JP3596954B2 - Method of manufacturing prismatic battery - Google Patents

Description

【００３１】
表１から明らかなように、開口部の拡口幅が前述した式Ａ_ｘ ＞Ａ_ｙ を満たし、かつ前記Ａ_ｙ が容器肉厚の３０〜６０％である容器を用いる実施例１〜２の電池は、封口後の開口部に変形がなく、かつ開口部が全周に亘り均等な幅で拡口された容器を用いる比較例の電池に比べて封口耐圧を高いことがわかる。特に、段部の段差が前述した式Ｂ_ｘ ＞Ｂ_ｙ を満たす構造を有する容器を用いる実施例２の電池は、実施例１に比べて封口耐圧が高いことがわかる。また、比較例の電池は、縮径工程の際に開口部のうち長手方向と直交する面において段部が更に内側に入り込み、次いで行われたカール工程において座屈変形を生じた。
【００３２】
なお、前記実施例では、防爆機構として、電池内のガス圧が所定の値以上になると開弁してガスを外部に放出し、その後は再び電池を密閉する復帰式の安全弁である弾性弁体を用いたが、前記防爆機構としては、非復帰式の安全弁である弁膜を用いても良い。前記弁膜は封口板と正極端子との間に前記封口板のガス抜き孔を覆うように配置すれば良い。
【００３３】
前記実施例では、封口板として打抜き加工によって作製された平板状のものを用いたが、封口板としては、板材から打抜き加工によって得られる矩形の板に絞り加工を施して中央に矩形溝を形成し、前記矩形溝の底部にガス抜き孔を開口することにより作製された矩形封口板を用いても良い。このような構造を有する封口板にその矩形溝を囲むように溶接によって正極端子を固定し、前記矩形溝と前記端子との間に前記ガス抜き孔を塞ぐように弾性弁体を配置して防爆機能及び正極端子を兼ねる封口部材を作製すると、前記矩形溝の深さを変化させることによって前記弾性弁体の圧縮度合いを調節することができるため、弁作動圧の調節を簡単に行える。
【００３４】
【発明の効果】
以上詳述したように本発明によれば、封口耐圧を向上でき、容器寸法に不具合がなく、歩留まりが向上された角形電池の製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明に係る製造方法で用いられる容器を示す斜視図。
【図２】図１の容器を長手方向に直交する面で切断した際の前記容器の開口部を示す部分断面図。
【図３】図１の容器を長手方向に沿う面で切断した際の前記容器の開口部を示す部分断面図。
【図４】図１の容器を示す上面図。
【図５】本発明に係る方法で製造された角形電池（例えば角形アルカリ二次電池）を示す部分断面図。
【符号の説明】
１…開口部、２…段部、３…容器、４…電極群、９…絶縁ガスケット、１０…封口部材。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a prismatic battery in which a sealing member is caulked and fixed to a container via an insulating gasket.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as batteries become smaller and lighter, prismatic batteries with high volumetric efficiency have been developed. As a method for sealing the prismatic battery, a method of fixing a sealing member to a container in which a power generating element is stored by laser welding, and a method of caulking and fixing the sealing member to an opening of the container in which the power generating element is stored via an insulating gasket. Methods and are known.
[0003]
A crimp-type prismatic battery that is sealed by swaging is conventionally manufactured by the following method. That is, the power generating element is housed in a bottomed rectangular cylindrical container having a stepped portion formed inwardly protruding at the lower end of the opening by opening the opening in advance. A sealing member and an insulating gasket in which the sealing member is stored are placed on the step in the container. After inserting the lower end of the container into the lower mold and fixing it, reducing the diameter of the opening of the container, compressing the gasket by bending the upper end of the opening inward, the repulsive elastic force of the insulating gasket Then, the sealing member is caulked and fixed to the container to manufacture the prismatic battery.
