JP2004253311A

JP2004253311A - Electrical connection member and connecting method of electrical connection member and battery pack

Info

Publication number: JP2004253311A
Application number: JP2003044188A
Authority: JP
Inventors: Toshimi Yamamoto; 聡美山本; Shigeru Takagi; 茂高城; Tomoyasu Takeuchi; 友康竹内; Yoshiaki Matsumoto; 恵明松本
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2003-02-21
Filing date: 2003-02-21
Publication date: 2004-09-09

Abstract

<P>PROBLEM TO BE SOLVED: To reduce internal resistance by reducing contact resistance of an electrical connection member used suitably, especially for the output terminal part of a battery. <P>SOLUTION: This electrical connection member comprises a first terminal part 2 and a second terminal part 3 and a part of the surface of the first terminal part 2 contacts a part of the surface of the second terminal part 3. The part of the surface has a sulfur atom concentration of less than 2.1 atomic%, and/or a thickness of an oxidized coating film of less than 140 Å. That is, by controlling the sulfur concentration and the thickness of the oxidized coated film at the part of the surface of the terminal parts of the electrical connection member which mutually contact, the contact resistance can be made small. The effect of the contact resistance which the sulfur concentration gives to the contact resistance is small immediately after the electrical connection member is manufactured, but as time elapses, the effect which the sulfur concentration gives to the contact resistance becomes larger. Then, by controlling the thickness of the oxidized coating film, a critical effect can be obtained for the large reduction of the contact resistance value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電気接続部材及び電気接続部材の接続方法に関し、詳細には大電流が流れる部位の接続に好適に用いることができる電気接続部材及び電気接続部材の接続方法に関する。更に、その電気接続部材を用いた組電池に関する。
【０００２】
【従来の技術】
自動車の分野では、環境問題、資源問題等に対処するために電気自動車、ハイブリッド型電気自動車の開発が行われている。これらの電気自動車等には高性能な二次電池やキャパシタ（以下「二次電池等」と称する）が用いられる。
【０００３】
電気自動車等に用いられる二次電池等は、加減速時等のように急速に充放電を行う場合が想定され、良好な出力特性及び回生特性が要求される。従って、電気自動車等に用いられる二次電池等には単位時間あたりにできるだけ多くのエネルギーの出し入れが可能なことが求められる。従って、用いられる二次電池等は内部抵抗ができるだけ小さいことが好ましい。
【０００４】
ところで、一般的な二次電池等は単独での端子電圧が低く、自動車の電源として用いる場合には多くの二次電池等を接続して組み合わせた組電池として使用される。組電池は二次電池等の間を接続するために多数の接続部分を有しており、個々の接続部分の抵抗は小さくても累積することで無視できない大きさとなる。つまり、組電池の内部抵抗を小さくするには組電池を構成する単独の二次電池等についての内部抵抗を小さくするとともに、接続部分の抵抗を小さくすることが必要である。
【０００５】
二次電池等の間の接続部分の抵抗値を小さくする従来技術としては、電池端子部の酸化皮膜が接触抵抗となり接触不良や放電電圧低下のおそれがあることが開示されている（特許文献１）。
【０００６】
【特許文献１】
特開２０００−１４９９１５号公報
【０００７】
【発明が解決しようとする課題】
しかしながら、特許文献１では接触抵抗という観点で酸化皮膜をどうするかということは開示されておらず、単に端子の材料強度を高め、強く締め付けることで接触抵抗を下げることが開示されるのみである。
【０００８】
そこで本発明者らは、端子部間の接触抵抗を小さくするために系統的な実験検討を行った結果、一定の条件を採用すると予測不能な際だった接触抵抗低減効果が発揮できることを見出し本発明を完成させた。
【０００９】
すなわち、本発明は接触抵抗が小さくできる電気接続部材及び電気接続部材の接続方法を提供することを解決すべき課題とする。更に、本発明は内部抵抗が小さい組電池を提供することを解決すべき課題とする。
【００１０】
【課題を解決するための手段及び発明の効果】
本発明の電気接続部材は、第１端子部と該第１端子部に接する第２端子部とを有する電気接続部材であって、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触し、該第１端子部の一部表面及び／又は該第２端子部の一部表面の硫黄原子濃度は２．１原子％未満であることを特徴とする（請求項１）。ここで、前記第１端子部の一部表面及び／又は前記第２端子部の一部表面の硫黄原子濃度は１．５原子％以下であることが好ましい（請求項２）。
【００１１】
そして、本発明の電気接続部材の接続方法は、第１端子部と該第１端子部に接する第２端子部とを有し、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触する電気接続部材の接続方法であって、該第１端子部の一部表面及び／又は該第２端子部の一部表面を本質的に硫黄元素を含まない洗浄液で洗浄する工程を有することを特徴とする（請求項６）。
【００１２】
つまり、電気接続部材の端子部の互いに接触する一部表面における硫黄濃度を制御することで接触抵抗を小さくできる。特に、硫黄濃度が接触抵抗に与える影響は、電気接続部材を製造した直後には小さいが、時間の経過に伴って硫黄濃度が接触抵抗に与える影響は大きくなってくる。
【００１３】
表面に存在する硫黄濃度を制御することにより接触抵抗を小さくできる機構は明らかでないが、硫黄の存在により端子部表面の酸化乃至は腐食が進行することによる接触抵抗増加が考えられる。
【００１４】
本発明の電気接続部材は、第１端子部と該第１端子部に接する第２端子部とを有する電気接続部材であって、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触し、該第１端子部の一部表面及び／又は該第２端子部の一部表面の酸化皮膜厚さは１４０Å未満であることを特徴とする（請求項３）。ここで、前記第１端子部の一部表面及び／又は前記第２端子部の一部表面の酸化皮膜厚さは１００Å以下であることが好ましい（請求項４）。
【００１５】
そして、本発明の電気接続部材の接続方法は、第１端子部と該第１端子部に接する第２端子部とを有し、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触する電気接続部材の接続方法であって、該第１端子部の一部表面及び／又は該第２端子部の一部表面の酸化皮膜を厚さが１４０Å未満となるまで除去する工程と、酸化皮膜を除去した該端子部表面の酸化皮膜が１４０Å以上となる前に該第１端子部及び該第２端子部間を密着接続する工程と、を有することを特徴とする（請求項７）。
【００１６】
電気接続部材の端子部の互いに接触する一部表面に存在する酸化皮膜の厚みを上述のように制御することで大幅な接触抵抗値の低減に臨界的な効果を得ることができる。その理由としては、酸化皮膜の厚みを制御することで、酸化皮膜がねじ締結等の端子部間の圧縮等により破壊されやすくなること、酸化皮膜がポーラスな状態であり端子部の表面をすべて覆っていないこと、等により酸化皮膜を介さずに電流が流れることができることが考えられる。
【００１７】
本発明の組電池は、端子部材をもつ複数の電池と、該電池の該端子部材間を電気的に接続するバスバーとを有する組電池であって、該端子部材から該バスバーに至る導電経路に存在する２以上の部材が接する界面のうちの少なくとも一つの表面は、硫黄原子濃度が２．１原子％未満及び／又は酸化皮膜厚さは１４０Å未満であることを特徴とする（請求項８）。つまり、組電池において導電経路上に存在する界面について上述した電気接続部材を適用することで内部抵抗の小さい組電池を提供できる。
【００１８】
【発明の実施の形態】
〔電気接続部材及びその接続方法〕
本発明の電気接続部材は２以上の部材を電気的に接続する部分であれば、どのようなものにも適用可能である。特に、大電流を流す必要がある部分に適用することが好ましい。例えば、電池等の電源の端子部と、端子部から電流を取り出すバスバー等とをそれぞれ本発明の電気接続部材の第１端子部と第２端子部とに対応させることができる。つまり、端子部材からバスバーに至る導電経路に存在する２以上の部材が接する界面を構成する２つの部材をそれぞれ第１端子部及び第２端子部とすることができる。
