Yongtao Tan

A dandelion-like carbon microsphere/MnO2 nanosheets composite for supercapacitors

This article reported the electrochemical performance of a novel cabon microsphere/MnO2 nanosheets (CMS/MnO2) composite prepared by a in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that MnO2 nanosheets homogeneously grew onto the surface of CMS to form a loose-packed and dandelion-like core/shell microstructure. The unique microstructure plays a basic role in electrochemical accessibility of electrolyte to MnO2 active material and a fast diffusion rate within the redox phase. The results of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry indicated that the prepared CMS/MnO2 composite presented high capacitance of 181 F·g−1 and long cycle life of 61% capacity retention after 2000 charge/discharge cycles in 1 mol/L Na2SO4 solution, which show strong promise for high-rate electrochemical capacitive energy storage applications.

Super long-life supercapacitor electrode materials based on hierarchical porous hollow carbon microcapsules

Remarkable supercapacitor electrodes with a high specific supercapacitance and a super long cycle life were achieved by using hierarchical porous hollow carbon microcapsules (HPHCMs) as active materials. HPHCMs were prepared by a facile chemical route based on pyrolysis of a soft sacrificial template involving a non-crosslinked core of poly(styrene-r-methylacrylic acid) and a crosslinked shell of poly(styrene-r-divinylbenzene-r-methylacrylic acid), which were synthesized by using traditional radical polymerization and emulsion polymerization. The results of scanning electron microscopy, transmission electron microscopy and Brunauer–Emmett–Teller characterizations revealed that HPHCM possessed the desired pore structure with apparent macro-/meso- and micropores, which not only provided a continuous electron-transfer pathway to ensure good electrical contact, but also facilitated ion transport by shortening diffusion pathways. As electrode materials for supercapacitor, a high specific capacitance of 278.0 F g−1 was obtained at the current density of 5 mA cm−2. Importantly, after 5000 potential cycles in 2 M KOH electrolyte at the discharge current density of 20 mA cm−2, the capacitance actually increased from 125 to 160 F g−1 and then remained 151 F g−1, corresponding to a capacitance retention of 120%, likely due to electrochemical self-activation.

New amphiphilic block copolymer-modified electrodes for supercapacitors

Herein, amphiphilic block copolymer-modified film electrodes were fabricated using poly(acrylic acid)-b-poly(acrylonitrile)-b-poly(acrylic acid) as a surface modifier, polyethersulfone as a matrix polymer, and activated carbon as an active substance by the phase separation method to enhance the wettability of the electrodes. The effect of the surface modifier on electrochemical performance was investigated. The results indicate that the hydrophilic polymer chains of poly(acrylic acid) are coated on the surface, and the wettability of the fabricated electrode film is largely improved. The prepared film shows good electrochemical performance and is further used as an electrode to assemble a symmetric supercapacitor. The high electrochemical performance of the device demonstrates that the rational coating of the amphiphilic block copolymer onto the surface of a film electrode can obviously improve the wettability and further enhance the electrolyte-affinity of the film electrode. More importantly, both the film electrode and the symmetric supercapacitor are flexible.

Concise N-doped Carbon Nanosheets/Vanadium Nitride Nanoparticles Materials via Intercalative Polymerization for Supercapacitors

N-doped carbon nanosheets/vanadium nitride nanoparticles (N-CNS/VNNPs) are synthesized via a novel method combining surface-initiated in-situ intercalative polymerization and thermal-treatment process in NH3/N2 atmosphere. The pH value of the synthesis system plays a critical role in constructing the structure and enhancing electrochemical performance for N-CNS/VNNPs, which are characterized by SEM, TEM, XRD, and XPS, and measured by electrochemical station, respectively. The results show that N-CNS/VNNPs materials consist of 2D N-doped carbon nanosheets and 0D VN nanoparticles. With the pH value decreasing from 2 to 0, the sizes of both carbon nanosheets and VN nanoparticles decreased to smaller in nanoscale. The maximum specific capacitance of 280 F g−1 at the current density of 1 A g−1 for N-CNS/VNNPs is achieved in three-electrode configuration. The asymmetric energy device of Ni(OH)2||N-CNS/VNNPs offers a specific capacitance of 89.6 F g−1 and retention of 60% at 2.7 A g−1 after 5000 cycles. The maximum energy density of Ni(OH)2 ||N-CNS/VNNPs asymmetric energy device is as high as 29.5 Wh kg−1.

A bird nest-like manganese dioxide and its application as electrode in supercapacitors

Abstract A novel bird nest-like nanostructured MnO2 (BNNS-MnO2) was prepared by a facile and cost-effective strategy. Their structures and morphologies were characterized by field emission scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction. Capacitive behaviors were investigated by cyclic voltammetry and galvanostatic charge-discharge. The obtained nano-MnO2 possesses a well designed loose-assembled hierarchical nanoarchitecture with an appropriate crystallinity which gives rise to excellent performances as an electrode material for supercapacitors. A maximum specific capacitance of 917 F/g has been obtained at a current density of 5 mA/cm2 in 6 mol/L KOH aqueous solution, and a specific capacitance of 210 F/g has been maintained for 500 cycles. As the low cost of MnSO4 and KCr2O7 and the low reaction temperature, the present method avoids the requirements for complicated operations, time/energy-consuming and expensive reagents, and perhaps is ready for the industrialization of nano-MnO2 production.

A polymer-supported electrolyte-affinity hybrid membrane and modification of the amphiphilic block copolymer for use as a super-high flexible and high-performance supercapacitor

In this study, a super-high flexible membrane electrode (FME) was developed via a facile method based on liquid–liquid phase separation involving the migration and self-assembly of the components. Note that the surface segregation and chain orientation of the amphiphilic block copolymer PAA-b-PAN-b-PAA on the membrane surface during the phase separation process provide the hierarchical porous structure and electrolyte-affinity electrode surface; this hierarchical porous structure provides pathways for the electrolyte ions into and from the electrolyte/solution interface for further contact and reaction of the electrochemically active materials with the electrolyte ions. In a three-electrode system, the specific capacitance of FME-Ni(OH)2 can reach up to 2198.6 F g−1 (769.5 C g−1) at the current density of 0.5 A g−1 from 0 to 0.35 V as compared to that for non-flexible Ni(OH)2 (1588.6 F g−1; 556.0 C g−1). Moreover, a flexible asymmetric supercapacitor with FME-Ni(OH)2 as the positive electrode and FME-AC (commercial activated carbon) as the negative electrode showed the high specific capacitance of 102.2 F g−1 (163.5 C g−1) and the maximum energy density of 36.3 W h kg−1 at the power density of 400 W kg−1; moreover, it retained the energy density of 20.6 W h kg−1 at the high power density of 4000 W kg−1 in the potential window ranging from 0 to 1.6 V in a 6 M KOH aqueous solution.

Author Correction: Concise N-doped Carbon Nanosheets/Vanadium Nitride Nanoparticles Materials via Intercalative Polymerization for Supercapacitors

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

MoO2/Mo2N hybrid nanobelts doped with gold nanoparticles and their enhanced supercapacitive behavior

MoO2/Mo2N hybrid nanobelts doped with gold nanoparticles (AuNPMoON) were synthesized via one-step thermal-treatment of MoO3 nanobelts and HAuCl4. AuNPMoON nanobelts with a width of ca. 200 nm and an Au content of 1.08 wt% prepared in the presence of HAuCl4 exhibited a higher specific capacitance of 348 F g−1 than those prepared in the absence of HAuCl4 (21 F g−1) at a current density of 0.5 A g−1. The influence of Au content on the electrochemical performance of AuNPMoON was investigated. For practical application, two types of supercapacitor devices, PANI||AuNPMoON and AC||AuNPMoON, were assembled. The PANI||AuNPMoON device delivered an energy density of 10.64 W h kg−1, which is higher than that of the AC||AuNPMoON device (8.11 W h kg−1). Meanwhile, the specific capacitance retentions were 87.8% and 85.5% for the PANI||AuNPMoON and AC||AuNPMoON devices after 2000 cycles, respectively.

Polyaniline nanoparticles for supercapacitor prepared by using polystyrene microsphere as carrier

Polyaniline nanopaticles for supercapacitor were prepared by using polystyrene microsphere as carrier. They were characterized by FTIR, SEM and TGA for structure and electrochemical station for supercapacitive performance. The results show that, the polystyrene-polyaniline composite, about 4∼5 µm, keep the microsphere structure of polystyrene, and was covered on its surface with polyaniline nanoparticle of about 50 nm. The composite shows excellent supercapacitive performance. Increasing the fraction of PANI/PS-PANI (w) result in an increase of capacitance of PS-PANI composite, and a maximum specific capacitance was 275 F/g, and capacitance of polyaniline first increased, then decreased. When w was 0.44, capacitance was a maximum capacitance of 498 F/g.