JP5712804B2 - Sealed battery and method for manufacturing the same - Google Patents

Description

  The present invention relates to a sealed battery having a safety valve and a manufacturing method thereof.

  In recent years, various sealed batteries have been proposed as power sources for portable devices and power sources for electric vehicles and hybrid vehicles. In such a sealed battery, for example, when a large current flows through the battery due to a short circuit or overcharge, and the temperature inside the battery case rises, the internal pressure of the battery case increases due to gasification of the electrolyte. May rise. In preparation for such a case, in the sealed battery, when the internal pressure of the battery case reaches the valve opening pressure, a safety valve for releasing the gas of the battery case to the outside and reducing the internal pressure of the battery case is provided. There is something. The safety valve is provided, for example, on a sealing lid that closes the battery case (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2002-367583

  The safety valve of Patent Document 1 is made of a metal plate, and has a concave portion (first thin portion) and a groove portion (a groove-like second thin portion) whose thickness is smaller than that of the concave portion (first thin portion). Yes. For this reason, when the internal pressure of the battery case reaches the valve opening pressure, the safety valve is cleaved at the groove-like second thin wall portion, thereby releasing the battery case gas to the outside and reducing the internal pressure of the battery case. Can do.

  Incidentally, the value of the valve opening pressure depends on the thickness of the second thin portion. However, since the second thin portion is formed by pressing or the like, the thickness (average thickness) varies (manufacturing variation). Due to the variation in the thickness (average thickness) of the second thin portion, the valve opening pressure of the battery varies. For this reason, when the thickness (average thickness) variation (manufacturing variation) of the second thin portion is large, the valve opening pressure value of the safety valve deviates from the allowable range (the valve opening pressure value deviates from the allowable range). Safety valves were sometimes manufactured).

However, since there is a limit to increasing the accuracy of press processing (increasing the press process capability), increasing the accuracy of press processing (by increasing the press process capability) causes variations in the thickness of the second thin part (manufacturing variations). ) Was difficult to achieve and was not practical.
On the other hand, as a result of research, the present inventor has made it possible to reduce the influence of the variation in the thickness of the second thin portion (manufacturing variation) on the variation in the valve opening pressure. As a result, the variation in the valve opening pressure can be reduced.

  The present invention has been made in view of the present situation, and is a sealed type in which the variation (manufacturing variation) of the thickness (average thickness) of the second thin portion of the safety valve has less influence on the variation of the valve opening pressure of the safety valve. It is an object of the present invention to provide a battery and a manufacturing method thereof.

One aspect of the present invention includes a first thin portion, the metal safety valve having a second thin portion of the groove having a reduced thickness than the first thin portion, the sealed battery comprising a said safety valve , made of aluminum, the second thin portion, said second thin portion Ri Na aluminum constituting provided an oxide film formed by oxidizing the, the thickness of the second thin portion, the range of 35~60μm And the thickness of the oxide film is a sealed battery having a thickness in the range of 50 to 300 nm .

In the above-described sealed battery, an oxide film (for example, an anodic oxide film) formed by oxidizing the metal constituting the second thin part is provided on the second thin part of the safety valve. Thereby, the influence which the variation (manufacturing variation) of the thickness (average thickness) of the second thin portion has on the variation of the valve opening pressure of the safety valve can be reduced. As a result, the variation in the valve opening pressure of the safety valve can be reduced. In other words, even when the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion is equal to that in the past, the variation in the valve opening pressure of the safety valve can be reduced.
Moreover, in the above-described sealed battery, the thickness of the oxide film is in the range of 50 to 300 nm. That is, an oxide film having a thickness in the range of 50 to 300 nm is provided on the second thin portion. By providing the oxide film having such a thickness on the second thin portion, it is possible to reliably reduce the influence of the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion on the variation in the valve opening pressure. it can.
The oxide film having a thickness in the range of 50 to 300 nm can be formed by, for example, anodizing the second thin portion.

