Syed Atif Pervez

Anodic WO3 mesosponge @ carbon: a novel binder-less electrode for advanced energy storage devices.

A novel design for an anodic WO3 mesosponge @ carbon has been introduced as a highly stable and long cyclic life Li-ion battery electrode. The nanocomposite was successfully synthesized via single-step electrochemical anodization and subsequent heat treatment in an acetylene and argon gas environment. Morphological and compositional characterization of the resultant materials revealed that the composite consisted of a three-dimensional interconnected network of WO3 mesosponge layers conformally coated with a 5 nm thick carbon layer and grown directly on top of tungsten metal. The results demonstrated that the carbon-coated mesosponge WO3 layers exhibit a capacity retention of 87% after completion of 100 charge/discharge cycles, which is significantly higher than the values of 25% for the crystalline (without carbon coating) or 40% for the as-prepared mesosponge WO3 layers. The improved electrochemical response was attributed to the higher stability and enhanced electrical conductivity offered by the carbon coating layer.

Comparative Electrochemical Analysis of Crystalline and Amorphous Anodized Iron Oxide Nanotube Layers as Negative Electrode for LIB

This work is a comparative study of the electrochemical performance of crystalline and amorphous anodic iron oxide nanotube layers. These nanotube layers were grown directly on top of an iron current collector with a vertical orientation via a simple one-step synthesis. The crystalline structures were obtained by heat treating the as-prepared (amorphous) iron oxide nanotube layers in ambient air environment. A detailed morphological and compositional characterization of the resultant materials was performed via transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy. The XRD patterns were further analyzed using Rietveld refinements to gain in-depth information on their quantitative phase and crystal structures after heat treatment. The results demonstrated that the crystalline iron oxide nanotube layers exhibit better electrochemical properties than the amorphous iron oxide nanotube layers when evaluated in terms of the areal capacity, rate capability, and cycling performance. Such an improved electrochemical response was attributed to the morphology and three-dimensional framework of the crystalline nanotube layers offering short, multidirectional transport lengths, which favor rapid Li(+) ions diffusivity and electron transport.

Electromechanical properties of Nb doped 0.76Bi0.5Na0.5TiO3–0.24SrTiO3 ceramic

In this report, the piezoelectric, dielectric and ferroelectric characteristics of 0.76Bi0.5Na0.5TiO3 (BNT)–0.24SrTiO3 (ST) with niobium (Nb) (Nb-added BNT–24ST) ceramics synthesized by using a solid-state reaction are described. The X-ray diffraction analysis and field effect scanning electron microscopy of Nb-added BNT–24ST ceramics reveal the influence of Nb on the perovskite structure and suppression of grain growth within the composition range studied. The electromechanical properties of BNT–24ST ceramics were significantly increased up to 0.5 wt% Nb, and decreased with a further increased Nb content. Around the critical composition (0.5 wt% Nb) with an electric field of 5 kV mm−1, a maximum strain (Smax) of 0.28% at room temperature was obtained. Saturated polarization reached a maximum value of 27 μC cm−2 at a level of 0.5% Nb. The depolarization temperature moved to lower temperatures with Nb content and the peaks became more diffuse with an increasing content of Nb. Using a study of kinetic dynamics, the activation energy drop with 24ST and Nb-added 24ST is well explained by Vogel–Fulcher (VF) behavior and the Kolmogorov–Avrami–Ishibashi (KAI) model, which suggest that the B site vacancy generation in the perovskite structure has a reduction in energy barrier (Ea) with Nb addition. Increase of the phase transition region also occurred in Nb-added 24ST (>50 °C). This work indicated that this material can be considered as a suitable candidate material for high temperature, stable, lead free actuators.

Rate-capability response of graphite anode materials in advanced energy storage systems: a structural comparison

The work presented in this report was a detailed comparative study of the electrochemical response exhibited by graphite anodes in Li-ion batteries having different physical features. A comprehensive morphological and physical characterization was carried out for these graphite samples via X-ray diffraction and scanning electron microscopy. Later, the electrochemical performance was analyzed using galvanostatic charge/discharge testing and the galvanostatic intermittent titration technique for these graphite samples as negative electrode materials in battery operation. The results demonstrated that a material having a higher crystalline order exhibits enhanced electrochemical properties when evaluated in terms of rate-capability performance. All these materials were investigated at high C-rates ranging from 0.1C up to 10C. Such improved response was attributed to the crystalline morphology providing short layers, which facilitate rapid Li+ ions diffusivity and electron transport during the course of battery operation. The values obtained for the electrical conductivity of these graphite anodes support this possible explanation.