As the market for electric vehicles and portable electronic devices continues to grow rapidly, sodium-ion batteries (SIBs) have emerged as energy storage systems to replace lithium-ion batteries (LIBs). However, sodium-ion is heavier and larger than lithium-ion, resulting in volume expansion and slower ion transfer. It is necessary to find suitable anode materials with high capacity and stability. In addition, wearable electronics are starting to be commercialized, requiring a binder-free electrode used in flexible batteries. In this work, we synthesized nano flake-like VSe₂ using organic precursor and combined it with MWCNT as carbonaceous material. VSe₂@MWCNT was mixed homogenously using sonication and fabricated film electrodes without a binder and substrate via vacuum filter. The hybrid electrode exhibited high-rate capability and stable cycling performance with a discharge capacity of 469.1 mAhg⁻¹ after 200 cycles. Furthermore, VSe₂@MWCNT exhibited coulombic efficiency of ~99.7%, indicating good cycle stability. Additionally, VSe₂@MWCNT showed a predominant 85.5% of capacitive contribution at a scan rate of 1 mVs⁻¹ in sodiation/desodiation process. These results showed that VSe₂@MWCNT is a suitable anode material for flexible SIBs.

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.