JP4222149B2 - Absorbent sheet and non-aqueous electrolyte battery pack - Google Patents

Description

  The present invention relates to a liquid-absorbent sheet for absorbing an electrolyte solution when a leakage of the electrolyte solution occurs from a non-aqueous electrolyte battery cell in the non-aqueous electrolyte battery pack, and a non-aqueous electrolysis using the same The present invention relates to a liquid battery pack.

  Battery packs in which a plurality of primary battery cells or secondary battery cells and a wiring circuit board are stored in a battery case are widely used. In such a battery pack, when leakage of the electrolytic solution occurs from the battery cell, the wiring of the printed circuit board may be corroded to cause poor conduction or, conversely, a short circuit may occur. Therefore, in order to prevent the above-described corrosion and short circuit problems from occurring even when the electrolyte leaks, the electrolyte should be placed at a position in contact with or close to the battery cell in the battery pack. It has been proposed to arrange a liquid-absorbing member provided with a liquid-absorbing agent having the ability to absorb liquid (Patent Document 1). Here, as the liquid-absorbing agent, various polymer materials of adsorption type, gelation type, and self-swelling type are used. Specifically, polyacrylate water absorbent resin, starch-graft copolymer water absorbent resin, polyvinyl alcohol water absorbent resin, polyacrylamide water absorbent resin, isobutylene-maleic acid copolymer water absorbent resin, long Examples are chain alkyl acrylate cross-linked polymers, polynorbornene and the like.

JP 2001-351588 A

  However, these liquid-absorbing agents are widely used in non-aqueous electrolyte battery packs that have been widely used in recent years, in particular, in non-aqueous electrolyte secondary batteries constituting lithium ion non-aqueous electrolyte secondary battery packs. There is a problem that the carbonate-based solvent, such as propylene carbonate and dimethyl carbonate, cannot be sufficiently absorbed. In addition, the liquid absorbing agent itself is not sticky or very small, so it cannot be easily attached to the nonwoven fabric serving as a support at room temperature, and must be attached using a thermal laminator. There was a problem of not getting. Moreover, in order to apply the liquid absorbent to the non-aqueous electrolyte secondary battery pack, it is necessary to newly provide an adhesive layer. For this reason, the amount of the liquid absorbent used is only the amount corresponding to the thickness of the adhesive layer. There was a problem that we had to reduce it. Furthermore, the liquid absorbing agent is also required to exhibit predetermined flame retardancy.

  The present invention is intended to solve the above-described problems of the prior art, and a non-aqueous electrolyte secondary battery constituting a non-aqueous electrolyte battery pack (particularly, a lithium ion non-aqueous electrolyte secondary battery pack). To provide a liquid-absorbent sheet having excellent liquid absorbency and adhesiveness with respect to the non-aqueous electrolyte, and further exhibiting excellent flame retardancy, and an electrolyte-absorbing member formed from such liquid-absorbent sheet An object is to provide a battery pack provided.

  The present inventors have absorbed a large amount of electrolytic solution by a resin layer obtained by polymerizing a monofunctional monomer and a polyfunctional monomer with a liquid phosphate ester flame retardant irradiated with ultraviolet rays. The present invention was completed by finding that it can be held and exhibits flame retardancy and also exhibits tackiness, and that it can unexpectedly maintain good insulating properties even after wet heat aging treatment.

That is, the present invention is a liquid-absorbent sheet comprising a liquid-absorbent resin layer, wherein the liquid-absorbent resin layer is an acrylate monofunctional monomer, a polyfunctional monomer having two or more acrylate residues, and a liquid all SANYO the ultraviolet and by polymerizing radiation to the monomer composition containing phosphoric acid ester-based flame retardant, the liquid phosphoric ester-based flame retardant, bisphenol a bis (diphenyl) phosphate, hydroquinol bis ( Diphenyl) phosphate, phenyldixylenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, resorcinol bis (diphenyl) phosphate, or 2-ethylhexyl diphenyl absorbent characterized by phosphate der Rukoto Provide a sheet.

