US2050172A - Electric primary cell - Google Patents

Description

Aug. 4, 1936. c. J. GORDON ELECTRIC PRIMARY CELL Filed April 5, 1954 2 Sheets-Sheet 1 1936- c. J. GORDON ELECTRIC PRIMARY CELL 'Filed April :5, 19:54 2 Sheets-Sheet 2 Fig. 10

Fig. 11.

HA5 HTZ'OR/VEYQ Patented Aug. 4, 1936 Christian Jensen Gordon, London, England Application April 3, 1934, Serial No. 718,769 In Great Britain April 6, 1933 16 Claims.

The object of this invention is to provide an improved primary cell of the kind in which magnesium is the electropositive electrode. Within the term magnesium, it is intended to include appropriate alloys in which magnesium is the predominating material. For such alloys to be suitable, it is necessary that the metals added to the magnesium should not be placed very far away from magnesium in the electro-chemical series- As an example of an alloy which is appropriate, one containing about 7% of aluminium and from 1-2% of manganese and the remainder magnesium may be mentioned. The addition of aluminium within the range of 2-7 has been found to be an improvement on commercially pure magnesium. Where the word magnesium is .used in the following specification and claims (unless the context indicates otherwise), it is to be assumed that it includes suitable alloys as well as substantially pure magnesium.

The invention relates to primary cells having a layer of fibrous material lying between and in contact with the magnesium electrode and the second electrode and serving as a carrier for the.

electrolyte.

The invention deals with the nature, form and disposition of the electrodes and the fibrous layer when assembled in their appropriate relationship for use in a cell. of the electrolyte. Electrolytes suitable for cells embodying the present invention are described in and form the subject of my continuation in part application Serial No. 42,039;

In accordance with the invention one of the electrodes is made of carbon of an open structure that is, porous or granular or powdered carbon, which is in contact with air on one or more of its surfaces, so that air can pass through the pores or spaces in the electrode material itself to the layer of fibrous material which is in contact with it.

The air is caused by the action of the fibrous layer to effect the depolarization. The full theory of this action is not understood but it appears evident that it is the oxygen in theair which is essential for the depolarizing and that it can be conveyed along the layer to the place where depolarization occurs. Where granular or powdered carbon is used, it must be carried on a suit able conducting support or held within a metal container which forms the outer part of the cell. The conducting support may be a metal gauze or a woven fabric made of a mixture of thread, such as cotton, with wire. In each case, the carbon powder can be made to adhere to its support by being pressed into the meshes thereof and on its It does not deal with the nature magnesium electrode to the other.

surface. In the case of a porous solid carbon body or of a woven material serving as a support for carbon powder, the electrode may be made as thewall of the cell and may have one surface in contact with the electrolyte and the opposite surface exposed to the air. In the case .of powdered or granular carbon-held in a solid metal container, only the end surface or surfaces can be exposed.

For the fibrous layer, material of open texture is used. Many fibres are suitable but have somewhat varying degrees of effectiveness. It is preferred to use cellulose fibres, such as Wood ,wool, or blotting paper. This material is inert and readily obtainable and has been found to be particularly effective for the purposes in view.

In orden to avoid cutting oif air from the fibrous layer, the electrolyte must be fed to the fibrous material without immersion of any important part of the area of the electrodes. The supply of the electrolyte, in accordance. with this condition, can be effected by placing the fibrous body in contact with a body of solidified material which is housed in an appropriate part of the container of the cell and is dissolved by the addition of water. By regulating the supply of water, some control of the action of the cell can be exercised. This is of importance in this type of cell since a slight chemical action on the magnesium electrode proceeds continuously while it is in contact with water and air.

It appears that, in this type of cell, it is'the reaction between the water and the magnesium which provides the E. M. F. of the cell. The electrolyte serves the purpose of providing a conductive path between the electrodes.

The method of supplying electrolyte above described has the advantage that the electrolyte may be fed progressively from one end of the This is of importance because, as the result of the action between the water and the magnesium electrode, a comparatively large body of a non-conducting or poorly conducting compound is produced. By arranging the feed of the electrolyte to take place from the end of the electrode remote from the terminal, it can be ensured that the absorption of the electrode proceeds progressively from the inner end to the terminal end and accordingly this means compensates approximately for the increase due to other causes so that the internal resistance of the cell remains approximately constant, at least until the latest stage of the life of the cell is reached.

