KR100614397B1 - Secondary battery - Google Patents

Abstract

The present invention relates to a secondary battery, and the technical problem to be solved is to improve the battery capacity by increasing the height of the internal electrode assembly while the same height of the can.

To this end, the gist of the solution according to the present invention includes an electrode assembly including two electrodes and a separator, an insulating can having an opening formed at an upper portion thereof to accommodate the electrode assembly, and an insulating can so that the electrode assembly does not escape to the outside. A secondary battery comprising an insulating cap plate that closes an opening is disclosed.

Description

Secondary battery {Secondary battery}

1 is an exploded perspective view illustrating a conventional secondary battery.

2 is a cross-sectional view of a conventional secondary battery.

3 is an exploded cross-sectional view illustrating a rechargeable battery according to the present invention.

4 is a plan view illustrating a cap plate in a secondary battery according to the present invention.

5 is a cross-sectional view illustrating a state in which a protective circuit board is connected in a secondary battery according to the present invention.

* Explanation of symbols for the main parts of the drawings

11: insulating can 22: electrode assembly

200: insulating cap plate 210: hole

220: plug 230: electrolyte injection hole

240,250 adhesive

The present invention relates to a secondary battery, and more particularly, to a secondary battery capable of improving battery capacity by increasing the height of an internal electrode assembly while having the same can height.

Secondary batteries have been researched and developed in recent years due to the possibility of recharging and miniaturization and large capacity. In recent years, nickel hydrogen (Ni-MH) batteries, lithium (Li) batteries, and lithium ion (Li-ion) batteries are mainly developed and used.

Most of these secondary batteries contain an electrode assembly consisting of an electrode (i.e., a positive electrode and a negative electrode) and a separator in a can usually made of aluminum or an aluminum alloy, the can is closed with a cap assembly, and then the electrolyte is injected into the can and sealed. It is formed by. The can may be formed of iron, but when it is formed of aluminum or an aluminum alloy, light weight of the battery may be achieved due to the light property of aluminum, and may not be corroded even when used for a long time under high voltage.

The sealed unit cell is housed in a separate hard pack in connection with safety devices such as PTC (positive temperature coefficient), thermal fuses and protective circuit modules (PCM) and other battery components. By using a hot melt resin, the finished appearance is formed through a mold.

1 is an exploded perspective view of a conventional rechargeable battery, and FIG. 2 is a top cross-sectional view of a conventional rechargeable battery.

Referring to FIGS. 1 and 2, a conventional method of forming a rechargeable battery in a bare cell state includes a rectangular can 100 formed in a substantially rectangular parallelepiped, an electrode assembly 12 accommodated inside the can 100, and And a cap assembly coupled to the open top of the can 100 to seal the top of the can.

The electrode assembly 12 is formed by winding or overlapping a stack of the positive electrode 13, the separator 14, and the negative electrode 15 formed in a thin plate or film form.

The positive electrode tab 16 is electrically connected to the positive electrode 13 in a region of the positive electrode current collector in which the positive electrode active material layer is not formed. The negative electrode tab 17 is also connected to a region of the negative electrode current collector in which the negative electrode active material layer is not formed.

The positive electrode 13 and the negative electrode 15 and the tabs 16 and 17 may be arranged with different polarities, and the tabs and the two electrode electrodes are disposed at the boundary where the tabs 16 and 17 are drawn out from the electrode assembly 12. Insulating tapes 18 may be respectively wound to prevent short circuits between the 13 and 15.

Separator 14 is formed to be wider than the positive electrode and negative electrode 13, 15, it is advantageous to prevent the short circuit between the electrodes.

The can 100 is formed of aluminum or an aluminum alloy having a substantially rectangular parallelepiped shape. The electrode assembly 12 is received through the open top of the can 100 so that the can 100 serves as a container for the electrode assembly and the electrolyte. The can 100 may itself serve as a terminal.

The cap assembly is provided with a flat conductive cap plate 110 having a size and shape corresponding to the open top of the can 100. The through hole 111 for the terminal is formed in the center portion of the cap plate 110 so that the electrode terminal 130 can pass therethrough. A tube-shaped gasket 120 is installed between the electrode terminal 130 penetrating the center portion of the cap plate 110 and the cap plate 110 for electrical insulation.

The insulating plate 140 is disposed on the lower surface of the conductive cap plate 110. The terminal plate 150 is provided on the bottom surface of the insulating plate 140. The bottom portion of the electrode terminal 130 is electrically connected to the terminal plate 150.

