Tin oxide based composites derived using electrostatic spray deposition technique as anodes for lithium-ion batteries

Recent advances in the electric & hybrid electric vehicles and rapid developments in the electronic devices have increased the demand for high power and high energy density lithium ion batteries. Graphite (theoretical specific capacity: 372 mAh/g) used in commercial anodes cannot meet these demands. Amorphous SnO2 anodes (theoretical specific capacity: 781 mAh/g) have been proposed as alternative anode materials. But these materials have poor conductivity, undergo a large volume change during charging and discharging, large irreversible capacity loss leading to poor cycle performances. To solve the issues related to SnO2 anodes, we propose to synthesize porous SnO2 composites using electrostatic spray deposition technique. First, porous SnO2/CNT composites were fabricated and the effects of the deposition temperature (200, 250, 300 °C) & CNT content (10, 20, 30, 40 wt %) on the electrochemical performance of the anodes were studied. Compared to pure SnO2 and pure CNT, the composite materials as anodes showed better discharge capacity and cyclability. 30 wt% CNT content and 250 °C deposition temperature were found to be the optimal conditions with regard to energy capacity whereas the sample with 20% CNT deposited at 250 °C exhibited good capacity retention. This can be ascribed to the porous nature of the anodes and the improvement in the conductivity by the addition of CNT. Electrochemical impedance spectroscopy studies were carried out to study in detail the change in the surface film resistance with cycling. By fitting EIS data to an equivalent circuit model, the values of the circuit components, which represent surface film resistance, were obtained. The higher the CNT content in the composite, lower the change in surface film resistance at certain voltage upon cycling. The surface resistance increased with the depth of discharge and decreased slightly at fully lithiated state. Graphene was also added to improve the performance of pure SnO2 anodes. The composites heated at 280 °C showed better energy capacity and energy density. The specific capacities of as deposited and post heat-treated samples were 534 and 737 mAh/g after 70 cycles. At the 70th cycle, the energy density of the composites at 195 °C and 280 °C were 1240 and 1760 Wh/kg, respectively, which are much higher than the commercially used graphite electrodes (37.2–74.4 Wh/kg). Both SnO2/CNTand SnO2/grapheme based composites with improved energy densities and capacities than pure SnO2 can make a significant impact on the development of new batteries for electric vehicles and portable electronics applications.

Effect of arginine and oscillatory calcium ion (II) on vascular response mediated via nitric oxide signaling in normal and salt sensitive hypertensive rat mesenteric arterioles

Hypertension, a major risk factor in the cardiovascular system, is characterized by an increase in the arterial blood pressure. High dietary sodium is linked to multiple cardiovascular disorders including hypertension. Salt sensitivity, a measure of how the blood pressure responds to salt intake is observed in more than 50% of the hypertension cases. Nitric Oxide (NO), as an endogenous vasodilator serves many important biological roles in the cardiovascular physiology including blood pressure regulation. The physiological concentrations for NO bioactivity are reported to be in 0-500 nM range. Notably, the vascular response to NO is highly regulated within a small concentration spectrum. Hence, much uncertainty surrounds how NO modulates diverse signaling mechanisms to initiate vascular relaxation and alleviate hypertension. Regulating the availability of NO in the vasculature has demonstrated vasoprotective effects. In addition, modulating the NO release by different means has proved to restore endothelial function. In this study we addressed parameters that regulated NO release in the vasculature, in physiology and pathophysiology such as salt sensitive hypertension. We showed that, in the rat mesenteric arterioles, Ca2+ induced rapid relaxation (time constants 20.8 ± 2.2 sec) followed with a much slower constriction after subsequent removal of the stimulus (time constants 104.8 ± 10.0 sec). An interesting observation was that a fourfold increase in the Ca 2+ frequency improved the efficacy of arteriolar relaxation by 61.1%. Our results suggested that, Ca2+ frequency-dependent transient release of NO from the endothelium carried encoded information; which could be translated into different steady state vascular tone. Further, Agmatine, a metabolite of L-arginine, as a ligand, was observed to relax the mesenteric arterioles. These relaxations were NO-dependent and occurred via &agr;-2 receptor activity. The observed potency of agmatine (EC50, 138.7 ± 12.1 ± μM; n=22), was 40 fold higher than L-arginine itself (EC50, 18.3 ± 1.3 mM; n = 5). This suggested us to propose alternative parallel mechanism for L-arginine mediated vascular relaxation via arginine decarboxylase activity. In addition, the biomechanics of rat mesentery is important in regulation of vascular tone. We developed 2D finite element models that described the vascular mechanics of rat mesentery. With an inverse estimation approach, we identified the elasticity parameters characterizing alterations in normotensive and hypertensive Dahl rats. Our efforts were towards guiding current studies that optimized cardiovascular intervention and assisted in the development of new therapeutic strategies. These observations may have significant implications towards alternatives to present methods for NO delivery as a therapeutic target. Our work shall prove to be beneficial in assisting the delivery of NO in the vasculature thus minimizing the cardiovascular risk in handling abnormalities, such as hypertension.

Tin Oxide Based Composites Derived Using Electrostatic Spray Deposition Technique as Anodes for Li-Ion Batteries

Recent advances in the electric & hybrid electric vehicles and rapid developments in the electronic devices have increased the demand for high power and high energy density lithium ion batteries. Graphite (theoretical specific capacity: 372 mAh/g) used in commercial anodes cannot meet these demands. Amorphous SnO2 anodes (theoretical specific capacity: 781 mAh/g) have been proposed as alternative anode materials. But these materials have poor conductivity, undergo a large volume change during charging and discharging, large irreversible capacity loss leading to poor cycle performances. To solve the issues related to SnO2 anodes, we propose to synthesize porous SnO2 composites using electrostatic spray deposition technique. First, porous SnO2/CNT composites were fabricated and the effects of the deposition temperature (200,250, 300 oC) & CNT content (10, 20, 30, 40 wt %) on the electrochemical performance of the anodes were studied. Compared to pure SnO2 and pure CNT, the composite materials as anodes showed better discharge capacity and cyclability. 30 wt% CNT content and 250 oC deposition temperature were found to be the optimal conditions with regard to energy capacity whereas the sample with 20% CNT deposited at 250 oC exhibited good capacity retention. This can be ascribed to the porous nature of the anodes and the improvement in the conductivity by the addition of CNT. Electrochemical impedance spectroscopy studies were carried out to study in detail the change in the surface film resistance with cycling. By fitting EIS data to an equivalent circuit model, the values of the circuit components, which represent surface film resistance, were obtained. The higher the CNT content in the composite, lower the change in surface film resistance at certain voltage upon cycling. The surface resistance increased with the depth of discharge and decreased slightly at fully lithiated state. Graphene was also added to improve the performance of pure SnO2 anodes. The composites heated at 280 oC showed better energy capacity and energy density. The specific capacities of as deposited and post heat-treated samples were 534 and 737 mAh/g after 70 cycles. At the 70th cycle, the energy density of the composites at 195 °C and 280 °C were 1240 and 1760 Wh/kg, respectively, which are much higher than the commercially used graphite electrodes (37.2-74.4 Wh/kg). Both SnO2/CNTand SnO2/grapheme based composites with improved energy densities and capacities than pure SnO2 can make a significant impact on the development of new batteries for electric vehicles and portable electronics applications.