JP4524982B2

JP4524982B2 - Cylindrical secondary battery

Info

Publication number: JP4524982B2
Application number: JP2002301609A
Authority: JP
Inventors: 直人荒井; 伸治村重
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-10-16
Filing date: 2002-10-16
Publication date: 2010-08-18
Anticipated expiration: 2022-10-16
Also published as: JP2004139777A

Description

【０００１】
【発明の属する技術分野】
本発明はリチウムイオン二次電池などの円筒型二次電池に関し、特にその集電構造に関するものである。
【０００２】
【従来の技術】
ニッケル水素蓄電池、ニッケルカドミウム蓄電池、リチウムイオン二次電池などの二次電池の中で電動工具用などの高出力を必要とするものは、従来から集電構造が工夫されていた。その中でも、一般的なものは、タブレス構造と呼ばれるもので、正極板と負極板を互いに上下方向にずらしてセパレータを介して渦巻き状に捲回して極板群とした後、この渦巻き状極板群の正極板端縁の集電体突出部に平板状正極集電板を溶接し、負極板端縁の集電体突出部に平板状負極集電板を溶接して電極体とする。この電極体を金属製外装缶に挿入し、負極集電板を外装缶の底部にスポット溶接し、正極集電板を、正極タブにより、正極端子を兼ねた封口板に溶接した構造である。電池容器は、この外装缶と封口板よりなっている。この構造にすることにより、使用時の正極板における電流分布および負極における電流分布が均一になり、高率放電特性が向上する。
【０００３】
これらタブレス構造の中でも、特に薄型の集電体を使用するリチウムイオン二次電池において、集電効率を高め、充放電時の温度上昇を小さくするために、集電体突出部を押圧して、突出部先端自身により平坦部を形成し、この平坦部に集電板を溶接する構造が提案されている（例えば特許文献１参照）。
【０００４】
この構造における集電板としては、集電板と集電リードが一体化されたものが（特許文献１、図３参照）に記載されている。この構成において、特に負極集電板は、集電リードにより外装缶に溶接されているが、電池に振動や衝撃力が加えられたときに、集電リードの外装缶との溶接部分が剥離しやすいという問題があった。
【０００５】
これに対し、外装缶に接合される集電板の接触部に弾性を持たせることにより、この接触部の弾性変形によって溶接部に付加される振動や衝撃力を緩衝し、溶接部の剥離を防止または抑制できるようにする構成が提案されている。（例えば特許文献２参照）この集電板は接触部のみに弾性があることから、集電板と極板の接続にリードを使わないタブレス構造に適用すると、溶接部の剥離の防止または抑制が十分で無く、また、（特許文献１）に記載されているような平坦部に集電板を溶接する構造では、集電板の接触部が中央にあるため、弾性を持たせるためのスリットなどを使用すると溶接する部分が少なくなるという問題があった。
【０００６】
【特許文献１】
特開２０００−２９４２２２号公報
【特許文献２】
特開２００１−２５６９５４号公報
【０００７】
【発明が解決しようとする課題】
電動工具などは、工事現場等で使用者からかなり乱暴に扱われる（ラフユース）ため、電池においても振動や衝撃力に強い電池が望まれている。ところが、前述のように突出部先端自身により平坦部を形成し、この平坦部に集電板を溶接するタブレス構造では、電池に振動や衝撃力が加えられたときに、集電板の外装缶との溶接部分が剥離しやすいという課題があった。
【０００８】
本発明の目的は、上記の課題を解決し、ラフユースにあっても安定して優れた集電構造をもつ二次電池を提供することにある。
【０００９】
【課題を解決するための手段】
上記の課題を解決するために、本発明は、正極芯材に正極材料を付着させて製造した正極板と負極芯材に負極材料を付着させて製造した負極板とをセパレータを介して捲回してなる極板群を電解液とともに封口板と金属製外装缶からなる電池容器内に収容した円筒型二次電池であって、前記正極板および前記負極板の少なくとも一方は、その長手方向に沿う端部に芯材露出部を有し、前記極板群の上面および下面の少なくとも一方には、前記正極板および前記負極板のいずれかの芯材露出部が突出しており、前記突出部の先端自身によって平坦部が形成されており、前記平坦部に集電板が接合されている円筒型二次電池において、前記集電板は、前記平坦部と接合される固定部と前記外装缶の底部と接合される可動部からなり、さらに前記集電板の外周面の外形が円形であり、前記可動部は、前記集電板外周面に沿った湾曲スリット部と前記集電板外周面とにより形成された円弧状の可動部Ａと、前記湾曲スリット部と連通するＵ字状のスリットにより形成され、かつ、外装缶の底部と接合される集電板の中心部を含む、直線状の可動部Ｂとの少なくとも二つの部分からなることを特徴とする円筒型二次電池とするものである。
