JP2008204839A - Sealing plate for cylindrical battery cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing plate for a cylindrical battery cell with high productivity at an assembly process and excellent in airtightness. <P>SOLUTION: For the cylindrical battery cell made by sealing in a battery outer package case nearly cylindrical electrode plate group spirally winding around a positive electrode plate consisting a positive electrode mixture containing a positive electrode active material in its strip positive electrode collector and a negative electrode plate consisting of a negative electrode mixture containing a negative electrode active material in its strip negative electrode collector with an interposition of strip separators, gasket layers of the sealing plate are made in multiple layers of two kinds or more of resin, made of either PBT, PPS, PP or nylon, and another layer over it made of either boron resin or acrylic resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a cylindrical battery sealing plate, and particularly to one having a particularly suitable outer gasket.

  In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless (portable), and these drive power sources are represented by various types of alkaline storage batteries and lithium secondary batteries with higher capacities. A non-aqueous electrolyte (organic solvent electrolyte) secondary battery is suitable. Furthermore, non-aqueous electrolyte secondary batteries are being promoted to be sealed batteries with high energy density and excellent load characteristics. These sealed batteries are widely used as power sources for portable devices such as watches and cameras. Has been.

  By the way, in a non-aqueous electrolyte battery, when a device including a charger is broken, overcharged, or misused, a power generation element inside the battery undergoes a chemical change. For example, the electrolyte solution or the active material is decomposed due to an abnormal reaction due to overcharge or short circuit, and abnormally gas is generated inside the battery, and the internal pressure of the battery becomes excessive. In such a case, the battery may explode or damage the equipment used. Therefore, the following explosion-proof safety function has been conventionally added to this type of battery. That is, when the battery internal pressure exceeds the set value, the valve body that has received the internal pressure is pressed and deformed in the internal pressure direction (the direction in which the internal pressure diffuses), thereby breaking the thin portion of the conductive member. Alternatively, the welded portion between the valve body and the conductive member is peeled off, and the energization current is interrupted at the initial stage of occurrence of overcharge or short circuit to stop the abnormal reaction. Thereby, the battery temperature rise and the battery internal pressure rise due to the charging current or the short-circuit current are suppressed to prevent the battery from firing or bursting.

  In addition, in a non-aqueous electrolyte battery, if the electrolyte leaks outside the battery, the electrolyte solution is organic, which causes inconveniences such as corrosion of battery equipment. It is necessary to seal the liquid tightly so as to completely prevent leakage by the plate. Therefore, in the explosion-proof sealing plate used for this type of application, both a valve body made of a thin conductive plate such as a metal foil and a conductive member are laminated with an insulating inner gasket interposed between the peripheral portions. After the body is housed in a metal case with a metal cap on top of the body, the opening end of the metal case is caulked inward, so that the peripheral edge of the ring-shaped inner gasket is formed by the metal case. The cylindrical part rising from the inside is bent inward and compressed, and the compressed inner gasket provides both insulation and liquid tightness.

  In addition, an outer gasket is also provided in order to maintain the airtightness of the sealing plate and the caulking portion of the case (see, for example, Patent Document 1 or 2).

Normally, it is difficult to secure the airtightness of the sealing plate and the case only by caulking the outer gasket of the sealing plate and the grooved portion of the case with a mold. Generally, a sealing agent such as a bronze agent is applied to the grooving portion.
JP 2004-241308 A JP 2000-067931 A

However, in the battery assembly process, there is a process of inserting an electrode group consisting of a positive electrode, a negative electrode, and a separator, and a process of injecting an electrically conductive electrolyte into the case to make it chargeable / dischargeable However, it has the following problems.
(1) Since an organic solvent is used as an electrolyte in a lithium (Li) ion battery, it is sufficient to dissolve the sealing agent when the electrolytic solution adheres to a grooved portion where the sealing agent is applied. Airtightness may not be maintained.
(2) It takes time to inject the electrolyte so as not to contact the groove.
(3) A process of applying and drying a sealant is required in the assembly process.
(4) When a resin such as bronze is applied to the metal part of the case, uneven coating tends to occur, and airtightness tends to vary.

  The present invention solves such a conventional problem, and its object is to provide a sealing plate for a cylindrical battery in which the airtightness is ensured more than the conventional sealing plate and the productivity of the assembly process is improved. To do.

  In order to solve the above problems, a cylindrical battery sealing plate of the present invention is a cylindrical battery sealing plate having an outer gasket that contacts a battery case of the cylindrical battery, wherein the outer gasket is a base resin layer. And at least two surface resin layers in contact with the battery case.

  The base resin layer is preferably at least one of polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), or polypropylene (PP), and the surface resin layer is preferably a bron resin or an acrylic resin.

