JP2016011859A - Deformation detection sensor for sealed secondary battery, sealed secondary battery, and deformation detection method for sealed secondary battery - Google Patents

Abstract

Disclosed is a sealed secondary battery deformation detection sensor, sealed secondary battery, and sealed type that can detect deformation of the sealed secondary battery due to swelling of the single cell with high sensitivity and have excellent sensor characteristic stability. A method for detecting deformation of a secondary battery is provided. A deformation detection sensor for a sealed secondary battery includes a polymer matrix layer 3 attached to a unit cell 2 that is an object to be detected, and a detection unit 4, and the polymer matrix layer 3 has a high height. It is a foam containing dispersed fillers that change the external field according to the deformation of the molecular matrix layer 3, and the detection unit 4 detects the change of the external field. [Selection] Figure 2

Description

  The present invention relates to a sensor for detecting deformation of a sealed secondary battery, a sealed secondary battery to which the sensor is attached, and a method for detecting deformation of the sealed secondary battery.

  In recent years, sealed secondary batteries represented by lithium ion secondary batteries (hereinafter sometimes referred to simply as “secondary batteries”) are not only mobile devices such as mobile phones and laptop computers, but also electric vehicles and hybrids. It is also used as a power source for electric vehicles such as cars. A single battery (cell) that constitutes a secondary battery includes an electrode group in which a positive electrode and a negative electrode are wound or stacked with a separator interposed therebetween, and an outer package that houses the electrode group. In general, a laminate film or a metal can is used as an exterior body, and an electrode group is accommodated together with an electrolytic solution in an enclosed space.

  The secondary battery is used in the form of a battery module or a battery pack including a plurality of single cells in an application where a high voltage is required, such as the power source for an electric vehicle described above. In the battery module, a plurality of single cells connected in series are accommodated in a housing, and, for example, four single cells are connected in two parallel two series or four series. In addition, in the battery pack, various devices such as a controller are accommodated in the casing in addition to the plurality of battery modules connected in series. In a secondary battery used as a power source for an electric vehicle, a battery pack housing is formed in a shape suitable for in-vehicle use.

  By the way, when the electrolytic solution is decomposed due to overcharge or the like, such a secondary battery has a problem that the single battery swells as the internal pressure increases due to the decomposition gas, and the secondary battery is deformed. In that case, if the charging current or discharging current is not stopped, it will ignite and the secondary battery will burst as the worst result. Therefore, in order to prevent the secondary battery from bursting, it is important to detect the deformation of the secondary battery due to the swelling of the single cell with high sensitivity so that the charging current and the discharging current can be stopped in a timely manner. In particular, when used for a long period of time, the sensor characteristics may vary due to positional deviation caused by vibrations. Therefore, it is important that the sensor characteristics have excellent stability in practical use.

  Patent Document 1 describes a method of forming a sensor insertion space in a battery module in order to attach a temperature sensor for detecting the temperature of the single battery in a battery module having a plurality of single batteries. Further, in Patent Document 2, a strain gauge is bonded to the surface of a cell case (an example of an exterior body), and a change in resistance value of the strain gauge according to the swelling of the case is detected, so that A method for reducing the charging or discharging current is described.

JP 2013-171697 A JP 2006-128062 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sealed secondary that can detect deformation of the sealed secondary battery due to the swelling of the single cell with high sensitivity and is excellent in stability of sensor characteristics. A battery deformation detection sensor, a sealed secondary battery, and a deformation detection method for a sealed secondary battery.

  The above object can be achieved by the present invention as described below. That is, the deformation detection sensor for a sealed secondary battery according to the present invention is a deformation detection sensor for a sealed secondary battery, comprising a polymer matrix layer attached to an object to be detected, and a detection unit, wherein the polymer The matrix layer is a foam containing dispersed fillers that change the external field according to deformation of the polymer matrix layer, and the detection unit detects the change of the external field.

  When the secondary battery is deformed by the swelling of the unit cell, the polymer matrix layer is deformed accordingly, and the detection unit detects a change in the external field due to the deformation of the polymer matrix layer. The polymer matrix layer that is a foam can be flexibly deformed, and the deformation of the secondary battery can be detected with high sensitivity. In addition, the polymer matrix layer, which is a foam, is easy to compress, is not subject to excessive load during compression, can be placed in a narrow gap in the secondary battery, and has excellent sensor property stability.

  In the deformation detection sensor for a sealed secondary battery according to the present invention, the polymer matrix layer contains a magnetic filler as the filler, and the detection unit detects a change in the magnetic field as the external field. preferable. According to this configuration, it is possible to detect a change in the magnetic field accompanying the deformation of the polymer matrix layer without wiring. In addition, since a Hall element having a wide sensitivity region can be used as the detection unit, highly sensitive detection can be performed over a wider range.

