U.S. patent application number 16/844854 was filed with the patent office on 2020-07-23 for battery and method for manufacturing battery.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to Akira KAKINUMA, Kenjin MASUMOTO, Junya NISHIMORI, Keisuke YONEDA.
Application Number | 20200235354 16/844854 |
Document ID | / |
Family ID | 46672027 |
Filed Date | 2020-07-23 |
United States Patent
Application |
20200235354 |
Kind Code |
A1 |
MASUMOTO; Kenjin ; et
al. |
July 23, 2020 |
BATTERY AND METHOD FOR MANUFACTURING BATTERY
Abstract
A manufacturing method of a battery including attaching a first
current collector lead to a first electrode plate; attaching a
second current collector lead to a second electrode plate; a step
of fabricating a wound electrode group by winding the first
electrode plate and the second electrode plate around a winding
core member with a separator interposed therebetween; accommodating
the wound electrode group in a closed-end cylindrical metal case
being a first electrode terminal; joining the first current
collector lead to an inner sidewall surface of the metal case (step
X); joining the second current collector lead to a sealing member
being a second electrode terminal; and sealing the metal case,
before step X, a joint portion of the first current collector lead
with the inner sidewall surface of the metal case is curved in a
same direction as a curve of the inner sidewall surface of the
metal case.
Inventors: |
MASUMOTO; Kenjin; (Hyogo,
JP) ; KAKINUMA; Akira; (Osaka, JP) ; YONEDA;
Keisuke; (Osaka, JP) ; NISHIMORI; Junya;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
46672027 |
Appl. No.: |
16/844854 |
Filed: |
April 9, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13984779 |
Aug 9, 2013 |
10658633 |
|
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PCT/JP2011/007119 |
Dec 20, 2011 |
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16844854 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2/0217 20130101;
H01M 10/0422 20130101; H01M 2/08 20130101; H01M 2/022 20130101;
H01M 4/742 20130101; Y10T 29/4911 20150115; H01M 10/0431 20130101;
H01M 4/661 20130101 |
International
Class: |
H01M 2/08 20060101
H01M002/08; H01M 10/04 20060101 H01M010/04; H01M 2/02 20060101
H01M002/02; H01M 4/66 20060101 H01M004/66; H01M 4/74 20060101
H01M004/74 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2011 |
JP |
2011-030708 |
Claims
1. A manufacturing method of a battery comprising: a step of
attaching a first current collector lead to a first electrode
plate; a step of attaching a second current collector lead to a
second electrode plate having polarity opposite to that of the
first electrode plate; a step of fabricating a wound electrode
group by winding the first electrode plate and the second electrode
plate around a winding core member with a separator interposed
between the first and second electrode plates; a step of
accommodating the wound electrode group in a closed-end cylindrical
metal case being a first electrode terminal; a step X of joining
the first current collector lead to an inner sidewall surface of
the metal case; a step of joining the second current collector lead
to a sealing member being a second electrode terminal; and a step
of sealing the metal case by disposing an insulating member at an
inner-surface side of an opening of the metal case, inserting the
sealing member in a position of the opening in which the insulating
member is disposed, and crimping the metal case to the sealing
member, wherein before the step X, a joint portion of the first
current collector lead with the inner sidewall surface of the metal
case is curved in a same direction as a curve of the inner sidewall
surface of the metal case.
2. A manufacturing method of a battery comprising: a step of
attaching a first current collector lead to a first electrode
plate; a step of attaching a second current collector lead to a
second electrode plate having polarity opposite to that of the
first electrode plate; a step of fabricating a wound electrode
group by winding the first electrode plate and the second electrode
plate around a winding core member with a separator interposed
between the first and second electrode plates; a step of
accommodating the wound electrode group in a closed-end cylindrical
metal case being a first electrode terminal; a step X of joining
the first current collector lead to an inner sidewall surface of
the metal case; a step of joining the second current collector lead
to a sealing member being a second electrode terminal; and a step
of sealing the metal case by disposing an insulating member at an
inner-surface side of an opening of the metal case, inserting the
sealing member in a position of the opening in which the insulating
member is disposed, and crimping the metal case around the sealing
member, wherein in the step X of joining, a joint portion of the
first current collector lead with the inner sidewall surface of the
metal case is curved in a same direction as a curve of the inner
sidewall surface of the metal case.
3. The manufacturing method of a battery of claim 1, wherein in the
step of accommodating the wound electrode group in a closed-end
cylindrical metal case being a first electrode metal, the first
current collector lead and the second current collector lead are
accommodated to be located at the opening side of the metal
case.
4. The manufacturing method of a battery of claim 1, further
comprising: after the step X and before the step of joining the
second current collector lead to a sealing member being a second
electrode terminal, a step of locating an intermediate member on
the wound electrode group.
5. The manufacturing method of a battery of claim 1, further
comprising: before the step of sealing, a step of applying
nonaqueous electrolyte fluid into the metal case by
depressurization.
6. The manufacturing method of a battery of claim 1, further
comprising: a step of extracting the winding core from the wound
electrode group, the wound electrode group, from which the winding
core has been extracted, being accommodated in the metal case.
7. The manufacturing method of a battery of claim 1, wherein a
thickness of the first current collector lead is 80 .mu.m or
less.
8. The manufacturing method of a battery of claim 1, wherein a
length of the first current collector lead in a circumferential
direction of the wound electrode group ranges from 10% to 30%, both
inclusive, of a length of an outer periphery of the wound electrode
group.
9. The manufacturing method of a battery of claim 2, wherein in the
step of accommodating the wound electrode group in a closed-end
cylindrical metal case being a first electrode metal, the first
current collector lead and the second current collector lead are
accommodated to be located at the opening side of the metal
case.
10. The manufacturing method of a battery of claim 2, further
comprising: after the step X and before the step of joining the
second current collector lead to a sealing member being a second
electrode terminal, a step of locating an intermediate member on
the wound electrode group.
