Atmospheric oxygen element with regenerating manganese chloride solution as electrolyte

An atmospheric oxygen element with a cathode of activated charcoal and carbon black. A manganese chloride solution is used as electrolyte. The anode consists of zinc sheets. The capacity of this element depends on the amount of MnCl.sub.2. This amount can be increased by adding manganomanganite (MN.sub.2 O3) produced by precipitation with an alkaline solution in the presence of oxygen. During the delivery of current, ZnCl.sub.2 is created, which replaces the bivalent manganese in the manganite with zinc ions and thus dissolves MnCl.sub.2.

BACKGROUND OF THE INVENTION 
An atmospheric oxygen element is described in U.S. Pat. No. 4,442,183, the 
disclosure of which is hereby incorporated by reference. The atmospheric 
oxygen element described contains cathode plates, the active part of which 
comprise a mixture of activated charcoal and carbon black with a manganese 
(II) chloride solution as electrolyte. During discharge of the cell the 
zinc dissolves into ZnCl.sub.2 and manganese chloride is transformed into 
Mn(OH).sub.2 at the cathode. Because of the oxygen contained in the 
atmospheric oxygen elements, the Mn(OH).sub.2 is oxidized into manganic 
acid and precipitates at the cathode as Mn.sub.2 O.sub.3. The Mn.sub.2 
O.sub.3 reacts with the ZnCl.sub.2, which increases during current 
delivery, in accordance with the formula: 
EQU Mn.sub.2 O.sub.3 +ZnCl.sub.2 .fwdarw.ZnMnO.sub.3 +MnCl.sub.2 
and since the MnCl.sub.2 which has been created continues to react at the 
cathode, the total formula of current generation in an atmospheric oxygen 
element with a manganese chloride solution as electrolyte can be written 
as follows: 
EQU 2Zn+3/2O.sub.2 +MnCl.sub.2 .fwdarw.ZnMnO.sub.3 +ZnCl.sub.2 
With this reaction it is of particular technical interest that it is 
possible to react 4 equivalents of zinc to generate current with 1 mol 
MnCl.sub.2. 
Oxygen is available in unlimited amounts, and the amount of zinc required 
is easily attainable by the choice of the thickness of the anode. However, 
the amount of MnCl.sub.2 is tied to the amount of electrolyte which can be 
accommodated in the cell. Solid MnCl.sub.2 .multidot.4(H.sub.2 O) cannot 
be added to the solution in excess, since it dissolves in moist air and 
would cause swelling of the cells. 
It is therefore an object of the present invention to provide a practical 
process for generating MnCl.sub.2 in the electrolyte of an atmospheric 
oxygen element as needed. 
It is also an object to provide an atmospheric oxygen element with a source 
of generating MnCl.sub.2 in the electrolyte. 
SUMMARY OF THE INVENTION 
In accordance with the above objects, there has been provided a process for 
generating MnCl.sub.2 in the electrolyte of the cathode of an atmospheric 
oxygen element comprising the following steps. First, a manganese (II) 
salt solution is precipitated by adding one equivalent of hydroxide for 
every equivalent of Mn++ in the presence of oxygen, whereby Mn.sub.2 
O.sub.3 is produced. Second, the insoluble Mn.sub.2 O.sub.3 is added to 
the electrolyte of the cathode. Third, the ZnCl.sub.2 concentration is 
enriched in the cell during current flow. Fourth, the added Mn.sub.2 
O.sub.3 reacts with the ZnCl.sub.2 to produce ZnMnO.sub.3 and MnCl.sub.2. 
The desired MnCl.sub.2 in the element is thereby generated. 
Also in accordance with the above objects, a second embodiment provides a 
process for generating MnCl.sub.2 in the electrolyte of the cathode of an 
atmospheric oxygen element comprising the following steps. First, 
Mn(OH).sub.2 is precipitated from a manganese (II) salt solution by the 
addition of alkali in the absence of oxygen. Second, the Mn(OH).sub.2 of 
the first step is purified. Third, the purified Mn(OH).sub.2 of the second 
step is added to the electrolyte of the cathode, whereby Mn.sub.2 O.sub.3 
is formed by oxygen uptake during mixing of the depolorization mass. 
