JP2008192323A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that a rupture plate, which is conventionally installed in a sealed type battery as one of a safety mechanism for maintaining stably a regular operation of the battery for a long period and which works as a barrier rib superior in sealing property for its characteristics especially in a non-aqueous battery, is made of a metal plate as it works also as current flowing passage, thereby, is apt to be corroded when in contact with moisture, and, therefore, may be possibly corroded by the moisture entered from outside of the battery while the battery is used or stored for a long period, and may not operate regularly as a current cut-off element and a pressure release valve. <P>SOLUTION: A metal rupture plate 331 is provided at a sealing lid 30 to seal the aperture of a bottomed envelope body 20 and a corrosion suppression film 332 to suppress corrosion of metal is laminated on the main surface on the downstream side of a gas release passage of the rupture plate 331. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sealed battery, and more particularly to corrosion inhibition of a safety mechanism.

Conventionally, a sealed battery is provided with various safety mechanisms in order to keep the normal operation of the battery stable for a long period of time. As one of these safety mechanisms, the sealed battery is provided with a rupture plate.
This rupture plate is a partition wall that isolates the outside from the inside of the battery in a normal state because, in particular, in non-aqueous batteries, it is not desirable for moisture to enter the battery.

  When the inside of the battery reaches a predetermined high pressure, a part of the rupture plate is broken due to a pressure difference between the inside and outside of the battery, and the high pressure inside the battery is released. Some of the rupture plates are given a function as an energization path. In such a case, the rupture plate is made of a metal plate, and is deformed before the breakage to cut off the energization path, thereby preventing unexpected chemical changes and thermal runaway in the battery.

For example, as disclosed in Patent Documents 1 and 2, the rupture plate seals an outer package containing an electrode body and a non-aqueous electrolyte solution, and a terminal cap with a hole is formed on the outer side of the rupture plate. In many cases, an internal component plate provided on the side and having a hole is provided on the electrode body side of the rupture plate.
JP-A-11-154001 Japanese Patent Laid-Open No. 10-302746

  However, foreign matter may enter from the vent hole and the rupture plate may be torn during normal operation. If the rupture plate is torn during normal operation, foreign matter may enter the battery, causing an internal short circuit or the like, and may cause leakage from the battery. Further, when the rupture plate is made of a metal plate, it corrodes when it comes into contact with moisture. Accordingly, there is a possibility that the rupture plate is corroded by moisture that has entered from the outside of the battery during long-term use or storage, so that it does not operate normally as a current interrupting element or a pressure release valve.

  The present invention has been made in view of the above problems, and it is possible to realize stable current interrupting operation and valve operation by suppressing the rupture plate from being broken at normal time and suppressing corrosion of the rupture plate. An object is to provide a sealed battery.

In order to achieve the above object, in the sealed battery according to the present invention, the rupture plate is provided on the main surface on the downstream side of the gas release path of the rupture plate with respect to the sealed battery in which the gas release path is blocked. Applied a protective film to protect the rupture plate.
The protective film is preferably broken together with the rupture plate due to a pressure difference between inside and outside the battery.

  The term “corrosion” here refers to all alteration phenomena that impair the function of the original rupture plate, including oxidation-reduction reactions.

  In the sealed battery according to the present invention, the protective film for protecting the rupture plate is attached to the main surface downstream of the gas release path of the rupture plate, so that the protective film is not attached. The rupture plate is difficult to break when normal. Therefore, the rupture plate is torn during normal operation, foreign matter can enter the battery, and internal short circuit can be prevented from occurring, and battery leakage can be suppressed. Furthermore, it can suppress that the metal which comprises an electrode raise | generates an unexpected chemical reaction.

  When the rupture plate is made of metal and the protective film is a corrosion-inhibiting film that suppresses corrosion of the metal, moisture or other substances that corrode the rupture plate enter from the downstream side of the gas release path to come into contact with the rupture plate. Even so, the corrosion inhibiting film prevents the substance from reaching the rupture plate, so that the rupture plate can be prevented from corroding. Thereby, in the sealed battery according to the present invention, the rupture plate can exhibit a stable current interrupting function and a valve function over a long period of time.

