KR100973423B1 - Cylindrical Battery of Improved Safety - Google Patents

Abstract

The present invention is a battery having a structure in which an electrode assembly (jelly-roll) having a cathode / separation membrane / cathode structure is embedded in a cylindrical can, and the cap assembly including the electrode terminal is installed in an insulated state through a gasket. A curved beading portion is formed near the open top of the can, and an insulating material layer is formed on an inner surface of the can including at least the beading portion, and the insulating material layer is a continuous annular contacting the bottom of the gasket. Providing a cylindrical battery is formed, the top of the insulating material layer is a structure that is not exposed to the outside.

In the cylindrical battery according to the present invention, the positive electrode tab inside the battery is released from its position due to leakage of the electrolyte due to deformation of the crimping portion and external shock, thereby preventing internal short circuit due to electrical contact with the inner wall of the can. It can greatly improve.

Description

Cylindrical Battery of Improved Safety

1 and 2 are vertical cross-sectional views of the structure of a conventional cylindrical secondary battery;

3 is a schematic diagram of an upper structure of a secondary battery according to an embodiment of the present invention;

4 and 5 are schematic views illustrating a manufacturing process of forming an insulating layer and an beading unit with an insulating material inside a can of a secondary battery according to another exemplary embodiment of the present invention.

The present invention relates to a cylindrical secondary battery with improved safety, and more particularly, a battery having a structure in which an electrode assembly (jelly-roll) having a cathode / separation membrane / cathode structure is embedded in a cylindrical can, and including a cap including electrode terminals. A beading portion, which is bent inwardly so that the assembly can be mounted insulated via a gasket, is formed near an open top end of the can, and an insulating material layer is formed on an inner surface of the can including at least the beading portion. The insulating material layer is formed with a continuous annular protrusion in close contact with the bottom of the gasket, the upper end of the insulating material layer relates to a secondary battery having a structure that is not exposed to the outside.

As the development and demand for mobile devices increases, the demand for secondary batteries as energy sources is increasing rapidly. Among them, many researches have been conducted and commercialized on lithium secondary batteries with high energy density and high discharge voltage. It is widely used.

As the application fields and products of secondary batteries are diversified as described above, the types of batteries are also diversified to provide outputs and capacities suitable for them. For example, small mobile devices such as mobile phones, PDAs, digital cameras, notebook computers, etc. have one or two or four small, lightweight secondary batteries (unit cells) per device according to the miniaturization tendency of the products. .

Secondary batteries are classified into roughly cylindrical cells, square cells, and pouch-type cells according to their external and internal structural characteristics, and are mainly jelly-roll type (wound type) according to the structure of the electrode assembly of the anode / separation membrane / cathode structure constituting the secondary battery. ) And stacked (stacked).

Among them, a commonly used jelly-roll type electrode assembly is coated with an electrode active material or the like on a metal foil used as a current collector, dried and pressed, cut into bands of a desired width and length, and a negative electrode and a positive electrode using a separator. After the diaphragm is wound into a spiral is produced. Jelly-roll type electrode assemblies are mainly used in cylindrical batteries, and in some cases, they are compressed into plate shapes and applied to square or pouch type batteries.

1 and 2 show the structure of a conventional cylindrical secondary battery as a vertical cross-sectional view.

Referring to FIG. 1, a cylindrical secondary battery 10 generally includes a cylindrical can 20, a jelly-roll electrode assembly 30 accommodated in the can 20, and a cap coupled to an upper portion of the can 20. Assembly 40 and a crimping portion 50 for mounting the cap assembly 40.

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

The cap assembly 40 includes a top cap 41 forming a positive electrode terminal, a positive temperature coefficient element 42 for blocking current due to a large increase in battery resistance when the temperature inside the battery increases, and a pressure increase inside the battery. Safety vents 43 for interrupting current and / or exhausting gas, insulating members 44 for electrically separating the safety vents 43 from the cap plate 45, except for certain parts, and connected to the anode 31. The cap plate 45 to which the positive electrode tab 34 is connected is sequentially stacked.

