On the Hydration of P2-Layered Sodium-Ion Cathode Materials in Aqueous Battery Applications

The high-performance seen in today’s lithium-ion and sodium-ion batteries is enabled by the use of organic alkyl-carbonate electrolytes mixtures which demonstrate high electrochemical stability. However, the use of these organic solvents has led to significant challenges related to their safety/flammability, in addition to stringent processing requirements during manufacturing to avoid contamination of the electrolyte with water. This has led to interest in utilizing lithium-ion and sodium-ion intercalation electrode material with aqueous-based electrolytes.

Recent work on the development of high-performance sodium-ion cathode materials has identified layered transition-metal oxides synthesized with a P2 stacking sequence demonstrate both high capacity and high capacity retention, which makes this class of intercalation compounds promising for use in battery applications.

Our work focuses on the consequences of utilizing P2-layered oxides in aqueous electrolytes; in particular, the vulnerability of these layered materials to hydration, in which water is incorporated into the layered structure. This phenomenon is not dissimilar to the weathering of many naturally occurring layered minerals such as Mica and Vermiculite. P2 compounds of multiple compositions will be studied using a variety of techniques including cycling results, x-ray diffraction, and thermo-gravimetric analysis in order to identify the onset of material hydration as well as the ramification of this phenomenon for aqueous battery applications.