JP3606139B2

JP3606139B2 - Battery electrode manufacturing method

Info

Publication number: JP3606139B2
Application number: JP32949799A
Authority: JP
Inventors: 直慶渋谷; 郁夫勝亦; 和史大川; 宏樹竹島
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1999-11-19
Filing date: 1999-11-19
Publication date: 2005-01-05
Anticipated expiration: 2019-11-19
Also published as: JP2001148245A

Description

【０００１】
【発明の属する技術分野】
本発明は、多孔性金属支持体内に活物質を充填して渦巻状に巻いて構成する電池用電極、特にタブレス方式電極の製造方法に関するものである。
【０００２】
【従来の技術】
２次電池の電極は、高多孔度を有する三次元的な網目構造を持った発泡メタル支持体に活物質を充填したものが比較的放電容量の面で優れている為に、大量に使用されている。更に、近年では効率放電特性の向上が求められており、その対応策として、電極の長手方向に沿った一辺に、活物質を充填しないで芯材を露出した部分を設け、セパレータを介して、正・負極電極を交互に重ね合わせて渦巻状に巻き付けて、略円筒状の電極群を形成して、前記略円筒状の電極群の端面を、活物質を充填しない芯材部分のみで構成することにより、溶接に適した金属の露出部を形成させて、この部分にリード片を溶接するタブレス方式により、集電特性を向上させ、前記要望に対応しようとしている。
【０００３】
しかし、芯材に発泡メタルを使用する電極の場合には、前記芯材部にリード片を直接溶接できるだけの強度がない。この対策として、溶接する電極の一辺に金属溶射層を設ける方法や、あらかじめ金属箔を溶着し補強する方法が開示されている。また、特開昭６２−１３９２５１号公報においては芯材のリード片溶着の補強策として、発泡メタルを用いた電極芯材の非活物質充填部分を電極の幅方向に圧縮して、金属部分の密度と強度を高めることにより、リード片溶接を可能とすることが開示されている。
【０００４】
しかしながら、この場合にはリード片を溶接するための補強を電極長手方向の一辺にのみ施しているため、電極の長さ方向での曲げ、引張り強度が電極両辺において著しく異なり、渦巻状の電池群構成時に電極の切れ、割れなどが生じ、満足できる電池群構成は困難であった。
【０００５】
【発明が解決しようとする課題】
上記のように、従来技術においては、発泡メタル電極の長手方向の一辺にのみリード片の溶接に適する高密度な金属部分を形成するため、電極の長さ方向での曲げ、引張り強度が電極両辺において異なるため、セパレータを介して正・負極の両極板を重ね合わし、渦巻き状に巻き上げて円筒状を形成する際に、電極の切れ、ひび割れを生じ満足する電池群の構成は困難であった。
【０００６】
本発明はこのような課題を解決するものであり、上記電池群構成時の電極の切れ、割れを防ぎ、電池生産性、電池特性を向上させることが可能な電極を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記の目的を達成するために、本発明は電極芯材として、発泡メタルを用いた電極の長手方向の両辺に、幅の狭い活物質の充填されていない部分を設け、それぞれにおいて活物質非充填部分を通り、電極の長さ方向と平行な直線に沿って、電極主要部である活物質充填部に対して直角に折り曲げた部分を形成し、この部分を座屈しないように支えた状態で、この折り曲げ部に、活物質の充填部に対して垂直な方向の加圧力を加えて、前記折り曲げ部の背丈を押しつぶして、電極の芯材の厚さになるまで圧縮することにより、電極の長手方向の両辺に高密度な金属部分を形成する。この高密度な金属部分を電極の長手方向の両辺に形成することにより、電極の長さ方向への曲げ、引張り強度が向上し、電極の切れ、割れが生じない電池群の構成が可能となる。
【０００８】
ただし、活物質の非充填部分を活物質充填部に対して直角に折り曲げる際の折り曲げ方向は同一方向とする。
【０００９】
【発明の実施の形態】
以下、図１を参照しながら本発明の実施の形態について説明する。
【００１０】
本発明の電極製造工程を図１（ａ），（ｂ），（ｃ）と工程順に従い図示する。図１（ａ）に示すような、長方形をした電極１の長さ方向に沿って活物質充填部２と、芯材のみからなる活物質非充填部３との間に境界線４を設け、活物質非充填部３内の前記境界線４と平行な直線７上において、活物質非充填部３の一部を図１（ｂ）に示すように活物質充填部２に対して直角に折り曲げた後、前記の幅の狭い直角に折り曲げた部分５の発泡メタルを、座屈しないように両側から支えた状態で、強制的に加圧力Ｆを矢印方向に加えて、折り曲げ部５の高さＨを圧縮して、活物質充填部２を有する電極面と同一厚さになるように成形するこることにより、図１（ｃ）に示すような、高密度な金属層６を電極１の長手方向の両辺に有する電極１を得ることができる。
【００１１】
このようにして得られた電極１は電極の長手方向の一辺に高密度な金属層を有する電極に比べて、はるかに優れた機械的強度を有する。また、電極１の長手方向の両辺に存在する高密度な金属層の幅は、それぞれ同一の幅を有している。
【００１２】
【実施例】
ニッケル−水素蓄電池の電極に対して、本発明を実施した一例について、図１を参照しながら説明する。まず図１（ａ）に示すように、電極芯材としてニッケル製の発泡メタルで目付け密度４３０ｇ／ｍ^２、厚さ１．２８ｍｍの長尺材を用い、活物質を充填後、圧縮して厚さｔ＝０．５５ｍｍとしたものを活物質充填部幅３２．５ｍｍ、電極の長手方向の両辺に活物質非充填部幅それぞれ４．８ｍｍを設けるように切断し、さらに、電池１個の電極長さに相当する２６０ｍｍに切断し、本発明の電極１の材料とした。続いて図１（ｂ）に示すように、電極１の活物質非充填部の端から３ｍｍのところを通る、電極の長手方向に平行な直線７に沿って直角に曲げた後、直角に折り曲げた幅３ｍｍの発泡メタルを、座屈しないように両側から支えた状態で、強制的に加圧力を活物質充填部に対して垂直に加えて、折り曲げ部の高さ３ｍｍを圧縮して、活物質充填部２を有する電極面と同一厚さになるように成形することにより、本発明の実施例による電極Ａを得た。比較のために電極の長手方向の一辺に高密度な金属層を有する電極を作成し、電極Ｂを得た。
【００１３】
電極Ａと電極Ｂにおける、電極の長手方向への引張り試験の結果を図２に示す。電極Ａにおいては電極Ｂに対して、２倍もの大きな引張り強度を得る事が可能である。図３では一例として、発泡ニッケルの目付け密度が４３０ｇ／ｍ^２のものの場合を示してあるが、この効果は目付け密度４００〜５５０ｇ／ｍ^２の発泡ニッケルにおいて特に顕著であった。
【００１４】
また、電極の長手方向の両辺に存在する高密度な金属層の幅をそれぞれ０．５ｍｍ以上とした場合に、電極の機械的強度の顕著な向上が見られた。しかし、高密度金属層幅の拡大による活物質量の減少を考慮すると、高密度な金属層の幅は両辺で０．５〜１．５ｍｍとなるのが最も望ましい。
【００１５】
電極の長手方向の両辺に存在する高密度な金属層の幅は、各辺において異なっていても電極の機械的強度の向上は望める。しかしながら、各辺における高密度な金属層の幅が同一である場合には、電極内部への応力が均一にかかることから、高密度な金属層の幅が同一の場合が最も望ましい。
【００１６】
【発明の効果】
以上のように本発明によれば、電極長手方向の両端辺に高密度な金属層を設けることにより、タブレス構造の電池の電池用極板の強度をはるかに向上させることが可能となる。つまり、タブレス構造の電池群構成における電極の切れ、割れが低減し、品質、電池特性の安定した電池の生産供給が可能となる。
【図面の簡単な説明】
【図１】（ａ）加工を行う前の本発明の電池用電極の斜視図
（ｂ）電池用電極材料の発泡メタル芯材の活物質非充填部に折り曲げ加工を施した様子を示す斜視図
（ｃ）本発明の加工を施した電極形状を示す斜視図
【図２】本発明の電池用電極の電極長手方向への引っ張り強度を示す図
【符号の説明】
１電極
２活物質充填部
３活物質非充填部
４活物質充填部と非充填部との境界線
５電極芯材折り曲げ部
６高密度金属部
７折り曲げ位置を示す直線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a battery electrode, particularly a tabless electrode, which is formed by filling a porous metal support with an active material and winding it in a spiral shape.
[0002]
[Prior art]