11. The manufacturing method of a battery of claim 2, further
comprising: before the step of sealing, a step of applying
nonaqueous electrolyte fluid into the metal case by
depressurization.
12. The manufacturing method of a battery of claim 2, further
comprising: a step of extracting the winding core from the wound
electrode group, the wound electrode group, from which the winding
core has been extracted, being accommodated in the metal case.
13. The manufacturing method of a battery of claim 2, wherein in
the first current collector lead, a plurality of grooves extending
along the center axis of the wound electrode group are formed.
14. The manufacturing method of a battery of claim 2, wherein in
the first current collector lead, a plurality of through-holes are
open in a grid pattern.
15. The manufacturing method of a battery of claim 2, wherein in
the first current collector lead, a plurality of through-holes are
open in a honeycomb pattern.
16. The manufacturing method of a battery of claim 2, wherein a
thickness of the first current collector lead is 80 .mu.m or
less.
17. The manufacturing method of a battery of claim 2, wherein a
length of the first current collector lead in a circumferential
direction of the wound electrode group ranges from 10% to 30%, both
inclusive, of a length of an outer periphery of the wound electrode
group.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional Application of U.S. patent
application Ser. No. 13/984,779, filed on Aug. 9, 2013, which is
the U.S. National Phase under 35 U.S.C. .sctn. 371 of International
Application No. PCT/JP2011/007119, filed on Dec. 20, 2011, which in
turn claims the benefit of Japanese Application No. 2011-030708,
filed on Feb. 16, 2011, the disclosures of which applications are
incorporated by reference herein.
TECHNICAL FIELD
[0002] The present disclosure relates to batteries and methods of
manufacturing the batteries.
BACKGROUND ART
[0003] Nonaqueous electrolyte secondary batteries have high energy
density, and are thus widely used as power supplies of portable
electronic devices such as mobile phones and laptop computers.
[0004] Out of nonaqueous electrolyte secondary batteries, lithium
ion secondary batteries have a high voltage of 3.6 V, and may be
50% by mass and about 20-50% by volume of nickel-hydrogen batteries
when compared at the same power generation energy. The lithium ion
secondary batteries have high energy density and can be thus
miniaturized. Furthermore, without memory effect, lithium ion
secondary batteries account for a largest share of power supplies
of mobile phones and laptop computers.
[0005] Small lithium ion secondary batteries are divided into those
in a cylindrical shape and those in a flat shape. The smaller, the
more easily the batteries are fabricated in the cylindrical shape.
As shown in Patent Document 1, a cylindrical lithium ion secondary
battery accommodates a wound electrode body inside a cylindrical
battery can. The battery can is formed by fixing a sealing plate to
an opening of a closed-end cylindrical body with an insulating
member interposed therebetween by crimping. The wound electrode
body is formed by interposing a separator between positive and
negative band-like electrodes and winding them in whorls. The wound
electrode body has a through-hole in a winding core center.
[0006] A positive electrode current collector plate is welded onto
the end edge of the positive electrode of the wound electrode body.
The top of the lead extending toward the positive electrode current
collector plate is welded onto the back surface of the sealing
plate. A positive electrode terminal projecting outside is formed
in the sealing plate. On the other hand, a negative electrode
current collector plate is welded onto the end edge of the negative
electrode of the wound electrode body (i.e., the bottom of the
battery can). The surface of the negative electrode current
collector plate is welded onto the bottom of the closed-end
cylindrical body. A plurality of projections extending to the
bottom of the closed-end cylindrical body are formed concyclically
on the surface of the negative electrode current collector plate in
a portion corresponding to the through-hole of the wound electrode
body.
[0007] In welding the negative electrode current collector plate
onto the bottom of the closed-end cylindrical body, a columnar
electrode rod is inserted into the through-hole of the wound
electrode body so that the top of the electrode rod comes into
contact with the back surface of the negative electrode current
collector plate, and so that an electrode piece comes into contact
with the back surface of the closed-end cylindrical body to face
the electrode rod, with the negative electrode current collector
plate accommodating the wound electrode body inside the closed-end
cylindrical body. By flowing a current between the electrode rod
and the electrode piece, the negative electrode current collector
plate and the closed-end cylindrical body are resistance-welded. As
a result, the negative electrode current collector plate and the
closed-end cylindrical body are jointed and electrically coupled
together at junctions between the tops of the projections of the
negative electrode current collector plate and the bottom of the
closed-end cylindrical body.
CITATION LIST
Patent Document
[0008] PATENT DOCUMENT 1: Japanese Patent Publication No.
2006-164713
[0009] PATENT DOCUMENT 2: Japanese Patent Publication No.
2007-95499
SUMMARY OF THE INVENTION
Technical Problem
[0010] In Patent Document 1, the columnar electrode rod is inserted
into the through-hole of the wound electrode body and pressed onto
the bottom of the cylindrical body to resistance-weld the negative
electrode current collector plate and the closed-end cylindrical
body. In this structure, if the columnar electrode rod is not
pressed onto the bottom of the cylindrical body with high pressure,
the electrical coupling between the negative electrode current
collector plate and the closed-end cylindrical body is
insufficient. Thus, the columnar electrode rod needs to have a
great radius to some extent not to curve by the pressure.
[0011] However, where a battery itself is small and a columnar
electrode rod has a great radius, there is a need to reduce the
amount of the positive electrode and the negative electrode
accordingly, thereby reducing the battery capacity. If the amount
of the positive electrode and the negative electrode is to be
increased, a fine columnar electrode rod is required, thereby
reducing the pressure. This results in insufficient electrical
coupling between the negative electrode current collector plate and
the closed-end cylindrical body. As such, the electrical resistance
increases at the coupling portion to reduce the extracted voltage
and the battery capacity. In particular, a voltage drop increases
due to the resistance inside the battery in extracting a large
current.
