JP5884703B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more specifically, by using a curable resin having a phenylene sulfide skeleton in the seal portion, excellent pressure-resistant adhesive force and sealing performance between an encapsulating bag and a lead wire The present invention relates to a pouch-type non-aqueous electrolyte secondary battery that can achieve the above.

  A pouch-type non-aqueous electrolyte battery in which a bag body is used as an enclosing container (or “encapsulating bag”) and a non-aqueous electrolyte, a positive electrode, and a negative electrode are enclosed inside the bag body is employed. Here, since the bag body is required to have a function of preventing permeation of electrolyte and gas and preventing moisture from entering from the outside, that is, barrier properties, a metal film is used as a material constituting the bag body. Alternatively, a laminated film having a multilayer structure having a metal plate and an insulating layer made of an insulating resin covering the metal film or the metal plate is often used.

  Non-aqueous electrolyte batteries usually produce an encapsulating bag by laminating the above-mentioned laminate film so that the insulator layer is on the inside, and the non-aqueous electrolyte, positive electrode, negative electrode, separator, etc. In addition, a conductor wire (lead wire), one end of which is connected to the positive electrode and the negative electrode, is disposed so as to extend from the opening of the encapsulating bag to the outside of the battery, and finally the opening is fused and sealed. Can be produced. The opening fused and sealed as described above is referred to as a “seal part”.

  The seal portion is required to have excellent adhesive force and sealability between the insulator layer of the encapsulating bag and the lead wire, but is also required to have the property that no short circuit occurs between the metal layer of the laminate film and the lead wire. In order to meet such demands, for example, as described in JP-A-9-283101, the sealing reliability of the seal portion is improved by using maleic acid-modified polyolefin as a material constituting the seal portion. Yes. In addition, as described in, for example, Japanese Patent Application Laid-Open No. 2009-123401, an insulation containing a modified polyolefin resin and an organic clay is used to achieve good barrier properties and good adhesion to lead conductors. An insulating layer is formed from a resin, and the lead conductor is covered with the same insulating resin coating from the viewpoint of preventing a short circuit. Furthermore, as described in, for example, Japanese Patent Application Laid-Open No. 2011-52298, various surface treatments including chemical conversion treatment are applied to a metal layer such as an aluminum foil from the viewpoint of sealing properties.

  Considering the future of pouch-type non-aqueous electrolyte batteries, there is an increasing demand for smaller and lighter batteries, and along with this, the internal pressure due to the gas generated from the inside of the enclosure is increasing at the seal part. In order to increase, stronger pressure resistance, adhesiveness, and sealability will be required. However, as described above, since the conventional insulator layer using an olefin resin has poor material strength, the insulator layer creep ruptures due to an increasing internal pressure over time, or else the conductor wire and As a result, the barrier portion cannot be maintained. In order to avoid such a problem, it can be considered that the insulator layer is formed using a resin having a high material strength instead of the olefin resin. Examples of the resin having high material strength include polyimide resin, polyether amide imide resin, polyamide imide resin, polyphenylene ether resin, polyphenylene sulfide resin, and epoxy resin. However, among these resins, polyimide resins, polyether amide imide resins, polyamide imide resins, polyphenylene ether resins, and polyphenylene sulfide resins are inferior in adhesiveness to conductor wires, and are therefore difficult to use as insulator layers. is there. Moreover, since an epoxy resin is inferior in the barrier property with respect to electrolyte solution, there exists a problem in use as an insulator layer.

JP-A-9-283101 JP 2009-123401 A JP 2011-52298 A

  The object of the present invention is to deal with the problem that the internal pressure increases due to the gas generated from the inside of the enclosed container in view of the problems of the conventional technology as described above, and has stronger pressure resistance, adhesiveness, and sealing properties. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery that can guarantee the above.

  The object of the present invention is also a non-aqueous electrolyte secondary that can achieve excellent pressure-resistant adhesive force and sealing property between the insulator layer of the encapsulating bag and the lead wire and prevention of short circuit between the metal layer of the encapsulating bag and the lead wire. To provide a battery.

