JP3973384B2 - Lithium secondary battery - Google Patents
Lithium secondary battery Download PDFInfo
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- JP3973384B2 JP3973384B2 JP2001262993A JP2001262993A JP3973384B2 JP 3973384 B2 JP3973384 B2 JP 3973384B2 JP 2001262993 A JP2001262993 A JP 2001262993A JP 2001262993 A JP2001262993 A JP 2001262993A JP 3973384 B2 JP3973384 B2 JP 3973384B2
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- secondary battery
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims description 27
- 229910052744 lithium Inorganic materials 0.000 title claims description 26
- 239000011247 coating layer Substances 0.000 claims description 83
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 28
- 238000007789 sealing Methods 0.000 claims description 21
- 229910052759 nickel Inorganic materials 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 13
- 229910052782 aluminium Inorganic materials 0.000 claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 10
- 239000010410 layer Substances 0.000 claims description 9
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 7
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 7
- 239000011651 chromium Substances 0.000 claims description 7
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 239000010949 copper Substances 0.000 claims description 7
- 229910052719 titanium Inorganic materials 0.000 claims description 7
- 239000010936 titanium Substances 0.000 claims description 7
- 239000003792 electrolyte Substances 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910001512 metal fluoride Inorganic materials 0.000 claims description 4
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 229910000838 Al alloy Inorganic materials 0.000 claims description 3
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 3
- 239000011810 insulating material Substances 0.000 claims description 2
- 238000010030 laminating Methods 0.000 claims description 2
- 230000007246 mechanism Effects 0.000 description 25
- 238000000034 method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000004804 winding Methods 0.000 description 11
- 230000006866 deterioration Effects 0.000 description 10
- 239000008151 electrolyte solution Substances 0.000 description 9
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 8
- -1 polypropylene Polymers 0.000 description 8
- 238000003860 storage Methods 0.000 description 7
- 239000002033 PVDF binder Substances 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000007747 plating Methods 0.000 description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 239000010408 film Substances 0.000 description 4
- 150000002222 fluorine compounds Chemical class 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000012046 mixed solvent Substances 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 2
- 238000010292 electrical insulation Methods 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 210000001217 buttock Anatomy 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000003682 fluorination reaction Methods 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910021450 lithium metal oxide Inorganic materials 0.000 description 1
- CJYZTOPVWURGAI-UHFFFAOYSA-N lithium;manganese;manganese(3+);oxygen(2-) Chemical compound [Li+].[O-2].[O-2].[O-2].[O-2].[Mn].[Mn+3] CJYZTOPVWURGAI-UHFFFAOYSA-N 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- VROAXDSNYPAOBJ-UHFFFAOYSA-N lithium;oxido(oxo)nickel Chemical compound [Li+].[O-][Ni]=O VROAXDSNYPAOBJ-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- RCYJPSGNXVLIBO-UHFFFAOYSA-N sulfanylidenetitanium Chemical compound [S].[Ti] RCYJPSGNXVLIBO-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
