Batteries metal-solution interphase

When the current does not flow through battery the measurable diflerence in electric potential between the terminals of the two electrodes is the result of all the equilibrium potential differences at the interphase between the conducting phases in contact. In the example of the Daniell cell, with both electrodes having copper terminals, there are three interfacial potential differences (apart from the small liquid junction potential difference at the contact between the two electrolyte phases) one potential difference at the contact between the zinc rod and the copper terminal (Zn/Cu) and two potential differences at the metal-solution interphases (Zn/Zn + and Cu/Cu +), which are mainly due to the charge transfer processes. 

When the current flows through the battery—a net reduction reaction takes place at one electrode and a net oxidation reaction takes place at the other—the potential difference at each metal solution interphase is different from that at equilibrium. 

Usually, in a given electrolyte solution, there is a similarity in the mechanism of SEI formation on carbon and metallic lithium.285 353 354 The mechanisms of SEI formation on lithium in numerous electrolytes are investigated since about three decades. In about the last 15 years, the focus continuously shifted from metallic lithium to carbon. There are a huge number of publications covering manifold aspects of the carbon s reactivity with the electrolytes and/or the SEI formation. The reader of this chapter is referred to the books published in this field recently and especially to the primary literature listed therein. Examples include Nonaqueous Electrochemistry from 1999 edited by Aurbach,355 Advances in Lithium-Ion Batteries from 2002 edited by van Schalkwijk and Scrosati,356 and Lithium-Ion Batteries Solid-Electrolyte Interphase from 2004 edited by Balbuena and Wang.281... 

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 has been suggested that in practical non-aqueous lithium battery systems the anode (Li or graphite) is always covered by a surface layer named the solid electrolyte interphase (SEI), 1-3 run thick, which is instantly formed by the reaction of the metal with the electrolyte. This film, which acts as an interphase between the metal and the solution, has the properties of a solid electrolyte. This layer has a corrosive effect and grows with the cycling life of the battery [52], Thermodynamic stability of a lithium cell requires the electrochemical potentials of electrodes a and Ec located within the energetic window of the electrolyte, which contrains the cell voltage Eq of th electrochemical ceU to ... 

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