JP2015191687A - power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of suppressing the movement (displacement) of an electrode assembly inside a case.SOLUTION: A power storage device is configured such that an electrode assembly is housed in a case, and that an insulator film is provided between the case and the electrode assembly. The insulator film includes resin with adhesion which increases when a load is applied thereto. For example, a layer 4b made of the resin may be formed on the case 2 side of an insulator film 4A. A layer 4d made of the resin may be formed on the electrode assembly 3 side of an insulator film 4B. Particles 4f made of the resin may be included inside an insulator film 4C.

Description

  The present invention relates to a power storage device in which an electrode assembly is accommodated in a case and an insulating film is provided between the case and the electrode assembly.

  A power storage device such as a lithium ion secondary battery is configured such that an electrode assembly in which a positive electrode and a negative electrode are stacked via a separator, an electrolytic solution, and the like are housed in a metal case. For example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte is used as an electrolyte, and an electrode body that is a power generation element is inserted into an outer can.

Japanese Patent Laid-Open No. 9-120836

  An insulating film is provided between the electrode assembly and the metal case to prevent a short circuit. Since the insulating film is made of polypropylene or the like, the coefficient of friction with the case is low, and the electrode assembly may move within the case. When the electrode assembly moves (displaces) in the case, for example, the welded portions between the tabs (metal foils) of the electrodes of the same polarity of the electrode assembly are peeled off, or the welded portion between the tabs and the conductive member is removed. It may come off.

  Therefore, in this technical field, there is a demand for a power storage device that can suppress the movement (displacement) of the electrode assembly in the case.

  A power storage device according to one aspect of the present invention is a power storage device in which an electrode assembly is housed in a case and an insulating film is provided between the case and the electrode assembly, and the insulating film is subjected to a load. Includes resins that increase adhesion.

  In this power storage device, an insulating film is provided outside the electrode assembly, and the electrode assembly is accommodated in a case. In particular, since this insulating film contains a resin whose adhesive force increases when a load is applied, the insulating film has a larger adhesive force after the load is applied than before the load is applied. This large adhesive force increases the coefficient of friction with the case, and makes it difficult for the electrode assembly to move within the case. However, before the load is applied, the adhesive strength of the insulating film does not increase. Therefore, when the electrode assembly is accommodated in the case with the insulating film provided outside the electrode assembly, the coefficient of friction with the case is not yet high. A solid can be inserted into the case. In this manner, the power storage device can suppress the movement (displacement) of the electrode assembly in the case after the load is added by including in the insulating film the resin whose adhesive force increases when the load is applied.

  In the power storage device of one embodiment, the insulating film has a resin layer formed on the case side. In the case of this insulating film, when a load is applied, the adhesive force of the resin layer on the case side increases, so the coefficient of friction with the case in contact with the resin layer increases.

  In the power storage device of one embodiment, the insulating film has a resin layer formed on the electrode assembly side. In the case of this insulating film, when a load is applied, the adhesive force of the resin layer on the electrode assembly side increases, and when the resin having increased adhesive force from the resin layer reaches the case side, The coefficient of friction increases. In the case of this insulating film, since the resin layer is on the electrode assembly side, the friction coefficient is low on the case side of the insulating film before the load is applied, and the electrode assembly with the insulating film provided is accommodated in the case. Can be inserted smoothly.

  In the power storage device of one embodiment, the insulating film contains particles made of resin inside. In the case of this insulating film, when a load is applied, the adhesive force of the resin particles increases, and when the resin particles having increased adhesive force reach the case side, the coefficient of friction with the case increases. Further, in the case of this insulating film, before the load is applied, the case side of the insulating film has a low coefficient of friction, and can be smoothly inserted when the electrode assembly in which the insulating film is provided is accommodated in the case.

  According to the present invention, by including the resin whose adhesive force increases when a load is applied to the insulating film, the movement (displacement) of the electrode assembly in the case can be suppressed after the load is applied.

