JPH11204130A - Cylindrical secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the battery rupture of a cylindrical secondary battery. SOLUTION: This battery consists of a battery can 1, a wound plate group stored in the battery can 1, and a cylindrical center pin 4 arranged in a hollow hole 3 in the center of the wound plate group 2. The cylindrical center pin 4 is constituted of a cylindrical surrounding wall 4a and a partition wall 14, by which the inside of the cylindrical surrounding wall 4a is divided to form at least two cylindrical spaces 13a and 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylindrical secondary battery.

[0002]

2. Description of the Related Art As a cylindrical secondary battery, a positive electrode plate and a negative electrode plate are laminated in a battery can with a separator interposed therebetween and spirally wound, a non-aqueous electrolyte, A cylindrical center pin formed of a pipe having or not having a slit made of a material having compressive strength disposed in a hollow hole at the center of the wound electrode group; and disposed above the cylindrical center pin. A safety valve mechanism and a battery lid hermetically sealed on the battery can are known. (See, for example,
87958 and JP-A-6-187959. ). In the above-mentioned conventional secondary battery, since the cylindrical center pin is a pipe made of a material having compressive strength, the center hollow of the wound electrode group is prevented from being deformed. In the case where gas generated in the battery can due to overcharge or short circuit is introduced into the pipe through the bottom of the pipe and a slit is provided on a side surface of the pipe, the gas is further passed through the slit. Thus, the battery can be directly introduced into the pipe and moved through the pipe to the side of the safety valve mechanism, so that rupture due to a local increase in the internal pressure of the battery can be prevented. However, even with such a cylindrical secondary battery having a cylindrical center pin, when the battery is deformed or crushed by a large external pressure, the cylindrical center pin is also crushed, and the internal space is reduced. May be blocked. In this case, when the battery is deformed or crushed, the wound electrode group in the battery can is deformed, when the separator is broken and the wound positive electrode plate and the wound negative electrode plate are short-circuited,
Since the resistance value of the lithium composite oxide, which is the active material of the positive electrode plate, is relatively high, when the short-circuit current passes through the positive electrode plate, the temperature of the positive electrode plate easily rises, and the heat generated by the temperature increase An organic solvent inside the battery causes a decomposition reaction. Accordingly, when the pressure of the generated gas or such a short circuit occurs in the charged battery, the lithium composite oxide in the charged state is in an unstable state in which lithium is released as ions, and the temperature increases. There was a danger that the battery would burst under the pressure of the active oxygen gas generated by the decomposition. To prevent this danger, refer to Japanese Patent Application Laid-Open No. 8-250155.
In the publication, a cylindrical center pin made of a conductive material, having cutouts at both ends in the circumferential direction, and using an eccentric one is used. There has been proposed an arrangement in which a notch of a center pin is pierced into a group of wound electrode plates to suppress heat generation caused by a short-circuit current between a positive electrode and a negative electrode, thereby positively preventing battery rupture.

[0003]

