Fluorine Doping Strengthens the Lithium-Storage Properties of the Mn-Based Metal-Organic Framework.

The electrochemical properties of the metal-organic framework (MOF)-based composite as electrode material can be significantly improved by means of partial destruction of the full coordination of linkers to metal ions and replacing with other small ions, which make metal centers become more accostable and consequently more effective for the lithiation/delithiation process. In this paper, F- was chosen to replace some of the benzenedicarboxylate (BDC) linkers because of its better interaction with the Li+ than the oxide ion. What's more, the formed M-F bond promotes the Li+ to transfer at the active material interface and protects the surface from HF attacking. The as-synthesized F-doped Mn-MOF electrode maintains a reversible capacity of 927 mA h g-1 with capacity retention of 78.5% after 100 cycles at 100 mA g-1 and also exhibits a high discharge capacity of 716 mA h g-1 at 300 mA g-1 and 620 mA h g-1 at 500 mA g-1 after 500 cycles. Even at 1000 mA g-1, the electrode still maintains a high reversible capacity of 494 mA h g-1 after 500 cycles as well as a Coulombic efficiency of nearly 100%, which is drastically increased compared with pure Mn-MOF material as expected.