KR102159974B1 - Cab assembly of cylindrical secondary battery, and cylindrical secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a cap assembly of a circular secondary battery and a circular secondary battery including the same, and more particularly, to a cap assembly of a circular secondary battery with improved weldability between a top cap and a safety vent, and a circular secondary battery including the same.

Description

Cap assembly of circular secondary battery and circular secondary battery including the same {CAB ASSEMBLY OF CYLINDRICAL SECONDARY BATTERY, AND CYLINDRICAL SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a cap assembly of a circular secondary battery and a circular secondary battery including the same, and specifically, to a cap assembly having improved weldability between a top cap and a safety vent, and a circular secondary battery including the same.

A secondary battery is a battery capable of charging and discharging, and is widely used in the field of advanced electronic devices such as cell phones, notebook computers, and camcorders. In particular, lithium secondary batteries have an operating voltage of 3.6V, which has three times higher operating voltage than nickel-cadmium batteries or nickel-hydrogen batteries, which are widely used as power sources for electronic equipment, and high energy density per unit weight.

These lithium secondary batteries are manufactured in various shapes, and typically include a circular shape, a square shape, and a pouch type.

Among them, the circular secondary battery includes an electrode assembly, a circular can for accommodating the electrode assembly, a cap assembly and a gasket provided on the circular can.

Specifically, FIG. 1 shows a schematic cross-sectional view of a cap assembly 40 of a conventional circular secondary battery 10.

In general, in a circular secondary battery, a jelly-roll type electrode assembly 30 is accommodated in a circular battery can 20, and an electrolyte solution is injected into the can.

The electrode assembly 30 has a structure wound in a jelly-roll type with a separator 33 interposed between the anode 31 and the cathode 32, and the anode tab 34 is attached to the anode 31. It is connected to the cap assembly 40, and a negative electrode tab (not shown) is attached to the negative electrode 32 and is connected to the lower end of the can 20.

A gasket 60 for insulation is installed at the opening of the can, and a cap assembly 40 for closing the opening of the can is installed inside the gasket. Then, the can is sealed by crimping the top cap 41 of the cap assembly. Thereafter, the assembly of the battery is completed by tubing to attach the exterior material to the outside of the battery.

In this case, in the circular secondary battery, the cap assembly 40 has an upper cap 41 forming a positive terminal that conducts current to the outside of the battery, and blocks current and/or exhausts gas when the pressure inside the battery increases. Vent 43, an insulating member 44 that electrically separates the safety vent 43 from the cap plate 45 except for a specific part, and the cap plate to which the positive electrode tab 34 connected to the positive electrode 31 is connected ( 45) are sequentially stacked.

In the conventional circular secondary battery, the top cap 41 of the cap assembly 40 is clamped to seal the can, and then the battery is assembled by a tubing operation of attaching an exterior material to the outside of the battery.

Meanwhile, since the circular secondary battery is used in a power tool or an electric vehicle, it is exposed to a lot of vibration and shock. Therefore, when manufacturing a circular secondary battery, the top cap 41 and the safety vent 43 that are directly in contact with the cap assembly 40 are connected and fixed so that the connection between the top cap and the safety vent can be maintained despite such vibrations and shocks. In order to do so, a welding process is performed on the joint portions between the component parts.

At this time, in the cap assembly, since the safety vent and the top cap are made of materials having different resistances and melting points, welding is not easy, and welding strength is lowered at the joint, resulting in poor welding.

When such a welding failure occurs, a crack occurs in the welding part due to shock or vibration applied to the secondary battery, creating a space between the top cap and the safety vent. As a result, resistance increases, making it difficult not only to discharge high rates, but also to heat There is a problem that there is a high risk of explosion due to this occurrence.

Korean Patent Application Publication No. 10-2009-026419 Republic of Korea Patent Publication No. 10-2014-106329

The present invention has been devised to solve the above problems, and is to provide a cap assembly of a circular secondary battery having a novel structure with improved weldability between a top cap and a safety vent.

In addition, the present invention is to provide a circular secondary battery with improved safety by including the cap assembly as described above.

In one embodiment for achieving the above object,

In the cap assembly for a secondary battery coupled to the open end of the battery can,

A top cap protruding from the top to form a positive terminal; And

The shape is deformed when the internal pressure of the battery can is increased from the bottom of the top cap, and at least a portion of the outer circumferential portion is formed to extend longer than the outer circumferential portion of the top cap, so that the extended portion is bent so as to surround the outer circumference of the top cap. It provides a cap assembly of a circular secondary battery including a vent.

In this case, in the cap assembly of the present invention, the top cap may be formed of stainless steel or an alloy of stainless steel and aluminum (Fe-Al alloy).

In addition, in the cap assembly of the present invention, when the top cap is made of stainless steel, a welding member may be further included on one or both surfaces of the top cap.

