Analysis of microstructural effects in multi layer lithium ion battery cathodes

A possible way to increase the energy density in lithium-ion batteries, and, at the same time, reduce the production costs, is to use thicker electrodes. However, transport limitations can occur in thick electrodes, leading to a drawback in performance. A way to mitigate this problem is a more sophisticated microstructure of the electrode, using, e.g., structural gradients. This can, for instance, be achieved by multi-layer casting, i.e., casting and drying of a first layer, and then adding a second layer. An important question is how the interface between the two layers is shaped and how the corresponding microstructure influences the electrochemical performance. In the present paper, two different two-layer cathodes are analyzed and compared to single-layer cathodes of the same thickness. The analysis involved tomographic imaging, a statistical analysis of the 3D microstructure of the active material particle systems with a focus on the interface between the layers, and electrochemical characterization of the active material systems using experimental measurements as well as electrochemical simulations. The analysis showed that at the interface the connectivity of active material particles decreases, which results in higher electric resistivity. This effect is stronger if an intermediate calendering step is performed, i.e., the first layer is calendered before casting the second layer

Electrochemical Behaviour of Sn and Sn-C Composite in LiBOB-Containing Electrolytes

2010, IMLB Meeting, Montreal, Canada, June27-July2 ads.#5

Sodium Insertion into Fe[Fe(CN)6] Framework Prepared by Microwave-Assisted Co-Precipitation

Prussian blue analogues (PBAs) are interesting materials for Na electrochemical insertion, owing to their ease of synthesis, rigid open framework and large interstitial space. In this work, iron hexacyanoferrate nanoparticles, FeIII[FeIII(CN)6], also known as Berlin green (BG), where both Fe centers are in the Fe(III) configuration, have been synthesized by an easy microwave assisted co-precipitation method, with an average particle size of around 44 nm. The BG nanoparticles exhibited a 120 mAh g−1 specific capacity with a capacity retention of 84.8 % over 100 cycles at 20 mA g−1 current and up to 80 mAh g−1 at 10 C rate. The initial charge and discharge processes were fully investigated by ex-situ X-ray absorption spectroscopy (XAS). The XAS results reveal that there is some irreversibility in the initial electrochemical processes and the Fe−C and Fe−N bond lengths change during the first charge/discharge cycle. This effect was attributed to BG electrode activation processes, and partly explained the observed capacity fading

Comportement du chrome et de l'arsenic dans une nappe libre sous un site industriel

Cette étude a porté sur l'identification des mécanismes géochimiques qui régissent le comportement de l'As et du Cr dans un aquifère de surface sous un site industriel (production d'acide sulfurique et de sulfate de cuivre). Trois approches ont été confrontées : une étude de terrain (réseau piézomètrique et carottages), des expériences en laboratoire (batch et colonne) et la modélisation géochimique (logiciel PHREEQC). La zone polluée du site est caractérisée par une forte acidité et des concentrations en Cu, As et Cr élevées. L'écoulement des eaux de la zone polluée vers la périphérie du site s'accompagne d'une augmentation du pH grâce à la dissolution des carbonates. Ce pouvoir tampon acido-basique des solides favorise la rétention de l'As et du Cr (pH proches de 7 et sans chélate). L'adsorption sur des hydroxydes de fer et la précipitation ont été mises en évidence. Le Cr précipiterait sous forme d'hydroxyde et l'As sous forme de coprécipité avec le FeIII et d'arséniates de cuivre.The main goal of this work is to identify the geochemical mechanisms controlling the solubility and mobility of As and Cr in a superficial aquifer under an industrial plant (production of sulphuric acid and copper sulphate. In this context, we used three approaches: water and solids sampling campaigns, laboratory experiments (batch and column experiments) and geochemical modelling (software PHREEQC). The contaminated zone is characterised by high concentrations of Cu, As and Cr and a strong acidic water. The unpolluted area is characterised by neutral to basic pH and low concentrations of elements. This neutral pH is probably due to carbonate dissolution. The buffer capacity of the solids induce the As and Cr sorption in the medium (especially in lack of chelating agent). The As and Cr solubility seems to be controlled by precipitation and adsorption onto iron hydroxides. Cr seems to precipitate in form of hydroxide and As in form of coprecipitate with Fe(III) and copper arsenates.PAU-BU Sciences (644452103) / SudocSudocFranceF

High performance, environmentally friendly and low cost anodes for lithium-ion battery based on TiO2 anatase and water soluble binder carboxymethyl cellulose

The challenge of producing lithium-ion batteries meeting performance requirements and low environ- mental impact is strictly related to the choice of materials as well as to the manufacturing processes. Most electrodes are currently prepared using poly(vinilydene fluoride) (PVDF) as binder. This fluorinated polymer is expensive and requires the use of a volatile and toxic organic solvent such as N-methyl- pyrrolidone (NMP) in the processing. Water soluble sodium carboxymethyl cellulose (CMC) can be a suitable substitute for PVDF as binder for both anodes and cathodes eliminating the necessity of NMP and thus decreasing the cost and the environmental impact of battery production. In this work, CMC has been successfully used to prepare efficient and stable anatase TiO2 anodes by optimizing the elec- trode manufacturing process in terms of composition and compression. The stability and the high rate performances of the TiO2/CMC are described and compared with those of TiO2/PVDF electrodes. The compatibility of the TiO2/CMC with a LiFePO4 cathode in a full-cell is also reported

Effect of Salt Concentration, Solvent Donor Number and Coordination Structure on the Variation of the Li/Li+ Potential in Aprotic Electrolytes

The use of concentrated aprotic electrolytes in lithium batteries provides numerous potential applications, including the use of high-voltage cathodes and Li-metal anodes. In this paper, we aim at understanding the effect of salt concentration on the variation of the Li/Li+ Quasi-Reference Electrode (QRE) potential in Tetraglyme (TG)-based electrolytes. Comparing the obtained results to those achieved using Dimethyl sulfoxide DMSO-based electrolytes, we are now able to take a step forward and understand how the effect of solvent coordination and its donor number (DN) is attributed to the Li-QRE potential shift. Using a revised Nernst equation, the alteration of the Li redox potential with salt concentration was determined accurately. It is found that, in TG, the Li-QRE shift follows a different trend than in DMSO owing to the lower DN and expected shorter lifespan of the solvated cation complex