionic conductivity and poor electrochemical stability; many inorganic solid compounds have been explored as fillers to address these issues. Herein, we report that Al‐metal organic framework (MOF) nanorods could work as efficient solid fillers to boost the electrochemical performance of PEO‐based SPEs. The addition of MOF nanorods was found to inhibit the crystallization of PEO and effectively weaken the interactions among the PEO chains, resulting in evidently enhanced ionic conductivity and improved electrochemical stability; moreover, when embedded in PEO, such Al‐MOF nanorods are microporous and micrometer long, which are expected to favor the transportation of Li+ over the significantly more bulky anions TFSI−. Compared with pure PEO SPE, our optimal sample PEO‐MOF5% SPE has higher ion conductivity (2.09×10−5 S/cm at 30 °C and 7.11×10−4 S/cm 60 °C), a larger lithium‐ion transference number (0.46) and an enlarged electrochemical window (4.7 V versus Li/Li+). Accordingly, the cell of LiFePO4/PEO‐MOF5%/Li shows excellent cycle performance and rate performance. Our work proved the advantages of MOF particles as solid fillers towards high‐performance PEO‐based SPE, and we also put emphasis on the shape effect of the solid fillers on the lithium‐ion transference number and, thus, the electrochemical performance of the resulting SPE. Stable cycling: The incorporation of microporous metal‐organic framework (MOF) nanorods in poly(ethylene oxide) (PEO)‐based solid polymer electrolyte leads to decreased polymeric crystallinity, improved ionic conductivity and enhanced lithium‐ion transference number, which enables better cycling stability and rate performance for the relevant all‐solid‐state battery LiFePO4/PEO‐MOF5%/Li.