Driven by the rise of the electric automotive industry, the Li-ion battery market is in strong expansion. This technology does not only fulfill the requirements of electric mobility, but is also found in most portable electric devices. Even though Li-ion batteries are known for their numerous advantages, they undergo serious performance degradation during their aging, and more particularly when used in specific conditions such as at low temperature or high charging current rates. Depending on the operational conditions, different aging mechanisms are favored and can induce physical and chemical modifications of the internal components, leading to performance decay. In this article, the identification of the degradation mechanisms was carried out thanks to an in-depth ante- and post mortem study on three high power and high energy commercial 18,650 cells. Li-ion cells were aged using a battery electric vehicle (BEV) aging profile at −20 °C, 0 °C, 25 °C, and 45 °C in accordance with the international standard IEC 62-660, and in calendar aging mode at 45 °C and SOC 100%. Internal components recovered from fresh and aged cells were investigated through different electrochemical (half-coin cell), chemical (EDX, GD-OES, NMR), and topological (SEM) characterization techniques. The influence of power and energy cells’ internal design and Si content in the negative electrode on cell aging has been highlighted vis-à-vis the capacity and power fade.

Broadband ferromagnetic resonance is measured in single crystalline Fe films of varying thickness sandwiched between MgO layers. An exhaustive magnetic characterization of the films (exchange constant, cubic, uniaxial and surface anisotropies) is enabled by the study of the uniform and the first perpendicular standing spin wave modes as a function of applied magnetic field and film thickness. Additional measurements of nonreciprocal spin-wave propagation allow us to separate each of the two interface contributions to the total surface anisotropy. The results are consistent with the model of a quasi-bulk film interior and two magnetically different top and bottom interfaces, a difference ascribed to different oxidation states.

The Li-ion battery is one of the key components in electric car development due to its performance in terms of energy density, power density and cyclability. However, this technology is likely to present safety problems with the appearance of cell thermal runaway, which can cause a car fire in the case of propagation in the battery pack. Today, standards describing safety compliance tests, which are a prerequisite for marketing Li-ion cells, are carried out on fresh cells only. It is therefore important to carry out research into the impact of cell aging on battery safety behavior in order to ensure security throughout the life of the battery, from manufacturing to recycling. In this article, the impact of Li-ion cell aging on safety is studied. Three commercial 18,650 cells with high-power and high-energy designs were aged using a Battery Electric Vehicle (BEV) aging profile in accordance with the International Electrotechnical Commission standard IEC 62-660. Several thermal (Accelerating Rate Calorimetry—ARC) and standardized safety (short-circuit, overcharge) tests were performed on fresh and aged cells. This study highlights the impact of aging on safety by comparing the safety behavior of fresh and aged cells with their aging conditions and the degradation mechanisms involved.

Broadband ferromagnetic resonance is measured in single crystalline Fe films of varying thickness sandwiched between MgO layers. An exhaustive magnetic characterization of the films (exchange constant, cubic, uniaxial and surface anisotropies) is enabled by the study of the uniform and the first perpendicular standing spin wave modes as a function of applied magnetic field and film thickness. Additional measurements of non-reciprocal spin wave propagation allow us to separate each of the two interface contributions to the total surface anisotropy. The results are consistent with the model of a quasi-bulk film interior and two magnetically different top and bottom interfaces, a difference ascribed to different oxidation states.