Cylindrical battery

To provide a method which allows a battery with a flat base to be produced in a cylindrical battery manufacturing method in which a metallic casing with a larger outside diameter than the outside diameter of the metallic casing in the finished battery is used, a battery element is housed in the said metallic casing, then the outside diameter of the metallic casing reduced; to reduce the occurrence of defective batteries due to deficient electric conduction between the metallic casing and the electrode lead; and to improve the safety of the said cylindrical battery in the event of an outside short circuit. In the making of a battery in which the outside diameter of the metallic casing in the finished battery is A, the outside diameter of the metallic casing used is made to satisfy the relationship L2>A.gtoreq.L3. The battery element, made by winding in a coil shape, is wound so that when winding is completed the end of electrode or electrode current collector of either the negative electrode or the positive electrode is positioned at the outermost periphery of the battery element, then the said battery element is housed in a cylindrical metallic casing, after which the outside diameter of the said metallic casing is reduced to strengthen the contact between the end of electrode or electrode current collector positioned at the outermost periphery of the battery element and the internal wall of the metallic casing, and make the electric resistance of contact between the electrode and metallic casing sufficiently small.

This invention uses a metallic casing, the outside diameter of which is 
larger than the outside diameter of the metallic casing in the finished 
battery, and relates to a cylindrical battery made by reducing the outside 
diameter of the metallic casing after the coiled battery element has been 
housed in the said metallic casing, being of relevance particularly to the 
improvement of manufacturing methods and reliability and safety. 
The dissemination of and advances in various portable electronic equipment, 
such as note-book computers and video cameras, has been accompanied by 
heightened demand for higher performance batteries as drive sources for 
these, with attention being focused particularly on lithium batteries and 
lithium ion secondary batteries. As lithium batteries and lithium ion 
secondary batteries have high voltages, their energy density is also high, 
contributing significantly to the down-sizing and reduction in weight of 
portable electronic equipment. 
Further movement towards smaller, lighter and more sophisticated portable 
electronic equipment, however, has given rise to even stronger demands for 
high performance batteries, and in turn a need to boost energy density, 
even in lithium batteries and lithium ion secondary batteries, as well as 
reliability and safety. 
To increase energy density a method was proposed which used a metallic 
casing with outside diameter larger than the outside diameter of the 
metallic casing in the finished battery, and increased the diameter of the 
battery element housed inside the metallic casing to boost capacity 
(JP-A-6-215792). In this method a metallic casing is used which has larger 
outside diameter (B) than the outside diameter (A) of the metallic casing 
in the finished battery, and after housing the battery element in the said 
metallic casing the outside diameter of the metallic casing is squeezed 
down to the outside diameters (A) of the metallic casing in the finished 
battery (herein the squeezing of the outside diameter of the metallic 
casing will be referred to as "Swaging", the machine which squeezes the 
outside diameter of the metallic casing as a "Swager", and the method of 
making a cylindrical battery in which the outside diameter of the metallic 
casing is squeezed, is called "Swage Method"). 
The use in the Swage Method of a metallic casing with outside diameter 
larger than that of the outside diameter of the metallic casing in the 
finished battery allows the diameter of the battery element that is housed 
in the metallic casing to be enlarged to boost capacity. As is shown in 
FIG. 2(b), however, a problem arises in the Swaging process in which the 
bottom of the metallic casing bulges, causing the external appearance to 
differ from that of conventional batteries (flat bottom). The bulging of 
the metallic casing bottom is something that is seen in conventional 
batteries when a defect in the battery has occurred leading to a rise in 
the battery's internal pressure, while normal batteries have a flat 
bottom. As batteries with bulged bottom tend to be deemed defective, and 
this is undesirable, the Swage Method has not yet been put to practical 
use. 
Portable electronic equipment, as typified by note-book computers and video 
cameras, require enormous amounts of power. When used as power sources for 
such equipment, non-aqueous batteries are also required to generate large 
currents. 
To create batteries from which large currents can be obtained, the internal 
resistance of the battery must be reduced as much as possible. Methods for 
reducing the internal resistance of batteries includes: 1) increasing 
electrode area, and; 2) reducing the resistance of electrode leads. 
In the prior art the use of strip-shaped electrodes has been adopted to 
increase the area of the electrodes. To increase the electrode area of 
strip-shaped electrodes it is necessary to reduce the thickness of the 
electrodes, with metallic foil generally being used as current collectors. 
That is to say, in the prior art, strip-shaped negative electrode (1) and 
positive electrode (2), the thicknesses of which have been reduced, are 
separated by separator (3), and rolled up to form coiled battery element 
(20), as shown in FIG. 13, with said battery element being housed in 
cylindrical metallic casing (4), the opening of which has a lid (7) 
affixed to it via a gasket (8) and is sealed to make a non-aqueous 
cylindrical battery, as shown in FIG. 14(b). 
In conventional non-aqueous cylindrical batteries in which the battery 
element is coiled, either the positive electrode lead or negative 
electrode lead taken from the battery element is spot welded to the bottom 
of the metallic casing to obtain the electrical conduction between the 
electrode and the metallic casing. In this case, the spot welder's 
rod-shaped electrode is inserted into the small hole formed in the center 
of the coiled battery element when winding is conducted, and the electrode 
lead is welded to the bottom of the metallic casing. Under this method 
there is just one welding site, welding defects are frequent, and it is 
not possible to confirm whether the welding is sufficient or not, leading 
to the problem in a conventional non-aqueous cylindrical battery of cases 
where the battery does not function due to improper electrical conduction 
between the metallic casing and the electrode. 