[0012] Patent Document 2 shows a small cylindrical (pin-like)
lithium ion battery having a different structure from Patent
Document 1. The battery is formed by winding a positive electrode
plate and a negative electrode plate around a negative electrode
pin with a separator interposed between the positive and negative
electrode plates. The head of the negative electrode pin is used as
a negative electrode terminal. In this structure, since there is no
need to weld the bottom of a cylindrical battery case and the
negative electrode pin, the problem of Patent Document 1 does not
occur.
[0013] In the battery of Patent Document 2, however, it is
difficult to sufficiently improve the sealing properties between
the head of the negative electrode pin and the battery case due to
its structure. In particular, where gas occurs inside the battery,
leakage is difficult to prevent. With a decrease in the size of the
battery, the problem of the sealing properties becomes difficult to
solve.
[0014] The present disclosure was made in view of the problems. It
is an objective of the present disclosure to provide a battery
accommodating a wound electrode group in a closed-end cylindrical
case, and having high sealing properties, great battery capacity,
and reliable low-resistive coupling between a current collector
lead and an electrode terminal.
Solution to the Problem
[0015] A battery according to the present disclosure includes a
first electrode plate; a second electrode plate having polarity
opposite to that of the first electrode plate; a separator
interposed between the first and second electrode plates; a
closed-end cylindrical metal case configured to accommodate the
first electrode plate, the second electrode plate, and the
separator; and a sealing member configured to seal an opening of
the metal case with an insulating member interposed therebetween.
The first and second electrode plates are wound with the separator
interposed therebetween to form a wound electrode group. A center
axis portion of the wound electrode group includes a center axis of
a cylinder of the metal case, and contains no power-generating
element. The metal case is a first electrode terminal, and the
sealing member is a second electrode terminal. A first current
collector lead electrically coupled to the first electrode plate
extends toward the opening of the metal case, and joined to an
inner sidewall surface of the metal case. A second current
collector lead electrically coupled to the second electrode plate
extends toward the opening of the metal case, and joined to the
sealing member.
[0016] Each "electrode plate" here denotes a flat plate containing
an active material, and is a positive electrode or a negative
electrode. The term "joined" denotes being firmly connected by
bonding or welding.
[0017] A first manufacturing method of a battery according to the
present disclosure includes a step of attaching a first current
collector lead to a first electrode plate; a step of attaching a
second current collector lead to a second electrode plate having
polarity opposite to that of the first electrode plate; a step of
fabricating a wound electrode group by winding the first electrode
plate and the second electrode plate around a winding core member
with a separator interposed between the first and second electrode
plates; a step of accommodating the wound electrode group in a
closed-end cylindrical metal case being a first electrode terminal;
a step X of joining the first current collector lead to an inner
sidewall surface of the metal case; a step of joining the second
current collector lead to a sealing member being a second electrode
terminal; and a step of sealing the metal case by disposing an
insulating member at an inner-surface side of an opening of the
metal case, inserting the sealing member in a position of the
opening in which the insulating member is disposed, and crimping
the metal case around the sealing member. Before the step X, a
joint portion of the first current collector lead with the inner
sidewall surface of the metal case is curved in a same direction as
a curve of the inner sidewall surface of the metal case.
[0018] A second manufacturing method of a battery according to the
present disclosure includes a step of attaching a first current
collector lead to a first electrode plate; a step of attaching a
second current collector lead to a second electrode plate having
polarity opposite to that of the first electrode plate; a step of
fabricating a wound electrode group by winding the first electrode
plate and the second electrode plate around a winding core member
with a separator interposed between the first and second electrode
plates; a step of accommodating the wound electrode group in a
closed-end cylindrical metal case being a first electrode terminal;
a step X of joining the first current collector lead to an inner
sidewall surface of the metal case; a step of joining the second
current collector lead to a sealing member being a second electrode
terminal; and a step of sealing the metal case by disposing an
insulating member at an inner-surface side of an opening of the
metal case, inserting the sealing member in a position of the
opening in which the insulating member is disposed, and crimping
the metal case around the sealing member. In the step X of joining,
a joint portion of the first current collector lead with the inner
sidewall surface of the metal case is curved in a same direction as
a curve of the inner sidewall surface of the metal case.
Advantages of the Invention
[0019] In the battery according to the present disclosure, the
first current collector lead is joined to the inner sidewall
surface of the metal case, and the second current collector lead is
joined to the sealing member which seals the opening of the metal
case with the insulating member interposed therebetween. This
increases the sealing properties, and provides reliable
low-resistive coupling between the current collector lead the
electrode terminal, thereby increasing the voltage and the
capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic cross-sectional view of a battery
according to an embodiment.
[0021] FIG. 2 illustrates an unwound electrode group.
[0022] FIG. 3 illustrates a negative electrode current collector
lead.
[0023] FIG. 4 illustrates an example structure of the negative
electrode current collector lead.
[0024] FIG. 5 illustrates another example structure of the negative
electrode current collector lead.
[0025] FIG. 6 illustrates still another example structure of the
negative electrode current collector lead.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0026] Embodiments of the present disclosure will be described
hereinafter in detail with reference to the drawings. In the
drawings, the same reference characters are used to represent
equivalent elements having substantially the same functions for
simplicity of explanation.
[0027] FIG. 1 illustrates the schematic cross-section of a battery
according to a first embodiment. The battery according to this
embodiment is in a substantially cylindrical shape. A closed-end
cylindrical metal case 8 accommodates a negative electrode 2 being
a first electrode plate and a positive electrode 4 being a second
electrode plate, which are wound with a separator 6 interposed
therebetween. That is, the negative electrode 2, the positive
electrode 4, and the separator 6 are wound to form a wound
electrode group. Although not shown, the metal case 8 also
accommodates a nonaqueous electrolyte. The center axis of the
cylindrical metal case 8 is located in a center axis portion 18 of
the wound electrode group. That is, the center axis portion 18 of
the wound electrode group includes the center axis of the metal
case 8. The center axis portion 18 of the wound electrode group
does not contain any active material which is a power-generating
element. The "center axis portion 18 of the wound electrode group"
denotes the region extending from the center axis of the wound
electrode group to the innermost portion of the electrode
group.
