High Magnetic Field-Engineered Bunched Zn–Co–S Yolk–Shell Balls Intercalated within S, N Codoped CNT/Graphene Films for Free-Standing Supercapacitors

The abundant mass and charge transfer involved in Faradaic redox reactions are largely determined by microstructures including the surface area and porosity, elemental composition and electrical conductivity of bimetallic sulfides. Here, a high magnetic field (HMF) was introduced to tune these intrinsic characters for superior supercapacitor electrodes. We developed a novel HMF-controlled anion-exchange methodology to prepare the one-dimensional (1D) bunched Zn-Co-S yolk-shell balls (ZCS^6T BYSBs). The HMF-induced directional growth and alignment of Zn_0.76Co_0.24S drive the directional 1D assembly. The as-obtained ZCS^6T BYSBs possess larger surface area/pore volume, higher crystallinity and electrical conductivity, richer electroactive elements, and favorable axial electron and ion transport because of HMF-enhanced favorable ion diffusion and exchange kinetics. Flexible S, N codoped carbon nanotubes/graphene films embedded with the ZCS^6T BYSBs (CZS^6T/CNTs/SNGS) were fabricated by vacuum filtration and one-step S, N codoping and reduction of graphene oxides to improve structural stability and charge transport. The CZS^6T/CNTs/SNGS electrode displayed impressive enhanced specific capacitance and rate capability with 78.7% capacitance retention at 30 A g^-1. Furthermore, the CZS^6T/CNTs/SNGS//CNTs/SNGS asymmetric supercapacitor delivered remarkable cycling stability with a high energy density of 41.1 W h kg^-1 at a large power density of 9022 W kg^-1.