U.S. patent application number 13/106917 was filed with the patent office on 2011-09-08 for electrode body for use in non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery.
Invention is credited to Hideaki Fujita, Tomohiro NAKANO.
Application Number | 20110217590 13/106917 |
Document ID | / |
Family ID | 44355097 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110217590 |
Kind Code |
A1 |
NAKANO; Tomohiro ; et
al. |
September 8, 2011 |
ELECTRODE BODY FOR USE IN NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY
AND NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY
Abstract
In an electrode body for use in non-aqueous electrolyte
secondary battery, a first end of a separator is located more
interiorly than one positive electrode end of a positive electrode
plate in a width direction, located more exteriorly than one end of
a coated positive electrode portion of the positive electrode
plate, and located more exteriorly than one end of a coated
negative electrode portion of a negative electrode plate. The first
end of the separator is thicker than an intermediate portion. A
second end of the separator is located more interiorly than an
other negative electrode end of the negative electrode plate in the
width direction, located more exteriorly than the other end of the
coated positive electrode portion of the positive electrode plate,
and located more exteriorly than an other end of the coated
negative electrode portion of the negative electrode plate. The
second end of the separator is thicker than the intermediate
portion.
Inventors: |
NAKANO; Tomohiro;
(Okazaki-shi, JP) ; Fujita; Hideaki;
(Kyotanabe-shi, JP) |
Family ID: |
44355097 |
Appl. No.: |
13/106917 |
Filed: |
May 13, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2010/051718 |
Feb 5, 2010 |
|
|
|
13106917 |
|
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Current U.S.
Class: |
429/208 |
Current CPC
Class: |
H01M 50/463 20210101;
H01M 10/058 20130101; Y02E 60/10 20130101; H01M 4/13 20130101 |
Class at
Publication: |
429/208 |
International
Class: |
H01M 4/13 20100101
H01M004/13; H01M 10/36 20100101 H01M010/36 |
Claims
1. An electrode body for use in non-aqueous electrolyte secondary
battery, the electrode body comprising a positive electrode plate,
a negative electrode plate and a separator interposed between the
positive and negative electrode plates, the positive electrode
plate, negative electrode plate and separator overlapping one
another with their widths oriented in the same direction, wherein
the positive electrode plate has a positive current collector and a
positive electrode mixture layer applied to a surface of the
positive current collector; the negative electrode plate has a
negative current collector and a negative electrode mixture layer
applied to a surface of the negative current collector; the
separator has a first end located at one end thereof and a second
end located at the other end thereof with respect to a width
direction and has an intermediate portion located between the first
and second ends; with respect to the width direction, the first
separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being thicker than the intermediate portion;
and with respect to the width direction, the second separator end
is located more interiorly than an other negative electrode end
which is located at an other end of the negative electrode plate
with respect to the width direction; located more exteriorly than
an other end of the coated positive electrode portion; and located
more exteriorly than an other end of the coated negative electrode
portion, the second separator end being thicker than the
intermediate portion.
2. An electrode body for use in non-aqueous electrolyte secondary
battery, the electrode body comprising a positive electrode plate,
a negative electrode plate and a separator interposed between the
positive and negative electrode plates, the positive electrode
plate, negative electrode plate and separator overlapping one
another with their widths oriented in the same direction, wherein
the positive electrode plate has a positive current collector and a
positive electrode mixture layer applied to a surface of the
positive current collector; the negative electrode plate has a
negative current collector and a negative electrode mixture layer
applied to a surface of the negative current collector; the
separator has a first end located at one end thereof and a second
end located at the other end thereof with respect to a width
direction and has an intermediate portion located between the first
and second ends; with respect to the width direction, the first
separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being thermally shrunken by heating beforehand;
and with respect to the width direction, the second separator end
is located more interiorly than an other negative electrode end
which is located at an other end of the negative electrode plate
with respect to the width direction; located more exteriorly than
an other end of the coated positive electrode portion; and located
more exteriorly than an other end of the coated negative electrode
portion, the second separator end being thermally shrunken by
heating beforehand.
3. An electrode body for use in non-aqueous electrolyte secondary
battery, the electrode body comprising a positive electrode plate,
a negative electrode plate and a separator interposed between the
positive and negative electrode plates, the positive electrode
plate, negative electrode plate and separator overlapping one
another with their widths oriented in the same direction, wherein
the positive electrode plate has a positive current collector and a
positive electrode mixture layer applied to a surface of the
positive current collector; the negative electrode plate has a
negative current collector and a negative electrode mixture layer
applied to a surface of the negative current collector; the
separator has a first end located at one end thereof and a second
end located at the other end thereof with respect to a width
direction and has an intermediate portion located between the first
and second ends; with respect to the width direction, the first
separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being heat-welded to a portion of the positive
electrode plate which portion is opposed to the separator in its
thickness direction; and with respect to the width direction, the
second separator end is located more interiorly than an other
negative electrode end which is located at an other end of the
negative electrode plate with respect to the width direction;
located more exteriorly than an other end of the coated positive
electrode portion; and located more exteriorly than an other end of
the coated negative electrode portion, the second separator end
being heat-welded to a portion of the negative electrode plate
which portion is opposed to the separator in its thickness
direction.
4. The electrode body for use in non-aqueous electrolyte secondary
battery according to claim 3, wherein the portion of the positive
electrode plate to which the first separator end is heat-welded is
at least a part of an uncoated positive electrode portion of the
positive electrode plate which portion is not coated with the
positive electrode mixture layer, whereas the portion of the
negative electrode plate to which the second separator end is
heat-welded is at least a part of an uncoated negative electrode
portion of the negative electrode plate which portion is not coated
with the negative electrode mixture layer.
5. A non-aqueous electrolyte secondary battery comprising the
electrode body for use in non-aqueous electrolyte secondary battery
set forth in claim 1.
6. A non-aqueous electrolyte secondary battery comprising the
electrode body for use in non-aqueous electrolyte secondary battery
set forth in claim 2.
7. A non-aqueous electrolyte secondary battery comprising the
electrode body for use in non-aqueous electrolyte secondary battery
set forth in claim 3.
8. A non-aqueous electrolyte secondary battery comprising the
electrode body for use in non-aqueous electrolyte secondary battery
set forth in claim 4.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application based upon
and claims the benefit of the prior PCT International Patent
Application No. PCT/JP2010/051718 filed on Feb. 5, 2010, the entire
contents of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to an electrode body for use
in non-aqueous electrolyte secondary battery and a non-aqueous
electrolyte secondary battery using the electrode body.
BACKGROUND ART
[0003] Non-aqueous electrolyte secondary batteries such as lithium
ion secondary batteries have gained considerable interest as
electric power sources for portable devices and as electric power
sources for driving vehicles such as electric cars and hybrid
electric vehicles. One known non-aqueous electrolyte secondary
battery has an electrode body which has a positive electrode plate,
a negative electrode plate and a separator interposed between the
positive and negative electrode plates, the positive and negative
electrode plates and the separator overlapping one another with
their widths oriented in the same direction (see e.g., Patent
Literatures 1 to 3).
CITATION LIST
Patent Literatures
[0004] Patent Literature 1: JP6 (1994)-150900A [0005] Patent
Literature 2: JP2004-95382A [0006] Patent Literature 3:
JP2006-278245A
[0007] The non-aqueous electrolyte secondary batteries such as
described above are sometimes heated to high temperature owing to
heat generation of the battery caused by overcharge or the like so
that heat shrinkage of the separator occurs in its width direction.
If the separator thermally shrinks in the width direction, the
separator becomes absent between the positive and negative
electrode plates at the widthwise ends, so that the positive and
negative electrode plates are likely to come into contact with each
other, causing electrical short circuit. This internal short
circuit could lead to further battery heat generation.
[0008] With the intent of overcoming the above problem, Patent
Literature 1 has proposed the following non-aqueous electrolyte
secondary battery. According to Patent Literature 1, positive and
negative electrode plates and a separator which is wider than these
electrode plates are used, and a rolled-up electrode body is formed
by winding the positive and negative electrode plates and the
separator such that the widthwise ends of the separator (i.e.,
first and second ends located at one end and the other end,
respectively, of the separator with respect to its width direction)
project outwardly from one end (upper end) and the other end (lower
end) of the electrode body. Then, the excessive end portions of the
separator (the first and second ends of the separator) outwardly
protruding from the one end (upper end) and the other end (lower
end) of the rolled-up electrode body are heated and thereby
thermally shrunken. The excessive end portions of the separator are
thus thermally contracted beforehand, thereby inhibiting the heat
shrinkage of the excessive end portions of the separator during
heat generation of the battery to prevent the contact between the
positive and negative electrode plates at the widthwise ends (upper
and lower ends).
[0009] Another non-aqueous electrolyte secondary battery is
disclosed in Patent Literature 2. This battery is composed of a
positive electrode plate having positive electrode mixture layers
applied to the surfaces of a positive current collector (aluminum
foil); a negative electrode plate having negative electrode mixture
layers applied to the surfaces of a negative current collector
(copper foil); and a separator wider than these electrode plates.
