JP3804702B2

JP3804702B2 - Nonaqueous electrolyte secondary battery

Info

Publication number: JP3804702B2
Application number: JP08610997A
Authority: JP
Inventors: 吉田　　浩明; 善三萩原; 正直寺崎
Original assignee: GS Yuasa Corp
Current assignee: GS Yuasa Corp
Priority date: 1997-03-18
Filing date: 1997-03-18
Publication date: 2006-08-02
Anticipated expiration: 2017-03-18
Also published as: JPH10261441A

Description

【０００１】
【発明の属する技術分野】
本発明は電子機器の駆動用電源もしくは電気自動車用電池として、高率放電性能が要求される非水電解質二次電池に関するものである。
【０００２】
【従来の技術】
駆動機器、携帯電子機器、電気自動車等の高率放電性能が要求される非水電解質二次電池は、電解質の抵抗が水溶液系と比較して著しく大きいために、極板面積を大きくして対向面積を増やす必要がある。このため、極板の基体には５〜５０μｍ程度の金属箔を使用し、正・負極活物質を塗布している。発電素子は、薄い帯状の正極および負極をセパレータを介して巻回、または積層して組み立てられている。
【０００３】
従来、発電素子の集電は図１に示すように、活物質を塗布していない極板の基体１が露出した部分（未塗布部４）に端子２を取り出していた。しかし電気自動車用電池等では高率放電性能が要求されるため、内部抵抗の低減や電流分布の均一化が必要となった。そこで、図２に示すように極板のいづれか一方の端縁部の長さ方向に連続した未塗布部４に多数の端子２を溶接し、集電をおこなう方法（多端子集電方式）を用いられていた。しかし、この方法では、端子の溶接個所が多くなり、かつ、各端子の取付け位置の精度が必要であった。１００〜４００Ｗｈ級の電池の、多端子集電方式での端子数は１０〜５０本が必要とされている。
【０００４】
【発明が解決しようとする課題】
これらの対策として、図３に示すように正負極板の少なくとも一方の極板の電極ペーストが塗布されていない側の端縁部を他方の極板の端縁部より突き出させ、
セパレータを介して巻回あるいは積層してなる発電素子の突出した端縁部を所要数ごとに収束させ、基体同一材質からなる例えば図４に示すような断面が略逆Ｖ字状が所要数連続した別部品の集電体のＶ字状の狭窄部に収束させた端縁部を差込み、集電体側の薄肉部をレーザー溶接する方法が採用されている。
【０００５】
しかしこの方法で製作された電池は、電池の内部抵抗のばらつきが大きいという欠点があった。そこで発明者らは、内部抵抗の高い電池を解体し詳細に調査した結果、発電素子の端縁部と集電体との溶接に不具合個所があり、接触不良が生じていた。
【０００６】
【課題を解決するための手段】
本発明は、正負極板の少なくとも一方の極板の端縁部を他方の極板の端縁部より突出させ、セパレータを介して巻回あるいは積層してなる発電素子を有し、少なくとも該発電素子の突出した極板の端縁部と集電体とを接合して集電する非水電解質二次電池において、前記集電体が波の山部分にスリットを形成したもので、前記スリットに前記突出した極板の端縁部を差込、前記集電体のスリット部と極板の端縁部とが接合されていることを特徴とするものである。本発明においては、前記集電体のスリット部の端面に対して、差し込まれた極板の端縁部の先端が±２ｍｍの範囲内に位置することが好ましく、集電体のスリット部と差込まれた極板の端縁部との間の隙間が０．２ｍｍ以下であることが好ましく、集電体が、板材により成形されたものであり、その板厚みが０．１ｍｍ〜２ｍｍであることが好ましく、極板の端縁部と集電体とはレーザー溶接されていることが好ましく、レーザー溶接の光軸を、溶接面に対して垂直から５度〜４５度傾けて溶接することが好ましく、レーザー溶接のパルス出力波形を段階的に減衰させることによって溶接するが好ましい。
【０００７】
【発明の実施の形態】
以下に、本発明を実施例に基づいて図面を参照しながら説明する。
【０００８】
【実施例】
参考例