In conventional aqueous electrolyte-type nickel-cadmium batteries and 
nickel-metal hydride batteries also, the battery element is coiled, but a 
method is used in which the coiled electrode element is made by 
positioning the end of the negative electrode on the outermost periphery 
of the coiled electrode element and housing it in a cylindrical metallic 
casing to allow the aforementioned end of the negative electrode 
positioned on the outermost periphery of the electrode element to come 
into contact with the internal wall of the metallic casing, enabling the 
electrical conduction between the cathode and the metallic casing. As 
alkaline electrolytes (for example, 30% KOH aqueous solution) have good 
conductivity, there is no need for unreasonable increases of electrode 
area, and relatively thick electrodes can be used, giving the electrodes a 
certain degree of resiliency. Accordingly, at the point in time when the 
electrode element is housed in the metallic casing the coiled electrode 
element has coil return due to the resiliency of the electrodes, giving 
enough contact strength for the electrical conduction between the 
electrode terminal and the internal wall of the metallic casing. 
As the resiliency of electrodes in non-aqueous batteries is weak, however, 
no method is adopted to bring the end of the electrode into contact with 
the internal wall of the metallic casing to allow the electrical 
conduction between the electrode and the metallic casing. In conventional 
non-aqueous cylindrical batteries (lithium batteries and lithium ion 
secondary batteries) which use a non-aqueous electrolyte (organic 
electrolyte) the conductivity of the electrolyte is no more than 1/50 of 
an alkaline electrolyte, meaning that to create a non-aqueous battery from 
which a large current can be obtained it is necessary to increase the 
electrode area immensely, necessitating an extremely thin electrode 
(100-200 microns). For this reason it is preferable to use metallic foil 
of no more than 0.03 mm in thickness as current collectors for these 
electrodes. Electrodes which have metallic foil of no more than 0.03 mm in 
thickness as the current collector have extremely little resiliency, 
however, and insufficient resiliency to provide enough return strength to 
allow electrical conduction between the end of the electrode and metallic 
casing. Accordingly, the only method adopted for obtaining the electrical 
conduction between the electrode and metallic casing in conventional 
non-aqueous cylindrical batteries is to spot weld the electrode lead taken 
from the electrode element to the bottom of the metallic casing as 
mentioned previously. 
In cases where the electrical conduction between the electrode and the 
metallic casing is obtained by spot welding the electrode to the metallic 
casing bottom, sufficient welding cannot be performed if the electrode 
lead is wet. As such the battery element has to first be put into the 
metallic casing and the electrode lead spot welded to the bottom of the 
metallic casing before the electrolyte could be impregnated into the 
battery element. If the necessary quantity of electrolyte is injected at 
one time with the battery element already inside the metallic casing it 
would overflow from the metallic casing, meaning that only a small amount 
could be injected at one time. In the actual production process, 
therefore, a considerable amount of time is allowed for the impregnating 
of the electrolyte, with a little electrolyte being injected each of three 
to five times, with a vacuum being created for each injection. The 
electrolyte injection process is a significant barrier in terms of actual 
mass production. 
Additionally, there is a problem with maintaining safety with conventional 
batteries in which the battery element is coiled. Because large currents 
can be obtained from coiled battery elements, an accidental external short 
circuit would result in the flow of an extremely large short circuit 
current. In such cases all currents which are generated at all electrodes 
would pass through the electrode leads, with the heating of the electrode 
leads being a safety problem. There are cases, particularly with 
non-aqueous batteries (lithium batteries and lithium ion secondary 
batteries) which use combustible organic electrolyte, in which the 
electrode leads overheat and become the source of ignition, causing the 
battery to catch fire. 
Accordingly, the reduction of electrode lead resistance is of great 
importance, not only in reducing the internal resistance of batteries, but 
also in respect of safety measures that reduce overheating of electrode 
leads when large currents are flowing through them. 
As shown in FIG. 14(b), in conventional cylindrical batteries the negative 
(or positive) lead (5) which is taken from the coiled battery element is 
welded to the bottom of metallic casing (4), the battery container 
(metallic casing) is the external terminal of the negative (or positive) 
electrode, the lead (6) of the other electrode, that is the positive (or 
negative) electrode, is welded to lid (7) to allow current to flow to the 
external terminal (10) of the positive (or negative) electrode. To reduce 
the resistance of the electrode lead the cross-sectional area of the 
electrode lead should be increased and the length of the electrode lead 
shortened but, as shown in FIGS. 13 and 14, due to the way the electrode 
leads are brought out, the way they are welded to the metallic casing and 
lid, and welding conditions, in conventional cylindrical batteries the 
electrode leads are normally limited to a thin metallic plate the width 
and thickness of which are normally 4-6 mm and 0.04-0.1 mm respectively, 
and which needs to be reasonably long. That is to say, if the electrode 
lead is not narrow in width, it would not be possible to bring the lead 
out of the coil as shown in FIG. 13(a), and if it is too thick proper 
welding will be difficult. Furthermore, as is shown in FIG. 14, lead (6) 
is made sufficiently long to allow fitting of lid (7) on the inside of 
gasket (8), and as lead (5) is welded to the center of the bottom of 
metallic casing (4) utilizing the hole in the center of the coiled battery 
element, lead (5) must be long enough to reach an appropriate welding 
point. In this conventional battery, therefore, it is not possible to 
sufficiently reduce the resistance value of the electrode lead, leaving an 
element of uncertainty as to safety in the event of an external short. 
One problem that this invention seeks to solve is to realize the 
manufacture of cylindrical batteries with a Swage Method which produces 
batteries with a flat bottom, and provide a battery with high energy 
density. Another problem the invention seeks to address in non-aqueous 
cylindrical batteries which have battery elements made from coiled, 
strip-shaped electrodes that have metallic foil of no more than 0.03 mm in 
thickness as current collectors, is the reduction in defective batteries 
due to poor electrical conduction between the metallic casing and 
electrode lead, and the improvement of safety in the event of external 
shorts of said cylindrical batteries. 
A method of solving the first problem is to have the external dimensions of 
the metallic casing used when making a battery in which the outside 
diameter of the metallic casing in the finished battery is A, satisfy the 
relationship L2.ltoreq.A.gtoreq.L3. Here L2 is the outside diameter of the 
central part of the metallic casing, and L3 is the "outside diameter of 
the casing bottom". 
