Method of forming button-type battery lithium electrodes

A method of forming a button-type lithium electrode includes: a) masking an electrically conductive sheet with a material to which elemental lithium will not appreciably adhere to define a masked portion and an unmasked portion, the unmasked portion being in the shape of the desired electrode being formed; c) applying molten lithium to the masked sheet to cause elemental lithium to adhere to the unmasked portion but not appreciably adhere to the masked portion; alternately, directing a lithium stream onto the sheet; d) solidifying the lithium on the unmasked portion to in situ form a lithium electrode; and e) after solidifying, removing the masking material from the masked portion of the sheet. An alternate method includes: a) providing a release liner sheet having elemental lithium adhered thereto in the form of a series of discrete patterns having a size and shape of the lithium electrodes being formed; b) providing an electrically conductive sheet having an exposed surface which is divisible into a plurality of areas; c) laminating the release liner sheet with the conductive sheet to adhere the series of discrete elemental lithium patterns onto the respective sheet areas; d) pulling the release liner sheet from the conductive sheet and discrete lithium patterns, leaving the discrete lithium patterns adhering to the conductive sheet; and e) cutting and forming a plurality of discrete battery terminal housing members from the areas of the sheet, with each of the discrete battery terminal housings bearing one of the discrete lithium patterns.

TECHNICAL FIELD 
This invention relates to forming button-type battery lithium electrodes. 
BACKGROUND OF THE INVENTION 
Button-type batteries are small, thin energy cells that are commonly used 
in watches and other electronic devices requiring a thin profile. A 
conventional button-type battery includes two electrodes in the form of an 
anode and a cathode. These are separated by a porous separator. An 
electrolyte is present within pores of the separator. 
These internal battery components are housed within a metal casing or 
housing formed by a lower conductive can and an upper conductive lid. A 
common prior art material for the can and lid is stainless steel. The can 
is typically in electrical contact with the cathode to form the positive 
battery terminal, and the lid is in electrical contact with the anode to 
form the negative battery terminal. The can and lid are crimped or pressed 
together to form a fluid-tight seal which entirely encloses the anode, 
cathode, separator, and electrolyte. An electrically insulating sealing 
gasket is provided within the primary seal between the lid and can to 
electrically isolate the two housing members. 
Typically, the can and lid are separately pre-formed with the anode and 
cathode materials being inserted after housing formation. One electrode 
material is elemental lithium, which is typically utilized within the lid 
as the anode electrode. The typical anode assembly method comprises 
placing a piece of lithium, already in its finished anode shape, to within 
the center of a pre-formed lid. The lithium adheres to the lid material, 
and the lid/lithium composite can then be easily moved in juxtaposition to 
the cathode can without dislodging the lithium. However, one difficulty 
with this method concerns handling of the elemental lithium. In short, 
lithium is sticky and adheres to most everything with which it comes into 
contact. This makes it extremely difficult for the assembler to 
appropriately and precisely position the lithium within the lid without it 
sticking to the insertion tool and other objects. 
It would be desirable to develop improved methods of forming button-type 
lithium electrodes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
This disclosure of the invention is submitted in furtherance of the 
constitutional purposes of the U.S. Patent Laws "to promote the progress 
of science and useful arts" (Article 1, Section 8). 
This invention concerns "coin" or "button-type" batteries, and their 
components. A button-type battery is typically a small, circular-shaped 
energy cell approximately the size of a coin. The button-type battery can 
be constructed in different sizes, with typical diameters being 12 mm, 16 
mm, and 20 mm. Other shapes are possible, but the circular shape is most 
common. 
In accordance with one aspect of the invention, a method of forming a 
button-type lithium electrode comprises the following steps: 
providing an electrically conductive sheet having an exposed surface, the 
electrically conductive sheet being comprised of a material to which 
elemental lithium will adhere; 
masking the electrically conductive sheet with a material to which 
elemental lithium will not appreciably adhere, the masking defining a 
masked portion and an unmasked portion, the unmasked portion of the 
conductive sheet having a cross-sectional size and shape of the desired 
electrode being formed; 
applying molten lithium to the masked electrically conductive sheet to 
cause elemental lithium to adhere to the unmasked portion but not 
appreciably adhere to the masked portion; 
solidifying the elemental lithium on the unmasked portion to in situ form a 
lithium electrode on the unmasked portion; and 
after solidifying, removing the masking material from the masked portion of 
the conductive sheet. 
