Engineering d-p orbital hybridization for high-stable lithium manganate cathode

Abstract

Spinel LiMn2O4 is a prevalent cathode material due to its environmental benignities and high operating voltage. Nevertheless, capacity attenuation and structural collapse are still inevitable, caused by the native Jahn–Teller distortion and spontaneous disproportionation of Mn3+. Hereby, LiMn2O4 cathode with stable crystallographic structure is rationally designed based on valence-bond theory with introduction of Ru dopant. The enhanced orbital hybridization between Mn 3d and O 2p is successfully achieved owing to the reinforcing band coherency of Mn–O aroused from the electrostatic interaction between Mn and Ru atoms. Notably, the robust crystal structure framework is effectively reconstructed, which is beneficial for ameliorating phase evolution and inhibiting structural degradation substantiated by the state-of-the-art synchrotron X-ray absorption spectroscopy and in-situ X-ray diffraction. Concomitantly, LiO4 tetrahedron is effectively weakened, further facilitating the rapid Li+ diffusion kinetics intensively confirmed by theoretical calculations and electrochemical tests. Remarkably, the as-designed Ru-doped LiMn2O4 manifests splendid long cycling stability, affording a respectable capacity retention of 88.2 % after 200 loops. Given this, the intriguing work might inaugurate an explicit direction for rationally tuning the orbital hybridization towards advanced electrodes in alkali metal batteries.