JP2006253095A - Manufacturing method of nonaqueous electrolyte secondary battery - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 31
- 239000011255 nonaqueous electrolyte Substances 0.000 title claims abstract description 15
- 239000011162 core material Substances 0.000 claims abstract description 48
- 239000004020 conductor Substances 0.000 claims abstract description 24
- 239000011149 active material Substances 0.000 claims description 113
- 239000007773 negative electrode material Substances 0.000 claims description 104
- 239000010410 layer Substances 0.000 claims description 78
- 239000002245 particle Substances 0.000 claims description 48
- 229910052744 lithium Inorganic materials 0.000 claims description 43
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 42
- 239000002344 surface layer Substances 0.000 claims description 35
- 239000011888 foil Substances 0.000 claims description 31
- 229910052751 metal Inorganic materials 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 22
- 239000007769 metal material Substances 0.000 claims description 16
- 238000004804 winding Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 9
- 238000009713 electroplating Methods 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 17
- 239000000463 material Substances 0.000 description 17
- 150000002642 lithium compounds Chemical class 0.000 description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 11
- 239000011889 copper foil Substances 0.000 description 11
- 238000007747 plating Methods 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 239000002002 slurry Substances 0.000 description 10
- 239000010949 copper Substances 0.000 description 8
- 239000008151 electrolyte solution Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 229910052802 copper Inorganic materials 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000000635 electron micrograph Methods 0.000 description 5
- -1 or even if formed Inorganic materials 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 238000003411 electrode reaction Methods 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 239000002210 silicon-based material Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000011800 void material Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 230000037303 wrinkles Effects 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 210000001787 dendrite Anatomy 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 238000013507 mapping Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000000116 mitigating effect Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 238000005488 sandblasting Methods 0.000 description 2
- KFJDQPJLANOOOB-UHFFFAOYSA-N 2h-benzotriazole-4-carboxylic acid Chemical compound OC(=O)C1=CC=CC2=NNN=C12 KFJDQPJLANOOOB-UHFFFAOYSA-N 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013372 LiC 4 Inorganic materials 0.000 description 1
- 229910013470 LiC1 Inorganic materials 0.000 description 1
- 229910012513 LiSbF 6 Inorganic materials 0.000 description 1
- 241000080590 Niso Species 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- 229910001080 W alloy Inorganic materials 0.000 description 1
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- CKFRRHLHAJZIIN-UHFFFAOYSA-N cobalt lithium Chemical compound [Li].[Co] CKFRRHLHAJZIIN-UHFFFAOYSA-N 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
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- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 235000015110 jellies Nutrition 0.000 description 1
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- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Inorganic materials [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 1
- RSNHXDVSISOZOB-UHFFFAOYSA-N lithium nickel Chemical compound [Li].[Ni] RSNHXDVSISOZOB-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
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- 238000005065 mining Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- MOWMLACGTDMJRV-UHFFFAOYSA-N nickel tungsten Chemical compound [Ni].[W] MOWMLACGTDMJRV-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- 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
Abstract
Description
本発明は、リチウム二次電池等の非水電解液二次電池の製造方法及び非水電解液二次電池に関する。 The present invention relates to a method for producing a nonaqueous electrolyte secondary battery such as a lithium secondary battery and a nonaqueous electrolyte secondary battery.
リチウム二次電池等の非水電解液二次電池のエネルギー密度を向上させるためには、電池に対する活物質の量を増大させる必要がある。そのためには、電池の構成部材の一つである集電体を薄くすることが考えられる。これによって、例えばジェリー・ロールタイプの電池を作製する場合には、巻き数を多くすることができ、電池の容量を高めることが可能となる。例えば特許文献１には、集電体として用いられる銅箔の両面に活物質層を形成してなる負極において、銅箔の厚さを０．１μｍから７μｍとしたものが提案されている。 In order to improve the energy density of a non-aqueous electrolyte secondary battery such as a lithium secondary battery, it is necessary to increase the amount of active material for the battery. For this purpose, it is conceivable to thin the current collector, which is one of the constituent members of the battery. Accordingly, for example, when a battery of a jelly roll type is manufactured, the number of windings can be increased, and the capacity of the battery can be increased. For example, Patent Document 1 proposes a negative electrode in which an active material layer is formed on both sides of a copper foil used as a current collector, and the thickness of the copper foil is 0.1 μm to 7 μm.
しかし、巻き数を多くすると、巻回体の中心部付近と外周部付近とで巻き径の相違に起因して、負極等に伸びが生じ、それが原因で負極等が断裂するおそれがある。このことは、円筒状の巻回体を加圧して扁平な角型パッケージを製造するときに特に顕著となる。 However, when the number of windings is increased, the negative electrode or the like may be stretched due to the difference in the winding diameter between the central portion and the outer peripheral portion of the wound body, which may cause the negative electrode or the like to break. This is particularly noticeable when a flat rectangular package is manufactured by pressing a cylindrical wound body.
従って本発明の目的は、前述した従来技術が有する欠点を解消し得るリチウム二次電池等の非水電解液二次電池の製造方法及び非水電解液二次電池を提供することにある。 Accordingly, an object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery such as a lithium secondary battery and the like and the non-aqueous electrolyte secondary battery capable of eliminating the above-described drawbacks of the prior art.
本発明は、それぞれ長尺帯状の形状である、正極と、第１のセパレータと、厚膜導電体を有していない第１の負極と、導電性芯材と、厚膜導電体を有していない第２の負極とをこの順で重ね合わせ、更に正極の外側又は第２の負極の外側に第２のセパレータを配し、次いで第２のセパレータが内側となるようにこれらを巻回することを特徴とする非水電解液二次電池の製造方法を提供することにより前記目的を達成したものである。 The present invention includes a positive electrode, a first separator, a first negative electrode that does not have a thick film conductor, a conductive core material, and a thick film conductor, each of which has a long strip shape. The second negative electrode is overlapped in this order, and a second separator is arranged outside the positive electrode or outside the second negative electrode, and then these are wound so that the second separator is inside. The object is achieved by providing a method for producing a non-aqueous electrolyte secondary battery.
また本発明は、それぞれ長尺帯状の形状である、正極と、第１のセパレータと、厚膜導電体を有していない第１の負極と、導電性芯材と、厚膜導電体を有していない第２の負極とがこの順で重ね合わされ、更に正極の外側又は第２の負極の外側に第２のセパレータが配された重ね合わせ体が、第２のセパレータが内側となるように巻回されてなる巻回体を備えたリチウム二次電池であって、
第１及び第２の負極と導電性芯材との間が、剥離可能なように電気的に接していることを特徴とする非水電解液二次電池を提供することにより前記目的を達成したものである。
The present invention also includes a positive electrode, a first separator, a first negative electrode that does not have a thick film conductor, a conductive core material, and a thick film conductor, each of which has a long strip shape. The superposed body in which the second negative electrode that has not been superposed is superposed in this order, and the second separator is disposed outside the positive electrode or outside the second negative electrode so that the second separator is inside. A lithium secondary battery having a wound body that is wound,
The object is achieved by providing a non-aqueous electrolyte secondary battery characterized in that the first and second negative electrodes and the conductive core material are in electrical contact so as to be peelable. Is.
本発明によれば、電池作製時の電極等の巻き上げ操作における電極の断裂を防止することができる。 According to the present invention, it is possible to prevent the electrodes from being broken during the winding operation of the electrodes and the like during battery production.
以下本発明を、その好ましい実施形態に基づき図面を参照しながら説明する。本実施形態では、角型パッケージと呼ばれる電池を作製する。本実施形態の製造方法は、厚膜導電体を有していない負極を用い、且つ該負極を導電性芯材と共に巻回するという構成を採用することで特徴付けられる。本実施形態の製造方法と異なり、従来の電池の製造方法においては、一般に集電体と呼ばれる集電用の厚膜導電体（例えば厚さ１２〜３５μｍ程度の金属箔やエキスパンドメタル）の少なくとも一面に負極活物質の層が形成された負極を、セパレータや正極と共に巻回していた。即ち、本実施形態の製造方法では、従来の方法で一体として巻回されていた負極活物質の層と厚膜導電体とからなる負極に代えて、負極活物質から実質的になる部材と、厚膜導電体とを別個の部材として取り扱い、これら別個の部材を重ね合わせて巻回している。従って、以下の説明においては、本実施形態の負極、即ち負極活物質から実質的になり且つ厚膜導電体を有していない負極が、従来の電池における負極、即ち厚膜導電体上に負極活物質の層が一体的に形成されてなる負極と異なる構造を有することを明確にする目的で、本実施形態の負極のことを負極用活物質シートと称する。 The present invention will be described below based on preferred embodiments with reference to the drawings. In this embodiment, a battery called a square package is manufactured. The manufacturing method of this embodiment is characterized by employing a configuration in which a negative electrode not having a thick film conductor is used and the negative electrode is wound together with a conductive core material. Unlike the manufacturing method of the present embodiment, in a conventional battery manufacturing method, at least one surface of a thick film conductor for current collection (for example, a metal foil or expanded metal having a thickness of about 12 to 35 μm) generally called a current collector The negative electrode on which the negative electrode active material layer was formed was wound together with the separator and the positive electrode. That is, in the manufacturing method of the present embodiment, instead of the negative electrode composed of the negative electrode active material layer and the thick film conductor that are integrally wound by the conventional method, a member substantially composed of the negative electrode active material; The thick film conductor is handled as a separate member, and these separate members are overlapped and wound. Therefore, in the following description, the negative electrode of the present embodiment, that is, the negative electrode that is substantially composed of the negative electrode active material and does not have the thick film conductor, is the negative electrode in the conventional battery, that is, the negative electrode on the thick film conductor. In order to clarify that the active material layer has a structure different from that of the negative electrode formed integrally, the negative electrode of this embodiment is referred to as a negative electrode active material sheet.
