KR20050113985A - Secondary battery - Google Patents

Abstract

The present invention relates to a secondary battery, and more particularly, to a secondary battery having improved mounting structures of electrode terminals and secondary protection devices used in the secondary battery in order to secure stability of the secondary battery.

Description

Secondary Battery

The present invention relates to a secondary battery, and more particularly, to a secondary battery having improved mounting structures of electrode terminals and secondary protection devices used in the secondary battery in order to secure stability of the secondary battery.

In general, as the light weight and high functionalization of portable wireless devices such as a video camera, a portable telephone, a portable computer, and the like progress, many studies have been conducted on secondary batteries used as driving power. Such secondary batteries include, for example, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among them, lithium secondary batteries are rechargeable, compact, and large-capacity, and are widely used in advanced electronic devices because of their high operating voltage and high energy density per unit weight.

Such a secondary battery is accommodated in a metal can containing an electrode assembly consisting of a positive electrode plate, a negative electrode plate, and a separator, and an electrolyte is injected into the can to seal the bare cell. The bare cell thus formed is usually provided with an electrode terminal insulated from the can at the top, so that the electrode terminal forms one pole of the battery, and the other electrode is the battery can itself.

A secondary protection device such as a PTC and a protection device such as a protection circuit module (PCM) are connected to an upper portion of the bare cell sealed as described above, and the secondary battery is formed in a battery pack or molded with resin to form a secondary battery. At this time, the safety devices of these secondary batteries are connected to the positive electrode and the negative electrode, respectively, to prevent the risk of battery rupture by cutting off the current when the battery voltage rises rapidly due to the high temperature rise of the battery or overcharge and discharge.

1 is a partial cross-sectional view showing a bare cell of a conventional secondary battery.

The bare cell 10 of the secondary battery includes a can 20, an electrode assembly 22, and a cap assembly 30. In addition, according to the configuration of the secondary battery includes a secondary protective element 40 on the top.

Referring to FIG. 1, the can 20 is a container made of a metal material having an open shape on an approximately rectangular parallelepiped and is formed by a processing method such as deep drawing. As the material constituting the can 20, aluminum or an aluminum alloy, which is a lightweight conductive metal and easily copes with corrosion, is preferable. The can 20 is a container of an electrode assembly 22 composed of a positive electrode plate 23, a separator 24, and a negative electrode plate 25 and an electrolyte solution, and the electrode assembly 22 is an open top of the can 20, that is, After the top opening is inserted into the can, the top opening of the can 20 is sealed by the cap assembly 30.

The cap assembly 30 is provided with a flat cap plate 31 having a size and shape corresponding to the top opening of the can 20.

The electrode assembly 22 is formed by winding a separator 25 between the positive electrode plate 23 and the negative electrode plate 24. The positive electrode plate 23 is electrically connected to the cap plate 31 through the positive electrode tab 26, and the negative electrode plate 25 is electrically connected to the negative electrode terminal 32 of the cap plate 31 through the negative electrode tab 27. Connected. Therefore, the can 20 is electrically insulated from the negative electrode terminal 32 to serve as a positive electrode terminal. After the cap assembly 30 is welded to the top of the can 20, the electrolyte is introduced through the electrolyte inlet 36 of the cap plate 31. The electrolyte injection hole 36 is sealed with a stopper 37 in which a ball is press-fitted.

The cap plate 31 is preferably formed of the same aluminum or aluminum alloy as the can 20 to improve weldability for coupling with the can 20. A terminal through-hole is formed in the center of the cap plate 31 so that the electrode terminal 32 can pass therethrough. A tube-shaped gasket 33 is installed outside the cathode terminal 32 penetrating the center of the cap plate 31 for electrical insulation between the cathode terminal 32 and the cap plate 31. The insulating plate 34 is disposed on the lower surface of the cap plate 31 near the terminal hole of the cap plate 31. The terminal plate 35 is provided on the lower surface of the insulating plate 34.

The secondary protection element 40 is seated on the upper surface of the cap plate 31 is connected between the negative electrode terminal 32 and the protection circuit board (not shown), the PCT or thermal fuse as the secondary protection element 40 Is used.

However, in the conventional secondary battery configured as described above, the secondary protection device to quickly detect the change in the temperature of the can to cut off the current, but is mounted on the top of the cap plate is far from the inside of the can, so the temperature sensitivity of the secondary protection device is inferior There is a problem.

