JP2009224087A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery hardly generating electric short-circuiting accidents even with external force added, and that, equipped with a center pin can secure enough ventilation even if a separator should be fused. <P>SOLUTION: Of the sealed battery 10A provided with an electrode body 14 formed by winding a cathode plate 11 and an anode plate 12 arranged in opposition with a separator 13 in between in a shape having a hollow part 14a at the center, a center pin 20a inserted into the hollow part 14a, a battery outer package can 17 housing the electrode body 14, and an external terminal also playing a role of a safety valve for exhausting gas in case gas pressure inside the battery outer package can goes over a predetermined value, as well as an insulating member for sealing the external terminal in a state electrically insulated into an opening of the outer package can, and one current-collecting tab with one end connected to one of the electrode plates at an innermost side of the electrode body and with the other end connected to the external terminal, the center pin 20a consists of a coil spring spirally winding metal wire rods. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sealed battery, and more particularly, to a sealed battery having a structure in which a cylindrical center pin is inserted into a hollow portion inside an electrode body wound in a spiral shape.

  With the spread of portable devices in recent years, compact, lightweight and high energy density sealed batteries are required as power sources for these portable devices. Among sealed batteries, secondary batteries that can be charged and discharged, such as nickel metal hydride storage batteries and lithium ion secondary batteries, are often used from the viewpoint of economy. In particular, non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries are used more frequently because they are lighter and have higher energy density than other secondary batteries.

  However, if the secondary battery becomes overcharged, in which current is supplied for a longer time than usual during charging, or if a large current flows due to misuse or failure of the equipment used, the electrolyte solution will The gas is decomposed to generate gas, and the internal pressure of the battery increases due to the generation of this gas. Furthermore, if such an overcharge or short circuit condition continues, the battery temperature rapidly rises due to rapid decomposition of the active material or heat generation due to the combustion of the electrolyte, and the sealed secondary battery suddenly explodes. The device you are using may be damaged. For this reason, in particular, in the case of a nonaqueous electrolyte secondary battery, a battery equipped with an explosion-proof safety valve has been used (see Patent Documents 1 and 2 below).

  This safety valve must be reliably operated from the viewpoint of preventing damage to equipment and preventing fire accidents. Therefore, conventionally, as shown in Patent Document 1 below, a positive electrode plate and a negative electrode plate arranged opposite to each other with a separator sandwiched in a battery outer can are wound into a shape having a hollow portion at the center. A cylindrical center pin is disposed in the hollow portion of the electrode body, and gas generated by overcharging or the like is guided to the safety valve via the center pin disposed in the hollow portion of the electrode body. I am doing so. In this center pin, the pressure generated by the gas generated inside the nonaqueous electrolyte secondary battery is applied in the overlapping direction of the positive electrode plate, the negative electrode plate and the separator, so that the hollow portion is not crushed and the gas passage is not blocked. It is provided to do.

  The center pin is usually formed by rolling a thin metal plate into a cylindrical shape from the viewpoint of cost and gas discharge efficiency. For this reason, the ends of the thin plates in the circumferential direction of the center pin are not joined to each other, and a slit is left between these both ends. The slit formed in the center pin not only ensures the passage of the gas generated inside the non-aqueous electrolyte secondary battery and operates the safety valve normally, but also allows the non-aqueous electrolyte to flow. Also plays the role of improving. That is, inside the non-aqueous electrolyte secondary battery, the non-aqueous electrolyte can flow inside and outside the center pin through the slit. Therefore, the flow of the electrolyte inside the non-aqueous electrolyte secondary battery is excellent, and ion exchange is smooth. Therefore, battery performance can be improved.

  However, when such a nonaqueous electrolyte secondary battery is dropped from a high place or an object is dropped on the nonaqueous electrolyte secondary battery, the battery outer can is deformed. When the battery outer can is thus deformed, the center pin inserted therein may also be deformed. If the center pin is deformed, the end facing the slit may pierce the electrode body and damage the separator, causing a short circuit locally inside the electrode body, causing an excessive short-circuit current to flow, and the non-aqueous electrolyte secondary The battery may overheat.

