In-situ electrolyte storage for batteries

The present invention provides in-situ electrolyte storage for batteries. The size of the reserve battery is significantly smaller due to the placement of an elastomeric sealed container within the interelectrode space of the battery. The sealed container contains the electrolyte. When punctured, the electrolyte flows out of the sealed container and into the electrode space. Substantially simultaneously, the elastomeric sealed container shrinks back allowing the electrolyte to flow into the interelectrode space allowing for the reaction. Preferably, the sealed container is made of elastomeric material that is flexible yet with good memory. This will allow the sealed container to shrink back to a small size when punctured. In addition, the sealed container should have have a low permeability to the electrolyte so as to minimize the amount of electrolyte that escapes from the sealed container while the electrolyte is being stored.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to in-situ storage of electrolyte for batteries, 
especially as applied to ambient temperature reserve batteries. 
2. Description of the Prior Art 
Electrolyte is typically stored outside of the battery cavity in most 
reserve batteries, so as to prevent leakage of the electrolyte to the 
vicinity of the anode and cathode prior to use. This location of 
electrolyte outside of the battery itself requires that the battery size 
be large in order to accommodate the electrolyte storage. 
There remains a need for a compact battery that provides storage of the 
electrolyte within the battery housing and separate from the battery 
electrodes. This need is especially critical in cases where the 
electrolyte can degrade other components of the battery. 
SUMMARY OF THE PRESENT INVENTION 
The present invention has met the above described needs by providing 
in-situ electrolyte storage for batteries. The size of the reserve battery 
is relatively smaller than prior art reserve batteries due to the 
placement of a sealed container, preferably having a flexible wall within 
the interelectrode space of the battery. The sealed container contains the 
electrolyte. When the sealed container is punctured by the user prior to 
use, the electrolyte flows out of the sealed container and into the 
interelectrode space. Substantially simultaneously the sealed container 
shrinks, allowing the electrolyte to flow into the interelectrode space 
activating the anode-cathode reaction. Preferably, the sealed container is 
made of elastomeric material that is flexible yet with good memory. This 
will allow the sealed container to shrink back to a small size when 
punctured. In addition, the sealed container should have a low 
permeability so as to resist escape of electrolyte from the sealed 
container while the electrolyte is being stored. 
It is an object of the present invention to provide in-situ electrolyte 
storage for reserve batteries. 
It is a further object of the present invention to provide such a battery 
of reduced size as compared with other batteries of this type. 
It is another object of the present invention to provide a sealed container 
which contains the electrolyte and preferably having a flexible wall 
composed of a material having a good memory. 
It is an object of the present invention to provide a sealed container 
containing electrolyte and disposed in the interelectrode space of the 
reserve battery. 
It is a further object of the present invention to provide a puncturing 
means for puncturing the sealed container, thereby flooding the 
interelectrode space with electrolyte. 
It is yet another object of the present invention to provide a method of 
in-situ electrolyte storage. 
It is yet a further object of the present invention to provide an in-situ 
electrolyte storage of a battery that provides long-term storage with 
minimal loss of electrolyte by either vaporization or chemical reaction. 
It is an object of the present invention to provide a method of providing 
long term, in-situ storage of electrolyte in a reserve battery. 
These and other objects of the present invention will be more fully 
understood from the following description of the invention on reference to 
the illustrations appended hereto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention relates to batteries and more specifically, to 
reserve batteries. It is preferred that reserve batteries have virtually 
extremely long shelf life. The prior art reserve batteries usually have 
electrolyte stored outside of the battery housing. The electrolyte storage 
area and battery are separated, usually by a separating means such as a 
diaphragm-like device. When the battery is used, the electrolyte then is 
forced into the battery housing by various means such as pressure. The 
presence of the electrolyte stored outside of the battery housing 
increases the size of the reserve battery by about two or three times. 
The present invention provides for in-situ storage of electrolyte in a 
battery. Referring now to the FIGS. 1 through 3, the battery 2 consists of 
a housing 1, an anode 4 disposed within the housing 1. Preferably, the 
anode is composed of an aluminum base anode. A cathode 6 is disposed 
within the housing 1, in a generally spaced relationship to the anode 4. 
Preferably, the cathode 6 is generally parallel to the anode 4. The 
cathode 6 is preferably an air cathode. 
The battery housing 1 may be preferably sealed. The presence of the spaced 
relationship between the anode 4 and cathode 6 creates an interelectrode 
space 12 (FIG. 2) within which electrolyte 3 (FIG. 1) is disposed. In one 
aspect, separator means 8, 10 may maintain a predetermined spacing between 
the anode 4 and cathode 6. 
The sealed container 14 which in the form shown is disposed within the 
housing 1 may be made of a butyl rubber elastomer having an unexpanded 
wall thickness of about 0.5 mm. Container 14 may contain electrolyte, such 
as 4N NaOH and 0.06N sodium stannate, for example. This embodiment showed 
a 0.74 percent weight increase in the electrolyte per year of storage. The 
weight increase will come from adsorption of carbon dioxide and water from 
the atmosphere. Alternatively, the sealed container may contain deionized 
water with the electrolyte materials such as the sodium hydroxide and 
sodium stannate may be stored within the interelectrode space 12 but 
outside of the sealed container. When activated, the water in the sealed 
container will flood the chamber and mix with the electrolyte materials to 
form electrolyte. This alternative embodiment showed a 2 percent weight 
decrease per year with the weight decrease probably due to water vapor 
loss from the sealed container. 
