Solid electrolyte interphase layer

Chagnes A, Swiatowska J (2012) Electrolyte and solid-electrolyte interphase layer in lithium-ion batteries. In Belharouak I (ed) Lithium ion batteries—new developments. InTech, Rijeka, Croatia, doi 10.5772/1358... 

Electrochemical impedance spectroscopy (EIS) was used for the characterization. The results showed that a great amount of the lithium ions remains on the solid electrolyte interphase layer of the mesocarbon microbeads half ceU with fluoro-o-phenylenedimaleim-ide additive, indicating that the ion moves easily because of high diffusion (32). 

In particular, tris(pentafluorophenyl) borane enables the improvement of the properties by forming stable sohd electrolyte interphase layers and suppressing a surface pulverization. The solid electrolyte interphase layers have been characterized by a variety of analytical tools, including SEM, EIS, and XPS (65). 

This enhanced electrochemical performance could be ascribed to the formation of a stable solid electrolyte interphase layer, smaller charge transfer resistance, and better dispersion of Mo3Sb7 nanoparticles in the carbon matrix (119). 

Nadimpalli SP, Sethuraman VA, Dalavi S, Lucht B, Chon MJ, Shenoy VB, Guduru PR (2012) Quantifying capacity loss due to solid-electrolyte-interphase layer formation on silicon negative electrodes in lithium-imi batteries. J Power Sourc 215 145-151... 

When the anode is first charged, it slowly approaches the lithium potential and begins to react with the electrolyte to form a film on the surface of the electrode. This film is composed of products resulting from the reduction reactions of the anode with the electrolyte. This film is called the solid electrolyte interphase (SEI) layer [30], Proper formation of the SEI layer is essential to good performance [31-34], A low surface area is desirable for all anode materials to minimize the first charge related to the formation of SEI layer. Since the lithium in the cell comes from the lithium in the active cathode materials, any loss by formation of the SEI layer lowers the cell capacity. As a result, preferred anode materials are those with a low Brunauer, Emmett, and Teller (BET) surface area... 

Figure 18 Various models proposed for the surface films that cover Li electrodes in nonaqueous solutions. The relevant equivalent circuit analog and the expected (theoretical) impedance spectrum (presented as a Nyquist plot) are also shown [77]. (a) A simple, single layer, solid electrolyte interphase (SEI) (b) solid polymer interphase (SPI). Different types of insoluble Li salt products of solution reduction processes are embedded in a polymeric matrix (c) polymeric electrolyte interphase (PEI). The polymer matrix is porous and also contains solution. Note that the PEI and the SPI may be described by a similar equivalent analog. However, the time constants related to SPI film are expected to be poorly separated (compared with a film that behaves like a PEI) [77]. (With copyrights from The Electrochemical Society Inc., 1998.)...

An example of an interphase is the well-known and explored electrical double layer. Another example is the passivating layer between electrode and electrolyte solutions. Such a layer on Li electrodes, which arises from the reductive decompositions of a small amount of the electrolyte solutions, was named SEI (solid electrolyte interphase). SEI is a crucial factor in the performance of Li-ion batteries since its nature and behavior affect Li-ion battery cycle-life, life time, power capability, and safety. Li electrodes (and Li-C electrodes as well) develop a classical interphase between them and all the relevant polar aprotic electrolyte solutions. All... 

We have seen that the idea of an electrode film system is useful for electrochemistry of molten salts including low-temperature ionic liquids. It is not restricted, however, to this field only. As an example, the protective layer on lithium metal in aprotic organic electrolytes could be mentioned. This layer, so-called solid electrolyte interphase (SEl), exhibits properties of a polyfunctional conductor with high ionic conductivity (Li ions are the carriers) and low electronic conductivity of semiconductive nature. Some peculiarities of film systems with semiconductive character of electronic conductivity are considered below. 

