Mesopore- and Macropore-Dominant Nitrogen-Doped Hierarchically
Porous Carbons for High-Energy and Ultrafast Supercapacitors in Non-Aqueous
Electrolytes
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Abstract
Non-aqueous electrolytes
(e.g., organic and ionic liquid electrolytes) can undergo high working
voltage to improve the energy densities of supercapacitors. However,
the large ion sizes, high viscosities, and low ionic conductivities
of organic and ionic liquid electrolytes tend to cause the low specific
capacitances, poor rate, and cycling performance of supercapacitors
based on conventional micropore-dominant activated carbon electrodes,
limiting their practical applications. Herein, we propose an effective
strategy to simultaneously obtain high power and energy densities
in non-aqueous electrolytes via using a cattle bone-derived porous
carbon as an electrode material. Because of the unique co-activation
of KOH and hydroxyapatite (HA) within the cattle bone, nitrogen-doped
hierarchically porous carbon (referred to as NHPC–HA/KOH) is
obtained and possesses a mesopore- and macropore-dominant porosity
with an ultrahigh specific surface area (2203 m<sup>2</sup> g<sup>–1</sup>) of meso- and macropores. The NHPC–HA/KOH
electrodes exhibit superior performance with specific capacitances
of 224 and 240 F g<sup>–1</sup> at 5 A g<sup>–1</sup> in 1.0 M TEABF<sub>4</sub>/AN and neat EMIMBF<sub>4</sub> electrolyte,
respectively. The symmetric supercapacitor using NHPC–HA/KOH
electrodes can deliver integrated high energy and power properties
(48.6 W h kg<sup>–1</sup> at 3.13 kW kg<sup>–1</sup> in 1.0 M TEABF<sub>4</sub>/AN and 75 W h kg<sup>–1</sup> at
3.75 kW kg<sup>–1</sup> in neat EMIMBF<sub>4</sub>), as well
as superior cycling performance (over 89% of the initial capacitance
after 10 000 cycles at 10 A g<sup>–1</sup>)