JP4204366B2 - Nonaqueous electrolyte secondary battery - Google Patents
Nonaqueous electrolyte secondary battery Download PDFInfo
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- JP4204366B2 JP4204366B2 JP2003089850A JP2003089850A JP4204366B2 JP 4204366 B2 JP4204366 B2 JP 4204366B2 JP 2003089850 A JP2003089850 A JP 2003089850A JP 2003089850 A JP2003089850 A JP 2003089850A JP 4204366 B2 JP4204366 B2 JP 4204366B2
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 52
- 238000007789 sealing Methods 0.000 claims description 46
- 229910052759 nickel Inorganic materials 0.000 claims description 26
- 229910052782 aluminium Inorganic materials 0.000 claims description 21
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 21
- 229910052802 copper Inorganic materials 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 229910052737 gold Inorganic materials 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 6
- 239000000956 alloy Substances 0.000 claims description 6
- 229910052725 zinc Inorganic materials 0.000 claims description 5
- 238000003466 welding Methods 0.000 description 16
- 238000004804 winding Methods 0.000 description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 9
- 239000010949 copper Substances 0.000 description 9
- 229910001416 lithium ion Inorganic materials 0.000 description 9
- 239000010931 gold Substances 0.000 description 7
- 239000010410 layer Substances 0.000 description 6
- 239000011701 zinc Substances 0.000 description 6
- 239000007773 negative electrode material Substances 0.000 description 5
- 239000007774 positive electrode material Substances 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- -1 composed of nickel Chemical compound 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 3
- 239000008151 electrolyte solution Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 229910021382 natural graphite Inorganic materials 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- KLKFAASOGCDTDT-UHFFFAOYSA-N ethoxymethoxyethane Chemical compound CCOCOCC KLKFAASOGCDTDT-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Sealing Battery Cases Or Jackets (AREA)
- Gas Exhaust Devices For Batteries (AREA)
- Secondary Cells (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、封口体によって封口された負極缶の内部に発電要素なる電極体が収容されている非水電解質二次電池に関し、特に封口体の十分な低抵抗化を図ることによって高出力を得ることが出来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】
従来の円筒型リチウムイオン二次電池は、例えば図５に示す如く、負極缶(10)の開口部に絶縁部材(30)を介して封口体(５)をかしめ固定して、密閉容器を形成し、該密閉容器内に巻き取り電極体(80)を収容して構成されている。尚、負極缶(10)は、負極電位で安定なニッケル、銅、ステンレス鋼などを用いて作製されている。