Since the action of the water on the magnesium during the life of the cell produces a substantial increase in the volume of the contents of the cell, it is important to provide for expansion within the cell to prevent the fibrous layer from being compressed too heavily. Such compression would render the layer incapable of carrying out properly its function of holding electrolyte and its function of bringing about depolarization. Room for expansion may be provided by making the cell with concentric electrodes and with the outer electrode expansible or the inner electrode collapsible or with both of these.

The invention will be further described in connection with two examples of cells embodying it, which are shown in the accompanying drawings.

Figures 1-4 show a type of cell suitable for comparatively light service and comprising three units connected in series.

Figure 1 is a vertical section on the line IV-'-IV of Figure 2.

Figure 2 is a horizontal section on the line VV of Figure 1.

Figure 3 is a side elevation of three groups of electrodes, one of these being shown in section, and Figure 4 is a side elevation of the container partly in section.

Figures 5 and 6 show in end elevation and side elevation an alternativeform of magnesium electrode suitable for use in cells as shown in Figures Figures 'l and 8 show in end and side elevation respectively another form of such an electrode.

Figure 9 corresponds to Figure 1 but includes an alternative form of outer electrode.

Figures 10 and 11 show developed views of alternative parts of the outer electrode included. in Figure 9.

Figure 12, which also corresponds to Figure 1, includes a further alternative form of outer electrode.

The type of cell in the drawings is intended for a comparatively small current; for instance, the current may be of the order 20 milliamperes. The surface of magnesium per amp. is of the order of 100 square inches (640 square centimeters). The open circuit voltage is about 1.3.

In cells of the kind shown, the magnesium I electrode 22 is placed in the centre of the cell and is in the form of a cylindrical rod with longitudinal flutes on the surface so as to increase the area. It has a terminal screw 23 at the upper end. The central rod is surrounded by a layer of fibrous material 24 formed by coiling a strip of wood wool into the form of a tube. Outside and in contact with this layer, is the second electrode 25. This is of porous carbon made in two half cylinders with longitudinal flutes on both the inner and the outer surface. These two halves are held together by a rubber'band 46.

From the two halves of the electrode 25, connec-' tions 26 are taken off. It will be seen from Figure 3 that, by means of these connections and the terminal screws 23, the three cells are connected in series and ar also connected with the aid of an additional'wire 21 to terminals 28 mounted on the top plate 29 of the-battery. This plate 29 and the casing 30 are made of insulating material. They are connected together by screws 3|. The casing 30 is divided panied by eXpansion.

into three chambers and each chamber is in communication with the exterior air by means of holes 32 which provide that the exterior surfaces of the carbon electrodes 25 are in contact with air.

e Near the lower end of the casing 30, is a partition 33 which separates the three chambers which contain the electrodes from three smaller chambers 34 in each of which is placed a pad 35 containing electrolyte material. Communication is provided between the upper and lower chambers by way of an aperture in the partition 33 through which passes fibrous material 36 which is spread out above and below the partition and serves to establish communication between the pad 35 and the fibrous layer 24. The chamber 34 is closed by a cup 31 which can be removed to receive the pad 35.

When the cell is complete it can be put into action by supplying water to the pad and the fibrous material. This can readily be done by removing the cup 31, filling with water and replacing it. The fibrous material 3'6 is then in contact with the water and feeds it to the layer 24. The cell will now remain active until substantially the whole of the water has been used up. Each pad of electrolyte material will generally sufiice for several fillings with water and will generally be so designed that it will be exhausted in about the same time as the magnesium electrode is used up.

The chemical transformation of the magnesium will proceed from the bottom upwards in such a way as to leave the electrical connections (both electrolytic and otherwise) complete in the upper part of the battery.

