Title: Electrolyte solution filling method and battery structure of lithium secondary battery
Abstract: Provided are a method for filling an electrolyte solution and a battery structure of a lithium secondary battery comprising an internal electrode body formed by winding a positive electrode, and a negative electrode, with a separator sandwiched therebetween around the outer periphery of a core, and an electrolyte solution to impregnate said internal electrode body; said method being excellent in productivity, and battery performance as well, and being characterized by an easy filling of an electrode solution, with minimization of excessive electrode solution in the battery, by virtue of the provision of an electrolyte solution injection opening in a specific position, through which the electrolyte solution is injected and extracting efficiently by using a nozzle for injection and/or extraction of electrolyte solution.
Patent Number: 6,858,342 Issued on 02/22/2005 to Nemoto, et al.
| Inventors:
|
Nemoto; Hiroshi (Nagoya, JP);
Kitoh; Kenshin (Nagoya, JP);
Enomoto; Akio (Chita-gun, JP)
|
| Assignee:
|
NGK Insulators, Ltd. (Nagoya, JP)
|
| Appl. No.:
|
106748 |
| Filed:
|
March 26, 2002 |
Foreign Application Priority Data
| Oct 13, 1998[JP] | 10-290832 |
| Nov 04, 1998[JP] | 10-313266 |
| Nov 25, 1998[JP] | 10-334291 |
| Current U.S. Class: |
429/72; 429/81; 429/170; 429/171; 429/185 |
| Intern'l Class: |
H01M 002//36; H01M 002//38; H01M 002//02; H01M 002//08 |
| Field of Search: |
429/94,170,171,181,72,80,81,185
|
References Cited [Referenced By]
U.S. Patent Documents
| 4663247 | May., 1987 | Smilanich et al.
| |
| 4767682 | Aug., 1988 | Dorogi et al.
| |
| 5015542 | May., 1991 | Chaney et al. | 429/56.
|
| 5017442 | May., 1991 | Watanabe et al. | 429/94.
|
| 5458993 | Oct., 1995 | Terao et al. | 429/94.
|
| 5525437 | Jun., 1996 | Freluche et al.
| |
| 5527644 | Jun., 1996 | Kita et al. | 429/247.
|
| 5571632 | Nov., 1996 | Teramoto | 429/94.
|
| 5896647 | Apr., 1999 | Shkuratoff.
| |
| 6071638 | Jun., 2000 | Fradin.
| |
| 6344292 | Feb., 2002 | Nemoto et al.
| |
| Foreign Patent Documents |
| 895 011 | Oct., 1953 | DE.
| |
| 0 660 431 | Jun., 1995 | DE.
| |
| 0 660 431 | Jun., 1995 | EP.
| |
| 0 771 040 | May., 1997 | EP.
| |
| 0 822 605 | Feb., 1998 | EP.
| |
| 0 913 874 | May., 1999 | EP.
| |
| 57-9074 | Jan., 1982 | JP.
| |
| 57-009074 | Jan., 1982 | JP.
| |
| 58-030072 | Feb., 1983 | JP.
| |
| 58-030073 | Feb., 1983 | JP.
| |
| 62-264563 | Nov., 1987 | JP.
| |
| 1-175176 | Jul., 1989 | JP.
| |
| 06-333599 | Dec., 1994 | JP.
| |
| 07-014609 | Jan., 1995 | JP.
| |
| 08-250084 | Sep., 1996 | JP.
| |
| 9-92241 | Apr., 1997 | JP.
| |
| 9-92338 | Apr., 1997 | JP.
| |
| 09-092238 | Apr., 1997 | JP.
| |
| 09-092250 | Apr., 1997 | JP.
| |
| 09-092335 | Apr., 1997 | JP.
| |
| 10-050347 | Feb., 1998 | JP.
| |
| 10-083805 | Mar., 1998 | JP.
| |
| 10-125347 | May., 1998 | JP.
| |
| 10-144339 | May., 1998 | JP.
| |
| 10-233233 | Sep., 1998 | JP.
| |
| 10-270048 | Oct., 1998 | JP.
| |
| 11-111259 | Apr., 1999 | JP.
| |
| 11-195425 | Jul., 1999 | JP.
| |
| 11-339758 | Dec., 1999 | JP.
| |
| 2000-082486 | Mar., 2000 | JP.
| |
Other References
Patent Abstracts of Japan, vol. 006, No. 067 (E-104), Apr. 28, 1982 & JP 57
009074 A (Matsushita Electric Ind. Co. Ltd.), Jan. 18, 1982.*
Patent Abstracts of Japan, vol. 007, No. 107 (E-174), May 11, 1983 & JP 58
030073 A (Matsushita Electric Ind. Co. Ltd.), Feb. 22, 1983.*
Patent Abstracts of Japan, vol. 007, No. 107 (E-174, May 1983 & JP 58
030072 A (Matsushita Denki Sangyo KK), Feb. 22, 1983.*
Patent Abstracts of Japan, vol. 006, No. 136 (E-120), Jul. 23, 1982 & JP 57
060674 A (Shin Kobe Electric Mach Co. Ltd.), Apr. 12, 1982.*
Patent Abstracts of Japan, vol. 006, No. 077 (E-106), May 14, 1982 & JP
015368 A (Shin Kobe Electric Mach Co. Ltd.), Jan. 26, 1982.*
Patent Abstracts of Japan, vol. 012, No. 150 (E-606), May 10, 1988 & JP 62
264563 (Xuasa Battery Co. Ltd.), Nov. 17, 1987.*
U.S. Appl. No. 09/819,329, filed Mar. 28, 2001, Enomoto et al.