[0004]
By the way, the side surface orthogonal to the longitudinal direction of the container has high strength like the corner portion of the container, but is not easily bent, and easily undergoes plastic deformation when an excessive force is applied. For this reason, if a container having a step formed at the lower end of the opening by expanding the opening with a substantially uniform width over the entire circumference is used, in the diameter reduction step, the step is orthogonal to the longitudinal direction. The part to do goes further inside. In the subsequent curling step, the upper end of the opening is bent inward while the lower part of the container is supported by the lower mold, so that a pressing force is applied to the container from above. When the step enters the inside in the diameter reduction step, the opening connected to the step decreases the strength against the pressing force, so buckling deformation occurs in the curl step, and the step enters further inside. . As a result, since the degree of bending at the upper end of the opening becomes shallow, the degree of compression of the gasket decreases, and a problem arises in that the sealing withstand pressure decreases. In addition, the step deformed inward in the sealing step may bulge outward due to the recoil that has entered the inside, which may cause a problem in dimensions.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method of manufacturing a rectangular battery in which deformation of a container in a sealing step is avoided, sealing reliability is improved, and dimensional defects are eliminated.
[0006]
[Means for Solving the Problems]
The method for manufacturing a prismatic battery according to the present invention is characterized in that a power generating element is provided in a bottomed rectangular cylindrical container having an inwardly projecting step formed at the lower end of the opening by opening the opening in advance. Storing the sealing member and an insulating gasket in which the sealing member is stored on the step portion in the container, and reducing the diameter of the opening of the container, and then closing the upper end of the opening. A step of caulking and fixing the sealing member to the container via the insulating gasket by bending the container inward,
拡口width of the opening, the拡口width when拡口in a direction perpendicular to the longitudinal direction and A _x, wherein A _x in the拡口width when拡口the longitudinal direction is A _y > _Ay , and the _Ay is 30 to 60% of the thickness of the container.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the manufacturing method according to the present invention will be described with reference to FIGS.
(First step)
As shown in FIG. 1, an opening 1 is previously widened to prepare a bottomed rectangular cylindrical container 3 in which a step 2 having a shape protruding inward is formed at a lower end of the opening 1. The拡口width of the opening 1, the拡口width when拡口in a direction perpendicular to the longitudinal direction as shown in FIG. 2 and A _x, when拡口in the longitudinal direction as shown in FIG. 3 satisfies expression _a x> _{a y} a拡口width upon the _{a y,} and the _{a y} is from 30 to 60% of the thickness of the container. The container 3 also serves as a negative electrode terminal.
[0008]
The reason why _Ay is set to 30 to 60% of the thickness of the container 3 is as follows. If the _Ay is less than 30% of the thickness of the container 3, it becomes difficult to place an insulating gasket on the step 2 in the container 3. On the other hand, if the _Ay exceeds 60% of the thickness of the container 3, it becomes difficult to reduce the inward deformation of the step portion 2 of the portion orthogonal to the longitudinal direction in the diameter reducing step. More preferably, _Ay is set to 40 to 50% of the thickness of the container 3.
[0009]
The container 3 is perpendicular to the longitudinal direction of the step portion 2 as shown in FIG. 3 that the stepped portion along the longitudinal direction of the step portion 2 as shown in FIG. 2 described above and B _x, and the aforementioned it is preferable that the structure satisfying the expression B _x ≧ B _y in the step portion was B _y to. In particular, the container 3, the _{B x} and the _{B y} shown in FIG. 4 and more preferably has a structure that satisfies the expression _B x> _{B y.} By adopting such a structure, it is possible to further improve the holding ability of the insulating gasket of the stepped portion 2 in the container 3 and to reduce the inside of the stepped portion 2 in the diameter reduction step of the portion orthogonal to the longitudinal direction. Since the deformation of the seal can be greatly reduced, the sealing pressure resistance can be drastically improved.
[0010]
The container 3 can be formed of, for example, a nickel-plated SPCC steel material (a low-carbon steel cold-rolled steel), a nickel-plated iron, stainless steel, or the like.
