Button primary cells

Zinc-silver oxide batteries as primary cells are known both as button cells, e.g., for hearing aids, watches, or cameras, and for military applications, usually as reserve batteries. Since the latter after activation have only a very short life (a few seconds to some minutes), a separation by cellulo-sic paper is generally sufficient. 

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. 

With regard to cylindrical manganese and alkaline dry cells, which account for some 98% (on a weight basis) of all primary cells sold in Japan, no mercury has been used in the production since 1992. Furthermore, as the production of mercury cells was stopped at the end of 1995, the amount of mercury contained in the dry cells sold in Japan was equal to 1.4 tons in 1997, i.e. only 3% with respect to the 1985 s total (45 tons). In addition, as button type cells (alkaline, silver oxide and zinc-air cells) still contain a small amount of mercury, BAJ will continue to reduce it and promote the collection and recycling of spent dry cells. 

Soluble-cathode lithium primary batteries most times contain very toxic cathodes and flammable solvents. These types of batteries are seldom seen outside of the military in sizes larger than a button/coin cell. They are common in some heavy industrial or remote processes including oil-drilling operations. They are extremely common in many military forces throughout the world. 

The profitability of the recycling of lead accumulators and Ni-Cd accumulators depends on the metal prices. Due to fluctuations it swings between losses and profits. The recycling process for mercury button cells and for Mn02-Zn primary cells require financial subsidues. 

Lithium has a number of advantages over other materials for battery manufacture. It is the lightest tme metal, and it also has a high electrochemical reduction potential, that is, it occurs at the bottom of Table 9.1. There is one disadvantage in using lithium in that it is very reactive, a feature that poses problems not only in manufacture but also in the selection of the other battery components. Despite this, there are a large number of lithium-based primary cells available, both in traditional cylindrical form and as button and flat coin cells. 

Gas-proof constructions are often designed like commercial batteries (including button cells), so they can replace the primary cells in portable electric and microelectric devices. Meanwhile, usage of nickel-cadmium batteries is strongly limited by law because of the dangers related to toxic cadmium. 

Alkaline Primary Cells, Fig. 9 Construction of a zinc-air (Zn-air) button cell with controlled air access, mainly used in hearing aids that fit into the ear hole. A tab is placed across the air access hole to prolong the shelf life... 

Carbon/Zinc Leclanche system 1.5 120 190 Primary cell as button, eyUndric, or prismatic cell... 

Besides the family of manganese dioxide cells with zinc as negative electrode during the last decades manifold other battery systems have been developed and produced for the market. More capacity and higher load ability were the motivation for research. Here can be named the mercury zinc cell, produced in millions of button cells each year for hearing aids, calculators, watches, cameras, etc. Never was it possible to create one universal cell doing the job for all kinds of applications. Always it has to be noticed that primary cells are specialists, exactly designed for a special application. So in 1980 the smallest button cell of the world was made by Varta with a diameter of 6.8 mm and a thickness of 0.7 mm for wristwatches. 

Most primary or dry cells with aqueous electrolytes employ single, thick electrodes arranged in parallel or concentric configurations. Typical battery configurations are categorized as cylindrical, bobbins, buttons, or coin cells. Some primary cells are made in prismatic and thin, flat constructions to achieve the lowest volume. These form factors yield poor energy density and power capacity levels. 

Fabrication of a battery or a cell determines how the device will function and how much it will cost to construct it. Several primary cells with aqueous electrolytes seem to use a single electrodes arranged in parallel or concentric configuration. Specific construction of this type of cell includes cylindrical or bobbin button, and coin. Small secondary cells use a wound or jelly roll construction feature, in which long thin electrodes are wound into a cylinder and placed in a metallic housing or container. This particular cell construction yields higher power density, but it... 

Alkaline-manganese dioxide primary cells and batteries are available in a variety of sizes, in both cylindrical and miniature (button-cell) configurations, as listed in Table 10.9. Some of the unit cell sizes listed are not available as single cells, but are used as components in multiple-cell batteries. Figure 10.21 shows the nominal capacity of various-size batteries as a function of weight and cell volume. 

In recent years, primary cells have been developed with improved voltage and reduced size. Cells the size of a large button are used in heart pacemakers, hearing aids and other medical uses as well as in watches and calculators. They have several advantages ... 

Metal-air and fuel cells are not discussed in detail in this book. A brief discussion follows in which the characteristics of zinc-air primary cells are eompared with those of other types of primary eell. Details are also given of zinc-air button cells. 

It is so universally applied that it may be found in combination with metal oxide cathodes (e.g., HgO, AgO, NiOOH, Mn02), with catalytically active oxygen electrodes, and with inert cathodes using aqueous halide or ferricyanide solutions as active materials ("zinc-flow" or "redox" batteries). The cell (battery) sizes vary from small button cells for hearing aids or watches up to kilowatt-hour modules for electric vehicles (electrotraction). Primary and storage batteries exist in all categories except that of flow-batteries, where only storage types are found. Acidic, neutral, and alkaline electrolytes are used as well. The (simplified) half-cell reaction for the zinc electrode is the same in all electrolytes ... 

Figure 1. Discharge curve of a primary button air - zinc cell PR-44 at the resistance 625 land at 293 K.

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

In Scotland, the cost of domestic mains electricity is 0.0713/kWh (in 1997). A D-size Leclanchd cell, delivering say 5 Wh, currently retails at 0.50. Thus, energy from the primary battery costs I00/kWh - a factor of over 1000 more expensive. For a 150 mWh zinc-silver oxide button cell, retailing at 1.50, the cost of energy is over 10 000/kWh ... 

Both of these copper-based lithium primaries are manufactured as button and bobbin-configured cylindrical cells. Copper oxyphosphate cells find particular application in high temperature environments. 

Nickel-cadmium sealed cells are now a commercially important consumer product. They find use, both as button and cylindrical cells, in portable cordless appliances such as power tools, electric razors and photoflash apparatus, and increasingly in hybrid mains/battery equipment such as portable tape recorders, radios and television receivers. Many of these cells are readily interchangeable with primary batteries. In recent years, advances in design have increased recharge rates cylindrical cells with sintered electrodes can now be fast charged from full discharge at up to the C/l rate of 80% of capacity. 

In the consumer sector uses for primary nonaqueous batteries include button or coin cells for watches, calculators and other small devices with relatively low power requirements. Larger cylindrical and prismatic rechargeable consumer-oriented nonaqueous batteries are essentially all based on a Li or, most frequently, Li-ion negative electrode technology and are increasingly widely used in many portable electronic devices. 

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