Alkaline batteries

The most common primary (nonrechargeable) batter) is the alkaline battery ( FIGURE 20.20). The anode is powdered zinc metal immobilized in a gel in contact with a concentrated solution of KOH (hence, the name alkaline battery). The cathode is a mixture of 

A FIGURE 20.20 Cutaway view of a miniature alkaline battery. 

Mn02(s) and graphite, separated from the anode by a porous fabric. The battery is sealed in a steel can to reduce the risk of any of the concentrated KOH escaping. 

The cell reactions are complex but can be approximately represented as follows  

---

Indium chemicals and electroplated metal deposits ate replacing mercury (qv) in the manufacture of alkaline batteries (qv). Indium, like mercury, functions to reduce outgassing within the battery and promotes the uniform corrosion of the anode and cathode while the battery is under electrical load. Indium inorganic chemicals also find use as catalysts in various chemical processes. 

Uses. Nickel nitrate is an intermediate in the manufacture of nickel catalysts, especially those that are sensitive to sulfur and therefore preclude the use of the less expensive nickel sulfate. Nickel nitrate also is an intermediate in loading active mass in nickel—alkaline batteries of the sintered plate type (see Batteries, SECONDARY cells). Typically, hot nickel nitrate symp is impregnated in the porous sintered nickel positive plates. Subsequendy, the plates are soaked in potassium hydroxide solution, whereupon nickel hydroxide [12054-48-7] precipitates within the pores of the plate. 

However, the reaction with water can be made to be extremely slow. Because the alkaline electrolyte is corrosive toward human tissue as well as toward the materials ia devices, it is more important to have a good seal toward preventing electrolyte leakage ia an alkaline battery than ia a carbon—2iac cell. The formation of a good seal is, however, iacompatible with the formation of a noncondensable gas like hydrogen. 

Cathode Reaction. There are many different types of manganese dioxide (18), having varying activity in batteries. The only type suitable for alkaline batteries is y-Mn02, the mineral form of which is nsutite. The chemical composition of has been described (19) by the general formula... 

Cylindrical alkaline cells are made in only a few standard si2es and have only one important chemistry. In contrast, miniature alkaline cells are made in a large number of different si2es, using many different chemical systems. Whereas the cylindrical alkaline batteries are multipurpose batteries, used for a wide variety of devices under a variety of discharge conditions, miniature alkaline batteries are highly speciali2ed, with the cathode material, separator type, and electrolyte all chosen to match the particular appHcation. 

The chemistry is the same as for alkaline manganese—dioxide batteries. The constmction features are typical of the other miniature alkaline batteries. 

Table 2. Technology and Processing Contributions to Alkaline Battery Development...

The potassium hydroxide electrolyte used in alkaline batteries is a corrosive hazardous chemical. It is a poison and if ingested attacks the throat and stomach linings. Immediate medical attention is required. It slowly attacks skin if not rapidly washed away. Extreme care should be taken to avoid eye contact that can result in severe bums and blindness. Protective clothing and face shields or goggles should be worn when filling cells with water or electrolyte and performing other maintenance on vented batteries. 

Because of increasing environmental concerns, the disposal of all batteries is being reviewed (70—76). Traditionally silver batteries were reclaimed for the silver metal and all other alkaline batteries were disposed of in landfills or incinerators. Some aircraft and industrial nickel —cadmium batteries are rebuilt to utilize the valuable components. 

Cadmium nitrate is the preferred starting material for Cd(OH)2 for use as the anode ia alkaline batteries. The siatered anode matrix of such batteries is saturated with cadmium nitrate (480—500 g/L Cd) and cadmium hydroxide is formed thereia by standardized electrolysis and dryiag (37). The tetrahydrate sells for 29.10/kg ia 20 kg lots. Other uses iaclude photographic emulsions and as a colorant ia glass and ceramics. 

Replace alkaline batteries frequently (once a month). Also carry fresh replacement batteries with the equipment. 

For small high-speed engines, electric start systems, incorporating lead-acid or alkaline batteries, are practical. 

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. 

For new components, the nickel coating is usually 25-250 im thick. Normally, the deposits are not machined. Applications include pump bodies, laundry plates, heat exchanger plates, evaporator tubes, alkaline battery cases and food-handling equipment of various sorts. 

Batteries using an alkaline solution for electrolyte are commonly called alkaline batteries. They are high-power owing to the high conductivity of the alkaline solution. Alkaline batteries include primary batteries, typical of which are alkaline-manganese batteries, and secondary batteries, typical of which are nickel-cadmium and nickel-metal hydride batteries. These batteries are widely used. 

Alkaline batteries were introduced in the early 1960s they last two to five times longer than Zn-carbon cells on continuous discharge and command two or three times the price in the USA (far more in Europe and the East). Alkaline cells became a necessary invention and they succeeded as a result of the requirements of the electronic devices. The essential improvement was the change from ammonium chloride and/or zinc chloride electrolyte to alkaline (KOH) electrolyte, the steel can construction, the outside cathode, and the zinc powder (large surface) anode. A main low-cost feature is that they use pressed cathodes and do not need to follow "jellyroll"... 

Table 1 showed that the growth in the primary (single-use) Zn - Mn02 battery market will be entirely in the alkaline field because in the less-developed countries there will be the strong trend toward alkaline batteries. Zn-Carbon batteries will certainly not disappear, but their poor quality in some regions is an area for improvements (Table 2). 

The Small-Format Alkaline Battery Market in the USA and Europe, and Internationally... 

Table 3 shows that the distribution of alkaline batteries correlates with the statistics of per-capita income. Zn-carbon batteries can be afforded more easily, alkaline batteries cost at least twice as much. However, the electronic "push" for high-quality batteries with good continuous load per-... 

The design of a AA-size alkaline manganese dioxide cell is shown in Fig. 1 (Sec. 3.1). Primary and secondary alkaline batteries are constructed in the same way and can be manufactured on essentially the same machinery. The separator material, electrode formulation, and the Mn02 Zn balance are different. Rechargeable cells are zinc-limited to prevent a discharge beyond the first electron-equivalent of the MnOz reduction. The electrolyte is 7-9 mol L KOH. The electrode reactions are ... 

However, a smart management of one of the large primary alkaline battery producers may do both, i.e., accelerate the alkaline conversion of the Zn-carbon batteries and at the same time supply the con-... 

Nickel hydroxides have been used as the active material in the positive electrodes of several alkaline batteries for over century [1], These materials continue to attract much attention because of the commercial importance of nickel-cadmium and nickel-metal hydride batteries. In addition to being the cathode active material in nickel-metal hydride batteries, Ni(OH)2 is an important corrosion product of the anode during cycling. There are several reviews of work in the field [2-10],... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

These parameters are critical to the operation of alkaline batteries. Evaluation of... 

Of all possible manufacturing proceses for macroporous separators to be employed in alkaline batteries, the wet-fleece process using paper machines is the predominant one [130] it permits a very uniform ( cloud-free ) production of such material and the use of different types of fibers as well as of short and very thin fibers, thus achieving a uniform structure of small pores (Table 15). 

Very different microporous separators for alkaline batteries are included in Table 16. The very thin (-25 ftm) films of stretched polypropylene ( Celgard ) are generally employed in combination with... 

---