  What the bubble content rate of the said foam is 20-80 volume% is preferable. When the bubble content is 20% by volume or more, the polymer matrix layer is flexible and easily deformed, and sensor sensitivity can be improved satisfactorily. Further, when the bubble content is 80% by volume or less, embrittlement of the polymer matrix layer is suppressed, and handling properties and stability are improved.

  It is preferable that the foam has an average cell diameter of 50 to 300 μm. If the average cell diameter is less than 50 μm, the stability of sensor characteristics tends to deteriorate due to an increase in the amount of foam stabilizer. On the other hand, if the average bubble diameter exceeds 300 μm, the contact area with the unit cell or the like, which is the object to be detected, tends to decrease and the stability tends to decrease.

  The polymer matrix layer preferably has an average cell diameter difference of 20 μm or more in the thickness direction. When the average bubble diameter difference is less than 20 μm, the bubbles are more uniformly compressed when the polymer matrix layer is deformed, and thus the sensor sensitivity tends to be lowered.

  It is preferable that the average cell diameter on one side of the polymer matrix layer attached to the object to be detected is smaller than the average cell size on the other side. Since one side with a small average bubble diameter contains a relatively large amount of filler and one side is directed to the object to be detected, the change in the external field against a small deformation of the polymer matrix layer is increased, and the sensor Sensitivity can be improved.

  What the closed cell rate of the said foam is 5-70% is preferable. Thereby, it is possible to exhibit excellent stability while ensuring ease of compression of the polymer matrix layer.

  The sealed secondary battery according to the present invention has the above-described deformation detection sensor attached thereto, and the form thereof may be any of a single battery, a battery module, and a battery pack. In such a sealed secondary battery, deformation due to swelling of the single battery is detected with high sensitivity by a deformation detection sensor. In addition, the polymer matrix layer, which is a foam, is easy to compress, and an excessive load is not easily applied during compression, and it can be placed in a narrow gap in the secondary battery, so that it has excellent stability of sensor characteristics.

  The deformation detection method for a sealed secondary battery according to the present invention is a deformation detection method for a sealed secondary battery, in which a polymer matrix layer is attached to an object to be detected, and the polymer matrix layer includes the polymer matrix layer. A foam containing a filler that changes the external field according to the deformation of the foam, and detecting the change of the external field accompanying the deformation of the polymer matrix layer, and based on the detection, the sealed secondary battery Is detected.

  When the secondary battery is deformed due to the swelling of the unit cell, the polymer matrix layer is deformed accordingly, and a change in the external field accompanying the deformation of the polymer matrix layer is detected. Since the polymer matrix layer, which is a foam, can be deformed flexibly, deformation of the secondary battery can be detected with high sensitivity. In addition, the polymer matrix layer, which is a foam, is easy to compress, is not subject to excessive load during compression, can be placed in a narrow gap in the secondary battery, and has excellent sensor property stability.

  It is preferable that the average bubble diameter on one side in the thickness direction of the polymer matrix layer is smaller than the average bubble diameter on the other side, and that one side is attached to the object to be detected. According to such a method, since one side containing a relatively large amount of filler is attached toward the object to be detected, the change in the external field with respect to a small deformation of the polymer matrix layer is increased, and the sensor sensitivity is improved. it can.

A perspective view schematically showing an example of a battery module Sectional drawing which shows typically the AA arrow cross section of FIG. The figure which shows an example of the cross section of a polymer matrix layer typically Sectional view schematically showing the structure used in the vibration test

  Hereinafter, embodiments of the present invention will be described.

  The battery module 1 shown in FIGS. 1 and 2 has a plurality of single cells 2 inside a casing 11. In the present embodiment, four unit cells 2 are connected in series (for example, 2 parallel 2 series or 4 series). Although not shown in detail, the unit cell 2 includes an electrode group in which a positive electrode and a negative electrode are wound or laminated with a separator interposed therebetween, and an exterior body that houses the electrode group. In the sealed space inside the exterior body, the electrode group is accommodated together with the electrolytic solution. A laminate film such as an aluminum laminate foil is used for the outer package of the unit cell 2, but a cylindrical or square metal can may be used instead.

  The battery module 1 is a lithium ion secondary battery that can be used as a power source for an electric vehicle, and is mounted on the vehicle in the form of a battery pack. In the battery pack, a plurality of battery modules 1 connected in series are accommodated in a casing together with various devices such as a controller. The casing of the battery pack is formed in a shape suitable for in-vehicle use, for example, a shape that matches the underfloor shape of the vehicle. In the present invention, the sealed secondary battery is not limited to a non-aqueous electrolyte secondary battery such as a lithium ion battery, and may be an aqueous electrolyte secondary battery such as a nickel metal hydride battery or a lead storage battery.