【００１０】
さらに、前記平坦部と前記固定部との接合は、レーザ溶接接合または抵抗スポット溶接接合であるのが効果的である。
【００１１】
また、可動部Ｂが線対称であり、その対称線およびその延長線が、集電板の中心と前記湾曲スリット部の終点を通ることが、特に好ましい。
【００１２】
上記のように構成された円筒形二次電池では、集電板が、平坦部と接合される固定部と外装缶の底部と接合される可動部からなり、さらに前記可動部の一部は、集電板外周面を含むように構成されているため、底部との接合部から集電板外周面を含む部分までの可動部全体が弾性体となるため振動や衝撃力に対して、接合部にかかる負荷を小さくするという作用がある。
【００１３】
さらに、平坦部と固定部との接合は、レーザ溶接接合または抵抗スポット溶接接合であると、簡便かつ確実に接合できるという作用があり効果的である。
【００１４】
また、集電板の外形が円形であり、その可動部は、集電板外周面に沿った湾曲スリット部と集電板外周面とにより形成された円弧状の可動部Ａと、この湾曲スリット部と連通するＵ字状のスリットにより形成された直線状の可動部Ｂとの少なくとも二つの部分からなる構成であると、可動部全体の長さが比較的長くなるため、可動部全体の弾性力が大きくなり、振動や衝撃力に対して、さらに接合部にかかる負荷を小さくするという作用がある。この可動部Ａの円弧の長さは湾曲スリット部の長さにより決まり、任意の長さを取ることができるが、平坦部により集電された電流が可動部を通って外装缶に流れるため、あまり可動部全体の長さが長くなると電気抵抗が大きくなり不都合である。また、衝撃力を受けた時の耐衝撃力のバランス上、可動部Ｂが線対称であり、その対称線およびその延長線が、集電板の中心と前記湾曲スリット部の終点を通ることが、特に好ましい。
【００１５】
【発明の実施の形態】
以下、本発明の円筒形二次電池の集電板の実施の形態について添付図面を参照して説明する。
【００１６】
図１は、本発明の一実施の形態である集電板の斜視図であり、図２は上面図である。
【００１７】
図１において、側面の稜線は物品の形状をわかりやすくするためのもので、実際はなめらかな曲線となっている。図１および図２において、集電板１ａは、外周面の外形は円形である。さらに、集電板１ａは、可動部２と固定部３の二つの部分に分けられ、湾曲スリット部４とそれと連通するＵ字状のスリット５がある。可動部２と固定部３の境界８は、湾曲スリット部４の終点６と集電板外周面７を最短に結ぶ線である。また、可動部２は、集電板外周面７に沿った湾曲スリット部４と集電板外周面７とにより形成された円弧状の可動部Ａ９と、この湾曲スリット部４と連通するＵ字状のスリット５により形成された直線状の可動部Ｂ１０との二つの部分からなっている。
【００１８】
このような構成になっているため、凸部１１を外装缶に溶接したとき、境界８までの長さが長くなるため十分な弾性が得られる。なお、終点６の位置を変えることにより自由に、境界８の位置を変えることができ、弾性力も変化することができる。ここで、衝撃力を受けた時の耐衝撃力のバランス上、本実施例のように可動部Ｂ１０が線対称であり、その対称線およびその延長線が、集電板の中心と前記湾曲スリット部４の終点６を通ることが、特に好ましい。
【００１９】
図３は、本発明のその他の実施の形態である集電板１ｂの斜視図であり、図４は上面図である。これらの図において、図１および図２と同じ符号は、同じ機能および名称を持つものを示す。集電体１ｂにおいては、湾曲スリット部４が２つあり、Ｕ字状のスリット５の両側に連通している。したがって、可動部Ａ９も２つになる。この実施の形態においても終点６の位置は自由に変えられ、左右対称でなくとも良い。
【００２０】
【実施例】
次に、実施例を用いて本発明の具体例について図５を参照して説明する。本実施例の二次電池はリチウムイオン二次電池である。
【００２１】
図５において、１２は正極板、１３は負極板で、微多孔ポリエチレンフィルムから成るセパレータ１４を介して互いに対向された状態で渦巻き状に巻回されて極板群２１が構成され、この極板群２１が電解液とともに電池容器１５内に収納配置されている。電池容器１５は負極端子となる円筒容器状の外装缶１６と正極端子となる電池蓋１７にて構成され、外装缶１６の上端開口部内周と電池蓋１７の外周との間に介装された絶縁パッキン１８にて相互に絶縁されるとともに電池容器１５が密閉されている。なお、極板群２１と外装缶１６の内周との間にもセパレータ１４は介装されている。
