JP2018174146A - Nonaqueous electrolyte secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery superior in load characteristic, etc.SOLUTION: A nonaqueous electrolyte secondary battery according to the present invention comprises a multilayer electrode body arranged by laminating a positive electrode, a negative electrode and a separator, in which any one electrode of the positive and negative electrodes is glued to the separator by an adhesive part. A method for manufacturing a nonaqueous electrolyte secondary battery according to the present invention comprises: a coating step of coating a belt-shaped separator 1 with a radiation-curable resin 3 to form an adhesive part; an electrode-disposing step of disposing an electrode 4 on the adhesive part; and a gluing step of applying radioactive rays 50a to the adhesive part to cure the radiation-curable resin, thereby gluing the electrode with the separator.SELECTED DRAWING: Figure 1

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 battery characteristics of the non-aqueous electrolyte secondary battery. Among them, a laminated laminate battery in which a positive electrode, a negative electrode, and a separator are laminated to form a laminated electrode body, and the laminated electrode body is housed in an exterior body made of a laminate film has been put into practical use. Multi-layer laminated batteries have excellent load characteristics, etc., and are used as a power source for in-vehicle power supplies and various power storage devices by combining multiple batteries, and also as a battery for mobile devices that require thin and light weight. ing.

  However, since a laminate-type laminate battery is manufactured by laminating a plurality of electrodes and separators, an accurate lamination process without positional displacement of electrodes is required, and various methods for the lamination method have been proposed.

  For example, Patent Document 1 discloses a method in which an ion conductive adhesive is applied to both sides of a separator, a positive electrode plate and a negative electrode plate are bonded and positioned on both surfaces, and then a multilayer electrode body is formed by diffracting a large number of times. Has been proposed.

JP 2001-229979 A (Patent No. 3358807)

  However, in Patent Document 1, an ion conductive adhesive is applied to the entire surface of both surfaces of the separator, and when applied to a certain thickness in order to increase the adhesive strength between the electrode and the separator, the ion conductive adhesive is used. Even so, the internal resistance of the battery increases. In the case of such a battery, if low-temperature charging, rapid charging, or the like is performed, it causes local precipitation of lithium on the separator, and the risk of a short circuit increases.

  The present invention solves the above-mentioned problems, and provides a laminated nonaqueous electrolyte secondary battery excellent in load characteristics and the like, and a manufacturing method thereof, while eliminating the displacement of electrodes.

  The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte secondary battery including a laminated electrode body in which a positive electrode, a negative electrode, and a separator are laminated, and one of the positive electrode and the negative electrode The separator is bonded by an adhesive portion.

Moreover, the manufacturing method of the nonaqueous electrolyte secondary battery of this invention arrange | positions an electrode on the apply | coating process which apply | coats a radiation curable resin to a strip | belt-shaped separator, and forms an adhesion part, and the said adhesion | attachment part applied The method includes an electrode arranging step and an adhesion step of irradiating the bonding portion with radiation to cure the radiation curable resin and bond the electrode and the separator.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery excellent in load characteristics and the like without any positional deviation of electrodes and a manufacturing method thereof.

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 a laminated electrode body 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 laminated electrode body 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 laminated electrode body in which a positive electrode, a negative electrode, and a separator are laminated. In addition, one of the positive electrode and the negative electrode is bonded to the separator by an adhesive portion.

  Since the electrode is bonded and fixed to the separator by the bonding portion, the electrode can be prevented from being displaced with respect to the separator. Thereby, the nonaqueous electrolyte secondary battery excellent in load characteristics etc. can be provided.

  Moreover, it is preferable that the said positive electrode and the said separator are adhere | attached by the said adhesion part, and the said negative electrode and the said separator are not adhere | attached. Since the negative electrode that accepts lithium ions is not bonded to the separator, the ion conductivity of the separator is not hindered, and even if low-temperature charging or rapid charging is performed, lithium deposition is suppressed and the risk of short-circuiting is small. Become.

