KR100770110B1 - Cylinderical lithium rechargeable battery - Google Patents

Abstract

The present invention relates to a cylindrical lithium secondary battery having a functional center pin. More specifically, after inserting a fire extinguish into the center pin in a cylindrical lithium secondary battery, the top and bottom of the center pin are blocked with a polymer resin or the like. In the initial stage of overcharging, the void volume inside the bare cell is reduced, and at high temperatures (80-200 ° C), the polymer resin melts at a specific temperature so that the extinguishing agent can act to prevent explosion and ignition. It relates to a cylindrical lithium secondary battery having a functional center pin with improved.

Cylindrical lithium secondary battery, center pin, extinguishing agent, stability

Description

Cylindrical lithium rechargeable battery

1 is a perspective view of a cylindrical lithium secondary battery according to an embodiment of the present invention

2 is a cross-sectional view taken along the line A-A of FIG.

Figure 3a is a perspective view of the center pin in accordance with an embodiment of the present invention

FIG. 3B is a cross-sectional view taken along the line B-B in FIG. 3A

Figure 4a is a perspective view of the center pin according to another embodiment of the present invention

4B is a cross-sectional view taken along the line C-C in FIG. 4A

<Description of Symbols for Main Parts of Drawings>

100-cylindrical lithium secondary battery 200-electrode assembly

210-Positive Plate 220-Negative Plate

230-Separator 241-Phase Insulation Plate

245-Under insulation board 260, 360-Center pin

270, 370-Body 280, 380-Blocking member

290, 390-Extinguishing Agent 300-Can

330-Crimping part 340-Beading part

400-cab assembly 410-safety band

420-CID 480-Secondary protection element

The present invention relates to a cylindrical lithium secondary battery having a functional center pin. More specifically, after inserting a fire extinguish into the center pin in a cylindrical lithium secondary battery, the top and bottom of the center pin are blocked with a polymer resin or the like. In the initial stage of overcharging, the void volume inside the bare cell is reduced, and at high temperatures (80-200 ° C), the polymer resin melts at a specific temperature so that the extinguishing agent can act to prevent explosion and ignition. It relates to a cylindrical lithium secondary battery having a functional center pin with improved.

In general, a cylindrical lithium secondary battery includes a cylindrical electrode assembly having a center pin coupled thereto, a cylindrical can coupled with the electrode assembly coupled thereto, and a cap assembly coupled to an upper opening of the can to seal the can. .

Such cylindrical lithium secondary batteries are typically used in notebooks, digital cameras, camcorders, and the like, which require large amounts of power because their capacity is about 2000-2800 mAh. Such a cylindrical lithium secondary battery is connected in series or in parallel by a required voltage or capacity, and is fitted with a safety device and assembled into a battery pack of a predetermined type.

In the cylindrical lithium secondary battery, a negative electrode plate coated with a negative electrode active material, a separator, and a positive electrode plate coated with a positive electrode active material are laminated together, and then, one end is bonded to a rod-shaped winding shaft and wound in a substantially cylindrical form to form an electrode assembly. Thereafter, a center pin is coupled to the electrode assembly and inserted into a cylindrical can. Thereafter, an electrolyte is injected into the cylindrical can, and the cap assembly is coupled to the upper portion of the cylindrical can to complete a bare cell having a substantially cylindrical shape.

The cylindrical lithium secondary battery has a safety vane that is deformed when the internal pressure increases due to overcharging, and a circuit breaker due to the change of the shape of the safety vane in order to prevent an explosion phenomenon during overcharging (CID). ), And a safety device composed of a secondary protection device that breaks the circuit as the temperature rises.

These safeguards work as follows:

When the cylindrical lithium secondary battery is in an overcharged state, the electrolyte solution evaporates from approximately the upper region of the electrode assembly and the resistance starts to increase. Further, at this time, deformation occurs from an approximately center region of the electrode assembly, and lithium begins to precipitate. Of course, as the resistance of the upper region of the electrode assembly increases, heat generation starts locally, and the battery temperature rapidly increases.

