Primary cathode materials

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). 

Conductive paints (resins) have recently been used for the cathodic protection of steel reinforcing bars in concrete, but they are always used in conjunction with a primary anode material, e.g. platinised-niobium or platinised-titanium wire or a conductive polymer rod. 

An inspection of Tables 1 and 2 shows that appropriate solvents for lithium batteries mainly belong to classes 6 and 7 and include cyclic (EC, PC) and open-chain (DMC, MEC, DEC, MPC) esters and ethers (DIOX, DME, THF) as well as inorganic sulfur compounds (S02, SOCl2). These sulfur compounds are mainly used as liquid cathode materials, simultaneously serving as solvents (S02C12, SOCl2) or cosolvents (S02) in primary or secondary lithium batteries. Recent developments of solvents include... 

Preliminary electrochemical tests of materials obtained have been performed in two types of cells. Primary discharge measurements have been executed in standard 2325 coin-type cells (23 mm diameter and 2.5 mm height) with an electrolyte based on propylene carbonate - dimethoxyethane solution of LiC104. Cathode materials have been prepared from thermally treated amorphous manganese oxide in question (0.70 0.02g, 85wt%.) mixed with a conductive additive (10 % wt.) and a binder (5wt%). Lithium anodes of 0.45 mm thickness have been of slightly excess mass if compared to the stoichiometric amount, so as to ensure maximal possible capacity of a cell and full consumption of the cathode material. 

The electrochemical behavior of thin-film oxide-hydroxide electrodes containing chromium, nickel and cobalt compounds was investigated. Experimental results have shown that such compounds can be successfully used as active cathodic materials in a number of emerging primary and secondary battery applications. 

Thin-film electrodes have promise in the development of flexible power sources (primary and secondary). It must be taken into account that change in cathodic material crystal lattice must not be over 20% as a result of intercalation of Li+, Na+ or FT [4], The electrodes must be chemically active and have both electron and ion conductivity. In connection with these... 

Reduction potentials also depend greatly on the nature of the cathode material as shown in Table 2 [8], For example, primary perfluoroalkyl iodides are ca. 0.3 V easier to reduce at mercury than at platinum due to the strong interaction of Rfl with mercury. In fact, cathodic reduction of Rfl at a mercury cathode provides RfHgl [9]. 

Fluorides of simple carbon are well-known they have the general formula (Cly) and are widely used as cathodic material in high-energy primary batteries. 

For secondary alkyl iodides, the two one-electron polarographic waves are more separated. Reduction of 2-iodooctane at the potential of the first wave alfords the dialkylmercury and 7,8-dimethyl-tetradecane by reactions of the sec-octyl radical. At the potential of the second wave only octane and octenes are isolated [37]. 2-Bromooctane shows only one polarographic wave and yields octane and octene on reduction at any potential [37]. Radicals generated by reduction of primary and secondary iodoalkanes will react with other cathode materials including tin, lead and thallium to form metal alkyls [48,49],... 

Electrolytes are generally lithium salts dissolved in aprotic solvents or added to the liquid electroactive molecules as supporting electrolytes to carry the current through the cell. Before describing a number of primary cells of technical and commercial importance, the general properties of the electrolytes, the lithium anode and the more common cathode materials will be discussed. Secondary cells are discussed in Chapter 7. 

Primary alkaline cells use sodium hydroxide or potassium hydroxide as tlie electrolyte. They can be made using a variety of chemistries and physical constructions. The alkaline cells of the 1990s are mostly of the limited electrolyte, dry cell type. Most primary alkaline cells are made sing zinc as the anode material a variety of cathode materials can be used. Primary alkaline cells are commonly divided into tW o classes, based on type of construction the larger, cylindrically shaped batteries, and the miniature, button-type cells. Cylindrical alkaline batteries are mainly produced using zinc-manganese dioxide chemistry, although some cylindrical zinc-mercury oxide cells are made. 

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