Even if the cylindrical center pin is made of a material having compressive strength, the withstand pressure is limited, and as described above, when a large external pressure is applied to the battery, the external pressure is limited. It is inevitable that the battery cannot be tolerated and the battery is deformed or crushed, and the conventional cylindrical center pin is also crushed. Therefore, when the cylindrical center pin is crushed, a short circuit occurs between the positive and negative electrodes of the group of wound electrode plates in the battery can as described above, thereby generating heat,
It is unavoidable that the organic solvent decomposes and gas is generated, the gas accumulates in the battery, and the gas pressure rises sharply, eventually causing a risk of rupture of the battery. Therefore, even if the battery is crushed, it is preferable that gas can be exhausted through the cylindrical center pin to ensure the safety of the battery. In the invention of JP-A-8-250155 proposed to prevent such a danger, since the cylindrical center pin is eccentric, when the wound electrode group is slightly expanded during use, The cut end may inadvertently break through the separator on the inner peripheral surface side of the wound electrode plate group to cause a short circuit between the positive electrode and the negative electrode, thereby possibly shortening the battery life. In addition, since the notched end of the cylindrical center pin is limited to one place on the circumference sandwiching one slit, when the battery is crushed, the cylindrical center pin is moved to the position of the wound electrode plate group. Since the battery short-circuiting point caused by piercing the inner peripheral side surface is limited to one place, it is not sufficient to prevent the battery short-circuiting when the battery is crushed. Therefore, it is possible to prevent an inadvertent early short circuit when the wound electrode group is expanded by the cylindrical center pin, and when the battery is crushed, the wound electrode plate is formed by the cylindrical center pin. It is desirable that the battery be pierced at a plurality of locations on the inner peripheral side at a plurality of locations on the inner peripheral side of the group to cause a battery short circuit, so that the breakdown of the battery can be more easily and reliably prevented.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a cylindrical secondary battery which satisfies the above-mentioned needs. A positive electrode plate and a negative electrode plate housed in a wound electrode plate group formed by laminating through a separator and being spirally wound, and an electrolytic solution and an electrolytic solution are arranged in a hollow hole at the center of the wound electrode plate group. A cylindrical center pin, a safety valve mechanism disposed above the cylindrical center pin, and a battery lid hermetically sealed to the battery can. It is characterized by comprising a peripheral wall and a partition wall which forms a cylindrical space inside the cylindrical peripheral wall into at least two cylindrical spaces. Further, according to the present invention, the cylindrical center pin absorbs the expansion of the wound electrode group, and when the battery is crushed, the inner circumferential side surface of the wound electrode group is formed at a plurality of locations on the cylindrical peripheral side wall. The present invention provides a cylindrical secondary battery that can break through and cause a wide-ranging short circuit and more reliably cause the battery to rupture, wherein the cylindrical center pin is made of a conductive material and has an S-shaped or swirled end face. There is a feature. Furthermore, the present invention, when the battery is crushed, the inner peripheral side surface of the group of wound electrode plates by the cylindrical center pin is more diversified, that is,
Cylindrical type 2 that breaks through in a wide area and prevents battery rupture
The present invention provides a secondary battery, wherein the cylindrical center pin is made of a conductive material, and is provided with a polygonal cylindrical partition wall in the cylindrical peripheral wall.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a cylindrical secondary battery according to one embodiment of the present invention. The battery is a bottomed cylindrical battery can 1
And a wound electrode plate group 2 housed in the battery can 1, a cylindrical center pin 4 disposed in a hollow hole 3 at the center of the wound electrode plate group 2, and an upper end opening of the battery can 1 A battery cover 5 hermetically sealed, and a safety valve mechanism 7 made of an elastic body and disposed above a through hole 6 for exhaust provided in the battery cover 5 above the cylindrical center pin 4. . More specifically, the battery lid 5 is a circular metal lid substrate 5 having the ventilation hole 6 formed in the center.
a and a cap-shaped cap 5b welded to its upper surface.
The battery lid 5 includes a thin metal sheet 7a for piercing and tearing, such as aluminum foil, sandwiched between the metal lid substrate 5a and the cap-shaped cap 5b, and a top wall of the cap-shaped cap 5b. And a piercing needle 7b protruding downward from the safety valve mechanism 7. Thus, the battery lid 5 in which the peripheral edge of the metal lid substrate 5a is crimped on the upper surface of the flange of the cap-shaped cap 5b and the metal sheet 7a is sandwiched between the two plates 5a and 5b is formed. The battery lid 5 thus configured is connected to the battery can 1
The outer peripheral edge is provided on an annular step 1a formed on the inner peripheral surface of the upper end opening of the battery can 1 through an annular packing 8, and the upper peripheral edge 1b of the battery can 1 is caulked and connected to the outer peripheral edge. The sealed battery is provided with the mechanism 7. The wound electrode group 2 is a LiMn that absorbs lithium ions as an active material by charging and releases lithium ions by discharging.
A sheet-shaped positive electrode plate 2a manufactured using at least one of lithium composite oxides such as ₂ O ₄ and LiNiO _2; and a sheet-shaped negative electrode plate 2 manufactured using a carbon material as an active material.
b, a separator 2 made of elongate microporous polyethylene or the like interposed between the positive electrode plate 2a and the negative electrode plate 2b.
c) are stacked and spirally wound by a winding device. In the battery can 1, any known non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent is injected and impregnated into the wound electrode group. The outermost negative electrode plate 2b of the wound electrode plate group 2 is pressed against the inner peripheral surface of the battery can 1 to form the battery can 1 as a negative electrode terminal, while the positive electrode plate 2a is a lead derived therefrom. The wire 9 is led out upward through a hole 11 formed in an insulating plate 10 provided on the upper surface of the wound electrode plate group 2, and the upper end thereof is connected to the metal cover substrate 5 of the battery cover 5.
a, and the cap-shaped cap 5b of the battery lid 5 was formed as a positive electrode terminal. Thus, the safety valve mechanism 7
In the lithium battery provided with the above, when an excessive gas pressure is generated in the battery can 1, the metal sheet 7a expands upward and is punctured by the piercing needle 7b located above the metal sheet 7a. The gas is configured to be discharged to the outside through an exhaust hole 12 opened in the top wall. The safety valve mechanism 7 is not limited to the above-described formation, but may employ a disk reversal + switch method, a metal peeling method, or the like instead.

The cylindrical lithium 2 constructed as described above
The secondary battery is the same as the conventional one. According to the present invention,
A cylindrical center pin 4 disposed in a hollow hole 3 at the center of the winding electrode group 2 is connected to a cylindrical peripheral wall 4a and a cylindrical space 13 inside the cylindrical peripheral wall 4a by at least two cylindrical spaces 13.
a, 13a and a partition wall 14 formed by partitioning.

The cylindrical center pin 4 is made of a thermosetting resin material such as polyimide resin, phenol resin, epoxy resin, thermosetting polyester, or a thermoplastic resin material such as polyvinyl chloride resin or polypropylene, stainless steel, iron, It is formed by molding a metal such as nickel or a carbon material, or a conductive material obtained by mixing a metal powder, a carbon powder, and the like with a synthetic resin material. The configuration of the cylindrical center pin 4 shown in FIG. 1 is clearly shown in FIGS. 2 (a) and 2 (b).
The outer diameter of the cylindrical peripheral wall 4 a of the cylindrical center pin 4 is formed to be slightly smaller than the diameter of the circular hollow hole 3 at the center of the wound electrode plate group 2. Circular hollow hole 3
To be in close contact with the inner peripheral side surface of the wound electrode plate group. In addition, the cylindrical center pin 4 is usually formed by using a winding pin attached to a winding device to form a wound electrode plate group 2 and then pulling out the winding pin. The center pin 4 may be used to be inserted into the center hollow hole 3 to be formed, but may also be used as a winding pin of the winding device. The cylindrical center pin 4 shown in FIG. 2 is formed by integral molding into a single partition wall 14 passing through a cylindrical space 13 opened at the upper and lower ends of the cylindrical peripheral wall 4a.
, Whereby two semicircular cylindrical spaces 13 are provided.
a, 13a.