By the way, after producing a safety valve, the 2nd thin part of the safety valve may corrode. As a result, the valve opening pressure of the safety valve may change (decrease).
On the other hand, in the above-mentioned sealed battery, an oxide film (for example, an anodic oxide film) formed by oxidizing the metal constituting the second thin part is provided on the second thin part of the safety valve. Thereby, corrosion of the 2nd thin part of a safety valve can be controlled. Therefore, it is possible to suppress “change (decrease) in the valve opening pressure of the safety valve due to corrosion of the second thin portion”.

  In the above-described sealed battery, when the internal pressure of the battery case reaches the valve opening pressure, the safety valve is cleaved at the groove-shaped second thin part. Thereby, the gas of a battery case can be discharge | released outside through the opened safety valve, and the internal pressure of a battery case can be reduced.

  Furthermore, in the above sealed battery, the oxide film may be a sealed battery that is an anodized film formed by anodizing the second thin portion.

  In the above-described sealed battery, an anodic oxide film formed by anodizing the second thin portion is provided as the oxide film. By providing an anodic oxide coating on the second thin portion of the safety valve, it is possible to appropriately reduce the influence of the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion on the variation in the valve opening pressure.

  In addition, you may make it form an anodic oxide film not only in a 2nd thin part but in the whole safety valve or the sealing lid which provided the safety valve.

Another aspect of the present invention is a method for manufacturing a sealed battery comprising: a metal safety valve having a first thin part and a groove-like second thin part having a thickness smaller than that of the first thin part. The safety valve is made of aluminum, the thickness of the second thin portion is in the range of 35 to 60 μm, and the second thin portion is anodized by anodization of aluminum constituting the second thin portion. e Bei anodic oxidation process to form a coating film, in the anodic oxidation step, a method of manufacturing a sealed battery in a range of 50~300nm the thickness of the anodic oxide coating.

  The above manufacturing method includes an anodizing step of forming an anodized film on the second thin portion by anodizing the second thin portion. Therefore, an anodized film can be provided on the second thin part of the safety valve. Thereby, the influence which the variation (manufacturing variation) of the thickness (average thickness) of the second thin portion has on the variation of the valve opening pressure can be reduced. As a result, the variation in the valve opening pressure can be reduced. That is, even if the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion is equal to that in the conventional case, the variation in the valve opening pressure can be reduced.

  In other words, when the valve opening pressure value falls within a certain allowable range, the allowable range (tolerance) of the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion is expanded. be able to. Thereby, even if there is a certain amount of variation (manufacturing variation) in the thickness of the second thin portion, the value of the valve opening pressure can be kept within an allowable range. Therefore, it is possible to reduce the manufacturing failure of the safety valve (thickness failure of the second thin portion).

  In the sealed battery manufactured by the above-described manufacturing method, when the internal pressure of the battery case reaches the valve opening pressure, the safety valve is cleaved at the groove-shaped second thin part. Thereby, the gas of a battery case can be discharge | released outside through the opened safety valve, and the internal pressure of a battery case can be reduced.

And in the above-mentioned manufacturing method, the thickness of the anodic oxide film formed in a 2nd thin part is made into the range of 50-300 nm in an anodizing process. By providing an anodic oxide coating with such a thickness on the second thin portion, it is possible to reliably reduce the influence of the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion on the variation in the valve opening pressure. Can do.

  When the safety valve is formed of aluminum, the anodic oxidation can be performed using an aqueous sulfuric acid solution, an aqueous phosphoric acid solution, an aqueous oxalic acid solution, or the like as the electrolytic solution. Specifically, for example, a 15 wt% aqueous sulfuric acid solution is used as the electrolytic solution, the applied voltage is within the range of 1.5 to 2.5 V, the treatment time (electrolysis time) is within the range of 10 to 20 minutes, and the treatment temperature ( By performing anodization with the electrolysis temperature in the range of 50 to 65 ° C., the thickness of the anodized film formed on the second thin portion can be in the range of 50 to 300 nm.

1 is a front view of a sealed battery according to an embodiment. It is a top view of the battery. It is an enlarged view of the safety valve of the battery. It is BB sectional drawing of FIG. It is the C section enlarged view of FIG. It is a figure explaining the measuring method of valve opening pressure. It is a graph which shows the relationship between the thickness of the 2nd thin part of a safety valve, and valve opening pressure. It is a partial expanded sectional view of the safety valve concerning a comparison form.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the sealed battery 100 according to the present embodiment is a lithium ion secondary battery including an electrode body 110 and a battery case 120 that accommodates the electrode body 110. The sealed battery 100 is used, for example, as a drive power source for an electric vehicle or a hybrid vehicle.

