Practical insights into high-temperature storage of lithium-rich layered oxide cathodes

Abstract Lithium-rich layered oxides (LRLOs) deliver exceptional gravimetric energy density (>1000 Wh kg−1 at 4.8 V) via anion redox reactions, but inherently suffer from low volumetric energy density (VED) due to Li-rich phase and inherent porous granular architecture. In practical industrial applications, the operating voltage window is strictly limited to ∼4.5 V to ensure long-term durability and safety, which further exacerbates the VED deficiency. To bridge this gap, industrial wide distribution composite strategies involving blending large polycrystalline matrices with small polycrystalline (PP) or single-crystalline (PS) interstitial fillers can improve electrode packing density. Although PP offers superior rate capability and cost-effectiveness, it suffers from severe high-temperature (HT) storage instability. In this study, we reveal a cathode-dominated failure driven by accelerated ligand-to-metal charge transfer (LMCT) that activates lattice oxygen, prompting their transformation into highly reactive O-O dimers. In the PP route, abundant intergranular boundaries act as nucleation sites, triggering a destructive feedback loop of secondary cracking, gas release, and detrimental phase transitions. Based on these mechanistic insights, we propose a targeted first-cycle formation voltage regulation strategy to thermodynamically suppress excessive initial oxygen activation. Validated in 60 Ah-level cells, this approach effectively mitigates intergranular degradation and significantly extends the HT storage lifespan of PP cathodes, thus supporting the practical application of high-VED LRLOs.