The positive and negative electrode plates and the separator are
wound to form a rolled-up electrode body such that the widthwise
ends of the separator (i.e., first and second ends located at one
end and the other end, respectively, of the separator with respect
to its width direction) project outwardly from one end and the
other end of the electrode body. Fixedly attached to both widthwise
ends of the positive electrode plate are insulating films to which
fine particles (such as aluminum) having a heat resistance of
500.degree. C. or more are bonded by binder resin. The widthwise
ends of the negative electrode plate are also provided with
insulating films fixed thereto, these insulating films containing
fine particles (such as aluminum) which are bonded to the
insulating films by binder resin and have a heat resistance of
500.degree. C. or more. This prevents occurrence of internal short
circuit between the positive and negative electrodes, because the
insulating films attached to the positive and negative electrode
plates come into contact with each other in the event that the
separator becomes absent between the positive and negative
electrode plates at the widthwise ends owing to shrinkage of the
separator in a width direction caused by heat generation of the
battery.
SUMMARY OF INVENTION
[0010] Technical Problem
[0011] The non-aqueous electrolyte secondary battery disclosed in
Patent Literature 3 has a rolled-up electrode body in which a first
separator end (i.e., the end located at one end of the separator
with respect to its width direction) is located more interiorly
with respect to the width direction than one positive electrode end
(i.e., the end located at one end of the positive electrode plate
with respect to its width direction), whereas a second separator
end (i.e., the end located at the other end of the separator with
respect to its width direction) is located more interiorly with
respect to the width direction than an other negative electrode end
(i.e., the end located at the other end of the negative electrode
plate with respect to its width direction). In other words, the
rolled-up electrode body is formed by winding such that the one
positive electrode end is more exteriorly located than the first
separator end with respect to the width direction whereas the other
negative electrode end is more exteriorly located than the second
separator end with respect to the width direction. The one positive
electrode end is constituted by an uncoated positive electrode
portion (or a part thereof) of the positive electrode plate which
portion is not coated with the positive electrode mixture layers,
and the positive electrode plate and the positive terminal are
electrically connected to each other by welding the one positive
electrode end to the positive terminal. The other negative
electrode end is constituted by an uncoated negative electrode
portion (or a part thereof) of the negative electrode plate which
portion is not coated with the negative electrode mixture layers,
and the negative electrode plate and the negative terminal are
electrically connected to each other by welding the other negative
electrode end to the negative terminal.
[0012] Such a non-aqueous electrolyte secondary battery is still
somewhat exposed to the risk of electrical short circuit that is
caused as described earlier by the contact between the positive
electrode plate and the negative electrode plate at the widthwise
ends when the separator thermally shrinks in the width direction
due to battery heat generation or the like. In this battery, since
the separator does not protrude outwardly from one end and the
other end of the rolled-up electrode body (that is, the separator
has no excessive end portions), the heating and heat shrinkage of
the excessive end portions of the separator such as seen in Patent
Literature 1 cannot be carried out. The technique disclosed in
Patent Literature 2 has not proved to be useful because insulating
resin needs to be prepared and applied to the widthwise ends of the
positive and negative electrode plates, which involves troublesome
manufacturing processes and, in consequence, incurs high costs.
[0013] The invention is directed to overcoming the foregoing
problems and a primary object of the invention is therefore to
provide an electrode body for use in non-aqueous electrolyte
secondary battery and a non-aqueous electrolyte secondary battery
which are capable of preventing "the undesirable electric short
circuit caused by the contact between the positive electrode plate
and the negative electrode plate at the widthwise ends due to heat
shrinkage of the separator in the width direction".
Solution to Problem
[0014] According to one aspect of the invention, there is provided
an electrode body for use in non-aqueous electrolyte secondary
battery, the electrode body comprising a positive electrode plate,
a negative electrode plate and a separator interposed between the
positive and negative electrode plates, the positive electrode
plate, negative electrode plate and separator overlapping one
another with their widths oriented in the same direction, wherein
the positive electrode plate has a positive current collector and a
positive electrode mixture layer applied to a surface of the
positive current collector; the negative electrode plate has a
negative current collector and a negative electrode mixture layer
applied to a surface of the negative current collector; the
separator has a first end located at one end thereof and a second
end located at the other end thereof with respect to a width
direction and has an intermediate portion located between the first
and second ends; with respect to the width direction, the first
separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being thicker than the intermediate portion;
and with respect to the width direction, the second separator end
is located more interiorly than an other negative electrode end
which is located at an other end of the negative electrode plate
with respect to the width direction; located more exteriorly than
an other end of the coated positive electrode portion; and located
more exteriorly than an other end of the coated negative electrode
portion, the second separator end being thicker than the
intermediate portion.
[0015] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, the separator has a first end
located at one end thereof, a second end located at the other end
thereof, and an intermediate portion located between the first and
second ends, with respect to its width direction.
[0016] Of these portions, the first separator end is located more
interiorly than one positive electrode end with respect to the
width direction which end is located at one end of the positive
electrode plate with respect to the width direction. In other
words, this one positive electrode end is located more exteriorly
than the first separator end with respect to the width direction.
This one positive electrode end is composed of, for instance, an
uncoated positive electrode portion (or a part thereof) of the
positive electrode plate which portion is not coated with the
positive electrode mixture layer. In this case, the positive
electrode plate and the positive terminal can be electrically
connected to each other by welding the one positive electrode end
to the positive terminal.
[0017] The second separator end is located more interiorly than an
other negative electrode end with respect to the width direction
which end is located at an other end of the negative electrode
plate with respect to the width direction. In other words, the
other negative electrode end is located more exteriorly than the
second separator end with respect to the width direction. This
other negative electrode end is composed of, for instance, an
uncoated negative electrode portion (or a part thereof) of the
negative electrode plate which portion is not coated with the
negative electrode mixture layer. In this case, the negative
electrode plate and the negative terminal are electrically
connected to each other by welding the other negative electrode end
to the negative terminal.
[0018] Further, with respect to the width direction, the first
separator end is located more exteriorly than one end of a coated
positive electrode portion of the positive electrode plate which
portion is coated with the positive electrode mixture layer and
located more exteriorly than one end (that corresponds to one end
of the negative electrode plate) of a coated negative electrode
portion of the negative electrode plate which portion is coated
with the negative electrode mixture layer. In addition, the first
separator end is thicker than the intermediate portion.
[0019] Further, with respect to the width direction, the second
separator end is located more exteriorly than an other end (that
corresponds to an other end of the positive electrode plate) of the
coated positive electrode portion and located more exteriorly than
an other end of the coated negative electrode portion. In addition,
the second separator end is thicker than the intermediate
portion.
[0020] Therefore, use of the above-described electrode body in a
non-aqueous electrolyte secondary battery makes it possible to
prevent "the undesirable electric short circuit caused by the
contact between the positive electrode plate and the negative
electrode plate at the widthwise ends due to heat shrinkage of the
separator in the width direction".
[0021] For example, even if the separator thermally shrinks in the
width direction so that the first separator end is displaced
inwardly (toward the other end) in the width direction whereas the
second separator end being displaced inwardly (toward the one end)
in the width direction, the first separator end will strike against
the end face of at least either the one end of the coated positive
electrode portion or the one end of the coated negative electrode
portion and therefore will be unable to further move inwardly in
the width direction (toward the other end), thanks to the
configuration of the first and second separator ends which are
thicker than the intermediate portion. Further, the second
separator end will strike against the end face of either the other
end of the coated positive electrode portion or the other end of
the coated negative electrode portion and therefore will be unable
to further move inwardly in the width direction (toward the one
end). This enables it to keep the separator present between the
positive and negative electrode plates with respect to the width
direction, thereby maintaining the electrical insulation between
the positive and negative electrode plates.
[0022] One form of the configuration in which the first and second
separator ends are thicker than the intermediate portion is such
that the first and second separator ends are folded back on
themselves (e.g., folded double) thereby to make them thicker
(e.g., twice thicker) than the intermediate portion.
[0023] According to another aspect of the invention, there is
provided an electrode body for use in non-aqueous electrolyte
secondary battery, the electrode body comprising a positive
electrode plate, a negative electrode plate and a separator
interposed between the positive and negative electrode plates, the
positive electrode plate, negative electrode plate and separator
overlapping one another with their widths oriented in the same
direction, wherein the positive electrode plate has a positive
current collector and a positive electrode mixture layer applied to
a surface of the positive current collector; the negative electrode
plate has a negative current collector and a negative electrode
mixture layer applied to a surface of the negative current
collector; the separator has a first end located at one end thereof
and a second end located at the other end thereof with respect to a
width direction and has an intermediate portion located between the
first and second ends; with respect to the width direction, the
first separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being thermally shrunken by heating beforehand;
and with respect to the width direction, the second separator end
is located more interiorly than an other negative electrode end
which is located at an other end of the negative electrode plate
with respect to the width direction; located more exteriorly than
an other end of the coated positive electrode portion; and located
more exteriorly than an other end of the coated negative electrode
portion, the second separator end being thermally shrunken by
heating beforehand.
[0024] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, the first separator end is located
more interiorly than one positive electrode end with respect to the
width direction which end is located at one end of the positive
electrode plate with respect to the width direction. In other
words, the one positive electrode end is located more exteriorly
than the first separator end with respect to the width direction.