Thus, in the secondary battery shown in FIG. 1 having the above-mentioned center pin 4, the hollow center 3 of the wound electrode plate group 2 is prevented from being deformed by the cylindrical center pin 4. That is, the battery is crushed by the external pressure in the laminating direction (radial direction intersecting with the central axis) of the wound electrode plate group in the battery can 1, and the separator of the wound electrode plate group is broken and broken. Even when a short circuit occurs between the positive electrode plate and the negative electrode plate at a location, heat is generated, and gas is generated by decomposition of the organic solvent, a partition wall is formed in the cylindrical space 13 inside the cylindrical peripheral wall 4a of the cylindrical center pin. 1
4 and two cylindrical spaces 13a, 13a are formed in advance by the partition walls 14, so that they are less likely to be crushed than the conventional cylindrical center pin, and both of the two cylindrical spaces 13a are formed. Is reduced, the risk of losing gas permeability due to crushing is reduced, the gas generated inside the battery is guided to the safety valve mechanism 7 side through this cylindrical center pin, and the safety against battery rupture is enhanced. The wall thickness of the cylindrical center pin 4 of the present invention is the cylindrical peripheral wall 4a.
In general, both the partition walls 14 have a thickness of about 0.1 mm to 1 mm. The length of the cylindrical center pin is equal to or slightly higher than the height of the wound electrode plate group 2 when housed in the battery can 1 as shown in FIG. Are preferred.

The partition wall 14 does not need to pass through the central axis of the cylindrical peripheral wall 4a. Although not shown, the partition wall 14 is provided at a position slightly deviated from the central axis, and two semicircles having different sizes on both sides thereof. May be formed in the cylindrical spaces 13a, 13a. In addition, the partition wall 14 is formed as an integral molding that looks like a Y-shape or a cross when viewed from three or four end faces extending radially from the central axis to the inner peripheral surface of the cylindrical peripheral wall 4a. You may.

FIGS. 3 (a) and 3 (b) show a modification of the cylindrical center pin 4 of the present invention.
A vertical slit 4b is formed on one side of the cylindrical can that opens from the upper end to the lower end thereof and is parallel to the central axis. Gas generated in the battery can is transferred from the side of the cylindrical peripheral wall to the cylindrical space through the slit 4b. This facilitates direct inflow into 13a and exhaust.

FIG. 4 shows still another embodiment of the cylindrical center pin 4, in which the slit 4b is formed as an inclined slit 4b which is obliquely inclined with respect to the vertical direction. Thereby, even if the slit has a relatively small width, the introduction width in the circumferential direction of the gas generated from the inner peripheral side surface of the wound electrode plate group on the outer periphery can be increased. The slits 4b have a linear shape, that is, the notch edges 4c, 4c opposed to the slits 4b have a straight line shape. Although not shown, the notch edges 4c, 4c have, for example, a triangular shape. It may be a saw-tooth shape composed of a series of uneven portions. FIG.
In FIG. 4, one slit 4b is formed in only one of the cylindrical spaces 13a, 13a divided into two, but the slits are formed so as to communicate with the other cylindrical space 13a. It is needless to say that may be formed.
In addition, the width of the slit 4b generally ranges from 0.5 to 2 mm.