  By using the cylindrical sealing plate of the present invention, it is possible to provide a battery with excellent airtightness, simplify the assembly line, and speed up the liquid injection process.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The sealing plate which is the essence of the present invention is a battery sealing plate in which an outer gasket layer is multilayered with two or more kinds of resins, unlike a normal sealing plate, and the gasket layer is PBT, PPS, PP And a layer selected from either Bron resin or acrylic resin, and it is not necessary to apply sealant in the assembly process. The application process can be omitted, and even at the time of liquid injection, it is possible to prevent a decrease in airtightness due to dissolution of the sealant due to adhesion of the electrolytic solution to the case groove, and it is possible to speed up the liquid injection process.

  Examples of the present invention will be described below.

(Conventional example 1)
<Preparation of positive electrode plate>
Li ₂ CO ₃ , Co ₃ O ₄ , NiO, and MnO ₂ are mixed to be Li _0.94 Ni _0.35 Mn _0.35 Co _0.35 O ₂ after firing, and fired at 900 ° C. for 10 hours. A positive electrode active material was prepared. 100 parts by weight of this positive electrode active material was stirred with a double-arm kneader together with 2.5 parts by weight of acetylene black, 4 parts by weight of a fluororesin binder and an appropriate amount of an aqueous solution of carboxymethyl cellulose to prepare a positive electrode paste. This paste was applied and dried on both sides of a 30 μm thick aluminum foil, rolled to a total thickness of 99 μm, and then cut into a coating width of 52 mm and a coating length of 1660 mm to obtain a positive electrode.

<Production of negative electrode plate>
Mesophase spherules graphitized at a high temperature of 2800 ° C. (hereinafter referred to as mesophase graphite) were used as the negative electrode active material. 100 parts by weight of this active material was stirred together with 2.5 parts by weight of SBR acrylic acid modified product, 1 part by weight of carboxymethyl cellulose, and an appropriate amount of water in a double-arm kneader to prepare a negative electrode paste. This paste was applied and dried on both sides of a copper foil having a thickness of 0.02 mm, and rolled so that the total thickness was 97 μm and the porosity of the composite material portion was 35%, and then the coating width was 57 mm and the length was 1770 mm. The negative electrode was obtained by cutting into dimensions.

<Battery assembly>
An electrode group produced by winding the positive electrode plate and the negative electrode plate together with a separator was delivered to a battery case having a case diameter of 26.0 mm and a height of 65 mm. Next, after providing a groove for placing the sealing plate on the case, a bronze agent was applied to the groove and dried. Next, 13 g of a nonaqueous electrolyte solution in which 1.40 M LiPF ₆ was dissolved in an organic solvent (volume ratio 15:15:70) mainly composed of EC, EMC, and DMC was injected into the case containing the electrode group. Then, as shown in FIG. 1, the height is 5.2 mm, the outer diameter is 25.3 mm, and the outer gasket 2 is made of PP with a sealing plate placed in the groove of the case 1 and caulked by a mold to produce a battery. did. This sealing plate is formed by using a C-shaped stamp with an outer diameter of φ4.0 mm at the center of the upper valve body 3 made of an aluminum metal foil having a thickness of 0.10 mm and an outer diameter of φ12.7 mm. 3a is used, and an O-shaped stamp with an outer diameter of 2.5 mm is used for the lower valve body 4 made of an aluminum metal foil having a thickness of 0.10 mm, an outer diameter of φ13.5 mm, and four vent holes of φ1.5 mm. The lower valve body thin portion 4 a is provided, and the two metal foils are welded to the central portion of each foil via the inner gasket 5. This is inserted into a lower filter 6 made of an aluminum metal case with four φ1.5 mm vents, and a temperature cap 7 and a metallic cap with four φ1.5 mm vents on the top. It was obtained by caulking 8 on.

(Conventional example 2)
The battery was assembled in the same manner as in Conventional Example 1 except that the material of the outer gasket of the sealing plate was PBT.

(Example 1)
The battery was assembled using the same electrode plate group and case as in Conventional Example 1, but for the sealing plate, the material of the outer gasket of the sealing plate is made of PBT, and the part that contacts the case groove is A battery was assembled using a sealing plate in which a bronze agent was applied to the surface layer and dried, that is, a sealing plate in which the base resin layer was PBT and the surface resin layer was Bron resin.

  In this case, after providing a groove for placing the sealing plate on the case, 13 g of nonaqueous electrolyte was injected as in the conventional example without providing a resin layer such as a bronze agent in the groove. After injecting the electrolyte, the electrolyte adhering to the battery case groove was completely removed by air suction, and then a sealing plate was placed on the groove of the case and caulked with a mold to prepare a battery.

(Example 2)
The material of the outer gasket of the sealing plate is made of PBT. For the portion that contacts the case groove, the sealing plate coated with acrylic agent on the surface layer and dried, that is, the base resin layer is PBT and the surface resin layer is acrylic. A battery was assembled in the same manner as in Example 1 except that a resin sealing plate was used.

(Example 3)
The material of the outer gasket of the sealing plate is made of PPS, and the portion that contacts the case groove is coated with a Bron agent on the surface layer and dried, that is, the base resin layer is PPS and the surface resin layer is Bron A battery was assembled in the same manner as in Example 1 except that a resin sealing plate was used.

