The Molecular Dynamics Study of Lithium Ion Conduction in Phosphate Glasses and the Role of Non-Bridging Oxygen

Molecular dynamics (MD) simulation of lithium phosphate (Li 2 O−P 2 O 5 ) glasses with varying Li 2 O content has been carried out. Two different P O distances corresponding to phosphorus coordination with bridging oxygen (BO) and non-bridging oxygen (NBO) were identified in the simulated glasses. NBO−BO interconversion or bond switching was noted, which results in a dynamic equilibration of the tetrahedral phosphate units (P n, n = 1,3 indicates the number of bridging oxygen atoms in the coordination of phosphorus). The NBO−BO bond switching is mildly activated with an effective activation barrier of 0.03−0.05 eV. Lithium ion jumps do not appear to be strongly coupled to bond switching. But the number of Li + ions coordinated to an optimum number of NBOs and the number of Li + ions jumping out of their sites appear to be correlated. Detailed analysis was made of the dynamics of P n species and new insights have been obtained regarding ion migration in network-modified phosphate glasses.