Batteries Leclanche

Sheets of galvanised iron are used for roofing, guttering and the like. Alloys of zinc, notably brass, are used extensively. The metal is used m wet and dry Leclanche batteries. 

Figure 2 shows a comparison of the discharge characteristics between alkaline-manganese batteries and Leclanche batteries. The capacity of the alkaline-manganese batteries is about three times as large as that of the Leclanche batteries. 

From the 1960s onward, alkaline zinc-manganese dioxide batteries started to be produced. They have appreciably better electrical performance parameters (see Section 19.4.3) but do not differ from Leclanche batteries in their operating features, are produced in identical sizes, and can be used interchangeably with them. Thus, a gradual changeover occurred and phaseout of the older system is now almost complete. 

Compared with the Leclanche batteries, alkaline manganese dioxide batteries offer better performance at high discharge currents and lower temperatures and a better shelf life. They are more expensive than Leclanche batteries, but their cost per unit of energy is competitive and resources of raw materials are sufficient for mass production of these batteries. 

Rather than natural ores as in Leclanche batteries, electrolytic manganese dioxide (EMD), which is produced by anodic oxidation of Mn ions at graphite electrodes in solutions of manganese salts, is used as the active material for the positive... 

Fig. 15.10. Two batteries in common use (a) The cylindrical Leclanche battery (b) The silver oxide/zinc button cell.

The long-familiar Daniell cell used a zinc electrode zinc sheeting is still much used in battery manufacture. Useful background material for this aspect of zinc chemistry is to be found in the article Electrochemistry Applications in Inorganic Chemistry, further details elsewhere.The original Leclanche battery (1866), based on the cell... 

The advantage of the latter system with respect to the Leclanche battery is closely related to the electrolyte insoluble reaction products are less involved and this results in an operating temperature that ranges further down the scale, and higher current densities. 

Table 1 T5 pical performance characteristics of the alkaline and the LeClanche batteries...

Fig. 8.5 Mental models on processes in Leclanche batteries and lead accumulators [16]...

Figure 2.1. Schematic of a paper-hned cylindrical manganese-zinc Leclanche battery.

Alkaline batteries are used in many household items. This includes MP3 players, CD players, digital cameras, pagers, toys, lights, and radios, to name a few. The most widespread production and application have cylindrical alkaline batteries which now can be found literally in every household. To provide interchangeability their size is standardized with that of Leclanche batteries. Most commonly the following sizes are used ... 

Figure 10.17 Construction of a flat cell Leclanche battery.

Figure 10.18 Discharge characteristics for a commercial Leclanche battery. The battery was discharged into a 5d resistance for 1 h each day.

Figure 2. Compari.son between the discharge characteristics of alkaline-manganese and Leclanche batteries (load 7.5 Q temperature 20 °C)...

Unlike the Pb-actd and the Ni-Cd systems, Leclanche batteries cannot be recharged effectively and hence, arc primary cells. Even so, Leclanche cells arc produced in many shapes and sizes (Fig. 11.2) and the total world production probably exceeds 10 per year they are truly the workhorses amongst consumer batteries. Their replacement by higher-performance or secondary batteries has frequently been predicted but the market has always held up because of their comparative cheapness, c,g. a Leclanche cell is typically a twentieth of the cost of a Pb-acid battery or a fiftieth of that for a Ni-td battery to provide the equivalent power supply Much of this cost difference lies in the materials of construction but the battery also benefits from the scale of manufacture since Leclanche cells are produced by fully automatic processes. 

Figures 11J5 and 11.16 illustrate two designs of Leclanche battery. The first shows the traditional cylindrical design. The negative zinc electrode is a zinc lining to the metal can which is amalgamated with mercury to minimize hydrogen gas formation by reaction of the metal with water the separator is a paper stiffened with cellulose or starch placed adjacent to the zinc can. The positive current collector is a carbon rod at the centre of the can, while most of the volume is taken up by the positive paste. This is a mixture of powdered manganese dioxide ainmotmtm chloride and acetylene black (carbon) to increase the conductivity the pores are filled with an aqueous electrolyte (NH Cl + ZnCl ) gelled by addition of starch. The can is totally scaled.

During this period, the zinc/alkaline manganese dioxide batery began to replace the zinc-carbon or Leclanche battery as the leading primary battery, capturing the major share of the US market. Environmental concerns led to the elimination of mercury in most batteries without any impairment of performance, but also led to the phasing out of those batteries. 

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