[0011]
The thickness of the container 3 is preferably set to 0.30 to 0.45 mm. This is due to the following reasons. If the thickness of the container 1 is less than 0.30 mm, the holding ability of the sealing member of the container 3 may be significantly reduced. If the thickness of the container 3 exceeds 0.45 mm, the processability of the container 3 may be reduced, and it may be difficult to increase the capacity and the weight of the battery. The more preferable thickness of the container 3 is 0.35 to 0.40 mm.
[0012]
The container 3 preferably has a Vickers hardness of 80 Hv to 150 Hv at the opening, and a Vickers hardness of 160 to 170 Hv at a portion (hereinafter, referred to as a trunk) located below the step portion. When only the hardness of the opening is reduced in this way, the workability of the opening can be enhanced while maintaining the strength of the body. The Vickers hardness of the opening is limited to the above range for the following reason. When the Vickers hardness is less than 80 Hv, the strength of the opening is inferior, and the opening may be deformed in the curling step. Further, when the gas pressure in the container rises, the opening easily expands, so that a gap may be formed between the inner peripheral surface of the opening and the insulating gasket, which may cause gas leakage. On the other hand, if the Vickers hardness exceeds 150 Hv, the processability of the opening decreases, and as a result, the body of the container may be deformed in the curling step. More preferably, the Vickers hardness of the opening is in the range of 90 Hv to 120 Hv.
[0013]
The prismatic battery shown in FIG. 5 is manufactured through the second to fourth steps described below.
(2nd process)
The electrode group 4 as a power generation element and the electrolyte are housed in the container 3 described above. The electrode group 4 is manufactured by laminating the positive electrode 5 and the negative electrode 6 with the separator 7 interposed therebetween so that the negative electrode 6 is located in the outermost layer.
[0014]
Next, the positive electrode 5, the negative electrode 6, the separator 7, and the electrolytic solution will be described.
1) Positive electrode 5
The positive electrode 5 preferably has a structure in which a paste containing a positive electrode active material is filled in a current collector.
[0015]
For the positive electrode, for example, after preparing a paste containing a positive electrode active material, a conductive agent, a binder, and water, filling the paste into a current collector, drying this, and pressing and molding with a press. Can be produced by
[0016]
Examples of the positive electrode active material include a nickel compound. Examples of the nickel compound include nickel hydroxide, nickel hydroxide in which zinc and cobalt are coprecipitated, and nickel oxide. Among them, it is preferable to use nickel hydroxide in which zinc and cobalt are coprecipitated.
[0017]
As the conductive agent, for example, one composed of one or more selected from a cobalt compound and metallic cobalt can be used. Examples of the cobalt compound include cobalt hydroxide (Co (OH) ₂ ) and cobalt monoxide (CoO). In particular, it is preferable to use a conductive material composed of cobalt hydroxide, cobalt monoxide, or both cobalt hydroxide and cobalt monoxide.
[0018]
Examples of the binder include hydrophobic polymers such as polytetrafluoroethylene (PTFE), polyethylene, and polypropylene, such as carboxymethylcellulose (CMC), methylcellulose (MC), and hydroxypropylmethylcellulose (HPMC), such as sodium polyacrylate Examples include hydrophilic polymers such as polyacrylates such as (SPA), polyvinyl alcohol (PVA), and polyethylene oxide, and rubber-based polymers such as latex.
[0019]
Examples of the current collector include nickel, metals such as stainless steel, mesh-like, sponge-like, fiber-like, or felt-like porous metal bodies formed from an alkali-resistant material such as a nickel-plated resin. Can be mentioned.
2) Negative electrode 6
The negative electrode 6 preferably has a structure in which a paste containing a negative electrode active material is filled in a current collector.
[0020]
Such a negative electrode is prepared, for example, by preparing a paste containing a negative electrode active material, a conductive material, a binder, and water, filling the paste into a current collector, drying the paste, and then pressing with a press. It can be produced by molding.
