JRC exploratory research: Safer Li-ion batteries by preventing thermal propagation

The Joint Research Centre (JRC) of the European Commission organised a workshop under the umbrella of its Exploratory Research Programme. The Workshop titled: 'Safer Li-ion batteries by preventing thermal propagation?' was held at the Directorate C-Energy, Transport and Climate in Petten on 8-9 March 2018. The workshop offered a platform where leading experts exchanged ideas and research efforts on thermal propagation testing, new methodologies, policy and standardisation issues and brain-stormed on the potential impact of preventing thermal propagation on the safety testing landscape. The input of some of the major stakeholders from industry and research to this event proved very participative on the relevant technical issues discussed, and on the identification of improvements of existing testing methodologies and mitigation strategies. This technical report presents a summary of the main discussion points, conclusions and outcomes of the workshop as agreed by their presenters.JRC.C.1-Energy Storag

Scientific Assessment in support of the Materials Roadmap enabling Low Carbon Energy Technologies: Hydrogen and Fuel Cells

A group experts from European research organisations and industry have assessed the state of the art and future eeds for materials' R&D for hydrogen and fuel cell technologies. The work was performed as input to the European Commission's roadmapping exercise on materials for the European Strategic Energy Technology Plan. The report summarises the results, including key targets identified for medium term (2020/2030) and long term (2050) timescales.JRC.F.2-Cleaner energ

Sustainability Assessment of Second Life Application of Automotive Batteries (SASLAB): JRC Exploratory Research (2016-2017): Final technical report: August 2018

The fast increase of the electrified vehicles market will translate into an increase of waste batteries after their use in electrified vehicles (xEV). Once collected, batteries are usually recycled; however, their residual capacity (typically varying between 70% and 80% of the initial capacity) could be used in other applications before recycling. The interest in this topic of repurposing xEV batteries is currently high, as can be proven by numerous industrial initiatives by various types of stakeholders along the value chain of xEV batteries and by policy activities related to waste xEV batteries. SASLAB (Sustainability Assessment of Second Life Application of Automotive Batteries), an exploratory project led by JRC under its own initiative in 2016-2017, aims at assessing the sustainability of repurposing xEV batteries to be used in energy storage applications from technical, environmental and social perspectives. Information collected by stakeholders, open literature data and experimental tests for establishing the state of health of lithium-ion batteries (in particular LFP/Graphite, NMC/Graphite and LMO-NMC/Graphite based battery cells) represented the necessary background and input information for the assessment of the performances of xEV battery life cycle. Renewables (photovoltaics) firming, photovoltaics smoothing, primary frequency regulation, energy time shift and peak shaving are considered as the possible second-use stationary storage applications for analysis within SASLAB. Experimental tests were performed on both, new and aged cells. The majority of aged cells were disassembled from a battery pack of a used series production xEV. Experimental investigations aim at both, to understand better the performance of cells in second use after being dismissed from first use, and to provide input parameters for the environmental assessment model. The experimental tests are partially still ongoing and further results are expected to become available beyond the end of SASLAB project. To obtain an overview of the size of the xEV batteries flows along their life cycle, and hence to understand the potential size of repurposing activities in the future, a predictive and parametrized model was built and is ready to be updated according to new future data. The model allows to take into account also the (residual) capacity of xEV batteries and the (critical) raw materials embedded in the various type of xEV batteries. For the environmental assessment, an adapted life-cycle based method was developed and applied to different systems in order to quantify benefits/drawbacks of the adoption of repurposed xEV batteries in second-use applications. Data derived from laboratory tests and primary data concerning energy flows of the assessed applications were used as input for the environmental assessment. Under certain conditions, the assessment results depict environmental benefits related to the extension the xEV batteries’ lifetime through their second-use in the assessed applications. In the analysis, the importance of using primary data is highlighted especially concerning the energy flows of the system in combination with the characteristics of the battery used to store energy. A more comprehensive environmental assessment of repurposing options for xEV batteries will need to look at more cases (other battery chemistries, other reuse scenarios, etc.) to derive more extensive and firmer conclusions. Experimental work is being continued at the JRC and the availability of further data about the batteries' performances could allow the extension of the assessment to different types of batteries in different second-use applications. A more complete sustainability assessment of the second-use of xEV batteries that could be useful to support EU policy development will also require more efforts in the future in terms of both the social and economic assessment.JRC.D.3-Land Resource

Fuel Cell Testing - Degradation of Fuel Cells and its Impact on Fuel Cell Applications

Fuel cells are expected to play a major role in the future energy supply, especially polymer electrolyte membrane fuel cells could become an integral part in future cars. Reduction of degradation of fuel cell performance while keeping fuel cell cost under control is the key for an introduction into mass markets.JRC.F.2-Cleaner energ

Microstructure Analysis and Calculation of Thermal Conductivity of Gas Diffusion Layers of PEM Fuel Cells