巻き取り電極体(80)の正極側の端部には集電板(70)が接合され、該集電板(70)に突設したリード片(73)の先端部が封口体(５)の裏面に溶接されている。又、巻き取り電極体(80)の負極側の端部にも同様に集電板(図示省略)が接合され、該集電板が負極缶(10)の底面に接合されている。
【０００３】
封口体(５)は、負極缶(10)の内側から外側へ向かって、アルミニウム製の蓋体ケース(51)と、アルミニウム製の薄板からなる安全弁(52)と、鉄製の基体にニッケル鍍金を施してなる蓋キャップ(53)とを重ね合わせ、これらを互いにスポット溶接して一体化したものである(特許文献１参照)。
この様に、巻き取り電極体(80)の正極が接続されるべき封口体(５)の構造において、負極缶(10)の内側の層(蓋体ケース(51))をアルミニウム製とする一方、複数本の電池を直列接続したとき隣接電池の負極缶と接合されるべき外側の層(蓋キャップ(53)の表層部)をニッケル製とした積層構成によれば、直列接続された２本の電池の接合部にて負極缶(10)のニッケル面と封口体(５)のニッケル面とが接触することとなるので、異種金属どうしの接触に起因する電気腐食の問題が回避される。
【０００４】
【特許文献１】
特開２０００−９０８９２号公報
【特許文献２】
特開２００２−１９８１００号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、図５に示す集電体(５)は、溶接性の悪いニッケルとアルミニウムの積層構造を有しているため、溶接不良によってニッケル層とアルミニウム層の接合界面で大きな電気抵抗が発生し、この結果、大きな電力損失が生じて、十分に高い出力特性を得ることが出来ない問題があった。
そこで本発明の目的は、封口体の低抵抗化を図ることによって高い出力特性を得ることが出来る非水電解質二次電池を提供することである。
【０００６】
【課題を解決する為の手段】
本発明に係る非水電解質二次電池においては、有底筒状を呈する負極缶(１)の開口部に絶縁部材(３)を介して封口体(２)が取り付けられ、該負極缶(１)内に、正極(81)及び負極(82)を積層してなる電極体(８)が収容され、正極(81)は封口体(２)に接続されると共に、負極(82)は負極缶(１)に接続され、封口体(２)と負極缶(１)に設けた正極端子部及び負極端子部から電極体(４)の発生電力を取り出すことが出来る。
ここで、封口体(２)は、負極缶(１)の内側に向けて配置されたアルミニウム製若しくはアルミニウムを主体とする合金からなる内板(21)と、負極缶(１)の外側に向けて配置されると共に少なくとも負極缶(１)の内側と外側を向く両表層部がニッケル製若しくはニッケルを主体とする合金からなる外板(22)と、内板(21)と外板(22)の間に介在する中間板(23)の３層構造を有し、該中間板(23)は、内板(21)及び外板(22)との接合性がアルミニウム−ニッケル間の接合性よりも良好となる金属から形成されている。
そして、内板 (21) の中央部にはガス排出弁となる円形の薄肉部 (24) が形成されると共に、中間板 (23) 及び外板 (22) の中央部には、前記薄肉部 (24) の外径よりも大きな内径を有する貫通孔 (23a)(22a) が開設されている。
具体的には、中間板(23)は、Ｆｅ、Ｃｕ、Ａｕ、Ｚｎから選ばれた少なくとも１つの金属を主体として作製され、内板(21)、中間板(23)及び外板(22)がレーザ溶接などによって互いに接合されている。
尚、「主体」とは、合金においてその元素が最も高い比率で含まれていることを意味する。
【０００７】
上記本発明の非水電解質二次電池に採用されている封口体(２)においては、アルミニウム製の内板(21)とニッケル製の外板(22)の間に、Ｆｅ、Ｃｕ、Ａｕ或いはＺｎからなる中間板(23)が介在しているので、内板(21)と中間板(23)の接合界面においては、アルミニウムとＦｅ、Ｃｕ、Ａｕ或いはＺｎとが接触し、中間板(23)と外板(22)の接合界面においては、Ｆｅ、Ｃｕ、Ａｕ或いはＺｎとニッケルとが接触することとなり、これらの互いに接触する金属どうしの溶接性は、従来の封口体におけるアルミニウムとニッケルとの溶接性よりも良好である。
従って、内板(21)と中間板(23)とは互いに良好に溶接されると共に、中間板(23)と外板(22)とは互いに良好に溶接されて、接合界面での電気抵抗が小さなものとなり、封口体(２)の低抵抗化が図られる。
【０００８】
【発明の効果】
本発明に係る非水電解質二次電池によれば、封口体(２)の低抵抗化が図られて、封口体(２)では電力損失が殆ど発生しないため、高い出力特性を得ることが出来る。
【０００９】
【発明の実施の形態】
以下、本発明を円筒型リチウムイオン二次電池に実施した形態につき、図面に沿って具体的に説明する。
図１に示す如く、本発明に係る円筒型リチウムイオン二次電池は、厚さ０.５ｍｍの鉄製の有底筒体にニッケル鍍金を施してなる負極缶(１)を具え、該負極缶(１)の開口部には、絶縁部材(３)を介して後述する封口体(２)がかしめ固定され、該負極缶(１)の内部に巻き取り電極体(８)が収容されている。
【００１０】
巻き取り電極体(８)の正極側の端部には、集電板(７)が溶接によって接合され、該集電板(７)はリード片(72)を介して封口体(２)の裏面に接続されている。又、巻き取り電極体(８)の負極側の端部には、集電板(71)が溶接によって接合され、該集電板(71)の背面が負極缶(１)の底面に溶接されている。
又、封口体(２)の表面には、ガス排出孔(41)を有する正極端子(４)が取り付けられている。
【００１１】
巻き取り電極体(８)は、図４に示す如く、それぞれ帯状の正極(81)と負極(82)の間に帯状のセパレータ(83)を介在させて、これらを渦巻き状に巻回して構成されている。