  Other objects of the present invention can be easily understood from the following detailed description.

  As a result of intensive studies to achieve the above-described object, the present inventors have found that the curable resin having a phenylene sulfide skeleton has excellent adhesiveness with a conductor wire despite the high material strength, and the electrolyte solution. The present invention was completed by obtaining the knowledge that it is useful for forming an insulating layer having a good barrier property against the above.

The present invention resides in a sealed pouch-type non-aqueous electrolyte secondary battery including a component of a non-aqueous electrolyte secondary battery and an enclosing container containing the component. In the nonaqueous electrolyte secondary battery of the present invention, the enclosure is a laminate film including at least a metal layer and a first insulator layer,
The opening of the enclosure is connected to each of a positive electrode and a negative electrode that are members of the battery component, and further includes lead wires extending from the inside to the outside of the enclosure,
In the opening, the first insulator layer constituting the innermost layer of the laminate film and the second insulator layer covering the lead wire are heat-sealed to form a seal portion, and the first and At least one of the second insulator layers is formed from a cured epoxy resin having a phenylene sulfide structure as a skeleton.

  In the nonaqueous electrolyte secondary battery of the present invention, at least one of the first and second insulator layers is formed from a cured product of an epoxy resin having a phenylene sulfide structure as a skeleton. As the epoxy resin, a known epoxy resin generally used as an insulating material can be used. Examples of usable epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, epoxy resins having a bisphenol skeleton containing these polymers, or glycidylamine type trifunctional or tetrafunctional. Examples thereof include a flexible epoxy resin, a glycidyl ester type epoxy resin, a rubber-modified epoxy resin, a flexible epoxy resin represented by a polyether skeleton epoxy resin, and the like. The epoxy resin having a phenylene sulfide structure as a skeleton may be used in combination with an epoxy resin not having a phenylene sulfide structure as a skeleton, if necessary.

  The epoxy resin used in the present invention needs to have a phenylene sulfide structure in its skeleton. Since the phenylene sulfide structure exhibits strong crystallinity, by introducing the phenylene sulfide structure into the epoxy resin skeleton, the intermolecular interaction is strengthened and chemicals and water are prevented from entering the cured epoxy resin. be able to.

  The epoxy resin having a phenylene sulfide structure is preferably a glycidylamine type epoxy resin and is represented by the following formula (I).

  X in the above formula is preferably hydrogen or otherwise represents a methyl group. In particular, hydrogen is the preferred X because it can provide the strongest crystallinity to the epoxy resin. Moreover, n in the above formula usually represents an integer of 1 to 10.

  The weight average molecular weight (Mw) of the glycidylamine type epoxy resin can be changed within a wide range. That is, the molecular weight (Mw) of the epoxy resin can be arbitrarily varied in two patterns, when n of the phenylene sulfide of the main skeleton is changed and when n is constant and oligomerization is performed by an epoxy reaction. The molecular weight (Mw) of the epoxy resin is usually in the range of about 100 to 10,000, preferably in the range of about 200 to 5000, and most preferably in the range of about 500 to 2500.

  In the nonaqueous electrolyte secondary battery of the present invention, the cured epoxy resin is preferably a cured product of a curable resin including an epoxy resin and a curing agent for curing the epoxy resin. The curing agent used here is not particularly limited as long as it does not adversely affect the effects of the present invention, but is represented by the following formula (II) in view of the presence of a phenylene sulfide structure in the skeleton of the epoxy resin. Such a diamine compound having a phenylene sulfide structure in the skeleton is preferable.

  In the above formula (II), X represents hydrogen or a methyl group, and n represents an integer of 1 to 10. Since the phenylene sulfide skeleton exhibits strong crystallinity, if n in the formula is larger than 10, the compatibility with the epoxy is lowered, and the melting point is considerably increased, so that the handleability may be lowered. On the contrary, if n in the formula is too small, the crystallinity becomes weak and the effect of the present invention is considered to be low. In the above formula (II), n is more preferably 3 to 5, and most preferably 3.