In addition, in the conventional secondary battery, since the head portion of the negative electrode terminal protrudes on the cap plate and is not formed on the same plane as the secondary protection device, it is difficult to connect the secondary protection device to the electrode terminal. In addition, there is a problem that the negative electrode terminal is rotated during the process of assembling the secondary protection device to the negative electrode terminal and the assembling process, so that the welded portions of the negative electrode terminal and the negative electrode tab become vulnerable or fall off.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a secondary battery having improved mounting structures of electrode terminals and secondary protection devices used in the secondary battery in order to secure stability of the secondary battery.

The present invention for achieving the above object is an electrode assembly formed by winding together a positive electrode plate and a negative electrode plate and a separator insulated between the positive electrode plate and the negative electrode plate, a can in which the electrode assembly is accommodated, and a cap plate for sealing the upper opening of the can And a cap assembly having an electrode terminal inserted into and insulated from a terminal through hole formed in the cap plate, wherein the cap assembly includes a cap assembly formed on an upper surface of the cap plate so as to correspond to a head shape of an electrode terminal. The head of the electrode terminal is seated and the terminal groove is formed to extend to the other side and the extension portion formed to extend to the other side of the terminal groove is seated spaced apart from the electrode terminal by a predetermined distance and one end is connected to the upper surface of the electrode terminal It characterized in that it comprises a secondary protective element.

In addition, in the present invention, the head of the electrode terminal is formed in a square pillar shape, the terminal groove is preferably formed in a square shape.

In addition, a safety vent may be formed at the lower side of the other side of the terminal groove in the present invention.

In addition, in the present invention, the secondary protection device may be formed of one of PTC, thermal fuse, and thermobreaker.

In addition, in the present invention, the PTC device may be formed as a composite device in which a thin film of a composite material in which resin and carbon powder are mixed between an upper plate and a lower plate formed of a metal is bonded.

In the present invention, the thermal fuse is preferably formed of a tin alloy that is operated at a temperature between 90 ~ 100 ℃.

In addition, in the present invention, the thermobreaker is formed with a case in which a bimetal and one end are connected to the electrode terminal and the other end is in contact with the bimetal to form a terminal lead wire and a sealed space, and the bimetal and terminal lead wire are inserted from both sides, respectively. Can be.

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

2 is a partial cross-sectional view showing a bare cell according to an embodiment of the present invention. 3 shows a plan view of FIG. 2. 4 is a sectional view of a thermobreaker which is a secondary protective element used in the present invention. 5 is a partial cross-sectional view showing a bare cell according to another embodiment of the present invention.

Referring to FIG. 2, the bare cell 100 of the secondary battery according to the present invention may include a can 200, an electrode assembly 210 accommodated in the can 200, and an upper end of the can 200. It is formed including a cap assembly 300 for sealing the opening. In addition, the cap assembly 300 is formed to include a secondary protective element 330.

The can 200 may be formed of a metal material having a substantially rectangular parallelepiped shape, and may itself serve as a terminal. An upper end of the can 200 is opened to form an upper opening, and the electrode assembly 210 is received through the upper opening.

The electrode assembly 210 includes a positive electrode plate 213, a negative electrode plate 215, and a separator 214. The positive electrode plate 213 and the negative electrode plate 215 may be stacked through a separator 214 and then wound in a jelly-roll form. The positive electrode tab 216 is welded to the positive electrode plate 213, and an end portion of the positive electrode tab 216 protrudes upward from the electrode assembly 210. The negative electrode tab 217 is also welded to the negative electrode plate 215, and an end portion of the negative electrode tab 217 also protrudes above the electrode assembly 210.

The cap assembly 300 includes a cap plate 310, an electrode terminal 320, and a secondary protective element 330.

The cap plate 310 is formed of a metal plate having a size and shape corresponding to that of the upper opening of the can 200.

A terminal hole 312 having a predetermined size into which the electrode terminal 320 is inserted is formed at the center of the cap plate 310. The terminal groove 314 is formed in the upper portion of the terminal through hole 312 in a shape corresponding to the head shape of the electrode terminal 320. The terminal groove 314 extends a predetermined distance to the other side, and an extension part is formed. Accordingly, the terminal groove 314 is formed in a shape in which the terminal through hole 312 is formed at one side of the terminal groove 314. Since the head of the electrode terminal 320 is formed in a square pillar shape, preferably the terminal groove 310 is also formed in a square shape.