図２に示す如く、正極(81)は、アルミニウム箔からなる帯状芯体(84)の両面にリチウム複合酸化物(ＬｉＣｏＯ２)からなる正極活物質(85)を塗布して構成され、負極(82)は、銅箔からなる帯状芯体(86)の両面に天然黒鉛を含む負極活物質(87)を塗布して構成されている。セパレータ(83)には、非水電解液が含浸されている。
【００１２】
図４に示す如く、正極(81)及び負極(82)はそれぞれセパレータ(83)上に幅方向へずらして重ね合わされ、渦巻き状に巻き取られている。これによって、巻き取り電極体(８)の巻き軸方向の両端部の内、一方の端部では、セパレータ(83)の端縁よりも外方へ正極(81)の芯体端縁が突出すると共に、他方の端部では、セパレータ(83)の端縁よりも外方へ負極(82)の芯体端縁が突出している。
【００１３】
負極側の集電板(７)は、厚さ１.０ｍｍのニッケル板から形成される一方、正極側の集電板(71)は、厚さ１.０ｍｍのアルミニウム板から形成され、これらの集電板(７)(71)はそれぞれ巻き取り電極体(８)の負極側の端縁と正極側の端縁に押し付けられ、レーザ溶接されている。
【００１４】
封口体(２)は、図２に示す如く、負極缶(１)の内側から外側に向けて、直径３４ｍｍ、厚さ０.３ｍｍのアルミニウム製の内板(21)と、直径３４ｍｍ、厚さ０.１ｍｍのＦｅ、Ｃｕ、Ａｕ或いはＺｎ製の中間板(23)と、直径３４ｍｍ、厚さ１.５ｍｍのニッケル製の外板(22)とを重ね合わせ、これらの板(21)(23)(22)に内板(21)側から円周線に沿ってレーザ溶接を施し、一体化したものである。
尚、外板(22)は、全体がニッケル製のものに限らず、その表面側及び内面側の表層部がニッケル製のものを用いることも可能である。
図３に示す如く、封口体(２)を構成する内板(21)の中央部には、外径６ｍｍの薄肉部(24)が形成されて、ガス排出弁を構成している。又、中間板(23)及び外板(22)にはそれぞれ、内径が８ｍｍの貫通孔(23a)(22a)が開設されている。
正極端子(４)は、ニッケル板のプレス成型によってキャップ状に形成されている。
【００１５】
尚、封口体(２)を構成するニッケル製の外板(22)の厚さは、電池内圧上昇時の変形防止や封口体の低抵抗化の観点から１.０〜２.０ｍｍが好ましい。１.０ｍｍ以下の厚さでは内圧上昇時に変形が発生するため、かしめ固定部の気密性が低下する虞がある。又、２.０ｍｍ以上の厚さでは、封口体自身の抵抗が大きくなり、十分な出力特性を確保することが出来ない。
封口体(２)を構成するアルミニウム製の内板(21)の厚さは、溶接を内板(21)側から行なう関係上、溶接時の熱放散を抑えて溶接性を高く維持するために、０.５ｍｍ以下が好ましい。
又、封口体(２)を構成する中間板(23)の厚さは、電気抵抗の低減、溶接時の熱放散抑制の観点から、薄いことが好ましいが、０.０５ｍｍ以下の厚さでは、内板(21)と中間板(23)の間の溶接性や、中間板(23)と外板(22)の間の溶接性に大きな改善が見られないため、０.０７５ｍｍ〜１.５０ｍｍの範囲が好ましい。
【００１６】
次に、上記本発明のリチウムイオン二次電池の製造工程について説明する。
巻き取り電極体の作製
ＬｉＣｏＯ２からなる正極活物質と、炭素からなる導電助剤と、ポリフッ化ビニリデン（ＰＶｄＦ）からなるバインダーとを混合して、正極合剤を調製し、該正極合剤を、アルミニウム箔からなる帯状の正極芯体の両面に塗布して、正極(81)を作製する。尚、正極芯体の一方の端部には、正極活物質層の塗布されていない幅１０ｍｍの非塗工部を形成する。
【００１７】
又、天然黒鉛からなる負極活物質と、ポリフッ化ビニリデン（ＰＶｄＦ）からなるバインダーとを混合して、負極合剤を調製し、該負極合剤を、銅箔からなる帯状の負極芯体の両面に塗布して、負極(82)を作製する。尚、負極芯体の一方の端部には、負極活物質の塗布されていない幅１０ｍｍの非塗工部を形成する。
又、多孔性を有するポリエチレン及びポリプロピレンからなる帯状のセパレータ(83)を、正極活物質塗工部及び負極活物質塗工部の幅より若干大きな幅に形成する。
【００１８】
その後、正極、セパレータ及び負極を重ね合わせ、これらを渦巻き状に巻き取って、巻き取り電極体(８)を作製する。この際、正極の活物質非塗工部と負極の活物質非塗工部の端縁がセパレータの端縁から外側へ突出する様に重ね合わせる。
【００１９】
正極集電板及び負極集電板の作製
厚さ１.０ｍｍのニッケル板からなる負極集電板(７)と、厚さ１.０ｍｍのアルミニウム板からなる正極集電板(71)を作製する。尚、正極集電板(71)の表面にはリード片(72)の基端部が連結されている。
【００２０】
封口体の作製
直径３４ｍｍ、厚さ１.５ｍｍのニッケル板の中央部に直径８ｍｍの貫通孔を開設した外板(22)と、直径３４ｍｍ、厚さ０.１ｍｍの銅板の中央部に直径８ｍｍの貫通孔を開設した中間板(23)と、直径３４ｍｍ、厚さ０.３ｍｍのアルミニウム板の中央部に直径６ｍｍの薄肉部からなるガス排出弁を形成した内板(21)とを作製し、これらの板(22)(23)(21)を内板(21)側から円周線に沿ってレーザ溶接し、一体化する。又、封口体(２)の表面にニッケル製の正極端子(４)をレーザ溶接する。
【００２１】
電池の組立
巻き取り電極体(８)の負極側の端縁に負極集電板(７)を設置し、該集電板(７)表面へレーザビームを照射して、該端縁に負極集電板(７)を溶接する。又、巻き取り電極体(８)の正極側の端縁に正極集電板(71)を設置し、該集電板(71)の表面へレーザビームを照射して、該端縁に正極集電板(71)を溶接する。
その後、負極缶(１)の内部に巻き取り電極体(８)を収容し、負極集電板(71)を負極缶(１)の底面に抵抗溶接によって接合する。又、正極集電板(71)から伸びるリード片(72)の先端部を、封口体(２)の裏面にレーザー溶接により接合する。その後、負極缶(１)の内部に電解液を注入する。尚、電解液は、エチレンカーボネートとジエチルカーボネートを体積比１：１で混合し、この混合溶媒にＬｉＰＦ６を１モル／リットルの割合で溶解させたものである。
