Coordination engineering of ion highways for ultrahigh flux and interfacial stabilization in MOF-based solid electrolytes

Solid polymer electrolytes face a fundamental trade-off between ionic conductivity and interfacial stability, particularly when incorporating the plasticizer succinonitrile (SN): specifically, SN boosts Li + conductivity by tailoring the Li + coordination environment and facilitating Li + transport; However, the uncontrolled diffusion and electrochemical degradation of SN undermine the stability of Li metal anode interface. We address this challenge by constructing coordination-engineered ion highways within a hierarchical iron-based metal-organic framework (MOF) architecture, through rationally designing Fe 3+ -cyano (CN - ) coordination bonds as molecular anchors to permanently immobilize SN within the MOF nanopores while simultaneously regulating the competitive coordination of Li + among MOF-immobilized SN, poly(ethylene oxide) (PEO), and TFSI - anions. This dual-regulation strategy simultaneously constructs continuous 3D Li + transport pathways and suppresses parasitic reactions, delivering a high room-temperature ionic conductivity (1.16 mS cm −1 ), a high Li + transference number (0.80), and a extended electrochemical window of 5.2 V. The dual-regulation strategy enables dendrite-free Li plating/stripping for 1600 h in Li/Li symmetric cells, while a LiFePO 4 (LFP) full cell retains 85.6% of its initial capacity after 1200 cycles at 2 C. Multiscale characterizations and modeling reveal how the Fe 3+ -CN “molecular lock” impedes SN degradation, while optimized Li + flux homogenization facilitates the formation of an inorganic-rich interphase that suppresses dendrite growth. This work provides a versatile strategy for decoupling ion conduction from interfacial degradation in solid-state batteries.