An electrode terminal, for example, a negative electrode terminal 320 is inserted into the terminal through hole 312 and the terminal groove 314. The negative electrode tab 217 of the electrode assembly 210 is welded to the center of the lower surface of the cap plate 310, and the positive electrode tab 216 of the electrode assembly 210 is welded to the other side of the cap plate 310.

The negative electrode terminal 320 is preferably a head portion is formed in a rectangular shape, is inserted into the terminal through hole 312, the head portion is seated on one side of the terminal groove 314 is assembled. Therefore, when the negative electrode terminal 320 is assembled to the terminal groove 314, the negative electrode terminal 3620 does not rotate in a process such as welding the secondary protective device 330. Accordingly, there is no problem that the negative electrode tab 217 welded to the lower portion of the negative electrode terminal 314 is deformed or the welded portion of the negative electrode tab 217 is weakened.

The negative electrode terminal 320 is provided with a tubular gasket 322 to insulate the cap plate 310. In addition, a lower surface of the cap plate 310 is formed with a terminal plate 326 electrically connected to the bottom of the negative electrode terminal 320, the terminal plate 326 and the negative electrode terminal 320 and the cap plate 310 of An insulating plate 324 is installed for electrical insulation. The insulating plate 324 may be an insulating tape such as PP tape. On the other hand, the electrode terminal 320 is formed of a positive electrode terminal depending on the formation position can be connected to the positive electrode tab 216 is a matter of course.

2, the secondary protection device 330 is seated spaced apart from the electrode terminal 320 by a predetermined distance from the other side of the terminal groove 314, and one end of the secondary protection device 330 is connected to the terminal. The lead wire 334 is coupled to the negative electrode terminal 320, and the other end thereof is coupled to the protective circuit board (not shown) by the connection lead wire 336. A protection device insulating plate 332 is installed below the secondary protection device 330 to insulate the secondary protection device 330 from the cap plate 310. Accordingly, the secondary protection device 330 is coupled at the same height as the negative electrode terminal 320 to facilitate coupling, and the secondary protection device 330 does not protrude from the negative electrode terminal 320, thereby facilitating pack formation. In addition, since the secondary protection device 330 is installed at a close distance to the inside of the can 200, the temperature inside the can 200 may be more effectively detected.

As the secondary protection device 330, a device capable of adjusting the flow of current according to the ambient temperature is used. Preferably, the PTC Thermistor (Positive Temperature Coefficient; hereinafter referred to as a "PTC device"), a thermal fuse, Thermal breakers are used.

The PTC device is a device that adjusts the flow of current by increasing the resistance as the ambient temperature increases. As the PTC device, a composite system using a resin such as styrene butadiene rubber (SBR) and a composite material formed of carbon powder or an oxide system formed of barium titanate is generally used, but the type thereof is not limited thereto. Preferably, the PTC device uses a composite device capable of minimizing the thickness of the device, and the composite device is manufactured by forming a carbon powder and a resin into a thin film between the upper plate and the lower plate. In the composite device, when the temperature is increased, the resin expands and the internal resistance increases as the contact between the carbon powder is partially cut off.

One end of the PTC device is connected to the negative electrode terminal 320 by a terminal lead line 334, and the other end thereof is connected to the protective circuit board by a connection lead line 336. Therefore, when the temperature inside the battery is increased, the PTC device reduces the flow of current between the protective circuit board and the negative electrode terminal 320 by increasing the internal resistance.

The thermal fuse is generally formed of a tin alloy containing tin as a main component, and is formed into a thin film to increase temperature sensitivity.

One end of the thermal fuse is connected to the negative electrode terminal 320 by the terminal lead wire 334, and the other end thereof is connected to the protection circuit board by the connection lead wire 336. Therefore, the cap plate is electrically insulated and mounted so that the temperature inside the battery is increased, and when the temperature reaches a predetermined temperature, it is melted and cut off to block the flow of current. Thermal fuse is preferably designed by adjusting the components to operate between 90 ~ 100 ℃ considering the general operating temperature of the battery and the manufacturing process. That is, when the operating temperature is 90 degrees or less, the problem of melting in the aging process during the manufacturing process of the secondary battery occurs. In addition, when the operating temperature is more than 100 degrees, it is impossible to effectively prevent the risk of explosion, such as overheating of the secondary battery.

