Synergistically boosting the performance of asymmetric supercapacitors: in-situ construction of NiCo2S4 on amino-functionalized and Zn2+-predoped multilayer MXene

MXene’s inherent tendency to aggregate and agglomerate poses critical challenges for its application in energy storage. This phenomenon results in reduced interlayer spacing, a decline in the number of active sites, diminished ion adsorption capacity, and obstructed ion transport pathways, all of which severely limit its practical utility. To address these limitations, this study presents a novel multi-dimensional performance optimization strategy for supercapacitor composite electrode materials. Amino functional groups were first adsorbed onto the surface of multilayer Ti-based MXene as a means of modification, giving rise to amino-MXene (N-MX). Subsequently, Zn²⁺ ions were intercalated into N-MX to fabricate Zn-amino-MXene (Zn-N-MX), which served as a substrate. Upon this, transition metal nickel–cobalt based sulfides were grown in situ and progressively nucleated, culminating in the synthesis of Zn-N-MX/NiCo₂S₄ composites (Zn-N-MX/NCS). The introduction of amino functional groups effectively reshapes the chemical surroundings on the surface of MXene and reduces the steric hindrance of Zn²⁺ insertion. At the same time, the coordination bond formed by the amino group and the metal ion further promotes the stable anchoring and embedding of Zn²⁺ ions in the interlayer, as if opening up a “fast lane” for their embedding. In addition, the homogeneous dispersion of NiCo₂S₄ nanoparticles in the MXene layer provides a complementary “quick channel” for ion migration, thus boosting the comprehensive electrochemical properties of Zn-N-MX/NCS. The composite manifests a conspicuously enhanced electrochemical performance of 1546.76 F g⁻¹ at 1 A g⁻¹. After Zn-N-MX/NCS was integrated into an asymmetric supercapacitor (ASC) Zn-N-MX/NCS//AC, it exhibits a high energy density of 53.3 Wh kg⁻¹ at 800 W kg⁻¹.