Pore structure unveiling effect to boost lithium-selenium batteries: selenium confined in hierarchically porous carbon derived from aluminum based MOFs

Abstract

Lithium-selenium (Li-Se) batteries have attracted much attention in recent years because of their high volumetric capacity (3253 mA h cm-3) compared to the current commercial Li-ion battery. The shuttle effect and large volume variation during the electrochemical reactions limit its practical applications. The widely accepted strategy to reduce these drawbacks is confining selenium (Se) in porous carbon materials. However, how to boost electrochemical kinetics, reduce the shuttle effect and accommodate volume expansion for maximized battery performance still remains highly challenging. Herein, we synthesized three kinds of hierarchically porous carbon materials by facile pyrolysis of aluminum-based metal-organic frameworks (MOFs) with different porous networks. The large surface area and high pore volume can ensure the excellent polyselenides adsorption while tailoring the ratio between micropores and mesopores of the hierarchically porous hosts can highly enhance electrolyte and electron transportation, leading to excellent electrochemical performance with a capacity as high as 530.1 mA h g-1 (Se@MIL-68-800) after 200 cycles, an excellent rate capability of 307 mA h g-1 at 5 C, and a high reversible capacity of 544 mA h g-1 when current density returns to 0.1 C. The present invention not only provides a facile way to obtain hierarchically porous carbon materials from MOFs but also gives insights on tailoring micropores and mesopores proportion to maximize Li-Se battery performance for their practical industrial implementation.