図１には、本実施形態に用いられる負極用活物質シートの一例が示されている。負極用活物質シート１０は、表裏一対の面である第１の面１ａ及び第２の面１ｂを有している。負極用活物質シート１０は、活物質層２を備えている。活物質層２は、該層２の各面にそれぞれ形成された一対の表面層３ａ，３ｂによって連続的に被覆されている。各表面層３ａ，３ｂは、第１の面１ａ及び第２の面１ｂをそれぞれ含んでいる。また図１から明らかなように負極用活物質シート１０は、従来の電極に用いられてきた集電体と呼ばれる集電用の厚膜導電体を有していない。 FIG. 1 shows an example of a negative electrode active material sheet used in the present embodiment. The negative electrode active material sheet 10 has a first surface 1a and a second surface 1b which are a pair of front and back surfaces. The negative electrode active material sheet 10 includes an active material layer 2. The active material layer 2 is continuously covered with a pair of surface layers 3 a and 3 b formed on each surface of the layer 2. Each surface layer 3a, 3b includes a first surface 1a and a second surface 1b, respectively. As is clear from FIG. 1, the negative electrode active material sheet 10 does not have a current collecting thick film conductor called a current collector, which has been used for conventional electrodes.
表面層３ａ，３ｂは導電性を有し、本実施形態の負極用活物質シート１０と、後述する導電性芯材とを電気的に導通させる機能を担っている。また表面層３ａ，３ｂは、活物質層２に含まれる活物質が充放電に起因して体積変化し微粉化して脱落することを防止するためにも用いられている。 The surface layers 3a and 3b have conductivity and have a function of electrically connecting the negative electrode active material sheet 10 of the present embodiment and a conductive core material described later. The surface layers 3a and 3b are also used to prevent the active material contained in the active material layer 2 from changing in volume due to charging / discharging and being pulverized and falling off.
各表面層３ａ，３ｂは、従来の電極に用いられている集電用の厚膜導電体よりもその厚みが薄いものである。具体的には０．３〜１０μｍ程度、特に０．４〜８μｍ程度、とりわけ０．５〜５μｍ程度の薄層であることが好ましい。これによって、必要最小限の厚みで活物質層２をほぼ満遍なく連続的に被覆することができる。その結果、微粉化した活物質の脱落を防止することができる。前記範囲の表面層３ａ，３ｂは、後述する実施例のように電解めっきによって形成されることが好ましい。なお２つの表面層３ａ，３ｂはその厚みが同じでもよく、或いは異なっていてもよい。 Each surface layer 3a, 3b is thinner than the thick film conductor for current collection used in the conventional electrode. Specifically, a thin layer of about 0.3 to 10 μm, particularly about 0.4 to 8 μm, particularly about 0.5 to 5 μm is preferable. As a result, the active material layer 2 can be continuously coated almost uniformly with the minimum necessary thickness. As a result, the pulverized active material can be prevented from falling off. The surface layers 3a and 3b in the above range are preferably formed by electrolytic plating as in the examples described later. The two surface layers 3a and 3b may have the same thickness or different thicknesses.
各表面層３ａ，３ｂは、非水電解液二次電池の集電体となり得る金属から構成されている。そのような金属としては例えば、リチウム化合物の形成能の低い元素が挙げられる。リチウム化合物の形成能の低い元素としては銅、ニッケル、鉄、コバルト又はこれらの金属の合金などが挙げられる。これらの金属のうち銅若しくはニッケル又はそれらの合金を用いることが特に好適である。特に、ニッケル−タングステン合金を用いると、表面層３ａ，３ｂを高強度となすことができるので好ましい。２つの表面層３ａ，３ｂは、その構成材料が同じであってもよく、或いは異なっていてもよい。「リチウム化合物の形成能が低い」とは、リチウムと金属間化合物若しくは固溶体を形成しないか、又は形成したとしてもリチウムが微量であるか若しくは非常に不安定であることを意味する。 Each surface layer 3a, 3b is comprised from the metal which can become a collector of a nonaqueous electrolyte secondary battery. Examples of such a metal include an element having a low ability to form a lithium compound. Examples of the element having a low ability to form a lithium compound include copper, nickel, iron, cobalt, and alloys of these metals. Of these metals, it is particularly preferable to use copper or nickel or an alloy thereof. In particular, it is preferable to use a nickel-tungsten alloy because the surface layers 3a and 3b can have high strength. The two surface layers 3a and 3b may have the same or different constituent materials. “Lithium compound forming ability is low” means that lithium does not form an intermetallic compound or solid solution, or even if formed, lithium is in a very small amount or very unstable.
各表面層３ａ，３ｂ間に位置する活物質層２は、活物質の粒子２ａを含んでいる。活物質層２は例えば、活物質の粒子２ａを含む導電性スラリーを塗布して形成されている。 The active material layer 2 positioned between the surface layers 3a and 3b includes active material particles 2a. The active material layer 2 is formed, for example, by applying a conductive slurry containing active material particles 2a.
活物質としては、例えばシリコン系材料やスズ系材料、アルミニウム系材料、ゲルマニウム系材料、グラファイトが挙げられる。特に、高容量の材料であるシリコン系材料が好ましい。活物質層２は２つの表面層３ａ，３ｂによって被覆されているので、充放電に起因して活物質が微粉化して脱落することが効果的に防止される。また、後述する孔が活物質層２に形成されていることによって、活物質の粒子２ａは電解液と接することができるので、電極反応が妨げられることもない。 Examples of the active material include silicon materials, tin materials, aluminum materials, germanium materials, and graphite. In particular, a silicon-based material that is a high-capacity material is preferable. Since the active material layer 2 is covered with the two surface layers 3a and 3b, the active material is effectively prevented from being pulverized and falling off due to charge / discharge. In addition, since the active material layer 2 has holes to be described later, the active material particles 2a can be in contact with the electrolytic solution, so that the electrode reaction is not hindered.
活物質の粒子２ａはその最大粒径が好ましくは３０μｍ以下であり、更に好ましくは１０μｍ以下である。また粒子の粒径をＤ50値で表すと０．１〜８μｍ、特に０．３〜２μｍであることが好ましい。最大粒径が３０μｍ超であると、粒子の脱落が起こりやすくなり、電極の寿命が短くなる場合がある。粒径の下限値に特に制限はなく小さいほど好ましい。該粒子の製造方法に鑑みると、下限値は０．０１μｍ程度である。粒子の粒径は、レーザ回折散乱式粒度分布測定、電子顕微鏡観察によって測定される。 The active material particles 2a preferably have a maximum particle size of 30 μm or less, and more preferably 10 μm or less. Moreover, when the particle diameter of the particle is expressed by a D 50 value, it is preferably 0.1 to 8 μm, particularly preferably 0.3 to 2 μm. When the maximum particle size is more than 30 μm, the particles are likely to fall off, and the life of the electrode may be shortened. There is no particular limitation on the lower limit of the particle size, and the smaller the better. In view of the method for producing the particles, the lower limit is about 0.01 μm. The particle size of the particles is measured by laser diffraction / scattering particle size distribution measurement or electron microscope observation.
負極用活物質シート全体に対する活物質の量が少なすぎると電池のエネルギー密度を十分に向上させにくく、逆に多すぎると活物質の脱落が起こりやすくなる傾向にある。これらを勘案すると、活物質の量は負極用活物質シートに対して好ましくは５〜８０重量％であり、更に好ましくは１０〜５０重量％、一層好ましくは２０〜５０重量％である。 If the amount of the active material relative to the whole negative electrode active material sheet is too small, it is difficult to sufficiently improve the energy density of the battery. Conversely, if the amount is too large, the active material tends to fall off. Considering these, the amount of the active material is preferably 5 to 80% by weight, more preferably 10 to 50% by weight, and still more preferably 20 to 50% by weight with respect to the negative electrode active material sheet.
活物質層２の厚みは、負極全体に対する活物質の量の割合や活物質の粒径に応じて適宜調節することができ、本実施形態においては特に臨界的なものではない。一般には１〜１００μｍ、特に３〜６０μｍ程度である。活物質層は、後述する実施例のように、活物質の粒子を含む導電性スラリーを塗布することによって形成されることが好ましい。 The thickness of the active material layer 2 can be appropriately adjusted according to the ratio of the amount of the active material to the whole negative electrode and the particle size of the active material, and is not particularly critical in the present embodiment. Generally, the thickness is about 1 to 100 μm, particularly about 3 to 60 μm. The active material layer is preferably formed by applying a conductive slurry containing active material particles, as in the examples described later.
