Porous NiCo2S4-halloysite hybrid self-assembled from nanosheets for high-performance asymmetric supercapacitor applications

- The NiCo2S4-HL nanomaterial is achieved via two-step hydrothermal approach.
- The unique structures are assembled self-assembly by nanosheets.
- The obtained electrode exhibits high capacitance and excellent retention.
- An asymmetric supercapacitor also displays high energy density and outstanding cycling stability.
- The high-performance of the device is possibly due to the introduction of HL and formation of composed nanosheets.

The porous nanostructures have drawn considerable attention because of their abundant pore volume and unique properties that provide outstanding performance in catalysis and energy storage applications. This study proposes the growth mechanism of porous NiCo2S4 composited with halloysite (HL) via a self-assembly method using halloysite as a template and component. Electrochemical tests showed that the NiCo2S4-HL exhibited an ultrahigh specific capacitance (Csp) (589C g−1 at 1A g−1) and good cycle stability (Csp retention of 86% after 1000 cycles). The desirable capacitive performance of the NiCo2S4-HL can be attributed to the large specific surface area and short diffusion path for electrons and ions in the hierarchical porous structure. The superior electrochemical performances with the energy density of 35.48 W h kg−1 at a power density of 199.9 W kg−1 were achieved in an assembled aqueous asymmetric supercapacitor (ASC) device using NiCo2S4-HL as a positive electrode and N-doped graphene (NG) as a negative electrode. Moreover, the NiCo2S4-HL//NG asymmetric supercapacitor achieved outstanding cycle stability (also retained 83.2% after 1700 cycles). The high-performance of the ASC device will undoubtedly make the porous NiCo2S4-HL as potential electrode materials attractive in energy storage systems.