最後に、負極缶(１)の開口部にポリプロピレン製の絶縁部材(３)を介して封口体(２)をかしめ固定する。これによって、図１に示す円筒型リチウムイオン二次電池が完成する。
【００２２】
尚、正極活物質としては、上述のＬｉＣｏＯ２に限定されるものではなく、ＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４等を採用することが出来、更に負極活物質としては、上述の天然黒鉛に限定されるものではなく、人造黒鉛、コークス等の他の炭素材料や、リチウムを吸蔵放出可能な種々の材料を採用することが出来る。又、電解液としては、上述のものに限定されるものではなく、ビニレンカーボネート、プロピレンカーボネートなどの有機溶媒や、これらとジメチルカーボネート、ジエチルカーボネート、１，２−ジメトキシエタン、エトキシメトキシエタンなどの低沸点溶媒との混合溶媒にＬｉＣｌＯ４、ＬｉＣＦ３ＳＯ４などの溶質を０.７〜１.５モル／リットルの割合で溶解させた溶液等を採用することが出来る。封口体(２)の溶接には、レーザ溶接に限らず、抵抗溶接、超音波溶接等の溶接方法を採用することが出来る。
【００２３】
実験
封口体(２)として、中間板(23)の材料がＦｅ、Ｃｕ、Ａｕ、Ｚｎである４種類の封口体１〜４を作製した。又、比較例として、中間板(23)を具えない内板(21)及び外板(22)からなる封口体５を作製した。そして、これらの封口体を用いて円筒型リチウムイオン二次電池を組み立て、各電池の交流１ｋＨｚにおける電池抵抗値を測定した。その結果を下記表１に示す。
【００２４】
【表１】
表１から明らかな様に、封口体１〜４においては、封口体５よりも低い電池内部抵抗を示している。これは、アルミニウム製の内板(21)とニッケル製の外板(22)との間にＦｅ、Ｃｕ、Ａｕ、或いはＺｎからなる外板(22)を介在させることによって、内板(21)と中間板(23)の間に優れた溶接性が得られると共に、中間板(23)と外板(22)の間にも優れた溶接が得られ、この結果、封口体(２)の低抵抗化が図れたものである。
【図面の簡単な説明】
【図１】本発明に係る円筒型リチウムイオン二次電池の断面図である。
【図２】該円筒型リチウムイオン二次電池の要部を拡大して示す断面図である。
【図３】封口体の分解斜視図である。
【図４】巻き取り電極体の一部展開斜視図である。
【図５】従来の円筒型リチウムイオン二次電池の要部を拡大して示す断面図である。
【符号の説明】
(１) 負極缶
(２) 封口体
(21) 内板
(22) 外板
(23) 中間板
(24) 薄肉部
(３) 絶縁部材
(４) 正極端子
(８) 巻き取り電極体
(７) 集電板
(71) 集電板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery in which an electrode body serving as a power generation element is accommodated in a negative electrode can sealed by a sealing body, and in particular, high output is obtained by sufficiently reducing the resistance of the sealing body. The present invention relates to a non-aqueous electrolyte secondary battery that can be used.
[0002]
[Prior art]
For example, as shown in FIG. 5, a conventional cylindrical lithium ion secondary battery forms a sealed container by caulking and fixing a sealing body (5) to an opening of a negative electrode can (10) via an insulating member (30). The wound electrode body (80) is housed in the sealed container. The negative electrode can (10) is made of nickel, copper, stainless steel or the like that is stable at the negative electrode potential.
A collector plate (70) is joined to the end of the winding electrode body (80) on the positive electrode side, and the tip of the lead piece (73) projecting from the collector plate (70) is the sealing body (5). It is welded to the back side. Similarly, a current collector plate (not shown) is joined to the negative electrode side end of the winding electrode body (80), and the current collector plate is joined to the bottom surface of the negative electrode can (10).