Fourth, the ZnCl.sub.2 concentration is enriched during current flow in 
the cell. Fifth, the Mn.sub.2 O.sub.3 formed reacts with the ZnCl.sub.2 to 
produce ZnMnO.sub.3 and MnCl.sub.2. The desired MnCl.sub.2 in the elements 
is thereby generated. 
Preferably, the third step of the second embodiment further comprises 
adding moist Mn(OH).sub.2 to the electrolyte, and further comprises the 
step, before the fourth step, of saturating the water added with the 
Mn(OH).sub.2 by the addition of MnCl.sub.2 .multidot.4H.sub.2 O. 
The present invention also preferably provides an atmospheric oxygen 
element comprising: a zinc anode; a cathode having an aqueous MnCl.sub.2 
electrolyte; and a non-soluble Mn.sub.2 O.sub.3 material in the 
electrolyte for producing MnCl.sub.2 in the electrolyte when current is 
produced in the element.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In accordance with the invention an insoluble material is therefore added, 
which only gives off MnCl.sub.2 by the formation of ZnCl.sub.2 during 
current delivery. Manganomanganite (Mn.sub.2 O.sub.3) is proposed as such, 
preferably as formed during precipitation from a manganese salt solution 
with an equivalent amount of an alkaline solution in the presence of 
oxygen. This product can be added to the electrolyte of the cathode in the 
form of a dry or wet powder. 
Another way of proceeding is to precipitate Mn(OH).sub.2 from the manganese 
salt solution with an alkaline solution in the absence of air. The 
substance purified by the alkaline salt is added, preferably wet, to the 
cathode mixture. The formation of manganite (Mn.sub.2 O.sub.3) occurs 
during the mixing process with the addition of oxygen. The water 
introduced into the mixture by the above reaction and along with the 
precipitated Mn(OH).sub.2 is saturated with salt by a corresponding 
addition of MnCl.sub.2 .multidot.4(H.sub.2 O). 
However, the manganite produced does not have to be in electronically 
conducting contact with the cathode. If the design of the cell permits it, 
it can also be provided at another place in the electrolyte. 
The following examples illustrate how the cathode mixture of the present 
invention is produced. 
Example I: Mixture with the addition of dry Mn.sub.2 O.sub.3 
(a) 5 kg carbon black, 5 kg activated charcoal, 5 kg powdered Mn.sub.2 
O.sub.3 and 15 kg of a saturated MnCl.sub.2 solution are placed in a 
mixing drum and mixed until a loose powder mixture is obtained. 
(b) If the Mn.sub.2 O.sub.3 is added moist, that is, without having been 
dried, the water content is determined and 2 kg MnCl.sub.2 
.multidot.4H.sub.2 O is added for every kg of water present. 3 kg 
saturated Managanese chloride solution is thereby produced. 
If, for example, the added Mn.sub.2 O.sub.3 contains 2 kg water for every 
five kg of dry material, the same mixture as in I(a), above, is obtained 
with the following components: 5 kg carbon black, 5 kg activated charcoal, 
7 kg moist Mn.sub.2 O.sub.3, 4 kg MnCl.sub.2 .multidot.4H.sub.2 O, and 9 
kg saturated MnCl.sub.2 solution. 
Example II: A mixture having the same composition as Example I after 
oxidation by atmospheric oxygen. 
The moisture content of the Mn(OH).sub.2 is 2 kg water per 5 kg 
Mn(OH).sub.2 If Mn(OH).sub.2 is used, then 5.6 kg of the dry product must 
be used; this results in 7.84 kg moist Mn(OH).sub.2 with 2.24 kg water. As 
a result of oxidizing 5.6 kg Mn(OH).sub.2 to 5 kg Mn.sub.2 O.sub.3, 1.13 
kg of water is formed so that the water content becomes 3.37 kg (i.e., 
2.24+1.13=3.37). One must therefor add 6.74 kg of solid MnCl.sub.2 
.multidot.4H.sub.2 O, and 10.11 kg saturated Manganese chloride solution 
results. 
The composition of the mixture is therefore as follows: 5 kg carbon black, 
7.84 kg moist Mn(OH).sub.2, 6.74 kg MnCl.sub.2 .multidot.4H.sub.2 O, and 
8.26 kg of saturated MnCl.sub.2 solution. 
Although specific embodiments are described it will be apparent to one of 
ordinary skill in the art that modifications can be made within the scope 
of the present invention which is determined by the appended claims.