This one positive electrode end is composed of, for instance, an
uncoated positive electrode portion (or a part thereof) of the
positive electrode plate which portion is not coated with the
positive electrode mixture layer. In this case, the positive
electrode plate and the positive terminal can be electrically
connected to each other by welding the one positive electrode end
to the positive terminal.
[0025] The second separator end is located more interiorly than an
other negative electrode end with respect to the width direction
which end is located at an other end of the negative electrode
plate with respect to the width direction. In other words, the
other negative electrode end is located more exteriorly than the
second separator end with respect to the width direction. This
other negative electrode end is composed of, for instance, an
uncoated negative electrode portion (or a part thereof) of the
negative electrode plate which portion is not coated with the
negative electrode mixture layer. In this case, the negative
electrode plate and the negative terminal are electrically
connected to each other by welding the other negative electrode end
to the negative terminal.
[0026] Further, with respect to the width direction, the first
separator end is located more exteriorly than one end of a coated
positive electrode portion of the positive electrode plate which
portion is coated with the positive electrode mixture layer and
located more exteriorly than one end (that corresponds to one end
of the negative electrode plate) of a coated negative electrode
portion of the negative electrode plate which portion is coated
with the negative electrode mixture layer. In addition, the first
separator end is thermally shrunken by heating beforehand (i.e.,
the first separator end is thermally shrunken by heating during the
process of manufacturing the electrode body).
[0027] Further, with respect to the width direction, the second
separator end is located more exteriorly than an other end (that
corresponds to an other end of the positive electrode plate) of the
coated positive electrode portion and located more exteriorly than
an other end of the coated negative electrode portion. In addition,
the second separator end is thermally shrunken by heating
beforehand (i.e., the second separator end is thermally shrunken by
heating during the process of manufacturing the electrode
body).
[0028] Therefore, use of the above-described electrode body in a
non-aqueous electrolyte secondary battery makes it possible to
prevent "the undesirable electric short circuit caused by the
contact between the positive electrode plate and the negative
electrode plate at the widthwise ends due to heat shrinkage of the
separator in the width direction".
[0029] Specifically, even if the separator is heated by heat
generation of the battery to a temperature that causes the
separator to thermally shrink in the width direction, the first and
second separator ends are unlikely to thermally shrink further in
the width direction because they have already been thermally
shrunken by heating beforehand. This enables it to keep the
separator present between the positive and negative electrode
plates with respect to the width direction, thereby maintaining the
electrical insulation between the positive and negative electrode
plates.
[0030] According to another aspect of the invention, there is
provided an electrode body for use in non-aqueous electrolyte
secondary battery, the electrode body comprising a positive
electrode plate, a negative electrode plate and a separator
interposed between the positive and negative electrode plates, the
positive electrode plate, negative electrode plate and separator
overlapping one another with their widths oriented in the same
direction, wherein the positive electrode plate has a positive
current collector and a positive electrode mixture layer applied to
a surface of the positive current collector; the negative electrode
plate has a negative current collector and a negative electrode
mixture layer applied to a surface of the negative current
collector; the separator has a first end located at one end thereof
and a second end located at the other end thereof with respect to a
width direction and has an intermediate portion located between the
first and second ends; with respect to the width direction, the
first separator end is located more interiorly than one positive
electrode end which is located at one end of the positive electrode
plate with respect to the width direction; located more exteriorly
than one end of a coated positive electrode portion of the positive
electrode plate which portion is coated with the positive electrode
mixture layer; and located more exteriorly than one end of a coated
negative electrode portion of the negative electrode plate which
portion is coated with the negative electrode mixture layer, the
first separator end being heat-welded to a portion of the positive
electrode plate which portion is opposed to the separator in its
thickness direction; and with respect to the width direction, the
second separator end is located more interiorly than an other
negative electrode end which is located at an other end of the
negative electrode plate with respect to the width direction;
located more exteriorly than an other end of the coated positive
electrode portion; and located more exteriorly than an other end of
the coated negative electrode portion, the second separator end
being heat-welded to a portion of the negative electrode plate
which portion is opposed to the separator in its thickness
direction.
[0031] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, the first separator end is located
more interiorly than one positive electrode end with respect to the
width direction which end is located at one end of the positive
electrode plate with respect to the width direction. In other
words, the one positive electrode end is located more exteriorly
than the first separator end with respect to the width direction.
This one positive electrode end is composed of, for instance, an
uncoated positive electrode portion (or a part thereof) of the
positive electrode plate which portion is not coated with the
positive electrode mixture layer. In this case, the positive
electrode plate and the positive terminal can be electrically
connected to each other by welding the one positive electrode end
to the positive terminal.
[0032] The second separator end is located more interiorly than an
other negative electrode end with respect to the width direction
which end is located at an other end of the negative electrode
plate with respect to the width direction. In other words, the
other negative electrode end is located more exteriorly than the
second separator end with respect to the width direction. This
other negative electrode end is composed of, for instance, an
uncoated negative electrode portion (or a part thereof) of the
negative electrode plate which portion is not coated with the
negative electrode mixture layer. In this case, the negative
electrode plate and the negative terminal are electrically
connected to each other by welding the other negative electrode end
to the negative terminal.
[0033] Further, with respect to the width direction, the first
separator end is located more exteriorly than one end of the coated
positive electrode portion of the positive electrode plate which
portion is coated with the positive electrode mixture layer and
located more exteriorly than one end (that corresponds to one end
of the negative electrode plate) of the coated negative electrode
portion of the negative electrode plate which portion is coated
with the negative electrode mixture layer. In addition, the first
separator end is heat-welded to a portion of the positive electrode
plate which portion is opposed to the separator in its thickness
direction (specifically, during the process of manufacturing the
electrode body, the first separator end is heat-welded to the
portion of the positive electrode plate which portion is opposed to
the separator in its thickness direction).
[0034] Further, with respect to the width direction, the second
separator end is located more exteriorly than an other end (that
corresponds to an other end of the positive electrode plate) of the
coated positive electrode portion and located more exteriorly than
an other end of the coated negative electrode portion. In addition,
the second separator end is heat-welded to a portion of the
negative electrode plate which portion is opposed to the separator
in its thickness direction (specifically, during the process of
manufacturing the electrode body, the second separator end is
heat-welded to the portion of the negative electrode plate which
portion is opposed to the separator in its thickness
direction).
[0035] Therefore, use of the above-described electrode body in a
non-aqueous electrolyte secondary battery makes it possible to
prevent "the undesirable electric short circuit caused by the
contact between the positive electrode plate and the negative
electrode plate at the widthwise ends due to heat shrinkage of the
separator in the width direction".
[0036] Specifically, even if the separator is heated by heat
generation of the battery to a temperature that causes the
separator to thermally shrink in its width direction, the first and
second separator ends are unlikely to thermally shrink further in
the width direction because they have already been thermally
shrunken by heating at the time of heat-welding. In addition, since
the first and second separator ends are adhered (heat-welded) to
the portions of the positive and negative electrode plates
respectively which portions are opposed to the separator, the
inward displacement of the first and second separator ends in the
width direction can be prevented even if heat shrinkage forces them
to move inwardly in the width direction. This enables it to keep
the separator present between the positive and negative electrode
plates with respect to the width direction, thereby maintaining the
electrical insulation between the positive and negative electrode
plates.
[0037] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, preferably, the portion of the
positive electrode plate to which the first separator end is
heat-welded is at least a part of an uncoated positive electrode
portion of the positive electrode plate which portion is not coated
with the positive electrode mixture layer, whereas the portion of
the negative electrode plate to which the second separator end is
heat-welded is at least a part of an uncoated negative electrode
portion of the negative electrode plate which portion is not coated
with the negative electrode mixture layer.
[0038] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, the portion of the positive
electrode plate to which the first separator end is heat-welded is
at least a part of the uncoated positive electrode portion (where
the positive current collector is exposed) of the positive
electrode plate which portion is not coated with the positive
electrode mixture layer. In other words, the first separator end is
heat-welded to the uncoated positive electrode portion (or at least
a part thereof) of the positive electrode plate which portion is
not coated with the positive electrode mixture layer. This enables
proper adhesion (heat-welding) of the first separator end to the
positive electrode plate.
[0039] In the above-described electrode body for use in non-aqueous
electrolyte secondary battery, the portion of the negative
electrode plate to which the second separator end is heat-welded is
at least a part of the uncoated negative electrode portion (where
the negative current collector is exposed) of the negative
electrode plate which portion is not coated with the negative
electrode mixture layer. In other words, the second separator end
is heat-welded to the uncoated negative electrode portion (or at
least a part thereof) of the negative electrode plate which portion
is not coated with the negative electrode mixture layer. This
enables proper adhesion (heat-welding) of the second separator end
to the negative electrode plate.
[0040] According to still another aspect of the invention, there is
provided a non-aqueous electrolyte secondary battery comprising any
one of the above-described electrode bodies for use in non-aqueous
electrolyte secondary battery.
