Coordination-Modulated Metal Tetrathiafulvalene Octacarboxylate Frameworks for High-Performance Lithium-Ion Battery Anodes

Modulation of the ligands and coordination environment of metal-organic frameworks (MOFs) has been an effective and relatively unexplored avenue for improving the anode performance of lithium-ion batteries (LIBs). In this study, three MOFs are synthesized, namely, M-4(o-TTFOB)(bpm)(2)(H2O)(2) (where M is Mn, Zn, and Cd; o-H8TTFOB is ortho-tetrathiafulvalene octabenzoate; and bpm is 2,2 '-bipyrimidine), based on a new ligand o-H8TTFOB with two adjacent carboxylates on one phenyl, which allows us to establish the impact of metal coordination on the performance of these MOFs as anode materials in LIBs. Mn-o-TTFOB and Zn-o-TTFOB, with two more uncoordinated oxygen atoms from o-TTFOB8-, show higher reversible specific capacities of 1249 mAh g(-1) and 1288 mAh g(-1) under 200 mA g(-1) after full activation. In contrast, Cd-o-TTFOB shows a reversible capacity of 448 mAh g(-1) under the same condition due to the lack of uncoordinated oxygen atoms. Crystal structure analysis, cyclic voltammetry measurements of the half-cell configurations, and density functional theory calculations have been performed to explain the lithium storage mechanism, diffusion kinetics, and structure-function relationship. This study demonstrates the advantages of MOFs with high designability in the fabrication of LIBs.