Resolving the second problem entails separating with a separator a 
strip-shaped positive electrode and negative electrode, which have a 
metallic foil of no more than 0.03 mm in thickness as a current collector, 
and winding them up into a jelly roll to make a battery element, the 
coiling of which is finished so that the end of the electrode or electrode 
current collector of the negative electrode or positive electrode is 
positioned on the outermost periphery of said battery element, and housing 
the said battery element in a cylindrical metallic casing, after which the 
outside diameter of the said cylindrical metallic casing is reduced to 
strengthen the contact between the end of electrode or electrode current 
collector positioned on the outermost periphery of the battery element and 
the internal wall of the metallic casing, reducing the electrical 
resistance of contact between the electrode and the metallic casing to a 
sufficiently small value. 
The first invention here proposes a metallic casing, the shape of the 
bottom and the dimension relationships of which differ from those of 
conventional metallic casings. FIG. 1(a) is a cross-section of the 
metallic casing prior to the Swaging used in this invention, and FIG. 1(b) 
is a cross-section after Swaging. Metallic casings used in this invention 
are characterized in that they have casing walls perpendicular to the 
casing bottom, except in the vicinity of the casing bottom where the 
casing wall slants toward the casing bottom, resulting in two bends in the 
joining of the casing wall and casing bottom. As shown in the detailed 
diagram, in FIG. 1(a) the joining of casing wall (12) and casing bottom 
(11) is accomplished with two bends represented by R1 and R2, thus making 
it possible to make the "outside diameter of the casing bottom" (L3) 
sufficiently small in comparison to the outside diameter (L2) of the 
central part of the metallic casing. More specifically, the characteristic 
of the metallic casing prior to the Swaging used in this invention is that 
the outside diameter of the metallic casing (L2=B) is larger than the 
outside diameter of the metallic casing in the finished battery (L2=A), 
(B&gt;A), and the "outside diameter of the casing bottom" (L3=C) is no larger 
than the outside diameter of the metallic casing in the finished battery 
(L2=A), (A.gtoreq.C) . Therefore, if the metallic casing has the 
aforementioned dimensional relationship (L2&gt;A.gtoreq.L3) prior to Swaging, 
there will be no change in the "outside diameter of the casing bottom" 
after Swaging, as shown in FIG. 1(b), and thus there will be no bulging of 
the metallic casing bottom during the Swaging process. 
In the second proposed invention there is no need for an electrode lead in 
at least one of either the negative electrode or the positive electrode in 
the coiled battery element (20) as shown in FIG. 9. That is, electrodes 
used in this invention are a strip-shaped electrode to which an electrode 
lead is not attached as shown in FIG. 8(a), and a strip-shaped electrode 
to which electrode lead (6) is attached as shown in FIG. 8(b). These are 
made by inserting a separator and winding the electrode into a coil shape, 
then as shown in FIG. 9(b), completing the winding so that the end of 
electrode or electrode current collector (31) of strip-shaped electrode 
(1) to which an electrode lead is not attached, is positioned at the 
outermost periphery rather than the separator (3). Electrode lead (6) 
taken from one of the electrodes of the said battery element is welded to 
a lid (7; normally also functions to prevent explosions) appropriately 
installed inside gasket (8), as shown in FIG. 10(a). Following this, the 
said battery element is impregnated with electrolyte, the battery element 
housed in cylindrical metallic casing (4), the outside diameter (L2) of 
which is B, as shown in FIG. 11(a), and the outside diameter (L2) of said 
cylindrical metallic casing reduced to A, (B&gt;A), as shown in FIG. 11(c), 
causing the end of the electrode or electrode current collector positioned 
on the outermost periphery of the aforementioned battery element and the 
inside of the aforementioned metallic casing to be in very close contact 
over a broad area. Even with electrodes with poor resiliency that have 
metallic foil of no more than 0.03 mm in thickness as current collectors, 
therefore, there is strong contact between the end of electrode or 
electrode current collector and the inside of the metallic casing, with 
sufficient electrical conduction between electrode (1) and metallic casing 
(4) which forms the electrode's external terminal, eliminating the need 
for an electrode lead for electrode (1). 
In cases where the active substance layer on the metallic foil current 
collector does not have sufficient conductivity also, with the end of the 
electrode positioned at the outermost periphery, if, as shown in FIG. 
8(a), there is an active substance layer (32) on just one side of current 
collector (31), electrode current collector (31) is positioned on the 
outermost periphery as shown in the enlarged sectional view of FIG. 9(b) 
so the said current collector is in close contact with the inside of the 
metallic casing, allowing for sufficient electrical conduction between the 
electrode and the metallic casing. Naturally when the active substance 
layer has sufficient conductivity, with the end of the electrode 
positioned at the outermost periphery, even when there is an active 
substance layer on both sides of the current collector, the active 
substance layer at the outermost periphery will be in close contact with 
the inside of the metallic casing, enabling sufficient electrical 
conduction between the electrode and the metallic casing. 
A machine marketed under the name Swager may be used to squeeze the outside 
diameter of the metallic casing. FIG. 15 shows the principle diagram for 
this machine. Held in die holder (23) and positioned in the center is die 
(22) which has a hole (21) of .phi.X in diameter in the center, and 
divided into two in the center, to the outside of which are attached 
several rollers (24) (FIG. 15 shows eight rollers). When die (22), which 
is split in two, rotates in the direction of the arrow together with die 
holder (23), it comes into contact with a roller (24) every 45.degree. of 
rotation, die (22) is tightened to the inside and the central gap in the 
split die (22) becomes smaller. Further rotation away from the rollers 
(24) results in the central gap widening. This means that the die (22) 
split in two, approaches and withdraws, causing the diameter .phi.X of the 
hole in the center of the die to increase and decrease in size. Inserting 
a cylindrical object into hole (21) in the center of die (22), which 
rotates, will squeeze the outside diameter of the object when the die 
(22), split into two, approaches (that is because it is tightened when 
diameter .phi.X of the hole in the center of the die becomes smaller). 
