WO2015163025A1 - 二次電池 - Google Patents
二次電池 Download PDFInfo
- Publication number
- WO2015163025A1 WO2015163025A1 PCT/JP2015/057000 JP2015057000W WO2015163025A1 WO 2015163025 A1 WO2015163025 A1 WO 2015163025A1 JP 2015057000 W JP2015057000 W JP 2015057000W WO 2015163025 A1 WO2015163025 A1 WO 2015163025A1
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- WO
- WIPO (PCT)
- Prior art keywords
- electrode
- negative electrode
- secondary battery
- positive electrode
- conductive
- Prior art date
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- 239000010410 layer Substances 0.000 claims abstract description 41
- 239000012790 adhesive layer Substances 0.000 claims abstract description 29
- 239000002390 adhesive tape Substances 0.000 claims abstract description 29
- 230000002093 peripheral effect Effects 0.000 claims abstract description 3
- 239000011231 conductive filler Substances 0.000 claims description 2
- 239000000853 adhesive Substances 0.000 abstract 1
- 230000001070 adhesive effect Effects 0.000 abstract 1
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- 239000008151 electrolyte solution Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
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- 229910001416 lithium ion Inorganic materials 0.000 description 3
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
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- 238000007599 discharging Methods 0.000 description 1
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- 238000004519 manufacturing process Methods 0.000 description 1
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- 238000004804 winding Methods 0.000 description 1
Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
- H01M10/0413—Large-sized flat cells or batteries for motive or stationary systems with plate-like electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
- H01M10/0436—Small-sized flat cells or batteries for portable equipment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/116—Primary casings; Jackets or wrappings characterised by the material
- H01M50/117—Inorganic material
- H01M50/119—Metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/116—Primary casings; Jackets or wrappings characterised by the material
- H01M50/121—Organic material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/116—Primary casings; Jackets or wrappings characterised by the material
- H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/10—Primary casings; Jackets or wrappings
- H01M50/116—Primary casings; Jackets or wrappings characterised by the material
- H01M50/124—Primary casings; Jackets or wrappings characterised by the material having a layered structure
- H01M50/126—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers
- H01M50/129—Primary casings; Jackets or wrappings characterised by the material having a layered structure comprising three or more layers with two or more layers of only organic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/463—Separators, membranes or diaphragms characterised by their shape
- H01M50/466—U-shaped, bag-shaped or folded
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/572—Means for preventing undesired use or discharge
- H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
- H01M50/588—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries outside the batteries, e.g. incorrect connections of terminals or busbars
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/572—Means for preventing undesired use or discharge
- H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
- H01M50/59—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries characterised by the protection means
- H01M50/595—Tapes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2200/00—Safety devices for primary or secondary batteries
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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
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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
- 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
Definitions
- the present invention relates to a secondary battery in which a positive electrode and a negative electrode are overlapped via a separator.
- Secondary batteries are widely used as power sources for vehicles and homes as well as portable devices such as mobile phones, digital cameras, and laptop computers.
- high-energy density and lightweight lithium-ion secondary batteries have become energy storage devices indispensable for daily life.
- Secondary batteries can be broadly classified into a wound type and a stacked type.
- the battery element of the wound secondary battery has a structure in which a long positive electrode sheet and a negative electrode sheet are wound a plurality of times in a state of being overlapped while being separated by a separator.
- the battery element of the stacked secondary battery has a structure in which positive electrode sheets and negative electrode sheets are alternately and repeatedly stacked while being separated by a separator.
- Patent Documents 1 and 2 disclose a configuration in which a sheet having high thermal conductivity is wound around a battery element.
- JP 2008-117604 A Japanese Patent Laid-Open No. 10-40959
- an object of the present invention is to provide a secondary battery that can suppress a problem that occurs due to an electrical short circuit between a positive electrode and a negative electrode when a foreign object is pierced.
- the secondary battery of the present invention is laminated on a battery element in which a positive electrode and a negative electrode overlap with each other through a separator, an adhesive layer having conductivity and adhesiveness, and an adhesive layer adhered to the surface of the battery element.