  The battery case 120 is made of aluminum and has a rectangular parallelepiped shape as shown in FIGS. 1 and 2. The battery case 120 includes a battery case main body 130 and a sealing lid 140. Among these, the battery case main body 130 is made of aluminum and has a bottomed rectangular box shape.

  The sealing lid 140 is made of aluminum and has a rectangular plate shape (see FIG. 2). The sealing lid 140 closes the opening of the battery case body 130 and is welded to the battery case body 130. The sealing lid 140 is provided with a safety valve 150. In the present embodiment, the safety valve 150 is formed integrally with the sealing lid 140. In this embodiment, the safety valve 150 (its base material) is made of aluminum.

  The safety valve 150 includes a first thin portion 151 and a groove-shaped second thin portion 152 having a substantially “8” shape, which is thinner than the first thin portion 151 (FIGS. 3 to 3). 5). When the internal pressure of the battery case 120 reaches the valve opening pressure, the safety valve 150 is cleaved at the groove-shaped second thin portion 152. Thereby, the gas in the battery case 120 can be released to the outside through the safety valve 150 that has been cleaved, and the internal pressure of the battery case 120 can be reduced.

In the present embodiment, the second thin portion 152 of the safety valve 150 is provided with an oxide film 155b (mainly Al ₂ O ₃ ) formed by oxidizing the metal (aluminum) constituting the second thin portion 152. (See FIG. 5). This oxide film 155 b is an anodized film formed by anodizing the second thin portion 152.

In this embodiment, the oxide film 155 (mainly Al ₂ O ₃ ) is formed not only on the second thin portion 152 but also on the entire sealing lid 140 on which the safety valve 150 is formed (see FIG. 5). ). Accordingly, the oxide film 155 b formed on the second thin portion 152 is a part of the oxide film 155.

  In this embodiment, the oxide film 155 is provided on both the front surface 140b and the back surface 140c of the sealing lid 140 (see FIG. 5). Therefore, in this embodiment, the oxide film 155b is provided on both the front surface 152b and the back surface 152c of the second thin portion 152. Moreover, the oxide film 155 is provided in both the front surface 151b and the back surface 151c also about the 1st thin part 151. FIG.

  Thus, by providing the second thin wall portion 152 of the safety valve 150 with an oxide film 155b (specifically, an anodic oxide film) formed by oxidizing the metal (aluminum) constituting the second thin wall portion 152, The influence of the variation in thickness (manufacturing variation) of the second thin portion 152 on the variation in the valve opening pressure of the safety valve 150 can be reduced. As a result, variation in the valve opening pressure of the safety valve 150 (internal pressure of the battery case 120 when the second thin portion 152 is cleaved) can be reduced. That is, the variation in the valve opening pressure of the safety valve 150 can be reduced even if the variation in thickness (manufacturing variation) of the second thin portion 152 is equivalent to the conventional one.

  Further, by providing the second thin part 152 of the safety valve 150 with an oxide film 155b (specifically, an anodic oxide film) formed by oxidizing the metal (aluminum) constituting the second thin part 152, Corrosion of the second thin portion 152 can be suppressed. Thereby, it is possible to suppress the “change (decrease) in the valve opening pressure of the safety valve 150 due to the corrosion of the second thin portion 152”.

  In particular, in this embodiment, the thickness of the oxide film 155 including the oxide film 155b is in the range of 50 to 300 nm. Therefore, the oxide film 155 b having a thickness in the range of 50 to 300 nm is provided on the second thin portion 152. By providing the oxide film 155b having such a thickness on the second thin portion 152, the influence of the thickness variation (manufacturing variation) of the second thin portion 152 on the variation of the valve opening pressure of the safety valve 150 is surely reduced. be able to. Furthermore, corrosion of the second thin portion 152 can be suppressed.

