Design of Quasi‐Metal–Organic Frameworks for Solid Polymer Electrolytes Enabling an Ultra‐Stable Interface with Li Metal Anode

Solid polymer electrolytes (SPEs) are crucial in the development of lithium metal batteries. Recently, metal-organic frameworks (MOFs) with open metal sites (OMSs) have shown promise as solid fillers to improve the performance of SPEs. However, the number of OMS-containing MOFs is quite limited, comprising less than 5% of the total MOFs. When considering yield, cost, and processability, the commonly used OMS-containing MOFs are no more than 10 types, causing great limitations. Herein, we reported a simple and universal methodology that converted OMS-free MOFs to OMS-rich quasi-MOFs for developing high-performance SPEs, and explored the underlying mechanism. The "OMS-polymer" and "OMS-ion" interactions were investigated in detail to elucidate the role of quasi-MOFs on battery performance. It was found that quasi-MOFs, functioning as ion sieves, can effectively regulate ion migration, thus promoting uniform Li deposition and enabling an ultra-stable interface. As a result, the Li symmetric cell stably ran over 3000 h at 0.3 mA cm^-2, while the full cell retained 85 % of its initial capacity after 1500 cycles at 1.0 C. Finally, universal testing was performed using other MOFs, confirming the generalizability and effectiveness of our design concept.