U.S. patent application number 13/133428 was filed with the patent office on 2012-12-20 for processing device of nonaqueous electrolyte secondary battery and manufacturing method thereof.
This patent application is currently assigned to TONGJI UNIVERSITY. Invention is credited to Katsuyuki Hojo.
Application Number | 20120321926 13/133428 |
Document ID | / |
Family ID | 44563001 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120321926 |
Kind Code |
A1 |
Hojo; Katsuyuki |
December 20, 2012 |
PROCESSING DEVICE OF NONAQUEOUS ELECTROLYTE SECONDARY BATTERY AND
MANUFACTURING METHOD THEREOF
Abstract
To melt and diffuse metallic foreign bodies immixed in
electrodes of a nonaqueous electrolyte secondary battery before
initial charging, electrodes (18) wound with a separator (24)
between a cathode plate (20) and an anode plate (22) are placed in
a battery case (16) and the battery case (16) is filled with an
electrolyte. After the case has been filled, the electrolyte is
allowed to permeate into the electrodes (S14). Then, the
electrolyte-filled battery (14) is placed in a processing device
(10), and fixed by means of a surface pressure between at least 0.1
MPa and 5.0 MPa (S16). Thereafter, the cathode potential is
adjusted and held for a period of one hour and 35 hours (S18) while
the battery remains fixed, after which the pre-initial charging
process is terminated (S20).
Inventors: |
Hojo; Katsuyuki;
(Toyota-shi, JP) |
Assignee: |
TONGJI UNIVERSITY
Shanghai
CN
|
Family ID: |
44563001 |
Appl. No.: |
13/133428 |
Filed: |
March 8, 2010 |
PCT Filed: |
March 8, 2010 |
PCT NO: |
PCT/JP10/53798 |
371 Date: |
June 8, 2011 |
Current U.S.
Class: |
429/100 ;
29/623.1; 429/163 |
Current CPC
Class: |
H01M 10/44 20130101;
H01M 10/0468 20130101; H01M 10/052 20130101; H01M 2/1077 20130101;
H01M 10/0413 20130101; Y10T 29/49108 20150115; H01M 10/0481
20130101; H01M 10/446 20130101; Y02T 10/70 20130101; Y02E 60/10
20130101; H01M 10/058 20130101 |
Class at
Publication: |
429/100 ;
429/163; 29/623.1 |
International
Class: |
H01M 2/10 20060101
H01M002/10; H01M 10/04 20060101 H01M010/04; H01M 2/02 20060101
H01M002/02 |
Claims
1. A processing device for a nonaqueous electrolyte secondary
battery having electrodes accommodated together with a nonaqueous
electrolyte in a battery case, the electrodes including a cathode
plate and an anode plate arranged on opposite sides of a separator,
for melting and diffusing metallic foreign bodies immixed in the
electrodes, the processing device comprising: a space reducing unit
for reducing a space in the uncharged electrodes, to thereby place
the nonaqueous electrolyte secondary battery in a space-reduced
state; and a holding unit for holding a cathode potential at a
melting potential of the metallic foreign bodies for a
predetermined period of time in the space-reduced state, the
melting potential of the metallic foreign bodies being lower than a
charge-discharge cathode potential for use in charging and
discharging the nonaqueous electrolyte secondary battery.
2. The processing device for a nonaqueous electrolyte secondary
battery according to claim 1, wherein the space reducing unit is a
battery fixing unit for fixing the battery case on an outer surface
thereof by applying a predetermined surface pressure sufficient to
bring the cathode plate into contact with the metallic foreign
bodies.
3. The processing device for a nonaqueous electrolyte secondary
battery according to claim 2, wherein the battery fixing unit
employs a surface pressure between 0.1 MPa and 5.0 MPa as the
predetermined surface pressure.
4. The processing device for a nonaqueous electrolyte secondary
battery according to claim 2, wherein the battery fixing unit
further comprises a battery heating unit for heating the nonaqueous
electrolyte secondary battery.
5. The processing device for a nonaqueous electrolyte secondary
battery according to claim 1, wherein the holding unit holds a
cathode potential of the nonaqueous electrolyte secondary battery
in an open-circuit state in a case that the metallic foreign bodies
are assumed to be of iron.
6. A method for manufacturing a nonaqueous electrolyte secondary
for melting and diffusing metallic foreign bodies immixed in a
nonaqueous electrolyte secondary battery having electrodes
accommodated together with a nonaqueous electrolyte in a battery
case, the electrodes including a cathode plate and an anode plate
arranged on opposite sides of a separator, the method comprising: a
space reducing step of reducing a space in the uncharged
electrodes, to thereby place the nonaqueous electrolyte secondary
battery in a space-reduced state; and a holding step of holding a
cathode potential at a melting potential of the metallic foreign
bodies for a predetermined period of time in the space-reduced
state, the melting potential of the metallic foreign bodies being
lower than a charge-discharge cathode potential for use in charging
and discharging the nonaqueous electrolyte secondary battery.
7. The method for manufacturing a nonaqueous electrolyte secondary
according to claim 6, wherein the space reducing step is a battery
fixing step comprising fixing the battery case on an outer surface
thereof by applying a predetermined surface pressure sufficient to
bring the cathode plate into contact with the metallic foreign
bodies.
8. The manufacturing method for a nonaqueous electrolyte secondary
battery according to claim 6, wherein the space reducing step is a
battery depressurizing step comprising reducing pressure in the
battery case.
