N/O co-doped poly(γ-glutamic acid)/Ni/melamine/chitosan nanoparticle-based hollow graphite carbon spheres for aqueous zinc-ion hybrid supercapacitors.

Hollow carbon spheres (HCSs) have attracted broad attention in aqueous zinc-ion hybrid supercapacitors (ZIHSCs) owing to their distinctive properties. However, traditional methods for fabricating HCSs face limitations, including complex multistep procedures, the use of corrosive chemicals, and stringent reaction conditions. In this work, biomass-based poly(γ-glutamic acid)/Ni/melamine/chitosan nanoparticles were used as the precursors to fabricate N/O co-doped hollow graphite carbon spheres (HGCSs). Thanks to the appropriate hydrophilic characteristic, specific surface area, pore size distribution, and electrical conductivity, the fabricated HGCSs cathode exhibited superior electrochemical properties. The assembled HGCSs-based ZIHSCs device showed a satisfactory specific capacitance of 133.2 mAh·g at a current density of 1.0 A·g, high energy densities of 75.2 Wh·kg at 10,000 W·kg and 107.9 Wh·kg at 1000 W·kg, respectively. Additionally, the assembled HGCSs-based ZIHSCs device displayed an exceptional cycling stability, enduring up to 10,000 cycles at 0.5 A·g with a capacity retention rate of 98.1 %. This work provides a facile and novel strategy to prepare superior electrochemical performance biomass-based HGCSs cathode for ZIHSCs.