  In the epoxy resin cured product, the compounding ratio of the epoxy resin and the curing agent can be changed in a wide range, and this compounding ratio is usually the epoxy group in the epoxy resin and the amino group (NH group) in the curing agent. The equivalent ratio of The equivalent ratio of the epoxy group in the epoxy resin and the amino group (NH group) in the curing agent may be in the range of epoxy group: NH group = 0.5: 1.0 to 1.0: 0.5. More preferably, it is the range of 0.8: 1.0-1.0: 0.8.

  When preparing a cured epoxy resin from a blend of epoxy resin and curing agent, various additives are optionally blended in conventional amounts as necessary to improve the physical properties of the resulting insulator layer. Can be added. Suitable additives include, for example, antioxidants, flame retardants, ultraviolet absorbers, light stabilizers, heat stabilizers, lubricants, colorants and the like. Further, inorganic fillers such as crystalline silica, fused silica, alumina, calcium carbonate, and calcium hydroxide, and organic fillers such as silicone resin, acrylic resin, urethane resin, and rubber can be added.

  Mixing, molding and curing of the formulation can optionally be performed using conventional equipment and conditions. For example, the compound can be mixed using a known mixing device such as a pressure kneader, a single screw mixer, a twin screw mixer, etc., formed into a film-like insulator layer with an extruder, etc., and cured. . As curing conditions, for example, a curing temperature of 80 ° C. or higher, preferably 120 ° C. or higher, more preferably 150 ° C. or higher can be applied. For the purpose of lowering the curing temperature, an amine catalyst such as imidazole or a metal catalyst such as tin compound can be used in combination.

  According to the present invention, as will be understood from the following detailed description, it is possible to cope with the problem that the internal pressure increases due to the gas generated from the inside of the enclosure, and guarantees stronger pressure resistance, adhesiveness, and sealing performance. The nonaqueous electrolyte secondary battery which can be provided can be provided. In addition, according to the present invention, it is possible to achieve excellent pressure-resistant adhesive force and sealability between the insulator layer of the encapsulating bag and the lead wire and prevention of short circuit between the metal layer of the encapsulating bag and the lead wire.

It is the fragmentary sectional view which showed one preferable form of the nonaqueous electrolyte secondary battery by this invention. It is a schematic cross section of a T-type peel test piece subjected to a peel strength test.

  Subsequently, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to these embodiments.

  In the present invention, the non-aqueous electrolyte secondary battery is a so-called “pouch” type, and the basic configuration can be the same as that of a conventional pouch-type non-aqueous electrolyte secondary battery. For example, although only a part is shown in FIG. 1, the nonaqueous electrolyte secondary battery 1 such as a lithium battery includes a substantially rectangular enclosing container composed of a laminate film 4 and a lead wire 6 extending from the inside of the enclosing container to the outside. have. Inside the enclosure, elements constituting the battery, for example, an electrolyte, a positive electrode plate and a negative electrode plate, a positive electrode active material, a negative electrode active material, a separator, and the like are incorporated.

  As shown in FIG. 1, the sealed container is formed of a two-layer laminate film 4 including a metal layer 2 and a first insulator layer 3 laminated on the metal layer 2. The metal layer 2 is formed from a metal material such as an aluminum foil. The film thickness of the metal layer 2 is usually in the range of 10 to 200 μm. In the laminate film 4, the first insulator layer 3 located inside the enclosure is formed from the cured epoxy resin of the present invention having a polyphenylene sulfide structure as a skeleton. The film thickness of the first insulator layer 3 is usually in the range of 10 to 200 μm. In the illustrated example, the laminate film 4 employs a two-layer structure, but may have a multilayer structure of three or more layers as necessary. In the enclosing container, two laminated films 4 are overlapped so that the first insulator layers 3 face each other, and then three sides other than the side through which the lead wire 6 passes are heat-sealed by, for example, heat sealing. Can be produced. The two metal layers 2 are bonded to each other through the first insulator layer 3 in the outer peripheral portion of the enclosure.