Next, a more detailed embodiment will be described together with a conventional example. Example 1 LiCoO ₂ as a positive electrode active material was applied to an aluminum foil as a current collector, dried and pressed, and a positive electrode for winding was formed. A carbon material as a negative electrode active material was formed into a copper foil as a current collector. A wound negative electrode plate that has been coated, dried and pressed is spirally wound via a separator formed by laminating a polyethylene film having a three-dimensional pore structure and a polypropylene film, and a wound electrode plate group Was prepared. An outer diameter of 4 mm, an inner diameter of 3 mm, and a height of 5
A stainless steel cylindrical center pin of the type shown in FIG. 2, which was produced by integrally forming a 4.5 mm cylindrical peripheral wall with a 1 mm thick partition wall inside, was closely inserted. Next, this electrode plate group is inserted into a bottomed cylindrical stainless steel battery can also serving as a negative electrode terminal, and EC (ethylene carbonate): PC
(Propylene carbonate): A mixed solvent prepared by mixing DMC (dimethyl carbonate) at a volume ratio of 1: 1: 2 to a total volume of 1 liter was mixed with 1 mol of LiPF ₆ as a solute.
A non-aqueous electrolyte solution obtained by dissolving the above is injected, a battery lid provided with a safety valve mechanism is applied to the battery can, and the battery can is airtightly caulked.
18650 size shown (diameter 18mm, height 65mm)
Thus, a cylindrical lithium secondary battery having a rated capacity of 5 hours and a rated capacity of 1300 mAh was produced. 200 batteries were produced, and a crush test was performed on 100 of the batteries by crushing using a round bar. However, none of the batteries had rupture accompanied by vigorous gas injection. Example 2 Instead of the stainless steel cylindrical center pin of Example 1,
A cylindrical lithium having the same 5-hour rate rated capacity as in Example 1 except that a stainless steel cylindrical center pin of the same dimensions as shown in FIG. 3 but having a vertical slit having a width of 1 mm was used. A secondary battery was manufactured. 200 batteries were produced. A crush test was carried out by crushing 100 of them with a round bar, and none of the batteries had a rupture accompanied by vigorous gas injection. Example 3 Instead of the stainless steel cylindrical center pin of Example 1,
A cylindrical lithium having the same 5-hour rate rated capacity as in Example 1 except that a stainless steel cylindrical center pin of the same dimensions as shown in FIG. 3 but having an inclined slit having a width of 1 mm was used. A secondary battery was manufactured. 200 batteries were produced. A crush test was carried out by crushing 100 of them with a round bar, and none of the batteries had a rupture accompanied by vigorous gas injection. Conventional Example 1 Example 1 having an outer diameter of 4 mm, an inner diameter of 3 mm, and a height of 54.5 mm.
Example 1 has the same dimensions as in Example 1 except that a conventional stainless steel cylindrical center pin lacking a partition is used instead of the cylindrical center pin of Example 1. In the same manner as in the above, a cylindrical lithium secondary battery having a rated capacity of 5 hours was produced. 200 batteries were manufactured, and 100 of the batteries were subjected to a crush test by crushing with a round bar. As a result, three batteries ruptured due to intense gas injection. That is, the occurrence rate of the rupture battery was 3%. Conventional Example 2 A 1 mm wide vertical slit is formed in the circumferential wall of a cylindrical center pin having the same dimensions as that used in Conventional Example 1, but a conventional stainless steel cylindrical center pin lacking a partition wall is used as an example. Except for using the cylindrical center pin 2 in place of the cylindrical center pin 2, it has the same configuration as that shown in FIG.
A cylindrical lithium secondary battery having an hourly rated capacity was produced.
200 batteries were manufactured, and a crush test was performed on 100 of the batteries by crushing the batteries with a round bar. As a result, eight batteries ruptured due to intense gas injection. That is, the occurrence rate of the rupture battery was 8%.

On the other hand, a charge / discharge cycle test was performed on each of the remaining 100 batteries produced according to Examples 1, 2 and 3 and Conventional Examples 1 and 2 as described in detail below. The capacity at the cycle and the capacity at the 500th cycle were measured. For each 100 batteries, the average capacity retention rate at the 500th cycle when the average capacity at the third cycle was 100 was determined. The average of the 100 batteries of Examples 1, 2, and 3 was obtained. Are 82% and 8%, respectively.
5% and 88%. In contrast, Conventional Examples 1 and 2
The average capacity retention rate of each of the 100 batteries is 81
%, 86%. Each battery was subjected to a charge / discharge cycle test at a temperature of 25 ° C. using a charge / discharge device as follows. That is, the battery is charged until the battery voltage reaches 4.1 V at a current value of the maximum charging current of 1 CmA. After a pause of 10 minutes, the battery is discharged at the same current until the battery voltage reaches 2.75 V. Was repeated 500 times.

As the cylindrical center pin, the volume of the electrode plate increases as the battery is repeatedly charged and discharged, and when the wound electrode group expands in the stacking direction, the diameter of the wound electrode plate shrinks in accordance with the expansion. It is preferable to absorb the expansion force. In addition, when the battery is deformed or crushed by external pressure, when the positive electrode plate and the negative electrode plate are short-circuited through the broken separator in the battery, the resistance value of the positive electrode active material composed of lithium composite oxide is compared. Temperature, the temperature of the lithium composite oxide is likely to rise due to the passage of the short-circuit current, and the heat generated by this temperature causes the decomposition of the organic solvent of the non-aqueous electrolyte by the gas generated by the decomposition reaction. When such a short circuit occurs in a battery in a charged state, the composite oxide in the charged state is in an unstable state in which lithium is released as ions, and thus the battery is decomposed by an increase in temperature to generate active oxygen gas. In order to prevent the risk of rupture, when the battery is deformed or crushed and the positive electrode plate and the negative electrode plate of the wound electrode plate group are short-circuited, as a cylindrical center pin,
The cylindrical center pin bites into the inner peripheral side surface of the wound electrode plate group at a plurality of positions on the circumference thereof, and a short-circuit current flowing through the positive electrode plate is led out to the cylindrical center pin, and lithium composite oxidation by the short-circuit current is performed. It is preferable that the battery can be positively prevented from being ruptured by suppressing the temperature rise due to the heat generation of the object and preventing the generation of gas due to the decomposition reaction of the organic solvent due to the temperature rise.