Use of the Swager allows the cylindrical battery of this invention to be 
made by squeezing the outside diameter of the metallic casing. FIG. 16(a) 
shows a vertical cross-section of the central part of the Swager's 
rotating die (22). The left and right die approach and withdraw as shown 
by the arrows. As shown in FIG. 16(b), by inserting metallic casing (4) 
into the center of the hole in the center of rotating die (22), the 
outside diameter of the metallic casing can be squeezed to the outside 
diameter of the metallic casing in the finished battery.

EXAMPLE 1 
The specific battery manufacturing procedures for the first invention will 
be explained with reference to FIGS. 1(a), 1(b), 3(a)-3(c) and 4(a)-4(c). 
The battery element for the implementation of this invention is prepared 
in the following manner. 
First the negative electrode is prepared under the publicly known 
conventional method as follows. Combine 87 parts by weight of mesocarbon 
micro beads (d002=3.37 .ANG.) which have been heat treated at 2800.degree. 
C. with 3 parts by weight of acetylene black and wet blend with 10 parts 
by weight of polyvinylidene fluoride (PVDF) as a binding agent and 
N-methyl-2-pyrrolidone as solvent to make a wet slurry. Next, apply the 
slurry evenly to both surfaces of a copper foil of 0.01 mm in thickness 
which is to be the negative electrode current collector, and once it has 
dried, conduct pressurized casting with a roll press to form a 
strip-shaped negative electrode. Have part of the current collector 
exposed at one edge of the strip-shaped negative electrode and onto it 
weld a nickel negative electrode lead. 
The positive electrode is also made under the publicly known conventional 
method as follows. Mix together manganese dioxide (MnO.sub.2) available on 
the market and lithium carbonate (Li.sub.2 CO.sub.3) in a ratio of 1 
mol:0.275 mol, and bake in air at 800.degree. C. for approximately 12 
hours. Repeat the baking process three times to synthesize a spinel-type 
lithium-manganese compound oxide. Make this spinel type lithium-manganese 
compound oxide into powder form with an average particle size of 0.025 mm, 
and to 89 parts by weight of this powder mix 3 parts by weight of 
acetylene black and 4 parts by weight of graphite as conduction agents, 
and then wet blend with N-methyl-2-pyrrolidone into which 4 parts by 
weight of PVDF has been dissolved as a binding agent, to form a slurry. 
Next, apply the slurry evenly to both surfaces of an aluminum foil of 0.02 
mm in thickness which is to be the positive electrode current collector, 
and once it has dried, conduct pressurized casting with a roll press to 
form a strip-shaped positive electrode. Have part of the aluminum exposed 
at one edge of the strip-shape positive electrode and onto it weld an 
aluminum positive electrode lead. 
Insert a porous, polypropylene separator between the prepared negative and 
positive electrodes and roll up to create a battery element (20) with an 
average outside diameter of 17.4 mm. Then battery element (20) is housed 
in metallic casing (4), as shown in FIG. 3(a). This embodiment seeks to 
make a battery in which the outside diameter (L2) of the metallic casing 
in the finished battery is 18.0 mm, while the metallic casing used is a 
nickel-plated iron casing with an outside diameter at the opening (L1) and 
outside diameter at the center part (L2) of 18.5 mm, "outside diameter of 
the casing bottom" (L3) of 17.5 mm, and a height of 65 mm. The bottom of 
the said metallic casing is shown in the detailed diagram of FIG. 1(a). 
FIG. 1(a) shows that it has two bends represented by R1 and R2 at the 
joint of casing wall (12) and casing bottom (11), making it possible to 
make the "outside diameter of the casing bottom" (L3) sufficiently small 
in comparison to the outside diameter of the center part of the metallic 
casing (L2). That is, the characteristic of the metallic casing prior to 
the Swaging used in this embodiment is that the outside diameter of the 
metallic casing (L2=B=18.5 mm) is larger than the outside diameter of the 
metallic casing in the finished battery (L2=A=18.0 mm), (B&gt;A), and the 
"outside diameter of the casing bottom" of the metallic casing (L3=C=17.5 
mm) is no more than the outside diameter of the metallic casing in the 
finished battery (L2=A=18.0 mm), (A.gtoreq.C). 
On the other hand, the outside diameter of the battery element is 17.4 mm, 
and the inside diameter of the aforementioned metallic casing 17.9 mm, 
making the outside diameter of the battery element 0.5 mm smaller than the 
inside diameter of the casing, and allowing easy insertion of the battery 
element into the metallic casing. Swaging is conducted after battery 
element (20) is housed in metallic casing (4), and the outside diameter of 
the metallic casing (except the area around the casing opening) reduced to 
18.0 mm, as shown in FIG. 3(b). As the "outside diameter of the casing 
bottom" (L3) of the metallic casing remains unchanged at 17.5 mm even 
after Swaging, as shown in the detailed diagram of FIG. 1(b) the casing 
bottom of the metallic casing does not bulge in the Swaging process. 
Following this, the metallic casing is squeezed at a position 60.5 mm from 
the casing bottom (near the metallic casing opening), as shown in FIG. 
3(c), and striations (42) to support the gasket are created. After this 
the process shown in FIG. 4(a) to (c) is followed to assemble the battery. 
That is, gasket (8) is installed in the opening of the metallic casing, 
and the negative lead and positive lead are welded to the casing bottom 
and aluminum sealing lid (7; also acts as an explosion-proof valve), 
respectively, as shown in FIG. 4(a). Next, electrolyte is injected, 
sealing lid (7) fitted to the gasket, doughnut-shaped PTC element (15) 
laid on top of and in contact with the sealing lid, positive external 
terminal (10) laid on top, and the Swager used once again to squeeze the 
outside diameter of the metallic casing opening (L1) to the same size as 
the outside diameter of the central part of the metallic casing (L2) (FIG. 
