Boosting Sodium-Ion Storage by Encapsulating NiS (CoS) Hollow Nanoparticles into Carbonaceous Fibers

Transition metal sulfides (TMSs) with high theoretical specific capacity and superior electrochemical performance are promising anode material candidates for sodium-ion batteries (SIBs). However, the structural pulverization because of the severe volume change in the discharge/charge process leads to a severe capacity decay, limited rate performance, and poor cycling stability, which inhibits their practical application. Herein, we report a novel strategy for the synthesis of TMS hollow nanoparticles@carbon fibers (TMS-HNP@CFs- T) by using seaweed-derived alginate as the template and precursor. When evaluated as anode materials for SIBs, the hybrids display excellent sodium storage performance. For instance, CoS-HNP@CFs-900 exhibits high reversible specific capacity, significant cycling stability (392.2 mA h g^-1 at 1000 mA g^-1 over 100 cycles), and rate performance (334.2 mA h g^-1 can be achieved at 5000 mA g^-1). The hollow TMP NPs and conductive carbon fibers could synergistically reduce the expansion of volume and shorten the ion transport path to boost the sodium storage performance.