  In the seal portion 9, the lead wire 6 is bonded to the enclosure (laminate film 4) via the second insulator layer 5. This adhesion can also be performed by heat-sealing by, for example, heat sealing. The lead wire 6 can be formed from, for example, a metal material such as aluminum, nickel, copper, nickel-plated copper, or the like in a shape and a size normally used for a nonaqueous electrolyte secondary battery. The second insulator layer 5 is preferably used in the form of a coating covering the lead wire 6, but depending on the function of the first insulator layer 3 as necessary, the second insulation layer 5 can be used. The use of the body layer 5 may be omitted. The second insulator layer 5 is preferably formed from the cured epoxy resin of the present invention having a phenylene sulfide structure as a skeleton.

  As described above, both the first insulator layer 3 and the second insulator layer 5 are preferably formed from the cured epoxy resin of the present invention having a phenylene sulfide structure as a skeleton. However, as a modification, if the effect of the present invention is not adversely affected, any one of these insulator layers may be a conventional insulating material layer, for example, a polyolefin resin such as polyethylene or polypropylene, or a modified polyolefin resin. You may form from resin.

In the non-aqueous electrolyte secondary battery 1, the positive electrode plate 11 and the negative electrode plate 13, the non-aqueous electrolyte 14, and the positive electrode plate 11 connected to the end portions of the lead wires 6 are disposed inside the enclosure. A positive electrode active material 12, a negative electrode active material 14 disposed in contact with the negative electrode plate 13, and a separator 7 that separates the positive electrode active material 12 and the negative electrode active material 14 are encapsulated. Each of these battery components enclosed in the enclosure can be arbitrarily configured from those commonly used in nonaqueous electrolyte secondary batteries. For example, in the case of a lithium battery, aluminum can be used for the positive electrode plate and nickel can be used for the negative electrode plate. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF _6, etc. can be used as the non-aqueous electrolyte.

Preparation Example 1
In this example, a diamine compound represented by the above formula (II) (wherein X = hydrogen, n = 3), that is, a phenylene sulfide oligomer having amino groups at both ends was prepared according to the following reaction formula.

A flask containing N, N-dimethylacetamide as a reaction solvent was charged with dithiodiphenylene sulfide and p-chloronitrobenzene in an equivalent ratio of SH: Cl = 1: 1.1. After raising the temperature of the flask to 60 ° C., potassium carbonate was added at a ratio of SH: K ₂ CO ₃ = 1: 1.1 and further reacted at 120 ° C. for 5 hours. Next, the reaction solution was poured into ion-exchanged water for reprecipitation, and a solid was obtained by filtration. The obtained solid was washed with hot ethanol and then dried. A phenylene sulfide oligomer (n = 3) having nitro groups at both ends was obtained in a yield of 80%.

  Subsequently, the phenylene sulfide oligomer and palladium carbon prepared in the above step were charged into a flask containing isopropyl alcohol as a reaction solvent in a weight ratio of phenylene sulfide oligomer: palladium carbon = 1: 0.05. After raising the temperature of the flask to 70 ° C., hydrated hydrazine was added at an equivalent ratio of nitro group: hydrated hydrazine = 1: 4 over 1 hour. When the reaction was further carried out at 80 ° C. for 5 hours, the terminal nitro group of the phenylene sulfide oligomer was reduced to an amino group. When palladium carbon was removed by hot filtration and then cooled, a solid was deposited. The resulting solid was removed by filtration and dried. A phenylene sulfide oligomer (n = 3) PhS2A having amino groups at both ends was obtained in a yield of 75%. In addition, MS and NMR were used for confirmation of the product of this example.

Preparation Example 2
In this example, from the diamine compound prepared in Preparation Example 1, a glycidylamine type epoxy resin represented by the above formula (I) (wherein X = hydrogen, n = 3), that is, a phenylene sulfide skeleton and both terminals. An epoxy resin having a glycidylamino group was prepared according to the following reaction formula.