  The present invention also provides an electrolyte for absorbing the electrolyte when a leakage of the electrolyte occurs from the nonaqueous electrolyte battery cell, the wiring circuit board, and the nonaqueous electrolyte battery cell in the battery case. A non-aqueous electrolyte battery pack having a liquid-absorbing member installed therein, wherein the electrolyte-absorbing member is formed from the liquid-absorbent sheet described above. To do.

  According to the present invention, the non-aqueous electrolyte battery pack (particularly, the lithium ion non-aqueous electrolyte secondary battery pack) has excellent liquid absorbency with respect to the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery. It is possible to provide a liquid-absorbent sheet exhibiting adhesiveness and further excellent flame retardancy, and a battery pack provided with an electrolyte-absorbing member formed from such a liquid-absorbent sheet.

  First, the liquid absorbent sheet of the present invention will be described.

  In the liquid-absorbent sheet of the present invention, as shown in FIG. 1 (a), not only the liquid-absorbent resin layer 1 is formed in a sheet shape alone, but also as shown in FIG. 1 (b), An aspect in which the liquid-absorbing resin layer 1 is formed on one side of the support 2 is included. In the liquid-absorbent sheet of the present invention, the liquid-absorbent resin layer 1 itself can absorb and retain a large amount of the electrolytic solution, and the liquid-absorbent resin layer 1 itself has adhesiveness, so a new adhesive layer is provided. There is no need, and the volume ratio of the liquid absorbent resin layer 1 in the liquid absorbent sheet can be increased. Therefore, the liquid absorbent sheet can be easily installed in the battery case. In addition, as shown in FIG.1 (c), you may form the adhesion layer 3 in the surface at the side of the liquid absorbing resin layer 1. FIG. In this case, the pressure-sensitive adhesive layer 3 is not particularly limited, and a known pressure-sensitive adhesive can be used.

  The support 2 that can be used in the liquid-absorbent sheet of the present invention may be a resin film that does not allow permeation of the electrolyte solution, for example, a plastic film such as polypropylene, but a plastic fiber such as polypropylene that can absorb and hold a nonaqueous solvent. A non-woven fabric or paper made of the above can be used. It is preferable to form the support from such a non-woven fabric because the absorption rate of the non-aqueous solvent can be increased.

  As the liquid-absorbent resin layer 1 constituting the liquid-absorbent sheet of the present invention, a monomer containing a monofunctional monomer as a film forming component, a polyfunctional monomer as a crosslinking component, and a liquid phosphate ester flame retardant A polymerized film polymerized into a sheet by irradiating the composition with ultraviolet rays is used.

In the present invention, since a phosphoric ester-based flame retardant is used, the liquid-absorbent resin layer 1 is flame retardant, specifically, UL-94 standard V-0, V-1 or V-2 grade. Flame retardancy can be imparted. Moreover, since the phosphate ester flame retardant is liquid at room temperature (usually −13 ° C. or higher) under atmospheric pressure, the liquid-absorbent resin layer 1 can be provided with adhesiveness. Furthermore, unexpectedly, good insulating properties can be imparted to the liquid absorbent resin layer 1 by using a liquid phosphate ester flame retardant. In particular, even after a wet heat aging process (for example, a process of maintaining for 96 hours in an environment of a temperature of 40 ° C. and a humidity of 90% RH), the insulation resistance value after the treatment should preferably be 1 × 10 ¹² Ω. be able to.

  Examples of the liquid phosphate ester flame retardant that can be used in the present invention include bisphenol A bis (diphenyl) phosphate, hydroquinol bis (diphenyl) phosphate, phenyldixylenyl phosphate, tricresyl phosphate, cresyl diphenyl Examples thereof include phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, resorcinol bis (diphenyl) phosphate, 2-ethylhexyl diphenyl phosphate, and the like. Of these, bisphenol A bis (diphenyl) phosphate, hydroquinol bis (diphenyl) phosphate, or phenyldixylenyl phosphate can be preferably used in terms of imparting tackiness.