  The electrode body 110 is a wound electrode body in which a belt-like positive electrode (not shown) and a negative electrode (not shown) are wound into a flat shape via a belt-like separator (not shown). Among these, the positive electrode is electrically connected to the external positive electrode terminal 111 inside the battery case main body 130. The negative electrode is electrically connected to the external negative electrode terminal 112 inside the battery case main body 130. In addition, an electrolytic solution (not shown) is injected into the battery case main body 130.

  The external positive terminal 111 is made of aluminum and has a flat plate shape. The external positive terminal 111 is sealed in a liquid-tight manner and electrically insulated from the sealing lid 140 by a first sealing member 113 fitted in a terminal insertion hole (not shown) of the sealing lid 140. It protrudes to the outside through a terminal insertion hole on one side (right side in FIG. 1) of the lid 140.

  The external negative terminal 112 is made of copper and has a flat plate shape. The external negative electrode terminal 112 is sealed in a liquid-tight manner and electrically insulated from the sealing lid 140 by a second sealing member 114 fitted in a terminal insertion hole (not shown) of the sealing lid 140. It protrudes to the outside through the terminal insertion hole on the other side (left side in FIG. 1) of the lid 140.

Next, the manufacturing method of the sealed battery according to this embodiment will be described.
First, an electrode body having a positive electrode, a negative electrode, and a separator is formed. Specifically, first, a positive electrode active material (for example, lithium nickelate), acetylene black, and PVdF (binder) were mixed, and NMP (solvent) was mixed therewith to prepare a positive electrode slurry. Next, this positive electrode slurry was coated on both surfaces of a positive electrode current collector made of aluminum foil, dried, and then pressed. This obtained the positive electrode.

Moreover, a negative electrode active material (for example, graphite), SBR (styrene butadiene rubber), CMC, and (carboxymethylcellulose) were mixed in water to prepare a negative electrode slurry. Next, this negative electrode slurry was coated on both sides of a negative electrode current collector made of copper foil, dried, and then pressed. This obtained the negative electrode.
After that, a wound electrode body 110 was formed by winding with a separator interposed between the negative electrode and the positive electrode.

  Separately, a sealing lid 140 provided with a safety valve 150 is produced. Specifically, a rectangular aluminum plate is prepared, and first, in the pressing process, an oval first thin portion 151 is formed by pressing in the central portion in the longitudinal direction of the aluminum plate (FIGS. 2 to 4). In addition, terminal insertion holes (not shown) are formed by pressing at both ends in the longitudinal direction of the aluminum plate. Further, the first thin portion 151 is pressed to form a second thin wall portion 152 having a substantially “8” shape that is thinner than the first thin portion 151 (see FIG. 3).

Next, the process proceeds to the anodic oxidation step, and an oxide film 155b (anodic oxide film, mainly Al ₂ O ₃ ) is formed on the second thin part 152 by anodizing the second thin part 152. In the present embodiment, not only the second thin portion 152 but also the entire sealing lid 140 is anodized to form an oxide film 155 (anodized film) on the entire surface of the sealing lid 140.

Specifically, a 15 wt% sulfuric acid aqueous solution is used as the electrolytic solution, the applied voltage is within the range of 1.5 to 2.5 V, the treatment time (electrolysis time) is within the range of 10 to 20 minutes, and the treatment temperature (electrolysis temperature). ) In the range of 50 to 65 ° C., the sealing lid 140 was anodized. Thereby, the oxide film 155 (anodized film, mainly Al ₂ O ₃ ) having a thickness in the range of 50 to 300 nm can be formed on the entire sealing lid 140.

  Specifically, an oxide film 155 (anodized film) having a thickness in the range of 50 to 300 nm can be formed on both the front surface 140b and the back surface 140c of the sealing lid 140 (see FIG. 5). Therefore, in this embodiment, the oxide film 155b (anodized film) having a thickness in the range of 50 to 300 nm is formed on both the front surface 152b and the back surface 152c of the second thin portion 152. Moreover, also about the 1st thin part 151, the oxide film 155 (anodic oxide film) of the thickness within the range of 50-300 nm is formed in both the surface 151b and the back surface 151c. As described above, the sealing lid 140 provided with the safety valve 150 having the oxide film 155 (anodized film) is produced.