  Moreover, it is preferable that the said adhesion part is formed from the radiation curable resin. This makes it possible to increase the adhesive strength of the adhesive portion compared to the case where an adhesive resin other than a radiation curable resin is used, and the resin can be cured by a simple process of irradiating radiation, thus simplifying the manufacturing process. Can be

Area per one place of the adhesive portion is preferably 0.3 mm ² or more 7.1 mm ² or less. Thereby, the area | region of an adhesion part can be made as small as possible, maintaining adhesive strength, and the fall of the ion conductivity of a separator can be suppressed.

  It is preferable that the thickness per one part of the said adhesion part is 5 micrometers or less. If the thickness of the adhesive part is 5 μm, the adhesive strength is sufficient, and conversely if the thickness of the adhesive part exceeds 5 μm, the adhesive part becomes convex and the laminated electrode body may be deformed. is there. From this viewpoint, the lower limit value of the thickness of the bonded portion is most preferably 0 μm as long as the bonding strength can be secured.

  The adhesive strength between the electrode and the separator may be 0.5 N or more, which can prevent the electrode from being displaced during the process.

  The arrangement position of the adhesive portion is preferably different for each electrode. Thereby, when the said adhesion part has thickness, the overlap of the said adhesion parts in the lamination direction of an electrode can be prevented, and a deformation | transformation of a laminated electrode body can be suppressed.

  The separator preferably forms a bag-like separator. Thereby, in the nonaqueous electrolyte secondary battery of this invention, the short circuit with a positive electrode and a negative electrode can be prevented more reliably. In the laminated electrode body, the bag-like separators may be independent or connected to each other.

  Moreover, the manufacturing method of the nonaqueous electrolyte secondary battery according to the present invention includes an application step of applying a radiation curable resin to a strip-shaped separator to form an adhesive portion, and disposing an electrode on the applied adhesive portion. An electrode placement step, and a bonding step of irradiating the bonding portion with radiation to cure the radiation curable resin and bond the electrode and the separator.

  Since a radiation curable resin is used for the adhesion, the adhesive strength can be increased compared to the case where an adhesive resin other than the radiation curable resin is used, and the resin can be cured by a simple process of irradiating radiation. Therefore, the manufacturing process can be simplified, and the nonaqueous electrolyte secondary battery of the present invention can be efficiently manufactured.

The coating amount of the radiation curable resin per location is preferably 0.005 mg or more and 0.15 mg or less. Thereby, the area per one place of the said adhesion part is 0.3 mm < ² >.
The thickness can be set to 7.1 mm ² or less, and as described above, a decrease in the ion conductivity of the separator can be suppressed. The coating amount is more preferably 0.07 mg or less. Thereby, the thickness per one place of the said adhesion part can be 5 micrometers or less, and a deformation | transformation of a laminated electrode body can be suppressed.

  The coating viscosity of the radiation curable resin is preferably 40 mPa · s or more at 30 ° C. If the viscosity is in the above range, the applied radiation curable resin does not penetrate the separator, so that contamination of the manufacturing apparatus can be prevented and a certain amount of radiation curable resin can be held on the surface of the separator. Therefore, the separator and the electrode can be securely bonded. Further, the coating viscosity is preferably 300 mPa · s or less in order to allow the radiation curable resin to penetrate into the separator to some extent.

  In the coating step, it is preferable that the bonding portion is disposed at a different position for each of the electrodes. Thereby, when the said adhesion part has thickness, the overlap of the said adhesion parts in the lamination | stacking method of an electrode can be prevented, and a deformation | transformation of a laminated electrode body can be suppressed.

  It is also possible to further include a separator stacking step in which another separator is disposed on the electrode after the bonding step, and a separator joining step in which the separators facing each other are joined to form a bag-like separator.

  The electrode bonded to the separator by the bonding portion is preferably a positive electrode. This is because the positive electrode is usually smaller in size than the negative electrode and is difficult to position compared to the negative electrode. Moreover, since the said adhesion part worsens acceptance of lithium ion, it is preferable that the negative electrode and the separator are not adhere | attached by the said adhesion part.

  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 electrode and the separator are 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.

  Next, the first separator 1 is fed horizontally from the first feeding roll 10, and the radiation curable resin 3 is applied onto the first separator 1 from the radiation curable resin coating machine 30. At that time, the radiation curable resin 3 is applied as 3a, 3b in the approximate center of the position where the positive electrode is to be disposed. However, the application position of the radiation curable resin 3 is not limited to the above position, and the application position may be different for each application. Furthermore, the number of application positions is not limited to two, and may be one or three or more.