[0028] A negative electrode current collector lead 22, which is
electrically coupled to the negative electrode 2, is joined (at a
welding point 26) and electrically coupled to an inner sidewall
surface of the metal case 8, which also serves as a negative
electrode terminal 10. On the other hand, a positive electrode
current collector lead 24, which is electrically coupled to the
positive electrode 4, is joined and electrically coupled to a
sealing member 12, which also serves as a positive electrode
terminal 14. The sealing member 12 is a member which seals the
opening of the metal case 8. An insulating member 16 is interposed
between the sealing member 12 and the metal case 8, and the metal
case 8 is crimped around the sealing member of the metal case 8 at
the opening. A ring intermediate member 28, which is an insulating
member, is disposed between the wound electrode group and the
sealing member 12 to reliably insulate the negative-electrode side
from the positive-electrode side. The portion of the sealing member
12, which projects outside the battery, is set in a hole of a
perforated circular plate 30 made of an insulating material,
thereby securing the insulation from the metal case 8.
[0029] As shown in FIG. 2, the negative electrode 2 is formed by
mounting a negative electrode active material on a negative
electrode core material 20, which is metal foil. The negative
electrode current collector lead (i.e., a first current collector
lead) 22 is joined to the negative electrode core material 20.
Similarly, the positive electrode 4 is formed by mounting a
positive electrode active material on a positive electrode core
material (not shown). The positive electrode current collector lead
(i.e., a second current collector lead) 24 is joined to the
positive electrode core material. The separator 6 is interposed
between the negative electrode 2 and the positive electrode 4, and
then wound around a winding core 50 to form the wound electrode
group. After the winding, the winding end is fixed with a fixing
tape 54 not to move, and the winding core 50 is extracted and put
into the metal case 8. At this time, the winding core 50 is put so
that both of the negative electrode current collector lead 22 and
the positive electrode current collector lead 24 are located at the
opening side of the metal case 8.
[0030] The active materials for the negative electrode 2 and the
positive electrode 4 are compressed and mounted on the core
materials to increase the battery capacity. If R at the winding
start is too small, the active materials may be removed by the core
materials to cause a short-circuit inside the battery. Therefore,
the winding core 50 needs to have great R to some extent. On the
other hand, if R of the winding core 50 is too great, the amount of
the active materials accommodated inside the battery decreases,
thereby reducing the battery capacity. In view of the two problems,
R of the winding core 50 is preferably 3.0 mm or less, and more
preferably less than 1.5 mm Therefore, the center axis portion of
the wound electrode group is preferably a space with a diameter of
3.0 mm or less without any active material, and more preferably a
space with a diameter of less than 1.5 mm without any active
material.
[0031] After the wound electrode group is put into the metal case
8, the negative electrode current collector lead 22 located in the
outer periphery of the wound electrode group comes into contact
with the inner sidewall surface of the metal case 8. Then, the
negative electrode current collector lead 22 and the metal case 8
are joined by spot welding. At this time, assume that the negative
electrode current collector lead 22 does not curve in the same
direction as the inner sidewall surface of the metal case 8. The
portions of the negative electrode current collector lead 22 and
the metal case 8, which form the welding point 26, are not
sufficiently in contact with each other, even if two electrodes to
be welded sandwich the negative electrode current collector lead 22
and the metal case 8 in the spot welding. That is, sufficient
welding is impossible. As a result, the resistance of the welding
portion increases, or in the worst case, the welding portion is
removed and no current is extracted.
[0032] Assume that the battery case is in a cylindrical shape, and
the negative electrode current collector lead is joined to the
sidewall of the battery case. The inner sidewall surface of the
battery case curves inside in a recess shape. The negative
electrode current collector lead is planar metal foil. Thus, the
negative electrode current collector lead does not curve along the
curve of the inner sidewall surface of the battery case. The both
ends of the negative electrode current collector lead are merely in
contact with the sidewall of the battery case. The center of the
negative electrode current collector lead, which is the portion to
be joined, is apart from the sidewall of the battery case. Thus,
the joint portion is insufficient if the center is joined by spot
welding etc. In the worst case, the center is not joined. This
problem does not occur in a flat battery case.
[0033] In order to curve the negative electrode current collector
lead 22 in the same direction as the curve of the inner sidewall
surface of the metal case 8, the negative electrode current
collector lead 22 may be curved before the welding. Alternatively,
the negative electrode current collector lead 22 may be made of a
material, which easily curves by pressure of an electrode to be
welded. For example, the negative electrode current collector lead
22 may be made of Ni foil with a thickness of 50 .mu.m, and may be,
as shown in FIG. 3, curved before winding the negative electrode 2,
the positive electrode 4, and the separator 6. The negative
electrode current collector lead 22 may curve at at least the
welding portion. The negative electrode current collector lead 22
is preferably made of metal foil with a thickness ranging from 20
.mu.m to 80 .mu.m, both inclusive.
[0034] In order to curve the negative electrode current collector
lead 22 in the same direction as the curve of the inner sidewall
surface of the metal case 8, and to perform strong welding, the
center of the radius of curvature of the negative electrode current
collector lead 22 is located inside the metal case 8, with the
negative electrode current collector lead 22 being in contact with
the inner surface of the metal case 8.
[0035] In this embodiment, the spot welding is performed at the
opening of the metal case 8, the welding portion is visually
confirmed to know whether or not the welding is reliably
preformed.
