Atomistic modeling of LiF microstructure ionic conductivity and its influence on nucleation and plating

Structural Toughness of Fluorinated–Nitrided Interphase Passivation Layers for Lithium-Ion Batteries: A Reactive Molecular Dynamics Study

“…In a quest to explain changes in lithium kinetics at the SEI level, theoretical investigations found higher Li + diffusivity along grain boundaries, compared to pure crystalline LiF. , In more recent advancements, we observed a direct link between enhanced Li transport properties and a disturbed amorphous phase that would normally be unstable under ambient conditions . Furthermore, the presence of highly lithiophilic impurities, like nitrides, in LiF has been found to facilitate the otherwise elusive amorphous phase stability, dramatically improving transport and mechanical properties in the context of interfacial passivation. , This is consistent with recent experimental reports on the stabilizing influence of fluorinated–nitrided (FN) SEI layers, formed from the incorporation of both LiF-forming additives [such as lithium bis (fluorosulfonyl)­imide (LiFSI)] and Li 3 N-forming additives [like lithium nitrate (LiNO 3 )] in carbonate electrolytes. − The effective role of LiNO 3 seems to be linked to its spontaneous Li-induced decomposition, helping form uniform surface films comprising nitrides, oxynitrides, and oxides. , The lithiophilic nature of such nitride and oxide species obtained through NO 3 – breakdown was also shown to facilitate the amorphization of the inner SEI layer, producing enhanced interface properties like super Li + -ion conductivity .…”

“…37 In a quest to explain changes in lithium kinetics at the SEI level, theoretical investigations found higher Li + diffusivity along grain boundaries, compared to pure crystalline LiF. 38,39 In more recent advancements, we observed a direct link between enhanced Li transport properties and a disturbed amorphous phase that would normally be unstable under ambient conditions. 40 Furthermore, the presence of highly lithiophilic impurities, like nitrides, in LiF has been found to facilitate the otherwise elusive amorphous phase stability, dramatically improving transport and mechanical properties in the context of interfacial passivation.…”

Amorphization of Inorganic Solid Electrolyte Interphase Components and Its Impact on Enhancing Their Transport and Mechanical Properties

“…In the case of LiF, the notion that it possesses an unacceptably low Li + conductivity was challenged by experimental reports that pointed to its presence in the SEI as being beneficial for a stable, homogeneous Li + flux. − Considering the likelihood of a polycrystalline coexistence at interfaces, faster Li diffusion channels were observed along mixed LiF/Li 2 O grain boundaries (GB) Furthermore, fast charging with desirable Li kinetics, along with improved stability, was attributed to amorphous or disordered looking SEI, notably rich in LiF . Additionally, detailed experimental analysis of electrolytes containing LiF salts as additives remarkably exhibited room temperature conductivities above 10 –3 S/cm over the range of LiF compositions considered .…”

“…47,48 Furthermore, fast charging with desirable Li kinetics, along with improved stability, was attributed to amorphous or disordered looking SEI, notably rich in LiF. 49 Additionally, detailed experimental analysis of electrolytes containing LiF salts as additives remarkably exhibited room temperature conductivities above 10 −3 S/cm over the range of LiF compositions considered. 50 Thus, it would appear plausible that idealized models with ordered structures and intrinsically low ionic diffusivity are quite different from their manifestations within the constraints of an SEI environment.…”

Data-Driven Path Collective Variables

“…Finally, we investigate the association of Li + and F – ions in solution; this mechanism is an important precursor of the formation of the solid electrolyte interphase (SEI) in Li-ion batteries; , its understanding is therefore crucial to design devices with greater lifetimes. We select water as a solvent, both for simplicity and because an LiF-rich SEI forms at the negative electrode in Li-ion batteries based on aqueous electrolytes .…”