JP2012014915A - Thin lithium secondary battery - Google Patents
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- JP2012014915A JP2012014915A JP2010149258A JP2010149258A JP2012014915A JP 2012014915 A JP2012014915 A JP 2012014915A JP 2010149258 A JP2010149258 A JP 2010149258A JP 2010149258 A JP2010149258 A JP 2010149258A JP 2012014915 A JP2012014915 A JP 2012014915A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 39
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 68
- 239000004743 Polypropylene Substances 0.000 claims abstract description 66
- -1 polypropylene Polymers 0.000 claims abstract description 66
- 229920001155 polypropylene Polymers 0.000 claims abstract description 61
- 239000000565 sealant Substances 0.000 claims abstract description 58
- 230000004927 fusion Effects 0.000 claims abstract description 4
- 230000004888 barrier function Effects 0.000 claims description 39
- 239000007773 negative electrode material Substances 0.000 claims description 10
- 239000007774 positive electrode material Substances 0.000 claims description 10
- 239000003792 electrolyte Substances 0.000 claims description 7
- 238000010248 power generation Methods 0.000 claims description 7
- 239000002253 acid Substances 0.000 abstract description 13
- 230000003449 preventive effect Effects 0.000 abstract 1
- 239000010410 layer Substances 0.000 description 163
- 238000007789 sealing Methods 0.000 description 23
- 229920005989 resin Polymers 0.000 description 13
- 239000011347 resin Substances 0.000 description 13
- 238000012360 testing method Methods 0.000 description 12
- 229910052782 aluminium Inorganic materials 0.000 description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 10
- 239000011888 foil Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 7
- 229920006284 nylon film Polymers 0.000 description 7
- 238000010030 laminating Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 4
- 238000009795 derivation Methods 0.000 description 4
- 239000002648 laminated material Substances 0.000 description 4
- 230000002265 prevention Effects 0.000 description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 3
- 239000005977 Ethylene Substances 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229920006267 polyester film Polymers 0.000 description 3
- 229920000139 polyethylene terephthalate Polymers 0.000 description 3
- 239000005020 polyethylene terephthalate Substances 0.000 description 3
- 229920000098 polyolefin Polymers 0.000 description 3
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 3
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 3
- 239000011342 resin composition Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 229920002302 Nylon 6,6 Polymers 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 229920005604 random copolymer Polymers 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- WSQZNZLOZXSBHA-UHFFFAOYSA-N 3,8-dioxabicyclo[8.2.2]tetradeca-1(12),10,13-triene-2,9-dione Chemical compound O=C1OCCCCOC(=O)C2=CC=C1C=C2 WSQZNZLOZXSBHA-UHFFFAOYSA-N 0.000 description 1
- LLLVZDVNHNWSDS-UHFFFAOYSA-N 4-methylidene-3,5-dioxabicyclo[5.2.2]undeca-1(9),7,10-triene-2,6-dione Chemical compound C1(C2=CC=C(C(=O)OC(=C)O1)C=C2)=O LLLVZDVNHNWSDS-UHFFFAOYSA-N 0.000 description 1
- GVNWZKBFMFUVNX-UHFFFAOYSA-N Adipamide Chemical compound NC(=O)CCCCC(N)=O GVNWZKBFMFUVNX-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 101000576320 Homo sapiens Max-binding protein MNT Proteins 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229920002292 Nylon 6 Polymers 0.000 description 1
- 229920000305 Nylon 6,10 Polymers 0.000 description 1
- 229920000393 Nylon 6/6T Polymers 0.000 description 1
- 229920006121 Polyxylylene adipamide Polymers 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 229920001400 block copolymer Polymers 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 239000012793 heat-sealing layer Substances 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 229920003207 poly(ethylene-2,6-naphthalate) Polymers 0.000 description 1
- 229920001707 polybutylene terephthalate Polymers 0.000 description 1
- 229920001225 polyester resin Polymers 0.000 description 1
- 239000004645 polyester resin Substances 0.000 description 1
- 239000011112 polyethylene naphthalate Substances 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 229920005629 polypropylene homopolymer Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium 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
Landscapes
- Sealing Battery Cases Or Jackets (AREA)
Abstract
Description
本発明は、外装材としてラミネート材を用いた薄型リチウム二次電池に関する。特に、「民生用」と呼ばれる比較的小電力の薄型リチウム二次電池に関する。 The present invention relates to a thin lithium secondary battery using a laminate material as an exterior material. In particular, the present invention relates to a relatively low-power thin lithium secondary battery called “consumer-use”.
リチウム二次電池は体積エネルギー密度が高く、ノートパソコン、ビデオカメラ、携帯電話、電気自動車等の電源として広く用いられている。これらリチウム二次電池の中でも、近年、軽量で放熱性に優れた、ラミネート材を外装材として用いた薄型リチウム二次電池の進展が目覚しい。この薄型リチウム二次電池は、自動車の動力源として用いられる、大電力の「車載用」と、携帯電話等に用いられる、小電力の「民生用」とに大別することができる。車載用の電池は、電力量、耐久性等が重視されるため、比較的厚いラミネート材や電極端子が用いられているが、民生用は軽量、薄肉であることが重視され、比較的薄いラミネート材や電極端子が用いられる。 Lithium secondary batteries have a high volumetric energy density and are widely used as power sources for notebook computers, video cameras, mobile phones, electric vehicles and the like. Among these lithium secondary batteries, in recent years, the progress of thin lithium secondary batteries using a laminate material as an exterior material that is lightweight and excellent in heat dissipation has been remarkable. This thin lithium secondary battery can be broadly classified into a high-power “on-vehicle” used as a power source for automobiles and a low-power “consumer” used for mobile phones and the like. In-vehicle batteries use relatively thick laminates and electrode terminals because power consumption, durability, etc. are important. For consumer use, light weight and thin walls are important, and relatively thin laminates are used. Materials and electrode terminals are used.
