Mitigating the Formation of Tetrahedral Zn in Layered Oxides Enables Reversible Lattice Oxygen Redox Triggering by the Na-O-Zn Configuration

摘要

Na-ion layered oxides with Na-O-A & PRIME;local configurations(A & PRIME; represents nonredox active cations such as Li+, Na+, Mg2+, Zn2+) are attractivecathode choices for energy-dense Na-ion batteries owing to the accumulationof cationic and anionic redox activities. However, the migration ofA & PRIME; would degrade the stability of the Na-O-A & PRIME;configuration, bringing about drastic capacity decay and local structuraldistortions upon cycling. Herein, we uncover the close interplay betweenirreversible Zn migration and the inactivation of lattice oxygen redox(LOR) for layered oxides based on Na-O-Zn configurationby Na-23 solid-state NMR and Zn K-edge EXAFS techniques.We further design a Na2/3Zn0.18Ti0.10Mn0.72O2 cathode in which irreversible Znmigration is effectively prevented, and the LOR reversibility is significantlyenhanced. Theoretical insights demonstrate that the migrated Zn2+ is more inclined to occupy the tetrahedral site rather thanthe prismatic site and can be effectively minimized by incorporationof Ti4+ into the transition-metal layer. Our findingssubstantiate that the Na-O-Zn configuration can be utilizedas an appropriate structure to achieve stable LOR by the cautiousmanipulating of intralayer cation arrangements.

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