Highly Stable Carbon-Free Cathodes for Li-Air Batteries with Aqueous Alkaline Electrolyte: Electrochemical and Structural Investigations

The operation of a secondary Li-air battery requires to run the battery in oxygen reduction reaction (ORR) as well as in oxygen evolution reaction (OER). OER represents the charge reaction and requires a sufficient catalyst for oxygen evolution. Currently carbon materials are widely used in cathodes of aqueous alkaline Li-air batteries due to their high electronic conductivity, stability, relatively low costs and catalytic activity towards oxygen reduction reaction (ORR). However, carbon-based cathode materials are non-stable in the potential range of OER as they start to corrode at potentials higher than open circuit voltage (OCV). Corrosion leads to high degradation corresponding to successive capacity loss and ultimately destruction of the cathode. To improve long-term stability and reduce side reactions such as H2 and CO2 evolution carbon-free bifunctional cathodes for aqueous alkaline Li-air batteries are of need. In this poster we present cathodes with a combination of Ag or Ni as conductive additive and Co3O4. Those were prepared with a dry-processed and solvent-free preparation method. Electrocatalytic activity regarding both ORR and OER was investigated by cyclic voltammetry (CV) for up to 300 cycles in half-cells. In addition structural and surface characteristics of the Ag/Co3O4 were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These combined measurements give new insights in the materials oxidation states and the stability of Ag oxides in Ag/Co3O4 cathodes throughout a complete battery cycle. Cathodes with the combination of Ag and Co3O4 show high activity for both reactions ORR and OER and a significant improvement in performance compared to both pure Ag and pure Co3O4 cathodes. Long-term tests show superior stability of the bimetal cathodes

Thermal processing of waste organic substrates: Developing and applying an integrated framework for feasibility assessment in developing countries

Against the background of global climate change and increasing prices of fossil fuel, the importance of producing sustainable renewable energy increases significantly. CO2-neutral energy generation using biomass or organic waste is an alternative option that deserves attention particularly in developing countries. Aim of this paper is to provide an integrated framework for the preparation of feasibility studies for the renewable energy sector there, considering technical, environmental, economic, socio-cultural, legal and institutional aspects which are particular applicable for developing countries. Such a feasibility framework involves a definition of the scope, which reflects the aims and objectives of the target groups (supplier, operator, etc. of renewable energy supply) and the methodologies and tools involved. All relevant aspects are covered: data collection, selection of sites and assessment of options. Furthermore, methods and tools for risk assessment and decision-making are presented and a practical plan of procedures is last provided. The proposed framework is then applied to a selected area in Vietnam and certain results of the study, showing that the implementation of a biogas plant utilizing organic waste would be feasible, are presented in this paper.Biomass Decentralized electricity Developing countries

Post Li-ion batteries

In the last decades, the investigation of new secondary cells has been increased considerably, because high energy density rechargeable batteries are supremely demanded for different applications, such as consumer electronic, electro mobility and renewable energy storage. Very promising battery systems are the so called “Post Li-ion batteries” (4. generation batteries) with metal anodes: metal-sulfur and metal-air (oxygen) batteries, in particular Li-sulfur and Li-air batteries. Li-sulfur battery is a promising system, due to its high theoretical capacity (1675 mAh/gsulfur), energy density (2500 Wh/kg), the low cost and non-toxicity of sulfur. Nevertheless, some of the drawbacks of lithium-sulfur batteries are the poor rechargeability and high self-discharge rates. Due to the low electrical conductivity of sulfur, electrical conductive material has to be added in order to encourage the electrochemical reaction. Furthermore, polysulfides of high order (Li2Sn with 2 ≤ n ≤ 8) dissolve in the electrolyte and can diffuse to the anode and react directly with lithium metal. This so-called shuttle mechanism causes irreversible loss of sulfur. Moreover, insulating and insoluble polysulfide discharge product (Li2S) can precipitate on the surface of electrodes, avoiding further electrochemical reaction. Metal-oxygen cells exhibit highest theoretical energy densities. Among them, the Li-O2 system offers highest theoretical gravimetric energy density (11680 Wh/kg) however, anodes of highly abundant elements, such as Al, Si or Zn, offer several advantages over lithium. Apart from the availability, these latter metals are safer and more stable, allowing the battery processing in air. State-of-the-art metal-oxygen cells mainly suffer from severe cyclic aging and low Coulombic efficiency. To overcome these challenges, the underlying complex electrochemical reactions between the electrolyte and the electrocatalyst and the electrodes have to be understood. One of the major challenges is the development of suitable electrolytes and electrocatalysts for the oxygen reduction and gas evolution reactions. One of the major limiting factors on performance and round-trip efficiency is the catalyst used. Today´s Lithium-air batteries still suffer from high charge- and discharge overpotentials caused by insufficient catalysts. The major goal is to reduce overpotentials by using bifunctional catalysts catalyzing both the oxygen reduction reaction (ORR) as well as the oxygen evolution reaction (OER). Noble metal catalysts show good performance on both reactions but with increasing prices of noble metals metal oxides have drawn attention recently. In the presentation new results from the production and characterization of Lihium-sulfur batteries and bifunctional cathodes for Li-air batteries will be shown