The positive electrode tab 16 drawn from the positive electrode 13 is welded to the lower surface of the cap plate 110, and the negative electrode tab 17 drawn from the negative electrode 15 is folded a plurality of times at the lower end of the electrode terminal 130. Are welded.

On the other hand, an insulating case 190 is provided on the upper surface of the electrode assembly 12 to electrically cover the electrode assembly 12 and the cap assembly and at the same time to cover the upper end of the electrode assembly 12. The insulating case 190 is preferably made of an insulating polymer resin, for example, polypropylene. A lead through hole 191 is formed in the center portion of the insulating case 190 to allow the negative electrode tab 17 to pass therethrough, and an electrolyte passage hole 192 is formed at the other side thereof. The electrolyte passage hole may not be formed separately.

An electrolyte injection hole 112 is formed at one side of the cap plate 110, and a stopper 160 is installed to seal the electrolyte injection hole after the electrolyte is injected. The stopper 160 is formed by placing a ball-shaped base material made of aluminum or an aluminum-containing metal on the electrolyte injection hole 112 and mechanically indenting the electrolyte injection hole 112. The stopper 160 is welded to the cap plate 110 around the electrolyte injection hole 112 for sealing. The cap assembly is joined to the can by welding the periphery of the cap plate 110 to the side walls of the can 100 opening.

However, there is a continuous need to develop a battery having a larger battery capacity and a smaller volume than the existing product or the same volume as a conventional product according to the demand for lighter weight and higher capacity of the secondary battery. In the conventional rectangular lithium ion secondary battery described with reference to FIG. 2, there is a large amount of empty space for connecting the tab of the electrode assembly to the cap plate.

Such empty space may be inevitable for safety and defect avoidance of the existing battery, but may be considered unnecessary in view of the capacity of the battery. Therefore, there is a need for development of a method or battery structure that can utilize the empty space of an existing secondary battery for expanding battery capacity without having a problem of structural safety.

The present invention is to solve the above-described problem of the conventional secondary battery structure, an object of the present invention is to provide a secondary battery that does not consume space in the can for the electrical connection between the tab and the cap plate of the electrode assembly.

Another object of the present invention is to provide a secondary battery which is easier to process than a conventional secondary battery and can reduce the consumption of processing time.

An object of the present invention is to provide a secondary battery having a structure capable of simplifying the structure of a can type secondary battery and reducing the number of parts.

In order to achieve the above object, a secondary battery according to the present invention includes an electrode assembly including two electrodes and a separator, an insulating can having an opening formed at an upper portion thereof to accommodate the electrode assembly, and an electrode assembly so as not to be separated out. And an insulating cap plate that closes the opening of the insulating can.

Here, the insulating can and the insulating cap plate may be formed of plastic, engineering plastic, or an equivalent thereof.

In addition, the electrode assembly is further provided with an electrode tab, one end of which is connected to two electrodes and the other end of which extends a predetermined length in an upward direction, and the insulating cap plate is fixed so that the electrode tab penetrates and protrudes to a predetermined length to the outside. Holes of size may be further formed.

In addition, an electrolyte injection hole may be formed in the insulating cap plate, and the electrolyte injection hole may be blocked by a plastic stopper.

As described above, in the secondary battery according to the present invention, the insulating case for preventing a short phenomenon between the electrode tab of the electrode assembly and the can or cap plate is removed, whereby the height of the electrode assembly can be further improved accordingly. Dose is also increased.

In addition, the present invention can eliminate the welding case between the electrode tab and the cap plate at the same time the insulating case is removed, thereby reducing the process time and also the manufacturing cost.

In addition, the present invention changes the material of both the can and cap plate to the plastic series, and also greatly reduces the components of the conventional cap assembly, thereby reducing the process time and manufacturing cost as well as significantly lighter weight.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Referring to FIG. 3, an exploded cross-sectional view of a secondary battery according to the present invention is illustrated, and referring to FIG. 4, a plan view of a cap plate in a secondary battery according to the present invention is illustrated.

Referring to FIGS. 3 and 4, the method for forming a secondary battery according to the present invention will be described. A rectangular lithium ion battery in a bare cell state has a rectangular insulating can 11 formed of a substantially rectangular parallelepiped, and the insulating can 11. And an insulating cap plate 200 coupled to the open top of the insulating can 11 to seal the top of the can.

