High Mass Loading\nof Flowerlike Ni-MoS₂ Microspheres toward Efficient Intercalation\nPseudocapacitive Electrodes

Abstract

This work reports the exploration of intercalation pseudocapacitance\nin a thicker electrode of flowerlike Ni-doped MoS₂ microspheres\nthat features a mass loading of ∼10 mg/cm² without\nsacrificing the gravimetric capacitance (∼425 F/g at 5 mV/s).\nIntegration of Ni atoms into MoS₂ microspheres not only\nstabilized the structural integrity but also ameliorated the rapid\nintercalation and deintercalation of electrolyte ions even at a commercial-level\nmass loading. The energy instability by Ni doping significantly changed\nthe local bonding behavior and the overall electronic structure of\nMoS₂, facilitating the breaking of the MoS₂ layer\nand generation of more active edge sites, which are responsible for\nfaster reaction kinetics. The experiments attribute the overall capacitance\nenhancement in (Mo-Ni)­S₂ to the increased rate of electrolyte\nion insertion and extraction, which is confirmed by <i>b</i>-values close to 0.5, at different potentials, indicating that the\ncurrent response predominantly depends on the diffusive mechanism\nfor both MoS₂ and Ni-MoS₂ thicker electrodes.\nThe symmetric device constructed with Ni-MoS₂ microspheres\nexhibited a capacitance value of 101 F/g in 1 mV/s, for which the\nenergy density is 9 Wh/kg, as well as attained an outstanding cycling\nstability of 10 000 cycles with 60% retention at 2 A/g. In\naddition to providing insights into the development of 2D TMDs, this\nwork explores the design of robust and highly efficient intercalation\nelectrode material for electrochemical energy storage devices.