Thesis

First-principle molecular dynamics of mixed lithium indium halides as solid electrolytes for batteries

The low ionic conductivity across solid-solid interfaces and through the solid electrolyte is a limiting factor for commercial implementation of all solid state batteries. Through the understanding of Li+ ion diffusion by using first-principles molecular dynamics, significant insights in developing new battery materials can be achieved. Previous research has determined the mechanism for the lithium ion diffusion pathway through Li3lnBr6 and noted its non-Arrhenius behavior at high temperatures.18 The results presented in this thesis expand on those previous findings by simulating diffusion in Li3lnBr6-xClx at temperatures between 700-900 K. It was determined that the substitution of Cl anions for Br anions changes the character of bonds, especially polar-covalent bonding interactions. The Li-Br/Cl bonds are not ideal in the octahedral site, especially in LisInBrsCb. These frustrated bonds could lead to an increased jump attempt frequency. This increased jump attempt frequency in Li3lnBr3Cb could be the cause for such high diffusivity despite LisInBrsCh’s high activation energy barrier.

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