[0041] The above non-aqueous electrolyte secondary battery is
provided with any one of the above-described electrode bodies for
use in non-aqueous electrolyte secondary battery. Therefore, the
above-described non-aqueous electrolyte secondary battery makes it
possible to prevent "the undesirable electric short circuit caused
by the contact between the positive electrode plate and the
negative electrode plate at the widthwise ends due to heat
shrinkage of the separator in the width direction".
BRIEF DESCRIPTION OF DRAWINGS
[0042] FIG. 1 is a top view of a non-aqueous electrolyte secondary
battery in first to third embodiments;
[0043] FIG. 2 is a front view of the non-aqueous electrolyte
secondary battery;
[0044] FIG. 3 is a longitudinal sectional view of the non-aqueous
electrolyte secondary battery, taken along a line C-C in FIG.
1;
[0045] FIG. 4 is a longitudinal sectional view of the non-aqueous
electrolyte secondary battery, taken along a line D-D in FIG.
1;
[0046] FIG. 5 is a perspective view of an electrode body of the
non-aqueous electrolyte secondary battery;
[0047] FIG. 6 is a cross sectional view of the electrode body in
the first embodiment, taken along a line E-E in FIG. 3;
[0048] FIG. 7 is a top view of a positive electrode plate in the
first to third embodiments;
[0049] FIG. 8 is a sectional view of the positive electrode plate,
taken along a line F-F in FIG. 7;
[0050] FIG. 9 is a top view of a negative electrode plate in the
first to third embodiments;
[0051] FIG. 10 is a sectional view of the negative electrode plate,
taken along a line G-G in FIG. 9;
[0052] FIG. 11 is a top view of a separator in the first
embodiment;
[0053] FIG. 12 is a sectional view of the separator taken along a
line H-H in FIG. 11;
[0054] FIG. 13 is an explanatory view showing a process of
manufacturing the electrode body in the first embodiment;
[0055] FIG. 14 is a cross sectional view of an electrode body in
the second embodiment, taken along the line E-E in FIG. 3;
[0056] FIG. 15 is a top view of a separator in the second
embodiment;
[0057] FIG. 16 is an explanatory view showing a thermal treatment
step in the second embodiment;
[0058] FIG. 17 is an explanatory view showing a process of
manufacturing the electrode body in the second embodiment;
[0059] FIG. 18 is a cross sectional view of an electrode body in
the third embodiment, taken along the line E-E in FIG. 3; and
[0060] FIG. 19 is an explanatory view showing a process of
manufacturing the electrode body in the third embodiment.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0061] Referring now to the accompanying drawings, the invention
will be described according to a first embodiment.
[0062] As shown in FIGS. 1 to 4, a non-aqueous electrolyte
secondary battery 100 constructed according to the first embodiment
is a rectangular sealed lithium ion secondary battery having a
rectangular parallelepiped battery case 110, a positive terminal
120 and a negative terminal 130. Of these components, the battery
case 110 is a hard case composed of a metallic rectangular storage
section 111 and a metallic lid 112, the storage section 111
including a rectangular parallelepiped storage space. Disposed
within the battery case 110 (rectangular storage section 111) are
an electrode body 150 and others. The rated capacity (nominal
capacity) of the non-aqueous electrolyte secondary battery 100 is
5.5 Ah.
[0063] The electrode body 150 is a flat rolled-up body having an
oval-shaped cross section and composed of a positive electrode
plate 155, a negative electrode plate 156 and a separator 157 which
are wound into a flat shape (see FIGS. 4 to 13). The positive
electrode plate 155, the negative electrode plate 156 and the
separator 157 overlap one another with their widths oriented in the
same direction (see FIGS. 6 and 13). It should be noted that the
longitudinal directions (perpendicular to the width directions) of
the positive electrode plate 155, the negative electrode plate 156
and the separator 157 coincide with the winding direction. The
lateral directions of FIGS. 6 and 13 coincide with the respective
width directions of the positive electrode plate 155, the negative
electrode plate 156 and the separator 157 and with the width
direction of the electrode body 150.
[0064] The positive electrode plate 155 is strip-like in shape and
includes a positive current collector 151 made of aluminum foil and
positive electrode mixture layers 152 (i.e., mixture layers
containing a positive active material 153) applied to the surfaces
(both surfaces), respectively, of the positive current collector
151 (see FIGS. 7 and 8). The positive electrode plate 155 is
composed of a coated positive electrode portion 155d in which the
surfaces of the positive current collector 151 are coated with the
positive electrode mixture layers 152 respectively and an uncoated
positive electrode portion 155b in which the surfaces of the
positive current collector 151 are not coated with the positive
electrode mixture layers 152. The uncoated positive electrode
portion 155b is composed of only the positive current collector 151
and located at one end of the positive electrode plate 155 with
respect to the width direction (located at the right end in FIGS.
7, 8), extending in the longitudinal direction of the positive
electrode plate 155. The lateral directions of FIGS. 7 and 8
coincide with the width direction of the positive electrode plate
155. The vertical direction of FIG. 7 coincides with the
longitudinal direction of the positive electrode plate 155. The
vertical direction of FIG. 8 coincides with the thickness direction
of the positive electrode plate 155.
[0065] The negative electrode plate 156 is strip-like in shape and
includes a negative current collector 158 made of copper foil and
negative electrode mixture layers 159 (mixture layers containing a
negative active material 154) applied to the surfaces,
respectively, of the negative current collector 158 (see FIGS. 9
and 10). The negative electrode plate 156 is composed of a coated
negative electrode portion 156d in which the surfaces of the
negative current collector 158 are coated with the negative
electrode mixture layers 159 respectively and an uncoated negative
electrode portion 156b in which the surfaces of the negative
current collector 158 are not coated with the negative electrode
mixture layers 159. The uncoated negative electrode portion 156b is
composed of only the negative current collector 158 and located at
the other end of the negative electrode plate 156 with respect to
the width direction (located at the left end in FIGS. 9, 10),
extending in the longitudinal direction of the negative electrode
plate 156. The lateral directions of FIGS. 9 and 10 coincide with
the width direction of the negative electrode plate 156. The
vertical direction of FIG. 9 coincides with the longitudinal
direction of the negative electrode plate 156. The vertical
direction of FIG. 10 coincides with the thickness direction of the
negative electrode plate 156.
[0066] The separator 157 is composed of a
polypropylene-polyethylene-polypropylene trilaminar composite
porous sheet and has a strip shape (see FIGS. 11 and 12). This
separator 157 is interposed between the positive electrode plate
155 and the negative electrode plate 156 so as to provide
electrical insulation between them (see FIG. 6). It should be noted
that the lateral directions of FIGS. 11 and 12 coincide with the
width direction of the separator 157. The vertical direction of
FIG. 9 coincides with the longitudinal direction of the negative
electrode plate 156. The vertical direction of FIG. 10 coincides
with the thickness direction of the negative electrode plate
156.
[0067] The separator 157 has a first end 157b, a second end 157c
and an intermediate portion 157d. When viewed in the width
direction, the first end 157b is located at one end (the right end
in FIGS. 11, 12), the second end 157c is located at the other end
(the left end in FIGS. 11, 12), and the intermediate portion 157d
is located between the first end 157b and the second end 157c.
[0068] As shown in FIG. 6, in the electrode body 150 of the first
embodiment, the first end 157b of the separator 157 is located more
interiorly than (located closer to the center of the electrode body
150 than) one positive electrode end 155c is, with respect to the
width direction (lateral direction in FIG. 6), the end 155c being
located at one end (right end in FIG. 6) of the positive electrode
plate 155 with respect to the width direction. In other words, the
one positive electrode end 155c is located more exteriorly than (is
more distant from the center of the electrode body 150 than) the
first end 157b of the separator 157 is, with respect to the width
direction. This one positive electrode end 155c is constituted by
the uncoated positive electrode portion 155b (or a part thereof) of
the positive electrode plate 155. Therefore, the positive electrode
plate 155 and the positive terminal 120 can be electrically
connected to each other by welding the one positive electrode end
155c to a positive current collecting portion 122 of the positive
terminal 120 as described later (see FIG. 3).
[0069] In addition, the second end 157c of the separator 157 is
located more interiorly than (located closer to the center of the
electrode body 150 than) an other negative electrode end 156c is,
with respect to the width direction (lateral direction in FIG. 6),
the end 156c being located at the other end (left end in FIG. 6) of
the negative electrode plate 156 with respect to the width
direction. In other words, the other negative electrode end 156c is
located more exteriorly than (is more distant from the center of
the electrode body 150 than) the second end 157c of the separator
157 is, with respect to the width direction. The other negative
electrode end 156c is constituted by the uncoated negative
electrode portion 156b (or a part thereof) of the negative
electrode plate 156. Therefore, the negative electrode plate 156
and the negative terminal 130 can be electrically connected to each
other by welding the other negative electrode end 156c to a
negative current collecting portion 132 of the negative terminal
130 as described later (see FIG. 3).
