Lithium ion migration pathways in LiTi2(PO4)3 and related materials

The diffusion pathways of Li+ ions within the frameworks of the high conductive solid electrolytes LiTi2(PO4)3 and the Al-doped one Li1.3Ti1.7Al0.3P3O12 are determined by molecular mechanics and molecular dynamics methods. From a potential energy profile for the lithium migration in LiTi2(PO4)3, the barrier height of lithium migration is estimated as 28.95 kJ/mol (0.30 eV) which is in excellent agreement with experimental data. The main influence on the activation energy of lithium diffusion is caused by changes in electrostatic interactions. Long molecular dynamics simulations for Li1.3Ti1.7Al0.3P3O12 also confirm a solid state diffusion process via rare and sporadic hopping of Li+ ions from their energy minimum site to a neighboring energy minimum site.