  By the way, the value of the valve opening pressure of the safety valve depends on the thickness of the second thin portion. However, since the second thin portion is formed by press working, the thickness thereof varies (manufacturing variation). Due to the influence of the thickness variation (manufacturing variation) of the second thin-walled portion, the valve opening pressure of the battery varies. For this reason, conventionally, when the thickness variation (manufacturing variation) of the second thin portion is large, a safety valve in which the value of the valve opening pressure is out of the allowable range may be manufactured.

  In contrast, in this embodiment, after the safety valve (second thin portion) is pressed, an oxide film 155b (anodized film) is formed on the second thin portion 152 of the safety valve 150. Thereby, the influence which the variation (manufacturing variation) of the thickness of the 2nd thin part 152 has on the variation of valve opening pressure can be made small. As a result, the variation in the valve opening pressure of the safety valve 150 can be reduced. That is, even if the thickness variation (manufacturing variation) of the second thin wall portion 152 is equivalent to the conventional one, the variation in the valve opening pressure can be reduced. Furthermore, corrosion of the second thin portion 152 can be suppressed.

  In other words, when the valve opening pressure value of the safety valve is within the allowable range, the allowable range (tolerance) of the thickness variation (manufacturing variation) of the second thin portion can be increased. Thereby, even if there is a certain amount of variation (manufacturing variation) in the thickness of the second thin portion 152, the value of the valve opening pressure can be within an allowable range. Accordingly, it is possible to reduce manufacturing defects of the safety valve 150 (thickness defects of the second thin portion 152).

  In particular, in the present embodiment, the thickness of the oxide film 155b (anodized film) is in the range of 50 to 300 nm. By providing the oxide film 155b (anodized film) having such a thickness on the second thin portion 152, the variation in the thickness (manufacturing variation) of the second thin portion 152 is surely the variation in the valve opening pressure of the safety valve 150. The influence given can be reduced.

  Next, the external positive electrode terminal 111 is welded to the positive electrode (positive electrode current collecting member) of the electrode body 110, and the external negative electrode terminal 112 is welded to the negative electrode (negative electrode current collecting member). Next, the electrode body 110 welded to the external positive terminal 111 and the external negative terminal 112 is inserted into the battery case body 130.

  Further, the first seal member 113 and the second seal member 114 are fitted into the terminal insertion holes of the sealing lid 140. Next, the external positive electrode terminal 111 and the external negative electrode terminal 112 are inserted into the first seal member 113 and the second seal member 114, respectively, and are hermetically sealed, and the opening of the battery case body 130 is closed with the sealing lid 140. . Further, the battery case main body 130 and the sealing lid 140 are welded.

  Thereafter, a predetermined amount of electrolyte (not shown) is injected into the battery case main body 130 through a liquid injection port (not shown) of the sealing lid 140. Then, the sealed battery 100 of this embodiment is completed by airtightly closing the liquid injection port with a liquid injection lid (not shown).

(Valve opening pressure measurement test)
Next, the valve opening pressure of the safety valve 150 according to the embodiment was investigated. Specifically, for the safety valve 150, the relationship between the thickness (average thickness T) of the second thin portion 152 and the value of the valve opening pressure was investigated. Thereby, the degree of the influence of the variation in the thickness of the second thin portion 152 (manufacturing variation) on the variation in the valve opening pressure of the safety valve 150 was investigated.

  First, the processing conditions of the press machine (the set value of the thickness of the second thin part, etc.) are set to predetermined conditions, and the first thin part of the aluminum plate (sealing lid) is pressed to obtain approximately “8”. A groove-shaped second thin portion having a letter shape is formed. Further, the first thin portion of another aluminum plate (sealing lid) is pressed under the same processing conditions to form a groove-shaped second thin portion.

  In this way, groove-shaped second thin portions were formed on a number of aluminum plates (sealing lids). When the average thickness T of the second thin portion was measured for the safety valve thus manufactured, the average thickness T of the second thin portion was not uniform even though the second thin portion was formed under the same processing conditions. (The average thickness of the second thin portion was different).

  Furthermore, the processing conditions of the press machine were changed (by changing the setting value of the thickness of the second thin portion), and groove-shaped second thin portions were formed on a number of aluminum plates (sealing lids). In this way, a large number of safety valves (sealing lids) having different (variable) thicknesses (average thickness T) of the second thin-walled portion were produced.

