JP3778802B2 - Aluminum alloy material for sealed prismatic secondary battery outer can excellent in swelling resistance and weldability and method for producing the same - Google Patents

Description

【００２８】
【表２】

【００２９】
【表３】

【００３０】
表３から明らかなように、本発明のＮｏ．１〜６はいずれも機械的性質、成形性、溶接性、耐膨れ性に優れた。
これに対し、比較例のＮｏ．７はＭｎ量（含有量）が少ないため耐膨れ性が劣った。Ｎｏ．８はＭｎ量が多いため強度が高く、晶出物も多いため成形性がやや劣った。Ｎｏ．９はＭｇ量が少ないため耐膨れ性が劣った。Ｎｏ．１０はＭｇ量が多いため成形速度を落としても設計寸法に成形できなかった。またレーザー溶接での亀裂長さが長く、溶接性も劣った。Ｎｏ．１１はＳｉ量が多いためＭｎの固溶量が減少し耐膨れ性が劣った。また凝固温度範囲が広がり溶接性も劣った。Ｎｏ．１２はＣｕが多く引張強さが高いため通常の成形速度では割れが発生し、速度を落として成形しても寸法が狂った。また溶接性も劣った。
【００３１】
Ｎｏ．１３は最終冷間圧延率が高すぎて転位が多量に導入されたため耐膨れ性が劣った。Ｎｏ．１４は中間焼鈍温度が低いためＭｎの固溶量が減少して耐膨れ性が劣った。Ｎｏ．１５は中間焼鈍をバッチ焼鈍で行ったためＭｎが多量かつ粗大に析出し、Ｍｎの固溶量が減少したため耐膨れ性が劣った。Ｎｏ．１６は最終焼鈍を行わなかったため回復が進まず可動転位が多くなり耐膨れ性が劣った。Ｎｏ．１７は最終焼鈍温度が高すぎて析出物が粗大に析出したため固溶Ｍｎ量が減少し耐膨れ性が劣った。
【００３２】
（実施例２）
最終冷間圧延での上がり温度を１２０℃以上として最終焼鈍は行わなかった他は、実施例１のＮｏ．１と同じ方法によりアルミニウム合金板材を製造した。
最終冷間圧延での上がり温度は、１パスあたりの圧延率および圧延速度を大きくすることにより高めた。
【００３３】
（比較例３）
実施例１で最終焼鈍を行わなかった他は、実施例１のＮｏ．１と同じ方法によりアルミニウム合金板材を製造した。
【００３４】
実施例２および比較例３で製造した各々のアルミニウム合金板材について、機械的性質、導電率、成形性、溶接性および耐膨れ性を実施例１の場合と同じ方法により調べた。製造条件を表４に、調査結果を表５に示す。
【００３５】
【表４】

