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Electrodes in nonaqueous electrolytes

On the fundamental front, Dahn et al. successfully accounted for the irreversible capacity that accompanies all carbonaceous anodes in the first cycling. They observed that the irreversible capacity around 1.2 V follows an almost linear relation with the surface area of the carbonaceous anodes and that this irreversible process is essentially absent in the following cycles. Therefore, they speculated that a passivation film that resembles the one formed on lithium electrode in nonaqueous electrolyte must also be formed on a carbonaceous electrode via similar electrolyte decompositions, and only because... [Pg.91]

Peled s Model Anode/Electrolyte Interface Film. In their proposal of SEI formation on a carbonaceous electrode in nonaqueous electrolytes, Dahn actually adopted Peled s model for lithium s surface and extended it to carbonaceous electrodes. By this model, a two-dimensional passivation film is established via a surface reaction. [Pg.92]

Needless to say that a deep understanding of both the formation mechanism of the SEI layer and the underlaying question of carbon s surface chemistry in a particular electrolyte solution is of utmost importance for battery developers. Clearly, the surface chemistry of graphite electrodes plays a key role in their performance.259 312 325 343-352 A lot of work was devoted to decipher this very complicated surface chemistry. It is therefore not surprising that the advancement in the understanding of surface chemistry of carbon electrodes in nonaqueous electrolytes correlates well with the worldwide production rate of lithium-ion batteries. [Pg.291]

Fig. 12. Solid electrolyte interface (SEI) model for surface formed on lithium metal and graphite electrodes in nonaqueous electrolytes. Fig. 12. Solid electrolyte interface (SEI) model for surface formed on lithium metal and graphite electrodes in nonaqueous electrolytes.
B. Markovsky, F. Amalraj, H. E. Gottlieb, Y. Gofer, S. K. Martha, D. Aurbach, J. Electrochem. Soc. 2010, 157, A423-A429. On the electrochemical behavior of aluminum electrodes in nonaqueous electrolyte solutions of lithium salts. [Pg.61]

Table 1.3. Metal electrode potentials in nonaqueous ) electrolyte systems ). Table 1.3. Metal electrode potentials in nonaqueous ) electrolyte systems ).
For most potentiometric measurements either the saturated calomel reference electrode or the silver/silver chloride reference electrode are used. These electrodes can be made compact, are easily produced, and provide reference potentials that do not vary more than a few millivolts. The discussion in Chapter 5 outlines their characteristics, preparation, and temperature coefficients. The silver/silver chloride electrode also finds application in nonaqueous titrations, although some solvents cause the silver chloride film to become soluble. Some have utilized reference electrodes in nonaqueous solvents that are based on zinc or silver couples. From our own experience, aqueous reference electrodes are as convenient for nonaqueous systems as are any of the prototypes that have been developed to date. When there is a need to rigorously exclude water, double-salt bridges (aqueous/nonaqueous) are a convenient solution. This is true even though they involve a liquid junction between the aqueous electrolyte system and the nonaqueous solvent system of the sample solution. The use of conventional reference electrodes does cause some difficulties if the electrolyte of the reference electrode is insoluble in the sample solution. Hence the use of a calomel electrode saturated with potassium chloride in conjunction with a sample solution that contains perchlorate ion can cause erratic measurements due to the precipitation of potassium perchlorate at the junction. Such difficulties normally can be eliminated by using a double junction that inserts another inert electrolyte solution between the reference electrode and the sample solution (e.g., a sodium chloride solution). [Pg.36]

FIGURE 8.31 Voltage profiles of various hybrid systems in nonaqueous electrolytes (NAH) including Li-intercalation electrodes compared with a nonaqueous (NA) EDLC based on activated carbon electrodes cycled to 3 V. All profiles are normalized with respect to each other. (From Plitz, I., et al., Appl. Phys. A, 82, 615, 2006. With permission.)... [Pg.362]

Ohzuku T, Iwakoshi Y, Sawai K. Formation of lithium-graphite intercalation compounds in nonaqueous electrolytes and their application as a negative electrode for a lithium ion (shuttlecock) cell. J Electrochem Soc 1993 140 2490-2498. [Pg.501]

