JP2016012414A - Method for inspecting secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting a secondary battery capable of efficiently inspecting characteristics of a secondary battery.SOLUTION: The method for inspecting a secondary battery 10 including a battery element 5 on which a positive electrode 1 and a negative electrode 6 are alternately laminated through a separator 20 includes: inserting an insulating protective member 4 inside the battery element 5; inserting a conductive foreign body piece 9 inside the battery element 5; and applying pressure to the battery element 5 along a direction in which the positive electrode 1 and the negative electrode 6 are laminated.

Description

  The present invention relates to a secondary battery inspection method.

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. In particular, high-energy density and lightweight lithium-ion secondary batteries have become energy storage devices indispensable for daily life. The secondary battery includes a battery element having a configuration in which a positive electrode and a negative electrode are alternately and repeatedly overlapped with each other while being separated by a separator, and an outer layer container that stores the battery element and an electrolytic solution. If a short circuit occurs between the positive electrode and the negative electrode inside the battery element, there is a risk of generating heat and causing damage to the battery element and the outer layer container. Therefore, in order to know how much heat is generated or damaged in the secondary battery due to an electrical short circuit inside the battery element, an inspection is performed.
As an example of a secondary battery inspection method, a nail-like pointed foreign object piece is inserted into the battery element, the positive electrode and the negative electrode are short-circuited through the foreign object piece, and the voltage change, heat generation, and damage state at that time are examined. There is. In Patent Document 1, a conductive foreign material piece made of metal or the like is inserted into the inner layer portion of the battery element, and then the battery element is pressurized. A method is disclosed in which a positive electrode and a negative electrode are short-circuited, and a voltage change, heat generation, or damage state at that time is examined.
Patent Document 2 discloses a secondary battery having a configuration in which one or both current collectors of a positive electrode and a negative electrode are formed by depositing metal foil on both surfaces of an insulating film such as polyimide.

JP 2008-270090 A Japanese Patent Laid-Open No. 09-120842

  In a secondary battery, for example, how many layers of positive and negative electrodes are short-circuited inside a battery element, and cannot be used due to overheating, ignition or damage, in other words, how many layers of positive and negative electrodes are allowed to be short-circuited It is important to know what.

The inspection method that punctures a battery element with a nail-like pointed foreign object piece and causes an electrical short circuit is suitable for the case where all the positive and negative electrodes are short-circuited through the battery element. Yes. However, this inspection method is not suitable for examining the state of a battery element when one positive electrode and negative electrode of a large number of stacked positive electrodes and negative electrodes, or a small number of positive electrodes and negative electrodes are short-circuited. That is, when the nail-like foreign object piece is inserted into the battery element, it is difficult to appropriately control the number of layers through which the foreign object piece penetrates. Further, in this method, a short circuit can be caused from the outermost layer of the battery element, but the state of the battery element when a short circuit occurs only in a part of the inner layer of the battery element cannot be examined.
In the invention described in Patent Document 1, a short circuit can be caused in the inner layer of the battery element. However, it is difficult to accurately control how many layers (positive electrode, separator, negative electrode) above and below the foreign material piece penetrate when pressed. Realistically, only by disassembling the battery element after inspecting the state of the battery element by pressurizing to cause a short circuit, the number of layers of the positive electrode and the negative electrode can be short-circuited through the number of layers of foreign particles. It turns out.
As described above, it is not easy to examine the state of the battery element when the positive electrode and the negative electrode having a specific number of layers are short-circuited inside the battery element, and the characteristics of the battery cannot be efficiently inspected.
In the invention described in Patent Document 2, the insulating film constituting the current collector of the electrode has an effect of preventing the electrical short circuit from spreading inside the battery element. However, as described above, the insulating film provided on each electrode rather hinders the inspection for intentionally generating an electrical short inside the battery element and examining the state of the battery element at that time. In particular, it is impossible to inspect by intentionally short-circuiting a plurality of layers of the positive electrode and the negative electrode by the insulating film of the cited document 2.

  Accordingly, an object of the present invention is to provide a secondary battery inspection method capable of solving the above-described problems and efficiently examining the characteristics of the secondary battery.

