JP2012243839A - Electric power storage device cell and electric power storage device cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power storage device cell or the like for not easily causing deformation and breakage of a flat rolled electrode when bearing is applied to a flat surface, and maintaining high battery performance and stability over a long period of time.SOLUTION: For a flat rolled electrode 4, a positive electrode 8 and a negative electrode 9 for which an electrode active material is applied to current collector foil, and a separator 11 are piled up and rolled into a flat shape. At positive electrode and negative electrode peripheral edge parts, respectively, side edge parts are electrically connected in a lamination direction, and a positive electrode terminal and a negative electrode terminal are connected. An exterior container 6 houses the flat rolled electrode, a connection part 12 between the positive electrode terminal and the positive electrode peripheral edge part, and a connection part 13 between the negative electrode terminal and the negative electrode peripheral edge part. A buffer material 5 is provided between the exterior container and the flat rolled electrode and the pair of connection parts, and the buffer material is thicker at a part covering the connection parts than at a part covering a flat part.

Description

  The present invention relates to a flat wound power storage device cell such as an electric double layer capacitor, a lithium ion battery, or a lithium ion capacitor, or a module in which a plurality of cells are connected in series.

  Examples of the power storage device cell accommodated in the container in a flat wound shape include a lithium ion battery, an electric double layer capacitor, and a lithium ion capacitor. A lithium ion battery uses an oxide such as cobalt, nickel, and manganese for a positive electrode and a carbon material for a negative electrode, and performs charge and discharge by inserting and removing lithium ions from and into the carbon negative electrode. The electric double layer capacitor is provided with polarizable electrodes (positive electrode and negative electrode) facing each other with a separator interposed therebetween, and utilizes the capacitance of the electric double layer formed on the surface of the polarizable electrode in the electrolytic solution. . Further, as a new electric double layer capacitor, a lithium ion capacitor in which the negative electrode of the electric double layer capacitor is doped with lithium ions has been developed.

  These power storage device cells are inexpensive and can be configured compactly, but the output voltage is about 2 to 4V, which is lower than the output voltage of the aluminum electrolytic capacitor, 400V. Used as.

  The electrode used in the flat wound power storage device cell is formed by applying a positive electrode layer and a negative electrode layer on both sides of a belt-like positive electrode collector foil and a negative electrode collector foil having a thickness of about 10 to 50 μm. It is wound several m to several tens of meters around a flat winding shaft core through a porous strip-shaped separator made of an olefin resin fiber or the like. The flat wound power storage device cell configured in this way can be manufactured in a shorter time than a stacked power storage device cell in which dozens of strip-shaped electrodes are stacked. It is also advantageous in terms of cost.

  Such flat-winding electric double layer capacitors and lithium ion capacitors are expected to be used for storing motor regenerative energy from the viewpoint of energy saving, and are required to have high current charge / discharge repetition characteristics exceeding 100A. Yes. When a large current flows, power loss is generated in proportion to the square of the current and the internal resistance, and charge / discharge efficiency deteriorates. Further, since this power loss directly generates heat, it is necessary to quickly dissipate heat from the current collector foil that is a heat conductor in order to maintain the quality. Therefore, in order to reduce the current collecting resistance and efficiently dissipate the heat of the current collecting foil to the outside, the positive electrode and the negative electrode are not coated with the electrode layer protruding from the separator in the opposite direction along the winding axis direction. The structure of the flat wound battery which provided the edge part and overlapped and welded the positive electrode terminal and the negative electrode terminal in this edge part is disclosed (for example, refer patent document 1).

  For the exterior of the flat wound electrode, a laminated film in which a metal is bonded to a metal container or a plastic film is used. Since the laminate film is thinner and lighter than the metal container, there is an advantage that the capacity per weight of the power storage device cell is improved.

  However, since the laminate film has low rigidity and is weak against external impact, it is protected from impact by forming a resin layer in the battery element or filling the resin before the wound element is housed and sealed in the exterior material. A flat wound type power storage device cell configuration is disclosed (for example, see Patent Document 2). In addition, a structure is disclosed in which an elastic body is disposed on at least one surface of a battery element in which current collector foils and separators serving as positive electrodes or negative electrodes are alternately laminated (see, for example, Patent Document 3).

  Flat wound electric double layer capacitors and lithium ion capacitor cells and modules reduce contact resistance and stabilize performance by applying a certain surface pressure in a direction perpendicular to the flat surface of the flat wound electrode. be able to.