【００１９】
電池としてはリチウム二次電池、ニッケル水素二次電池、鉛二次電池等の二次電池が例示できる。更に、キャパシタ等についても電池と同様に扱うことができる。
【００２０】
図１に電池の端子部材６付近の拡大図を示す。端子部材６にはセルナット４がワッシャ５を介して螺着され、セルナット４の上からバスバー３及びバズバワッシャ２を介してバスバーナット１が螺着されている。
【００２１】
図１に示す端子部材６を持つ電池に本発明の電気接続部材を適用する場合について以下に説明する。本発明の電気接続部材における第１端子部及び第２端子部は、図１における、端子部材６及びバスバーナット１、端子部材６及びセルナット４、バスバーナット１及びバスバーワッシャ２、バスバーワッシャ２及びバスバー３、バスバー及びセルナット４に対応させることができる。つまり、電気が流れる可能性がある組み合わせの部分のすべてに適用できる。
【００２２】
（第１形態）
本実施形態の電気接続部材は第１端子部と第２端子部とを有し、第１端子部と第２端子部とはそれぞれの一部表面が接触することで両者を電気的に接続する部材である。
【００２３】
第１端子部及び第２端子部が接するそれぞれの一部表面は密着性が向上できるように充分な平滑性を持つことが好ましい。また、接触面積を大きくすることが好ましい。
【００２４】
第１端子部及び第２端子部が接するそれぞれの一部表面の少なくとも一方について硫黄濃度を制御する。好ましくは第１端子部及び第２端子部が接するそれぞれの一部表面について硫黄濃度を制御する。硫黄濃度は２．１原子％未満、好ましくは１．５原子％以下とする。硫黄濃度はバルクについても制御を行ってもよいが、少なくとも最表面について制御すれば接触抵抗を小さくする効果を発揮できる。
【００２５】
硫黄濃度の測定はオージェ電子分光法（ＡＥＳ）により行う。具体的にはＡＥＳにより最表面の原子についてスペクトルを測定し、測定された最表面の原子の各ピークの高さから硫黄原子の存在量を原子％で算出する。各ピークの高さは各ピークごとに設定されるベースラインに基づき決定される。ＡＥＳの測定条件は設定電流１．５×１０^−７、照射ビーム径５μｍである。
【００２６】
第１端子部及び／又は第２端子部の一部表面の硫黄濃度を制御する方法としては特に限定しない。本発明者らの研究によると、表面に存在する硫黄元素は端子部を構成する材料のバルクに由来するほか、端子部の機械的加工により付着する場合もある。機械加工時に用いる機械油は硫黄を含むことがあることを本発明者らは見出している。
【００２７】
バルクに由来する硫黄元素は硫黄元素の含有量を調節した材料を用いて端子部を製造することで低減できる。加工により付着する硫黄元素は、本質的に硫黄元素を含まない洗浄液で洗浄することで制御できる。洗浄液としては液性をアルカリ性に調節したもの、エーテル系のもの、グリコール系のもの等が例示できる。界面活性剤等の添加剤を含むこともできる。洗浄により端子部表面の硫黄濃度が制御できたか否かは洗浄液中の硫黄濃度を監視することで推測できる。すなわち、洗浄液中に含まれる硫黄濃度が所定値以下（又は未満）であるときに端子部表面に存在する硫黄濃度も目的の範囲であるとする方法である。その場合に洗浄液中に含まれる硫黄濃度と端子部表面の硫黄濃度との関係は洗浄液の種類に応じてあらかじめ求めておく。
【００２８】
第１端子部及び第２端子部は導電性をもつ材料から構成される。例えば、銅、アルミニウム、鋼及びそれらの合金等の金属が挙げられる。必要に応じて表面にはめっき等の表面処理を行うことができる。特に、スズめっきを行った端子部に対して表面の硫黄濃度を制御する効果が高いと考えられる。
【００２９】
（第２実施形態）
本実施形態の電気接続部材は第１実施形態と同じく、第１端子部と第２端子部とを有し、第１端子部と第２端子部とはそれぞれの一部表面が接触することで両者を電気的に接続する部材である。
【００３０】
第１端子部及び第２端子部は導電性をもつ材料から構成される。例えば、銅、アルミニウム、鋼及びそれらの合金等の金属が挙げられる。必要に応じて表面にはめっき等の表面処理を行うことができる。
【００３１】
第１端子部及び第２端子部が接するそれぞれの一部表面は密着性が向上できるように充分な平滑性を持つことが好ましい。好ましくは第１端子部及び第２端子部は空気中の酸素が進入しない程度にまで密着することが好ましい。また、接触面積は大きくすることが好ましい。
【００３２】
第１端子部及び第２端子部が接するそれぞれの一部表面の少なくとも一方について酸化皮膜の厚みを制御する。好ましくは第１端子部及び第２端子部が接するそれぞれの一部表面について酸化皮膜の厚みを制御する。酸化皮膜の厚みは１４０Å未満、好ましくは１００Å以下とする。
【００３３】
酸化皮膜の厚みの測定はＡＥＳにより行う。具体的にはＡＥＳにより酸素元素が検出されなくなるまで、最表面の原子についてエッチングを行い酸素元素が検出されなくなった部分の深さまでを酸化皮膜の厚みとする。エッチングはどのような方法により行ってもよく設定されたエッチング条件によりどの程度端子部表面がエッチングされるかはあらかじめ実験により求めておく。ここで、「酸素元素が検出されなくなる」とは、エッチングにより掘り進む過程で、母材のピークが安定して一定値として出てくるところまで測定し、その値に達することをもって酸素元素が検出されなくなるものと判断する。
【００３４】
第１端子部及び／又は第２端子部の一部表面の酸化皮膜の厚みを制御する方法としては特に限定しない。例えば、端子部を製造後、表面に酸化皮膜が生成することを抑制することで酸化皮膜の厚みを制御する方法、端子部表面の研削、研磨等により酸化皮膜を除去する機械的方法、還元処理等で酸化皮膜を還元する化学的方法、イオン等によるエッチング等により酸化皮膜を除去する物理的な方法等が挙げられる。これらの中でも端子部を製造後、表面に酸化皮膜が生成することを抑制することで酸化皮膜の厚みを制御する方法が簡便であり好ましい。
【００３５】
（組電池）
本実施形態の組電池は、端子部材をもつ複数の電池と、その電池のその端子部材間を電気的に接続するバスバーとを有する組電池であって、その端子部材からバスバーに至る導電経路に存在する２以上の部材が接する界面のうちの少なくとも一つの表面は、硫黄原子濃度が２．１原子％未満及び／又は酸化皮膜厚さは１４０Å未満であることを特徴とする。
【００３６】
本実施形態の組電池は、図２に示すように、２つの端子部材６をもつ複数（図２では４個）の電池がバスバー３を介して電気的に接続されている。接続部材６とバスバー３とは、図１に示す構成と同様の構成をもって固定されている。つまり、電池の接続部材６は電池の集電材に直接接続されており、図３に示すように、ケースにセルナット４で固定されている。セルナット４及び端子部材６はケースから絶縁されている。バスバー３は、図４に示すように、セルナット４の上部に載置されバスバーワッシャ２を介してバスバーナット１で端子部材６に固定されている。
【００３７】
図１〜４に示す本実施形態の組電池において、端子部材６からバスバー３に至る導電経路に存在する２以上の部材が接する界面は複数存在する。例えば、図１及び図４における、端子部材６及びバスバーナット１、端子部材６及びセルナット４、バスバーナット１及びバスバーワッシャ２、バスバーワッシャ２及びバスバー３、バスバー及びセルナット４が接する界面である。この界面のうちの少なくとも一つの表面は、硫黄原子濃度が２．１原子％未満及び／又は酸化皮膜厚さは１４０Å未満である。特に、接触面積の大きい界面について表面の硫黄濃度及び／又は酸化皮膜の厚みを規定すると、より効果的である。なお、できるだけ多くの界面をなす表面について硫黄濃度及び／又は酸化皮膜の厚みを制御することが好ましい。
【００３８】
ここで、硫黄濃度の制御及び酸化皮膜の厚みの制御は独立した事項であるのでいずれの制御を行うかは独立して決定できる。硫黄濃度の制御及び酸化皮膜の厚みの制御については前述した「電気接続部材」欄で説明した通りであるので説明を省略する。
【００３９】
【実施例】
以下に本発明の電気接続部材について実施例に基づき説明する。本実施例では、バスバーを模した部材であるスズめっきを行った銅製の板材（第１端子部）と電池の端子部材を模したアルミニウム製の板材（第２端子部）とを用いて試験を行った。
【００４０】
第１端子部及び第２端子部が接触する一部表面の大きさは二面幅１４ｍｍの六角ナットで面積は１２６ｍｍ^２であった。第１端子部及び第２端子部の固定はねじ（Ｍ６×１．０）を用いて行い、締結トルクを５．０Ｎｍとした。
【００４１】
（試験１：硫黄濃度が接触抵抗に与える影響について）
第１端子部について第２端子部と固定する前にアルカリ洗浄液を用いて表面を洗浄した。アルカリ洗浄液は日本パーカライジング株式会社製のファインクリーナー３１５（ホウ酸ナトリウム（水和物）；６０〜６５質量％、縮合リン酸塩；２５〜３０質量％、界面活性剤；５〜１０質量％、キレート剤；１質量％以下）の３％水溶液を用いた。
【００４２】
アルカリ洗浄液は更に硫黄を含有する機械油を添加することで硫黄濃度を２００ｐｐｍ、３００ｐｐｍ、４００ｐｐｍ及び５００ｐｐｍに調整した。硫黄濃度はＩＣＰ分光分析により測定した。
【００４３】
硫黄濃度が異なるアルカリ洗浄液で洗浄することで第１端子部表面の硫黄濃度は表１に示す値となった。なお、第１端子部及び第２端子部の酸化皮膜の厚みはそれぞれ１０Å及び１０Åであり、第２端子部の表面の硫黄濃度は０．７原子％であった。
【００４４】
第１端子部の表面の硫黄濃度はＡＥＳにより測定した。ＡＥＳの測定条件は設定電流、１．５×１０^−７Ａ、照射ビーム径５μｍである。測定されたスペクトルにおける硫黄以外の元素（スズ、銅、酸素等）に由来するピークの高さと、硫黄に由来するピークの高さとからそれぞれの原子数の比を求め、表面の硫黄濃度（原子％）を算出した。ピークの高さは個々のピークについてベースラインを設定し、そのベースラインからの高さとした。
【００４５】
それぞれのピークの高さから原子数の比を求める方法は以下の通りである。検出された全成分に対して、予め作成してあるそれぞれの原子が１００％となるピーク高さとの比の係数を掛け合わせて表面の原子数を算出し原子数の比を求めた。
【００４６】
第１端子部及び第２端子部間の抵抗値について、第１端子部及び第２端子部を固定した直後の抵抗値（初期抵抗値）及び高温高湿雰囲気（６０℃、９５％ＲＨ）下で１０００時間放置した後の抵抗値（経年後抵抗値）をそれぞれ測定した値を表１に示す。抵抗値の測定はマイクロオームメーター（日置電機（株）製、商品名バッテリハイテスタ、型番３５５０）を用い、第１端子部及び第２端子部の表面に直接プローブを接触させて行った。
【００４７】
【表１】