正極活物質として炭酸リチウム０．５モルと炭酸コバルト１モルとを混合して、９００℃で空気中にて焼成してＬｉＣｏＯ_２を得た。このＬｉＣｏＯ_２を９１重量％と導電剤としてグラファイトを６重量％と結着剤としてポリフッ化ビニリデン（ＰＶＤＦ）３重量％を混合し正極合剤とした。この正極合剤にＮメチル２ピロリドンを溶剤として添加し、混合分散してスラリー状にした。極板の基体として厚さ２０μｍの帯状アルミニウム箔を用い、この基体に正極合剤スラリーを均一に塗布し、乾燥させた後にロールプレス機を用いて厚さを２００μｍに調整して長さ９５６０ｍｍ、幅１７１ｍｍの帯状の正極板を作製した。この極板の長辺の一方の端縁部には、１０ｍｍの幅の未塗布部を設けた。
【０００９】
負極には、リチウムのドープ・脱ドープが可能な炭素材料（グラファイト）粉末を用いた。グラファイト粉末を９０重量％、結着剤としてのＰＶＤＦを１０重量％を混合して負極合剤とした。この負極合剤にＮメチル２ピロリドンを溶剤として添加し、混練してスラリー状にした。極板の基体として厚さ２０μｍの帯状銅箔を用い、この基体１に負極合剤スラリーを均一に塗布し、乾燥させた後にロールプレス機を用いて厚さを２３０μｍに調整して長さ９９００ｍｍ、幅１７２ｍｍの帯状の負極を作製した。この極板の一方の端縁部にも正極と同様に、１０ｍｍの幅の未塗布部を設けた。
【００１０】
このようにして作製した正負極板を図５に示されるように、ポリエチレン製の微多孔膜よりなるセパレータ７を介しポリエチレンテレフタレート製のパイプからなる巻芯８を中心として極板の端縁部（未塗布部４）を他方の極板の端縁部より突出させるように渦巻き状に巻回して円筒形の発電素子を得た。図において、５は正極板、６は負極板である。
【００１１】
次に、円筒形の発電素子の外周部をテープで固定し、押し圧を加えて長円形の断面を有する図６に示すような発電素子に成形した。図において９は固定用テープである。この発電素子の上下端縁部の直線部を治具を用いて、図７に示すように極板の端縁部を所用数ごとに分割して収束するように成形した。この部位に図８に示す極板の基体と同じ材質で厚さが５ｍｍ（スリット部の隙間は０．２ｍｍ）の集電体１０を図９に示すようにスリット部の端面に対して、集電体の端縁部が約０．５ｍｍ突出するように調整して図１０に示すように装着し、集電体のスリット部から突出した電極の端縁部に沿って、集電体のスリット部と電極の端縁部とをレーザー溶接した。このとき、該レーザー溶接の光軸を、溶接面に対して垂直から１５度傾けた。
【００１２】
レーザー溶接には、スラブ型ＹＡＧパルスレーザーを用いておこなった。レーザー溶接は正極の基体（アルミニウム箔）と集電体（アルミニウム）では出力：２５０Ｗ，パルス周波数：２０ｐｐｓ，パルス幅：４．０ｍｓで、負極の基体（銅箔）と集電体（銅）では出力：５００Ｗ，パルス周波数：１５ｐｐｓ，パルス幅：６．０ｍｓの条件でおこなった。１パルスのレーザー出力波形（電流変化）を、それぞれ図１１及び図１２に示した。
【００１３】
この発電素子を長円形の電池容器（縦５０ｍｍ×横１３０ｍｍ×高さ２１０ｍｍ）に挿入し封口した。このとき、正極集電体及び負極集電体は電池容器に設けられた正極端子及び負極端子にそれぞれ接続した。次に、この電池容器内に、エチレンカーボネート及びジメチルカーボネートの１：１（体積比）の混合溶液に１ｍｏｌ／ｌ（リットル）の六フッ化燐酸リチウム（ＬｉＰＦ₆）を溶解した電解液を減圧注入した。この電池の容量は１００Ａｈであった。
【００１４】
実施例１
参考例と同様に極板の端縁部を分割・収束した後、集電体１０を装着するかわりに、図８に示す波形状の集電体１１を用いた。
【００１５】
集電体１１は、極板の基体と同じ材質で厚さが１．５ｍｍの板材をプレス加工したものである（スリット部の隙間は１．０ｍｍ）。集電体１１を図１３に示すようにスリット部のエッジに対して、集電体の端縁部が約０．５ｍｍ突出するように調整して図１４のように装着した。スリット部と集電体端部との隙間が０．１ｍｍ以下になるように加工後、集電体１１のスリット部から突出した極板の端縁部に沿って、集電体のスリット部と極板の端縁部とをレーザー溶接した（該レーザー溶接の光軸を、溶接面に対して垂直から１５度傾けた）。この発電素子を実施例１で用いたものと同じ長円形の電池容器に挿入し封口した。正極及び負極の端子２は電池容器に設けられた正極端子及び負極端子にそれぞれ接続した。次に、実施例１と同様に電池容器内に電解液を注入した。この電池の容量も１００Ａｈであった。
【００１６】
比較例（従来例）