Next, the large number of sealing lids produced as described above were each subjected to anodizing treatment in the same manner as in the above-described anodizing step. Specifically, a 15 wt% sulfuric acid aqueous solution is used as the electrolytic solution, the applied voltage is within a range of 1.5 to 2.5 V, and the treatment time (electrolysis time) is within a range of 10 to 20 minutes. The sealing lid 140 was anodized for a predetermined time at a processing temperature (electrolysis temperature) of 50 to 65 ° C. As a result, an oxide film 155 (anodized film, mainly Al ₂ O ₃ ) having a thickness in the range of 50 to 300 nm was formed on the entire sealing lid 140.

  Specifically, an oxide film 155 (anodized film) having a thickness in the range of 50 to 300 nm was formed on both the front surface 140b and the back surface 140c of the sealing lid 140. Therefore, an oxide film 155b (anodized film) having a thickness in the range of 50 to 300 nm was formed on both the front surface 152b and the back surface 152c of the second thin portion 152. Moreover, also about the 1st thin part 151, the oxide film 155 (anodic oxide film) of the thickness within the range of 50-300 nm was formed in both the surface 151b and the back surface 151c. Thus, many sealing lids 140 provided with the safety valve 150 having the oxide film 155 (anodic oxide film) were produced.

  When the average thickness T of the second thin portion 152 having the oxide film 155b was measured for each of the many sealing lids 140 thus produced, the second thin portion before anodizing (after press working) was performed. The average thickness T of the second thin portion 152 was varied (the average thickness of the second thin portion 152 was different). That is, there was no change in the degree of variation in the thickness (average thickness T) of the second thin portion before and after the anodizing treatment.

  Note that the average thickness T of the second thin portion is measured as follows using a known laser measuring instrument. Specifically, the thickness of the second thin portion is measured by irradiating laser light onto the front surface 152b and the back surface 152c (see FIG. 5) of the second thin portion 152 and receiving the reflected wave with a laser measuring instrument. . Thus, the thickness was measured using the laser measuring device about several places of the 2nd thin part 152, and these average values were made into the average thickness T of a 2nd thin part.

Next, the value of the valve opening pressure was measured for many safety valves 150 produced as described above.
Specifically, the seal rubber 10 is interposed in a compressed state between the nozzle 20 connected to the compressor and the periphery of the back surface 151c of the first thin portion 151 of the safety valve 150, so that the space between the nozzle 20 and the safety valve 150 is reduced. To be airtight. In this state, compressed air was flowed from the compressor through the nozzle 20 to pressurize the safety valve 150 at a speed of 0.01 MPa / s. And the pressure when the safety valve 150 opened was measured as a valve opening pressure. The result is shown in FIG.

  FIG. 7 is a graph showing the relationship between the average thickness T (horizontal axis in FIG. 7) of the second thin portion of the safety valve and the valve opening pressure value (vertical axis in FIG. 7). In addition, the above-mentioned measurement result is shown with the continuous line as embodiment in FIG. The slope of the straight line in FIG. 7 represents “the degree of the influence of the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion of the safety valve on the variation in the valve opening pressure of the safety valve”.

  Further, the relationship between the average thickness T of the second thin portion 352 and the value of the valve opening pressure was also investigated for the safety valve 350 (see FIG. 8) of the comparative form (conventional). Specifically, the processing conditions (such as the setting value of the thickness of the second thin portion) of the press machine are set to predetermined conditions, and the first thin portion 351 of the aluminum plate (sealing lid) equivalent to the embodiment is pressed. Processing is performed to form a groove-shaped second thin portion 352 having a substantially “8” shape. Further, the first thin portion 351 of another aluminum plate (sealing lid) equivalent to the embodiment is pressed under the same processing conditions to form the groove-shaped second thin portion 352.

  In this way, groove-shaped second thin portions 352 were formed on a number of aluminum plates (sealing lids). When the average thickness T (see FIG. 8) of the second thin portion 352 was measured for the safety valve 350 thus manufactured, the second thin portion 352 was formed despite the formation of the second thin portion 352 under the same processing conditions. There was variation in the average thickness T of the portion 352 (the thickness of the second thin portion 352 was different).

