Lithium cathode reaction

The CF cathode reaction is beheved to be a heterogeneous process, initiated by the insertion of lithium ions between the CF planes. It is completed by the extmsion of LiF and the coUapse of the stmcture to carbon. 

The cathodic reaction is the reduction of iodine to form lithium iodide at the carbon collector sites as lithium ions diffuse to the reaction site. The anode reaction is lithium ion formation and diffusion through the thin lithium iodide electrolyte layer. If the anode is cormgated and coated with PVP prior to adding the cathode fluid, the impedance of the cell is lower and remains at a low level until late in the discharge. The cell eventually fails because of high resistance, even though the drain rate is low. 

In batteries of this type, solntions of lithium salts in thionyl chloride, SOCI2, are nsed as the electrolyte. Exceptionally, this strongly oxidizing solvent also serves as the active material for the cathodic reaction. Thus, during discharge thionyl chloride is electrochemicaUy reduced at a cathode made of carbon materials ... 

Yet we can note that there is still another mechanistic possibility in at least reactions nos. 3 and 10. In both cases blank runs revealed that lithium metal precipitated on the cathode at very negative potentials, and in one instance (Sternberg et al., 1966) it was suggested that the reaction takes place via solvated lithium metal, i.e. an indirect reaction analogous to the Birch reduction. One could even say that the reaction takes place at a lithium cathode. 

The Birch and Benkeser reactions of some unsaturated organic compounds [318 and references therein], which consist of a reduction by sodium or lithium in amines, can be mimicked electrochemically in the presence of an alkali salt electrolyte. The cathodic reaction is not the deposition of alkali metal on the solid electrode but the formation of solvated electrons. Most of the reactions described were performed in ethylenediamine [319] or methylamine [308,320]. A feature of these studies is variety introduced by the use of a divided or undivided cell. In a divided cell, the product distribution appears to be the same as that in the classic reduction by metal under similar conditions. In contrast, in an undivided cell the corresponding ammonium salt is formed at the anode it plays the role of an in situ generated proton donor. Under such conditions, the proton concentration... 

Lithium batteries can be either primary or secondary, depending on which reduchon reachons are coupled to the oxidahon of hthium. For example, some hthium batteries use the same cathode reaction as zinc-carbon dry cells, the reduchon of manganese(IV) oxide (Mn02) to manganese(III) oxide (Mn203). These baheries produce electric current at about 3 V compared to 1.5 V for zinc-carbon cells. Lithium batteries last much longer than other kinds of batteries. As a result, they are often used in watches, computers, and cameras to maintain hme, date, memory, and personal sethngs—even when the device is turned off. 

Lithium aluminates are also important in the development of molten carbonate fuel cells (MCFC) [82, 83], In these fuel cells, a molten carbonate salt mixture is used as an electrolyte. These fuel cells operate through an anode reaction, which is a reaction between carbonate ions and hydrogen. A cathode reaction combines oxygen, C02, and electrons from the cathode to produce carbonate ions, which enter the electrolyte. These cells operate at temperatures of 650°C and the electrolyte, which is usually lithium and potassium carbonate, is suspended in an inert matrix, which is usually a lithium aluminate. 

In other cases, crystal lattice decomposition occurs under cathodic insertion of lithium, and the cathodic process becomes irreversible. In this case, the product of the cathodic reaction is a mixture of a lithium compound (oxide, chalcogenide) with a reduced form, particularly, directly with a metal. It is such processes that occur when iron sulfide or copper oxide are used ... 

Lithium-air batteries [28] may also use a solid separator that will block dendrite growth from the anode to the cathode but allows permeation of the Li" ion between an anolyte and a catholyte. The simplest such separator would be a solid Li -ion solid electrolyte, but a porous glass containing the liquid electrolyte has been used where the anolyte and the catholyte are identical. As in the Zn-air primary battery, a porous carbon containing an oxygen-reduction catalyst on the pore walls and the liquid electrolyte in the pores provides the structure needed to facilitate the catalytic reaction of Li" ions with the gaseous O2 cathode. The cathodic reaction... 

Pensado et al. [2001] Lithium. Cation and anion vacancies, LiH hydride barrier layer, LiOH outer layer Irreversible reactions with kinetic effects, barrier layer and outer layer dissolution Concentrations of cation and anion vacancies and barrier layer thickness First impedance analysis of bilayer structure and of hydride barrier layer. Cathodic reaction included in the model... 

Kruesi, W.F. and Fray, D.J. (1994) Fundamental study of the anodic and cathodic reactions during the electrolysis of a lithium carbonate-lithium chloride melt using a carbon anode. J. Appl. Electrochem., 24, 1102-1108. 

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