ところでラミネート材を外装材として用いた薄型リチウム二次電池には、端子導出部において、密封性の向上、短絡防止を目的とし、タブテープが用いられている。図６に、このような薄型リチウム二次電池の一例を示す。このリチウム二次電池６は、二組の外装材６０間に正極端子６５および負極端子６６が挟み込まれ、外装材６０の端部が熱融着されてなるが、このとき外装材６０と端子６５、６６との間にタブテープ６７が介在し、端子導出部Ｚにおける接着性、密封性の向上に寄与する。
また、該タブテープ６７は外装材６０の端部を熱融着する際に、端子導出部Ｚにおいて、外装材６０に含まれる金属箔のバリア層と端子６５、６６とが接触し、電池が短絡することも防止する。しかしながら図６に示す薄型リチウム二次電池は、タブテープ６７によって外装材と端子との間隔が広げられているため、短絡が抑制されている。
しかしながら、タブテープ６７を用いることは電池のコストアップに繋がる。また図６に示す薄型リチウム二次電池を製造するためには、予め電極端子６５、６６にタブテープ６７を貼り合せる必要があり、製造工程が煩雑であった。
By the way, in the thin lithium secondary battery using the laminate material as the exterior material, a tab tape is used in the terminal lead-out portion for the purpose of improving the sealing property and preventing the short circuit. FIG. 6 shows an example of such a thin lithium secondary battery. In this lithium secondary battery 6, the positive electrode terminal 65 and the negative electrode terminal 66 are sandwiched between two sets of the exterior material 60, and the ends of the exterior material 60 are heat-sealed. , 66 is interposed between the tab tape 67 and the terminal lead-out portion Z, thereby improving the adhesion and sealing performance.
Further, when the tab tape 67 is heat-sealed at the end of the exterior material 60, the barrier layer of the metal foil contained in the exterior material 60 and the terminals 65 and 66 come into contact at the terminal lead-out portion Z, and the battery is short-circuited. It also prevents it. However, in the thin lithium secondary battery shown in FIG. 6, since the gap between the exterior material and the terminals is widened by the tab tape 67, the short circuit is suppressed.
However, using the tab tape 67 leads to an increase in battery cost. In addition, in order to manufacture the thin lithium secondary battery shown in FIG. 6, it is necessary to attach the tab tape 67 to the electrode terminals 65 and 66 in advance, and the manufacturing process is complicated.
特許文献１の発明はタブテープを用いることなく、端子導出部における短絡を防止した薄型電池用袋体である。この薄型電池袋体は、各シーラント層の厚みが端子の厚みの１／２よりも大きいため、シーラント層の樹脂組成によっては端子とバリア層との接触が抑制され、短絡を防止することができる。しかしながらシーラント層の樹脂組成によっては、短絡を防止することができなかった。例えばシーラント層が融点の低い樹脂から形成されている場合、シーラント層の厚みを端子の厚みの１／２以上としても、シール時にシーラント層が潰れて短絡を起こすことがある。
特許文献２は、電極端子構造に特徴を有する薄型電池に関するものである。特許文献２には、短絡を防ぐ手段として電極端子の厚みをシーラント層（熱融着性高分子膜層）の厚みより薄くする、或いはシーラント層の厚みを厚くする方法が提案されている（特許文献２段落番号００２９）。しかしながら、特許文献１と同様に、樹脂組成を限定せずに端子やシーラント層の厚みをコントロールするだけでは、短絡を確実に防止することはできなかった。
The invention of Patent Document 1 is a thin battery bag that prevents a short circuit in the terminal lead-out portion without using a tab tape. In this thin battery bag body, since the thickness of each sealant layer is larger than ½ of the thickness of the terminal, the contact between the terminal and the barrier layer is suppressed depending on the resin composition of the sealant layer, and a short circuit can be prevented. . However, depending on the resin composition of the sealant layer, a short circuit could not be prevented. For example, when the sealant layer is formed of a resin having a low melting point, even if the thickness of the sealant layer is set to 1/2 or more of the thickness of the terminal, the sealant layer may be crushed during sealing to cause a short circuit.
Patent Document 2 relates to a thin battery characterized by an electrode terminal structure. Patent Document 2 proposes a method of making the electrode terminal thinner than the sealant layer (heat-fusible polymer film layer) or increasing the thickness of the sealant layer as a means for preventing a short circuit (patent). Reference 2, paragraph number 0029). However, as in Patent Document 1, short-circuiting cannot be reliably prevented by controlling the thickness of the terminal and sealant layer without limiting the resin composition.
尚、特許文献３では、二次電池外装材のシーラント層（熱封緘層）としてポリプロピレンフィルムの両面に酸変性ポリオレフィンフィルムを備えた三層構造のポリオレフィン系フィルムが提案されている（特許文献３段落番号００１３）。この外装材は、酸変性ポリオレフィンによって、シーラント層とバリア層との密封性が改善されている。 Patent Document 3 proposes a polyolefin film having a three-layer structure in which an acid-modified polyolefin film is provided on both surfaces of a polypropylene film as a sealant layer (heat sealing layer) for a secondary battery exterior material (paragraph 3 of Patent Document 3). Number 0013). In this exterior material, the sealing property between the sealant layer and the barrier layer is improved by the acid-modified polyolefin.
本発明は、タブテープを用いることなく、タブテープを用いた場合と同等の接着性、密封性、短絡防止性を有する薄型リチウム二次電池の提供を目的とする。 An object of this invention is to provide the thin lithium secondary battery which has the adhesiveness, sealing performance, and short circuit prevention property equivalent to the case where a tab tape is used, without using a tab tape.
本発明によると、上記課題を解決するための手段として、基材層、バリア層、シーラント層が順に積層されてなる外装材に、正極材、負極材、セパレータ及び電解質を含む発電要素が封入され、更に正極端子が正極材から電池外部まで延在し、負極端子が負極材から電池外部まで延在するように、外装材端部が熱融着されてなるリチウム二次電池において、
前記シーラント層が、バリア層側から順に、外側酸変性ポリプロピレン層／ポリプロピレン層／内側酸変性ポリプロピレン層が積層された三層構造であり、
熱融着前の外側酸変性ポリプロピレン層の厚みをαμｍ、ポリプロピレン層の厚みをβμｍ、内側酸変性ポリプロピレン層の厚みをγμｍとし、前記正極端子と前記負極端子のうちの厚い方の厚さをＴμｍとしたとき、
２Ｔ／３≦α＋β＋γ≦３Ｔ／２
８≦α≦２０
１０≦γ≦２５
であることを特徴とする、薄型リチウム二次電池が提供される。
また前記Ｔが、８０≦Ｔ≦１２０であることを特徴とする前記薄型リチウム二次電池が提供される。
According to the present invention, as a means for solving the above problems, a power generation element including a positive electrode material, a negative electrode material, a separator, and an electrolyte is enclosed in an exterior material in which a base material layer, a barrier layer, and a sealant layer are sequentially laminated. In addition, in the lithium secondary battery in which the outer material end is thermally fused so that the positive electrode terminal extends from the positive electrode material to the outside of the battery and the negative electrode terminal extends from the negative electrode material to the outside of the battery,
The sealant layer has a three-layer structure in which an outer acid-modified polypropylene layer / a polypropylene layer / an inner acid-modified polypropylene layer are laminated in order from the barrier layer side,
The thickness of the outer acid-modified polypropylene layer before heat fusion is α μm, the thickness of the polypropylene layer is β μm, the thickness of the inner acid-modified polypropylene layer is γ μm, and the thickness of the positive electrode terminal and the negative electrode terminal is T μm When
2T / 3 ≦ α + β + γ ≦ 3T / 2
8 ≦ α ≦ 20
10 ≦ γ ≦ 25
A thin lithium secondary battery is provided.
