Reversible formation of coordination bonds in Sn-based metal-organic frameworks for high-performance lithium storage

Abstract Sn-based compounds with buffer matrixes possessing high theoretical capacity, low working voltage, and alleviation of the volume expansion of Sn are ideal materials for lithium storage. However, it is highly challenging to confine well-dispersed Sn within a lithium active matrix because low-melting-point Sn tends to agglomerate. Here, for the first time, we apply a metal-organic framework (MOF) chemistry between Sn-nodes and lithium active ligands to create two Sn-based MOFs comprising Sn2(dobdc) and Sn2(dobpdc) with extended ligands from H4dobdc (2,5-dioxido-1,4-benzenedicarboxylate acid) to H4dobpdc (4,4’-dioxidobiphenyl-3,3’-dicarboxylate acid) with molecule-level homodispersion of Sn in organic matrixes for lithium storage. The enhanced utilization of active sites and reaction kinetics are achieved by the isoreticular expansion of the organic linkers. The reversible formation of coordination bonds during lithium storage processes is first revealed by X-ray absorption fine structure characterization, providing an in-depth understanding of the lithium storage mechanism in coordination compounds.