Investigation of Layer Structured NbSe₂ as an Intercalation Anode Material for Sodium-Ion Hybrid Capacitors

We synthesized a layer structured NbSe 2 material through gas-phase solid state reaction, and its electrochemical performance was examined as an intercalation anode for sodium-ion hybrid capacitor. The NbSe 2 electrode showed a reversible capacity of 142.5 mAh g −1 at 200 mA g −1 over 100 cycles with good capacity retention of 94.0%, and it delivered a high discharge capacity of 100.7 mAh at 1000 mA g −1 . The surface capacitive process mainly contributed to the charge storage in the NbSe 2 electrode. Its superior electrochemical performance arose from the layered structure of NbSe 2 that offered the easy pathway for sodium ion diffusion and accommodated the volume strain during sodiation/de-sodiation processes. The sodium-ion hybrid capacitor assembled with NbSe 2 anode and activated carbon cathode exhibited a high power density of 599.6 W kg −1 at energy density of 17.3 Wh kg −1 with good capacity retention of 93.2% at 300 mA g −1 after 3000 cycles. Our results demonstrate that the NbSe 2 can be a promising anode material for sodium-ion hybrid capacitor.