[0070] As shown in FIG. 6, in the electrode body 150 of the first
embodiment, the first end 157b of the separator 157 is located more
exteriorly than (located, in FIG. 6, on the right side of) one end
155f of the coated positive electrode portion 155d of the positive
electrode plate 155 and located more exteriorly than (located, in
FIG. 6, on the right side of) one end 156f (which corresponds to
one end of the negative electrode plate 156) of the coated negative
electrode portion 156d of the negative electrode plate 156, with
respect to the width direction (lateral direction in FIG. 6). In
addition, the first end 157b of the separator 157 is thicker than
the intermediate portion 157d (see FIGS. 6, 12). More specifically,
the first end 157b of the separator 157 is folded double so as to
be thicker than the intermediate portion 157d (twice thicker than
the intermediate portion 157d).
[0071] The second end 157c of the separator 157 is located more
exteriorly than (located, in FIG. 6, on the left side of) an other
end 155g (which corresponds to the other end of the positive
electrode plate 155) of the coated positive electrode portion 155d
of the positive electrode plate 155 and located more exteriorly
than (located, in FIG. 6, on the left side of) an other end 156g of
the coated negative electrode portion 156d of the negative
electrode plate 156 with respect to the width direction (lateral
direction in FIG. 6). In addition, the second end 157c of the
separator 157 is thicker than the intermediate portion 157d (see
FIGS. 6, 12). More specifically, the second end 157c of the
separator 157 is folded double so as to be thicker than the
intermediate portion 157d (twice thicker than the intermediate
portion 157d).
[0072] Since the non-aqueous electrolyte secondary battery 100 of
the first embodiment has the above-described electrode body 150, it
is possible to prevent "the undesirable electric short circuit
caused by the contact between the positive electrode plate 155 and
the negative electrode plate 156 at the widthwise ends (the lateral
ends of the coated positive electrode portion 155d and the coated
negative electrode portion 156d in FIG. 6) due to heat shrinkage of
the separator 157 in the width direction (lateral direction in FIG.
6)".
[0073] Concretely, if the temperature of the non-aqueous
electrolyte secondary battery 100 becomes high for some reason, the
separator 157 made of resin thermally shrinks in the width
direction. At that time, the first end 157b of the separator 157
moves inwardly in the width direction (toward the left in FIG. 6)
while the second end 157c moving inwardly in the width direction
(toward the right in FIG. 6).
[0074] However, in the separator 157 of the first embodiment, the
first end 157b of the separator 157 strikes against the end face of
the one end 155f of the coated positive electrode portion 155d or
the one end 156f of the coated negative electrode portion 156d and
therefore cannot inwardly move further in the width direction (to
the left in FIG. 6), because the first end 157b and the second end
157c are thicker than the intermediate portion 157d. This enables
it to prevent "the undesirable contact between the one end 155f of
the coated positive electrode portion 155d and the one end 156f of
the coated negative electrode portion 156d which contact is caused
by the first end 157b of the separator 157 getting into the
interface between the positive electrode plate 155 (coated positive
electrode portion 155d) and the negative electrode plate 156
(coated negative electrode portion 156d)". It should be noted that
the first end 157b formed by folding the separator 157 double is
softened by heat so that it becomes an integral portion (mass).
[0075] The second end 157c of the separator 157 strikes against the
end face of the other end 155g of the coated positive electrode
portion 155d or the other end 156g of the coated negative electrode
portion 156d and therefore cannot inwardly move further in the
width direction (to the right in FIG. 6). This enables it to
prevent "the undesirable contact between the other end 155g of the
coated positive electrode portion 155d and the other end 156g of
the coated negative electrode portion 156d which contact is caused
by the second end 157c of the separator 157 getting into the
interface between the positive electrode plate 155 (coated positive
electrode portion 155d) and the negative electrode plate 156
(coated negative electrode portion 156d)". It should be noted that
the second end 157c formed by folding the separator 157 double is
softened by heat so that it becomes an integral portion (mass).
[0076] Therefore, in the non-aqueous electrolyte secondary battery
100 of the first embodiment, even if the temperature of the
separator 157 rises to a temperature (e.g., 150.degree. C.) that
causes heat shrinkage of the separator 157, the separator can be
kept present between the positive electrode plate 155 and the
negative electrode plate 156 with respect to the width direction
(lateral direction in FIG. 6) of the electrode body 150, thereby
maintaining the electric insulation between the positive electrode
plate 155 and the negative electrode plate 156.
[0077] Next, the process of manufacturing the non-aqueous
electrolyte secondary battery 100 will be explained.
[0078] First, the positive electrode plate 155, having the positive
electrode mixture layers 152 applied to the surfaces of the
strip-shaped positive current collector 151 as shown in FIGS. 7 and
8, is prepared. Then, the negative electrode plate 156, having the
negative electrode mixture layers 159 applied to the surfaces of
the strip-shaped negative current collector 158 as shown in FIGS. 9
and 10, is prepared. Then, the separator 157, the widthwise ends
(the first end 157b and the second end 157c) of which are folded
double such that they become thicker than the intermediate portion
157d (twice thicker than the intermediate portion 157d) as shown in
FIGS. 11 and 12, is prepared.
[0079] Next, the positive electrode plate 155, the negative
electrode plate 156 and the separator 157 are wound into a flat
roll such that they overlap one another as shown in FIG. 13,
whereby the electrode body 150 is formed (see FIG. 5). More
specifically, the positive electrode plate 155, the negative
electrode plate 156 and the separator 157 are arranged as follows
when they are rolled up. With respect to the width direction, the
first end 157b of the separator 157 is located more interiorly than
(located, in FIG. 13, on the left side of) the one positive
electrode end 155c of the positive electrode plate 155; located
more exteriorly than (located, in FIG. 13, on the right side of)
the one end 155f of the coated positive electrode portion 155d of
the positive electrode plate 155; and located more exteriorly than
(located, in FIG. 13, on the right side of) the one end 156f of the
coated negative electrode portion 156d of the negative electrode
plate 156. Further, with respect to the width direction (lateral
direction in FIG. 13), the second end 157c of the separator 157 is
located more interiorly than (located, in FIG. 13, on the right
side of) the other negative electrode end 156c of the negative
electrode plate 156; located more exteriorly than (located, in FIG.
13, on the left side of) the other end 155g of the coated positive
electrode portion 155d of the positive electrode plate 155; and
located more exteriorly than (located, in FIG. 13, on the left side
of) the other end 156g of the coated negative electrode portion
156d of the negative electrode plate 156.
[0080] Then, the positive current collecting portion 122 of the
positive terminal 120 is welded to the upper end of the one
positive electrode end 155c of the electrode body 150 (see FIG. 3).
The negative current collecting portion 132 of the negative
terminal 130 is welded to the upper end of the other negative
electrode end 156c of the electrode body 150. After this electrode
body 150 is accommodated within the rectangular storage section
111, the opening of the rectangular storage section 111 is closed
with the lid 112. Thereafter, the lid 112 is welded to the
rectangular storage section 111. Subsequently, a non-aqueous
electrolytic solution is poured into the rectangular storage
section 111 through a pouring port (not shown) formed in the lid
112 (at that time, the electrode body 150 is impregnated with the
non-aqueous electrolytic solution). The pouring port is then sealed
and the manufacture of the non-aqueous electrolyte secondary
battery 100 of the first embodiment is accordingly completed.
Second Embodiment
[0081] A non-aqueous electrolyte secondary battery 200 constructed
according to the second embodiment does not differ from the
non-aqueous electrolyte secondary battery 100 of the first
embodiment except the separator of the electrode body. Therefore,
the points different from the first embodiment are mainly discussed
herein while explanation of the similar or identical points is
omitted or simplified.
[0082] Similarly to the first embodiment, a separator 257 of the
second embodiment is composed of a
polypropylene-polyethylene-polypropylene trilaminar composite
porous sheet and has a strip shape (see FIG. 15). The separator 257
has a first end 257b (indicated by hatching in FIG. 15) located at
one end (right end in FIG. 15) with respect to the width direction,
a second end 257c (indicated by hatching in FIG. 15) located at the
other end (left end in FIG. 15), and an intermediate portion 257d
located between the first end 257b and the second end 257c. It
should be noted that the lateral direction of FIG. 15 corresponds
to the width direction of the separator 157 and the vertical
direction of FIG. 15 corresponds to the longitudinal direction of
the separator 157.
[0083] As shown in FIG. 14, in an electrode body 250 of the second
embodiment, the first end 257b of the separator 257 is located more
interiorly than (located, in FIG. 14, on the left side of) the one
positive electrode end 155c with respect to the width direction
(lateral direction in FIG. 14), the end 155c being located at one
end (right end in FIG. 14) of the positive electrode plate 155 with
respect to the width direction. In other words, the one positive
electrode end 155c is located more exteriorly than (located, in
FIG. 14, on the right side of) the first end 257b of the separator
257 with respect to the width direction. This one positive
electrode end 155c is constituted by the uncoated positive
electrode portion 155b (or a part thereof) of the positive
electrode plate 155. Therefore, the second embodiment is also
configured such that the positive electrode plate 155 and the
positive terminal 120 can be electrically connected to each other
by welding the one positive electrode end 155c to the positive
current collecting portion 122 of the positive terminal 120 (see
FIG. 3).
[0084] The second end 257c of the separator 257 is located more
interiorly than (located closer to the center of the electrode body
250 than) the other negative electrode end 156c is, with respect to
the width direction (lateral direction in FIG. 14), the end 156c
being located at the other end (left end in FIG. 14) of the
negative electrode plate 156 with respect to the width direction.
