JP2015053224A - Nonaqueous electrolyte secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery excellent in charge/discharge cycle characteristics.SOLUTION: A method for manufacturing a nonaqueous electrolyte secondary battery of the present invention includes: a separator preparation step of preparing a band-like first separator and a band-like second separator; a coating step of coating an adhesive resin at a planned location of the first separator, where an outer periphery of a positive electrode is arranged; a positive electrode arrangement step of arranging the outer periphery of the positive electrode to be on a side of an inner periphery of the coated adhesive resin or to be brought into contact with the inner periphery; a separator lamination step of arranging the second separator on the positive electrode arranged on the first separator; and a separator joining step of bringing the second separator into close contact with along the outer shape of the positive electrode, hardening the adhesive resin and joining the first separator with the second separator to form a bag-shaped separator.

Description

  The present invention relates to a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery and a method for producing the same.

  Nonaqueous electrolyte secondary batteries represented by lithium ion secondary batteries are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. As mobile devices become more sophisticated, lithium ion secondary batteries tend to have higher capacities and longer lifetimes, and further research and development are underway.

  Under such circumstances, various measures have been conventionally studied in order to improve the charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery. Among them, the positive electrode is positioned and arranged in a bag-shaped separator, the alignment between the positive electrode and the negative electrode is facilitated, and the stacking deviation between the positive electrode and the negative electrode is prevented, so that there is no lithium deposition, A nonaqueous electrolyte secondary battery excellent in charge and discharge cycle characteristics without occurrence of an internal short circuit has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 7-302616 (Japanese Patent No. 3380935)

  However, in Patent Document 1, the bag separator is formed by simply fusing the end of a strip-shaped microporous plastic film, so the positive electrode is not completely fixed to the bag separator. May shift in the bag-shaped separator. In addition, since the bag-like separator is formed by fusion, the heat-fusing member of the fusion device needs a certain size, so that the width of the sealing portion of the bag-like separator can be reduced. could not.

  The present invention solves the above problem, and eliminates the displacement of the positive electrode in the bag-shaped separator and reduces the sealing portion of the bag-shaped separator, and is excellent in charge / discharge cycle characteristics. And a manufacturing method thereof.

  The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery including a bag-shaped separator and a positive electrode disposed in the bag-shaped separator, wherein the bag-shaped separator is a first separator. And a second separator facing the first separator, wherein the first separator and the second separator are joined by an adhesive resin to form the bag-shaped separator. And

  A non-aqueous electrolyte secondary battery manufacturing method according to the present invention is a method for manufacturing the non-aqueous electrolyte secondary battery according to the present invention, comprising: a strip-shaped first separator; and a strip-shaped second separator. A separator preparation step to be prepared, an application step of applying an adhesive resin to a predetermined position of the first separator where the outer periphery of the positive electrode is disposed, and an inner peripheral side of the applied adhesive resin or on the inner periphery A positive electrode disposing step of disposing an outer periphery of the positive electrode so as to be in contact; a separator stacking step of disposing the second separator on the positive electrode disposed on the first separator; and the second separator Including a separator joining step in which the adhesive resin is cured along the outer shape of the positive electrode and the adhesive resin is cured to join the first separator and the second separator to form a bag-like separator. The features.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery excellent in the charge / discharge cycle characteristic and its manufacturing method can be provided.

FIG. 1 is a schematic side view showing an example of the manufacturing process of the nonaqueous electrolyte secondary battery of the present invention. FIG. 2 is a schematic plan view showing an example of a manufacturing process of the nonaqueous electrolyte secondary battery of the present invention. FIG. 3 is a bottom view showing an example of an electrode laminate used in the nonaqueous electrolyte secondary battery of the present invention. FIG. 4 is a schematic view showing another example of the manufacturing process of the nonaqueous electrolyte secondary battery of the present invention. FIG. 5 is a bottom view showing another example of the electrode laminate used in the nonaqueous electrolyte secondary battery of the present invention. FIG. 6 is a plan view showing an example of the nonaqueous electrolyte secondary battery of the present invention.