  In the method for inspecting a secondary battery according to the present invention including a battery element in which positive and negative electrodes are alternately stacked via separators, an insulating protective member is inserted into the battery element, and the battery element is electrically conductive. The foreign element piece is inserted, and the battery element is pressurized along the stacking direction of the positive electrode and the negative electrode.

  According to the present invention, the characteristics of the secondary battery can be examined efficiently.

It is a top view which shows the basic structure of an example of the laminated type secondary battery used as the object of the test | inspection method of this invention. It is AA sectional view taken on the line of FIG. 1A. It is a perspective view which shows an example of the foreign material piece used in the test | inspection method of this invention. It is sectional drawing of the principal part which shows the test | inspection state of the secondary battery by this invention. It is sectional drawing of the principal part which shows the other example of the test | inspection state of the secondary battery by this invention. It is sectional drawing which shows typically 1 process of the inspection method of this invention. It is sectional drawing which shows the process following the process shown to FIG. 5A typically. It is sectional drawing which shows the process following the process shown to FIG. 5B typically. It is sectional drawing which shows the process following the process shown to FIG. 5C typically. It is sectional drawing of the principal part which shows the test | inspection state of the secondary battery by the modification of the test | inspection method of this invention. It is sectional drawing of the principal part which shows the test | inspection state of the secondary battery by the other modification of the test | inspection method of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
[Structure of secondary battery]
1A and 1B schematically show an example of the configuration of a stacked lithium ion secondary battery 10 that is an object of the inspection method of the present invention. A lithium ion secondary battery 10 of the present invention includes an electrode stack (battery element) 5 in which a plurality of positive electrodes (positive electrode sheets) 1 and negative electrodes (negative electrode sheets) 6 are alternately stacked via separators 20. Yes. The battery element 5 is housed together with the electrolyte solution 12 in an outer container 30 made of a flexible film. One end of a positive electrode terminal 11 is connected to the positive electrode 1 of the battery element 5, and one end of a negative electrode terminal 16 is connected to the negative electrode 6. The other end side of the positive electrode terminal 11 and the other end side of the negative electrode terminal 16 are each drawn out of the flexible film 30. In FIG. 1B, a part of each layer constituting the battery element 5 (a layer located at an intermediate portion in the thickness direction) is not shown, and the electrolytic solution 12 is shown.

  The positive electrode 1 includes a positive electrode current collector foil 3 and a positive electrode mixture layer 2 formed on the positive electrode current collector foil 3. The negative electrode 6 includes a negative electrode current collector foil 8 and a negative electrode mixture layer 7 formed on the negative electrode current collector foil 8. An uncoated portion where the positive electrode mixture layer 2 is not provided on the positive electrode current collector foil 3 and an uncoated portion where the negative electrode material mixture layer 7 is not provided on the negative electrode current collector foil 8 are an electrode terminal (positive electrode terminal 11). Or it is used as a tab for connecting with the negative electrode terminal 16). The positive electrode tabs connected to the positive electrode 1 are gathered on the positive electrode terminal 11 and connected together with the positive electrode terminal 11 by ultrasonic welding or the like. The negative electrode tabs connected to the negative electrode 6 are gathered on the negative electrode terminal 16 and are connected together with the negative electrode terminal 16 by ultrasonic welding or the like. In addition, the other end of the positive electrode terminal 11 and the other end of the negative electrode terminal 16 are drawn out of the outer container 30. The external dimension of the application part (negative electrode mixture layer 7) of the negative electrode 6 is larger than the external dimension of the application part (positive electrode mixture layer 2) of the positive electrode 1 and smaller than the external dimension of the separator 20.

