Colloidal Synthesis and Analysis of CNT-Cu₂S for Stability and Capacity Increase Alleviation in Sodium-Ion Storage

With the growing interest in energy storage, significant research has focused on finding suitable anode materials for sodium-ion batteries (SIBs). While developing high-capacity nanosized metal sulfides, issues like low stability and rapid initial capacity decline are common. Instead of maintaining steady capacity, they also tend to exhibit an increase in discharge capacity as cycling continues. We introduce CNT-Cu₂S, featuring Cu₂S nanoplates integrated onto the surface of MWCNTs, and assess its electrochemical properties for SIBs. Cu₂S initially exhibited a rapid decrease in capacity and then showed increased capacity. In contrast, CNT-Cu₂S demonstrated a stable capacity of 344.8 mAh g^-1 at 2.0 A g^-1 over 800 cycles, close to the theoretical capacity with capacitive behavior. This paper carried out analysis using data from in situ EIS and overpotential data from GITT to explain the different outcomes between the Cu₂S and CNT-Cu₂S experiments. These results show that CNT-Cu₂S is a suitable anode material for SIBs.