4(b)). Finally, the caulking machine is adjusted to a level where the 
tightening pressure will not damage the functions of the PTC element, and 
the edge of the metallic casing caulked and sealed to make battery (U) 
having the battery structure shown in FIG. 4(c) with an outside diameter 
of 18.0 mm, a height of 65 mm, and a flat bottom. 
EXAMPLE 2 
Another specific example of the first invention will be explained with 
reference to FIGS. 5(a)-5(c). First, battery element (20) with an average 
outside diameter of 17.4 mm is made in exactly the same way as in Example 
1. This example also seeks to make a battery in which the outside diameter 
of the metallic casing in the finished battery (L2) is 18.0 mm using the 
same metallic casing that was used in Example 1. Battery element (20) is 
housed in this metallic casing and, as shown in FIG. 5(a), the metallic 
casing is squeezed at a position 60.5 mm from the casing bottom (near the 
metallic casing opening), and striations (42) to support the gasket are 
created. At the point in time when the striations are created the 
relationship between the outside diameter of the metallic casing opening 
(L1) and the outside diameter of the central part of the metallic casing 
(L2) is L1=L2=18.5 mm. Next, as shown in FIG. 5(a), gasket (8) is 
installed at the opening of the metallic casing, and the negative lead and 
positive lead welded to the casing bottom and sealing lid (7; also acts as 
an explosion-proof valve), respectively, as shown in FIG. 5(a). Next, the 
same electrolyte as example 1 is injected, sealing lid (7) fitted in the 
gasket, doughnut-shaped PTC element (15) laid on top of and in contact 
with the sealing lid, positive external terminal (10) laid on top, and the 
Swager used to squeeze the entire outside diameter of the metallic casing 
from the bottom to the opening to reduce the outside diameter of the 
metallic casing to 18.0 mm (FIG. 5(b)). As shown in the detailed diagram 
of FIG. 1(b), the bottom of the metallic casing after Swaging has an 
"outside diameter of the casing bottom" (L3) which remains unchanged at 
17.5 mm even after Swaging, thus the bottom of the metallic casing does 
not bulge in the Swaging process. Finally, the caulking machine is 
adjusted to a level where the tightening pressure will not damage the 
functions of the PTC element, and the edge of the metallic casing caulked 
and sealed to make battery (V) with a structure having an outside diameter 
of 18.0 mm and a height of 65 mm as shown in FIG. 5(c). 
As presented above, the Swage Method has been used also in Example 2 to 
make battery (V). This differs from batteries made with a conventional 
Swage Method in that there is no building at the casing bottom of the 
metallic casing, enabling a battery with frat casing bottom to be made. 
Furthermore, although the creation of a lithium ion secondary battery using 
lithium-manganese oxide as the positive electrode active substance and 
carbon material as the negative electrode active substance was indicated 
as a specific embodiment of the first invention in Examples 1 and 2; this 
invention is essentially concerned with proposals for methods of making 
cylindrical batteries, and can naturally be applied to making cylindrical 
batteries for other battery systems. 
EXAMPLE 3 
Specific procedures for making batteries will be explained in relation to 
the second invention, with reference to FIGS. 6, and 8 to 11. Preparation 
of the battery element to implement the second invention differs from a 
conventional method and is as follows. 
First dry blend 70 parts by weight of mesocarbon micro beads (d002=3.37 
.ANG.) which have been heat treated at 2800.degree. C. with 20 parts by 
weight of pitch coke, then wet blend with N-methyl-2-pyrrolidone, into 
which 10 parts by weight of polyvinylidene fluoride (PVDF) has been 
dissolved as a binding agent, to create a negative electrode slurry. Apply 
the negative electrode slurry evenly to both sides of copper foil of 0.01 
mm in thickness which is to be the negative electrode current collector, 
leaving only 56 mm on one side of the copper foil uncoated, as shown in 
FIG. 8(a). Once it has dried, conduct pressurized casting with a roll 
press to prepare strip-shaped negative electrode (1) which has a 
high-density active substance layer (32) on current collector (31). As 
shown in FIG. 8(a), the end of electrode of prepared strip-shaped negative 
electrode (1) has no active substance layer on one side surface of the 
current collector, with current collector (31) exposed. 
The positive electrode is made under the publicly known method as follows. 
A spinel-type lithium-manganese compound oxide is synthesized as in 
Example 1. Make this spinel-type lithium-manganese compound oxide into 
powder form with an average particle size of 0.015 mm, and to 88 parts by 
weight of this powder, mix 6 parts by weight of graphite as a conductive 
agent, and then wet blend with N-methyl-2-pyrrolidone into which 6 parts 
by weight of PVDF has been dissolved as a binding agent, to form a 
positive electrode slurry. Next, apply the slurry evenly to both surfaces 
of an aluminum foil of 0.02 mm in thickness which is to be the positive 
electrode current collector, and once it has dried, conduct pressurized 
casting with a roll press to form, as shown in FIG. 8(b), a strip-shaped 
positive electrode (2) which has a high density active substance layer 
(32) on current collector (31). As with the positive electrode in Example 
1, have part of the current collector of strip-shaped positive electrode 
(2) exposed at one end and onto it weld aluminum positive electrode lead 
(6) of 4 mm in width and 0.04 mm in thickness. 
Insert a porous, polypropylene separator (3) in between negative electrode 
(1) and positive electrode (2), and wind into a jelly roll to create a 
battery element (20) with an average outside diameter of 17 mm, as shown 
in FIG. 9 (a). As the cross-section of battery elements made by coiling 
strip-shaped electrodes generally will not be a complete circle, there are 
maximum and minimum values for the outside diameter of battery element 
(20), with the maximum outside diameter value for battery element (20) 
made here being 17.15 mm. When winding, electrode lead (6) attached to the 
positive electrode is positioned in the center of the jelly roll and, as 
shown in FIG. 9(b), winding is completed so that the end of electrode with 
the exposed current collector of negative electrode (1), rather than 
separator (3), is positioned at the outermost periphery. Additionally, as 
shown in FIG. 10(a), lead (6) taken from the center of the battery element 
is welded to lid (7) which is installed inside gasket (8). After this, 
electrolyte, consisting of a blended solvent of ethylene carbonate (EC) 
and diethyl carbonate (DEC) into which 1 mol/1 of LiPF6 has been 
dissolved, is impregnated into the said battery element, and put into 
cylindrical metallic casing (4) as shown in FIG. 11 (a). 
