A novel "dissolution-capture" method for the fabrication of nitrogen-doped hollow mesoporous spherical carbon capsules (N-HMSCCs) with high capability for supercapacitor is developed. The fabrication process is performed by depositing mesoporous silica on the surface of the polyacrylonitrile nanospheres, followed by a dissolution-capture process occurring in the polyacrylonitrile core and silica shell. The polyacrylonitrile core is dissolved by dimethylformamide treatment to form a hollow cavity. Then, the polyacrylonitrile is captured into the mesochannel of silica. After carbonization and etching of silica, N-HMSCCs with uniform mesopore size are produced. The N-HMSCCs show a high specific capacitance of 206.0 F g(-1) at a current density of 1 A g(-1) in 6.0 M KOH due to its unique hollow nanostructure, high surface area, and nitrogen content. In addition, 92.3% of the capacitance of N-HMSCCs still remains after 3000 cycles at 5 A g(-1). The "dissolution-capture" method should give a useful enlightenment for the design of electrode materials for supercapacitor.
Summary
With the rapid development of power electronics technology, modular series‐parallel structures have attracted more and more attention due to high reliability and good redundancy. Especially in the occasion of high input voltage and low output voltage, the input‐series output‐parallel (ISOP) DC–DC converter is applied to reduce the stress of the device. Although this modular approach has many advantages, there is a problem of unbalanced voltage and current caused by component parameter errors in each module. Therefore, this paper proposes an inverse droop control equalization method based on coefficient adaptation. This method can not only keep the input voltage sharing (IVS) of the modules among the ISOP system but also solve the problem of the deviation of the traditional inverse droop control output voltage from the reference value, which increases the dynamic response of the system. This article first introduces the principle and control logic of the method and builds a three‐way module ISOP circuit. The experiment verifies the input voltage equalization effect and dynamic performance of the control method on the ISOP system under various working conditions.
Monodispersed nitrogen-doped hollow mesoporous carbon spheres (N-HMCSs) have been successfully synthesized using a novel "dissolution-capture" method. The mesoporous silica is uniformly coated on the surface of the polystyrene/polyacrylonitrile composite nanospheres (PS@PAN) core by using a modified Stöber method. Then a hollow cavity is formed through the dissolution of the PS@PAN in organic solvent. The dissolved PS@PAN as the carbon and nitrogen precursor is captured in the mesochannels of the silica shell. The obtained N-HMCSs have high specific surface area of 807 m 2 g −1 , uniform mesopore size of 4.1 nm, and nitrogen content of 3.6 at.%. In addition, the N-HMCSs show a high specific capacitance of 212 F g −1 at a current density of 1 A g −1 in 6 M KOH electrolyte and capacitance retention of 93.9% after 10000 charge/discharge cycles at 5 A g −1 . The "dissolution-capture" method can give a useful enlightenment for the design of electrode materials for supercapacitors.
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