FIGS. 5A and 5B show an example of a cylindrical center pin of the present invention which satisfies the above-mentioned demands. More specifically, the cylindrical center pin 4 is made of metal such as stainless steel, and has vertical slits 4 b having a desired width between the cylindrical peripheral wall 4 a and the partition wall 14 at two locations on the circumference thereof.
4b, which is formed on an S-shaped cylindrical center pin 4 which looks like an S-shape when viewed from the end face. Thus, the cylindrical space 13 inside the cylindrical peripheral wall 4a is formed.
Are formed on both sides of the partition wall 14 in a substantially semicircular arc-shaped peripheral wall 4a1,
4a1, and are formed into two cylindrical spaces 13a, 13a through the slits 4b, 4b, and the free edges 4c, 4c of the respective arc-shaped peripheral walls 4a1, 4a1 are formed.
Is formed so as to face the side surface of the partition wall 14. Thus, in the state of use, when the battery is overcharged or the battery is crushed, the gas generated in the battery is transferred from the lower end of the cylindrical center pin 4 to the two cylindrical spaces 13a, 13a.
a, and can immediately flow into the respective cylindrical spaces 13a, 13a through the two vertical slits 4b, 4b formed on the peripheral side surface thereof, and can be guided to the safety valve mechanism 7. It is preferable that the arc-shaped peripheral wall 4a is formed as a thin flexible wall. According to this, the winding electrode group 2 on the outer peripheral surface can be formed in the laminating direction by repeated use of charge and discharge. When it expands, it adapts to its expansion force.
As shown in (c), each of the arc-shaped peripheral walls 4a1, 4a
1 is that the free end 4c side is inwardly surrounded, contracts in diameter, and absorbs the expansion force, so that the wound electrode plate group 2 can be maintained in a good state and the cycle life of the battery can be extended. it can.
When the battery is crushed, as shown in FIG. 5D, the free edges 4c, 4c of the arc-shaped peripheral walls 4a, 4a1 are formed.
4c protrudes outward from the partition wall 14, penetrates the inner peripheral side surface of the wound electrode plate group 2 on its outer periphery at two places on its circumferential surface, penetrates through the separator, penetrates the positive electrode plate, and generates a short-circuit current. The lead-out from the positive electrode plate to the cylindrical center pin 4 can suppress the heat generation and temperature rise of the positive electrode plate, and can prevent gas generation due to thermal decomposition of the organic solvent. On the other hand, FIG.
In the state of (d), as shown in the figure, the exhaust passage is maintained without blocking both of the two cylindrical spaces 13a, 13a. In this way, the rupture of the battery can be reliably prevented.

As shown in FIG. 5, the cylindrical center pin 4 has a thickness of 0.1 mm when the arc-shaped peripheral walls 4a1 and 4a1 are formed thin so as to be easily surrounded inward by external pressure.
It is preferable to set it to 0.5 mm. The thickness of the partition wall 14 is preferably 1 mm to 1.2 mm in order to maintain pressure resistance.

FIGS. 6 (a) and 6 (b) show a further modification of the cylindrical center pin of the present invention. Center pin 4, but in particular, left and right arc-shaped peripheral walls 4 a 1, 1
4a1 is a tapered shape which becomes narrower as it reaches the free edges 4c, 4c, so that when the battery is crushed, the sharp free edges are formed as shown in FIG. 6 (d). 4 c, 4 c easily penetrate the inner peripheral surface of the wound electrode plate group 2.

FIGS. 7 (a) and 7 (b) show still another modified example of the cylindrical center pin 4 of the present invention. It was formed on the center pin 4. That is, the cylindrical center pin 4 is formed by dividing the cylindrical peripheral wall 4a into four slits 4b, 4b, 4 on the circumference.
b and 4b, and are formed on the four arc-shaped peripheral walls 4a1, 4a1, 4a1, and 4a1 via the b and 4b.
The cylindrical space 13 inside the cylindrical peripheral wall is divided by four partition walls 14 intersecting in a cross shape to form four cylindrical spaces 13a, 1a.
3a, 13a, and 13a. Thus, by increasing the number of the cylindrical spaces 13a, the danger of all of them being closed is further reduced, safety is ensured, and at the same time, four free edges 4c, 4c, 4c, 4
Since it has c, it can break through at four places with respect to the inner peripheral side surface of the electrode plate group, so that the battery rupture prevention is further ensured. As shown, each of the arc-shaped peripheral walls 4a1, 4a
It is preferable that 1,4a1 and 4a1 have a tapered shape.

Next, more specific embodiments will be described. Example 4 Instead of the stainless steel cylindrical center pin of Example 1,
A cylindrical center pin made of stainless steel having an S-shaped end face shown in FIG. 5 (outer diameter 4 mm, inner diameter 4.5 mm, that is, the arc-shaped peripheral wall thickness 0.5 mm, height 54.5 mm, partition wall thickness 1 m)
Except for using m), a cylindrical lithium secondary battery having the same configuration as shown in FIG. 1 and having the same 5-hour rate rated capacity as in Example 1 was produced. 200 batteries were produced. A crush test was carried out by crushing 100 of them with a round bar.
Not at all. On the other hand, for the remaining 100 batteries,
The same charge / discharge cycle test as described above was performed, and the capacities at the third cycle and the 500th cycle were measured in the same manner as described above.
The average capacity retention rate at the 500th cycle when the value was set to 0 was determined. As a result, the capacity retention was 90%. Example 5 Instead of the stainless steel cylindrical center pin of Example 1,
A cylindrical center pin made of stainless steel having an S-shaped end surface shown in FIG. 6 (outer diameter 4 mm, height 54.5 mm, thickness of arc-shaped peripheral wall: base portion 0.4 mm, tip portion 0.2 mm, partition wall thickness 1)
mm), a cylindrical lithium secondary battery having the same configuration as shown in FIG. 1 and having the same 5-hour rate rated capacity as in Example 1 was produced. 200 batteries were produced. A crush test was carried out by crushing 100 of them with a round bar, and none of the batteries had a rupture accompanied by vigorous gas injection. On the other hand, the remaining 100 batteries were subjected to the same charge / discharge cycle test as above, and the capacities at the third cycle and the 500th cycle were measured in the same manner as above,
With respect to the 100 batteries, the average capacity retention rate at the 500th cycle was determined when the average capacity at the third cycle was 100. As a result, the capacity retention was 86%.

