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 (CoyP/C, CoxP/Co3(PO4)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 CoxP/Co3(PO4)2/C exhibited better catalytic performance for converting polysulfides, owing to the combination of CoxP with Co3(PO4)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.