The irreversible part of the potential curve in Fig. 5.11 is the charge loss, which corresponds to the formation of a passivation layer at the graphite surface. This so-called solid electrolyte interphase (SEI) layer is formed by electrolyte decomposition products. The SEI layer is essential for the reversible electrochemical process because it passivates the graphite surface against further electrolyte decomposition. " However, the charge loss related to the SEI layer formation needs to be minimized, since it detreases the energy density of the ceU. 

Although reports following the initial marketing of Sony Corporation s batteries focused not only on metallic lithium anodes and graphite anodes but also on the solid electrolyte interphase (SEI), which forms on the anode as a result of electrolyte decomposition, intentional control of SEI was not considered in sufficient depth. The concept of SEI was advocated by Peled from Tel-Aviv University and Aurbach from Bar-Ilan University [8-10]. Nevertheless, upon entering the industry in 1997, Ube Industries, Ltd. started adding small amounts of additives to the electrolyte, which allowed for the undesirable thick SEI to be controlled by deliberately causing additive decomposition in order to form a controlled thin layer (CTL). 

Fig. 7.14 ExsituHRTEM near the surface of an epitaxial graphene film on a SiC [2 12 0] substrate after cathodic polarization in a Li metal cell, showing the structure of the SiC, the graphene layers, and the solid electrolyte interphase (SEl) with LiF crystals.

The layer of electrolyte decomposition products that forms at the interface between an electrode (primarily the anode) and the electrolyte, called the solid electrolyte interphase or solid electrolyte interface. The SEI is believed to be comprised of an inner SEI layer and an outer SEI layer. 

Anodic etching (AE) 2 Coulombic efficiency 5 Electrospraying (ES) 2 Lithium-ion batteries (LIBs) 1 Magnesiothermic reduction 2 Metal-assisted chemical etching (MACE) 2, 4 Solid-electrolyte interphase (SEI) layer 5... 

Note that in lead secondary batteries, the electrolyte is considered to be active material, because it takes part in the electrochemical reactions. In lithium secondary batteries, however, the role of the electrolyte is to transport the hthium ions from one electrode to the other. In the electrolyte, the concentration of lithium ions therefore remains constant, even down to the consumption of hthium over time to reconstitute the interface layer between the electrolyte and the carbon of the electrodes. This interface layer is called the SEI (Solid-Electrolyte Interphase). It is a passivation layer, whose role is explained in section 4.1. 

The layer formed instantaneously upon contact of the metal with the solution, consists of insoluble and partially soluble reduction products of electrolyte components. The thickness of the freshly formed layer is determined by the electron-tunneling range. The layer acts as an interphase between the metal and the solution and has the properties of a solid electrolyte with high electronic resistivity. For this reason it was called a solid-electrolyte interphase SEI. The batteries, consisting of SEI electrode, were called SEI batteries. ... 

It is well known that graphite is unstable in some aprotic electrolytes. For instance, when propylene carbonate (PC) is used as a solvent, the cointercalation of solvent molecules and the Li ions will lead to the exfoliation of graphite layers Only in some selected electrolyte systems such as LiPF in EC/DEC (EC for ethylene carbonate and DEC for diethyl carbonate), can graphite show better cycling behavior. Solvent decomposition on the surface of conductive carbon or lithium electrodes will lead to the formation of a passivating layer. Peled named this layer as solid electrolyte interphase (SEI). ° It is an ionic conductor but electron insulator, mainly composed of LijCOj and various lithium alkylcarbonates (ROCO Li) as well as small amounts of LiE, LijO, and nonconductive polymers. These compounds have been detected on carbon and Li electrodes in various electrolyte systems. Therefore, it would be an interesting question whether semiconductive nano-SnO anode is also sensitive to electrolyte and electrolyte decomposition takes place on it. This section will characterize the structures and compositions of the... 

The Solid-Electrolyte Interphase (SEI) layer formed on cycling the graphite anode of a Li-ion battery has been studied extensively in recent years since the first suggestion of its existence by Peled more than twenty years ago see elsewhere in this book. More recently, the cathode-electrolyte interface has also come to attract considerable attention. 

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