活物質層２においては、図１に示すように、該層中に含まれる粒子間に、リチウム化合物の形成能の低い金属材料４が浸透している。金属材料４は、電解めっきによって粒子間に析出したものである。金属材料４は、活物質層２の厚み方向全域に亘って浸透していることが好ましい。そして浸透した当該材料中に活物質の粒子２ａが存在していることが好ましい。つまり活物質の粒子２ａは負極用活物質シート１０の表面に実質的に露出しておらず表面層３ａ，３ｂの内部に包埋されていることが好ましい。これによって、活物質層２と表面層３ａ，３ｂとの密着性が強固なものとなり、活物質の脱落が一層防止される。また活物質層２中に浸透した前記材料４を通じて表面層３ａ，３ｂと活物質との間に電子伝導性が確保されるので、電気的に孤立した活物質が生成すること、特に活物質層２の深部に電気的に孤立した活物質が生成することが効果的に防止され、集電機能が保たれる。その結果、負極としての機能低下が抑えられる。更に長寿命化も図られる。このことは、活物質として半導体であり電子伝導性の乏しい材料、例えばシリコン系材料を用いる場合に特に有利である。 In the active material layer 2, as shown in FIG. 1, a metal material 4 having a low lithium compound forming ability penetrates between particles contained in the layer. The metal material 4 is deposited between the particles by electrolytic plating. It is preferable that the metal material 4 penetrates over the entire thickness direction of the active material layer 2. The active material particles 2a are preferably present in the permeated material. That is, it is preferable that the active material particles 2a are not substantially exposed on the surface of the negative electrode active material sheet 10 and are embedded in the surface layers 3a and 3b. Thereby, the adhesiveness between the active material layer 2 and the surface layers 3a and 3b becomes strong, and the active material is further prevented from falling off. In addition, since electronic conductivity is ensured between the surface layers 3a and 3b and the active material through the material 4 that has penetrated into the active material layer 2, an electrically isolated active material can be generated, particularly the active material layer. The generation of an electrically isolated active material in the deep part of 2 is effectively prevented, and the current collecting function is maintained. As a result, functional degradation as a negative electrode is suppressed. In addition, the life can be extended. This is particularly advantageous when a material that is a semiconductor and has poor electron conductivity, such as a silicon-based material, is used as the active material.
活物質層２中に浸透しているリチウム化合物の形成能の低い金属材料４は導電性を有するものであり、その例としては銅、ニッケル、鉄、コバルト又はこれらの金属の合金などの金属材料が挙げられる。当該材料は、表面層３ａ，３ｂを構成する材料と同種の材料であってもよく、或いは異種の材料であってもよい。 The metal material 4 having a low ability to form a lithium compound penetrating into the active material layer 2 has conductivity, and examples thereof include metal materials such as copper, nickel, iron, cobalt, and alloys of these metals. Is mentioned. The material may be the same type of material as that constituting the surface layers 3a and 3b, or may be a different type of material.
活物質層２中に浸透しているリチウム化合物の形成能の低い金属材料４は、活物質層２をその厚み方向に貫いていることが好ましい。それによって２つの表面層３ａ，３ｂは金属材料４を通じて電気的に導通することになり、負極用活物質シート１０全体としての電子伝導性が一層高くなる。リチウム化合物の形成能の低い金属材料４が活物質層２の厚み方向全域に亘って浸透していることは、該材料を測定対象とした電子顕微鏡マッピングによって確認できる。リチウム化合物の形成能の低い金属材料４を、電解めっきによって活物質層２中に浸透している。 It is preferable that the metal material 4 having a low ability of forming a lithium compound penetrating into the active material layer 2 penetrates the active material layer 2 in the thickness direction. Thereby, the two surface layers 3a and 3b are electrically connected through the metal material 4, and the electron conductivity of the negative electrode active material sheet 10 as a whole is further increased. The permeation of the metal material 4 having a low lithium compound forming ability throughout the thickness direction of the active material layer 2 can be confirmed by electron microscope mapping using the material as a measurement target. A metal material 4 having a low lithium compound forming ability penetrates into the active material layer 2 by electrolytic plating.
活物質層２における活物質の粒子２ａの間は、リチウム化合物の形成能の低い金属材料４で完全に満たされているのではなく、該粒子間に空隙が存在していることが好ましい。この空隙の存在によって、充放電に起因する活物質の粒子２ａの体積変化が緩和される。この観点から、活物質層２における空隙の割合は０．１〜３０体積％程度、特に０．５〜５体積％程度であることが好ましい。空隙の割合は、電子顕微鏡マッピングによって求めることができる。活物質層２は活物質の粒子２ａを含む導電性スラリーを塗布し乾燥させることによって形成されることから、活物質層２には自ずと空隙が形成される。従って空隙の割合を前記範囲にするためには、例えば活物質の粒子２ａの粒径、導電性スラリーの組成、スラリーの塗布条件を適切に選択すればよい。またスラリーを塗布乾燥して活物質層２を形成した後、適切な条件下でプレス加工して空隙の割合を調整してもよい。 The space between the active material particles 2a in the active material layer 2 is preferably not completely filled with the metal material 4 having a low lithium compound forming ability, but preferably has voids between the particles. Due to the presence of the voids, the volume change of the active material particles 2a due to charging / discharging is alleviated. From this viewpoint, the proportion of voids in the active material layer 2 is preferably about 0.1 to 30% by volume, particularly about 0.5 to 5% by volume. The void ratio can be determined by electron microscope mapping. Since the active material layer 2 is formed by applying and drying a conductive slurry containing the active material particles 2 a, voids are naturally formed in the active material layer 2. Accordingly, in order to set the void ratio within the above range, for example, the particle diameter of the active material particles 2a, the composition of the conductive slurry, and the application conditions of the slurry may be appropriately selected. In addition, after the slurry is applied and dried to form the active material layer 2, the proportion of voids may be adjusted by pressing under appropriate conditions.
活物質層中には活物質の粒子２ａに加えて導電性炭素材料が含まれていても良い。これによって負極用活物質シート１０に電子伝導性が一層付与される。例えば、先に述べた導電性スラリーを用いて活物質層を形成する場合には、該スラリー中に好ましくは０．１〜２０重量％、更に好ましくは１〜１０重量％の導電性炭素材料を配合することで、十分な電子伝導性を付与することができる。導電性炭素材料としては例えばアセチレンブラックやグラファイトなどの粒子が用いられる。これらの粒子の粒径は４０μｍ以下、特に２０μｍ以下であることが、電子伝導性の一層付与の点から好ましい。該粒子の粒径の下限値に特に制限はなく小さいほど好ましい。該粒子の製造方法に鑑みると、その下限値は０．０１μｍ程度となる。 The active material layer may contain a conductive carbon material in addition to the active material particles 2a. This further imparts electronic conductivity to the negative electrode active material sheet 10. For example, when an active material layer is formed using the conductive slurry described above, the conductive carbon material is preferably 0.1 to 20 wt%, more preferably 1 to 10 wt% in the slurry. By blending, sufficient electron conductivity can be imparted. For example, particles such as acetylene black and graphite are used as the conductive carbon material. The particle diameter of these particles is preferably 40 μm or less, and particularly preferably 20 μm or less from the viewpoint of further imparting electron conductivity. The lower limit of the particle size of the particles is not particularly limited and is preferably as small as possible. In view of the method for producing the particles, the lower limit is about 0.01 μm.
図１に示すように、負極用活物質シート１０においては、その各表面において開孔し且つ活物質層２及び各表面層３ａ，３ｂの厚み方向に延びる孔５を多数有している。孔５は、負極用活物質シート１０の厚み方向に貫通している。活物質層２においては、孔５の壁面において活物質層２が露出している。孔５の役割は大別して次の２つである。 As shown in FIG. 1, the negative electrode active material sheet 10 has a large number of holes 5 that are open on each surface and extend in the thickness direction of the active material layer 2 and the surface layers 3 a and 3 b. The holes 5 penetrate through the negative electrode active material sheet 10 in the thickness direction. In the active material layer 2, the active material layer 2 is exposed on the wall surface of the hole 5. The role of the hole 5 is roughly divided into the following two.
一つは、孔５の壁面において露出した活物質層２を通じて電解液を活物質層内に供給する役割である。この場合、孔５の壁面において活物質層２が露出しているが、活物質層内の活物質の粒子２ａ間に金属材料４が浸透しているので、該粒子２ａが脱落することが防止されている。 One is the role of supplying the electrolytic solution into the active material layer through the active material layer 2 exposed on the wall surface of the hole 5. In this case, the active material layer 2 is exposed on the wall surface of the hole 5, but the metal material 4 permeates between the active material particles 2a in the active material layer, so that the particles 2a are prevented from falling off. Has been.
もう一つは、充放電に起因して活物質層内の活物質の粒子２ａが体積変化した場合、その体積変化を緩和する役割である。体積変化は、主として負極用活物質シート１０の平面方向に生ずる。従って、充電によって活物質の粒子２ａの体積が増加しても、その増加分が、空間となっている孔５に吸収される。その結果、負極用活物質シート１０の著しい変形が効果的に防止される。 The other is the role of relaxing the volume change when the volume of the active material particles 2a in the active material layer changes due to charge / discharge. The volume change occurs mainly in the planar direction of the negative electrode active material sheet 10. Therefore, even if the volume of the active material particles 2a is increased by charging, the increased amount is absorbed by the holes 5 which are spaces. As a result, significant deformation of the negative electrode active material sheet 10 is effectively prevented.