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.)... 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.)...
Nonaqueous electrolyte solutions can be reduced at negative electrodes, because of an extremely low electrode potential of lithium intercalated carbon material. The reduction products have been identified with various kinds of analytical methods. Table 3 shows several products that detected by in situ or ex situ spectroscopic analyses [16-29]. Most of products are organic compounds derived from solvents used for nonaqueous electrolytes. In some cases, LiF is observed as a reduction product. It is produced from a direct reduction of anions or chemical reactions of HF on anode materials. Here, HF is sometimes present as a contaminant in nonaqueous solutions containing nonmetal fluorides. Such HF would be produced due to instability of anions. A direct reduction of anions with anode materials is a possible scheme for formation of LiF, but anode materials are usually covered with a surface film that prevents a direct contact of anode materials with nonaqueous electrolytes. Therefore, LiF formation is due to chemical reactions with HF [19]. Where does HF come from Originally, there is no HF in nonaqueous electrolyte solutions. HF can be produced by decomposition of fluorides. For example, HF can be formed in nonaqueous electrolyte solutions by decomposition of PF6 ions through the reactions with H20 [19,30]. [Pg.526]

Winter, M. Wrodnigg, G.H. Besenhard, J.O. Biberacher, W. Novak, P. Dilatometric investigations of graphite electrodes in nonaqueous lithium battery electrolytes. J. Electrochem. Soc. 2000, 147, 2427. [Pg.1481]

Bulk electrolyses are used to prepare one-electron reduction or oxidation products. If cyclic voltammetry (CV) reveals reversible redox, the bulk preparation of the reduced (or oxidized) product may be attained. The overall electrode process may be different in controlled-potential electrolysis and in CV because of the time factor (see below). The iron cluster, (h -CjHjFeCO), in nonaqueous electrolytes undergoes a four-membered electron-transfer CV series through three steps. The potentials measured (in CHjCN/O.l M [n-Bu N] [PFJ) are ... [Pg.213]

Oxalic acid is formed as a major product in nonaqueous electrolytes, and is further reduced to higher carboxylic acids (glyox 1-ic acid, glycolic acid etc.) at Cr-Ni-Mo steel electrodes,Pb and Hg electro des ... [Pg.113]

Table 6 and the discussion above showed tliat Ni, Fe, Pt, and Ti electrodes, inert to CO2 reduction in aqueous media at 1 atm, yield products in nonaqueous electrolyte solution. HER and CO2 reduction proceed in parallel competitively in aqueous electrolytes saturated with CO2. Nonaqueous electrolyte solution does not contain water except small amount of residual one, and thus CO2 reduction will take place with HER severely suppressed. [Pg.116]

Cd, Sn, and In, of medium CO selectivity, do not strongly adsorb CO2 . CO2 will be mostly freely present in aqueous electrolyte owing to the hydrogen bond stabilization by water molecules high dielectric constant of water molecule will also contribute to the stabihzation of CO2 . CO2 " stabihzed in the electrolyte will be further reduced to HCOO . However, CO2 is not sufficiently stabilized in nonaqueous electrolyte due to lack of hydrogen bond formation and low dielectric constant of the solvents. Thus CO2 adsorbed on Cd, Sn, and In may be relatively stabler than CO2 dissolved in the electrolyte. These metals yield CO in nonaqueous media in the same manner as Au. Ag, and Zn in Fig. 11(2). The CO selectivity mentioned above will be closely connected to the stability of adsorbed CO2 on the electrode. [Pg.139]

The 17fb in nonaqueous electrolytes has been reported for some semiconductor electrodes [13,14]. [Pg.157]

In nonaqueous electrolytes based on some organic solvents metallic lithium is stable and can be used as anodes in batteries. Lithium and other alkali metals have highly negative electrode potentials (see Table 1.1). Thus batteries with lithium anodes have much higher EMF and OCV values than batteries with aqueous electrolytes. [Pg.68]


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Electrodes in Electrolytes

Electrolytes nonaqueous

In electrolytes

Nonaqueous

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