KR100696786B1 - cylinder type rechargeable battery - Google Patents

Abstract

An electrode assembly having two electrodes with electrode tabs formed therebetween and a separator interposed between the two electrodes to prevent a short circuit between the two electrodes, a canister containing the electrode assembly, and a cap assembly closing the can at the opening of the can; In a secondary battery, a secondary battery is disclosed, which is provided with a buffer material to fill at least a part of the space between a cap assembly and an upper end of an electrode assembly. The cushioning material is preferably formed to have a thickness that is at least half of the space between the cap assembly and the electrode assembly, and may be installed separately from the upper insulating plate above the bottom of the bead portion.

The buffer serves to inhibit movement of the electrode assembly when it is flowed toward the cap assembly by an external shock such as dropping the secondary battery from the high place to the floor.

Description

Secondary battery {cylinder type rechargeable battery}

1 and 2 are a front sectional view and an exploded perspective view showing a structure of an example of a conventional cylindrical secondary battery,

3 is a front sectional view showing a cross section of a cylindrical secondary battery as an embodiment in which a cushioning material is provided in a space between a cap assembly and an electrode assembly according to the present invention.

* Explanation of symbols for the main parts of the drawings

10: cans

13a, 13b, 113a, and 113b: insulating plate 20: electrode assembly

21, 23 separator 25: electrode

27,29,127,129: electrode tab 30: gasket

40,140: Vent 50,150: Current interrupt device (CID)

60,160: positive thermal coefficient

70,170: Cap up 80,180: Cap assembly

250: cushioning material

The present invention relates to a secondary battery, and more particularly, to a coupling structure of a tab and a can in a secondary battery and a method of forming the same.

Secondary batteries have been rapidly developed and used in recent years due to the advantages of being rechargeable and capable of miniaturization and large capacity. Secondary batteries may be divided into nickel-hydrogen (Ni-MH) batteries, lithium-ion (Li-ion) batteries, and the like according to electrode active materials.

Lithium secondary batteries may be divided into a case of using a liquid electrolyte and a case of using a solid polymer electrolyte or a gel electrolyte, depending on the type of electrolyte. Lithium secondary batteries can also be divided into cans and pouches according to the type of container in which the electrode assembly is accommodated.

In a can-type lithium secondary battery, an electrode assembly is embedded in a can formed of a metal such as an aluminum-containing metal by a K drawing (deep drawing) method. In general, a liquid electrolyte is used in a can type secondary battery structure.

On the other hand, the can-type secondary battery can be divided into a rectangular and a cylindrical battery according to the shape. A square shape is formed by thinly forming a container in a cuboid shape or by giving a curvature to the sidewall edge of the cube. Cylindrical is used in a relatively large amount of electronic and electrical equipment, a plurality is used in the form of a combination to form a battery pack.

1 and 2 are a front sectional view and an exploded perspective view showing a structure of an example of a conventional cylindrical lithium secondary battery.

Referring to FIGS. 1 and 2, a method of forming a cylindrical secondary battery is described. First, a separator for preventing a short circuit between two electrodes 25 interposed between the two electrodes 25 formed in a rectangular plate shape and the electrodes 21, 23) The electrode assembly 20 is laminated, wound in a spiral shape and collectively called jelly roll. Each electrode plate is made by coating an active material slurry on a current collector made of a metal foil.

In the direction in which the electrode plate is wound, there is a non-coated portion at which the slurry is not applied at the start end and the end of the current collector. In the uncoated portion, electrode tabs 27 and 29 are usually provided on one electrode plate one by one. The electrode tabs 27 and 29 are electrically connected to the cylindrical can 10 and the cap assembly 80 insulated from the can 10 to form part of a passage for connecting the electrode assembly and an external circuit during charging and discharging. In the electrode assembly 20, the electrode tab is formed to be pulled out of the electrode, one upward in the direction of the opening of the cylindrical can 10 and the other downward.

The electrode assembly is introduced into the cylindrical can 10 through the can openings in order with the upper and lower insulating plates 13a and 13b positioned up and down. Beads are formed in the can to prevent flow in the can of the electrode assembly, and the electrolyte is injected. An insulating gasket 30 is installed on the inner wall of the opening of the can, and a cap assembly 80 that closes the opening of the can 10 is installed inside the gasket 30.

As the cap assembly 80, a cap assembly 70 having a vent assembly, a positive thermal coefficient (PTC) 60, and electrode terminals is inserted. The vent assembly is typically provided with a current interrupter (CID: Current Interrupt Device) 50 that breaks with the action of the vent 40 and the vent below and breaks the path of the current.