【００２２】
正極板１２は、正極芯材１２ｂの両面に正極材料１２ａを塗工して構成されるとともに、その正極芯材１２ｂの一側部（図示例では上側部）が正極材料１２ａの塗工部より突出されている。また、負極板１３は、負極芯材１３ｂの両面に負極材料１３ａを塗工して構成されるとともに、その負極芯材１３ｂの他側部（図示例では下側部）が負極材料１３ａの塗工部より突出されている。セパレータ１４は正極板１２及び負極板１３の塗工部の両側縁よりも外側に突出されている。
【００２３】
そして、正極芯材１２ｂのセパレータ１４より突出した部分を塑性変形させて正極平坦部２２が形成され、この平坦部２２に正極集電板１９が接合されている。正極集電板１９は電池蓋１７に接続されている。１９ａは、正極集電板１９を電池蓋１７の内面に接合するためその外周から延出された接続片である。
【００２４】
同様に、負極芯材１３ｂのセパレータ１４より突出した部分を塑性変形させて負極平坦部２３が形成され、この平坦部２３に負極集電板２０として、前述の集電板１ａが接合されている。負極集電板２０は、凸部１１により外装缶１６の底面に溶接されている。
【００２５】
次に、製造方法を具体的に示す。正極板１２は、電解二酸化マンガン（ＥＭＤ：ＭｎＯ₂）と炭酸リチウム（Ｌｉ₂ＣＯ₃）とをＬｉ／Ｍｎ＝１／２となるように混合し、８００℃で２０時間大気中で焼成して製造した正極活物質のＬｉＭｎ₂Ｏ₄と、導電剤のアセチレンブラックと、結着剤のポリフッ化ビニリデンとを、それぞれ重量比で９２：３：５の割合で混合したものを正極材料１２ａとした。
【００２６】
なお、正極材料１２ａをペースト状に混練するために結着剤としてのポリフッ化ビニリデンはＮメチルピロリドンディスパージョン液を用いた。上記混合比率は固形分としての割合である。この正極材料ペーストを、厚み２０μｍのアルミ箔から成る正極芯材１２ｂの両面に一側縁部に幅６．５ｍｍの非塗工部を残した状態で塗工し、正極材料層を形成した。正極材料層の両膜厚は同じで、塗工、乾燥後の両膜厚の和は２８０μｍで、正極板１２の厚さを３００μｍとした。その後、正極板１２の厚みが２００μｍになるように直径３００ｍｍのプレスロールにより圧縮成形した。このとき、正極材料密度は３．０ｇ／ｃｍ³であった。
【００２７】
負極板１３は、人造黒鉛と結着剤のスチレンブタジエンゴム（ＳＢＲ）とを重量比９７：３の割合で混合したものを負極材料１３ａとした。なお、負極材料１３ａをペースト状に混練するために結着剤としてのスチレンブタジエンゴムは水溶性のディスパージョン液を用いた。上記混合比率は固形分としての割合である。この負極合剤ペーストを厚み１４μｍの銅箔から成る負極芯材１３ｂの両面に一側縁部に幅４ｍｍの非塗工部を残した状態で塗工し、負極材料層を形成した。その後、負極板１３の厚みが１７０μｍになるように直径３００ｍｍのプレスロールにより圧縮成形した。このとき、負極材料密度は１．４ｇ／ｃｍ³であった。
【００２８】
電解液は、エチレンカーボネイト（ＥＣ）とジエチレンカーボネイト（ＤＥＣ）を体積比１：１の配合比で混合した混合溶媒に、溶質として６フッ化リン酸リチウム（ＬｉＰＦ₆）を１ｍｏｌ／ｄｍ³の濃度に溶解したものを用いた。
【００２９】
このリチウムイオン二次電池の製造に当たっては、上記のようにして作製した正極板１２と負極板１３とをセパレータ１４を介して対向させかつそれらの集電体１２ｂ、１３ｂの突出部を両端に突出させた状態で渦巻き状に巻回して極板群２１を形成した。
【００３０】
この極板群２１において平坦部２２および２３を作成した。まず、正極集電板１９を平坦部２２に押し付けるように配置して両者を圧接させた状態で、正極集電板１９の表面の周方向複数箇所を中心部から外周縁まで放射状にレーザビームを照射することによって集電板１９と平坦部２２をレーザ溶接した。
【００３１】
次に、集電体１ａを平坦部２３に押し付けるように配置して両者を圧接させた状態で、集電板１ａの固定部３を放射状の模様でレーザビームを数本照射することによって集電板１ａと平坦部２３をレーザ溶接した。
【００３２】
その後、この集電板１９、１ａを接合した極板群２１を外装缶１６内に収容し、巻き芯部を利用して集電板１ａの凸部１１と外装缶１６を溶接し、集電板１９を正極接続片１９ａにより電池蓋１７にレーザ溶接した。
【００３３】
最後に外装缶１６内に電解液を注液し、真空含浸させ、電池蓋１７で密閉した。
【００３４】
（電池の評価)
作成した実施例の電池は、内部抵抗が２８ｍΩで、従来の電池（１３〜２６ｍΩ）とほぼ同じ内部抵抗を示した。また、電池の落下試験では、７５ｃｍの高さからコンクリート床に落とした場合に、６０回まで内部抵抗の上昇が見られず、安定な導電接続が得られた。