In this secondary battery, as the material constituting the cathode active material layer 2, for example _{LiCoO 2, LiNiO 2, LiNi (} 1-x) CoO 2, LiNi x (CoAl) (1-x) O 2, Li 2 MnO ₃ -LiMO ₂ (where, M is a transition metal, Ni as an example, Co, Fe, Cr or the like can be mentioned), Ya layered oxide materials such as _{LiNi x Co y Mn (1-} xy) O 2 Spinel materials such as LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiMn _(2-x) M _x O ₄ , olivine materials such as LiMPO ₄ , Li ₂ MPO ₄ F, Li ₂ MSiO ₄ F, etc. Examples thereof include fluorinated olivine-based materials and vanadium oxide-based materials such as V ₂ O _5, and one of these or a mixture of two or more thereof can be used.
Materials constituting the negative electrode active material layer 7 include carbon materials such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, and carbon nanohorn, lithium metal materials, alloy materials such as silicon and tin, Nb An oxide-based material such as ₂ O ₅ or TiO ₂ or a composite thereof can be used.
The material constituting the positive electrode active material layer 2 and the negative electrode active material layer 7 may be a mixture to which a binder, a conductive auxiliary agent, and the like are appropriately added. As a conductive support agent, 1 type in carbon black, carbon fiber, or graphite can be used, or a combination of 2 or more types can be used. As the binder, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, carboxymethyl cellulose, modified acrylonitrile rubber particles, and the like can be used.
As the positive electrode current collector 3, aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used, and aluminum is particularly preferable. As the negative electrode current collector 8, copper, stainless steel, nickel, titanium, or an alloy thereof can be used.

  Further, as the electrolytic solution 12, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC) ) And other organic solvents such as chain carboxylates, aliphatic carboxylic acid esters, γ-lactones such as γ-butyrolactone, chain ethers, and cyclic ethers. Mixtures of the above can be used. Furthermore, lithium salts can be dissolved in these organic solvents.

The separator 20 is mainly made of a resin porous film, woven fabric, non-woven fabric, and the like, and as its resin component, for example, a polyolefin resin such as polypropylene or polyethylene, a polyester resin, an acrylic resin, a styrene resin, or a nylon resin is used. it can. In particular, a polyolefin-based microporous membrane is preferable because of its excellent ion permeability and performance of physically separating the positive electrode and the negative electrode. Further, if necessary, the separator 20 may be formed with a layer containing inorganic particles, and examples of the inorganic particles include insulating oxides, nitrides, sulfides, carbides, etc. It is preferable to contain TiO ₂ or Al ₂ O ₃ .

  A case made of a flexible film, a can case, or the like can be used for the outer container 30. From the viewpoint of reducing the weight of the battery, the flexible film 30 is preferably used. As the flexible film 30, a film in which a resin layer is provided on the front surface and the back surface of a metal layer serving as a base material can be used. As the metal layer, a metal layer having barrier properties such as preventing leakage of the electrolyte solution 12 and moisture from the outside can be selected, 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. The exterior container 30 is formed by making the heat-fusible resin layers of the flexible film face each other and heat-sealing the periphery of the portion that houses the battery element 5. 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.

  The positive electrode terminal 11 can be made of aluminum or an aluminum alloy, and the negative electrode terminal 16 can be made of copper, a copper alloy, or those plated with nickel. The other end side of each terminal 11, 16 is drawn out of the outer container 30. A heat-sealable resin can be provided in advance at a location corresponding to a portion of each terminal 11, 16 that is thermally welded to the outer peripheral portion of the outer container 30.

[Inspection method of secondary battery]
In this invention, the test | inspection for investigating the state of a battery element when a short circuit arises inside the battery element of a secondary battery is performed.
First, the secondary battery 10 shown in FIGS. 1A and 1B is once completed and charged. Then, the outer layer film constituting the outer layer container 30 of the completed secondary battery 10 is partially peeled, and each layer of the battery element 5 is partially peeled to expose a part of the inner layer portion of the battery element 5. And the conductive foreign material piece 9 is arrange | positioned in this exposed part. In addition, an insulating protective film 4 (protective member) is disposed at a position overlapping the foreign object piece 9 in a plan view.

As shown in FIG. 2, the foreign material piece 9 is made of, for example, a metal such as nickel having an L-shaped planar shape. Can do. The thickness of the foreign material piece 9 is preferably equal to or more than the sum of the thicknesses of the positive electrode 1 and the negative electrode 6 having the number of layers to be subjected to an electrical short circuit, which will be described later, and the separator 20 positioned therebetween. As an example, the negative electrode 6 and the positive electrode 1 both have a thickness of about 130 to 150 μm, the separator 20 has a thickness of about 25 μm, and the inspection is performed by short-circuiting only one layer of the positive electrode 1 and the negative electrode 6. When performing, it is preferable to use the foreign material piece 9 having a thickness of about 600 μm.
The protective film 4 is a film made of, for example, polyimide such as Kapton (trademark), resin such as polypropylene or polyethylene terephthalate (PET). The protective film 4 has a strength that does not break even when the foreign material piece 9 is brought into contact with and pressed.