Then, a crimping operation is performed to seal the can by applying pressure to the opening wall of the cylindrical can 10 inward and downward with a cap up 70 inserted into the gasket 30. After the first crimping operation is performed, an operation of increasing the sealing pressure by applying pressure to both ends of the battery is usually added. In addition, a tubing operation of applying an exterior material to the outside of the battery is performed.

In the process of connecting the electrode tabs, the lower part of the electrode tab of the electrode assembly extends to the bottom of the can and upwards through the lower insulator plate or bypassing the lower insulator plate between the electrode assembly and the can. It is usually welded to the vent of the cap assembly through the hole in the top insulation plate.

In order to weld the upward electrode tab 27 and the recess 42 of the vent 40 drawn upward, the electrode tab 27 is formed to have an extra length so as to facilitate the welding operation. Then, the electrode tab is bent and the vent assembly is inserted into the opening above the can into which the gasket 30 is fitted. This process requires some space between the vent assembly and the electrode assembly 20 for convenience of the process.

If the upward electrode tab is too long, the treatment of the tab after welding is difficult, so the length of the upward electrode tab is determined within the range of workability. After welding, the remaining portion of the upward electrode tab may be positioned as a meander in the space between the cap assembly and the electrode assembly, and the phase insulator may serve to prevent other polarities and short circuits of the upward electrode tab and the electrode assembly.

The center pin 18 may be installed in the hollow for winding the electrode assembly 20 after the downward electrode tab welding.

However, when the electrode tabs of the electrode assembly are welded with safety vents or cans, they must be of substantial strength so that the welding can be maintained even with some external impact during use. If the tab is dropped from the weld, the battery cannot be used at all, or the electrical connection between the electrode tab and the safety vent or can is likely to be made by surface contact. In the case of electrical connection by surface contact, there arises a problem that the internal resistance of the battery increases and the charge / discharge efficiency decreases.

In the conventional secondary battery, there is a space between the electrode assembly and the cap assembly, so that there is a flow of the electrode assembly during an external impact. Even if beads were formed in the can to define the position of the electrode assembly, flow in the can of the electrode assembly due to external impact could not be completely prevented. When the flow of the electrode assembly in the can is part of the welding portion of the electrode tab is connected to the electrode assembly external force according to the flow of the electrode assembly, there was a problem that the electrode tab falls from the weld. In severe cases, the vent or CID may be damaged by the flow of the electrode assembly.

The present invention is to solve the problems of the conventional secondary battery described above, an object of the present invention is to provide a secondary battery having a structure that can mitigate the problem that the electrode assembly in the case flows due to external impact.

In another aspect, an object of the present invention is to provide a secondary battery having a configuration that can reduce the problem that the tabs of the electrode assembly falling from the weld of the can or cap assembly while the electrode assembly or the like flows due to external impact.

Ultimately, the present invention provides a secondary battery that does not damage a structure such as a cap assembly while the battery is in use, and maintains the welding state of the electrode tabs to operate normally, thereby improving product reliability, and preventing a decrease in charge and discharge efficiency and a decrease in charge amount. It aims to do it.

The secondary battery of the present invention for achieving the above object,

An electrode assembly having an electrode tab formed therebetween and a separator interposed between the two electrodes to prevent a short circuit between the two electrodes, a canned container housing the electrode assembly, and a can through the gasket in the opening of the can. In the secondary battery having a cap assembly to be finished, it can be made by installing a buffer to fill at least a portion of the space in the space between the cap assembly and the top of the electrode assembly.

In the present invention, the cushioning material is preferably formed to have a thickness that is at least half of the space between the cap assembly and the electrode assembly, and may replace the phase insulating plate installed on the electrode assembly of the secondary battery, or may be installed separately from the phase insulating plate. have. The buffer serves to inhibit movement of the electrode assembly when it is flowed toward the cap assembly by an external shock such as dropping the secondary battery from the high place to the floor.

Therefore, it is preferable that the shock absorbing material is made of a material having a certain modulus of elasticity so as not to contract or deform too easily to prevent the flow of the electrode assembly. On the other hand, the cushioning material is interposed between the electrode assembly and the cap assembly, it is preferable to be made of a soft, elastic material that is enough to cushion the shock, as it does not transmit the shock as it is when the external impact. For example, the buffer may be made of a rubber-based having chemical resistance to the electrolyte.

On the other hand, in terms of form, the cushioning material in the present invention may be made of a simple cylinder or disc, or may have a passage hole through which the upward electrode tab extending toward the cap assembly of the electrode assembly can pass.

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

3 is a front sectional view showing a cross section of a cylindrical secondary battery as an embodiment in which a cushioning material is provided in a space between a cap assembly and an electrode assembly according to the present invention.

