Open Access

Lithium-ion batteries (LIBs) are extensively employed to power small electric and stationary devices as well as electric vehicles (EVs), due to their high energy density, long cycle life, and relatively low self discharge. The rapid expansion of the EV market is expected to increase significantly the global demand for LIBs, with sales projected to reach 245 million units by 2030, according to the International Energy Agency. In order to meet this demand, it is essential to reduce manufacturing scrap rates and extend battery life. [1,2] Production efficiency can be increased by limiting production failures and detecting process deflections at early stages of manufacturing chain, for example through rigorous control of the electrode homogeneity. On the other hand, the prolongation of a battery life assumes deep knowledge of the degradation processes, such as dendrite formation and electrolytes degradation, directly correlated with a change in the elemental distribution inside the battery. [3] As techniques capable of in-depth elemental analysis at scales from a few nm to 100 μm, Glow Discharge Optical Emission Spectroscopy (GD-OES) and Glow Discharge Mass Spectrometry (GD-MS) are suited for investigating both the homogeneity of the cathodic material in the manufacturing phase, as well as changes in its elemental distribution caused by aging. Focus has been given to lithium and fluorine distribution, whose migration inside the battery is correlated to the cycling and the electrolyte and binder degradation, respectively. A few previous reports described depth profiling of positive and negative electrodes in LIBs using GD OES. [4 6] In this work, GD-OES spectroscopic analysis has been performed on self-made cathodes for LIBs to gain insight into the quality of the manufacturing process, targeting a standardized electrodes production. With the same cathode material, coin cells have been built and artificially aged. Post mortem analysis conducted by GD-OES with the use of an argon/neon mixture as discharge gas, helped correlating the variation of fluorine distribution with the battery state of health (SOH). GD MS analysis was employed to gain insight into battery degradation phenomena upon aging, such as transition metal dissolution from the positive electrode and lithium isotopic fractionation [3,7]. This work marks GD-techniques as versatile and efficient tools to study LIBs, unveiling significant application in both academical research and industrial manufacture.

Uncovering Li-ion Battery Degradation: Possibilities Offered by GD-MS Analysis Since their introduction, lithium-ion batteries (LIBs) have revolutionized the energy storage market, which they now dominate thanks to their high energy density, power capability, and efficiency.1, 2 Despite widespread adoption, global demand for LIBs is projected to grow by around 27% per year.3 This raises concerns about the availability of critical minerals essential to LIB production. Meeting future demand will therefore require next-generation LIBs—an ambition that hinges on a deeper understanding of the degradation processes that limit performance and lifetime. Because LIBs are chemically and physically complex systems, capacity fade stems from multiple degradation phenomena that act concurrently as cells age.4 In particular, the formation and growth of interfacial layers at the electrodes during repeated charge–discharge cycling make a substantial contribution to component degradation.5 Glow Discharge Mass Spectrometry (GD-MS) offers depth-resolved elemental and isotopic analysis of battery electrodes and has proven to be a powerful tool for tracking degradation in LIBs. Using a ASTRUM Swift GD-MS spectrometer, we identified degradation pathways in both cathodes and anodes across various cell chemistries, linking electrochemical behavior with changes in structure and elemental distributions. These insights help clarify the mechanisms that accelerate aging and capacity loss.