Further, the thin lithium secondary battery is characterized in that T is 80 ≦ T ≦ 120.
本発明によるとシーラント層の層構成を特定し、更に端子厚みに対するシーラント層の厚みと、シーラント層を成す各層の厚みを特定することにより、タブテープを用いていない薄型リチウム二次電池に、タブテープを用いた場合と同等の接着性、密封性、短絡防止機能を付与することができる。
尚、本発明の薄型リチウム二次電池は、端子が厚くなるに伴ってシーラント層の厚みが大きくなり、外装材の水分バリア性が低下する。よって本発明は、端子が薄い（８０〜１２０μｍ程度の）民生用のリチウム二次電池に特に好適に用いることができる。
According to the present invention, the layer structure of the sealant layer is specified, and the thickness of the sealant layer with respect to the terminal thickness and the thickness of each layer constituting the sealant layer are specified, so that the tab tape is applied to a thin lithium secondary battery not using the tab tape. Adhesiveness, sealing performance, and short-circuit prevention function equivalent to those used can be provided.
In the thin lithium secondary battery of the present invention, as the terminal becomes thicker, the thickness of the sealant layer increases, and the moisture barrier property of the exterior material decreases. Therefore, the present invention can be particularly suitably used for a consumer lithium secondary battery having a thin terminal (about 80 to 120 μm).
本発明の薄型リチウム二次電池の一実施例を表す模式的側断面図を図１に、本電池の密封前の分解斜視図を図２に記す。本発明の薄型リチウム二次電池１は、基材層、バリア層、シーラント層が順に積層された二組の外装材１０の間に、正極材１１、負極材１２、セパレータ１３及び電解質（図示せず）を含む発電要素１４が封入され、更に正極端子１５が正極材１１から電池外部まで延在し、負極端子１６が負極材１２から電池外部まで延在するよう、各端子を挟みながら外装材１０の端部が熱融着されてなる。
本発明における発電要素１４は、薄型リチウム二次電池において一般的に用いられるものと同様のものを用いることができ、正極材１１、負極材１２は、それぞれ集電体上に電極活物質を塗布したものが用いられ、セパレータ１３としては多孔性樹脂膜等が、電解質としては液状またはゲル状のリチウム塩電解質が用いられる。
FIG. 1 is a schematic sectional side view showing an embodiment of the thin lithium secondary battery of the present invention, and FIG. 2 is an exploded perspective view of the battery before sealing. The thin lithium secondary battery 1 of the present invention includes a positive electrode material 11, a negative electrode material 12, a separator 13 and an electrolyte (not shown) between two sets of exterior materials 10 in which a base material layer, a barrier layer, and a sealant layer are sequentially laminated. Power generation element 14 is further enclosed, and further, the positive electrode terminal 15 extends from the positive electrode material 11 to the outside of the battery, and the negative electrode terminal 16 extends from the negative electrode material 12 to the outside of the battery. Ten end portions are heat-sealed.
The power generation element 14 in the present invention can be the same as that generally used in a thin lithium secondary battery, and the positive electrode material 11 and the negative electrode material 12 are each coated with an electrode active material on a current collector. The separator 13 is a porous resin film or the like, and the electrolyte is a liquid or gel lithium salt electrolyte.
正極端子１５は通常、アルミニウムやチタン、あるいはこれらの合金から成形され、負極端子１６は通常、ニッケル、銅、あるいはこれらの合金から形成されるが、これに限定されるものではない。また正極端子１５及び負極端子１６は必要に応じて絶縁処理等の表面処理が施される。
尚、正極端子１５、負極端子１６の厚みは特に限定されないが、本発明によると、シーラント層全体の厚み（即ちα＋β＋γ）は、端子厚みＴの２／３〜３／２倍とするので、端子の厚みが大きくなるに伴い、シーラント層全体の厚みも大きくなり、外装材のコストアップに繋がる。またシーラント層の端面からは水分が電池内部へ浸透する恐れがある。よってシーラント層の厚みが大きくなると、シーラント層端面積も増大し、水分が浸透し易くなる。そこで本発明は、端子Ｔの厚みが比較的薄い、具体的には８０〜１２０μｍ程度の「民生用」の薄型リチウム二次電池に対して用いることが望ましい。
The positive electrode terminal 15 is usually formed from aluminum, titanium, or an alloy thereof, and the negative electrode terminal 16 is usually formed from nickel, copper, or an alloy thereof, but is not limited thereto. The positive electrode terminal 15 and the negative electrode terminal 16 are subjected to surface treatment such as insulation treatment as necessary.
The thicknesses of the positive electrode terminal 15 and the negative electrode terminal 16 are not particularly limited. However, according to the present invention, the thickness of the entire sealant layer (that is, α + β + γ) is 2/3 to 3/2 times the terminal thickness T. As the thickness of the sealant increases, the thickness of the entire sealant layer also increases, leading to an increase in the cost of the exterior material. In addition, moisture may permeate into the battery from the end face of the sealant layer. Therefore, when the thickness of the sealant layer is increased, the end area of the sealant layer is also increased, so that moisture easily penetrates. Therefore, the present invention is desirably used for a “consumer-use” thin lithium secondary battery in which the thickness of the terminal T is relatively thin, specifically about 80 to 120 μm.
