Segmented printed circuit board electrode for locally-resolved current density measurements in all-vanadium redox flow batteries

One of the most important parameters for the design of redox flow batteries is a uniform distribution of the electrolyte solution over the complete electrode area. The performance of redox flow batteries is usually investigated by general measurements of the cell in systematic experimental studies such as galvanostatic charge-discharge cycling. Local inhomogeneity within the electrode cannot be locally-resolved. In this study a printed circuit board (PCB) with a segmented current collector was integrated into a 40 cm2 all-vanadium redox flow battery to analyze the locally-resolved current density distribution of the graphite felt electrode. Current density distribution during charging and discharging of the redox flow battery indicated different limiting influences. The local current density in redox flow batteries mainly depends on the transport of the electrolyte solution. Due to this correlation, the electrolyte flow in the porous electrode can be visualized. A PCB electrode can easily be integrated into the flow battery and can be scaled to nearly any size of the electrode area. The carbon coating of the PCB enables direct contact to the corrosive electrolyte, whereby the sensitivity of the measurement method is increased compared to state-of-the-art methods

Battery Systems and Energy Storage beyond 2020

Currently, the transition from using the combustion engine to electrified vehicles is a matter of time and drives the demand for compact, high-energy-density rechargeable lithium ion batteries as well as for large stationary batteries to buffer solar and wind energy. The future challenges, e.g., the decarbonization of the CO2-intensive transportation sector, will push the need for such batteries even more. The cost of lithium ion batteries has become competitive in the last few years, and lithium ion batteries are expected to dominate the battery market in the next decade. However, despite remarkable progress, there is still a strong need for improvements in the performance of lithium ion batteries. Further improvements are not only expected in the field of electrochemistry but can also be readily achieved by improved manufacturing methods, diagnostic algorithms, lifetime prediction methods, the implementation of artificial intelligence, and digital twins. Therefore, this Special Issue addresses the progress in battery and energy storage development by covering areas that have been less focused on, such as digitalization, advanced cell production, modeling, and prediction aspects in concordance with progress in new materials and pack design solutions

Advanced Battery Technologies: New Applications and Management Systems

In recent years, lithium-ion batteries (LIBs) have been increasingly contributing to the development of novel engineering systems with energy storage requirements. LIBs are playing an essential role in our society, as they are being used in a wide variety of applications, ranging from consumer electronics, electric mobility, renewable energy storage, biomedical applications, or aerospace systems. Despite the remarkable achievements and applicability of LIBs, there are several features within this technology that require further research and improvements. In this book, a collection of 10 original research papers addresses some of those key features, including: battery testing methodologies, state of charge and state of health monitoring, and system-level power electronics applications. One key aspect to emphasize when it comes to this book is the multidisciplinary nature of the selected papers. The presented research was developed at university departments, institutes and organizations of different disciplines, including Electrical Engineering, Control Engineering, Computer Science or Material Science, to name a few examples. The overall result is a book that represents a coherent collection of multidisciplinary works within the prominent field of LIBs

Colorimetric sensor array for identification of fungi & ultrasonic spray synthesis for supercapacitor materials