In other words, the other negative electrode end 156c is located
more exteriorly than (is more distant from the center of the
electrode body 250 than) the second end 257c of the separator 257
is, with respect to the width direction. The other negative
electrode end 156c is constituted by the uncoated negative
electrode portion 156b (or a part thereof) of the negative
electrode plate 156. Therefore, the second embodiment is also
configured such that the negative electrode plate 156 and the
negative terminal 130 can be electrically connected to each other
by welding the other negative electrode end 156c to the negative
current collecting portion 132 of the negative terminal 130 (see
FIG. 3).
[0085] In addition, the electrode body 250 of the second embodiment
is configured as shown in FIG. 14. In this figure, the first end
257b of the separator 257 is located more exteriorly than (located,
in FIG. 14, on the right side of) the one end 155f of the coated
positive electrode portion 155d of the positive electrode plate 155
and located more exteriorly than (located, in FIG. 14, on the right
side of) the one end 156f (that corresponds to the one end of the
negative electrode plate 156) of the coated negative electrode
portion 156d of the negative electrode plate 156, with respect to
the width direction (lateral direction in FIG. 14).
[0086] In addition, in the second embodiment, the first end 257b of
the separator 257 is thermally shrunken by heating beforehand. More
concretely, the first end 257b of the separator 257 is thermally
shrunken by heating to 200.degree. C. in the course of
manufacturing the electrode body 250 (i.e., thermal treatment step)
as described later.
[0087] Further, the second end 257c of the separator 257 is located
more exteriorly than (located, in FIG. 14, on the left side of) the
other end 155g (which corresponds to the other end of the positive
electrode plate 155) of the coated positive electrode portion 155d
of the positive electrode plate 155 and located more exteriorly
than (located, in FIG. 14, on the left side of) the other end 156g
of the coated negative electrode portion 156d of the negative
electrode plate 156, with respect to the width direction (lateral
direction in FIG. 14).
[0088] In addition, in the second embodiment, the second end 257c
of the separator 257 is thermally shrunken by heating beforehand.
More concretely, the second end 257c of the separator 257 is
thermally shrunken by heating to 200.degree. C. in the course of
manufacturing the electrode body 250 (i.e., thermal treatment step)
as described later.
[0089] Since the non-aqueous electrolyte secondary battery 200 of
the second embodiment has the above-described electrode body 250,
it is possible to prevent "the undesirable electric short circuit
caused by the contact between the positive electrode plate 155 and
the negative electrode plate 156 at the widthwise ends (the lateral
ends of the coated positive electrode portion 155d and the coated
negative electrode portion 156d in FIG. 14) due to heat shrinkage
of the separator 257 in the width direction (lateral direction in
FIG. 14)".
[0090] Concretely, since the first end 257b and second end 257c of
the separator 257 are thermally shrunken by heating beforehand,
they do not thermally shrink any more in the width direction even
if the temperature of the non-aqueous electrolyte secondary battery
200 rises to a temperature (e.g., 150.degree. C.) that causes heat
shrinkage of the separator 257. More specifically, the first end
257b of the separator 257 can be prevented from shrinking inwardly
in the width direction (to the left in FIG. 14). Also, the second
end 257c can be prevented from shrinking inwardly in the width
direction (to the right in FIG. 14).
[0091] This enables it to prevent "the undesirable contact between
the one end 155f of the coated positive electrode portion 155d and
the one end 156f of the coated negative electrode portion 156d
which contact is caused by the first end 257b of the separator 257
getting into the interface between the positive electrode plate 155
(coated positive electrode portion 155d) and the negative electrode
plate 156 (coated negative electrode portion 156d)". This further
enables it to prevent "the undesirable contact between the other
end 155g of the coated positive electrode portion 155d and the
other end 156g of the coated negative electrode portion 156d which
contact is caused by the second end 257c of the separator 257
getting into the interface between the positive electrode plate 155
(coated positive electrode portion 155d) and the negative electrode
plate 156 (coated negative electrode portion 156d)".
[0092] Therefore, in the non-aqueous electrolyte secondary battery
200 of the second embodiment, even if the temperature of the
separator 257 rises to a temperature (e.g., 150.degree. C.) that
causes heat shrinkage of the separator 257, the separator can be
kept present between the positive electrode plate 155 and the
negative electrode plate 156 with respect to the width direction
(lateral direction in FIG. 14) of the electrode body 250, thereby
maintaining the electric insulation between the positive electrode
plate 155 and the negative electrode plate 156. Note that since the
intermediate portion 257d of the separator 257 is interposed
between and pressed by the positive electrode plate 155 (coated
positive electrode portion 155d) and the negative electrode plate
156 (coated negative electrode portion 156d), the intermediate
portion 257d is unlikely to shrink in the width direction even if
the temperature of the separator 257 rises to a temperature (e.g.,
150.degree. C.) that causes heat shrinkage of the separator
257.
[0093] Next, the process of manufacturing the non-aqueous
electrolyte secondary battery 200 will be explained.
[0094] First, the positive electrode plate 155, having the positive
electrode mixture layers 152 applied to the surfaces of the
strip-shaped positive current collector 151 as shown in FIGS. 7 and
8, is prepared. Then, the negative electrode plate 156, having the
negative electrode mixture layers 159 applied to the surfaces of
the strip-shaped negative current collector 158 as shown in FIGS. 9
and 10, is prepared.
[0095] In the thermal treatment step, the widthwise ends (the first
end 257b and the second end 257c) of the separator 257 are
thermally shrunken by heating.
[0096] Concretely, as shown in FIG. 16, the first end 257b of the
separator 257 is pinched in its thickness direction by heat rollers
11 and 12 heated to 200.degree. C. whereas the second end 257c of
the separator 257 is pinched in its thickness direction by heat
rollers 13, 14 heated to 200.degree. C., and the separator 257 is
moved in its longitudinal direction while the heat rollers 11 to 14
being rotated. Thereby, the first end 257b and second end 257c of
the separator 257 can be thermally shrunken. In this way, the
separator 257 having the thermally shrunken first end 257b and
second end 257c can be manufactured.
[0097] Next, the positive electrode plate 155, the negative
electrode plate 156 and the separator 157 are wound into a flat
roll such that they overlap one another as shown in FIG. 17,
whereby the electrode body 150 is formed (see FIG. 5). More
specifically, the positive electrode plate 155, the negative
electrode plate 156 and the separator 257 are arranged as follows
when they are rolled up. With respect to the width direction
(lateral direction in FIG. 17), the first end 257b of the separator
257 is located more interiorly than (located, in FIG. 17, on the
left side of) the one positive electrode end 155c of the positive
electrode plate 155; located more exteriorly than (located, in FIG.
17, on the right side of) the one end 155f of the coated positive
electrode portion 155d of the positive electrode plate 155; and
located more exteriorly than (located, in FIG. 17, on the right
side of) the one end 156f of the coated negative electrode portion
156d of the negative electrode plate 156. Further, with respect to
the width direction, the second end 257c of the separator 257 is
located more interiorly than (located, in FIG. 17, on the right
side of) the other negative electrode end 156c of the negative
electrode plate 156; located more exteriorly than (located, in FIG.
17, on the left side of) the other end 155g of the coated positive
electrode portion 155d of the positive electrode plate 155; and
located more exteriorly than (located, in FIG. 17, on the left side
of) the other end 156g of the coated negative electrode portion
156d of the negative electrode plate 156.
[0098] Then, the positive current collecting portion 122 of the
positive terminal 120 is welded to the upper end of the one
positive electrode end 155c of the electrode body 250 (see FIG. 3).
The negative current collecting portion 132 of the negative
terminal 130 is welded to the upper end of the other negative
electrode end 156c of the electrode body 250. After this electrode
body 250 is accommodated within the rectangular storage section
111, the opening of the rectangular storage section 111 is closed
with the lid 112. Thereafter, the lid 112 is welded to the
rectangular storage section 111. Subsequently, a non-aqueous
electrolytic solution is poured into the rectangular storage
section 111 through the pouring port (not shown) formed in the lid
112 (at that time, the electrode body 250 is impregnated with the
non-aqueous electrolytic solution). The pouring port is then sealed
and the manufacture of the non-aqueous electrolyte secondary
battery 200 of the second embodiment is accordingly completed.
Third Embodiment
[0099] A non-aqueous electrolyte secondary battery 300 constructed
according to the third embodiment does not differ from the
non-aqueous electrolyte secondary battery 100 of the first
embodiment except the electrode body. Therefore, the points
different from the first embodiment are mainly discussed herein
while explanation of the similar or identical points is omitted or
simplified.
[0100] As shown in FIG. 18, in an electrode body 350 of the third
embodiment, a first end 357b of a separator 357 is located more
interiorly than (located, in FIG. 18, on the left side of) the one
positive electrode end 155c with respect to the width direction
(lateral direction in FIG. 18) which end 155c is located at one end
(right end in FIG. 18) of the positive electrode plate 155 with
respect to the width direction. In other words, the one positive
electrode end 155c is located more exteriorly than (located, in
FIG. 18, on the right side of) the first end 357b of the separator
357 with respect to the width direction. This one positive
electrode end 155c is constituted by the uncoated positive
electrode portion 155b (or a part thereof) of the positive
electrode plate 155. Therefore, the third embodiment is also
configured such that the positive electrode plate 155 and the
positive terminal 120 can be electrically connected to each other
by welding the one positive electrode end 155c to the positive
current collecting portion 122 of the positive terminal 120 (see
FIG. 3).
