JP3349529B2 - Lithium ion secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery, and more particularly to a lithium ion secondary battery in which an electrode as a power generating element has improved insertability into a battery outer can.

[0002]

2. Description of the Related Art In recent years, there has been remarkable progress in cordless, high-performance, and compact and lightweight electronic devices such as mobile phones and portable notebook personal computers. For this reason, demands for higher capacity and higher energy density of a secondary battery serving as a power supply of the electronic device are increasing. Conventionally, lead secondary batteries and nickel cadmium secondary batteries have been used as secondary batteries, but recently, non-aqueous electrolytes such as lithium ion secondary batteries, which can achieve even higher energy densities, have been used. The development of secondary batteries is in progress. Further, as the capacity of the battery increases, the size of the electrode body tends to be as large as possible.

However, when assembling the lithium ion secondary battery, if an electrode body as large as possible for increasing the capacity is inserted into the outer can, the dimension between the electrode body and the outer can becomes large. Since there is almost no gap, the opening of the outer can and the outer peripheral portion of the electrode body may interfere with each other, making insertion difficult, or the outer peripheral surface of the electrode body may be damaged. In particular, if the electrode body is damaged, an internal short circuit occurs.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium ion secondary battery in which the electrode body can be easily inserted into an outer can.

[0005]

SUMMARY OF THE INVENTION The present invention provides an outer can,
In a lithium ion secondary battery including an electrode body that is a power generation element inserted into the outer can,

[0006] The electrode body has an outer peripheral side surface including a bottom wrapped with a conductive cover and inserted into the outer can, and the conductive cover is a pair of opposed side walls that tilt about the bottom and the bottom as a fulcrum. a lithium ion secondary battery, characterized in that a shape that having a and.

The side surface of the conductive cover abuts on the side surface of the electrode body when the electrode body is inserted into the outer can to protect the electrode body. It is desirable to make it equal to the height of the electrode body.

It is preferable that the pair of opposed side walls of the conductive cover have a shape in which both side sides are bent inward. Such a conductive cover can cover the opposing side surfaces of the electrode body with the pair of opposing side walls, and also cover other opposing narrow side surfaces of the electrode body on both sides of the pair of side walls. It can be covered by the bent part of the side.

It is desirable that an insulating plate be disposed between the bottom surface of the electrode body and the bottom of the conductive cover, or that the top surface of the bottom of the cover be covered with an insulating layer. With the interposition of the insulating plate and the coating of the insulating layer, it is possible to reliably prevent the positive electrode and the negative electrode of the electrode body from coming into contact with the bottom of the conductive cover to cause an internal short circuit.

[0010] The lithium ion secondary battery according to the present invention allows a safety valve mechanism to be further attached to a sealing body attached to an upper opening of the outer can. The safety valve mechanism comprises a pressure-release hole opened in the sealing body, and a thin film in which a valve membrane is formed at the bottom by a groove attached to the outer surface of the sealing body and provided at least at a location corresponding to the hole. Be composed. The lithium ion secondary battery according to the present invention may further include a plate-shaped PTC element fixed to a bottom surface of the outer can via a conductive adhesive layer.

[0011]

According to the present invention, with the bottom and this bottom serving as a fulcrum,
Conducting shape having a pair of opposed side walls that tilt
By inserting the outer peripheral side surface including the bottom of the electrode body with the conductive cover into the outer can, the conductive cover serves as an insertion guide during the insertion operation.
For this reason, the work of inserting the electrode body can be simplified. In addition, since the bottom and the outer periphery of the electrode body can be prevented from being damaged due to interference between the outer can and the electrode body at the time of insertion, an internal short circuit due to the damage can be prevented.

Further, if a sealing member is attached to the upper opening of the outer can and a safety valve mechanism is provided in the sealing member, when gas is generated due to a short circuit or the like and the internal pressure of the battery rises,
Since the safety valve mechanism operates to allow gas to escape to the outside of the outer can, it is possible to prevent the outer can from being ruptured or deformed due to an excessive increase in the battery internal pressure.

That is, when an overcharged state or a short-circuited state occurs in a lithium ion secondary battery due to failure or misuse of equipment, gas may be generated inside the outer can, and the internal pressure of the battery increases. An increase in battery internal pressure may cause damage to the outer can, thereby leaking the electrolyte in the outer can to the outside and damaging peripheral devices. For this reason, in a conventional secondary battery, a safety valve mechanism is provided in a sealing body attached to an upper opening of an outer can. However, when gas generation occurs in the outer can, and the gas generation is at a position near the bottom of the electrode body, that is, at a place distant from the safety valve mechanism, when the electrode body is inserted into the outer can without a gap. The gas generated at the bottom of the electrode body cannot reach the safety valve mechanism because there is no passage of gas of a sufficient size. As a result, the gas accumulates at the bottom inside the outer can, and the safety valve mechanism may not operate, possibly leading to battery rupture.

