Cathode Reactions in the Leclanche Dry Cell

Complete discharge curves of electrodeposited a-and ~-MnO~ electrodes in an electrolyte of pH 7.5 are compared. Oxide on the electrode at the end of discharge had the composition MnOL57 for 7-and MnO~.GG for a-MnO~.. In the later portions of both discharges the rate of increase of Mn § in the electrolyte is equivalent to the current. The effect of larger concentrations of Mn § in the electrolyte on the discharge curve is shown. A method is developed for the dissolving of surface oxides from a partially or wholly discharged electrode and measuring Mn (II) and Mn (III). The amounts recovered were only a small fraction of Mn(IV) reduced even when no Mn ++ was appearing in solution.

Section: Preparation and Discharge Of Electrodesmentioning

confidence: 99%

“…A different theory (4) has been based mainly on experiments with Leclanch6 cells. An important difference between the discharges of the two types of electrode is pointed out.…”

mentioning

confidence: 99%

Experiments on the Discharge Mechanism of the Manganese Dioxide Electrode

Vosburgh¹,

Lou²

1961

“…MnO~ + 4H + + 2e--> Mn 2+ + 2H20 [1] This reaction predominates in acid electrolyte (14)(15)(16)(17) but is also observed in neutral electrolytes up to about pH 8, (12,(18)(19)(20). It was assumed that in neutral electrolyte (pH 6-8) the dissolution reaction and solidstate diffusion occur simultaneously (17), while in alkaline electrolyte only a solid-state diffusion mechanism is envisaged (9,17,(21)(22)(23)(24).…”

Section: Electrolytic Mnoz--figures 4a-e and The Values Compiled Inmentioning

confidence: 99%

“…Cahoon et al (18) pointed out that the primary (electrochemical) reaction consumes protons (Eq. [1]), consequently increasing the pH, and the secondary (chemical) reaction (MnO2 + Mn 2+ + 2 OH--* 2MnOOH) consumes OH-, thus increasing acidity in the electrolyte at the surface of the depolarizer and that this increase will be faster for the more active types of MnO.~.…”

Section: Electrolytic Mnoz--figures 4a-e and The Values Compiled Inmentioning

confidence: 99%

The Reduction of Manganese Dioxide in Leclanché‐Type Dry Cells as Displayed by Derivative Discharge Functions

Clauss¹,

Schweigart

1976

q ABSTRACTThe derivative discharge curves for ~-and 7-MnO2 down to ,~0.7V open cell voltage were resolved into one characteristic set of four normal distribution functions (peaks). Only peak positions shift to lower voltages for ~-compared to 7-MnO2. When the ratio of electrolyte to MnO2 is increased, the first peak increases while the other peaks decrease (the second passes through a maximum) and at a mass ratio above 14 only the first peak remains. The first peak represents direct reduction of Mn 4+ to soluble Mn e+ which ends at pH 7.5, the second is attributed to the formation of Mn(OH)~, and the third to the formation of MnOOH. Each reaction takes place throughout the depolarizer pellet before the next becomes significant. Electrochemical tests for the evaluation of the dry cell activity of MnO2 samples should be performed at the same mass ratio of electrolyte to MnO2 as used in commercial dry cells. Higher ratios lead to an overestimation of samples with Iow activity.

“…These studies have yielded the "Alclad"-type anode and the chloride-chromate type electrolyte (1, 3). 5 Our studies have been concerned primarily with the selection of an improved separator for this system. An effective separator medium is essential if a battery is to operate satisfactorily and to possess acceptable keeping quality.…”

mentioning

confidence: 99%

A New Separator for the Aluminum Dry Cell

Cahoon¹,

Korver²

1959

A new and improved separator medium for the aluminum dry cell is described. It provides an adhesive contact with the anode and a satisfactory electrolytic contact with the cathode. The method by which this separator is prepared involves a new technique which is described. The separator layer significantly improves the keeping quality and delayed service performance of the aluminum‐manganese dioxide cell.