U.S. Appl. No. 09/870,372, filed May 30, 2001, Nemoto et al.
|
Primary Examiner: Ryan; Patrick
Assistant Examiner: Mercado; Julian
Attorney, Agent or Firm: Burr & Brown
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a divisional application of U.S. application Ser. No.
09/415,164 filed Oct. 8, 1999, now allowed, the entirety of which is
incorporated herein by reference.
Claims
What is claimed is:
1. A lithium secondary battery comprising:
an internal electrode body comprising a positive electrode, a negative
electrode, and a separator positioned between said positive electrode and
said negative electrode, said electrode body being wound around the outer
periphery of a core, and
an electrolyte solution impregnating said internal electrode body;
wherein an electrolyte solution injection opening is provided in an
extended position of a through hole of the core on one end surface of a
case for said battery, or an electrolyte solution injection opening is
integrally formed with an external terminal in an extended position of
said through hole of the core on one end surface of a case for said
battery.
2. The lithium secondary battery according to claim 1, wherein said
electrolyte solution injection opening is disposed in the center of one
end surface of the case for said battery.
3. The lithium secondary battery according to claim 1, wherein said
electrolyte solution injection opening is closed from outside with
screwing, pressure fitting or filling with a sealing material.
4. A lithium secondary battery comprising:
an internal electrode body comprising a positive electrode, a negative
electrode, and a separator positioned between said positive electrode and
said negative electrode, said electrode body being wound around the outer
periphery of a core, and
an electrolyte solution impregnating said internal electrode body,
wherein the core is fixedly sandwiched between caps for sealing the end
surfaces of a battery case, and wherein said core is made of an insulating
material or a metal, the surfaces of which are coated with an insulating
material.
5. The lithium secondary battery according to claim 4,
wherein either hole portions or slits are provided on at least one end
portion of the core.
6. A lithium secondary battery comprising:
an internal electrode body comprising a positive electrode, a negative
electrode, and a separator positioned between said positive electrode and
said negative electrode, said electrode body being wound around the outer
periphery of a core, and
an electrolyte solution impregnating said internal electrode body, wherein
the core is fixedly sandwiched between caps for sealing the end surfaces
of a battery case, and wherein one of said caps is provided with an
electrolyte solution injection opening in an extended position of a hollow
portion in said core.
7. The lithium secondary battery according to claim 6, wherein a recessed
portion is formed in an inner center portion of an end surface of a case
for said battery where an electrolyte solution injection opening is not
formed, or a recessed portion is provided by making said center portion of
an end surface a convex shape outwardly.
8. A lithium secondary battery comprising:
an internal electrode body comprising a positive electrode, a negative
electrode, and a separator positioned between said positive electrode and
said negative electrode, said electrode body being wound around the outer
periphery of a core, and
an electrolyte solution impregnating said internal electrode body,
wherein insulating members are disposed at both ends of the core to extend
the length of the core, and the core and the insulating members are
fixedly sandwiched between caps to seal end surfaces of a case for said
battery.
9. The lithium secondary battery according to claim 8, wherein one of said
caps is provided with an electrolyte solution injection opening in an
extended position of a hollow portion in said core or said insulating
members.
10. The lithium secondary battery according to claim 8, wherein either hole
portions or slits are provided on at least one end portion of the core or
at least one of said insulating members.
11. The lithium secondary battery according to claim 10, wherein a recessed
portion is formed in an inner center portion of an end surface of a case
for said battery where said electrolyte solution injection opening is not
formed, or a recessed portion is provided by making said center portion of
an end surface a convex shape outwardly.
Description
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
This invention relates to a method for filling an electrolyte solution into
a lithium secondary battery; said method capable of filling electrolyte
solution into a case and extracting an excessive electrolyte solution
therefrom, and sealing easily a battery, thereby the simplification of
fabrication process, the reduction in the production cost, and the
improvement in compaction of energy density can be achieved, and a battery
structure of the lithium secondary battery; said battery having a reduced
current collection resistance from positive electrodes and negative
electrodes, and a narrowed deviation in the fluctuation in the resistances
among the tabs engaged in current collection as well, and having a simple
structure as a battery so as to enable easier assembly of the battery and
to effectuate the aforementioned method for filling an electrolyte
solution into the case easily.
In recent years, the lithium secondary battery has been widely used as a
power battery for handy electronic appliances such as personal handy phone
systems, video tape recorders, notebook-type computers, or the like.
Additionally, in the case of a lithium secondary battery, a single battery
can generate a voltage of approximately 4 V, and this level of voltage is
higher than that of conventional secondary batteries such as a lead
battery, or the like, and its energy density is also high. Thus, much
attention has been paid to it not only as a power source for the
aforementioned handy electronic appliances, but also as a motor driving
power source for an electric vehicle (EV) or a hybrid electric vehicle
(HEV), of which penetration among the general public is being earnestly
planned as a low-pollution vehicle due to the recent development in the
environmental problems.
In a lithium secondary battery, in general, a lithium-transition metal
compound oxide as a positive active material, a carbon material as a
negative active material, and an organic electrolyte solution obtained by
dissolving a Li-ion forming electrolyte in an organic solvent as an
electrolyte solution are used. And, for an internal electrode body as a
portion where battery reaction is carried out, various types are
available.
For example, in a coin-shaped battery with a small capacity, a
sandwiched-type internal electrode body in which a separator is sandwiched
between a positive electrode and a negative electrode is used. Here, as
the positive electrode and the negative electrode, those that are formed
in a disk like shape, or in a coin like shape by subjecting positive
material and negative material to press-forming processing or the like,
respectively are suitably used.
