Efficient charge transfer at the donor-bridge-acceptor interface for excellent supercapacitors

The intrinsic electrochemical activity and active sites of the battery-like electrode in supercapacitors originate from efficient charge transfer at the interface. A seamless all-carbon graphdiyne layer on CoNi2S4 yolk-shell spheres (CoNi2S4/GDY YSSs) provides a unique structure of a flawless "donor-bridge-acceptor" interface, where Ni atoms and Co atoms serve as electron donors and acceptors, respectively, connected by the sp-C-Ni and sp-C-Co bonds as bridges. Importantly, this particular can facilitate effective electron transfer from the Ni atoms to the Co atoms, resulting in more interfacial Co2+ active sites and reversible redox coupling of Co-S/Co-S-OH and Co-S-OH/Co-S-O to increase the specific capacitance. Additionally, the seamless all-carbon graphdiyne layer greatly enhances the structural and interfacial stability of CoNi2S4 yolk-shell spheres, effectively avoiding structural deterioration to enhance cycling stability performance. Profiting from its structural merits, the CoNi2S4/GDY YSSs electrode delivers a considerable capacitance of 856C/g at 1 A/g, along with exceptional rate capability (61.9 % for 50-fold current density increase). Furthermore, an asymmetric supercapacitor with the CoNi2S4/GDY YSSs electrode cathode achieves a remarkable maximum energy density of 91.7 Wh/kg at a power density of 793 W/kg. Furthermore, the strategy proposed in this study has the potential to open up new pathways for the battery-like electrode design with realistic supercapacitor applications.