【００３５】
【発明の効果】
本発明の二次電池によれば、以上の説明から明らかなように、ラフユースにあっても安定して優れた集電構造を持つ二次電池が提供できる。
【図面の簡単な説明】
【図１】本発明の一実施形態における集電板の斜視図
【図２】本発明の一実施形態における集電板の上面図
【図３】本発明の別の実施形態における集電板の斜視図
【図４】本発明の別の実施形態における集電板の上面図
【図５】本発明の一実施例におけるリチウムイオン二次電池の縦断面図
【符号の説明】
１ａ，１ｂ集電板
２可動部
３固定部
４湾曲スリット部
５スリット
６終点
７外周面
８境界
９可動部Ａ
１０可動部Ｂ
１１凸部
１２正極板
１２ａ正極材料
１２ｂ正極芯材
１３負極板
１３ａ負極材料
１３ｂ負極芯材
１４セパレータ
１５電池容器
１６外装缶
１７電池蓋
１８絶縁パッキン
１９正極集電板
１９ａ正極接続片
２０負極集電板
２１極板群
２２正極平坦部
２３負極平坦部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylindrical secondary battery such as a lithium ion secondary battery, and more particularly to a current collecting structure thereof.
[0002]
[Prior art]
Among secondary batteries such as nickel metal hydride storage batteries, nickel cadmium storage batteries, and lithium ion secondary batteries that require a high output, such as for power tools, a current collecting structure has been conventionally devised. Among them, a general one is called a tabless structure. After the positive electrode plate and the negative electrode plate are shifted from each other in the vertical direction and wound into a spiral shape through a separator, this spiral plate is formed. A plate-like positive current collector plate is welded to the current collector protruding portion at the edge of the positive electrode plate of the group, and a plate-like negative electrode current collector plate is welded to the current collector protruding portion at the edge of the negative electrode plate. This electrode body is inserted into a metal outer can, the negative electrode current collector plate is spot welded to the bottom of the outer can, and the positive electrode current collector plate is welded to the sealing plate that also serves as the positive electrode terminal by the positive electrode tab. The battery container is composed of the outer can and the sealing plate. By adopting this structure, the current distribution in the positive electrode plate and the current distribution in the negative electrode during use become uniform, and the high rate discharge characteristics are improved.