  If the amount of the liquid phosphate ester flame retardant used is too small, sufficient flame retardancy cannot be obtained, and if it is too much, sufficient flame retardancy cannot be obtained. The amount is preferably 70 to 200 parts by weight, more preferably 100 to 150 parts by weight with respect to 100 parts by weight of the total.

In the present invention, the monofunctional monomer, the polymer absorbs the non-aqueous electrolyte, which holds, and specific examples thereof, imide acrylate, A acryloyl morpholine, benzyl acrylate, phenoxyethyl acrylate, N , N-diethylacrylamide, methoxypolyethylene glycol acrylate (ethylene oxide addition moles (n) = 6), methoxypolyethylene glycol acrylate (ethylene oxide addition moles (n) = 3), tetrahydrofurfuryl acrylate, phenoxypolyethylene glycol acrylate ( Ethylene oxide addition mole number (n) = 6) etc. are mentioned. Among them, benzyl acrylate, acryloyl morpholine, Te tiger tetrahydrofurfuryl acrylate preferred in view of the absorption of the electrolytic solution. Two or more of these may be used in combination, and it is particularly preferable to use benzyl acrylate and acryloylmorpholine in combination from the viewpoint of the balance between absorbability and film hardness in the electrolyte. In the case of this combined use, the blending ratio (weight) of benzyl acrylate and acryloyl morpholine is good when the latter is large, but the absorbability of the electrolyte is good, but the film is hard and easily broken, so preferably 30/70 to 70 / 30.

  Further, the proportion of the monofunctional monomer in the total monomer constituting the liquid-absorbing resin layer described above is preferably at least 20 mol% since the liquid absorption amount of the non-aqueous solvent tends to decrease if it is too small. .

  In addition to the monofunctional monomers exemplified above, other monofunctional monomers such as hydroxyethyl acrylate, acrylic acid, 2-ethylhexyl acrylate, lauryl acrylate and the like may be used in combination as long as the effects of the present invention are not impaired.

  In the present invention, the polyfunctional monomer is a component for introducing a crosslinked structure into the liquid-absorbent resin layer 1, and a monomer having two or more acrylate residues is preferably used. For example, hydroxypivalate neopentyl glycol diacrylate, polyethylene glycol diacrylate (ethylene oxide addition moles (n) = 14), bisphenol A diacrylate, phenyl glycidyl ether acrylate, hexamethylene diisocyanate prepolymer, and the like can be used.

  If the proportion of the polyfunctional monomer in the total monomer constituting the liquid-absorbing resin layer 1 is too small, the shape-retaining property of the liquid-absorbing resin layer 1 is not sufficient, and if it is too large, the non-aqueous solvent cannot be sufficiently absorbed. Since there exists a possibility, it may mix | blend in the quantity from which a crosslinking density becomes like this. Preferably it is 0.0001-0.17, More preferably, it is 0.001-0.1.

  Here, the crosslink density is defined as a, where the number of functional groups in the polyfunctional monomer in one molecule is a, the number of moles of the polyfunctional monomer in the monomer composition is b, and the number of moles c of the monofunctional monomer in the monomer composition. Is a numerical value defined by the following formula.