図３は本発明に用いられる外装材３０の一例の模式的断面図である。外装材３０は、基材層３１、バリア層３２、シーラント層３３が順に積層されてなる。
基材層３１は、電池の外側になる層であってハードウェアと直接接触するので、ある程度強靭で、絶縁性を有する樹脂フィルムが適する。具体的には、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリエチレンナフタレート、エチレンテレフタレート／エチレンイソフタレート共重合体、ブチレンテレフタレート／ブチレンイソフタレート共重合体等のポリエステル樹脂からなるフィルムを二軸延伸した二軸延伸ポリエステルフィルムや、ナイロン６、ナイロン６，６、ナイロン６，６とナイロン６の共重合体、ナイロン６，１０、ポリメタキシリレンアジパミド（ＭＸＤ６）等のナイロンフィルムを二軸延伸した二軸延伸ナイロンフィルムが適し、特に二軸延伸ポリエステルフィルムと二軸延伸ナイロンフィルムを積層した二層フィルムが適する。この場合、ナイロン樹脂は電解質によって変質しやすいので、基材層のバリア層と接する層３１ｂを二軸延伸ナイロンフィルムに、基材層の最外層となる層３１ａを二軸延伸ポリエステルフィルムにするとよい。
基材層３１の厚みは特に限定されないが１０〜５０μｍが適する。１０μｍ以下であると強度が不十分な場合があり、５０μｍを越えても強度の向上が見られない。また基材層３１が二層である場合は最外層となる層３１ａを５〜２５μｍ、バリア層と接する層３１ｂを５〜２５μｍとするとよい。
FIG. 3 is a schematic cross-sectional view of an example of the exterior material 30 used in the present invention. The packaging material 30 is formed by laminating a base material layer 31, a barrier layer 32, and a sealant layer 33 in this order.
Since the base material layer 31 is a layer that becomes the outside of the battery and is in direct contact with the hardware, a resin film that is strong to some extent and has an insulating property is suitable. Specifically, a biaxially stretched biaxially stretched film of a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, ethylene terephthalate / ethylene isophthalate copolymer, butylene terephthalate / butylene isophthalate copolymer, etc. Biaxially stretched by biaxially stretching polyester film, nylon 6, nylon 6,6, nylon 6,6 and nylon 6 copolymer, nylon 6,10, nylon film such as polymetaxylylene adipamide (MXD6) A nylon film is suitable, and in particular, a bilayer film obtained by laminating a biaxially stretched polyester film and a biaxially stretched nylon film is suitable. In this case, since the nylon resin is easily altered by the electrolyte, the layer 31b in contact with the barrier layer of the base material layer may be a biaxially stretched nylon film, and the outermost layer 31a of the base material layer may be a biaxially stretched polyester film. .
Although the thickness of the base material layer 31 is not specifically limited, 10-50 micrometers is suitable. If it is 10 μm or less, the strength may be insufficient, and if it exceeds 50 μm, no improvement in strength is observed. Moreover, when the base material layer 31 is two layers, it is good to set the layer 31a used as the outermost layer to 5-25 micrometers, and the layer 31b which touches a barrier layer to 5-25 micrometers.
バリア層３２は、外部から電池内部に酸素や水分が浸入することを防止するための層であり、アルミニウム、ニッケル、ステンレス等の金属箔を好適に用いることができるが、経済性を考慮するとアルミニウム箔が特に適する。尚、アルミニウム箔は若干の鉄を含有することで展延性が改善されること、折り曲げによるピンホールの発生が少なくなることが知られている。そこでバリア層３２としてアルミニウム箔を用いる場合は、鉄を０．３〜９．０重量％、好ましくは０．７〜２．０重量％含有したものを用いとよい。また、冷間圧延で製造されるアルミニウム箔は焼きなまし（いわゆる焼鈍処理）条件でその柔軟性・腰の強さ・硬さが変化するが、本発明においてアルミニウム箔を用いる場合は、焼きなましをしていない硬質処理品より、多少または完全に焼きなまし処理をした軟質傾向にあるものがよい。
バリア層３２の厚さは、酸素や水分に対して十分なバリア性を発揮し、加工適性（製袋加工、深絞り加工性等）を安定化させ、更に耐ピンホール性をもたせるために、１５μｍ以上であることが好ましく、特に２０μｍ以上であることが好ましい。また加工適性を考慮するとバリア層３２は８０μｍ以下であることが望まれる。
The barrier layer 32 is a layer for preventing oxygen and moisture from entering the battery from the outside, and a metal foil such as aluminum, nickel, and stainless steel can be suitably used. A foil is particularly suitable. In addition, it is known that aluminum foil contains a slight amount of iron to improve the spreadability and to reduce the occurrence of pinholes due to bending. Therefore, when an aluminum foil is used as the barrier layer 32, iron containing 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight may be used. In addition, the aluminum foil produced by cold rolling changes its flexibility, waist strength, and hardness under annealing (so-called annealing treatment) conditions. However, when aluminum foil is used in the present invention, it is annealed. It is better to have a soft tendency to be annealed somewhat or completely than a hard-treated product.
The thickness of the barrier layer 32 exhibits sufficient barrier properties against oxygen and moisture, stabilizes processability (bag making, deep drawing processability, etc.), and further has pinhole resistance. It is preferably 15 μm or more, particularly preferably 20 μm or more. In consideration of processability, the barrier layer 32 is preferably 80 μm or less.
また、金属箔（特にアルミニウム箔）は酸性物質等によって表面が溶解、腐食しやすい。そこでバリア層３２には耐酸処理を行うことが望ましい。耐酸処理を施すと、電池等の内部からフッ酸等の酸性物質等が発生した場合であっても、バリア層３２の表面が溶解、腐食することを防止できる。更に耐酸処理は、バリア層３２とシーラント層３３との接着性を向上させる効果も奏す。耐酸処理方法としてはクロメート処理が一般的であるが、ベーマイト処理、パーカライジング処理、トリアジンチオール処理等の非クロメート系処理等も可能である。また、耐酸処理はバリア層３２の両面に施しても良いが、シーラント層３３側の面だけに施しても良い。 Moreover, the surface of metal foil (particularly aluminum foil) is easily dissolved and corroded by an acidic substance or the like. Therefore, it is desirable to perform acid resistance treatment on the barrier layer 32. When acid-resistant treatment is performed, the surface of the barrier layer 32 can be prevented from being dissolved and corroded even when an acidic substance such as hydrofluoric acid is generated from the inside of the battery or the like. Furthermore, the acid resistance treatment also has an effect of improving the adhesion between the barrier layer 32 and the sealant layer 33. As the acid-resistant treatment method, chromate treatment is generally used, but non-chromate treatment such as boehmite treatment, parkerizing treatment, triazine thiol treatment, and the like are also possible. The acid resistance treatment may be performed on both surfaces of the barrier layer 32, but may be performed only on the surface on the sealant layer 33 side.