The chemical change will in general be accom- This can be accommodated by the split construction of the carbon electrodes, the two halves of which can move apart commencing at the lower end as the action proceeds. Alternatively or in addition increase in volume may be provided by the collapse of the magnesium electrode, For this purpose it can be made as a hollow rod, preferably in a form which favours inward collapse. An example is shown in Figures 5 and 6 where the electrode is an oval tube with comparatively thin walls.

As an alternative to the arrangement described. the supply of water may be effected through apertures in the top plate 29 and for this purpose it is preferable to use magnesium electrodes of tubular form with radial perforations through which the water can flow outwards t0 the fibrous layer 24. An example of such an electrode is shown in Figures 7 and 8. In this example the electrode 22 has a central circular bore 38 which communicates with the exterior through a large number of perforations 39.

The solid carbon electrode shown in Figures 1, 2' and 3 may be replaced by a granular carbon electrode as shown in Figure 9 or by a powdered carbon electrode as shown in Figure 12. The

general construction of this cell is similar to that just described and corresponding parts are indicated by the same reference letters in Figure 1 and Figure 9.' The carbon granules 40 are enclosed in a tube 4| which may be either of the construction shown in Figure 10 or that shown in Figure 11. In Figure 10, the tube 4| is formed from a strip of copper gauze which is shown there as afiat strip as it is prepared with a terminal wire 42 ready for being bent into cylindrical form for insertion in the container 30. The

electrode 22 is held in place by its terminal screw 23 which passes through a cover plate 43. This plate has a second hole through which passes the The tube 48 may alternatively be formed of a strip of cotton fabric 44 (Figure 11) through which are passed a number of wires 45 which are twisted together to form the terminal connection 42. These wires serve as electrical connection to the carbon and also give sufficient stiffness to the fabric 44.

Figure 12 shows an arrangement similar to that of Figure 9 with the exception that the outer electrode is formed from carbon powder I40 carried by a tube of copper gauze 4| which is similar to the tube shown in Figure 9 and described in connection with Figure 10. The carbon powder is caused to adhere to the gauze by pressure assisted by a binding agent. This may be a tarry body from which volatile parts can be driven oif by heat after the attachment of the carbon powder to the gauze has been effected, thereby leaving a residue consisting only of carbon.

It will be recognized from the preceding description that this type of cell is inert until water is added and becomes inert again when the water has been used up and can then be brought again into activity by the addition of a further supply of water. Throughout its active life, the cell has a practically constant open circuit voltage. It can be short-circuited without permanent injury and with no other effect than an increased consumption of the magnesium electrode. Polarization is negligible under proper working conditions and even after short-circuiting normal conditions are very rapidly restored.

The construction of these cells is suchas to facilitate the use of electrolyte material in a solid form, that is to say, in a form which can be handled in one piece per cell and placed in position as a pad sufiicing for a complete working charge.

The chemical compound formed by the action in the cell is not deposited on the surface of the magnesium electrode and therefore does not hinder the flow of current.

What I claim is:-

1. A primary cell of the type having its electromotive-force generated by the action of water on magnesium comprising an electrode of magnesimn, a second electrode of carbon of open structure exposed to air and a layer of fibrous material of open texture lying between and in contact with the two electrodes and exposed to air through the carbon electrode and serving as a carrier for the electrolyte and for air for depolarizing.

2. A primary cell comprising an electrode of,

magnesium, a second electrode" of carbon of open structure exposed to air, terminal connections located at one end of the electrodes, a body of electrolyte material separate from the electrodes and located adjacent to the end of the electrodes remote from the terminals, a layer of fibrous material of open texture lying between and in contact with both electrodes and with the electrolyte material and exposed to air through the carbon electrode and serving as a carrier for the electrolyte and for air for depolarizing.

3. A primary cell of the type having its electromotive force generated by the action of water on magnesium, comprising an electrode of magnesium, a second electrode of finely divided carbon exposed to air and forming a non-self-sup porting structure, a. conductive member supporting the second electrode, and a layer of fibrous material of open texture lying between and in contact with the two electrodes exposed to air through the carbon electrode and serving as a. carrier for an electrolytaand for air for depolarizing.