【００４８】
表１より明らかなように、硫黄濃度がある程度以上多くても初期抵抗値は０．９ｍΩ程度で飽和することが分かった。しかしながら、表面の表面の硫黄濃度が１．５原子％未満、更には０．７原子％以下では初期抵抗値が低く好ましいことが分かった。
【００４９】
そして、硫黄濃度が２．１原子％未満、更には１．５原子％以下では経年後の抵抗値が低く好ましいことが分かった。特に硫黄濃度が０．７原子％である試験例１では経年後の抵抗値が著しく低かった。また、硫黄濃度は洗浄液中に含まれる硫黄濃度を調節することで制御可能であることが分かった。
【００５０】
表面における硫黄濃度の影響が経年後の抵抗値に大きく出現する理由は定かでないが、表面に存在する硫黄が雰囲気中に存在する水分と反応して生成する硫化水素、硫酸等により第１端子部表面に存在するスズめっきや第２端子部の表面を腐食、酸化等することにより接触抵抗が増加することが推測される。
【００５１】
（試験２：酸化皮膜の厚みが接触抵抗に与える影響について）
第１端子部の製造時に基材である銅板について研削を行い表面の酸化皮膜を除去した後にスズめっきを行った後、高温高湿雰囲気（６０℃、９０％ＲＨ）下で放置することで種々の厚みの酸化皮膜を表面に形成させた。酸化皮膜の厚みは１０Å、５０Å、１００Å及び１４０Åとした。酸化皮膜の厚みは試料を真空下でＡｒイオンによりエッチングを行いながらＡＥＳにより酸素のピークを測定することで酸素原子のデプスプロファイルを算出し酸素原子が検出されなくなった深さを酸化皮膜の厚みとした。エッチング速度は予想される酸化物（本試験では酸化スズ）に応じた予備実験から算出した。
【００５２】
なお、第１端子部及び第２端子部の表面の硫黄濃度はそれぞれ０．７原子％であり、第２端子部の表面の酸化皮膜の厚みは１０Åであった。
【００５３】
第１端子部及び第２端子部間の抵抗値について、第１端子部及び第２端子部を固定した直後の抵抗値を測定した値を表２に示す。抵抗値の測定は試験１と同様の方法で行った。
【００５４】
【表２】

