Single-ion conductor covalently grafted onto MOFs to realize solid polymer electrolyte tripartite conducting channels in lithium metal batteries

Composite solid polymer electrolytes (SPEs) with metal organic frameworks (MOFs) fillers offer a promising route to improve lithium (Li)-ion transport and mechanical stability, but challenges such as poor filler/polymer compatibility and uncontrolled anion mobility. Herein, we present a molecularly engineered approach by covalently grafting a single-ion conductor (LiSTFSI) onto UIO-66-OH via an organosilane coupling agent (KH570), yielding a functional filler denoted as Li@UIO. When integrated into a PEO/LiTFSI matrix, Li@UIO constructs tripartite Li + conduction pathways through polymer segmental motion, intrinsic MOF ion-conducting sites, and MOF/polymer interfacial transport routes, while simultaneously immobilizing TFSI − anions and weakening Li + solvation structure. This synergistic design significantly enhances ion transport dynamics, achieving high ionic conductivity (2.57 × 10 −4  S/cm at 30 °C), enabling stable Li plating/stripping for over 3000 h with a low overpotential of 19 mV. In LiFePO 4 ‖Li@UIO/PL‖Li full cells, it delivers 85.1 % capacity retention after 600 cycles at 1C (60 °C). This study provides a new paradigm for designing multi-channel, single-ion-enhanced SPEs, offering a viable route toward safe, dendrite-free, high-energy-density lithium metal batteries.