Analysis of acidic organo(fluoro)phosphates as decomposition product of lithium ion battery electrolytes via derivatization gas chromatography-mass spectrometry

Preparative hydrophilic interaction liquid chromatography of acidic organofluorophosphates formed in lithium ion battery electrolytes

The expansion of lithium ion battery (LIB) application is accompanied by the growth of battery pack sizes. This progression emphasizes the consideration of electrolyte safety as well as environmental aspects in case of abuse, accident, or recycling. Hexafluorophosphate is one of the most commonly used conducting salt anions in electrolytes. It has great potential to degrade to various acidic and non-acidic organo(fluoro)phosphates with presence of water and during battery cell operation. Consequently, toxicological investigation on these organo(fluoro)phosphates has emerged because they either have structural similarities as chemical warfare agents or play a widespread physiological role as phosphates in the human body. This circumstance underlines the need of isolated examination of these compounds for safety assessment. In this work, we used hydrophilic interaction liquid chromatography for the extraction of acidic organofluorophosphates from thermally aged LIB electrolytes. The developed two-step fractionation method provided high separation selectivity towards acidic head groups, which allowed the separation of undesired matrix and target compounds. These findings facilitate isolated toxicological investigations on organofluorophosphates that are beneficial for environmental and safety research, the battery cell industry, and human safety surveillance in regard to aged LIB electrolytes.

Chromatographic Techniques in the Research Area of Lithium Ion Batteries: Current State-of-the-Art

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.

A new HILIC-ICP-SF-MS method for the quantification of organo(fluoro)phosphates as decomposition products of lithium ion battery electrolytes

The lithium ion battery (LIB) is the most popular choice for powering consumer electronics, grid storage and electric vehicles. Decomposition reactions in LIBs, leading to so-called aging, are the main reason for loss of capacity and power and will affect LIB safety. Organo(fluoro)phosphates (O(F)Ps) as decomposition products of LIB electrolytes have been identified in several studies in the literature but quantitative data of O(F)Ps in LIBs are only scarcely available. In terms of toxicity, this substance class is highly relevant as it shows structural similarities to chemical warfare agents. Thus, approaches that can deliver quantitative data are in need. In this study, acidic O(F)Ps were quantified with an inductively coupled plasma-sector field-mass spectrometer (ICP-SF-MS) after separation of species with hydrophilic interaction liquid chromatography (HILIC). The formation of OFPs exceeds the amount of non-fluorine containing OPs by a factor of up to 15. A total of 16 different O(F)P compounds could successfully be quantified. Organic mass spectrometry was used for the assignment of quantitative data.

The lithium ion battery (LIB) is the most popular choice for powering consumer electronics, grid storage and electric vehicles.