Direct electrodeposition of aluminium nano-rods

Electrodeposition of aluminium within an alumina nano-structured template, for use as high surface area current collectors in Li-ion microbatteries, was investigated. The aluminium electrodeposition was carried out in the ionic liquid 1-ethyl-3-methylimidazolium chloride:aluminium chloride (1:2 ratio). First the aluminium electrodeposition process was confirmed by combined cyclic voltammetry and electrochemical quartz crystal microbalance measurements. Then, aluminium was electrodeposited under pulsed-potential conditions within ordered alumina membranes. A careful removal of the alumina template unveiled free standing arrays of aluminium nano-rods. The nano-columns shape and dimensions are directly related to the template dimensions. To our knowledge, this is the first time that direct electrodeposition of aluminium nano-pillars onto an aluminium substrate is reported

Tracking the structural arrangement of ions in carbon supercapacitor nanopores using in situ small-angle X-ray scattering

The charge storage mechanism and ion arrangement inside electrically charged carbon nanopores is a very active research field with tremendous importance for advanced electrochemical technologies, such as supercapacitors or capacitive deionization. Going far beyond the state of art, we present for the first time a comprehensive study of tracking ion electrosorption in aqueous electrolytes during charging and discharging of porous carbon electrodes using in situ X-ray scattering. We provide novel and quantitative insights into the local concentration of anions and cations and demonstrate that the global number of ions within the pores does not vary during charging and discharging. In addition, we have unique access to the spatial arrangement of ions inside carbon nanopores by using a simple, yet powerful two-phase model. Applying this model to our data, we show that double-layer formation is accomplished by a unique combination of preferred counter-ion adsorption directly at the pore wall which drains ions from their local surrounding inside carbon nanopores. Effectively, this leads to a situation which globally appears as ion swapping

Electrodeposited Cu2Sb as anode material for 3-dimensional Li-ion microbatteries

An increasing demand on high energy and power systems has arisen not only with the development of electric vehicle (EV), hybrid electric vehicle (HEV), telecom, and mobile technologies, but also for specific applications such as powering of microelectronic systems. To power those microdevices, an extra variable is added to the equation: a limited footprint area. Three-dimensional (3D) microbatteries are a solution to combine high-density energy and power. In this work, we present the formation of Cu2Sb onto three-dimensionally architectured arrays of Cu current collectors. Sb electrodeposition conditions and annealing post treatment are discussed in light of their influence on the morphology and battery performances. An increase of cycling stability was observed when Sb was fully alloyed with the Cu current collector. A subsequent separator layer was added to the 3D electrode when optimized. Equivalent capacity values are measured for at least 20 cycles. Work is currently devoted to the identification of the causes of capacity fading

Nanoarchitectured 3D cathodes for Li-Ion microbatteries

Microbatteries with large area capacity and no power limitation can be obtained by designing 3D structured batteries. 3D electrodes composed of 30 nm-thick films of LiCoO2 coating free-standing columns of Al current collector were achieved. By comparison with a planar electrode presenting an equivalent nominal capacity, a 3D electrode exhibits improved capacity retention: 68% of the nominal capacity at 8C instead of 11%

3D lithium ion batteries—from fundamentals to fabrication

3D microbatteries are proposed as a step change in the energy and power per footprint of surface mountable rechargeable batteries for microelectromechanical systems (MEMS) and other small electronic devices. Within a battery electrode, a 3D nanoarchitecture gives mesoporosity, increasing power by reducing the length of the diffusion path; in the separator region it can form the basis of a robust but porous solid, isolating the electrodes and immobilising an otherwise fluid electrolyte. 3D microarchitecture of the whole cell allows fabrication of interdigitated or interpenetrating networks that minimise the ionic path length between the electrodes in a thick cell. This article outlines the design principles for 3D microbatteries and estimates the geometrical and physical requirements of the materials. It then gives selected examples of recent progress in the techniques available for fabrication of 3D battery structures by successive deposition of electrodes, electrolytes and current collectors onto microstructured substrates by self-assembly methods

