Improvement of life-time is an important issue in the development of Li-ion batteries. Aging mechanisms limiting the life-time can efficiently be characterized by physico-chemical analysis of aged cells with a variety of complementary methods. This study reviews the state-of-the-art literature on Post-Mortem analysis of Li-ion cells, including disassembly methodology as well as physicochemical characterization methods for battery materials. A detailed scheme for Post-Mortem analysis is deduced from literature, including pre-inspection, conditions and safe environment for disassembly of cells, as well as separation and post-processing of components. Special attention is paid to the characterization of aged materials including anodes, cathodes, separators, and electrolyte. More specifically, microscopy, chemical methods sensitive to electrode surfaces or to electrode bulk, and electrolyte analysis are reviewed in detail. The techniques are complemented by electrochemical measurements using reconstruction methods for electrodes built into half and full cells with reference electrode. The changes happening to the materials during aging as well as abilities of the reviewed analysis methods to observe them are critically discussed. Li-ion batteries are currently used in everyday objects such as smart-phones, power tools and tablet computers as well as in the growing fields of light electric vehicles (LEVs), unmanned aerial vehicles (UAVs), battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). [1][2][3][4] Furthermore, the rise of renewable energy sources like wind and solar power, which are only intermittently available, demands reliable and highly flexible stationary energy storage solutions, which provide high capacities and predictable life-times. 2,5Aging of Li-ion batteries is a general problem for manufacturers as they have to guarantee long-term reliability of their products. For state-of-the-art cells, degradation effects on the material level lead to capacity fade and resistance increase on the cell level. The aging state of a battery is often characterized by the state-of-health (SOH) in % according to 3,16,22,[29][30][31] SO H(t) = discharge capacity (t) discharge capacity (t = 0)[1]where t represents the aging time. In general, one has to differentiate between cycling 7,16,18,21,[23][24][25]32 and calendar aging. 7,19,[21][22][23][24]27 Since commercial Li-ion cells can be subject to calendar aging in the time between manufacturing and delivery, it is good practice to measure the discharge capacity at t = 0 for each cell that undergoes an aging test. Since the discharge capacity depends mainly on temperature, depth-of-discharge (DOD), and discharge current, the SOH is usually monitored by regular check-ups with defined parameter sets, 7,16,21,23,24 which can vary depending on the application. Typically, a temperature of 25• C, 16,22,24 DOD of 100%, 16,21 and discharge rates of 1C 7,16,21,22,24 or lower 23 are used in check-ups. The performance dec...

Nowadays, the electric vehicle is one of the most promising alternatives for sustainable transportation. However, the battery, which is one of the most important components, is the main contributor to environmental impact and faces recycling issues. In order to reduce the carbon footprint and to minimize the overall recycling processes, this paper introduces the concept of re-use of electric vehicle batteries, analyzing some possible second-life applications.\ud Methods\ud First, the boundaries of the life cycle assessment of an electric vehicle are defined, considering the use of the battery in a second-life application. To perform the study, we present eight different scenarios for the second-life application. For each case, the energy, the efficiency, and the lifetime of the battery are calculated. Additionally, and based on the global warming potential, the environmental impact of the electric vehicle and its battery on a second-life application is determined for each scenario. Finally, an environmentally focused discussion on battery electrodes and research trends is presented.\ud Results and discussion\ud For the selected scenarios, the second life of the battery varies from 8 to 20 years depending on the application and the requirements. It has been observed that the batteries connected to the electricity grid for energy arbitrage storage have the highest impact per provided kilowatt hour. On the contrary, the environmental benefit comes from applications working with renewable energy sources and presenting a longer lifetime. We pointed out that a correlation between cycling conditions and degradation mechanisms of the electrode materials is compulsory for proper use of the electric vehicle battery in a second-life application.\ud Conclusions\ud To limit the environmental impact, batteries should be associated with renewable energy sources in stationary applications. However, it is more profitable to re-use Li-ion batteries than to use new lead-acid batteries. Although many batteries applied for electric vehicles use graphite-based anodes, the latter may not be the most suitable for the second-life application. A better understanding of Li-ion battery degradation during the second-life application is required for the different existing chemistries.Postprint (author's final draft

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Application of Li-ion batteries for transportation not only requires long cycling life but also the preservation of the electrochemical performance during the resting period. For certain car usage this resting time could be predominant compared with the cycling activity and is referred to as calendar aging. To understand the aging mechanisms during calendar aging, an extensive post-mortem study was conducted on commercial 16 Ah NMC/graphite pouch cells stored at 5, 25, 45, and 60 °C. The post-mortem analyses were performed in parallel within three separate laboratories across Europe. They included visual inspection and structural and microstructural analysis along with a combination of analytical techniques to determine accurately the composition of positive (NMC) and negative (graphite) electrodes and the electrolyte. A direct correlation was established between the calendar-aging temperature and the degradation of the cells. The measurements revealed a severe deterioration phenomenon for the electrodes aged at 45 and 60 °C. These results are explained by the formation of a resistive interface on top of the negative electrodes due to a continuous and heterogeneous growth of a surface layer. Electrochemical impedance spectroscopy and electrochemical measurements confirm the resistance increase during cell degradation. At high temperatures, this occasionally leads to a Li deposition phenomenon. Nonetheless, we revealed that this degradation process does not affect the bulk structure of the materials but only the surface of the particles.

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