Influence of magnetic ordering and Jahn-Teller distortion on the lithiation process of LiMn2O4.

We performed extensive first-principles studies on the magnetic ordering and Jahn-Teller (JT) distortion of spinel LiMn2O4, a promising candidate for cathode materials in Li-ion batteries. We find that the ground state of LiMn2O4 is an anti-ferromagnetic (AFM) orthorhombic spinel structure, where AFM Mn3+ layers and FM Mn4+ layers alternate along the [001] direction and the 90° Mn3+-O2--Mn3+ in the Mn3+-(001) planes are AFM coupling, forming an indirect Kramers-Anderson superexchange. The coplanar Mn3+ ions maximize the JT distortion and the AFM magnetic orderings further strengthen the interaction between Mn3+ cations and O2- anions, making the structure stable. Li diffusion in such a stable LiMn2O4 material will occur through a ring consisting of six Mn atoms, and the energy barrier of Li diffusion is dependent on the valence states of those Mn atoms. Our theoretical results give insights into exploring the ground state of related JT magnetic materials, and also provide information on the performance improvement of LiMn2O4 cathode materials.