【００５５】
表２より明らかなように、酸化皮膜の厚みが５０Å未満、更には１０Å以下で初期抵抗値が極めて低く好ましいことが分かった。そして、酸化皮膜の厚みが１４０Å未満、更には１００Å以下で初期抵抗値が低く好ましいことが分かった。
【００５６】
酸化皮膜の厚みが抵抗値に与える影響が臨界的意義（特に酸化皮膜の厚みが１００Å〜１４０Åの間で抵抗値が劇的に小さくなること）を有する理由としてはよく分かっていないが、酸化皮膜の厚みが小さいために第１端子部及び第２端子部を固定する際に酸化皮膜が破壊されること、酸化皮膜の厚みを小さくすることで酸化皮膜がポーラスな状態となること、により酸化皮膜が電気の流れを妨害しなくなることが考えられる。
【００５７】
また、第１端子部及び第２端子部を固定すると、第１端子部及び第２端子部が接触するそれぞれの一部表面には空気が侵入せず酸化皮膜の厚みはほぼ変化しないことを確認している。
【図面の簡単な説明】
【図１】本発明の電気接続部材の一実施形態を示した概略断面図である。
【図２】本発明の組電池の一実施形態を示した概略図である。
【図３】本発明の組電池の一実施形態を示した概略図である。
【図４】本発明の組電池の一実施形態を示した概略図である。
【符号の説明】
１…バスバーナット
２…バスバーワッシャ
３…バスバー
４…セルナット
５…ワッシャ
６…端子部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric connection member and a method for connecting the electric connection members, and more particularly, to an electric connection member and a method for connecting the electric connection members that can be suitably used for connection of a portion where a large current flows. Further, the present invention relates to an assembled battery using the electric connection member.
[0002]
[Prior art]
In the field of automobiles, electric vehicles and hybrid electric vehicles are being developed to address environmental issues, resource issues, and the like. For these electric vehicles and the like, high-performance secondary batteries and capacitors (hereinafter referred to as “secondary batteries and the like”) are used.
[0003]
A secondary battery or the like used in an electric vehicle or the like is expected to rapidly charge and discharge such as during acceleration and deceleration, and is required to have good output characteristics and regenerative characteristics. Therefore, it is required that a secondary battery or the like used for an electric vehicle or the like can transfer as much energy as possible per unit time. Therefore, it is preferable that the internal resistance of the secondary battery or the like used is as small as possible.
[0004]
By the way, a general secondary battery or the like has a low terminal voltage by itself, and when used as an automobile power supply, it is used as an assembled battery in which many secondary batteries and the like are connected and combined. An assembled battery has a large number of connection parts for connecting between secondary batteries and the like, and the resistance of each connection part is small but cannot be ignored even if it is accumulated. That is, in order to reduce the internal resistance of the assembled battery, it is necessary to reduce the internal resistance of a single secondary battery or the like constituting the assembled battery and to decrease the resistance of the connection portion.
[0005]
As a conventional technique for reducing the resistance value of a connection portion between secondary batteries and the like, it is disclosed that an oxide film on a battery terminal portion becomes a contact resistance, which may cause a contact failure or a decrease in discharge voltage (Patent Document 1). ).
[0006]
[Patent Document 1]
JP 2000-149915 A
[Problems to be solved by the invention]
However, Patent Document 1 does not disclose how to treat an oxide film from the viewpoint of contact resistance, but only discloses that the material strength of the terminal is increased and the contact resistance is reduced by strongly tightening the terminal.
[0008]
Therefore, the present inventors conducted a systematic experimental study in order to reduce the contact resistance between the terminal portions, and as a result, they found that the use of certain conditions can exert an unpredictable contact resistance reduction effect. Completed the invention.
[0009]
That is, an object of the present invention is to provide an electric connection member and a method for connecting the electric connection member that can reduce the contact resistance. Still another object of the present invention is to provide a battery pack having a low internal resistance.
[0010]
Means for Solving the Problems and Effects of the Invention
The electric connection member of the present invention is an electric connection member having a first terminal portion and a second terminal portion in contact with the first terminal portion, wherein the first terminal portion has a partial surface of the first terminal portion. A part of the surface of the second terminal part is in contact with the part of the first terminal part and / or a part of the surface of the second terminal part has a sulfur atom concentration of less than 2.1 at%; (Claim 1). Here, the sulfur atom concentration on the partial surface of the first terminal portion and / or the partial surface of the second terminal portion is preferably 1.5 atomic% or less (claim 2).
[0011]
The method for connecting an electrical connection member according to the present invention includes a first terminal portion and a second terminal portion that is in contact with the first terminal portion, and the first terminal portion has a partial surface of the first terminal portion. A method for connecting an electrical connection member that is in contact with a partial surface of a second terminal portion, wherein the partial surface of the first terminal portion and / or the partial surface of the second terminal portion is essentially made of sulfur element. The method further includes a step of cleaning with a cleaning liquid that does not include the cleaning liquid.
[0012]
That is, the contact resistance can be reduced by controlling the sulfur concentration on the partial surfaces of the terminal portions of the electrical connection member that are in contact with each other. In particular, the influence of the sulfur concentration on the contact resistance is small immediately after the production of the electric connection member, but the influence of the sulfur concentration on the contact resistance increases with time.
[0013]
The mechanism by which the contact resistance can be reduced by controlling the concentration of sulfur present on the surface is not clear, but it is considered that the contact resistance increases due to the progress of oxidation or corrosion of the terminal portion surface due to the presence of sulfur.
[0014]
The electric connection member of the present invention is an electric connection member having a first terminal portion and a second terminal portion in contact with the first terminal portion, wherein the first terminal portion has a partial surface of the first terminal portion. The thickness of the oxide film on a part of the surface of the first terminal part and / or a part of the surface of the second terminal part is less than 140 °. Claim 3). Here, the thickness of the oxide film on a part of the surface of the first terminal part and / or a part of the surface of the second terminal part is preferably 100 ° or less (claim 4).
[0015]
The method for connecting an electrical connection member according to the present invention includes a first terminal portion and a second terminal portion that is in contact with the first terminal portion, and the first terminal portion has a partial surface of the first terminal portion. A method for connecting an electrical connection member that is in contact with a partial surface of the second terminal portion, wherein the oxide film on a partial surface of the first terminal portion and / or a partial surface of the second terminal portion has a thickness. A step of removing the oxide film on the surface of the terminal portion from which the oxide film has been removed to less than 140 °, and a step of closely connecting the first terminal portion and the second terminal portion before the oxide film on the surface of the terminal portion has become 140 ° or more. (Chart 7).
[0016]
By controlling the thickness of the oxide film present on the part of the terminal portion of the electrical connection member that is in contact with each other as described above, a critical effect can be obtained to significantly reduce the contact resistance value. The reason is that by controlling the thickness of the oxide film, the oxide film is easily broken by compression between the terminal parts such as screw fastening, and the oxide film is in a porous state and covers the entire surface of the terminal part. It is conceivable that a current can flow without passing through the oxide film due to the absence of the oxide film.
[0017]
An assembled battery of the present invention is an assembled battery including a plurality of batteries having terminal members and a bus bar for electrically connecting the terminal members of the battery, wherein the battery has a conductive path extending from the terminal members to the bus bar. At least one of the surfaces at which two or more existing members contact each other has a sulfur atom concentration of less than 2.1 atomic% and / or an oxide film thickness of less than 140 ° (claim 8). . That is, by applying the above-described electric connection member to the interface existing on the conductive path in the battery pack, a battery pack having a small internal resistance can be provided.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
[Electrical connection member and connection method thereof]
The electric connection member of the present invention can be applied to any part as long as it electrically connects two or more members. In particular, it is preferably applied to a portion where a large current needs to flow. For example, a terminal portion of a power source such as a battery, and a bus bar or the like for extracting current from the terminal portion can correspond to the first terminal portion and the second terminal portion of the electric connection member of the present invention, respectively. In other words, two members forming an interface where two or more members existing in the conductive path from the terminal member to the bus bar contact each other can be a first terminal portion and a second terminal portion, respectively.
[0019]
Examples of the battery include a secondary battery such as a lithium secondary battery, a nickel hydride secondary battery, and a lead secondary battery. Further, capacitors and the like can be handled in the same manner as batteries.
[0020]
FIG. 1 shows an enlarged view of the vicinity of the terminal member 6 of the battery. A cell nut 4 is screwed to the terminal member 6 via a washer 5, and the bus bar nut 1 is screwed from above the cell nut 4 via a bus bar 3 and a buzz b washer 2.
[0021]
The case where the electric connection member of the present invention is applied to a battery having the terminal member 6 shown in FIG. 1 will be described below. The first terminal portion and the second terminal portion in the electric connection member of the present invention are the terminal member 6 and the bus bar nut 1, the terminal member 6 and the cell nut 4, the bus bar nut 1, the bus bar washer 2, the bus bar washer 2, and the bus bar in FIG. 3, bus bar and cell nut 4. In other words, the present invention can be applied to all the combinations in which electricity may flow.
[0022]
(First form)
The electric connection member of the present embodiment has a first terminal portion and a second terminal portion, and the first terminal portion and the second terminal portion are electrically connected to each other by partially contacting the respective surfaces. It is a member.
[0023]
It is preferable that a partial surface of each of the first terminal portion and the second terminal portion to be in contact has a sufficient smoothness so that the adhesion can be improved. Further, it is preferable to increase the contact area.
[0024]