[0021]
As the negative electrode active material, a material which directly participates in a charge / discharge reaction, or a material which inserts / extracts a substance directly involved in a charge / discharge reaction can be used. Examples of the former include powders of cadmium compounds such as metal cadmium and cadmium hydroxide. Examples of the latter include a hydrogen storage alloy that stores and releases hydrogen. Among them, a secondary battery provided with a negative electrode containing the hydrogen storage alloy can discharge at a higher current than a secondary battery provided with a negative electrode containing the cadmium compound powder, and has a low risk of environmental pollution. Therefore, it is suitable.
[0022]
The hydrogen storage alloy is not particularly limited as long as it can store hydrogen electrochemically generated in an electrolytic solution and can easily release the stored hydrogen during discharge. For example, LaNi ₅ , MmNi ₅ (Mm; misch metal), LmNi ₅ (Lm; lanthanum-enriched misch metal), or a part of these Nis is Al, Mn, Co, Ti, Cu, Zn, Zr, Cr , B, or a multi-element type substituted with an element such as TiNi type, TiFe type, ZrNi type, or MgNi type. Among them, the formula LmNi _x Mn _y A _z (However, A is shown Al, at least one metal selected from Co, the atomic ratio x, y, z is the total value of 4.8 ≦ x + y + z ≦ 5.4) It is desirable to use a hydrogen storage alloy represented by the following formula. The cylindrical secondary battery provided with the negative electrode containing the hydrogen storage alloy having such a composition can improve the discharge capacity and the charge / discharge cycle life.
[0023]
Examples of the conductive material include nickel powder, cobalt oxide, titanium oxide, and carbon black. In particular, it is preferable to use the carbon black as a conductive material.
[0024]
As the binder, the same binder as described for the positive electrode described above can be used.
Examples of the current collector include a two-dimensional substrate such as a punched metal, an expanded metal, a perforated rigid plate, and a nickel net, a felt-like metal porous body, and a three-dimensional substrate such as a sponge-like metal substrate. Can be.
3) Separator 7
Examples of the separator 7 include a nonwoven fabric made of a polyolefin fiber such as a nonwoven fabric made of a polyethylene fiber, a nonwoven fabric made of an ethylene-vinyl alcohol copolymer fiber, and a nonwoven fabric made of a polypropylene fiber, to which a hydrophilic functional group is imparted. 6 and the like. Examples of a method for imparting a hydrophilic functional group to the polyolefin fiber nonwoven fabric include a corona discharge treatment, a sulfonation treatment, a graft copolymerization, and the application of a surfactant or a hydrophilic resin.
4) Electrolyte solution Examples of the electrolyte solution include an aqueous solution of sodium hydroxide (NaOH), an aqueous solution of lithium hydroxide (LiOH), an aqueous solution of potassium hydroxide (KOH), a mixed solution of NaOH and LiOH, and a mixed solution of KOH and LiOH. An alkaline electrolyte such as a mixture of KOH, LiOH and NaOH can be used.
(3rd step)
A sealing member 10 serving also as a positive electrode terminal is accommodated in a synthetic resin insulating gasket 9 having a bottomed rectangular cylindrical shape having a hole 8 at the bottom. The sealing member 10 includes a rectangular sealing plate 12 having a gas vent hole 11, a positive electrode terminal 14 having a gas passage hole 13 disposed in the sealing plate 12 so as to surround the gas vent hole 11, And an elastic valve body 15 arranged between the positive electrode terminal 14 and the gas vent hole 11. After connecting the lower surface of the sealing plate 12 of the sealing member 10 housed in the gasket 9 and the positive electrode 5 with a positive electrode lead 16, the gasket 9 housing the sealing member 10 is connected to the step portion of the container 3. Place on 2.
(4th process)
After reducing the diameter of the opening 1 of the container 3, the upper end of the opening 1 is bent inward to compress the gasket 9, and the sealing member 10 is swaged to the container 3 by the repulsive elastic force of the gasket 9. A prismatic battery is manufactured by fixing.
