Molecular‐Scale Interface Engineering of Metal–Organic Frameworks toward Ion Transport Enables High‐Performance Solid Lithium Metal Battery

Abstract Metal–organic frameworks (MOFs) have drawn considerable interest as solid electrolytes (SEs) by virtue of their talents for rational design as ion channels. The crystal interface plays a significant role in ion transport and is thus of vital importance to the performance of solid batteries, however, interface effects of MOFs in SEs are not yet fully understood, especially at the molecular level, and not engineered as well. In this work, MOFs engineered with diverse molecules (Lewis bases) are designed for an optimized interfaces and the impact of interfaces for ion transport is analyzed by using engineered MOFs as SEs. The results show that the ion conductivity of MOFs decorated with a long chain Lewis base (LCLB) has been greatly improved. The interface resistance of the SEs composed of MOFs with LCLB has decreased markedly. Most importantly, the corresponding Li|SE|LiPO 4 solid‐state battery (SSB) shows an improved specific capacity of 47% and longer lifetime at 5 C compared with the SSB without interface engineering. Such results shed new light on the understanding of ion transport at interfaces and suggest the feasibility of interface engineered MOFs as advanced SEs.