The crimping portion 50 is formed at the top of the can 20 so that the cap assembly 40 can be mounted on the open top of the can 20. More specifically, the crimping portion 50 forms the beading portion 21 inwardly by indenting the upper end of the can 20, and the cap plate 45 and the insulating member 44 on the gasket 60. After inserting the outer circumferential surface of the safety vent 43 and the upper cap 41 in turn, it is formed by bending the upper end. As a result, the cap assembly 40 is formed by enclosing the gasket 60 positioned on the inner surface of the crimping portion 50 and performing a crimping and pressing process.

However, when the positive electrode tab 34 deviates from its position as shown in FIG. 2 due to an external shock, the secondary battery having such a structure may have a tab 20 electrically having a positive electrode and an electrically negative electrode 20 having a negative electrode. ) Inner wall is contacted and internal short circuit, ignition and explosion occur. This short circuit also occurs in some defective products during the mass production of batteries.

In addition, the application range of secondary batteries, which were limited to digital devices, has been expanded to devices and devices in harsher environments, such as electric tools, vacuum cleaners, electric scooters, electric vehicles, and hybrid electric vehicles. There is a greater risk that the tab will fall out of position.

Moreover, during frequent vibrations and strong external shocks, the electrolyte leaks to the outside as the sealing part is partially or temporarily released. The electrolyte of a lithium secondary battery has a disadvantage in that it is highly flammable and generates a large amount of gas as it decomposes during a chemical reaction, so the risk of fire and explosion is very high.

In this regard, in Korean Utility Model Publication No. 2000-0015920, a lithium roll in which a positive electrode, a negative electrode, and a separator are wound together is stored inside a battery can, and a cap assembly is crimped and sealed in an opening of the can. In a secondary battery, a technique of coating a protective film between the inner circumferential surface of the can and the outer circumferential surface of the jelly-roll is disclosed.

However, if the can is damaged by an external impact or a sharp tool, it is difficult for the protective film having a relatively low hardness to prevent the short-circuit of the jelly-roll compared to the material of the can, and the protective film is coated on the entire inner peripheral surface of the can. In the manufacturing process, there is a high possibility of coating to the bottom of the can, and if the bottom of the can is coated, there may be a problem in the resistance welding operation used for bonding the negative tab of the jelly-roll and the bottom of the can.

In addition, since the protective film is formed over the entire surface with its upper end exposed to the outside of the can, there is a problem that the possibility of leakage of the electrolyte solution is very high. That is, the continuous interface between the gasket and the protective film is formed over the entire surface, so that the close sealing state between the gasket and the protective film is partially or temporarily released during frequent vibration or strong external impact, thereby causing the electrolyte inside the can to be discharged. It leaks out along a continuous interface. In addition, the above technique has the disadvantage that by applying the protective film to the entire side along the inner circumferential surface of the battery can, the battery capacity is reduced, the manufacturing cost for such application is increased.

Therefore, there is a high need for a technology that can fundamentally solve these problems.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After extensive research and various experiments, the inventors of the present application have an insulating material on the inner surface of a can including a bead portion that is bent inward so that the cap assembly can be mounted in an insulating state through a gasket in a conventional cylindrical secondary battery. When the layer is formed in a specific shape, the battery can be prevented when an external external force such as vibration, drop, impact, etc. is applied or in the battery manufacturing process, the internal short circuit due to the deviation of the position of the positive electrode tab due to an error in operation, and leakage of the electrolyte solution are prevented. It has been found that the safety of the present invention can be improved, and the present invention has been completed.

The secondary battery according to the present invention is a battery having a structure in which an electrode assembly (jelly-roll) having a cathode / separation membrane / cathode structure is embedded in a cylindrical can, and a cap assembly including an electrode terminal may be mounted in an insulated state through a gasket. A beading portion, which is bent inwardly, is formed near the open top of the can, and an insulating material layer is formed on an inner surface of the can including at least the beading portion, and the insulating material layer is in close contact with the bottom of the gasket. A continuous annular protrusion is formed, and the upper end of the insulating material layer is configured not to be exposed to the outside.