負極用活物質シート１０の表面において開孔している孔５の開孔率、即ち孔５の面積の総和を、負極用活物質シート１０の表面の見掛けの面積で除して１００を乗じた値は、好ましくは０．３〜３０％、更に好ましくは２〜１５％であることが、活物質層内に電解液を十分に供給する観点及び活物質の粒子２ａの体積変化を効果的に緩和する観点から有効である。本実施形態においては、負極用活物質シート１０の第１の面１ａ及び第２の面１ｂの何れにおいても孔５が開孔しており、且つ面１ａ，１ｂの同位置に実質的に同寸で開孔しているので、面１ａの開孔率と面１ｂの開孔率とは実質的に同じになっている。しかし、各面での開孔率は同じである必要はなく、少なくとも一方の面における開孔率が前述の範囲内であれば、所期の目的は達成される。 The opening ratio of the holes 5 opened on the surface of the negative electrode active material sheet 10, that is, the total area of the holes 5, was divided by the apparent area of the surface of the negative electrode active material sheet 10 and multiplied by 100. The value is preferably 0.3 to 30%, more preferably 2 to 15%, in order to effectively supply the electrolytic solution into the active material layer and to change the volume of the active material particles 2a effectively. It is effective from the viewpoint of mitigating. In the present embodiment, the hole 5 is open on both the first surface 1a and the second surface 1b of the negative electrode active material sheet 10, and substantially the same position on the surfaces 1a and 1b. Since the holes are sized, the opening ratio of the surface 1a and the opening ratio of the surface 1b are substantially the same. However, the aperture ratios on each surface do not need to be the same. If the aperture ratio on at least one surface is within the above range, the intended purpose is achieved.
孔５の開孔率を前記の範囲に設定することに加えて、負極用活物質シート１０の表面において開孔している孔５の直径は、好ましくは５〜５００μｍ、更に好ましくは２０〜１００μｍであることが、活物質層内に電解液を十分に供給する観点及び活物質の粒子２ａの体積変化を効果的に緩和する観点から有効である。なお、前述した通り、本実施形態においては、負極用活物質シート１０の第１の面１ａにおいて開孔している孔５の直径と、第２の面１ｂにおいて開孔している孔５の直径とは同じになっているが、両者は異なっていてもよい。また、第１の面１ａにおいて開孔している孔５の直径は何れも同じになっているが、前記の範囲の直径を満たす限り、異なる直径の孔５が形成されていてもよい。更に、本発明の効果を損なわない範囲において、前記の範囲外の直径を有する孔が小数形成されていてもよい。これらのことは、第２の面１ｂに関しても同様である。 In addition to setting the opening ratio of the holes 5 in the above range, the diameter of the holes 5 opened on the surface of the negative electrode active material sheet 10 is preferably 5 to 500 μm, more preferably 20 to 100 μm. It is effective from the viewpoint of sufficiently supplying the electrolytic solution into the active material layer and from the viewpoint of effectively mitigating the volume change of the active material particles 2a. As described above, in the present embodiment, the diameter of the hole 5 opened in the first surface 1a of the negative electrode active material sheet 10 and the hole 5 opened in the second surface 1b. The diameter is the same, but they may be different. In addition, the diameters of the holes 5 opened in the first surface 1a are the same, but holes 5 having different diameters may be formed as long as the diameters in the above range are satisfied. Furthermore, in a range that does not impair the effects of the present invention, a small number of holes having a diameter outside the above range may be formed. The same applies to the second surface 1b.
前述の開孔率及び直径と関係するが、孔５のピッチも重要である。ピッチを好ましくは２０〜６００μｍに設定することで、活物質層内に電解液を十分に供給でき、また活物質の粒子２ａの体積変化を効果的に緩和できるようになる。ピッチは、隣り合う孔５の中心を結ぶ長さで定義される。孔５の配置がランダムな場合には、平均値をもってピッチの値とする。本実施形態においては、負極用活物質シート１０の第１の面１ａにおけるピッチと、第２の面１ｂにおけるピッチは実質的に同じになっている。しかし、各面でのピッチは同じである必要はなく、少なくとも一方の面におけるピッチが前述の範囲内であれば、所期の目的は達成される。 The pitch of the holes 5 is also important, although it is related to the aforementioned open area ratio and diameter. By setting the pitch to preferably 20 to 600 μm, the electrolytic solution can be sufficiently supplied into the active material layer, and the volume change of the active material particles 2a can be effectively mitigated. The pitch is defined by the length connecting the centers of the adjacent holes 5. If the arrangement of the holes 5 is random, the average value is used as the pitch value. In the present embodiment, the pitch on the first surface 1a of the negative electrode active material sheet 10 and the pitch on the second surface 1b are substantially the same. However, the pitch on each surface does not need to be the same. If the pitch on at least one surface is within the aforementioned range, the intended purpose is achieved.
孔５は、負極用活物質シート１０の第１の面１ａ及び第２の面１ｂの何れにおいても、均一に分布していることが好ましい。この観点から、負極用活物質シート１０の表面における任意の部分に着目したとき、１ｃｍ×１ｃｍの正方形の観察視野内に平均して１００〜２５００００個、特に１０００〜４００００個、とりわけ５０００〜２００００個の孔５が開孔していることが好ましい。 It is preferable that the holes 5 are uniformly distributed on both the first surface 1 a and the second surface 1 b of the negative electrode active material sheet 10. From this point of view, when paying attention to an arbitrary part on the surface of the negative electrode active material sheet 10, an average of 100 to 250,000, particularly 1000 to 40000, particularly 5000 to 20000, in a 1 cm × 1 cm square observation visual field. The holes 5 are preferably open.
負極用活物質シート１０においては、孔５は負極用活物質シート１０の厚さ方向に貫通している。しかし、活物質層内に電解液を十分に供給し、また活物質の粒子２ａの体積変化を緩和するという孔５の役割に鑑みると、孔５は負極用活物質シート１０の厚さ方向に貫通している必要はなく、負極用活物質シート１０の表面において開孔し且つ少なくとも活物質層２において、その厚さ方向に延びていればよい。孔５が負極用活物質シート１０の一方の面のみで開孔している場合には、電解液の流通を確保する観点から、負極用活物質シート１０の二つの面のうち、セパレータと対向する面において孔５が開孔していることが好ましい。 In the negative electrode active material sheet 10, the holes 5 penetrate in the thickness direction of the negative electrode active material sheet 10. However, in view of the role of the holes 5 to sufficiently supply the electrolytic solution into the active material layer and relieve the volume change of the active material particles 2 a, the holes 5 extend in the thickness direction of the negative electrode active material sheet 10. It is not necessary to penetrate, and it is sufficient that the hole is formed in the surface of the negative electrode active material sheet 10 and extends in the thickness direction at least in the active material layer 2. When the hole 5 is opened only on one surface of the negative electrode active material sheet 10, it faces the separator among the two surfaces of the negative electrode active material sheet 10 from the viewpoint of ensuring the flow of the electrolytic solution. It is preferable that the hole 5 is opened in the surface to be performed.
孔５は、例えばレーザ加工によって形成することができる。或いは針やポンチによって機械的に穿孔を行うこともできる。更に、サンドブラスト加工によって穿孔を行うこともできる。また、活物質の粒子を含む活物質層の表面に、表面層３ａ，３ｂを電解めっきで形成することによって、負極用活物質シート１０の厚み方向に延びる孔（微細空隙）を形成することも可能である（後述する実施例１における図８参照）。尤も、孔の径やピッチを正確に制御する観点からは、レーザ加工、機械的穿孔、サンドブラスト加工などを用いることが好ましい。 The hole 5 can be formed by, for example, laser processing. Alternatively, drilling can be performed mechanically with a needle or punch. Further, the perforation can be performed by sandblasting. Moreover, the surface layer 3a, 3b may be formed on the surface of the active material layer containing the particles of the active material by electrolytic plating to form a hole (a fine void) extending in the thickness direction of the negative electrode active material sheet 10. It is possible (see FIG. 8 in Example 1 described later). However, from the viewpoint of accurately controlling the diameter and pitch of the holes, it is preferable to use laser machining, mechanical drilling, sandblasting, or the like.
以上の構成を有する負極用活物質シート１０を用いた本発明の製造方法の一実施形態を図２に示す。図２に示すように、先ず、電池を構成する各部材を重ね合わせる。ここで用いられる構成部材は、第１のセパレータＳ１、第２のセパレータＳ２、正極Ｃ、第１の負極用活物質シートＡ１、第２の負極用活物質シートＡ２、及び導電性芯材Ｆである。これらの部材はすべて長尺帯状の形状をしている。これらの部材はすべて同幅になっている。第１のセパレータＳ１と第２のセパレータＳ２とは同一のものでもよく、或いは異なっていてもよい。同様に、第１の負極用活物質シートＡ１と第２の負極用活物質シートＡ２とは同一のものでもよく、或いは異なっていてもよい。導電性芯材Ｆの長手方向の一側縁部には、芯材Ｆの長手方向と直交する方向に延びるタブＴ１が取り付けられている。同様に、正極Ｃの長手方向の一側縁部には、正極Ｃの長手方向と直交する方向に延びるタブＴ２が取り付けられている。タブＴ１，Ｔ２は、それぞれ電流取り出し用の出力端子として用いられる。タブＴ１，Ｔ２は、例えば超音波溶接、レーザ溶接、ハンダ接続、抵抗溶接等の方法で正極Ｃ及び芯材Ｆにそれぞれ取り付けられている。 One embodiment of the production method of the present invention using the negative electrode active material sheet 10 having the above-described configuration is shown in FIG. As shown in FIG. 2, first, the members constituting the battery are overlapped. The constituent members used here are the first separator S1, the second separator S2, the positive electrode C, the first negative electrode active material sheet A1, the second negative electrode active material sheet A2, and the conductive core material F. is there. All of these members have a long strip shape. These members are all the same width. The first separator S1 and the second separator S2 may be the same or different. Similarly, the first negative electrode active material sheet A1 and the second negative electrode active material sheet A2 may be the same or different. A tab T <b> 1 extending in a direction orthogonal to the longitudinal direction of the core material F is attached to one side edge portion of the conductive core material F in the longitudinal direction. Similarly, a tab T <b> 2 extending in a direction orthogonal to the longitudinal direction of the positive electrode C is attached to one side edge of the positive electrode C in the longitudinal direction. The tabs T1 and T2 are used as output terminals for extracting current, respectively. The tabs T1 and T2 are respectively attached to the positive electrode C and the core material F by a method such as ultrasonic welding, laser welding, solder connection, resistance welding, or the like.