In this thesis, functional materials synthesis and fabrication is described within the two areas of (1) colorimetric sensor array for identification of fungi, and (2) ultrasonic spray synthesis for supercapacitor electrode materials. Human fungal infections have attracted intense current interest, especially in the light of recent outbreaks from pharmaceutical contamination, but also due to infections of immunocompromised patients by opportunistic fungal strains. Fungi stink: that is to say, they produce distinctive volatile organic compounds. The profiles of these VOCs provide a potential diagnostic method that may be able to overcome current limitations in traditional fungal diagnostics. Previous methods for VOC profiling, however, are either costly, non-portable (e.g., GC-MS) or insensitive and intolerant to humidity variation (e.g., electronic noses). In this project, an optoelectronic nose approach was used with our disposable colorimetric sensor array for rapid differentiation and identification of human pathogenic fungi based on their smell (i.e., the volatiles that they produce). Twelve clinically relevant fungal strains gave unique sensor array responses and were correctly clustered using hierarchical cluster analysis within 3 hours, which is a clinically relevant time frame. Classification prediction accuracy was 94%, based on standard jackknifed linear discriminant analysis. We also introduce the application of a cutting-edge statistical method, tensor discriminant analysis, which takes advantage of the high dimensionality of our sensor array data, giving a prediction accuracy of 98.1%. Furthermore, we have shown that our sensor array has great potential for rapid screening the effects of anti-fungal drugs on particular fungal strains. This is the first example of colorimetric volatile profiling for fungal strain identification. Compared to single-data-point analysis methods, this inexpensive technique (~$3 for each test kit using an ordinary flatbed scanner) allows for real-time identification of fungi in culture. We expect this is the first step in the development of a rapid, facile, and low-cost tool for diagnosis of fungal infections with potential additional applications for environmental monitoring (e.g., “sick-building syndrome”). Conjugated polymers have been intensively investigated as electrode materials for supercapacitors because of their excellent electrochemical reversibility, fast switching between redox states, high conductivity in a doped state, mechanical flexibility, and low cost. Among them, poly(3,4-ethylenedioxythiophene) (PEDOT) is especially attractive due to its high stability and low toxicity. Prior PEDOT materials are generally synthesized with surfactants or template methods so as to achieve nano- or micro-structures with high surface area and to maximize capacitance at high charge and discharge rates. These synthesis methods, however, are generally cumbersome (multiple steps) or expensive (such as nano-structured sacrificial templates), and can easily introduce impurities that negatively affect the electrochemical properties of the PEDOT products. In this project, we used ultrasonic spray polymerization (USPo) method for facile and continuous PEDOT microsphere synthesis without the addition of templates or surfactants. During this USPo process, PEDOT is synthesized by polymerization of the monomer 3,4-ethylenedioxythiophene in the precursor solution in micron-sized droplets that are generated during ultrasonic nebulization. Here, three types of morphologies (solid, porous, and hollow) are synthesized by simply controlling oxidants and precursor solvents. Supercapacitor behavior is characterized and determined to be as high as 160 F/g (Farad/gram), which is the highest of reported PEDOT microspheres. Moreover, taking advantage of the USPo setup, we also demonstrate an innovative spray coating method as a useful electrode fabrication process. This is the first synthetic route to provide PEDOT microsphere production with controllable morphologies, and it does not require additional stabilizing agents or sacrificial templates. In addition, it also covers a little-investigated area of ultrasonic spray techniques for polymer microsphere synthesis. The potential impact of a facile, cost-effective, and scalable synthetic method for PEDOT supercapacitor materials makes our approach significant to the field of energy storage materials as well as more generalized microsphere materials synthesis. The second example of using an ultrasonic spray technique is in the synthesis of manganese oxide (MnO2) microspheres. In this case, a mixed solution of potassium permanganate and hydrochloric acid was nebulized into micro-sized droplets, which were then carried by air flow through a furnace tube. Each micro-droplet serves as one micro-reactor and produces one microsphere. Upon heating, KMnO4 was decomposed into MnO2 microspheres; this synthetic process can easily be scaled up. Characterization of the MnO2 microspheres by SEM, TEM, powder XRD, Raman Spectroscopy, and XPS is described. Different morphologies of MnO2 microspheres could be controlled by tuning the precursor concentrations (and ratios) and furnace temperatures; for example, microspheres synthesized at 150 °C gave polycrystalline MnO2 while synthesis at 500 °C yielded needle-shape α-MnO2 crystals. The electrochemical properties investigated by cyclic voltammetry gave specific capacitance as high as 320 F/g, demonstrating promising properties as supercapacitors. In addition, these microspheres can be directly sprayed on conductive substrates, such as carbon fiber paper, and may have useful applications as a supercapacitor electrode coating. The supercapacitive properties of MnO2 microspheres at higher charge and discharge rates can be improved by increasing the surface area coverage or coating them with a thin layer of conductive polymer

EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

Application of hydroxyapatite granules in posterolateral intertransverse lumbar spinal fusion

In many clinical disciplines used of bone graft is unavoidable such as to replace bone loss due to trauma, to fill in bone defect after tumour excision, for reconstructive surgery or spinal fusion. Calcium phosphate based hydroxyapatite is widely used bone graft substitute due to its similarity with the mineral components of bone matrix. This study was conducted to evaluate bone formation effect of this biomaterial in posterolateral intertransverse lumbar fusion, a novel site for its application. Twelve adult New Zealand white rabbits underwent bilateral intertransverse lumbar spinal fusion at L5-L6 vertebrae. One site of the animals was implanted with hydroxyapatite granules (HA group) while the contralateral sides received autograft and served as the control (AUTO group). Bone formation was assessed at 6 and 16 weeks by undecalcified histology and scanning electron microscopy. New bone was formed on the surface of hydroxyapatite granules and continually formed even at 16 weeks. Close contact between new bone and hydroxyapatite granules was demonstrated by scanning electron microscopy