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
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Other Surface Treatments For Metallic Materials (AREA)
- Secondary Cells (AREA)
- Connection Of Batteries Or Terminals (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、電池缶内に発電要素となる電極体が収容されて、該電極体が発生する電力を外部へ取り出すことが可能なリチウム二次電池に関するものである。
【０００２】
【従来の技術】
従来、携帯型電子機器、電気自動車等の電源として、大きなエネルギー密度を有するリチウム二次電池が使用されている。
リチウム二次電池は、例えば図３及び図４に示す如く、筒体(11)の両端部に蓋体(12)(12)を溶接固定してなる円筒状の電池缶(１)の内部に、巻き取り電極体(４)を収容して構成されている。両蓋体(12)(12)には、正負一対の電極端子機構(70)(70)が取り付けられており、巻き取り電極体(４)と各電極端子機構(70)とが、複数の集電タブ(６)を介して互いに接続されて、巻き取り電極体(４)が発生する電力を一対の電極端子機構(70)(70)から外部に取り出すことが可能となっている。又、各蓋体(12)には圧力開閉式のガス排出弁(８)が取り付けられている。
【０００３】
巻き取り電極体(４)は、図４に示す様に、正極(41)と、非水電解液が含浸されたセパレータ(42)と、負極(43)とを重ね合わせ、これらを渦巻状に巻回して構成されている。正極(41)及び負極(43)からは夫々複数本の集電タブ(６)が引き出され、極性が同じ複数本の集電タブ(６)の先端部(61)が１つの電極端子機構(70)に接続されている。尚、図４においては、便宜上、正極の電極端子機構(70)の構成を示しており、負極の電極端子機構(70)の構成も同様であるので図示を省略している。又、一部の集電タブ(６)の先端部(61)が電極端子機構(70)に接続されている状態のみを示し、他の集電タブ(６)については、先端部(61)が電極端子機構(70)に接続されている状態の図示を省略している。
【０００４】
各電極端子機構(70)はそれぞれ、電池缶(１)の蓋体(12)を貫通して取り付けられたネジ部材からなる電極端子(71)を具え、該電極端子(71)の基端部には鍔部(72)が形成されている。蓋体(12)の貫通孔には、該貫通孔の内周壁(15)及び両開口縁(14)(14)を覆う樹脂製のシール部材(16)が装着され、蓋体(12)と電極端子(71)の間の電気的絶縁性とシール性が保たれている。電極端子(71)には、電池缶(１)の外側からワッシャ(74)が嵌められると共に、ナット(75)が螺合している。そして、該ナット(75)を締め付けて、電極端子(71)の鍔部(72)とワッシャ(74)によってシール部材(16)を狭圧することにより、シール性を高めている。
正極の電極端子(71)は、高電位において化学的な安定性に優れているアルミニウム或いはその合金を用いて作製されており、負極の電極端子は、負極電位において化学的な安定性に優れている銅或いはその合金を用いて作製されている。
又、正極の電極端子の化学的な安定性を向上させるために、該端子の表面をフッ素化合物を主成分とする皮膜で覆う方法が提案されている(特開平１１−７９６２号公報)。
【０００５】
【発明が解決しようとする課題】
ところで、リチウム二次電池に外部回路を接続する方法の１つとして、図４に示す如く、外部回路から伸びる外部リード(９)の先端部(91)を電極端子(71)にレーザー溶接する方法がある。該接続方法においては、正極の電極端子の材質であるアルミニウム或いはその合金や、負極の電極端子の材質である銅或いはその合金が、金属材料の中でも比較的大きな熱伝導率を有しているために、電極端子(71)の表面と接触しているシール部材(16)に溶接部(92)の熱が伝わり易く、シール部材(16)が劣化する問題があった。これによって、蓋体(12)と電極端子(71)の間のシール性が低下するので、二次電池を長期間保存した後の放電容量が、保存前の放電容量に比べて小さくなっていた。
又、上記特開平１１−７９６２号公報に記載の方法によっても、フッ素化合物を主成分とする皮膜の熱遮断性が不十分なために、上述の如きシール部材が劣化する問題を解決することは出来なかった。
【０００６】
本発明の目的は、外部リードを電極端子に溶接するときの熱によってシール部材が劣化する問題を解決することである。
【０００７】
【課題を解決する為の手段】
本発明に係るリチウム二次電池は、電池缶(１)の内部に、正極(41)と負極(43)の間に電解液を含むセパレータ(42)を介在させてこれらを積層してなる電極体が収納され、該電極体が発生する電力を正負一対の電極端子部から外部へ取り出すことが可能であって、正負極の電極端子部は、電池缶(１)に開設されている貫通孔を貫通して取り付けられている電極端子を有し、該電極端子と該貫通孔の内周壁(15)との間には、絶縁材料からなるシール部材(16)が介在している。
前記電極端子の表面には、少なくとも前記シール部材(16)と対向する領域に、電極端子の材料よりも熱伝導率の小さい金属を材料として第１被覆層(22)が形成されると共に、該第１被覆層(22)の表面には、該第１被覆層(22)を形成する金属のフッ化物からなる第２被覆層(23)が形成されており、該第２被覆層(23)の表面が前記シール部材(16)の表面と接触している。
【０００８】
上記本発明のリチウム二次電池においては、電極端子の表面とシール部材(16)の表面との間に、電極端子の材料よりも熱伝導率の小さい金属を材料とする第１被覆層(22)が介在しており、該第１被覆層(22)の表面に、第１被覆層(22)を形成する金属のフッ化物からなる第２被覆層(23)が形成されているので、従来の二次電池の如く、電極端子の表面とシール部材の表面とが互いに接触している構造や、電極端子の表面とシール部材の表面との間にフッ素化合物を主成分とする皮膜のみが介在している構造に比べて、電極端子の表面とシール部材(16)の表面との間の熱伝導率が小さい。このために、電極端子に外部回路から伸びる外部リードをレーザー溶接しても、溶接部の熱がシール部材に伝わり難く、従って、シール部材(16)は劣化し難い。
又、第１被覆層(22)の表面に形成されている第２被覆層(23)は、第１被覆層(22)を形成する金属のフッ化物によって形成されているので、電池缶(１)内の電解液に対して化学的に安定であり、第２被覆層(23)が腐食することはない。従って、電解液は第２被覆層(23)によって遮断され、第１被覆層(22)に至ることはない。これによって第１被覆層(22)の腐食が防止される。
【０００９】
具体的構成において、正極の電極端子部を構成する電極端子が、アルミニウム若しくはアルミニウム合金によって形成されている。該具体的構成によれば、正極の電極端子は、アルミニウム或いはその合金によって形成されているので、高電位において化学的な安定性に優れている。
他の具体的構成において、負極の電極端子部を構成する電極端子が、銅若しくは銅合金によって形成されている。該具体的構成によれば、負極の電極端子は、銅若しくは銅合金によって形成されているので、負極電位において化学的な安定性に優れている。
【００１０】
更に他の具体的構成において、前記第１被覆層(22)は、ニッケル、クロム、及びチタンの中から選択される１以上の材質を用いて形成されている。該具体的構成によれば、第１被覆層(22)の熱伝導率は、アルミニウムや銅よりも充分に小さい。
【００１１】
【発明の効果】
本発明のリチウム二次電池によれば、外部リードを電極端子に溶接するときの熱によるシール部材の劣化が抑制される。
【００１２】
【発明の実施の形態】
以下、本発明の実施の形態につき、図面に沿って具体的に説明する。