Therefore, in the secondary battery according to the present invention, an insulating material layer is formed on the bead portion of the inner surface of the can, and thus, when a physical shock is applied from the outside due to a drop, vibration, or the like, the positive electrode tab is moved out of position to provide a negative electrode. It is possible to prevent fire or explosion due to internal short circuit caused by contact of the inner wall of the floating can.

In addition, the insulating material layer of the upper end portion thereof is not exposed to the outside of the can or gasket, the annular projection is continuously formed in the portion in contact with the lower end of the gasket, when applying an external force such as vibration, drop, impact, The leakage of electrolyte solution can be prevented.

In the present invention, the insulating material layer is an insulating layer which is attached to the inside of the bead portion of the can without affecting the operation of the battery and forms a layer with a predetermined thickness, thereby preventing electrical connection between the cylindrical can and the positive electrode tab. It is not particularly limited, and examples thereof are as follows.

First, it may be a configuration to form an insulating layer by coating an insulating material inside the bead portion of the battery can. For example, the insulating material may be a material having insulation and chemical resistance, and may be one or more materials selected from the group consisting of polyethylene, polypropylene, polybutylene, polyethylene terephthalate, synthetic rubber, and silicone resin.

Second, the insulating layer may be formed by attaching an insulating tape to the inside of the bead of the battery can. For example, the insulating tape may be coated with a silicone-based or acrylic adhesive layer on one surface of a film substrate of polypropylene, polyimide (PI) or polyethylene sulfide (PPS).

In forming the insulating coating layer inside the bead portion of the cylindrical can, the thickness of the insulating coating layer may be preferably 15 ㎛ to 30 ㎛. If the thickness of the coating layer is too thin, it may be difficult to obtain electrical insulation to prevent the electrical connection between the positive electrode tab and the cylindrical can, and conversely, if the thickness of the coating layer is too thick, the battery capacity and material cost will increase accordingly. It is not preferable because the insulating coating layer may be separated from the inside of the bead portion of the can due to an increase in the solidification time of the coating or an external impact such as vibration.

In addition, in forming the insulating layer inside the bead by attaching the insulating tape, the insulating tape may be a thickness of 20 ㎛ to 40 ㎛, as mentioned earlier if the thickness of the insulating tape is too thin to the electrical insulation On the contrary, if the thickness is too thick, the space inside the battery can is reduced, thereby reducing the battery capacity, and the tape can be easily separated from the inner wall of the can due to the tape relaxation and shrinkage caused by the temperature change of the battery. not.

This layer of insulating material is characterized by having a continuous annular projection that is in close contact with the bottom of the gasket, as described above, and that the top is not exposed to the outside of the can or gasket.

First, the annular protrusion is formed along the outer circumferential surface of the lower end of the gasket to increase the sealing property between the lower end of the gasket and the insulating material layer. The leakage of the electrolyte starts from the lower end of the gasket, which is the interface starting point between the gasket and the insulating material layer, and the annular protrusion is in close contact with the lower end of the gasket to fundamentally suppress the initiation of such leakage.

Protruding size of the annular protrusion is not particularly limited as long as it can exert the above effects, for example, it may be 0.2 to 1.0 mm. In some cases, the annular protrusion may be partially pressurized by the lower end of the gasket.

Second, the top of the insulating material layer is not exposed to the outside, thereby forming a discontinuous contact interface between the gasket and the insulating material layer. As described above, in the case where a continuous connection interface is formed between the gasket and the insulating material layer, the electrolyte tends to leak along the interface upon application of external force, especially frequent vibration. On the other hand, when configured to form a discontinuous contact interface as in the present invention, the continuous flow of such electrolyte can be blocked to minimize the occurrence of leakage.

Accordingly, the present invention prevents the electrolyte from flowing into the interface between the gasket-insulating material layer primarily by the above-described configuration, and nevertheless, when the electrolyte flows in, the liquid leaks by the secondary non-combined interface. The phenomenon is suppressed as much as possible.

In one preferred example, the top of the layer of insulating material may be located on an area that is not exposed to the outside of the can at least 50% of the height from the bottom contact surface relative to the total contact surface height with the gasket.

