Ledanche cell

If too large a current is drawn from a Ledanche cell, the ammonia forms a gaseous insulating layer around the carbon cathode. When this happens, the voltage drops sharply and then returns slowly to its normal value of 1.5 V. This problem can be avoided by using an alkaline dry cell, in which the paste between the electrodes contains KOH rather than NH4CL In this case the overall cell reaction is simply... 

Ledanche cell (battery) one of the earliest practical non-rechargeable batteries (Georges-Lionel Leclanche, 1866). It uses a zinc anode (negative electrode) and a manganese dioxide cathode (positive electrode) with ammonium chloride solution as electrolyte. The initially liquid electrolyte... 

Fig. IIJ The Ever Ready range of Ledanch cells. (Courtesy Berec Ltd)...

A number of batteries are based on modifications of the technology or the substitution of electrode reactions into either the Ni-Cd or Ledanche cells the changes usually improve one characteristic of importance to a particular duty but usually only at an increased cost. In an alkaline manganese battery, the cathode is manganese dioxide and graphite in the form of compressed tablets, and the electrolyte is a strongly alkaline solution. The overall cell reaction is ... 

The classical Ledanche cell uses zinc sheet formed into a cylindrical can serving simultaneously as the anode and as the cell container (ABICI). The cathode is a mixture of Mn02 and graphite wrapped into a piece of separator and contacted by a central carbon rod. The can dissolves slowly when the cell is not in use and faster when the cell delivers electrical energy. 

The alkaline version of the Mn02/zinc cell follows a different concept because it turns the construction of the Ledanche cell completely around now the cathode (Mn02 + carbon) forms a hollow cylinder contacting the inner wall of the cell container (steel) along its outer surface. The itmer cavity has to accommodate anode, electrolyte, separator, and current collector. Usually, the separator forms... 

For about a century after the invention of the Ledanche cell (and the lead-acid rechargeable battery) the highest voltage attained in any battery was 2.1V, and primary cells delivered a maximum voltage of about 1.5 V. This changed in the mid 1960s, when the Li-thionyl chloride (LiSOCb) battery was introduced. In this and other nonaqueous lithium batteries, a potential of about 3.0 V was achieved. 

In Ledanche cells the casing is made of zinc and serves as the anode. This design increases to some extent the chances of leakage, but makes manufacturing very cheap. 

The introduction of the li-thionyl chloride primary battery represented a major advance in battery technology. The voltage of a single cell was more than twice that of the Ledanche cell and other primary batteries, energy density was increase by an even higher factor and shelf life was improved by a factor of 5 at least. It became immediately obvious that the next breakthrough would be achieved with the introduction of a rechargeable li battery. This happened about two decades later, with the introduction of the li-ion battery. 

An engineer suggests using a plastic can instead of a zinc can as a way to reduce the cost of producing a common flashlight battery (Ledanche dry cell). What is wrong with this idea ... 

---