First, referring to the process of forming the secondary battery of the present invention, two electrodes formed in a rectangular plate shape are stacked and wound in a spiral shape to form a jellyroll type electrode assembly as in the related art. At this time, since the separators 21 and 23 are positioned one by one between these electrodes and below or above the two electrodes 25, the separators 21 and 23 are interposed where the separators 21 and 23 come into contact with each other. To prevent.

Each electrode plate is made of an active material slurry coated on a current collector made of aluminum or copper metal foil or metal mesh. The slurry is usually formed by stirring a granular active material, auxiliary conductor, binder, plasticizer, and the like in a state where a solvent is added. The solvent is removed in the subsequent electrode formation process.

In the direction in which the electrode plate is wound, there is a non-coated portion at which the slurry is not applied at the start end and the end of the current collector. Electrode tabs are provided one by one on the electrode plate, and the electrode tabs are formed to be drawn out from the electrodes, one upward in the direction of the opening of the cylindrical can and the other downward.

The can 10 is cylindrical and is formed by a deep drawing method using an iron material, an aluminum alloy, or the like. The electrode assembly 20 is then inserted into the can through the can's opening. At this time, before inserting the electrode assembly, the lower insulating plate 13b is first covered on the lower surface of the electrode assembly, and the electrode tab 29 drawn downward from the outer portion of the electrode assembly bypasses the outer side of the lower insulating plate and the bottom surface of the can 10. It is bent side by side. The lower insulating plate 13b and the electrode assembly 20 are inserted together into the can.

At this time, the electrode assembly forms a cylindrical jelly roll, and the portion of the mandrel electrode and the separator held for winding is separated from the electrode assembly, and the center of the jelly roll forms a via hollow. The center of the lower insulating plate also has a hole in the area corresponding to the hollow of the electrode assembly. The bent portion of the electrode tab 29 crosses the central hole of the lower insulating plate 13b downward.

In this state, a welding rod (not shown) descends toward the bottom of the can through the hollow of the electrode assembly from above. After passing through the central through hole of the lower insulating plate, the lower portion of the lower insulating plate meets the portion of the electrode tab 29 crossing the central through hole. The electrode tab portion is in contact with the electrode upwards and downwardly in contact with the bottom of the can.

The end of the electrode is usually made of one point welding due to the limitation of the space inside the electrode assembly, but the welding part and the contact part of the welding part to increase the welding strength to prevent failure factors such as disconnection of the welding part due to external impact during battery use. To form a wide or to form a number of points are newly explored.

In addition, according to the embodiment, the center pin is installed in the hollow of the electrode assembly. The center pin may be installed in the can together with the electrode assembly in a state of being inserted into the electrode assembly, or may be inserted into the central cavity of the electrode assembly after welding of the bottom of the can as described above. When installed together with the electrode assembly, the metal center pin is inserted into the can while being inserted into the hollow, and a welding rod is connected to the top of the center pin to allow current to flow through the center pin itself, thereby welding the electrode tab and the bottom of the can. have.

After welding the downward electrode tab to the bottom of the can, the upper insulating plate 13a is installed on the electrode assembly 20. At this time, the upward electrode tab 27 of the electrode assembly is led out through the through hole of the upper insulating plate 13a. When the upper insulating plate has a central hole, welding of the lower electrode tab 29 may be performed after the upper insulating plate is installed.

After the phase insulation plate is installed, a beading process of forming the convex bead portion 15 inward on the sidewall of the can 10 is generally performed, followed by injection of electrolyte.

Before and after these operations, the cushioning material 250, which is the main component of the present invention, is installed on the phase insulation plate. The buffer 250 fills at least a portion of the space between the cap assembly 180 and the top of the electrode assembly 20. In terms of form, the cushioning material in the present invention is usually formed in a cylinder or disc shape. The shock absorbing material has a through hole in the upward electrode tab 27 like the upper insulating plate 13a. The upward electrode tab may be drawn out through a through hole formed in the buffer material and welded to the lower vent part 140 of the cap assembly 180 installed thereafter. The electrode tab 17 pulled upward from the electrode assembly is longer than the space between the top of the electrode assembly and the bottom of the cap assembly of the completed secondary battery for convenience of welding. Therefore, after welding, the folded material is maintained in a meandering state in the space between the through holes of the buffer material 250 for the remaining length treatment. In consideration of this, the shock absorbing material 250 has a sufficient inner diameter space for processing the electrode tab 27, and is formed to have the same thickness as the space between the electrode assembly 20 and the cap assembly 180 in an uncompressed state, or It is preferably formed to a thickness that is at least half of the space between the 180 and the electrode assembly 20. The buffer member may replace the phase insulating plate installed above the electrode assembly of the secondary battery, and may be installed above the bottom of the bead part separately from the phase insulating plate limited by the bead part 15 as in the present embodiment.