On the other hand, the lower end of the insulating material layer is located at least on the portion surrounding the bottom surface of the bead portion, the electrode assembly in the can is separated from the correct position by the application of an external force or the positive electrode tab is moved to the negative electrode and Internal short circuits can be prevented from coming into contact.

The battery according to the present invention may be preferably applied to a lithium secondary battery manufactured by impregnating a lithium-containing electrolyte in a state in which an electrode assembly is embedded in a battery case.

In the method of manufacturing a secondary battery according to the present invention, a jelly-roll is inserted into a cylindrical can, an insulating material layer is formed on an inner surface of a can including at least a portion where a bead is formed, and a bead is formed on an open top of the can. After mounting the gasket mounting cap assembly on the open top, and then crimping the top of the can, the manufacturing operation can be facilitated and productivity can be improved.

In the secondary battery manufacturing method, the insulating material layer formed by attaching an insulating material tape is attached so that both ends partially overlap when attaching the insulating material tape to the corresponding part, and then heat presses the overlapping part to attach the tape. By making the thickness uniform, the electrical insulation effect can be obtained uniformly.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

3 is a schematic diagram of an upper structure of a secondary battery according to an embodiment of the present invention.

Referring to FIG. 3, a cylindrical secondary battery is a battery in which an electrode assembly 30 is embedded in a cylindrical can 20, and a cap assembly including an electrode terminal may be mounted in an insulated state through a gasket 60. The beading portion 21 bent inwardly is formed near the open top of the can 20, and an insulating material layer 100 is formed on an inner surface of the can including the beading portion 21.

When the insulating material layer 100 is subjected to a physical shock from the outside due to a drop, vibration, etc., the insulating material layer 100 may occur when the electrical contact with the beading portion 21 of the can, which has a negative electrode, is caused by the positional deviation of the positive electrode tab 34. Prevent internal short circuit.

That is, the insulating material layer 100 is formed at a height of 50% or more from the bottom contact surface with respect to the contact surface of the gasket without the top 110 thereof being exposed to the outside of the cylindrical can. In addition, an annular protrusion 130 is continuously formed at the lower end of the insulating material layer 100 to be in close contact with the lower end of the gasket 60, and surrounds the lower end surface of the beading part 21. Therefore, the contact interface between the can 20 and the gasket 60 is effectively sealed, so that when an external shock is applied in the direction of the outer edge of the crimping portion 50, between the can 20 and the gasket 60. Even if a minute spacing occurs, it is possible to prevent the electrolyte from leaking to these spacing sites.

4 and 5 are schematic views illustrating a manufacturing process of forming an insulating layer and an beading part with an insulating material inside a can of a secondary battery according to another exemplary embodiment of the present invention.

Referring to these drawings, the process of manufacturing a secondary battery according to the present invention, first by coating an insulating material or attaching an insulating tape so that the annular projection 130 is formed on the inner portion of the can 20 of the metal as shown in FIG. After the insulating material layer 100 is formed, the bead 21 is formed by deforming the portion to which the insulating material is applied so as to be indented into the can 20 as shown in FIG. 5. The beading portion 21 is formed by using a beading knife (not shown) when the upper and lower portions of the can 20 are rotated while being fixed using a predetermined die (not shown).

As a result, the insulating material layer 100 is formed in a structure extending to a predetermined length toward the upper side of the bead 21, the annular projection 130 is in close contact with the bottom of the gasket when the gasket (not shown) is mounted do.

Hereinafter, the present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.

Example 1

Using Ni-plated SPCE (cold rolled steel sheet), the upper cap and the cylindrical can are manufactured.Including the lower surface of the beading portion inside the cylindrical can, polyethylene resin is applied up to a height of 3 mm from the lower contact surface based on the contact surface of the gasket. It was coated with a thickness of 20 μm and an annular protrusion layer was formed at the bottom of the gasket as shown in FIG. 3. The electrode assembly was mounted on a cylindrical can coated with polyethylene resin, and then a beading process was performed on a cylindrical can at a portion corresponding to the upper end of the electrode assembly, a gasket was inserted on the beading portion, and then a capping was performed to mount the cap assembly. .

