Sodium ion battery(SIB)is considered as the potential alternative for next generation energy system to succeed the lithium ion battery(LIB)due to the low price and vast abundance of Na resource.Ternary metal sulfide is identified as an important redox conversion type of negative electrode for SIB.In this study,amorphous nickel boride(Ni-B)nanoflakes are introduced into the hollow Ni-Co sulfide nanospheres by a facile in situ solution growth route to promote the electrochemical performance of Na+-storage.Elec-trochemical measurements demonstrate that the Ni-B component could effectively improve the redox kinetics of the conversion reaction and structural stability during long-term Na+insertion/extraction.For example,the NiCo2S4@Ni-B composites display a high reversible capacity of 251.9 mA h g-1 at the current density of 1.0 A g-1 after 200 cycles,much higher than that of bare NiCo2S4(37.4 mA h g-1 at 1.0 A g-1 after 200 cycles).As a consequence,these results demonstrate a new sight to explore heterostructures of mixed metal-sulfides electrode materials with superior Na+-storage performances.