[0025]
The method for manufacturing a prismatic battery of the present invention uses a bottomed square cylindrical container having an inwardly protruding step formed at the lower end of the opening by opening the opening in advance.拡口width of the opening of the container, the拡口width when拡口in a direction perpendicular to the longitudinal direction and A _x, a拡口width when拡口longitudinally upon the A _y The formula A _x > A _y is satisfied, and the A _y is 30 to 60% of the thickness of the container. The container having such a structure can suppress the inward deformation of the portion of the step portion orthogonal to the longitudinal direction in the diameter reducing step, and push the opening connected to the step portion from above in the curl step. Strength against pressure can be improved. Further, in order to suppress the inward deformation of the step, the opening width of the surface of the container that is orthogonal to the longitudinal direction is reduced, that is, the opening is formed at the lower end of the surface. Even if the step of the step is narrowed, the insulating gasket is held at the portion along the longitudinal direction of the step, so that the holding property of the insulating gasket of the container is not impaired. Therefore, by using the container, the upper end of the opening can be bent deeply inward without causing buckling deformation on the surface of the opening perpendicular to the longitudinal direction during the curling step, so that the sealing pressure resistance is improved. In addition, it is possible to manufacture a prismatic battery in which the problem of the container dimensions is eliminated.
[0026]
【Example】
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1
A prismatic nickel-metal hydride secondary battery for sealing pressure resistance measurement having the same structure as the battery shown in FIG. 5 described above except that the electrode group and the electrolyte were not housed in the container was assembled.
[0027]
Bottom rectangular cylindrical container whose width along the longitudinal direction is 16.4 mm, width perpendicular to the longitudinal direction is 5.6 mm, and thickness is 0.4 mm by drawing from nickel-plated SPCC steel. Was prepared. The opening of the container to form a stepped portion having a shape that protrudes inward below the opening as shown in FIG. 1 described above with拡口to satisfy equation A _x> A _y described above. That is,拡口width _{A x} of拡口along the direction perpendicular to the longitudinal direction is 0.25 mm, in拡口width _{A y} is 0.2mm in拡口along the longitudinal direction, the wall thickness of the container 50 %. In the container, the step of the step portion was made equal to 0.2 mm over the entire circumference. The Vickers hardness of the opening was 90 to 120 Hv, and the Vickers hardness of the trunk was 160 Hv.
[0028]
An asphalt-based sealant was applied to the inner peripheral surface of the opening of the container. After inserting an elastic valve body made by compression-molding synthetic rubber into the top of a hat-shaped terminal, the elastic valve body is placed in a rectangular sealing plate having a gas vent hole. Was mounted so as to close it, and a flange member of the terminal was fixed to the sealing plate by spot welding to assemble a sealing member having both an explosion-proof function and a terminal. After the sealing member was housed in a bottomed rectangular cylindrical insulating gasket made of nylon 6, 6 and having a hole at the bottom, the insulating gasket was placed on the step of the container. After reducing the diameter of the opening of the container, a bent portion is formed by bending the upper end of the opening inward, and the sealing plate is caulked and fixed to the container via the insulating gasket to measure the sealing pressure resistance. Was manufactured.
Example 2
Structure satisfies the expression _B x> _{B y} the step _{B x} of a portion along the longitudinal direction and 0.25 mm, and a step _{B y} of a portion perpendicular to the longitudinal direction of the step portion as 0.2mm of the stepped portion A prismatic nickel-metal hydride secondary battery for sealing pressure resistance measurement was manufactured in the same manner as in Example 1 using the same container as in Example 1 except for the above.
Comparative Example Similar to Example 1 except that the opening width of the opening was 0.25 mm and was uniform over the entire circumference, and the step of the step was 0.25 mm and was uniform over the entire circumference. Using a container, a prismatic nickel-metal hydride secondary battery for sealing pressure measurement was manufactured in the same manner as in Example 1.