[0101] A second end 357c of the separator 357 is located more
interiorly than (located closer to the center of the electrode body
350 than) the other negative electrode end 156c is, with respect to
the width direction (lateral direction in FIG. 18), the end 156c
being located at the other end (left end in FIG. 18) of the
negative electrode plate 156 with respect to the width direction.
In other words, the other negative electrode end 156c is located
more exteriorly than (is more distant from the center of the
electrode body 350 than) the second end 357c of the separator 357
is, with respect to the width direction. The other negative
electrode end 156c is constituted by the uncoated negative
electrode portion 156b (or a part thereof) of the negative
electrode plate 156. Therefore, the third embodiment is also
configured such that the negative electrode plate 156 and the
negative terminal 130 can be electrically connected to each other
by welding the other negative electrode end 156c to the negative
current collecting portion 132 of the negative terminal 130 (see
FIG. 3).
[0102] In addition, the electrode body 350 of the third embodiment
is configured as shown in FIG. 18. In this figure, the first end
357b of the separator 357 is located more exteriorly than (located,
in FIG. 18, on the right side of) the one end 155f of the coated
positive electrode portion 155d of the positive electrode plate 155
and located more exteriorly than (located, in FIG. 18, on the right
side of) the one end 156f (that corresponds to the one end of the
negative electrode plate 156) of the coated negative electrode
portion 156d of the negative electrode plate 156, with respect to
the width direction (lateral direction in FIG. 18).
[0103] In addition, in the third embodiment, the first end 357b of
the separator 357 is heat-welded to a portion of the positive
electrode plate 155, the portion being opposed to the separator 357
in the thickness direction (this portion is located under the
separator 357 in FIG. 18). Specifically, the first end 357b of the
separator 357 is heat-welded to the portion (uncoated positive
electrode portion 155b) of the positive electrode plate 155 which
portion is opposed to the separator 357 in the thickness direction,
as described later in the process of manufacturing the electrode
body 350. In FIG. 18, the separator 357 in contact with the upper
surface of the negative electrode plate 156 (coated negative
electrode portion 156d) is heat-welded to the uncoated positive
electrode portion 155b, with the first end 357b being integral with
another first end 357b located thereunder.
[0104] Additionally, in the third embodiment, the first end 357b of
the separator 357 is heat-welded to the uncoated positive electrode
portion 155b (or a part thereof). Therefore, the first end 357b of
the separator 357 can be properly adhered (welded) to the positive
electrode plate 155.
[0105] Further, the second end 357c of the separator 357 is located
more exteriorly than (located, in FIG. 18, on the left side of) the
other end 155g (which corresponds to the other end of the positive
electrode plate 155) of the coated positive electrode portion 155d
of the positive electrode plate 155 and located more exteriorly
than (located, in FIG. 8, on the left side of) the other end 156g
of the coated negative electrode portion 156d of the negative
electrode plate 156, with respect to the width direction (lateral
direction in FIG. 18).
[0106] Additionally, in the third embodiment, the second end 357c
of the separator 357 is heat-welded to a portion of the negative
electrode plate 156, the portion being opposed to the separator 357
in the thickness direction (in the vertical direction in FIG. 18).
Specifically, the second end 357c of the separator 357 is
heat-welded to the portion (uncoated negative electrode portion
156b) of the negative electrode plate 156 which portion is opposed
to the separator 357 in the thickness direction, as described later
in the process of manufacturing the electrode body 350.
[0107] In the third embodiment, the second end 357c of the
separator 357 is heat-welded to the uncoated negative electrode
portion 156b (or a part thereof). Therefore, the second end 357c of
the separator 357 can be properly adhered (welded) to the negative
electrode plate 156.
[0108] Since the non-aqueous electrolyte secondary battery 300 of
the third embodiment has the above-described electrode body 350, it
is possible to prevent "the undesirable electric short circuit
caused by the contact between the positive electrode plate 155 and
the negative electrode plate 156 at the widthwise ends (the lateral
ends of the coated positive electrode portion 155d and the coated
negative electrode portion 156d in FIG. 18) due to heat shrinkage
of the separator 357 in the width direction (lateral direction in
FIG. 18)".
[0109] Specifically, even if the temperature of the non-aqueous
electrolyte secondary battery 300 rises to a temperature (e.g.,
150.degree. C.) that causes heat shrinkage of the separator 357,
the first end 357b and second end 357c of the separator 357 are
unlikely to thermally shrink further in the width direction because
they have already been thermally shrunken by heating at the time of
heat-welding.
[0110] In addition, since the first end 357b of the separator 357
is adhered (heat-welded) to the portion of the positive electrode
plate 155 which portion is opposed to the separator in the
thickness direction, the inward displacement of the first end 357b
of the separator 357 in the width direction can be prevented even
if it is forced by heat shrinkage to move inwardly in the width
direction (to the left in FIG. 18). This enables it to prevent "the
undesirable contact between the one end 155f of the coated positive
electrode portion 155d and the one end 156f of the coated negative
electrode portion 156d which contact is caused by the first end
357b of the separator 357 getting into the interface between the
positive electrode plate 155 (coated positive electrode portion
155d) and the negative electrode plate 156 (coated negative
electrode portion 156d).
[0111] In addition, since the second end 357c of the separator 357
is adhered (heat-welded) to the portion of the negative electrode
plate 156 which portion is opposed to the separator 357 in the
thickness direction, the inward displacement of the second end 357c
of the separator 357 in the width direction can be prevented even
if it is forced by heat shrinkage to move inwardly in the width
direction (to the right in FIG. 18). This enables it to prevent
"the undesirable contact between the other end 155g of the coated
positive electrode portion 155d and the other end 156g of the
coated negative electrode portion 156d which contact is caused by
the second end 357c of the separator 357 getting into the interface
between the positive electrode plate 155 (coated positive electrode
portion 155d) and the negative electrode plate 156 (coated negative
electrode portion 156d).
[0112] Therefore, in the non-aqueous electrolyte secondary battery
300 of the third embodiment, even if the temperature of the
separator 357 rises to a temperature (e.g., 150.degree. C.) that
causes heat shrinkage of the separator 357, the separator can be
kept present between the positive electrode plate 155 and the
negative electrode plate 156 with respect to the width direction
(lateral direction in FIG. 18) of the electrode body 350, thereby
maintaining the electric insulation between the positive electrode
plate 155 and the negative electrode plate 156.
[0113] Next, the process of manufacturing the non-aqueous
electrolyte secondary battery 300 will be explained.
[0114] Firstly, the positive electrode plate 155, having the
positive electrode mixture layers 152 applied to the surfaces,
respectively, of the strip-shaped positive current collector 151 as
shown in FIGS. 7 and 8, is prepared. Then, the negative electrode
plate 156, having the negative electrode mixture layers 159 applied
to the surfaces, respectively, of the strip-shaped negative current
collector 158 as shown in FIGS. 9 and 10, is prepared. Then, the
strip-shaped separator 357, composed of a
polypropylene-polyethylene-polypropylene trilaminar composite
porous sheet, is prepared.
[0115] Next, the positive electrode plate 155, the negative
electrode plate 156 and the separator 357 are stacked as
illustrated in FIG. 19. In this case, the positive electrode plate
155, the negative electrode plate 156 and the separator 357 are
arranged as follows. With respect to the width direction (lateral
direction in FIG. 19), the first end 357b of the separator 357 is
located more interiorly than (located, in FIG. 19, on the left side
of) the one positive electrode end 155c of the positive electrode
plate 155; located more exteriorly than (located, in FIG. 19, on
the right side of) the one end 155f of the coated positive
electrode portion 155d of the positive electrode plate 155; and
located more exteriorly than (located, in FIG. 19, on the right
side of) the one end 156f of the coated negative electrode portion
156d of the negative electrode plate 156. Further, with respect to
the width direction, the second end 357c of the separator 357 is
located more interiorly than (located, in FIG. 19, on the right
side of) the other negative electrode end 156c of the negative
electrode plate 156; located more exteriorly than (located, in FIG.
19, on the left side of) the other end 155g of the coated positive
electrode portion 155d of the positive electrode plate 155; and
located more exteriorly than (located, in FIG. 19, on the left side
of) the other end 156g of the coated negative electrode portion
156d of the negative electrode plate 156.
