Glassy Metal–Organic‐Framework‐Based Quasi‐Solid‐State Electrolyte for High‐Performance Lithium‐Metal Batteries

Abstract Enhancing ionic conductivity of quasi‐solid‐state electrolytes (QSSEs) is one of the top priorities, while conventional metal–organic frameworks (MOFs) severely impede ion migration due to their abundant grain boundaries. Herein, ZIF‐4 glass, a subset of MOFs, is reported as QSSEs (LGZ) for lithium‐metal batteries. With lean Li content (0.12 wt%) and solvent amount (19.4 wt%), LGZ can achieve a remarkable ion conductivity of 1.61 × 10 −4 S cm −1 at 30 °C, higher than those of crystalline ZIF‐4‐based QSSEs (LCZ, 8.21 × 10 −5 S cm −1 ) and the reported QSSEs containing high Li contents (0.32–5.4 wt%) and huge plasticizer (30–70 wt%). Even at −56.6 °C, LGZ can still deliver a conductivity of 5.96 × 10 −6 S cm −1 (vs 4.51 × 10 −7 S cm −1 for LCZ). Owing to the grain boundary‐free and isotropic properties of glassy ZIF‐4, the facilitated ion conduction enables a homogeneous ion flux, suppressing Li dendrites. When paired with LiFePO 4 cathode, LGZ cell demonstrates a prominent cycling capacity of 101 mAh g −1 for 500 cycles at 1 C with the near‐utility retention, outperforming LCZ (30.7 mAh g −1 ) and the explored MOF‐/covalent–organic frameworks (COF)‐based QSSEs. Hence, MOF glasses will be a potential platform for practical quasi‐solid‐state batteries in the future.