Dual-Phase Coexistence Design and Advanced Electrochemical Performance of Cu₂MoS₄ Electrode Materials for Supercapacitor Application

The tetragonal layered transition metal copper–molybdenum sulfide Cu₂MoS₄ (CMS) possesses a high theoretical electrochemical potential because of its abundant redox properties and large layered surface area, which is favorable for ion adsorption/desorption and transport. Cu₂MoS₄ contains P and I phases, exhibiting different crystal structures, ion transport characteristics, and electrochemical properties accordingly. In this work, for the first time, Cu₂MoS₄ electrode materials with dual-phase compositions are designed and prepared for supercapacitor application, providing a synergistic effect with high electron transport efficiency and structural stability. Upon an in-depth optimization process, the optimal CMS-4 sample having P and I phases coexisting yields the optimal electrochemical behavior. The CMS-4@carbon cloth (CC) electrode provides a specific capacity of 33.9 mAh g^–1 at 1 A g^–1, which is 12.6 and 4.0 times higher than the pure P and I phases, respectively. The assembled MnO₂@CC//CMS-4@CC supercapacitor exhibits a high energy density of 16.8 Wh kg^–1 at 800 W kg^–1 power density. The results demonstrate that two-phase coexistence of Cu₂MoS₄ significantly enhances the electrochemical activities owing to the synergistic effects of P and I phases and provides a promising material for supercapacitor negative electrodes.