XPS Analysis of Lithium Surfaces Following Immersion in Various Solvents Containing LiBF4

Abstract

The surface film on lithium immersed in various electrolytes was analyzed by x‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, and the potential sweep method. The surface film formed on lithium immersed in propylene carbonate or γ‐butyrolactone containing 1.0 mol dm−3 LiBF4 ( LiBF4/PC or LiBF4/γ‐BL ) for 3 days consists of normalLiF and a small amount of organic compounds. On the other hand, the surface film on lithium immersed in tetrahydrofuran (THF) containing 1.0 mol dm−3 LiBF4 false(LiBF4/THFfalse) consists of a large amount of organic compounds and normalLiF . normalLiF and organic compounds are formed by the chemical reaction of normalLiOH , Li2CO3 , and Li2O with HF involved in the electrolyte plus the direct reaction of the solvent with the lithium metal, respectively. The amount of organic compounds produced was influenced by the kind of solvent. For the formation of organic compounds, solvents have to permeate the normalLiF layer on the lithium. Probably, the permeability of the solvent is related to the formation of organic compounds. The permeability of the electrolyte is estimated quantitatively from the surface tension and viscosity. The surface tension and viscosity were obtained using the capillary rise method and Ostwald's viscometer, respectively. The surface tension and viscosity of LiBF4/THF were much smaller than those of LiBF4/PC or LiBF4/γ‐BL . This indicates that THF is more permeable than PC and γ‐BL. THF may easily reach the lithium metal surface to form a large amount of organic compounds. From these results, it can be concluded that the surface reaction of the lithium dose not only depends on the chemical properties of the lithium surface and electrolyte, but also on the physicochemical properties of the electrolyte.

Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries

“…[7][8][9] Research over the past four decades has contributed to an extensive understanding of the SEI formation and composition [26][27][28][29] and this understanding has been summarized in other reviews. [22][23][24] Briefly, the SEI is a thin film with a complex and heterogeneous sub-structure.…”

A Review of Solid Electrolyte Interphases on Lithium Metal Anode

“…(2) The mosaic model (Figure 2 b). [ 23,24 ] Relative to the preceding model, several reductive decompositions are proceeding on the negatively charged anode surface simultaneously and a mixture of insoluble multiphase products deposits on the anode. The formed SEI has a mosaic morphology, allowing the Li ions to migrate through the boundary of multiphase products.…”

Review of Local In Situ Probing Techniques for the Interfaces of Lithium‐Ion and Lithium–Oxygen Batteries

“…Thec oncept of the SEI was introduced for metallic Li, [21] for which am ultilayer structure was suggested. [23][24][25] Ac ompact inner layer (for instanceo fL i 2 Oa nd LiF) is covered by ap orous outer layer of organic compounds such as ROCO 2 Li. Them ultilayer structure emerges due to the changeo fd riving force during formation.…”