次にシーラント層３３について説明する。本発明に用いられる外装材のシーラント層３３は、図３に示すように、ポリプロピレン層３３ｂのバリア層３２側に外側酸変性ポリプロピレン層３３ａ、発電要素側に内側酸変性ポリプロピレン層３３ａ’が設けられた三層構成をなす。外側酸変性ポリプロピレン層３３ａはバリア層３２とシーラント層３３との接着性向上に、内側酸変性ポリプロピレン層３３ａ’は端子とシーラント層３３との接着性向上に寄与する。また酸変性ポリプロピレンは極性基を持つため、端子やバリア層との接着性に優れる反面、水分バリア性が乏しく、ポリプロピレンよりも更に水分を電池内部へ浸透させやすい。そこで本発明のシーラント層３３は、バリア層３２や端子との接着に直接関与しない中間層をポリプロピレン層３３ｂとする。 Next, the sealant layer 33 will be described. As shown in FIG. 3, the sealant layer 33 of the exterior material used in the present invention is provided with an outer acid-modified polypropylene layer 33a on the barrier layer 32 side of the polypropylene layer 33b and an inner acid-modified polypropylene layer 33a ′ on the power generation element side. It has a three-layer structure. The outer acid-modified polypropylene layer 33 a contributes to improving the adhesion between the barrier layer 32 and the sealant layer 33, and the inner acid-modified polypropylene layer 33 a ′ contributes to improving the adhesion between the terminal and the sealant layer 33. In addition, since acid-modified polypropylene has a polar group, it has excellent adhesion to terminals and barrier layers, but has poor moisture barrier properties, and allows moisture to penetrate more into the battery than polypropylene. Therefore, in the sealant layer 33 of the present invention, an intermediate layer that does not directly participate in adhesion with the barrier layer 32 or the terminal is a polypropylene layer 33b.
ポリプロピレン層３３ｂは、ポリプロピレンホモポリマー、プロピレン・エチレンブロック共重合体、プロピレン・エチレンランダム共重合体、プロピレン・エチレン・ブテンランダム共重合体等のポリプロピレン系樹脂からなる。一方、酸変性ポリプロピレン層３３ａ、３３ａ’は、不飽和カルボン酸やアクリル酸、メタクリル酸、無水マレイン酸等の酸で変性したポリプロピレン系樹脂から形成されるが、端子やバリア層との接着性を考慮すると無水マレイン酸で変性されたポリプロピレンからなることが望ましい。
またポリプロピレン層３３ｂ及び酸変性ポリプロピレン層３３ａ、３３ａ’を成す樹脂は、端部導出部Ｘにおいて端子とバリア層との接触をより確実に防止する為に、熱融着時に潰れ難いことが望ましい。具体的にはＪＩＳ Ｋ７２１０によって測定されるメルトインデックス（以下、ＭＩ）が３ｇ／ｍｉｎ以上、８ｇ／ｍｉｎ未満のものを用いることが望ましく、特にＭＩが３ｇ／ｍｉｎ以上、５ｇ／ｍｉｎ未満のものが望ましい。ＭＩが３ｇ／ｍｉｎ未満であると樹脂を溶融押出成形法にてフィルム状にする場合に、押出機に高負荷がかかる。またＭＩが８ｇ／ｍｉｎを超えると、外装材の端部を熱融着する際に、シール圧によっては、シーラント層３３が潰れて短絡防止機能を発揮できない場合がある。
The polypropylene layer 33b is made of polypropylene resin such as polypropylene homopolymer, propylene / ethylene block copolymer, propylene / ethylene random copolymer, propylene / ethylene / butene random copolymer. On the other hand, the acid-modified polypropylene layers 33a and 33a ′ are formed of a polypropylene resin modified with an acid such as unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic anhydride, etc. In view of the above, it is desirable to be made of polypropylene modified with maleic anhydride.
In addition, it is desirable that the resin forming the polypropylene layer 33b and the acid-modified polypropylene layers 33a and 33a ′ is not easily crushed at the time of heat-sealing in order to more reliably prevent contact between the terminal and the barrier layer in the end lead-out portion X. Specifically, it is desirable to use those having a melt index (hereinafter referred to as MI) measured by JIS K7210 of 3 g / min or more and less than 8 g / min, particularly those having MI of 3 g / min or more and less than 5 g / min. desirable. When MI is less than 3 g / min, a high load is applied to the extruder when the resin is formed into a film by a melt extrusion method. On the other hand, if MI exceeds 8 g / min, the sealant layer 33 may be crushed and the short-circuit preventing function may not be exhibited depending on the seal pressure when heat-sealing the end of the exterior material.
シーラント層３３の厚さは、端子の厚さに合せて決定される。図４は、図３と同様の外装材を用いて製造した、図１に示す薄型リチウム二次電池の端子導出部Ｘ部の拡大図である。熱融着前（即ち、加熱されていない部分）の外側酸変性ポリプロピレン層１０３ａの厚みをαμｍ、ポリプロピレン層１０３ｂの厚みをβμｍ、内側酸変性ポリプロピレン層１０３ａ’の厚みをγμｍとし、正極端子と負極端子のうちの厚い方の厚さをＴμｍとしたとき、シーラント層１０３の厚さ、即ちα＋β＋γは、２Ｔ／３以上、３Ｔ／２以下となるようにする。シーラント層１０３の厚さが２Ｔ／３よりも小さいと、二組の外装材で端子を挟み、外装材の端部を熱融着する際に、バリア層１０２と電極端子１５との距離が縮まるため、電池の短絡の可能性が上がる。逆にシーラント層１０３の厚さが、上記範囲より大きくなっても密封性、短絡防止性の向上は期待できず、薄型リチウム二次電池の嵩が増しコストアップに繋がる。またシーラント層１０３の厚みが増大するにつれ、シーラント層１０３の端面積が増えるため、電池内部に水分が浸透し易くなる。 The thickness of the sealant layer 33 is determined according to the thickness of the terminal. 4 is an enlarged view of a terminal lead-out portion X part of the thin lithium secondary battery shown in FIG. 1 manufactured using the same exterior material as FIG. The thickness of the outer acid-modified polypropylene layer 103a before heat fusion (that is, the unheated portion) is α μm, the thickness of the polypropylene layer 103b is β μm, the thickness of the inner acid-modified polypropylene layer 103a ′ is γ μm, and the positive electrode terminal and the negative electrode When the thicker one of the terminals is T μm, the thickness of the sealant layer 103, that is, α + β + γ is set to be 2T / 3 or more and 3T / 2 or less. When the thickness of the sealant layer 103 is smaller than 2T / 3, the distance between the barrier layer 102 and the electrode terminal 15 is reduced when the terminals are sandwiched between the two sets of exterior materials and the ends of the exterior materials are heat-sealed. This increases the possibility of a short circuit of the battery. On the contrary, even if the thickness of the sealant layer 103 is larger than the above range, improvement in sealing property and short circuit prevention property cannot be expected, and the bulk of the thin lithium secondary battery increases, leading to an increase in cost. Further, as the thickness of the sealant layer 103 increases, the end area of the sealant layer 103 increases, so that moisture easily penetrates into the battery.