【００３６】
【表５】

【００３７】
表５より明らかなように、本発明例のＮｏ．２１、２２は実施例１で最終焼鈍を施したＮｏ．１と同等の特性を示した。これにより最終冷間圧延での上がり温度を１２０℃以上とすることにより最終焼鈍を省略できることが判る。
これに対し、比較例のＮｏ．２３は最終冷間圧延での上がり温度が低く、しかも最終焼鈍を行わなかったため、特性が劣った。
【００３８】
実施例１および２で製造した本発明の各アルミニウム合金板材を、リチウムイオン二次電池で用いられる種々の非水電解液（リチウム塩を有機溶媒に溶解したもの）に浸漬してその耐食性を調べたが、本発明のＡｌ合金材はいずれも、いずれの非水電解液に対しても腐食することはなかった。
なお、前記非水電解液は、ＬｉＣｌＯ₄ 、ＬｉＰＦ₆ 、ＬｉＢＦ₄ またはＬｉＣＦ₃ ＳＯ₃ のリチウム塩の１種を、エチレンカーボネート、プロピレンカーボネート、γ−ブチロラクタン、スルホラン、ジエチルカーボネート、ジメチルカーボネート、ジメトキシエタン、ジエトキシエタン、２−メチル−テトラヒドロフラン、各種グライム類などを単独または２種類以上混合した有機溶媒のうちの１種に溶解して作製した。
【００３９】
【発明の効果】
以上に説明したように、本発明のアルミニウム合金板材は、ＭｎおよびＭｇを適量含有し、またＳｉおよびＣｕの含有量を抑え、さらに導電率を４５％ＩＡＣＳ以下、耐力と引張強さの比（耐力／引張強さ）を０．８〜０．９５に規定したもので、機械的性質、導電率、成形性、溶接性、耐膨れ性などに優れるため、リチウムイオン電池などに使用される密閉角形二次電池外装缶に好適である。前記アルミニウム合金板材は、所定組成のアルミニウム合金に熱間圧延、冷間圧延、中間焼鈍、最終冷間圧延および最終焼鈍を一部条件を規定して施すことにより製造できる。しかも前記最終焼鈍は省略することも可能である。依って、工業上顕著な効果を奏する。
【図面の簡単な説明】
【図１】成形性、溶接性、耐膨れ性を調べるために試作した密閉角形二次電池外装缶の斜視説明図である。[0001]
BACKGROUND OF THE INVENTION
The present invention is an aluminum alloy material for sealed rectangular secondary battery outer cans, which has excellent swelling resistance and laser weldability, has sufficient strength and formability as an outer can, and can sufficiently cope with thinning, and its manufacture Regarding the method.
[0002]
[Prior art]
In recent years, OA equipment typified by notebook computers and communication equipment typified by mobile phones have been rapidly ported, miniaturized, and lightened, and have become nickel-hydrogen secondary batteries and lithium-ion secondary batteries that serve as power sources. However, there is a demand for miniaturization and weight reduction. In addition, as a secondary battery used for a power source of a mobile phone, use of a square battery having high mounting efficiency is increasing. Nickel-plated steel and stainless steel are generally used for the outer cans of these secondary batteries, but aluminum alloys are also being studied for the purpose of weight reduction.
[0003]
By the way, since the internal pressure of the secondary battery increases when charging and discharging are repeated, there is a problem that the outer can made of an aluminum alloy having low strength swells.
This blistering is not a simple deformation.For example, if the secondary battery is held for a certain period of time under heat generation and increased internal pressure during charging, the outer can is swollen. Even if the internal pressure recovers to the normal state, it is caused by a phenomenon in which a swollen shape remains without being completely restored.
When the outer can expands, the electrode body easily swells. As a result, the utilization factor of the active material decreases and the cycle life deteriorates. It also increases the contact resistance of the electrode body, increases the contact resistance between the active material in the electrode body and the current collector (core body), which increases the internal resistance of the battery, and further decreases the discharge voltage. The energy that can be extracted from the battery is reduced. Further, when the outer can is swollen, the printed circuit board and the terminal part inside the device may be deformed by the pressure, and the reliability of the device is lowered. In the lithium ion secondary battery, the carbon negative electrode intercalated with lithium ions easily swells.
[0004]
For this reason, prevention of blistering of the outer can is an important issue, and methods for improving the structure of the outer can (Japanese Patent Laid-Open No. 10-284016, etc.) and methods for improving the material of the outer can are being studied. Of these, the latter is promising because existing molds can be used.
Among the methods for improving the material, (1) the method of adding 0.2 to 0.5 mass% of Cu to Al (Japanese Patent Laid-Open No. 10-284014) inevitably causes deterioration in formability and weldability when Cu is added In order to prevent deterioration of the formability, it is necessary to take measures to deteriorate the productivity such as reducing the forming speed and increasing the number of forming steps to reduce the forming amount per time. It goes against the demand for improved performance.
In addition, (2) the method (JP-A-2000-239775) that regulates the electrical conductivity to 45% IACS or less is insufficient in strength and cannot sufficiently meet the recent demand for thinning.
[0005]
In addition to preventing blistering, the outer can is desired to have improved weldability.
In other words, the outer can is used by joining the lid by laser welding or caulking, but if the caulking is not thick, sufficient joining strength cannot be obtained, so laser welding that can cope with thinning has become the mainstream. Yes. Therefore, improvement in laser weldability is desired for aluminum alloy materials for exterior cans.
[0006]
[Problems to be solved by the invention]
The present invention is an aluminum alloy material for sealed rectangular secondary battery outer cans, which has excellent swelling resistance and laser weldability, has sufficient strength and formability as an outer can, and can sufficiently cope with thinning, and its manufacture The purpose is to provide a method.
[0007]
[Means for Solving the Problems]
