SnS2-CoS2@C nanocubes as high initial coulombic efficiency and long-life anodes for sodium-ion batteries

Abstract

Bimetallic sulfides are considered as one of the most promising anode materials for sodium ion batteries (SIBs) due to their high conductivity and electrochemical activity. However, they still suffer from challenges such as large volume changes, low initial coulombic efficiency and poor cycling performance. Herein, we synthesize SnS2-CoS2@C (SCS@C) core-shell nanocubes with abundant mesopores through simple carbon coating and sulfidation strategies using polymeric resorcinol-formaldehyde as carbon source. The porous nanostructure of SCS@C is conducive to shortening the transport path of sodium ions and facilitating the infiltration of electrolyte, while the carbon shell can buffer volume expansion stress during charging and discharging processes. As a result, the SCS@C electrode exhibits an excellent sodium storage: an outstanding initial coulomb efficiency of 92.8%, remarkable cycling performance of 662 mAh g−1 at 100 mA g−1 after 70 cycles with extremely low capacity decay of 0.00013% per cycle, and long cycle durability of 402.5 mAh g−1 at 5 A g−1 over 500 cycles. Our study provides a viable strategy for the rational design of bimetallic sulfides anode materials with high efficiency and long term stability for sodium storage.