In addition, in the present invention

An electrode assembly,

A can accommodating the electrode assembly,

In the circular secondary battery comprising a cap assembly installed in the opening of the can to seal the can,

The cap assembly provides a circular secondary battery including the cap assembly of the present invention.

According to the present invention, the weldability of the top cap and the safety vent made of different materials is improved, so that even if vibration or shock is applied to the secondary battery during use of the circular secondary battery including the same, the connection portion between the top cap and the safety vent is separated. The resistance may be increased or the cap assembly may be prevented from being damaged or broken. Therefore, it is possible to prevent a situation where high rate discharge is not possible due to an increase in battery resistance.

Moreover, in the case of a battery used in a power tool such as a power tool or an electric vehicle or a hybrid vehicle, it may be exposed to a lot of shocks and vibrations.In the case of the present invention, the top cap and the safety vent are strongly attached despite the shock and vibration Therefore, it can be more usefully applied to such a power tool or an electric vehicle.

1 is a photograph of a cross-section of a cap assembly portion of a conventional circular secondary battery.
2 to 4 are cross-sectional views showing the configuration of a welding portion between a top cap and a safety vent in a cap assembly according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In this case, the terms or words used in the specification and claims should not be interpreted as being limited to a conventional or dictionary meaning, and the inventor appropriately defines the concept of the term in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

Specifically, in one embodiment of the present invention

In the cap assembly for a secondary battery coupled to the open end of the battery can,

A top cap protruding from the top to form a positive terminal; And

The shape is deformed when the internal pressure of the battery can is increased from the bottom of the top cap, and at least a portion of the outer circumferential portion is formed to extend longer than the outer circumferential portion of the top cap, so that the extended portion is bent so as to surround the outer circumference of the top cap. It provides a cap assembly of a circular secondary battery including a vent.

In addition, the cap assembly of the present invention may provide a cap assembly of a circular secondary battery further including a welding member on one or both sides of the top cap according to the material of the top cap.

2 to 4 are cross-sectional views schematically showing the configuration of a cap assembly of a circular secondary battery according to an embodiment of the present invention.

In this case, a circular secondary battery (not shown) according to an embodiment of the present invention largely includes an electrode assembly, a battery can for accommodating the electrode assembly, and a cap assembly mounted on the battery can.

In the electrode assembly, a positive electrode plate and a negative electrode plate are wound in the form of a jelly roll with a separator interposed therebetween, and stored in a battery can. The electrode plates of the electrode assembly may be formed in a structure in which an active material slurry is applied to a current collector, and the slurry may be formed by stirring a particulate active material, an auxiliary conductor, a binder, and a plasticizer in a state in which a solvent is added. .

Here, in the direction in which the electrode plates are wound, uncoated portions to which the slurry is not applied may exist at the beginning and end of the current collector, and electrode leads corresponding to respective electrode plates may be attached to the uncoated portions. In general, in a circular secondary battery, the positive lead is attached to the upper end of the electrode assembly and electrically connected to the cap assembly, and the negative lead is attached to the lower end of the electrode assembly and connected to the bottom of the battery can.

Meanwhile, an upper insulating plate serving to insulate between the electrode assembly and the cap assembly may be disposed on an upper end of the electrode assembly.

The battery can is made of a lightweight conductive metal material such as aluminum, stainless steel, or an alloy thereof, and may have a circular or rectangular structure having an open portion having an open top and a closed bottom portion opposed thereto. The electrolyte solution is accommodated together with the electrode assembly in the inner space of the battery can.

The battery can may be formed in a circular shape, but may be formed in various shapes other than a circular shape, such as a square.

In addition, the cap assembly of the circular secondary battery according to the present invention includes a top cap and a safety vent.

The cap assembly is a component of a secondary battery that is coupled to the upper end of the battery can to be sealed, and may be formed in various shapes such as a circular shape or a square shape according to the shape of the battery can.

In addition, the safety vent may be positioned under the top cap and disposed so that the top cap and the outer circumferential portion, that is, a rim portion, are in contact. In addition, when the internal pressure of the secondary battery, that is, the internal pressure of the battery can increases above a certain level, the safety vent is configured to deform. For example, the safety vent may be configured to be deformed and burst when the internal pressure of the secondary battery is 12 to 25 kgf/cm 2.

To this end, the safety vent is formed so that the central portion protrudes downward, and a predetermined notch may be formed near the central portion. Accordingly, when gas is generated from the inside of the secondary battery, that is, from the side of the electrode assembly and the internal pressure of the battery can increases, the safety vent protrudes upward while its shape is reversed, and may be ruptured around the notches. The gas filled in the battery can can be discharged to the outside through the ruptured portion of the safety vent.

