A ZIF-L derived carbon flower with in situ grown CNTs accelerates the reaction kinetics of Li–Se batteries†

Lithium–selenium (Li–Se) batteries have attracted increasing attention for their exceptionally high energy density. However, the sluggish electrochemical reaction kinetics and low utilization of Se hinder their development. Herein, we prepared a hierarchically porous carbon encapsulated with Se by the diffusion of molten Se into the ZIF-L derived matrix (Se/CNTs@HPC). In this composite, abundant in situ nitrogen doping and formation of Se–C bonds synergistically strengthen the anchoring of Se species, while the nanosheet-assembled conductive network provides shorter paths for mass transfer by confining charges and ions within a plane. Moreover, the flower-like architecture can effectively prevent mechanical aggregation and fragmentation of 2D nanosheets to achieve high structural stability of the cathode. After in situ growth of carbon nanotubes (CNTs), superior capacitive contribution (92%) and cycling performance are achieved due to the enhanced electrochemical reaction kinetics. As a result, the optimized Se/CNTs@HPC-5 cathode delivers a specific capacity of 606 mA h g⁻¹ after 350 cycles at 0.5C, with only 0.013% decay per cycle. Even at 5C, it can still retain a reversible capacity of 355 mA h g⁻¹. This work provides valuable insights into the future development of carbon materials for high-performance Li–Se batteries.