  The nonaqueous electrolyte secondary battery of the present invention includes a bag-shaped separator and a positive electrode disposed in the bag-shaped separator. The bag-shaped separator includes a first separator and a second separator facing the first separator, and the first separator and the second separator are joined by an adhesive resin. The bag-shaped separator is formed. Furthermore, the positive electrode is fixed to the bag-shaped separator with the adhesive resin.

  In the nonaqueous electrolyte secondary battery of the present invention, since the bag-like separator is formed by bonding with an adhesive resin, the width of the sealing portion can be reduced as compared with the case of forming by fusion bonding. That is, in the case of fusion, the width of the sealing portion is required to be at least about 1.5 mm, but in the case of adhesion, the width of the sealing portion can be set to about 0.5 to 1.0 mm.

  Moreover, since the said positive electrode is being fixed to the said bag-shaped separator by the said adhesive resin, the shift | offset | difference of the positive electrode in a bag-shaped separator can be eliminated completely. Thereby, the nonaqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics can be provided.

  The adhesive resin is preferably a radiation curable resin. This is because the resin can be cured by a simple process of irradiating radiation, so that the manufacturing process can be simplified.

  In the nonaqueous electrolyte secondary battery of the present invention, the bag-shaped separator on which the positive electrode is disposed and the negative electrode are alternately laminated to form an electrode laminate. Thereby, the short circuit with a positive electrode and a negative electrode can be prevented. In the electrode laminate, the bag-like separators may be independent or connected.

  The first separator and the second separator are each composed of a heat-resistant layer and a non-heat-resistant layer, and the heat-resistant layer is preferably opposed to the positive electrode, and the heat-resistant layer contains an inorganic filler, The non-heat resistant layer preferably contains a thermoplastic resin. The first separator and the second separator constituting the bag-shaped separator are each composed of a heat-resistant layer and a non-heat-resistant layer, so that the shrinkage of the separator is suppressed by the heat-resistant layer when the battery is abnormally overheated. Therefore, the non-heat-resistant layer melts and plugs the pores of the separator to increase the internal resistance, so that a shutdown effect that cuts off the current can be exhibited, and the safety is high. A water electrolyte secondary battery can be provided.

  Polyolefins such as polyethylene and polypropylene can be used as the thermoplastic resin, and inorganic fillers such as alumina and silica can be used as the inorganic filler.

  Moreover, the deterioration by the oxidation of the separator accompanying charging / discharging of a battery can be suppressed by making the said heat-resistant layer oppose the said positive electrode.

  Moreover, the manufacturing method of the non-aqueous electrolyte secondary battery according to the present invention includes a separator preparation step of preparing a strip-shaped first separator and a strip-shaped second separator, and the first first described above in which the outer periphery of the positive electrode is disposed. An application step of applying an adhesive resin to a predetermined position of the separator, a positive electrode arrangement step of arranging an outer periphery of the positive electrode on the inner peripheral side of the applied adhesive resin or in contact with the inner periphery, and the first A separator laminating step of disposing the second separator on the positive electrode disposed on the separator; and adhering the second separator along the outer shape of the positive electrode, and curing the adhesive resin. And a separator joining step of joining the first separator and the second separator to form a bag-like separator. By the above process, the above-described non-aqueous electrolyte secondary battery of the present invention can be efficiently produced.

  Moreover, it is preferable that the said positive electrode is fixed to the said bag-shaped separator by the said adhesive resin in the said separator joining process.

  The adhesive resin is preferably a radiation curable resin. This is because the resin can be cured by a simple process of irradiating radiation, so that the manufacturing process can be simplified.