The sulfur concentration is controlled on at least one of the partial surfaces where the first terminal portion and the second terminal portion are in contact. Preferably, the sulfur concentration is controlled on a partial surface of each of the first and second terminal portions in contact. The sulfur concentration is less than 2.1 atomic%, preferably 1.5 atomic% or less. The sulfur concentration may be controlled for the bulk, but if at least the outermost surface is controlled, the effect of reducing the contact resistance can be exhibited.
[0025]
The measurement of the sulfur concentration is performed by Auger electron spectroscopy (AES). Specifically, a spectrum is measured for the atoms on the outermost surface by AES, and the abundance of sulfur atoms is calculated in atomic% from the heights of the measured peaks of the atoms on the outermost surface. The height of each peak is determined based on a baseline set for each peak. The measurement conditions for AES are a set current of 1.5 × 10 ⁻⁷ and an irradiation beam diameter of 5 μm.
[0026]
The method for controlling the sulfur concentration on the partial surface of the first terminal portion and / or the second terminal portion is not particularly limited. According to the study of the present inventors, the sulfur element present on the surface is derived from the bulk of the material constituting the terminal part, and sometimes adheres by mechanical processing of the terminal part. The present inventors have found that the machine oil used during machining may contain sulfur.
[0027]
The sulfur element derived from the bulk can be reduced by manufacturing the terminal using a material in which the content of the sulfur element is adjusted. Sulfur element adhered by processing can be controlled by washing with a cleaning liquid essentially containing no sulfur element. Examples of the washing liquid include those whose liquid properties are adjusted to alkaline, ether-based ones, and glycol-based ones. An additive such as a surfactant may be included. Whether or not the sulfur concentration on the terminal portion surface can be controlled by the cleaning can be estimated by monitoring the sulfur concentration in the cleaning liquid. That is, the method is such that when the sulfur concentration contained in the cleaning liquid is equal to or less than (or less than) a predetermined value, the concentration of sulfur existing on the surface of the terminal portion is also within a target range. In this case, the relationship between the concentration of sulfur contained in the cleaning liquid and the concentration of sulfur on the surface of the terminal portion is determined in advance according to the type of the cleaning liquid.
[0028]
The first terminal portion and the second terminal portion are made of a conductive material. For example, metals such as copper, aluminum, steel, and alloys thereof are included. If necessary, the surface can be subjected to surface treatment such as plating. In particular, it is considered that the effect of controlling the sulfur concentration on the surface of the tin-plated terminal portion is high.
[0029]
(2nd Embodiment)
As in the first embodiment, the electric connection member of the present embodiment has a first terminal portion and a second terminal portion, and the first terminal portion and the second terminal portion contact each other by partially contacting their surfaces. It is a member that electrically connects both.
[0030]
The first terminal portion and the second terminal portion are made of a conductive material. For example, metals such as copper, aluminum, steel, and alloys thereof are included. If necessary, the surface can be subjected to surface treatment such as plating.
[0031]
It is preferable that a partial surface of each of the first terminal portion and the second terminal portion to be in contact has a sufficient smoothness so that the adhesion can be improved. Preferably, the first terminal portion and the second terminal portion are in close contact with each other to such an extent that oxygen in the air does not enter. Further, it is preferable to increase the contact area.
[0032]
The thickness of the oxide film is controlled on at least one of the partial surfaces where the first terminal portion and the second terminal portion are in contact. Preferably, the thickness of the oxide film is controlled on a partial surface of each of the first terminal and the second terminal. The thickness of the oxide film is less than 140 °, preferably 100 ° or less.
[0033]
The thickness of the oxide film is measured by AES. Specifically, the atoms on the outermost surface are etched until the oxygen element is no longer detected by AES, and the depth of the portion where the oxygen element is no longer detected is defined as the thickness of the oxide film. The etching may be performed by any method, and the extent to which the terminal portion surface is etched under the set etching conditions is determined in advance by experiments. Here, "Oxygen element is no longer detected" means that in the process of digging by etching, the peak of the base material is measured until it stably appears as a constant value, and the oxygen element is detected when it reaches that value. Judge that it is gone.
[0034]
The method for controlling the thickness of the oxide film on a part of the surface of the first terminal portion and / or the second terminal portion is not particularly limited. For example, after manufacturing the terminal part, a method of controlling the thickness of the oxide film by suppressing the formation of an oxide film on the surface, a mechanical method of removing the oxide film by grinding and polishing the surface of the terminal part, a reduction treatment And the like, and a physical method of removing the oxide film by etching with ions or the like. Among them, a method of controlling the thickness of the oxide film by suppressing the formation of the oxide film on the surface after the terminal portion is manufactured is simple and preferable.
[0035]
(Assembled battery)
The assembled battery of the present embodiment is an assembled battery including a plurality of batteries having terminal members, and a bus bar for electrically connecting the terminal members of the battery, and includes a conductive path from the terminal members to the bus bar. At least one surface of the interface where two or more members are in contact with each other is characterized by a sulfur atom concentration of less than 2.1 atomic% and / or an oxide film thickness of less than 140 °.
[0036]
As shown in FIG. 2, a plurality of (four in FIG. 2) batteries having two terminal members 6 are electrically connected to each other via a bus bar 3 in the battery pack of the present embodiment. The connecting member 6 and the bus bar 3 are fixed with the same configuration as the configuration shown in FIG. That is, the connection member 6 of the battery is directly connected to the current collector of the battery, and is fixed to the case with the cell nut 4 as shown in FIG. The cell nut 4 and the terminal member 6 are insulated from the case. As shown in FIG. 4, the bus bar 3 is mounted on the cell nut 4 and is fixed to the terminal member 6 with the bus bar nut 1 via the bus bar washer 2.
[0037]
In the assembled battery of the present embodiment shown in FIGS. 1 to 4, there are a plurality of interfaces where two or more members existing in the conductive path from the terminal member 6 to the bus bar 3 are in contact. For example, the interface where the terminal member 6 and the bus bar nut 1, the terminal member 6 and the cell nut 4, the bus bar nut 1 and the bus bar washer 2, the bus bar washer 2 and the bus bar 3, the bus bar and the cell nut 4 in FIGS. At least one of the interfaces has a sulfur atom concentration of less than 2.1 atomic% and / or an oxide film thickness of less than 140 °. In particular, it is more effective to define the sulfur concentration on the surface and / or the thickness of the oxide film on the interface having a large contact area. Note that it is preferable to control the sulfur concentration and / or the thickness of the oxide film on the surface forming as many interfaces as possible.
[0038]
Here, since the control of the sulfur concentration and the control of the thickness of the oxide film are independent items, it is possible to independently determine which control is performed. The control of the sulfur concentration and the control of the thickness of the oxide film are the same as those described in the “Electrical connection member” section, and thus the description is omitted.
[0039]
【Example】
Hereinafter, the electrical connection member of the present invention will be described based on examples. In this example, a test was performed using a tin-plated copper plate material (first terminal portion), which is a member simulating a bus bar, and an aluminum plate material (second terminal portion), simulating a battery terminal member. went.
[0040]
The size of a part of the surface in contact with the first terminal portion and the second terminal portion was a hexagonal nut having a width across flats of 14 mm and an area of 126 mm ² . The first terminal portion and the second terminal portion were fixed using screws (M6 × 1.0), and the fastening torque was 5.0 Nm.
[0041]
(Test 1: Effect of sulfur concentration on contact resistance)
Before fixing the first terminal portion to the second terminal portion, the surface was cleaned using an alkaline cleaning solution. The alkaline cleaning liquid is Fine Cleaner 315 (sodium borate (hydrate); 60 to 65% by mass, condensed phosphate; 25 to 30% by mass, surfactant: 5 to 10% by mass, chelate manufactured by Nippon Parkerizing Co., Ltd. (1% by mass or less).
[0042]
The sulfur concentration of the alkaline cleaning solution was adjusted to 200 ppm, 300 ppm, 400 ppm, and 500 ppm by adding a machine oil containing sulfur. The sulfur concentration was measured by ICP spectroscopy.
[0043]
By cleaning with an alkaline cleaning liquid having a different sulfur concentration, the sulfur concentration on the surface of the first terminal portion became the value shown in Table 1. The thicknesses of the oxide films of the first terminal portion and the second terminal portion were 10 ° and 10 °, respectively, and the sulfur concentration on the surface of the second terminal portion was 0.7 atomic%.
[0044]
The sulfur concentration on the surface of the first terminal was measured by AES. The AES measurement conditions are a set current, 1.5 × 10 ⁻⁷ A, and an irradiation beam diameter of 5 μm. From the height of the peak derived from elements other than sulfur (tin, copper, oxygen, etc.) in the measured spectrum and the height of the peak derived from sulfur, the ratio of the number of each atom is determined, and the sulfur concentration on the surface (atomic% ) Was calculated. The peak height was set as a baseline for each peak and the height from the baseline.
[0045]
The method of obtaining the ratio of the number of atoms from the height of each peak is as follows. The ratio of the number of atoms on the surface was calculated by multiplying all the detected components by a coefficient of the ratio of the peak height at which each of the atoms was prepared in advance to 100%, and the number of atoms on the surface was calculated.
[0046]
Regarding the resistance value between the first terminal portion and the second terminal portion, under the resistance value (initial resistance value) immediately after fixing the first terminal portion and the second terminal portion and in a high-temperature and high-humidity atmosphere (60 ° C., 95% RH). Table 1 shows the measured values of the resistance values (aged resistance values) after standing for 1000 hours. The resistance value was measured by using a micro ohm meter (manufactured by Hioki Electric Co., Ltd., trade name: Battery Hitester, model number 3550) by directly contacting the probes with the surfaces of the first terminal portion and the second terminal portion.
[0047]
[Table 1]