  The corrosion inhibiting film may be applied to the entire main surface of the rupture plate on the downstream side of the gas release path, or may be partially applied. The rupture plate usually makes a part thereof easier to break than the other part, and when the pressure inside the battery reaches a predetermined high pressure, the part is actively broken by the pressure difference inside and outside the battery, Since the rupture plate exerts a valve function, by applying the corrosion inhibiting film to the entire main surface downstream of the partial gas release path, a region of the rupture plate that functions mainly as a current interrupting element and a valve is formed. Corrosion can be reliably suppressed and the current interrupt function and the valve function can be maintained.

Furthermore, since the corrosion inhibiting film is attached to the rupture plate, the corrosion inhibiting film is basically adhered to the rupture plate even after the rupture plate is broken. Therefore, even when the terminal cap provided with the gas vent hole is disposed on the downstream side of the gas release path of the rupture plate, the corrosion inhibiting film does not block the gas vent hole of the terminal cap when the rupture plate is broken.
Further, in the present invention, since the corrosion inhibiting film is applied to the rupture plate, for example, it is applied by attaching a sheet-like corrosion preventing film, or a liquid precursor is sprayed and dried. Therefore, it is possible to adopt a method for depositing the corrosion-inhibiting film, and it is possible to employ various methods at the time of manufacture.

The rupture plate may be provided at a location different from the terminal cap of the battery. However, it is preferable to arrange the terminal cap on the gas release path downstream side of the rupture plate, since this contributes to the downsizing of the battery.
If what has waterproofness is used as the said corrosion inhibitory film, it is excellent in the effect which suppresses that the said rupture board corrodes resulting from a water | moisture content.

Hereinafter, a sealed battery according to the present invention will be described using a lithium ion battery as an example. However, the embodiment described below exemplifies a sealed battery that embodies the technical idea of the present invention, and the present invention is not limited to the following.
Moreover, this Embodiment does not limit the member described in the claim to the member described in this Embodiment. The size, positional relationship, and the like of the members shown in each drawing may be exaggerated to facilitate understanding. Further, in the following description, the same name and reference sign indicate the same and the same members, and the detailed description will be omitted as appropriate.

[Embodiment 1]
<Configuration of Lithium Ion Battery 100>
FIG. 1 is a perspective configuration diagram of a lithium ion battery according to Embodiment 1 of the present invention. As shown in FIG. 1, the lithium ion battery 100 according to the present embodiment mainly includes an electrode body 80 housed inside a bottomed cylindrical outer packaging body 20 having one end opened, and the outer packaging body 20. The opening end of each is sealed by a substantially disc-shaped sealing lid 30.

Specifically, a reduced diameter portion 20a is provided on the inner side of the outer cover 20 relative to the sealing cover body 30, and a sealing cover body is formed via a gasket 40 on a shelf portion formed on the inner side of the outer packet body 20 by the reduced diameter. The outer packaging body 20 is sealed by mounting 30 and caulking the open end of the outer packaging body 20.
A ring-shaped gasket 40 is fitted between the outer package 20 and the sealing lid 30. The gasket 40 assists the sealing function of the sealing lid body 30 to reliably seal the opening of the outer packaging body 20, and also exhibits a function of electrically insulating the outer packaging body 20 and the sealing lid body 30 during charging and discharging.

The outer package 20 is made of, for example, a metal plate mainly composed of stainless steel, iron, or aluminum, and has a function of a unipolar terminal (for example, a negative electrode terminal). The material of the outer package 20 may be a material other than metal as long as it has the characteristics required for the outer package 20.
In the electrode body 80, the positive electrode plate 82 and the negative electrode plate 83 are wound in a spiral shape with the separator 81 interposed therebetween, and disk-shaped insulators 61 and 62 having a hole in the center are disposed at each of the winding ends. The positive electrode tab 50 extends from one winding end, and the negative electrode tab (not shown) extends from the other winding end.

  The positive electrode tab 50 electrically connected to the positive electrode plate 82 extends from one winding end to the sealing lid body 30 through the hole of the insulator 61, and the extended end of the positive electrode tab 50 reaches the sealing lid body 30. It is electrically connected to this. A negative electrode tab (not shown) that is electrically connected to the negative electrode plate 83 extends from the other winding end to the bottom of the outer package 20 through the space between the inner surface of the outer package 20 and the outer edge of the insulator 62, The extending end of the tab is electrically connected to the outer packaging body 20 with the insulator 62 and the bottom of the outer packaging body 20 being sandwiched.

