Trace Moisture\nDrives Lithium Volatility during Cathode\nSynthesis

Synthesis of cathodes for lithium ion batteries is typically\nconducted\nvia a reaction between a mixed metal hydroxide precipitate and a lithium\nsource at elevated temperatures. While anecdotal evidence suggests\nthat some portion of lithium may vaporize during thermal treatment,\na thermodynamic analysis of lithium volatility has not been previously\npublished. The formation of lithium vapor would be beneficial for\novercoming mass transport limitations in otherwise solid–solid\nreactions but may also result in lithium loss and alteration of the\nintended stoichiometry of the final product. To rigorously quantify\nthe extent to which lithium vaporization is thermodynamically feasible\nand the nature of the lithium species involved, high-level quantum\nchemical calculations have been performed on gaseous molecular lithium\noxides and hydroxides and their extents of formation assessed from\nGibbs Free Energy considerations. Results show that while the volatility\nof lithium oxide is negligible under dry conditions, ppm concentrations\nof water vapor are sufficient to dramatically enhance lithium vaporization\nvia gaseous LiOH intermediates. Controlling the moisture level during\nsynthesis is therefore of paramount importance in the production of\nhigh-quality lithium ion cathode materials.