1957-10-16

Abstract of GB784851 784,851. Batteries. ACCUMULATORENFABRIK AKT.-GES. Nov. 28, 1952 [Dec. 1, 1951], No. 30287/52. Class 53. To prevent gassing in a sealed alkaline accumulator if the polarity should become reversed when a number of such cells having positive and negative electrodes of the same capacity are joined in series, the positive electrode contains a quantity of negative active material in addition to the normal positive material, and the negative electrode contains some positive active material in addition to the negative material. Only one of the electrodes has the additional active material if the other electrode is large and is provided with an excess of the normal active material. The additional active material may be mixed with the normal active material or it may be contained in separate pockets or tubes forming a part of the electrode. In an example the positive electrode comprises nickel hydroxide, nickel flakes and graphite with an addition of cadmium oxide or hydroxide. The negative electrode may consist of cadmium or iron with an addition of nickel hydroxide, cobalt hydroxide or copper powder. Specification 433,809 is referred to.

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1957-10-16

H01M4/24 ; H01M4/02 ; H01M4/36 ; H01M4/52 ; H01M4/62 ; H01M4/76 ; H01M4/24 ; H01M4/02 ; H01M4/36 ; H01M4/52 ; H01M4/62 ; H01M4/70

H01M4/24

GB19520030287 19521128

DE1951A014618 19511201

FR1066769 (A); CH314756 (A); BE515722 (A); NL88619C (C); DE899216 (C1)

1	Improvements in or relating to alkaline electrlc accumulators
	Inventor:	Applicant: ACCUMULATOREN FABRIK AG (DE)
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: AT181300B B - 1955-03-10
2	Improvements in or relating to alkaline electrlc accumulators
	Inventor:	Applicant:
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: BE515722 A - 0000-00-00
3	Improvements in or relating to alkaline electrlc accumulators
	Inventor: DASSLER ADOLF DR (DE)	Applicant: ACCUMULATOREN FABRIK AKTIENGES (DE)
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: CH314756 A - 1956-06-30
4	Improvements in or relating to alkaline electrlc accumulators
	Inventor: DASSLER DIPL-CHEM DR ADOLF	Applicant: ACCUMULATOREN FABRIK AG
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: DE899216 C - 0000-00-00
5	Improvements in or relating to alkaline electrlc accumulators
	Inventor:	Applicant: ACCUMULATOREN FABRIK AG
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: FR1066769 A - 1954-06-09
6	Improvements in or relating to alkaline electrlc accumulators
	Inventor:	Applicant: ACCUMULATOREN FABRIK AG
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: GB784851 A - 1957-10-16
7	Improvements in or relating to alkaline electrlc accumulators
	Inventor:	Applicant:
	EC:H01M4/24	IPC: H01M4/24;H01M4/02; H01M4/36(+9)
	Publication info: NL88619C C - 0000-00-00

What we claim is:

1 A gas-tight alkaline accumulator in which either only the electrode having the smaller capacity or each electrode contains 65 an additive which, in the event of a current continuing to flow through the accumulator in the discharge direction after the polarity of the accumulator has become reversed.

undergoes an electro-chemical reaction and 70 thereby suppresses the evolution of gas from the said electrode or electrodes.

2 A gas-tight alkaline accumulator as claimed in Claim 1, in which the negative electrode is of larger capacity than the posi 75 tive electrode, the said additive is cadmium oxide or cadmium hydroxide and only the positive electrode contains the said additive.

3 A gas-tight alkaline accumulator as claimed in Claim I, in which the positive 80 electrode is of larger capacity than the negative electrode, the said additive is nickel 2-hydroxide and only the negative electrode contains the said additive.

4 A gas-tight alkaline accumulator as 85 claimed in Claim 1, in which the capacity of the positive electrode is substantially equal to that of the negative electrode and each electrode contains an additive, the said additive being cadmium oxide or cadmium hy 90 droxide in the case of the positive electrode and nickel 2-hydroxide in the case of the negative electrode.

A gas-tight alkaline accumulator as claimed in any one of Claims 1 to 4, in 95 which the said additive is contained in pockets, tubes, a plate, or a portion of a plate of the electrode or electrodes that does not contain the active mass.

6 A gas-tight alkaline accumulator as 100 claimed in any one of Claims 1 to 4, in which the said additive is intimately mixed with the active mass.

7 A gas-tight alkaline accumulator as claimed in Claim 6 in which the active mass 10 os and the said additive are precipitated from a single solution.

ABEL & IMRAY.

Agents for the Applicants, Quality House, Quality Court.

Chancery Lane, London W C 2.

P;.Tred '-r Mer in:tv' tt',necrv Office by Kingston Printers Ltd, Pnrtniouth 3 < _i-lat .;t'lhed it rhe Patent Offete, 25, Southampton Buildings, L indeon, W C 2 frum: z T, -f .qy be obtair ed.

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PATENT SPECIFICATION

Date of Application and Filing Complete Specification: Nov 28, 1952.

784,851 No 30237 t 52, l;)) Application made in Germany on Dec 1, 1951.

