A quantification method for Fe based particle contaminants in high purity materials for lithium-ion batteries

Abstract

The technological growth, the increasing safety, and production standards cascade down to the quality of the raw materials. The development of analytical methods for high quality powder analysis needs to grow parallel to this trend. It is established that particle metal contaminants could trigger violent failures of lithium-ion batteries and compromise the battery performance, and the safety of the end user.Increased miniaturization requires exponential increases in quality of raw materials putting laboratories in a continuous process of development to achieve ever higher standards. Trace elements in a powder material can be present in different states, and their effect on the application can therefore be different according to the status. Trace elements can be present in the material as a dissolved impurity or as a particle contamination.Here we present an experimental method which is easy to implement and use, and is sensitive to contaminants (i.e. external particles that are not part of the material of interest) over total trace elements. Contaminants typically are a few orders of magnitude lower in concentration than total trace elements. The method focuses on the quantification of Fe, Ni and Cr in high purity carbon powders used in the lithium-ion battery industry. We present test sample size calculations prior to the method description to ensure high precision and assess possible bias. The method is based on the magnetic extraction of a large test sample, followed by acid digestion and quantification. The procedure and the method performance are described. The method ensures low levels of detection and quantification, high precision, and accuracy.