Therefore, in the invention disclosed in Patent Document 2 below, the end of the center pin facing the slit is arranged inward from the virtual outer periphery of the center pin, and even if the center pin is deformed by an external force, The slit end portion disposed in is made difficult to damage the electrode body and prevents an internal short circuit. Further, Patent Document 2 shown below also shows an example in which a plurality of windows are formed on the side surface of the center pin to further improve the flow of the electrolytic solution inside the battery.
JP-A-6-196138 JP 2003-229177 A

  However, in the conventional nonaqueous electrolyte secondary battery, the center pin disposed in the hollow portion of the electrode body is merely inserted into the hollow portion of the electrode body, and thus may move during use of the sealed battery. There is. In particular, when subjected to shock or vibration, the center pin moves greatly and the end portion protrudes. In such a state, if there is a defect in the routing path of the current collector tab that is pulled out of the electrode body and connected to the sealing body, it will hit the bent portion of the current collector tab and damage the insulation film of the current collector tab. May cause a short circuit. The trouble in handling the current collecting tab is caused when the outer can is sealed with the sealing body, because it is not formed into a predetermined handling shape due to a dimensional variation of each part, an error of a manufacturing apparatus, or the like.

  In particular, when the lower part of the non-aqueous electrolyte secondary battery is heated, the separator or the like may dissolve and the melt may block the lower part of the center pin. Even in this case, the gas permeability is maintained to some extent by the slit formed in the peripheral surface of the center pin. However, when dissolution of the separator becomes significant, the lower part of the center pin is completely blocked by the melt, and ventilation with only the slit of the center pin becomes insufficient, resulting in an increase in gas pressure in the battery, The battery may be destroyed.

  Therefore, the present invention has been made in view of the above problems, and even when an external force is applied, the current collecting tab is rarely damaged by the center pin, and an electrical short-circuit accident or the like is unlikely to occur. An object of the present invention is to provide a sealed battery equipped with a center pin that can ensure sufficient air permeability even when the separator is melted.

  In order to solve the above-described problems, a sealed battery according to the present invention includes a positive electrode plate and a negative electrode plate that are arranged to face each other with a separator interposed therebetween, and an electrode body that is formed by winding in a shape having a hollow portion at the center, and the hollow A center pin inserted into the part; a battery outer can that houses the electrode body; and an external terminal that also serves as a safety valve that discharges gas when the gas pressure in the battery outer can exceeds a specified value. A sealing plate for sealing the opening of the can, and one current collecting tab having one end connected to one electrode plate on the innermost peripheral side of the electrode body and the other end connected to the external terminal, In the sealed battery provided, the center pin is formed of a coil spring in which a metal wire is spirally wound.

  In the sealed battery of the present invention, since the center pin disposed in the hollow portion of the electrode body is made of a coil spring, the center pin itself can absorb the impact. Therefore, even if the sealed battery itself receives an impact or vibration, and the center pin jumps out of the hollow portion, the center pin is difficult to damage the insulating coating of the current collecting tab, so that an electrical short circuit accident is less likely to occur. . In addition, since the gap formed between the coil spring lines is formed over the entire circumference of the coil spring-shaped center pin, even if the electrode body is deformed by an external force, the inside of the battery outer can and the coil spring-shaped center pin A gas passage is secured between the interior and the interior. Therefore, even if the end of the coil spring-shaped center pin is blocked by the melt, the gas generated in the battery outer can smoothly flows to the safety valve side through the gap formed between the coil spring lines. As a result, the safety valve can be operated reliably.

  Moreover, since the center pin that brings about such an effect is merely a metal wire formed in a coil shape, a high-quality sealed battery can be obtained at low cost. Note that the present invention is equally applicable to non-aqueous electrolyte secondary batteries, nickel metal hydride secondary batteries, and the like as long as they are sealed batteries having a center pin at the center of a spirally wound electrode body. is there.

  In the sealed battery of the present invention, the metal wire is stainless steel.

  In the sealed battery of this aspect, since the center pin is made of stainless steel, it does not melt at high temperatures and has excellent corrosion resistance, so that the safety valve can be stably operated over a long period of time. Become. Since stainless steel has great rigidity, the shape of the coil spring-like center pin can be maintained even if the electrode body is deformed by an external force, so that the safety valve can be operated normally. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to Examples, Comparative Examples, and the drawings. However, the examples shown below illustrate a nonaqueous electrolyte secondary battery as an example for embodying the technical idea of the present invention, and the present invention is intended to be specified in this embodiment. The present invention is equally applicable to other embodiments within the scope of the claims.