- the present invention it is possible to suppress problems caused by an electrical short circuit between the positive electrode and the negative electrode when a foreign object is stuck.
- FIG. 2 is an enlarged cross-sectional view illustrating a state in which a foreign object is stuck in the secondary battery illustrated in FIG. 1.
- FIG. 2 is an enlarged cross-sectional view illustrating a state in which a foreign object is stuck in the secondary battery illustrated in FIG. 1.
- FIG. 2 is an enlarged cross-sectional view illustrating a state in which a foreign object is stuck in the secondary battery illustrated in FIG. 1.
- FIG. 2 is an enlarged cross-sectional view illustrating a state in which a foreign object is stuck in the secondary battery illustrated in FIG. 1.
- FIG. 2nd Embodiment of this invention shows the secondary battery of the 2nd Embodiment of this invention.
- the lithium ion secondary battery 100 of the present invention includes an electrode laminate (battery element) 4 in which a plurality of positive electrodes 1 and negative electrodes 2 are alternately laminated via separators 3.
- a conductive adhesive tape 5 is wound around the electrode laminate 4.
- the conductive adhesive tape 5 has a multilayer structure, the inner layer is an adhesive layer 5a having conductivity and adhesiveness, and the outer layer is a conductive layer 5b.
- the electrode laminated body 4 and the electrolyte solution 6 which were covered with the electroconductive adhesive tape 5 are accommodated in the exterior container.
- the electrolytic solution 6 is shown by omitting a part of each layer constituting the electrode laminate 4 (a layer located in an intermediate portion in the thickness direction).
- the positive electrode 1 and the negative electrode 2 are provided with tabs 1 a and 2 a, respectively.
- the positive electrode tab 1 a is connected to one end portion of the positive electrode terminal 8
- the negative electrode tab 2 a is connected to one end portion of the negative electrode terminal 9. It is connected.
- the other end portion of the positive electrode terminal 8 and the other end portion of the negative electrode terminal 9 are each drawn out of the exterior container.
- the outer dimension of the negative electrode 2 is larger than the outer dimension of the positive electrode 1 and smaller than the outer dimension of the separator 3.
- the adhesive layer 5 a that is the inner layer of the conductive adhesive tape 5 is in close contact with and bonded to the negative electrode 2 located on the surface of the electrode laminate 4 and is electrically connected.
- the pressure-sensitive adhesive layer 5a of the conductive pressure-sensitive adhesive tape 5 of the present embodiment is formed from, for example, a mixture obtained by mixing a conductive filler (conductive resin, carbon particles, metal particles, etc.) with an acrylic pressure-sensitive adhesive.
- the conductive layer 5b is made of, for example, a conductive nonwoven fabric obtained by plating copper or nickel on a nonwoven fabric made of polyester or the like, or a metal such as copper or aluminum.
- a case made of a flexible film 7, a can case, or the like can be used. From the viewpoint of reducing the weight of the battery, it is preferable to use a case made of the flexible film 7.
- the flexible film 7 has, for example, a multilayer structure in which a resin layer is provided on the front and back surfaces of a metal layer serving as a base material. In that case, it is preferable to select a metal layer having a barrier property such as preventing leakage of the electrolytic solution 6 or intrusion of moisture from the outside, and aluminum, stainless steel, or the like can be used. On at least one surface of the metal layer, a heat-fusible resin layer such as a modified polyolefin is provided.
- An exterior container is formed by making the heat-fusible resin layers of the flexible film 7 face each other and heat-sealing the periphery of the portion that houses the electrode laminate 4.
- a resin layer such as a nylon film or a polyester film can be provided on the surface of the outer container that is the surface opposite to the surface on which the heat-fusible resin layer is formed.
- an embossed portion for accommodating the electrode laminate 4 is formed on the flexible film 7 positioned above, but the embossed portion is formed on both of the pair of flexible films 7. It may be formed. Alternatively, the embossed portion may not be formed in advance, and the electrode laminate 4 may be accommodated by deforming the flexible film 7 when the electrode laminate 4 is sandwiched between the pair of flexible films 7.