[0036] In FIG. 2, the length W of the negative electrode current
collector lead 22 in the circumferential direction of the wound
electrode group preferably ranges from 10% to 30%, both inclusive,
of the length of the outer periphery of the wound electrode group.
This is because welding is reliably performed and the battery
capacity is sufficiently secured within the range. Specifically, if
the length W is too small, the welding is not reliably performed.
With an increase in the length W, the loss of the active material
by the formation of the negative electrode current collector lead
22 increases.
[0037] In the battery shown in Patent Document 2, electrical
conduction is made by pressing the current collector lead against
the exterior. If an oxide film is formed on the surface of the
current collector lead, the contact resistance increases. It is
important to control the position so that the extending top of the
current collector lead is located around the portion with a reduced
diameter near the sealing portion. If the position is not correctly
controlled, the current collector lead is caught in the sealing
portion. Then, a space is formed in the sealing portion, thereby
degrading the sealing properties. In the battery according to this
embodiment, since the current collector lead is welded in a
position apart from the sealing portion, the problem in the battery
of Patent Document 2 does not occur. The positive electrode 4, the
negative electrode 2, the separator 6, and the nonaqueous
electrolyte forming the battery according to this embodiment will
be described below in detail.
[0038] First, the positive electrode will be described in
detail.
Positive Electrode
[0039] The positive electrode core material (i.e., a positive
electrode current corrector) and a positive electrode mixture
layer, which form the positive electrode 4, will be described
sequentially.
[0040] The positive electrode current corrector is a long conductor
substrate with a porous structure or a non-porous structure. The
positive electrode current corrector is mainly made of metal foil
of aluminum. The thickness of the positive electrode current
corrector is not particularly limited, but preferably ranges from 1
.mu.m to 500 .mu.m, both inclusive, and more preferably ranges from
10 .mu.m to 20 .mu.m, both inclusive. As such, the thickness of the
positive electrode current corrector falls within the
above-described range, thereby maintaining the strength of the
positive electrode 4 and reducing the weight of the positive
electrode 4.
[0041] The positive electrode active material, a binder, and a
conductive agent, which are contained in the positive electrode
mixture layer, will be described sequentially.
Positive Electrode Active Material
[0042] The positive electrode active material is preferably
lithium-containing composite oxide, for example, LiCoO.sub.2,
LiNiO.sub.2, LiMnO.sub.2, LiCo.sub.xNi.sub.1-xO.sub.2,
LiCo.sub.xM.sub.1-xO.sub.2, LiNi.sub.xM.sub.1-xO.sub.2,
LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2, LiMn.sub.2O.sub.4,
LiMnMO.sub.4, LiMePO.sub.4, Li.sub.2MePO.sub.4F, where M is at
least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb,
or B, x is expressed by 0<x<1, and Me is a metal element
containing at least one element selected from the group consisting
of Fe, Mn, Co, or Ni. Alternatively, part of the elements of the
lithium-containing compound may be replaced with another type of
element. The positive electrode active material may be a positive
electrode active material being subjected to surface treatment with
metal oxide, lithium oxide, a conductive agent, etc. The surface
treatment may be, for example, hydrophobization.
[0043] The positive electrode active material preferably has an
average particle diameter ranging from 5 .mu.m to 20 .mu.m, both
inclusive. If the average particle diameter of the positive
electrode active material is less than 5 .mu.m, the surface areas
of the active material particles extremely increase, thereby
extremely increasing the amount of the binder satisfying the
bonding strength for sufficiently handling a positive electrode
plate. This reduces the amount of the active material per electrode
plate, thereby reducing the battery capacity. On the other hand, if
the average particle diameter is more than 20 .mu.m, a coating
streak tends to occur in coating the positive electrode current
corrector with positive electrode mixture slurry.
Binder
[0044] The binder is made of, for example, PVDF,
polytetrafluoroethylene, polyethylene, polypropylene, aramid resin,
polyamide, polyimide, polyamide imide, polyacrylonitrile,
polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid
ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid,
polymethacrylic acid methyl ester, polymethacrylic acid ethyl
ester, polymethacrylic acid hexyl ester, polyvinyl acetate,
polyvinyl pyrrolidone, polyether, polyether sulfone,
hexafluoropolypropylene, styrene butadiene rubber, carboxymethyl
cellulose, etc. Alternatively, the binder may be made of a
copolymer formed by copolymerizing two or more materials selected
from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene,
perfluoroalkyl vinyl ether, vinylidene fluoride,
chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene,
fluoromethylvinylether, acrylic acid, or hexadiene, or a mixture
formed by mixing the selected two or more materials.
[0045] Out of the above-listed binders, PVDF and PVDF derivative
are particularly chemically stable in the nonaqueous electrolyte
secondary battery, sufficiently binds the positive electrode
mixture layer and the positive electrode current corrector, and the
positive electrode active material forming the positive electrode
mixture layer, the binder, and the conductive agent. This provides
excellent charge-discharge cycle characteristics and discharge
performance Therefore, PVDF and PVDF derivative are preferably used
as the binder of this embodiment. In addition, PVDF and PVDF
derivative are available at low costs and thus preferable. In order
to fabricate the positive electrode using PVDF as a binder, for
example, PVDF is dissolved in N methyl pyrrolidone, or PVDF powder
is dissolved in the positive electrode mixture slurry when
fabricating the positive electrode.
Conductive Agent
[0046] The conductive agent is, for example, graphites such as
natural graphite or artificial graphite; carbon blacks such as
acetylene black (AB), ketjen black, channel black, furnace black,
lamp black, or thermal black; conductive fibers such as carbon
fiber or metal fiber; fluorocarbon, powders of metal such as
aluminum, conductive whiskers such as zinc oxide or potassium
titanate, conductive metal oxide such as titanium oxide, organic
conductive materials such as phenylene derivative, etc.
