Synthesis of Free‐Standing CoxP/Co3(PO4)2/C Composite Nanofiber Mats and Their Characteristics as Multi‐functional Interlayers for Lithium‐Sulfur Batteries

Abstract The free‐standing cobalt phosphides‐based composite nanofiber mats with different compositions (Co y P/C, Co x P/Co 3 (PO 4 ) 2 /C, where 2>x>y>1) were synthesized by electrospinning with heat treatments and applied as multi‐functional interlayers for lithium‐sulfur batteries. The polysulfide confining ability of the interlayers was evaluated by a static polysulfide adsorption test and an electrochemical conversion test using symmetric cells. The Co x P/Co 3 (PO 4 ) 2 /C exhibited better catalytic performance for converting polysulfides, owing to the combination of Co x P with Co 3 (PO 4 ) 2 and P‐doped carbon. As a result, the lithium‐sulfur cell with this interlayer delivered a high initial discharge capacity of 1483 mAh g −1 at 0.1 C, retaining 705 mAh g −1 after 200 cycles at 0.5 C with 100 % Coulombic efficiency. The polysulfide trapping by the interlayer was further elucidated from the results of its ex situ characterizations after discharge and charge processes at different cycles in lithium‐sulfur cells.