(Equation 1)
Crosslink density = a × b / (b + c)

As described above, the liquid absorbent sheet of the present invention is obtained by applying a monomer composition containing a monofunctional monomer, a polyfunctional monomer, and a liquid phosphate ester flame retardant on a release film such as a polyethylene terephthalate film. When the obtained coating film is polymerized into a sheet by ultraviolet irradiation and peeled off from the release sheet, the embodiment shown in FIG. 1 (a) is obtained, and the monomer composition is applied onto the nonwoven fabric, When polymerized or laminated on a non-woven fabric without heating using the adhesiveness shown in FIG. 1A, the one shown in FIG. 1B can be obtained. In addition, if an adhesive is further formed by application or lamination on the liquid-absorbent resin layer in the embodiment of FIG. 1 (b), the embodiment of FIG. 1 (c) is obtained. Here, as a method for applying the monomer composition onto the release sheet or the nonwoven fabric, a conventionally known application method such as a roll coater method can be employed. Moreover, as an example of ultraviolet polymerization conditions, the conditions which irradiate the ultraviolet-ray with a wavelength of 250-350 nm with an energy density of 100-2000 mJ / cm < ² > normally at 15-25 degreeC are mentioned. In addition, since the liquid-absorbent resin layer 1 in the present invention itself exhibits tackiness, it is directly attached to the battery pack in the form of FIG. 1A or FIG. 1B without providing an adhesive layer. In addition, the liquid-absorbing resin layer can be attached to the support with a hand roller at room temperature without using the thermal laminating method. In addition, the planar shape of the liquid-absorbent sheet is a donut shape so that it can be attached around the positive electrode terminal in view of the fact that most of the liquid leakage of the cylindrical battery is from the positive electrode. It is preferable.

  The liquid-absorbent sheet of the present invention absorbs the electrolytic solution when a leakage of the electrolytic solution occurs from the non-aqueous electrolytic battery cell, the wiring circuit board, and the non-aqueous electrolytic battery cell in the battery case. Therefore, it can be preferably used as the electrolyte solution absorbing member in the nonaqueous electrolyte battery pack in which the electrolyte solution absorbing member is installed. For example, as shown in FIG. 2, in a battery pack in which nonaqueous electrolyte battery cells 23 are arranged on a printed circuit board 22 installed in a battery case 21, electrolyte leakage from the nonaqueous electrolyte battery cells 23. 1 (a) and 1 (b) between the printed circuit board 22 and the non-aqueous electrolyte battery cell 23 as an electrolyte solution absorbing member for absorbing the electrolyte solution in the case of occurrence of Such a liquid-absorbent sheet 26 may be disposed. Here, the nonaqueous electrolyte battery cell 23 and the printed circuit board 22 are connected by a metal lead 24 and further communicated with the external terminal 25. Further, as shown in FIG. 3, the liquid absorbent sheet 27 as described in FIG. 1C is placed on the nonaqueous electrolyte battery cell 23 so that the support is on the nonaqueous electrolyte battery cell 23 side. You may arrange in.

  2 and 3, the shape of the battery case in the nonaqueous electrolyte battery pack is a rectangular parallelepiped and the shape of the battery cell is cylindrical. However, in the nonaqueous electrolyte battery pack of the present invention, It is not limited but it can be set as the shape and arrangement according to the purpose of use. Further, the type of battery cell is not limited.

  The non-aqueous electrolyte battery pack of the present invention described above is a non-aqueous electrolyte formed from a composition comprising a monofunctional monomer, a polyfunctional monomer, and a liquid phosphate ester flame retardant as a non-aqueous electrolyte absorbing member material. Since a liquid-absorbent sheet with a liquid-absorbent resin layer with excellent electrolyte absorption and retention is used, even when non-aqueous electrolyte leaks from battery cells, wiring circuit corrosion or short-circuiting occurs. Can be greatly suppressed. Moreover, since the liquid absorbent resin layer itself exhibits adhesiveness, it can be easily attached to the battery pack. Furthermore, even after the liquid absorbent resin layer has been subjected to wet heat aging treatment, good insulating properties can be maintained, so that the storage properties of the liquid absorbent sheet can be improved.