  FIG. 1 is a perspective view showing a cylindrical non-aqueous electrolyte secondary battery as a sealed battery in the embodiment cut in the vertical direction. 2A is a front view showing the center pin in FIG. 1, and FIG. 2B is a partially enlarged sectional view of FIG. FIG. 3 is a perspective view showing a cylindrical nonaqueous electrolyte secondary battery as a sealed battery in a comparative example cut in the vertical direction. FIG. 4 is an enlarged cross-sectional view showing an example of a defective routing path of the positive electrode current collecting tab. FIG. 5 is an enlarged cross-sectional view showing an example of a normal routing path of the positive electrode current collecting tab.

[Manufacture of Battery of Example]
As shown in FIG. 1, the nonaqueous electrolyte secondary battery 10 </ b> A of the example uses an electrode body 14 in which a positive electrode plate 11 and a negative electrode plate 12 are spirally wound via a separator 13. A hollow portion 14 a is formed at the center of the electrode body 14. Insulating plates 15 and 16 are arranged on the upper and lower sides of the electrode body 14, respectively, and are housed in a cylindrical battery outer can 17 having a bottom that also serves as a negative electrode terminal. The battery outer can 17 is made of iron with nickel plating on the surface.

  The insulating plates 15 and 16 are notched in the same shape as the opening of the hollow portion 14a at the center. Then, the current collecting tab 12 a of the negative electrode plate 12 is welded to the inner bottom portion of the battery outer can 17, and the current collecting tab 11 a of the positive electrode plate 11 passes through a through hole 15 a formed in the insulating plate 15 and serves as a safety valve 18. It is welded to the bottom plate. A non-aqueous electrolyte (not shown) is injected into the battery outer can 17, and the opening of the battery outer can 17 is sealed by a positive electrode terminal 19 that also serves as a safety valve 18.

  An example of a method for producing the positive electrode plate 11 is as follows. First, the positive electrode active material was weighed so that the ratio of lithium nickel cobalt manganese composite oxide: lithium cobaltate = 1: 9 (mass ratio), carbon as the positive electrode conductive agent, polyvinylidene fluoride as the binder ( PVdF) powder is charged into N-methyl-2-pyrrolidone (NMP) at a mass ratio of positive electrode active material: carbon: PVdF = 94: 3: 3 and kneaded to prepare a slurry. This slurry is applied to both surfaces of a 15 μm thick aluminum foil core by the doctor blade method and then dried to form a positive electrode active material layer on both surfaces of the positive electrode current collector. Then, it compresses using a compression roller and the positive electrode plate 11 is produced. The produced positive electrode plate 11 has, for example, a length of 700 mm, a width of 55 mm, and a thickness of 100 μm.

  An example of a method for producing the negative electrode plate 12 is as follows. First, a graphite powder as a negative electrode active material and a dispersion of styrene butadiene rubber (SBR) (styrene: butadiene = 1: 1) as a binder are dispersed in water, and carboxymethyl cellulose (CMC) as a thickener is further dispersed. ) To prepare a negative electrode active material mixture slurry. In addition, the dry mass ratio of this negative electrode active material mixture slurry is prepared such that, for example, graphite: SBR: CMC = 95: 3: 2. The negative electrode active material mixture slurry is applied to both surfaces of a copper foil core having a thickness of 10 μm by the doctor blade method, dried, and then compressed by a compression roller to produce the negative electrode plate 12. The produced negative electrode plate 12 has, for example, a length of 750 mm, a width of 57 mm, and a thickness of 75 μm.

As an example of the method for producing the electrolyte, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) are each 15: 10: 65: 10 (volume ratio, 20 ° C.). LiPF ₆ was dissolved in the mixed solvent so as to be 1 mol / liter, and then vinylene carbonate (VC) was added in an amount of 2% by mass and phenylcyclohexane was added in an amount of 2% by mass. Use electrolyte.

