Synergistic integration of amorphous MoSx nanoparticles with Ti3C2Tx MXene layers for high-performance ammonium-ion supercapacitors

The introduction of non-metallic charge carriers in electrochemical energy storage devices offers a significant advantage in compatibility with aqueous electrolytes. However, the development of suitable electrode materials for these carriers remains comparatively slower than other energy storage technologies. Here, the amorphous MoS_x nanoparticles grow in situ on the surface of Ti₃C₂T_x nanosheets as host material for ammonium-ion supercapacitors. The Ti₃C₂T_x nanosheets provide a growth environment with large specific surface area for MoS_x. The synergistic effect of heterojunction enhances the specific capacity of the composite. Amorphous MoS_x nanoparticles form via an ethylene glycol solvent strategy. Compared with MoS₂, the amorphous MoS_x exhibits abundant defects and sulfur vacancies, which facilitate rapid NH₄⁺ insertion/de-insertion and promote hydrogen bond formation. Specifically, the Ti₃C₂T_x@MoS_x delivers a high specific capacity of 196.94 mAh·g⁻¹ at 1 A·g⁻¹ and retains 91.01 % of its initial specific capacity after 10000 cycles. Moreover, the assembled symmetric supercapacitor achieves energy density of 50.08 Wh·kg⁻¹ at 500.81 W·kg⁻¹ and satisfactory cyclic stability. This work highlights the broad potential of composite engineering in optimizing the performance of ammonium-ion supercapacitor and reveals its important role in improving energy storage efficiency and performance stability.