[0029]
Regarding the obtained batteries of Examples 1 and 2 and Comparative Example, the appearance of the container was observed, and the presence or absence of deformation in the sealing step was examined. The results are shown in Table 1 below.
In addition, a hole is provided in the lower side surface of the container of each of the batteries of Examples 1 and 2 and the comparative example, and gas is sent into the container from the hole, the opening is curved outward, and the inner periphery of the opening is formed. A gap is formed between the surface and the insulating gasket, and when the gas leaks from this gap, the pressure in the container is measured to determine the sealing pressure resistance. The results are also shown in Table 1 below.
[0030]
[Table 1]

[0031]
Table 1 As is apparent from, satisfies Expression A _x> A _y where拡口width of the opening is above, and the A _y is Examples 1-2 using containers 30 to 60% of the container wall thickness It can be seen that the battery has a higher sealing pressure than the battery of the comparative example using a container in which the opening after sealing is not deformed and the opening is widened over the entire circumference with a uniform width. In particular, the battery of Example 2 in which the step of the step portion is used a container having a structure that satisfies the expression B _x> B _y described above is found to have high sealing breakdown voltage as compared with Example 1. Further, in the battery of the comparative example, the step portion further entered inside the opening perpendicular to the longitudinal direction during the diameter reduction step, and buckling deformation occurred in the subsequent curling step.
[0032]
In the above-described embodiment, the explosion-proof mechanism is an elastic valve element that is a reset-type safety valve that opens when the gas pressure in the battery becomes equal to or higher than a predetermined value and releases gas to the outside, and thereafter seals the battery again. However, as the explosion-proof mechanism, a valve membrane which is a non-return type safety valve may be used. The valve membrane may be disposed between the sealing plate and the positive electrode terminal so as to cover the gas vent hole of the sealing plate.
[0033]
In the above embodiment, a flat plate manufactured by punching was used as the sealing plate. However, as the sealing plate, a rectangular plate obtained by punching from a plate material was subjected to drawing to form a rectangular groove in the center. Then, a rectangular sealing plate manufactured by opening a gas vent hole at the bottom of the rectangular groove may be used. The positive electrode terminal is fixed to the sealing plate having such a structure by welding so as to surround the rectangular groove, and an elastic valve body is arranged between the rectangular groove and the terminal so as to close the gas vent hole. When a sealing member that also functions as a positive electrode terminal is manufactured, the degree of compression of the elastic valve body can be adjusted by changing the depth of the rectangular groove, so that the valve operating pressure can be easily adjusted.
[0034]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide a method of manufacturing a prismatic battery in which the sealing pressure resistance can be improved, the size of the container is not defective, and the yield is improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a container used in a manufacturing method according to the present invention.
FIG. 2 is a partial cross-sectional view showing an opening of the container of FIG. 1 when cut along a plane orthogonal to the longitudinal direction.
FIG. 3 is a partial cross-sectional view showing an opening of the container of FIG. 1 when the container is cut along a surface along a longitudinal direction.
FIG. 4 is a top view showing the container of FIG. 1;
FIG. 5 is a partial cross-sectional view showing a prismatic battery (for example, a prismatic alkaline secondary battery) manufactured by the method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... opening part, 2 ... step part, 3 ... container, 4 ... electrode group, 9 ... insulating gasket, 10 ... sealing member.

Claims (1)

A step of storing the power generating element in a bottomed rectangular cylindrical container having an inwardly protruding step formed at the lower end of the opening by opening the opening in advance,
A step of placing a sealing member and an insulating gasket in which the sealing member is stored on the step in the container,
After reducing the diameter of the opening of the container, bending the upper end of the opening inward and caulking and fixing the sealing member to the container via the insulating gasket. In the method,
拡口width of the opening, the拡口width when拡口in a direction perpendicular to the longitudinal direction and A _x, wherein A _x in the拡口width when拡口the longitudinal direction is A _y > _Ay is satisfied, and the _Ay is 30 to 60% of the thickness of the container.

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