State of the Art of Batteries of the 4th Generation

In the last decades, the investigation of new secondary cells has been increased considerably, because high energy density rechargeable batteries are supremely demanded for different applications, such as consumer electronic, electro mobility and renewable energy storage. Very promising battery systems are the so called “Post Li-ion batteries” (4th generation batteries) with metal anodes: metal-sulfur and metal-air (oxygen) batteries, in particular Li-sulfur and Li-air batteries. Li-sulfur battery is a promising system, due to its high theoretical capacity (1675 mAh/gsulfur), energy density (2500 Wh/kg), the low cost and non-toxicity of sulfur. Nevertheless, some of the drawbacks of lithium-sulfur batteries are the poor rechargeability and high self-discharge rates. Due to the low electrical conductivity of sulfur, electrical conductive material has to be added in order to encourage the electrochemical reaction. Furthermore, polysulfides of high order (Li2Sn with 2 ≤ n ≤ 8) dissolve in the electrolyte and can diffuse to the anode and react directly with lithium metal. This so-called shuttle mechanism causes irreversible loss of sulfur [1-2]. Moreover, insulating and insoluble polysulfide discharge product (Li2S) can precipitate on the surface of electrodes, avoiding further electrochemical reaction. As a result, the specific capacity of the battery decreases considerably, especially in the first cycles. In order to optimize the performance of the cell, it is highly important to understand the degradation processes of sulfur cathode under operating conditions.In the present work, x-ray diffraction (XRD) and electrical impedance spectroscopy (EIS) were measured during cycling. The formation of crystalline products was monitored in-situ and semi-quantitatively determined by XRD- analysis. Impedance measurements were performed during the first cycle at a frequency range of 1 MHz to 60 mHz. Impedance spectra were investigated at several states of charge distinguishing the impedance contributions of the different physical/chemical phenomena occurring in the battery. Furthermore, the aging during cycling was studied until fifteen cycles. Our results shown in figure 1 provide new insights into the discharging and charging processes of Li-Sulfur batteries by means of XRD and EIS characterization

Highly Stable Carbon-Free Ag/Co3O4 Cathodes for Li-Air Batteries with Aqueous Alkaline Electrolyte: Electrochemical and Structural Investigations