次に各層の厚み（α、β、γ）について説明する。外側酸変性ポリプロピレン層１０３ａはバリア層１０２とシーラント層１０３との接着性向上に寄与するが、αが８μｍ未満では接着性が十分でなく、逆にαが２０μｍを越えても接着性の向上は見られず、電池の嵩が増してコストアップに繋がる。更に外側酸変性ポリプロピレン層１０３ａの厚みの増加は電池の水分バリア性を低下させる。これらのことを考慮すると、８μｍ≦α≦２０μｍが適する。
内側酸変性ポリプロピレン層１０３ａ’は端子との接着性に寄与することはもちろん、外装材の端部を熱融着する際に、適度に溶融して端子側面に回り込み、外装材と端子側面との間にできる間隙（図５の「Ｙ」）を埋め、端子周辺を確実に密封させなければならない。よって、内側酸変性ポリプロピレン層１０３ａ’の好適な厚さは、外側変性ポリプロピレン層１０３ａよりも、端子側面に回り込む分、若干大きくなる。具体的には１０μｍ≦γ≦２５μｍが適する。γが１０μｍ未満では密封性が十分でなく、逆にγが２５μｍを越えても密封性、接着性の向上は見られず、電池の嵩が増し、コストアップ、水分バリアー性の低下をもたらすだけである。
尚、本発明によると２Ｔ／３≦α＋β＋γ≦３Ｔ／２であるが、水分バリア性を考慮するとシーラント層１０３における内側及び外側酸変性ポリプロピレン層は接着性、密封性を発現する為に必要な最低限度の厚さとし（即ち、８μｍ≦α≦２０μｍ、１０μｍ≦γ≦２５μｍとし）、その他はポリプロピレン層１０３ｂとすることが望ましい。酸変性ポリプロピレン樹脂は、変性されていないポリプロピレン樹脂よりも親水性であるため、シーラント層における酸変性ポリプロピレン層の厚さ割合が低下するほど、シーラント層の端面から水分が電池内部に侵入し難くなる。
Next, the thickness (α, β, γ) of each layer will be described. The outer acid-modified polypropylene layer 103a contributes to improving the adhesion between the barrier layer 102 and the sealant layer 103. However, if α is less than 8 μm, the adhesion is not sufficient, and conversely, even if α exceeds 20 μm, the adhesion is not improved. It is not seen, and the bulk of the battery increases, leading to an increase in cost. Furthermore, an increase in the thickness of the outer acid-modified polypropylene layer 103a reduces the moisture barrier property of the battery. Considering these matters, 8 μm ≦ α ≦ 20 μm is suitable.
The inner acid-modified polypropylene layer 103a ′ contributes not only to the adhesion to the terminal, but also when the end of the exterior material is heat-sealed, the inner acid-modified polypropylene layer 103a ′ appropriately melts and wraps around the terminal side surface. A gap formed between them (“Y” in FIG. 5) must be filled to securely seal the periphery of the terminal. Therefore, the preferred thickness of the inner acid-modified polypropylene layer 103a ′ is slightly larger than the outer-modified polypropylene layer 103a because it wraps around the terminal side surface. Specifically, 10 μm ≦ γ ≦ 25 μm is suitable. If γ is less than 10 μm, the sealing performance is not sufficient. Conversely, even if γ exceeds 25 μm, no improvement in sealing performance and adhesiveness is observed, the bulk of the battery is increased, the cost is increased, and the moisture barrier property is reduced. It is.
According to the present invention, 2T / 3 ≦ α + β + γ ≦ 3T / 2, but considering the moisture barrier property, the inner and outer acid-modified polypropylene layers in the sealant layer 103 are the minimum necessary for exhibiting adhesiveness and sealing properties. It is desirable that the thickness is the limit (that is, 8 μm ≦ α ≦ 20 μm, 10 μm ≦ γ ≦ 25 μm), and the other is the polypropylene layer 103b. Since the acid-modified polypropylene resin is more hydrophilic than the unmodified polypropylene resin, the lower the thickness ratio of the acid-modified polypropylene layer in the sealant layer, the less moisture enters the battery from the end surface of the sealant layer. .
本発明に用いられる外装材の製造方法は特に限定されないが、例えば、三層のシーラント層をインフレーション共押出法、Ｔダイ共押出法等の公知の製膜方法を用いて製造し、シーラント層にバリア層、基材層を順次積層し、製造することができる。また、予めポリプロピレン層と内側酸変性ポリプロピレン層からなる二層のフィルムを製膜し、該フィルムとバリア層とを溶融状態の酸変性ポリプロピレン樹脂を介して貼り合せ、内側酸変性ポリプロピレン層／ポリプロピレン層／外側酸変性ポリプロピレン層／バリア層の積層体を製造し、その後更に基材層を貼り合わせることによって製造することもできる。 The manufacturing method of the exterior material used in the present invention is not particularly limited. For example, a three-layer sealant layer is manufactured using a known film-forming method such as an inflation co-extrusion method or a T-die co-extrusion method. A barrier layer and a base material layer can be sequentially laminated and manufactured. Also, a two-layer film comprising a polypropylene layer and an inner acid-modified polypropylene layer is formed in advance, and the film and the barrier layer are bonded together via a molten acid-modified polypropylene resin, and the inner acid-modified polypropylene layer / polypropylene layer It can also be produced by producing a laminate of / an outer acid-modified polypropylene layer / barrier layer, and then further laminating a base material layer.