First aspect of the present invention, Mn of 0.5~1.5mass%, Mg of 0.05~ 0.29 mass%, 0.2mass% or less Si, and Cu containing less than 0.2 mass%, the balance Is an aluminum alloy material composed of Al and inevitable impurities, having an electrical conductivity of 45% IACS or less and a ratio of proof stress to tensile strength (proof strength / tensile strength) of 0.8 to 0.95. It is an aluminum alloy material for a sealed prismatic secondary battery outer can excellent in swelling resistance and weldability.
[0008]
Invention of Claim 2 contains Mn 0.5-1.5 mass%, Mg 0.02-0.29 mass%, Si 0.2 mass% or less, Cu less than 0.2 mass%, and remainder is An aluminum alloy material composed of Al and inevitable impurities is hot-rolled and then cold-rolled, and then held at a temperature of 500 to 600 ° C. for 20 seconds or less, and intermediate annealing is performed at a heating rate and a cooling rate of 10 ° C./sec or more. And then subjected to final cold rolling at a cross-section reduction rate of 30 to 60%, followed by a final annealing treatment at a temperature of 120 to 240 ° C., and a sealed rectangular secondary battery excellent in swell resistance and weldability It is a manufacturing method of the aluminum alloy material for exterior cans.
[0009]
The invention according to claim 3 is characterized in that the rising temperature in the final cold rolling is 120 ° C. or higher, and the final annealing treatment is not performed, and the sealed square secondary having excellent swell resistance and weldability according to claim 2 It is a manufacturing method of the aluminum alloy material for battery exterior cans.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the first aspect of the present invention, Mn as an alloy element contributes to strength improvement without impairing ductility, and precipitates finely to prevent dislocation movement, thereby contributing to prevention of blistering. The reason why the Mn content is specified to be 0.5 to 1.5 mass% is that the effect cannot be sufficiently obtained when the content is less than 0.5 mass%, and the moldability deteriorates when the content exceeds 1.5 mass%.
The fine precipitates of Mn are mainly generated during final annealing. Accordingly, it is desirable that Mn is dissolved in a larger amount in the aluminum alloy material.
[0011]
In this invention, Mg contributes to strength improvement and also prevents blistering by hindering the movement of dislocations in a solid solution state. The Mg content is specified to be 0.05 to 0.29 mass % because the effect cannot be sufficiently obtained if it is less than 0.05 mass %, and if it exceeds 0.29 mass % , the material strength becomes too high. This is because cracks and wrinkles are likely to occur during molding. Also, since work hardening is likely to occur, when multi-stage drawing or ironing is added like a lithium ion secondary battery outer can, cracking will occur during the next molding even if the first drawing can be performed. It is easy for wrinkles to occur. In addition, voids are easily generated during welding, and the weldability is also lowered. In particular, during laser welding, the condenser lens may be soiled with Mg vapor to reduce the laser output.
[0012]
The Si content is specified to be 0.2 mass% or less. If it exceeds 0.2 mass%, the solid solution amount of Mn decreases and the blistering resistance is lowered, and the solidification temperature range is widened and cracking occurs during laser welding. It is because it becomes easy to generate | occur | produce.
[0013]
The reason why Cu is defined to be less than 0.2 mass% is that when the mass is 0.2 mass% or more, the strength becomes too high and the formability deteriorates, and the solidification temperature range is widened, so that cracking is likely to occur during laser welding. .
[0014]
In this invention, the ratio of the proof stress / tensile strength is set to 0.8 to 0.95 because if the ratio is less than 0.8, the recovery is excessive and there are many relatively coarse Mn precipitates that do not contribute to the bulging resistance. As a result, the solid solution amount of Mn is lowered and the blistering resistance is deteriorated, and when it exceeds 0.95, the number of movable dislocations increases and the blistering is likely to occur.
[0015]
In the present invention, the reason why the electrical conductivity is specified to be 45% IACS or less is that when the electrical conductivity exceeds 45% IACS, the solid solution amount of Mn and Mg is insufficient and the swelling resistance deteriorates.
[0016]
The invention according to claim 2 is a method for producing an aluminum alloy material, wherein the aluminum alloy according to claim 1 is subjected to hot rolling, cold rolling, intermediate annealing, final cold rolling, and final annealing in this order.
In the present invention, the holding condition in the intermediate annealing is defined within 20 seconds at a temperature of 500 to 600 ° C. If the temperature is less than 500 ° C, the solid solution amount of Mn is insufficient. This is because the surface quality deteriorates even if it exceeds, and the temperature rising rate and cooling rate in the intermediate annealing are regulated to 10 ° C./sec or more. This is because the amount of Mn to be performed cannot be ignored, and the Mn solid solution amount decreases.
