Mitigating the Jahn-Teller distortion driven by the spin-orbit coupling of lithium manganate cathode

Abstract

Spinel LiMn2O4 is recognized as one of the most competitive cathode candidates for lithium-ion batteries ascribed to environmentally benign and rich sources. However, the wholesale application of LiMn2O4 is predominately plagued by its severe capacity degradation, mainly associated with the innate Jahn-Teller effect. Herein, single-crystalline LiMn2O4 with Eu3+ doping is rationally designed to mitigate the detrimental Jahn-Teller distortion by tuning the chemical environment of MnO6 octahedra and accommodating localized electron, based on the unique aspheric flexible 4f electron orbit of rare-earth metal ions. Notably, the stretching of MnO6 octahedron stemmed from the Jahn-Teller effect in Eu-doped LiMn2O4 is effectively suppressed, confirmed by theoretical calculation. Meanwhile, the structural stability of the material has been significantly enhanced due to the robust Mn–O band coherency and weakened phase transition, proved by synchrotron radiation absorption spectrum and operando X-ray diffraction. The corresponding active cathode manifests superior long-cycle stability after 300 loops at 2C and displays only a 0.011% capacity drop per cycle even at 5C. Given this, this modification tactic sheds new light on achieving superior long-cycle performances by suppressing distortion in various cathode materials.