  In the method for producing a nonaqueous electrolyte secondary battery according to the present invention, the application step, the positive electrode arrangement step, the separator lamination step, and the separator bonding step are repeated, and the positive electrode-filled bag-like separator in which the positive electrode is arranged is obtained. It is preferable to form continuously in a connected state to form a positive electrode-filled bag-like separator connector. Thereby, the said bag-like separator with a positive electrode can be manufactured continuously and efficiently.

  In the non-aqueous electrolyte secondary battery manufacturing method of the present invention, the positive electrode-containing bag-like separator is separated by cutting the connecting portion of the positive-electrode-containing bag-like separator assembly, and then separating the positive electrode-containing bag-like separator. The electrode laminate can be formed by alternately laminating the negative electrode and the negative electrode.

  Furthermore, in the method for producing a non-aqueous electrolyte secondary battery according to the present invention, the negative electrode is disposed on the front side and the back side of the positive electrode bag-like separator assembly corresponding to the positive electrode bag-like separator. It is also possible to form an electrode stack by alternately folding the positive electrode-filled bag-shaped separator and the negative electrode by folding the connecting portion of the connecting body as a crease.

  In the method for producing a non-aqueous electrolyte secondary battery of the present invention, the first separator and the second separator are each composed of a heat-resistant layer and a non-heat-resistant layer, and the heat-resistant layer faces the positive electrode. Can do. In the method for producing a nonaqueous electrolyte secondary battery of the present invention, since the bag-shaped separator is formed using the adhesive resin, the surface characteristics of the separator do not affect the mutual adhesiveness of the separator by the adhesive resin. It is. However, since the bag-like separator has been conventionally formed by fusion, the heat-resistant layer, which is difficult to heat-fuse, cannot be directed to the inside (positive electrode side).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
First, an embodiment of a method for producing a nonaqueous electrolyte secondary battery of the present invention will be described.

  FIG. 1 is a schematic side view showing an example of the manufacturing process of the nonaqueous electrolyte secondary battery of the present invention, and FIG. 2 shows an example of the manufacturing process of the nonaqueous electrolyte secondary battery of the present invention corresponding to FIG. It is a schematic plan view to show. However, in FIG. 2, only the positive electrode-containing bag-like separator assembly is shown.

  In this embodiment, first, the strip-shaped first separator 1 is prepared for the first feeding roll 10, and the strip-shaped second separator 2 is prepared for the second feeding roll 20.

  The first separator 1 and the second separator 2 are each formed in a two-layer structure including a heat-resistant layer and a non-heat-resistant layer. However, the separator to be used may have a multilayer structure of three or more layers, or may have a single layer structure consisting of only one layer.

  Next, the first separator 1 is fed horizontally from the first feed roll 10, and the radiation curable resin 3 is applied as an adhesive resin from the adhesive resin coating machine 30 onto the heat-resistant layer 1 a side of the first separator 1. Apply. At that time, the radiation curable resin 3 is applied as 3a, 3b, and 3c at the planned positions where the outer periphery of the positive electrode is disposed. However, the application position of the radiation curable resin 3 is not limited to the above three sides, and may be applied in a frame shape having four sides along the outer periphery of the positive electrode.

  Although it does not specifically limit as the radiation curable resin 3, The bifunctional or more radiation curable resin with favorable sclerosis | hardenability is preferable. Specifically, for example, acrylic acid, acrylic acid ester, acrylamide, methacrylic acid ester, methacrylic acid amide, allyl compound, vinyl ether, vinyl ester and the like can be used. These resins can be used alone or in combination. The radiation used for curing is not limited to ultraviolet rays to be described later, and an electron beam, visible light, or the like can be used. However, ultraviolet rays are preferable because they can be irradiated with high energy at low cost.

  Moreover, as said adhesive resin, it can replace with the said radiation curable resin and can also use a thermosetting resin or a thermoplastic resin.