The effective thermal conductivity of gas diffusion layers (GDL) is an important parameter for the analysis of polymer electrolyte membrane (PEM) fuel cells as thermal conductivity strongly influences fuel cell performance. The accuracy of modeling heat transfer ¿ and therefore also performance - in a PEM fuel cell relies on the accurate estimation of effective thermal conductivity. Commercially available gas diffusion layers were investigated by 3D x-ray computed tomography (CT). Based on the 3D structure reconstructed from tomography data, the macroscopic effective thermal conductivity of the gas diffusion layers was calculated by solving the energy equation considering a pure thermal conduction problem.JRC.F.2-Cleaner energ

Quantitative Measurement of Fiber Pull-out by Laser Scanning Confocal Microscopy

The mechanical properties and failure behavior of carbon/carbon composites are strongly influenced by the bonding between fiber and matrix which has a strong impact on fiber pull-out. A new method of determining quantitatively the distribution of fiber pull-out length is presented. Fracture surfaces of carbon/carbon (c/c) composites – polyacrylonitrile (PAN)-based carbon fibers infiltrated with pyrolytic carbon – are investigated by laser scanning confocal microscopy (LSCM) to measure the three-dimensional surface topography and thereby the fiber pull-out length of carbon fibers. The distribution of fiber pull-out lengths is successfully determined, and it is shown that the average fiber pull-out length increases with the temperature of heat treatment before tensile testing. C/c composites can exhibit excellent mechanical properties, such as high strength, and particularly, sufficient fracture toughness even at temperatures up to 2000 °C. These properties are strongly influenced by the strength of the fiber/matrix interface, therefore knowledge of the interfacial shear strength is of fundamental importance. While experiments on a single fiber,[1, 2] or a fiber bundle,[3, 4] in a matrix can be performed to determine interfacial shear strength, a statistically meaningful result can only be achieved by repeating such a complex experiment many times. An alternative method is based on the quantitative determination of fiber pull-out length which, in principle, allows the calculation of interfacial shear strengthJRC.F.2-Energy Conversion and Storage Technologie

Life Cycle Assessment of repurposed electric vehicle batteries: an adapted method based on modelling energy flows

After their first use in electric vehicles (EVs), the residual capacity of traction batteries can make them valuable in other applications. Although reusing EV batteries remains an undeveloped market, second-use applications of EV batteries are in line with circular economy principles and the waste management hierarchy. Although substantial environmental benefits are expected from reusing traction batteries, further efforts are needed in data collection, modelling the life-cycle stages and calculating impact indicators to propose a harmonized and adapted life-cycle assessment (LCA) method. To properly assess the environmental benefits and drawbacks of using repurposed EV batteries in second-use applications, in this article an adapted LCA is proposed based on the comparison of different scenarios from a life-cycle perspective. The key issues for the selected life-cycle stages and the aspects and parameters to be assessed in the analysis are identified and discussed for each stage, including manufacturing, repurposing, reusing and recycling. The proposed method is applied to a specific case study concerning the use of repurposed batteries to increase photovoltaic (PV) self-consumption in a given dwelling. Primary data on the dwelling's energy requirements and PV production were used to properly assess the energy flows in this specific repurposed scenario: both the literature search performed and the results obtained highlighted the relevance of modelling the system energy using real data, combining the characteristics of both the battery and its application. The LCA results confirmed that the environmental benefits of adopting repurposed batteries to increase PV self-consumption in a house occur under specific conditions and that the benefits are more or less considerable depending on the impact category assessed. Higher environmental benefits refer to impact categories dominated by the manufacturing and repurposing stages. Some of the most relevant parameters (e.g. residual capacity and allocation factor) were tested in a sensitivity analysis. The method can be used in other repurposing application cases if parameters for these cases can be determined by experimental tests, modelling or extracting data from the literature

Analysis of the Effect of Thermal Runaway Initiation Conditions on the Severity of Thermal Runaway—Numerical Simulation and Machine Learning Study

The main goal of this work is to understand the effect of thermal runaway initiation conditions on the severity of thermal runaway (TR) of Graphite—NMC (111) cells. A coupled electrical-thermal model is developed, which includes the initial energy input, the chemical decomposition processes of the anode, cathode and the electrical energy released by an internal short circuit. 780 different thermal runaway events are simulated and the output is analysed by machine learning techniques such as principal component analysis and clustering. It was found that TR events form 5 clusters between no thermal runaway and severe thermal runaway. Sensitivity analysis is applied on the 39 input invariants and the triggering energy input, resistance ratio, the heat convection coefficient, the ratio of activation energy of oxygen liberation and electrolyte evaporation are found to be the most important parameters. The later one determines the amount of electrolyte combustion. The probability of thermal runaway is calculated taking into account the most important parameters and their interactions. Finally, a combination of initiation parameters is suggested, which most likely results in a repeatable and reproducible outcome.JRC.C.1-Energy Storag