[0048]
As is evident from Table 1, even when the sulfur concentration is higher than a certain level, the initial resistance value is saturated at about 0.9 mΩ. However, it was found that when the sulfur concentration at the surface of the surface was less than 1.5 atomic%, and more preferably 0.7 atomic% or less, the initial resistance value was low, which was preferable.
[0049]
When the sulfur concentration was less than 2.1 atomic%, and more preferably 1.5 atomic% or less, the resistance value after aging was low and it was found to be preferable. In particular, in Test Example 1 in which the sulfur concentration was 0.7 atomic%, the resistance value after aging was extremely low. It was also found that the sulfur concentration can be controlled by adjusting the sulfur concentration contained in the cleaning liquid.
[0050]
The reason why the influence of the sulfur concentration on the surface greatly appears in the aged resistance value is unknown, but the first terminal portion is formed by hydrogen sulfide, sulfuric acid, etc. generated by the reaction of sulfur present on the surface with moisture present in the atmosphere. It is presumed that the contact resistance is increased by corroding, oxidizing, or the like the tin plating existing on the surface or the surface of the second terminal portion.
[0051]
(Test 2: Effect of oxide film thickness on contact resistance)
After manufacturing the first terminal portion, the copper plate as the base material is ground, and after removing the oxide film on the surface, tin plating is performed, and then the substrate is left in a high-temperature and high-humidity atmosphere (60 ° C., 90% RH) for various purposes. An oxide film having a thickness of 5 mm was formed on the surface. The thickness of the oxide film was 10 °, 50 °, 100 ° and 140 °. The depth of the oxide film is calculated by measuring the peak of oxygen by AES while etching the sample with Ar ions under vacuum and calculating the depth profile of oxygen atoms. did. The etching rate was calculated from a preliminary experiment corresponding to the expected oxide (tin oxide in this test).
[0052]
The sulfur concentration on the surfaces of the first terminal portion and the second terminal portion was 0.7 atomic%, respectively, and the thickness of the oxide film on the surface of the second terminal portion was 10 °.
[0053]
Table 2 shows the measured values of the resistance between the first terminal and the second terminal immediately after the first and second terminals were fixed. The resistance value was measured in the same manner as in Test 1.
[0054]
[Table 2]