As one example of preferable structures of internal electrode bodies to be
used for a lithium secondary battery with a comparatively large capacity
usable for an EV, or the like, as is shown in FIG. 18, there is given a
wound-type internal electrode body 1 being formed by winding around the
outer periphery of a hollow cylinder-shaped core 6 a positive electrode 2
having one or more tabs 5 for current collection and a negative electrode
3 having one or more tabs 5 for current collection, in such a manner that
the positive electrode 2 and negative electrode 3 are not brought into
direct contact with each other, by sandwiching a separator 4 between the
positive electrode 2 and the negative electrode 3. Here, in general, the
length of the core 6 is set equal to the width of the positive electrode 2
and that of the negative electrode 3. Incidentally, there is also proposed
a battery using a laminate-type internal electrode body formed by
laminating alternately via separators 4 a plurality of positive electrodes
2 and negative electrodes 3 having been prepared by cutting the
above-mentioned positive and negative electrodes, respectively into those
with small areas.
Now, in any case where any of the above-described structures is adopted as
an internal electrode body, it is necessary to soak the internal electrode
body in an electrolyte solution. Here, as an electrolyte solution, a
non-aqueous electrolyte solution (hereinafter to be referred to as an
"electrolyte solution"), which is obtained by dissolving a lithium
electrolyte in an organic solvent, is used. In the case of a coin-shaped
battery, for example, there is employed such a technique that a
predetermined quantity of an electrolyte solution is injected by using a
metering pump, or the like, under a reduced atmosphere and the battery
case is sealed so as to fill the case with the electrolyte solution, after
the internal electrode body is mounted inside a battery case. In addition,
even in the case where a wound-type internal electrode body is used, a
similar technique is used as long as a small capacity battery such as a
common 18650 (with a diameter of 18 mm.phi. and a length of 65 mm)
cylinder-type battery is produced. In such a method, an excessive amount
of electrolyte solution that is not actually required is liable to be
filled therein.
Since electrolyte solution is generally expensive, the percentage of
battery costs attributable to electrolyte solution is not small.
Nevertheless, in the case of those batteries having a small capacity, the
reasons why the aforementioned method for filling an electrolyte solution
is adopted are considered that:
the space where excessive electrolyte solution (hereinafter to be referred
to as a "excessive electrolyte solution") is filled in is small in the
absolute value, the cost for the electrolyte solution used for filling
such a small space is considered not to be so high since the internal
electrode body does not occupy much space in the interior of the battery
in a small capacity battery;
a desired battery performance is obtainable if a minimum required quantity
of an electrolyte solution is filled in a case since the area of reaction
in the battery is small; and
an introduction of a step for recovering excessive electrolyte solution
results in raising production costs unintentionally, etc.
On the contrary, in the case of a battery having a relatively large
capacity (hereinafter to be referred to as a "large capacity battery") to
be applied to an EV, or the like, the size of a battery itself will
necessarily become large. In such a case, the use of the wound-type
internal electrode body 1 shown in FIG. 18 requires a larger space for
housing the current collection tabs 5 at both ends or one end of the case
for the battery. Additionally, since a hollow cylinder-shaped type core is
generally used for the core 6, the absolute volume to be occupied by these
spaces inside the case for the battery becomes large.
Accordingly, if an electrolyte solution is filled into a case for a large
capacity battery by using a technique similar to that for the
above-described small capacity battery, an expensive electrolyte solution
is used not in an economic manner. This would bring about an increase in
the production cost and a reduction in the energy density of the battery,
as well. Furthermore, it is not preferable, from the viewpoint of
durability, for metal members other than the internal electrode body,
sealing members of the battery case, and the like, to be always in contact
with the electrolyte solution since it causes often the leakage of the
electrolyte solution, the corrosion of said members, or the like.
On the other hand, the electrolyte solution is required to fill in an
amount sufficient to impregnate the internal electrode body properly even
in the case of a large internal electrode body having a large battery
area. And in the case where this is not fulfilled, not only the desired
battery performance cannot be attained, but also the fluctuation in the
performance of respective batteries will take place. Accordingly, in the
case of a large capacity battery, it is preferable to impregnate the
internal electrode body thoroughly in an excessive amount of an
electrolyte solution under a reduced atmosphere, and thereafter the
excessive electrolyte solution is removed.
Therefore, in a large capacity battery, if one wants to fill an electrolyte
solution by employing a technique similar to that for a small capacity
battery, the following steps would be given as an example:
as shown in FIG. 17, at first, a case for battery 65 with one end portion
61 having been sealed is disposed in a globe box or the like with the
sealed end 61 being placed downward,
then an electrolyte solution transferred from another end portion 62 of the
case which is open at the upper portion with a metering pump or the like
is injected by using a nozzle 63 or the like after reducing the atmosphere
of the globe box in such a manner that the electrolyte solution is
injected intermittently until the liquid surface does not go down so as to
subject the internal electrode body to the impregnation treatment with the
electrolyte solution for a predetermined period of time,
the interior of the globe box or the like is purged with inert gas,
thereafter the excessive electrolyte solution is drained by putting the
case for battery 65 upside down, and
finally the end portion 62 which has been left open is sealed.
However, in the case of such a method that an electrolyte solution is
supplied from the upper portion of the case for the battery, the
impregnation of an electrolyte solution starts mainly from the upper
portion of the internal electrode body under a reduced atmosphere.