In this state, the internal pressure is rapidly increased by the action of electrolyte additives such as cyclohexylbenzene (CHB) and biphenyl (BP), which are usually decomposed during overcharge to generate gas. This internal pressure pushes the safety vane, which is a component of the cap assembly, toward the electrode assembly, that is, the upper direction, thereby breaking the current by breaking the current blocking means CID installed thereon. That is, the wiring pattern formed in the current interruption means CID is broken, so that no current flows any more. Of course, when the current is cut off, the overcharge state is stopped, thereby preventing the explosion and fire of the battery. On the other hand, when the internal pressure of the battery is above the threshold by the overcharge phenomenon as described above, all of the internal gas is released to the outside of the bare cell through the opening of the cap-up while destroying the safety vent itself.

The center pin may be manufactured in a cylindrical shape by rolling a metal plate roundly, or may be molded into an integral cylindrical shape from the beginning. In the former case, a slit exists at a portion where both ends of the metal plate meet, and electrolyte or gas can move through this space. In the latter case, there is a void volume, which is an empty space inside the center pin. Such void volume is considered to be one cause of delaying the deformation or rupture time of the above-described safety vent. In the early stage of overcharging, the voids are reduced and the safety vents operate quickly, and when the internal temperature of the battery reaches 80 ~ 200 ℃, the center pin needs to be used as the gas discharge passage. In addition, it is necessary to insert a fire extinguishing agent into the center pin to prevent the battery from ignition when the internal temperature of the battery reaches a high temperature.

The present invention is to solve the problems of the conventional secondary battery described above, by closing the top and bottom of the center pin with a blocking member and inserting a fire extinguishing agent, such as to reduce the void volume in the early stage of overcharging so that the safety band to operate quickly. In addition, when the internal temperature of the battery becomes a high temperature, the obstruction member is melted, and the center pin serves as a gas outlet and at the same time, an extinguishing agent acts to provide a secondary battery having improved safety.

Cylindrical lithium secondary battery according to an embodiment of the present invention for achieving the above object, a cylindrical lithium including an electrode assembly with a center pin inserted in the center, a can containing the electrode assembly, a cap assembly for sealing the can In the secondary battery, the upper and lower ends of the center pin are closed by a blocking member, and a fire extinguishing agent is inserted into the center pin. In this case, the center pin may include a body of a predetermined length penetrating in the up and down direction, and a blocking member for closing the top and bottom of the body.

In this case, the body may be formed of any one of steel (steel), stainless steel (stainless steel), copper (Cu), and the body may be formed with a taper at the top and bottom.

In addition, the closure member may be a film surrounding the whole in an envelope including the top and bottom of the body, the closure member may be a lid for blocking the top and bottom of the body.

In addition, the blocking member may be formed of any one of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), and the body may further include a gasification material therein. In this case, the gasification material may be cyclohexylbenzene (CHB) or biphenyl (BP). In addition, the extinguishing agent may include any one of sodium hydrogen carbonate (NaHCO 3), ammonium phosphate (NH 4 H 2 PO 4), sodium hydroxide (NaOH).

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

1 is a perspective view of a cylindrical lithium secondary battery according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line A-A of FIG. Figure 3a is a perspective view of a center pin surrounded by a closure member in the form of an envelope in accordance with an embodiment of the present invention is inserted into the extinguishing agent. 3B is a cross-sectional view taken along line B-B in FIG. 3A. Figure 4a is a perspective view of the center pin with the top and bottom of the body is blocked with a closure member in the form of a lid according to another embodiment of the present invention and the extinguishing agent is inserted therein. 4B is a cross-sectional view taken along the line C-C in FIG. 4A.

1 and 2, the cylindrical lithium secondary battery 100 according to the present invention includes an electrode assembly 200 having a center pin 360 inserted therein, a cylindrical housing accommodating the electrode assembly 200 and an electrolyte solution. And a cap assembly 400 which is assembled to the can 300 and the cylindrical can 300 to seal the cylindrical can 300 and flows current generated from the electrode assembly 200 to an external device. do.