  Next, the positive electrode 4 is disposed on the heat-resistant layer 1 a of the first separator 1 on the pedestal 50 by the positive electrode feeder 40 so as to be in contact with the inner periphery of the applied radiation curable resins 3 a, 3 b, 3 c. At this time, the outer periphery of the positive electrode 4 may be placed on the radiation curable resins 3a, 3b, and 3c. Further, the outer periphery of the positive electrode 4 may not be in contact with the radiation curable resins 3a, 3b, and 3c. That is, the positive electrode 4 may be disposed on the inner peripheral side of the radiation curable resins 3a, 3b, and 3c. Further, in order to fix the positive electrode 4 in advance, a radio curable resin is separately applied to a position where the inside of the positive electrode of the first separator 1 is arranged, and the radio curable resin is first cured. May be. The positive electrode 4 includes a terminal 4a.

  Next, the second separator 2 is placed on the positive electrode 4 by feeding the second separator 2 so that the heat-resistant layer 2 a side of the second separator 2 faces the positive electrode 4. Subsequently, the second separator 2 is brought into close contact with the outer shape of the positive electrode 4 using a pressing member 70 made of silicone rubber on the glass base 60, and radiation is applied using the radiation irradiation devices 80a and 80b. 8 is cured to cure the radiation curable resin 3, and the first separator 1 and the second separator 2 are joined together to form a bag-like separator 5 containing a positive electrode. At this time, the positive electrode 4 is fixed to the bag-shaped separator by the cured radiation curable resin 3, and the positive electrode 4 is never displaced in the bag-shaped separator in the subsequent process. At this time, the positive electrode-filled bag-like separator 5 has the connecting portion 6a, and the positive-electrode-filled bag-like separator connector 6 is formed.

  Next, the connecting portion 6a of the positive electrode bag-like separator connector 6 is cut and removed to separate the positive electrode bag-like separator 5. Subsequently, the separately prepared negative electrode 7 and the separated positive electrode-containing bag-like separator 5 are alternately laminated to produce an electrode laminate 9A shown in FIG. FIG. 3 is a bottom view of the electrode laminate 9A. Although FIG. 3 shows an example in which five negative electrodes 7 and four positive electrode-containing bag-like separators 5 are stacked, the number of electrodes is not limited thereto.

  Finally, the produced electrode laminate 9A is inserted into the outer package, an electrolyte is injected, and the outer package is sealed. Thus, the nonaqueous electrolyte secondary battery of the present invention is completed. The said exterior body and electrolyte solution are mentioned later.

  Next, another embodiment of the method for producing a nonaqueous electrolyte secondary battery of the present invention will be described. FIG. 4 is a schematic view showing another example of the manufacturing process of the nonaqueous electrolyte secondary battery of the present invention. In FIG. 4, parts corresponding to those shown in FIGS. 1 to 3 are given the same reference numerals, and detailed description thereof is omitted.

  Also in the present embodiment, the positive electrode-filled bag-like separator connector 6 is formed in the same manner as the steps described with reference to FIGS. In this embodiment, the positive electrode-containing bag-like separator connector 6 includes four positive-electrode-containing bag-like separators 5, but the number of positive-electrode-containing bag-like separators 5 can be increased or decreased according to the capacity of the battery.

  Next, as shown in FIG. 4, the negative electrode 7 is arrange | positioned at the front side and back side corresponding to the positive electrode containing bag-like separator 5 of the positive electrode containing bag-like separator connecting body 6, respectively, and the connection part of the positive electrode containing bag-like separator connecting body 6 6a is folded as a crease, and the positive electrode-filled bag-like separator 5 and the negative electrode 7 are alternately laminated to produce an electrode laminate 9B shown in FIG.

  Thereafter, as described above, the nonaqueous electrolyte secondary battery of the present invention is manufactured by a normal method. In this embodiment, it is not necessary to cut and remove the connecting portion 6a of the positive electrode bag-like separator connecting body 6, and the electrode laminate 9B can be continuously produced only by adjusting the width of the connecting portion 6a, thereby improving the production efficiency. it can.