[0047] Next, the negative electrode will be described in
detail.
Negative Electrode
[0048] The negative electrode core material (i.e., a negative
electrode current corrector) and a negative electrode mixture
layer, which form the negative electrode 2, will be described
sequentially.
[0049] The negative electrode current corrector is a long conductor
substrate with a porous structure or a non-porous structure. The
negative electrode current corrector is made of, for example,
stainless steel, nickel, copper, etc. The thickness of the negative
electrode current corrector is not particularly limited, but
preferably ranges from 1 .mu.m to 500 .mu.m, both inclusive, and
more preferably ranges from 5 .mu.m to 20 .mu.m, both inclusive. As
such, the thickness of the negative electrode current corrector
falls within the above-described range, thereby maintaining the
strength of the negative electrode 2 and reducing the weight of the
negative electrode 2.
[0050] The negative electrode mixture layer preferably contains a
binder in addition to the negative electrode active material.
[0051] The negative electrode current collector lead 22 is
preferably made of nickel, iron, stainless steel, copper, etc. The
thickness preferably ranges from 10 .mu.m to 120 .mu.m, both
inclusive, and more preferably ranges from 20 .mu.m to 80 .mu.m.
The shape is not particularly limited, and may be a strip having a
tab for welding with the negative electrode core material, and a
tab for welding with an exterior case, an oval being in internal
contact with the strip, a polygon, etc. The negative electrode
current collector lead 22 is characterized by curving by small
pressure.
[0052] The negative electrode active material contained in the
negative electrode mixture layer will be described below.
Negative Electrode Active Material
[0053] The negative electrode active material is a material capable
of inserting and extracting lithium ions, and may be, for example,
metal, metal fiber, a carbon material, oxide, nitride, a silicon
compound, a tin compound, various types of alloy material, etc. Out
of them, the carbon material is, for example, various types of
natural graphite, coke, partially graphitized carbon, carbon fiber,
spherical carbon, various types of artificial graphite, amorphous
carbon, etc.
[0054] A single element such as silicon (Si) or tin (Sn), a silicon
compound, or a tin compound have a high capacitance density.
Therefore, the negative electrode active material is, for example,
preferably silicon, tin, a silicon compound, and a tin compound.
Out of them, the silicon compound is specifically, for example,
SiOx, where 0.05<x<1.95, or silicon alloy, silicon solid
solution, etc., in which part of Si is replaced with at least one
element selected from the group consisting of B, Mg, Ni, Ti, Mo,
Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, or Sn. The tin
compound is specifically, for example, Ni.sub.2Sn.sub.4,
Mg.sub.2Sn, SnO.sub.x, where 0<x<2, SnO.sub.2, SnSiO.sub.3,
etc. The negative electrode active material may be one of the above
examples, or may be a combination of two or more of the
examples.
[0055] Furthermore, a negative electrode is provided, which is
formed by depositing the silicon, the tin, the silicon compound, or
the tin compound as a thin film on the negative electrode current
corrector.
[0056] Next, the separator will be described.
Separator (Porous Insulator)
[0057] The separator 6 interposed between the positive electrode 4
and the negative electrode 2 is, for example, made of a microporous
thin film, woven fabric, non-woven fabric, etc., which have great
ion transmittance, predetermined mechanical strength, and
insulating properties. In particular, the separator 6 is
preferably, for example, polyolefin such as polypropylene and
polyethylene. Polyolefin has excellent durability and a shutdown
function, thereby improving the safety of the lithium ion secondary
battery.
[0058] The thickness of the separator 6 generally ranges from 10
.mu.m to 300 .mu.m, both inclusive, but preferably ranges from 10
.mu.m to 40 .mu.m, both inclusive. More preferably, the thickness
of the separator 6 ranges from 15 .mu.m to 30 .mu.m, both
inclusive, and furthermore preferably ranges from 10 .mu.m to 25
.mu.m, both inclusive. Where the separator 6 is a microporous thin
film, the microporous thin film may be a single-layer film made of
a single material, or a composite film or a multilayer film made of
a single material, or two or more materials. The porosity of the
separator 6 preferably ranges from 30% to 70%, both inclusive, and
more preferably ranges from 35% to 60%, both inclusive. The
"porosity" here denotes the ratio of the volume of the pores to the
entire volume of the separator.
[0059] Then, the nonaqueous electrolyte will be described in
detail.
Nonaqueous Electrolyte
[0060] The nonaqueous electrolyte is, for example, a liquid, gel,
or solid nonaqueous electrolyte.
[0061] The liquid nonaqueous electrolyte (nonaqueous electrolyte
fluid) contains an electrolyte (e.g., lithium salts) and a
nonaqueous solvent dissolving the electrolyte.
[0062] The gel nonaqueous electrolyte contains a nonaqueous
electrolyte, and a polymer material holding the nonaqueous
electrolyte. The polymer material is, for example, polyvinylidene
fluoride, polyacrylonitrile, polyethylene oxide, polyvinyl
chloride, polyacrylate, polyvinylidene fluoride
hexafluoropropylene, etc.
[0063] The solid nonaqueous electrolyte contains a solid polymer
electrolyte.
[0064] The nonaqueous electrolyte fluid will be described below in
detail.
[0065] The nonaqueous solvent dissolving the electrolyte may be a
known nonaqueous solvent. The type of the nonaqueous solvent is not
particularly limited, but may be, for example, cyclic carbonic
ester, chain carbonic ester, cyclic carboxylate ester, etc. The
cyclic carbonic ester is specifically, for example, propylene
carbonate (PC), ethylene carbonate (EC), etc. The chain carbonic
ester is specifically, for example, diethyl carbonate (DEC),
ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), etc. The
cyclic carboxylate ester is specifically, for example,
gamma-butyrolactone (GBL), gamma-valerolactone (GVL), etc. The
nonaqueous solvent may be one of the above examples, or may be a
combination of two or more of the examples.
