Anode in batteries

Electrode corrosion is the critical problem associated with the use of metal hydride anodes in batteries. The extent of corrosion is essentially determined by two factors alloy expansion and contraction in the charge-discharge cycle, and chemical surface passivation by the formation of corrosion—resistant oxides or hydroxides. 

Graphene hybrids with Sn02, MoS2 and WS2 as anodes in batteries... 

There are studies in which the fact that active metal electrodes are covered with surface films is not so important, e.g., when these metals are used as counterelectrodes, or when they are studied as practical anodes in batteries. However, even in these cases, the native active metals as received may be covered with two thick films. It is therefore, necessary to remove the initial native film covering the active metal under an inert atmosphere. The passivating films of lithium and calcium can be scraped off with a stainless steel knife. In the case of harder active metals such as magnesium and aluminum, an abrasive cloth or... 

As discussed in Ref. 84, Li/Hg amalgam cannot be a model system for solid Li surfaces, because reduction of solution species on the liquid Li/Hg interface does not produce stable surface films. Thus, a massive solvent reduction may occur on Li/Hg in which each solvent molecule reacts directly with the bare active surface. In such a situation, PC and EC are indeed reduced directly to Li2C03 [84,131], However, R0C02Li species are major reduction products of PC and EC on Li/Hg as well. It should be noted that when the Li is initially covered by native surface films (Li20, Li2C03), the situation is more complicated. Only part of the native surface films may be replaced upon storage in the solutions thus, in such a case the nature of the surface films remains more inorganic than in the case of fresh Li surfaces [101-105], In any event, upon Li deposition or dissolution, the replacement of the native surface films by solution reduction products is fast and pronounced, and the above-described surface chemistry is very relevant to practical Li anodes in batteries. 

It has been mentioned already that polypyrrole (25) and polythiophene (26) play an important role as electrical conductors and polymeric anodes in battery cells [2,47,226]. Since the charging and discharging of the conjugated polymer is accompanied by the incorporation and removal of counterions it is clear that the material can also act as a carrier of chemically different anions which influence the physical, chemical and physiological properties of the material [292]. With regard to the full structural elucidation of the polymers it must be added, however, that the electropolymerization process of pyrrole and thiophene does not provide a clean coupling of the heterocycles in the 2,5-positions. Instead, the 3- and 4-position can also be involved giving rise to further fusion processes under formation of complex polycyclic structures [47]. 

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. 

Electrode corrosion is the critical problem associated with the use of MH anodes in batteries. The extent of corrosion is essentially determined by two factors alloy expansion and contraction in the charge-discharge cycle and chemical surface passivation via the formation of corrosion resistant oxides or hydroxides. Both factors are sensitive to alloy composition, which can be adjusted to produce electrodes having an acceptable cycle life. In AB5 alloys the effects of Ce, Co, Mn, and Al upon cycle life in commercial type AB5 electrodes are correlated with lattice expansion and charge capacity. Ce was shown to inhibit corrosion even though lattice expansion increases. Co and Al also inhibit corrosion. XAS results indicate that Ce and Co inhibit corrosion via surface passivation. 

Silver reduces the oxygen evolution potential at the anode, which reduces the rate of corrosion and decreases lead contamination of the cathode. Lead—antimony—silver alloy anodes are used for the production of thin copper foil for use in electronics. Lead—silver (2 wt %), lead—silver (1 wt %)—tin (1 wt %), and lead—antimony (6 wt %)—silver (1—2 wt %) alloys ate used as anodes in cathodic protection of steel pipes and stmctures in fresh, brackish, or seawater. The lead dioxide layer is not only conductive, but also resists decomposition in chloride environments. Silver-free alloys rapidly become passivated and scale badly in seawater. Silver is also added to the positive grids of lead—acid batteries in small amounts (0.005—0.05 wt %) to reduce the rate of corrosion. 

Batteries. Many batteries intended for household use contain mercury or mercury compounds. In the form of red mercuric oxide [21908-53-2] mercury is the cathode material in the mercury—cadmium, mercury—indium—bismuth, and mercury—zinc batteries. In all other mercury batteries, the mercury is amalgamated with the zinc [7440-66-6] anode to deter corrosion and inhibit hydrogen build-up that can cause cell mpture and fire. Discarded batteries represent a primary source of mercury for release into the environment. This industry has been under intense pressure to reduce the amounts of mercury in batteries. Although battery sales have increased greatly, the battery industry has aimounced that reduction in mercury content of batteries has been made and further reductions are expected (3). In fact, by 1992, the battery industry had lowered the mercury content of batteries to 0.025 wt % (3). Use of mercury in film pack batteries for instant cameras was reportedly discontinued in 1988 (3). 

Electronic and Electrical Applications. Sulfolane has been tested quite extensively as the solvent in batteries (qv), particularly for lithium batteries. This is because of its high dielectric constant, low volatUity, exceUent solubilizing characteristics, and aprotic nature. These batteries usuaUy consist of anode, cathode polymeric material, aprotic solvent (sulfolane), and ionizable salt (145—156). Sulfolane has also been patented for use in a wide variety of other electronic and electrical appHcations, eg, as a coil-insulating component, solvent in electronic display devices, as capacitor impregnants, and as a solvent in electroplating baths (157—161). 

Adding teUurium to lead and to lead aUoyed with sUver and arsenic improves the creep strength and the charging capacity of storage battery electrodes (see Batteries). These aUoys have also been suggested for use as insoluble anodes in electrowinning. 