Example 4
The material of the outer gasket of the sealing plate is made of PPS. For the portion that contacts the case groove, an acrylic agent is applied to the surface layer and dried, that is, the base resin layer is PPS and the surface resin layer is acrylic. A battery was assembled in the same manner as in Example 1 except that a resin sealing plate was used.

(Example 5)
As for the material of the outer gasket of the sealing plate, which is made of PP and the portion contacting the case groove, the sealing plate coated with the bronze agent on the surface layer and dried, that is, the base resin layer is PP and the surface resin layer is Bron A battery was assembled in the same manner as in Example 1 except that a resin sealing plate was used.

(Example 6)
The material of the outer gasket of the sealing plate is made of PP, and for the portion that contacts the case groove, an acrylic agent is applied to the surface layer and dried, that is, the base resin layer is PP and the surface resin layer is acrylic. A battery was assembled in the same manner as in Example 1 except that a resin sealing plate was used.

<Battery Evaluation 1>
Next, regarding the battery example of the present invention and the battery of the conventional example, the following leakage resistance was evaluated.

(heat cycle)
50 cycles of −20 ° C., 11h → 20 ° C., 1h → 80 ° C., 11h → 20 ° C., 1h were performed, and the presence or absence of liquid leakage or rust in the battery sealing part was confirmed.

(Humidity cycle)
After leaving in a 40 ° C 95% atmosphere for 1 month, check for leakage and rust on the battery seal.

(heat shock)
After 10 cycles of −20 ° C., 1 h → 80 ° C., 1 h, the battery sealing part was checked for leakage and rust.

  The evaluation results are shown in (Table 1).

  As can be seen from (Table 1), in the conventional example, the leakage of the battery sealing portion and the occurrence of rust are confirmed after the test, whereas the sealing plate of the present invention prevents the leakage. it can.

This is the case of the conventional example, after applying bronze to the groove part and drying, the electrolytic solution is injected, but at that time, adhesion of the electrolytic solution to bron is seen and dissolution of bron occurs, The adhesion between the gasket of the sealing plate and the case is lowered, and as a result, liquid leakage is likely to occur.

  On the other hand, in the case of Examples 1-6, the liquid adhering to a groove part can be completely removed after electrolyte solution injection | pouring, Bron resin for improving the adhesiveness with a metal to the outer gasket of a sealing board after that, or Since the surface resin layer of acrylic resin is present, the adhesion between the sealing plate and the gasket is maintained, and it can be seen that the leakage resistance is improved.

  Moreover, when Example 5, 6 and 1-4 are compared, when the direction of Examples 1-4 is exposed to the high temperature environment of a heat cycle and a heat shock, the liquid-proof property is going up. This indicates that the heat resistance is improved by increasing the heat resistance of the material of the outer gasket from PP, and the effect becomes clearer by improving the adhesion between the case and the gasket according to the present invention. It is shown that.

<Battery evaluation 2>
Next, cycle characteristics of the battery example of the present invention and the battery of the conventional example were evaluated.

(Cycle conditions)
Charging: charging current 10A, charging voltage 4.2V, cut current 0.25A, discharging: 30A, ambient temperature: 30 ° C.

  These evaluation results are shown in (Table 2).

  It can be seen that the example has a higher capacity retention rate in the cycle and a lower internal resistance (IR) than the conventional example. As described above, when discharging with a large current as described above, the temperature of the battery itself rises due to the generation of Joule heat. For this reason, in the case of the conventional example having poor adhesion to the case, it is considered that the outer gasket of the sealing plate was softened by heat, thereby lowering the sealing property, and as a result, the electrolyte leaked, the IR increased, and the capacity also decreased.

  On the other hand, in the embodiment, since the sealing property between the case and the outer gasket is good, the occurrence of liquid leakage is not seen, and as a result, the increase in IR and the decrease in capacity can be suppressed.

  Further, when Examples 1 to 4 are compared with Examples 5 and 6, Examples 1 to 4 are further improved in IR and capacity retention rate. This indicates that the sealing performance is further improved by using a material having a higher heat resistance as the material of the outer gasket.

  Since a sealing plate with high productivity in the assembly process and excellent airtightness can be supplied, its utility value is very large.

Top sectional view showing an example of a cylindrical battery used in the examples

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2 Outer gasket 3 Upper valve body 3a Upper valve body thin part 4 Lower valve body 4a Lower valve body thin part 5 Inner gasket 6 Lower filter 7 Temperature resistor 8 Cap

Claims (2)

  A sealing plate for a cylindrical battery having an outer gasket in contact with a battery case of the cylindrical battery, wherein the outer gasket includes at least two layers of a base resin layer and a surface resin layer in contact with the battery case. A cylindrical battery sealing plate.   2. The cylindrical battery sealing plate according to claim 1, wherein the base resin layer is at least one of polybutylene terephthalate, polyphenylene sulfide, or polypropylene, and the surface resin layer is bron resin or acrylic resin. .

Images