High-performance ternary NiFeCo-LDH nanosheets for supercapacitors by cation modulation and sodium dodecyl sulfonate intercalation

Abstract

Layered double hydroxides (LDHs) hold significant promise for supercapacitors owing to their superior redox properties and customizable structure. Nevertheless, LDHs exhibit an experimental specific capacity lower than the theoretical value due to their undesirable electronic structure and limited electrical conductivity resulting from narrow interlayer spacing. Herein, we prepared Ni₃FeCo₂(SDS)-LDH through Co control and sodium dodecyl sulfate (SDS) intercalation, exhibiting both high capacitance properties and high conductivity. Initially, Ni₃FeCo₂-LDH demonstrated an optimum specific capacitance of 1251 C g⁻¹ (2553 F g⁻¹), and commendable capacitance retention of 68.82% over 5000 cycles at 1 A g⁻¹. The optimized intrinsic electronic structure from Co element control provided more active sites and a stable structure and facilitated a redox reaction in the distributed structure (Fig. 5d and e). On this basis, the as-fabricated electrode using Ni₃FeCo₂(SDS)-LDH exhibits an excellent specific capacitance of 1356 C g⁻¹ (2825 F g⁻¹), which reaches about 2.8 times that of traditional NiCo-LDH, and a capacitance retention of 65.29% after 5000 cycles at 1 A g⁻¹. Additionally, a Ni₃FeCo₂(SDS)-LDH@NF//AC asymmetric supercapacitor could deliver a notable power density of 767.928 W kg⁻¹ at an energy density of 39.015 W h kg⁻¹, and showed a capacity retention of 61.29% after 5000 cycles at 1 A g⁻¹. This phenomenon arose from the expansion of the interlayer spacing, which reduced diffusion resistance, enhanced electron storage capacity, and increased the contact area between LDH and the electrolyte. Furthermore, the enhanced conductivity resulted from the introduction of the sulfur (S) element. Consequently, this study had far-reaching implications for ternary LDHs to improve capacitive performance.