Metal-Organic Frameworks for High Charge-Discharge Rates in Lithium-Sulfur Batteries.

We report a new method to promote the conductivities of metal-organic frameworks (MOFs) by 5 to 7 magnitudes, thus their potential in electrochemical applications can be fully revealed. This method combines the polarity and porosity advantages of MOFs with the conductive feature of conductive polymers, in this case, polypyrrole (ppy), to construct ppy-MOF compartments for the confinement of sulfur in Li-S batteries. The performances of these ppy-S-in-MOF electrodes exceed those of their MOF and ppy counterparts, especially at high charge-discharge rates. For the first time, the critical role of ion diffusion to the high rate performance was elucidated by comparing ppy-MOF compartments with different pore geometries. The ppy-S-in-PCN-224 electrode with cross-linked pores and tunnels stood out, with a high capacity of 670 and 440 mAh g-1 at 10.0 C after 200 and 1000 cycles, respectively, representing a new benchmark for long-cycle performance at high rate in Li-S batteries.