  The protective film 4 is disposed on one or both of the layer located above the foreign material piece 9 and the layer located below. Specifically, the position of the protective film 4 is determined depending on how many layers of the positive electrode 1 and the negative electrode 6 are short-circuited. For example, as shown in FIG. 3, in order to investigate the state of the battery element 5 when the positive electrode 1 and the negative electrode 6 are short-circuited for each two layers, two layers of the positive electrode 1 including the layer in which the foreign material pieces 9 are arranged A pair of protective films 4 are arranged so as to sandwich the two layers of negative electrodes 6 from above and below. Similarly, in order to examine the state of the battery element 5 when the positive electrode 1 and the negative electrode 6 of each layer are short-circuited, as shown in FIG. The protective film 4 is arranged so as to sandwich the one and one negative electrode 6 from above and below. In order to investigate the state of the battery element 5 when a desired number of positive electrodes 1 and negative electrodes 6 of three or more layers are short-circuited, a desired number of positive electrodes 1 and negative electrodes 6 including the layer in which the foreign material pieces 9 are arranged are included. The protective film 4 is disposed so as to be sandwiched from above and below. The separator 20 positioned between the positive electrode 1 and the negative electrode 6 is also partially peeled in the same manner as the positive electrode 1 and the negative electrode 6, and the foreign material piece 9 and the protective film 4 are disposed.

  As a specific example, as shown in FIG. 5A, the layers of the battery element 5 are peeled off as necessary, and then the lower protective film 4 is arranged, and as shown in FIG. Then, as shown in FIG. 5C, the upper protective film 4 is disposed at a position above the lower protective film 4 by a desired number of layers. When the pair of protective films 4 and the foreign substance piece 9 positioned between them are arranged in the inner layer portion of the battery element 5, the layers of the battery element 5 are again overlapped as shown in FIG. The outer container 30 is configured by sealing with a film, and the secondary battery 10 is completed again. Then, the secondary battery 10 is pressurized by the pressure device 13. By this pressurization, the foreign substance piece 9 makes a hole in each layer (the positive electrode 1, the separator 20, and the negative electrode 6) sandwiched between the upper protective film 4 and the lower protective film 4 and penetrates them. However, since the protective film 4 has high strength, it is not pierced by the foreign object piece 9 and is not penetrated. Therefore, a state in which only the positive electrode 1 and the negative electrode 6 having a desired number of layers are penetrated by the foreign substance piece 9 is realized. Therefore, a predetermined current is supplied to electrically connect the positive electrode 1 and the negative electrode 6 having a desired number of layers (two layers in the example shown in FIGS. 5A to 5D) through the foreign material piece 9, and the battery element at that time 5 such as voltage change, temperature change, and the presence or absence of ignition or damage. Thus, the state of the battery element 5 when the positive electrode 1 and the negative electrode 6 having a desired number of layers are electrically short-circuited can be examined. The current is supplied from the positive electrode terminal 11 and the negative electrode terminal 16 to the battery element 5. 5A to 5D, in order to facilitate understanding, the state where each layer is peeled off and the state where each layer is raised by the protective film 4 and the foreign material piece 9 before pressurization are highlighted.

  According to the present invention, when the battery element 5 is pressurized, the foreign substance piece 9 penetrates through the positive electrode 1, the negative electrode 6, and the separator 20, but does not penetrate through the protective film 4. Accordingly, only the positive electrode 1 and the negative electrode 6 within the range surrounded by the protective film 4 are electrically short-circuited. Accordingly, by disposing the protective film 4 at a position sandwiching the positive electrode 1 and the negative electrode 6 having the number of layers to be short-circuited, only the positive electrode 1 and the negative electrode having a desired number of layers are short-circuited, and more positive electrodes 1 and 6 than necessary. Can be surely prevented from being short-circuited. Thus, the inspection is performed while changing the number of layers of the positive electrode 1 and the negative electrode 6 to be short-circuited, and if the number of layers of the positive electrode 1 and the negative electrode 6 short-circuited within the battery element 5 with a relatively small number of inspections, overheating, ignition, It can be easily checked whether it becomes unusable due to damage, that is, how many layers of the positive electrode 1 and the negative electrode 6 can be tolerated. Thus, the characteristics of the secondary battery 10 can be known efficiently.