本発明の薄型リチウム二次電池の製造方法は特に限定されないが、例えば正極材の一端に正極端子を溶接し、負極材の一端に負極端子を圧着し、該正極材と該負極材とを電解質を含浸したセパレータを介して積層した後、二組の外装材間に発電要素をセットし、電極端子を挟み込みながら外装材端部を熱融着し、製造することができる。 The manufacturing method of the thin lithium secondary battery of the present invention is not particularly limited. For example, the positive electrode terminal is welded to one end of the positive electrode material, the negative electrode terminal is crimped to one end of the negative electrode material, and the positive electrode material and the negative electrode material are connected to the electrolyte. Can be manufactured by setting the power generation element between two sets of exterior materials and heat-sealing the exterior material end portions while sandwiching the electrode terminals.
次に、以下の方法にて作成した外装材１〜８を用い、本発明の効果を確認した。
＜外装材の作成＞
まず、厚さ９μｍの二軸延伸ポリエチレンテレフタレートフィルム（ＰＥＴ）と厚さ１５μｍの二軸延伸ナイロンフィルム（ＮＹ）とをドライラミネート法にて貼り合せ、これを基材層とする。また片面にクロメート処理を施した厚さ４０μｍのアルミニウム箔（ＡＬ）を用意し、これをバリア層とする。更に中間層がポリプロピレン樹脂（ＰＰ）［ＭＩ＝８．０、融点＝１３８℃］からなり、両外層が酸変性ポリプロピレン樹脂（酸変性ＰＰ）［ＭＩ＝３．５、融点＝１２４℃］からなる三層フィルムをＴダイ共押出法にて成形し、これをシーラント層とする。各層の厚みを表１に記す。バリア層の片面に基材層をドライラミネート法にて積層し、他面（クロメート処理面）にシーラント層を熱ラミネート法にて積層し、外装材を製造する。尚、このとき基材層のＮＹがバリア層と接するよう、積層する。
Next, the effect of this invention was confirmed using the exterior materials 1-8 created with the following method.
<Creation of exterior materials>
First, a biaxially stretched polyethylene terephthalate film (PET) having a thickness of 9 μm and a biaxially stretched nylon film (NY) having a thickness of 15 μm are bonded together by a dry laminating method to form a base material layer. A 40 μm thick aluminum foil (AL) having a chromate treatment on one side is prepared and used as a barrier layer. Further, the intermediate layer is made of polypropylene resin (PP) [MI = 8.0, melting point = 138 ° C.], and both outer layers are made of acid-modified polypropylene resin (acid-modified PP) [MI = 3.5, melting point = 124 ° C.]. A three-layer film is formed by a T-die coextrusion method and used as a sealant layer. The thickness of each layer is shown in Table 1. A base material layer is laminated on one side of the barrier layer by a dry laminating method, and a sealant layer is laminated on the other side (chromate treated surface) by a thermal laminating method to produce an exterior material. At this time, lamination is performed so that NY of the base material layer is in contact with the barrier layer.
幅１５ｍｍ、長さ８ｍｍ、厚さ１００μｍのアルミニウムからなる端子を用い、外装材１乃至８について、密着性試験及び密着性試験後の残存厚みの測定を行い、本発明の効果（接着性、密封性、短絡防止機能）を確認した。
＜密着性試験＞
薄型リチウム二次電池の端子導出部における密封性、接着性を確認する為に、外装材１〜８から１０ｃｍ×１０ｃｍの試験片を二枚用意する。次に二枚の試験片でアルミニウム端子を挟み、１９０℃に加熱したシール機にてシール圧力１ＭＰａで１０秒間シールする。尚、このとき外装材のシーラント層が端子と接するようにする。
その後、オートグラフにてＴ型剥離試験を行い、密着強度を測定した。外装材と端子との接着性が良好であれば密着強度が高くなる。また端子導出部においてシーラント層が端子の周辺部に回り込んでいれば、シーラント層と端子との接触面積が増すため、密着強度が増加する。結果を表２に記す。また外装材２、外装材７については、端子導出部の断面の電子顕微鏡写真を図７、図８に記す。
＜残存厚みの測定＞
上記密着性試験に使用した外装材の、シール後のシーラント層の厚みを測定した。これを残存厚みとして表２に記す。一般にシール後の厚みが厚いほど絶縁性が保持され、短絡が抑制される。端子が８０〜１２０μｍの民生用の電池においては、シール後の厚みが４０μｍを越えていれば、通常、絶縁性は保持され、短絡は抑制される。
Using a terminal made of aluminum having a width of 15 mm, a length of 8 mm, and a thickness of 100 μm, the adhesive materials 1 to 8 were subjected to an adhesion test and a measurement of the remaining thickness after the adhesion test. And short circuit prevention function).
<Adhesion test>
In order to confirm the sealing property and adhesiveness in the terminal lead-out part of the thin lithium secondary battery, two test pieces of 10 cm × 10 cm are prepared from the exterior materials 1 to 8. Next, the aluminum terminal is sandwiched between the two test pieces, and sealed with a sealing machine heated to 190 ° C. at a sealing pressure of 1 MPa for 10 seconds. At this time, the sealant layer of the exterior material is in contact with the terminal.
Thereafter, a T-type peel test was performed with an autograph, and the adhesion strength was measured. If the adhesion between the exterior material and the terminal is good, the adhesion strength becomes high. Further, if the sealant layer wraps around the peripheral portion of the terminal in the terminal lead-out portion, the contact area between the sealant layer and the terminal increases, so that the adhesion strength increases. The results are shown in Table 2. Moreover, about the exterior material 2 and the exterior material 7, the electron micrograph of the cross section of a terminal derivation | leading-out part is described in FIG. 7, FIG.
<Measurement of remaining thickness>
The thickness of the sealant layer after sealing of the exterior material used in the adhesion test was measured. This is shown in Table 2 as the remaining thickness. In general, the greater the thickness after sealing, the better the insulation and the shorter the short circuit. In a consumer battery having a terminal of 80 to 120 μm, if the thickness after sealing exceeds 40 μm, the insulation is usually maintained and short circuit is suppressed.