[0003]
The sealing body (5) has an aluminum lid case (51), a safety valve (52) made of a thin aluminum plate, and a nickel plating on an iron base from the inside to the outside of the negative electrode can (10). The lid cap (53) thus formed is superposed and integrated by spot welding to each other (see Patent Document 1).
In this way, in the structure of the sealing body (5) to which the positive electrode of the winding electrode body (80) is to be connected, the inner layer (cover case (51)) of the negative electrode can (10) is made of aluminum. When a plurality of batteries are connected in series, the outer layer (surface layer part of the lid cap (53)) to be joined to the negative electrode can of the adjacent battery is made of nickel. Since the nickel surface of the negative electrode can (10) and the nickel surface of the sealing body (5) are brought into contact with each other at the joint portion of the battery, the problem of electrical corrosion due to the contact between different metals is avoided.
[0004]
[Patent Document 1]
JP 2000-90892 A [Patent Document 2]
Japanese Patent Laid-Open No. 2002-198100
[Problems to be solved by the invention]
However, since the current collector (5) shown in FIG. 5 has a laminated structure of nickel and aluminum with poor weldability, a large electrical resistance is generated at the joint interface between the nickel layer and the aluminum layer due to poor welding, As a result, there is a problem that a large power loss occurs and a sufficiently high output characteristic cannot be obtained.
Therefore, an object of the present invention is to provide a nonaqueous electrolyte secondary battery that can obtain high output characteristics by reducing the resistance of the sealing body.
[0006]
[Means for solving the problems]
In the nonaqueous electrolyte secondary battery according to the present invention, a sealing body (2) is attached to an opening of a negative electrode can (1) having a bottomed cylindrical shape via an insulating member (3), and the negative electrode can (1 ) Accommodates an electrode body (8) formed by laminating a positive electrode (81) and a negative electrode (82), the positive electrode (81) is connected to the sealing body (2), and the negative electrode (82) is a negative electrode can. The generated power of the electrode body (4) can be taken out from the positive electrode terminal part and the negative electrode terminal part connected to (1) and provided in the sealing body (2) and the negative electrode can (1).
