Core cation tuned M_xCo_3-xS₄@NiMoS₄ [M = Ni, Mn, zn] core–shell nanomaterials as advanced all solid-state asymmetric supercapacitor electrodes

A supercapacitor would be one of the most reliable energy storage device, but due to inadequate energy density, it is restricted to commercialization. The bimetallic core nanoparticles possess multiple oxidation states in their core@shell design, and understanding the effect of tuning of core cations are noble artifacts for effective research. Here, an effective strategy of varying the cations (M = Ni, Zn and Mn) in the M_xCo_3-xS₄@NiMoS₄ core@shell is demonstrated. Among the M_xCo_3-xS₄@NiMoS₄ electrodes, the NiCo₂S₄@NiMoS₄ core@shell showed better electrochemical storage properties with areal capacity/gravimetric capacity of 0.92 mAh cm⁻²/287.5 mAh g⁻¹ at 3 mA cm⁻² (3410.0 F g⁻¹ capacitance), and superior cycle life with ca. 92.3% capacity retention at high current density of 50.0 mA cm⁻² after 10,000 cycles. Moreover, real–time application was monitored by assembling an asymmetric solid–state device, taking NiCo₂S₄@NiMoS₄ as the cathode and Fe₂O₃/NG hydrogel as the anode. The device delivers an excellent cell capacity of 90.4 mA hg⁻¹ with a remarkable cycle life of 90.5% after 10,000 cycles. The device stored a very high energy density of 72.3 Wh kg^–1at 460.0 W kg⁻¹ and retained an energy density of 32.6 Wh kg⁻¹ at a high power density of 11,844.0 W kg⁻¹, demonstrating high applicability towards practical energy storage devices.