Deep dive into anionic metal-organic frameworks based quasi-solid-state electrolytes

The development and application of high-capacity energy storage has been crucial to the global transition from fossil fuels to green energy. In this context, metal–organic frameworks (MOFs), with their unique 3D porous structure and tunable chemical functionality, have shown enormous potential as energy storage materials for accommodating or transporting electrochemically active ions. In this perspective, we specifically focus on the current status and prospects of anionic MOF-based quasi-solid-state-electrolytes (anionic MOF-QSSEs) for lithium metal batteries (LMBs). An overview of the definition, design, and properties of anionic MOF-QSSEs is provided, including recent advances in the understanding of their ion transport mechanism. To illustrate the advantages of using anionic MOF-QSSEs as electrolytes for LMBs, a thorough comparison between anionic MOF-QSSEs and other well-studied electrolyte systems is made. With these in-depth understandings, viable techniques for tuning the chemical and topological properties of anionic MOF-QSSEs to increase Li+ conductivity are discussed. Beyond modulation of the MOFs matrix, we envisage that solvent and solid–electrolyte interphase design as well as emerging fabrication techniques will aid in the design and practical application of anionic MOF-QSSEs.