  As shown in FIG. 2, a deformation detection sensor is attached to the sealed secondary battery. The deformation detection sensor includes a polymer matrix layer 3 attached to an object to be detected and a detection unit 4. In the present embodiment, the unit cell 2 is an object to be detected, and the polymer matrix layer 3 is attached to the unit cell 2. The polymer matrix layer 3 is formed in a sheet shape, and an adhesive or an adhesive tape is used for the application as necessary.

  The polymer matrix layer 3 is a foam containing dispersed fillers that change the external field according to deformation of the polymer matrix layer 3. The detection unit 4 detects a change in the external field. The detection unit 4 is disposed at a location where a change in the external field can be detected, and is preferably attached to a relatively firm location that is not easily affected by the swelling of the unit cell 2. In the present embodiment, the detection unit 4 is affixed to the outer surface of the casing 11, but the present invention is not limited thereto, and the detection unit 4 may be affixed to the inner surface of the casing 11 or the casing of the battery pack. These cases are formed of, for example, metal or plastic, and a laminate film may be used for the case of the battery module.

  When the unit cell 2 swells, the polymer matrix layer 3 is deformed accordingly, and a change in the external field accompanying the deformation of the polymer matrix layer 3 is detected by the detection unit 4. The detection signal output from the detection unit 4 is sent to a control device (not shown), and when a change in the external field exceeding a set value is detected by the detection unit 4, the switching (not shown) connected to the control device. The circuit cuts off power and stops charging or discharging current. In this way, the deformation of the secondary battery due to the swelling of the unit cell 2 is detected with high sensitivity, and the secondary battery is prevented from bursting.

  The polymer matrix layer 3 which is a foam can be flexibly deformed according to the swelling of the unit cell 2, and the deformation of the secondary battery is detected with high sensitivity. In addition, the polymer matrix layer 3 that is a foam is easily compressed, and an excessive load is not easily applied during compression, and the polymer matrix layer 3 can be disposed in a narrow gap in the secondary battery, and is excellent in stability of sensor characteristics. The polymer matrix layer 3 of the present embodiment is disposed between the unit cell 2 and the casing 11 that accommodates it (gap G2), but may be disposed between the unit cells 2 adjacent to each other. . The polymer matrix layer 3 can be bent and attached to the corners of the unit cell 2 or the casing 11. The polymer matrix layer 3 is not necessarily attached in a compressed state, and may be attached in an uncompressed state.

  In the example of FIG. 2, one polymer matrix layer 3 and one detection unit 4 are shown, but a plurality of them may be used according to various conditions such as the shape and size of the secondary battery. Furthermore, a plurality of polymer matrix layers 3 are attached to the same object to be detected (in this embodiment, a single cell 2), or a plurality of detectors 4 detect changes in the external field due to deformation of the same polymer matrix layer 3. It may be configured to do so.

  In this embodiment, the polymer matrix layer 3 contains a magnetic filler as the filler, and the detection unit 4 detects a change in the magnetic field as the external field. In this case, the polymer matrix layer 3 is preferably a magnetic elastomer layer in which a magnetic filler is dispersed in a matrix made of an elastomer component.

  Examples of the magnetic filler include rare earth-based, iron-based, cobalt-based, nickel-based, and oxide-based materials, but a rare earth-based material that can obtain higher magnetic force is preferable. The shape of the magnetic filler is not particularly limited, and may be spherical, flat, needle-like, columnar, or indefinite. The average particle size of the magnetic filler is preferably 0.02 to 500 μm, more preferably 0.1 to 400 μm, and still more preferably 0.5 to 300 μm. When the average particle size is smaller than 0.02 μm, the magnetic properties of the magnetic filler tend to be lowered, and when the average particle size exceeds 500 μm, the mechanical properties of the magnetic elastomer layer tend to be lowered and become brittle.

  The magnetic filler may be introduced into the elastomer after magnetization, but is preferably magnetized after being introduced into the elastomer. Magnetization after introduction into the elastomer facilitates control of the polarity of the magnet and facilitates detection of the magnetic field.

