Spatial carbon channel with confined ultrafine nano-phosphides for boosted reversible sulfur redox in lithium-sulfur batteries

Abstract

Sluggish kinetics coupled with parasitic shuttling reactions are pivotal challenges hindering the performance of lithium-sulfur (Li-S) batteries. Improving areal capacity and cyclability of Li-S batteries can be achieved by addressing these challenges. A composite sulfur host material is synthesized herein by in situ anchoring ultrafine cobalt-iron phosphide nanoparticles (5–7 nm) onto a hollow mesoporous carbon sphere (HMCS) framework. This strategy achieved exceptional spatial restriction and a high density of catalytically active sites through the encapsulation of sulfur within a hollow-structured framework. Specifically, HMCS expedites rapid Li₂S nucleation kinetics, while CoFeP facilitates robust Li₂S dissolution kinetics by mitigating decomposition barriers. This synergistic integration equips CoFeP@HMCS with robust bi-directional catalytic activity, significantly promoting interfacial charge-transfer, facilitate sulfur multistep catalytic conversion, and inhibiting shuttling. Consequently, the battery exhibits excellent rate performance (991 mA h g⁻¹ at 5.0 C) and retains a high areal capacity of 6.06 mA h cm⁻² after 200 cycles under a high areal sulfur loading of 8.2 mg cm⁻² but a low electrolyte/sulfur ratio of 4.8 μL mg⁻¹. This work contributes to enhancing the practical specific capacity of lithium-sulfur batteries and deepens the understanding of catalysts enabling bidirectional electrocatalytic sulfur conversion.