Defect-Modulated MOF Nanochannels for the Quasi-Solid-State Electrolyte of a Dendrite-Free Lithium Metal Battery

Efficient and selective Li+ transport within the nanochannel is essential for high-performance solid-state electrolytes (SSEs) in lithium metal batteries. Introducing Li+ hopping sites into SSEs shows great potential for promoting Li+ transport; however, it typically reduces the Li+ transport nanochannel size, consequently increasing the energy barrier for Li+ transport. Herein, we present a molecular defect strategy for MOFs to introduce Li+ hopping sites and increase the nanochannel size simultaneously as quasi-solid-state electrolytes (QSSEs). Compared with the defect-free Li@UiO-66-based QSSE, the optimized Li@UiO-66-D2-based QSSE exhibits a remarkable 343% enhancement in Li+ conductivity and improved Li+ selectivity. Furthermore, the 9 cm × 6 cm Li|Li@UiO-66-D2|LFP pouch cell exhibits excellent cycling performance with high capacity retention. An in-depth mechanism study has unveiled the significant impact of both hopping sites and nanochannel size on Li+ transport, emphasizing the importance of a molecular defect strategy in enhancing the overall Li+ transport performance of MOF-based QSSEs.