  A 500 ml four-necked flask was charged with 40 g (0.0925 mol) of a phenylene sulfide oligomer PhS2A (prepared in Preparation Example 1), 80 g of ethanol and 10 g of distilled water, and heated to 60 ° C. with stirring. Subsequently, 85.5 g (0.0925 mol) of epichlorohydrin was dropped, and the temperature of the flask was raised to 80 ° C. Thereafter, the reaction was continued for 4 hours under reflux. After the temperature of the flask was lowered to 60 ° C., 37 g (0.462 mol) of a 50% NaOH aqueous solution was added dropwise, and the reaction was continued for another 1 hour. Subsequently, epichlorohydrin and ethanol were removed under reduced pressure, followed by extraction with 150 g of toluene. After completion of extraction, the toluene layer was washed with 100 g of distilled water. Then, when toluene was removed under reduced pressure, 49 g (yield 81%) of a tan oil was obtained. This oily substance is mainly composed of a glycidylamine type epoxy resin represented by the above formula (I) (wherein X = hydrogen, n = 3), potentiometric titration (epoxy equivalent measurement) and GPC (gel This could be confirmed by transmission chromatography).

Example 1
In this example, how the resistance of the electrolyte solution of the nonaqueous electrolyte secondary battery varies depending on the composition of the insulator layer was evaluated by measuring the change in the peel strength of the insulator layer.

  A bag-like sealed container having the same structure as that shown in FIG. 1 uses an aluminum foil (thickness: 200 μm) as a metal layer and an insulator layer having the composition described in Table 1 below. It was produced by using (thickness: 80 μm). The size of the enclosure was 100 mm × 150 mm. The lead wire was an aluminum plate having a thickness of 0.4 mm, a width of 50 mm, and a length of 30 mm.

  Subsequently, the seal part was cut out from the enclosed container, and a T-type peel test piece 20 schematically shown in FIG. 2 was produced. As shown in the figure, two L-shaped aluminum foils 22 are firmly bonded via an insulator layer 23.

[Measurement of initial peel strength]
Using a tensile tester (trade name “Autograph”, manufactured by Shimadzu Corporation), the initial peel strength (N / min) according to the procedure of 180 ° peel test (tensile speed: 5 mm / min) defined in JISK6854-2. cm). In this measurement test, a criterion of evaluating “possible (◯)” when the peel strength was 200 N / cm or more and applying “impossible (×)” when less than 200 N / cm was applied.

  When the aluminum part of the produced test piece was sandwiched by a tensile tester and measured, the initial peel strength was 220 N / cm, which was evaluated as “good”. The results obtained are shown in Table 1.

[Evaluation of electrolyte resistance]
After mixing ethylene carbonate and diethylene carbonate in a volume ratio of 1: 1, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte was dissolved in the obtained mixture to a concentration of 0.05 mol / l. An electrolyte solution was prepared. This electrolyte solution (8 ml) was then poured into the enclosure made in the above step and, as described in Table 1 below, at 60 ° C./hour over different times (immersion time: zero, 2 weeks and 4 weeks). It was left in a constant temperature bath of 90% RH. After elapse of a predetermined time, the T-type peel test piece shown in FIG. 2 was cut out from each sealed container as described above, and peel strength was measured by the same method as described above.

In this evaluation test, each peel strength measured after leaving for a predetermined time was compared with the initial peel strength,
The strength retention rate (%) is evaluated as “excellent (◎)” when 80% or more.
The strength retention rate (%) is evaluated as “good (◯)” when 60% or more and less than 80%.
The strength retention rate (%) is evaluated as “possible (△)” when 30% or more and less than 60%.
A criterion for evaluating that the strength retention (%) is less than 30% as “impossible (×)” was applied.