比較例として、従来の方法による電池を次のようにして作製した。実施例１や２と同様に極板の端縁部を分割・収束した後、図４に示す形状の集電体１２を図１５に示すように装着した。集電体１２は、極板の基体と同じ材質で厚さが５ｍｍ（溶接部（薄肉部）は５００μｍ）であり、切削加工により作製した。集電体１２を図１６に示すように装着し、集電体１２の溶接部（薄肉部）に沿ってレーザー溶接を用いて極板の端縁部と集電体１２とを溶接した（該レーザー溶接の光軸は、溶接面に対して垂直とした）。この発電素子を実施例１や２で用いたものと同じ長円形の電池容器に挿入し封口した。正極及び負極の端子２は電池容器に設けられた正極端子及び負極端子にそれぞれ接続した。次に、実施例１や２と同様に電池容器内に電解液を注入した。比較例の電池の容量も１００Ａｈであった。
【００１７】
上記参考例、実施例１、と比較例（従来例）の電池をそれぞれ１００個作製し、電池の内部抵抗を交流１ｋＨｚ法で測定した。図１６は参考例、図１７は実施例１、図１８は比較例（従来例）の内部抵抗測定結果である。
【００１８】
図１６、図１７、図１８を比較すれば明らかなごとく、本発明の実施例１の集電構造を有する非水電解質二次電池は内部抵抗のばらつきを低減することができ、電池の信頼性を向上させることが明らかである。
【００１９】
なお、実施例１では、発電素子を長円状に巻回したものを用いたが、発電素子の形状はこれに限定されず、円筒状であってもよい。また、集電体の形状も実施例のものに限定されるものではなく、電極の端縁部に適した形状を用いることができる。たとえば、発電素子の形状が円筒形状の場合はその曲率にあわせた図１９のような形状を用いることができる。電極を積層する場合には本実施例１と同様の形状のものを用いることができる。
【００２０】
本実施例では、集電体のスリット部の端面に対して、極板の端縁部が０．５ｍｍ突出する場合を説明したが特に限定されない。上記範囲が±２ｍｍ以内の範囲であれば実施例と同様な結果が得られる。しかし、上記範囲が±２ｍｍを越えると、集電体のスリット部と極板の端縁部との距離が離れるために、溶接が不十分となり、電池内部抵抗のばらつきが大きくなる。
【００２１】
また、本実施例では、集電体のスリット部と極板の端縁部との隙間を０．１ｍｍ以下とする場合を説明したが特に限定されない。上記隙間が０．２ｍｍ以内の範囲であれば実施例と同様な結果が得られる。しかし、上記範囲が０．２ｍｍを越えると、レーザー光線が集電体のスリット部と極板の端縁部との隙間を通って正・負極の活物質塗布部やセパレーターに到達しやすくなる。レーザー光線がセパレーターに到達すると、セパレーターが熱溶解して、正負極が短絡する。
【００２２】
さらに、本実施例では、レーザー光線の光軸を溶接面に対して垂直から１５度傾けた場合を説明したが特に限定されない。傾斜角度が５度から４５度の範囲にあれば実施例と同様の効果が得られる。しかし、傾斜角度が５度未満の場合レーザー光線が集電体のスリット部と極板の端縁部との隙間を通ってセパレーターに到達しやすくなり上述と同様の不具合が発生する。この場合、集電体のスリット部と電極の端縁部との隙間を限りなくゼロにすることにより上記問題を解決することができるが、量産上制約が多くなり製品のコストアップにつながる。傾斜角度を５度以上にすれば、集電体のスリット部と極板の端縁部との隙間が０．２ｍｍ以下であれば、上記問題は解決される。一方、傾斜角度が４５度を越えると、溶接面でレーザー光線が反射されやすくなり、十分な溶接が困難となる。
【００２３】
実施例２では、集電体を厚み１．５ｍｍの板材をプレス加工により作製する場合を説明したが、特に限定されない。厚みが０．１ｍｍ〜２ｍｍの範囲にあれば実施例と同様の効果が得られる。板材をプレス加工により作製した集電体は、実施例１で述べた切削加工した集電体と比較して、部品コストが大幅に削減できるという効果がある。なぜならば、板材にスリット部の穴開け加工後、板材を波形に成形するだけで製作が容易となるためであり、本発明において最適な集電体形状であるといえる。さらに、製作に用いる板材の厚みが０．１ｍｍ以下の場合集電体の形状を保持する強度が小さいために、量産機にかかりにくいという問題が生じ、板材の厚みが２ｍｍを越えると、集電体の強度が大きくなりすぎるために、集電体のスリット部と極板の端縁部との隙間を０．２ｍｍ以下に調整しにくくなるという問題が生じる。
【００２４】
また、極板の基体の材質として、アルミニウム及び銅を用いたが、アルミニウムの他にアルミニウム−マンガン合金，アルミニウム−マグネシウム合金等が、銅の他に銅−亜鉛合金，銅−ニッケル合金，銅−アルミニウム合金等も用いることが可能である。ただし、これらの合金よりも純アルミニウム及び純銅の方が溶接は容易であった。
【００２５】
