Preparation of NiCo2S4@Nd2O3 composite electrode materials and investigation of their electrochemical performance in supercapacitor devices

In this study, a NiCo 2 S 4 @Nd 2 O 3 core–shell structured positive electrode was constructed via a two-step strategy. First, NiCo 2 S 4 nanorod cores were synthesized through a hydrothermal–sulfidation process, followed by the in situ coating of Nd 2 O 3 nanosheet shells using a sol–gel method. The CNT negative electrode was fabricated by loading carbon nanotubes onto a carbon paper substrate via vacuum filtration. Multiscale characterizations confirm the formation of a tightly integrated heterogeneous interface between the NiCo 2 S 4 nanorod core and the Nd 2 O 3 nanosheet shell, which effectively mitigates the volume expansion of NiCo 2 S 4 and accelerates charge transport. Electrochemical measurements reveal that the NiCo 2 S 4 @Nd 2 O 3 core–shell electrode delivers a high specific capacitance of 2351 F g − 1 at 1 A g − 1 , with a capacitance retention of 77.4% at 20 A g − 1 , significantly outperforming pristine NiCo 2 S 4 or Nd 2 O 3 electrodes. An asymmetric supercapacitor assembled using the NiCo 2 S 4 @Nd 2 O 3 positive electrode and the CNT negative electrode exhibits outstanding overall performance within a wide voltage window of 0–1.6 V. It achieves a specific capacitance of 242 F g − 1 at 1 A g − 1 and retains approximately 93% of its initial capacitance after 6000 charge–discharge cycles. Moreover, the device delivers an energy density of 86.4 Wh kg − 1 at a power density of 800 W kg − 1 , and still maintains 62.4 Wh kg − 1 when the power density increases to 12 000 W kg − 1 . The core–shell structural design strategy proposed in this work provides an effective pathway for the development of high-performance supercapacitors and holds significant promise for applications in flexible energy storage systems.