Phase engineered multicomponent composites as efficient sulfur hosts synergistic adsorption and electrocatalysis for...

The high theoretical energy density and low cost of room-temperature sodium‑sulfur batteries (RT NaS batteries) make them promising for grid-scale energy storage, yet polysulfide shuttling and sluggish conversion kinetics impede their development. This study designed a phase-engineered multicomponent composite Mo₂C/Fe_0.5Mn_0.2Ni_0.3/FeCo/Ni₃Mo₃C (CAT) as an advanced sulfur host, which synergistically integrated adsorption, conduction, and electrocatalysis. The heterogeneous interface of the Mo₂C matrix and Fe-based alloy phases induced a built-in electric field via interfacial electron coupling, which enhanced polysulfide adsorption through optimized d-band centers and significantly lowered the energy barrier of the solid-solid Na₂S₂/Na₂S conversion rate-determining step. Consequently, the CAT S/C cathode exhibited a high initial capacity of 1308 mAh g^-1 at 0.1C. It achieved an initial capacity of 1140 mAh g^-1 at 1C and maintained stable performance over 1600 cycles with minimal decay. Furthermore, in situ impedance and distribution of relaxation times analyses revealed highly reversible interfacial kinetics and stable charge-transfer behavior during cycling. This study highlighted a rational phase-engineering strategy for constructing multiphase synergistic systems. Additionally, it provided deep mechanistic insights into interfacial electrocatalysis for stable RT NaS batteries.