The leading edge 4c of each arc-shaped peripheral wall 4a1 of each cylindrical center pin 4 shown in FIG. 5 and FIG.
Although the linear shape is shown as described above, a triangular mountain-shaped concave portion and a convex portion may be formed in a saw-tooth shape alternately arranged.

FIGS. 8 to 12 show still another modification of the cylindrical center pin 4 of the present invention. The common feature of these five modified examples is that a separately formed polygonal cylindrical partition wall 14 is accommodated inside a cylindrical peripheral wall 4a having or not having a slit, whereby the inside of the cylindrical peripheral wall 4a is formed. Cylindrical space 1
3 is formed into four or more cylindrical spaces 13a, 13a,..., So that even if the battery is deformed or crushed by an external force, the cylindrical center pin A cylindrical space 13a formed in the center pin 4 inside the polygonal cylindrical partition wall 14 itself and each side wall 1 of the polygonal shape
, And four or more cylindrical spaces 13a, 13a, 13a formed between the cylindrical peripheral wall 4a are not blocked, and the exhaust is further secured. When the battery is crushed, its polygonal cylindrical partition wall 1
4 can be used to pierce the inner peripheral side surface of the wound electrode plate group from various angles, thereby suppressing gas generation in the battery, preventing battery rupture more reliably, and further improving safety. It is like that.

8 (a) and 8 (b).
The cylindrical center pin 4 of the present invention shown in FIG. 3B accommodates a thick regular triangular cylindrical partition wall 14 in contact with the inner peripheral surface thereof in a thin cylindrical wall 4a. The cylindrical space 13 in the cylindrical peripheral wall 4a is divided into four cylindrical spaces 13a, 13a, 13a, 13a by the partition walls 14. The cylindrical center pin 4 of the present invention shown in FIGS. 9 (a) and 9 (b) has a vertical slit 4b formed in the thin cylindrical peripheral wall 4a, and has an inner peripheral surface formed in the cylindrical peripheral wall 4a. And an equilateral triangular cylindrical partition wall 14 is inserted loosely with a slight interval 15 between the two. In this case, it is preferable to accommodate the vertical slit 4b with the ridge angle 14b of the equilateral triangular cylindrical partition wall 14 facing the same. FIGS. 10A and 10
(B) accommodates a thick rectangular cylindrical partition wall 14 in a thin cylindrical peripheral wall 4a in which a vertical slit 4b is formed,
Thereby, five cylindrical spaces 13 are formed in the cylindrical peripheral wall 4a.
a, 13a,... are formed. FIG.
(A) and FIG. 11 (b) show that a regular pentagonal cylindrical partition wall 14 is accommodated in a cylindrical peripheral wall 4a, and six cylindrical spaces 13a, 13a,... Are formed in the cylindrical wall 4a. It was done. The opposite free edges 4c, 4c forming the vertical slit 4b formed in the cylindrical peripheral wall 4a formed with the vertical slit 4b are formed, for example, in a triangular sawtooth shape. FIGS. 12 (a) and 12 (b) show a hexagonal cylindrical partition wall 14 in which a vertical slit 4b is accommodated in a cylindrical wall 4a, and seven gas passage spaces are formed inside the cylindrical wall 4a. It is a division formed. The wall thickness of the thin cylindrical peripheral wall 4a in all the above embodiments is, for example, 0.2 mm.
The thickness of the polygonal cylindrical partition wall 8 is, for example, 1 mm. Similarly, the cylindrical center pin 4 of the present invention shown in FIGS. 10 to 12 is preferably housed with the ridge angle 14b of the regular polygonal cylindrical partition wall 14 facing the vertical slit 4b.