Lithium-Ion Batteries (LIBs) dominate the energy storage market due to their high energy density, lightweight, and substantial power output.[1] Since their manufacture involves the usage of critical materials such as lithium, cobalt and copper, Sodium-Ion Batteries (SIBs) are currently emerging as a more sustainable alternative due to the high availability of sodium and other required raw materials on Earth.[2] These two technologies share similar electrochemical principles and currently find different applications in the global market.[3] While LIBs dominate the portable electric devices and electromotive field, SIBs are becoming relevant for stationary energy storage applications, for which energy density plays a less decisive role. The increasing global demand for LIBs, expected to grow by about 27% annually,[4] raises questions about the fate of the millions of tons of exhausted batteries generated. Considering that battery production gigafactories have a scrap rate of about 30% across the entire production chain,[5] it appears evident that improved manufacturing processes and increased battery lifetime are demanded. To meet these requirements, a deeper understanding of the processes that concur with battery degradation is essential. With the aim of gaining further insight into these aspects, this work focuses on the formation, composition, and degradation of the Solid Electrolyte Interphase (SEI). This complex, heterogeneous passivation layer that forms on the negative electrode is essential for the reversible charging of batteries and the understanding of its formation and degradation is essential for producing batteries with superior performances.[6] To gain insight into these intricate phenomena, the distribution of the main elemental components of SEI in LIBs and SIBs electrodes is investigated. Positive electrodes are self made using lithium- and sodium-layered transition metal oxides as active material, while graphite and hard carbon are used to produce the negative electrodes. After their assembly, the cells are formed and artificially aged under different conditions. Post mortem analysis is performed on freshly formed, early failed, and differently aged cells by lateral profile (Laser-Induced Breakdown Spectroscopy LIBS) and in-depth profile (Glow-Discharge Optical Emission Spectroscopy GD-OES and Mass Spectrometry GD-MS) techniques.[7] We present a new GD-OES analytical method where electrodes are sputtered with a neon/argon mixture. This allows for in-depth profiling of fluorine (IE 17.4 eV) due to the higher ionization energy of neon (IE 21.6 eV) compared to argon (IE 15.8 eV). Qualitative analysis of solvents and electrolytes degradation products is performed by GC-MS. Furthermore, Electrochemical Impedance Spectroscopy analysis (EIS), performed on each cell at different stages of life, facilitates the correlation between internal resistance and degradation process. The pool of experimental data is used as feedstock for Machine Learning (ML) methods. By merging data obtained from multiple sources, ML algorithms can unveil correlations between the data sets and, thus, provide insight into the cell’s chemical/physical deterioration. Furthermore, ML tools are employed to correlate chemical degradation of the cells with their electrochemical features, investigated by non-destructive analysis (EIS). Using the acquired experimental data as training set, this work targets the development of a data-driven approach for battery State of Health (SOH) and Remaining Useful Lifetime (RUL) evaluation based on non-destructive analysis results. The method aims to offer a simple way to establish battery RUL, avoiding time consuming and expensive end of life chemical analysis, which offers remarkable implications to the large-scale battery production.[8]

The presentation summarizes the research work of division 1.6 on Li isotope fractionation in Li-ion batteries (LIB). This work interrogates whether changes in Li isotopic distribution in LIB components can be used as a diagnostic tool to monitor interphases growth at the electrodes surfaces and as a benchmark to track battery degradation. For this purpose, different analytical techniques have been employed to study the electrodes of commercial and lab-scale cells, providing bulk (MC-ICP-MS) and local (GD-MS, LA-ICP-MS) information about the Li isotope distribution changes upon cells cycle aging. The results show Li isotope fractionation in full Li ion cells upon aging, suggesting that the 6Li accumulation on the surface of the negative electrode might be used as a new benchmark to track the solid electrolyte interphase growth

The research conducted at the Federal Institute for Material Research and Testing (BAM) focuses on key challenges of the energy transition, spanning hydrogen technologies, electrical energy storage, and renewable energy systems. In the field of energy storage, our primary areas of interest include the safety of electrical energy storage systems, sustainable energy materials, and advanced battery diagnostics. One of our central objectives is to deepen our understanding of the processes contributing to lithium-ion cell degradation, an essential step toward improving next-generation systems and meeting the rapidly growing demand for lithium-ion battery technology. The complexity of these systems, which comprise organic and inorganic compounds in multiple aggregation states, presents significant analytical challenges. To address these challenges, we are developing novel analytical methods to further expand our insight into battery degradation mechanisms. Using GD-MS for depth-resolved lithium isotope analysis, we have recently established a correlation between lithium isotope fractionation and the growth of electrode–electrolyte interphases at electrode surfaces. In addition, we are developing GD-OES and LIBS methods for depth-resolved and lateral fluorine analysis, respectively, of lithium-ion battery electrodes to monitor electrolyte and additive degradation. These approaches might also provide valuable analytical tools for assessing the homogeneity of fluorinated active materials.