2D ZIF-8 derived N-doped porous carbon nanosheets for high-performance Li-Se batteries

Lithium-selenium (Li-Se) batteries have attracted increasing attention because of excellent carbonate electrolyte compatibility, comparable theoretical volumetric specific capacity and high electrical conductivity. However, there are still unavoidable issues such as large volume expansion, rapid capacity decay and slow electrochemical reaction kinetics for practical applications. In this work, we report 2D ZIF-8 derived N-doped porous carbon nanosheets (NPC-NS) as Se host for high-performance Li-Se batteries. The unique 2D structure of Se@NPC-NS facilitates Li+ diffusion and charge transfer, thus the Se@NPC-NS cathode exhibits fast electrochemical reaction kinetics. In addition, the N doping enhances electronic conductivity and porous structure mitigates the volume expansion. As a result, the Se@NPC-NS cathode delivers a high reversible capacity of 585 mAh/g with a capacity retention of 99.1 % at 0.5C (1C = 675 mA g−1) after 225cycles. Especially after 500 cycles at a high current density of 10C, the Se@NPC-NS cathode still displays a reversible specific capacity of 307 mAh/g with only 0.03 % capacity decay per cycle. This work would shed some light on the 2D carbon host as Se-based cathode for high-rate and long-life performance Li-Se batteries.