Metal-organic frameworks derived in situ carbon-doped hollow nickel-cobalt phosphate microspheres for high performance zinc-ion hybrid supercapacitors

Transition metal phosphates (TMPs) represent a highly attractive candidate for prospective electrode material. However, it is still needed to boost its poor conductivity and irregular morphology. In this work, using the designed nickel-cobalt metal-organic frameworks (NiCo-MOFs) solid spheres as the precursors, nickel-cobalt phosphate hollow microspheres with in situ doped carbon (MCNPha) are synthesized by Kirkendall effect during the solvothermal process. The perfect flower like spherical morphology of MCNPha-3 is composed of thin crisscross nanosheets and demonstrates a three-dimensional open feature with extensive pores and channels. Consequently, the optimized sample of MCNPha-3 generates a specific capacitance of 1024 F g-1 at 1 A g-1 and exceptional cycling survivability about 71.3% after 26,000 cycles at 40 mV s-1, belonging to the hollow nano- structure and in situ doped carbon upgrading its conductivity. The assembled MCNPha-3//Zinc hybrid super- capacitor (AZISC) evaluates an energy density of 238.18 Wh kg-1 at 1.70 kW kg-1 . A single MCNPha-3//Zn device can illuminate a yellow light-emitting diode (LED), and power a hygrometer more than 2 h, which illustrates the promising application prospect of MCNPha-3.