[0017]
The cross-section reduction rate in the final cold rolling is defined as 30 to 60% because sufficient strength cannot be obtained if it is less than 30%, and if it exceeds 60%, the strength becomes too high and formability deteriorates. This is because the introduced movable dislocation increases and the swell resistance also deteriorates.
[0018]
The reason why the final annealing temperature is set to 120 to 240 ° C. is to improve the swelling resistance by recovering the processed structure and reducing the movable dislocation, and if it is less than 120 ° C., a sufficient effect cannot be obtained. If the temperature exceeds 240 ° C., a large amount of Mn precipitates during the final annealing, and the amount of fine Mn compound that precipitates after molding decreases, and swelling is likely to occur.
[0019]
The invention according to claim 3 is a cost-effective method in which the rising temperature in the final cold rolling is set to 120 ° C. or higher so that the work structure is recovered after winding the coil to reduce movable dislocations, thereby improving the swell resistance. Is advantageous.
The reason why the rising temperature is set to 120 ° C. or higher is that when the temperature is lower than 120 ° C., the processed structure is not sufficiently recovered, and good swelling resistance cannot be obtained without final annealing.
In order to increase the rising temperature to 120 ° C. or higher, a method of increasing the reduction amount per rolling or rolling speed in the final cold rolling is applied.
[0020]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
Example 1
An Al alloy (No. A to F) having the composition defined in the present invention shown in Table 1 was cast by a semi-continuous casting method to form an ingot, and this ingot was subjected to a soaking treatment at 560 ° C. for 4 hours, and then the thickness Hot-rolled to 5 mm, then cold-rolled to various thicknesses, subjected to intermediate annealing on the cold-rolled material, then finally cold-rolled to a thickness of 0.8 mm, and then subjected to final annealing. An Al alloy material was manufactured.
The rising temperature in the hot rolling was controlled at 340 ° C., and the rising temperature in the final cold rolling was controlled at 105 ° C. A continuous annealing line (CAL) capable of rapid heating and rapid cooling was used for the intermediate annealing, and a batch annealing furnace was used for the final annealing. As shown in Table 2, the intermediate annealing conditions, the final cold rolling rate, and the final annealing conditions were variously changed within the specified values of the present invention.
[0021]
(Comparative Example 1)
An Al alloy material was produced by the same method as in Example 1 except that an Al alloy (No. GL) having a composition outside the scope of the present invention shown in Table 1 was used.
[0022]
(Comparative Example 2)
Al alloy material by the same method as in Example 1 except that any of the intermediate annealing conditions, the final cold rolling rate, and the final annealing conditions were changed outside the specified values of the present invention (Nos. 13 to 17) shown in Table 2. Manufactured.
[0023]
The mechanical properties, electrical conductivity, formability, weldability, and swell resistance of each of the Al alloy sheets produced in Example 1 and Comparative Examples 1 and 2 were examined.
[0024]
The mechanical properties were examined according to JISH2241, and the conductivity was examined according to JISH0505. Formability was evaluated by forming the Al alloy sheet material into a sealed prismatic secondary battery outer can having the dimensions shown in FIG. 1 in 7 steps including blanking, drawing, and ironing.
Evaluation is that cracks etc. do not occur, those that can be molded to the specified dimensions are good moldability (○), those that are out of dimension if not molded at low speed, moldability is somewhat poor (△), those that cracked It was determined that the moldability was poor (x).
The design dimensions (outer dimensions) of the outer can are 35.0 mm in length, 10.0 mm in width, 40.0 mm in height, the wall thickness is 0.6 mm for the long diameter part a and the short diameter part b, and the bottom plate part c is 0. 8 mm.
[0025]
Weldability was evaluated by laser welding a lid made of an Al alloy plate having a thickness of 0.8 mm to the outer can. The outer can and the lid were made of the same material.
In the evaluation, when the length of the weld crack was less than 1 mm, the weldability was good (◯), 1 to 3 mm was slightly weldable (Δ), and the weld crack length was more than 3 mm, the weldability was bad.
[0026]
The swelling resistance was measured by measuring a swelling rate when a lid was joined to the outer can by laser welding (internal pressure after joining: 2 kgf / cm ² ) and kept at a temperature of 80 ° C. for 24 hours. The swelling rate is determined by measuring the amount of swelling (mm) at the center of the long-diameter portion a having the largest deformation, and substituting this into the formula [swelling amount / base length (10.0 mm)] × 100%. Asked.
The results are shown in Table 3.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
[Table 3]