Therefore, bubbles generated in the lower portion of the internal
electrode body will hardly be liberated form the upper portion of the case
for the battery. Accordingly, it will require holding the resultant for a
long period of time under reduced atmosphere. In this case, if an organic
solvent being highly volatile is solely used for an electrolyte solution,
the evaporation of the solvent will bring about a problem in that the
density of electrolyte fluctuates from product to product. In addition, in
the case where a highly volatile organic solvent is mixed with one or more
other non-volatile solvent or the like for use, the predominant
evaporation of the volatile organic solvent causes the deviation in mixing
ratio from product to product. This would bring about a problem in that
the density of the electrolyte fluctuates from product to product. Anyhow,
in any one of these cases, the full extent of exertion of the performance
of electrolyte solution cannot be expected.
Moreover, in the case of a large capacity battery, due to a big shape of
the battery itself, the sealing of an open end of the case for the battery
within the globe box or the like would bring about various problems. That
is, an enlargement of the globe box or the like is required since a
sealing device should be installed within the globe box or the like.
Furthermore, the enlargement of the globe box results in the decrease in
the degree of the reduction of the interior pressure thereof, the
enlargement of the vacuum pump, and the mass consumption of purge gas or
the like. Thus, it is not realistic.
Therefore, the present inventors have extensively studied, in particular,
the simplification of a method for filling an electrolyte solution in the
production of a large capacity battery. As a result, they reached the
present invention to be described later. Moreover, various studies have
been made at the same time so as to find out not only a battery structure
suitable for using the method of filling an electrolyte solution according
to the present invention, but also a battery structure capable of
improving the battery performance and productivity even in the case where
the method for filling an electrolyte solution according to the present
invention is not used.
One of the problems to be solved is the reduction in current collection
resistance from the internal electrode body and the reduction in
difference in current collection resistance of each tab. A tab is
connected directly with an external terminal of the battery, that is,
directly with an electrode terminal to extract current out from the
battery, or is connected with an internal terminal thereof, that is, a
terminal to which the tabs are intermediately connected collectively
inside the battery. Accordingly, in the case where the tabs are connected
with the internal terminal, it is necessary that the internal terminal is
made conductive to the external terminal to form a current path between
the tabs and the external terminal.
As a method for forming the conductive state between the tabs and the
external terminal, there is proposed, for example, in JP-A-9-92338, a
lithium secondary battery 27 in which a series of flexible leads
(equivalent to "tabs" in meaning) 37 is sandwiched between the electrode
terminal 38 and the hold-down hardware 33, forming a warping shape as
shown in FIG. 16; said leads 37 being welded to the electrode terminal 38
by laser beam. In this lithium secondary battery 27, the electrode
terminal 38 is attached to a cap (ceiling plate) 29 by using a nut 34, and
the cap 29 is provided with not only electrolyte solution injection
opening 32 which is to be sealed with a blank cap 30 but also a pressure
release valve 26.
However, in case of the lithium secondary battery 27 disclosed in the
JP-A-9-92338, the leads 37 may be sandwiched with the hold-down hardware
33 at any position of the outer periphery of the electrode terminal 38; as
a corollary, the leads 37 disposed in the inner periphery of the internal
electrode body 35 become long, and, on the contrary, the leads 37 disposed
in the outer periphery become short. In his case, since the quantity of
current flow in each lead 37 is different due to the difference in
resistance of each lead 37, depending upon its length, there is a fear
that the uniformity in the battery reaction cannot be maintained when used
as a battery for an EV which requires the frequent flow of a large
current.
In addition, since the leads 37 may be attached to any position of the
outer periphery of the electrode terminals 38 with laser welding, and the
structure at the end portion of the battery is complicated and various
parts are installed therein, as shown in FIG. 16, thus the work efficiency
(productivity) of the battery assembly is considered to be not necessarily
good.
Moreover, a battery 27 disclosed in JP-A-9-92338 has the configuration at
both ends, as shown in FIG. 16. It is stated in the laid-open invention
that the injection of electrolyte solution is carried out by injecting
electrolyte solution from one end of the injection opening 32 for
electrolyte solution, while keeping the interior of the battery 27 under a
reduced pressure by deaerating from the other end of the injection opening
32 for electrolyte solution, and this step should be repeated several
times. However, it is not advantageous to assemble a battery with the
repetition of such steps several times. Moreover, it is not advantageous
to provide both ends with the injection openings 32 for electrolyte
solution which eventually will be sealed since the leakage of the
electrolyte solution and the decrease in air tightness are liable to
occur.
Furthermore, the battery disclosed in JP-A-9-92338 has been proposed to
prevent damage to leads 37 under severe vibrations when the battery is
used as for the battery for an EV. Therefore, it proposes to use a
flexible material for lead 37. At the same time, it refers to the
reduction in internal resistance by virtue of a broadened welded portion
between the leads 37 and the electrode terminals 38 formed by laser
welding, however, it is quite silent about the reduction in fluctuation in
the resistance among respective leads 37.
Another problem is how to secure the durability against vibration during
driving since the durability is an essential requirement in the case of a
battery for an EV. For example, when the internal electrode body vibrates
or moves inside the battery case, there is a fear that the electrode
active materials coated on the positive electrode and the negative
electrode are peeled, thereby the battery capacity is reduced.
Furthermore, it is not preferable since there is a fear of formation of a
short circuit between the positive electrode and the negative electrode
due to the peeled electrode active materials. Moreover, the end surface of
the internal electrode body is apt to be deformed from an initial plain
shape into a shape such as spiral waves or the like due to vibration, and
such a deformation of the internal electrode becomes a cause of an
unfavorable uneven battery reaction.