集電体の材質は、基本的には基体と同じものを用いることが好ましいが、加工性等の理由により基体と異なる合金等と組み合わせることも可能である。
【００２６】
アルミニウム製の基体と集電体をレーザー溶接する条件は、出力：２００〜３５０Ｗ、パルス周波数：５〜３５ｐｐｓである。好ましくは出力：２５０〜３００Ｗ、パルス周波数：１０〜３０ｐｐｓである。銅製の基体１と集電体をレーザー溶接する条件は、出力：３００〜５５０Ｗ、パルス周波数：５〜２５ｐｐｓである。好ましくは出力：４００〜５００Ｗ、パルス周波数：１０〜２０ｐｐｓである。また、パルスの出力波形も実施例のものに限定されるものではなく、基体及び集電体の材質や厚さを考慮し、段階的に出力を減衰するような波形で溶接が可能な条件であればよい。出力を段階的に減衰させることで溶接部のクラックの発生が抑制でき、電気抵抗の増大及び溶接強度の低下を防止することができる。パルス周波数を落とす（パルス幅を広げる）ことによって、タクトは低下するが厚い集電体（溶接部）の溶接も可能である。極板の基体には任意の厚さのものを使用することができるが、極板の強度や電池のエネルギー密度、さらにレーザー溶接可能な厚さを考慮し検討した結果、５〜５０μｍの範囲において好適な結果が得られた。
【００２７】
また、実施例では活物質の未塗布部の幅を１０ｍｍとしたが、レーザー溶接時の熱によってセパレータ及び活物質の合剤が影響を受けない範囲であれば特に限定はされない。未塗布部の幅を大きくするほど熱の影響を受けにくくなるが、電池のエネルギー密度は低下する。よって、実用性を考慮すると１ｍｍ〜５ｃｍ，好ましくは３ｍｍ〜３ｃｍである。
【００２８】
さらに、正極活物質として実施例の他に、リチウムニッケル複合酸化物，スピネル型リチウムマンガン酸化物，五酸化バナジウム，二硫化チタン等を用いることができる。また、負極には実施例のグラファイト粉末の他、低結晶性の炭素材料，アモルファスの炭素材料，金属酸化物等を用いることができる。
【００２９】
また、本発明は、リチウム二次電池に限らず同様な構成すなわち金属箔に活物質を塗布し、その金属箔から集電する非水電解質二次電池にも適用することができる。
【００３０】
【発明の効果】
本発明は、以上のごとく生産性を低下させることなく、高信頼に極板に集電体を接合することが出来、電池の内部抵抗のバラツキが低減できる効果がある。
【図面の簡単な説明】
【図１】従来の極板を示す平面図である。
【図２】従来の多端子集電方式を用いた極板を示す平面図である。
【図３】比較例（従来例）の集電体を装着した発電素子の要部拡大縦断面図である。
【図４】比較例（従来例）の集電体の斜視図である。
【図５】本発明の渦巻き状に巻回した円筒形の発電素子の図である。
【図６】本発明の発電素子の斜視図である。（電極の端縁部を治具を用いてくせをつけた後の発電素子）
【図７】本発明の発電素子の要部拡大縦断面図である。（電極の端縁部を治具を用いてくせをつけた後の発電素子）
【図８】参考例および本発明の実施例１の集電体の斜視図である。
【図９】参考例における集電体を装着した発電素子の溶接条件を示す要部拡大縦断面図である。
【図１０】参考例における集電体を装着した発電素子の斜視図である。
【図１１】本発明の実施例におけるアルミ製の基体と集電体とをレーザー溶接したときの出力波形を示す図である。
【図１２】本発明の実施例における銅製の基体と集電体とをレーザー溶接したときの出力波形を示す図である。
【図１３】本発明の実施例１における集電体を装着した発電素子の溶接条件を示す要部拡大縦断面図である。
【図１４】本発明の実施例１における集電体を装着した発電素子の斜視図である。
【図１５】比較例（従来例）における集電体を装着した発電素子の斜視図である。
【図１６】本発明の参考例における電池の内部抵抗測定結果である。
【図１７】本発明の実施例１における電池の内部抵抗測定結果である。
【図１８】比較例（従来例）における電池の内部抵抗測定結果である。
【図１９】本発明の他の実施例における円筒形電池用集電体の斜視図である。
【符号の説明】
１．基体
２．端子
３．合材層
４．未塗布部
５．正極
６．負極
７．セパレータ
８．巻芯
９．テープ
１０．集電体
１１．集電体
１２．集電体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery that requires high rate discharge performance as a power source for driving electronic equipment or a battery for an electric vehicle.
