Zinc chloride cells

The so-called zinc chloride cells are basically Leclanche cells in which the ammonium chloride has been completely, or almost completely, replaced by ZnCl2. (Up to 1 % of NH4CI is reported to improve high rate performance.) The resulting cells have a better service capacity at high current drain, at low temperatures and on continuous discharge. 

The improved performance of the ZnCl2 cell is offset by the higher cost incurred through using a better quality cathode mix and more complex fabrication due to the requirement of more reliable seals. Since the improvement in performance out-matches the price differential between Leclanche and zinc chloride cells, there is an increasing tendency to phase out the classical Leclanche formulation in favour of the latter. The best zinc chloride cells, sometimes referred to as extra heavy duty (EHD), have at least twice the service life of even the best Leclanche cells. 

In recent years, there have been further improvements in the performance of zinc chloride cells. These have been brought about principally by use of laser welding to increase the internal active volume, and by improvements to materials, especially by synthesizing acetylene black with optimized surface area and water absorption characteristics. 

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Zinc chloride cell Zinc-chlorine cell Zinc chromate... 

The zinc chloride cell, which was first patented in 1899, IS actually an adaptation of the Leclanche cell. The major innovation was the development of plastic seals that permitted the replacement of animoliitim chloride in the electrolyte. 

Figure 2. Schematic semi-ideal discharge curves of Mn02 in 9 mol L 1 and 5 mol L 1 NH4CI2 + 2 mol L l ZnCl2 solutions. IL, range of discharge capacity of commercial alkaline MnO, - Zn R2, range of discharge capacity of commercial Leclanche or zinc chloride cells.

Fig. 3.18 Cross-section of a D-size zinc chloride cell, (By courtesy of Union Carbide,)...

The alkaline manganese dioxide cell is most widely available either as standard sized cylindrical cells with capacities ranging from 0.6 to 22 Ah or as button cells. Batteries having a wide variety of capacities and voltages are also readily available. These are all interchangeable with Leclanche and zinc chloride cells. 

Fig, 3.22 Comparison of the performances of Zn-Mn02 primary systems under 2,25 ft continuous lest (a) standard Lcclanchfi cell based on natural ore (b) high power Leclanche cell based on electrolytic Mn02 (c) zinc chloride cell (d) alkaline manganese cell... 

D-size cells on 2.25 O continuous test are reported. Cell (a) is a standard Leclanchd cell using a natural ore cell (b) is a HD Leclanche with electrolyte Mn02 cell (c) is a zinc chloride cell and cell (d) is an alkaline manganese primary unit. The differences at this current drain are striking the discharge capacities with a 0.9 V cut-off are in the ratio 0.12 0.24 0.55 1.00 for the four types. However, when less severe tests are considered, the disparities are less pronounced. Thus for the light industrial flashlight (LIF) test, the ratios are 0.40 0.61 0.96 1.00. 

Cylindrical alkaline cells are zinc-manganese dioxide cells having an alkaline electrolyte, which arc constructed in the standard cylindrical sizes, R2D D, R14 C . R6 AA , ROT AAA, as well as a few other less common sizes, llley can be used in the same types of devices as ordinary Leclanchd and zinc chloride cells. Moreover, die high level of performance makes them ideally suited for applications such as toys, audio devices, and cameras. 

Carbon-zinc cells are distinguished by the composition of the electrolyte. The Leclanche cell has an aqueous ammonium chloride-zinc chloride electrolyte. The higher performance zinc chloride cell mainly has zinc chloride electrolyte and may contain a small amount of ammonium chloride. Cells are available in cylindrical and flat plate constructions, as well as combinations of cells for higher voltage applications. Approximately 30 billion carbon-zinc cells are manufactured annually. 

The zinc chloride cell is a high performance version of the carbon-zinc cell. As its name implies, the zinc chloride cell uses a ZnCl2 electrolyte, along with synthetic or electrolytic Mn02 (EMD). The cell reaction is given in Equation 10.2. 

A variation of the Leclanche cell is the zinc chloride cell in which the ammonium chloride is completely replaced... 

In the zinc chloride cell, precipitated basic zinc chloride is the primary anode product because of the low concentration of ammonium chloride in the cell. Water and zinc chloride are consumed in equations 1 and 7 and must be provided in adequate amounts for the cell to discharge efficiently. Usually more carbon is used in zinc chloride cells than in Leclanchn cells in order to increase the electrolyte absorptivity of the cathode and thus allow the use of a larger volume of electrolyte. Also, the use of a thin paper separator, which decreases internal resistance, allows less space for water storage than the thick, pasted separator construction traditionally used in Ledanchit cells. 

Leclanche cells may be divided into general purpose (intermittent low-rate discharge) and industrial heavy duty (intermittent medium/heavy rates) grades. Zinc-chloride cells also afford continuous discharge and have, in addition, an extra/superheavy duty grade for continuous medium/heavy rates. 

The alkaline zinc-manganese dioxide ceU was introduced in 1959 as a high-performance primary cell to replace the Leclanche (carbon-zinc) cell that was developed by Georges Leclanche in 1860 and is still the battery of choice in the developing countries because of its low cost. The zinc chloride cell was introduced... 

The alkaline Zn-Mn02 cell has higher capacity compared to the cells with Leclanche and zinc chloride electrolyte. In the D-size cell configuration, it can deliver about 15 Ah compared to about 7 Ah for the zinc chloride cell and 5 Ah for the Leclanche or carbon-zinc version. In addition, the zinc chloride and Leclanche versions exhibit a significant fall off in capacity on higher-rate discharges. 

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