The electrode assembly 200 includes a positive electrode plate 210 coated with a positive electrode active material layer on a surface of a positive electrode current collector, a negative electrode plate 220 coated with a negative electrode active material layer on a surface of a negative electrode current collector, and the positive electrode plate 210 and a negative electrode plate 2200. The separator 230, which is disposed between and electrically insulates the positive electrode plate 210 and the negative electrode plate 220, is wound and formed in a jelly-roll shape.

Although not shown in detail in the drawing, the positive electrode plate 210 includes a positive electrode current collector made of a thin metal plate having excellent conductivity, for example, aluminum (Al) foil, and a positive electrode active material layer coated on both surfaces thereof. Doing. Both ends of the positive electrode plate 210 are provided with a positive electrode current collector region, that is, a positive electrode non-coating portion, in which a positive electrode active material layer is not formed. One end of the positive electrode non-coating portion is generally formed of aluminum (Al), and the positive electrode tab 215 protruding a predetermined length to the upper portion of the electrode assembly 200 is bonded.

In addition, the negative electrode plate 220 includes a negative electrode current collector made of a conductive metal thin plate, for example, copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces thereof. Both ends of the negative electrode plate 220 are provided with a negative electrode current collector region, that is, a negative electrode non-coating portion, in which a negative electrode active material layer is not formed. One end of the negative electrode non-coating portion is generally formed of a nickel (Ni) material, the negative electrode tab 225 protruding a predetermined length to the lower portion of the electrode assembly 200 is bonded. In addition, upper and lower portions of the electrode assembly 200 may further include insulating plates 241 and 245 for preventing contact with the cap assembly 400 or the cylindrical can 300, respectively.

The cylindrical can 300 has a cylindrical side plate 310 having a predetermined diameter and a bottom plate sealing the lower portion of the cylindrical side plate 310 so that a predetermined space in which the cylindrical electrode assembly 200 can be accommodated is formed. 320 is formed, and an upper portion of the cylindrical side plate 310 is opened to insert the electrode assembly 200. By bonding the negative electrode tab 225 of the electrode assembly 200 to the center of the lower plate 320 of the cylindrical can 300, the cylindrical can 300 itself serves as a negative electrode. In addition, the cylindrical can 300 is generally formed of aluminum (Al), iron (Fe) or an alloy thereof. In addition, the cylindrical can 300 is formed with a crimping portion 330 bent from the top to the top to press the upper portion of the cap assembly 400 coupled to the upper opening. In addition, the cylindrical can 300 is beaded inwardly to press the lower portion of the cap assembly 400 at a position spaced apart from the crimping portion 330 by a distance corresponding to the thickness of the cap assembly (beading) A portion 340 is further formed.

The cap assembly 400 includes a safety vent 410, a current blocking means 420, a secondary protective element 480, and a cap up 490. The safety vent 410 has a plate-like protrusion formed at the center to protrude downward, and is positioned below the cap assembly 400, and the protrusion is deformed upward by the pressure generated inside the secondary battery. The positive electrode tab 215 drawn from the positive electrode plate 210 and the negative electrode plate 220 of the electrode assembly 200, for example, the positive electrode plate 210, is welded to a predetermined surface of the lower surface of the safety vent 410. The safety vent 410 and the positive electrode plate 210 of the electrode assembly 200 are electrically connected. Here, in the remaining electrode plate of the positive electrode plate 210 and the negative electrode plate 220, for example, the negative electrode plate 220, the negative electrode tab 225 drawn from the negative electrode plate 220 is welded to the bottom surface 320 of the bare cell, and the can 300. ) Is electrically connected. The safety vent 410 is deformed or ruptured when the pressure inside the can 300 rises, which serves to damage the current interruption means 420. In addition, the current blocking means 420 is further located on the upper portion of the safety van 410 is broken when the safety van 410 is deformed, the current blocking means 420, the upper portion of the current blocking means 420 The secondary protection element 480 is cut off the current. In addition, an upper portion of the secondary protection element 480 is further provided with a conductive cap up 490 for providing a positive voltage or a negative voltage to the outside.