  As the elastomer component, a thermoplastic elastomer, a thermosetting elastomer, or a mixture thereof can be used. Examples of the thermoplastic elastomer include styrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, polybutadiene-based thermoplastic elastomer, polyisoprene-based thermoplastic elastomer, A fluororubber-based thermoplastic elastomer can be used. Examples of the thermosetting elastomer include polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, polychloroprene rubber, nitrile rubber, ethylene-propylene rubber and other diene synthetic rubbers, ethylene-propylene rubber, butyl rubber, acrylic rubber, Non-diene synthetic rubbers such as polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, and natural rubber can be mentioned. Among these, a thermosetting elastomer is preferable because it can suppress the sag of the magnetic elastomer accompanying heat generation and overload of the battery. More preferred is polyurethane rubber (also referred to as polyurethane elastomer) or silicone rubber (also referred to as silicone elastomer).

  The polyurethane elastomer is obtained by reacting a polyol and a polyisocyanate. When using a polyurethane elastomer as an elastomer component, an active hydrogen-containing compound and a magnetic filler are mixed, and an isocyanate component is mixed here to obtain a mixed solution. Moreover, a liquid mixture can also be obtained by mixing a magnetic filler with an isocyanate component and mixing an active hydrogen-containing compound. The mixed liquid is poured into a mold subjected to a release treatment, and then heated to a curing temperature and cured to produce a magnetic elastomer. When a silicone elastomer is used as an elastomer component, a magnetic elastomer can be produced by adding a magnetic filler to a silicone elastomer precursor, mixing it, putting it in a mold, and then heating and curing it. In addition, you may add a solvent as needed.

  As the isocyanate component that can be used in the polyurethane elastomer, compounds known in the field of polyurethane can be used. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene Aromatic diisocyanates such as diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, nor It can be mentioned alicyclic diisocyanates such as Renan diisocyanate. These may be used alone or in combination of two or more. The isocyanate component may be modified such as urethane modification, allophanate modification, biuret modification, and isocyanurate modification. Preferred isocyanate components are 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, more preferably 2,4-toluene diisocyanate, 2,6-toluene diisocyanate.

  As the active hydrogen-containing compound, those usually used in the technical field of polyurethane can be used. For example, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polyether polyols typified by copolymers of propylene oxide and ethylene oxide, polybutylene adipates, polyethylene adipates, and 3-methyl-1,5-pentane adipates Polyester polyol such as polyester polyol, polycaprolactone polyol, reaction product of polyester glycol and alkylene carbonate such as polycaprolactone, and the like, and the reaction of the resulting reaction mixture with organic polyol. Polyester polycarbonate polyol reacted with dicarboxylic acid, esterification of polyhydroxyl compound and aryl carbonate High molecular weight polyol polycarbonate polyols obtained by the reaction can be mentioned. These may be used alone or in combination of two or more.

  In addition to the high molecular weight polyol component described above as the active hydrogen-containing compound, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6- Hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, and triethanolamine Low molecular weight polyol component equal, ethylenediamine, tolylenediamine, diphenylmethane diamine, may be used low molecular weight polyamine component of diethylenetriamine. These may be used alone or in combination of two or more. Furthermore, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5-bis ( Methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6- Diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4'-diamino-3,3 ' -Diethyl-5,5'-dimethyldiphenylmethane, N, N'-di-sec-butyl-4,4'-diaminodiphenylmethane, 4,4'-diamy −3,3′-diethyldiphenylmethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, 4,4′-diamino-3,3′-diisopropyl-5,5′- Dimethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4,4′-diamino-3,3 ′, 5,5′-tetraisopropyldiphenylmethane, m-xylylenediamine, Polyamines exemplified by N, N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine, p-xylylenediamine and the like can also be mixed. Preferred active hydrogen-containing compounds are polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, a polyester polyol composed of 3-methyl-1,5-pentanediol and adipic acid, more preferably polypropylene glycol, propylene It is a copolymer of oxide and ethylene oxide.

  Preferred combinations of the isocyanate component and the active hydrogen-containing compound include, as the isocyanate component, one or more of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and 4,4′-diphenylmethane diisocyanate, and active hydrogen. The containing compound is polytetramethylene glycol, polypropylene glycol, a copolymer of propylene oxide and ethylene oxide, and a combination of one or more of 3-methyl-1,5-pentaneadipate. More preferably, it is a combination of 2,4-toluene diisocyanate and / or 2,6-toluene diisocyanate as the isocyanate component and polypropylene glycol and / or a copolymer of propylene oxide and ethylene oxide as the active hydrogen-containing compound. is there.

  The amount of the magnetic filler in the magnetic elastomer is preferably 1 to 450 parts by weight, more preferably 2 to 400 parts by weight with respect to 100 parts by weight of the elastomer component. If it is less than 1 part by weight, it tends to be difficult to detect a change in the magnetic field, and if it exceeds 450 parts by weight, the magnetic elastomer itself may become brittle.