As the thermal fuse, tin alloy containing 70 to 90% of tin (Sn), 5 to 10% of zinc (Zn), 1 to 4% of lead (Pb), and other metals is used. In addition, an alloy containing 22% tin, 28% lead, and 50% bismuth may be used as the thermal fuse.

Since the thermal fuse is mounted in the protective device groove 316 as a thin film, it is preferable to form an insulating film with polyethylene or polyurethane film for insulation from the outside.

As shown in FIG. 4, the thermal breaker includes a bimetal 340 and a case 350 in which the bimetal 340 is accommodated, and is inserted into and fixed in the protective device groove 316.

The bimetal 340 is formed by joining two kinds of metal foils having different expansion coefficients, that is, expansion coefficients according to temperature, and are deformed toward smaller thermal expansion coefficients according to temperature change. In the present embodiment, a bimetal is formed such that the metal 340a having a large expansion coefficient is positioned at the top and the metal 340b having a small expansion coefficient is positioned at the bottom. Therefore, when the temperature is elevated at a low temperature and the temperature is raised, the metal 340b having a small expansion coefficient is deformed downward, whereby the contact between the bimetal 340 and the terminal lead wire 334 is broken. The bimetal 340 may be formed by bonding various metal foils. As the metal 340a having a high expansion coefficient, an alloy of copper and zinc, an alloy of nickel and manganese and iron, an alloy of nickel and chromium and iron, an alloy of nickel, manganese and copper, and the like may be used. As the metal 340b having a small expansion coefficient, an alloy of nickel and iron is used. The bimetal is preferably formed by joining an alloy of nickel, manganese, iron, and an alloy of nickel and iron with good reaction at low temperatures.

The bimetal 340 is preferably formed in 0.1 ~ 1.0mm. If the thickness of the bimetal 340 is too thin, it may be difficult for the bimetal 340 to be horizontal and the contact with the terminal lead wire 334 may become unstable. In addition, if the thickness of the bimetal 340 is too thick, the operation according to the temperature is not sensitive.

One end of the bimetal 340 is connected to the upper portion of the negative electrode terminal 320 by the terminal lead wire 334, and the other end thereof is connected to the protection circuit board by the connection lead wire 336.

The case 350 includes a case body 352 and a cover 358. The case body 352 is a box-type bimetal hole (353) and the terminal lead wire hole 354 is formed in the upper end of both sides of the bimetal hole 340 and the terminal lead wire 334 is fixed and the bottom is open Is formed. The bimetal hole 353 and the terminal lead wire hole 354 protrude to the outside of the case 350 by a predetermined length so that the reinforcement parts 353a and 354a are formed so that the bimetal 340 and the terminal lead wire 334 move up and down. It is fixed so that it is not. The case body 352 preferably forms a step on the upper inner surface such that the bimetal 340 and the terminal lead wire 346 are seated at a predetermined position.

The case is preferably formed of polypropylene or polyimide or PPS resistant to the electrolyte.

The bimetal 340 and the terminal lead wire 334 are preferably fixed to the bimetal hole 353 and the terminal lead wire hole 354 of the case body 352 by using an adhesive. In other words, the adhesive is sealed between each of the holes, the bimetal 340, and the terminal lead wire 346 so that moisture does not flow into the case. Alternatively, the bimetal 340 and the terminal lead wire 346 may be molded together when the case body 352 is molded. Since the bimetal 340 and the terminal lead wire 346 are in physical contact with each other, when moisture flows into the case 330, an electrolytic solution is applied to the surface of the bimetal 340 or the terminal lead wire 334, thereby providing the bimetal 340. And the contact between the terminal lead wire 334 can be unstable.

The cover 358 is coupled to the lower portion of the case body 352 to seal the inside of the case 350.

5 shows another embodiment according to the invention.

Referring to FIG. 5, the cap plate 310 is further provided with a safety vent 360 under the other side of the terminal groove. The safety vent 360 is formed to be concave upward from the bottom surface of the cap plate 310, and is released when the internal pressure is increased to release the gas. On the other hand, since the thickness of the cap plate 310 is reduced by the safety vent 360, heat transfer to the secondary protection device 330 is facilitated, so that the secondary protection device 330 is faster than the temperature inside the can 200. Changes can be detected.

Next, the operation of the secondary battery according to the present invention will be described.

