Thermal Stress Synergizes Oxygen Vacancies Alleviate Jahn–Teller Distortion in Lithium Manganate Cathode

Abstract The Jahn–Teller (JT) distortion induced by the asymmetric electron configuration (t 2g 3 e g 1 ) of high‐spin Mn 3 + ions in LiMn 2 O 4 (LMO) triggers distortion of MnO₆ octahedra, specifically manifested as a cubic to tetragonal transition, which limits the continued development of the commercial electrode material LMO. Herein, it is theoretically found that the strain field applied by the pressure cooperates with the oxygen vacancies (OVs) to reduce the d z 2 occupied state of the e g orbital and suppress the distortion of the MnO 6 axial bonds. Afterward, spinel LMO with coexisting lattice stress and OVs is synthesized via a high‐pressure and high‐temperature synthesis method assisted by a quenching strategy (HPHTQ). Under the synergistic induction of stress and OVs, a reversible capacity of 90.6 mAh g −1 is still obtained after 1000 cycles at 2C, with a capacity retention rate of 94.7%, nearly double the pristine LMO. This innovative strategy has the potential to be applied to a wider range of transition metal oxide systems to alleviate JT distortion caused by crystal field splitting.