Comparative Example 1

A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that a coating layer was not formed inside the cylindrical can.

Comparative Example 2

A cylindrical secondary battery was prepared in the same manner as in Example 1, except that the entire inner surface of the cylindrical can was coated with a polyethylene resin to a thickness of 50 μm.

Comparative Example 3

Including the bottom surface of the bead portion inside the cylindrical can, the polyethylene resin was coated with a thickness of 20 μm up to a height of 3 mm from the bottom contact surface with respect to the contact surface of the gasket, except that the annular protrusion layer was not formed at the bottom of the gasket. Was manufactured in the same manner as in Example 1.

Experimental Example 1

In the state in which 30 batteries manufactured in Example 1 and 30 batteries manufactured in Comparative Examples 1 to 3 were inverted, the electrolyte solution leaked before the current blocking member was shorted while applying pressure to the inside of the cell to 15 kgf. It was confirmed. The results are shown in Table 1 below.

TABLE 1

As shown in Table 1, in the batteries of Example 1 according to the present invention, no leakage of the electrolyte occurred in any case, while the current blocking member was short-circuited before and after the comparative example 1 and the comparative example 2. The cells leaked from 10 and 8 electrolytes, respectively. Therefore, it can be seen that the batteries according to the present invention exhibit excellent sealing properties not only before the short circuit but also after the short circuit.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

As described above, the secondary battery according to the present invention has an insulating material layer formed on the inner surface of the can including the bead portion of the cylindrical can, the positive electrode inside the battery due to leakage of the electrolyte due to deformation of the crimping portion and external impact When the tab is released from the fixed position to prevent the internal short circuit caused by electrical contact with the inner wall of the can, and even when pressed by applying a predetermined external force to the cylindrical can, the CID filter is squeezed and deformed to contact the beading part. By preventing it, the safety of a battery can be improved significantly.

Claims (12)

A battery in which an electrode assembly (jelly-roll) having a positive electrode / membrane / cathode structure is embedded in a cylindrical can, and a cap assembly including electrode terminals is bent inwardly so that the cap assembly including the electrode terminal can be mounted in an insulating state via a gasket. A beading portion is formed near an open top end of the can, and an insulating material layer is formed on at least an inner surface of the can including the beading portion, and the insulating material layer is formed with a continuous annular protrusion in close contact with the bottom of the gasket. And the upper end of the insulating material layer is not exposed to the outside. The battery of claim 1, wherein the insulating material layer is formed by coating an insulating material. The battery of claim 1, wherein the insulating material layer is formed by attaching an insulating material tape. The battery according to claim 2, wherein the insulating material is one or more selected from the group consisting of polyethylene, polypropylene, polybutylene, polyethylene terephthalate, synthetic rubber and silicone resin. The battery according to claim 3, wherein the insulating tape is coated with a silicone-based or acrylic adhesive layer on one surface of a film substrate of polypropylene, polyimide (PI), or polyethylene sulfide (PPS). The battery according to claim 2, wherein the coating layer of the insulating material is formed to have a thickness of 15 µm to 30 µm. The battery according to claim 2, wherein the insulating tape has a thickness of 20 µm to 40 µm. The battery of claim 1 wherein the top of the layer of insulating material is located on an area not exposed to the outside of the can at least 50% above the bottom contact surface with respect to the total contact surface height with the gasket. The battery of claim 1, wherein the lower end of the insulating material layer is positioned on at least a portion surrounding the lower end of the bead portion. The battery according to claim 1, wherein the battery is a lithium secondary battery using a lithium salt-containing electrolyte solution. Inserting a jelly-roll into the cylindrical can, forming an insulating material layer on an inner surface of the can including at least a portion where the bead is formed, forming a bead on the open top of the can, and mounting a gasket mounting cap assembly on the open top Then, the method of manufacturing a battery according to claim 1, comprising the step of crimping the top of the can. 12. The method of claim 11, wherein the insulating material layer is formed by attaching both ends of the insulating material to partially overlap when attaching the tape of the insulating material, and then pressurizing the overlapping portion to make the tape adhesion thickness uniform. Manufacturing method characterized in that.

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