Therefore, there is proposed, in JP-A-9-92241, a battery 28 having such a
structure that, as shown in FIG. 15, an electrode pole 25 having its lower
surface covered with insulator collar 39 is inserted into a hollow portion
of a cylindrical core 31 around which an electrode spiral body 36
(equivalent to the internal electrode body 1) is formed, and said
electrode pole 25 is fixed to a cap 29 with a nut 34. In addition, there
is proposed, in JP-A-1-751-76, a battery structure in which an internal
electrode body formed by inserting a bar-shaped insulating body into a
portion formed by using a tentative core which was removed thereafter is
housed in the battery case.
However, in the case of the electrode spiral body 36 proposed in
JP-A-9-92241, the inner peripheral surface of the battery case 19 and the
electrode pole 25 function only as a stopper so as to suppress the
movement of the electrode spiral body 36 in the diameter direction.
However, it does not suppress the movement in the diameter direction, and
it has such a structure that the movement in the longitudinal direction of
the electrode spiral body 36 takes places easily in the distance of the
gap with the electrode pole 25. If the movement to the longitudinal
direction of the electrode spiral body 36 takes place, the electrode
spiral body 36 collides with the electrode pole 25, which would damage the
leads 37 (equivalent to tabs 5) attached on the end surfaces of the
electrode spiral body 36. Moreover, it is considered that it is liable to
receive such damage that the electrode active material is peeled, etc. at
the end portions of the electrode spiral body 36.
Furthermore, in case of the invention disclosed in JP-A-1-175176, it is not
formed in such a structure that the movement in the longitudinal direction
of the internal electrode body is suppressed. This is because the internal
electrode body is fixed by pressure formed between a solid bar of an
insulator inserted into the inner peripheral surface of the battery case,
and the core of the internal electrode body. Thus, no positive attempt has
been made hitherto so as to suppress the movement in the longitudinal
direction since much attention has been given to the fixation of the
internal electrode body in the diametrical direction.
SUMMARY OF THE INVENTION
The present invention has been made so as to solve problems of the prior
art mentioned above. Thus, the present invention is aiming to minimize the
amount of the excessive electrolyte solution to be filled inside the
battery on the occasion of forming a comparatively large capacity battery.
Moreover, the present invention is aiming to provide a simple method for
filling an electrolyte solution, and provide a battery structure capable
of operating said filling method easily. Furthermore, the present
invention is aiming to attain improvement in the battery performance such
as reduction in current collection resistance and improvement of
anti-vibration performance.
That is, one of the aspects of the present invention is directed to a
method for filling an electrolyte solution into a lithium secondary
battery comprising an internal electrode body formed by winding a positive
electrode, and a negative electrode, with a separator sandwiched
therebetween around the outer periphery of a core, and an electrolyte
solution to impregnate said internal electrode, which comprises the steps
of:
inserting a tip of a nozzle for injecting said electrolyte solution in such
a depth that at least it reaches a position on an end surface of said
internal electrode body located on an opposite side through a through hole
of said core and an electrolyte solution injection opening being provided
in an extended position of said through hole on one end surface of the
battery, or an electrolyte solution injection opening being integrally
formed with an external terminal in an extended position of the through
hole of the core on one end surface of the battery,
injecting the electrolyte solution until at least the internal electrode
body is immersed, and
thereafter extracting an excessive electrolyte solution remaining inside
the battery by using a nozzle for extraction of electrolyte solution.
The method for filling an electrolyte solution of the present invention is
preferably used in a battery where the electrolyte solution injection
opening is disposed in the center of one end surface of the battery and/or
the core is disposed in the center of the battery. In addition, one nozzle
may be used as a nozzle for injection of electrolyte solution and a nozzle
for extraction of electrolyte solution as well. It is preferable to insert
the tip of the nozzle for injection of electrolyte solution or that of the
nozzle for extraction of electrolyte solution in such a manner that it
reaches the other end of the battery to implement injection or extraction
of electrolyte solution under this state. In this case, if a recessed
portion is provided in the inner center of the other end of the battery,
or if a recessed portion is provided by forming the center portion of the
other end of the battery in a convex shape outward, an excessive
electrolyte solution remaining in this recessed portion is easily
extracted by a nozzle for extraction of electrolyte solution.
After extraction of the excessive electrolyte solution, the electrolyte
solution injection opening is enclosed from outside with screwing or
pressure fitting or filling with a sealing material to implement sealing
of the battery easily. Moreover, the assembly work of the battery becomes
preferably good, if the electrolyte solution is extracted and/or injected
by using a pipe as a body member of the battery case after the battery is
sealed by subjecting both ends of the pipe to caulking processing in order
to occlude the ends of the pipe with the cap. The method for filling an
electrolyte solution of the present invention is suitably applied to a
battery having a capacity of 2 Ah or more.
Now, as a first embodiment of a battery structure according to the present
invention, there is provided a battery structure of a lithium secondary
battery comprising an internal electrode body formed by winding appositive
electrode, and a negative electrode, with a separator sandwiched
therebetween around the outer periphery of a core, and an electrolyte
solution to impregnate said internal electrode body;
wherein an electrolyte solution injection opening is provided in an
extended position of the through hole of the core on one end surface of
the battery, or an electrolyte solution injection opening is integrally
formed with an external terminal in an extended position of the through
hole of the core on one end surface of the battery.
In this first battery structure, the electrolyte solution injection opening
is preferably disposed in the center of one end surface of the battery
and/or the core is preferably disposed in the center of the battery. In
addition, it is preferable that the electrolyte solution injection opening
preferably may be sealed from outside with screwing or pressure fitting or
filling with a sealing material.
