Colloidal Synthesis\nand Analysis of CNT-Cu<sub>2</sub>S for Stability and Capacity Increase\nAlleviation in Sodium-Ion Storage

With the growing interest in energy storage, significant\nresearch\nhas focused on finding suitable anode materials for sodium-ion batteries\n(SIBs). While developing high-capacity nanosized metal sulfides, issues\nlike low stability and rapid initial capacity decline are common.\nInstead of maintaining steady capacity, they also tend to exhibit\nan increase in discharge capacity as cycling continues. We introduce\nCNT-Cu<sub>2</sub>S, featuring Cu<sub>2</sub>S nanoplates integrated\nonto the surface of MWCNTs, and assess its electrochemical properties\nfor SIBs. Cu<sub>2</sub>S initially exhibited a rapid decrease in\ncapacity and then showed increased capacity. In contrast, CNT-Cu<sub>2</sub>S demonstrated a stable capacity of 344.8 mAh g<sup>–1</sup> at 2.0 A g<sup>–1</sup> over 800 cycles, close to the theoretical\ncapacity with capacitive behavior. This paper carried out analysis\nusing data from in situ EIS and overpotential data from GITT to explain\nthe different outcomes between the Cu<sub>2</sub>S and CNT-Cu<sub>2</sub>S experiments. These results show that CNT-Cu<sub>2</sub>S\nis a suitable anode material for SIBs.