  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. As radiation used for curing, ultraviolet rays, electron beams, visible light, and the like can be used, but ultraviolet rays are preferable because they can be irradiated with high energy at low cost.

  Next, after the positive electrode 4 provided with the terminal 4a is disposed on the first separator 1 so as to be in contact with the radiation curable resins 3a and 3b applied by the positive electrode feeder 40, the radiation 50a is irradiated with the radiation 50a. Is irradiated from the separator 1 side to cure the radiation curable resins 3a and 3b, and the separator 1 and the positive electrode 4 are bonded. At this time, the positive electrode 4 is fixed to the separator 1 by the cured radiation curable resin 3, and the positive electrode 4 is not displaced from the separator 1 by any subsequent process.

  Next, the second separator 2 is fed out from the second feeding roll 20, and the second separator 2 is disposed on the positive electrode 4. Subsequently, using the heating device 70 on the pedestal 60, the second separator 2 is brought into close contact with the outer shape of the positive electrode 4, and the first separator 1 and the second separator 2 are joined by thermal welding. Thus, the positive electrode-containing bag-like separator 5 is formed. At this point, the positive electrode-filled bag-shaped separator 5 has the joining portion 5a and the connecting portion 6a, and forms the positive-electrode-filled bag-shaped separator connector 6.

  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-filled bag-like separator 5 are alternately laminated to produce a laminated electrode body 9A shown in FIG. FIG. 3 is a bottom view of the laminated electrode body 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 multilayer electrode body 9A is inserted into the exterior body, an electrolytic solution is injected, and the exterior body 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 a laminated electrode body 9B shown in FIG.

  Thereafter, as described above, the nonaqueous electrolyte secondary battery of the present invention is manufactured by a normal method. In the present 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 laminated electrode body 9B can be continuously produced simply by adjusting the width of the connecting portion 6a. It can be improved.

(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 oxide such as LiCoO ₂ , LiM
Although lithium manganese oxides such as n ₂ O ₄ and lithium nickel oxides such as LiNiO ₂ can be used, there is no limitation to these as long as they can occlude and release lithium ions.

  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.

  As the negative electrode active material, for example, natural graphite, or carbon materials such as artificial graphite such as massive graphite, flake graphite, earthy graphite, etc. are used, but there is no limitation to these as long as lithium ions can be occluded / released. Not.

  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, a microporous film made of a thermoplastic resin having a large ion permeability and a predetermined mechanical strength can be used.

  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, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, LiC
An electrolytic solution in which at least one lithium salt selected from F ₃ SO _{3 and the} like is dissolved may be used. The concentration of Li ions in the electrolytic solution may be 0.5 to 1.5 mol / L.

  Hereinafter, the present invention will be described by way of examples.

First, the positive electrode 4 and the separator 1 were bonded with the radiation curable resin 3 by the manufacturing method shown in FIGS. 1 and 2. At that time, various samples were prepared by changing the coating amount per one place of the radiation curable resin 3. As the positive electrode 4, a positive electrode having a thickness of 106 μm, a length of 200 mm, and a width of 84 mm was used. As the separator 1, a polyethylene microporous film having a thickness of 21 μm was used. As the radiation curable resin, 68 parts by mass of DPHA (dipentaerystol hexaacrylate) as a main agent, 29 parts by mass of HDDA (1,6-hexanediol diacrylate) as a diluent, and 2,4,4 as a photoinitiator. Three parts by mass of 6-trimethylbenzoyl-diphenylphosphine oxide were mixed and used. At this time, the viscosity of the radiation curable resin 3 measured at 30 ° C. was 160 mPa · s.

  Next, the area and thickness per one part of the adhesion part by the radiation curable resin 3 of each sample were measured. Thereafter, for each sample, the separator 1 was pulled from the positive electrode 4 in a direction perpendicular to the positive electrode 4 using a tensile tester, and the adhesive strength was measured. The pulling speed was 100 mm / min. As the adhesive strength, the maximum tensile strength until the separator 1 was peeled from the positive electrode 4 was measured.