The positive electrode plate 82 is mainly composed of a lithium metal oxide. For example, lithium nickelate (LiNiO ₂ ), lithium cobaltate (LiCoO ₂ ), or lithium manganate (LiMn ₂ O ₄ ) is used as the material of the positive electrode plate 82. It is done.
The negative electrode plate 83 is mainly composed of carbon, and for example, graphite and coke are used as the material of the negative electrode plate 83.

The electrode body 80 is infiltrated with a nonaqueous electrolytic solution.
<Configuration of sealing lid 30>
FIG. 2 is a cross-sectional view of a main part of the lithium ion battery in the present embodiment.
As shown in FIG. 2, the sealing lid 30 generally includes an internal component plate 31, an insulator 32, a rupture plate 331, a corrosion inhibiting film 332, a PTC element 34, and a terminal cap in the order from the battery inner side to the outer side. 35 has a laminated structure, and these are integrated by caulking the outer edge portion of the internal component plate 31.

Specifically, in the sealing lid 30, the outer edge portion is occupied by the peripheral edge portion of the internal component plate 31 and the ring-shaped insulator 32. The insulating plate 32 is attached to the substantially disc-shaped rupture plate 331, the PTC element 34 and the terminal cap 35 so as to cover the outer edge portions, and the peripheral portion of the internal component plate 31 is covered so as to cover the insulating plate 32. It is in a worn state.
One end of a positive electrode tab 50 extending from the electrode body 80 is connected to the dish-shaped internal component plate 31. The dish-shaped terminal cap 35 has a function of a unipolar terminal (for example, a positive electrode terminal). When the pressure in the battery reaches a predetermined high pressure, each of the terminal cap 35 and the internal component plate 31 Degassing holes 31a and 35a are provided to form a gas release path for releasing the pressure.

A plate-shaped terminal cap 35 and a rupture plate 331 are stacked with a ring-shaped PTC element 34 interposed therebetween, and an opening 34 a of the PTC element 34 is formed between a recess inside the terminal cap 35 and a recess of the rupture plate 331. Accordingly, a gas reservoir space 70 is formed, and the gas reservoir space 70 is opened to the outside air through the gas vent hole 35 a of the terminal cap 35.
The PTC element 34 has a ring shape having an opening 34a in the center, is sandwiched between outer edges of both the rupture plate 331 and the terminal cap 35, and is electrically connected to both. The PTC element 34 has a characteristic that the electric resistance value changes in proportion to the temperature rise. That is, at the temperature of the lithium ion battery 100 in a steady state, the electrical resistance of the PTC element 34 is also low. For example, when an overcurrent starts flowing in the lithium ion battery 100 due to an external short circuit, the lithium ion battery 100 When the temperature rises and the temperature exceeds the threshold value, the electrical resistance value of the PTC element 34 suddenly rises and the conduction between the rupture plate 331 and the terminal cap 35 is cut off, and the lithium ion battery 100 The power supply is substantially cut off.

<Configuration of Rupture Plate 331 and Corrosion Suppression Film 332 and Their Operation>
The rupture plate 331 is made of a metal plate such as aluminum or stainless steel, and its thickness is set in the range of 0.1 [mm] to 0.5 [mm]. The rupture plate 331 is a partition wall that blocks the gas release path under normal conditions, and a corrosion inhibiting film 332 is laminated on the main surface of the gas reservoir space 70 (downstream side of the gas release path). The rupture plate 331 is formed with a convex portion 33a protruding toward the internal component plate at a substantially central portion thereof. The convex portion 33 a is processed on a spherical surface and is thinner than the peripheral portion of the rupture plate 331.

Since the convex portion 33a of the rupture plate 331 is thinned, the convex portion 33a is easily deformed and finally broken as compared with the peripheral edge portion as the internal / external pressure difference of the rupture plate 331 increases.
The convex portion 33a of the rupture plate 331 can be formed by, for example, extruding the center portion of a flat disc with a tool, and in this case, the top portion of the convex portion 33a is the thinnest of the rupture plate 331. Therefore, the top portion of the convex portion 33a is most easily broken during the valve operation.