これらの部材は、図２に示す通り、正極Ｃ、第１のセパレータＳ１、第１の負極用活物質シートＡ１、導電性芯材Ｆ、第２の負極用活物質シートＡ２がこの順で重ね合わされる。更に、第２の負極用活物質シートＡ２の外側に第２のセパレータＳ２が配されている。これらの部材の重ね合わせに際しては、図２に示す通り、各部材の一端部の位置が順次ずれるようにする。後述する巻回工程においてこれらの部材が一体的に巻回されると、内側に位置する部材と、外側に位置する部材との間で、巻き径の相違が発生するので、その相違を吸収するために、巻き始めの位置である各部材の一端部の位置をずらしている。 As shown in FIG. 2, these members include a positive electrode C, a first separator S1, a first negative electrode active material sheet A1, a conductive core material F, and a second negative electrode active material sheet A2 stacked in this order. Is done. Furthermore, the second separator S2 is disposed outside the second negative electrode active material sheet A2. In superimposing these members, as shown in FIG. 2, the position of one end of each member is sequentially shifted. When these members are integrally wound in the winding step described later, a difference in winding diameter occurs between the member positioned on the inner side and the member positioned on the outer side, and the difference is absorbed. Therefore, the position of the one end part of each member which is a position of the winding start is shifted.
各部材の重ね合わせにおいては、隣り合う部材間は、重ね合わせのみによって接しており、接着剤などの接合手段によっては接合されていない。つまり、各部材は、機械的に剥離可能なように接しているだけである。 In overlapping of each member, adjacent members are in contact only by overlapping, and are not joined by a joining means such as an adhesive. That is, each member is only in contact with each other so as to be mechanically peelable.
前記の各部材を前述した順序で重ね合わせて、これらを巻回して巻回体を得る。巻回は、図３に示すように、第２のセパレータＳ２の側が内向きになるように行う。このように巻回することで、巻回体においては、第２のセパレータＳ２、第２の負極用活物質シートＡ２、導電性芯材Ｆ、第１の負極用活物質シートＡ１、第１のセパレータＳ１、正極Ｃがこの順で層状に配される。 The above-mentioned members are overlapped in the order described above, and these are wound to obtain a wound body. As shown in FIG. 3, the winding is performed so that the second separator S2 side faces inward. By winding in this way, in the wound body, the second separator S2, the second negative electrode active material sheet A2, the conductive core material F, the first negative electrode active material sheet A1, the first The separator S1 and the positive electrode C are arranged in layers in this order.
このようにして得られた巻回体には、図４に示すように、その軸線と直交する方向から加圧力が加えられる。この加圧力によって、円筒状をしている巻回体は変形して扁平体ＦＢとなる。この変形工程において、巻回体を構成する各部材は塑性変形する。変形の程度が最も大きい部位は、扁平体ＦＢにおける左右両側部Ｓ，Ｓである。従って、側部Ｓには変形に際して大きな応力が加わる。その結果、側部Ｓに位置する各部材が断裂を起こしやすい。特に、電池の容量を高める目的で巻回数を多くすると、各部材の巻き径の違いに起因する伸びの違いが顕著となり、断裂が一層起こりやすい。断裂が起こると、タブＴ１，Ｔ２から見て、断裂した位置よりも遠い側に位置する部分は電極反応に寄与しなくなるので、著しい容量低下が起こってしまう。この場合、厚みが薄く、また活物質層内に金属材料が析出しており剛性の高い部材である負極用活物質シートＡ１，Ａ２が厚膜導電体上に一体的に密着形成されていると、負極用活物質シートＡ１，Ａ２と厚膜導電体との伸びの違いや厚みの違いに起因して断裂が生じやすい。しかしながら、本実施形態においては、負極用活物質シートＡ１，Ａ２は、厚膜導電体上に密着形成されておらず、厚膜導電体に相当する部材である導電性芯材Ｆ上に重ね合わされているだけなので、負極用活物質シートＡ１，Ａ２と導電性芯材Ｆとは別個独立に伸びることが可能になり、負極用活物質シートＡ１，Ａ２の断裂が効果的に防止される。仮に断裂が起こったとしても、タブＴ１，Ｔ２から見て、断裂した位置よりも遠い側に位置する部分は、導電性芯材Ｆによって電気的接触が維持されるので、当該部分も電極反応に寄与することができる。 As shown in FIG. 4, pressure is applied to the wound body obtained in this way from the direction orthogonal to the axis. By this applied pressure, the cylindrical wound body is deformed into a flat body FB. In this deformation process, each member constituting the wound body is plastically deformed. The portions with the greatest degree of deformation are the left and right side portions S, S in the flat body FB. Therefore, a large stress is applied to the side portion S during deformation. As a result, each member located on the side portion S is likely to tear. In particular, when the number of windings is increased for the purpose of increasing the capacity of the battery, the difference in elongation due to the difference in the winding diameter of each member becomes remarkable, and tearing is more likely to occur. When tearing occurs, the portion located farther from the tearing position when viewed from the tabs T1 and T2 does not contribute to the electrode reaction, so that the capacity is significantly reduced. In this case, the active material sheets A1 and A2 for the negative electrode, which are thin and have a metal material deposited in the active material layer and have high rigidity, are integrally formed on the thick film conductor. Further, tearing is likely to occur due to differences in elongation and thickness between the negative electrode active material sheets A1 and A2 and the thick film conductor. However, in the present embodiment, the negative electrode active material sheets A1 and A2 are not formed in close contact with the thick film conductor, but are superimposed on the conductive core material F that is a member corresponding to the thick film conductor. Therefore, the negative electrode active material sheets A1 and A2 and the conductive core material F can be extended independently and the negative electrode active material sheets A1 and A2 are effectively prevented from being broken. Even if tearing occurs, the portion located on the far side from the tearing position when viewed from the tabs T1 and T2 is maintained in electrical contact by the conductive core material F, so that the portion is also subjected to electrode reaction. Can contribute.
このように、本実施形態の製造方法によれば、電池作製時の各部材の巻き上げ操作における負極用活物質シートＡ１，Ａ２の断裂を効果的に防止することができる。このようにして得られた扁平体ＦＢは、所定の容器に入れられる。容器内には非水電解液が充填され、次いで該容器を密封することで、目的とする角型パッケージの二次電池が得られる。 As described above, according to the manufacturing method of the present embodiment, it is possible to effectively prevent the active material sheets A1 and A2 for the negative electrode from being ruptured during the winding operation of each member during battery production. The flat body FB thus obtained is placed in a predetermined container. The container is filled with a non-aqueous electrolyte, and then the container is sealed to obtain a target secondary battery having a square package.
本製造方法に用いられる各部材について説明すると、負極用活物質シートＡ１，Ａ２の詳細は既に述べた通りであり、また両負極用活物質シートＡ１，Ａ２の間に配置される導電性芯材Ｆとしては、薄く且つ高強度を有する導電性材料を用いることが、断裂の発生防止及びエネルギー密度の向上の点から好ましい。更に導電性芯材Ｆは、リチウム化合物の形成能の低い材料からなることが好ましい。これらの観点から、導電性芯材Ｆとしては、高強度銅箔、靱性の高い材料であるＮｉ−Ｗからなる箔、ステンレス箔などを用いることができる。高強度銅箔としては、圧延銅箔や圧延銅合金箔などを用いることができる。またＨＴＥ箔（三井金属鉱業株式会社の商品名）のような延び特性の高い電解銅箔を用いることも好ましい。導電性芯材Ｆの種類にもよるが、その厚みは１〜４０μｍ、特に３〜１２μｍであることが好ましい。なお、導電性芯材Ｆには、先に説明した負極用活物質シート１０に形成されている孔５と同様の又は異なる直径及び／又はピッチを有する孔を形成してもよい。 The members used in the production method will be described. Details of the negative electrode active material sheets A1 and A2 are as described above, and the conductive core material disposed between the negative electrode active material sheets A1 and A2. As F, it is preferable to use a thin and high-strength conductive material from the viewpoint of preventing the occurrence of tearing and improving the energy density. Furthermore, the conductive core material F is preferably made of a material having a low ability to form a lithium compound. From these viewpoints, as the conductive core material F, a high-strength copper foil, a foil made of Ni-W which is a material having high toughness, a stainless steel foil, or the like can be used. As the high-strength copper foil, a rolled copper foil, a rolled copper alloy foil, or the like can be used. It is also preferable to use an electrolytic copper foil having high elongation characteristics such as HTE foil (trade name of Mitsui Mining & Smelting Co., Ltd.). Although depending on the type of the conductive core material F, the thickness is preferably 1 to 40 μm, particularly preferably 3 to 12 μm. The conductive core material F may be formed with holes having the same or different diameter and / or pitch as the holes 5 formed in the negative electrode active material sheet 10 described above.