- FIG. 3 schematically shows two types of electrical short-circuit paths when a foreign object (for example, a metal piece such as a nail) 10 is stuck in the secondary battery 100.
- a foreign object for example, a metal piece such as a nail
- some of the positive electrodes 1 and the negative electrode 2 adjacent thereto may be electrically short-circuited through the foreign material 10.
- the current flowing by this electrical short circuit is guided to the conductive adhesive tape 5 covering the electrode laminate 4.
- the positive electrode 1 and the negative electrode 2 adjacent to the positive electrode 1 are short-circuited via the foreign material 10, and the adhesive layer is bonded to the electrode laminate 4 from the negative electrode 2.
- a current is guided to the conductive layer 5b located outside the electrode laminate 4 via 5a. Then, a current flows again from the conductive layer 5b to the negative electrode 2 through the adhesive layer 5a.
- the conductive adhesive tape 5 of the present embodiment has a low electric resistance of 1.0 ⁇ / cm 2 or less in the thickness direction, so that the current is easily transmitted in the thickness direction of the conductive adhesive tape 5. It is. As a result, the current follows a path from the positive electrode 1 and the negative electrode 2 to the negative electrode 2 after passing through the conductive layer 5 b that is the outer layer of the conductive adhesive tape 5. Further, in another path of the electrical short circuit schematically shown in FIG.
- the current from the positive electrode 1 of the electrode laminate 4 is guided to the conductive layer 5b through the foreign matter 10, and the conductive layer 5b is connected to the adhesive layer. It flows to the negative electrode 2 of the electrode laminate 4 via 5a.
- the position where the current flows through the negative electrode 2 in this path is considered to be a position away from the position where the current flows through the negative electrode 2 in the other path described above. That is, in two examples of the electrical short circuit schematically shown in FIG. 3, the positions where current flows through the negative electrode 2 are different from each other. In this way, the short-circuit current paths are dispersed, and the short-circuit current does not flow intensively only at specific positions inside the electrode stack 4 (in the vicinity of the foreign material 10).
- the heat generation is dispersed and the generation of large heat generation locally can be suppressed.
- the heat generated by the current flowing through the conductive adhesive tape 5 located outside the electrode laminate 4 is transmitted to the air interposed between the exterior film 7 and further released from the air through the exterior film 7 to the outside. Therefore, an excessive temperature rise of the electrode laminate 4 itself can be suppressed.
- the conductive adhesive tape 5 of the present embodiment has an adhesive layer 5a having adhesiveness and conductivity as an inner layer, and is as low as 1.0 ⁇ / cm 2 or less in the thickness direction. Has electrical resistance.
- the adhesiveness with the electrode (the negative electrode 2 in this embodiment) located in the outermost layer of the electrode laminate 4 is low. It is difficult for current to be guided from the outermost electrode to the non-adhesive layer. Therefore, in the electrode laminate 4, current flows in the shortest path where the adjacent positive electrode 1 and negative electrode 2 are short-circuited via the foreign material 10, and the current flows to a position on the path (near the foreign material 10). There is a high possibility that an excessive current flows and generates a large amount of heat.
- the conductive adhesive tape 5 having the adhesive layer 5a having adhesiveness and conductivity as the inner layer and having a low electric resistance of 1.0 ⁇ / cm 2 or less in the thickness direction.
- the conductive adhesive tape 5 preferably covers the entire electrode laminate 4, but may be configured to cover only a part of the electrode laminate 4. In that case, it is effective that the conductive adhesive tape 5 covers the central portion of the electrode laminate 4 where the possibility of the foreign object 10 sticking is relatively high.
- an insulating member 11 made of, for example, an insulating resin film and covering the side surface of the electrode laminate 4 is disposed.
- the insulating member 11 prevents the side edge of the positive electrode 1 and the side edge of the negative electrode 2 from coming into contact with the adhesive layer 5a of the conductive adhesive tape 5, and the positive electrode 1 and the negative electrode 2 are electrically conductive at the respective side edges. This prevents electrical short circuit through the adhesive layer 5 a of the adhesive tape 5. Since other configurations are the same as those of the first embodiment, description thereof is omitted. As shown in FIGS.