The separator means 8, 10 are disposed between the anode 4 and cathode 6 in 
a relatively spaced relationship. Preferably the separator means 8, 10 are 
in a spaced relationship and preferably are generally parallel to each 
other. The separator means 8, 10, anode 4, and cathode 6 define an 
interelectrode space 12 (FIG. 2). 
A pair of electrically conductive tabs 11, 13 are connected respectively to 
anode 4 and cathode 6 for electrical connections. A sealed container 14 
(FIG. 3) is disposed within the interelectrode space 12. The sealed 
container 14 contains the electrolyte 3. The sealed container 14 should 
preferably be composed of an elastomeric material of low permeability to 
vapors. The sealed container 16 should be filled with sufficient 
electrolyte 3 to activate the battery and when in this expanded state 
should be easily puncturable. The elastomeric material of sealed container 
14 should have good memory so that after the sealed container is 
punctured, the elastomeric sealed container 14 will shrink back into 
minimal space. 
The presence of electrolyte in the interelectrode space 12 prior to 
activation may reduce the activity and therefore, the power of the battery 
when activated. The sealed container 14 material should be of low 
permeability to electrolyte, so as to minimize the escape of electrolyte 
into the interelectrode space 12. The elastomeric material should be 
chemically inert with respect to the electrolyte material. 
As shown in FIG. 4, disposed along the wall of the separator means 10 is an 
activating pin or puncturing means 16. When the battery is desired to be 
used, the puncturing means 16 is inserted into and pierces the elastomeric 
sealed container 16, thereby puncturing the sealed container 14. 
Preferably, the puncturing means may be a needle. The puncturing means 16 
may be disposed in the separator 10 by passing it through a septum (not 
shown in FIG. 1). Alternatively, the puncturing means 16 may be inserted 
through the housing. 
FIG. 4 shows a cross-sectional illustration of separator means 10. 
Puncturing means 16 have a shaft 20 and a head 22. Puncturing means 16 are 
preferably disposed within separator means 10 through a septum 24. When 
activation of the battery is desired, the head 22 of puncturing means 16 
is pressed, pushing the puncturing means 16 into the interelectrode space 
12 (FIG. 2) and into the wall of the sealed container 14 (FIGS. 3 and 4). 
Referring again to FIGS. 1 and 2, once the sealed container 14 is freed 
electrolyte 3 floods the interelectrode space 12. Substantially 
simultaneously, the elastomeric sealed container 14 collapses to its 
original shape prior to being filled with electrolyte. Preferably, the 
sealed container 14 shrinks back to less than about 10% of the volume of 
its size when expanded with electrolyte. 
In a preferred embodiment shown in FIGS. 5-7, the battery 26 consists of a 
housing 28, an anode 30 and its associated separator 31 disposed within 
the housing 28. A cathode 32 is disposed within the housing 28 in a 
generally spaced relationship to the anode 30. Electrically conductive 
tabs 38,40 are, respectively, connected to anode 30 and cathode 32. The 
support frame 33 has grid 35. The anode 30 is composed of an aluminum base 
alloy which is secured on a frame (not shown) such as plexiglass by means 
of silicone rubber cement or tape. An electrode separator 34 may be 
disposed between the anode 30 and cathode 32. The electrode separator 34 
may preferably be about 0.5 cm thick. The electrode separator 34 is 
preferably generally parallel to the anode and cathode. In one aspect a 
cathode support frame (not shown) may be placed behind the electrode 32. 
The anode-cathode assembly may advantageously be secured by mechanical 
fasteners such as bolts 36 and the associated nuts. 
When an aluminum-air battery is used, it is preferred that the electrolyte 
be either caustic or saline. Caustic electrolytes may be sodium hydroxide, 
potassium hydroxide and the like. It is preferred that the caustic 
solution be about 4M or greater. 
In an alternate embodiment, the battery may be composed of flexible 
materials. A piston (not shown) may be used to compress the battery 
housing, thereby allowing the elastomeric sealed container to burst, 
shrink back, and allow the electrolyte to flood the interelectrode space. 
It will be appreciated that the present invention provides a compact 
reserve battery with long-term storage capabilities. The reserve battery 
has a housing. An anode and a cathode are both disposed within the 
housing. The anode and cathode are in a relative spaced relationship 
within the housing, thereby creating an interelectrode space. The battery 
contains an elastomeric sealed container which contains electrolyte and is 
disposed within the interelectrode space. When it is desired for the 
battery to be activated, puncturing means pierce the sealed container. The 
sealed container collapses to its original size and causes the electrolyte 
to flood the interelectrode space. 
The present invention also discloses a method of providing long-term 
in-situ storage of electrolyte in a reserve battery. The reserve battery 
discussed hereinbefore is provided. The sealed container is punctured by 
puncturing means to release the electrolyte contained therein. The sealed 
container shrinks when the electrolyte floods the interelectrode space. 
Whereas particular embodiments of the present invention have been described 
above for purposes of illustration, it will be evident to those skilled in 
the art that numerous variations of the details may be made without 
departing from the invention as defined in the appended claims.