Standards Development

Scope

This document specifies the method for determining the content of metal ions in Lithium Bis (fluorosulfonyl)imide (LiFSI) using Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES).

This method is applicable to the quantification of aluminium (Al), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), nickel (Ni), and lead (Pd) in Lithium Bis(fluorosulfonyl)imide.

Purpose

Lithium difluorosulfonylimide (LiFSI) is widely applied in fields such as batteries, electronics, and pharmaceuticals due to its excellent chemical stability and electrochemical performance, occupying a significant position in numerous industries. With the growing global emphasis on environmental protection and clean energy, the rapid development of new energy vehicles, energy storage, and other sectors has driven the vigorous growth of the lithium battery market. The demand for LiFSI in the lithium battery industry has been increasing year by year, particularly in the areas of new energy vehicles, energy storage, and portable electronic products. As the global demand for battery materials rises annually, the demand for LiFSI also continues to grow. The Asia-Pacific region (China, South Korea, and Japan) accounts for over 70% of the market share, while the European and American markets make up approximately 20%.

At present, China has made stage-by-stage progress in the field of standardization for lithium bis (fluorosulfonyl)imide (LiFSI). The sole publicly implemented special standard in this regard is the industry standard YS/T 1302-2019, titled "Lithium Bis(fluorosulfonyl)imide Salt for Power Battery Electrolyte". This standard establishes a quality framework for power battery applications from dimensions such as purity (99.9%) and impurity control (moisture content 50ppm, metal ion content 1ppm), providing a unified technical benchmark for the domestic industrial chain. However, authoritative organizations such as the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the American Society for Testing and Materials (ASTM) have not yet formulated special standards for LiFSI, nor have they specified detection methods for its technical indicators. This has resulted in core challenges for the global market, including a lack of quality evaluation criteria and difficulties in product benchmarking.

It is worth noting that some research institutions and enterprises have jointly developed a highprecision testing technology system, encompassing core methods such as the determination of impurity elements using inductively coupled plasma optical emission spectrometry (ICP-OES). The technological maturity and accuracy of this system have reached international leading levels. However, due to the absence of standards, the relevant achievements have not yet become a globally recognized language, resulting in cognitive biases and efficiency losses for domestic and foreign manufacturers in trade negotiations, quality traceability, and other aspects. Therefore, promoting the internationalization of LiFSI standards has become a consensus in the industry. This involves collaborating with international standardization organizations to formulate ISO international standards based on Chinese testing methods. Through a three-stage approach of "method unification - indicator classification - scenario adaptation," a global standard system covering the entire chain of raw materials, production, and application will be constructed. Ultimately, this will facilitate the transformation of the "advanced technical solution" into an "international general rule," providing quality infrastructure support for the large-scale and high-end development of the LiFSI industry. Hence, it is recommended to formulate relevant testing method standards for LiFSI.

It is understood that impurity elements in LiFSI have a lower reduction potential than lithium ions. During the charging process, these impurity elements will be the first to be intercalated into the carbon anode, reducing the available positions for lithium ion intercalation and decreasing the reversible capacity of the lithium-ion battery. The precipitation of metal ions may also prevent the formation of an effective passivation layer on the surface of the graphite electrode, leading to the damage of the entire battery. Using an inductively coupled plasma optical emission spectrometer (ICP-OES), a quantitative analytical instrument with high testing accuracy and a low detection limit, to determine the impurity metal ions is a viable approach. This project plans to formulate a testing method standard for the determination of impurity elements in LiFSI, which will fill the gap in domestic and international standards and is of great significance.The trace metal ion content was determined using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) equipped with a hydrofluoric acid-resistant sample introduction system. The primary metal ions measured included aluminium (Al), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), nickel (Ni), and lead (Pb).