[0055]
As is clear from Table 2, when the thickness of the oxide film is less than 50 °, and more preferably 10 ° or less, the initial resistance value is extremely low, which is preferable. And it turned out that when the thickness of an oxide film is less than 140 degrees, and also 100 degrees or less, initial resistance is low and preferable.
[0056]
The reason why the influence of the thickness of the oxide film on the resistance value has a critical significance (especially that the resistance value decreases drastically when the thickness of the oxide film is between 100 ° and 140 °) is not well understood. The oxide film is broken when the first terminal portion and the second terminal portion are fixed because the thickness of the oxide film is small, and the oxide film becomes porous by reducing the thickness of the oxide film. May not block the flow of electricity.
[0057]
In addition, when the first terminal portion and the second terminal portion were fixed, it was confirmed that air did not enter the respective partial surfaces where the first terminal portion and the second terminal portion were in contact, and the thickness of the oxide film did not substantially change. are doing.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an embodiment of an electric connection member of the present invention.
FIG. 2 is a schematic view showing an embodiment of the battery pack of the present invention.
FIG. 3 is a schematic view showing an embodiment of the battery pack of the present invention.
FIG. 4 is a schematic view showing an embodiment of the battery pack of the present invention.
[Explanation of symbols]
1 busbar nut 2 busbar washer 3 busbar 4 cell nut 5 washer 6 terminal

