An imine-linked covalent organic framework as the host material for sulfur loading in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries have high theoretical specific capacity, providing new opportunities for the next generation of secondary battery. Covalent organic framework (COF) as a new porous crystalline material has been used as the host material in Li–S battery to improve the cell's cycling stability. In this paper, an imine-linked TAPB-PDA-COF was applied as the host material for sulfur loading (60%) in Li–S battery. The TAPB-PDA-COF has a beehive-like morphology with high thermal stability (up to 500 °C). In the electrochemical experiment, the performance of the composite cathode with acetylene black (A-B) and super-P (S-P) as the conductive additives was studied individually. The initial discharge capacity under 0.2 A/g current density was 991 mAh/g and 1357 mAh/g for TAPB-PDA-COF/S@A-B and TAPB-PDA-COF/S@S-P, respectively. The better result of S-P based cathode than A-B could be due to the better conductivity of the S-P, as proved by the EIS results. When further increased the current density to 2 A/g, the S-P based composite cathode can still deliver a comparable initial discharge capacity of 630 and 274 mAh/g capacity remained after 940 cycles. This results will inspire researchers develop more suitable conductive additives together with the host materials for high performance Li–S battery.