4 years ago

High-Stacking-Density, Superior-Roughness LDH Bridged with Vertically Aligned Graphene for High-Performance Asymmetric Supercapacitors

High-Stacking-Density, Superior-Roughness LDH Bridged with Vertically Aligned Graphene for High-Performance Asymmetric Supercapacitors
Mengdi Zhang, Juan Yang, Changtai Zhao, Huawei Huang, Zhibin Liu, Chang Yu, Xiaotong Han, Shaofeng Li, Jieshan Qiu, Yingying Niu, Wei Guo
The high-performance electrode materials with tuned surface and interface structure and functionalities are highly demanded for advanced supercapacitors. A novel strategy is presented to conFigure high-stacking-density, superior-roughness nickel manganese layered double hydroxide (LDH) bridged by vertically aligned graphene (VG) with nickel foam (NF) as the conductive collector, yielding the LDH-NF@VG hybrids for asymmetric supercapacitors. The VG nanosheets provide numerous electron transfer channels for quick redox reactions, and well-developed open structure for fast mass transport. Moreover, the high-stacking-density LDH grown and assembled on VG nanosheets result in a superior hydrophilicity derived from the tuned nano/microstructures, especially microroughness. Such a high stacking density with abundant active sites and superior wettability can be easily accessed by aqueous electrolytes. Benefitting from the above features, the LDH-NF@VG can deliver a high capacitance of 2920 F g−1 at a current density of 2 A g−1, and the asymmetric supercapacitor with the LDH-NF@VG as positive electrode and activated carbon as negative electrode can deliver a high energy density of 56.8 Wh kg−1 at a power density of 260 W kg−1, with a high specific capacitance retention rate of 87% even after 10 000 cycles. High-stacking-density, superior-roughness integrated architectures made of layered double hydroxide (LDH) bridged with vertically aligned graphene (VG) are configured, indicative of a superior hydrophilic behavior derived from controllable nano/microstructures. As such, an asymmetric supercapacitor made up of LDH-nickel foam@VG and activated carbon delivers high energy density and excellent cycling retention rate.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201701288

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