The center pin 360 is inserted into the center portion of the electrode assembly 200, and may be considered to be inserted for approximately two reasons. First, as the lithium ion battery repeats charging and discharging, the electrode assembly 200 expands. However, since the lithium ion battery cannot expand to the outside blocked by the can 300, the lithium ion battery expands to the center of the electrode assembly 200 to deform the electrode plate. As a result, the cycle life of the battery is reduced, as well as the risk of short circuit. The center pin 360 serves to prevent deformation of the electrode plate. Second, when the inside of the battery is in a high temperature state due to overcharging or the like, a large amount of gas is generated inside, which functions as a discharge passage of the gas. The center pin 360 is formed by rolling a thin board of a metal material in terms of manufacturing cost and efficiency of gas discharge, and has a slit at the end thereof. Alternatively, as in the present invention, the slit may be manufactured in the form of an integral cylindrical shape without a joint from the beginning.

3A to 4B, the upper and lower ends of the center pin are blocked by the blocking members 280 and 380, and the extinguishing agents 290 and 390 are inserted into the center pins 260 and 360. . The center pins 260 and 360 block the upper and lower ends of the body 270 and 370 having a predetermined length penetrating in the up and down directions, and the blocking member is melted or ruptured at a specific temperature. And 280 and 380. Since the bodies 270 and 370 are required to have sufficient strength to prevent deformation of the electrode assembly 200, the bodies 270 and 370 may be formed of steel, stainless steel, copper, or the like. . In addition, a taper 275 may be formed at upper and lower ends of the center pins 260 and 360. When the center pins 260 and 360 are deformed by an external impact, the upper and lower ends of the center pins may be relatively easily deformed than the center part of the center pins. A taper 275 may be formed.

3A and 3B, the blocking member 280 may be formed of a film that encloses the whole of the body 270 including an upper end and a lower end in an envelope form. The blocking member 280 should be a material that is melted or ruptured at a predetermined temperature. In the present invention, a polymer resin, in particular polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET) was used. Polyethylene (PE) has a low density, insufficient molecular arrangement, good ductility, and easy processing. In addition, it is excellent in electrical insulation because it is composed of only CH2, and as shown in the structural formula is symmetrical around the carbon (C) chain is also excellent as a high frequency insulating material. Melting point is slightly different depending on the type, but is about 107 ~ 112 ℃.

The blocking member 280 is melted or ruptured when the internal temperature of the battery reaches approximately 80 ° C. to 200 ° C., so that the upper and lower ends of the body 270 constituting the center pin 260 are opened. That is, the upper and lower ends of the body 270 are penetrated. In this case, the extinguishing agent 290 inserted into the body 270 flows out of the center pin 260 to prevent the battery from firing. In this way, the center pin 260 according to the present invention significantly reduces the void volume by closing the top and bottom at the beginning of overcharging, thereby allowing the safety van 410 to operate quickly. However, since the battery is exposed to the risk of explosion and ignition when the internal temperature of the battery reaches a high temperature, the occluded center pin 260 is not meaningful at this time, rather it is better to act as a chimney. That is, the gas is formed by decomposing cyclohexylbenzene (CHB), biphenyl (BP), etc. contained in the electrolyte is concentrated in the safety vent 410 along the body 270 of the center pin 260 Is better in terms of safety.

In addition, a gasification material that decomposes at a predetermined voltage or higher to generate a gas may be further inserted into the body 270. Such gasification materials are usually decomposed and gasified when the battery is in an overcharge state, that is, when the battery voltage is 4 to 4.5 V or more. As the gasification material, cyclohexylbenzene (CHB), biphenyl (BP), etc., such as those added to the electrolyte, may be used, but the material is not limited thereto. Cyclohexylbenzene (CHB), biphenyl (BP), etc. included in the electrolyte has a reverse function of reducing battery life, but the gasification material inserted into the body 270 of the center pin 260 does not normally react with the electrolyte. You may use any material. That is, if the safety vent 410 is deformed anyway, the entire battery can no longer be used, and thus the gasification material can be used as long as it generates a material that generates as much gas as possible.