1 is a perspective view schematically showing a power storage device according to one embodiment. It is a perspective view which shows typically the state by which the electrode assembly of the electrical storage apparatus of FIG. 1 was wrapped in the insulating film. It is a figure which shows typically the cross-sectional structure of the case in the electrical storage apparatus of FIG. 1, an insulating film, and an electrode assembly, (a) is a case where the layer which consists of pressure-sensitive adhesive resin exists in the case side of an insulating film. (B) is a case where there is a layer made of a pressure-sensitive adhesive resin on the electrode assembly side of the insulating film. (C) is a case where the pressure-sensitive adhesive resin particles are contained inside the insulating film.

  Hereinafter, a power storage device according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the element which is the same or it corresponds in each figure, and the overlapping description is abbreviate | omitted.

  The power storage device according to one embodiment is a rectangular power storage device in which an electrode assembly or the like is accommodated in a case. This power storage device is a power storage device such as a secondary battery or an electric double layer capacitor. The secondary battery is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. In this embodiment, it is assumed that the power storage device is applied to a lithium ion secondary battery.

  Note that the power storage device may be used alone, or may be used as a power storage module in which a plurality of power storage devices are electrically connected in parallel and / or in series. In the case of the power storage module, for example, a plurality of power storage devices are arranged along the direction in which the positive electrode and the negative electrode of the electrode assembly are stacked. Incidentally, in the conventional power storage module, in order to suppress the movement (displacement) of the electrode assembly in the case, the plurality of power storage devices are arranged in the stacking direction using a restraining member in a state where the plurality of power storage devices are arranged. Was restrained along.

  With reference to FIG.1 and FIG.2, the electrical storage apparatus 1 which concerns on one Embodiment is demonstrated. FIG. 1 is a perspective view schematically showing a power storage device 1 according to an embodiment. FIG. 2 is a perspective view schematically showing a state in which the electrode assembly of the power storage device 1 of FIG. 1 is wrapped in an insulating film.

  In the power storage device 1, an electrode assembly 3 or the like is accommodated in a case 2, and an insulating film 4 is provided between the case 2 and the electrode assembly 3. In particular, in order to hold the electrode assembly 3 in the case 2 by the insulating film 4, the insulating film 4 contains a resin whose adhesive force increases when a load (pressure from the outside) is applied. After that, the load is applied and the adhesive force of the insulating film 4 is increased. It should be noted that well-known components may be appropriately applied to the components other than the case 2, the electrode assembly 3, and the insulating film 4 of the power storage device 1, and detailed description thereof is omitted.

  The case 2 includes a bottomed rectangular tube-shaped main body 2a and a lid 2b that covers an opening at the top of the main body 2a. The case 2 is made of a metal such as aluminum or stainless steel. The main body 2a is composed of a rectangular flat plate-shaped bottom plate and four rectangular flat plate-shaped side plates extending vertically upward from four sides of the bottom plate. The lid 2b has a rectangular flat plate shape. The case 2 has a rectangular parallelepiped sealed space formed by the body 2a and the lid 2b. A positive electrode terminal 2c and a negative electrode terminal 2d projecting to the outside and inside of the case 2 are attached to the lid portion 2b.

  The electrode assembly 3 includes a positive electrode, a negative electrode, and a separator that insulates the positive electrode from the negative electrode, and the positive electrode, the negative electrode, and the separator are laminated. The electrode assembly 3 is accommodated in the case 2 in a state of being wrapped in an insulating film 4. The positive electrode includes a metal foil and a positive electrode active material layer formed on at least one surface of the metal foil. The positive electrode has a tab on which the positive electrode active material layer is not formed at the end of the metal foil. The tab is provided on the upper edge of the positive electrode (edge on the positive electrode terminal 2c side), and is electrically connected to the positive electrode terminal 2c through a conductive member. The negative electrode includes a metal foil and a negative electrode active material layer formed on at least one surface of the metal foil. The negative electrode has a tab on which the negative electrode active material layer is not formed at the end of the metal foil. The tab is provided on the upper edge of the negative electrode (the edge on the negative electrode terminal 2d side), and is electrically connected to the negative electrode terminal 2d via a conductive member. The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes.