[0003]
Among these tabless structures, particularly in lithium ion secondary batteries using a thin current collector, in order to increase the current collection efficiency and reduce the temperature rise during charge and discharge, press the current collector protrusion, There has been proposed a structure in which a flat portion is formed by the protrusion tip itself and a current collector plate is welded to the flat portion (for example, see Patent Document 1).
[0004]
As the current collector plate in this structure, a plate in which the current collector plate and the current collector lead are integrated is described (see Patent Document 1 and FIG. 3). In this configuration, in particular, the negative electrode current collector plate is welded to the outer can by the current collecting lead. However, when vibration or impact force is applied to the battery, the welded portion of the current collecting lead to the outer can is peeled off. There was a problem that it was easy.
[0005]
In contrast, by giving elasticity to the contact portion of the current collector plate joined to the outer can, the vibration and impact force applied to the welded portion are buffered by elastic deformation of the contact portion, and the welded portion is peeled off. Configurations that allow prevention or suppression have been proposed. (For example, refer to Patent Document 2) Since this current collector plate is elastic only in the contact portion, when applied to a tabless structure that does not use a lead to connect the current collector plate and the electrode plate, prevention or suppression of peeling of the welded portion is prevented. In addition, in the structure in which the current collector plate is welded to a flat portion as described in (Patent Document 1), since the contact portion of the current collector plate is in the center, a slit for giving elasticity, etc. When using, there was a problem that the number of parts to be welded was reduced.
[0006]
[Patent Document 1]
JP 2000-294222 A [Patent Document 2]
Japanese Patent Laid-Open No. 2001-256554
[Problems to be solved by the invention]
Since electric tools and the like are handled fairly roughly by users at construction sites and the like (rough use), batteries that are resistant to vibration and impact are also desired. However, in the tabless structure in which the flat portion is formed by the protrusion tip itself as described above and the current collector plate is welded to the flat portion, when the vibration or impact force is applied to the battery, the outer can of the current collector plate There was a problem that the welded part was easily peeled off.
[0008]
An object of the present invention is to solve the above problems and provide a secondary battery having a stable current collecting structure even in rough use.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention winds a positive electrode plate manufactured by attaching a positive electrode material to a positive electrode core material and a negative electrode plate manufactured by attaching a negative electrode material to a negative electrode core material through a separator. A positive electrode plate and a negative electrode plate along a longitudinal direction thereof, wherein the electrode plate group is housed in a battery container including a sealing plate and a metal outer can together with an electrolyte. A core material exposed portion is provided at an end, and a core material exposed portion of either the positive electrode plate or the negative electrode plate protrudes from at least one of the upper surface and the lower surface of the electrode plate group, and the tip of the projecting portion In the cylindrical secondary battery in which a flat portion is formed by itself and a current collector plate is joined to the flat portion, the current collector plate includes a fixed portion joined to the flat portion and a bottom portion of the outer can consists movable portion joined with the collection to further An outer shape of the outer peripheral surface of the plate is circular, and the movable portion includes an arc-shaped movable portion A formed by a curved slit portion along the outer peripheral surface of the current collector plate and the outer peripheral surface of the current collector plate, and the curved portion. It is formed by a U-shaped slit that communicates with the slit portion , and includes at least two portions including a linear movable portion B including the central portion of the current collector plate joined to the bottom portion of the outer can. And a cylindrical secondary battery.
[0010]
Further, it is effective that the flat portion and the fixed portion are joined by laser welding or resistance spot welding.
[0011]
Further, it is particularly preferable that the movable part B is line symmetric, and the symmetry line and its extension line pass through the center of the current collector plate and the end point of the curved slit part.
[0012]
In the cylindrical secondary battery configured as described above, the current collector plate includes a fixed part joined to the flat part and a movable part joined to the bottom part of the outer can, and a part of the movable part includes: Since it is configured to include the current collector outer peripheral surface, the entire movable part from the joint with the bottom to the part including the current collector outer peripheral surface becomes an elastic body, so the joint is resistant to vibration and impact force. There is an effect of reducing the load applied to.