[0066] The electrolyte dissolved in the nonaqueous solvent is, for
example, LiClO.sub.4, LiBF.sub.4, LiPF.sub.6, LiAlCl.sub.4,
LiSbF.sub.6, LiSCN, LiCF.sub.3SO.sub.3, LiCF.sub.3CO.sub.2,
LiAsF.sub.6, LiB.sub.10Cl.sub.10, lower aliphatic lithium
carboxylate, LiCl, LiBr, LiI, chloroborane lithium, borates,
imidates, etc. The borates are specifically, for example, lithium
bis(1,2-benzendiolate(2-)-O,O')borate, lithium
bis(2,3-naphthalenediolate(2-)-O,O') borate, lithium
bis(2,2'-biphenyldiolate(2-)-O,O') borate, lithium
bis(5-fluoro-2-olate-1-benzenesulfonic acid-O,O') borate, etc. The
imidates are specifically, for example, lithium
bis(trifluoromethanesulfonyl)imide ((CF.sub.3SO.sub.2).sub.2NLi),
lithium trifluoromethanesulfonate nonafluorobutanesulfonimide
(LiN(CF.sub.3SO.sub.2)(C.sub.4F.sub.9SO.sub.2)), lithium
bispentafluoroethanesulfonimide
((C.sub.2F.sub.5SO.sub.2).sub.2NLi), etc. The electrolyte may be
one of the above examples, or may be a combination of two or more
of the examples.
[0067] The amount of dissolution of the electrolyte to the
nonaqueous solvent preferably ranges from 0.5 mol/m.sup.3 to 2
mol/m.sup.3, both inclusive.
[0068] In addition to the electrolyte and the nonaqueous solvent,
the nonaqueous electrolyte fluid may contain, for example, an
additive which decomposes on the negative electrode and forms a
film with high lithium ion conductivity to increase the
charge-discharge efficiency of the battery. The addictive with this
function is made of, for example, vinylene carbonate (VC),
4-methylvinylene carbonate, 4,5-dimethylvinylene carbonate,
4-ethylvinylene carbonate, 4,5-diethylvinylene carbonate,
4-propylvinylene carbonate, 4,5-dipropylvinylene carbonate,
4-phenylvinylene carbonate, 4,5-diphenylvinylene carbonate, vinyl
ethylene carbonate (VEC), divinylethylene carbonate, etc. The
addictive may be only one of the above examples, or may be a
combination of two or more of the examples. In particular, the
addictive is preferably at least one selected from the group
consisting of vinylene carbonate, vinylethylene carbonate, or
divinylethylene carbonate of the above examples. The addictive may
be made of the above examples, in which part of hydrogen atoms is
replaced with fluorine atoms.
[0069] In addition to the electrolyte and the nonaqueous solvent,
the nonaqueous electrolyte fluid may further contain a known
benzene derivative which decomposes at an overcharge and forms a
film on the electrode to inactivate the battery. The benzene
derivative with this function preferably has a phenyl group or a
cyclic compound group adjacent to the phenyl group. The benzene
derivative is specifically, for example, cyclohexylbenzene,
biphenyl, diphenyl ether, etc. The cyclic compound group contained
in the benzene derivative is specifically, for example, a phenyl
group, a cyclic ether group, a cyclic ester group, a cycloalkyl
group, a phenoxy group, etc. The benzene derivative may be only one
of the above examples, or may be a combination of two or more of
the examples. The amount of the benzene derivative contained in the
nonaqueous solvent is preferably 10 vol % or less of the entire
nonaqueous solvent.
[0070] Next, a manufacturing method of the battery according to the
first embodiment will be described using a lithium ion secondary
battery as a specific example.
[0071] A fabrication method of the positive electrode 4, a
fabrication method of the negative electrode 2, and a manufacturing
method of the battery will be described sequentially.
Fabrication Method of Positive Electrode
[0072] The fabrication method of the positive electrode 4 is as
follows. First, the positive electrode active material, the binder,
which is preferably made of, for example, the PVDF, the PVDF
derivative, or a rubber binder as described above, and the
conductive agent are mixed into a liquid component to prepare the
positive electrode mixture slurry. Next, the obtained positive
electrode mixture slurry is applied to the surface of the positive
electrode current corrector made of aluminum foil and dried. Then,
the positive electrode current corrector with the positive
electrode mixture slurry applied and dried on the surface is rolled
(i.e., compressed) to fabricate the positive electrode (i.e., the
positive electrode plate) with a predetermined thickness.
[0073] The amount of the binder contained in the positive electrode
mixture slurry preferably ranges from 3.0 vol % to 6.0 vol %, both
inclusive, of the positive electrode active material of 100 vol %.
In other words, the amount of the binder contained in the positive
electrode mixture layer preferably ranges from 3.0 vol % to 6.0 vol
%, both inclusive, of the positive electrode active material of 100
vol %.
Fabrication Method of Negative Electrode
[0074] The fabrication method of the negative electrode 2 is as
follows. First, the negative electrode active material and the
binder are mixed into the liquid component to prepare the negative
electrode mixture slurry. The obtained negative electrode mixture
slurry is applied to the surface of the negative electrode current
corrector and dried. Then, the negative electrode current corrector
with the negative electrode mixture slurry applied and dried on the
surface is rolled to fabricate the negative electrode with a
predetermined thickness.
Manufacturing Method of Battery
[0075] The manufacturing method of the battery is as follows.
First, the positive electrode current collector lead 24 made of
aluminum is attached to the positive electrode current corrector.
