Extraordinary Ionic Conductivity Excited by Hierarchical Ion‐Transport Pathways in MOF‐Based Quasi‐Solid Electrolytes

Abstract

AbstractLiquid‐electrolyte‐laden metal–organic frameworks (LE‐laden MOFs) are promising quasi‐solid electrolytes (QSEs) for metal‐anode batteries. To achieve a high ionic conductivity, considerable efforts have been devoted to designing continuous and compact LE‐laden MOF layers. Surprisingly, in this work, an extraordinarily high ionic conductivity (1.02 mS cm−1) is observed in an LE‐laden MOF electrolyte with abundant interstices and cracks. Herein, various macroscopic and mesoscopic pore structures of Li‐LE‐laden HKUST‐1 QSEs are prepared via morphology control and different cold‐pressing procedures. Thereinto, Li‐LE‐laden cuboctahedron HKUST‐1 prepared under 150 MPa cold‐pressing with an optimal hierarchical pore structure (Li‐Cuboct‐H) exhibits the highest ambient ionic conductivity (1.02 mS cm−1). It is found that interstices and cracks in electrolytes construct a set of interconnected Li‐LE networks with innate MOF channels and facilitate Li+ transfer in the hybrid ion‐transport pathways. The Li/LiFePO4 cells based on Li‐Cuboct‐H deliver a splendid capacity retention of 93% over 210 cycles at 1 C. Meanwhile, the high ionic conductivities (higher than 10−4 S cm−1) can be achieved in different ion conductor systems (Na, Mg, and Al) under the same guideline. This work redefines the understanding of ion transport in MOF‐based QSEs and breaks the bottleneck of MOF‐based QSEs.