Elucidation of Li+ Conduction Behavior in MOF Glass Electrolyte Toward Long‐Cycling and High C‐Rate Lithium Metal Batteries

Fast Li⁺ migration in cascade structure composed of inorganic-dominated cathode/anode interphase and glassy metal-organic framework electrolyte enables long-life and high C-rate lithium metal batteries.

Abstract

Vitrified metal–organic frameworks (MOFs) are promising solid-state electrolytes for lithium metal batteries due to their unique structures. Nevertheless, the effect of distorted molecular structures in glassy MOFs on Li⁺ migration behavior at the molecular level remains largely unexplored, posing a huge obstacle to further boosting their electrochemical performances. Herein, Li⁺ conduction behavior in glassy ZIF-62 quasi-solid-state electrolyte (GZ-62-QSSE) is molecularly elucidated, in which Li⁺ migration is accomplished by the continuous delivery of N sites in imidazole and benzimidazole ligands like the process of relay race. Such fast Li⁺ migration in GZ-62-QSSE demonstrates more than 1.5-time increase in transference number and helps to generate inorganic-dominated cathode/anode interphases for unblocked ion transport compared with crystalline ZIF-62 electrolyte. Consequently, the long-term stability with remarkable high-rate capability is realized in the proof-of-the-concept full cells, which represents one of best values among all reported MOF-based solid-state batteries. For example, LiFePO₄ ||Li full cells employing GZ-62-QSSE brilliantly undergo 3000 cycles with high initial capacity of 132.1 mAh g⁻¹ and ultralow decay rate of 0.009% at 1 C. Full cells still display high discharge capacity of 83.6 mAh g⁻¹ at 5  C. The elaborated high-performance glassy ZIF-62 electrolyte offers new insights for exploiting advanced solid-state electrolytes and propels the development of solid-state lithium metal batteries.