特に導電性芯材Ｆとして、前述の各種材料からなる導電性箔の少なくとも一面に金属リチウム層が形成されたものを用いることが好ましい。このような導電性芯材Ｆを用いると、得られる電池においては、負極用活物質シートＡ１，Ａ２と導電性箔との間に金属リチウム層が配置されることになる。このような構成にすることで、金属リチウム層は、非水電解液の存在下に、負極活物質との間に局部電池を構成する。これによって金属リチウムが、金属リチウム層の近傍に位置する活物質と化学的に反応してリチウム化物を形成する。或いはリチウムの濃度勾配に起因してリチウムが活物質と反応してリチウム化物を形成する。つまり、金属リチウム層はリチウムの供給源として作用する。その結果、充放電サイクル或いは長期保存時における電解液との反応などによってリチウムが消費されても、リチウム化物からリチウムが供給されるので、リチウム枯渇の問題が解消される。それによって電池の長寿命化が図られる。金属リチウム層は、負極用活物質シートの表面に露出しておらず、負極用活物質シートの内部に位置しており、またリチウムは活物質中と反応してリチウム化物を形成するので、内部短絡や発火の原因となるリチウムのデンドライトが生成するおそれも少ない。 In particular, as the conductive core F, it is preferable to use a conductive lithium foil having a metal lithium layer formed on at least one surface thereof. When such a conductive core material F is used, in the battery obtained, a metal lithium layer is disposed between the negative electrode active material sheets A1 and A2 and the conductive foil. With such a configuration, the metal lithium layer forms a local battery with the negative electrode active material in the presence of the non-aqueous electrolyte. Thereby, metallic lithium chemically reacts with an active material located in the vicinity of the metallic lithium layer to form a lithiated product. Alternatively, lithium reacts with the active material due to a lithium concentration gradient to form a lithiated product. That is, the metal lithium layer functions as a lithium supply source. As a result, even if lithium is consumed due to a reaction with the electrolyte during charge / discharge cycles or long-term storage, the lithium depletion problem is solved because lithium is supplied from the lithiated product. Thereby, the life of the battery is extended. The metal lithium layer is not exposed on the surface of the negative electrode active material sheet and is located inside the negative electrode active material sheet, and the lithium reacts with the active material to form a lithiated material. There is little risk of lithium dendrites that can cause short circuits or fire.
特筆すべきは、金属リチウム層を備えた電池は、充電を行わずとも金属リチウムと負極活物質との反応が起こることである。充電前に金属リチウムと負極活物質との反応が起こることで、負極活物質は、充電前に既に体積が増加した状態になっている。従って、その後に充放電を行っても、充放電に起因する負極用活物質シートの膨張率は極めて小さい。その結果、本実施形態に従い得られる電池は、充放電による負極活物質の体積変化に起因する変形が極めて起こりづらいという非常に有利な効果を奏する。 It should be noted that a battery having a metallic lithium layer undergoes a reaction between metallic lithium and the negative electrode active material without being charged. The reaction between metallic lithium and the negative electrode active material occurs before charging, so that the negative electrode active material has already increased in volume before charging. Therefore, even if it charges / discharges after that, the expansion coefficient of the active material sheet for negative electrodes resulting from charging / discharging is very small. As a result, the battery obtained according to the present embodiment has a very advantageous effect that deformation due to the volume change of the negative electrode active material due to charge / discharge is extremely difficult to occur.
金属リチウムの量は、負極活物質の飽和可逆容量に対して０．１〜７０％、特に５〜３０％であることが、容量回復特性が良好になることから好ましい。 The amount of metallic lithium is preferably 0.1 to 70%, particularly 5 to 30%, based on the saturation reversible capacity of the negative electrode active material, because the capacity recovery characteristics are good.
前記と同様の目的で、第１の負極用活物質シートＡ１と第１のセパレータＳ１との間に金属リチウム箔を配置することも可能である。但し、その場合には、第１の負極用活物質シートＡ１と第１のセパレータＳ１との界面に、充放電に起因するリチウムデンドライトが発生しないようにするために、電池の使用前に、金属リチウムを負極活物質層内に取り込む必要がある。そのためには、金属リチウムの量やエージングの条件を適宜調整すればよい。第１の負極用活物質シートＡ１と第１のセパレータＳ１との間に金属リチウム箔を配することに代えて、又はそれに加えて、第２のセパレータＳ２の外側又は第２の負極用活物質シートＡ２の外側に金属リチウム箔を配することもできる。 For the same purpose as described above, it is also possible to dispose a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1. However, in that case, in order to prevent generation of lithium dendrite due to charge / discharge at the interface between the first negative electrode active material sheet A1 and the first separator S1, a metal is used before using the battery. It is necessary to incorporate lithium into the negative electrode active material layer. For this purpose, the amount of metallic lithium and aging conditions may be adjusted as appropriate. Instead of or in addition to arranging a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1, the outside of the second separator S2 or the second negative electrode active material A metallic lithium foil can also be disposed on the outside of the sheet A2.
正極Ｃとしては、正極合剤を、厚膜導電材の各面に塗布し、その後にロール圧延、プレスして得られたものを用いることができる。正極合剤は、正極活物質並びに必要により導電剤及び結着剤を適当な溶媒に懸濁したものである。正極活物質としては、リチウムニッケル複合酸化物、リチウムマンガン複合酸化物、リチウムコバルト複合酸化物等の従来公知の正極活物質が用いられる。 As the positive electrode C, a positive electrode material mixture obtained by applying a positive electrode mixture on each surface of a thick film conductive material and then rolling and pressing it can be used. The positive electrode mixture is obtained by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent. As the positive electrode active material, conventionally known positive electrode active materials such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used.
セパレータとしては、合成樹脂製不織布、ポリエチレン又はポリプロピレン多孔質フイルム等が好ましく用いられる。非水電解液は、支持電解質であるリチウム塩を有機溶媒に溶解した溶液からなる。リチウム塩としては、例えば、ＬｉＣ１Ｏ4、ＬｉＡ１Ｃｌ4、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＳＣＮ、ＬｉＣ１、ＬｉＢｒ、ＬｉＩ、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3等が例示される。 As the separator, a synthetic resin non-woven fabric, polyethylene, polypropylene porous film or the like is preferably used. The nonaqueous electrolytic solution is a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. The lithium salt, for example, LiC1O 4, LiA1Cl 4, LiBF 4, LiPF 6, LiAsF 6, LiSbF 6, LiSCN, LiC1, LiBr, LiI, etc. LiCF 3 SO 3, LiC 4 F 9 SO 3 are exemplified.
以上の方法に従い作製された電池は、第２の負極用活物質シートＡ２と、導電性芯材Ｆと、第１の負極用活物質シートＡ１と、第１のセパレータＳ１と、正極Ｃとがこの順で重ね合わされ、更に第２の負極用活物質シートＡ２の外側に第２のセパレータＳ２が配された重ね合わせ体が、第２のセパレータＳ２が内側となるように巻回されてなる巻回体を備えたものである。先に述べた通り、これら各部材間は、重ね合わせのみによって接している。従って、第１の負極用活物質シートＡ１及び第２の負極用活物質シートＡ２と、導電性芯材Ｆとの間は、機械的に剥離可能なように電気的に接している。このような構成になっていることで、充放電に起因して負極活物質が体積変化して、負極用活物質シートＡ１，Ａ２が変形しても、導電性芯材Ｆはその変形による影響を受けにくくなる。例えば、導電性芯材Ｆの皺の発生や、導電性芯材Ｆの断裂が起こりにくくなる。その結果、導電性芯材Ｆによる集電性が確保され、電池の長寿命化が図られる。 The battery manufactured according to the above method has the second negative electrode active material sheet A2, the conductive core material F, the first negative electrode active material sheet A1, the first separator S1, and the positive electrode C. A stack in which the second separator S2 is placed on the outer side of the second negative electrode active material sheet A2 is wound in such a manner that the second separator S2 is on the inner side. It has a round body. As described above, these members are in contact with each other only by overlapping. Therefore, the first negative electrode active material sheet A1 and the second negative electrode active material sheet A2 are electrically in contact with the conductive core material F so as to be mechanically peelable. With such a configuration, even if the negative electrode active material changes in volume due to charge / discharge and the negative electrode active material sheets A1 and A2 are deformed, the conductive core material F is affected by the deformation. It becomes difficult to receive. For example, generation of wrinkles of the conductive core material F and tearing of the conductive core material F are less likely to occur. As a result, the current collecting property by the conductive core material F is ensured, and the life of the battery is extended.