  Specifically, the electrode body 14 wound in a spiral shape is manufactured by the following method. First, the positive electrode plate 11 and the negative electrode plate 12 are overlapped with each other while being insulated from each other with a polyethylene microporous membrane separator 13 interposed therebetween, and are wound around a winding core member (not shown). Here, in the overlapped state, the separators 13 are arranged on the lowermost layer and the uppermost layer. The separator 13 is longer and wider than the positive electrode plate 11 and the negative electrode plate 12. On the other hand, the negative electrode plate 12 is wider than the positive electrode plate 11.

  One end of an aluminum current collecting tab 11 a is welded to the winding start portion of the positive electrode plate 11. Similarly, one end of a current collecting tab 12a made of nickel is welded to the winding end portion of the negative electrode plate 12. The current collecting tabs 11a and 12a are flexible flat plates, and their surfaces are covered with an insulating film except for welded portions at both ends. Further, the outermost periphery of the electrode body 14 wound in a spiral shape is stopped with an insulating tape so that the wound state is maintained. Further, the winding core member is removed, and the electrode body 14 wound in a spiral shape is inserted into the cylindrical battery outer can 17 while contacting the insulating plate 16 having an opening formed in the center at the bottom, and this electrode body. The negative electrode current collecting tab 12 a is welded to the center of the inner surface of the battery outer can 17 through the hollow portion 14 a generated by removing the winding core member from the battery 14.

  Next, a coil spring-shaped center pin 20a as shown in FIGS. 2A and 2B is prepared as the center pin of the embodiment. The coil spring-shaped center pin 20a has the same length as the electrode body 14 wound in a spiral shape, and has a diameter that can be smoothly inserted into the hollow portion 14a. As the wire constituting the coil spring-shaped center pin 20a, a metal wire such as stainless steel which has a diameter of about 0.2 to 0.5 mm and does not melt even at a high temperature of 500 to 600 ° C. or higher is used. The pitch of the center pins 20a is set so as to generate a gap between the lines in the state of being arranged in the hollow portion 14a. Here, as the coil spring-shaped center pin 20a, for example, a stainless steel pin having a free height of 59.2 mm, a diameter of 3 mm, a material diameter of 0.33 mm, and a spring interval of 0.1 mm was used.

  Here, a coil spring-shaped center pin 20 a is attached to a separator (not shown) having a certain area enough to cover the lower end opening of the center pin 20 a, and this attached separator is attached to the inner bottom of the battery outer can 17. It inserted in the hollow part 14a of the electrode body 14 wound by the spiral shape so that it might contact | abut. The separator attached to the lower end of the coil spring-shaped center pin 20a is provided to make the lower end of the center pin 20a easily clogged in order to confirm the effect of the present invention. The configuration of the water electrolyte secondary battery 10A is not necessary.

  Further, an insulating plate 15 having an opening formed in the center is brought into contact with the upper portion of the electrode body 14 wound in a spiral shape, and the positive electrode current collecting tab 11a is passed through the opening of the insulating plate 15, and the positive electrode current collecting tab 11a. The tip is welded to a positive electrode terminal 19 that also serves as a safety valve 18. Here, in order to confirm the effect of the coil spring-shaped center pin 20a, as shown in FIG. 4 from the innermost peripheral side of the electrode body 14 in which the positive electrode current collecting tab 11a is spirally wound, It arrange | positioned so that it might be bent to the hollow part 14a side of the electrode body 14 through the opening 15a. As shown in FIG. 5, the normal shape of this portion is formed so as to be bent from the innermost peripheral side of the electrode body 14 to the outer peripheral direction of the electrode body 14 through the opening 15 a of the insulating plate 15.

  Next, after injecting a predetermined amount of nonaqueous electrolyte into the battery outer can 17, an insulating gasket 21 is brought into contact with the periphery of the positive electrode terminal 19 also serving as a safety valve 18 to electrically connect the positive electrode terminal 19 and the battery outer can 17. The battery outer can 17 was crimped on the front end portion thereof to obtain a nonaqueous electrolyte secondary battery 10A as a sealed battery of the example. The safety valve 18 is provided to discharge the gas to the outside of the non-aqueous electrolyte secondary battery 10A when gas is generated inside the non-aqueous electrolyte secondary battery 10A and the pressure inside the battery exceeds a specified value. It is what was done. The nonaqueous electrolyte secondary battery 10A of this example has a diameter of 18 mm, a height of 65 mm, and a design capacity of 2800 mAh.