[0002]
[Prior art]
Non-aqueous electrolyte secondary batteries that require high-rate discharge performance, such as drive devices, portable electronic devices, and electric vehicles, are opposed to each other because the electrolyte resistance is significantly higher than that of aqueous solutions. It is necessary to increase the area. For this reason, about 5-50 micrometers metal foil is used for the base | substrate of an electrode plate, and the positive / negative electrode active material is apply | coated. The power generating element is assembled by winding or laminating thin strip-shaped positive and negative electrodes with a separator interposed therebetween.
[0003]
Conventionally, as shown in FIG. 1, current collection of the power generation element has taken out the terminal 2 in a portion (uncoated portion 4) where the base 1 of the electrode plate not coated with the active material is exposed. However, since high rate discharge performance is required for batteries for electric vehicles, etc., it is necessary to reduce internal resistance and make current distribution uniform. Therefore, as shown in FIG. 2, there is a method (multi-terminal current collecting method) in which a large number of terminals 2 are welded to an uncoated portion 4 continuous in the length direction of one of the end portions of the electrode plate to collect current. It was used. However, with this method, the number of welded portions of the terminals is increased, and the accuracy of the mounting positions of the terminals is required. The number of terminals of the 100-400 Wh class battery in the multi-terminal current collecting system is required to be 10-50.
[0004]
[Problems to be solved by the invention]
As these countermeasures, as shown in FIG. 3, the edge of the electrode plate on the side where at least one of the positive and negative electrodes is not applied is projected from the edge of the other electrode,
The projecting edge portions of the power generating element wound or laminated through the separator are converged for each required number, and the required number of continuous cross sections having the substantially same V-shaped cross section as shown in FIG. A method is adopted in which an edge portion converged on a V-shaped constriction portion of a separate current collector is inserted, and a thin portion on the current collector side is laser-welded.
[0005]
However, the battery manufactured by this method has a drawback that the internal resistance of the battery varies greatly. Therefore, the inventors disassembled a battery having a high internal resistance and investigated in detail, and as a result, there was a defect in welding between the edge of the power generation element and the current collector, resulting in poor contact.
[0006]
[Means for Solving the Problems]
The present invention has a power generating element in which an end edge portion of at least one electrode plate of a positive and negative electrode plate protrudes from an end edge portion of the other electrode plate and is wound or laminated via a separator, and at least the power generation device In the non-aqueous electrolyte secondary battery that collects current by joining the edge of the protruding electrode plate and the current collector, the current collector is formed by forming a slit at the peak portion of the wave. the insertion of the edge portion of the protruding plate, and the edge portion of the slit portion and the electrode plate of the current collector is characterized in that it is joined. In the present invention, the tip of the end edge of the inserted electrode plate is preferably located within a range of ± 2 mm with respect to the end surface of the slit portion of the current collector, which is different from the slit portion of the current collector. The gap between the end of the inserted electrode plate is preferably 0.2 mm or less, the current collector is formed of a plate material, and the plate thickness is 0.1 mm to 2 mm. it rather preferred, preferred to be laser welded to the electrode edge portion of the plate and the current collector, the optical axis of the laser welding, welded tilted 5 degrees to 45 degrees from the normal to the weld surface It is preferable to perform welding by gradually damping the pulse output waveform of laser welding.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on examples with reference to the drawings.
[0008]
【Example】
Reference Example As a positive electrode active material, 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed and baked in air at 900 ° C. to obtain LiCoO ₂ . 91% by weight of LiCoO ₂ , 6% by weight of graphite as a conductive agent, and 3% by weight of polyvinylidene fluoride (PVDF) as a binder were mixed to obtain a positive electrode mixture. N-methyl-2-pyrrolidone was added to this positive electrode mixture as a solvent, mixed and dispersed into a slurry. A strip-shaped aluminum foil having a thickness of 20 μm was used as the base of the electrode plate, and the positive electrode mixture slurry was uniformly applied to the base and dried, and then adjusted to a thickness of 200 μm using a roll press machine to have a length of 9560 mm. A strip-like positive electrode plate having a width of 171 mm was produced. An uncoated portion having a width of 10 mm was provided on one end edge of the long side of the electrode plate.
[0009]
For the negative electrode, a carbon material (graphite) powder capable of being doped / undoped with lithium was used. A negative electrode mixture was prepared by mixing 90% by weight of graphite powder and 10% by weight of PVDF as a binder. N-methyl-2-pyrrolidone was added to this negative electrode mixture as a solvent and kneaded to form a slurry. A strip-shaped copper foil having a thickness of 20 μm was used as the substrate of the electrode plate, and the negative electrode mixture slurry was uniformly applied to the substrate 1 and dried, and then the thickness was adjusted to 230 μm using a roll press machine to obtain a length of 9900. A strip-shaped negative electrode with a width of 172 mm was prepared. Similarly to the positive electrode, an uncoated portion having a width of 10 mm was provided on one end edge portion of the electrode plate.
