NiCo2S4 nanoparticles encapsulated within hollow mesoporous carbon spheres enabling rapid and stable sodium storage

Poor rate capability and cycling performance significantly impair the utilization of NiCo 2 S 4 as an anode material in sodium-ion batteries. Herein, hollow mesoporous carbon spheres (HMCSs) are synthesized using a hard-template method. NiCo 2 S 4 nanoparticles with sizes ranging from 15 to 43 nm are grown in-situ within HMCSs (NiCo 2 S 4 @HMCS) by melt adsorption, solution impregnation, and gas-phase sulfurization. Specifically, NiCo 2 S 4 nanoparticles are uniformly distributed on the inner walls of HMCSs and within the mesoporous channels of spherical shells. In half-cells, NiCo 2 S 4 @HMCS exhibits reversible capacities of 482 mAh g −1 after 340 cycles at 1.0 A g −1 , 340 mAh g −1 after 600 cycles at 5.0 A g −1 , and 271 mAh g −1 after 700 cycles at 10.0 A g −1 . In NiCo 2 S 4 @HMCS//Na 3 V 2 (PO 4 ) 3 full-cells, NiCo 2 S 4 @HMCS maintain reversible capacities of 203 mAh g −1 after 1200 cycles at 1.0 A g −1 and 122 mAh g −1 after 2000 cycles at 5.0 A g −1 . The unique nano-encapsulated structure prevents the detachment of NiCo 2 S 4 from HMCSs, maintaining electrochemical activity and stability of NiCo 2 S 4 . Additionally, the nano-encapsulated structure also facilitates electrolyte penetration and enhances the electronic conductivity of NiCo 2 S 4 . These effects synergistically result in rapid and stable sodium storage performance. • NiCo 2 S 4 nanoparticles are encapsulated within hollow mesoporous carbon spheres. • Nanoencapsulation improves reaction kinetics and electrochemical impedance. • Nanoencapsulation enhances cycling performance and rate capability of NiCo 2 S 4 .