本発明に係るリチウム二次電池は、図１に示す如く、筒体(11)の両端部に蓋体(12)(12)を溶接固定してなる円筒状の電池缶(１)の内部に、巻き取り電極体(４)を収容して構成されている。
蓋体(12)(12)には、正負一対の電極端子機構(２)(３)が取り付けられており、巻き取り電極体(４)と両電極端子機構(２)(３)とがそれぞれ、複数の集電タブ(６)を介して互いに接続されて、巻き取り電極体(４)が発生する電力を一対の電極端子機構(２)(３)から外部に取り出すことが可能となっている。又、各蓋体(12)には圧力開閉式のガス排出弁(８)が取り付けられている。尚、図１においては、便宜上、一部の集電タブ(６)の先端部(61)が、電極端子機構(２)(３)に接続されている状態のみを示し、他の集電タブ(６)については、先端部(61)が電極端子機構(２)(３)に接続されている状態の図示を省略している。
【００１３】
正極の電極端子機構(２)は、電池缶(１)の蓋体(12)を貫通して取り付けられたネジ部材からなる正極の電極端子(20)(以下、正極端子という)を具え、該正極端子(20)の基端部には鍔部(21)が形成されている。蓋体(12)の貫通孔には、該貫通孔の内周壁(15)及び両開口縁(14)(14)を覆うポリプロピレン製のシール部材(16)が装着され、蓋体(12)と正極端子(20)の間の電気的絶縁性とシール性が保たれている。
正極端子(20)の表面の内、シール部材(16)の表面と対向する領域には、ニッケルを材料として第1被覆層(22)が形成されており、該第1被覆層(22)の表面には、第1被覆層(22)の表面をフッ化処理することによって第２被覆層(23)が形成されている。該第２被覆層(23)の表面は、シール部材(16)の表面と接触している。
該正極端子(20)には、電池缶(１)の外側からワッシャ(24)が嵌められると共に、ナット(25)が螺合しており、該ナット(25)を締め付けて、正極端子(20)の鍔部(21)とワッシャ(24)によってシール部材(16)を狭圧することにより、シール性を高めている。
負極の電極端子機構(３)は、正極の電極端子機構(２)と同様に負極の電極端子(30)(以下、負極端子という)を具え、正極の電極端子機構(２)と同様の構成であり、説明を省略する。
【００１４】
次に、上記リチウム二次電池の製造方法について説明する。
第１被覆層と第２被覆層の形成及び電極端子機構の組み立て
先ず、正極の電極端子機構(２)の構成部材であるアルミニウム製の正極端子(20)の表面の内、二次電池の完成時にシール部材(16)と接触する領域にニッケルをめっきして、第１被覆層(22)を形成する。更に、フッ酸を用いて第１被覆層(22)の表面をフッ素化処理して、第２被覆層(22)を形成する。
次に、シール部材(16)を介して蓋体(12)の貫通孔に正極端子(20)の先端を挿入して、正極端子(20)の先端側からワッシャ(24)を嵌めた後、ナット(25)を螺合せしめて、正極の電極端子機構(２)を組み立てる。
負極の電極端子機構(３)の構成部材である銅製の負極端子(30)にも、正極端子(20)と同様にして第1被覆層(32)と第２被覆層(33)を形成し、負極の電極端子機構(３)を、正極の電極端子機構(２)と同様にして組み立てる。ここで、正極端子(20)及び負極端子(30)の表面に形成される第１被覆層(22)(32)の厚さは１００μｍであり、該第１被覆層(22)の表面に形成される第２被覆層(23)(33)の厚さは２〜３μｍである。
【００１５】
正極の作製
先ず、コバルト酸リチウム(ＬｉＣｏＯ２)粉末と、炭素粉末からなる導電剤と、ポリフッ化ビニリデン(ＰＶｄＦ)からなる結着剤とを、重量比で９０：５：５の割合に混合して正極合剤を作製する。次に、この正極合剤にＮ−メチル−２−ピロリドンを加えてスラリー状としてアルミニウム箔に塗布し、圧延を施し、幅２４０ｍｍに切断して帯状の正極(41)を作製する。
負極の作製
先ず、天然の黒鉛粉末と、ポリフッ化ビニリデン(ＰＶｄＦ)からなる結着剤を、重量比で９０：１０の割合に混合して負極合剤を作製する。次に、この負極合剤にＮ−メチル−２−ピロリドンを加えてスラリー状としたものを銅箔に塗布し、圧延を施し、幅２５０ｍｍに切断して帯状の負極(43)を作製する。
【００１６】
電解液の調製
エチレンカーボネート(ＥＣ)とジエチルカーボネート(ＤＥＣ)とを体積比で1：1の割合に混合して混合溶媒を作製する。この混合溶媒に六フッ化リン酸リチウムを１モル／リットルの割合で溶解して電解液を調製する。
巻き取り電極体の作製
前記正極の作製工程において作製した正極(41)と、前記負極の作製工程において作製した負極(43)の間にポリエチレン製の微多孔性薄膜からなるセパレータ(42)を挟んで重ね合わせ、これらを渦巻き状に巻き取って巻き取り電極体(４)を作製する。尚、正極(41)及び負極(43)からは夫々複数本の集電タブ(６)が引き出されている。
【００１７】
電池の組立
先ず、筒体(11)の内部に巻き取り電極体(４)を収容して、巻き取り電極体(４)の正極(41)から伸びている集電タブ(６)の先端部(61)を、蓋体(２)に取り付けられている正極端子(20)の鍔部(21)に接続する。同様にして、巻き取り電極体(４)の負極(43)から伸びている集電タブ(６)の先端部(61)を、蓋体(12)に取り付けられている負極端子(30)の鍔部(31)に接続する。その後、筒体(11)の両開口部に蓋体(12)(12)を溶接固定して、一方の蓋体(12)のガス排出弁取付孔にガス排出弁(８)を取り付け、他方の蓋体(12)のガス排出弁取付孔から電池缶(１)内に電解液を注入する。最後に、該取付孔にガス排出弁(８)を取り付けて、円筒型のリチウム二次電池を組み立てる。
尚、上記第１被覆層を形成するためのめっきの方法としては、公知の方法を採用すればよい。又、上記第２被覆層の形成方法、即ち第１被覆層の表面をフッ素化処理する方法としては、第１被覆層の表面をフッ酸によって処理する方法の他に、第１被覆層の表面を高温下でフッ素ガスと反応させる方法等を採用することも出来る。又、第１被覆層の厚さは、数十μｍから数百μｍであることが好ましく、第２被覆層の厚さは、数μｍであることが好ましい。
【００１８】
図２は、上記リチウム二次電池と外部回路とを電気的に接続した状態を示しており、正極端子(20)に外部リード(９)の先端部(91)を溶接固定している。尚、図示省略する負極端子にも、正極端子(20)と同様に、外部リードを溶接固定している。
本発明に係る上記リチウム二次電池においては、第１被覆層(22)の材料であるニッケルの熱伝導率が正極端子(20)の材料であるアルミニウムよりも小さく、更に、第１被覆層(22)の表面には、第１被覆層(22)の表面をフッ素化処理することによって第２被覆層(23)が形成されているので、従来の二次電池のように正極端子の表面とシール部材の表面とが互いに接触している構造や、正極端子の表面に形成されたフッ素化合物層の表面とシール部材の表面とが互いに接触している構造に比べて、正極端子(20)の表面とシール部材(16)の表面との間の熱伝導率が小さくなっている。又、図示省略する負極端子の表面とシール部材の表面との間にも、第１被覆層及び第２被覆層が介在しているので、負極端子の表面とシール部材の表面との間の熱伝導率も小さくなっている。
【００１９】
これによって、正極端子(20)に外部リード(９)をレーザー溶接したときの溶接部(92)の熱は、正極端子(20)の表面からシール部材(16)の表面へ伝わり難くなっており、シール部材(16)の劣化が抑制されて、正極端子(20)と蓋体(12)の間のシール性の低下が改善される。負極端子に外部リードをレーザー溶接した場合においても、正極端子(20)に外部リード(９)をレーザー溶接した場合と同様の理由によってシール部材の劣化が抑制されて、負極端子と蓋体の間のシール性の低下が改善される。この結果、本発明に係る上記リチウム二次電池を長期間保存した後の放電容量の低下は、従来の二次電池に比べて小さくなる。
【００２０】
更に、第２被覆層は、第１被覆層の表面をフッ素化処理することによって形成されているので、電池缶(１)内の電解液に対して化学的に安定であり、第２被覆層が腐食することはない。従って、電解液は第２被覆層によって遮断され、第１被覆層に至ることはない。これによって第１被覆層の腐食が防止される。
【００２１】