  Table 1 shows the above results.

From Table 1, it can be seen that, in order to increase the adhesive strength to 0.5 N or more, it is necessary to set the application amount of the radiation curable resin per location to 0.005 mg or more. Further, it can be seen that if the coating amount per spot of the radiation curable resin is 0.15 mg, the adhesive strength is 7 N or more, and the adhesive strength is sufficient. Further, if the application amount is 0.005 mg or more and 0.15 mg or less, the area per one part of the bonded portion can be 0.3 mm ² or more and 7.1 mm ² or less, and the application amount is 0.07 mg or less. In other words, it can be seen that the thickness of each bonded portion can be 5 μm or less.

  Next, the coating viscosity at 30 ° C. of the radiation curable resin was changed, and the penetration time of the radiation curable resin with respect to the separator after coating was measured. The results are shown in Table 2.

  From Table 2, if the coating viscosity at 30 ° C. of the radiation curable resin is 40 mPa · s or more, the penetration time can be set to 1 second or more, and the curing time of the radiation curable resin is usually 1 second. Since it is the following, the applied radiation curable resin does not penetrate the separator. Moreover, since it is necessary to permeate a certain amount of radiation-curable resin into the separator, the coating viscosity is preferably 300 mPa · s or less.

As described above, the present invention can provide a nonaqueous electrolyte secondary battery excellent in load characteristics and the like 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 containing positive electrode 6 Bag-like separator connected with positive electrode 7 Negative electrode 9A, 9B Laminated electrode body 10 First feeding roll 20 Second feeding Roll 30 Radiation curable resin coating machine 40 Positive electrode feeder 50 Radiation irradiation device 50a Radiation 60 Base 70 Heating device 100 Laminated lithium ion secondary battery 200 Exterior body 300 Positive electrode external terminal 400 Negative electrode external terminal

Claims (14)

A non-aqueous electrolyte secondary battery including a laminated electrode body in which a positive electrode, a negative electrode, and a separator are laminated,
The nonaqueous electrolyte secondary battery, wherein either the positive electrode or the negative electrode and the separator are bonded by an adhesive portion.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the positive electrode and the separator are bonded by the bonding portion, and the negative electrode and the separator are not bonded.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the adhesion portion is formed of a radiation curable resin. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein an area per one portion of the bonding portion is 0.3 mm ² or more and 7.1 mm ² or less.   The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein a thickness per one portion of the adhesion portion is 5 µm or less.   The non-aqueous electrolyte secondary battery according to claim 1, wherein an adhesive strength between the electrode and the separator is 0.5 N or more.   The non-aqueous electrolyte secondary battery according to claim 1, wherein an arrangement position of the adhesive portion is different for each of the electrodes.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator forms a bag-shaped separator. A method for producing the nonaqueous electrolyte secondary battery according to any one of claims 1 to 8,
An application step of applying a radiation curable resin to a strip-shaped separator to form an adhesive portion;
An electrode placement step of placing an electrode on the applied adhesive portion;
The manufacturing method of the nonaqueous electrolyte secondary battery characterized by including the adhesion | attachment process of irradiating a radiation to the said adhesion part, hardening | curing the said radiation curable resin, and adhere | attaching the said electrode and the said separator.   The method for producing a nonaqueous electrolyte secondary battery according to claim 9, wherein an application amount of the radiation curable resin per place is 0.005 mg or more and 0.15 mg or less.   The method for producing a nonaqueous electrolyte secondary battery according to claim 9 or 10, wherein the coating viscosity of the radiation curable resin is 40 mPa · s or more and 300 mPa · s or less at 30 ° C.   The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 9, wherein in the application step, the adhesive portion is disposed at a different position for each of the electrodes.   Any of Claims 9-12 further including the separator lamination process which arrange | positions another separator on the said electrode after the said adhesion process, and the separator joining process which joins the said separators which oppose and form a bag-shaped separator. A method for producing a non-aqueous electrolyte secondary battery according to claim 1.   The method for producing a nonaqueous electrolyte secondary battery according to any one of claims 9 to 13, wherein the electrode is a positive electrode.

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