Lithium ion batteries (LIBs) are known for their efficient storage of electrical energy in many applications such as electric vehicles and in mobile terminals. Today’s state-of-the-art LIBs use graphite as the anode active material due to its high cycling stability and low cost. A promising alternative anode active material is silicon (Si), offering high energy densities (due to its high theoretical capacity), low costs and abundant availability. Therefore, the implementation of small amounts of Si in graphite anodes is already achieved for commercial LIBs. However, increasing the silicon content in LIB anodes is accompanied by limited cycle life due to structural and chemical instabilities of the active and inactive material.
In order to check the quality of newly produced anodes or to be able to use anodes with unknown composition, it is necessary to determine their composition using analytical methods. Furthermore, the composition of the anodes after cycling of the cells is worth knowing in order to draw conclusions about the processes taking place during cycling. Most analytical methods for the determination of the elemental electrode composition (e.g., ICP-OES) are based on acidic digestion of the anode material. The digestion of Si-based anodes is challenging, as it requires hydrofluoric acid or other time-consuming sample preparation steps.
As a promising alternative, high-resolution continuum source atomic absorption spectroscopy (HR-CS-AAS) enables direct solid sampling of the anode material and quantitative determination of the silicon content. By using a continuum source, measurements can be performed at different wavelengths with high wavelength resolution. This enables the possibility to quantify the silicon content using multiple wavelengths to avoid possible interferences. In addition, the simultaneous determination of other elements, such as transition metals deposited on the anode, is possible.