In addition, as a second battery structure according to the present
invention, there is provided a battery structure of a lithium secondary
battery comprising an internal electrode body formed by winding a positive
electrode, and a negative electrode, with a separator sandwiched
therebetween around the outer periphery of a core, and an electrolyte
solution to impregnate said internal electrode body,
wherein the core is sandwiched between caps for sealing the end surfaces of
the battery case, and is fixed.
And in this second battery structure, insulating materials or metal
materials the surfaces of which are covered with insulating materials are
preferably used as a core.
Moreover, as a third battery structure according to the present invention,
there is provided a battery structure of a lithium secondary battery
comprising an internal electrode body formed by winding a positive
electrode, and a negative electrode, with a separator sandwiched
therebetween around the outer periphery of a core, and an electrolyte
solution to impregnate said internal electrode body,
wherein insulating members are disposed at both ends of the core to extend
the length of the core, and the core as well as the insulating member are
sandwiched between caps to seal the end surfaces of the battery case, and
are fixed.
In these second and third battery structures where the core, and the like
are sandwiched between caps, it is preferred to provide an electrolyte
solution injection opening on one of the caps at the position extended
from the hollow portion of the core or the insulating member. At this
time, it is preferred that hole portions or slits are provided on the end
portions of the core or the insulating members. It is also preferred to
provide a recessed portion in the inner center portion of the end surface
of a case for battery where the electrolyte solution injection opening is
not formed. It is also preferred to provide a recessed portion by forming
a convex shape outwardly on the center portion of the end surface.
Incidentally, such an arrangement to provide a recessed portion is
suitably applied to the first battery structure, too.
Next, as a fourth battery structure according to the present invention,
there is also provided a battery structure of a lithium secondary battery
comprising an internal electrode body formed by winding a positive
electrode, and a negative electrode, with a separator sandwiched
therebetween around the outer periphery of a core, and an electrolyte
solution to impregnate said internal electrode body,
wherein one collective connection portion is provided in one internal
terminal to connect a plurality of tabs together in one place, and the
collective connection portion is positioned within an extended range in
the axial direction of the core covering from the outer periphery of the
core to the outer periphery of the internal electrode body.
In the case of the fourth battery structure, it is preferred to provide one
collective connection portion capable of connecting a plurality of tabs
together in one place in one internal terminal; said collective connection
portion being positioned within a range which is extended, in the axial
direction of the core, from the outer periphery of the core to the outer
periphery of the internal electrode body. Moreover, it is also preferred
to form this collective connection portion in such a structure that a
plurality of tabs provided so as to be positioned on an approximately
straight line within a range, in the direction of diameter, which is
extended from the outer periphery of the core to the outer periphery of
the internal electrode body are collectively connected with one internal
terminal. The internal terminal is suitably disposed in the caps sealing
the end portions of the battery.
Moreover, a plurality of internal terminals is preferably disposed for the
positive electrode and the negative electrode, respectively. And the
collective connection portions of the internal terminals are preferably
placed in the extended position in the center direction of diameter from
the outer periphery of the core to reach the outer periphery of the
internal electrode body. The collective connection of tabs with the
internal terminal is preferably formed by means of welding, or caulking,
or an eyelet. The material for the internal terminal is preferably
produced from aluminum, aluminum alloy, copper or copper alloy.
Incidentally, if the caps sealing the end portions of the battery can act
as a path for electric current, the battery structure will not become
complicated and is preferable.
It is preferable to use commonly a battery case of which caps are employed
as the end surfaces of the battery, in any of the above-mentioned first to
fourth battery structures; said battery cases being preferably configured
in such a manner that the caps are sandwiched between the end portions of
the pipe, and the end portions of the pipe are sealed by caulking process.
In addition, between an end portion of the internal electrode body and a
cap, it is preferable to provide a necked portion in the inner periphery
portion of the pipe so as to suppress the movement of the internal
electrode body inside the battery. The battery structure of the present
invention is suitably applied to a battery with battery capacity of 2 Ah
and more, but there are no reasons to exclude application to a battery
using a wound-type internal electrode body with a lower battery capacity.
In addition, the battery structure of the present invention can be
suitably applied to a battery to be used as a motor driving power source
for an electric vehicle or a hybrid electric vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating one of the embodiments of the present
method for filling an electrolyte solution and that of the embodiments of
the present inventive battery structures.
FIG. 2 is an illustrative drawing of an example of a method for measuring
the period for the impregnation in the electrolyte solution.
FIG. 3 is a graph showing a relationship between the period of impregnation
time with electrolyte solution and the change of alternate impedance.
FIG. 4(a) and FIG. 4(b) are sectional views showing embodiments of a cap of
the bottom of a battery usable suitably for the present invention,
respectively.
FIG. 5(a), FIG. 5(b), and FIG. 5(c) are sectional views showing embodiments
of electrolyte solution injection openings usable suitably for the present
invention, respectively.
FIG. 6 is a sectional view showing another embodiment of a battery
structure of the present invention.
FIG. 7(a) and FIG. 7(b) are plan views showing embodiments of suitable
attachment position of tabs of the present invention, respectively.
FIG. 8(a) and FIG. 8(b) are sectional views showing embodiments of a place
for disposing collective connection portions in the internal terminals in
correspondence with the tab attachment position described in FIG. 7,
respectively.
FIG. 9 is a perspective view showing the structure of a wound-type internal
electrode body usable suitably for the present invention.
FIG. 10 is a sectional view showing still another embodiment of the battery
structure of the present invention.
FIG. 11 is a perspective view showing an embodiment of a core usable
suitably for the battery structure of the present invention.
FIG. 12 is a sectional view showing still another embodiment of the battery
structure of the present invention.
FIG. 13 is a perspective view showing another embodiment of a core usable
suitably for the battery structure of the present invention.
