A novel RuP2-infused heteroatom-doped porous carbon for high-durability lithium-sulfur batteries

Nitrogen and phosphorus co-doped three-dimensional porous carbon encapsulated ruthenium diphosphide (PCS900@RuP2-2) is successfully synthesized via a phytic acid-assisted phosphating process. The resulting RuP2 nanoparticles, ranging in size from 10 to 50 nm, are encapsulated within a carbon matrix, providing a stable catalytic structure. Nitrogen adsorption and desorption tests reveal that PCS900@RuP2-2/S possesses a high specific surface area and a rich micro/mesoporous structure. This high porosity facilitates multi-directional ion diffusion and offers ample buffer space to accommodate sulfur volume expansion during cycling. Density functional theory (DFT) calculations confirm that PCS900@RuP2-2/S enables efficient adsorption of soluble polysulfides, thereby minimizing the notorious "shuttle effect." Electrochemical testing demonstrates the remarkable durability of PCS900@RuP2-2/S. After 500 cycles at a 1 C current density, the reversible capacity remains at 511.6 mAh g⁻¹, with an average capacity decay rate of just 0.047 % per cycle. Even under heavy sulfur loading conditions (4.2 mg cm⁻²), the composite maintains a high reversible capacity of 386.6 mAh g⁻¹ after 500 cycles. The combination of high porosity, stable catalytic structure, and efficient redox reaction facilitation contributes to the exceptional performance and longevity of PCS900@RuP2–2/S. •A novel RuP2-infused porous carbon was synthesized using a simple phytic acid-assisted calcination process.•Multi-directional ion diffusion is facilitated by high porosity (1.7 cm³ g⁻¹).•The formation of Ru-S and Ru-P bonds on the surface of RuP2(110) through Li2S adsorption was confirmed by DFT.•The PCS900@RuP2-2/S composite demonstrate a high areal capacity of 4.2 mAh cm⁻² (with a sulfur loading of 4.2 mg cm⁻²).