以下、本発明に係るリチウム二次電池の効果を確認するために行なった実験１〜実験３の内容及びその結果について説明する。
実験１
以下に述べる発明電池１、比較電池１〜比較電池３を作製し、各電池の保存前と保存後の放電容量を測定した。保存前の放電容量は、各電池を１０Ａの一定電流で４.２Ｖまで充電した後、２.７Ｖまで放電した後に測定した。保存後の放電容量は、保存前の放電容量を測定した後の各電池を、１０Ａの一定電流で４.２Ｖまで充電した後、６０℃の恒温槽中に１０日間保存した後、恒温槽から取り出し、１０Ａの一定電流で２.７Ｖまで放電した後に測定した。充放電装置の一対の外部リードは、レーザー溶接によって各電池の両極端子に接続した。各電池の自己放電率を、下記数１によって算出した。
【００２２】
【数１】
自己放電率＝(保存前の放電容量−保存後の放電容量)／保存前の放電容量
【００２３】
発明電池１は、上記本発明に係るリチウム二次電池の製造方法と同様にして作製した。該電池の直径は６０ｍｍ、高さは３３０ｍｍであった。
比較電池１は、発明電池１と同様にして作製したが、正極端子の表面には第１被覆層を形成せず、又第２被覆層も形成しなかった。
比較電池２は、発明電池１と同様にして作製したが、正極端子の表面には第１被覆層を形成せず、正極端子の表面の内、シール部材と接触する部分をフッ酸で処理してフッ化物層を形成した。
比較電池３は、発明電池１と同様にして作製したが、正極端子の表面には第１被覆層を形成して、第２被覆層は形成しなかった。
各電池の自己放電率を表１に示す。
【００２４】
【表１】
【００２５】
表１に示す結果から明らかな様に、発明電池１は、比較電池１〜比較電池３に比べて自己放電率が小さく、正極端子と蓋体の間のシール性は改善されている。
この理由は、正極端子の表面に第１被覆層を形成し、更に第１被覆層の表面に第２被覆層を形成したことによって、外部リードを正極端子に溶接したときの熱によるシール部材の劣化が抑制されたためである。
【００２６】
実験２
以下に述べる発明電池２〜発明電池４を作製し、実験１と同様にして、各電池の自己放電率を算出した。
発明電池２は、発明電池１と同様にして作製したが、正極端子の表面には、ニッケルに代えてクロムをめっきして第１被覆層を形成した。
発明電池３は、発明電池１と同様にして作製したが、正極端子の表面には、ニッケルに代えてチタンをめっきして第１被覆層を形成した。
発明電池４は、発明電池１と同様にして作製したが、正極端子の表面には、ニッケルに代えて亜鉛をめっきして第１被覆層を形成した。
各電池の自己放電率を表２に示す。
【００２７】
【表２】
【００２８】
表２に示す結果から明らかな様に、ニッケル、クロム、チタンの何れかを材料として形成された第１被覆層は、シール部材の劣化を抑制する効果が大きい。
【００２９】
実験３
以下に述べる発明電池５〜発明電池７、比較電池４〜比較電池６を作製し、実験１と同様にして、各電池の自己放電率を算出した。
発明電池５は、発明電池１と同様にして作製したが、負極端子の表面には、ニッケルに代えてクロムをめっきして第１被覆層を形成した。
発明電池６は、発明電池１と同様にして作製したが、負極端子の表面には、ニッケルに代えてチタンをめっきして第１被覆層を形成した。
発明電池７は、発明電池１と同様にして作製したが、負極端子の表面には、ニッケルに代えて亜鉛をめっきして第１被覆層を形成した。
比較電池４は、発明電池１と同様にして作製したが、負極端子の表面には第１被覆層を形成せず、又第２被覆層も形成しなかった。
比較電池５は、発明電池１と同様にして作製したが、負極端子の表面には第１被覆層を形成せず、負極端子の表面の内、シール部材と接触する部分をフッ酸で処理してフッ化物層を形成した。
比較電池６は、発明電池１と同様にして作製したが、負極端子の表面には第１被覆層を形成して、第２被覆層は形成しなかった。
各電池の自己放電率を表３に示す。
【００３０】
【表３】
【００３１】
表３に示す結果から明らかな様に、発明電池１及び発明電池５〜発明電池７は、比較電池４〜比較電池６に比べて自己放電率が小さく、負極端子と蓋体の間のシール性は改善されている。この理由は、負極端子の表面に第１被覆層を形成し、該第１被覆層の表面に第２被覆層を形成したことによって、シール部材の劣化が抑制されたためである。
又、発明電池１、発明電池５、発明電池６は、発明電池７に比べて自己放電率が小さい。この理由は、第１被覆層がニッケル、クロム、チタンの何れかを材料として形成されているので、シール部材の劣化を抑制する効果が大きいからである。
【００３２】
尚、本発明の各部構成は上記実施の形態に限らず、特許請求の範囲に記載の技術的範囲内で種々の変形が可能である。例えば、正極端子の材質として、アルミニウムに代えてアルミニウム合金を使用することも可能であり、この場合においても上述の効果と同様の効果を得ることが出来る。
又、第１被覆層を形成する金属としては、亜鉛、ニッケル、クロム、チタンの他に、スズ、鉄を用いることも可能であり、これらの合金を用いて形成することも可能である。この場合においても上述の効果と同様の効果を得ることが出来る。
更に、電極端子の表面がシール部材の表面と対向する領域に第１被覆層を形成するだけでなく、直接若しくは間接的に、シール部材に熱を供給する領域に第１被覆層を形成しても良い。例えば、図２に示す如く、シール部材(16)と接触しているワッシャ(24)の表面や、ワッシャ(24)と接触しているナット(25)の表面に第１被覆層を形成しても良い。この場合には、シール部材(16)に供給される熱量が極めて少なくなるので、シール部材(16)の劣化が一層改善されることとなる。尚、第１被覆層の表面の内、電解液と接触する虞のない領域には、第２被覆層の形成を省略してもよい。
【００３３】
更に又、本発明に係る二次電池における正極材料としては、従来から使用されている種々の材料を用いることが出来る。例えば、リチウムコバルト酸化物(ＬｉＣｏＯ２)、リチウムニッケル酸化物(ＬｉＮｉＯ２)、リチウムマンガン酸化物(ＬｉＭｎ２Ｏ４)等のリチウム金属酸化物、酸化クロム、酸化チタン、酸化コバルト、五酸化バナジウム等の金属酸化物、硫化チタン、硫化モリブデン等の遷移金属のカルコゲン化合物等である。これらをアセチレンブラック、カーボンブラック等の導電剤、及びポリテトラフルオロエチレン(ＰＴＦＥ)、ポリフッ化ビニリデン(ＰＶｄＦ)等の結着剤と混合して、正極合剤として用いることが出来る。
【００３４】
更に又、本発明に係る二次電池における負極材料としては、リチウム原子の挿入及び離脱が可能な、金属リチウム、リチウム合金、炭素材料、金属酸化物等を用いることが出来る。
更に又、本発明に係る二次電池における電解液としては、エチレンカーボネート(ＥＣ)とジエチルカーボネート(ＤＥＣ)の混合溶媒等、種々の電解液を用いることができる。又、電解質として六フッ化リン酸リチウム(ＬｉＰＦ６)等、種々の電解質を用いることが出来る。
更に又、本発明に係る二次電池におけるセパレータとしては、イオン導電性に優れたポリエチレン製やポリプロピレン製の微多孔性膜など、従来からリチウム二次電池用として使用されている種々のセパレータを用いることが出来る。
更に又、本発明に係る二次電池の形状は、円筒状に限定されることなく、角筒形状等、種々の形状とすることが出来る。
【図面の簡単な説明】
【図１】本発明に係るリチウム二次電池の断面図である。
【図２】該二次電池の要部を表わす拡大断面図である。
【図３】従来のリチウム二次電池の外観斜視図である。
【図４】該二次電池の部分断面図である。
【符号の説明】
(１) 電池缶
(16) シール部材
(２) 電極端子機構
(20) 正極端子
(22) 第１被覆層
(23) 第２被覆層
(４) 巻き取り電極体
(６) 集電タブ
(９) 外部リード
(92) 溶接部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium secondary battery in which an electrode body serving as a power generation element is accommodated in a battery can and the electric power generated by the electrode body can be taken out to the outside.