The extinguishing agent 290 may include any one of sodium hydrogen carbonate (NaHCO 3), ammonium monophosphate (NH 4 H 2 PO 4), and sodium hydroxide (NaOH). Sodium bicarbonate is a colorless crystalline powder that, when heated, generates carbon dioxide (CO2) and water (H2O), and turns into sodium carbonate anhydride (Na2CO3). Melting point is about 300 ℃. Ammonium monophosphate cools the combustion products by the endothermic action during thermal decomposition, and generates a deliquescent phosphoric acid compound to cover the combustibles. Melting point is about 200 ℃. Sodium hydroxide is pyrolyzed to produce carbon dioxide and water, which blocks oxygen. Since it is used as a powder, it is used as a powder fire extinguisher. Melting point is about 320 ℃.

4A and 4B, the blocking member 380 may be formed in the form of a lid blocking the upper and lower ends of the body 370. That is, after forming the closure member 380 in the form of a lid, it is coupled to the upper and lower ends of the body 370, respectively. Similarly, as described above, the extinguishing agent 390 is inserted into the body 370, and in addition, a gasification material may be inserted. Therefore, even in this case, when the internal temperature reaches 80 ° C. or more, the cap member 380 in the form of a lid is melted or ruptured, so that the gas due to decomposition of the extinguishing agent 390 and the gasifier is directed toward the electrolyte solution and the electrode assembly 200. Delivered. As a result, the safety vent 410 quickly operates to stop the overcharge state and also suppresses the ignition phenomenon.

Next will be described the operation of the cylindrical lithium secondary battery according to an embodiment of the present invention.

3B and 4B, when the internal temperature of the battery becomes approximately 80 to 120 ° C. due to overcharging, the blocking members 280 and 380 are melted or ruptured, whereby the extinguishing agents 290 and 390 become center pins 260. 360). Therefore, since the inside of the center pins (260, 360) is empty, the gas inside the battery is quickly delivered to the electrode assembly direction through the inside of the center pins (260, 360) to deform or burst the safety vents more quickly, It destroys the current blocking means (CID) to cut off the current and prevent the internal temperature rise. In addition, due to the extinguishing agents 290 and 390 leaking out of the center pins 260 and 360, the possibility of ignition is significantly lowered. That is, until the blocking members 280 and 380 are opened, the extinguishing agents 290 and 390 are solid and there is no volume change. After the blocking members 280 and 380 are opened, the extinguishing agents 290 and 390 are opened. Penetrates into the battery to suppress ignition.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

According to the cylindrical lithium secondary battery according to the present invention, by closing the top and bottom of the center pin with the extinguishing agent is inserted into the block member by reducing the void volume inside the battery at the initial stage of overcharge, safety vent and current blocking means (CID) is fast When the temperature inside the battery becomes high, the extinguishing agent leaks out of the center pin and the center pin is used as a gas discharge passage to prevent explosion and ignition of the battery, thereby improving the safety of the secondary battery.

Claims (10)

In the cylindrical lithium secondary battery comprising an electrode assembly having a center pin inserted in the center, a can containing the electrode assembly, a cap assembly for sealing the can, The center pin is a cylindrical lithium secondary battery, characterized in that it comprises a body of a predetermined length penetrating in the up and down direction, the closing member in the form of a lid to close the top and bottom of the body. delete The method of claim 1, The body is a cylindrical lithium secondary battery, characterized in that formed of any one of steel (steel), stainless steel (stainless steel), copper (Cu). The method of claim 1, The body is a cylindrical lithium secondary battery, characterized in that the taper is formed on the top and bottom. delete delete The method of claim 1, The blocking member is a cylindrical lithium secondary battery, characterized in that formed of polyethylene (PE). The method of claim 1, The body is a cylindrical lithium secondary battery, characterized in that the further gasification material is inserted therein. The method of claim 8, The gasification material is a cylindrical lithium secondary battery, characterized in that cyclohexylbenzene (CHB) or biphenyl (BP). The method of claim 1, The extinguishing agent is a cylindrical lithium secondary battery comprising any one of sodium hydrogen carbonate (NaHCO 3), ammonium phosphate (NH 4 H 2 PO 4), sodium hydroxide (NaOH).

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