  For example, a magnetoresistive element, a Hall element, an inductor, an MI element, a fluxgate sensor, or the like can be used as the detection unit 4 that detects a change in the magnetic field. Examples of the magnetoresistive element include a semiconductor compound magnetoresistive element, an anisotropic magnetoresistive element (AMR), a giant magnetoresistive element (GMR), and a tunnel magnetoresistive element (TMR). Among these, a Hall element is preferable because it has high sensitivity over a wide range and is useful as the detection unit 4.

  The thickness of the polymer matrix layer 3 in an uncompressed state is preferably 300 to 3000 μm, more preferably 400 to 2000 μm, and still more preferably 500 to 1500 μm. When the thickness is smaller than 300 μm, the handling property tends to be deteriorated due to brittleness when a required amount of filler is added. On the other hand, if the thickness is larger than 3000 μm, the polymer matrix layer 3 disposed in the gap in the secondary battery is excessively compressed and hardly deformed, and the sensor sensitivity may be lowered.

  For the purpose of preventing rust of the magnetic filler, a sealing material for sealing the polymer matrix layer 3 may be provided to the extent that the flexibility of the polymer matrix layer 3 is not impaired. As the sealing material, a thermoplastic resin, a thermosetting resin, or a mixture thereof can be used. Examples of the thermoplastic resin include styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polybutadiene-based thermoplastic elastomers, polyisoprene-based thermoplastic elastomers, Fluorine-based thermoplastic elastomer, ethylene / ethyl acrylate copolymer, ethylene / vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, chlorinated polyethylene, fluororesin, polyamide, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polybutadiene Etc. Examples of the thermosetting resin include polyisoprene rubber, polybutadiene rubber, styrene / butadiene rubber, polychloroprene rubber, diene-based synthetic rubber such as acrylonitrile / butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, butyl rubber, Non-diene rubbers such as acrylic rubber, polyurethane rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, natural rubber, polyurethane resin, silicone resin, epoxy resin and the like can be mentioned.

  As described above, the polymer matrix layer 3 is a foam containing dispersed fillers and bubbles. A general resin foam can be used as the foam, but it is preferable to use a thermosetting resin foam in consideration of characteristics such as compression set. Examples of the thermosetting resin foam include a polyurethane resin foam and a silicone resin foam. Among these, a polyurethane resin foam is preferable. The above-mentioned isocyanate component and active hydrogen-containing compound can be used for the polyurethane resin foam.

  As the catalyst used for the polyurethane resin foam, a known catalyst can be used without limitation, but triethylenediamine (1,4-diazabicyclo [2,2,2] octane), N, N, N ′, N ′. -Tertiary amine catalysts such as tetramethylhexanediamine and bis (2-dimethylaminoethyl) ether, and metal catalysts such as tin octylate, lead octylate, zinc octylate, and bismuth octylate can be used. These may be used alone or in combination of two or more.

  As commercial products of the above-mentioned catalyst, “TEDA-L33” manufactured by Tosoh Corporation, “NIAX CATALYST A1” manufactured by Momentive Performance Materials, “Caorizer NO.1”, “Kaorizer NO.30P” manufactured by Kao Corporation. "DABCO T-9" manufactured by Air Products, "BTT-24" manufactured by Toei Chemical Co., "Pucat 25" manufactured by Nippon Chemical Industry Co., Ltd., and the like.

  As a foam stabilizer used for a polyurethane resin foam, what is used for manufacture of a normal polyurethane resin foam, such as a silicone type foam stabilizer and a fluorine type foam stabilizer, can be used, for example. The silicone-based surfactant and fluorine-based surfactant used as the silicone-based foam stabilizer and the fluorine-based foam stabilizer have a polyurethane-soluble part and an insoluble part in the molecule. The insoluble part uniformly disperses the polyurethane material and lowers the surface tension of the polyurethane system, so that bubbles are easily generated and are hard to break. Of course, if the surface tension is too low, bubbles are not easily generated. Become. In the resin foam of the present invention, for example, when the silicone surfactant is used, the dimethylpolysiloxane structure as the insoluble part can reduce the cell diameter or increase the number of cells. It becomes.

  Examples of commercially available silicone foam stabilizers include “SF-2962”, “SRX 274DL”, “SF-2965”, “SF-2904”, “SF-2908” manufactured by Toray Dow Corning, Examples thereof include “SF-2904”, “L5340”, “Tegostarb B-8017”, “B-8465”, “B-8443” manufactured by Evonik Degussa. Moreover, as a commercial item of the said fluorine-type foam stabilizer, "FC430", "FC4430" by 3M company, "FC142D", "F552", "F554", "F558" by Dainippon Ink & Chemicals, Inc., for example. ”,“ F561 ”,“ R41 ”, and the like.

