Lithium Diffusion Mechanism through Solid–Electrolyte Interphase in Rechargeable Lithium Batteries

Abstract

The composition, structure, and the formation mechanism of the solid–electrolyte interphase (SEI) in lithium-based (e.g., Li-ion and Li metal) batteries have been widely explored in the literature. However, very little is known about the ion transport through the SEI. Understanding the underlying ion diffusion processes across the SEI could lead to a significant progress, enabling the performance increase and improving safety aspects of batteries. Herein, we report the results of first-principles density functional theory calculations on the dominant diffusion pathways, energetics, and the corresponding diffusion coefficients associated with Li diffusion through the polycrystalline SEI. This paper is particularly concerned with the Li diffusion through the grain boundary (GB) formed between the three major inorganic components of the SEI, such as Li2O, LiF, and Li2CO3. It is found that Li diffusion occurs through the numerous open channels formed by the GB. The energetics and potential barriers vary significantly depending upon the structure of these channels, with the general trend being that Li diffusion in the GB is generally faster than in the neighboring crystalline regions within the grain interiors. In addition, the elastic properties of the GB are calculated allowing for more profound understanding of the SEI stability and formation.

Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model‐Type Solid Electrolyte Interphases

“…At present, the transport mechanism of the Li + ions across the galvanostatically formed SEI is not clear. It is conceivable that the Li + ions are either transported very slowly across the pores due to specific ion/pore wall interactions or pore transport is so strongly hindered that the Li + ions move across the solid phase of the SEI, e. g. along grain boundaries . Independent of which transport mechanism predominates, our results imply that ion transport across the solid phase of the SEI must be very slow.…”

A Sustainable Solid Electrolyte Interphase for High‐Energy‐Density Lithium Metal Batteries Under Practical Conditions

“…There are much different grain boundaries in SEI, mainly including heterogeneous and homogeneous grain boundaries. The heterogeneous grain boundaries are proven to exhibit the faster diffusion of Li ions than the homogeneous grain boundaries . The diffusion of Li ions in SEI are positively correlated with exchange current density ( I 0 , Figure h) .…”

“…[15,55] There are much different grain boundaries in SEI, mainly including heterogeneous and homogeneous grain boundaries.T he heterogeneous grain boundaries are proven to exhibit the faster diffusion of Li ions than the homogeneous grain boundaries. [59] Thed iffusion of Li ions in SEI are positively correlated with exchange current density (I 0 ,F igure 3h). [60,61] Theexchange current density of FN-SEI (I 0 = 5.21 mA cm À2 ) is much larger than that in F-SEI (I 0 = 0.15 mA cm À2 )and N-SEI (I 0 = 0.06 mA cm À2 ).…”

Active formation of Li-ion batteries and its effect on cycle life

“…The electrolyte decomposes upon the surface of the fresh graphite anode and this results in the formation of the solid electrolyte interface (SEI) layer. This is a passivation layer, which is electrically resistive but conductive to the Li ions [16][17][18]. The SEI layer acts as a protective layer to prevent continuous electrolyte decomposition and solvent co-intercalation into graphitic layers during subsequent cycles [6,19].…”