DE1671671C3 - Method for storing and delivering electrical energy with the aid of a galvanic cell - Google Patents

Description

The invention relates to a method for storing and supplying electrical energy with the aid of a galvanic cell with negative zinc electrode, a * 5 Separator and a depolarizer mixture of azodicarbonamide and carbon black.

A variety of organic compounds have already been used as organic depolarizers in the black Cathode mixture proposed for electrical primary cells or primary batteries. These usually Cells functioning as "primary" cells are discarded after being discharged in use. Low output voltages also limit the usefulness of such batteries.

In addition, such cells can hardly be effectively used as secondary cells; H. as rechargeable cells, although in some cases they are treated a few times with a usual, im Commercially available »charger« for electrical cells can be reactivated. The primary dry cells, which are normally commercially available, in general, cannot be reloaded, in particular when they are deeply discharged. Attempts have been made to use secondary dry cells with usable To produce organic depolarizers, however, such dry cells have so far not been found to be satisfactory have been shown, although there is a great need for such cells.

The object on which the invention is based is seen in providing a method of the type mentioned create that makes it possible to use the listed galvanic cell very effectively as a secondary cell, which can easily be stored in the uncharged state for long periods of time and otherwise very much can often be loaded and unloaded.

According to the invention, this object is achieved in that shortly before the cell is used for the first time, the depolarizer mixture consisting of soot with a surface area of at least 2OOm ² / g, zinc and / or barium oxide, aqueous solution of zinc salt and hydrazodicarbonamide is oxidized with current by at least to oxidize a portion of the hydrazodicarbonamide to azodicarbonamide, that then current is withdrawn, wherein azodicarbonamide is reduced to hydrazodicarbonamide, whereupon this cycle is repeated,

It has been found that galvanic cells constructed and treated in this way also after a large number of of loading and unloading processes is still usable. There are special advantages:

1. Long service life at voltages of 0.8 volts and below

2. Long discharge curve over a long period of time, i.e. H. quality Voltage regulation

3. Large energy per cell down to a voltage of 0.8 volts and below

4. Sufficient initial tension and sufficient average tension for practical applications

5. high efficiency, d. H. actually more available theoretical amp-minute output

6. High performance when operated as a secondary cell over numerous charge and discharge cycles

It is emphasized that the exact mechanism of the chemical reaction or the chemical action of the Charging current is not fully clarified.

Conventional components are used in the manufacture of the cells according to the invention, e.g. B. a zinc container or a zinc anode, a carbon collector, a cathodic mixture which is carbon, an aqueous one Has electrolytes and a depolarizer, and a separator. The coal collector, the zinc container or the anode, the gasket and the like can be manufactured by conventional methods.

Round lines, as they are commonly used, give very good results, as do flat cells, rectangular cells and cells of other formats and sizes also give satisfactory results Results. Many such sizes and shapes are known. It is desired that the coal be a has high electrolyte storage capacity, d. H. which added large amounts of aqueous electrolyte to the mixture and these still have the required consistency for common dry cell constructions maintains.

The usual electrolyte salts, provided they are compatible with the zinc anode, can be used, e.g. B. zinc, ammonium, mangano or magnesium salts, in the form of their chlorides or bromides or mixtures thereof. In secondary cells, however, it is desirable to have a high content of zinc ions with an ammonium salt. The best results are obtained with an electrolyte which consists of ZnCl ₂ and NH ₄ Cl or ZnCl ₂ and MnCl ₂ in various mixtures.

Satisfactory results are obtained using conventional separators, e.g. B. Kraft Papicr, Kraft paper coated or impregnated with starch or other gel-like material, e.g. B. carboxymethyl cellulose and / or cereal flour paste, vegetable parchment and the like. Very good results are obtained, when a layered cell glass separator is used. This separator can be more precise as a laminate made from a film with a small pore size (e.g. cellulose glass with an average Pore diameter of 16 Å) and a cellulose paper, which has a high water storage capacity, the as a binder z. B. gum arabic can be described. Other films or foils, e.g. B. porous nylon, polyester films, polyolefin films, polyacrylate films, Polyvinyl acetate sheets, polyvinyl chloride sheets, and other sheets or films with low porosity and pore sizes in the range of 5 to 40 Å are also useful. The pores must have the ions

16 7!