[0013]
Furthermore, the joining of the flat portion and the fixed portion is effective because it can be simply and reliably joined by laser welding joining or resistance spot welding joining.
[0014]
The outer shape of the current collector plate is circular, and the movable portion includes an arcuate movable portion A formed by the curved slit portion along the outer peripheral surface of the current collector plate and the outer peripheral surface of the current collector plate, and the curved slit. Since the length of the entire movable part becomes relatively long when the structure is composed of at least two parts with the linear movable part B formed by the U-shaped slit communicating with the part, the elasticity of the entire movable part The force is increased, and the load applied to the joint portion is further reduced with respect to vibration and impact force. The length of the arc of the movable part A is determined by the length of the curved slit part and can take any length, but the current collected by the flat part flows through the movable part to the outer can, If the length of the entire movable part is too long, the electric resistance increases, which is inconvenient. Moreover, the movable part B is line-symmetrical on the balance of the impact resistance when receiving an impact force, and the symmetry line and its extension line pass through the center of the current collector plate and the end point of the curved slit part. Is particularly preferred.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a current collector plate of a cylindrical secondary battery according to the present invention will be described below with reference to the accompanying drawings.
[0016]
FIG. 1 is a perspective view of a current collector plate according to an embodiment of the present invention, and FIG. 2 is a top view.
[0017]
In FIG. 1, the ridgeline on the side surface is for making the shape of the article easy to understand, and is actually a smooth curve. 1 and 2, the current collector plate 1a has a circular outer peripheral surface. Further, the current collector plate 1a is divided into two parts, a movable part 2 and a fixed part 3, and includes a curved slit part 4 and a U-shaped slit 5 communicating with the curved slit part 4. A boundary 8 between the movable portion 2 and the fixed portion 3 is a line connecting the end point 6 of the curved slit portion 4 and the current collector plate outer peripheral surface 7 in the shortest distance. The movable portion 2 includes an arc-shaped movable portion A9 formed by the curved slit portion 4 along the current collector outer peripheral surface 7 and the current collector outer peripheral surface 7, and a U-shape communicating with the curved slit portion 4. It consists of two parts with the linear movable part B10 formed by the slit 5 of the shape.
[0018]
Since it has such a structure, when the convex part 11 is welded to an exterior can, the length to the boundary 8 becomes long, and sufficient elasticity is obtained. Note that the position of the boundary 8 can be freely changed by changing the position of the end point 6, and the elastic force can also be changed. Here, in view of the balance of impact resistance when receiving an impact force, the movable portion B10 is axisymmetric as in this embodiment, and the symmetry line and its extension line are the center of the current collector plate and the curved slit. Passing through the end point 6 of the part 4 is particularly preferred.
[0019]
FIG. 3 is a perspective view of a current collector plate 1b according to another embodiment of the present invention, and FIG. 4 is a top view. In these drawings, the same reference numerals as those in FIGS. 1 and 2 denote the same functions and names. In the current collector 1 b, there are two curved slit portions 4 that communicate with both sides of the U-shaped slit 5. Therefore, there are two movable parts A9. Also in this embodiment, the position of the end point 6 can be freely changed and does not have to be symmetrical.
[0020]
【Example】
Next, a specific example of the present invention will be described with reference to FIG. 5 with reference to examples. The secondary battery of this example is a lithium ion secondary battery.
[0021]
In FIG. 5 , 12 is a positive electrode plate, 13 is a negative electrode plate, and is wound in a spiral shape in a state of being opposed to each other via a separator 14 made of a microporous polyethylene film. The group 21 is accommodated in the battery container 15 together with the electrolytic solution. The battery container 15 includes a cylindrical container-shaped outer can 16 serving as a negative electrode terminal and a battery lid 17 serving as a positive electrode terminal. The battery container 15 is interposed between the inner periphery of the upper end opening of the outer can 16 and the outer periphery of the battery cover 17. The battery case 15 is sealed while being insulated from each other by the insulating packing 18. The separator 14 is also interposed between the electrode plate group 21 and the inner periphery of the outer can 16.