In particular, in the cap assembly of a circular secondary battery according to an embodiment of the present invention, the top cap may be formed of stainless steel, or an alloy of stainless steel and aluminum in which aluminum as a safety vent material is added to stainless steel (Fe -Al alloy). In addition, the safety vent is formed such that at least a portion of the outer circumferential portion extends longer than the outer circumferential portion of the top cap. In addition, the extension portion of the safety vent may be formed to be bent to surround the outer periphery of the top cap.

This, an embodiment of the present invention will be described in more detail with reference to FIGS. 2 to 4.

2 to 4 are views showing the configuration of the cap assembly of the circular secondary battery of the present invention according to the material of the top cap.

Specifically, FIGS. 2 and 3 show that when the top cap is made of stainless steel in the cap assembly according to an embodiment of the present invention, the safety vent 120 is additionally included in the state including the welding members 130 and 140. It is a view schematically showing the configuration of the junction of the top cap 110 and the safety vent 120 formed in a state where the extension portion is bent.

In addition, Figure 4 is a state in which the extended portion of the safety vent 120 is bent in a state in which a welding member is not included when the top cap is formed of stainless steel and aluminum alloy material in the cap assembly according to an embodiment of the present invention. It is a view schematically showing the configuration of the junction of the top cap 110 and the safety vent 120 formed of.

First, referring to Figures 2 and 3, in the cap assembly of the circular secondary battery of the present invention, when the top cap 110 is made of stainless steel, welding on one or both sides of the top cap 110 A member 140 may be further included.

The welding member is preferably made of a metal of the same kind as the material constituting the safety vent, or an alloy including the same, and specifically, it is preferably made of aluminum or an aluminum alloy.

The welding member is formed on one side or both sides of the top cap using a conventional bonding method, for example, a plating method such as a vapor deposition method, an electroplating and an electroless plating, or a clad (hot rolling) method. can do.

In the case of the above plating method, it can be carried out in a solution in which aluminum ions are present. Specifically, a target to be plated, that is, a top cap, is installed on the cathode, and a metal capable of consistently adjusting the concentration of aluminum ions in the solution is applied under an electrolytic plating system equipped with a counter electrode (an oxidizing electrode). The voltage applied at this time should be higher than the aluminum reduction voltage.

In addition, the cladding method is carried out before the top cap is pressed, and dissimilar metal (Al) that can improve weldability when rolling a steel sheet that becomes the raw material (stainless steel) of the top cap is used in the top cap. It can be carried out by placing it above or below the raw material, and then rolling by applying heat and pressure.

In this case, the thickness of the welding member is preferably at least 0.5 μm or more, specifically 1 μm or more. If it is less than 0.5㎛, there is a disadvantage that the effect of improving the weldability is insufficient. In addition, it is preferable that the thickness of the welding member is at least 20 μm. I can.

In addition, referring to FIG. 4, in the cap assembly of the circular secondary battery of the present invention, the top cap 110 may be made of a stainless steel and aluminum alloy (Fe-Al alloy).

At this time, the weight ratio of the stainless steel and aluminum is preferably in the range of 1: 1 to 30. If the content ratio of the aluminum is less than 1% by weight, the effect on the weldability is insignificant, and when the content ratio exceeds 30% by weight, the physical properties of stainless steel are weakened, thereby changing the mechanical properties of the top cap. .

As such, referring to FIGS. 2 to 4, in the cap assembly of the circular secondary battery of the present invention, the safety vent 120 is disposed under the top cap 110 in contact with the outer periphery of the top cap 110. In addition, the outer peripheral portion of the safety vent 120 is formed to extend longer than the outer peripheral portion of the top cap 110. And the extended outer peripheral portion (120-1, 120-2, 120-3) of the safety vent is formed in a form bent to surround the outer peripheral portion of the top cap 110, can be welded together with the outer peripheral portion of the top cap. .

In this case, the welding may be performed by conventional ultrasonic welding or laser welding.

As a result, it is possible to implement an effect of improving weldability (bonding) between the top cap and the safety vent even in the absence of a fastening member such as a rivet according to an embodiment of the present invention.

Moreover, the cap assembly of the circular secondary battery of the present invention is made of stainless steel and aluminum in which a welding member made of a safety vent material is added to one or both sides of a top cap made of stainless steel, or aluminum is added to stainless steel as a top cap material. By using a Fe-Al alloy, it is possible to further improve the weldability (bonding) between the top cap and the safety vent because welding between the same metal can be performed instead of welding between dissimilar metals.

In addition, in an embodiment of the present invention

An electrode assembly,

A can accommodating the electrode assembly,

In the circular secondary battery including a cap assembly installed at the opening of the can to seal the can, the cap assembly provides a circular secondary battery including the cap assembly of the present invention.