In batteries, a zinc anode undergoes the oxidation reaction,... 

Lithium as an anode in alkaline electrolyte has been considered in the battery system shown in Figure 29. Even though lithium reacts dkecdy with water, it was possible to operate the battery because of a protective lithium hydroxide film that forms on the anode. However, the film was not totally protective and units exhibited poor efficiency and were very complex. 

J.R. Dahn, A.K. Sleigh, Hang Shi, B.W. Way, W.J. Weydanz, J.N. Reimers, Q. Zhong, and U. von Sacken, Carbons and Graphites as Substitutes for the Lithium Anode , in Lithium Batteries, G. Pistoia, Elsevier, North Holland (1993). 

U. von Sacken, Q. Zhong, Tao Zheng, and J.R. Dahn, Phenolic Resin Precursor Pregraphitic Carbonaceous Insertion Compounds and Use as Anodes in Rechargeable Batteries, Canadian Patent Application 2,146,426... 

Chapter 11 reports the use of carbon materials in the fast growing consumer eleetronies applieation of lithium-ion batteries. The principles of operation of a lithium-ion battery and the mechanism of Li insertion are reviewed. The influence of the structure of carbon materials on anode performance is described. An extensive study of the behavior of various carbons as anodes in Li-ion batteries is reported. Carbons used in commereial Li-ion batteries are briefly reviewed. 

The major uses of lead in the UK are in batteries, and in sheet and pipe of which the vast majority is sheet for building purposes. These applications account for about one third each of lead used. This situation is unique, since in all other countries batteries account for most of the lead market. A small but very important application is sheet and pipe for the chemical industry. Lead is no longer installed for water services. Lead cable sheathing which accounts for 5% is in general decline, but is valued in niche applications such as on oil rigs where resistance to hydrocarbons is important. The use of lead for anodes accounts for a very small tonnage, but is still of great importance to the industries which use them. 

Lead is characterised by a series of anodic corrosion products which give a film or coating that effectively insulates the metal mechanically from the electrolyte (e.g. PbS04, PbClj, PbjO, PbCrO<. PbO, PbO, 2PbC03.Pb<0H)z), of which PbS04 and Pb02 are the most important, since they play a part in batteries and anodes. Lead sulphate is important also in atmospheric passivation and chemical industry applications. 

In many aqueous solutions nickel has the ability to become passive over a wide range of pH values. The mechanism of passivation of nickel and the properties of passive nickel have been studied extensively—perhaps more widely than for any other element, except possibly iron. In recent years the use of optical and surface analytical techniques has done much to clarify the situation . Early studies on the passivation of nickel were stimulated by the use of nickel anodes in alkaline batteries and in consequence were conducted in the main in alkaline media. More recently, however, attention has been directed to the passivation of nickel in acidic and neutral as well as alkaline solutions. 

Lead dioxide on graphite or titanium substrates has been utilised as an anode in the production of chlorate and hypochlorites and on nickel as an anode in lead-acid primary batteries Lead dioxide on a titanium substrate has also been tested for use in the cathodic protection of heat exchangers and in seawater may be operated at current densities up to lOOOAm" . However, this anode has not gained general acceptance as a cathodic protection anode for seawater applications, since platinised Ti anodes are generally preferred. 

Aluminum is directly applied in its metallic form when it serves as battery anode. The battery concepts considered are in general single-use types (primary batteries). The most developed systems belong to the metal-air batteries, using the reduction of atmospheric oxygen as the cathode reaction, e.g., (-) A1 / KOH / 02 (+) or (-) A1 / seawater / 02 (+). The main discharge reactions are ... 

The lead electrode used as anode in the well-known lead-acid battery is a rather... 

Unfortunately, both lithium and the lithiated carbons used as the anode in lithium ion batteries (Li C, l>x>0) are thermodynamically unstable relative to solvent molecules containing polar bonds such as C-O, C-N, or C-S, and to many anions of lithium salts, solvent or salt impurities (such as water, carbon dioxide, or nitrogen), and intentionally added traces of reactive substances (additives). 

Electrons appear as products, so this half-reaction is the oxidation, which takes place at the anode. The lead electrode is an active anode in a lead storage battery. 

It follows that in batteries, the negative electrode is the anode and the positive electrode is the cathode. In an electrolyzer, to the contrary, the negative electrode is the cathode and the positive electrode is the anode. Therefore, attention must be paid to the fact that the concepts of anode and cathode are related only to the direction of current flow, not to the polarity of the electrodes in galvanic cells. 

Cathodic hydrogen evolution is one of the most common electrochemical reactions. It is the principal reaction in electrolytic hydrogen production, the auxiliary reaction in the production of many substances forming at the anode, such as chlorine, and a side reaction in many cathodic processes, particularly in electrohydrometallurgy. It is of considerable importance in the corrosion of metals. Its special characteristic is the fact that it can proceed in any aqueous solution particular reactants need not be added. The reverse reaction, which is the anodic ionization of molecular hydrogen, is utilized in batteries and fuel cells. 

Another group of important battery characteristics are the lifetime parameters. For primary batteries and charged storage batteries, a factor of paramount importance is the rate of self-discharge. Self-discharge may be the result of processes occurring at one of the electrodes (e.g., corrosion of zinc in batteries with zinc anodes or the decomposition of higher metal oxides in batteries with oxide cathodes), or it... 

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