This title appears in the Scientific Report : 2015 

Lithium distribution as function of state of charge in thin film all solid state batteries characterized by time of flight secondary ion mass spectrometry
Dellen, Christian (Corresponding author)
Lobe, Sandra / Möller, Sören / Breuer, Uwe / Finsterbusch, Martin / Uhlenbruck, Sven / Guillon, Olivier / Bram, Martin
Analytik; ZEA-3
Plasmaphysik; IEK-4
Werkstoffsynthese und Herstellungsverfahren; IEK-1
20th International Conference on Secondary Ion Mass Spectrometry, Seattle (USA), 2015-09-13 - 2015-09-18
Helmholtz Interdisciplinary Doctoral Training in Energy and Climate Research (HITEC)
Electrochemical Storage
Time of flight secondary ion mass spectrometry (ToF-SIMS) is an appropriate analytical technique for the investigation of thin film Li ion battery components, especially when the depth and spatial distribution of lithium inside a battery component or even the whole thin film cell are of interest. Analytical techniques using electron or x-ray beams for elemental detection are not able to access lithium in a sufficient way due to its low atomic number of Z=3. The low detection limits of ToF-SIMS and its eminent spatial resolution make this technique a suitable candidate to investigate the interface between different functional battery layers or to visualize the lithium distribution within e.g. the active cathode layer. Therefore, a layered structure of a thin film all solid state battery system with a typical thickness of a few micrometers is an ideal model system for a detailed ToF-SIMS study. While operating in the dual beam mode, the ToF-SIMS is able to investigate all electrochemical active layers of the battery in one depth profile.The starting point of this study is the investigation of thin films of the commonly used cathode material LiCoO2. The thin film cathodes are prepared by a radio frequency sputter deposition process. The first aspect is the investigation of the deposition process by ToF-SIMS and by other analytical methods like e.g. scanning electron microscopy or x-ray diffraction. Using these techniques, the impact of different deposition parameters like e.g. the deposition temperature or the effect of an additional interlayer as diffusion barrier and adhesion layer is investigated. This knowledge is applied to enable the reproducible production of samples. The key aspect of this study is monitoring the lithiation and delithiation process of the LiCoO2 cathode material using post mortem ToF-SIMS analysis. Therefore, different thin film batteries with LiCoO2 cathodes in combination with liquid electrolytes and also solid state electrolytes are cycled to different states of charge. Afterwards elemental distributions (especially Li) within the cathode are measured by ToF-SIMS and the different states of charge (SOC) are compared in a semi quantitative way. It is discussed, how the deintercalation of lithium during charging affects the matrix environment and hence the characteristics of the depth profiles. In order to get also a quantitative insight into the Li distribution within the thin films, 2 MeV p nuclear reaction analysis and glow discharge optical emission spectroscopy are used as quantitative comparison methods.