9. The method for manufacturing a nonaqueous electrolyte secondary
battery according to claim 6, wherein the space reducing step is a
battery heating step comprising heating the battery, based on a
predetermined heating condition, after the battery fixing step, and
thereafter releasing the battery from the fixed state.
10. The manufacturing method for a nonaqueous electrolyte secondary
battery according to claim 6, wherein, at the holding step, a
cathode potential of the nonaqueous electrolyte secondary battery
in an open-circuit state is maintaining, in a case that the
metallic foreign bodies are assumed to be of iron.
Description
TECHNICAL FIELD
[0001] The present invention relates to a processing device for a
nonaqueous electrolyte secondary battery and a manufacturing method
thereof and, more particularly, to a processing device before
initial charging and a manufacturing method including a pre-initial
charging process.
BACKGROUND ART
[0002] In recent years, the popularity of portable and cordless
electronic devices has rapidly increased. Accordingly, there has
also been a great increased in the desire for small and light
nonaqueous electrolyte secondary batteries having a high energy
density to use as a driving power source of such an electronic
device. The development of techniques for nonaqueous electrolyte
secondary batteries, not only for electronic devices but also for
power storage or electric vehicles with longer durability or the
like, has accelerated.
[0003] In order to obtain longer durability and other improvements,
nonaqueous electrolyte secondary batteries free from internal
short-circuits, voltage drop defects, and the like are desirable,
with some attention focusing on prevention of the immixing of
metallic foreign bodies during the process of manufacturing such a
nonaqueous electrolyte secondary battery has been pointed out. The
possibility that immixed metallic foreign bodies may melt and be
disposed within a battery in such a manner as to penetrate a
separator and cause a short-circuit has been noted.
[0004] Conventionally, in order to avoid internal short-circuiting,
voltage drop defects, and the like in the secondary batteries, it
has been assumed that metallic foreign bodies are immixed in
nonaqueous electrolyte secondary batteries and pre-shipment
preparation processes for foreign body removal and the like have
been performed.
[0005] Japanese Patent Laid-open Publication No. 2005-158643
(Patent Document 1) discloses, as a method for testing a lithium
ion secondary battery, which is a nonaqueous electrolyte secondary
battery in which reliable and quick discovery of defective
batteries, a method in which a lithium ion battery is held in an
environment in which the temperature is 45.degree. C. or hotter for
ten or more days, or 60.degree. C. to 70.degree. C. for four or
more days, before detection of a voltage drop, and presence of
electrically conductive foreign bodies in the lithium ion battery
is determined upon detection of a voltage drop larger than a
predetermined voltage drop reference.
[0006] Japanese Patent Laid-open Publication No. 2005-243537
(Patent Document 2) discloses a method for suppressing occurrence
of minute short-circuiting between a cathode and an anode by
initially charging a lithium ion secondary battery which is a
nonaqueous electrolyte secondary battery to 0.01% to 0.1% of the
battery capacity to thereby set the anode potential to 1.5 v or
larger under the Li/Li.sup.+ reference and the cathode potential to
3.5 v or larger under the Li/Li.sup.+ reference, and then allowing
the battery to stand for one to 48 hours.
RELATED ART DOCUMENTS
[0007] Patent Document 1: Japanese Patent Laid-open Publication No.
2005-158643
[0008] Patent Document 2: Japanese Patent Laid-open Publication No.
2005-243537
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0009] However, according to the above-noted Patent Document 1, it
is necessary to leave a lithium ion secondary battery alone in a
heating environment for four to ten days, which problematically
increases manufacturing costs. According to the above-noted Patent
Document 2, a charging device is necessary to charge a battery to
0.01% to 0.1% of the battery capacity, which also problematically
increases manufacturing costs. In view of these problems, a more
efficient selection method has been desired.
[0010] An object of the present invention is to provide a
processing device for a nonaqueous electrolyte secondary battery
capable of melting and diffusing metallic foreign bodies immixed in
the nonaqueous electrolyte secondary battery before initially
charging the battery, and to provide a method of manufacturing a
nonaqueous electrolyte secondary battery.
Means to Solve the Problem
[0011] A processing device for a nonaqueous electrolyte secondary
battery according to the present invention is a processing device
for a nonaqueous electrolyte secondary battery having electrodes
accommodated, together with nonaqueous electrolyte, in a battery
case, the electrodes including a cathode plate and an anode plate
arranged with a separator in-between, for melting and diffusing
metallic foreign bodies immixed in the electrodes, the processing
device comprising a space reducing unit for reducing a space
present in the electrodes being uncharged, to thereby place the
nonaqueous electrolyte secondary battery in a space-reduced state,
and a holding unit for holding a cathode potential at a melting
potential of the metallic foreign bodies for a predetermined period
of time in the space-reduced state, the melting potential of the
metallic foreign bodies being lower than a charge-discharge cathode
potential for use in charging and discharging the nonaqueous
electrolyte secondary battery.
[0012] Preferably, in a processing device for a nonaqueous
electrolyte secondary battery according to the present invention,
the space reducing unit may be a battery fixing unit for fixing the
battery case on an outer surface thereof by applying a
predetermined surface pressure sufficient to bring the cathode
plate into contact with the metallic foreign bodies.
[0013] Also preferably, in a processing device for a nonaqueous
electrolyte secondary battery according to the present invention,
the battery fixing unit may use a surface pressure between 0.1 MPa
and 5.0 MPa as the predetermined surface pressure.