[Manufacture of Comparative Battery]
As shown in FIG. 3, a nonaqueous electrolyte secondary battery 10B as a sealed battery of a comparative example is a stainless steel hollow pipe having a length of 60 mm, an outer diameter of 3 mm, and a thickness of 0.35 mm as a center pin 20b. The center pin 20b was prepared in the same manner as the nonaqueous electrolyte secondary battery 10A of the example except that the center pin 20b was used in place of the coil spring-shaped center pin 20a of the example. Also in the nonaqueous electrolyte secondary battery 10B of this comparative example, in order to confirm the effect of the center pin 20b, a separator having a certain area enough to cover the opening is attached to the lower end of the center pin 20b. The positive electrode current collecting tab 11a is bent from the innermost peripheral side of the electrode body 14 wound in a spiral shape to the electrode body hollow portion 14a side through the opening 15a of the insulating plate 15 as shown in FIG. It is arranged in.

[Heating test]
For each of the 20 non-aqueous electrolyte secondary batteries 10A of the example manufactured as described above and the non-aqueous electrolyte secondary battery 10A of the comparative example, a constant current of 1 It = 2800 mA until the battery voltage reaches 4.2V. After the battery voltage reaches 4.2 V, the battery is charged at a constant voltage of 4.2 V until the current value becomes 1/50 It = 56 mA, and the non-aqueous electrolyte secondary batteries 10A and 10B are fully charged. Got. Ten of each of these fully charged non-aqueous electrolyte secondary batteries 10A and 10B were placed vertically on a hot plate, and the hot plate was heated to 300 ° C. to determine whether it would burn or burst. The results are summarized in Table 1.

The numerical values in Table 1 indicate (number of ruptured batteries / number of batteries subjected to test). As shown in Table 1, in the comparative example, bursting or combustion occurred at a rate of 1 out of 10 but according to the example of the present invention, none occurred. In the conventional example, the difference is caused when the lower end of the center pin 10b is closed by the melted separator, and the gas generated inside the spirally wound electrode body 14 enters the center pin 20b. Since it is not possible, it is presumed that the pressure inside the battery is not transmitted to the safety valve 18 and the safety valve 18 does not operate normally. On the other hand, the non-aqueous electrolyte secondary battery 10A of the embodiment uses the coil spring-shaped center pin 20a, so that even if the lower end of the coil spring-shaped center pin 20a is closed with a melted separator, the gap between the coil spring wires is gas. Since the gas generated inside the spirally wound electrode body 14 can enter the coil spring-shaped center pin 20a, the safety valve 18 operates normally according to the gas pressure. Become.
[Vibration test]

  Next, in order to confirm the behavior of the battery when subjected to an external force such as impact or vibration, a vibration test was performed on the nonaqueous electrolyte secondary battery 10A of the example and the nonaqueous electrolyte secondary battery 10B of the comparative example. It was. Ten non-aqueous electrolyte secondary batteries 10A of the example and the non-aqueous electrolyte secondary battery 10B of the comparative example that were fully charged in the same manner as those employed in the heating test described above were used in the vibration tester. The battery was fixed and loaded with a predetermined vibration for a predetermined time, and then the voltage and internal resistance of the battery were measured to determine the presence or absence of an electrical internal short circuit.

  In addition, for vibration, the vibration amplitude is increased by 2 mm, the period is increased from 10 Hz to 55 Hz, and further decreased from 55 Hz to 10 Hz, and the sweep speed is reduced to 1 Hz / min in two directions perpendicular to the height of the battery. As 90 to 100 minutes. The results are summarized in Table 2.