  The blending amount of the foam stabilizer is preferably 1 to 15 parts by mass, more preferably 2 to 12 parts by mass with respect to 100 parts by mass of the resin component. If the blending amount of the foam stabilizer is less than 1 part by mass, foaming is not sufficient, and if it exceeds 10 parts by mass, bleeding may occur.

  The foam content of the foam forming the polymer matrix layer 3 is preferably 20 to 80% by volume. When the bubble content is 20% by volume or more, the polymer matrix layer 3 is flexible and easily deformed, and the sensor sensitivity can be improved satisfactorily. Further, when the bubble content is 80% by volume or less, embrittlement of the polymer matrix layer 3 is suppressed, and handling properties and stability are improved. The bubble content is calculated based on the specific gravity measured in accordance with JIS Z-8807-1976, and the specific gravity value of the non-foamed material.

  The average cell diameter of the foam forming the polymer matrix layer 3 is preferably 50 to 300 μm. The average opening diameter of the foam is preferably 15 to 100 μm. When the average bubble diameter is less than 50 μm or the average opening diameter is less than 15 μm, the stability of the sensor characteristics tends to deteriorate due to an increase in the amount of the foam stabilizer. In addition, when the average bubble diameter exceeds 300 μm or the average opening diameter exceeds 100 μm, the contact area with a single cell or the like, which is the object to be detected, tends to decrease and stability tends to decrease. The average bubble diameter and the average opening diameter were determined by observing the cross section of the polymer matrix layer with a SEM at a magnification of 100 times, and using the image analysis software for the obtained image, all the bubbles present in the arbitrary range of the cross section. The bubble diameter and the opening diameter of all open bubbles are measured and calculated from the average value.

  In the example of FIG. 3, the polymer matrix layer 3 has an average cell diameter difference in the thickness direction. That is, in the polymer matrix layer 3, bubbles 30 having different sizes are unevenly distributed on one side (lower side in FIG. 3) and the other side (upper side in FIG. 3) in the thickness direction. The average bubble diameter difference is obtained as a value obtained by subtracting three straight lines L1 to L3 that divide the polymer matrix layer 4 into four in the thickness direction and subtracting the minimum value from the maximum value of the average bubble diameters related to the straight lines L1 to L3. It is done. The average bubble diameter related to the straight line is calculated as an average value of the lengths of line segments passing through the bubbles 30 on the respective straight lines. Usually, the average bubble diameter difference is the difference between the average bubble diameter related to the straight line L3 on one side and the average bubble diameter related to the straight line L1 on the other side.

  The difference in average bubble diameter is preferably 20 μm or more. If this is less than 20 μm, the bubbles 30 are more uniformly compressed when the polymer matrix layer 3 is deformed, so that the sensor sensitivity tends to decrease. Moreover, the average bubble diameter difference is preferably 150 μm or less. If this exceeds 150 μm, the degree of compression of the bubbles 30 becomes too uneven, and the stability of the sensor characteristics may be deteriorated.

  The polymer matrix layer 3 shown in FIG. 3 is preferably attached to the unit cell 2 on one side, and the average cell diameter on the one side is smaller than the average cell size on the other side. As a result, one side containing a relatively large amount of magnetic filler is directed to the unit cell 2, and the change in the magnetic field with respect to a small deformation of the polymer matrix layer 3 can be increased to improve the sensor sensitivity. Specifically, it is preferable that the average bubble diameter related to the straight line L3 is smaller than the average bubble diameter related to the straight line L1. And the difference of those average bubble diameters has preferable 20 micrometers or more, and 150 micrometers or less are preferable.

  The closed cell ratio of the foam forming the polymer matrix layer 3 is preferably 5 to 70%. Thereby, excellent stability can be exhibited while ensuring ease of compression of the polymer matrix layer 3. Moreover, it is preferable that the volume fraction of the filler (this embodiment magnetic filler) with respect to the foam which forms the polymer matrix layer 3 is 1-30 volume%.

The polyurethane resin foam described above can be produced by an ordinary method for producing a polyurethane resin foam except that it contains a magnetic filler. The method for producing a polyurethane resin foam containing the magnetic filler includes, for example, the following steps (i) to (v).
(I) Step of forming isocyanate group-containing urethane prepolymer from polyisocyanate component and active hydrogen component (ii) Mixing and pre-stirring the isocyanate group-containing urethane prepolymer, foam stabilizer, catalyst and magnetic filler, and non-reacting A primary stirring step of vigorously stirring so as to take in bubbles in a natural gas atmosphere (iii) a step of further adding an active hydrogen component and secondary stirring to prepare a cell-dispersed urethane composition containing a magnetic filler (iv) A step of forming the urethane-dispersed urethane composition into a desired shape and curing to produce a urethane resin foam containing a magnetic filler. (V) A step of magnetizing the urethane resin foam to form a magnetic urethane resin foam.