This embodiment seeks to make a battery in which the outside diameter (A) 
of the metallic casing of the finished battery is 17.5 mm, while the 
metallic casing used is a nickel-plated iron casing with an outside 
diameter at the opening (L1) and outside diameter at the center part (L2) 
of B=18.0 mm, "outside diameter of the casing bottom" (L3) of C=16.5 mm, 
and a height of 65 mm. The outside diameter of the metallic casing used in 
this example (L2=B=18.0 mm) is larger than the outside diameter of the 
metallic casing in the finished battery (L2=A=17.5 mm), (B&gt;A), and the 
"outside diameter of the casing bottom" of the metallic casing (L3=C=16.5 
mm) is no more than the outside diameter of the metallic casing in the 
finished battery (L2=A=17.5 mm), (A.gtoreq.C). 
As a matter of interest, the inside diameter of the aforementioned metallic 
casing is 17.4 mm, and as the outside diameter of the battery element is 
made smaller than the inside diameter of the metallic casing the battery 
element can be easily inserted into the metallic casing. After housing 
battery element (20) in metallic casing (4), the metallic casing is 
squeezed down at a point 60.5 mm from the casing bottom, as shown in FIG. 
11(b), and striations (42) to support the gasket are created. Following 
this, positive external terminal (10) is laid on top and in contact with 
sealing lid (7), and the outside diameter of the metallic casing squeezed 
to outside diameter of L2=A=17.5 mm, as shown in FIG. 11(c) . The edge of 
the metallic casing is then caulked to create battery (A) with a structure 
having an outside diameter of 17.5 mm and a height of 65 mm, as shown in 
FIG. 6. 
In battery (A) made in this way, because the battery element (20) is housed 
in metallic casing (4), after which the outside diameter of the metallic 
casing is reduced, the end of electrode positioned at the outermost 
periphery of the battery element is in very close contact over a large 
area with the internal wall of the metallic casing. Naturally the degree 
of contact between the end of electrode and internal wall of the metallic 
casing closely correlates to the degree of change in the outside diameter 
of the battery element at this time. That is, it can be said that if the 
maximum value of the outside diameter of the battery element prior to 
insertion in the metallic casing is D mm, and the maximum value of the 
inside diameter of the metallic casing after squeezing the outside 
diameter is d mm, then the greater (D-d) is, the stronger the degree of 
contact between the end of electrode and the internal wall of the metallic 
casing. As in this embodiment, D=17.15 mm and d=16.95 mm, (D-d)=0.20 mm 
and, as shown in the enlarged sectional view of FIG. 9(b), since electrode 
current collector (31) is positioned at the outermost periphery of the 
battery element, the said current collector is in appropriate close 
contact over a large area with the inside of metallic casing (4). Thus, as 
in this embodiment, by setting (D-d) appropriately, positioning the end of 
one electrode or current collector at the outermost periphery of the 
battery element, housing it in a cylindrical metallic casing and reducing 
the outside diameter of the metallic casing, good electrical conduction 
can be obtained between at least one electrode, without the need for an 
electrode lead, and metallic casing (4), which is the electrode external 
terminal. Furthermore, if (D-d) is too large the battery element may be 
overly tightened, causing internal shorts. Other experiments confirmed 
that this value should be 0&lt;(D-d).ltoreq.0.3, with this example being 
(D-d)=0.20 mm. A preferable range of (D-d) is about 0.1 mm to about 0.25 
mm. 
In this example also, the outside diameter of the metallic casing prior to 
Swaging (L2=B) is larger than the outside diameter of the metallic casing 
in the finished battery (L2=A), (B&gt;A), and the "outside diameter of the 
casing bottom" of the metallic casing (L3=C) is no more than the outside 
diameter of the metallic casing in the finished battery (L2=A), 
(A.gtoreq.C). As such, there is no change in the "outside diameter casing 
bottom" (L3) even after Swaging and no bulging of the casing bottom of the 
metallic casing in the Swaging process. 
EXAMPLE 4 
Another specific example of the second invention will be explained with 
reference to FIGS. 7 to 10, and 12. A coiled battery element is made in 
the same manner as Example 3, as shown in FIG. 9(a). An aluminum rod (40) 
with diameter 4.0 mm is inserted into the center hole (41) of the battery 
element as shown in FIG. 10(b), and electrode lead taken from the center 
of the coil is welded to one end of the said aluminum rod. Following this, 
the same type of electrolyte as was used in Example 1 is impregnated into 
said battery element and, as shown in FIG. 12(a), the battery element is 
then housed in the cylindrical metallic casing with the side to which 
electrode lead (6) is welded facing the casing bottom. This embodiment 
also seeks to create a battery in which the outside diameter of the 
metallic casing in the finished battery is 17.5 mm, using the same 
metallic casing as used in Example 3. After housing the battery element in 
metallic casing (4), the metallic casing is squeezed in at a point 60.5 mm 
from the casing bottom, as shown in FIG. 12(a), striations (42) are 
created to support a gasket, and gasket (8) is installed in the opening of 
the metallic casing. The other end of the aforementioned aluminum rod is 
showing from the gasket's central hole, and when lid (7) is fitted inside 
the gasket the central part of the lid is in contact with the said end of 
the aluminum rod. Lid (7) is welded to at its center point (9) to the end 
of the aluminum rod with a laser welder. In the center of the lid used 
here is created a thinner section in the shape of a cross, so that the lid 
functions to prevent explosion by splitting and safely releasing internal 
pressure when internal pressure in the battery rises. Positive external 
terminal (10) is then laid on top of and in contact with sealing lid (7), 
and, as shown in FIG. 12(b), the outside diameter of metallic casing 
B=18.0 mm, is squeezed to A=17.5 mm using the same method as in the 
aforementioned example. The edge of the metallic casing is then caulked to 
create battery (B) with a structure having an outside diameter of 17.5 mm 
and a height of 65 mm as shown in FIG. 7. As electrode lead (6), which is 
welded to one end of the aluminum rod, is in close proximity to the hole 
in the center of the coiled battery element it need only be a mere 4 mm in 
length. In the end, in battery (B) made in this embodiment, electrode lead 
with a tiny cross-sectional area of 0.16 mm.sup.2 has a mere 4 mm lying 
between the battery element and the external terminal. 