In accordance with another aspect of the invention, a method of forming a 
plurality of button-type lithium electrodes comprises the following steps: 
providing an electrically conductive sheet having an exposed surface, the 
electrically conductive sheet being comprised of a material to which 
elemental lithium will adhere; 
masking the electrically conductive sheet with a material to which 
elemental lithium will not appreciably adhere, the masking defining a 
masked portion and an unmasked portion, the unmasked portion of the 
conductive sheet having a cross-sectional size and shape of the desired 
electrode being formed; 
providing and directing a lithium stream onto the electrically conductive 
sheet to cause elemental lithium to adhere to the unmasked portion but not 
appreciably adhere to the masked portion; and 
solidifying the lithium stream on the unmasked portion to in situ form a 
lithium electrode. 
In accordance with still another aspect of the invention, a method of 
forming a plurality of button-type lithium electrodes comprises the 
following steps: 
providing a release liner sheet having elemental lithium adhered thereto, 
the adhered elemental lithium being in the form of a series of discrete 
patterns having a size and shape of the lithium electrodes being formed; 
providing an electrically conductive sheet having an exposed surface, the 
exposed surface being divisible into a plurality of areas; 
laminating the release liner sheet with the electrically conductive sheet 
to adhere the series of discrete elemental lithium patterns onto the 
respective sheet areas; 
pulling the release liner sheet from the electrically conductive sheet and 
discrete lithium patterns, leaving the discrete lithium patterns adhering 
to the electrically conductive sheet; and 
cutting and forming a plurality of discrete battery terminal housing 
members from the areas of the electrically conductive sheet, with each of 
the discrete battery terminal housings bearing one of the discrete lithium 
patterns. 
The discussion proceeds first with respect to FIGS. 1-6 with the 
description of one preferred embodiment of the invention. Referring first 
to FIGS. 1-2, there illustrated is a release liner sheet 10 (polypropylene 
being an example) having an exposed surface 12. An example thickness of 
sheet 10 is 3 mils. Sheet 10 has elemental lithium adhered thereto in the 
form of a series of discrete patterns 14a, 14b, 14c, and 14d (collectively 
referred to as patterns 14) which each has a size and shape of the 
resultant lithium electrodes being formed. 
Referring to FIG. 3, an electrically conductive sheet 16 in the form of an 
elongated continuous strip is provided. Conductive sheet 16 is comprised 
of a material to which elemental lithium will adhere, with 304 stainless 
steel being a preferred example. An example thickness is 6 mils. Sheet 16 
includes an exposed surface 18 which is divisible into a plurality of 
areas 20a, 20b, 20c, and 20d (collectively referred to as areas 20). Sheet 
16 constitutes the material from which a series of discrete battery 
terminal housing members will be cut and formed for retaining the 
button-type lithium electrodes. 
Referring to FIG. 4, release liner sheet 10 is laminated with sheet 16 to 
adhere the series of discrete elemental lithium patterns 14 onto the 
respective sheet areas 20. Release liner sheet 10 is thereafter pulled 
away at location 25 from electrically conductive sheet 16 and discrete 
lithium patterns 14, with the discrete lithium patterns 14 adhering to 
sheet 16. Thereafter, sheet 16 is cut and formed into a plurality of 
discrete terminal housing members from areas 20, with each of the discrete 
battery terminal housings bearing one of the discrete lithium patterns 14. 
An example finished construction is shown in FIGS. 5 and 6. Such comprises 
a battery terminal housing member 26 comprised of a central portion 28 and 
an annular surrounding peripheral portion 30. Peripheral portion 30 angles 
away from central portion 28 at a continuous circle, peripheral angle 32. 
Accordingly, angle 32 defines a cross-sectional shape and periphery for 
central portion 28. Peripheral portion 30 includes an angling section 34 
and a upper flat, horizontal portion 36. Angling portion 34 defines an 
internal receptacle volume, while annular portion 36 is utilized for 
joining with a corresponding juxtaposed section (not shown) of the can 
portion of the button-type battery. Materials of the tooling utilized to 
bend or form sheet sections 20 into housing 26 which might come into 
contact are preferably composed of or coated with a material to which 
lithium will not adhere. An example material is Delrin.TM., available from 
DuPont. 