[0002]
[Prior art]
Conventionally, lithium secondary batteries having a large energy density have been used as power sources for portable electronic devices, electric vehicles and the like.
For example, as shown in FIGS. 3 and 4, the lithium secondary battery is provided in a cylindrical battery can (1) formed by welding and fixing lids (12) and (12) to both ends of the cylinder (11). The winding electrode body (4) is accommodated. A pair of positive and negative electrode terminal mechanisms (70), (70) is attached to the lids (12), (12), and the winding electrode body (4) and each electrode terminal mechanism (70) include a plurality of Connected to each other via the current collecting tab (6), the electric power generated by the winding electrode body (4) can be taken out from the pair of electrode terminal mechanisms (70) and (70). Each lid (12) is provided with a pressure open / close type gas discharge valve (8).
[0003]
As shown in FIG. 4, the take-up electrode body (4) is composed of a positive electrode (41), a separator (42) impregnated with a non-aqueous electrolyte, and a negative electrode (43), which are spirally formed. It is composed by winding. A plurality of current collecting tabs (6) are drawn out from the positive electrode (41) and the negative electrode (43), respectively, and the tip portions (61) of the plurality of current collecting tabs (6) having the same polarity are provided as one electrode terminal mechanism ( 70). In FIG. 4, for the sake of convenience, the configuration of the positive electrode terminal mechanism (70) is shown, and the configuration of the negative electrode terminal mechanism (70) is the same, and is not shown. Further, only the state in which the tip part (61) of some of the current collecting tabs (6) is connected to the electrode terminal mechanism (70) is shown, and the tip part (61) is shown for the other current collecting tabs (6). Is not shown in the state of being connected to the electrode terminal mechanism (70).
[0004]
Each electrode terminal mechanism (70) includes an electrode terminal (71) made of a screw member attached through the lid (12) of the battery can (1), and a base end portion of the electrode terminal (71). The ridge part (72) is formed in. A resin sealing member (16) that covers the inner peripheral wall (15) and both opening edges (14), (14) of the through hole is attached to the through hole of the lid (12), and the lid (12) Electrical insulation and sealing properties between the electrode terminals (71) are maintained. A washer (74) is fitted to the electrode terminal (71) from the outside of the battery can (1), and a nut (75) is screwed. The nut (75) is tightened, and the sealing member (16) is narrowed by the flange (72) and the washer (74) of the electrode terminal (71), thereby improving the sealing performance.
The positive electrode terminal (71) is made of aluminum or an alloy thereof excellent in chemical stability at a high potential, and the negative electrode terminal is excellent in chemical stability at a negative potential. It is made using copper or its alloy.
Further, in order to improve the chemical stability of the electrode terminal of the positive electrode, a method of covering the surface of the terminal with a film containing a fluorine compound as a main component has been proposed (Japanese Patent Laid-Open No. 11-7962).
[0005]
[Problems to be solved by the invention]
By the way, as one method of connecting an external circuit to a lithium secondary battery, as shown in FIG. 4, a method of laser welding the tip (91) of an external lead (9) extending from the external circuit to an electrode terminal (71). There is. In the connection method, aluminum or an alloy thereof, which is a material of the positive electrode terminal, or copper or an alloy thereof, which is a material of the negative electrode terminal, has a relatively large thermal conductivity among metal materials. In addition, there is a problem that heat of the welded portion (92) is easily transmitted to the seal member (16) in contact with the surface of the electrode terminal (71), and the seal member (16) is deteriorated. As a result, the sealing performance between the lid (12) and the electrode terminal (71) is lowered, so that the discharge capacity after storing the secondary battery for a long time is smaller than the discharge capacity before storage. .
Further, even by the method described in JP-A-11-7962, it is possible to solve the above-described problem of deterioration of the sealing member due to insufficient heat barrier properties of the film mainly composed of a fluorine compound. I could not do it.
[0006]
An object of the present invention is to solve the problem that a seal member deteriorates due to heat when an external lead is welded to an electrode terminal.
[0007]
[Means for solving the problems]
The lithium secondary battery according to the present invention is an electrode formed by laminating a separator (42) containing an electrolyte between a positive electrode (41) and a negative electrode (43) inside a battery can (1). The body is housed and the electric power generated by the electrode body can be taken out from a pair of positive and negative electrode terminal portions, and the positive and negative electrode terminal portions are through holes formed in the battery can (1). The seal member (16) made of an insulating material is interposed between the electrode terminal and the inner peripheral wall (15) of the through hole.
On the surface of the electrode terminal, at least in a region facing the seal member (16), a first covering layer (22) is formed using a metal having a lower thermal conductivity than the material of the electrode terminal, A second coating layer (23) made of a metal fluoride forming the first coating layer (22) is formed on the surface of the first coating layer (22), and the second coating layer (23) Is in contact with the surface of the seal member (16).