(Embodiment 2)
Next, a non-aqueous electrolyte secondary battery according to an embodiment of the present invention will be described using a lithium ion secondary battery, which is a typical non-aqueous electrolyte secondary battery, as an example.

  FIG. 6 is a plan view showing an example of a laminated lithium ion secondary battery of the present invention. 6, in the laminated lithium ion secondary battery 100 of the present embodiment, the laminated electrode body 9A or 9B and the non-aqueous electrolyte described in the first embodiment are inside the outer package 200 made of a rectangular laminated film in plan view. Is housed in. The positive external terminal 300 and the negative external terminal 400 are drawn from the same side of the exterior body 200.

  The positive electrode used in the present embodiment is a mixture of positive electrode active material, positive electrode conductive additive, positive electrode binder, and the like, and a positive electrode mixture paste obtained by sufficiently kneading the mixture with a solvent. After being applied to and dried, the positive electrode mixture layer can be formed by controlling it to a predetermined thickness and a predetermined electrode density.

Examples of the positive electrode active material include lithium cobalt oxides such as LiCoO ₂ , lithium manganese oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO _2, etc., and can absorb and release lithium ions. If it is, it will not be limited to these.

  The positive electrode current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the battery. As the positive electrode current collector, for example, an aluminum foil or the like is used.

  The negative electrode used in the present embodiment is obtained by adding a negative electrode mixture paste obtained by sufficiently kneading a mixture containing a negative electrode active material, a conductive aid for negative electrode, a binder for negative electrode, and the like, to both surfaces of the negative electrode current collector. After coating and drying, the negative electrode mixture layer can be formed by controlling the thickness to a predetermined thickness and a predetermined electrode density.

  Examples of the negative electrode active material include carbon materials such as natural graphite or artificial graphite such as massive graphite, flaky graphite, and earthy graphite, but are not limited thereto as long as lithium ions can be occluded / released. .

  The negative electrode current collector is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the constituted battery. For example, a copper foil or the like is used as the negative electrode current collector.

  As the separator used in the present embodiment, as described in the first embodiment, a heat-resistant separator having a shutdown function having a two-layer structure including a heat-resistant layer and a non-heat-resistant layer is preferable, but a large ion permeability and a predetermined mechanical property are used. An insulating microporous film having strength can also be used as a separator having a single layer structure.

  As the exterior body 200, a laminate film in which a metal layer such as aluminum and a thermoplastic resin layer are laminated can be used.

Examples of the non-aqueous electrolyte include vinylene carbonate (VC), propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate ( MEC), an organic solvent such as γ- butyrolactone to one or more kinds mixed solvent, for example, at least one selected from _{LiClO 4, LiPF 6, LiBF 4} , LiAsF 6, LiSbF 6, LiCF 3 SO 3 , etc. An electrolytic solution in which the lithium salt is dissolved may be used. The concentration of Li ions in the electrolytic solution may be 0.5 to 1.5 mol / L.

  As described above, the present invention can provide a nonaqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics and a method for manufacturing the same.

DESCRIPTION OF SYMBOLS 1 1st separator 2 2nd separator 3 Radiation curable resin 4 Positive electrode 5 Bag-like separator with positive electrode 6 Bag-like separator connected with positive electrode 7 Negative electrode 8 Radiation 9A, 9B Electrode laminated body 10 First feeding roll 20 Second Feeding roll 30 Adhesive resin coating machine 40 Positive electrode supply machine 50 Base 60 Base 70 Pressing member 80a, b Radiation irradiation device 100 Laminated lithium ion secondary battery 200 Exterior body 300 Positive electrode external terminal 400 Negative electrode external terminal

Claims (16)

