Mechanisms of Enhanced Electrochemical Performance by Chemical Short-Range Disorder in Lithium Oxide Cathodes

LiCoO₂ has been one of the dominant cathode materials commercially used in rechargeable lithium-ion batteries, while the performance is severely limited by its low reversible capacity (∼140 mAh/g), primarily due to the destructive phase transitions at high voltages (>4.2 V vs Li/Li⁺), leading to structural degradation and rapid decay of capacity. A recent experimental study [Wang et al. <i>Nature</i> <b>2024</b>, <i>629</i>, 341] showed that chemical short-range disorder (CSRD) in LiCoO₂ can effectively prevent phase transitions and structural deterioration. To better understand the underlying mechanisms, we carry out a theoretical study on CSRD-based LiCoO₂ by performing <i>ab initio</i> molecular dynamics simulations accelerated by machine learning and find that CSRD effectively suppresses phase transitions from hexagonal to monoclinic at Li_0.5CoO₂ and from O3 to H1-3 at Li_0.25CoO₂. The enhanced phase stability is attributed to the reduced lattice variation in the <i>c</i>-axis, the increased oxygen vacancy formation energies, the higher oxygen dimer formation energies, and the stabilization of Co atoms in the Li layers during delithiation. The high Li⁺ diffusion coefficients are found to arise from the low-barrier 0-TM diffusion channels and an expanded diffusion network from 2D to quasi-3D induced by CSRD. Furthermore, CSRD narrows the band gap of LiCoO₂ with enhanced electronic conductivity, driven by the changes in the Co valence state and the introduction of linear Li-O-Li configurations. Equally important, CSRD can also enhance the stability of Li-rich cathode Li_1.2Co_0.8O₂ for high capacity and excellent cycling performance. This work provides theoretical insights into the effects of CSRD on LiCoO₂ and Li-rich cathodes for rational design and synthesis.