Secondary battery electrodes are used in large quantities because a foam metal support with a high porosity and a three-dimensional network structure filled with an active material is relatively superior in terms of discharge capacity. ing. Furthermore, in recent years, an improvement in the efficiency discharge characteristics has been demanded, and as a countermeasure, a part where the core material is exposed without being filled with an active material is provided on one side along the longitudinal direction of the electrode, through a separator, The positive and negative electrodes are alternately overlapped and wound in a spiral shape to form a substantially cylindrical electrode group, and the end surface of the substantially cylindrical electrode group is composed of only a core portion not filled with an active material. Thus, by using a tabless method in which a metal exposed portion suitable for welding is formed, and a lead piece is welded to this portion, the current collection characteristics are improved, and the above-described demand is to be met.
[0003]
However, in the case of an electrode using metal foam as the core material, there is not enough strength to directly weld the lead piece to the core material portion. As measures against this, a method of providing a metal spray layer on one side of the electrode to be welded and a method of previously welding and reinforcing a metal foil are disclosed. Further, in Japanese Patent Laid-Open No. Sho 62-139251, as a measure for reinforcing the lead piece of the core material, the inactive material filling portion of the electrode core material using the foam metal is compressed in the width direction of the electrode, It is disclosed that lead piece welding is possible by increasing the density and strength.
[0004]
However, in this case, since the reinforcement for welding the lead piece is applied only to one side in the longitudinal direction of the electrode, the bending and tensile strength in the length direction of the electrode are remarkably different on both sides of the electrode, and the spiral battery group Satisfactory battery group construction was difficult due to electrode breakage and cracking during construction.
[0005]
[Problems to be solved by the invention]
As described above, in the prior art, in order to form a high-density metal part suitable for welding the lead piece only on one side in the longitudinal direction of the foam metal electrode, bending and tensile strength in the length direction of the electrode are Therefore, when the positive and negative electrode plates are overlapped with each other through a separator and wound into a spiral shape to form a cylindrical shape, it is difficult to construct a satisfactory battery group due to electrode breakage and cracking.
[0006]
This invention solves such a subject, and it aims at providing the electrode which can prevent the cutting | disconnection and crack of the electrode at the time of the said battery group structure, and can improve battery productivity and a battery characteristic. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an electrode core material that is provided with a portion that is not filled with a narrow active material on both sides in the longitudinal direction of an electrode using foam metal, and is not filled with an active material in each. Form a part that is bent at right angles to the active material filling part, which is the main part of the electrode, along a straight line that passes through the part and parallel to the length direction of the electrode, and supports this part so that it does not buckle. By applying a pressing force in a direction perpendicular to the filling portion of the active material to the bent portion, the height of the bent portion is crushed and compressed to the thickness of the core material of the electrode. High density metal parts are formed on both sides in the longitudinal direction. By forming these high-density metal portions on both sides in the longitudinal direction of the electrode, the bending and tensile strength in the length direction of the electrode are improved, and a battery group configuration in which the electrode is not cut or cracked becomes possible. .