[0116] With the positive electrode plate 155, the negative
electrode plate 156 and the separator 357 being in such an
overlapped condition, the first end 357b of the separator 357 and
the uncoated positive electrode portion 155b of the positive
electrode plate 155 are pinched (held in pressure contact) in the
thickness direction by the heat rollers 11 and 12 heated to
200.degree. C., while the second end 357c of the separator 357 and
the uncoated negative electrode portion 156b of the negative
electrode plate 156 are pinched (held in pressure contact) in the
thickness direction by the heat rollers 13 and 14 heated to
200.degree. C. Then, the positive electrode plate 155, the negative
electrode plate 156 and the separator 357 are moved in the
longitudinal direction (upwardly in FIG. 19), while the heat
rollers 11 to 14 being rotated. Note that the heat roller 12 is
positioned on the back of the heat roller 11 (on the farther side
when viewed in a direction perpendicular to the plane of the
drawing) in FIG. 19, whereas the heat roller 14 is positioned on
the back of the heat roller 13 (on the farther side when viewed in
a direction perpendicular to the plane of the drawing) in FIG.
19.
[0117] This enables it to heat-weld the first end 357b of the
separator 357 to the portion (uncoated positive electrode portion
155b) of the positive electrode plate 155 which portion is opposed
to the separator 357 in the thickness direction. Further, the
second end 357c of the separator 357 can be heat-welded to the
portion (uncoated negative electrode portion 156b) of the negative
electrode plate 156 which portion is opposed to the separator 357
in the thickness direction. After heat-welding, they (positive
electrode plate 155, negative electrode plate 156 and separator
357) are wound into a flat roll thereby to form the electrode body
350 (see FIG. 5).
[0118] In the third embodiment, an adhesive agent (e.g.,
polyolefin-based adhesive agents) is applied beforehand to the
portion (uncoated positive electrode portion 155b) of the positive
electrode plate 155 which portion is opposed to the first end 357b
of the separator 357 in the thickness direction. Also, an adhesive
agent (e.g., polyolefin-based adhesive agents) is applied
beforehand to the portion (uncoated negative electrode portion
156b) of the negative electrode plate 156 which portion is opposed
to the second end 357c of the separator 357 in the thickness
direction.
[0119] Then, the positive current collecting portion 122 of the
positive terminal 120 is welded to the upper end of the one
positive electrode end 155c of the electrode body 350 (see FIG. 3).
The negative current collecting portion 132 of the negative
terminal 130 is welded to the upper end of the other negative
electrode end 156c of the electrode body 350. After this electrode
body 350 is accommodated within the rectangular storage section
111, the opening of the rectangular storage section 111 is closed
with the lid 112. Thereafter, the lid 112 is welded to the
rectangular storage section 111. Subsequently, a non-aqueous
electrolytic solution is poured into the rectangular storage
section 111 through the pouring port (not shown) formed in the lid
112 (at that time, the electrode body 350 is impregnated with the
non-aqueous electrolytic solution). The pouring port is then sealed
and the manufacture of the non-aqueous electrolyte secondary
battery 300 of the third embodiment is accordingly completed.
[0120] (Heating Test)
[0121] Five samples were prepared for each of the non-aqueous
electrolyte secondary batteries 100 to 300 of the first to third
embodiments. Also, five non-aqueous electrolyte secondary batteries
were prepared as a comparative example which differed from the
non-aqueous electrolyte secondary battery 200 of the second
embodiment in that the first end and second end of the separator
had not undergone preliminary heat shrinkage (that is, the thermal
treatment step had not been applied to the first and second ends).
A heating test was conducted on these batteries (twenty batteries
in total) to check whether internal electric short circuit would
occur.
[0122] First, the capacities of the batteries of the first to third
embodiments and the comparative example (twenty batteries in total)
were measured at a temperature of 25.degree. C. prior to the
heating test. Specifically, each battery was charged with a
constant current of 1 C (5.5 A) until the battery voltage reached
4.2V and then subsequently was charged while keeping the battery
voltage at 4.2V until the current reached 0.1 C (0.55 A). Thus, the
non-aqueous electrolyte secondary battery 100 was charged up to SOC
100%.
[0123] It should be noted that 1 C is the value of current required
to complete a constant current discharge of the rated capacity
(nominal capacity) of a battery in one hour. The rated capacities
(nominal capacities) of the non-aqueous electrolyte secondary
batteries 100 to 300 and the non-aqueous electrolyte secondary
batteries of the comparative example are 5.5 Ah, and therefore 1
C=5.5 A.
[0124] SOC is the abbreviation of "State of Charge" (=charging
rate).
[0125] Thereafter, each battery was discharged with a constant
current of 1 C (5.5 A) until the battery voltage reached 2.5V.
Thus, each battery was discharged down to SOC 0%. The quantity of
electricity discharged at that time was measured as the capacity of
each battery, and the average (average capacity) of the batteries
was calculated for each of the first to third embodiments and the
comparative example. Table 1 shows the result.
TABLE-US-00001 TABLE 1 NUMBER AVERAGE BATTERY MAXIMUM OF CAPACITY
VOLTAGE TEMPERATURE SHORTED (Ah) (V) (.degree. C.) BATTERIES COM-
5.52 0 210 5 PAR- ATIVE EX- AMPLE EMBOD- 5.48 3.8 160 0 IMENT 1
EMBOD- 5.50 3.8 160 0 IMENT 2 EMBOD- 5.47 3.8 160 0 IMENT 3
[0126] As shown in Table 1, the average capacity of the batteries
of the first embodiment (the average of the capacities of the five
sample batteries prepared for the first embodiment) was 5.48 Ah.
The average capacity of the batteries of the second embodiment was
5.50 Ah. The average capacity of the batteries of the third
embodiment was 5.47 Ah. The average capacity of the batteries of
the comparative example was 5.52 Ah.
[0127] Next, a heating test was conducted on each battery.
Specifically, the SOC of each battery was set to 80% (battery
voltage=3.8V) and all the batteries were placed in the test room of
heating test equipment. Then, the interior temperature of the test
room was raised 5.degree. C. per minute, thereby setting the
interior temperature of the test room to 160.degree. C. Thereafter,
the internal temperature of the test room was kept at 160.degree.
C. and each battery was left to stand in the test room having a
temperature of 160.degree. C. for 30 minutes. In the mean time, the
temperature of each battery was measured to obtain the maximum
temperature the battery had reached. It should be noted that
160.degree. C. is a temperature that causes heat shrinkage of the
separator.
[0128] Further, the voltage of each battery was measured during the
heating test and the battery voltage after the heating test was
obtained. Incidentally, in a battery in which internal short
circuit has occurred (i.e., the positive electrode plate and the
negative electrode plate have come into contact with each other at
the widthwise ends of the separator), the battery voltage generally
drops to 0 V. It is therefore conceivable that, in the batteries
whose voltage dropped to 0 V after the heating test, the positive
electrode plate and the negative electrode plate had come into
contact with each other at the widthwise ends (first and second
ends) of the separator owing to heat shrinkage of the separator so
that internal short circuit had occurred. Table 1 shows the
result.
[0129] As shown in Table 1, the voltages of all the batteries of
the comparative examples dropped to 0 V after the heating test. The
maximum temperature that they reached during the heating test was
210.degree. C. which was 50.degree. C. higher than the interior
temperature (160.degree. C.) of the test room. It can be assumed
from this result that, in the batteries of the comparative
examples, the positive electrode plate and the negative electrode
plate came into contact with each other at the widthwise ends
(first and second ends) of the separator owing to heat shrinkage of
the separator, causing internal short circuit. The heat generation
of the batteries is thought to be accelerated by this internal
short circuit so that the temperature of the batteries is elevated
to 210.degree. C.
[0130] The batteries of the first to third embodiments, on the
other hand, are all kept at a voltage of 3.8V. The maximum
temperature that they reached during the heating test was
160.degree. C. which was the same as the interior temperature
(160.degree. C.) of the test room. It is understood from this
result that the batteries of the first to third embodiments could
maintain the separator interposed between the positive electrode
plate and the negative electrode plate with respect to the width
direction of the electrode body, keeping the electric insulation
between the positive and negative electrode plates even though they
underwent the heating test (in which the batteries were heated to a
temperature that causes heat shrinkage of the separator). That is,
"the undesirable electric short circuit caused by the contact
between the positive electrode plate and the negative electrode
plate at the widthwise ends due to heat shrinkage of the separator
in the width direction" can be prevented in the first to third
embodiments. The reason for this is as explained earlier in the
description of each embodiment.
[0131] The above explanations are provided for the first to third
embodiments, but do not limit the invention thereto. The present
invention may be embodied in other specific forms without departing
from the essential characteristics thereof.
EXPLANATION OF REFERENCE SIGNS
[0132] 100, 200, 300 Non-aqueous electrolyte secondary battery
[0133] 110 Battery case [0134] 150, 250, 350 Electrode body
(Electrode body for non-aqueous electrolyte secondary battery)
[0135] 155 Positive electrode plate [0136] 155b Uncoated positive
electrode portion [0137] 155c One positive electrode end [0138]
155d Coated positive electrode portion [0139] 151 Positive current
collector [0140] 152 Positive electrode mixture layer [0141] 156
Negative electrode plate [0142] 156b Uncoated negative electrode
portion [0143] 156c Other negative electrode end [0144] 158
Negative current collector [0145] 159 Negative electrode mixture
layer [0146] 157, 257, 357 Separator [0147] 157b, 257b, 357b First
end of separator [0148] 157c, 257c, 357c Second end of separator
[0149] 157d, 257d, 357d Intermediate portion of separator
* * * * *