All-Climate Long-Life and Fast-Charging Sodium-Ion Battery using Co 3 S 4 @NiS 2 Heterostructures Encapsulated in Carbon Matrix as Anode.

Sodium-ion (Na-ion) battery is one of the research focuses because of high theoretical capacity and low cost. However, seeking for ideal anodes remains a big challenge. Here, a Co 3 S 4 @NiS 2 /C synthesized by in situ growing NiS 2 on CoS spheres then converting to Co 3 S 4 @NiS 2 heterostructures encapsulated by carbon matrix, is developed as a promising anode. Co 3 S 4 @NiS 2 /C as anode displays a high capacity of 654.1 mAh g -1 after 100 cycles. Even over 2000 cycles at a high rate of 10 A g -1 , capacity exceeds 143.2 mAh g -1 . Heterostructures between Co 3 S 4 and NiS 2 improve electron transfer as verified by density functional theory (DFT) calculations. In addition, when cycling at a high temperature of 50 °C, the Co 3 S 4 @NiS 2 /C anode displays 525.2 mAh g -1 , while it remains 340 mAh g -1 at -15 °C, indicating all-climate potential for using under different temperatures.