Li2MnSiO4 lithium battery material: Atomic-scale study of defects, lithium mobility, and trivalent dopants

A new family of silicate materials has attracted interest for potential use in rechargeable lithium batteries. The defect chemistry, doping behavior, and lithium diffusion paths in the Li₂MnSiO₄ cathode material are investigated by advanced modeling techniques. Our simulations show good reproduction of both monoclinic and orthorhombic structures of Li ₂MnSiO₄. The most favorable intrinsic defect type is found to be the cation anti-site defect, in which Li and Mn ions exchange positions. The migration energies suggest differences in intrinsic Li mobility between the monoclinic and orthorhombic polymorphs, which would affect their rate capability as rechargeable electrodes. The results indicate curved Li diffusion paths and confirm the anisotropic nature of Li transport, which is probably general for the Li₂MSiO₄ (M = Mn, Fe, Co) family of compounds. Subvalent doping by Al on the Si site is energetically favorable and could be a synthesis strategy to increase the Li content.