Growing Co–Ni–Se nanosheets on 3D carbon frameworks as advanced dual functional electrodes for supercapacitors and sodium ion batteries

The reasonable design of electrode materials is crucial for tuning the electrochemical performances of advanced energy storage systems. Co–Ni–Se nanosheets uniformly growing on a butterfly-wing-derived carbon framework (Co–Ni–Se/BWCF) with strong anchoring are devised and prepared by a microwave treatment–ion exchange–chemical etching–hydrothermal selenization technique. Benefiting from its multi-components and unique structure, Co–Ni–Se/BWCF-160 exhibits excellent supercapacitor and sodium storage performances as self-supporting electrodes. When Co–Ni–Se/BWCF-160 is used as a supercapacitor electrode, its capacity is as high as 3050 F g−1 at 1.0 A g−1 and maintained 1006 F g−1 at 20.0 A g−1. The asymmetric supercapacitor based on Co–Ni–Se/BWCF-160 and a-BWC achieved a high energy density of 49.7 W h kg−1 at 1052 W kg−1, and the capacity retention reaches 93.3% at 10 A g−1 after 5000 cycles. Evaluated as a sodium ion battery self-supporting anode, the initial discharge specific capacity is up to 703 mA h g−1 at 0.1 A g−1, and retains 403 mA h g−1 after 100 cycles. More importantly, it still achieves 211 mA h g−1 at 1.0 A g−1. The overall outstanding electrochemical performances can be explained in that the Co–Ni–Se nanosheets expose more active sites, and the ordered hole arrays ensure sufficient wetting between the electrolyte and electrode materials. Additionally, this unique structure enables more efficient ion/electron transfer and diffusion between the BWCF and Ni–Co–Se, effectively accelerating the electrochemical reaction kinetics.