In this work, commercial 18650 lithium-ion cells with LiMn₂O₄, LiFePO₄, and Li(Ni_0.33Mn_0.33Co_0.33)O₂ cathodes were exposed to external heating in an accelerating rate calorimeter (es-ARC, Thermal Hazard Technology (THT), Bletchley, UK), to investigate the thermal behavior under abuse conditions. New procedures for measuring the external and internal pressure change of cells were developed. The external pressure was measured utilizing a gas-tight cylinder inside the calorimeter chamber, in order to detect the venting of the cells. For internal pressure measurements, a pressure line connected to a pressure transducer was directly inserted into the cell. During the thermal runaway experiments, three stages (low rate, medium rate, and high rate reactions) were observed. Both the pressure and temperature change indicated different stages of exothermic reactions, which produced gases or/and heat. The onset temperature of the thermal runaway was estimated according to the temperature and pressure changes. Moreover, the different activation energies for the exothermic reactions could be derived from Arrhenius plots.

In this experimental investigation, we studied the safety and thermal runaway behavior of commercial lithium-ion batteries of type 21700. The different cathode materials NMC, NCA and LFP were compared, as well as high power and high energy cells. After characterization of all relevant components of the batteries to assure comparability, two abuse methods were applied: thermal abuse by the heat-wait-seek test and mechanical abuse by nail penetration, both in an accelerating rate calorimeter. Several critical temperatures and temperature rates, as well as exothermal data, were determined. Furthermore, the grade of destruction, mass loss and, for the thermal abuse scenario, activation energy and enthalpy, were calculated for critical points. It was found that NMC cells reacted first, but NCA cells went into thermal runaway a little earlier than NMC cells. LFP cells reacted, as expected, more slowly and at significantly higher temperatures, making the cell chemistry considerably safer. For mechanical abuse, no thermal runaway was observed for LFP cells, as well as at state of charge (SOC) zero for the other chemistries tested. For thermal abuse, at SOC 0 and SOC 30 for LFP cells and at SOC 0 for the other cell chemistries, no thermal runaway occurred until 350 °C. In this study, the experimental data are provided for further simulation approaches and system safety design.

As a promising hydrogen storage material, sodium borohydride (NaBH₄) exhibits superior stability in alkaline solutions and delivers 10.8 wt.% theoretical hydrogen storage capacity. Nevertheless, its hydrolysis reaction at room temperature must be activated and accelerated by adding an effective catalyst. In this study, we synthesize Co nanoparticles supported on bagasse-derived porous carbon (Co@xPC) for catalytic hydrolytic dehydrogenation of NaBH₄. According to the experimental results, Co nanoparticles with uniform particle size and high dispersion are successfully supported on porous carbon to achieve a Co@150PC catalyst. It exhibits particularly high activity of hydrogen generation with the optimal hydrogen production rate of 11086.4 mL_H2∙min⁻¹∙g_Co⁻¹ and low activation energy (E_a) of 31.25 kJ mol⁻¹. The calculation results based on density functional theory (DFT) indicate that the Co@xPC structure is conducive to the dissociation of [BH₄]⁻, which effectively enhances the hydrolysis efficiency of NaBH₄. Moreover, Co@150PC presents an excellent durability, retaining 72.0% of the initial catalyst activity after 15 cycling tests. Moreover, we also explored the degradation mechanism of catalyst performance.

Lithium-ion batteries have become the most promising energy storage devices in recent years. However, the simultaneous increase of energy density and power density is still a huge challenge. Ultrafast laser structuring of electrodes is feasible to increase power density of lithium-ion batteries by improving the lithium-ion diffusion kinetics. The influences of laser processing pattern and film thickness on the rate capability and energy density were investigated using Li(Ni_0.6Mn_0.2Co_0.2)O₂ (NMC 622) as cathode material. NMC 622 electrodes with thicknesses from 91 µm to 250 µm were prepared, while line patterns with pitch distances varying from 200 µm to 600 µm were applied. The NMC 622 cathodes were assembled opposing lithium using coin cell design. Cells with structured, 91 µm thick film cathodes showed lesser capacity losses with C-rates 3C compared to cells with unstructured cathode. Cells with 250 µm thick film cathode showed higher discharge capacity with low C-rates of up to C/5, and the structured cathodes showed higher discharge capacity, with C-rates of up to 1C. However, the discharge capacity deteriorated with higher C-rate. An appropriate choice of laser generated patterns and electrode thickness depends on the requested battery application scenario; i.e., charge/discharge rate and specific/volumetric energy density.

Quantitative chemical mapping of battery electrodes is a rather new post-mortem analytics method for identifying and describing chemical degradation processes in lithium-based battery systems. In consideration of future applications, the development of lithium-ion batteries is quite essential in order to meet requirements such as improved cell lifetime (>5000 cycles), high energy density at the cell level (>250 W h kg⁻¹), reduced charging times (2500 W kg⁻¹), and reduced manufacturing costs (<150 $ per kW h). One novel approach that can handle a contemporaneous enhancement of energy and power density is the development of a novel cell design, mandated in a three-dimensional (3D) arrangement. This so-called “3D battery concept” enables electrode configurations with improved lithium-ion diffusion kinetics and provides reduced mechanical stresses which could arise during battery cycling. Within this study, laser-induced breakdown spectroscopy (LIBS) was applied quantitatively as a powerful analytical tool in order to study chemical degradation mechanisms and the impact of 3D electrode architectures on lithium distribution. It could be shown so far that free-standing electrode architectures can provide new lithium-insertion pathways which enhance the capability of the electrode material to operate under abuse conditions. Elemental mapping and elemental depth-profiling were applied for characterizing the electrode as a function of cell lifetime and architecture. For the first time, it was demonstrated that LIBS can be used to quantitatively describe lithium distribution in a 3D battery with specific design parameters. Finally, new scientific findings regarding electrochemically driven degradation and aging mechanisms of laser-structured, embossed, and unstructured NMC electrodes were explored.

The first experimental thermophysical properties of two cathodes containing LiCoO₂and LiMn₂O₄blended active materials combine application oriented and fundamental research.