The operation of the thus configured cylindrical center pin 4 of the present invention will be described in detail. FIG. 8 (a)
The cylindrical center pin 4 shown in FIG. 8B has a hollow center at the center of the wound electrode plate group 2 housed in the battery can 1 shown in FIG. 1, similarly to the cylindrical center pin 4 shown in FIG. It is used by being arranged in the hole 3. When the battery is deformed or crushed,
As shown in (c), the cylindrical peripheral wall 4a is deformed, and the triangular cylindrical space 13a of the thick triangular cylindrical partition wall 14, the three side walls 14a, 14a, 14a, and the cylindrical peripheral wall 4a are formed.
While three cylindrical spaces 13a, 13a, 13a are secured between the two cylindrical walls 13a, 13a, while the deformed cylindrical peripheral wall 4a is formed on two side walls 14b, 14 on both sides of the ridge angle 8a of the triangular cylindrical partition wall 14.
b to form a triangular corner portion 4a2 supported from the inside by the triangular cylindrical partition wall 14, which pierces the wound electrode plate group, breaks the separator, rushes into the positive electrode plate, and generates a short-circuit current. It is introduced into the cylindrical center pin, whereby the heat generation of the active material of the positive electrode plate can be suppressed, the gas generation due to the thermal decomposition of the organic solvent can be prevented, and the battery can be prevented from bursting. The cylindrical center pin 4 shown in FIGS. 9A and 9B operates as follows. That is, when the wound electrode plate group expands, the cylindrical peripheral wall 4a is pushed by the expansion force, the diameter is reduced as shown in FIG. 9C, and the expansion force is absorbed. In the process of contraction, the vertical slit 4
Even when b is closed, four cylindrical spaces 13a, 13a,... are secured in the cylindrical peripheral wall 4a between the inside of the triangular cylindrical partition wall 14 and the three-sided wall 14a. When a large external force is applied to the battery and the battery is crushed, for example, FIG.
As shown in (d), the vertical slit 4 of the cylindrical peripheral wall 4a is formed.
b, the ridge angle 14 of the triangular cylindrical partition wall 14 therein.
b protrudes outward, penetrates the inner peripheral side surface of the wound electrode plate group on the outer periphery thereof, and draws out a short-circuit current from the positive electrode plate to the outside to suppress gas generation and prevent battery rupture beforehand. it can. When the cylindrical center pin 4 is deformed as shown in FIG. 9E, the cylindrical peripheral wall 4a having the vertical slit 4b has the free edge portions 4c on both sides of the slit 4b projecting outward. In addition, a part of the deformed cylindrical peripheral wall 4a is bent in a V-shape along the ridge angle 8a of the inner triangular cylindrical partition wall 14, and the corner supported by the triangular partition wall 14 from the inside. The portion 4a2 is formed, and the inner peripheral side surface of the wound electrode plate group can be pierced at two places of the free edge 4c and the corner portion 4a2 to prevent gas ejection and battery rupture. Further, the cylindrical center pin 4 is deformed as shown in FIG. In this case, the wound electrode group is pierced at three circumferential locations on the inner peripheral side surface of the wound electrode group 2. That is, the deformed free edge portion 4c of the cylindrical peripheral wall 4a projects outward,
Three ridge angles 14b, 14b, 1 of the triangular cylindrical partition wall 14
Of the cylindrical peripheral wall 4b
Exposed to the outside from the torn part of a, piercing, other 1
Since a part of the cylindrical peripheral wall 4a is bent in a V-shape on the outer surface of the two ridge angles 14b to form a corner 4a2,
These three parts of the free edge 4c, the ridge 14b, and the corner 4a2 pierce the wound electrode plate group, thereby suppressing gas generation and rupture of the battery more reliably. Further secured. In addition, the cylindrical center pin 4 of the present invention
9 (d), (e), and (f), in any of the deformed states, all of the cylindrical spaces 13a and 13
are not blocked, a space for exhaust passage is secured, and safety is ensured. The cylindrical center pin 4 of the present invention shown in FIGS. 10 (a) and 10 (b) has a square cylindrical partition wall 14 formed in a cylindrical peripheral wall 4a having a vertical slit 4b and four ridge angles 14b therebetween. It is inserted and accommodated with a slight gap 15 between them. 11 (a) and 11
The cylindrical center pin 4 of the present invention shown in (b) has a regular pentagonal cylindrical partition wall 14 inserted and accommodated in a cylindrical peripheral wall 4a having a vertical slit 4b, and both sides of the vertical slit 4b. Opposing free edges 4c, 4c are formed in a jagged shape. FIG. 12A and FIG.
The cylindrical center pin 4 of the present invention shown in (b) is one in which a regular hexagonal cylindrical partition wall 14 is similarly inserted and accommodated. The operation of these cylindrical center pins 4 is substantially the same as the operation described in detail in FIG.

Although not shown in the drawings, as the cylindrical partition 14,
When viewed from the end face, a long molded body that looks like a V-shape, U-shape or W-shape may be used.

[0025]