[0014] Also preferably, in a processing device for a nonaqueous
electrolyte secondary battery according to the present invention,
the battery fixing unit may further have a battery heating unit for
heating the nonaqueous electrolyte secondary battery.
[0015] Also preferably, in a processing device for a nonaqueous
electrolyte secondary battery according to the present invention,
the holding unit may hold a cathode potential of the nonaqueous
electrolyte secondary battery in an open-circuit state in a case
where the metallic foreign bodies are assumed to be of iron.
[0016] A manufacturing method for a nonaqueous electrolyte
secondary battery according to the present invention is a method
for manufacturing a nonaqueous electrolyte secondary for melting
and diffusing metallic foreign bodies immixed in a nonaqueous
electrolyte secondary battery having electrodes accommodated,
together with nonaqueous electrolyte, in a battery case, the
electrodes including a cathode plate and an anode plate arranged
with a separator in-between, the method comprising a space reducing
step of reducing a space in the uncharged electrodes to thereby
place the nonaqueous electrolyte secondary battery in a
space-reduced state, and a holding step of holding a cathode
potential at a melting potential of the metallic foreign bodies for
a predetermined period of time in the space-reduced state, the
melting potential of the metallic foreign bodies being lower than a
charge-discharge cathode potential for use in charging and
discharging the nonaqueous electrolyte secondary battery
[0017] In a manufacturing method for a nonaqueous electrolyte
secondary battery according to the present invention, preferably,
the space reducing step may be a battery binding step of binding
the battery case on an outer surface thereof by applying a
predetermined surface pressure sufficient to bring the cathode
plate into contact with the metallic foreign bodies.
[0018] Also, in a manufacturing method for a nonaqueous electrolyte
secondary battery according to the present invention, preferably,
the space reducing step may be a battery depressurizing step of
reducing pressure in the battery case.
[0019] Also, in a manufacturing method for a nonaqueous electrolyte
secondary battery according to the present invention, preferably,
the space reducing step may be a battery heating step of heating
the battery, based on a predetermined heating condition, after the
battery binding step, and thereafter releasing the battery.
[0020] Also, in a manufacturing method for a nonaqueous electrolyte
secondary battery according to the present invention, at the
holding step, preferably, a cathode potential of the nonaqueous
electrolyte secondary battery in an open-circuit state may be held
in a case where the metallic foreign bodies are assumed to be of
iron.
Advantage of Present Invention
[0021] By employing a processing device for a nonaqueous
electrolyte secondary battery having the above described structure
and a method for manufacturing a nonaqueous electrolyte secondary
battery, with an arrangement in which metallic foreign bodies are
kept contacting the cathode plate having a potential equal to that
at which the metallic foreign bodies melt, the metallic foreign
bodies will melt and be diffused before initial charging. This can
suppress occurrence of internal short-circuiting, voltage drop
defects, and other problems which may result from the inmixing of
metallic foreign bodies in a nonaqueous electrolyte secondary
battery.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a diagram explaining a device for processing a
nonaqueous electrolyte secondary battery in an embodiment according
to the present invention;
[0023] FIG. 2 is a diagram explaining a structure of a battery in
an embodiment according to the present invention;
[0024] FIG. 3 is a diagram explaining a structure of electrodes in
an embodiment according to the present invention;
[0025] FIG. 4 is a diagram explaining batteries fixed in the
processing device according to an embodiment of the present
invention;
[0026] FIG. 5 is a flowchart explaining a procedure of a method for
manufacturing a nonaqueous electrolyte secondary battery in an
embodiment according to the present invention;
[0027] FIG. 6 is diagram explaining a result of observation of a
cathode plate, an anode plate, and a separator in an example in an
embodiment according to the present invention;
[0028] FIG. 7 is a flowchart explaining a procedure of a method of
manufacturing a nonaqueous electrolyte secondary battery when a
space reducing step and a holding step are not performed in the
embodiment according to the present invention;
[0029] FIG. 8 is diagram explaining a result of observation of a
cathode plate, an anode plate, and a separator in a comparative
example in an embodiment according to the present invention;
[0030] FIG. 9 is a flowchart explaining a procedure of a method of
manufacturing a nonaqueous electrolyte secondary battery in an
embodiment according to the present invention, in which the space
reducing step is a battery heating step;
[0031] FIG. 10 is a diagram explaining batteries placed in the
processing device and further in a high temperature furnace in an
embodiment according to the present invention;
[0032] FIG. 11 is a diagram explaining a structure of a heating
function-equipped processing device in an embodiment according to
the present invention;
[0033] FIG. 12 is a flowchart of a procedure of a method of
manufacturing a nonaqueous electrolyte secondary battery in an
embodiment according to the present invention, in which the cathode
potential is adjusted and maintained;
[0034] FIG. 13 is a diagram explaining a structure of a power
source device, processing device, and batteries in an embodiment
according to the present invention;
[0035] FIG. 14 is a diagram explaining a structure in which surface
pressure is applied to batteries, using a vacuum furnace in an
embodiment according to the present invention; and
[0036] FIG. 15 is a diagram explaining a structure in which surface
pressure is applied to batteries, using a high pressure furnace in
an embodiment according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] In the following, embodiments of the present invention will
be described in detail with reference to the diagrams. The
materials, shapes, dimensions, and the like described below are
merely examples for illustration, and any other appropriate
materials, shapes, dimensions and the like can be employed
according to the specification of a product.