Another alternate method in accordance with the invention is described with 
reference to FIGS. 7-9. FIG. 7 illustrates an electrically conductive 
sheet 40 which essentially constitutes the formed battery terminal housing 
member 26 of FIG. 5, less the lithium. Like numbers of construction from 
FIG. 5 for receptacle 26 formed by sheet 40 are utilized where 
appropriate. Thus, the stated electrically conductive sheet in this 
described embodiment is in the form of a pre-formed electrically 
conductive terminal housing member. Such is comprised of a material to 
which elemental lithium will adhere, with 304 stainless steel being but 
one example. 
Pre-formed sheet 40 is masked with a masking material 42 which is comprised 
of a substance to which elemental lithium will not appreciably adhere. An 
example and preferred masking material is TC 580.TM. available from 
Techform Laboratories of Orange, Calif. Masking material 42 defines a 
masked portion 44 where material of sheet 40 is covered, and an unmasked 
portion 46 where masking material 42 does not cover sheet 40. Unmasked 
portion 46 has a cross-sectional size and shape of the desired lithium 
electrode being formed. Accordingly, the masked portion 44 comprises 
peripheral portion 30, as well as the back portion of sheet 40. In the 
illustrated and preferred embodiment, masked portion 44 at least covers 
all of the internal peripheral portion 30 such that only and all of 
central portion 28 within housing 26 is exposed. 
Referring to FIG. 8, masked sheet 40 is dipped into molten elemental 
lithium to cause a film 48 of elemental lithium to adhere to unmasked 
portion 46, but not appreciably adhere to masked portion 44. Typically and 
preferably, sheet 40 is at a temperature below the melting temperature of 
lithium (180.54.degree. C.) prior to its dipping into the molten lithium 
to facilitate lithium adherence to the unmasked portion. Thereafter, the 
sheet is removed from the molten lithium such that the temperature of film 
48 falls to below the melting temperature of elemental lithium. This 
solidifies film 48 on unmasked portion 46 to in situ form a lithium 
electrode in the form of layer 48. After solidifying, the masking material 
is simply removed from masked portion 44 of sheet 40 to leave the finished 
construction of FIG. 9, which is essentially identical to the construction 
of first embodiment FIG. 5. 
The above-described embodiment provides but one example where an 
electrically conductive sheet is pre-formed prior to the masking and 
applying steps. An alternate embodiment where masking and applying occur 
prior to the housing bending/forming steps is described below with 
reference to FIGS. 10-13. Referring first to FIGS. 10 and 11, an 
electrically conductive sheet in the form of a continuous strip of 304 
stainless steel is indicated generally by reference numeral 55. Such is 
masked with the same masking material 56 to which elemental lithium will 
not appreciably adhere. The masking material 56 atop sheet 55 defines 
masked portions 58 and unmasked portions or holes 60. Holes 60 are of the 
same cross-sectional size and shape of the desired electrodes to be 
formed. Thus, FIGS. 10 and 11 represent a negative image of the embodiment 
shown by FIGS. 1 and 2. 
Referring to FIG. 12, strip 55 is dipped or passed over a wave of molten 
elemental lithium (a process analogous to wave soldering of printed 
circuit boards) to cause unmasked regions or holes 60 to be filled with 
elemental lithium blocks 62. Such solidify when the temperature is lowered 
below lithium's melting point. Thereafter, masking material 56 is removed 
from sheet 55, producing the construction shown by FIG. 13. FIG. 13 is 
identical to the sheet shown by FIG. 1. Subsequently, sheet 55 is cut and 
formed into a plurality of discrete battery terminal housing members. 
The above examples describe processes wherein dipping into a molten bath of 
elemental lithium is the method by which lithium is provided to the 
unmasked portions. Alternately in accordance with the invention, an 
elemental lithium stream could be provided and directed onto the 
electrically conductive sheet for causing the lithium to adhere to the 
unmasked portions. By way of example only and not of limitation, one 
technique would be to direct a stream of liquid lithium against the 
conductive sheet. 
In compliance with the statute, the invention has been described in 
language more or less specific as to structural and methodical features. 
It is to be understood, however, that the invention is not limited to the 
specific features shown and described, since the means herein disclosed 
comprise preferred forms of putting the invention into effect. The 
invention is, therefore, claimed in any of its forms or modifications 
within the proper scope of the appended claims appropriately interpreted 
in accordance with the doctrine of equivalents.