Complete Specification Published: Oct 16, 1957.

Index at Acceptance-Class 53, BD(IOA: 12), BSIA( 3: 5: 6: 7; 10: 14: X), B 53 A Lo International Classification:-H Olm.

COMPLETE SPECIFICATION.

Improvements in or relating to Alkaline Electr Ic Accumulators.

We, ACCUMULATOREN-FAB Ri K AKTIENGESELLSCHAFT, a German Company, of Dieckstrasse 42, Hagen in Westfalen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to gas-tight alkaline accumulators.

It has been shown by experience that after long use under practical conditions the individual cells of alkaline accumulator batteries do not always possess uniform capacity with respect to one another even when they are provided in manufacture with equal quantities of active material having the same properties In spite of similar electrical treatment, the series-arranged individual cells of the battery wear out in course of time with varying rapidity In the discharge of the battery the voltage across some elements prematurely drops whilst others still have sufficient voltage to enable further current to be taken from the battery Finally, the differences in capacity of the individual cells-especially with defective servicingcan be so great that some cells reverse their polarity when the battery is completely discharged In the further discharge flow of current after this reversal of polarity, oxygen or hydrogen or both are soon generated at the electrodes of such elements after the potential thereof has fallen below zero point and after change of their polarity and according as to whether the positive or negative electrodes, or both together, reverse their polarity, such generation of gas corresponding to the discharge current This generation of gas on the one hand produces a risk of the battery casing exploding if hydrogen or an explosive mixture of hydrogen and oxygen is formed, and on the other hand the elements enclosed in a gas-tight manner in the casing are liable to swell up and explode owing to the gas formation.

This is also to be feared with elements provided with gas absorbing electrodes, for example according to British Patent Specificatiin No 433,809, since these electrodes are 50 only able to cope with the small quantities of gas generated due to charging and fail to function in the event of reversal of their polarity.

It is an object of this invention to provide 55 a gas-tight alkaline accumulator in which gas formation does not occur when the accumulator is discharged beyond the point at which reversal of polarity of the electrodes occurs 60 This invention provides a gas-tight alkaline accumulator in which either only the electrode having the smaller capacity or each electrode contains an additive which, in the event of a current continuing to flow through 65 the accumulator in the discharge direction after the polarity of the accumulator has become reversed, undergoes an electrochemical reaction and thereby suppresses the evolution of gas from the said electrode 70 or electrodes.

It has been found that the generation of hydrogen which occurs at the positive electrode (nickel-oxide electrode) immediately after reversal of polarity may be effectively 75 suppressed by loading this electrode not only with the normal mass usually employed (nickel hydroxide + conductive material, for example, graphite or nickel flakes), but also with an 'anti-polar' mass, that is, in 80 this case, with a cathodic reducible oxide, for example cadmium oxide or cadmium hydroxide, that is to say with a material like that previously used in alkaline accumulators for loading the negative electrode 85 and which is reducible at a potential value below the separation potential of hydrogen.

The cadmium oxide present in the positive electrode to a certain extent acts as an acceptor for hydrogen in that with pole re 90 784,851 -ersal of the element it is reduced at a malerially lower potential than is necessary for generation of hydrogen at the electrode It s only after the cadmium oxide present has been reduced to metal that the electrode can generate hydrogen upon further passage of current If, moreover, the opposite electrode, i e the negative electrode of the element is made sufficiently large and efficient, i e is provided with the necessary excess of negative mass, such element is unable to generate any gas, either hydrogen or oxygen, at the end of the discharge with reversal of polarity.

Conversely, according to the invention the capacity of the positive electrode may be made greater than that of the negative electrode and the negative electrode may be provided with an 'anti-polar' mass, i e besides being loaded with the normal negative mass (cadmium or iron) is also loaded with an anodic oxidisable oxide (for example nickel 2-hydroxide, cobalt 2-hydroxide etc) or with an anodic oxidisable metal (which is nobler than that of the normal negative mass), for example with copper powder In this case the nickel 2-hydroxide or the copper in the electrode acts as an acceptor for oxygen formerly produced upon reversal of polarity of the electrode In order to improve the efficiency of the 'anti-polar' mass employed there is added thereto inter alia a sufficiently large quantity of conductive material (for example, graphite or nickel flakes.

Alternatively, according to the invention both electrodes of the element may be provided with normal and also with anti-polar masses, i e the positive electrode with a cathodic reducible oxide and the negative electrode with an anodic oxidisable oxide or metal which is nobler than the metal employed as the normal negative and which can only display its effectiveness after discharge of the normal negative mass.

The plates of alkaline accumulators commonly consist of a structure such as, for example, a number of small tubes joined to form a plate, or a body of sintered metal, which provides a number of pockets or pores which contain the active mass The aforesaid 'anti-polar' mass may be mounted in separate pockets or pores or in a separate dlate connected to the plate carrying the active mass Alternatively, the 'anti-polar' mass may be in admixture with the active -mass Thus for example the active mass and the 'anti-polar' mass may be deposited in the pockets or pores of the electrode carrier by precipitation from a common solution 60