Therefore, when the electrode assembly is inserted into the outer can together with the conductive cover, the secondary battery according to the present invention has the outer can between the outer can and the conductive cover. Since the space extending in the depth direction is formed, even when the gas is generated as described above, the generated gas can be reliably guided to the safety valve mechanism attached to the sealing body through the space. Therefore, the safety valve mechanism can be reliably operated to allow the gas to escape to the outside of the outer can, so that the outer can can be prevented from being ruptured or deformed due to an excessive increase in the battery internal pressure.

Further, a plate-like PTC is provided on the bottom of the outer can.
If the element is fixed, when an abnormal current flows at the time of overcurrent or short circuit and the temperature inside the battery rises, the heat can be quickly transmitted to the PTC element arranged in close contact with the bottom of the outer can. . Further, the abnormal current is determined by the PTC
It also flows to the element. Therefore, when the temperature exceeds a predetermined temperature due to the positive characteristics of the PTC element, the resistance sharply increases and the flow of the abnormal current can be minutely limited, so that excessive heat generation of the battery can be suppressed. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a prismatic lithium ion secondary battery will be described in detail with reference to FIGS.

FIG. 1 is a front sectional view of a prismatic lithium ion secondary battery according to the present invention, FIG. 2 is a top view of the secondary battery of FIG. 1, FIG. 3 is a sectional view taken along line III-III of FIG. FIG. 4 shows FIG.
FIG. 3 is an exploded perspective view of FIG.

For example, an outer can 1 having a bottomed rectangular cylindrical body made of stainless steel also serves as a negative electrode terminal, and is inserted with an electrode body 2 as a power generating element wrapped by a conductive cover 3. As shown in FIG. 4, the electrode body 2 includes, for example, a negative electrode using a carbonaceous material as an active material, a separator made of a porous sheet made of polypropylene impregnated with an electrolytic solution,
It is manufactured by spirally winding a positive electrode using oO ₂ as an active material so that the negative electrode is located at the outermost periphery, and then press-molding it into a flat shape. The conductive cover 3
Is a sheet metal formed from, for example, a copper plate. As shown in FIG. 4, a bottom 4 and a pair of opposed side walls 5 tilting with the bottom 4 as a fulcrum, and both side sides of the pair of side walls 5 face inward. And a bent portion 6 which is bent. That is,
The electrode body 2 has a bottom surface and a side surface having a large area facing the bottom surface 4 of the conductive cover 3 and a pair of side walls 5.
Further, another opposing side surface of the electrode body 2 having a small opposing area is covered by a bent portion 6 of the conductive cover 3. Such a conductive cover 3
When the electrode body 2 wrapped in is inserted into the outer can 1, gas guide spaces 7 are respectively formed between the corners in the outer can 1 and the conductive cover 3 as shown in FIG. The insulating plate 8 is interposed between the bottom surface of the electrode body 2 and the bottom 6 of the conductive cover 3, and the positive electrode and the negative electrode located on the bottom surface of the electrode body 2 come into contact with the bottom of the conductive cover 3. Prevents short circuit. The positive electrode lead 9 is connected to a positive electrode (not shown) exposed on the upper surface of the electrode body 2.

A flange 10 is provided at the upper part, and a hole 11 is provided near the center.
Is fitted by bringing the flange 10 into contact with the upper opening of the outer can 1 by contacting the upper end of the opening of the outer can 1 with the lower surface of the flange 10 and the outer casing. The can 1 is hermetically attached to the outer can 1 by performing laser welding on a contact portion with the upper end of the opening. A spacer 14 made of an insulating material having a hole 13 in the center is interposed between the electrode body 2 and the sealing plate 12.
With such an arrangement of the spacer 14, the positive electrode lead 9 is inserted into the hole 13 of the spacer 14. The insulating ring 15 is provided at the center lower surface of the sealing body 12 with the hole 1.
1 so as to cover it. For example, a positive electrode pin terminal 16 made of stainless steel is hermetically sealed in the hole 11 of the sealing body 12 via a glass insulating material 17, and a lower end of the positive electrode pin terminal 16 penetrates the insulating ring 15. And is connected to the positive electrode lead 9 inserted into the hole 13 of the spacer 14. In addition,
The insulating material 17 made of glass is used for the outer can 1 serving as the negative electrode terminal.
Insulation between the sealing member 12 and the positive electrode pin terminal 16 electrically connected to each other is achieved.