[0030]
As is clear from Table 3, the No. of the present invention. Nos. 1 to 6 were excellent in mechanical properties, formability, weldability, and swelling resistance.
In contrast, No. of the comparative example. No. 7 was inferior in blistering resistance because of its low Mn content (content). No. Since No. 8 had a large amount of Mn, its strength was high, and because there were many crystallized products, its moldability was slightly inferior. No. No. 9 was inferior in swelling resistance due to a small amount of Mg. No. Since No. 10 had a large amount of Mg, it could not be molded to the design dimensions even if the molding speed was reduced. Moreover, the crack length by laser welding was long and the weldability was also inferior. No. Since No. 11 had a large amount of Si, the solid solution amount of Mn decreased and the blistering resistance was poor. Moreover, the solidification temperature range was widened and the weldability was poor. No. No. 12 had a large amount of Cu and high tensile strength, so cracking occurred at the normal molding speed, and the dimensions were out of order even when molding was performed at a reduced speed. Also, the weldability was poor.
[0031]
No. No. 13 was inferior in blistering resistance because the final cold rolling rate was too high and a large amount of dislocations were introduced. No. No. 14 had a low intermediate annealing temperature, so the amount of Mn dissolved decreased and the blistering resistance was poor. No. In No. 15, since intermediate annealing was performed by batch annealing, Mn was precipitated in a large amount and coarsely, and the solid solution amount of Mn was reduced, so that the swelling resistance was inferior. No. Since No. 16 was not subjected to final annealing, recovery did not proceed and the number of movable dislocations increased and the blistering resistance was poor. No. In No. 17, since the final annealing temperature was too high and precipitates were coarsely deposited, the amount of dissolved Mn was reduced and the blistering resistance was poor.
[0032]
(Example 2)
No. 1 in Example 1 except that the rising temperature in the final cold rolling was 120 ° C. or higher and the final annealing was not performed. In the same manner as in Example 1, an aluminum alloy sheet was produced.
The rising temperature in the final cold rolling was increased by increasing the rolling rate and rolling speed per pass.
[0033]
(Comparative Example 3)
Example No. 1 in Example 1 except that the final annealing was not performed in Example 1. In the same manner as in Example 1, an aluminum alloy sheet was produced.
[0034]
For each aluminum alloy sheet manufactured in Example 2 and Comparative Example 3, mechanical properties, electrical conductivity, formability, weldability, and swell resistance were examined by the same method as in Example 1. The manufacturing conditions are shown in Table 4, and the survey results are shown in Table 5.
[0035]
[Table 4]