- the part follows a path that flows through the conductive layer 5 b of the conductive adhesive tape 5 and then returns to the negative electrode 2. Further, a path through which a short-circuit current flows from the positive electrode 1 of the electrode laminate 4 to the negative electrode 2 of the electrode laminate 4 through the foreign matter 10, the conductive layer 5b, and the adhesive layer 5a is also generated. For this reason, it is possible to prevent an excessive current from concentrating only on a specific position inside the electrode laminate 4 (in the vicinity of the foreign material 10). As a result, it is possible to eliminate or reduce the risk of causing a large amount of heat generation inside the electrode laminate 4 to cause rupture or ignition.
- FIG. 6 shows a modification of the secondary battery of this embodiment.
- the side portion of the separator 3 is bent, and the bent portion 3 a functions as an insulating member that prevents a short circuit between the positive electrode 1 and the negative electrode 2. That is, since the bent portion 3a of the separator 3 covers the side edge of the positive electrode 1 and the side edge of the negative electrode 2 so as not to contact the conductive layer 5b of the conductive adhesive tape 5, the positive electrode 1 and the negative electrode 2 are There is no electrical short circuit through the conductive layer 5b.
- the separator 3 is formed in a bag shape that accommodates the positive electrode 1. That is, the separator 3 is formed in a bag shape in which one side (the right side in FIG. 7a) is opened and the other three sides (the left side in FIG. 7a and the left and right sides in FIG. 7b) are closed. Yes.
- the positive electrode 1 is accommodated in the bag-shaped separator 3.
- the bag-shaped separator as shown in FIGS. 7a and 7b can be formed by folding one long separator in half and joining the overlapping portions on two sides other than the bent portion by, for example, heat welding or the like. . It can also be formed by stacking two separators and joining the three sides together.
- the positive electrode 1 can be accommodated in the bag-shaped separator 3 by inserting the positive electrode 1 from one side that remains open without being joined.
- the negative electrode 2 can be accommodated in the bag-shaped separator 3.