  As a method for producing a polyurethane resin foam, a chemical foaming method using a reactive foaming agent such as water is known, but mechanical stirring is performed in a non-reactive gas atmosphere as in the above step (ii). It is preferable to use a foaming method. According to the mechanical foaming method, the molding operation is simpler than the chemical foaming method, and water is not used as the foaming agent. Therefore, the molded product has tough and excellent resilience (restorability) with fine bubbles. Is obtained.

  First, as in the above step (i), an isocyanate group-containing urethane prepolymer is formed from a polyisocyanate component and an active hydrogen component. Next, as in the above step (ii), the isocyanate group-containing urethane prepolymer, the foam stabilizer, the catalyst and the magnetic filler are mixed and pre-stirred, and vigorously stirred to capture bubbles in a non-reactive gas atmosphere. Then, as in the above step (iii), an active hydrogen component is further added and stirred to prepare a cell-dispersed urethane composition containing a magnetic filler. In the polyurethane resin foam containing a polyisocyanate component, an active hydrogen component and a catalyst as in the above steps (i) to (iii), a method for forming a polyurethane resin foam after forming an isocyanate group-containing urethane prepolymer in advance is as follows. It is known to those skilled in the art, and the production conditions can be appropriately selected depending on the compounding material.

  As the formation conditions of the above step (i), first, the blending ratio of the polyisocyanate component and the active hydrogen component is the ratio of the isocyanate group in the polyisocyanate component to the active hydrogen group in the active hydrogen component (isocyanate group / active hydrogen). Group) is selected to be 1.5 to 5, preferably 1.7 to 2.3. The reaction temperature is preferably 60 to 120 ° C., and the reaction time is preferably 3 to 8 hours. Furthermore, conventionally known urethanization catalysts and organic catalysts such as lead octylate commercially available from Toei Chemical Co., Ltd. under the trade name “BTT-24”, “TEDA-L33” manufactured by Tosoh Corporation, Momentive Performance Material "NIAX CATALYST A1" manufactured by KK, "Caorizer No. 1" manufactured by Kao Corporation, "DABCO T-9" manufactured by Air Products, etc. may be used. As an apparatus used in the step (i), any apparatus can be used as long as it can react by stirring and mixing the above materials under the above-described conditions, and an apparatus used for ordinary polyurethane production can be used. it can.

  Examples of the method for performing preliminary stirring in the step (ii) include a method using a general mixer capable of mixing a liquid resin and a filler, and examples thereof include a homogenizer, a dissolver, and a planetary mixer.

  In the step (ii), a foam stabilizer is added to the isocyanate group-containing urethane prepolymer having a high viscosity and stirred (primary stirring). In the step (iii), an active hydrogen component is further added and secondary stirring is performed. Therefore, it is preferable because bubbles taken into the reaction system are difficult to escape and efficient foaming can be performed.

  The non-reactive gas in the step (ii) is preferably a non-flammable gas, and specifically, nitrogen, oxygen, carbon dioxide gas, helium, argon and other rare gases, and mixed gases thereof are exemplified, and dried to moisture. It is most preferable to use air from which air has been removed. Further, the conditions for the primary stirring and the secondary stirring, particularly the primary stirring, can be used at the time of urethane foam production by a normal mechanical foaming method, and are not particularly limited. Using a mixer, the mixture is vigorously stirred for 1 to 30 minutes at a rotational speed of 1000 to 10,000 rpm. Examples of such an apparatus include a homogenizer, a dissolver, and a mechanical floss foaming machine.

  In the step (iv), the method of forming the cell-dispersed urethane composition into a desired shape such as a sheet is not particularly limited. For example, a batch type in which the mixed solution is injected into a mold subjected to a release treatment and cured. A molding method or a continuous molding method in which the cell-dispersed urethane composition is continuously supplied and cured on a release-treated face material can be used. Also, the curing conditions are not particularly limited, and preferably from 60 to 200 ° C. for 10 minutes to 24 hours. If the curing temperature is too high, the resin foam is thermally deteriorated, the mechanical strength is deteriorated, and the curing temperature is If it is too low, curing failure of the resin foam will occur. On the other hand, if the curing time is too long, the resin foam is thermally deteriorated and mechanical strength is deteriorated. If the curing time is too short, the resin foam is poorly cured. In the process of curing the bubble-dispersed urethane composition, large bubbles tend to rise faster than small bubbles, and by using this, a state in which bubbles of different sizes are unevenly distributed as shown in FIG. 3 is obtained. .

