Ultra‐High Capacity Density Lithium Metal Battery is Effectuated via Coupling Single Lithium‐Ion Conductor and Lithium‐Ion Sieve Within Yttrium‐Organic Framework

Among various strategies to solve the issue of lithium dendrites in high voltage lithium metal batteries (HV-LMBs), lithium-ion sieves (LISs) and single lithium-ion conductors (SLICs) are considered the most effective and fundamental approaches. However, the performance improvement of HV-LMBs achieved through a single strategy remains significantly below the expected level. We aimed to couple a LIS with an SLIC to synergistically enhance the performance of HV-LMBs and successfully synthesized the rare earth MOF-based SLIC [LiY(BDC)₂(H₂O)]·2H₂O (LiYBDC-H₂O, H₂BDC = 1,4-dicarboxybenzene) via in-situ synthesis. Its conductivity is significantly enhanced following solvation and gelation (0.972/0.228 mS cm^-1 vs. 0.036 mS cm^-1). More importantly, NMR/IR characterization and theoretical calculation demonstrate that LiYBDC preferentially coordinates with EC (EC = ethylene carbonate) in gelated quasi-SLIC LFE@LiYBDC. This interaction facilitates the formation of LIS resulting in an exceptionally high lithium-ion transfer number of 0.92. Last but not the least, the synergetic strategy combining the LIS and SLIC not only greatly improved the LiNi_1/3Co_1/3Mn_1/3O₂|Li with the second highest capacity density (167.82 mAh g^-1) but also markedly enhanced Li|Li and Cu|Li batteries with the longest Li|Li and Cu|Li cycle stability of 3000 h and 700 h.