15th

easily let through and the dilusion of the other materials impede.

The use of this separator in the form of a cellular glass laminate is true for the production of a usable, repeatedly chargeable cell. »'. however, it leads to a considerable improvement the cyclic charging characteristics of the cell. Using an ordinary kraft paper separator (or a separator that is impregnated with starch or carboxymethyl cellulose or made from porous nylon or vegetable parchment, etc.) gives the cell with hydrazodicarbonamide normally satisfactory results as a depolarizer, up to about 10 charge and discharge cycles. On the other hand, using the cellular glass laminate separator, the cell operates normally over 40 or more cycles satisfactorily. It is indeed the use of cellular glass chloride that is essential not absolutely necessary, but this laminate is used because of its excellent properties preferred in these cells.

The zinc oxide protects the zinc anode by offsetting the effects of the presence of acid which is released during the charging of the cell as a result of the hydrazodicarbonamide. Any basic Material that is insoluble in the electrolyte can likewise be used, e.g. B. barium oxide. For experimental purposes, the secondary cells are usually at high speed over a Discharge the 12 ohm resistor for two hours. On that a direct current is applied for charging and then discharged again. With each unloading will be the discharge properties of the cells were determined.

The invention is illustrated by means of the following examples.

lulls or until the specified times have passed, and then down to a minimum voltage at one reloaded such cycle. The voltage meters. are done with a DC voltmeter.

Using the manufacturing method described above, cells A, B, C, and D were prepared and tested as follows.

A cellular glass laminate separator was used, unless otherwise stated.

Cell A

3.0 g of azodicarboxamide
0.8 g carbon black (HR 1670)
2.8 ml of electrolyteJ

35% ZnCl,
20% NH ₄ Cl

35

example 1

Cell B 3.0 g 0.8 g 2.8 ml azodicarboxamide
Carbon black (HR 1670)
electrolyte
17% ZnCI ₁
27% NH ₄ Cl

The dry cells operated according to the method according to the invention are generally made according to the following Process made:

The depolarizer is mixed dry through and through with the carbon black and then the aqueous electrolyte added. The Syrians are then mixed thoroughly until the electrolyte is dry from the mix is recorded. The resulting uniform mixture is called the cathode mixture.

A zinc container is made by lining the inner surface with a low resistance separator so that about 6.35 mm of the separator protrudes from the edge of the container. The cathode mix is filled in small quantities and tamped down with a glass rod. After filling the cells a carbon rod with a brass cap (the "collector") is inserted concentrically into the mixture and the excess paper is folded over and the mixture is completed. A paper disk is on top placed on the completed mixture and a head gasket is sealed with a sealant, e.g. B. a high melting point wax, an epoxy resin or the like.

Experimental procedure

Cells are tested by either continuously or intermittently using a known Resistance will be discharged until the voltage in the closed circuit falls below a certain value

Cell C 1.0 g azodicarboxamide
1.3 g carbon black (HR 1670)
2.8 ml of electrolyte

17% ZnCl,

27% NH ₄ Cl

Cell D

like cell A with the exception of one
Starch kraft paper separator

These cells were then repeatedly discharged and recharged. For each cell it will be the number of complete charge and discharge cycles indicated before the voltage during the discharge phase of a cycle falls below a certain fixed voltage value. This lower limit is generally set at 0.9 volts.

results

Cell A was alternated across a 12 ohm resistor Discharged for 2 hours and charged with a current of 40 milliamps for 4.5 hours, 18 full cycles were performed before the discharge voltage fell below 0.9 volts fell.

Cell B was treated according to the same program as cell A. 18 complete cycles have been completed, before the discharge voltage dropped below 1.0 volts.