  The positive electrode and the negative electrode have a thin sheet shape, and have a rectangular shape and a tab portion at the upper edge of the rectangular shape. The separator has a thin sheet shape or a bag shape, and has a rectangular shape. The electrode assembly 3 is formed by laminating a large number of positive electrodes and negative electrodes of this shape with a separator interposed therebetween, thereby forming a rectangular parallelepiped laminated structure having tabs of the respective electrodes at the upper edge. The rectangular parallelepiped shape of the electrode assembly 3 is substantially the same as the rectangular parallelepiped shape inside the case 2 and is slightly smaller in size. In FIGS. 1 and 2, the tabs on the upper edge of the electrode assembly 3 are omitted.

  The insulating film 4 is interposed between the case 2 and the electrode assembly 3 in order to prevent a short circuit due to the electrode assembly 3 coming into contact with the metal case 2. This is a film for insulation between the two. The insulating film 4 has a bag shape that wraps around the periphery of the electrode assembly 3 other than the upper surface portion without any gaps, and has respective side surface portions and lower surface portions that respectively cover the four side surfaces and the lower surface of the rectangular parallelepiped shape of the electrode assembly 3. Yes. As a method for forming the insulating film 4 into a bag shape, a conventional well-known method is applied. Examples of the insulating material of the insulating film 4 include polypropylene (PP), polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyester, polycarbonate, polystyrene, polyacrylonitrile, ethylene vinyl acetate copolymer, ethylene- Vinyl alcohol copolymer, ethylene-methacrylic acid copolymer, and nylon. Incidentally, the insulating film 4 has a low friction coefficient in the initial state (before the load is applied).

  Before the electrode assembly 3 is accommodated in the case 2, the electrode assembly 3 is wrapped with the bag-like insulating film 4, and the electrode assembly 3 is pulled out from the opening at the top of the insulating film 4 by the plurality of connection tapes 5. Is preventing. The connecting tape 5 is bridged between the opposing side portions at the opening of the insulating film 6, and the end portion of the connecting tape 5 is attached to the upper end portion of the side portion. The connection tape 5 may be an adhesive tape having insulating properties. In FIG. 2, two connection tapes 5 are drawn, but three or more or one connection tape 5 may be used.

  The insulation film 4 can hold the electrode assembly 3 in the case 2 and can be loaded (pressure from the outside) so that the electrode assembly 3 wrapped in the bag-like insulation film 4 can be smoothly inserted into the case 2. ) Is added, it contains a resin whose adhesive strength increases. This resin is a pressure-sensitive adhesive resin, for example, a resin constituted by blending various polymer elastomers with a tackifier, a crosslinking agent, a stabilizer, a plasticizer and the like as required. Depending on the type of elastomer, there are rubber type, acrylic type, silicone type and the like. The rubber-based elastomer is, for example, natural rubber or synthetic rubber (SIS, SBR). The acrylic elastomer is, for example, an acrylic ester copolymer. The silicone-based elastomer is, for example, silicone rubber. Other elastomers are, for example, vinyl ether copolymers and urethane resins. This pressure-sensitive adhesive resin, when a predetermined load (predetermined pressure) is applied for a predetermined time (for example, 1 hour, 2 hours) or more, the adhesive force becomes larger than before the load is applied, and the load is applied. It has the property of maintaining its high adhesive strength even after it is no longer used. The predetermined load and the predetermined time are determined depending on the type of pressure-sensitive adhesive resin used in the insulating film 4.

  With reference to FIG. 3, three forms in which the insulating film 4 contains a pressure-sensitive adhesive resin will be described. FIG. 3 is a diagram schematically showing a cross-sectional configuration of the case 2, the insulating film 4, and the electrode assembly 3 in the power storage device 1 of FIG. 1, and shows cross-sectional configurations of three forms. In FIG. 3, only a part of the case 2, the insulating film 4, and the electrode assembly 3 whose cross-sectional configurations are known is illustrated.

  In the case of the insulating film 4A in the form shown in FIG. 3A, the insulating film body 4a on the electrode assembly 3 side (bag-shaped inner side) and the pressure-sensitive adhesive resin layer 4b on the case 2 side (bag-shaped outer side) Composed. The insulating film body 4a is formed in a thin film shape using an insulating material. The pressure-sensitive adhesive resin layer 4b is a layer coated very thinly on the surface side of the insulating film body 4a using a pressure-sensitive adhesive resin. When the electrode assembly 3 encased in the bag-like insulating film 4A is accommodated in the case 2 and a load is applied, the adhesive force at the pressure-sensitive adhesive resin layer 4b in contact with the case 2 increases. The friction coefficient between the case 2 and the pressure sensitive adhesive resin layer 4b is increased.