When the battery is overcharged or overdischarged due to an abnormality in charging or discharging the secondary battery according to the present invention, the temperature inside the battery is increased. In this case, when the temperature inside the battery is overheated above a certain temperature, the secondary protection device 330 formed between the negative electrode terminal 320 and the protective circuit board is more sensitive to the current between the negative electrode terminal 320 and the protective circuit board. The flow is cut off. Therefore, the overcharge or overdischarge state of the secondary battery is stopped and it is possible to prevent the explosion due to excessive pressure increase inside the secondary battery due to the abnormality of the battery. Therefore, it is possible to secure the safety of the secondary battery by preventing the risk caused by the malfunction of the secondary battery.

In addition, since the electrode terminal 320 is seated in the terminal groove 314 when the secondary protection device 330 is welded to the electrode terminal 320, the electrode terminal 320 may be prevented from rotating or moving. It does not affect the welding part with the negative electrode tab 217 welded to the lower part.

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 secondary battery according to the present invention, by mounting the secondary protection element close to the inside of the can, it is possible to operate more sensitively to temperature changes inside the battery. Therefore, if the temperature inside the battery increases due to overcharging or overdischarging of the battery, the current flow of the battery is interrupted to stop the overcharging or overdischarging state of the secondary battery, and the explosion due to excessive pressure rise inside the secondary battery due to the battery abnormality. There is an effect that can prevent.

In addition, according to the present invention, since the secondary protection device is not mounted higher than the negative electrode terminal, the height of the secondary battery can be reduced, and pack formation can be easily performed.

In addition, according to the present invention can be fixed to the terminal groove in the terminal groove can prevent the negative electrode is rotated during the process, there is an effect that can prevent the phenomenon that the welding portion of the negative electrode terminal and the negative electrode tab falls.

In addition, according to the present invention, since the negative electrode terminal and the secondary protection element are seated in one groove, only the terminal groove is formed on the cap plate, thereby facilitating the formation of the terminal groove.

1 is a partial cross-sectional view showing a bare cell of a conventional secondary battery.

2 is a partial cross-sectional view showing a bare cell according to an embodiment of the present invention.

3 is a plan view of FIG.

4 is a cross-sectional view of a thermobreaker that is a secondary protective element used in the present invention.

5 is a partial cross-sectional view showing a bare cell according to another embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

100-bare cell 200-can

300-Cap Assembly 310-Cap Plate

312-Terminal Holes 314-Terminal Groove

320-electrode terminal 324-insulation plate

326-Terminal Plate 330-Secondary Protection Devices

332-Protective element insulation plate 334-Terminal lead wire

336-Lead Wire 340-Bimetal

350-Case 352-Case Body

353-Bimetal Hole 354-Terminal Lead Wire Hole

358-Cover 360-Safety Band

Claims (7)

An electrode assembly formed by winding a positive electrode plate and a negative electrode plate and a separator insulating the positive electrode plate and the negative electrode plate, a can containing the electrode assembly, a cap plate sealing the upper opening of the can, and a terminal through hole formed in the cap plate. In the secondary battery comprising a cap assembly having an electrode terminal is insulated and inserted, A terminal groove formed on an upper portion of the terminal hole so as to correspond to the shape of the head of the electrode terminal, the head of the electrode terminal is seated, and a groove is extended to the other side; A secondary battery comprising a secondary protection element which is seated spaced apart from the electrode terminal by a predetermined distance and extended to the other side of the terminal groove, and has one end connected to an upper surface of the electrode terminal. The method of claim 1, The head of the electrode terminal is formed in a square pillar shape, The terminal groove is a secondary battery, characterized in that formed in a square shape. The method of claim 1, Secondary battery, characterized in that the safety vent is formed on the other side lower portion of the terminal groove. The method of claim 1, The secondary protection device is a secondary battery, characterized in that formed of one of the PTC, the thermal fuse, the thermobreaker. The method of claim 4, wherein The PTC device is a secondary battery, characterized in that formed of a composite-based device in which a thin film of a composite material in which resin and carbon powder are mixed between an upper plate and a lower plate formed of a metal. The method of claim 4, wherein The thermal fuse is a secondary battery, characterized in that formed of a tin alloy operating at a temperature between 90 ~ 100 ℃. The method of claim 4, wherein The thermobreaker Bimetallic, A terminal lead wire having one end connected to the electrode terminal and the other end contacting the bimetal; A secondary battery comprising a case forming a sealed space and the bimetal and the terminal lead wire are inserted at both sides thereof.