Nitrogen-enriched carbon nanofibers carried Sn and Zn bimetallic composites with outstanding storage capacity and superior mechanical strength were facilely fabricated by electrospinning technology, amidoximation reaction modified polymer fiber, ion coordination technique introduced Zn 2+ and carbonization of composite nanofibers. The introduction of amidoxime groups not only enhanced the coordination ability with Zn 2+ , but also increased the content of nitrogen element. In addition, due to the different thermal stability of amidoxime groups, the regulation of different types of nitrogen content can be achieved by changing the carbonization temperature, and the influence of nitrogen on the electrochemical performance was explained. At the same time, due to the role of carbothermal reduction , tin in different valence ratios was obtained and its contribution to the energy storage performance of supercapacitors was explored. Benefiting from high nitrogen-enriched level, mutation between Sn 2+ and Sn 4+ oxidation state and synergistic mechanism of ZnO-SnO x bimetal, the prepared composite had a high specific capacitance of 810.89 F g −1 at a current density of 0.5 A g −1 , outstanding cycling stability of 119% over 5000 cycles in 4 M KOH electrolyte. What’s more, we conducted a two-electrode test with the energy density of 50 Wh kg −1 at a power density of 374 W kg −1 . In consequence, this novel design is believed to have great potential in high energy and power density of energy storage devices in the future.
Flexible and portable supercapacitors as a variety of energy storage devices are used in wearable electronic devices. However, the practical application of flexible supercapacitors is still restricted by comparatively poor performance. Herein, we have successfully prepared porous carbon nanofibers supported Sn and Zn bimetallic composites as flexible and freestanding electrode material in supercapacitors. Sn element encapsulated in nano-fiber films were prepared by electrospinning technique, the SnO x -ZnO/MCNFs composites were formed by immersion of different proportions of Zn 2+ , and further high temperature carbonization process. In addition, on the basis of comparative experiments, a possible mechanism for effective synergy between the two metals were raised. The specific capacitance of SnO x -ZnO/MCNFs-10 mmol/L at 0.5 A g −1 is 783 F g −1 with the retention rate of 87% after 5000 cycles, which is higher than their respective counterparts SnO x /MCNFs (599 F g −1 ) and ZnO/MCNFs (429 F g −1 ). Moreover, a flexible all-solid-state asymmetric supercapacitor (ASC) was further assembled with the energy density of 37.7 Wh kg −1 at the power density of 374.9 W kg −1 , and long-term cyclic stability (76.2% after 5000 cycles). The reason for the remarkable electrochemical performance could be the reasonable combination of the two electrode materials, which provides a new idea for the application of composite materials in supercapacitors.
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