  In the case of the insulating film 4B in the form shown in FIG. 3B, the insulating film body 4c on the case 2 side (bag-shaped outer side) and the pressure-sensitive adhesive resin layer 4d on the electrode assembly 3 side (bag-shaped inner side). Composed. The insulating film body 4c is formed into a thin film using an insulating material and is porous. The pressure-sensitive adhesive resin layer 4d is a layer that is very thinly coated on the back surface side of the insulating film body 4c using a pressure-sensitive adhesive resin. When the electrode assembly 3 wrapped in the bag-like insulating film 4B is accommodated in the case 2 and a load is applied, the pressure-sensitive adhesive resin layer 4d on the electrode assembly 3 side has a large adhesive force. When the pressure-sensitive adhesive resin layer 4d has increased in adhesive strength into the insulating film body 4c and the resin reaches the case 2 side through the porous insulating film body 4c, The coefficient of friction with the case 2 increases. In the case of this insulating film 4B, since the case 2 side is the insulating film body 4c, the coefficient of friction is low, and it can be smoothly inserted when the electrode assembly 3 wrapped in the bag-like insulating film 4B is accommodated in the case 2. .

  In the case of the insulating film 4C in the form shown in FIG. 3C, the insulating film body 4e and a large number of pressure-sensitive adhesive resin particles 4f,. The insulating film body 4e is formed in a thin film shape using an insulating material and is porous. The pressure-sensitive adhesive resin particles 4f are particles made of a pressure-sensitive adhesive resin and are scattered in the insulating film body 4e. When the electrode assembly 3 wrapped in the bag-like insulating film 4C is accommodated in the case 2 and a load is applied, the pressure-sensitive adhesive resin particles 4f in the insulating film body 4e are adhered. When the force increases and a part of the pressure-sensitive adhesive resin particles 4f,... Having increased adhesive strength reaches the case 2 side through the inside of the porous insulating film body 4e, The coefficient of friction between them increases. In the case of this insulating film 4C, since the case 2 side is the insulating film main body 4e (there may be pressure-sensitive adhesive resin particles 4f in part), the friction coefficient is low and the case is wrapped in a bag-like insulating film 4B. The electrode assembly 3 can be smoothly inserted when accommodated in the case 2.

  Note that the pressure-sensitive adhesive resin may be included in the insulating film 4 or may be included in the entire surface of the insulating film 4, or a side surface facing the side surface in the stacking direction of the positive electrode and the negative electrode in the electrode assembly 3 ( It may be included only in the wide side shown in FIG. Incidentally, in the case of the above-described conventional power storage module, the side surfaces in the stacking direction of the positive electrode and the negative electrode are constrained by a constraining member.

  The effect | action by this insulating film 4 is demonstrated. The electrode assembly 3 is wrapped with a bag-like insulating film 4, and the connection tapes 5, 5 are bridged and pasted on the opening of the insulating film 4. The electrode assembly 3 wrapped in the insulating film 4 is inserted into the main body 2 a of the case 2. At this time, since the load is not yet applied to the insulating film 4, the adhesive force of the pressure-sensitive adhesive resin is not increased. Therefore, the electrode assembly 3 wrapped in the insulating film 4 can be inserted into the main body 2a without having a high coefficient of friction with the inner surface of the main body 2a. And after connecting each terminal 2c, 2d and the tab of each electrode of the electrode assembly 3 via each conductive member, the cover part 2b is attached to the main body part 2a, and the electrode assembly 3 is in the case 2 Is housed in.

  In an initial charging step before shipment of the power storage device 1, a predetermined load is applied between the side surfaces in the stacking direction of the main body 2 a of the case 2 for a predetermined time or more. Then, the adhesive force of the pressure-sensitive adhesive resin contained in the insulating film 4 increases, and the adhesive force of the insulating film 4 becomes larger than before receiving the load. Due to the increased adhesive force, the coefficient of friction with the inner surface of the main body 2a is increased, and the electrode assembly 3 is held against the case 2 by the insulating film 4, and the electrode assembly 3 moves in the case 2. It becomes difficult (it becomes difficult to slip). Even after the addition of the load is finished, the increased adhesive force is maintained, and the electrode assembly 3 is difficult to move in the case 2.