JP 2000-040501 A JP 2000-173641 A JP 2004-103415 A

  However, the surface pressure applied to the flat surface by the unevenness that occurs in the flat surface of the flat wound electrode due to the situation such as deviation or looseness when winding the flat wound electrode, the tape that holds the wound shape, or the welding part of the electrode terminal There is a problem in that the surface pressure is excessively applied locally without being uniform, and as a result, the electrode layer may be peeled off or the separator may be damaged at a portion where the surface pressure is excessively applied. Moreover, in the module using the cell which has those unevenness | corrugations, when the structure laminated | stacked so that the flat surfaces of a cell may overlap, there exists a possibility that the surface pressure concerning each cell may become more non-uniform | heterogenous.

  Furthermore, when a flat wound electrode without a wound core material is subjected to surface pressure, the bent portion is deformed, and the electrode layer and the separator may be stretched or broken to be damaged.

  When the separator is damaged or when an electrode piece peeled off from the electrode penetrates the separator, a short circuit is caused, and heat generation or a rapid decrease in cell performance occurs.

  In the configuration in which the terminal is overlapped and welded to the peripheral edge of the electrode to which the electrode layer is not applied as in Patent Document 1, unevenness caused by welding of the flat wound electrode and the current collecting terminal may damage the exterior material. When the exterior material is damaged, the enclosed electrolyte leaks out or impurities are mixed into the cell. In particular, when an exterior made of an aluminum laminate film is used, the exterior is likely to be damaged. Although the configuration of Patent Document 3 is not a wound type and is a laminated type, it cannot be compared uniformly, but the elastic body protects the flat part of the electrode, but it does not protect the terminal welded part and may damage the exterior. It was. Further, in the configuration of Patent Document 2, the flat wound electrode is protected against an impact from the outside, but when the surface pressure is applied, the internal irregularities cannot be relaxed, and there is a possibility that an internal short circuit occurs.

  The present invention has been made in view of the above, and a power storage device that maintains high battery performance and stability over a long period of time when deformation and breakage of a flat wound electrode are difficult to occur when surface pressure is applied to a flat surface. An object is to provide cells and modules.

  In order to achieve the above-described object, the power storage device cell of the present invention includes a flat wound electrode, a positive electrode terminal and a negative electrode terminal, and an outer container, and the flat wound electrode has electrode active surfaces on both sides of the current collector foil. A belt-like positive electrode and negative electrode coated with a substance, and a belt-like separator having electrical insulation sandwiched between them are overlapped and wound into a flat shape. In addition, edge portions where no electrode active material is formed are provided, and these edge portions protrude from the separator in directions opposite to each other in the winding axis direction. Positioned on both sides of the flat portion, a positive electrode peripheral edge and a negative electrode peripheral edge are formed, and the positive electrode peripheral edge and the negative electrode peripheral edge are respectively electrically connected in the stacking direction between the corresponding peripheral edges. The positive terminal and The electrode terminal is connected, and the exterior container is provided with the electrolyte solution, the flat wound electrode, the connection part between the positive electrode terminal and the positive electrode peripheral part, and the connection part between the negative electrode terminal and the negative electrode peripheral part. And a cushioning material is provided between the outer casing, the flat wound electrode and the pair of connection portions, and the cushioning material has a portion covering the connection portion, It is thicker than the part covering the flat part.

  According to the present invention, in the power storage device cell or the power storage device cell module configured as described above, when surface pressure is applied to the flat surface of the cell in order to reduce the contact resistance and stabilize the cell performance, It is difficult for deformation and breakage of the rotating electrode, and high battery performance and stability can be maintained over a long period of time.

It is a plane schematic diagram for demonstrating the power storage device cell which concerns on this invention. It is a perspective schematic diagram for demonstrating the flat winding electrode of the power storage device cell which concerns on this invention. It is a schematic diagram for demonstrating the manufacturing process of the flat winding electrode of the power storage device cell which concerns on this invention. It is typical sectional drawing which shows the A-A 'line cross section of FIG. It is typical sectional drawing which shows the B-B 'line cross section of FIG. It is an expansion schematic diagram of the welding part between the terminal-periphery part of FIG. It is a schematic diagram for demonstrating the power storage device cell module which concerns on this invention.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts. Note that the drawings are described in a simplified manner in order to facilitate the understanding of the description, and the dimensions and shapes are not necessarily accurate.

  FIG. 1 is a schematic plan view of a power storage device cell according to an embodiment in which the present invention is applied to an electric double layer capacitor. In addition, this invention is not restricted to an electric double layer capacitor, Even if it is a lithium ion battery, a lithium ion capacitor, etc., it can implement similarly.