Cell C had a 5 hour discharge through a 25 ohm resistor and a charge time of 12 hours at a current of 20 milliamps. 21 cycles were completed before the Discharge voltage fell below 0.9 volts and an overall efficiency of 97% was measured.

Cell D had an original discharge characteristic the same as that of cell A, but this one Cell could only be discharged and recharged for limited cycles. On the third discharge the voltage fell below 0.8 volts during the 2 hour cycle.

Example 2

Dry cells with hydrazodicarbonamide in the cathode mix were prepared as described in Example 1.

The hydrazodicarboiiumide and zinc oxide if this was used, was dry mixed with carbon black and then added the aqueous electrolyte. The The system is then mixed thoroughly until the electrolyte is absorbed by the dry mix was. Using this mixture, cells were prepared as described in Example 1 above.

Trial procedure

The cell was first activated by exposure to direct current. The charged cell could then by discharging over a known resistance (for example over 150 ohms and slow Discharge) can be tested as a primary cell or it could be used as a secondary or rechargeable cell tested by repeated charging and discharging until the voltage reaches a predetermined value dropped during a discharge portion of a cycle.

Using the procedure described above, cells were made with cellulose laminate separators manufactured and tested as follows

Cell E. G ml Hydrazodicarbonamide 2.0 G Carbon black (HR 1670) 1.0 ml electrolyte 3.0 35% ZnCl 20VoNH ₄ CI Cell F. G Hydrazodicarbonamide 1.6 G Zinc oxide 0.6 G Carbon black (HR 1690) 0.8 ml electrolyte 2.5 35% ZnCI ₂ 20% NH ₄ CI 0.3% HgCl ₃ Cell G G Hydrazodicarbonamide 2.0 G Carbon black (HR 1670) 1.0 0.75 g Zinc oxide 2.4 electrolyte 35% ZnCl 20% NH ₄ Cl 0.3% HgCl ₂

Cell H

like cell G with the exception of the electrolyte
2.4 ml of electrolyte

17% ZnCl ₁

27% NH ₄ CI

0.3% HgCI,

Cell I.

1.0 G I lydrazodicarbonamide electrolyte 1.0 G Azodicarboxamide M % ZnCl, 1.0 G Carbon black (HR 1670) 27% NH ₄ Cl 2.4 ml Electrolvt 0.3% HgCl ₁ 35% ZnCI ₁ 20% NH ₄ CI 0.3% HgCI, Cell J how Cell I with the exception of the electrical unit 2.4 ml

Mercury chloride was found in the cells described above introduced in small amounts. This amalgamated the zinc surfaces and yielded an equipotential surface. This is a common practice.

results

Cell E: This cell was charged using a current of 5.2 milliamps for 88 hours (0.46 ampere-hours or approximately ^[ h full charged.). When discharging through a resistor of 150 ohms, the time until the voltage had dropped to 0.8 volts was 45 hours (efficiency 83%).

Cell F: This cell was originally constructed using a current of 40 milliamps II Charged for hours. It was then discharged through a 12 ohm resistor for 2 hours. The charge-discharge cycles were performed using a 5 hour charge at 40 milliamps of current and a subsequent 2 hour discharge a resistance of 12 ohms continued until the discharge over the 2 hour discharge part of the cycle did not stay constant above 0.9 volts.

Cells G to J: These cells were charged and discharged, as described for cell F above. Similar results were obtained.

Claims (1)

16 71 67! Claim: Procedure for storing and delivering electrical energy with the help of a galvanic cell with a negative zinc electrode, a separator and a depolarizer mixture of azodicarbonamide and carbon black, characterized in that shortly before the first use of the cell the from carbon black with a surface area of at least 200 nr / g, zinc and / or barium oxide, aqueous solution Depolarizer mixture consisting of zinc salt and hydrazodicarbonamide is oxidized with electricity is to oxidize at least part of the hydrazodicarbonamide to A / odicarbonamid that electricity is then withdrawn, the azodicarbonamide being reduced to hydrazodicarbonamide and this cycle is repeated.