Revealing Gliding-Induced Structural Distortion in High-Nickel Layered Oxide Cathodes for Lithium-Ion Batteries.

ABSTRACT

After charging to a high state-of-charge (SoC), layered oxide cathodes exhibit high capacities but suffer from gliding-induced structural distortions caused by deep Li depletion within alkali metal (AM) layers, especially for high-nickel candidates. In this study, we identify the essential structure of the detrimental H3 phase formed at high SoC to be an intergrowth structure characterized by random sequences of the O3 and O1 slabs, where the O3 slabs represent Li-rich layers and the O1 slabs denote Li-depleted (or empty) layers that glide from the O3 slabs. Moreover, we adopt two doping strategies targeting different doping sites to eliminate the formation of Li-vacant O1 slabs. First, we introduce direct transition metal (TM) pillars between TMO2 slabs achieved through dopants (e.g., Nb) positioned within AM layers, significantly improving the cycling stability. Second, we introduce indirect Li pillars achieved through dopants located at TM layers to adjust the Li-O bond strength. While this strategy can regulate the uniformity of Li at the slab level, it results in an uneven Li distribution at the particle scale, ultimately failing to enhance the electrochemical performance. Our established research strategy facilitates the realization of diverse pillars between TMO2 slabs through doping, thereby offering guidance for stabilizing high-capacity layered oxide cathodes at high SoC.