FIG. 14(a) and FIG. 14(b) are plan views showing embodiments of pressure
release valves suitably disposed in the battery structure of the present
invention, respectively.
FIG. 15 is a sectional view showing an example of the end structure in the
conventional lithium secondary battery.
FIG. 16 is a sectional view showing another example of the end structure in
the conventional lithium secondary battery.
FIG. 17 is an illustrative drawing showing an example of the conventional
method for filling electrolyte solution.
FIG. 18 is a perspective view showing a general structure of a wound-type
internal electrode body.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will next be described with
reference to the drawings, however, it goes without saying that the
present invention is not limited to those embodiments.
In the case of a lithium secondary battery of the present invention
(hereinafter referred to as a "battery"), as is previously explained with
reference to FIG. 18, there is employed a wound-type internal electrode
body 1 (hereinafter referred to as an "internal electrode body 1") which
is formed by winding around the exterior circumference of a core 6 a
positive electrode 2 and a negative electrode 3 to which tabs 5 are
respectively attached, with a separator 4 sandwiched therebetween so as to
prevent the positive electrode 2 and the negative electrode 3 from
contacting directly with each other.
The positive electrode 2 and the negative electrode 3 are produced,
respectively by coating electrode active material (hereinafter the term
"electrode active material" is used to refer to either positive active
materials or the negative active material) on both sides of the respective
electrode substrates; such electrode substrates (electricity collecting
body) being a foil made of aluminum, titanium, or the like for the
positive electrode 2, and a foil made of copper, nickel, or the like for
the negative electrode 3.
The positive active material to be used for forming the positive electrode
2 is not limited, and a lithium transition metal compound oxide such as
lithium cobalt oxide (LiCoO.sub.2), lithium nickel oxide (LiNiO.sub.2),
lithium manganese oxide spinel (LiMn.sub.2 O.sub.4), or the like is
suitably used, and it is preferable that carbon fine powder such as
acetylene black, or the like is added so as to improve conductivity. On
the other hand, as a negative active material, an amorphous carbon
material such as soft carbon or hard carbon, or highly graphitized carbon
powder such as artificial graphite is used.
Coating of electrode active material onto these respective electrodes is
carried out generally by coating, on both sides of the electrodes, a
slurry or a paste which is prepared by adding a solvent, a binder, or the
like to an electrode active material powder, by way of a roll coater
technique, or the like etc., and adhering the material thereon, thereby
the positive electrode 2 or the negative electrode 3 is formed.
In addition, the tabs 5 can be attached to a sideline of the electrode
substrate by means of ultrasonic welding, or the like at the time when the
positive electrode 2 and the negative electrode 3 are wound together with
the separator 4. At this time, the tabs 5 are preferably spaced at
approximately even distances so as to equalize the electricity collecting
area of each tab. In many cases, the material of the tabs 5 is the same as
that for the electrode substrate to which the tab 5 is attached.
A cylindrical member having a through hole (or internal vacant portion) 7
is preferably used as a core 6, and one prepared from any of various
materials such as metals, resins, and ceramics, can be used if it has a
sufficient mechanical strength and anti-corrosion resistance against an
electrolyte solution to maintain the battery structure.
In addition, as the separator 4, it is preferable to use a three-layer
structural material in which a polyethylene film (PE film) having lithium
ion permeability and micropores is sandwiched between porous polypropylene
films (PP films) having lithium ion permeability. This serves also as a
safety mechanism in which when the temperature of the internal electrode
body 1 is raised, the PE film is softened at about 130.degree. C. so that
the micropores are collapsed to suppress the movement of lithium ions,
that is, the battery reaction. And by sandwiching this PE film between the
PP film having a higher softening temperature, the PP film maintains its
shape and prevents the contact/short circuit between the positive
electrode 2 and the negative electrode 3 even in the case where the PE
film gets softened, and thus concrete control of the battery reaction and
reservation of safety becomes possible.
As the electrolyte solution, it is suitable to use a non-aqueous organic
electrolyte solution prepared by dissolving as an electrolyte at least one
member selected from lithium fluoride complex compounds such as
LiPF.sub.6, and LiBF.sub.4, and lithium halide such as LiClO.sub.4, etc.,
into an electrolyte solution selected from the group consisting of
carbonate type electrolyte solutions such as ethylene carbonate (EC),
propylene carbonate (PC), diethyl carbonate (DEC), and dimethyl carbonate
(DMC), and organic solvents such as .gamma.-butyrolactone,
tetrahydrofuran, acetonitrile, and the like or a mixture thereof.
The internal electrode body 1 having been prepared from the above-described
materials, and the like is housed inside the battery case in such a manner
that conductivity between the tab 5 and the external terminal of the
battery is secured, and the internal electrode body 1 is impregnated in
the non-aqueous electrolyte solution. And, thereafter, the battery case is
tightly sealed. Incidentally, as will be described later, since a battery
case made of a metal is suitably used, it is preferable that the outer
periphery of the internal electrode body 1 be configured to be covered by
the separator 4 in advance so as to attain insulation against the battery
case when the internal electrode body 1 is inserted in the battery case.
In addition, it is preferable that the outer periphery of the internal
electrode body 1 be fixed with an insulating tape, etc., so that the
internal electrode body 1 is not dissolved.
Next, an embodiment of the structure of a battery to be formed as described
above as well as the diagram illustrating the method for filling an
electrolyte solution of the present invention is shown in FIG. 1. Here, a
pipe 23 is used as the body member of the battery case for the battery 10,
and those made of metals, such as aluminum, or stainless steel are
suitably used.
