The degradation of lithium-ion cells is an important aspect, not only for quality management, but also for the customer of the application like, e.g., scooters or electric vehicles. During the lifetime of the system, the overall health on the battery plays a key role in its depreciation. Therefore, it is necessary to monitor the health of the battery during operation, i.e., cycle life, but also during stationary conditions, i.e., calendar aging. In this work, the degradation due to calendar aging is analyzed for six different cell chemistries in terms of capacity degradation and impedance increase and their performance are being compared. In a new proposed metric, the relative deviations between various cells with the exact identical aging history are being analyzed for their degradation effects and their differences, which stands out in comparison to similar research. The capacity loss was found to be most drastic at 60 °C and at higher storage voltages, even for titanate-oxide cells. LiNiMnCoO₂ (NMC), LiNiCoAlO₂ (NCA) and Li₂TiO₃ (LTO) cells at 60 °C showed the most drastic capacity decrease. NMC and NCA cells at 60 °C and highest storage voltage did not show any open circuit voltage, as their current interrupt mechanism triggered. The effect of aging shows no uniform impact on the changes in the capacity variance when comparing different aging conditions, with respect to the evaluated standard deviation for all cells. The focus of this work was on the calendar aging effect and may be supplemented in a second study for cyclic aging.

Scanning electron microscopy (SEM), when combined with secondary ion mass spectrometry (SIMS) enables spatially resolved detection of lithium. The time-of-flight detector allows the precise identification of each fragment. Quantitative results are obtained through inductively coupled plasma optical emission spectrometry (ICP-OES). This innovative technique combination provides new insights into the chemical composition of three morphologies found on the anode surface in a long-term cycled lithium-ion battery, compared to a reference battery. The three morphologies are a) fine-grained precipitations, b) fiber structures and c) spherical particles. The fine-grained precipitations are inhomogeneous and composed of Li, F, O, P, Cu and S. Their thickness ranges from 50 to 100 nm. The fiber structures appear in three different shapes: round, helically twisted and flattened with a thicker rim. Their length spans from 1 to 14 µm and their width varies between 50 and 900 nm. The fibers contain the same elements as the fine-grained precipitations. The spherical particles predominantly range from 300 to 600 nm in size and have a fine-grained surface. They consist of Li, F, O, Si, Al and S. Also traces of Ni, Mn and Co are detected with ICP-OES. SIMS mappings and mass spectra of small regions of interest suggest that the fine-grained precipitations contain LiF, probably LiOH, Li- and Cu-oxides and phosphate compounds. The fiber structures contain no phosphate but additionally Li- and Cu-phosphides whereas the spherical particles consist of a silicate or aluminosilicate structure combined with LiF. Further studies are required to clarify the sequence of formation.

We examine the impact of water (160 ± 41 ppm of reference) on the anode, cathode, separator and electrolyte in two aging scenarios: calendric aging (60 °C, 80 days, charged state), resulting in a triggered current interrupt device (CID), and cycling 1680 times (charge/discharge with 1C, 2.75–4.2 V, 20 ± 2 °C), resulting in 24.5% residual capacity. We applied computer tomography (CT), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and secondary ion mass spectrometry (SIMS) to understand the capacity loss. The aged NMC/LCO–graphite cells were compared to a reference cell in pristine state. Both aging scenarios showed (a) thick depositions on the anode and cathode consisting mainly of oxygen, fluorine and phosphorous, (b) reduced separator pore sizes, (c) the deposition of Mn, Co and Ni on top of the anode and (d) the decomposition of the conductive salt LiPF₆ accompanied by HF formation and a loss of active lithium. Calendric aging consumes the water content and additionally leads to (e) the decomposition of the organic solvent followed by CO₂ gas formation. Cyclic aging increases the water content and additionally results in (f) the consumption of the additive fluoroethylene carbonate (FEC). These findings show how water affects aging phenomena and results in a capacity decrease in the cell.

The deployment of battery-powered electric vehicles in the market has created a naturally increasing need for the safe deactivation and recycling of batteries. Various deactivating methods for lithium-ion cells include electrical discharging or deactivation with liquids. Such methods are also useful for cases where the cell tabs are not accessible. In the literature analyses, different deactivation media are used, but none include the use of calcium chloride (CaCl₂) salt. As compared to other media, the major advantage of this salt is that it can capture the highly reactive and hazardous molecules of Hydrofluoric acid. To analyse the actual performance of this salt in terms of practicability and safety, this experimental research aims to compare it against regular Tap Water and Demineralized Water. This will be accomplished by performing nail penetration tests on deactivated cells and comparing their residual energy against each other. Moreover, these three different media and respective cells are analysed after deactivation, i.e., based on conductivity measurements, cell mass, flame photometry, fluoride content, computer tomography and pH value. It was found that the cells deactivated in the CaCl₂ solution did not show any signs of Fluoride ions, whereas cells deactivated in TW showed the emergence of Fluoride ions in the 10th week of the insertion. However, with the addition of CaCl₂ in TW, the deactivation process > 48 h for TW declines to 0.5–2 h, which could be an optimal solution for real-world situations where deactivating cells at a high pace is essential.

Trace amounts of oxygen and hydrogen can strongly influence the formation of negative carbon ions during focused ion beam–secondary ion mass spectrometry (SIMS) analysis of graphite. In this study, the sputtering behavior of graphite and the detection of single and clustered carbon ions were investigated under systematically varied measurement conditions. Experiments were performed by varying the primary ion current and the analysis field size, enabling a systematic evaluation of ion dose effects. A linear relationship between sputter rate and ion dose was observed. The sputter yield increases at low ion doses and stabilizes at approximately 1.6 C atoms/Ga+ ion for ion doses above 15 nC/μm2. Large analysis fields lead to a decrease in sputter yield accompanied by increased scatter, indicating the onset of sample swelling. Signal stability strongly depends on ion dose. At high ion doses, stable sputtering conditions are reached within about 1 min, whereas up to 20 min are required at low ion doses. Under stable conditions, mass spectral peak heights correspond well with constant signal levels observed in multiple ion detection profiles. Carbon ion intensities vary strongly with measurement parameters but become stable when normalized to simultaneously detected oxygen, hydrogen, or hydroxide signals. These results indicate that trace surface impurities modify the electronic structure of graphite and significantly affect negative ion formation. The findings highlight the importance of surface chemistry for the interpretation of SIMS measurements, particularly in the analysis of graphite-based lithium-ion battery materials.