%0 Journal Article %A KyuJung Jun %A Lori A Kaufman %A Wangmo Jung %A Byungchun Park %A Chiho Jo %A Taegu Yoo %A Donghun Lee %A Byungju Lee %A Bryan D McCloskey %A Haegyeom Kim %A Gerbrand Ceder %B Advanced Energy Materials %D 2023 %G eng %R 10.1002/aenm.202301132 %T Understanding the Irreversible Reaction Pathway of the Sacrificial Cathode Additive Li6CoO4 %U https://onlinelibrary.wiley.com/doi/10.1002/aenm.202301132 %8 06/2023 %! Advanced Energy Materials %X

The use of a sacrificial cathode additive that contains a large amount of lithium is one potential solution to compensate for the irreversible capacity loss associated with next-generation anodes such as silicon. Antifluorite-type Li₆CoO₄ has attracted attention as a potential cathode additive owing to its remarkably high theoretical lithium extraction capacity. However, the complex mechanism of lithium extraction as well as the oxygen loss from Li₆CoO₄ is not well understood. A generalizable computational thermodynamics and experimental framework is presented to understand the lithium-extraction pathway of Li₆CoO₄. It is found that one lithium per formula unit can be topotactically extracted from Li₆CoO₄, followed by an irreversible and nontopotactic phase transformation to Li₂CoO₃ or LiCoO₂ depending on the temperature. The results show that peroxide species may form to charge-compensate for Li extraction which is undesirable as this can lead to gas release during battery operation. It is suggested that charging Li₆CoO₄ at an elevated temperature that the electrolyte can withstand, redirects the reaction pathway and prevents the formation of intermediate peroxide species making it an effective and stable sacrificial cathode additive.