The negative electrode current collector lead 22 made of nickel is
attached to the negative electrode current corrector. After that,
the positive electrode 4 and the negative electrode 2 are wound
around the winding core 50 with the separator 6 interposed between
the positive and negative electrodes to form the wound electrode
group. Next, the wound electrode group, from which the winding core
50 has been extracted, is accommodated in the metal case 8. At this
time, the wound electrode group is accommodated so that the
negative electrode current collector lead 22 and the positive
electrode current collector lead 24 are located at the opening side
of the metal case 8. Then, the negative electrode current collector
lead 22 is welded onto the metal case 8, and the intermediate
member 28 is located on the wound electrode group. The positive
electrode current collector lead 24 is welded onto the sealing
member 12. After that, the nonaqueous electrolyte fluid is applied
into the metal case 8 by depressurization. Finally, the ends of the
metal case 8 at the opening are crimped around the sealing member
12 with the insulating member 16 interposed therebetween to set the
perforated circular plate 30 in the sealing member 12. As a result,
the battery is manufactured.
First Variation
[0076] FIG. 4 illustrates a negative electrode current collector
lead 22a according to a first variation. This variation differs
from the above-described embodiment only in the negative electrode
current collector lead 22a. The other members, the structures, and
the manufacturing method are the same as those in the
above-described embodiment.
[0077] FIG. 4 illustrates the top surface of the negative electrode
current collector lead 22a as viewed from the opening of the metal
case 8. In the negative electrode current collector lead 22a, a
plurality of grooves 60 extending along the center axis of the
wound electrode group are formed. That is, these grooves 60 extend
in the direction orthogonal to the circumferential direction of the
wound electrode group. The grooves 60 may be formed in the negative
electrode current collector lead 22a on the surface facing the
center axis portion 18 of the wound electrode group or on the
opposite surface.
[0078] In this variation, the grooves 60 are formed in the negative
electrode current collector lead 22a. Thus, the negative electrode
current collector lead 22a reliably curves in spot welding along
the curve of the inner sidewall surface of the metal case 8 even
with the low pressure of the welded electrode applied onto the
negative electrode current collector lead 22a. Therefore, without
extra work for curving the negative electrode current collector
lead 22a in advance, the negative electrode current collector lead
22a curves along the inner sidewall surface of the metal case 8 in
the step of the spot welding. As a result, the negative electrode
current collector lead 22a is reliably welded onto the metal case
8.
Second Variation
[0079] FIG. 5 illustrates a negative electrode current collector
lead 22b according to a second variation. This variation differs
from the above-described embodiment only in the negative electrode
current collector lead 22b. The other members, the structures, and
the manufacturing method are the same as those in the
above-described embodiment.
[0080] A plurality of through-holes 61 are open in a grid pattern
in the negative electrode current collector lead 22b. In this
variation, the plurality of through-holes 61 allow the negative
electrode current collector lead 22b to reliably curve in spot
welding along the curve of the inner sidewall surface of the metal
case 8 even with the low pressure of the welded electrode applied
to the negative electrode current collector lead 22b. Therefore,
without extra work for curving the negative electrode current
collector lead 22b in advance, the negative electrode current
collector lead 22b curves along the inner sidewall surface of the
metal case 8 in the step of the spot welding. As a result, the
negative electrode current collector lead 22b is reliably welded
onto the metal case 8.
Third Variation
[0081] FIG. 6 illustrates a negative electrode current collector
lead 22c according to a third variation. This variation differs
from the above-described embodiment only in the negative electrode
current collector lead 22c. The other members, the structures, and
the manufacturing method are the same as those in the
above-described embodiment.
[0082] A plurality of through-holes 62 are open in a honeycomb
pattern in the negative electrode current collector lead 22c. In
this variation, the plurality of through-holes 62 allow the
negative electrode current collector lead 22c to reliably curve in
spot welding along the curve of the inner sidewall surface of the
metal case 8 even with the low pressure of the welded electrode
onto the negative electrode current collector lead 22c. Therefore,
without extra work for curving the negative electrode current
collector lead 22c in advance, the negative electrode current
collector lead 22c curves along the inner sidewall surface of the
metal case 8 in the step of the spot welding. As a result, the
negative electrode current collector lead 22c is reliably welded
onto the metal case 8. In addition, since the plurality of
through-holes 62 are arranged in the honeycomb pattern, the
negative electrode current collector lead 22c maintains great
mechanical strength as compared to the second variation.
[0083] As described above, in each of the batteries of the
embodiment and the variations, the negative electrode current
collector lead 22, 22a, 22b, or 22c is reliably jointed to the
metal case 8, thereby providing excellent impedance characteristics
and excellent high-load characteristics when a large current
flows.
Other Embodiments
[0084] The above-described embodiments are mere examples of the
present disclosure, and the present disclosure is not limited
thereto. The type of battery is not limited to the lithium ion
battery. While the battery may be in any size, it is advantageous
if the outer diameter of the battery is 10 mm or less, and more
advantageous if the outer diameter is 6 mm or less. The winding
core may not be extracted and may be left in the battery. The
sealing member, the insulating member, etc. may be formed by
combining two or more members.
INDUSTRIAL APPLICABILITY
[0085] As described above, the battery according to the present
disclosure has excellent high-load characteristics, and is useful
as a power supply etc. requiring a large current.
DESCRIPTION OF REFERENCE CHARACTERS
[0086] 2 Negative Electrode [0087] 4 Positive Electrode [0088] 6
Separator [0089] 8 Metal Case [0090] 10 Negative Electrode Terminal
[0091] 12 Sealing Member [0092] 14 Positive Electrode Terminal
[0093] 16 Insulating Member [0094] 18 Center Axis Portion of Wound
Electrode Group [0095] 20 Negative Electrode Core Material [0096]
22 Negative Electrode Current Collector Lead [0097] 22a Negative
Electrode Current Collector Lead [0098] 22b Negative Electrode
Current Collector Lead [0099] 22c Negative Electrode Current
Collector Lead [0100] 24 Positive Electrode Current Collector Lead
[0101] 26 Welding Point [0102] 50 Winding Core
* * * * *