As described above, the cylindrical center pin disposed in the hollow hole at the center of the wound electrode plate group housed in the battery can is provided with a cylindrical peripheral wall and a partition wall in the hollow hole therein. Accordingly, since the hollow hole is configured to be divided into a plurality of gas passage spaces, even when the battery is deformed or crushed, a plurality of cylindrical spaces defined by the cylindrical center pin are formed. The exhaust passage can be secured without all being in the closed state,
It is possible to eliminate the inconvenience of causing the battery to be destroyed as a result of completely closing the exhaust passage, which is seen when a conventional cylindrical center pin consisting of a simple pipe is used. In this case, when a cylindrical center pin having an S-shaped end surface or a swirl-shaped cylindrical peripheral wall having an arc shape is used, a plurality of cylindrical spaces are formed in the same manner as described above, so that the battery is crushed. In addition to ensuring the exhaust passage, the diameter of the wound electrode group can be reduced due to the expansion of the wound electrode group, and the cycle life can be increased by absorbing the expansion of the wound electrode group. When the battery is crushed, when the battery is crushed, the plurality of free edges of the arc-shaped cylindrical peripheral wall penetrate the inner peripheral side surface of the wound electrode plate group to obtain electrical connection with the positive electrode plate. As a result, heat generation due to the short-circuit current of the positive electrode plate due to the derivation of the short-circuit current is prevented, and therefore, gas generation of the organic electrolyte solution due to the heat generation and, thereby, battery rupture are prevented. Further, when the partition is formed into a polygonal partition and is housed in a cylindrical peripheral wall with or without a slit, the number of cylindrical spaces defined and formed is increased, and the exhaust gas passage is further secured. When the battery is crushed when the polygonal partition wall and the cylindrical peripheral wall are formed of a conductive material, and the cylindrical peripheral wall is formed to have a thickness that is easily deformed by pressure. The inner peripheral side surface of the wound electrode plate group is divided into a plurality of circumferential portions by a free edge of the cylindrical peripheral wall deformed into a shape, a corner portion of the cylindrical peripheral wall partially deformed, a ridge angle of a polygonal partition wall, and the like. The short-circuit current can be taken out by electrical connection to the short-circuited positive electrode plate at a plurality of locations, and furthermore, the heat generation of the positive electrode plate can be more reliably prevented, and thus the thermal decomposition of the organic solvent can be prevented. It can be prevented more reliably and increases safety.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical lithium secondary battery according to one embodiment of the present invention.

FIG. 2 (a) shows a cylindrical center pin 1 used in the present invention.
The perspective view which cut out some examples.

FIG. 2 (b) is an end view of the cylindrical center pin.

FIG. 3 (a) is a perspective view in which a part of a modification of the cylindrical center pin of the present invention is cut away.

FIG. 3B is an end view of the cylindrical center pin.

FIG. 4 is a perspective view in which a part of still another modification of the cylindrical center pin of the present invention is cut away.

FIG. 5 (a) is a perspective view of a cylindrical center pin according to the present invention, in which a part of still another modification is cut away.

FIG. 5 (b) is an end view of the cylindrical center pin.

FIG. 5C is an end view showing a state where the cylindrical center pin is compressed.

FIG. 5 (d) is an end view of the state where the cylindrical center pin is further compressed.

FIG. 6 (a) is a perspective view of a cylindrical center pin according to the present invention in which a part of still another modified example is cut away.

FIG. 6B is an end view of the cylindrical center pin.

FIG. 6 (c) is an end view of the state where the cylindrical center pin is compressed.

FIG. 6D is an end view of the state where the cylindrical center pin is further compressed.

FIG. 7A is a perspective view of a cylindrical center pin according to the present invention, in which a part of still another modified example is cut away.

FIG. 7 (b) is an end view of the cylindrical center pin.

FIG. 8A is a perspective view of a cylindrical center pin according to the present invention, in which a part of still another modification is cut away.

FIG. 8B is an end view of the cylindrical center pin.

FIG. 8 (c) is an end view of the state where the cylindrical center pin is compressed.

FIG. 9A is a perspective view of a cylindrical center pin of the present invention, in which a part of still another modification is cut away.

FIG. 9B is an end view of the cylindrical center pin.

FIG. 9C is an end view of the state where the cylindrical center pin is compressed.

9 (d) to 9 (f) are end views showing a state where the cylindrical center pin is further compressed.

FIG. 10A is a perspective view of a cylindrical center pin according to the present invention, in which a part of still another modified example is cut away.

FIG. 10 (b) is an end view of the cylindrical center pin.

FIG. 11 (a) is a perspective view of a cylindrical center pin of the present invention in which a part of still another modified example is cut away.

FIG. 11 (b) is an end view of the cylindrical center pin.

FIG. 12 (a) is a perspective view of a cylindrical center pin according to the present invention, in which a part of still another modified example is cut away.

FIG. 12 (b) is an end view of the cylindrical center pin.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Battery can 2 Wound electrode group 3 Hollow hole of wound electrode group 4 Cylindrical center pin 4a Cylindrical peripheral wall 4a1 Arc-shaped peripheral wall 4a2 Corner of arc-shaped peripheral wall 4b Slit 4c Free edge 5 Battery cover 7 Safety valve mechanism 13 cylindrical space inside cylindrical peripheral wall 13a cylindrical space defined and formed 14 partition wall 14a side wall 14b ridge angle

Claims (3)

[Claims] 1. A battery group having a bottomed cylindrical battery can, a positive electrode plate and a negative electrode plate housed in the battery can being laminated via a separator and spirally wound, and An electrolytic solution, a cylindrical center pin disposed in a hollow hole at the center of the wound electrode group, a safety valve mechanism disposed above the cylindrical center pin, and a battery hermetically sealed in the battery can. A cylindrical secondary battery comprising a lid, wherein the cylindrical center pin comprises a cylindrical peripheral wall, and a partition which forms a cylindrical space inside the cylindrical peripheral wall into at least two cylindrical spaces. A cylindrical secondary battery, comprising: 2. The cylindrical secondary battery according to claim 1, wherein the cylindrical center pin is made of a conductive material and has an S-shaped end face or a swirl end face. 3. The cylindrical secondary battery according to claim 1, wherein the cylindrical center pin is made of a conductive material, and is provided with a polygonal cylindrical partition wall inside the cylindrical peripheral wall.