Selenium confined in ZIF-8 derived porous carbon@MWCNTs 3D networks: tailoring reaction kinetics for high performance lithium-selenium batteries

Lithium-selenium battery is nowadays a highly competing technology to the commercial Li-ion battery because it has a high volumetric capacity of 3253 mAh cm-3 and gravimetric capacity of 675 mAh g-1. However, the practical application of lithium-selenium (Li-Se) batteries is impeded by the shuttle effect of the soluble polyselenides during the cycling process. Herein, we report the in situ growth and pyrolysis of the metal-organic framework zeolitic imidazolate framework-8 (ZIF-8) on three-dimensional (3D) interconnected highly conductive multiwalled carbon nanotubes (MWCNTs). The obtained composites are used to anchor Se for advanced Li-Se batteries. Compared with the isolated ZIF-8 derived microporous carbon, our synthesized ZIF-8 derived porous carbon@MWCNTs (ZIF-8-C@MWCNTs) 3D highly conductive networks facilitate lithium ion diffusion and electron transportation. The particle size of ZIF-8 crystals has an important impact on the battery performance. By adjusting the particle size of ZIF-8, the electrochemical reaction kinetics in ZIF-8-C@MWCNTs 3D networks can be tuned. The optimized particle size of ZIF-8 around 300-500 nm coated on MWCNTs composite achieves an excellent initial discharge capacity of 756 mAh g-1 and a stabilized capacity of 468 mAh g-1 at 0.2 C after 200 cycles. Combining the 3D MWCNTs with the appropriate size of ZIF-8 derived microporous carbon particles could highly improve the performance of the Li-Se battery. This work provides significant guidance for further structural design and host particle size selection for high-performance Li-Se batteries.