Highly Stable Carbon-Free Ag/Co3O4 Cathodes for Li-Air Batteries with Aqueous Alkaline Electrolyte: Electrochemical and Structural Investigations Dennis Wittmaier 1,*, Norbert Wagner 1, K. Andreas Friedrich 1,2 1 German Aerospace Center (DLR), Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany 2 Institute for Energy Storage, University of Stuttgart, Pfaffenwaldring 31, Germany *Corresponding author. Phone: +4971168628068; Fax +497116862747; E-mail: [email protected] The operation of a secondary lithium-air battery requires to run the battery in oxygen reduction reaction (ORR) as well as in oxygen evolution reaction (OER). OER represents the charge reaction and requires a sufficient catalyst for oxygen evolution. Currently carbon materials are widely used in cathodes of aqueous alkaline lithium-air batteries due to their high electronic conductivity, stability, relatively low costs and catalytic activity towards oxygen reduction reaction (ORR) [1, 2]. However, carbon-based cathode materials are non-stable in the potential range of OER as they start to corrode at potentials higher than open circuit voltage (OCV) [3, 4]. Corrosion leads to high degradation corresponding to successive capacity loss and ultimately destruction of the cathode. To improve long-term stability and reduce side reactions such as H2 and CO2 evolution carbon-free bifunctional cathodes for aqueous alkaline lithium-air batteries are of need [5, 6]. In this poster we present cathodes with a combination of Ag and Co3O4. Those were prepared with a dry-processed and solvent-free preparation method [7, 8]. Electrocatalytic activity regarding both ORR and OER was investigated by cyclic voltammetry (CV) for up to 300 cycles in half-cells. In addition structural and surface characteristics were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These combined measurements give new insights in the materials’ oxidation states and the stability of Ag oxides in Ag/Co3O4 cathodes throughout a complete battery cycle [9]. Cathodes with the combination of Ag and Co3O4 show high activity for both reactions ORR and OER and a significant improvement in performance compared to both pure Ag and pure Co3O4 cathodes. Long-term tests show superior stability of the bimetal cathodes [6]. [1] H. Ohkuma, I. Uechi, M. Matsui, Y. Takeda, O. Yamamoto, N. Imanishi, J. Power Sources 245 (2014) 947. [2] H. Arai, S. Müller, O. Haas, J. Electrochem. Soc. 147 (2000) 3584. [3] P. N. Ross, M. Sattler, J. Electrochem. Soc. 135 (1988) 1464. [4] P. N. Ross, H. Sokol, J. Electrochem. Soc. 131 (1984) 1742. [5] D. Wittmaier, T. Danner, N. Wagner, K. A. Friedrich, J. App. Electrochem. 43 (2013) 73. [6] D. Wittmaier, N. Wagner, K. A. Friedrich, H.A. Amin, H. Baltruschat, J. Power Sources 265 (2014) 299. [7] D. Wittmaier, N. Wagner, H.A. Amin, H. Baltruschat, Patent App. PCT/EP2015/053586. [8] D. Wittmaier, N. Wagner, H.A. Amin, H. Baltruschat, Patent App. DE 102014102304 A1. [9] D. Wittmaier, Natalia A. Canas, I. Biswas, K. A. Friedrich, Adv. Energy Mater. 2015, doi: 10.1002/aenm.201500763

Hybrid Materials for Electrochemical Energy Conversion

Electrodes in electrochemical reactors – in particular batteries, electrolyzers and fuel cells -for energy conversion need to fulfill several functionalities that often lead to materials problems. In general, a combined electronic and ionic conductivity is needed with adequate gas or mass transport (porosity) properties as well as chemical and mechanical stability in aggressive environments. These conflicting properties are rarely achieved with homogeneous materials and therefore a hybrid material approach is quite common in electrochemical energy conversion. Hybrid materials are often a nanometer dispersed combination of metal or metal oxides with polymeric materials, e.g. ionomers with ionic conductivity or polymeric binders. This contribution will present selected examples for electrolyzers, fuel cells and lithium batteries and discuss how technological driven approaches can help to design electrodes with superior performance and stability. Characterization to evaluate performance structure relationships will be discussed with respect to the following hybrid configurations: • Electrodes for oxygen evolution reaction with amorphous IrOx and electroceramic supports with ionomer • Ceramic perovskites/Ni anode materials as alternative solid oxide fuel cell anodes • Cathode composites with sulfur, carbon and polymer • Gas diffusion electrodes for metal air and polymer electrolyte fuel cell

Carbon dioxide balance and cost analysis for different solid waste management scenarios

In order to determine the optimal final destination of municipal solid waste, it is necessary to consider both monetary costs and environmental externalities, such as carbon balance and GHG production, as well as the local availability of waste-processing industrial infrastructure. In order to develop a strategy for the selection of the optimal waste management system, in the present work we consider a specific city located in Piedmont (northern Italy). The volume of municipal solid waste produced in the city is about 540,000 ton/year. To determine the best method for management and disposal of this volume, we considered three different scenarios, using the best available technologies. The scenarios included the use of both thermal processing systems (incineration and gasification plants) and other systems (mechanical separation plants, anaerobic digestion plants). The scenarios were analyzed and compared, considering environmental, construction and operating costs, in order to develop a model for making an objective comparison. The results of the analysis for this specific case revealed that direct combustion in an incineration plant delivered the best outcome for both environmental impacts and economic convenience. More generally, the comparison methodology for the scenarios can be a useful approach for determining the best solution for waste management planning for a specific locality

Entwicklung eines Verfahrens 'Zur In-Situ-Sanierung von Altlasten mit Hilfe standorteigener Bakterien am Beispiel eines aufgelassenen Industriegelaendes' Abschlussbericht

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