- the positive electrode 1 and the negative electrode 2 are electrically short-circuited through the foreign material 1 due to the foreign object 10 being pierced
- the positive electrode 1 and the negative electrode 2 pierced with the foreign material 10 are electrically conductive.
- a current is guided to the conductive layer 5 b through the conductive adhesive layer 5 a of the tape 5. That is, a part of the current generated by the electrical short circuit follows a path returning to the negative electrode 2 after flowing through the conductive layer 5 b of the conductive adhesive tape 5 wound around the electrode laminate 4.
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
- Connection Of Batteries Or Terminals (AREA)
- Sealing Battery Cases Or Jackets (AREA)
- Cell Separators (AREA)
Abstract
Description
二次電池は大別して巻回型と積層型に分類できる。巻回型二次電池の電池素子は、長尺の正極シートと負極シートとがセパレータによって隔離されつつ重ね合わされた状態で複数回巻き回された構造を有する。積層型二次電池の電池素子は、正極シートと負極シートとがセパレータによって隔離されながら交互に繰り返し積層された構造を有する。巻回型二次電池と積層型二次電池のいずれにおいても、電池素子と電解液が外装容器に収容されている。特許文献1,2には、熱伝導性の高いシートを電池素子に巻き付けた構成が開示されている。
しかし、仮に二次電池に例えば釘などの鋭利な金属片が突き刺さると、突き刺さった金属片を介して正極と負極とが電気的に短絡して過大な電流が流れて、電池が発熱して破裂や発火を生じるおそれがある。特に、二次電池は年々大容量化する傾向にあり、これに伴って、電気的短絡が発生した場合の発熱がより大きくなり、特許文献1,2に記載されているような熱伝導性の高いシートによる放熱ではもはや不十分である。従って、二次電池のさらなる安全対策が求められている。
そこで本発明の目的は、異物が突き刺さったときに正極と負極の電気的短絡により発生する不具合を抑えることができる二次電池を提供することにある。
図1,2a,2bは、本発明を採用した積層型のリチウムイオン二次電池の構成の一例を模式的に示している。本発明のリチウムイオン二次電池100は、正極1と負極2とが、セパレータ3を介して交互に複数層積層された電極積層体(電池素子)4を備えている。この電極積層体4に導電性粘着テープ5が巻き付けられている。導電性粘着テープ5は多層構造であり、内側に位置する層は導電性と粘着性を有する粘着層5aであり、外側に位置する層は導電層5bである。そして、導電性粘着テープ5によって覆われた電極積層体4と電解液6が、外装容器内に収納されている。図2a,2bでは、電極積層体4を構成する各層の一部(厚さ方向の中間部に位置する層)を図示省略して、電解液6を示している。
図1に示すように、正極1と負極2にはそれぞれタブ1a,2aが設けられており、正極タブ1aは正極端子8の一端部に接続され、負極タブ2aは負極端子9の一端部に接続されている。正極端子8の他端部および負極端子9の他端部は、それぞれ外装容器の外部に引き出されている。負極2の外形寸法は正極1の外形寸法よりも大きく、セパレータ3の外形寸法よりも小さい。この二次電池100では、導電性粘着テープ5の内側層である粘着層5aが、電極積層体4の表面に位置する負極2に密着して接着し、電気的に接続されている。
本実施形態の導電性粘着テープ5の粘着層5aは、例えばアクリル系粘着剤に導電性フィラー(導電性樹脂、炭素粒子、金属粒子など)を混入した混合物から形成されている。導電層5bは、例えばポリエステル等からなる不織布に銅やニッケルのメッキを施した導電性不織布や、銅やアルミニウム等の金属からなる。
また、図3に模式的に示す電気的短絡のもう1つの経路では、電極積層体4の正極1からの電流が、異物10を介して導電層5bに導かれ、この導電層5bから粘着層5aを介して、電極積層体4の負極2に流れる。この経路において負極2に電流が流れる位置は、上述したもう1つの経路において負極2に電流が流れる位置とは一致せず離れた位置になると考えられる。すなわち、図3に模式的に示す電気的短絡の2つの例において、負極2に電流が流れる位置が互いに異なる。このように、短絡電流の経路は分散して、電極積層体4の内部の特定の位置(異物10の近傍)のみに集中的に短絡電流が流れることはない。従って、発熱は分散され、局所的に大きな発熱を生じることが抑えられる。電極積層体4の外側に位置する導電性粘着テープ5に電流が流れることにより生じる熱は、外装フィルム7との間に介在する空気に伝わり、さらにこの空気から外装フィルム7を通して外部に放出されるため、電極積層体4自体の過度の温度上昇が抑えられる。