[0022]
The positive electrode plate 12 is configured by coating the positive electrode material 12a on both surfaces of the positive electrode core material 12b, and one side portion (the upper portion in the illustrated example) of the positive electrode core material 12b is from the coated portion of the positive electrode material 12a. It is protruding. The negative electrode plate 13 is configured by coating the negative electrode material 13a on both surfaces of the negative electrode core material 13b, and the other side portion (lower side portion in the illustrated example) of the negative electrode core material 13b is coated with the negative electrode material 13a. It protrudes from the construction part. The separator 14 protrudes outward from both side edges of the coating portions of the positive electrode plate 12 and the negative electrode plate 13.
[0023]
And the part which protruded from the separator 14 of the positive electrode core material 12b is plastically deformed, the positive electrode flat part 22 is formed, and the positive electrode current collecting plate 19 is joined to this flat part 22. FIG. The positive electrode current collector plate 19 is connected to the battery lid 17. 19a is a connection piece extended from the outer periphery in order to join the positive electrode current collecting plate 19 to the inner surface of the battery lid 17.
[0024]
Similarly, a negative electrode flat portion 23 is formed by plastic deformation of a portion of the negative electrode core member 13 b protruding from the separator 14, and the aforementioned current collector plate 1 a is joined to the flat portion 23 as the negative electrode current collector plate 20. . The negative electrode current collector plate 20 is welded to the bottom surface of the outer can 16 by the convex portion 11.
[0025]
Next, a manufacturing method is shown concretely. The positive electrode plate 12 is obtained by mixing electrolytic manganese dioxide (EMD: MnO ₂ ) and lithium carbonate (Li ₂ CO ₃ ) so that Li / Mn = 1/2, and firing in the atmosphere at 800 ° C. for 20 hours. A positive electrode material 12a was prepared by mixing LiMn ₂ O ₄ as a positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder in a weight ratio of 92: 3: 5, respectively. .
[0026]
In order to knead the positive electrode material 12a into a paste, N-methylpyrrolidone dispersion liquid was used as polyvinylidene fluoride as a binder. The mixing ratio is a ratio as a solid content. This positive electrode material paste was applied in a state where a non-coated portion having a width of 6.5 mm was left on one side edge on both surfaces of a positive electrode core material 12b made of an aluminum foil having a thickness of 20 μm to form a positive electrode material layer. Both film thicknesses of the positive electrode material layer were the same, the sum of both film thicknesses after coating and drying was 280 μm, and the thickness of the positive electrode plate 12 was 300 μm. Thereafter, the positive electrode plate 12 was compression-molded by a press roll having a diameter of 300 mm so that the thickness of the positive electrode plate 12 was 200 μm. At this time, the positive electrode material density was 3.0 g / cm ³ .
[0027]
The negative electrode plate 13 was prepared by mixing artificial graphite and a binder styrene butadiene rubber (SBR) at a weight ratio of 97: 3 as a negative electrode material 13a. In order to knead the negative electrode material 13a into a paste, a water-soluble dispersion liquid was used as the styrene butadiene rubber as a binder. The mixing ratio is a ratio as a solid content. This negative electrode mixture paste was applied on both surfaces of a negative electrode core material 13b made of a copper foil having a thickness of 14 μm, leaving a non-coated portion with a width of 4 mm on one side edge portion, thereby forming a negative electrode material layer. Thereafter, the negative electrode plate 13 was compression-molded by a press roll having a diameter of 300 mm so that the thickness of the negative electrode plate 13 became 170 μm. At this time, the negative electrode material density was 1.4 g / cm ³ .
[0028]
The electrolyte is a mixed solvent in which ethylene carbonate (EC) and diethylene carbonate (DEC) are mixed at a mixing ratio of 1: 1 by volume, and lithium hexafluorophosphate (LiPF ₆ ) is used as a solute at a concentration of 1 mol / dm ³ . What was melt | dissolved in was used.
[0029]
In manufacturing the lithium ion secondary battery, the positive electrode plate 12 and the negative electrode plate 13 manufactured as described above are opposed to each other through the separator 14, and the protruding portions of the current collectors 12b and 13b protrude at both ends. In this state, the electrode plate group 21 was formed by spirally winding.
