Converting Li-Rich Layered Oxide Cathode into Non-Shrinking Sacrificial Prelithiation Agent.

Abstract

To improve the energy density of Li-ion batteries, conventional sacrificial prelithiation agents (Li₅FeO₄, Li₂O and Li₂CO₃, etc.) are introduced to compensate for active lithium loss, but they undergo serious volumetric shrinkage during decomposition, generating voids that compromise electrode architecture integrity and deteriorate electrochemical performance. Herein, the typical Li-rich layered oxide cathode is converted into Li-rich disordered rocksalt oxide (LRDO) prelithiation agent, achieving 330 mAh g^-1 charge capacity and retaining 130 mAh g^-1 reversible capacity (contributing 200 mAh g^-1 irreversible prelithiation capacity). Compared with the layered structure, the cation-disordered structure in LRDO tunes the local oxygen environment, completely activating oxygen-related anionic oxidation activity at lower potential (<4.5 V). Moreover, coupled with a fluorinated electrolyte additive, the nucleophilic oxygen species released during de-lithiation of LRDO are synergistically utilized, constructing a gradient cathode-electrolyte interphase architecture with enhanced interfacial stability during the cell formation process. Most importantly, the phase-transition-free nature of LRDO during prelithiation completely eradicates volume shrinkage, effectively preventing electrode architecture degradation. Furthermore, a long-life graphite||LiFePO₄ pouch cell with high discharge capacity of 150.02 mAh (7.59% higher than without prelithiation) are achieved, maintaining 91.33% capacity after 1800 cycles.