Battery unit with reinforced current collector tabs and method of making a battery unit having strengthened current collector tabs

A battery unit includes a battery having an anode including an anode current collector tab, a cathode including a cathode current collector tab, and an electrolyte disposed between the anode and the cathode. The battery is sealed by packaging material such that portions of the anode current collector tab and the cathode current collector tab extend past the exterior of the packaging material. The extended portions of the anode current collector tab and the cathode current collector tab are secured to the exterior of the packaging material to reinforce the extended portions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to batteries and, more particularly, to 
batteries including current collecting tabs. 
2. State of the Art 
In recent years, workers in the battery art have begun to understand the 
advantages of manufacturing batteries that have polymer electrolytes and 
sheet-like anodes and cathodes. The advantages of such so-called "thin 
package" batteries include lower battery weight than comparably-sized 
batteries that employ liquid electrolytes, longer service life, relatively 
high power densities, relatively high specific energies, and the 
elimination of danger due to the spillage of acidic liquid electrolytes. 
Anode and cathode materials used in such batteries may be poor conductors 
of electricity. Thus, in fabricating such batteries, it is generally 
necessary to connect an anode to an anode current collector and a cathode 
to a cathode current collector so that electric energy can be efficiently 
drawn from the battery by an external load. In most of these batteries, 
current collectors are electrically connected to each anode and each 
cathode. Because it is generally an objective, in designing such 
batteries, to make a small, light-weight, yet powerful battery, it is 
desirable to keep the size and weight of the current collectors to a 
minimum. The small, light-weight current collectors are generally 
electrically connected to external loads by known electrical connectors. 
Often, connections formed with connectors such as alligator clips and the 
like damage the current collectors and result in poor performance of the 
battery. It is desirable, therefore, to provide a battery unit having a 
strong current collector arrangement. 
SUMMARY OF THE PRESENT INVENTION 
The present invention, generally speaking, provides a battery unit 
including a reinforced current collector arrangement. 
In accordance with one aspect of the present invention, a battery unit 
includes a battery, the battery having an anode including an anode current 
collector tab, a cathode including a cathode current collector tab, and an 
electrolyte disposed between the anode and the cathode. Packaging material 
surrounds the battery to form a package having top and bottom sides. At 
least a portion of the anode current collector tab and at least a portion 
of the cathode current collector tab extend past an exterior surface of 
the packaging material. The extended portions of the anode current 
collector tab and the cathode current collector tab are secured to the 
exterior surface of the packaging material on at least one of the top and 
bottom sides of the package. 
In accordance with another aspect of the present invention, a method of 
making a battery unit includes the steps of attaching together an anode 
including an anode current collector tab, an electrolyte, and a cathode 
including a cathode current collector tab, such that the electrolyte is 
disposed between the anode and the cathode, thereby forming a battery. The 
battery is surrounded with a packaging material to form a package having a 
top and a bottom side. At least a portion of the anode current collector 
tab and at least a portion of the cathode current collector tab extend 
past the exterior of the packaging material. The anode current collector 
tab and the cathode current collector tab are secured to the exterior of 
the packaging material on at least one of the top and bottom sides of the 
package.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIGS. 1-3, a battery unit 11 includes an anode 23, a cathode 
25, and an electrolyte 27 disposed between the anode and the cathode. The 
anode 23, the cathode 25, and the electrolyte, together, form a battery 
15. In the illustrated embodiment, the anode 23 includes a sheet-like 
anode current collector 29, the anode current collector being formed with 
at least one anode current collector tab 31 extending from an edge of the 
anode current collector, and anode material 33 disposed on at least one 
side of the anode current collector. The cathode 25 includes a sheet-like 
cathode current collector 35, the cathode current collector being formed 
with at least one cathode current collector tab 37 extending from an edge 
of the cathode current collector, and cathode material 39 disposed on at 
least one side of the cathode current collector. The electrolyte 27 is 
disposed between the anode material 33 and the cathode material 39 and is 
preferably a polymer electrolyte. 
The anode current collector 29 and the cathode current collector 35 are 
preferably formed from conductive web or sheet-like materials, the web or 
sheet-like materials preferably having a thickness of approximately 
0.001". In a presently preferred embodiment, the anode current collector 
29 and the cathode current collector 35 are formed from nickel or copper 
webs or sheets. U.S. Pat. No. 4,925,751 to Shackle et al. describes 
certain anode, cathode, and polymer electrolyte materials useful in 
forming the battery unit 11 and is incorporated by reference only to the 
extent that it describes such materials. While only a single cell battery 
15 is shown in FIGS. 1-3, it will be appreciated that many repeating 
layers of anodes 23, cathodes 25, and electrolytes 27 can be stacked on 
top of one another to achieve desired power characteristics in a battery. 