For example, a rectangular hole 18 is opened in the sealing body 12 at a desired distance from the hole 11. For example, a rectangular thin film 19 is hermetically attached to the upper surface of the sealing body 12 by laser welding so as to cover the rectangular hole 18. For example, a linear portion and a groove 20 having both ends formed in a V-shape are formed on the upper surface of the thin film 19 so as to correspond to the rectangular holes 18. The thin film 19 at the bottom of the groove 20 functions as the valve membrane 21. A safety valve mechanism 22 is constituted by the valve hole 21 formed in the thin film 19 by the rectangular hole 18 opened in the sealing body 12, the thin film 19 and the groove 20.

The rectangular PTC element 23 is provided in the outer can 1.
Is fixed to the bottom surface of the substrate via a conductive adhesive layer (not shown). For example, a terminal plate 24 made of stainless steel is fixed to the bottom surface of the PTC element 23 via a conductive adhesive layer (not shown).

According to such a configuration, the conductive cover 3 having a shape having the bottom 4 and the pair of opposed side walls 5 tilting around the bottom 4 as the fulcrum in the outer can 1.
The conductive cover 3 serves as an insertion guide at the time of insertion work. For this reason, the work of inserting the electrode body 2 can be simplified and the work of insertion can be automated.
In addition, since the conductive cover 3 can prevent the bottom and outer periphery of the electrode body 2 from being damaged by the interference between the outer can 1 and the electrode body 2 during the insertion, the internal short circuit of the battery due to the damage is prevented. can do.

Further, if a safety valve mechanism 22 is provided on the sealing body 12 attached to the upper opening of the outer can 1, if a gas is generated due to a short circuit or the like and the internal pressure of the battery rises, the safety valve mechanism 22 is opened. Since the gas can escape to the outside of the outer can by operating, the rupture or deformation of the outer can caused by the excessive increase in the internal pressure of the battery can be prevented. That is, when the electrode body 2 is inserted into the outer can 1 together with the conductive cover 3,
As shown in FIG. 3, a space 7 extending in the depth direction is formed between the outer can 1 and the conductive cover 3 at a corner portion of the outer can 1. Therefore, when a gas is generated inside the outer can 1 due to an overcharged state or a short-circuited state due to misuse of the lithium ion secondary battery or the like, the gas is attached to the sealing body 12 through the space 7. It can be reliably guided to the valve membrane 21 of the safety valve mechanism 22. Therefore, the valve membrane 21 of the safety valve mechanism 22 is reliably broken, and the gas can escape to the outside of the outer can 1, so that the outer can can be prevented from being ruptured or deformed due to an excessive increase in the internal pressure of the battery.

Further, a rectangular P
If the TC element 23 is fixed via a conductive adhesive layer, when an abnormal current flows during an overcurrent and a short circuit and the temperature inside the battery rises, the heat is disposed in close contact with the bottom of the outer can 1. It can be transmitted to the PTC element 23 quickly. The abnormal current also flows through the PTC element 23. Therefore, if the temperature exceeds a predetermined temperature due to the positive characteristic of the PTC element 23, the resistance increases rapidly and the flow of the abnormal current can be minutely limited, so that excessive heat generation of the battery can be suppressed. it can.

[0025]

As described in detail above, according to the lithium ion secondary battery of the present invention, by providing the conductive cover for enclosing the electrode body, it is possible to improve the insertability of the electrode body into the outer can. Also, even when gas is generated in the inside, a remarkable effect is obtained such that the safety valve mechanism can be reliably operated to ensure safety.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a prismatic lithium ion secondary battery according to an embodiment of the present invention.

FIG. 2 is a top view of the secondary battery in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is an exploded perspective view of the secondary battery of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer can, 2 ... Electrode body, 3 ... Conductive cover, 12 ... Sealing body, 16 ... Positive electrode pin terminal, 18 ... Rectangular hole, 19 ... Thin film, 21 ... Valve membrane, 22 ... Safety valve mechanism, 23 ... PTC element .

Continued on the front page (72) Inventor Masamichi Kawabe 72 Horikawacho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Horikawacho Plant (72) Inventor Shigeo Kasahara 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Incorporated (72) Inventor Yasufumi Minato 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Asahi Kasei Kogyo Co., Ltd. (72) Gen Takayama 3-4-1, Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery (56) References JP-A-4-10361 (JP, A) JP-A-4-206167 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40

Claims (1)

(57) [Claims] 1. A lithium ion secondary battery comprising an outer can and an electrode body which is a power generating element inserted into the outer can, wherein the electrode body has an outer peripheral side including a bottom wrapped with a conductive cover. The lithium ion secondary battery is characterized in that the conductive cover is inserted into the outer can and the conductive cover has a shape having a bottom and a pair of opposed side walls that tilt about the bottom.