Rational design of hedgehog-like NiMn2S4 architectures for energy storage devices

Abstract

In this work, the NiMn₂S₄ nanomaterials were prepared by a two-step hydrothermal method with an external morphology similar to that of a sea hedgehog, with an overall micro-spherical shape surrounded by nanosheets (NSs). This unique nanostructure helps enhance the electrode material's specific surface area (SSA) and achieve a better pore size distribution, facilitating complete interaction among the electrolyte and the active materials. Moreover, it promotes the quick flow of electrons and smooth transport of ions, thus improving NiMn₂S₄ electrode electrochemical performance. The NiMn₂S₄ electrode achieved an capacitance of 1426.2 mF cm⁻² at 1 mA cm⁻², with good rate performance (∼896.6 mF cm⁻² at 10 mA cm⁻²) and cycle stability (∼83.8 % retention after 6000 cycles). Sweep voltammetry analysis of its electrochemical behavior reveals that the primary energy storage mechanism is the capacitive contribution based on surface diffusion. This finding lays a foundation for future work on regulating and optimizing the electrochemical properties.