[0008]
In the lithium secondary battery of the present invention, the first coating layer (22) made of a metal having a lower thermal conductivity than the material of the electrode terminal is formed between the surface of the electrode terminal and the surface of the sealing member (16). ) And a second coating layer (23) made of a metal fluoride forming the first coating layer (22) is formed on the surface of the first coating layer (22). As in the case of the secondary battery, the structure in which the surface of the electrode terminal and the surface of the sealing member are in contact with each other, or only the film mainly composed of a fluorine compound is interposed between the surface of the electrode terminal and the surface of the sealing member The thermal conductivity between the surface of the electrode terminal and the surface of the seal member (16) is smaller than that of the structure. For this reason, even if the external lead extending from the external circuit is laser welded to the electrode terminal, the heat of the welded portion is not easily transmitted to the seal member, and therefore the seal member (16) is unlikely to deteriorate.
Further, since the second coating layer (23) formed on the surface of the first coating layer (22) is formed of a metal fluoride forming the first coating layer (22), the battery can (1 The second coating layer (23) does not corrode because it is chemically stable with respect to the electrolyte solution in (). Accordingly, the electrolytic solution is blocked by the second coating layer (23) and does not reach the first coating layer (22). This prevents corrosion of the first coating layer (22).
[0009]
In a specific configuration, the electrode terminals constituting the electrode terminal portion of the positive electrode are formed of aluminum or an aluminum alloy. According to this specific configuration, since the electrode terminal of the positive electrode is formed of aluminum or an alloy thereof, the chemical stability is excellent at a high potential.
In another specific configuration, the electrode terminal constituting the negative electrode terminal portion is formed of copper or a copper alloy. According to this specific configuration, since the electrode terminal of the negative electrode is formed of copper or a copper alloy, it has excellent chemical stability at the negative electrode potential.
[0010]
In still another specific configuration, the first covering layer (22) is formed using one or more materials selected from nickel, chromium, and titanium. According to this specific configuration, the thermal conductivity of the first coating layer (22) is sufficiently smaller than aluminum or copper.
[0011]
【The invention's effect】
According to the lithium secondary battery of the present invention, deterioration of the seal member due to heat when the external lead is welded to the electrode terminal is suppressed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
As shown in FIG. 1, a lithium secondary battery according to the present invention has a cylindrical battery can (1) formed by welding and fixing lids (12) and (12) to both ends of a cylindrical body (11). The winding electrode body (4) is accommodated.
A pair of positive and negative electrode terminal mechanisms (2) and (3) are attached to the lid (12) and (12), and the winding electrode body (4) and both electrode terminal mechanisms (2) and (3) The power generated by the winding electrode body (4) connected to each other via the plurality of current collecting tabs (6) can be taken out from the pair of electrode terminal mechanisms (2) and (3). Yes. Each lid (12) is provided with a pressure open / close type gas discharge valve (8). In FIG. 1, for the sake of convenience, only the state in which the tip portions (61) of some of the current collecting tabs (6) are connected to the electrode terminal mechanisms (2) and (3) are shown. As for (6), illustration of a state in which the distal end portion (61) is connected to the electrode terminal mechanisms (2) and (3) is omitted.
[0013]
The positive electrode terminal mechanism (2) includes a positive electrode terminal (20) (hereinafter referred to as a positive electrode terminal) made of a screw member attached through the lid (12) of the battery can (1). A flange portion (21) is formed at the base end portion of the positive electrode terminal (20). A polypropylene sealing member (16) covering the inner peripheral wall (15) and both opening edges (14), (14) of the through hole is attached to the through hole of the lid (12), and the lid (12) Electrical insulation and sealability between the positive terminals (20) are maintained.
Of the surface of the positive electrode terminal (20), a first coating layer (22) is formed of nickel as a material in a region facing the surface of the sealing member (16), and the first coating layer (22) On the surface, the second coating layer (23) is formed by subjecting the surface of the first coating layer (22) to fluorination treatment. The surface of the second coating layer (23) is in contact with the surface of the seal member (16).
The positive terminal (20) is fitted with a washer (24) from the outside of the battery can (1), and a nut (25) is screwed into the positive terminal (20). The seal member (16) is narrowed by the flange portion (21) and the washer (24), thereby improving the sealing performance.
The negative electrode terminal mechanism (3) includes a negative electrode terminal (30) (hereinafter referred to as a negative electrode terminal) similar to the positive electrode terminal mechanism (2), and has the same configuration as the positive electrode terminal mechanism (2). Therefore, the description is omitted.
[0014]
Next, a method for manufacturing the lithium secondary battery will be described.
Formation of first coating layer and second coating layer and assembly of electrode terminal mechanism First, two of the surfaces of the positive electrode terminal (20) made of aluminum, which is a component of the positive electrode terminal mechanism (2), When the secondary battery is completed, nickel is plated in a region that comes into contact with the seal member (16) to form the first coating layer (22). Further, the surface of the first coating layer (22) is fluorinated using hydrofluoric acid to form the second coating layer (22).
Next, after inserting the tip of the positive electrode terminal (20) into the through hole of the lid (12) through the seal member (16) and fitting the washer (24) from the tip side of the positive electrode terminal (20), The nut (25) is screwed together to assemble the positive electrode terminal mechanism (2).
A first coating layer (32) and a second coating layer (33) are formed on the copper negative electrode terminal (30), which is a component of the negative electrode terminal mechanism (3), in the same manner as the positive electrode terminal (20). The negative electrode terminal mechanism (3) is assembled in the same manner as the positive electrode terminal mechanism (2). Here, the thickness of the first coating layers (22) and (32) formed on the surfaces of the positive electrode terminal (20) and the negative electrode terminal (30) is 100 μm, and is formed on the surface of the first coating layer (22). The thickness of the second covering layers (23) and (33) is 2 to 3 μm.
[0015]
Preparation of positive electrode <br/> First, lithium cobaltate (LiCoO 2) powder, a conductive agent consisting of carbon powder, and a binder consisting of polyvinylidene fluoride (PVdF), a weight ratio of 90: 5: 5 A positive electrode mixture is prepared by mixing in proportions. Next, N-methyl-2-pyrrolidone is added to this positive electrode mixture and applied to an aluminum foil as a slurry, rolled, and cut into a width of 240 mm to produce a strip-shaped positive electrode (41).