  In this example, the peel strength immediately after immersion was 207 N / cm (strength retention: 94%), and was evaluated as “excellent (◎)”. The peel strength after immersion for 2 weeks was 188 N / cm (strength retention: 85%), which was also evaluated as “excellent (◎)”. Furthermore, the peel strength after immersion for 4 weeks was 172 N / cm (strength retention: 78%), which was evaluated as “good (◯)”. The obtained evaluation results are shown in Table 1.

Examples 2 and 3, Comparative Examples 1 and 2
Although the method described in Example 1 was repeated, in this example, the composition of the insulator layer was changed as shown in Table 1 below. Table 1 shows the evaluation results obtained in each example. In Table 1 below, “epoxy resin 1” is a bisphenol A type epoxy resin (trade name “D.E.R 331J”, manufactured by Dow Chemical Japan). “Epoxy resin 2” is a glycidylamine-type epoxy resin having a phenylene sulfide structure as a skeleton obtained in Preparation Example 2, and “curing agent A” is an amine-terminated phenylene sulfide oligomer obtained in Preparation Example 1. Further, “curing agent B” is diaminodiphenylsulfone, and “acid-modified PP” is acid-modified polypropylene.

  As understood from the evaluation results described in Table 1, according to the present invention, each non-aqueous electrolyte secondary battery has excellent results in terms of both the peel strength of the conductor layer and the resistance to electrolytic solution. Therefore, these nonaqueous electrolyte secondary batteries can be advantageously applied to the production of lithium batteries and the like.

  The non-aqueous electrolyte secondary battery of the present invention has great applicability in lithium ion batteries and other pouch-type non-aqueous electrolyte batteries that are increasingly required to be smaller and lighter. According to the present invention, even when the internal pressure of the container is increased due to the generation of gas inside the enclosed container, it is possible to ensure stronger pressure resistance, adhesiveness, and sealability, and the insulator layer Can creep rupture, or otherwise, the adhesion portion with the conductor wire peels off, so that the problem that the barrier property cannot be maintained can be solved.

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Metal layer 3 1st insulator layer 4 Laminate film 5 2nd insulator layer 6 Lead wire 7 Separator 8 Nonaqueous electrolyte 9 Seal part 11 Positive electrode plate 12 Positive electrode active material 13 Negative electrode plate 14 Negative electrode active material

Claims (4)

In a sealed pouch-type non-aqueous electrolyte secondary battery including a component of a non-aqueous electrolyte secondary battery and an enclosing container containing the component,
The enclosure is a laminate film including at least a metal layer and a first insulator layer,
The opening of the enclosure is connected to each of a positive electrode and a negative electrode that are members of the constituent components, and includes lead wires extending from the inside to the outside of the enclosure.
In the opening, the first insulator layer constituting the innermost layer of the laminate film and the second insulator layer covering the lead wire are heat-sealed to constitute a seal portion, And both the first and second insulator layers are formed from a cured epoxy resin having a phenylene sulfide structure as a skeleton, or only the first insulator layer has a phenylene sulfide structure as a skeleton. It is formed from a cured epoxy resin,
The cured epoxy resin is a cured product of a curable resin containing an epoxy resin having a phenylene sulfide structure and a curing agent for curing the epoxy resin, or for curing the epoxy resin and the epoxy resin. A cured product of a curable resin containing a curing agent having a phenylene sulfide structure, or an epoxy resin having a phenylene sulfide structure, and a curing agent having a phenylene sulfide structure for curing the epoxy resin. A non-aqueous electrolyte secondary battery , which is a cured product of a curable resin . The curing agent is a diamine compound represented by the following formula:

(In the above formula, X is indicates whether a methyl group is hydrogen, n is integer of 1 to 10) is a non-aqueous electrolyte secondary battery according to claim 1. The nonaqueous electrolyte secondary battery according to claim 2 , wherein n in the formula is 3. The equivalent ratio of the epoxy group in the epoxy resin to the amino group (NH group) in the curing agent is in the range of epoxy group: NH group = 0.5: 1.0 to 1.0: 0.5. The non-aqueous electrolyte secondary battery according to claim 2 or 3 .

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