ABSTRACT
Zn ion capacitors (ZICs) composed of a carbon-based cathode and a Zn anode are one of the most promising energy storage devices due to their inherent safety and high-power output. However, their poor cycling stability originating from the Zn dendrites' formation and low energy density limited by insufficient activated carbon properties remain major challenges for development of high-performance ZICs. Hence, we constructed a facile and effective strategy to alleviate "edge effects" and suppress Zn dendrites by growing ZnO nanowire arrays on Zn foil (ZnO@Zn) using a horizontally potentiostatic anodizing technique. The electrochemical characterizations and in situ optical microscopy observation revealed that the introduction of ZnO nanowire arrays can significantly suppress the growth of Zn dendrites and enhance the cycling stability of the Zn anode. The superfine and interlaced ZnO nanowire arrays provide uniform nucleation sites and high electrical conductivity for the Zn metal anode, reducing the local current density and promoting the rapid diffusion and migration of Zn ions on the Zn anode surface. As a result, the ZnO@Zn electrode has a very low nucleation overpotential and excellent cycle stability, far superior to the bare Zn anode. Furthermore, a ZnO@Zn//NPHC ZIC assembled with an N, P-codoped hard carbon (NPHC) cathode delivers a high specific capacity of 110.3 mAh g-1 at 0.1 A g-1 and achieves outstanding cycling stability with 90% capacity retention together with â¼100% Coulombic efficiency after 20000 cycles.
ABSTRACT
Herein, the novel acacia wood based hierarchical porous activated carbons (AWCs) are easily prepared, low cost and have excellent characterization, such as special biomass nanopores via structural stability and large specific surface areas. Activating agents such as KOH, ZnCl2, and H3PO4 have been used to convert acacia wood carbon into active carbons such as AWC-K, AWC-Z, and AWC-P, respectively, which are named after the activating agent. As a supercapacitor electrode, the AWC-K sample has a high yield was 69.8%, significant specific surface area of 1563.43 m2g-1 and layer thickness of 4.6 mm. Besides that, it showed specific capacitance of 224.92 F g-1 at 0.5 A g-1 in 2 M KOH as electrolyte. In addition, the AWC-K//AWC-K symmetrical supercapacitor device displays high energy density of 23.98 Wh kg-1 at 450 W kg-1 power density with excellent cycling number stability was 93.2% long lifetime of 10,000 cycles using 0.5 M Na2SO4 as electrolyte. The high electrochemistry performance mainly contributed the special biomass pores structure. Therefore, the presented approach opens new avenues in supercapacitor applications to meet energy storage.