[0010]
As shown in FIG. 5, the positive and negative electrode plates produced in this manner are arranged with an edge of the electrode plate centered on a core 8 made of a polyethylene terephthalate pipe through a separator 7 made of a polyethylene microporous film ( The uncoated portion 4) was spirally wound so as to protrude from the edge of the other electrode plate to obtain a cylindrical power generating element. In the figure, 5 is a positive electrode plate and 6 is a negative electrode plate.
[0011]
Next, the outer peripheral part of the cylindrical power generation element was fixed with a tape, and a pressing force was applied to form a power generation element as shown in FIG. 6 having an oval cross section. In the figure, 9 is a fixing tape. The linear portions of the upper and lower edge portions of the power generating element were formed using a jig so that the edge portions of the electrode plate were divided for each required number and converged as shown in FIG. A current collector 10 having the same material as that of the substrate of the electrode plate shown in FIG. 8 and a thickness of 5 mm (a gap of the slit portion is 0.2 mm) is collected on the end face of the slit portion as shown in FIG. The edge of the current collector is adjusted so that it protrudes by about 0.5 mm, and is mounted as shown in FIG. 10, along the edge of the electrode protruding from the slit of the current collector, the slit of the current collector And the edge of the electrode were laser welded. At this time, the optical axis of the laser welding was inclined 15 degrees from the perpendicular to the welding surface.
[0012]
Laser welding was performed using a slab type YAG pulse laser. Laser welding uses a positive electrode substrate (aluminum foil) and a current collector (aluminum) with an output of 250 W, a pulse frequency of 20 pps, a pulse width of 4.0 ms, and a negative electrode substrate (copper foil) and a current collector (copper). The output was 500 W, the pulse frequency was 15 pps, and the pulse width was 6.0 ms. One pulse laser output waveform (current change) is shown in FIGS. 11 and 12, respectively.
[0013]
This power generation element was inserted into an oval battery container (length 50 mm × width 130 mm × height 210 mm) and sealed. At this time, the positive electrode current collector and the negative electrode current collector were respectively connected to the positive electrode terminal and the negative electrode terminal provided in the battery container. Next, an electrolytic solution in which 1 mol / l (liter) of lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a 1: 1 (volume ratio) mixed solution of ethylene carbonate and dimethyl carbonate is injected into the battery container under reduced pressure. did. The capacity of this battery was 100 Ah.
[0014]
Example 1
Similar to the reference example , after the edge of the electrode plate was divided and converged, a wave-shaped current collector 11 shown in FIG. 8 was used instead of mounting the current collector 10.
[0015]
The current collector 11 is obtained by pressing a plate material having the same material as the substrate of the electrode plate and having a thickness of 1.5 mm (the gap between the slit portions is 1.0 mm). As shown in FIG. 13, the current collector 11 was mounted as shown in FIG. 14 so that the edge of the current collector protruded about 0.5 mm from the edge of the slit portion. After processing so that the gap between the slit portion and the current collector end is 0.1 mm or less, along the edge portion of the electrode plate protruding from the slit portion of the current collector 11, The edge of the electrode plate was laser welded (the optical axis of the laser welding was tilted 15 degrees from the perpendicular to the weld surface). This power generation element was inserted into the same oval battery container as used in Example 1 and sealed. The positive electrode terminal 2 and the negative electrode terminal 2 were respectively connected to a positive electrode terminal and a negative electrode terminal provided in the battery container. Next, an electrolyte solution was injected into the battery container in the same manner as in Example 1. The capacity of this battery was also 100 Ah.
[0016]
Comparative example (conventional example)
As a comparative example, a battery by a conventional method was produced as follows. After dividing and converging the edge of the electrode plate in the same manner as in Examples 1 and 2, the current collector 12 having the shape shown in FIG. 4 was mounted as shown in FIG. The current collector 12 was made of the same material as the substrate of the electrode plate, had a thickness of 5 mm (the welded portion (thin portion) was 500 μm), and was manufactured by cutting. The current collector 12 is mounted as shown in FIG. 16, and the edge of the electrode plate and the current collector 12 are welded using laser welding along the welded portion (thin wall portion) of the current collector 12 (this The optical axis of laser welding was perpendicular to the weld surface). This power generation element was inserted into the same oval battery container as used in Examples 1 and 2 and sealed. The positive electrode terminal 2 and the negative electrode terminal 2 were respectively connected to a positive electrode terminal and a negative electrode terminal provided in the battery container. Next, an electrolyte solution was injected into the battery container in the same manner as in Examples 1 and 2. The capacity of the battery of the comparative example was also 100 Ah.
