Open AccessStudy of the Reactions between Ni-Rich Positive Electrode Materials and Aqueous Solutions and their Relation to the Failure of Li-Ion Cells
Author(s) -
Ines Hamam,
Ning Zhang,
Aaron Liu,
Michel B. Johnson,
J. R. Dahn
Publication year - 2020
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/abb9cd
Subject(s) - thermogravimetric analysis , aqueous solution , secondary ion mass spectrometry , lithium (medication) , inductively coupled plasma , scanning electron microscope , electrode , impurity , chemistry , titration , inorganic chemistry , mass spectrometry , inductively coupled plasma mass spectrometry , analytical chemistry (journal) , materials science , chemical engineering , chromatography , plasma , composite material , organic chemistry , medicine , physics , quantum mechanics , engineering , endocrinology
The handling of positive electrode active materials must be done carefully due to their propensity to degrade when exposed to ambient atmosphere. The growth of impurities on Ni-rich layered lithium transition metal oxides (LTMOs) is particularly concerning as these materials readily react with H 2 O and CO 2 in atmosphere. The resulting surface impurity species have detrimental effects on the performance of the Li-ion cell and are commonly removed by washing the positive electrode active materials. However, little is understood about the reaction between these materials and aqueous solutions. In this study, LTMOs samples were exposed to acidic and neutral aqueous solutions for various periods of time. The resulting material samples were analysed by X-ray powder diffraction (XRD), thermogravimetric analysis coupled with mass spectrometry (TGA-MS), and by scanning electron microscopy (SEM). The solutions collected after washing were analysed by pH titration and inductively coupled plasma optical emission spectrometry (ICP-OES). From this, we propose two pH-dependent regimes that define the reaction between the positive electrode material and the aqueous solution used for washing. Possible consequences of these reactions on cell performance and lifetime are discussed.