The battery 15 including the anode 23, the cathode 25, and the electrolyte 
27 is surrounded by insulative packaging material 41 to form a thin 
package 21 having a top surface 43 and a bottom surface 45. The anode 
material 33 preferably includes lithium, because of its position in the 
electromotive series, and the packaging material 41 sealing the battery 
components prevents damage to the battery 15 due, for example, to exposure 
of the anode material to moisture. Portions 47, 49 of the anode current 
collector tab 31 and the cathode current collector tab 37, respectively, 
extend past the exterior 51 of the packaging material to facilitate 
forming an electrical connection with an external load. Presently 
preferred packaging materials 41 include moisture-impermeable plastic 
sheets that are sealed around the battery components by means of an 
adhesive or by shrink-wrapping. 
As shown in FIGS. 2 and 3, means 53 are provided for securing the extended 
portions 47, 49 of the anode current collector tab 31 and the cathode 
current collector tab 37 to one of the top and bottom surfaces 43, 45 of 
the package 21 on the exterior 51 of the packaging material such that the 
secured extended portions are reinforced and strengthened. The securing 
means 53 secures the extended portions 47, 49 of the anode current 
collector tab 31 and the cathode current collector tab 37 to the exterior 
51 of the packaging material 41 such that, as shown in FIG. 6, at least a 
portion of the extended portions secured to the packaging material are 
connectable to an external load 59 by known electrical connection means 
57. The extended portions 47, 49 of the anode current collector tab 31 and 
the cathode current collector tab 37 are preferably folded back, as shown 
in FIG. 3, relative to the package 21, to secure the extended portions to 
the exterior 51 of the packaging material 41. The extended portions 47, 49 
are bent around a sufficiently large radius, and are formed of a 
sufficiently flexible, bendable material, such that the extended portions 
are not damaged when they are bent. 
As shown in FIG. 4, the extended portion 47 of the anode current collector 
tab 31 and the extended portion 49 of the cathode current collector tab 37 
are preferably folded relative to the exterior 51 of the package 21 such 
that the extended portion of the anode current collector tab is secured to 
the top surface 43 of the package and the cathode current collector tab is 
secured to the bottom surface 45. If desired, however, the extended 
portions 47, 49 of the anode current collector tab 31 and the cathode 
current collector tab 37 may be folded in the same direction such that the 
extended portions are secured to only one of the top or the bottom 
surfaces 43, 45 of the package 21, as shown in FIG. 5. 
As shown in FIGS. 4 and 5, the anode and cathode current collector tabs 31 
and 37 preferably extend past the exterior 51 of the packaging material 41 
at different points such that the extended portions 47, 49 are not 
disposed close enough to one another to inadvertently contact one another. 
The extended portions 47, 49 of the anode current collector tab 31 and the 
cathode current collector tab 37 preferably extend from the same side of 
the package 21. However, if desired, the extended portions 47, 49 may 
extend from different sides of the package 21. 
As shown in FIGS. 2 and 3, the securing means 53 preferably includes a 
small piece of double-sided, electrically insulative tape adhering, on one 
side of the tape, to one side of the extended portions 47, 49 of the anode 
current collector tab 31 and the cathode current collector tab 37 and, as 
shown in FIG. 3, on the other side of the tape, to the exterior 51 of the 
top or bottom surfaces 43, 45 of the packaging material 41. Other securing 
means 53 may include, for example, known adhesive materials. 