About the area | region which adheres the corrosion suppression film | membrane 332 in the main surface of the gas release path downstream side of the rupture board 331, since the thin convex part 33a is easy to deform | transform and fracture | rupture, the gas release path of this area | region It is preferable to deposit at least the entire main surface on the downstream side.
In the present embodiment, a corrosion-inhibiting film is provided on the main surface of the rupture plate 331 on the downstream side of the gas release path where the PTC element 34 is not provided, that is, on the main surface on the downstream side of the gas release path of the convex portion 33a. 332 is attached, and the corrosion prevention film 332 is not attached to the outer peripheral edge of the rupture plate 331 in order to conduct the PTC element 34. However, the outer peripheral edge and the PTC element 34 are electrically connected. If possible, the corrosion inhibiting film 332 may be applied to the outer peripheral edge.

  The step of depositing the corrosion inhibiting film 332 may be before or after assembling the battery. For example, after completion of the sealing lid 30 or after completion of the lithium ion battery 100, a nozzle is inserted into the gas reservoir space 70 from the gas vent hole 35a of the terminal cap 35, and the liquid film precursor is passed through the nozzle to the gas on the rupture plate 331. Applying to the area in contact with the outside air of the main surface on the reservoir space 70 side, and drying the film precursor to easily attach the corrosion inhibiting film 332 to the main surface on the downstream side of the gas release path of the convex portion 33a. Can do.

Alternatively, the corrosion-inhibiting film 332 may be attached in advance to the main surface on the outer side of the rupture plate 331 before assembling the battery.
The vicinity of the top of the convex portion 33a of the rupture plate 331 is in point contact with the bottom of the dish-shaped internal component plate 31, and the insulator 32 is disposed as described above. Therefore, the rupture plate 331 and the internal component plate are arranged. The current path to 31 is secured only at the point contact portion.

  The rupture plate 331 is normally in contact with the internal component plate 31 and is conductive. However, as described above, the convex portion 33a of the rupture plate 331 is easily deformed, so that the pressure in the battery becomes a predetermined high pressure. When this happens, the convex portion 33a is pushed outward by the pressure difference between the inside and outside of the battery and deforms to break the point contact with the internal component plate 31 and cut off the current path. In addition, when the high pressure further rises and the pressure difference between the inside and outside of the battery increases, the top of the convex portion 33a that is most likely to break is ruptured, and the corrosion inhibiting film 332 is also ruptured along with the rupture inside the battery. The high pressure of is released. Thus, the rupture plate 331 functions as a safety mechanism that blocks the energization path in the battery and releases the high pressure.

The thickness and components of the corrosion inhibiting film 332 do not hinder the operation of the rupture plate 331 as a gas discharge valve, and before the rupture plate 331 is ruptured, the moisture is on the outer side main surface of the rupture plate 331. It is preferable to adjust so as to exhibit waterproofness to prevent contact with the water.
From this point of view, silicon-based oils, oils, rubber-based resins, urethane-based resins, epoxy-based resins, etc. are easy to form thin and moisture-impermeable films. Or it is preferable to use a combination of these as the main component.

  However, the resin material of the corrosion inhibiting film 332 is not limited to silicon, oil, rubber, urethane, epoxy resin, or the like. For example, a metal film having a higher ionization tendency than the metal rupture plate 331 is adopted as the corrosion inhibition film 332 as long as the function of the corrosion inhibition film 332 described above is not impaired, and this is applied to the outside air side of the rupture plate 331. A so-called sacrificial anticorrosion treatment may be applied.

