PNNL

Abstract

We simulated amorphization of lithium aluminate by atomic displacement using molecular dynamics to understand the effect of defects on fast lithium ion transport in disordered ceramics. We analyzed the evolution of the AlO4, LiO4, and OLi2Al2 tetrahedral clusters as a function of damage dose calculated in displacements per atom (dpa). The amorphization was associated with the loss of long-range ordering in the network of AlO4 tetrahedra, even though each AlO4 cluster remained tetrahedrally coordinated. The transition from crystalline to amorphous state occured gradually between 0.1 to 0.2 dpa. The structural damage also induced chemical composition separation, resulting in (Al+O)-rich and Li-rich regions. As a result of the disorder, the Li diffusion coefficient was found to increase to the order of 10-6 cm2/s