  In the power storage device cell 1 of the present embodiment, a flat wound electrode 4 and an electrolytic solution are enclosed in an outer container 6. In order to increase the capacity per volume of the cell and to remove moisture inside, the electrolytic solution may be sealed after degassing the exterior container. In the present embodiment, a gas release valve 7 is attached to the outer container 6 and these components are not necessarily required, but an effect of suppressing an increase in cell internal pressure due to gas generated during operation can be obtained.

  The electrolyte enclosed in the power storage device cell differs depending on the electric double layer capacitor, lithium ion battery and lithium ion capacitor, but commonly used materials can be used as they are. For example, a combination of a cation and an anion, where the cation is quaternary ammonium, 1,3-dialkylimidazolium, or 1,2,3-trialkylimidazolium, and the anion is BF4-, PF6-, ClO4-, or A salt of CF3SO3-, a salt of 1-ethyl-3-methylimidazolium (EMI), 1,2-dimethyl-3-propylimidazolium (DMPI) such as AlCl4- or BF4- is used, and the solvent As propylene carbonate, ethylene carbonate, dimethyl carbonate, sulfo Emissions, diethyl carbonate, dimethoxymethane, diethoxyethane, .gamma.-butyrolactone, acetonitrile, etc. One or these two or more mixed solvents selected from propionitrile is used. In the present embodiment, the electrolytic solution means a liquid electrolyte solution containing these.

  As shown in FIG. 2, the peripheral portion of the positive electrode current collector foil (a portion in the winding state of the edge portion described later) 14 and the peripheral edge portion of the negative electrode current collector foil (a portion in the wound state of the edge portion described later) 15 The welded portions 12 and 13 are connected by ultrasonic welding in the laminating direction, respectively, and the peripheral edge portion 14 of the positive electrode current collector foil is the positive electrode terminal 2, and the peripheral edge portion 15 of the negative electrode current collector foil is the negative electrode terminal 3. Connected by ultrasonic welding. Since the laminated current collector foil and the electrode terminal are electrically connected, the current collection resistance is reduced and the heat generated by the internal current collector foil is quickly stored via the electrode terminal. Since it can transmit to the exterior of a device cell, the thermal radiation characteristic of a cell can be improved.

  An aluminum foil having a thickness of about 20 to 30 μm is used for the positive electrode current collector foil, and an aluminum foil having a thickness of about 20 μm or a copper foil having a thickness of about 10 to 20 μm is used for the negative electrode current collector foil. As the positive electrode terminal 2, aluminum or stainless steel having a thickness of about 0.3 to 1 mm is used, and as the negative electrode terminal 3, aluminum having a thickness of about 0.3 to 1 mm or nickel-plated copper is used. The thicknesses of these metal foils and current terminals are selected depending on the magnitude of the current to be extracted, and thicker materials are used because it is necessary to reduce the resistance as the current increases.

  In the present embodiment, as shown in FIG. 6A, the current collecting terminal 17 such as the positive electrode terminal 2 or the negative electrode terminal 3 is formed by bending a single aluminum plate to form the peripheral edge portion 14 of the positive electrode side current collector foil or the negative electrode side current collector. Although the current collector foil peripheral portion 18 such as the peripheral portion 15 of the electric foil is sandwiched, the current collector foil peripheral portion 18 may be sandwiched by a plurality of current collector terminals 17 as shown in FIG. Further, the current collecting terminal 17 may be joined to the current collecting foil peripheral portion 18 without being sandwiched as shown in FIG. Further, it is not necessary for all the current collecting foils to be laminated, but it is preferable that a plurality of current collecting foils are joined to the current collecting terminals 17 in order to conduct heat quickly. Since welding of the current collecting terminal 17 is performed by ultrasonic welding or spot welding, welding marks remain in the welded portion 12 between the positive electrode terminal and the positive electrode peripheral portion and the weld portion 13 between the negative electrode terminal and the negative electrode peripheral portion. It becomes.

  FIG. 4 shows an A-A ′ cross section of the power storage device cell 1. A buffer material 5 is provided between the flat wound electrode 4 and the exterior material 6. The buffer material 5 covers the flat surface of the flat wound electrode 4, the positive electrode current collector foil peripheral part 14, and the negative electrode current collector foil peripheral part 15, and has a structure in which these do not directly contact the outer container 6. The buffer material 5 has a thicker structure at a portion in contact with the welded portion 12 between the positive electrode terminal and the positive electrode peripheral portion and a portion in contact with the welded portion 13 between the negative electrode terminal and the negative electrode peripheral portion than the portion in contact with the flat surface of the flat wound electrode.