以上、本発明をその好ましい実施形態に基づき説明したが、本発明は前記実施形態に制限されない。例えば前記実施形態における負極用活物質シートＡ１，Ａ２は、活物質層２の各面に表面層３ａ，３ｂが形成されていたが、これら表面層の一方又は双方を形成しなくてもよい。活物質層２の一方の面にのみ表面層を形成する場合には、該表面層がセパレータと対向するように、負極用活物質シートとセパレータとを重ね合わせることが好ましい。また、活物質層２には金属材料が浸透していたが、当該金属材料を浸透させない状態の活物質層を用いてもよい。 As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the negative electrode active material sheets A1 and A2 in the above embodiment, the surface layers 3a and 3b are formed on each surface of the active material layer 2, but one or both of these surface layers may not be formed. When a surface layer is formed only on one surface of the active material layer 2, it is preferable that the negative electrode active material sheet and the separator are overlapped so that the surface layer faces the separator. Further, although the metal material has permeated into the active material layer 2, an active material layer in a state in which the metal material does not penetrate may be used.
また、負極用活物質シートとしては、図１に示す形態のものの他に、リチウム化合物の形成能の高い材料からなる箔（例えばスズ箔、スズ合金箔、アルミニウム箔、アルミニウム合金箔等）や、当該箔の一面にリチウム化合物の形成能の低い材料からなる薄層が形成されたものなどを用いることができる。 Further, as the negative electrode active material sheet, in addition to the form shown in FIG. 1, a foil made of a material having a high ability to form a lithium compound (for example, tin foil, tin alloy foil, aluminum foil, aluminum alloy foil, etc.), For example, a thin layer made of a material having a low lithium compound forming ability may be used on one surface of the foil.
また活物質層や表面層は、スパッタリング法や真空蒸着法、めっき法によって形成してもよい。 The active material layer and the surface layer may be formed by a sputtering method, a vacuum deposition method, or a plating method.
また前記実施形態においては、第２の負極用活物質シートＡ２の外側に第２のセパレータＳ２を配し、第２のセパレータＳ２が内側になるように巻回を行ったが、これに代えて、正極Ｃの外側に第２のセパレータＳ２を配し、第２のセパレータＳ２が内側になるように巻回を行ってもよい。その場合にも、第１の負極用活物質シートＡ１と第１のセパレータＳ１との間に金属リチウム箔を配置することが可能である。更に、第１の負極用活物質シートＡ１と第１のセパレータＳ１との間に金属リチウム箔を配することに代えて、又はそれに加えて、正極Ｃの外側又は第２のセパレータＳ２の外側に金属リチウム箔を配することもできる。 In the embodiment, the second separator S2 is disposed outside the second negative electrode active material sheet A2 and wound so that the second separator S2 is inside. Alternatively, the second separator S2 may be disposed outside the positive electrode C, and winding may be performed so that the second separator S2 is on the inner side. Also in that case, it is possible to arrange a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1. Further, instead of or in addition to arranging a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1, on the outside of the positive electrode C or on the outside of the second separator S2. A metallic lithium foil can also be provided.
以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲はかかる実施例に制限されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.
〔実施例１〕
図５（ａ）〜（ｇ）に示す方法に従い図１に示す負極用活物質シート１０を製造した。先ず、図５（ａ）に示すように、電解によって得られた銅製のキャリア箔１１（厚さ３５μｍ）を室温で３０秒間酸洗浄した。引き続き室温で３０秒間純水洗浄した。次いで、４０℃に保った状態の３．５ｇ／ｌのＣＢＴＡ（カルボキシベンゾトリアゾール）溶液中に、キャリア箔１１を３０秒間浸漬した。これにより図５（ｂ）に示すように剥離層１２を形成した。剥離層１２の形成後、溶液から引き上げて１５秒間純水洗浄した。
[Example 1]
The negative electrode active material sheet 10 shown in FIG. 1 was manufactured according to the method shown in FIGS. First, as shown in FIG. 5A, the copper carrier foil 11 (thickness: 35 μm) obtained by electrolysis was acid-washed at room temperature for 30 seconds. Subsequently, it was washed with pure water at room temperature for 30 seconds. Next, the carrier foil 11 was immersed in a 3.5 g / l CBTA (carboxybenzotriazole) solution kept at 40 ° C. for 30 seconds. As a result, a release layer 12 was formed as shown in FIG. After the release layer 12 was formed, it was lifted from the solution and washed with pure water for 15 seconds.
キャリア箔１１を、Ｈ2ＳＯ4／ＣｕＳＯ4系のめっき浴に浸漬させて電解めっきを行った。これによって図５（ｃ）に示すように、銅からなる表面層３ｂをキャリア箔１１の一面上に形成した。めっき浴の組成は、ＣｕＳＯ4が２５０ｇ／ｌ、Ｈ2ＳＯ4が７０ｇ／ｌであった。電流密度は５Ａ／ｄｍ2とした。表面層３ｂは５μｍの厚さに形成した。めっき浴から引き上げた後、３０秒間純水洗浄して大気中で乾燥させた。 The carrier foil 11 was immersed in an H 2 SO 4 / CuSO 4 plating bath for electrolytic plating. As a result, a surface layer 3b made of copper was formed on one surface of the carrier foil 11, as shown in FIG. The composition of the plating bath was 250 g / l for CuSO 4 and 70 g / l for H 2 SO 4 . The current density was 5 A / dm 2 . The surface layer 3b was formed to a thickness of 5 μm. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.
次に、図５（ｄ）に示すように、表面層３ｂ上に負極活物質の粒子を含むスラリーを膜厚１５μｍになるように塗布し活物質層２を形成した。活物質粒子はＳｉからなり、平均粒径はＤ50＝２μｍであった。スラリーの組成は、活物質：アセチレンブラック：スチレンブタジエンラバー＝９８：２：１．７であった。 Next, as shown in FIG. 5 (d), the active material layer 2 was formed by applying a slurry containing negative electrode active material particles on the surface layer 3 b to a thickness of 15 μm. The active material particles were made of Si, and the average particle size was D 50 = 2 μm. The composition of the slurry was active material: acetylene black: styrene butadiene rubber = 98: 2: 1.7.
活物質層２が形成されたにキャリア箔１１を、以下の浴組成を有するワット浴に浸漬させ、電解により、活物質層２に対してニッケルの浸透めっきを行った。電流密度は５Ａ／ｄｍ2、浴温は５０℃、ｐＨは５であった。陽極にはニッケル電極を用いた。電源は直流電源を用いた。この浸透めっきは、めっき面から一部の活物質粒子が露出する程度に行った。めっき浴から引き上げた後、３０秒間純水洗浄して大気中で乾燥させた。
・ＮｉＳＯ4・６Ｈ2Ｏ ２５０ｇ／ｌ
・ＮｉＣｌ2・６Ｈ2Ｏ ４５ｇ／ｌ
・Ｈ3ＢＯ3 ３０ｇ／ｌ
After the active material layer 2 was formed, the carrier foil 11 was immersed in a Watt bath having the following bath composition, and nickel was applied to the active material layer 2 by electrolysis. The current density was 5 A / dm 2 , the bath temperature was 50 ° C., and the pH was 5. A nickel electrode was used as the anode. A DC power source was used as the power source. This infiltration plating was performed to such an extent that some active material particles were exposed from the plating surface. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.
・ NiSO 4・ 6H 2 O 250g / l
・ NiCl 2・ 6H 2 O 45g / l
・ H 3 BO 3 30g / l
次に、Ｃｕ系のめっき浴にキャリア箔１１を浸漬させて電解めっきを行った。めっき浴の組成は、Ｈ3ＰＯ4が２００ｇ／ｌ、Ｃｕ3（ＰＯ4）2・３Ｈ2Ｏが２００ｇ／ｌであった。また、めっきの条件は、電流密度５Ａ／ｄｍ2、浴温度４０℃であった。これによって図５（ｅ）に示すように、銅からなる表面層３ａを活物質層２上に形成した。この表面層３ａは９μｍの厚さに形成した。めっき浴から引き上げた後、３０秒間純水洗浄して大気中で乾燥させた。 Next, electrolytic plating was performed by immersing the carrier foil 11 in a Cu-based plating bath. The composition of the plating bath was 200 g / l for H 3 PO 4 and 200 g / l for Cu 3 (PO 4 ) 2 .3H 2 O. The plating conditions were a current density of 5 A / dm 2 and a bath temperature of 40 ° C. As a result, a surface layer 3a made of copper was formed on the active material layer 2 as shown in FIG. The surface layer 3a was formed to a thickness of 9 μm. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.
次に、図５（ｆ）に示すように、活物質層２上に形成された表面層３ａに向けてＹＡＧレーザを照射し、孔５を規則的に形成した。孔５は、両表面層３ａ，３ｂ及びそれらの間に位置する活物質層２を貫通するように形成した。孔５の直径は２５μｍ、ピッチは１００μｍ（１００００孔／ｃｍ2）とした。 Next, as shown in FIG. 5F, the surface layer 3a formed on the active material layer 2 was irradiated with a YAG laser to form the holes 5 regularly. The hole 5 was formed so as to penetrate both the surface layers 3a and 3b and the active material layer 2 positioned therebetween. The diameter of the holes 5 was 25 μm, and the pitch was 100 μm (10000 holes / cm 2 ).
