separations Review Chromatographic Techniques in the Research Area of Lithium Ion Batteries: Current State-of-the-Art Yannick Philipp Stenzel 1, Fabian Horsthemke 1, Martin Winter 1,2 and Sascha Nowak 1,* 1 University of Münster, MEET Battery Research Center, Corrensstraße 46, 48149 Münster, Germany;
[email protected] (Y.P.S.);
[email protected] (F.H.);
[email protected] (M.W.) 2 Helmholtz Institute Münster, IEK-12, Forschungszentrum Jülich, Corrensstraße 46, 48149 Münster, Germany * Correspondence:
[email protected]; Tel.: +49-251-83-36735 Received: 27 February 2019; Accepted: 16 April 2019; Published: 13 May 2019 Abstract: Lithium ion batteries (LIBs) are widely used in numerous application areas, including portable consumer electronics, medicine, grid storage, electric vehicles and hybrid electric vehicles. One major challenge during operation and storage is the degradation of the cell constituents, which is called aging. This phenomenon drastically reduces both storage lifetime and cycle lifetime. Due to numerous aging effects, originating from both the individual LIB cell constituents as well as their interactions, a wide variety of instruments and methods are necessary for aging investigations. In particular, chromatographic methods are frequently applied for the analysis of the typically used liquid non-aqueous battery electrolytes based on organic solvents or ionic liquids. Moreover, chromatographic methods have also been recently used to investigate the composition of electrode materials. In this review, we will give an overview of the current state of chromatographic methods in the context of LIB cell research. Keywords: lithium ion batteries; electrolyte; ionic liquids; aging; gas chromatography; ion chromatography; liquid chromatography; capillary electrophoresis; chemical ionization; hyphenated techniques 1.