The buffer serves to inhibit movement of the electrode assembly when it is flowed toward the cap assembly by an external shock such as dropping the secondary battery from the high place to the floor.

Therefore, the shock absorbing material is preferably made of a material having a certain modulus of elasticity so that the shock absorber is not easily contracted or deformed by an external impact to prevent the flow of the electrode assembly. On the other hand, the cushioning material is interposed between the electrode assembly and the cap assembly, it is preferable to be made of a soft, elastic material that is enough to cushion the shock, as it does not transmit the shock as it is when the external impact. For example, the buffer may be made of a rubber-based having chemical resistance to the electrolyte.

In addition, the buffer member may also serve to reduce the total empty space filled with air in the battery by occupying the empty space between the electrode assembly and the cap assembly. Reducing this empty space may be of importance in the operation of the vent 140. That is, when the internal gas is generated over the battery and the vent should be operated, if there is a large amount of empty space in the battery, there is a tendency to buffer the internal pressure to delay the vent operation. As a result, the buffer 250 may serve to reduce the empty space in the battery to assist the normal operation of the vent. For this purpose, it is preferable that the cushioning material is not a material whose volume is easily reduced by pressure, and in general, most non-gas objects have this property.

In the present embodiment, the process after installing the shock absorbing material may be performed in the same manner as in the assembly process of a conventional cylindrical secondary battery.

For example, the gasket 30 is inserted into the opening of the can 10. If the cushioning material sufficiently occupies the space between the cap assembly and the electrode assembly, the lower periphery of the gasket 30 and the cushioning material 250 may come into contact with each other or interfere with the installation, so that the cushioning material rather than the inner diameter of the lower end facing the inside of the gasket 30 may be reduced. Smaller outer diameters can be helpful for battery assembly. After the gasket is installed, the cap assembly 180 is inserted into contact with the inner diameter of the gasket 30. The cap assembly 180 may be installed with each of the stacked parts in turn, and may be installed with the entire parts assembled or partially assembled. In either case, the lower part of the cap assembly is electrically coupled with the upward electrode tab and by welding.

Cap assembly installation is made, the can 10 and the gasket 30 is pressed down to the inside bending and clamping is performed to seal the gasket and the cap assembly and the can contact. Following clamping, pressure is applied to both ends of the cell to increase sealing and internal pressure. Processes, such as tubing which installs an exterior material outside a battery, are normally performed.

According to the present invention, the void space between the cap assembly and the electrode assembly can be reduced in the cell through a simple process called inserting a buffer material, and in case of an external impact, the electrode assembly moves to destroy the CID of the cap assembly, or can or The problem of damaging the weld between the cap assembly and the electrode tab can be significantly reduced.

Therefore, the service life of the battery can be probabilisticly increased and the reliability can be improved.

In addition, it is possible to increase the safety and reliability of the battery by eliminating the operation delay of the vent by reducing the empty space.

Claims (7)

delete An electrode assembly having two electrodes having electrode tabs formed thereon and a separator interposed between the two electrodes to prevent a short circuit between the two electrodes, A container-shaped can containing the electrode assembly, In the secondary battery having a cap assembly for closing the can in the opening of the can, It is made by installing a buffer to fill at least a portion of the space in the space between the cap assembly and the electrode assembly, The buffer material is a secondary battery, characterized in that installed separately from the phase insulating plate installed on the top of the electrode assembly. The method of claim 2, The buffer material is a secondary battery, characterized in that formed to a thickness that is at least half of the space between the cap assembly and the electrode assembly of the completed secondary battery. The method of claim 2, The cap assembly is press-sealed while the insulating material gasket is interposed in the can, The buffer member has a passage hole through which the electrode tab, which is pulled upward from the electrode assembly, passes through the electrode tab, and has a size smaller than the inner diameter of the lower end of the gasket. The method of claim 2, The buffer material is a secondary battery, characterized in that installed on the lower end of the bead portion formed on the can wall to fix the electrode assembly in the can. The method of claim 2, The buffer material is a secondary battery, characterized in that made of a rubber material having chemical resistance to the electrolyte. The method of claim 2, The buffer member has a thickness corresponding to a space between the electrode assembly and the cap assembly in the uncompressed state, and includes a through hole through which a portion of the electrode tab passes. The inside of the through-hole secondary battery characterized in that the electrode tab is bent in a meandering state.

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