The increasing demand for energy has triggered tremendous research efforts for the development of lightweight and durable energy storage devices. Herein, we report a simple, yet effective, strategy for high-performance supercapacitors by building three-dimensional pseudocapacitive CuO frameworks with highly ordered and interconnected bimodal nanopores, nanosized walls (∼4 nm) and large specific surface area of 149 m(2) g(-1). This interesting electrode structure plays a key role in providing facilitated ion transport, short ion and electron diffusion pathways and more active sites for electrochemical reactions. This electrode demonstrates excellent electrochemical performance with a specific capacitance of 431 F g(-1) (1.51 F cm(-2)) at 3.5 mA cm(-2) and retains over 70% of this capacitance when operated at an ultrafast rate of 70 mA cm(-2). When this highly ordered CuO electrode is assembled in an asymmetric cell with an activated carbon electrode, the as-fabricated device demonstrates remarkable performance with an energy density of 19.7 W h kg(-1), power density of 7 kW kg(-1), and excellent cycle life. This work presents a new platform for high-performance asymmetric supercapacitors for the next generation of portable electronics and electric vehicles.
The search for faster, safer, and
more efficient energy storage
systems continues to inspire researchers to develop new energy storage
materials with ultrahigh performance. Mesoporous nanostructures are
interesting for supercapacitors because of their high surface area,
controlled porosity, and large number of active sites, which promise
the utilization of the full capacitance of active materials. Herein,
highly ordered mesoporous CuCo2O4 nanowires
have been synthesized by nanocasting from a silica SBA-15 template.
These nanowires exhibit superior pseudocapacitance of 1210 F g–1 in the initial cycles. Electroactivation of the electrode
in the subsequent 250 cycles causes a significant increase in capacitance
to 3080 F g–1. An asymmetric supercapacitor composed
of mesoporous CuCo2O4 nanowires for the positive
electrode and activated carbon for the negative electrode demonstrates
an ultrahigh energy density of 42.8 Wh kg–1 with
a power density of 15 kW kg–1 plus excellent cycle
life. We also show that two asymmetric devices in series can efficiently
power 5 mm diameter blue, green, and red LED indicators for 60 min.
This work could lead to a new generation of hybrid supercapacitors
to bridge the energy gap between chemical batteries and double layer
supercapacitors.
Hierarchical CuCo2S4 hollow nanoneedle arrays have been firstly synthesized on a Ni foam using a facile template-free hydrothermal method and applied as novel binder-free electrodes for high-performance asymmetric supercapacitors with ultrahigh specific capacitance, high energy density, excellent rate capability and outstanding long-term cycling stability.
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