Oxygen Redox in Alkali-Ion Battery Cathodes

• Published in: Annual review of materials research 2024-08, Vol.54 (1), p.199-221
• Main Authors: Menon, Ashok S, Ogley, Matthew J.W, Genreith-Schriever, Annalena R, Grey, Clare P, Piper, Louis F.J
• Format: Article
• Language: English
• Subjects: electrochemical energy storage; Li-ion battery cathodes; oxygen redox; X-ray spectroscopy
• ISSN: 1531-7331; 1545-4118
• DOI: 10.1146/annurev-matsci-080222-035533

Current high-energy-density Li-ion batteries use stoichiometric Li 3d transition metal oxides as positive electrodes, which are conventionally described purely by transition-metal redox during routine operating windows. Their practical specific capacities (mAh/g) may be increased by widening their operational voltage window, using Li-excess compositions, or a combination of the two, both of which have shown increasing evidence of O participation in the charge-compensation mechanism. Understanding how this influences the electrochemical performance of these cathodes has been of great interest. Therefore, this review summarizes the current understanding of O participation in alkali-ion battery cathode charge compensation. Particular scrutiny is applied to the experimental observations and theoretical models used to explain the consequences of O participation in charge compensation. The charge-compensation mechanism of LiNiO 2 is revisited to highlight the role of O hole formation during delithiation and is discussed within the wider context of Li-excess cathodes.