仮に、粘着層5aの代わりに、粘着性を持たない非粘着層が存在すると、電極積層体4の最外層に位置する電極(本実施形態の場合は負極2)との密着性が低いので、最外層の電極から非粘着層に電流が導かれにくい。そのため、電極積層体4の内部において、隣接する正極1と負極2とが異物10を介して短絡する最短の経路のみに集中して電流が流れ、その経路上の位置(異物10の近傍)に過大な電流が流れて大きな発熱を生じる可能性が高い。また、仮に導電性粘着テープの厚さ方向の電気抵抗が大きいと、内側の粘着層5aが粘着性を有していても電流が外側の導電層5bに導かれにくく、やはり電極積層体4の内部の特定の位置(異物10の近傍)のみに集中して過大な電流が流れて大きな発熱を生じる可能性が高い。本発明のように、内側層として粘着性と導電性を備えた粘着層5aを有し、かつ厚さ方向に1.0Ω/cm2以下の低い電気抵抗を有している導電性粘着テープ5を用いて電極積層体4を覆うことによって、最短経路に限られず、図3に示す2つの経路にも分散して電流が流れるため、電極積層体4の内部での過度の発熱を抑制する効果が得られる。
図1,2a,2bに示すように絶縁部材11を持たない構成においては、正極1と負極2の電気的短絡を防ぐために、正極1の側端縁と負極2の側端縁の少なくとも一方が導電性粘着テープ5の粘着層5aに接触しないように各部材の寸法を適宜に調整する必要がある。図1,2a,2bに示す例では、正極1の寸法を小さくしている。しかし、本実施形態では、各部材の寸法を調整する必要はなく、確実な短絡防止が可能である。
そして、第1の実施形態と同様に、仮に二次電池100に釘などの異物10が刺さって一部の正極1とそれに隣接する負極2が電気的に短絡したとしても、短絡による電流の一部は、導電性粘着テープ5の導電層5bを流れてから負極2に戻る経路をたどる。また、電極積層体4の正極1から、異物10と導電層5bと粘着層5aとを介して、電極積層体4の負極2に短絡電流が流れる経路も生じる。そのため、電極積層体4の内部の特定の位置(異物10の近傍)のみに集中して過大な電流が流れることが防げる。その結果、電極積層体4の内部で大きな発熱を生じて破裂や発火を引き起こす危険性を解消または低減できる。
本変形例では、正極1および負極2の側端縁における短絡を防ぐために、セパレータ3の一部を屈曲させるだけでよいため、絶縁部材を別部材として用意する必要がなく、絶縁部材の位置合わせも不要であり、製造工程が煩雑になることはない。
図6に示す例では、全てのセパレータ3に屈曲部3aを形成して、正極1の側端縁と負極2の側端縁のいずれも導電性粘着テープ5の粘着層5aに接触しないようにしている。しかし、正極1の側端縁と負極2の側端縁のいずれか一方のみが導電性粘着テープ5の粘着層5aに接触しないようにするだけでも、短絡防止の効果は得られる。その場合、図示しないが、一部のセパレータ3(概ね半数のセパレータ3)のみに屈曲部3aを形成するだけでよい。
図7a,7bに示すような袋状のセパレータは、1枚の長尺のセパレータを2つ折りにして、折り曲げ部以外の2辺において重なり合う部分同士を、例えば熱溶着等によって接合することによって形成できる。また、2枚のセパレータを重ね合わせて、3辺を互いに接合することによって形成することもできる。いずれの場合も、接合されずに開口したままである1辺から正極1を挿入することによって、袋状のセパレータ3の内部に正極1が収容された状態にすることができる。もちろん、正極1ではなくて負極2が袋状のセパレータ3の内部に収容された構成にすることもできる。
本実施形態では、絶縁部材を別途用意する必要がなく容易に電気的短絡が防止でき、しかも、正極1と負極2がセパレータ3を介して積層された状態にする作業が簡単である。
前記した各実施形態は積層型の二次電池に関するものであるが、巻回型の二次電池においても、第1~2の実施形態と同様な構成を採用して、前記したのと同様な効果を得ることができる。
本出願は、2014年4月25日に出願された日本特許出願2014-91108号を基礎とする優先権を主張し、日本特許出願2014-91108号の開示の全てをここに取り込む。
Claims (5)
- 正極と負極とがセパレータを介して重なり合っている電池素子と、
導電性と粘着性を有し前記電池素子の表面に接着している粘着層と前記粘着層に積層された導電層とを含む多層構造であり、厚さ方向の電気抵抗が1.0Ω/cm2以下であり、前記電池素子の外周部分の少なくとも一部を覆って巻き付けられている導電性粘着テープと、
を有する二次電池。 - 前記電池素子の側面に位置し、前記正極と前記負極の少なくとも一方の側端縁を、前記粘着層と接触しないように覆う絶縁部材をさらに有する、請求項1に記載の二次電池。
- 前記絶縁部材は前記セパレータの側部に設けられた屈曲部である、請求項2に記載の二次電池。
- 前記セパレータは袋状に形成されており、前記正極と前記負極のいずれか一方が、袋状の前記セパレータ内に収容されており、前記電池素子は、前記正極と前記負極のうちの一方を収容している袋状の前記セパレータと、前記正極と前記負極のうちの他方とが交互に積層されて構成されている、請求項1に記載の二次電池。
- 前記導電性粘着テープの前記粘着層は導電性フィラーを含有している、請求項1から4のいずれか1項に記載の二次電池。
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