Production of negative electrode First, a negative electrode mixture is produced by mixing natural graphite powder and a binder composed of polyvinylidene fluoride (PVdF) in a weight ratio of 90:10. Next, a slurry obtained by adding N-methyl-2-pyrrolidone to this negative electrode mixture is applied to a copper foil, rolled, and cut into a width of 250 mm to produce a strip-shaped negative electrode (43).
[0016]
Preparation of electrolyte solution A mixed solvent is prepared by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1: 1. An electrolytic solution is prepared by dissolving lithium hexafluorophosphate in this mixed solvent at a rate of 1 mol / liter.
Production of wound electrode body Separator made of a microporous thin film made of polyethylene between the positive electrode (41) produced in the production process of the positive electrode and the negative electrode (43) produced in the production process of the negative electrode ( 42) are put on top of each other, and these are wound up in a spiral shape to produce a wound electrode body (4). A plurality of current collecting tabs (6) are drawn out from the positive electrode (41) and the negative electrode (43), respectively.
[0017]
Assembling the battery First, the winding electrode body (4) is accommodated in the cylindrical body (11), and the current collecting tab (6) extending from the positive electrode (41) of the winding electrode body (4). ) Is connected to the flange (21) of the positive terminal (20) attached to the lid (2). Similarly, the tip end portion (61) of the current collecting tab (6) extending from the negative electrode (43) of the winding electrode body (4) is connected to the negative electrode terminal (30) attached to the lid body (12). Connect to the buttocks (31). Thereafter, the lids (12) and (12) are welded and fixed to both openings of the cylinder (11), the gas exhaust valve (8) is attached to the gas exhaust valve mounting hole of one lid (12), and the other The electrolyte is injected into the battery can (1) from the gas discharge valve mounting hole of the lid (12). Finally, a gas discharge valve (8) is attached to the attachment hole to assemble a cylindrical lithium secondary battery.
In addition, what is necessary is just to employ | adopt a well-known method as a plating method for forming the said 1st coating layer. In addition to the method of forming the second coating layer, that is, the method of fluorinating the surface of the first coating layer, the surface of the first coating layer is not only the method of treating the surface of the first coating layer with hydrofluoric acid. It is also possible to employ a method of reacting with fluorine gas at a high temperature. The thickness of the first coating layer is preferably several tens of μm to several hundreds of μm, and the thickness of the second coating layer is preferably several μm.
[0018]
FIG. 2 shows a state in which the lithium secondary battery and the external circuit are electrically connected, and the tip end portion (91) of the external lead (9) is fixed by welding to the positive terminal (20). Note that, as with the positive electrode terminal (20), an external lead is also welded to the negative electrode terminal (not shown).
In the lithium secondary battery according to the present invention, the thermal conductivity of nickel, which is the material of the first coating layer (22), is smaller than that of aluminum, which is the material of the positive electrode terminal (20). Since the second coating layer (23) is formed on the surface of 22) by fluorinating the surface of the first coating layer (22), the surface of the positive electrode terminal is different from the surface of the positive electrode terminal as in the conventional secondary battery. Compared to the structure in which the surface of the seal member is in contact with each other and the structure in which the surface of the fluorine compound layer formed on the surface of the positive electrode terminal and the surface of the seal member are in contact with each other, The thermal conductivity between the surface and the surface of the seal member (16) is small. In addition, since the first coating layer and the second coating layer are interposed between the surface of the negative electrode terminal (not shown) and the surface of the seal member, the heat between the surface of the negative electrode terminal and the surface of the seal member is also present. The conductivity is also small.
[0019]
This makes it difficult for the heat of the welded portion (92) when the external lead (9) is laser welded to the positive electrode terminal (20) to be transferred from the surface of the positive electrode terminal (20) to the surface of the seal member (16). Deterioration of the sealing member (16) is suppressed, and a decrease in sealing performance between the positive electrode terminal (20) and the lid body (12) is improved. Even when the external lead is laser welded to the negative electrode terminal, the deterioration of the seal member is suppressed for the same reason as when the external lead (9) is laser welded to the positive electrode terminal (20). The deterioration of the sealing performance is improved. As a result, the decrease in the discharge capacity after storing the lithium secondary battery according to the present invention for a long period of time is smaller than that of the conventional secondary battery.
[0020]
Furthermore, since the second coating layer is formed by fluorinating the surface of the first coating layer, the second coating layer is chemically stable with respect to the electrolytic solution in the battery can (1), and the second coating layer Will not corrode. Accordingly, the electrolytic solution is blocked by the second coating layer and does not reach the first coating layer. This prevents corrosion of the first coating layer.
[0021]
Hereinafter, the contents and results of Experiments 1 to 3 performed to confirm the effects of the lithium secondary battery according to the present invention will be described.
Experiment 1
Invention battery 1 and comparative battery 1 to comparative battery 3 described below were prepared, and the discharge capacities of each battery before and after storage were measured. The discharge capacity before storage was measured after each battery was charged to 4.2 V with a constant current of 10 A and then discharged to 2.7 V. The discharge capacity after storage was determined by charging each battery after measuring the discharge capacity before storage to 4.2 V at a constant current of 10 A, and then storing the battery in a thermostat at 60 ° C. for 10 days, and then from the thermostat. The measurement was taken after discharging to 2.7 V at a constant current of 10 A. The pair of external leads of the charging / discharging device was connected to the bipolar terminals of each battery by laser welding. The self-discharge rate of each battery was calculated by the following formula 1.
[0022]
[Expression 1]
Self-discharge rate = (discharge capacity before storage−discharge capacity after storage) / discharge capacity before storage
Invention battery 1 was produced in the same manner as the method for producing a lithium secondary battery according to the present invention. The battery had a diameter of 60 mm and a height of 330 mm.
The comparative battery 1 was produced in the same manner as the inventive battery 1, but the first coating layer was not formed on the surface of the positive electrode terminal, and the second coating layer was not formed.
The comparative battery 2 was produced in the same manner as the inventive battery 1, but the first coating layer was not formed on the surface of the positive electrode terminal, and the portion of the positive electrode terminal surface that was in contact with the seal member was treated with hydrofluoric acid. Thus, a fluoride layer was formed.
The comparative battery 3 was produced in the same manner as the inventive battery 1, but the first coating layer was formed on the surface of the positive electrode terminal, and the second coating layer was not formed.
Table 1 shows the self-discharge rate of each battery.
