Lithium loss in the solid electrolyte interphase: Lithium quantification of aged lithium ion battery graphite electrodes by means of laser ablation inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectroscopy

• Published in: Journal of power sources Vol. 356; pp. 47 - 55
• Main Authors: Schwieters, Timo, Evertz, Marco, Mense, Maximilian, Winter, Martin, Nowak, Sascha
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2017
• Subjects: Graphite anode; Graphite intercalation compounds; Inductively coupled plasma optical emission spectroscopy; Laser ablation inductively coupled plasma mass spectrometry; Lithium loss; Solid electrolyte interphase; Solid electrolyte interphase; Lithium loss; Graphite intercalation compounds; Graphite anode; Inductively coupled plasma optical emission spectroscopy; Laser ablation inductively coupled plasma mass spectrometry
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2017.04.078

In this work we present a new method using LA-ICP-MS to quantitatively determine the lithium content in aged graphite electrodes of a lithium ion battery (LIB) by performing total depth profiling. Matrix matched solid external standards are prepared using a solid doping approach to avoid elemental fractionation effects during the measurement. The results are compared and matched to the established ICP-OES technique for bulk quantification after performing a microwave assisted acid digestion.
The method is applied to aged graphite electrodes in order to determine the lithium immobilization (= “Li loss”) in the solid electrolyte interphase after the first cycle of formation. For this, different samples including a reference sample are created to obtain varying thicknesses of the SEI covering the electrode particles. By applying defined charging voltages, an initial lithiation process is performed to obtain specific graphite intercalation compounds (GICs, with target stoichiometries of LiC30, LiC18, LiC12 and LiC6). Afterwards, the graphite electrode is completely discharged to obtain samples without mobile, thus active lithium in its lattice. Taking the amount of lithium into account which originates from the residues of the LiPF6 (dissolved in the carbon components containing electrolyte), it is possible to subtract the amount of lithium in the SEI.
•Quantification of the lithium consumption during SEI formation in aged graphite.•Four different GICs and an uncycled reference sample were analyzed.•Development of self made standards and first LA-ICP-MS application for SEI analysis.