NiCo₂O₄ nanostructure-decorated PAN/lignin based carbon nanofiber electrodes with excellent cyclability for flexible hybrid supercapacitors

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Nanostructured binary metal oxide-decorated carbon nanofibers (CNFs) were utilized as flexible electrodes for hybrid supercapacitor applications. Polyacrylonitrile (PAN)/lignin based carbon nanofibers (PAN/lignin CNFs) with different contents of lignin were prepared by electrospinning, stabilization and carbonization. Afterwards, the NiCo<SUB>2</SUB>O<SUB>4</SUB> oxides were deposited on the surface of CNFs by a facile hydrothermal method without any toxic reagents. SEM images confirmed that the NiCo<SUB>2</SUB>O<SUB>4</SUB> (nanosheet and nanoneedle) nanostructures were uniformly grown on the surface of every carbon fiber. The obtained flexible NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated PAN/lignin CNFs with 50% lignin (NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNF55) electrode exhibited high specific capacitance of the ∼1757 F g<SUP>−1</SUP> at 2 mA cm<SUP>−2</SUP> and excellent cyclability with ∼138% capacitance retention after 5000 cycles at 7 mA cm<SUP>−2</SUP>, suggesting lower internal resistance and higher electrochemical reversibility. In addition, the NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNFs//N-rGO solid state asymmetric supercapacitor devices were assembled in order to evaluate their practical applications. The NiCo<SUB>2</SUB>O<SUB>4</SUB>@CNF55//N-rGO asymmetric supercapacitor device exhibited a specific capacitance of 134.3 F g<SUP>−1</SUP> at a current densities of 1 A g<SUP>−1</SUP>, and possessed a maximum energy density of 47.75 Wh kg<SUP>−1</SUP> with a power density of 799.53 W kg<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAN/lignin-based carbon fibers were prepared by electrospinning, stabilization and carbonization. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB> nanostructures were fabricated on PAN/lignin-based carbon nanofibers. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated fiber electrode exhibits highest specific capacitance of the ∼1757 Fg<SUP>-1</SUP>. </LI> <LI> The NiCo<SUB>2</SUB>O<SUB>4</SUB>-decorated fiber electrode shows excellent capacitance retention of ∼138% after 5000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>