As described above, in the case of the circular secondary battery including the cap assembly of the circular secondary battery of the present invention, even if a vibration or shock is applied during use, the connection portion between the top cap and the safety vent is separated to increase resistance or damage or damage the cap assembly. Can be prevented. Therefore, it is possible to prevent a situation where high rate discharge is not possible due to an increase in battery resistance.

Moreover, in the case of a battery used in a power tool such as a power tool or an electric vehicle or a hybrid vehicle, it may be exposed to a lot of shocks and vibrations.In the case of the present invention, the top cap and the safety vent are strongly attached despite the shock and vibration Therefore, it can be more usefully applied to such a power tool or an electric vehicle.

Meanwhile, the cap assembly of the circular secondary battery according to the present invention may further include a gasket (not shown).

The gasket may be configured to surround the edge of the top cap and the safety vent, that is, the outer circumference. In particular, in the cap assembly according to the present invention, at least a portion of the outer periphery of the safety vent is extended longer than the outer periphery of the top cap and is bent to surround the outer periphery of the top cap, and the gasket has a configuration surrounding the bent portion of the safety vent. I can.

The gasket may be made of a material having electrical insulating properties so that the edge portions of the top cap and the safety vent are insulated from the battery can. In addition, the gasket may be made of a material having impact resistance, elasticity, and durability to support and protect the cap assembly. For example, the gasket may be made of polyolefine or polypropylene (PP). In addition, the gasket is preferably bent by mechanical processing, not by heat treatment, in order to prevent the electrical insulation from deteriorating.

In addition, the cap assembly of the circular secondary battery according to an embodiment of the present invention may further include a current blocking member.

The current blocking member is also called CID (Current Interrupt Device), and is located between the safety vent and the electrode assembly so that the electrode assembly and the safety vent are electrically connected. That is, at least a portion of the current blocking member is connected to the lower portion of the central protruding portion of the safety vent, and at least a portion of the lower portion is connected to the electrode lead of the electrode assembly, such as the anode lead. Accordingly, in a normal state, the current generated from the electrode assembly flows through the positive electrode to the current blocking member, the safety vent, and the top cap, thereby discharging the secondary battery. However, if the shape of the safety vent is reversed due to an increase in the internal pressure of the battery due to gas generation, the contact between the safety vent and the current blocking member is broken or the current blocking member is damaged, so that the electrical connection between the safety vent and the electrode assembly is cut off. do.

As such, the cap assembly may include a current blocking member, and in this case may further include an insulating member.

The insulating member is interposed between the safety vent and the current blocking member so that the current blocking member and the safety vent are electrically insulated from each other except for a portion in which the central protruding portion of the safety vent and the current blocking member are in contact.

As described above, although the present invention has been described by a limited embodiment and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those of ordinary skill in the art to which the present invention pertains. It goes without saying that various modifications and variations are possible within the equivalent range of the claims to be described.

10: circular secondary battery
20: circular battery can
21:
30: electrode assembly
31: anode
32: cathode
33: separator
34: positive electrode tab
40: cap assembly
41: top cap
43: safety vent
44: insulation member
45: cap plate
60: gasket
110: top cap
120: safety vent
130, 140: welding member
120-1, 120-2, 120-3: Extended outer peripheral part of the safety vent

Claims (17)

In the cap assembly for a secondary battery coupled to the open end of the battery can,
A top cap protruding from the top to form a positive terminal; And
The shape is deformed when the internal pressure of the battery can is increased from the bottom of the top cap, and at least a portion of the outer circumference is formed to extend longer than the outer circumference of the top cap, so that the extended portion is bent so as to surround the outer circumference of the top cap vent; And
Welding members formed on both sides of the top cap; Including,
The safety vent is made of aluminum or aluminum alloy,
The welding member is made of aluminum or aluminum alloy,
The top cap is made of a stainless steel and aluminum alloy (Fe-Al alloy),
The welding member is a cap assembly of a circular secondary battery, characterized in that formed on the upper and lower surfaces of the top cap. delete delete delete delete The method according to claim 1,
The welding member is formed by performing at least one method selected from the group consisting of a deposition method, a plating method, and a clad method.
The method according to claim 1,
The cap assembly of the circular secondary battery, characterized in that the thickness of the welding member is 0.5㎛ or more and 20㎛ or less.
delete The method according to claim 1,
The cap assembly of the circular secondary battery, characterized in that the weight ratio of the stainless steel and aluminum is in the range of 1: 1 to 30.
The method according to claim 1,
The cap assembly of the circular secondary battery, characterized in that the top cap and the safety vent are joined by ultrasonic welding or laser welding.
delete delete delete delete delete delete An electrode assembly,
A can accommodating the electrode assembly,
In the circular secondary battery comprising a cap assembly installed in the opening of the can to seal the can,
The cap assembly is a circular secondary battery comprising the cap assembly of claim 1.

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