Engineering a nitrogen-doped 3D coral-like carbon architecture for ultralong-cycle NiS anodes in half- and full-cell sodium-ion storage

Nickel sulfide (NiS) offers immense promise as a sodium-ion battery (SIB) anode with its high theoretical capacity, metallic conductivity, and rich redox chemistry, yet its potential is crippled by violent volume fluctuations, sluggish Na + kinetics and polysulfide shuttling. Here, we architect a defect-rich, nitrogen-doped three-dimensional (3D) hollow coral-like carbon scaffold encapsulating NiS nanocrystals (NiS@N-HCC) via a scalable precursor-pyrolysis strategy. The tailored interfacial electronic coupling between NiS and the N-doped carbon realigns charge density and unleashes intrinsic conductivity, while polar defect sites act as powerful chemical anchors to immobilize polysulfides and eradicate shuttle loss. Encasing it all, the conductive hollow network brims with high-affinity Na + docking sites, channels ions through compressed diffusion corridors and absorbs drastic volume surges without fracture. As a result, NiS@N-HCC delivers 410.8 mAh g −1 after 1000 cycles at 1 A g −1 (92.5% retention), 357.5 mAh g −1 at 15 A g −1 , and only 0.003% decay per cycle over 3000 cycles at 10 A g −1 . Full cells with Na 3 V 2 (PO 4 ) 3 @C cathodes reach an energy density of 149.4 Wh kg −1 and a peak power density of 1572.9 W kg −1 , maintaining 82.1% capacity retention over 1600 cycles, while pouch-type devices sustain bright, stable high-power output, propelling NiS@N-HCC to the forefront of next-generation, high-power, long-life sodium-ion energy storage.