Co2P Nanoparticles Decorated Porous Carbon Nanofibers as Self-Standing Cathode for High-Performance Li-S Batteries

Abstract

Lithium-sulfur (Li-S) batteries, with their high theoretical specific capacity, are regarded as the orientation of next-generation energy storage techniques. However, suppressing the shuttle effect of lithium polysulfides (LiPSs) and accelerating the conversion kinetics of Li₂S₂ and Li₂S are extremely important but tricky issues in the design of sulfur cathodes. In this study, porous carbon nanofibers decorated with Co₂P nanoparticle (Co₂P@PCNFs) are designed by combining an electrospinning method with an in situ phosphorization process. The obtained Co₂P@PCNFs porous fibers, which stack in the form of a film, are used as a substrate for encapsulating elemental S. The fabricated S/Co₂P@PCNFs films are then utilized as the self-standing composite cathode for lithium-sulfur batteries. The network structure and porous architecture of the Co₂P@PCNFs substrates ensure rapid charge transfer kinetics and provide abundant active interfaces to effectively anchor LiPSs and suppress their shuttling. Ascribing to the high electronegativity and catalytic nature of the Co₂P nanoparticles embedded therein, the Co₂P@PCNFs not only shows strong adsorption to LiPSs but also endows superior catalytic capability to the rapid transformation of Li₂S₂ to Li₂S. The Li-S cell assembled with S/Co₂P@PCNFs as the cathode exhibits outstanding electrochemical performance. It delivers an impressive initial capacity of 1240.4 mAh g^-1 at 0.2 C and shows excellent rate performance with a capacity of 526 mAh g^-1 at a current density of 2 C. Over 500 cycles at 1 C, the capacity decay rate is 0.0198% per cycle. Even under extreme conditions with a sulfur loading of 4.48 mg cm^-2 and an electrolyte/sulfur ratio of 7.8 μL/mg, it still retains a capacity of 457.3 mAh g^-1 after 150 cycles. Such a composite cathode can effectively promote the solid-solid conversion process and suppress the "shuttle effect" of LiPSs. This work provides a strategy for the rational design of self-standing cathodes for lithium-sulfur batteries with the potential for practical applications.

Keywords: catalytic conversion; cobalt phosphides; lithium−sulfur batteries; self-standing cathode; shuttle effect.