Surfactant-Mediated Regulation of Interlayer Spacing and Hierarchical Architecture in NiMn-LDH Nanoflowers for High-Performance Flexible Supercapacitors

Abstract

Multiscale structural regulation is critical for improving ion accessibility and redox utilization in layered double hydroxide (LDH) electrodes. Here, cetyltrimethylammonium bromide (CTAB) was introduced into a one-step hydrothermal process to simultaneously regulate the particle size and interlayer spacing of NiMn-LDH nanoflowers. Increasing the CTAB dosage reduced the particle diameter from approximately 1.5 µm to 266 nm while enlarging the interlayer spacing from 9.45 to 9.68 Å. The optimized NML-2C exhibited a core-shell nanoflower architecture, a BET surface area of 143.4 m2 g−1, and an interlayer spacing of 9.60 Å, providing abundant accessible sites and shortened ion-transport pathways. Consequently, NML-2C delivered a specific capacity of 946.5 C g−1 at 1 A g−1 and retained 677.0 C g−1 at 20 A g−1, with 87.5% capacity retention after 5500 cycles. Density functional theory calculations indicated that the enlarged interlayer spacing strengthens OH⁻ adsorption and facilitates interfacial Faradaic reactions. Moreover, the flexible asymmetric hybrid supercapacitor achieved an energy density of 51.0 Wh kg−1 at a power density of 800.2 W kg−1 and retained 88.4% capacitance after 12,000 cycles. These results demonstrate that surfactant-assisted simultaneous regulation of particle architecture and interlayer spacing provides an effective strategy for developing high-performance NiMn-LDH electrodes for flexible electrochemical energy-storage devices.