[0017]
100 batteries of the above reference example, Example 1 and comparative example (conventional example) were produced, respectively, and the internal resistance of the battery was measured by the AC 1 kHz method. 16 shows a reference example , FIG. 17 shows the results of internal resistance measurement of Example 1 , and FIG. 18 shows the results of measurement of internal resistance of a comparative example (conventional example).
[0018]
As is apparent from a comparison of FIGS. 16, 17, and 18, the nonaqueous electrolyte secondary battery having the current collecting structure of Example 1 of the present invention can reduce variations in internal resistance, and the reliability of the battery. It is clear to improve.
[0019]
In Example 1 , the power generation element wound in an oval shape was used, but the shape of the power generation element is not limited to this and may be cylindrical. Further, the shape of the current collector is not limited to that of the embodiment, and a shape suitable for the edge portion of the electrode can be used. For example, when the shape of the power generation element is a cylindrical shape, a shape as shown in FIG. 19 that matches the curvature can be used. When the electrodes are stacked, one having the same shape as in the first embodiment can be used.
[0020]
In the present embodiment, the case where the end edge portion of the electrode plate protrudes 0.5 mm from the end face of the slit portion of the current collector has been described, but the present invention is not particularly limited. If the above range is within ± 2 mm, the same result as in the example can be obtained. However, if the above range exceeds ± 2 mm, the distance between the slit portion of the current collector and the end edge portion of the electrode plate is increased, so that welding becomes insufficient and variation in battery internal resistance increases.
[0021]
Moreover, although the present Example demonstrated the case where the clearance gap between the slit part of an electrical power collector and the edge part of an electrode plate shall be 0.1 mm or less, it is not specifically limited. When the gap is within a range of 0.2 mm, the same result as in the example can be obtained. However, when the above range exceeds 0.2 mm, the laser beam easily reaches the positive / negative active material application part and the separator through the gap between the slit part of the current collector and the edge part of the electrode plate. When the laser beam reaches the separator, the separator is melted by heat and the positive and negative electrodes are short-circuited.
[0022]
Further, in the present embodiment, the case where the optical axis of the laser beam is tilted 15 degrees from the perpendicular to the welding surface has been described, but there is no particular limitation. If the inclination angle is in the range of 5 to 45 degrees, the same effect as in the embodiment can be obtained. However, when the inclination angle is less than 5 degrees, the laser beam easily reaches the separator through the gap between the slit portion of the current collector and the end edge portion of the electrode plate, and the same problem as described above occurs. In this case, the above problem can be solved by setting the gap between the slit portion of the current collector and the edge portion of the electrode to zero as much as possible, but there are many restrictions on mass production, leading to an increase in product cost. If the inclination angle is 5 degrees or more, the above problem can be solved if the gap between the slit portion of the current collector and the end edge portion of the electrode plate is 0.2 mm or less. On the other hand, when the inclination angle exceeds 45 degrees, the laser beam is easily reflected on the welding surface, and sufficient welding becomes difficult.
[0023]
In the second embodiment, the case where the current collector is manufactured by pressing a plate material having a thickness of 1.5 mm is not particularly limited. If the thickness is in the range of 0.1 mm to 2 mm, the same effect as the embodiment can be obtained. The current collector produced by pressing the plate material has an effect that the component cost can be greatly reduced as compared with the cut current collector described in the first embodiment. This is because the plate material is easily formed by simply forming the corrugated plate into a corrugated shape after the slit portion is drilled in the plate material, and can be said to be an optimal current collector shape in the present invention. Furthermore, when the thickness of the plate material used for production is 0.1 mm or less, the strength of holding the shape of the current collector is small, which causes a problem that it is difficult to be applied to a mass production machine. If the thickness of the plate material exceeds 2 mm, the current collector Since the strength of the body becomes too large, there arises a problem that it becomes difficult to adjust the gap between the slit portion of the current collector and the end edge portion of the electrode plate to 0.2 mm or less.
[0024]
Moreover, aluminum and copper were used as the material of the substrate of the electrode plate, but in addition to aluminum, aluminum-manganese alloy, aluminum-magnesium alloy, etc., besides copper, copper-zinc alloy, copper-nickel alloy, copper- An aluminum alloy or the like can also be used. However, pure aluminum and pure copper were easier to weld than these alloys.
[0025]
The material of the current collector is basically preferably the same as that of the substrate, but may be combined with an alloy or the like different from the substrate for reasons such as workability.