Nano-structured 3D Electrodes for Li-ion Micro-batteries

A new challenging application for Li-ion battery has arisen from the rapid development of micro-electronics. Powering Micro-ElectroMechanical Systems (MEMS) such as autonomous smart-dust nodes using conventional Li-ion batteries is not possible. It is not only new batteries based on new materials but there is also a need of modifying the actual battery design. In this context, the conception of 3D nano-architectured Li-ion batteries is explored. There are several micro-battery concepts that are studied; however in this thesis, the focus is concentrated on one particular architecture that can be described as the successive deposition of battery components (active material, electrolyte, active material) on free-standing arrays of nano-sized columns of a current collector. After a brief introduction about Li-ion batteries and 3D micro-batteries, the electrodeposition of Al through an alumina template using an ionic liquid electrolyte to form free-standing columns of Al current collector is described. The crucial deposition parameters influencing the nucleation and growth of the Al nano-rods are discussed. The deposition of active electrode material on the nano-structured current collector columns is described for 2 distinct active materials deposited using different techniques. Deposition of TiO2 using Atomic Layer Deposition (ALD) as active material on top of the nano-structured Al is also presented. The obtained deposits present high uniformity and high covering of the specific surface of the current collector. When cycled versus lithium and compared to planar electrodes, an increase of the capacity was proven to be directly proportional to the specific area gained from shifting from a 2D to a 3D construction. Cu2Sb 3D electrodes were prepared by the electrodeposition of Sb onto a nano-structured Cu current collector followed by an annealing step forcing the alloying between the current collector and Sb. The volume expansion observed during Sb alloying with Li is buffered by the Cu matrix and thus the electrode stability is greatly enhanced (from only 20 cycles to more than 120 cycles). Finally, the deposition of a hybrid polymer electrolyte onto the developed 3D electrodes is presented. Even though the deposition is not conformal and that issues of capacity fading need to be addressed, preliminary results attest that it is possible to cycle the obtained 3D electrode-electrolyte versus lithium without the appearance of short-circuits

Machine learning processing of microalgae flow cytometry readings: illustrated with Chlorella vulgaris viability assays

International audienceA flow cytometry viability assay protocol is proposed and applied to model microalgae Chlorella vulgaris. The protocol relies on concomitant dual staining of the cells (Fluorescein DiAcetate (FDA), Propidium Iodide (PI)) and machine learning processing of the results. Protocol development highlighted that working at 4°C allows to preserve the stained sample for 15 minutes before analysis. Furthermore the inclusion of an extracellular FDA washing step in the protocol improves the signal to noise ratio, allowing better detection of active cells. Once established, this protocol was validated against 7 test cases (controlled mixtures of active and non-viable cells). Its performances on the test cases is good:-0.19 %abs deviation on active cell quantification (processed by humans). Furthermore, a machine learning workflow, based on DBSCAN algorithm, was introduced. After a calibration procedure, the algorithm provided very satisfactorily results with-0.10 %abs deviation compared to human processing. This approach permitted to automate and speed up (15 folds) cytometry readings processing. Finally, the proposed workflow was used to assess Chlorella vulgaris cryostorage procedure efficiency. The impact of freezing protocol on cells viability was first investigated over 48 hours storage (-20°C). Then the most promising procedure (pelleted,-20°C) was tested over one month. The observed trends and values cell in viability loss correlate well with literature. This shows that flow cytometry is a valid tool to assess for microalgae cryopreservation protocol efficiency

Impact of duration of critical illness on the adrenal glands of human intensive care patients

Context: Adrenal insufficiency is considered to be prevalent during critical illness, although the pathophysiology, diagnostic criteria and optimal therapeutic strategy remain controversial. During critical illness, reduced cortisol breakdown contributes substantially to elevated plasma cortisol and low plasma ACTH concentrations. Objective: As ACTH has a trophic impact on the adrenal cortex, we hypothesized that with longer duration of critical illness, subnormal ACTH adrenocortical stimulation predisposes to adrenal insufficiency. Design, Setting and Participants: Adrenal glands were harvested ≤24h of death from 13 long ICU-stay patients, 27 short ICU-stay patients and 13 controls. Prior glucocorticoid treatment was excluded. Main Outcome and Measure(s): Microscopic adrenocortical zonational structure was evaluated by H&E staining. The amount of adrenal cholesterol-esters was determined by Oil-Red-O staining and mRNA expression of ACTH-regulated steroidogenic enzymes was quantified. Results: The adrenocortical zonational structure was disturbed in patients as compared with controls (P<0.0001), with indistinguishable adrenocortical zones only present in long ICU-stay patients (P=0.003 vs. controls). Adrenal glands from long ICU-stay patients, but not those of short ICU-stay patients, contained 21% less protein (P=0.03) and 9% more fluid (P=0.01) than those from controls, while they tended to weigh less for comparable adrenal surface area. There was 78% less Oil-Red-O staining in long ICU-stay patients than in controls and in short-stay patients (P=0.03), the latter similar to controls (P=0.31). The mRNA expression of MC2R, SCARB1, HMGCR, STAR and CYP11A1 was at least 58% lower in long ICU-stay patients than in controls (all P≤0.03), and of MC2R, SCARB1, STAR and CYP11A1 at least 53% lower than in short ICU-stay patients (all P≤0.04), whereas gene expression in short ICU-stay patients was similar to controls. Conclusion and Relevance: Lipid depletion and reduced ACTH-regulated gene expression in prolonged critical illness suggest that sustained lack of ACTH may contribute to risk of adrenal insufficiency in long-stay ICU patients.status: publishe