The electrode assembly 22 is formed by winding a laminate of the positive electrode 13, the separator 14, and the negative electrode 15 formed in a thin plate or film form in a spiral shape. In order to prevent a short circuit between the positive electrode and the negative electrode during winding, a separator may be further added to the outside of the negative electrode.

The positive electrode 13 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, such as aluminum foil, and a positive electrode active material layer composed mainly of lithium-based oxide coated on both surfaces thereof. In the positive electrode 13, an electrode tab (eg, a positive electrode tab) 16 is electrically connected to a region of a positive electrode current collector in which a positive electrode active material layer is not formed.

The negative electrode 15 includes a negative electrode current collector made of a conductive metal plate such as copper foil, and a negative electrode active material layer mainly composed of a carbon material coated on both surfaces thereof. An electrode tab (for example, a negative electrode tab) 17 is connected to a region of the negative electrode current collector in which the negative electrode 15 is also not provided with the negative electrode active material layer.

Herein, the positive electrode 13 and the negative electrode 15 and the tabs 16 and 17 may be arranged with different polarities, and the tabs 16 and 17 may be disposed at the boundary where the tabs 16 and 17 are drawn out from the electrode assembly 22. And an insulating tape may be wound respectively to prevent a short circuit between the two electrodes 13 and 15.

The separator 14 mainly consists of polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene. Separator 14 is formed to be wider than the positive electrode 13 and the negative electrode 13 is advantageous to prevent short circuit between the electrodes.

The can 11 may be formed of an insulator having a substantially rectangular parallelepiped shape, for example, plastic, engineering plastic, or an equivalent thereof, but the material is not limited thereto. The electrode assembly 22 is received through the open top of the insulating can 11 so that the insulating can 11 serves as a container of the electrode assembly and the electrolyte. As described above, since the can 11 itself is insulative, the present invention does not perform a terminal role as in the related art. In addition, according to the present invention, a step 19 is formed at an upper end of the can 11 in which the opening is formed, and the cap plate 200 to be described below can be strongly coupled to the step 19.

The cap plate 200 is provided in the form of an insulating flat plate having a size and shape corresponding to the open upper end of the insulating can 11. The cap plate 200 may be formed of a non-metal insulating material, for example, plastic, engineering plastic, or equivalent thereof, but is not limited thereto.

In the cap plate 200, a through hole 210 is formed to allow the electrode tabs (eg, the positive electrode tab and the negative electrode tab) 16 and 17 of the electrode assembly 22 to pass therethrough, and an electrolyte injection hole for injecting the electrolyte solution. 230 is also formed. In addition, the cap plate 200 is coupled to the step 19 formed at the upper end of the can 11 and then strongly fixed to the can 11 by an adhesive or heat welding method.

In addition, since the electrolyte may leak into the gap between the tabs 16 and 17 and the cap plate 200 penetrating the cap plate 200, the gap may be a welding rod made of a plastic material having good bondability with the metal forming the tabs. It can also be finished by welding. However, it is preferable from the standpoint of workability to seal the gap with an adhesive or an adhesive filler having adhered the cap plate and the opening of the can.

The insulating plate, the terminal plate, the electrode terminal, the gasket, and the like, which were conventionally disposed on the lower surface of the cap plate 200, are not necessary in the present invention and are removed. In addition, since the electrode tab may be bent a plurality of times and not welded to the inside, the electrode tab may be straightly drawn out, and thus a polypropylene (PP) case or an insulating case that is placed on the electrode assembly may be omitted.

Accordingly, the present invention can further increase the height of the electrode assembly 22 by the removed component, thereby enabling battery capacity improvement. Of course, the removal of the components as described above not only simplifies the assembly process, but also reduces the manufacturing cost. Moreover, by using plastic-based cans and cap plates instead of metallic cans and cap plates, the weight is lighter.

On the other hand, the electrolyte injection hole 230 for injecting the electrolyte is formed by placing a step so that it can be closed with a plastic stopper 220, rather than indenting and welding the aluminum ball. When the plug is closed, an adhesive may be used to increase the sealing force, and a screw may be formed by screwing the plug and the electrolyte inlet. Plastic welding may be used instead of the adhesive. Since there is no insulation case, electrolyte injection can be made more quickly.

Referring to FIG. 5, a state in which a protection circuit board is connected in a secondary battery according to the present invention is illustrated.