[0036]
[Table 5]

[0037]
As is apparent from Table 5, No. of the present invention example. Nos. 21 and 22 were No. 1 subjected to the final annealing in Example 1. The characteristic equivalent to 1 was shown. Thereby, it turns out that the final annealing can be omitted by setting the rising temperature in the final cold rolling to 120 ° C. or higher.
In contrast, No. of the comparative example. Since No. 23 had a low rising temperature in the final cold rolling and was not subjected to final annealing, the characteristics were inferior.
[0038]
Each aluminum alloy sheet material of the present invention produced in Examples 1 and 2 was immersed in various non-aqueous electrolytes (lithium salts dissolved in an organic solvent) used in lithium ion secondary batteries, and their corrosion resistance was examined. However, none of the Al alloy materials of the present invention corroded against any non-aqueous electrolyte.
The non-aqueous electrolyte is composed of one of lithium salts of LiClO ₄ , LiPF ₆ , LiBF ₄ or LiCF ₃ SO ₃ , ethylene carbonate, propylene carbonate, γ-butyrolactan, sulfolane, diethyl carbonate, dimethyl carbonate, dimethoxyethane. , Diethoxyethane, 2-methyl-tetrahydrofuran, various glymes, and the like were dissolved in one kind or an organic solvent in which two or more kinds were mixed.
[0039]
【The invention's effect】
As described above, the aluminum alloy sheet material of the present invention contains appropriate amounts of Mn and Mg, suppresses the contents of Si and Cu, further reduces the electrical conductivity to 45% IACS or less, and the ratio of proof stress to tensile strength ( (Yield strength / tensile strength) is defined as 0.8 to 0.95 and is excellent in mechanical properties, electrical conductivity, formability, weldability, swell resistance, etc., and is used in lithium ion batteries and the like. Suitable for prismatic secondary battery outer cans. The aluminum alloy sheet can be produced by subjecting an aluminum alloy having a predetermined composition to hot rolling, cold rolling, intermediate annealing, final cold rolling, and final annealing under certain conditions. In addition, the final annealing can be omitted. Therefore, there is an industrially significant effect.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective explanatory view of a sealed prismatic secondary battery outer can made as a trial for examining formability, weldability, and swelling resistance.

Claims (3)

Aluminum containing 0.5 to 1.5 mass % of Mn, 0.05 to 0.29 mass % of Mg, 0.2 mass % or less of Si, and less than 0.2 mass % of Cu, with the balance being Al and inevitable impurities It is an alloy material having an electrical conductivity of 45% IACS or less and a ratio of proof stress to tensile strength (proof strength / tensile strength) of 0.8 to 0.95. Excellent aluminum alloy material for sealed rectangular secondary battery outer cans. Aluminum containing 0.5 to 1.5 mass % of Mn, 0.05 to 0.29 mass % of Mg, 0.2 mass % or less of Si, and less than 0.2 mass % of Cu, with the balance being Al and inevitable impurities The alloy material is hot-rolled and then cold-rolled, then held at a temperature of 500 to 600 ° C. for 20 seconds, subjected to intermediate annealing at a temperature rising rate and a cooling rate of 10 ° C./sec or more, and then 30 to 60 % Of the aluminum alloy material for a sealed prismatic secondary battery outer can excellent in swell resistance and weldability, characterized by being subjected to final cold rolling at a cross-sectional reduction rate of 10%, and then subjected to final annealing treatment at a temperature of 120 to 240 ° C. Production method. The rising temperature in the final cold rolling is set to 120 ° C or higher, and the final annealing treatment is not performed. The aluminum alloy material for a sealed prismatic secondary battery outer can having excellent swell resistance and weldability according to claim 2, Production method.

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