[0008]
However, the bending direction when the non-filled portion of the active material is bent at a right angle with respect to the active material filling portion is the same direction.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
[0010]
The electrode manufacturing process according to the present invention is illustrated in accordance with the order of steps shown in FIGS. As shown in FIG. 1A, a boundary line 4 is provided between the active material filling portion 2 and the active material non-filling portion 3 made of only the core material along the length direction of the rectangular electrode 1; On a straight line 7 parallel to the boundary line 4 in the active material unfilled portion 3, a part of the active material unfilled portion 3 is bent at a right angle with respect to the active material filled portion 2 as shown in FIG. After that, in the state where the foam metal of the portion 5 bent at a narrow right angle is supported from both sides so as not to buckle, the applied force F is forcibly applied in the direction of the arrow so that the height of the bent portion 5 is increased. By compressing H so as to have the same thickness as the electrode surface having the active material filling portion 2, a high-density metal layer 6 as shown in FIG. An electrode 1 having both sides in the direction can be obtained.
[0011]
The electrode 1 thus obtained has a mechanical strength far superior to that of an electrode having a high-density metal layer on one side in the longitudinal direction of the electrode. The widths of the high-density metal layers present on both sides in the longitudinal direction of the electrode 1 have the same width.
[0012]
【Example】
An example in which the present invention is applied to an electrode of a nickel-hydrogen storage battery will be described with reference to FIG. First, as shown in FIG. 1 (a), a long metal material having a basis weight of 430 g / m ² and a thickness of 1.28 mm made of nickel foam metal is used as an electrode core material. The thickness t = 0.55 mm was cut to provide an active material filling portion width of 32.5 mm and active material non-filling portion widths of 4.8 mm on both sides in the longitudinal direction of the electrode. It was cut into 260 mm corresponding to the length, and used as the material of the electrode 1 of the present invention. Subsequently, as shown in FIG. 1B, after bending at a right angle along a straight line 7 passing through the end of the active material unfilled portion of the electrode 1 and parallel to the longitudinal direction of the electrode, the electrode 1 is bent at a right angle. The foam metal with a width of 3 mm was supported from both sides so as not to buckle, and a force was applied perpendicularly to the active material filling part to compress the height of the bent part to 3 mm. The electrode A according to the example of the present invention was obtained by forming the electrode to have the same thickness as the electrode surface having the substance filling portion 2. For comparison, an electrode having a high-density metal layer on one side in the longitudinal direction of the electrode was prepared, and an electrode B was obtained.
[0013]
The result of the tensile test in the longitudinal direction of the electrode A and the electrode B is shown in FIG. In the electrode A, it is possible to obtain a tensile strength twice as large as that of the electrode B. As an example, FIG. 3 shows a case where the weight density of the foamed nickel is 430 g / m ² , but this effect is particularly remarkable in the foamed nickel having a weight density of 400 to 550 g / m ² .
[0014]