4. A primary cell having an electrode of magnesium, a second electrode of finely divided carbon exposed to air, a conductive support for the second electrode, comprising a woven fabric having conductive wires therein, and a layer of fibrous material of open texture lying betweenand in contact with the two electrodes and exposed to air through the carbon electrode and serving as a carrier for an electrolyte and for air for depolarizing.

5. A primary cell having an'electrode of magnesium, a second electrode of finely divided carbon exposedto air a wire gauze conductive support for the second electrode and a layer of fibrous material of' open texture lying between and in contact with the two electrodes and exposed to air through the carbon electrode and serving as a carrier 'for an electrolyte and for air for depolarizing.

6. A primary cell having an electrode of magnesium, a second electrcde,-a layer of fibrous material of open texture lying between and in contact with the two electrodes and serving as a carrierfor the electrolyte and for air for depolarizing and a metal container for the electrodes and fibrous material, the second electrode being formed of finely divided carbon disposed between the wall of the container and the fibrous layer and exposed to air and the fibrous layer being exposed to air through the carbon electrode.

7. A primary cell comprising a central electrode of magnesium, an electrode of carbon of open structure surrounding the central electrode and exposed to air, a layer of fibrous material of open texture interposed between the two electrodes and lying in contact with both of them and exposed to the air through the carbon electrode and serving to carry electrolyte and air for open structure and surrounding the central electrode and exposed to air, and a fibrous layer of open texture interposed between the two electrodes and exposed to air through the carbon electrode and serving to carry electrolyte and air for depolarizing.

9. A primary cell comprising a central collapsible. tubular electrode of non-circular, crosssection made of magnesium, an electrode of carbon of open structure surrounding the central electrode and exposed to air, and a layer 01. fibrous material of open texture interposed between the two electrodes and lying in contact with both of them and exposed to air through the carbon" electrode and serving as a carrier for electrolyte and for air for depolarizing.

10. A primary cell comprising a' central tubular and perforated electrode of magnesium, an electrode of carbon of open structure surrounding the central electrode and exposed to air and a layer of fibrous material of open texture interposed between the two electrodes and lying in contact with both of them and exposed to air through the carbon electrode and serving to carry electrolyte and air for depolarizing.

11. A primary cell comprising an electrode 01' magnesium, a second electrode, terminal connections located at one end of said electrodes, a layer of fibrous material of open texture lying between and in contact with the electrodes and exposed to air and means for feeding electrolyte to said layer at the end remote from the terminals. 7 v

12. A primary cell comprising a central electrode of magnesium, an outwardly expansible tubular electrode of carbon of open structure surrounding the central electrode and exposed to air and permitting increase of the volume enclosed between the two electrodes, a fibrous layer of open texture interposed between the two electrodes and exposed to air through the carbon electrode and serving to carry electrolyte and air for depolarizing.

13. A primary cell comprising a central inwardly collapsible tubular electrode of magnesium, an electrode of carbon of open structure surrounding the central electrode and exposed to air, and a fibrous layer of open texture interposed betweenthe two electrodes and exposed to air through the carbon electrode and serving to carry electrolyte and air for depolarizing.

14. A primary cell comprising a central electrode of magnesium, an electrode of carbon of open structure surrounding the central electrode and exposed to air, and a layer of fibrous material of open texture lying between and in contact with both electrodes and exposed to air through the carbon electrode and serving to carry electrolyte and air for depolarizing, an insulating casing pervious to air enclosing the whole, a chamber in the base of the casing, a partition, separating the chamber in the base from the remainder of the casing, the said partition having an aperture through which passes the fibrous material.

15. A primary cell comprising a central electrode of magnesium, an outwardly movable electrode surrounding the said magnesium electrode and permitting increase in volume of the space between the two electrodes, and a layer of fibrous material of open texture lying between and in contact with the electrodes and exposed to air and serving as a carrier for the electrolyte and for air for depolarizing.

16. A primary cell comprising a central tubular inwardly collapsible electrode of magnesium, an outer electrode surrounding the said magnesium electrode and a. layer of fibrous material of open texture between and in contact with the electrodes and exposed to air and serving as a carrier for electrolyte and for air for depolarizing.

CHRISTIAN JENSEN GORDON.

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