This example also seeks to create a battery in which the outside diameter 
of the metallic casing in the finished battery is 17.5 mm, using the same 
metallic casing with an outside diameter of 18.0 mm as used in Example 3, 
and as the end of negative electrode (1) is positioned at the outermost 
periphery of the battery element, by housing the battery element in the 
cylindrical metallic casing and reducing the outside diameter of the 
metallic casing good electrical conduction between the negative electrode 
and metallic casing (4) is enabled. 
In this example also, the outside diameter (B) of the metallic casing prior 
to Swaging is larger than the outside diameter (A) of the metallic casing 
in the finished battery, (B&gt;A), and the "outside diameter of the casing 
bottom" (C) of the metallic casing is no more than the outside diameter 
(A) of the metallic casing in the finished battery, (A.gtoreq.C). As such, 
there is no change in the "outside diameter of the casing bottom" even 
after Swaging and no bulging of the bottom of the metallic casing in the 
Swaging process. 
COMATIVE EXAMPLES 
The conventional procedures for making batteries will be explained with 
reference to FIGS. 13 and 14. In conventional battery-making methods the 
battery element is prepared as follows. 
First, negative electrode (1) and positive electrode (2) are created with 
the same method as in the aforementioned example, with the current 
collectors coated with an active substance layer, then pressurized casting 
is conducted to make strip-shaped electrodes. Under the conventional 
method, part of the current collector at one end of both the strip-shaped 
positive electrode and negative electrode are left exposed, to which 
electrode leads of 4 mm in width and 0.04 mm in thickness are welded. 
A separator is inserted between the prepared negative electrode and 
positive electrode, then this is wound into a jelly roll to make battery 
element (20) with an average outside diameter of 17.2 mm, as shown in FIG. 
13(a). Winding is done so electrode lead (6) attached to positive 
electrode (2) is positioned in the central part of the coil, and electrode 
lead (5) attached to negative electrode (1) is positioned at the outside 
of the coil. When winding is completed, separator (3) is positioned at the 
outermost periphery, as shown in FIG. 13(b). In the battery element made 
in this way, negative electrode lead (5) is bent towards the center of the 
battery element, as shown in FIG. 14(a), the battery element housed in 
cylindrical metallic casing (4) so negative electrode lead (5) is in 
contact with the casing bottom, the spot welder's rod-shaped electrode is 
inserted into hole (41) formed in the center of the coiled battery element 
when winding is conducted, and negative electrode lead (5) welded to the 
center of the bottom of the metallic casing. This necessitates negative 
electrode lead (5) to have sufficient length to reach the center of the 
casing bottom. Thus, the battery made in this comparative example having 
an outside diameter of .phi.18 mm requires a 13 mm negative electrode 
lead. Lid (7) is welded to positive electrode lead (6) taken from battery 
element (20) housed in the metallic casing, as shown in FIG. 14(a). This 
is followed by the injection into the metallic casing a little at a time 
over five occasions of the same electrolyte as used in Example 1. The 
method involves a vacuum being created inside the metallic casing each 
time the electrolyte is injected, after which the electrolyte is injected, 
followed by pressurization to promote the impregnation of the electrolyte 
into the battery element. After this, electrode lead (6) is folded, as 
shown in FIG. 14(b), lid (7) fitted inside gasket (8), positive external 
terminal (10) laid on top of and in contact with lid (7), and the edge of 
the metallic casing caulked and sealed to create battery (C) with the 
battery structure of an outside diameter of 18 mm and a height of 65 mm, 
as shown in FIG. 14(b). 
In battery-making procedures under this conventional method, electrode lead 
(6) needs to be long enough to fold to ensure the appropriate installment 
of lid (7) in the process of installing lid (7) inside gasket (8). The 
length electrode lead (6) needs to be in order for it to be folded differs 
according to the outside diameter of the battery, that length being 22 mm 
in the case of the battery with an outside diameter of .phi.18 mm in this 
comparative example. Ultimately, in battery (C) of this comparative 
example, an electrode lead with a very small cross-sectional area of 0.16 
mm.sup.2 and a length of 35 mm when those of the positive electrode and 
negative electrode are combined, lies between the battery element and the 
external terminals. 
As conducted in Examples 3 and 4, with this invention, by positioning the 
end of electrode of the negative electrode at the outermost periphery of 
the battery element, housing the battery element in the metallic casing 
and then reducing the outside diameter of the said metallic casing, good 
electric conduction between the negative electrode and the metallic casing 
can be obtained, making it unnecessary to spot weld the negative electrode 
lead to the casing bottom. This enables the battery element to be 
impregnated with electrolyte and the battery element housed in the 
metallic casing, something which will lead to significant improvements in 
the battery manufacturing process. Specifically, this method in which the 
battery element is impregnated with electrolyte and the battery element 
then housed in the metallic casing allows the elimination of the process 
in which electrolyte is injected into the metallic casing. 
