High Mass Loading of Flowerlike Ni-MoS2 Microspheres toward Efficient Intercalation Pseudocapacitive Electrodes

Abstract

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