  In the weld between the current collector terminal and current collector foil, the outer container may be damaged by sharp irregularities in the weld marks that occur during welding, in addition to the step created by overlapping the material of the current collector terminal and current collector foil. The outer container is protected by covering them. In particular, when a laminate film is used, the outer container is likely to be damaged in a structure that does not have a buffer material, and when the cell is sealed in a decompressed state, the outer container is in close contact with the flat wound electrode. Significant damage occurs.

  The material of the buffer material may be a synthetic resin porous material having a closed pore that is soft and does not adsorb an electrolyte solution, or a synthetic resin material having no pores. For example, chloroprene rubber, silicone rubber, natural rubber, styrene butadiene rubber, nitrile rubber, ethylene-propylene rubber, fluorine rubber, butyl rubber, urethane rubber and the like can be used.

  As the thickness of the buffer material increases, the unevenness of the cell can be flattened better. On the other hand, by increasing the thickness of the buffer material, the cell volume increases and the capacity per volume decreases. Therefore, the buffer material preferably has a thickness of 50 μm to 5 mm in a region in contact with the flat surface of the flat wound electrode.

  FIG. 3 shows an electrode laminated structure in a flat wound electrode manufacturing process. An insulating separator 11 is installed between the positive electrode 8 and the negative electrode 9. The positive electrode current collector foil and the negative electrode current collector foil are coated with the electrode active material on both sides, and the edge portions where the electrode active material is not formed protrude from the separator in directions opposite to each other with respect to the winding axis direction. .

  A B-B ′ cross section of the power storage device cell 1 is shown in FIG. 5, and the flat wound electrode 4 is formed around the wound core material 16. The wound core material is used only for flat winding and is often pulled out at the time of the completed cell, but it may be left or after the winding core material used at the time of winding is removed Another core material may be inserted.

  The separator 11 is made of cellulose such as natural pulp, natural cellulose, solvent-spun cellulose, and bacterial cellulose, non-woven fabric containing glass fiber and non-fibrillated organic fiber, aromatic polyamide, wholly aromatic polyamide, aromatic polyester, all Aromatic polyesters, wholly aromatic polyester amides, wholly aromatic polyethers, wholly aromatic polyazo compounds, polyphenylene sulfide (PPS), poly-p-phenylenebenzobisthiazole (PBZT), poly-p-phenylenebenzobisoxazole (PBO) ), Polybenzimidazole (PBI), polyetheretherketone (PEEK), polyamideimide (PAI), polyimide, polytetrafluoroethylene (PTFE), and the like. The thickness is about 15 μm to 50 μm, the porosity (porosity) is about 50% to 80% by volume, and the average pore diameter is several μm to several tens μm. There are various average pore diameters, and the same material can be easily changed with the basis weight.

  The wound core member 16 can be made of a flat resin plate or metal plate having a high rigidity and a small deformation amount with respect to the surface pressure applied to the flat surface. However, when using a metal plate, it is necessary to coat the surface of the metal plate with a non-conductive material or to prevent the short circuit between the positive and negative electrodes or to contact the positive and negative electrodes. Examples of the metal plate used include aluminum, copper, and stainless steel. When using a resin plate, polyethylene, polypropylene, epoxy resin, polytetrafluoroethylene, polyetheretherketone, polyamideimide, polyimide and the like can be used.

  The materials for the positive electrode layer and the negative electrode layer differ depending on the electric double layer capacitor, the lithium ion battery and the lithium ion capacitor, but generally used materials can be used as they are. Can be obtained by adding carbon black as a conductive material to activated carbon fine particles, adding a thickener and a binder, forming a paste, applying and drying. Although the thickness changes with uses, about 10-100 micrometers is preferable.

  FIG. 7 shows a structural example of the power storage device cell module. The power storage device cell module 19 is formed by connecting a plurality of the above-described power storage device cells 1 in series in order to increase the output voltage, and is stacked so that the flat surfaces of the power storage device cells 1 are in contact with each other. Yes. However, the structure of the power storage device cell module is not limited to a structure in which cells are stacked, and may be arranged and connected in a planar shape, for example. When arranged in a plane, it is difficult to apply a surface pressure because the module area becomes large, but heat radiation is advantageous.

