Redox-Mediating Mo₂C Nanoparticles Confined Within Nitrogen- and Phosphorus-Codoped Amorphous Carbon Matrix for Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) suffer from sluggish lithium polysulfides (LiPS) conversion and severe interfacial instability, which limit their rate performance and cycle life. Herein, we report a multifunctional interlayer comprising Mo₂C nanoparticles confined within a nitrogen- and phosphorus-codoped amorphous carbon matrix supported on reduced graphene oxide (MNPG). H₃PMo₁₂O₄₀ was chosen as a final polyoxometalate (POM) precursor because it was transformed into the tubular nanoparticles, while Na₃PMo₁₂O₄₀ was converted to irregular micrometer-sized particles. In particular, the hierarchical structure of MNPG is synthesized via electrostatic self-assembly of POM and pyrrole on graphene oxide, followed by thermal transformation. The embedded Mo₂C domains act as efficient redox mediators that accelerate LiPS conversion, while the polar doped carbon shell suppresses parasitic reactions and facilitates ion transport. Consequently, the MNPG-coated separator allows LSBs to deliver a high specific capacity of 1549 mAh g⁻¹ at 0.1 C and 802 mAh g⁻¹ at 5.0 C, along with 81.1% capacity retention after 200 cycles. This study provides a straightforward and effective interfacial engineering strategy that combines redox-mediating domains and transport regulation within a unified structure to overcome key bottlenecks of LSBs.