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 LiFePO4 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.