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Halogenated Sulfide-Based Solid Electrolytes and Their Interface with Lithium-Metal
Abstract
Electric vehicles (EV) require energetically strong and gravimetrically light rechargeable batteries. Presently, the most popular commercial rechargeable batteries are Li-ion batteries (LIBs) with up to 250 Wh/kg. EV industry requires competitive driving range with combustion engine vehicles by improving battery energy density to 500 Wh/kg. Li-metal anodes and commercial cathodes can increase battery energy density to more than 408.5 Wh/kg. However, dendrite formation appears when Li-metal batteries (LMBs) are used with commercial carbonate-based liquid electrolytes and practically with all sorts of recently developed electrolytes, including solid electrolytes. An alternative to inhibit dendrite growth at the interface anode/electrolyte is perhaps a solid one instead of a liquid simply because the much higher hardness of the solid to the growth of a dendrite. Thus, a suitable solid-state electrolyte (SSE) characterized by low electrical conductivity, high Li-ion conductivity, being stable with Li-metal and metal oxide interfaces, and a wide electrochemical window would be required features to strongly increase the specifications so it can be use in EV.
Sulfide-based type SSE showed the highest ionic conductivity, in the range of 10⁻² S/cm, among SSE developed by now and wide electrochemical window to be used with high-voltage cathode materials. Li₇P₂S₈I (iodide-based) is characterized by high ionic conductivity and wide electrochemical window (EW).
In this thesis, we use ab initio methods to characterize the SSE Li₇P₂S₈X (LPSX) where X = F, Cl, or Br, through the computation of structure, energetics, bandgap, and ionic conductivity. The initial interphase formation LPSX (X = F, Cl, Br)/Li-metal is analyzed by solving the many-body Schrödinger equation using density functional theory (DFT). Ab initio simulations are performed with defined settings such as the number of atoms and temperature. The ensembles used are NVT (constant number of atoms, constant-volume, and constant-temperature) and NPT (constant number of atoms, constant pressure, and constant temperature).
Citation
Gamero Tornero, Milenka Karolyn (2022). Halogenated Sulfide-Based Solid Electrolytes and Their Interface with Lithium-Metal. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198479.