  Note that the upper protective film 4 is not necessary when the uppermost negative electrode 6 is short-circuited to the lower positive electrode 1 as in the modification shown in FIG. If the inspection is performed by short-circuiting the lowermost negative electrode 6 to the upper positive electrode 1 as in the modification shown in FIG. 7, the lower protective film 4 is not necessary. Further, depending on the position of the foreign object piece 9 and the pressurizing method, the protective film may be disposed only at one of the upper position and the lower position of the foreign object piece 9.

In the example shown in FIGS. 1A, 1B, and 5A to 5D, the positive electrode terminal 11 and the negative electrode terminal 16 of the stacked secondary battery 10 extend from the same side of the outer layer container 30 to the outside. And the positive electrode 1, the separator 20, and the negative electrode 6 are partially peeled, and the protective film 4 and the foreign material piece 9 are arrange | positioned. However, the present invention can also be applied to a secondary battery having a configuration in which the positive electrode terminal 11 and the negative electrode terminal 16 extend outward from the opposite sides of the outer container 30. Further, the protective film 4 may be partially provided as shown in FIGS. 5A to 5D or may be provided entirely as shown in FIGS.
5A to 5D show a configuration in which an independent sheet-like separator 20 is laminated between the positive electrode 1 and the negative electrode 6, but the positive electrode 1 (or the negative electrode 6) is included in the separator 20 formed in a bag shape. You may make it the structure which inserts. In that case, the protective film 4 and the foreign material piece 9 may be inserted into the bag-shaped separator 20 together with the positive electrode 1 (or the negative electrode 6).
Furthermore, the present invention can be applied to a wound type secondary battery instead of a stacked type. In that case, after the winding type secondary battery is once completed and charged, the battery element is taken out from the outer layer container (may be a can case or the like), and the protective film 4 and the foreign material piece 9 are inserted therein. . Then, the battery element is pressurized without returning into the can case, and the positive electrode 1, the separator 20, and the negative electrode 6 are opened by the foreign material piece 9, as in the case of the laminated secondary battery described above, The positive electrode 1 and the negative electrode 6 having a desired number of turns are short-circuited, and the state of the battery element at that time (voltage change, presence of ignition or damage) is examined. In this case as well, the protective film may be disposed so as to sandwich the positive electrode 1 and the negative electrode 6 having the number of turns to be short-circuited.

1 Positive electrode 4 Protective film (protective member)
5 Battery element 6 Negative electrode 9 Foreign material piece 10 Secondary battery 12 Electrolytic solution 20 Separator 30 Exterior container

Claims (8)

A method for inspecting a secondary battery including a battery element in which a positive electrode and a negative electrode are alternately stacked via separators,
Inserting an insulating protective member inside the battery element,
An inspection method for a secondary battery, wherein a conductive foreign material piece is inserted into the battery element, and the battery element is pressurized along the stacking direction of the positive electrode and the negative electrode.   The method for inspecting a secondary battery according to claim 1, wherein the foreign material piece is disposed at a position overlapping the protection member when seen in a plan view.   The secondary battery inspection method according to claim 1, wherein the protective member has higher strength than the positive electrode, the negative electrode, and the separator.   4. The method for inspecting a secondary battery according to claim 1, wherein protective members are respectively disposed at a position corresponding to an upper layer and a position corresponding to a lower layer across the insertion position of the foreign substance piece. 5.   The inspection method of the secondary battery according to any one of claims 1 to 3, wherein a protective member is disposed at one of a position corresponding to an upper layer and a position corresponding to a lower layer of the insertion position of the foreign material piece.   The secondary battery according to any one of claims 1 to 5, wherein the protective member is arranged in one or both of the upper layer and the lower layer of the positive electrode and the negative electrode in the number of layers to be electrically short-circuited. Inspection method.   The method for inspecting a secondary battery according to claim 1, wherein the foreign material piece is made of nickel, and the protective member is a film made of polyimide.   The secondary battery inspection method according to claim 1, wherein the protection member and the foreign substance piece are inserted into the battery element and a current is passed through the pressurized battery element.

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