[0038] Although in the following, a lithium ion secondary battery
having a lithium nickel oxide cathode and a graphite anode is
described as an object to be processed, a nonaqueous electrolyte
secondary battery having a cathode and an anode made of any other
appropriate material may be used. In this specification, a lithium
ion secondary battery will be referred to simply as "a
battery".
[0039] Although an example in which a polyethylene separator is
used will be described in the following, a polyolefin-based
insulating porous film may be used instead. For example, a
polyethylene film, a film made of laminated polyethylene and
polypropylene or the like may be desirably used.
[0040] Although rolled-up electrodes including a cathode plate, an
anode plate, and a separator will be described in the following,
multi-plate stacked electrodes or the like may be used instead.
Further, although flat electrodes will be described in the
following, cylindrical electrodes or the like may be used
instead.
[0041] Although an example in which nonaqueous electrolyte produced
by mixing ethylene carbonate and diethyl carbonate, or nonaqueous
solvent, at a volume ratio 4:6 and dissolving lithium
hexafluorophosphate, or solute, with a density of 1.0 mol/L is used
will be described in the following, any other appropriate
nonaqueous solvent and solute may be used instead.
[0042] In the following, identical elements are given identical
reference numerals throughout all diagrams, and their description
is not duplicated. Reference numerals having been mentioned thus
far may be used when necessary in the description.
First Embodiment
[0043] FIG. 1 is a diagram explaining a processing device 10 for a
nonaqueous electrolyte secondary battery. The XYZ axis shown in
FIG. 1 is defined such that the x direction corresponds to the
width direction of the processing device 10, the y direction
corresponds to the thickness thereof, and the z direction
corresponds to the height direction thereof. The processing device
10 is a device for holding one or more batteries 14 to be described
in detail referring to FIG. 2 in a frame 11, then applying constant
surface pressure to the batteries 14, using a pressing portion 13,
preferably, via a fixing element 12, to thereby reduce the space d
between the cathode plate 20 and the anode plate 22 to be described
in detail referring to FIG. 3, and thereafter maintaining the state
in which the space d is reduced (a space-reduced state) for a
predetermined period of time. The processing device 10 can apply
surface pressure to one or more batteries 14 at the same time. The
processing device 10 comprises the frame 11, the fixing element 12,
and the pressing portion 13, with the fixing element 12 being
omissible.
[0044] The frame 11 has a function of serving as an outer frame of
the processing device 10, and at least the fixing element 12, the
pressing portion 13, and the battery 14 can be accommodated in the
frame 11. At least one or more batteries 14 can be accommodated in
the frame 11, and the number of fixing elements 12 same as that of
the batteries 14 accommodated are used. In the example below, it is
assumed that five batteries 14 are accommodated. In accommodation
into inside the frame 11, a battery 14 is put onto a fixed side
wall disposed on the shorter edge of the frame 11, and thereafter
the fixing element 12 is positioned on the battery 14. Five
batteries and five fixing elements 12 are alternately placed in
this order. Thereafter, the pressing portion 13 is set in a
position next to the fixing element 12 last placed.
[0045] The frame 11 can be made of, for example, aluminum alloy.
Alternatively, a material such as stainless steel or the like which
is unlikely to rust, can be used. In these cases, preferably, an
insulating layer may be provided on the outermost surface of the
frame 11. Other materials available for the frame 11 may include
polytetrafluoroethylene or the like. The dimensions of the frame 11
can be determined in accordance with the shape and dimension of a
battery 14 to be accommodated therein. If a battery 14 to be
accommodated has a width 100 mm, thickness 20 mm, and height 150
mm, the dimensions of the frame 11 can be width 120 mm, thickness
200 mm, and height 170 mm.
[0046] The fixing element 12 has a function of binding the
installed battery 14, and may be of the same width and height as
the battery 14 to be accommodated. While the fixing element 12 can
be made using a flat panel of the same material as that of the
frame 11, desirably, fire-resistive heat insulating material may be
used for the fixing element 12. Preferably, an insulating layer may
be provided on the outermost surface of the fixing element 12,
similar to the frame 11, because the fixing element 12 is to
contact a battery 14. The dimensions of the fixing element 12 may
be set in accordance with the shape and dimension of a battery 14
to be accommodated. If the dimensions of the battery 14 to be
accommodated are width 100 mm, thickness 20 mm, and height 150 mm,
the fixing element 12 may be designed with dimensions of width 100
mm, thickness 10 mm, and height 150 mm.
[0047] The pressing portion 13 is a flat panel having, for example,
four pressing pins coupled on one side thereof and with an external
force applied to the other side of the flat panel can apply
pressure to the fixing element 12 via the pressing pins. Use of
four pressing pins makes it possible to apply substantially
constant pressure onto the fixing element 12. That is, the pressing
portion 13 has a function of applying substantially constant
surface pressure to a surface having a larger area of the battery
14 by means of pressure applied to the fixing element 12.
[0048] To apply an external force to the pressing portion 13, a
screw mechanism or the like for moving the pressing portion 13
relative to the frame 11 can be used. For example, a screw
mechanism comprises a fixing panel, a nut and a bolt, in which the
nut and the bolt are fixed to the fixing panel with, when
necessary, an elastic member or the like, such as a spring or
rubber, interposed between the fixing panel and the nut, the fixing
panel having a threaded hole formed thereon for receiving the bolt.