  Furthermore, groove-like second thin portions 352 were formed on a number of aluminum plates (sealing lids) by changing the processing conditions of the press machine (changing the setting value of the thickness of the second thin portion). In this way, a large number of sealing lids 340 (safety valves 350) having different (variable) thicknesses (average thickness T) of the second thin portion 352 were produced. As described above, the safety valve 350 according to the comparative example is different from the safety valve 150 according to the embodiment only in that the anodizing treatment is not performed after the press working, and the rest is the same.

  When the average thickness T of the second thin portion 352 was measured for each of the many sealing lids 340 thus produced, the average thickness T varied as much as the second thin portion 152 of the embodiment. (The average thickness of the second thin portion was different). The average thickness T is measured using a laser measuring instrument as described above.

  Next, as shown in FIG. 6, the value of the valve opening pressure was measured in the same manner as the safety valve 150 of the above-described embodiment for a number of safety valves 350 manufactured as described above. The result is shown by a broken line in FIG. 7 as a comparative form.

  Here, the results of the safety valve 150 of the embodiment and the safety valve 350 of the comparative embodiment will be compared and examined. The slope of the straight line shown in FIG. 7 represents the degree of the influence that the variation (manufacturing variation) in the thickness (average thickness) of the second thin portion of the safety valve has on the variation in the valve opening pressure of the safety valve. Therefore, as shown in FIG. 7, the safety valve 150 of the embodiment has a difference in the thickness (average thickness) of the second thin portion of the safety valve (manufacturing variation) compared to the safety valve 350 of the comparative embodiment. It can be said that the “influence” is small.

  Therefore, the second thin wall portion 152 of the safety valve 150 is provided with an oxide film 155b (specifically, an anodic oxide film) formed by oxidizing the metal (aluminum) constituting the second thin wall portion 152. It can be said that the influence of the variation in the thickness of the thin portion 152 (manufacturing variation) on the variation in the valve opening pressure of the safety valve 150 can be reduced. Specifically, by providing the second thin portion 152 with the oxide film 155b (anodized film) having a thickness in the range of 50 to 300 nm, the thickness variation (manufacturing variation) of the second thin portion 152 is reliably ensured. It can be said that the influence on the variation in the valve opening pressure of the safety valve 150 can be reduced.

  Specifically, even if the safety valve 150 of the embodiment and the safety valve 350 of the comparative embodiment have the same thickness variation (manufacturing variation) of the second thin portion, the safety valve 150 of the embodiment has a valve opening pressure. The variation in the size can be reduced.

  For example, consider a case where the thickness variation (manufacturing variation) of the second thin portion is 10 μm at the maximum due to the manufacturing process capability. In this case, in the safety valve 350 of the comparative form, the variation in the valve opening pressure is about 0.2 MPa. Specifically, for example, in the safety valve 350 of the comparative form, when the thickness of the second thin portion 352 varies in the range of 40 to 50 μm, the valve opening pressure varies in the range of 1.04 to 1.24 MPa. (See FIG. 7).

  On the other hand, in the safety valve 150 of the embodiment, the variation in the valve opening pressure is about 0.14 MPa. Specifically, for example, in the safety valve 150 of the embodiment, when the thickness of the second thin portion 152 varies in the range of 45 to 55 μm, the valve opening pressure varies in the range of 1.03 to 1.17 MPa. (See FIG. 7). Therefore, the variation in the valve opening pressure is smaller in the safety valve 150 of the embodiment than in the safety valve 350 of the comparative embodiment.

  From another point of view, in the safety valve 150 of the embodiment and the safety valve 350 of the comparative embodiment, when the valve opening pressure value of the safety valve is to be within a certain allowable range, the safety valve 150 of the embodiment is the second one. The allowable range (tolerance) of the thickness variation (manufacturing variation) of the thin wall portion can be increased.