In addition, when the width of the high-density metal layer existing on both sides in the longitudinal direction of the electrode was 0.5 mm or more, significant improvement in the mechanical strength of the electrode was observed. However, considering the decrease in the amount of active material due to the expansion of the high-density metal layer width, the width of the high-density metal layer is most preferably 0.5 to 1.5 mm on both sides.
[0015]
Even if the width of the high-density metal layer existing on both sides in the longitudinal direction of the electrode is different on each side, it is possible to improve the mechanical strength of the electrode. However, when the width of the high-density metal layer on each side is the same, the stress is uniformly applied to the inside of the electrode. Therefore, the case where the width of the high-density metal layer is the same is most desirable.
[0016]
【The invention's effect】
As described above, according to the present invention, it is possible to significantly improve the strength of the battery electrode plate of the battery having a tabless structure by providing the high-density metal layers on both ends in the longitudinal direction of the electrode. That is, the breakage and cracking of the electrode in the battery group configuration of the tabless structure is reduced, and the production and supply of the battery having stable quality and battery characteristics can be realized.
[Brief description of the drawings]
FIG. 1A is a perspective view of a battery electrode of the present invention before processing. FIG. 1B is a perspective view showing a state in which an active material non-filling portion of a foam metal core of a battery electrode material is bent. (C) Perspective view showing the shape of the electrode processed according to the present invention. FIG. 2 is a diagram showing the tensile strength in the longitudinal direction of the battery electrode of the present invention.
DESCRIPTION OF SYMBOLS 1 Electrode 2 Active material filling part 3 Active material non-filling part 4 The boundary line 5 of an active material filling part and a non-filling part 5 Electrode core material bending part 6 High-density metal part 7 The straight line which shows a bending position

Claims

A method for manufacturing a battery electrode in which a thin plate-shaped core material made of foam metal is filled with an active material, and the active material filling portion and an active material narrower than the width along the length direction of the rectangular electrode A boundary line with the non-filling portion consisting of a portion not filled with the material is provided, and the bending direction when folding a part of the non-filling portion perpendicular to the active material filling portion on a straight line parallel to the boundary line is the same direction After being bent as described above, the height of the foam metal of the portion bent at a right angle is compressed by applying a force in a direction perpendicular to the active material filling portion in a state where it is supported so as not to buckle. A method of manufacturing a battery electrode in which high-density metal portions are formed on both sides in the longitudinal direction of the electrode by compressing the right-angled bent portion so as to have the same thickness as the electrode surface.

^2. The battery according to claim 1, wherein a high-density metal layer is formed by crushing voids caused by foaming on both sides of the electrode along the longitudinal direction of the electrode having nickel foam as a core material having a basis weight of 400 to 550 g / m ² . Electrode manufacturing method.

2. The battery for a battery according to claim 1, wherein a high-density metal layer having a width of 0.5 to 1.5 mm is formed on both sides of the electrode along the longitudinal direction of the electrode having nickel foam as a core material by crushing voids due to foaming. Electrode manufacturing method.