[0024]
[Table 1]
[0025]
As is clear from the results shown in Table 1, the inventive battery 1 has a lower self-discharge rate than the comparative batteries 1 to 3, and the sealing performance between the positive electrode terminal and the lid is improved.
This is because the first coating layer is formed on the surface of the positive electrode terminal, and the second coating layer is further formed on the surface of the first coating layer, so that the seal member by heat when the external lead is welded to the positive electrode terminal is used. This is because deterioration was suppressed.
[0026]
Experiment 2
Invention batteries 2 to 4 described below were prepared, and the self-discharge rate of each battery was calculated in the same manner as in Experiment 1.
Inventive battery 2 was produced in the same manner as Inventive battery 1, but the first coating layer was formed on the surface of the positive electrode terminal by plating with chromium instead of nickel.
Inventive battery 3 was prepared in the same manner as Inventive battery 1, but the first coating layer was formed on the surface of the positive electrode terminal by plating with titanium instead of nickel.
Inventive battery 4 was produced in the same manner as Inventive battery 1, but the first coating layer was formed on the surface of the positive electrode terminal by plating with zinc instead of nickel.
Table 2 shows the self-discharge rate of each battery.
[0027]
[Table 2]
[0028]
As is apparent from the results shown in Table 2, the first coating layer formed using any one of nickel, chromium, and titanium as a material has a great effect of suppressing deterioration of the seal member.
[0029]
Experiment 3
Inventive batteries 5 to 7 and comparative batteries 4 to 6 described below were prepared, and the self-discharge rate of each battery was calculated in the same manner as in Experiment 1.
Inventive battery 5 was prepared in the same manner as Inventive battery 1, but the first coating layer was formed on the surface of the negative electrode terminal by plating with chromium instead of nickel.
Inventive battery 6 was produced in the same manner as Inventive battery 1, but the surface of the negative electrode terminal was plated with titanium instead of nickel to form a first coating layer.
Inventive battery 7 was produced in the same manner as Inventive battery 1, but the first coating layer was formed on the surface of the negative electrode terminal by plating with zinc instead of nickel.
The comparative battery 4 was produced in the same manner as the inventive battery 1, but the first coating layer was not formed on the surface of the negative electrode terminal, and the second coating layer was not formed.
The comparative battery 5 was produced in the same manner as the inventive battery 1, but the first coating layer was not formed on the surface of the negative electrode terminal, and the portion of the surface of the negative electrode terminal that was in contact with the seal member was treated with hydrofluoric acid. Thus, a fluoride layer was formed.
The comparative battery 6 was produced in the same manner as the inventive battery 1, but the first coating layer was formed on the surface of the negative electrode terminal, and the second coating layer was not formed.
Table 3 shows the self-discharge rate of each battery.
[0030]
[Table 3]
[0031]
As is apparent from the results shown in Table 3, the inventive battery 1 and the inventive batteries 5 to 7 have a smaller self-discharge rate than the comparative batteries 4 to 6, and the sealing property between the negative electrode terminal and the lid. Has been improved. This is because the deterioration of the sealing member is suppressed by forming the first coating layer on the surface of the negative electrode terminal and forming the second coating layer on the surface of the first coating layer.
Inventive battery 1, inventive battery 5 and inventive battery 6 have a smaller self-discharge rate than that of inventive battery 7. This is because the first covering layer is formed of any one of nickel, chromium, and titanium, so that the effect of suppressing deterioration of the seal member is great.
[0032]
In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, it is possible to use an aluminum alloy as the material of the positive electrode terminal instead of aluminum. In this case, the same effect as described above can be obtained.
Moreover, as a metal which forms a 1st coating layer, it is also possible to use tin and iron other than zinc, nickel, chromium, and titanium, and it is also possible to form using these alloys. In this case, the same effect as described above can be obtained.
Furthermore, not only the first coating layer is formed in the region where the surface of the electrode terminal faces the surface of the sealing member, but also the first coating layer is formed in the region for supplying heat directly or indirectly to the sealing member. Also good. For example, as shown in FIG. 2, a first coating layer is formed on the surface of the washer (24) in contact with the seal member (16) and the surface of the nut (25) in contact with the washer (24). Also good. In this case, since the amount of heat supplied to the seal member (16) is extremely small, the deterioration of the seal member (16) is further improved. In addition, you may abbreviate | omit formation of a 2nd coating layer in the area | region which does not have a possibility of contacting with electrolyte solution among the surfaces of a 1st coating layer.
[0033]
Furthermore, as the positive electrode material in the secondary battery according to the present invention, various conventionally used materials can be used. For example, lithium metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium manganese oxide (LiMn 2 O 4 ), chromium oxide, titanium oxide, cobalt oxide, vanadium pentoxide, etc. Metal oxides, transition metal chalcogen compounds such as titanium sulfide and molybdenum sulfide. These can be mixed with a conductive agent such as acetylene black and carbon black, and a binder such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), and used as a positive electrode mixture.
[0034]
Furthermore, as the negative electrode material in the secondary battery according to the present invention, metallic lithium, lithium alloy, carbon material, metal oxide, or the like capable of inserting and removing lithium atoms can be used.
Furthermore, as the electrolytic solution in the secondary battery according to the present invention, various electrolytic solutions such as a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) can be used. In addition, various electrolytes such as lithium hexafluorophosphate (LiPF 6 ) can be used as the electrolyte.
Furthermore, as the separator in the secondary battery according to the present invention, various separators conventionally used for lithium secondary batteries, such as polyethylene and polypropylene microporous films having excellent ionic conductivity, are used. I can do it.
Furthermore, the shape of the secondary battery according to the present invention is not limited to a cylindrical shape, and can be various shapes such as a rectangular tube shape.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a lithium secondary battery according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a main part of the secondary battery.
FIG. 3 is an external perspective view of a conventional lithium secondary battery.
FIG. 4 is a partial cross-sectional view of the secondary battery.
[Explanation of symbols]
(1) Battery can
(16) Seal member
(2) Electrode terminal mechanism
(20) Positive terminal
(22) First coating layer
(23) Second coating layer
(4) Winding electrode body
(6) Current collection tab
(9) External lead
(92) Welded part
Claims (4)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001262993A JP3973384B2 (en) | 2001-08-31 | 2001-08-31 | Lithium secondary battery |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001262993A JP3973384B2 (en) | 2001-08-31 | 2001-08-31 | Lithium secondary battery |
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| JP2003077455A JP2003077455A (en) | 2003-03-14 |
| JP3973384B2 true JP3973384B2 (en) | 2007-09-12 |
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