端子厚み（Ｔ）は１００μｍであるので、シーラント総厚み（α+β+γ）が６６．７〜１５０μｍ、外側酸変性ポリプロピレン層厚み（α）が８〜２０μｍ、内側酸変性ポリプロピレン層厚み（γ）が１０〜２５μｍである外装材１乃至３は、本発明の薄型リチウム二次電池に適用できる。これら外装材１乃至３は密着性試験による密着強度がいずれも１００Ｎ／１５ｍｍを超えており、良好であったが、外側酸変性ＰＰ層（α）が８μｍに満たない外装材６、内側酸変性ＰＰ層（γ）が１０μｍに満たない外装材４、外装材７、外装材８は密着強度が不十分であった。特に、酸変性ＰＰ層を持たない外装材８は端子と接着していなかった。また図７をみると、シーラント層が本発明にて特定する条件を満たす外装材２は、密封試験の際に、シーラント層が端子の周辺部に回り込んでいることが分かる。一方、図８を見ると外装材７は、総厚みが外装材２よりも厚いにもかかわらず、密封試験の際に、シーラント層が端子の周辺部に回りこまず、端子とシーラント層との間に間隙Ａ（図中丸印中の黒い影部分）ができることが分かる。
また総厚みが２Ｔ／３未満である外装材４、５は、何れも残存厚みが４０μｍ以下であった。よって、短絡を十分に抑制できないことが予想される。
Since the terminal thickness (T) is 100 μm, the total sealant thickness (α + β + γ) is 66.7 to 150 μm, the outer acid-modified polypropylene layer thickness (α) is 8 to 20 μm, and the inner acid-modified polypropylene layer thickness (γ ) Is from 10 to 25 μm, and can be applied to the thin lithium secondary battery of the present invention. These exterior materials 1 to 3 were all good in adhesion strength by an adhesion test exceeding 100 N / 15 mm, but the exterior acid modified PP layer (α) was less than 8 μm, and the interior acid modified The exterior material 4, the exterior material 7, and the exterior material 8 whose PP layer (γ) is less than 10 μm had insufficient adhesion strength. In particular, the exterior material 8 having no acid-modified PP layer was not bonded to the terminal. Moreover, when FIG. 7 is seen, in the exterior material 2 which satisfy | fills the conditions which a sealant layer specifies in this invention, it turns out that the sealant layer wraps around the peripheral part of a terminal in the sealing test. On the other hand, when FIG. 8 is seen, although the exterior material 7 is thicker than the exterior material 2, the sealant layer does not wrap around the periphery of the terminal during the sealing test. It can be seen that a gap A (a black shadow portion in a circle in the figure) is formed between them.
The exterior materials 4 and 5 having a total thickness of less than 2T / 3 all had a residual thickness of 40 μm or less. Therefore, it is expected that the short circuit cannot be sufficiently suppressed.
本発明は、外装材としてラミネート材を用いた薄型リチウム二次電池に利用することができる。特に、民生用と呼ばれる比較的小電力の薄型リチウム二次電池に、好適に用いることができる。 The present invention can be used for a thin lithium secondary battery using a laminate material as an exterior material. In particular, it can be suitably used for a comparatively low-power thin lithium secondary battery called consumer use.
１、６ 薄型リチウム二次電池
１０、３０、５０、６０ 外装材
１１、６１ 正極材
１２、６２ 負極材
１３、６３ セパレータ
１４、６４ 発電要素
１５、５５、６５、７１、８１ 正極端子
１６、６６ 負極端子
６７ タブテープ
３１、１０１、７４、８４ 基材層
３１ａ 最外層となる層
３１ｂ バリア層と接する層
３２、１０２、７３、８３ バリア層
３３、１０３、７２、８２ シーラント層
３３ａ、１０３ａ 外側酸変性ポリプロピレン層
３３ｂ、１０３ｂ ポリプロピレン層
３３ａ’、１０３ａ’ 内側酸変性ポリプロピレン層
1,6 Thin lithium secondary battery 10, 30, 50, 60 Exterior material 11, 61 Positive electrode material 12, 62 Negative electrode material 13, 63 Separator 14, 64 Power generation element 15, 55, 65, 71, 81 Positive electrode terminal 16, 66 Negative electrode terminal 67 Tab tape 31, 101, 74, 84 Base material layer 31a Outermost layer 31b Layer 32, 102, 73, 83 Barrier layer 33, 103, 72, 82 Sealant layer 33a, 103a Outer acid modification Polypropylene layer 33b, 103b Polypropylene layer 33a ', 103a' Inner acid-modified polypropylene layer
Claims (2)
前記シーラント層が、バリア層側から順に、外側酸変性ポリプロピレン層／ポリプロピレン層／内側酸変性ポリプロピレン層が積層された三層構造であり、
熱融着前の外側酸変性ポリプロピレン層の厚みをαμｍ、ポリプロピレン層の厚みをβμｍ、内側酸変性ポリプロピレン層の厚みをγμｍとし、前記正極端子と前記負極端子のうちの厚い方の厚さをＴμｍとしたとき、
２Ｔ／３≦α＋β＋γ≦３Ｔ／２
８≦α≦２０
１０≦γ≦２５
であることを特徴とする、薄型リチウム二次電池。 A power generation element including a positive electrode material, a negative electrode material, a separator and an electrolyte is enclosed in an exterior material in which a base material layer, a barrier layer, and a sealant layer are sequentially laminated, and a positive electrode terminal extends from the positive electrode material to the outside of the battery, In the lithium secondary battery in which the exterior material end is heat-sealed so that the negative electrode terminal extends from the negative electrode material to the outside of the battery,
The sealant layer has a three-layer structure in which an outer acid-modified polypropylene layer / a polypropylene layer / an inner acid-modified polypropylene layer are laminated in order from the barrier layer side,
The thickness of the outer acid-modified polypropylene layer before heat fusion is α μm, the thickness of the polypropylene layer is β μm, the thickness of the inner acid-modified polypropylene layer is γ μm, and the thickness of the positive electrode terminal and the negative electrode terminal is T μm When
2T / 3 ≦ α + β + γ ≦ 3T / 2
8 ≦ α ≦ 20
10 ≦ γ ≦ 25
A thin lithium secondary battery, characterized in that
2. The thin lithium secondary battery according to claim 1, wherein T is 80 ≦ T ≦ 120.
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