The method of forming the secondary battery illustrated in FIG. 5 may be similar to that described in the embodiment illustrated in FIGS. 3 to 4. However, the opening of the cap plate 200 and the can 11 is an adhesive 240, and seals the gap between the hole of the cap plate 200 and the electrode tab formed so that the electrode tabs 16 and 17 are drawn out. Also, the adhesive 250 is used.

The electrode tabs 16 and 17 drawn out through the holes of the cap plate are themselves connected to the lead plates 320 of the protection circuit board 300 by welding or the like. Reference numeral 310 denotes an external input / output terminal.

Subsequently in this configuration, the secondary battery is mounted in a mold in a core cell state in which a protection circuit board and a bare cell are coupled. The hot melt resin is injected into the mold, and the protection circuit board and the bare cell are combined without any gaps through cooling or curing to form a hard pack battery in which appearance is completed.

As the plastic that can be used in the above embodiments, it is preferable to use engineering plastics excellent in weldability with metal and workability. Engineering plastics developed in recent years are those that are lighter than aluminum and can maintain high mechanical strength, and it is preferable to use those having chemical resistance and heat resistance so that the adhesive is not decomposed or modified by the electrolyte.

For example, an epoxy or the like may be used as the adhesive to closely contact the insulating can and the cap plate. At this time, the epoxy is preferably shortened the curing time in order to increase the processing efficiency.

In the above example, the center plate for drawing the electrode tab is formed in the cap plate, but the groove for drawing the tab is formed at the periphery of the cap plate, and the groove where the opening of the cap plate and the can meets. It is also possible to present another embodiment of the present invention having the effect of forming a hole for electrode tab withdrawal.

As described above, in the secondary battery according to the present invention, the insulating case for preventing a short phenomenon between the electrode tab of the electrode assembly and the can or cap plate is removed, whereby the height of the electrode assembly can be further improved accordingly. Dose is also increased.

In addition, the present invention can eliminate the welding case between the electrode tab and the cap plate at the same time the insulating case is removed, thereby reducing the process time and also the manufacturing cost.                     

In addition, the present invention changes the material of both the can and cap plate to the plastic series, and also greatly reduces the components of the conventional cap assembly, thereby reducing the process time and manufacturing cost as well as significantly lighter weight.

What has been described above is just one embodiment for carrying out the secondary battery according to the present invention, and the present invention is not limited to the above-described embodiment, and the scope of the present invention is departed from the scope of the following claims. Without this, anyone skilled in the art to which the present invention pertains will have the technical spirit of the present invention to the extent that various modifications can be made.

Claims (13)

An electrode assembly having two electrodes and a separator, the two electrodes having one end connected to each other and having an electrode tab extending at a predetermined length in an upward direction thereof; An insulating can having an opening formed therein to accommodate the electrode assembly; An insulating cap plate closing the opening of the insulating can so that the electrode assembly is not separated outward; The insulating cap plate is provided with a hole having a predetermined size so that the electrode tab of the electrode assembly can protrude to a certain length through the electrode tab, and an electrolyte injection hole is formed to inject the electrolyte solution, and the electrolyte injection hole is formed of a plastic stopper. A secondary battery characterized in that the occlusion. The secondary battery of claim 1, wherein the insulating can and the insulating cap plate are made of plastic. The secondary battery of claim 1, wherein the insulating can and the insulating cap plate are bonded to each other by an adhesive. The secondary battery of claim 1, wherein the insulating can and the insulating cap plate are thermally welded to each other. The rechargeable battery as claimed in claim 1, wherein a step is formed at an end of the opening of the insulating can such that a coupling force of the cap plate is improved. The secondary battery of claim 1, wherein the insulating can and the insulating cap plate are made of an engineering plastic having higher mechanical strength than aluminum. delete The secondary battery of claim 1, wherein the gap between the hole and the electrode tab is sealed with an adhesive. According to claim 1, wherein the insulating cap plate is formed in the periphery of the groove for the extraction of the electrode tab, the groove is characterized in that the hole is formed in a state that the cap plate is coupled to the opening of the can. Secondary battery. The secondary battery of claim 9, wherein the gap between the hole and the electrode tab is sealed with an adhesive. delete The secondary battery of claim 1, wherein a corresponding screw thread is formed on an inner surface of the electrolyte injection hole and an outer surface of the stopper so that the electrolyte injection hole is screwed to the stopper. The secondary battery of claim 3, wherein the adhesive is an epoxy resin.

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