  As described above, according to the present embodiment, the situation such as deviation or looseness when winding the flat wound electrode, the unevenness caused by the tape that holds the wound shape, and the unevenness caused by the welded portion of the electrode terminal. By covering with the buffer material, the surface pressure applied to the flat surface of the cell can be made uniform, and the peeling of the electrode layer and the breakage of the separator caused by the uneven surface pressure can be prevented. In addition, the buffer material at the part in contact with the terminal welded part of the flat wound electrode is made thicker than the buffer material at the part in contact with the flat part of the flat wound electrode, so that sharp metal irregularities caused by terminal welding are buffered. Since it is suppressed that the exterior is damaged by being covered with the material, it is possible to prevent the deterioration of the performance due to leakage of the electrolyte solution due to the breakage of the cell or mixing of impurities. These preferable actions mean that even if a surface pressure is applied in a direction perpendicular to the flat surface of the flat wound electrode, damage to each part can be prevented, that is, surface pressure is applied to the flat surface. It is possible to ensure the reduction of contact resistance due to. As described above, in this embodiment, when a surface pressure is applied to the flat surface of the cell in order to reduce the contact resistance and stabilize the cell performance, it is difficult for the flat wound electrode to be deformed and damaged, and for a long time. High battery performance and stability can be maintained.

  In addition, the buffer material is composed of a synthetic resin porous material having closed pores or a synthetic resin material having no pores, so that the buffer material avoids adsorbing the electrolytic solution, and the electrolytic material sealed in the cell is used. The liquid can be held on the flat wound electrode, and the addition of excess electrolyte can be made unnecessary.

  In addition, since the thickness of the flat wound electrode is reduced by providing a rigid wound core material, the flat wound electrode may be damaged when the electrode layer and separator are stretched or bent at the bent portion. Can also be prevented.

  Further, in the configuration in which a plurality of positive electrode terminals of each power storage device cell and negative electrode terminals of other adjacent power storage device cells are adjacent to each other, and the positive electrode terminal and the negative electrode terminal are connected, the flatness of the cell Even in a module structure in which the surfaces overlap each other, the flat surface of the device cell is flat due to the buffer material, and the surface pressure is uniformly applied to all the cells, so that damage to the cell can be reduced.

  Although the contents of the present invention have been specifically described with reference to the preferred embodiments, various modifications can be made by those skilled in the art based on the basic technical idea and teachings of the present invention. It is self-explanatory.

  DESCRIPTION OF SYMBOLS 1 Power storage device cell, 2 Positive electrode terminal, 3 Negative electrode terminal, 4 Flat wound electrode, 5 Buffer material, 6 Exterior container, 7 Gas release valve, 8 Positive electrode, 9 Negative electrode, 11 Separator, 12 Positive electrode terminal-positive electrode periphery Welded part (connecting part) between parts, 13 welded part (connected part) between negative electrode terminal and negative electrode peripheral part, 14 positive electrode peripheral part, 15 negative electrode peripheral part, 16 wound core material, 17 current collecting terminal, 18 electrode peripheral part Section 19 Power storage device cell module.

Claims (5)

A flat wound electrode, a positive electrode terminal and a negative electrode terminal, and an outer container,
The flat wound electrode has a flat shape in which a strip-like positive electrode and negative electrode each coated with an electrode active material on both sides of a current collector foil and a strip-like separator having electrical insulation sandwiched therebetween are overlapped. That was turned,
Each of the positive electrode and the negative electrode is provided with an edge portion where no electrode active material is formed, and the edge portions protrude in the opposite directions from the separator in the winding axis direction and are wound. In the flat wound electrode, located on both sides of the flat portion, forming a positive electrode peripheral edge and a negative electrode peripheral edge,
Each of the positive electrode peripheral edge and the negative electrode peripheral edge is electrically connected in the stacking direction between the corresponding peripheral edges, and the positive electrode terminal and the negative electrode terminal are connected,
The outer container accommodates the flat wound electrode, a connection portion between the positive electrode terminal and the positive electrode peripheral portion, and a connection portion between the negative electrode terminal and the negative electrode peripheral portion, together with the electrolyte,
A buffer material is provided between the outer container, the flat wound electrode and the pair of connection portions,
The buffer material is a power storage device cell in which a portion covering the connection portion is thicker than a portion covering the flat portion.   The power storage device cell according to claim 1, wherein the buffer material is a synthetic resin porous material having closed pores or a synthetic resin material having no pores.   The power storage device cell according to claim 1 or 2, wherein the flat wound electrode has a wound core material.   The power storage device cell according to claim 3, wherein the wound core member is formed of a flat resin plate or a metal plate. Comprising a plurality of power storage device cells,
The power storage device cell is the power storage device cell according to any one of claims 1 to 4,
The plurality of power storage device cells are power storage device cell modules provided so as to connect a positive terminal of one power storage device cell and a negative terminal of another adjacent power storage device cell.

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