Alkaline manganese cell

This type of cell is another variant on the basic Leclanche cell. In this case, the electrolyte is a concentrated aqueous solution of potassium hydroxide (about 30%), partly converted to potassium zincate by the addition of zinc oxide. The main advantage of alkaline manganese cells over Leclanche cells is their relatively constant capacity over a wide range of current drains and under severe service schedule conditions. Another feature of this system is that it can be the basis of a secondary battery system. The cell reaction may be written formally as 

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. 

A variable quantity of ZnO is added to the concentrated KOH solution, depending on the system characteristics required. ZnO can also act as a gassing suppressor. The electrolyte is immobilized generally using carboxy-methylcellulose, and a non-woven fabric separator made of natural or synthetic fibres resistant to the high pH is placed between the electrodes. 

The cathode mix is a compressed mixture of electrolytic Mn02 (EMD) and synthetic graphite or acetylene black to provide electronic conductivity, in a ratio of 4—5 1, wetted with electrolyte. The cathode current collector is generally the external steel can, which may be nickel-plated or coated with conductive carbon. Reduction of Mn02 in alkaline conditions is a complex process and follows a number of steps which can be written formally as 

Provided that the reduction does not exceed a level equivalent to Mn0li33 the reaction can be reversed and the cathode recharged. In practice this means limiting the discharge at 0.9 V. The rechargeable alkaline manganese (RAM) cell is discussed in Chapter 6. 

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Zinc/carbon and alkaline/manganese cells are primary battery systems lead, nickel/cadmium, and nickel/metal hydride accumulators are secondary batteries with aqueous electrolyte solutions. Their per-... 

Figure 3. Variation of internal impedance of alkaline-manganese cells with the additives content of the zinc powder o, Hg additive , In additive.

Figure 4. Comparison between the discharge characteristics of newly developed and conventional alkaline-manganese cells (load 7.5 Q temperature 20 °C)...

Rechargeable alkaline manganese cells made according to BTI s RAM technology meet the requirements of the electrical abuse tests as described in the IEC 86-1 International Standard [41],... 

This system, known as primary alkaline manganese cells, has been further devel-... 

Alkaline manganese cell Consists of Zn anode and Mn02 cathode with KOH as the electrolyte is saturated with zincate ions Zn + 2 MnOj + 2 H20 —> Zn(OH)2 + 2 MnO (OH) 11 ZnO + H20... 

Alkaline manganese cells are broadly similar in design to the Leclanche cell, but they contain concentrated KOH as the electrolyte instead of NH4CI. 

For battery separators, regenerated cellulose is placed on the surface of nonwoven so that the nonwoven is available to promote the wicking of the electrolyte. The nonwovens should not allow the penetration of viscose into itself. Suitable nonwovens are made from polypropylene, poly(vinyl alcohol), and hardwood hemps. Regenerated cellulose films are commonly used in alkaline manganese cells, both primary and secondary, in NiCd industrial batteries, as well as in silver—zinc batteries. 

An alternative to the Leclanche cell is the alkaline manganese cell, in which the electrolyte is a strongly alkaline paste and the anode and cathode reactions in their respective compartments are... 

Fig. 3.19 Cell voltage of an alkaline manganese cell as a function of the degree of reduction of Mn02...

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... 

Fig. 4.24 Capacity of lithium-copper oxide button cells (LC 01) as a function of discharge current (solid lines). Dashed lines indicate the characteristics of alkaline manganese cells of similar dimensions. (By courtesy of SAFT Gipclec.)...

Fig. 4.30 Comparison of the discharge curves of AA-sizc lithium-iron sulphide and alkaline manganese cells 3,9 ft continuous load) at (a) 21°C and (b) — 20°C, (By permission of Evcready.)...

Fig. A 1.2 (a) Pulse charge and OCV sensing of a RENEWAL rechargeable alkaline manganese cell, (b) Typical current and voltage profiles during charging of an AA sized RENEWAL rechargeable alkaline manganese cell using the pulse taper charge method. (By permission of Rayovac.)...

A further variation of the Leclanche cell is the so-called alkaline manganese cell. The negative pole is a hollow cylinder of powdered amalgamated zinc set in carboxymethylcellulose gel. The current collector is usually made of brass and the interior space is filled with irmnobilized KOH electrolyte solution. The positive pole consists of a mixture of electrolytic Mn02 and graphite in a ratio of 4- 5 1 wetted with electrolyte solution. The cell reaction is given approximately by the equation... 

Another variant of the Leclanche cell is the so-called alkaline manganese cell, which with its cell reaction may be written ... 

All the zinc-based cells, except for the alkaline manganese cell under certain conditions, are primary cells. Secondary (rechargeable) cells are generally based on cadmium rather than zinc, especially in the form of nickel-cadmium cells. 

Essentially the same constituents as alkaline manganese cells, except that mercuric oxide has replaced manganese dioxide. Silver may be present in the cathode. Mercury cells are being phased out wherever feasible. 

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