Facilitating Lithium-Ion Conduction in Gel Polymer Electrolyte by Metal-Organic Frameworks

Gel polymer electrolytes (GPL) that comprise polymer, lithium salts, and organic plasticizers hold great promise for safer lithium-ion batteries, because of liquid-like ionic conductivity, as well as solid-like leakage-free property. However, only a small portion of ion conduction effectively carried by Li+ ions (or low Li+ transference number) gives rise to poor interfacial stability between GPL with electrodes and limited practicability. Here, metal-organic framework (MOF) containing open-metal sites (OMSs) are used as fillers that endow GPL simultaneously with high ionic conductivity (>1 mS cm–1) and a high Li+ transference number (up to 0.66), which results from immobilized anions and facilitated cation conduction by virtue of OMSs. Implementations of the GPL with OMSs-laden MOF in pseudo-solid-state batteries afford affinitive interfaces involving metallic Li and intercalation-type electrodes (LiFePO4, Li4Ti5O12), which contribute to significant improvements in battery durability and thereby could introduce a new type of MOF fillers for solid-state polymer electrolytes.