A non-aqueous electrolyte secondary battery comprising a bag-shaped separator and a positive electrode disposed in the bag-shaped separator,
The bag-shaped separator comprises a first separator and a second separator facing the first separator,
The non-aqueous electrolyte secondary battery, wherein the first separator and the second separator are joined by an adhesive resin to form the bag-like separator.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode is fixed to the bag-like separator by the adhesive resin.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the adhesive resin is a radiation curable resin.   The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the bag-shaped separator on which the positive electrode is disposed and the negative electrode are alternately laminated to form an electrode laminate.   The nonaqueous electrolyte secondary battery according to claim 4, wherein in the electrode laminate, the bag-like separators are independent from each other.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the bag-like separator is connected to the electrode laminate.   The non-water according to claim 1, wherein each of the first separator and the second separator includes a heat-resistant layer and a non-heat-resistant layer, and the heat-resistant layer faces the positive electrode. Electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 7, wherein the heat-resistant layer includes an inorganic filler, and the non-heat-resistant layer includes a thermoplastic resin. A method for producing the nonaqueous electrolyte secondary battery according to any one of claims 1 to 8,
A separator preparation step of preparing a strip-shaped first separator and a strip-shaped second separator;
An application step of applying an adhesive resin to a predetermined position of the first separator where the outer periphery of the positive electrode is disposed;
A positive electrode disposing step of disposing an outer periphery of the positive electrode so as to be in contact with or on the inner peripheral side of the applied adhesive resin;
A separator laminating step of disposing the second separator on the positive electrode disposed on the first separator;
The second separator is adhered along the outer shape of the positive electrode, and the adhesive resin is cured, and the first separator and the second separator are joined to form a bag-shaped separator. A non-aqueous electrolyte secondary battery manufacturing method comprising a joining step.   The method for producing a nonaqueous electrolyte secondary battery according to claim 9, wherein in the separator joining step, the positive electrode is fixed to the bag-like separator by the adhesive resin. A method for producing the nonaqueous electrolyte secondary battery according to any one of claims 1 to 8,
A separator preparation step of preparing a strip-shaped first separator and a strip-shaped second separator;
An application step of applying an adhesive resin to a predetermined position of the first separator where the outer periphery and the inside of the positive electrode are disposed;
A positive electrode disposing step of disposing an outer periphery of the positive electrode on the inner peripheral side of the adhesive resin applied at a predetermined position where the outer periphery of the positive electrode is disposed, or in contact with the inner periphery;
A positive electrode fixing step of fixing the positive electrode to the first separator by curing the adhesive resin applied to a position where the inside of the positive electrode is disposed;
A separator laminating step of disposing the second separator on the positive electrode disposed on the first separator;
The second separator is adhered along the outer shape of the positive electrode, and the adhesive resin applied at a position where the outer periphery of the positive electrode is to be disposed is cured, and the first separator and the second separator A method for manufacturing a non-aqueous electrolyte secondary battery, comprising: a separator joining step for joining a separator to form a bag-like separator.   The method for producing a nonaqueous electrolyte secondary battery according to any one of claims 9 to 11, wherein the adhesive resin is a radiation curable resin.   The said each process is repeated, the positive electrode containing bag-shaped separator which has arrange | positioned the said positive electrode is continuously formed in a connection state, and the positive electrode containing bag-like separator coupling body is formed. A method for producing a water electrolyte secondary battery.   After cutting the connecting portion of the positive electrode-containing bag-like separator and separating the positive electrode-containing bag-like separator, the positive electrode-containing bag-like separator and the negative electrode are alternately laminated to form an electrode laminate. The manufacturing method of the nonaqueous electrolyte secondary battery of Claim 13.   A negative electrode is disposed on each of the front side and the back side of the positive electrode bag-like separator connected body corresponding to the positive electrode bag-like separator, and the positive bag containing the positive electrode bag-like separator connected body is folded with the connecting portion as a fold. The method for producing a nonaqueous electrolyte secondary battery according to claim 13, wherein an electrode laminate is formed by alternately laminating a separator and the negative electrode.   The non-water according to claim 9, wherein each of the first separator and the second separator includes a heat-resistant layer and a non-heat-resistant layer, and the heat-resistant layer faces the positive electrode. Manufacturing method of electrolyte secondary battery.

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