As shown in the comparative example, however, to obtain the electrical 
conduction between the negative electrode and the metallic casing under a 
conventional method, the negative electrode lead taken from the battery 
element is spot welded to the casing bottom. In this case, welding cannot 
be performed properly if the negative electrode lead is wet with 
electrolyte, necessitating a method in which the battery element must 
first be housed in the metallic casing, the negative electrode lead spot 
welded to the casing base, and the electrolyte injected a little at a time 
over a number of times into the metallic casing and then impregnated into 
the battery element. 
Performance Test Results 
Ten of each of battery (A), (B) and (C) were made in the aforementioned 
manner on which performance experiments were conducted. Ten cycles of 
charging-discharging were conducted by setting the charging voltage of 
each of the batteries at 4.2 V, charging them for eight hours at a 
charging current of 500 mA, then discharging at a discharge current of 500 
mA to a cut-off voltage of 3.0 V. In the discharge characteristic of the 
tenth cycle, a discharge capacity of 1200 mAh at an average discharge 
voltage of 3.75 V was obtained for all, except one of the ten (C) 
batteries of the comparative example. Table 1 shows the average internal 
resistance values for each type of battery after charging for the tenth 
cycle. 
TABLE 1 
______________________________________ 
internal resistance 
number of sample 
(milliohms) 
______________________________________ 
Battery A 10 53 
Battery B 10 50 
Battery C 9 62 
______________________________________ 
The above results show that batteries (A) and (B) of this invention 
achieved a 15-20% reduction in internal resistance without any 
deterioration of discharging characteristics in comparison with battery 
(C) of the conventional method. This is because this invention allows the 
electrode lead, which needs to have a very small cross-sectional area, to 
be made very short. A 15-20% reduction in internal resistance means a 
15-20% reduction in the internal heating of the battery even when large 
currents are being discharged, which is of great significance from a 
safety perspective. In conventional battery (C) the entire 15-20% of extra 
heat arises only at the electrode leads which have very small heat 
capacity in relation to the total heat capacity inside the battery, 
leading to large temperature increases of the electrode leads when large 
currents are being discharged. This means that the electrode leads may 
become the source of ignition, particularly in the lithium ion secondary 
battery shown in this embodiment which uses combustible, organic 
electrolyte, causing the battery to catch fire. 
There was also one battery amongst the ten (C) batteries which did not 
function properly due to poor electric conduction between the metallic 
casing and the electrode. It is not possible when making battery (C) to 
confirm whether the welding of the negative electrode lead to the center 
of the casing bottom has been properly conducted or not, thus batteries 
may be created which do not function fully due to poor electrical 
conduction between the metallic casing and the electrode. The battery may 
also be subjected to vibrations in processes after the welding of the 
electrode lead, causing the welding to dislodge, with sufficient 
likelihood that the electrical conduction between the metallic casing and 
the electrode will be poor. 
In contrast, batteries (A) and (B) of the embodiments involved the battery 
element being housed in a cylindrical metallic casing, and the outside 
diameter of the said metallic casing being reduced, thus enabling very 
close contact over a large area between the end of electrode (electrode 
current collector) positioned at the outermost periphery of the battery 
element and the inside of the metallic casing. This means that there will 
be no batteries which do not function due to poor electric conduction 
between the metallic casing and the electrode. 
Furthermore, in Examples 3 and 4, a specific embodiment for the second 
invention indicated a lithium ion secondary battery using 
lithium-manganese oxide as the positive electrode active substance, and a 
carbon material as the negative electrode active substance; this second 
invention is essentially concerned with proposals for methods of obtaining 
the electric conduction between electrodes and the external terminals. 
Non-aqueous cylindrical batteries naturally can be applied to other 
battery systems if they are batteries with a battery element that has a 
coiled structure. 
As the "outside diameter of the casing bottom" (L3=C) of the metallic 
casing prior to Swaging in this invention is no more than the outside 
diameter of the metallic casing (L2=A) in the finished battery, 
(A.gtoreq.C), there is no change in the "outside diameter of the casing 
bottom" (L3) even after Swaging. Thus, there is no bulging of the bottom 
of the metallic casing in the Swaging process, enabling batteries with the 
same external appearance as conventional batteries (having a flat bottom) 
to be made with the Swage Method, and making possible battery 
manufacturing by the Swage Method characterized by boosted capacity due to 
a bigger battery element diameter. 
Furthermore, the coiled battery element in this invention is made by 
finishing the winding so as the end of electrode or electrode current 
collector of the negative electrode or the positive electrode is 
positioned at the outermost periphery of the battery element, then the 
said battery element is housed in the metallic casing, after which the 
outside diameter of the said metallic casing is reduced, thus the end of 
an electrode or electrode current collector positioned at the outermost 
periphery of the battery element is in very close contact under high 
contact pressure with the inside wall of the metallic casing. This ensures 
a good electrical conduction between either the negative electrode or the 
positive electrode and the metallic casing which is the external terminal 
of the electrode. 
In the method in which a metallic rod is inserted into the hole in the 
center of the coiled battery element, to one end of said metallic rod is 
welded the electrode lead brought into the center of the coiled battery 
element, and a lid welded to the other end of the said metallic rod, there 
is no need to fold the electrode lead to enable the installation of the 
lid as in conventional methods, meaning that only a very short electrode 
lead is required. Accordingly, under this invention there will be no 
batteries which do not function fully due to poor electric conduction 
between the metallic casing and the electrode, boosting battery 
reliability. As this invention requires only a very short electrode lead, 
which needs to have a very small cross-sectional area, there is also no 
concern about temperature increases in the electrode lead due to the 
passage of large currents. This removes the danger of batteries catching 
fire when the electrode lead becomes the source of ignition, particularly 
in non-aqueous cylindrical batteries which use combustible organic 
electrolyte. Eliminating the need to spot weld the electrode lead to the 
casing bottom also allows the housing of the battery element after 
electrolyte has been impregnated into the battery element, enabling the 
removal of the process of injecting electrolyte into the metallic casing, 
which has seriously hampered productivity. 
As a result, the mass supply of high performance batteries of great 
reliability and safety for a broad range of applications has been made 
possible, having enormous industrial value.