As shown in FIG. 5, the battery unit 11 is preferably further provided with 
cushioning means 55 for cushioning the battery unit when certain types of 
electrical connection means 57 (FIG. 6) are used to electrically connect 
the battery unit to the extended portions 47, 49 of the anode current 
collector tab 31 and the cathode current collector tab 37 to external 
loads. The cushioning means 55 are secured to the exterior surface 51 of 
the package 21 on the opposite sides 43, 45 of the package from the 
securement of the extended portions 47, 49 of the anode current collector 
tab 31 and the cathode current collector tab 37 are secured. When 
electrical connection means 57 such as known alligator clips, as shown in 
FIG. 6, are used to form electrical connections between the battery unit 
11 and an external load 59, the connection means may be to indelicate for 
the battery unit and may, in certain instances, cause damage to the 
battery or to the extended portions 47, 49 of the anode current collector 
tab 31 and the cathode current collector tab. The cushioning means 55 
facilitates using electrical connection means 57 of the type that connect 
by compressively gripping the object to be connected in that the 
cushioning means prevents the electrical connection means from accidently 
deforming the battery unit or tearing through the packaging material 41 on 
the side opposite from the securement of the extended portions 47, 49. The 
cushioning means 55 is preferably formed of one or more layers of an 
insulative tape. 
The battery unit 11 is made by attaching together the anode 23 including 
the anode current collector tab 31, the electrolyte 27, and the cathode 25 
including the cathode current collector tab 37, such that the electrolyte 
is disposed between the anode and the cathode, the layered anode, 
electrolyte, and cathode thereby forming the battery 15. In accordance 
with a presently preferred embodiment, the anode material 33 (usually 
lithium) is deposited on the anode current collector tab 31 by a 
chemical-vapor deposition process. The anode material 33 may, however, be 
applied, in the form of a thin sheet, to the anode current collector tab 
31. In accordance with a presently preferred embodiment, the cathode 
material 39 is coated on the cathode current collector 35 by extruding 
cathode material onto a web of material for forming the cathode current 
collector and rolling the cathode material to a uniform thickness on the 
cathode current collector. In accordance with a presently preferred 
embodiment, the electrolyte 27 is applied on top of a uniform thickness 
layer of cathode material 39 on the cathode current collector 35 by, e.g., 
a doctor blade assembly. 
The battery 15 is sealed with packaging material 41, such that it is 
moisture-impermeable, to form the package 21 having the top surface 43 and 
the bottom surface 45. The packaging material 41 is preferably sealed 
around the battery 15 with an adhesive (not shown) for sealing edges of 
the packaging material together. However, the packaging material 41 may be 
shrink-wrap material and may be seal the battery 15 by being shrunk around 
the battery. The extended portion 47 of the anode current collector tab 31 
and the extended portion 49 of the cathode current collector tab 37 extend 
past the exterior 51 of the packaging material 41. As shown in FIGS. 2 and 
3, the extended portion 47 of the anode current collector tab 31 and the 
extended portion 49 of the cathode current collector tab 37 are secured to 
the exterior 51 of the packaging material 41 on at least one of the top 
and bottom surfaces 43, 45 of the package 21. The extended portions 47, 49 
are folded around a sufficiently large radius and are formed of a 
sufficiently bendable and flexible material such that they are not damaged 
when being folded back to be secured to the exterior 51 of the packaging 
material. Preferably, the extended portions 47, 49 are sufficiently 
bendable and flexible that they fold around thin packaging material 41 
without being damaged. 
The anode current collector tab 31 and the cathode current collector tab 37 
are secured to the exterior 51 of the packaging material 41 with securing 
means 53 such as an adhesive or double-sided tape. If desired, the 
extended portions 47, 49 of the anode current collector tab 31 and the 
cathode current collector tab 37 may be attached to the same or to 
opposite ones of the top and bottom surfaces 43, 45 of the package 21. 
Cushioning means 55 may be secured on the top and bottom surfaces 43, 45 
the battery unit 11 opposite to the securement of the extended portion 47 
of the anode current collector tab 31 and the extended portion 49 of the 
cathode current collector tab 37. The cushioning means 55 preferably are 
formed from insulative tape of sufficient integrity to withstand clamping 
forces from means for forming an electrical connection 57 with the battery 
unit 11. Means for forming an electrical connection 57 to the anode 
current collector tab 31 and the cathode current collector tab 37 are 
attached to the extended portions 47, 49. Preferably, the electrical 
connection means 57, such as alligator clips, grip the battery unit 11 
around the cushioning means 55 and the extended portions 47, 49 of the 
anode current collector tab 31 and the cathode current collector tab 37. 
The foregoing has described the principles, preferred embodiments and modes 
of operation of the present invention. However, the invention should not 
be construed as limited to the particular embodiments discussed. Instead, 
the above-described embodiments should be regarded as illustrative rather 
than restrictive, and it should be appreciated that variations may be made 
in those embodiments by workers skilled in the art without departing from 
the scope of present invention as defined by the following claims.