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. Nature 2024, 629, 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 ab initio molecular dynamics simulations accelerated by machine learning and find that CSRD effectively suppresses phase transitions from hexagonal to monoclinic at Li0.5CoO2 and from O3 to H1–3 at Li0.25CoO2. The enhanced phase stability is attributed to the reduced lattice variation in the c-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 Li1.2Co0.8O2 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.