最後に、図５（ｇ）に示すように、キャリア箔１１とそれに接する表面層３ｂとを剥離して、負極用活物質シート５を得た。得られた負極用活物質シートの断面及び表面の電子顕微鏡写真を図６及び図７にそれぞれ示す。また表面の拡大像を図８に示す。これらの電子顕微鏡写真から、負極用活物質シートに多数の貫通孔が規則的に形成されていることが判る。また表面層に微細空隙が形成されていることも判る。 Finally, as shown in FIG.5 (g), the carrier foil 11 and the surface layer 3b which contact | connects it were peeled, and the active material sheet 5 for negative electrodes was obtained. The cross section and surface electron micrographs of the obtained negative electrode active material sheet are shown in FIGS. 6 and 7, respectively. An enlarged image of the surface is shown in FIG. From these electron micrographs, it can be seen that a large number of through holes are regularly formed in the negative electrode active material sheet. It can also be seen that fine voids are formed in the surface layer.
このようにして得られた負極用活物質シートと、正極と、セパレータと、導電性芯材とを用い、図１〜図３に示す方法に従い、角型パッケージのリチウム二次電池を得た。正極としては、２０μｍのアルミニウム箔の各面に、Ｌｉ、Ｍｎ、Ｃｏ及びＮｉを含む酸化物を用いた。セパレータとしては、ポリエチレンフィルムを一軸延伸して得られた微多孔質膜を用いた。導電性芯材としては、１８μｍの圧延銅箔を用いた。非水電解液としては、ＬｉＰＦ6／エチレンカーボネートとジメチルカーボネートの混合液（１：１容量比）を用いた。 Using the thus obtained negative electrode active material sheet, positive electrode, separator, and conductive core material, a square package lithium secondary battery was obtained according to the method shown in FIGS. As the positive electrode, an oxide containing Li, Mn, Co, and Ni was used on each surface of a 20 μm aluminum foil. As the separator, a microporous film obtained by uniaxially stretching a polyethylene film was used. As the conductive core material, 18 μm rolled copper foil was used. As the non-aqueous electrolyte, a mixed solution of LiPF 6 / ethylene carbonate and dimethyl carbonate (1: 1 volume ratio) was used.
〔比較例１〕
実施例１において、キャリア箔１１として、実施例１において用いた導電性芯材（１８μｍの圧延銅箔）を用いた。この圧延銅箔の一面に、図５（ａ）〜（ｆ）に示す方法で負極用活物質シートを形成した。図５（ｇ）に示す操作は行わなかった。このようにして、圧延銅箔の一面に負極用活物質シートが一体的に形成された負極を得た。実施例１における負極用活物質シートと導電性芯材に代えてこの負極を用い、実施例１と同様の操作で角型パッケージのリチウム二次電池を得た。このようにして得られた電池においては、負極を構成する負極用活物質シートと圧延銅箔とは機械的に剥離可能なように接している状態になっていない。
[Comparative Example 1]
In Example 1, as the carrier foil 11, the conductive core material (18 μm rolled copper foil) used in Example 1 was used. An active material sheet for a negative electrode was formed on one surface of this rolled copper foil by the method shown in FIGS. The operation shown in FIG. 5 (g) was not performed. In this way, a negative electrode was obtained in which the negative electrode active material sheet was integrally formed on one surface of the rolled copper foil. Using this negative electrode in place of the negative electrode active material sheet and conductive core in Example 1, a lithium secondary battery having a square package was obtained in the same manner as in Example 1. In the battery thus obtained, the negative electrode active material sheet constituting the negative electrode and the rolled copper foil are not in a state of being in contact with each other so as to be mechanically peelable.
〔評価〕
このようにして得られた電池を、充放電させる前に解体し、負極用活物質シート等に断裂が生じているか否かを観察した。その結果を図９及び図１０に示す。図９は実施例１で得られた電池を解体した状態を示しており、上側が負極用活物質シートを、下側が正極を示している。この結果から、実施例１で得られた電池では、負極用活物質シートに断裂が発生していないことが判る。一方、図１０は比較例１で得られた電池を解体した状態を示しており、上側が負極（導電性芯材上に負極用活物質シートが一体的に形成されたもの）を、下側が正極を示している。この結果から、比較例１で得られた電池では、負極用活物質シートが断裂していることが判る。
[Evaluation]
The battery thus obtained was disassembled before being charged and discharged, and it was observed whether or not tearing occurred in the negative electrode active material sheet or the like. The results are shown in FIGS. FIG. 9 shows a state in which the battery obtained in Example 1 is disassembled, with the upper side showing the negative electrode active material sheet and the lower side showing the positive electrode. From this result, in the battery obtained in Example 1, it can be seen that no tearing occurred in the negative electrode active material sheet. On the other hand, FIG. 10 shows a state in which the battery obtained in Comparative Example 1 is disassembled, with the upper side being a negative electrode (in which a negative electrode active material sheet is integrally formed on a conductive core material) and the lower side being a negative electrode. The positive electrode is shown. From this result, it can be seen that in the battery obtained in Comparative Example 1, the negative electrode active material sheet was torn.
前記の観察とは別に、得られた電池を２０回充放電させた。その後に電池を解体し、導電性芯材の表面状態を観察した。実施例１においては、負極用活物質シートと導電性芯材とは剥離可能な状態になっているので、導電性芯材の表面を露出させることは容易である。比較例１においては、導電性芯材の一面にのみ負極用活物質シートが一体的に形成されているので、該負極用活物質シートが形成されていない面の側から導電性芯材の表面状態を観察した。結果を図１１及び図１２に示す。図１１は実施例１で得られた電池における導電性芯材の表面状態を示しており、図１２は比較例１で得られた電池における導電性芯材の表面状態を示している。図１１では、導電性芯材に皺や断裂の発生が観察されない。これに対して図１２では、導電性芯材に多数の皺が発生している。 Separately from the above observation, the obtained battery was charged and discharged 20 times. Thereafter, the battery was disassembled, and the surface state of the conductive core material was observed. In Example 1, since the negative electrode active material sheet and the conductive core material are in a peelable state, it is easy to expose the surface of the conductive core material. In Comparative Example 1, since the negative electrode active material sheet is integrally formed only on one surface of the conductive core material, the surface of the conductive core material from the side where the negative electrode active material sheet is not formed. The condition was observed. The results are shown in FIG. 11 and FIG. FIG. 11 shows the surface state of the conductive core material in the battery obtained in Example 1, and FIG. 12 shows the surface state of the conductive core material in the battery obtained in Comparative Example 1. In FIG. 11, generation | occurrence | production of a wrinkle or a tear is not observed in a conductive core material. On the other hand, in FIG. 12, many wrinkles are generated in the conductive core material.
更に、実施例１で得られた負極用活物質シートについて、これを負極用活物質シート、導電性芯材、負極用活物質シート、セパレータ、正極、セパレータの順で重ねた。そして、セパレータ上に、その長手方向と直交する方向に直径３．５ｍｍの金属製の丸棒を載置し、これら重ね合わせ体の全体を丸棒に沿って折り曲げたときに断裂が生じるか否かを観察した。その結果を図１３に示す。比較例１で得られた負極用活物質シートについても同様の観察を行った。その結果を図１４に示す。これらの結果から明らかなように、実施例１で得られた負極用活物質シートを含む重ね合わせ体には断裂が生じていないのに対して、比較例１で得られた負極用活物質シートを含む重ね合わせ体は破断したことが判る。 Furthermore, about the active material sheet for negative electrodes obtained in Example 1, this was laminated | stacked in order of the active material sheet for negative electrodes, the electroconductive core material, the active material sheet for negative electrodes, the separator, the positive electrode, and the separator. Then, a metal round bar having a diameter of 3.5 mm is placed on the separator in a direction perpendicular to the longitudinal direction, and whether or not tearing occurs when the whole of these stacked bodies is bent along the round bar. Was observed. The result is shown in FIG. The same observation was performed on the negative electrode active material sheet obtained in Comparative Example 1. The result is shown in FIG. As is clear from these results, the laminate including the negative electrode active material sheet obtained in Example 1 was not torn, whereas the negative electrode active material sheet obtained in Comparative Example 1 was obtained. It can be seen that the superposed body including ruptured.
１ａ，１ｂ 表面
２ 活物質層
３，３ａ，３ｂ 表面層
４ リチウム化合物の形成能の低い金属材料
５ 孔
１０，Ａ１，Ａ２ 負極用活物質シート
Ｃ 正極
Ｆ 導電性芯材
Ｓ１，Ｓ２ セパレータ
1a, 1b Surface 2 Active material layer 3, 3a, 3b Surface layer 4 Metal material with low lithium compound forming ability 5 Hole 10, A1, A2 Negative electrode active material sheet C Positive electrode F Conductive core material S1, S2 Separator
Claims (10)
第１及び第２の負極と導電性芯材との間が、剥離可能なように電気的に接していることを特徴とする非水電解液二次電池。
Each of which is in the shape of a long strip, the positive electrode, the first separator, the first negative electrode not having the thick film conductor, the conductive core material, and the second not having the thick film conductor. The stacked body in which the second separator is disposed in this order, and the second separator is disposed outside the positive electrode or the second negative electrode is wound so that the second separator is located inside. A lithium secondary battery provided with a wound body,
A non-aqueous electrolyte secondary battery, wherein the first and second negative electrodes and the conductive core member are in electrical contact so as to be peelable.
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| JPWO2017150264A1 (en) * | 2016-02-29 | 2018-12-27 | パナソニックＩｐマネジメント株式会社 | Electrochemical device, negative electrode used therefor and method for producing the same |
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