Incidentally, while it is not shown in FIG. 1, in the case where the metal
pipe 23 is used, it is preferable to dispose an insulating film or a tube
to be sandwiched between the internal surface of the pipe 23 and the outer
periphery of the internal electrode body 1 so as to prevent conductivity
between the internal electrode body 1 and the pipe 23 as well as the
conductivity between the tab 5 and the pipe 23. Of course, as described
before, when the outer periphery of the internal electrode body 1 is
configured to be covered by the separator 4, the insulating film or the
tube is not necessarily required to be disposed between the internal
surface of the pipe 23 and the outer periphery of the internal electrode
body 1.
After the internal electrode body 1 is inserted into the pipe 23, a necked
portion 24 is formed at a predetermined position (around the end portion
of the internal electrode body 1) of the pipe 23 to suppress easily the
movement of the internal electrode body 1 in the longitudinal direction
inside the battery. In addition, with the tabs 5 being connected with the
internal terminals 14 respectively mounted onto the caps 21 and 22, the
pipe 23 is subjected to caulking processing so that the caps 21 and 22 are
used to seal both end surfaces of the pipe 23, making use of the formed
necked portions 24, thereby a battery case with a tight-sealed
configuration can be easily formed.
Here, the term "internal terminal" 14 means a member which tentatively and
collectively connects the tabs 5 to extract electricity from the internal
electrode body 1. Therefore, aluminum, aluminum alloy, copper, or copper
alloy is preferably used as a material for the internal terminal 14.
Incidentally, as the internal terminal 14 in the battery 10, a
rivet-shaped one to which the tabs 5 are pressure-attached for connection
is shown as an example, but there are no limitations on its shape.
In addition, the caps 21 and 22 are members for sealing the end portions of
the battery, and the same metal material as used for the internal terminal
14 such as aluminum or copper is suitably used, but an insulating material
such as a hard resin or a ceramic may also be used. Accordingly, in the
case where the cap 21 is made of a metal material, the internal terminal
14 and the external terminal 13 necessarily become conductive and the
current path is formed. In this case, the configuration of the end
portions of the battery is made simple and improvement in terms of the
battery assembly process is attained. On the other hand, in the case where
an insulating member is used as the caps 21 and 22, the internal terminals
14 and the external terminals 13 may be electrically connected through
outer periphery of the caps 21 and 22 or by providing conducting holes in
the caps 21 and 22, etc. But, in this case, such problems that the shapes
of components will get complicated and result in decrease in tightness of
sealing of the battery, etc., will be inevitably presented.
It goes without saying that the external terminal 13 is a member to be
disposed outside the battery 10 to extract the current of the battery
outward, and there are no limitations on kinds of materials if a metal
material is used. In the case where the caps 21 and 22 to be used are made
of a metal, it is preferable that the internal terminal 14 and the
external terminal 13 are firmly attached to the caps 21 and 22 by means of
welding, etc., so as to minimize the resistance of the connecting portion
of these members.
Incidentally, in the battery 10, a male screw configuration is used as the
one of the external terminals 13, and a female screw configuration is used
as the other thereof respectively. Adopting such a configuration is
advantageous to the extent that a plurality of batteries 10 can be
connected in series easily and firmly so as to minimize the contact
resistance.
Incidentally, the internal electrode body 1 is normally disposed at the
center (i.e., the center in the diameter direction) of the battery 10, and
at this time, the core 5 of the internal electrode body 1 is necessarily
disposed at the center of the battery 10. Therefore, in the battery 10,
the electrolyte solution injection opening 11 is disposed in a position on
the extended line of the through hole 7 of the core 6 in the cap 21 (this
cap 21 is placed at the upper party) forming one end surface. In addition,
the electrolyte solution injection opening 11 is integrally disposed at
the center portion of the cap 21 with the external terminal 13.
With the battery 10 having the above-described configuration, the tip of
the nozzle (hereinafter referred to as a "nozzle",) 12 to be used for the
injection and/or the extraction of the electrolyte solution may be
inserted so as to reach the other end of the battery 10 through the
electrolyte solution injection opening 11 and the through hole 7.
Incidentally, it is preferable to use one nozzle 12 for both of injection
and extraction of the electrolyte solution, but a nozzle for electrolyte
solution injection and a nozzle for electrolyte solution extraction may be
used separately.
Now, the battery 10 is placed in a space where atmospheric adjustment is
possible, such as a globe box, when the electrolyte solution is filled in.
As described above, since both ends of the battery 10 have already been
sealed with the caps 21 and 22, it is not necessary to seal the end
portions of the battery 10 after the injection of the electrolyte solution
is completed. Accordingly, it is not necessary to place a device, etc. to
implement the sealing work inside the globe box, etc., and thus, as the
globe box, etc., a small-sized one in accordance with the size of the
battery 10 may be used.
When the air of the interior of the globe box, etc. is evacuated with a
vacuum pump, the interior atmosphere of the battery 10 necessarily becomes
a vacuum since the battery 10 is provided with the electrolyte solution
injection opening 11. Here, it is preferable to make a degree of vacuum of
0.1 Torr (13.3 Pa), or less.
Under this state, the tip of the nozzle 12 is inserted through the
electrolyte solution injection opening 11, and next through the through
hole 7 of the core 6 to reach, at the shallowest, the opposite other end
(bottom) portion, in particular, the position of the end surface of the
internal electrode body 1, namely the position shown by the broken line
AA' in FIG. 1, and thereafter, the electrolyte solution is injected to get
at least the internal electrode body 1 dipped, i.e., to reach the level
shown by the broken line BB' in FIG. 1. Here, when the tip of the nozzle
12 is inserted
