Varta Microbattery (Germany)

Screen-printed thin-film batteries comprise current collectors typically realised with commercially available conductive silver inks primarily designed for non-critical printed electronics applications. The avoidance of electrochemical interaction of metallic silver with the respective battery chemistry requires printing of an additional passivation layer. The wide range of printing inks available makes it difficult for researchers to select and qualify battery specific inks that ensure a long-life cycle without limitation of relevant battery performance parameters. This study presents a novel method to quantify the passivation capability of carbon black passivation layers for silver current collectors in 6.0 M potassium hydroxide and 5.8 M zinc chloride aqueous electrolyte solutions. Cyclic voltammetry is used to determine possible electrochemical interaction of passivated current collectors with the electrolyte media which constitute battery performance degrading parasitic side reactions. An innovative approach based on Faraday’s law of electrolysis is presented to transform cyclic voltammogram curve progressions into comparable numerical values. The mathematical approach allows quantitative comparison of individually fabricated passivation layers with respect to their passivation capability instead of interpreting a large number of cyclic voltammograms.

This work presents an innovative bendable module for solar-energy harvesting. The module consists of a mechanically flexible organic photovoltaic device (OPV), a rechargeable battery, and an a-IGZO TFT charge-control circuit. The total thickness of the module is 1.1 mm. We present measurements of hardware implementations and simulations. On this basis, voltage converter schemes based on a charge pump in the flexible a-IGZO TFT technology are explored, to enhance the range of operation of the module, particularly under low-light conditions. All investigations and data are presented with focus on two variants of the energy harvesting module that differ in nominal output voltage and capacity: a 6 V variant with capacity of 14.4 mAh and a 24 V variant with capacity of 5.5 mAh. Under exposure to 1 sun, both can be charged in less than 4 hours.

One of several challenges in improving the performance of lithium-ion batteries is the enhancement of energy density. Apart from the development of ever better active materials, considerable potential for improvement can be found in the complex manufacturing process. The manufacturing of lithium-ion battery cells exhibits a long, mostly sequential process chain with numerous interdependent parameters and quality-determining characteristics. Among slurry mixing and coating, calendering is the most challenging process step and considered of superior importance to the quality of the electrode. Calendering refers to compressing the porous coating layers of the electrode to a predetermined thickness. To obtain the desired energy density and to prepare a homogeneous electrode thickness it is necessary to densify the coating of the electrodes. In this, more electrochemically active material can be accommodated in every unit of electrode volume. In essence, this defines the potential energy density of the cell. As for high-energy battery cells energy density is one of the most important optimization criteria to achieve ambitious requirements for automotive applications calendering is of crucial importance.However, compression of the electrode is not merely beneficial to the overall performance of the cell. It is a trade-off between achieving high energy density and, on the contrary, damaging the electrode’s structure by applying high mechanical forces. An effect rarely taken into account is mechanical strain induced to the electrode’s metal foil underlying the coating, which can lead to serious issues in manufacturing and malfunction of the battery cell.This paper addresses macroscopic changes in electrode’s metal foils resulting from intense calendering procedures of high-energy NMC cathodes. Figure 1 exemplarily depicts an area-resolved longitudinal strain map showing irreversible deformation from calendering. The left green section reflects an uncoated edge of the electrode which is not deformed during calendering. The coated section of the specimen is deformed significantly. The data is derived from before/after comparison of the electrode’s surface, conducted with a non-contact optical 3D deformation measuring system. To minimize undesired strain inducement, multi-calendering strategies are assessed which gently apply loads and at the same time still provide for highly compressed electrodes.

LaNi5 nano-powders with additions of Ce, Mn, Co (high and low content of cobalt) and Al were obtained by means of MBN technology, based on the high energy ball milling with different energy and protective atmosphere (Ar or H2). The microstructure and composition of all prepared nano-powders were investigated using the TEM/HRTEM, SEM/EDS, XRD and XPS techniques. Research showed that used technology allowed to produce materials distinguished by a fine and homogeneous chemical distribution of elements and an "ultrafine" (the nanometric size) crystalline structure. The results were then related to the preparation conditions.