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

Example 1 (Experiments a to e), Comparative Example 1 (Experiments f to h) and Comparative Example 2
Monofunctional monomers listed in Tables 1 and 2, urethane acrylate (AH600, Kyoeisha) as a polyfunctional monomer, and 2-hydroxy-2-methyl-1-phenylpropan-1-one (D1173) as a polymerization initiator , Ciba Specialty Chemicals) and a liquid phosphate ester flame retardant or a solid ammonium polyphosphate flame retardant in the blending amounts shown in Table 1 or Table 2, and then on a polyethylene terephthalate film by a roll coater method. Apply, polymerize by irradiating ultraviolet light with a wavelength of 365 nm at an energy density of 2000 mJ / cm ² , laminate a flame retardant nonwoven fabric (Nippon Vilene) at room temperature on the polymerized film, and pull it away from the polyethylene terephthalate film As a result, a two-layer liquid-absorbent sheet was obtained.

  The obtained liquid-absorbent sheet was tested as described below for flame retardancy, adhesiveness, swelling ratio of the electrolyte, and insulation.

(Flame retardance)
The obtained liquid-absorbent sheet was tested and evaluated for flame retardancy in accordance with UL-94 standards. The obtained results are shown in Tables 1 and 2. If it is V-0, V-1, or V-2 grade, it will show the flame retardance which is satisfactory practically.

(Adhesive)
A 5 cm wide polypropylene non-woven fabric (Nippon Vilene Co., Ltd.) is attached to the exposed liquid-absorbent resin layer of the liquid absorbent sheet by the hand roller method (23 ° C.), and a tensile tester (Tensilon, Orientec Co., Ltd.) Was used to measure the adhesive strength in the T peel mode. The obtained results are shown in Tables 1 and 2.

(Swelling ratio)
An electrolyte solution prepared by dissolving lithium hexafluorophosphate as an electrolyte in an equal volume mixed solvent of dimethyl carbonate / propylene carbonate / ethylene carbonate so as to be 1 mol / l as an electrolyte was prepared. 3 hours later, the electrolyte was pulled up from the electrolyte, and the electrolyte on the surface was immediately wiped off. The weight was measured and the swelling ratio was calculated. The obtained results are shown in Tables 1 and 2.

(Insulation)
The insulation resistance value (Ω) of the liquid absorbent resin layer of the obtained liquid absorbent sheet before and after wet heat treatment was measured. The obtained results are shown in Tables 1 and 2.

  From the results in Table 1, it can be seen that the liquid-absorbent sheets of Experiments a to d of Example 1 exhibit good flame retardancy and adhesiveness, have a swelling ratio of 6 times or more, and are excellent in insulating properties. . In addition, in the case of the liquid absorption sheet of experiment e, in terms of a flame retardance, adhesiveness, and swelling magnification, there is no inferiority with the liquid absorption sheet of experiment a-d, and adhesiveness is rather excellent. However, it can be said that the level of insulation is slightly low. However, the change before and after the wet heat treatment is small, and the storage stability is excellent.

  In addition, from the result of Table 2, in the case of the liquid-absorbent sheet of Experiments f to h of Comparative Example 1, not only the case where bisphenol A bis (diphenyl) phosphate is not added as a liquid phosphate ester flame retardant, the addition thereof It can be seen that even if the amount is too small or too large, the expected flame retardancy tends not to be obtained. Moreover, in the case of the comparative example 2 which uses a solid ammonium polyphosphate type flame retardant, it turns out that there is no stickiness in the first place, and insulation property has fallen greatly after wet heat processing.

Example 2 (Electrolytic solution absorption test with a simulated battery pack)
As shown in FIG. 4, an ABS resin box 41 having a length of 7.0 cm, a width of 7.9 cm, and a height of 2.3 cm is prepared, and the bottom of the box is 6.5 cm long × 6.5 cm wide × 100 μm thick. The liquid-absorbent sheet 42 of Example 1 was affixed with a commercially available adhesive, three lithium ion batteries 43 were loaded thereon, and a glass epoxy substrate 44 was installed as a circuit board in a portion adjacent to the battery.

