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Structures, Li + mobilities, and interfacial properties of solid electrolytes Li 3 PS 4 and Li<mml:…

2013; American Physical Society; Volume: 88; Issue: 10 Linguagem: Inglês

10.1103/physrevb.88.104103

1550-235X

Nicholas Lepley, N. A. W. Holzwarth, Yaojun A. Du,

Layered Double Hydroxides Synthesis and Applications

This work reports a computer modeling comparison of two solid electrolyte materials, Li${}_{3}$PO${}_{4}$ and Li${}_{3}$PS${}_{4}$, in terms of the bulk structures, Li ion mobilities, and their interface properties with vacuum and with Li metal. The simulations show that for some forms of Li${}_{3}$PS${}_{4}$, Li ions can move from a host lattice site to an interstitial site with negligible net energy change. This favorable process for the formation of vacancy-interstitial pairs is undoubtedly important for the structural and ion migration properties of $\ensuremath{\beta}$-Li${}_{3}$PS${}_{4}$. Our model results for the idealized interfaces between the electrolytes and Li metal show that Li${}_{3}$PO${}_{4}$ /Li interfaces are stable, while Li${}_{3}$PS${}_{4}$ /Li interfaces are not. We find that a Li${}_{3}$PS${}_{4}$ surface in the presence of a small amount of Li relaxes to a complicated structure involving broken P-S bonds. On the other hand, the computer models show that a very thin film of Li${}_{2}$S on the Li${}_{3}$PS${}_{4}$ surface can provide a protective buffer layer to stabilize the interface between the Li${}_{3}$PS${}_{4}$ electrolytes and the Li metal anode.