Further, the corrosion inhibiting film 332 may be provided with, for example, alkali resistance, acid resistance, or the like. By providing this function, the usage environment of the battery can be expanded.
[Embodiment 2]
FIG. 3 is a cross-sectional view of a main part of the lithium ion battery according to Embodiment 2 of the present invention. In the sealing lid 10 in the present embodiment, as shown in FIG. 3, the PTC element 34 shown in the first embodiment is not provided, and other configurations are the same as the sealing lid 30 in the first embodiment. It is the same.
<< Effect of sealed battery in this embodiment >>
As described above, when nothing is attached to the main surface of the rupture plate on the downstream side of the gas release path, the rupture plate may be torn during normal operation. Then, foreign matter may enter the battery and cause an internal short circuit or the like, or cause an unexpected chemical change in the electrode material, and may leak from the battery. Further, in such a case, the rupture plate may corrode, and along with the corrosion, stable current interruption operation and valve operation of the rupture plate may be impaired. On the other hand, in the present embodiment, the corrosion suppression film 332 is attached to the gas release path downstream main surface of the rupture plate 331 provided in the sealing lid 30, and waterproofing is imparted to the corrosion suppression film 332. Therefore, the moisture that has entered through the gas vent hole 35a of the terminal cap 35 is blocked by the corrosion inhibiting film 332, and corrosion of the rupture plate 331 (particularly, the convex portion 33a) can be suppressed. . As a result, the rupture plate 331 can ensure a stable current interruption operation and valve operation over a long period of time.

In addition, since the corrosion inhibiting film 332 functions as a protective film for protecting the rupture plate 331, it is possible to prevent the rupture plate 331 from being broken at normal time, and therefore, foreign matter can enter the battery and cause an internal short circuit or the like. Or the occurrence of unexpected chemical changes in the electrode material can be suppressed, and leakage from the battery can be suppressed.
In the present embodiment, since the corrosion inhibiting film 332 is attached to the rupture plate 331, even when the rupture plate 331 is ruptured, it is basically attached to the rupture plate 331 in a ruptured state. Therefore, even if the terminal cap 35 provided with the gas vent hole 35a is arranged on the downstream side of the gas release path of the rupture plate 331, the corrosion inhibiting film 332 does not block the gas vent hole 35a, and the high pressure in the battery is ensured. Can be opened to the outside of the battery.

If the configuration of the above variation is employed, the number of components of the sealing lid 30 can be reduced, so that the number of parts can be reduced and the cost can be reduced.
<Others>
In the present embodiment, the terminal cap 35 is arranged on the outer side of the rupture plate 331 and the sealing lid body 30 is configured including these, but the terminal cap and the rupture plate body are provided at different locations. The present invention can also be applied to certain types.

  The present invention can be widely applied to the field of sealed batteries that require a valve mechanism, including lithium ion batteries, and its industrial applicability is extremely large.

It is a cross-sectional perspective view of the lithium ion battery in Embodiment 1 of this invention. It is principal part sectional drawing of the lithium ion battery in Embodiment 1 of this invention. It is principal part sectional drawing of the lithium ion battery in Embodiment 2 of this invention.

Explanation of symbols

20 Outer package 20a Reduced diameter portion 30 Sealing lid 31 Internal component plates 31a, 35a Gas vent hole 32 Insulator 33a Protruding portion 34 PTC element 34a Opening portion 35 Terminal cap 40 Gasket 50 Current collecting tabs 61, 62 Insulating plate 70 Gas reservoir Space 80 Electrode body 81 Separator 82 Positive electrode plate 83 Negative electrode plate 100 Lithium ion battery 331 Rupture plate 332 Corrosion inhibiting film

Claims (6)

A sealed battery in which a rupture plate is provided in a state of blocking a gas release path,
A sealed battery, wherein a protective film for protecting the rupture plate is attached to a main surface of the rupture plate on the downstream side of the gas release path. The rupture plate is made of metal,
The sealed battery according to claim 1, wherein the protective film is a corrosion-inhibiting film that suppresses corrosion of a metal. The rupture plate is configured such that a part thereof is more easily broken than the other part due to a pressure difference inside and outside the battery,
3. The sealed battery according to claim 2, wherein the corrosion-inhibiting film is deposited on an entire region of the main surface downstream of the partial gas release path.   The sealed battery according to claim 2, wherein the corrosion inhibiting film is broken together with the rupture plate due to a pressure difference between the inside and outside of the battery. A dish-shaped terminal cap is disposed on the downstream side of the gas release path of the rupture plate,
The terminal cap is provided with a vent hole,
The sealed battery according to claim 1, wherein a space is formed between the rupture plate and the terminal cap, and the space is open to the outside through the gas vent hole.   The sealed battery according to claim 2, wherein the corrosion-inhibiting film is waterproof.

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