  Then, a test was conducted in which one hole h was opened with an electric drill in the side portion of the middle battery of the three batteries 43, and the liquid electrolyte leaked from the hole h was absorbed by the liquid absorbent sheet. When the hole h was opened and the battery pack was left to stand for a whole day and night, the glass epoxy substrate 44 was not wet. Moreover, since the weight reduction amount of the battery in which the hole h was opened was 2.5 g and the weight increase amount of the liquid absorbent sheet was 2.5 g, all of the leaked electrolyte solution was liquid absorbent sheet. It was found that it was absorbed.

  The liquid-absorbent sheet of the present invention is excellent in absorbing the non-aqueous electrolyte of the non-aqueous electrolyte secondary battery constituting the non-aqueous electrolyte battery pack (particularly, the lithium ion non-aqueous electrolyte secondary battery pack). It exhibits liquidity and tackiness, as well as excellent flame retardancy. Therefore, the liquid-absorbent sheet of the present invention is useful as an electrolyte absorbing member for a non-aqueous electrolyte battery pack.

It is sectional drawing of the liquid absorbing sheet of this invention. It is a perspective view of the nonaqueous electrolyte battery pack of the present invention. It is a perspective view of the nonaqueous electrolyte battery pack of the present invention. It is explanatory drawing of the electrolyte solution absorption test in a simulation battery pack.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid absorbing resin layer 2 ... Support body 3 ... Adhesive layer 21 ... Battery case 22 ... Wiring circuit board 23 ... Nonaqueous electrolyte battery cell 24 ... Metal lead 25 ... External terminal 26, 27 ... Liquid absorbing sheet

Claims (7)

A liquid absorbing sheet made of a liquid absorbing resin layer, at least one absorbent resin layer is a polyfunctional monomer and a liquid phosphate ester flame retardant having a acrylate monofunctional monomer, two or more acrylate residues DOO all SANYO the ultraviolet and by polymerizing radiation to the monomer composition containing, the liquid phosphoric ester-based flame retardant, bisphenol a bis (diphenyl) phosphate, hydroquinol bis (diphenyl) phosphate, phenyl magnetic Sile nil phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, carboxymethyl Les sulfonyl diphenyl phosphate, resorcinol bis (diphenyl) phosphate, or 2-ethylhexyl diphenyl phosphate der Rukoto Liquid-absorbent sheet characterized by The monomer composition, a liquid phosphate ester flame retardant, according to claim 1 Symbol placement relative to total 100 parts by weight of a monofunctional monomer and a polyfunctional monomer in a proportion of 70 to 200 parts by weight liquid absorbing sheet . Monofunctional monomer is benzyl acrylate, Lee bromide acrylate, acryloyl morpholine, phenoxyethyl acrylate, N, N-diethyl acrylamide, methoxy polyethylene glycol acrylate, according to claim 1 or 2, wherein the tetrahydrofurfuryl acrylate or phenoxy polyethylene glycol acrylate Liquid absorbent sheet. Multifunctional monomers, hydroxypivalic acid neopentyl glycol diacrylate, polyethylene glycol diacrylate (ethylene oxide addition mole number (n) = 14), one of the claims 1-3 is bisphenol A diacrylate or phenyl glycidyl ether acrylate The liquid-absorbent sheet according to crab. The liquid-absorbent sheet according to any one of claims 1 to 4 , wherein the liquid-absorbent resin layer is formed on a support. The liquid-absorbent sheet according to claim 5 , wherein the support is capable of absorbing and holding a non-aqueous electrolyte. Installed in the battery case are a non-aqueous electrolyte battery cell, a wiring circuit board, and an electrolyte absorbing member for absorbing the electrolyte when the electrolyte leaks from the non-aqueous electrolyte battery cell. A nonaqueous electrolyte battery pack, wherein the electrolyte absorbing member is formed from the liquid absorbent sheet according to any one of claims 1 to 6. pack.

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