  The numerical values in Table 2 indicate (number of short-circuited batteries / number of batteries subjected to test). As shown in the table, in the comparative example, a short circuit occurred at a rate of 1 out of 10, but according to the example of the present invention, no short circuit occurred. The reason for this difference is that in the conventional example, the center pin 20b moves during vibration and contacts the current collecting tab 11a of the positive electrode 11 many times, and an insulating tape formed on the surface of the current collecting tab 11a is used. Since the destruction or the current collecting tab 11a itself is broken, it is considered that a short circuit has occurred. On the other hand, since the coil spring-shaped center pin 20a used in the embodiment has elasticity, even if the coil spring-shaped center pin 20a moves during vibration and contacts the current collecting tab 11a of the positive electrode 11 many times, the coil spring-shaped center pin 20a is used. This is because the pin 20a is deformed and absorbs the impact, so that the insulating tape formed on the surface of the current collecting tab 11a is not destroyed and the current collecting tab 11a itself is not broken. .

  Therefore, in the sealed battery of the present invention, even if the sealed battery itself receives impact, vibration, or the like and the center pin 20a jumps out of the hollow portion, the center pin 20a is the positive electrode of the current collecting tab 11a. Since it becomes difficult to damage the insulating coating, an electrical short circuit accident is unlikely to occur. Further, in the center pin 20a, the gap generated between the coil spring lines is formed over the entire circumference of the coil spring-shaped center pin, so that the electrode body 14 wound in a spiral shape is deformed by receiving an external force. However, a gas passage is secured between the inside of the battery outer can 17 and the inside of the coil spring-shaped center pin. Therefore, even if the end of the coil spring-shaped center pin 20a is blocked by the melt, the gas generated in the battery outer can 17 smoothly flows to the safety valve 18 through the gap generated between the coil spring lines. Therefore, the safety valve 18 can be operated reliably. Moreover, since the center pin that brings about such an effect is merely a metal wire formed in a coil shape, a high-quality sealed battery 10A can be obtained at low cost.

  In the above embodiment, the negative electrode 12 is also provided with the current collecting tab 12 a and the current collecting tab 12 a is welded to the inner bottom portion of the battery outer can 17. However, the current collecting tab 12 is connected to the battery outer can 12. The battery outer can 17 may be welded anywhere, or the outermost electrode may be formed in direct contact with the battery outer can 17. Further, in the embodiment of the present invention, the case of the electrode body 14 wound in a spiral shape in which the positive electrode 11 is on the inner peripheral side and the negative electrode 12 is on the outer peripheral side has been described, but the arrangement of the positive electrode 11 and the negative electrode 12 is described. Even if the operation is reversed, the same effect can be obtained.

It is a perspective view which cuts the cylindrical nonaqueous electrolyte secondary battery as a sealed battery in an example in the lengthwise direction. 2A is a front view showing the center pin in FIG. 1, and FIG. 2B is a partially enlarged sectional view of FIG. It is a perspective view which cuts and shows the cylindrical nonaqueous electrolyte secondary battery as a sealed battery in a comparative example to the vertical direction. It is an expanded sectional view which shows the example of the troubled handling path | route of a positive electrode current collection tab. It is an expanded sectional view which shows the example of the normal handling path | route of a positive electrode current collection tab. It is an expanded sectional view which shows an example of the bending state of a positive electrode current collection tab.

Explanation of symbols

  10A, 10B: Nonaqueous electrolyte secondary battery 11: Positive electrode plate 11a: Current collecting tab 12: Negative electrode plate 12a: Current collecting tab 13: Separator 14: Spiral electrode body 14a: Hollow portion 15, 16: Insulating plate 17: Battery outer can 18: Safety valve 19 Positive terminal 20a, 20b: Center pin 21: Insulating gasket

Claims (2)

An electrode body formed by winding a positive electrode plate and a negative electrode plate opposed to each other with a separator in a shape having a hollow portion at the center, a center pin inserted in the hollow portion, and a battery exterior housing the electrode body A can, an external terminal also serving as a safety valve for discharging gas when the gas pressure in the battery outer can exceeds a specified value, and the external terminal is electrically insulated from the opening of the battery outer can A sealed battery comprising: an insulating member for sealing; and one current collecting tab having one end connected to one electrode plate on the innermost peripheral side of the electrode body and the other end connected to the external terminal In
The center pin comprises a coil spring in which a metal wire is spirally wound.   The sealed battery according to claim 1, wherein the metal wire is made of stainless steel.

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