  According to the power storage device 1, the insulating film 4 includes a resin that increases in adhesive strength when a load is applied, so that the electrode assembly 3 moves in the case 2 by the insulating film 4 after the load is applied. (Displacement) can be suppressed. Since the adhesive force of the insulating film 4 does not increase before the load is applied, the electrode assembly 3 wrapped in the insulating film 4 can be inserted into the case 2.

  Further, according to the power storage device 1, the pressure-sensitive adhesive resin layer 4b on the case 2 side of the insulating film 4A is formed, so that the adhesive force of the pressure-sensitive adhesive resin layer 4b on the case 2 side is increased after the load is applied. Since it becomes large, the coefficient of friction between the case 2 and the pressure sensitive adhesive resin layer 4b is increased.

  Moreover, according to the electrical storage device 1, the pressure-sensitive adhesive resin layer 4d on the electrode assembly 3 side after the load is applied by forming the pressure-sensitive adhesive resin layer 4d on the electrode assembly 3 side of the insulating film 4B. When the resin having increased adhesive force coming out of the pressure-sensitive adhesive resin layer 4d reaches the case 2 side, the coefficient of friction with the case 2 increases. Further, in the case of this insulating film 4B, since the pressure-sensitive adhesive resin layer 4d is on the electrode assembly 3 side, the friction coefficient on the case 2 side is low before the load is applied, and the electrode assembly is wrapped in the insulating film 4B. 3 can be inserted into the case 2 smoothly.

  In addition, according to the power storage device 1, the pressure-sensitive adhesive resin particles 4 f are included in the insulating film 4 </ b> C, so that the adhesive force of the pressure-sensitive adhesive resin particles 4 f increases after the load is applied, and the adhesive force increases. When the pressure-sensitive adhesive resin particles 4f that have reached the case 2 side, the friction coefficient with the case 2 increases. Further, in the case of this insulating film 4C, the friction coefficient on the case 2 side is low before the load is applied, and the electrode assembly 3 wrapped in the insulating film 4C can be smoothly inserted into the case 2.

  In the case of a power storage module including a plurality of power storage devices 1, the electrode assembly 3 is difficult to move in the case 2 due to the pressure-sensitive adhesive resin contained in the insulating film 4 after the load is applied to each power storage device 1. Therefore, it is not necessary to restrain the power storage device with a restraining member like a conventional power storage module.

  As mentioned above, although embodiment of this invention was described, it is implemented in various forms, without being limited to the said embodiment.

  For example, in the above embodiment, the present invention is applied to a rectangular power storage device (lithium ion secondary battery), but the present invention can also be applied to a power storage device having another shape such as a cylindrical (winding body). Moreover, it is applicable also to electrical storage apparatuses other than a lithium ion secondary battery.

  In the above embodiment, three forms of including the pressure-sensitive adhesive resin in the insulating film are shown, but other forms may be included. In the above embodiment, an example of the pressure-sensitive adhesive resin is shown, but other pressure-sensitive adhesive resins may be used.

  DESCRIPTION OF SYMBOLS 1 ... Power storage device, 2 ... Case, 2a ... Main body part, 2b ... Cover part, 2c ... Positive electrode terminal, 2d ... Negative electrode terminal, 3 ... Electrode assembly, 4 (4A-4C) ... Insulating film, 4a, 4c, 4e ... Insulating film body, 4b, 4d ... Pressure-sensitive adhesive resin layer, 4f ... Pressure-sensitive adhesive resin particles, 5 ... Connection tape.

Claims (4)

A power storage device in which an electrode assembly is accommodated in a case, and an insulating film is provided between the case and the electrode assembly,
The said insulating film is an electrical storage apparatus containing resin with which adhesive force increases when a load is added.   The power storage device according to claim 1, wherein the insulating film has a layer made of the resin formed on the case side.   The power storage device according to claim 1, wherein the insulating film has a layer made of the resin formed on the electrode assembly side.   The power storage device according to claim 1, wherein the insulating film includes particles made of the resin.

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