Regulating Li Extraction in Transition Metal Layer for High-Performance Li-Excess Layered Oxide Cathode with Intergrowth Structure.
basic_science · Level V
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- Record sourced from PubMed, PMID 42124518.
- Also identified by DOI 10.1002/adma.202520981.
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Abstract
In lithium-excess layered oxide cathodes, the extra lithium within transition metal (TM) layers (i.e., Li<sub>[TM]</sub>) can trigger anionic redox to provide additional capacity. However, substantial extraction of Li<sub>[TM]</sub> may induce irreversible/detrimental local structural rearrangements. The conventional edge-shared connecting configuration between LiO<sub>6</sub> and TMO<sub>6</sub> octahedra facilitates interlayer migration of Li<sub>[TM]</sub>. In contrast, the face-shared configuration has the potential to limit the mobility of Li<sub>[TM]</sub>, but this metastable configuration cannot be harvested via traditional calcination. Herein, during Na-to-Li ion exchange in P2 phase Na<sub>0.66</sub>[Li<sub>0.22</sub>TM<sub>0.78</sub>]O<sub>2</sub> precursor, we observe that the random gliding of TMO<sub>2</sub> layers yielding Li<sub>0.66</sub>[Li<sub>0.22</sub>TM<sub>0.78</sub>]O<sub>2</sub> with O2/O6 intergrowth structure. Despite the random gliding, the functional face-shared configuration is successfully obtained and proven to effectively restrict interlayer migration of Li<sub>[TM]</sub> during charging. Consequently, we observe the suppressed formation of aggregated vacancies and O-O dimers within the TM layers. Ultimately, our synthesized O2/O6 Li-excess demonstrates enhanced structural reversibility and improved capacity/voltage retention. This oxygen-stacking engineering provides a compelling strategy for developing cathodes with enhanced local structural reversibility.