Claims

第１端子部と該第１端子部に接する第２端子部とを有する電気接続部材であって、
該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触し、
該第１端子部の一部表面及び／又は該第２端子部の一部表面の硫黄原子濃度は２．１原子％未満であることを特徴とする電気接続部材。An electrical connection member having a first terminal portion and a second terminal portion in contact with the first terminal portion,
The first terminal portion has a partial surface of the first terminal portion in contact with a partial surface of the second terminal portion,
An electrical connection member, wherein a sulfur atom concentration of a partial surface of the first terminal portion and / or a partial surface of the second terminal portion is less than 2.1 atomic%.

前記第１端子部の一部表面及び／又は前記第２端子部の一部表面の硫黄原子濃度は１．５原子％以下である請求項１に記載の電気接続部材。The electrical connection member according to claim 1, wherein a sulfur atom concentration on a partial surface of the first terminal portion and / or a partial surface of the second terminal portion is 1.5 atomic% or less.

第１端子部と該第１端子部に接する第２端子部とを有する電気接続部材であって、
該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触し、
該第１端子部の一部表面及び／又は該第２端子部の一部表面の酸化皮膜厚さは１４０Å未満であることを特徴とする電気接続部材。An electrical connection member having a first terminal portion and a second terminal portion in contact with the first terminal portion,
The first terminal portion has a partial surface of the first terminal portion in contact with a partial surface of the second terminal portion,
An electrical connection member, wherein an oxide film thickness on a partial surface of the first terminal portion and / or a partial surface of the second terminal portion is less than 140 °.

前記第１端子部の一部表面及び／又は前記第２端子部の一部表面の酸化皮膜厚さは１００Å以下である請求項３に記載の電気接続部材。The electrical connection member according to claim 3, wherein the thickness of the oxide film on a part of the surface of the first terminal part and / or a part of the surface of the second terminal part is 100 ° or less.

前記第１端子部は電池の端子部材である請求項１〜４のいずれかに記載の電気接続部材。The electrical connection member according to claim 1, wherein the first terminal portion is a terminal member of a battery.

第１端子部と該第１端子部に接する第２端子部とを有し、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触する電気接続部材の接続方法であって、
該第１端子部の一部表面及び／又は該第２端子部の一部表面を本質的に硫黄元素を含まない洗浄液で洗浄する工程を有することを特徴とする電気接続部材の接続方法。An electrical terminal having a first terminal part and a second terminal part in contact with the first terminal part, wherein the first terminal part has a part of the first terminal part in contact with a part of the second terminal part; A connection method of a connection member,
A method for connecting an electric connection member, comprising a step of cleaning a partial surface of the first terminal portion and / or a partial surface of the second terminal portion with a cleaning liquid containing essentially no sulfur element.

第１端子部と該第１端子部に接する第２端子部とを有し、該第１端子部は該第１端子部の一部表面が該第２端子部の一部表面と接触する電気接続部材の接続方法であって、
該第１端子部の一部表面及び／又は該第２端子部の一部表面の酸化皮膜を厚さが１４０Å未満となるまで除去する工程と、
酸化皮膜を除去した該端子部表面の酸化皮膜が１４０Å以上となる前に該第１端子部及び該第２端子部間を密着接続する工程と、を有することを特徴とする電気接続部材の接続方法。An electrical terminal having a first terminal part and a second terminal part in contact with the first terminal part, wherein the first terminal part has a part of the first terminal part in contact with a part of the second terminal part; A connection method of a connection member,
Removing an oxide film on a partial surface of the first terminal portion and / or a partial surface of the second terminal portion until the thickness becomes less than 140 °;
Contacting the first terminal portion and the second terminal portion before the oxide film on the surface of the terminal portion from which the oxide film has been removed becomes 140 ° or more. Method.

端子部材をもつ複数の電池と、該電池の該端子部材間を電気的に接続するバスバーとを有する組電池であって、
該端子部材から該バスバーに至る導電経路に存在する２以上の部材が接する界面のうちの少なくとも一つの表面は、硫黄原子濃度が２．１原子％未満及び／又は酸化皮膜厚さは１４０Å未満であることを特徴とする組電池。A battery pack having a plurality of batteries having terminal members, and a bus bar for electrically connecting the terminal members of the batteries,
At least one surface of an interface where two or more members existing in a conductive path from the terminal member to the bus bar contact each other has a sulfur atom concentration of less than 2.1 atomic% and / or an oxide film thickness of less than 140 °. An assembled battery, comprising: