Bilayered microelectrodes based on electrochemically deposited MnO2/polypyrrole towards fast charge transport kinetics for micro-supercapacitors.

Micro-supercapacitors (MSCs) are promising power solution facilities for miniaturized portable electronic devices. Microfabrication of on-chip MSC with high specific capacitance and high energy density is still a great challenge. Herein, we report a high-performance MnO2/polypyrrole (PPy) microelectrode based MSC (MnO2/PPy-MSC) by modern micromachining technology. Interdigital Au micro current collectors were obtained by photolithography, physical vapor deposition and lift off. A layer of PPy was electrochemically deposited on Au current collectors followed by deposition of urchin-like MnO2 micro/nanostructures. The electrochemical performance of MnO2/PPy-MSC was explored employing LiClO4/PVA gel electrolyte. The assembled MSC demonstrated a high areal capacitance of 13 mF cm-2, an energy density of 1.07 × 10-3 mW h cm-2 and a power density of 0.53 mW cm-2. In addition, the MnO2/PPy-MSC showed an improved cycling stability, retaining 84% of the initial capacitance after 5000 CV cycles at a scan rate of 500 mV s-1. Our proposed strategy provides a versatile and promising method for the fabrication of high-performance MSCs with large-scale applications.

Interwoven three-dimensional architecture of cobalt oxide nanobrush-graphene@Ni(x)Co(2x)(OH)(6x) for high-performance supercapacitors.

Development of pseudocapacitor electrode materials with high comprehensive electrochemical performance, such as high capacitance, superior reversibility, excellent stability, and good rate capability at the high mass loading level, still is a tremendous challenge. To our knowledge, few works could successfully achieve the above comprehensive electrochemical performance simultaneously. Here we design and synthesize one interwoven three-dimensional (3D) architecture of cobalt oxide nanobrush-graphene@Ni(x)Co(2x)(OH)(6x) (CNG@NCH) electrode with high comprehensive electrochemical performance: high specific capacitance (2550 F g(-1) and 5.1 F cm(-2)), good rate capability (82.98% capacitance retention at 20 A g(-1) vs 1 A g(-1)), superior reversibility, and cycling stability (92.70% capacitance retention after 5000 cycles at 20 A g(-1)), which successfully overcomes the tremendous challenge for pseudocapacitor electrode materials. The asymmetric supercapacitor of CNG@NCH//reduced-graphene-oxide-film exhibits good rate capability (74.85% capacitance retention at 10 A g(-1) vs 0.5 A g(-1)) and high energy density (78.75 Wh kg(-1) at a power density of 473 W kg(-1)). The design of this interwoven 3D frame architecture can offer a new and appropriate idea for obtaining high comprehensive performance electrode materials in the energy storage field.

Synergistic effect of hierarchical nanostructured MoO2/Co(OH)2 with largely enhanced pseudocapacitor cyclability.

Pseudocapacitors have demonstrated an ability to deliver high energy and power densities. The main limitation is their poor cyclability and for this reason the architectural design of electrode materials has attracted considerable attention. Here we report the synthesis of hierarchical nanostructured material by growing Co(OH)2 nanoflakes onto MoO2 thin film. The electrode material exhibits a high capacitance of 800 F g(-1) at 20 A g(-1) with only 3% capacitance loss after 5000 cycles and high rate capability with increasing current density from 2 to 40 A g(-1), which are better than those of individual component. The enhanced pseudocapacitor performances benefit from the synergistic effect of the hierarchical nanostructure: (1) faster ion diffusion and electron transport at electrode/electrolyte interface, and (2) mitigation of the electrode destruction caused by ion insertion/deinsertion during charge-storage process. This facile design and rational synthesis offers an effective strategy to enhance the electrochemical performance of pseudocapacitors and shows promising potential for large-scale application in energy storage.

Substrate-assisted self-organization of radial ß-AgVO3 nanowire clusters for high rate rechargeable lithium batteries.

Rational assembly of unique complex nanostructures is one of the facile techniques to improve the electrochemical performance of electrode materials. Here, a substrate-assisted hydrothermal method was designed and applied in synthesizing moundlily like radial ß-AgVO(3) nanowire clusters. Gravitation and F(-) ions have been demonstrated to play important roles in the growth of ß-AgVO(3) nanowires (NWs) on substrates. The results of cyclic voltammetry (CV) measurement and X-ray diffraction (XRD) characterization proved the phase transformation from ß-AgVO(3) to Ag(1.92)V(4)O(11) during the redox reaction. Further electrochemical investigation showed that the moundlily like ß-AgVO(3) nanowire cathode has a high discharge capacity and excellent cycling performance, mainly due to the reduced self-aggregation. The capacity fading per cycle from 3rd to 51st is 0.17% under the current density of 500 mA/g, which is much better than 1.46% under that of 20 mA/g. This phenomenon may be related to the Li(+) diffusion and related kinetics of the electrode. This method is shown to be an effective and facile technique for improving the electrochemical performance for applications in rechargeable Li batteries or Li ion batteries.