Here, the sealing body (2) is oriented toward the outside of the negative electrode can (1) and the inner plate (21) made of aluminum or an alloy mainly composed of aluminum and arranged toward the inside of the negative electrode can (1). An outer plate (22) made of nickel or an alloy mainly composed of nickel, and an inner plate (21) and an outer plate (22). The intermediate plate (23) has a three-layer structure interposed between the inner plate (23) and the inner plate (21) and the outer plate (22) are more bonded than the aluminum-nickel. It is formed from a metal that is also good.
A circular thin portion (24) serving as a gas discharge valve is formed in the central portion of the inner plate (21) , and the thin portion is formed in the central portion of the intermediate plate (23) and the outer plate (22). Through holes (23a) and (22a) having an inner diameter larger than the outer diameter of (24) are established.
Specifically, the intermediate plate (23) is made mainly of at least one metal selected from Fe, Cu, Au, and Zn, and the inner plate (21), the intermediate plate (23), and the outer plate (22). Are joined together by laser welding or the like.
The “main body” means that the element is contained in the highest ratio in the alloy.
[0007]
In the sealing body (2) employed in the nonaqueous electrolyte secondary battery of the present invention, Fe, Cu, Au or the like is interposed between the aluminum inner plate (21) and the nickel outer plate (22). Since the intermediate plate (23) made of Zn is interposed, aluminum and Fe, Cu, Au, or Zn are in contact with each other at the bonding interface between the inner plate (21) and the intermediate plate (23), and the intermediate plate (23 ) And the outer interface (22), Fe, Cu, Au or Zn and nickel are in contact with each other. The weldability of these mutually contacting metals is the same as that of aluminum and nickel in the conventional sealing body. It is better than the weldability.
Therefore, the inner plate (21) and the intermediate plate (23) are well welded to each other, and the intermediate plate (23) and the outer plate (22) are well welded to each other, so that the electric resistance at the joint interface is increased. As a result, the resistance of the sealing body (2) is reduced.
[0008]
【The invention's effect】
According to the nonaqueous electrolyte secondary battery according to the present invention, the sealing body (2) is reduced in resistance, and the sealing body (2) generates almost no power loss, so that high output characteristics can be obtained. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention applied to a cylindrical lithium ion secondary battery will be described in detail with reference to the drawings.
As shown in FIG. 1, a cylindrical lithium ion secondary battery according to the present invention includes a negative electrode can (1) obtained by applying nickel plating to a steel bottomed cylinder having a thickness of 0.5 mm. A sealing body (2), which will be described later, is caulked and fixed to the opening of 1) via an insulating member (3), and the winding electrode body (8) is accommodated inside the negative electrode can (1).
[0010]
A current collector plate (7) is joined to the end of the winding electrode body (8) on the positive electrode side by welding, and the current collector plate (7) is connected to the sealing body (2) via a lead piece (72). Connected to the back side. Further, a current collector plate (71) is joined to the negative electrode side end of the winding electrode body (8) by welding, and the back surface of the current collector plate (71) is welded to the bottom surface of the negative electrode can (1). ing.
A positive electrode terminal (4) having a gas discharge hole (41) is attached to the surface of the sealing body (2).
[0011]
As shown in FIG. 4, the take-up electrode body (8) is formed by interposing a strip-shaped separator (83) between a strip-shaped positive electrode (81) and a negative electrode (82) and winding them in a spiral shape. Has been.
As shown in FIG. 2, the positive electrode (81) is configured by applying a positive electrode active material (85) made of a lithium composite oxide (LiCoO 2 ) to both surfaces of a strip-shaped core (84) made of an aluminum foil. 82) is configured by applying a negative electrode active material (87) containing natural graphite to both surfaces of a strip-shaped core (86) made of copper foil. The separator (83) is impregnated with a non-aqueous electrolyte.