Then, by turning the bolt around, the pressing portion 13 is
pressed by the tip end of the bolt, whereby an external force is
applied to the pressing portion 13.
[0049] With a configuration as above, a surface pressure can be
measured using a load cell attached to the pressing portion 13.
Alternatively, another method may be used for the measurement,
including use of a surface pressure measurement sheet provided
between the battery 14 and the fixing element 12.
[0050] In the above, the function of the screw mechanism which
generates a predetermined surface pressure by turning the bolt
corresponds to a space-reducing function or unit of the processing
device 10. The function of using the nut to fix the bolt so that it
will no longer turn once a predetermined surface pressure has been
obtained, and of then holding that state, corresponds to the
holding function or unit of the processing device 10.
[0051] FIG. 2 is a diagram explaining a structure of the battery
40. For example, a vehicle battery to be mounted on a vehicle is a
battery assembly comprising two or more electric cells. As each of
the electric cells constituting an assembled battery, e.g., a
lithium ion secondary battery having an average voltage being about
3.5 v is available, wherein the average voltage is a average of
inter-electrode potential differences between a lithium nickel
oxide cathode and a graphite anode in the plurality of electric
cells constituting the battery assembly. In this embodiment, an
electric cell of a lithium ion secondary battery is used as a
battery 14. A battery 14 is placed in the processing device 10, and
subjected to a pre-initial charging processing. A battery 14
comprises electrodes 18 and electrolyte (not shown) in a battery
case 16 having a sealing valve 17, a cathode terminal 21, and an
anode terminal 23.
[0052] The battery case 16 is made of aluminum or made using an
aluminum and resin-laminated sheet, or the like. The battery case
16 has a sealing valve 17 on an upper portion thereof. The sealing
valve 17 is kept open when pouring electrolyte and then closed
after the pouring. The cathode terminal 21 is a terminal adapted to
electrical connection to the cathode plate 20, while the anode
terminal 23 is a terminal adapted to electrical connection to the
anode plate 22.
[0053] FIG. 3 is a diagram explaining a structure of the electrodes
18. The electrodes 18 comprise a cathode plate 20, an anode plate
22, and a separator 24. The electrodes 18 are wound such that the
separator 24 sandwiched by the cathode plate 20 and the anode plate
22. When the battery 14 is charged, lithium ions are discharged
from the cathode plate 20 and lithium ions are absorbed by the
anode plate 22, causing the electrodes 18 to expand. Generally, the
battery 14 has the dimensions defined in consideration of change in
thickness of the electrodes 18 due to the expansion. An uncharged
battery 14 before expansion leaves a small space "d" between the
cathode plate 20 and anode plate 22 of the electrodes 18.
[0054] FIG. 4 is a diagram explaining batteries 14 installed and
fixed in the processing device 10. As has been described referring
to FIG. 1, the battery 14 is accommodated in the frame 11 of the
processing device 10, and the fixing element 12 is provided on the
side of the battery 14 where the pressing portion 13 is located.
Thereafter, a predetermined surface pressure is applied to the
battery 14 by the pressing portion 13.
[0055] An operation produced by the above described structure will
be described in detail referring to the flowchart of FIG. 5. FIG. 5
is a flowchart explaining a procedure within a method of
manufacturing a nonaqueous electrolyte secondary battery. In this
procedure, a battery 14 having electrodes 18 in the battery case 16
is provided; electrolyte is introduced and allowed to permeate
through the electrodes 18; surface pressure is applied to the
battery 14; and a space-reduced state with the space "d" reduced is
maintained for a predetermined period of time; and thereafter the
pre-initial charging process is terminated.
[0056] During initial preparation of a battery 14 (S10), electrodes
18 such that the cathode plate 20 and the anode plate 22 sandwich
the separator 24 are installed in the battery case 16.
[0057] Then, electrolyte is poured into the battery case 16 in
which the electrodes 18 has been installed (S12). The sealing valve
17 provided on the battery case 16 is opened for the pouring
procedure, and closed after pouring has been completed. After the
pouring, the electrolyte may be allowed to permeate (S14) by
allowing the battery 14 to sit.
[0058] While the cathode terminal 21 and the anode terminal 23 of
the battery 14 are left open, or in an open circuit state, such
five batteries 14 into which have been filled with electrolyte are
placed in the processing device 10, as shown in FIG. 4, and then
fixed by applying a surface pressure between at least 0.1 MPa and
5.0 MPa (S16). This step corresponds to the space reducing step at
which the space "d" between the cathode plate 20 and the anode
plate 22 is reduced. Concerning surface pressure, surface pressure
is applied using the processing device 10 to eliminate the space
"d" and ensure that, e.g., iron-based foreign bodies contact the
cathode plate 20, because it can be expected that any metallic
foreign bodies 26 which are the iron-based foreign bodies, present
near the cathode plate 20, may not contact the cathode plate 20
when there exists in such the space "d". In view of the above, a
surface pressure of between at least 0.1 MPa and 5.0 MPa, more
preferably, between at least 0.1 MPa and 2.0 MPa, is applied. The
applied pressure must be no less than 0.1 Mpa because a surface
pressure of less than 0.1 MPa is too small to maintain a constant
surface pressure, such that an inconstant surface pressure will be
applied to the electrodes 18. Meanwhile, because application of a
too high surface pressure when a porous film is used for the
separator may crush the pores of the separator, the upper limit of
the surface pressure is defined such that the extent of porousness
of the separator does not drop.
[0059] After preparation, the space-reduced state is maintained for
between at least one to 35 hours (S18). While the holding time may
differ depending on the nature, dimensions, and the like, of
metallic foreign bodies 26 which can be removed by the time of
initial charging, it can be understand based on the melting speed
of the metallic foreign bodies 26 that such a state must be held
for at least one hour. A longer holding time ensures reliable
melting of metallic foreign bodies 26. However, as the copper or
the like constituting the anode charge collector which is a
component of the electrodes 18 could melt at some potential, the
holding time must be limited to, for example, 35 hours or shorter,
that is, within a range which will not adversely affect the battery
functionality.
[0060] After elapse of a predetermined period of time at the
holding step, the pre-initial charging process step is terminated
(S20). The initial charging is applied after the holding step (S18)
because it has been confirmed through experimental observation
that, because the melting potential of metallic foreign bodies 26
is lower than the charge/discharge cathode potential when the
battery 14 has yet to be charged and remains in an open-circuit
state, electrically conductive metallic foreign bodies 26
contacting the cathode plate 20 will gradually melt and be
diffused, even if the battery 14 is not yet charged. In other
words, so-called galvanic corrosion will occur, whereas such
metallic foreign bodies 26 will not melt when not contacting the
cathode plate 20.
[0061] An example in which the metallic foreign bodies 26 are
iron-based foreign bodies will be described here. The electrically
conductive iron-based foreign bodies are brought into reliable
contact with the cathode plate 20 before initial charging with the
cathode potential being equal to the melting potential of the
iron-based foreign bodies, so that the iron-based foreign bodies
melt and iron ions of the iron-based foreign bodies solvated in the
electrolyte are diffused in the battery 14 before application of
initial charging. With the above processing, it is possible to
suppress occurrence of internal short-circuiting of the battery 14,
voltage drop defects, and other disadvantages.
[0062] In the following, an example and comparative example will be
used to illustrate embodiments of the present invention. It should
be noted that the present inventions is not limited to this
example.
EXAMPLE
[0063] An example was prepared, following the procedure shown in
FIG. 5. Initially, a battery 14 was prepared (S10). For
preparation, electrodes 18 wound with the cathode plate 20 and the
anode plate 20 sandwiching the separator 18 were installed in the
battery case 16. The sealing valve 17 of the battery case 16 having
the electrodes 18 therein was opened, and the battery case was
filled with electrolyte (S12). After the pouring of the
electrolyte, the sealing valve 17 was closed, and the electrolyte
was allowed to permeate (S14).
[0064] Then, as shown in FIG. 4, five batteries 14 into which
electrolyte have been poured were set in the frame 11, and fixed
with a surface pressure of 2.0 MPa (S16) by the fixing element 12.
The batteries 14 were held fixed for fifteen hours (S18) before the
pre-initial charging process was terminated (S20). After
termination of the pre-initial charging process, initial charging
was performed.
[0065] FIG. 6 is a diagram explaining results of observation of the
cathode plate 20, the anode plate 22, and the separator 24 in the
example. In order to verify the effects of the example, disk-like
iron-based foreign bodies having a diameter of 100 .mu.m and
thickness of 20 .mu.m were placed in advance in the vicinity of the
cathode plate 20 when performing the example, following the
procedure shown in FIG. 5. After initial charging, in order to
verify the effects of the example, the battery 14 was decomposed
and structural components, namely, the cathode plate 20, the anode
plate 22, and the separator 24, were removed and observed with a
microscope appropriate to the observation of metal.
[0066] FIG. 6A shows an observation of the cathode plate 20, in
which a trace where the disk-like iron-based foreign bodies were
placed could be observed. FIG. 6B shows an observation of a
position on the separator 24 on the cathode plate 20 side, the
position being opposed to the position where the iron-based foreign
bodies were placed on the cathode plate 20, in which the iron-based
foreign bodies were observed diffused in a larger area, leaving a
stain. FIG. 6C shows an observation of a position on the separator
24 on the anode plate 22 side, the position being opposed to the
position where the iron-based foreign bodies were placed on the
cathode plate 20, in which the iron-based foreign bodies were
observed diffused in a larger area, leaving a stain. FIG. 6D shows
an observation of a position on the anode plate 22, the position
being opposed to the position where the iron-based foreign bodies
were placed on the cathode plate 20, in which the iron-based
foreign bodies were observed diffused in a larger area, leaving a
stain.
[0067] Based on the result observed with the example, it was
confirmed that the iron-based foreign bodies in the battery 14 were
melted and diffused, and no deposition of iron-based foreign bodies
which reaches from the anode plate 22 to the cathode plate 20 was
observed.
Comparative Example
[0068] FIG. 7 is a flowchart explaining a procedure of a
manufacturing method for a nonaqueous electrolyte secondary battery
in which the battery fixing step (S16) and the holding step (S18),
which correspond to the space reducing step, were not performed.
The comparative example was carried out following the procedure
shown in FIG. 7. Specifically, following a procedure similar to
that shown in FIG. 5, respective steps from preparation (S10) to
electrolyte permeation (S14) were performed. Thereafter, without
performing the battery fixing step (S16) and the holding step
(S18), corresponding to the space reducing step, the pre-initial
charging process was terminated (S20).
[0069] FIG. 8 is a diagram explaining results of observation of the
cathode plate 20, the anode plate 22, and the separator 24 in the
comparative example. Similar to the example of the embodiment, in
order to verify the effects of the comparative example, disk-like
iron-based foreign bodies having a diameter of 100 .mu.m and
thickness of 20 .mu.m were placed in advance in the vicinity of the
cathode plate 20, following the procedure shown in FIG. 7. After
initial charging, in order to verify the effects of the comparative
example, the battery 14 was decomposed and structural components,
namely, the cathode plate 20, the anode plate 22, and the separator
24, were removed and observed with the above microscope.
[0070] FIG. 8A shows results of observation of the cathode plate
20, in which a trace where the disk-like iron-based foreign bodies
were placed could be observed. FIG. 8B shows an observation of a
position on the separator 24 on the cathode plate 20 side, the
position being opposed to the position where the iron-based foreign
bodies were placed on the cathode plate 20, in which the iron-based
foreign bodies were observed locally deposited, causing internal
short-circuiting. FIG. 8C shows an observation of a position on the
separator 24 on the anode plate 22 side, the position being opposed
to the position where the iron-based foreign bodies were placed on
the cathode plate 20, in which locally deposited iron-based foreign
bodies were observed. FIG. 8D shows an observation of a position on
the anode plate 22, the position being opposed to the position
where the iron-based foreign bodies were placed on the cathode
plate 20, in which locally deposited iron-based foreign bodies were
observed.
[0071] Based on the results observed with the comparative example,
it was confirmed that the iron-based foreign bodies in the battery
14 were melted, but deposited so as to reach from the anode plate
22 to the cathode plate 20.
[0072] Comparison between the example and the comparative example
shows that, while the iron-based foreign bodies were observed
melted and diffused but no deposition was observed in the example,
the iron-based foreign bodies were observed both melted and
deposited in the comparative example. From these observations, it
was recognized that internal short-circuiting, voltage drop
defects, and other defects, were probable in the comparative
example, but that the process of the example was effective in
suppressing occurrence of internal short-circuits, voltage drop
defects, and other defects.
Second Embodiment
[0073] In the above first embodiment of the present invention, the
battery 14 is fixed and held for a predetermined period of time.
Alternatively, the battery 14 may be heated while fixed, then
released from being fixed, and maintained for a predetermined
period of time. In this case, the battery heating step corresponds
to the space reducing step.
[0074] FIG. 9 is a flowchart explaining processes in a method of
manufacturing a nonaqueous electrolyte secondary battery, in which
the space reducing step is replaced by the battery heating step
(S17a). Specifically, respective steps until the battery fixing
step (S16) are performed, following a procedure similar to that
shown in FIG. 5. Then, the battery 14 is heated while fixed, using
the structure shown in FIG. 10 or FIG. 11 until the temperature
inside the battery 14 reaches 25.degree. C. to 60.degree. C.
(S17a). After the heating, the battery 14 is released (S17b). Then,
respective steps from the holding step (S18) to the pre-initial
charging process are performed, following a procedure similar to
that shown in FIG. 5.
[0075] FIGS. 10 and 11 are diagrams explaining devices having a
function of heating the battery 14. These devices can heat the
fixed battery 14 so that the electrodes 18 are brought to and
maintained in a closely contacting state, even after the battery 14
is released. With such configuration, a battery fixing device need
only be used for a shorter period of time to maintain a reliable
connection of the metallic foreign bodies 26 with the cathode plate
20. This can enable further cost reductions.
[0076] FIG. 10 is a diagram showing batteries 14 placed in the
processing device 10 within a high temperature furnace 38. The
batteries 14 arranged in the processing device 10 are placed in the
high temperature furnace 38, which is then operated to heat the
batteries 14 so that the temperature inside the batteries 14
increases to 25.degree. C. to 60.degree. C. The upper limit of the
temperature is set to 60.degree. C. in order to suppress
dissolution of electrolyte which is known to begin dissolving at
about 70.degree. C. or higher. The electrodes 18 are maintained in
a closely contacting state and remain so thereafter, even after the
batteries 14 are released from being fixed.
[0077] FIG. 11 is a diagram explaining a structure of a heating
function-equipped processing device 40. The heating
function-equipped processing device 40 includes a heating
function-equipped fixing element 42 and a heating control device
44. That is, the fixing element 12 of the above described
processing device 10 is replaced by the heating function-equipped
fixing element 42, and the heating control device 44 for
controlling the heating function-equipped fixing element 42 is
additionally provided. The heating function-equipped fixing element
42 has a function of heating the battery 14 to the above described
temperature of, for example, 25.degree. C. to 60.degree. C., while
applying a surface pressure between at least 0.1 MPa and 5.0 MPa to
the batteries 14. The heating control device 44 has a function of
controlling the heat temperature of the heating function-equipped
fixing element 42.
Third Embodiment
[0078] With iron-based foreign bodies, it is possible to process a
battery 14 being uncharged and in an open circuit state as
described above because the melting potential of iron is equal to
the cathode potential before initial charging. However, there may
be situations in which foreign bodies made of a material other than
iron, such as a stainless steel material represented by SUS304,
that is, stainless steel foreign bodies, may possibly be immixed in
a battery manufacturing process. In such a case, it is necessary to
apply a predetermined surface pressure to the battery 14 to keep
the stainless steel foreign bodies contacting the cathode plate 20
during a period after start of pouring electrolyte and before
initial charging, and moreover to keep the cathode potential lower
than the charge/discharge cathode potential so that the cathode
potential is intentionally set equal to the melting potential of
the stainless steel foreign bodies so that the stainless steel
foreign bodies melt.
