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.

Automated summary

Modulating the ligands and coordination environment of MOFs can improve the anode performance of LIBs. Three new MOFs were synthesized and Mn-o-TTFOB and Zn-o-TTFOB showed higher reversible specific capacities compared to Cd-o-TTFOB.