[0012]
As shown in FIG. 4, the positive electrode (81) and the negative electrode (82) are superimposed on the separator (83) while being shifted in the width direction, and wound in a spiral shape. As a result, the core body edge of the positive electrode (81) protrudes outward from the edge of the separator (83) at one of the ends in the winding axis direction of the winding electrode body (8). At the other end, the core body edge of the negative electrode (82) protrudes outward from the edge of the separator (83).
[0013]
The current collector plate (7) on the negative electrode side is formed from a nickel plate having a thickness of 1.0 mm, while the current collector plate (71) on the positive electrode side is formed from an aluminum plate having a thickness of 1.0 mm. The current collector plates (7) and (71) are pressed against the negative electrode side edge and the positive electrode side edge of the winding electrode body (8), respectively, and laser-welded.
[0014]
As shown in FIG. 2, the sealing body (2) has an inner plate (21) made of aluminum having a diameter of 34 mm and a thickness of 0.3 mm and a diameter of 34 mm and a thickness from the inside to the outside of the negative electrode can (1). An intermediate plate (23) made of 0.1 mm Fe, Cu, Au or Zn and a nickel outer plate (22) having a diameter of 34 mm and a thickness of 1.5 mm are overlapped, and these plates (21) (23 ) (22) is integrated by laser welding along the circumferential line from the inner plate (21) side.
The outer plate (22) is not limited to nickel as a whole, and the surface layer and inner surface of the outer plate (22) can be made of nickel.
As shown in FIG. 3, a thin portion (24) having an outer diameter of 6 mm is formed in the central portion of the inner plate (21) constituting the sealing body (2) to constitute a gas discharge valve. The intermediate plate (23) and the outer plate (22) have through holes (23a) and (22a) each having an inner diameter of 8 mm.
The positive terminal (4) is formed in a cap shape by press molding of a nickel plate.
[0015]
The thickness of the nickel outer plate (22) constituting the sealing body (2) is preferably 1.0 to 2.0 mm from the viewpoint of preventing deformation when the internal pressure of the battery is increased and reducing the resistance of the sealing body. If the thickness is 1.0 mm or less, deformation occurs when the internal pressure is increased, and thus the airtightness of the caulking fixing portion may be lowered. On the other hand, when the thickness is 2.0 mm or more, the resistance of the sealing body itself increases, and sufficient output characteristics cannot be ensured.
The thickness of the aluminum inner plate (21) that constitutes the sealing body (2) is so that welding is performed from the inner plate (21) side in order to suppress heat dissipation during welding and maintain high weldability. 0.5 mm or less is preferable.
Further, the thickness of the intermediate plate (23) constituting the sealing body (2) is preferably thin from the viewpoint of reducing electric resistance and suppressing heat dissipation during welding, but at a thickness of 0.05 mm or less, Since there is no significant improvement in the weldability between the inner plate (21) and the intermediate plate (23) and the weldability between the intermediate plate (23) and the outer plate (22), 0.075 mm to 1.50 mm. The range of is preferable.
[0016]
Next, the manufacturing process of the lithium ion secondary battery of the present invention will be described.
Preparation of Winding Electrode Body A positive electrode active material made of LiCoO 2 , a conductive auxiliary agent made of carbon, and a binder made of polyvinylidene fluoride (PVdF) were mixed to prepare a positive electrode mixture. Then, it is applied to both surfaces of a strip-like positive electrode core made of aluminum foil to produce a positive electrode (81). In addition, an uncoated part with a width of 10 mm where the positive electrode active material layer is not applied is formed at one end of the positive electrode core.
[0017]
Also, a negative electrode active material made of natural graphite and a binder made of polyvinylidene fluoride (PVdF) are mixed to prepare a negative electrode mixture, and the negative electrode mixture is mixed with both sides of a strip-like negative electrode core made of copper foil. To produce a negative electrode (82). In addition, an uncoated portion having a width of 10 mm where no negative electrode active material is applied is formed at one end of the negative electrode core.
In addition, a strip-shaped separator (83) made of polyethylene and polypropylene having porosity is formed to have a width slightly larger than the widths of the positive electrode active material coating portion and the negative electrode active material coating portion.
[0018]
Then, a positive electrode, a separator, and a negative electrode are overlap | superposed and these are wound up in the shape of a spiral, and a winding electrode body (8) is produced. At this time, the active material non-coated portion of the positive electrode and the active material non-coated portion of the negative electrode are overlapped so as to protrude outward from the edge of the separator.