[0079] For example, stainless steel foreign bodies are known to be
passivated at a potential lower than that required for foreign
bodies made of iron. Therefore, if 18% of the mass of Cr is
comprised of stainless steel foreign bodies, the cathode potential
is adjusted to -0.25 v to +0.25 v according to the Standard
Hydrogen Electrode Reference (2.8 v to 3.2 v according to the
Li/Li.sup.+ Reference) and so held.
[0080] FIG. 12 is a flowchart explaining processes of a method of
manufacturing a nonaqueous electrolyte secondary battery when the
cathode potential is adjusted and so held. In this method,
respective steps up to the battery fixing step (S16) are performed
following a procedure similar to that shown in FIG. 5, and
thereafter the cathode potential is adjusted and maintained using a
power source device 36 having the structure shown in FIG. 13 (S19).
In this embodiment, the state of holding corresponds to a state in
which a surface pressure is maintained at a predetermined value and
the cathode potential is kept at a potential which is lower than
the charge/discharge cathode potential and at which metallic
foreign bodies 26 melt. After maintenance of the potential is
halted, a pre-initial charging process is terminated (S20),
similarly as in FIG. 5.
[0081] FIG. 13 is a diagram explaining structures of the power
source device 36, the processing device 10, and the battery 14. The
power source device 36 can be connected to the cathode terminal 21
and the anode terminal 23 of the battery 14, and has a function of
adjusting and maintaining the cathode potential. In order to melt
the stainless steel foreign bodies, the power source device 36 has
a function of adjusting and maintaining the cathode potential while
the battery is kept fixed. For adjustment, the cathode potential
can be adjusted to -0.25 v to +0.25 v according to the Standard
Hydrogen Electrode Reference. Alternatively, the battery voltage
may be adjusted based on the relationship between the battery
voltage and the desired cathode potential. The holding time is set
to between at least one hour and 35 hours for the reasons described
above.
Fourth Embodiment
[0082] In the first embodiment, the battery fixing step is
described as a step corresponding to the space reducing step, while
the battery fixing step (S16) is a step at which a surface pressure
is externally applied to the battery 14. However, according to the
method described here, the pressure inside the battery 14 is
reduced to thereby eliminate the space "d" in the electrodes 18 so
that the metallic foreign bodies 26 contact the cathode plate
20.
[0083] This procedure includes a battery depressurizing step
instead of the battery fixing step (S16) corresponding to the space
reducing step in the flowchart shown in FIG. 5. That is, respective
steps until electrolyte permeation (S14) are performed.
[0084] Then, instead of carrying out the battery fixing step (S16)
corresponding to the space reducing step, the battery 14 is
depressurized using the structure shown in FIG. 14 or FIG. 15,
which are described below. Thereafter, respective steps from the
holding step (S18) to termination of the pre-initial charging
process (S20) are performed.
[0085] FIGS. 14 and 15 are diagrams explaining the operation and
structure of a device having a function of applying a surface
pressure to the electrodes 18. In a method of manufacturing a
nonaqueous electrolyte secondary battery, a surface pressure
between at least 0.1 MPa and 5.0 MP may be applied to the battery
14 at the space reducing step (S16). In such a case, the device
shown in FIGS. 14 and 15 may be used instead of the processing
device 10.
[0086] FIG. 14 is a diagram explaining a structure for applying
surface pressure to the battery 14 using a vacuum furnace 30. Here,
five (for example) batteries 14 are placed in the vacuum furnace
30, and depressurized to between 10 kPa and 100 kPa, and surface
pressure is externally applied to the batteries 14. The batteries
14 are placed in the vacuum furnace 30 while the sealing valve 17
kept open, and then depressurized. Then, the sealing valve 17 is
closed while the batteries 14 remain depressurized, and the
batteries 14 are removed from the vacuum furnace 30. As a result,
an effect similar to that obtained with the configuration shown in
FIG. 4 can be attained.
[0087] FIG. 15 is a diagram explaining a structure for applying
surface pressure to the battery 14 using a high pressure furnace
34. Because the pressure of the high pressure furnace 34 can be
increased and maintained at a relatively high pressure, an effect
similar to that described with reference to FIG. 14 can be produced
using the high pressure furnace 34.
INDUSTRIAL APPLICABILITY
[0088] A processing device for a nonaqueous electrolyte secondary
battery and a manufacturing method thereof according to the present
invention are useful for nonaqueous electrolyte secondary batteries
and their manufacture because of their ability to melt and diffuse
metallic foreign bodies immixed in the nonaqueous electrolyte
secondary battery before performance of initial charging.
REFERENCE NUMERALS
[0089] 10 processing device, 11 frame, 12 fixing element, 13
pressing portion, 14 battery, 16 battery case, 17 sealing valve, 18
electrodes, 20 cathode plate, 21 cathode terminal, 22 anode plate,
23 anode terminal, 24 separator, 26 metallic foreign bodies, 30
vacuum furnace, 34 high pressure furnace, 36 power source device,
38 high temperature furnace, 40 heating function-equipped
processing device, 42 heating function-equipped fixing element, 44
heating control device.
* * * * *