  For example, consider a case where the allowable range of the opening pressure of the safety valve is 1.0 to 1.15 MPa. In this case, in the safety valve 350 of the comparative form, the allowable range of the thickness of the second thin portion 352 is 38 to 46 μm (see FIG. 7). Therefore, the allowable range (tolerance) of the thickness variation (manufacturing variation) of the second thin portion 352 is 8 μm. For this reason, when the variation in the thickness of the second thin portion (manufacturing variation) is 10 μm at the maximum due to the normal manufacturing process capability, a large number of safety valves 350 that cause the valve opening pressure to deviate from the allowable range are generated. It will be. Therefore, in the comparative embodiment, a large number of manufacturing defects of the safety valve 350 (thickness defects of the second thin portion 352) occur.

  On the other hand, in the safety valve 150 of the embodiment, the allowable range of the thickness of the second thin portion 152 is 43 to 54 μm (see FIG. 7). Therefore, the allowable range (tolerance) of the thickness variation (manufacturing variation) of the second thin portion 152 is 11 μm. For this reason, when the variation in the thickness of the second thin portion (manufacturing variation) is 10 μm at the maximum due to the normal manufacturing process capability, the valve opening pressure is normally within an allowable range in all the safety valves 150. Become. Accordingly, a manufacturing failure of the safety valve 150 according to the embodiment (thickness failure of the second thin portion 152) does not normally occur.

  As described above, according to the sealed battery 100 and the manufacturing method thereof of the present embodiment, even if the thickness of the second thin portion 152 has a certain degree of variation (manufacturing variation), the value of the valve opening pressure is within the allowable range. Can fit. Therefore, manufacturing defects of the safety valve 150 (thickness defects of the second thin portion 152) can be reduced.

  In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.

  For example, in the embodiment, the oxide film 155b (anodic oxide film) is formed on both the front surface 152b and the back surface 152c of the second thin portion 152. However, the oxide film 155b (anodic oxide film) may be formed on at least the surface 152b of the second thin portion 152. In the case where the oxide film 155b (anodized film) is formed only on the surface 152b of the second thin part 152, the back surface 152c of the second thin part 152 (or the entire back surface 140c of the sealing lid 140 may be masked). Therefore, anodizing treatment may be performed.

  By providing the oxide film 155b (anodic oxide film) on at least the surface 152b of the second thin portion 152, the variation in the thickness (manufacturing variation) of the second thin portion 152 affects the variation in the valve opening pressure of the safety valve 150. Can be small. Thereby, the variation in the valve opening pressure of a safety valve can be made small.

  In the embodiment, the safety valve 150 is integrally formed with the sealing lid 140. However, the safety valve may be a separate body (separate part) from the sealing lid. Also for this safety valve, by providing an oxide film (anodized film) on the second thin part, it is possible to reduce the influence of the variation in the thickness of the second thin part (manufacturing variation) on the variation in the valve opening pressure of the safety valve. it can. Thereby, the variation in the valve opening pressure of a safety valve can be made small.

100 Sealed Battery 110 Electrode Body 120 Battery Case 130 Battery Case Body 140 Sealing Cover 150 Safety Valve 151 First Thin Wall 152 Second Thin Wall 155, 155b Oxide Film (Anodized Film)

Claims (3)

In a sealed battery comprising: a metal safety valve having a first thin portion and a groove-shaped second thin portion having a thickness smaller than that of the first thin portion,
The safety valve is made of aluminum,
In the second thin wall portion, Ri Na provided an oxide film formed by oxidizing the aluminum constituting the second thin portion,
The thickness of the second thin portion is in the range of 35 to 60 μm,
The sealed battery has a thickness of the oxide film in a range of 50 to 300 nm . The sealed battery according to claim 1,
The sealed battery, wherein the oxide film is an anodized film formed by anodizing the second thin portion. In a method for manufacturing a sealed battery, comprising: a metal safety valve having a first thin part and a groove-like second thin part having a thickness smaller than that of the first thin part,
The safety valve is made of aluminum,
The thickness of the second thin portion is in the range of 35 to 60 μm,
By anodic oxidation of the aluminum constituting the second thin portion, e Bei anodic oxidation step of forming an anodic oxide film on the second thin portion,
The method for manufacturing a sealed battery, wherein in the anodic oxidation step, the thickness of the anodic oxide coating is in the range of 50 to 300 nm .

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