[0019]
Production of positive electrode current collector plate and negative electrode current collector plate A negative electrode current collector plate (7) made of a nickel plate with a thickness of 1.0 mm and a positive electrode current collector plate (71 with an aluminum plate with a thickness of 1.0 mm) ). The base end portion of the lead piece (72) is connected to the surface of the positive electrode current collector plate (71).
[0020]
Production of sealing body An outer plate (22) having a through hole with a diameter of 8 mm in the center of a nickel plate with a diameter of 34 mm and a thickness of 1.5 mm, and the center of a copper plate with a diameter of 34 mm and a thickness of 0.1 mm An intermediate plate (23) having a through hole with a diameter of 8 mm in the part, and an inner plate (21) with a gas discharge valve formed of a thin part with a diameter of 6 mm in the center of an aluminum plate with a diameter of 34 mm and a thickness of 0.3 mm These plates (22), (23), and (21) are laser welded along the circumferential line from the inner plate (21) side and integrated. Further, a nickel positive electrode terminal (4) is laser-welded to the surface of the sealing body (2).
[0021]
Assembling of the battery A negative electrode current collector plate (7) is installed on the negative electrode side edge of the winding electrode body (8), and the surface of the current collector plate (7) is irradiated with a laser beam so that the end A negative electrode current collector plate (7) is welded to the edge. In addition, a positive electrode current collector plate (71) is installed on the positive electrode side edge of the winding electrode body (8), and a laser beam is irradiated on the surface of the current collector plate (71), so that the positive electrode current collector is applied to the edge. Weld the electrical plate (71).
Thereafter, the wound electrode body (8) is accommodated in the negative electrode can (1), and the negative electrode current collector plate (71) is joined to the bottom surface of the negative electrode can (1) by resistance welding. Further, the tip of the lead piece (72) extending from the positive electrode current collector (71) is joined to the back surface of the sealing body (2) by laser welding. Thereafter, an electrolytic solution is injected into the negative electrode can (1). The electrolytic solution is prepared by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 and dissolving LiPF6 in this mixed solvent at a ratio of 1 mol / liter.
Finally, the sealing body (2) is caulked and fixed to the opening of the negative electrode can (1) through the polypropylene insulating member (3). Thereby, the cylindrical lithium ion secondary battery shown in FIG. 1 is completed.
[0022]
The positive electrode active material is not limited to the above-described LiCoO 2 , and LiNiO 2 , LiMn 2 O 4 and the like can be adopted, and the negative electrode active material is limited to the above-mentioned natural graphite. Instead, other carbon materials such as artificial graphite and coke, and various materials capable of occluding and releasing lithium can be employed. In addition, the electrolytic solution is not limited to the above-described ones, and organic solvents such as vinylene carbonate and propylene carbonate, and low solvents such as dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, and ethoxymethoxyethane. A solution or the like in which a solute such as LiClO 4 or LiCF 3 SO 4 is dissolved at a rate of 0.7 to 1.5 mol / liter in a mixed solvent with a boiling point solvent can be employed. The welding of the sealing body (2) is not limited to laser welding, and welding methods such as resistance welding and ultrasonic welding can be employed.
[0023]
Experiment As the sealing body (2), four kinds of sealing bodies 1 to 4 in which the material of the intermediate plate (23) was Fe, Cu, Au, and Zn were produced. Further, as a comparative example, a sealing
[0024]
[Table 1]
As is apparent from Table 1, the sealing bodies 1 to 4 show a lower battery internal resistance than the sealing
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical lithium ion secondary battery according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a main part of the cylindrical lithium ion secondary battery.
FIG. 3 is an exploded perspective view of a sealing body.
FIG. 4 is a partially developed perspective view of a wound electrode body.
FIG. 5 is an enlarged cross-sectional view showing a main part of a conventional cylindrical lithium ion secondary battery.
[Explanation of symbols]
(1) Negative electrode can
(2) Sealing body
(21) Inner plate
(22) Outer plate
(23) Intermediate plate
(24) Thin part
(3) Insulation material
(4) Positive terminal
(8) Winding electrode body
(7) Current collector
(71) Current collector
Claims (4)
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