[0026]
The conditions for laser welding the aluminum substrate and the current collector are: output: 200 to 350 W, pulse frequency: 5 to 35 pps. The output is preferably 250 to 300 W and the pulse frequency is 10 to 30 pps. Conditions for laser welding the copper substrate 1 and the current collector are: output: 300 to 550 W, pulse frequency: 5 to 25 pps. The output is preferably 400 to 500 W and the pulse frequency is 10 to 20 pps. Also, the output waveform of the pulse is not limited to that of the embodiment, and it is possible to perform welding with a waveform that attenuates the output step by step in consideration of the material and thickness of the substrate and the current collector. I just need it. By gradually attenuating the output, the occurrence of cracks in the welded portion can be suppressed, and an increase in electrical resistance and a decrease in welding strength can be prevented. By reducing the pulse frequency (increasing the pulse width), the tact is reduced, but a thick current collector (welded part) can also be welded. The substrate of the electrode plate can be of any thickness, but as a result of examination considering the strength of the electrode plate, the energy density of the battery, and the thickness capable of laser welding, in the range of 5 to 50 μm Good results have been obtained.
[0027]
Moreover, although the width | variety of the non-application part of an active material was 10 mm in the Example, it will not specifically limit if it is a range in which the mixture of a separator and an active material is not influenced by the heat at the time of laser welding. Increasing the width of the uncoated portion is less affected by heat, but the energy density of the battery decreases. Therefore, considering practicality, it is 1 mm to 5 cm, preferably 3 mm to 3 cm.
[0028]
Further, as the positive electrode active material, lithium nickel composite oxide, spinel lithium manganese oxide, vanadium pentoxide, titanium disulfide and the like can be used in addition to the examples. In addition to the graphite powder of the embodiment, a low crystalline carbon material, an amorphous carbon material, a metal oxide, or the like can be used for the negative electrode.
[0029]
The present invention can be applied not only to a lithium secondary battery but also to a non-aqueous electrolyte secondary battery in which an active material is applied to a metal foil with a similar configuration, that is, collecting current from the metal foil.
[0030]
【The invention's effect】
As described above, the present invention can join the current collector to the electrode plate with high reliability without reducing the productivity, and has an effect of reducing variation in the internal resistance of the battery.
[Brief description of the drawings]
FIG. 1 is a plan view showing a conventional electrode plate.
FIG. 2 is a plan view showing a plate using a conventional multi-terminal current collecting system.
FIG. 3 is an enlarged vertical cross-sectional view of a main part of a power generating element equipped with a current collector of a comparative example (conventional example).
FIG. 4 is a perspective view of a current collector of a comparative example (conventional example).
5 is a diagram of the power generating element cylindrical and wound spirally of the present invention.
FIG. 6 is a perspective view of the power generating element of the present invention. (Power generation element after the edge of the electrode is crushed using a jig)
FIG. 7 is an enlarged vertical cross-sectional view of a main part of the power generating element of the present invention. (Power generation element after the edge of the electrode is crushed using a jig)
FIG. 8 is a perspective view of a current collector according to a reference example and Example 1 of the present invention .
FIG. 9 is an enlarged vertical cross-sectional view of a main part showing welding conditions of a power generating element equipped with a current collector in a reference example .
FIG. 10 is a perspective view of a power generation element equipped with a current collector in a reference example .
FIG. 11 is a diagram showing an output waveform when laser welding a base made of aluminum and a current collector in an example of the present invention.
FIG. 12 is a diagram showing an output waveform when a copper base and a current collector are laser welded in an example of the present invention.
FIG. 13 is an enlarged vertical cross-sectional view of a main part showing welding conditions of a power generating element equipped with a current collector in Example 1 of the present invention.
FIG. 14 is a perspective view of a power generation element equipped with a current collector in Example 1 of the present invention.
FIG. 15 is a perspective view of a power generation element equipped with a current collector in a comparative example (conventional example).
FIG. 16 is a measurement result of internal resistance of a battery in a reference example of the present invention.
FIG. 17 is a measurement result of internal resistance of the battery in Example 1 of the present invention.
FIG. 18 is a measurement result of internal resistance of a battery in a comparative example (conventional example).
FIG. 19 is a perspective view of a cylindrical battery current collector in another embodiment of the present invention.
[Explanation of symbols]
1. 1. Substrate Terminal 3. Compound material layer 4. 4. Uncoated part Positive electrode 6. Negative electrode 7. Separator 8. Winding core9. Tape 10. Current collector 11. Current collector 12. Current collector

Claims

It has a power generation element in which the end edge part of at least one electrode plate of the positive and negative electrode plates protrudes from the end edge part of the other electrode plate and is wound or laminated via a separator, and at least the power generation element protrudes In a non-aqueous electrolyte secondary battery that collects current by joining an edge of an electrode plate and a current collector, the current collector is formed with a slit at a peak portion of a wave, and the projecting electrode in the slit inserting the edge portion of the plate, a non-aqueous electrolyte secondary battery characterized in that the edges of the slit portion and the electrode plate of the current collector are joined.