[0030]
Flat portions 22 and 23 were formed in the electrode plate group 21. First, in a state in which arranged to press the positive electrode current collector plate 19 to the flat portion 22 is pressed against the two, the laser beam radially in the circumferential direction a plurality of locations of the surface of the positive electrode current collector plate 19 to the outer peripheral edge from the center The current collector plate 19 and the flat portion 22 were laser welded by irradiation.
[0031]
Next, the current collector 1a is arranged so as to be pressed against the flat portion 23 and in contact with the current collector 1a, the current collector 1a is irradiated with several laser beams in a radial pattern on the fixed portion 3 of the current collector plate 1a. The plate 1a and the flat part 23 were laser welded.
[0032]
Thereafter, the electrode plate group 21 to which the current collector plates 19 and 1a are joined is accommodated in the outer can 16, and the convex portion 11 of the current collector plate 1a and the outer can 16 are welded using the winding core portion. The plate 19 was laser welded to the battery lid 17 by the positive electrode connection piece 19a.
[0033]
Finally, the electrolyte solution was poured into the outer can 16, vacuum impregnated, and sealed with the battery lid 17.
[0034]
(Battery evaluation)
The battery of the created example had an internal resistance of 28 mΩ, which was almost the same as the conventional battery (13 to 26 mΩ). In addition, in the battery drop test, when dropped from a height of 75 cm onto a concrete floor, the internal resistance did not increase up to 60 times, and a stable conductive connection was obtained.
[0035]
【The invention's effect】
According to the secondary battery of the present invention, as is clear from the above description, a secondary battery having a stable current collecting structure can be provided even in rough use.
[Brief description of the drawings]
1 is a perspective view of a current collector plate according to an embodiment of the present invention. FIG. 2 is a top view of a current collector plate according to an embodiment of the present invention. FIG. 3 is a view of a current collector plate according to another embodiment of the present invention. FIG. 4 is a top view of a current collector plate according to another embodiment of the present invention. FIG. 5 is a longitudinal sectional view of a lithium ion secondary battery according to an embodiment of the present invention.
1a, 1b Current collector plate 2 Movable part 3 Fixed part 4 Curved slit part 5 Slit 6 End point 7 Outer peripheral surface 8 Boundary 9 Movable part A
10 Movable part B
DESCRIPTION OF SYMBOLS 11 Protrusion part 12 Positive electrode plate 12a Positive electrode material 12b Positive electrode core material 13 Negative electrode plate 13a Negative electrode material 13b Negative electrode core material 14 Separator 15 Battery container 16 Outer can 17 Battery cover 18 Insulation packing 19 Positive electrode current collection plate 19a Positive electrode connection piece 20 Negative electrode current collection Plate 21 Electrode group 22 Positive electrode flat portion 23 Negative electrode flat portion

Claims

A positive electrode plate manufactured by attaching a positive electrode material to a positive electrode core material and a negative electrode plate manufactured by attaching a negative electrode material to a negative electrode core material through a separator, together with an electrolyte, a sealing plate and a metal A cylindrical secondary battery housed in a battery case made of an outer can, wherein at least one of the positive electrode plate and the negative electrode plate has a core exposed portion at an end portion along a longitudinal direction thereof, and the electrode At least one of the upper surface and the lower surface of the plate group protrudes a core material exposed portion of either the positive electrode plate or the negative electrode plate, and a flat portion is formed by the tip of the protruding portion itself, and the flat portion In the cylindrical secondary battery in which the current collector plate is joined to
The current collector plate is composed of a fixed portion joined to the flat portion and a movable portion joined to the bottom portion of the outer can, and the outer shape of the outer peripheral surface of the current collector plate is circular. An arcuate movable portion A formed by the curved slit portion along the outer peripheral surface of the current collector plate and the outer peripheral surface of the current collector plate, a U-shaped slit communicating with the curved slit portion , and A cylindrical secondary battery comprising at least two parts including a linear movable part B including a central part of a current collector plate joined to a bottom part of an outer can .

The cylindrical secondary battery according to claim 1, wherein the flat portion and the fixed portion are joined by laser welding or resistance spot welding.

A movable portion B is line symmetry, the symmetry line and its extension is cylindrical secondary battery according to claim 1, wherein the passing through the center and end point of the curved slit portion of the current collector plate.