  In the step (v), the method of magnetizing the magnetic filler is not particularly limited, and a commonly used magnetizing apparatus, for example, “ES-10100-15SH” manufactured by Electromagnetic Industry Co., Ltd., “TM” manufactured by Tamagawa Manufacturing Co., Ltd. -YS4E "or the like. Usually, a magnetic field having a magnetic flux density of 1 to 3T is applied. The magnetic filler may be added in the step (ii) after forming the magnetic filler dispersion after magnetization, but in the step (v) from the viewpoint of handling workability of the magnetic filler in the intermediate step. It is preferable to magnetize.

  In the present embodiment, as described above, when the polymer matrix layer 3 which is a foam in which the filler is dispersed is attached to the unit cell 2 and the unit cell 2 expands and the polymer matrix layer 3 is deformed, A change in the external field accompanying the deformation of the polymer matrix layer 3 is detected, and the deformation of the secondary battery is detected based on the change. In addition, when the average cell diameter on one side in the thickness direction of the polymer matrix layer 3 is smaller than the average cell diameter on the other side, the one side is attached to the unit cell 2 to improve the sensor sensitivity. Can be expected.

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

  In the above-described embodiment, the example in which the unit cell 2 is the object to be detected and the polymer matrix layer 3 is attached to the unit cell 2 is shown, but the present invention is not limited to this. In particular, in a laminated film type battery module, the battery module housing is used as an object to be detected, and a polymer matrix layer is attached to the battery module housing, thereby preventing deformation of the sealed secondary battery due to swelling of the single cell. Detection is also conceivable.

  In the above-described embodiment, an example in which a change in a magnetic field is used has been described. However, a configuration in which a change in another external field such as an electric field is used may be used. For example, the polymer matrix layer may contain conductive fillers such as metal particles, carbon black, and carbon nanotubes as fillers, and the detector may detect changes in the electric field (changes in resistance and dielectric constant) as external fields. It is done.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

The following raw materials were used for the production of a magnetic polyurethane resin foam (one of the magnetic elastomers in which the elastomer component is a polyurethane elastomer) to be a polymer matrix layer.
TDI-80: Toluene diisocyanate (Mitsui Chemicals, 2,4-body = 80%, Cosmonate T-80)
Polyol A: Polyoxypropylene glycol using propylene glycol as an initiator, OH value 56, number of functional groups 2 (Asahi Glass Co., Ltd., EX-2020)
Polyol B: Polyoxypropylene glycol using glycerol as an initiator, OH value 56, functional group number 3 (EX-3030, manufactured by Asahi Glass Co., Ltd.)
Polyol C: polyoxypropylene glycol using glycerol as an initiator, OH value 84, functional group number 3 (Asahi Glass Co., Ltd., EX-2030)
Bismuth octylate: Pucat 25 (Nippon Chemical Industry Co., Ltd.)
Lead octylate: BTT-24 (manufactured by Toei Chemical Company)
Neodymium filler: MF-15P (average particle size 33 μm, manufactured by Aichi Steel Corporation)
Samarium-based filler: SmFeN alloy fine powder (average particle size 2.5 μm, manufactured by Sumitomo Metal Mining)
Foam stabilizer: silicone surfactant (manufactured by Dow Corning Toray, L-5340)

  Moreover, the prepolymer A shown in Table 1 was used for the prepolymer.

Example 1
In a reaction vessel, polyol A (polyoxypropylene glycol using propylene glycol as an initiator, OH number 56, functional group number 2, manufactured by Asahi Glass Co., Ltd., EX-2020) 42.6 parts by weight, polyol B (glycerin and initiator) 42.6 parts by weight of polyoxypropylene glycol, OH number 56, functional group number 3, manufactured by Asahi Glass Co., Ltd., EX-3030) was added, and vacuum dehydration was performed for 1 hour while stirring. Thereafter, the inside of the reaction vessel was purged with nitrogen. Next, 14.8 parts by weight of toluene diisocyanate (Mitsui Chemicals, 2,4 = 80%, Cosmonate T-80) was added to the reaction vessel, and the temperature in the reaction vessel was maintained at 80 ° C. By reacting for a period of time, isocyanate-terminated prepolymer A (NCO% = 3.58%) was synthesized.

  Next, 60.8 parts by weight of prepolymer A, 4.8 parts by weight of a silicone foam stabilizer (manufactured by Dow Corning Toray, L-5340) and bismuth octylate (manufactured by Nippon Kagaku Sangyo Co., Ltd., PACCAT 25) 0.11 4 parts by weight of NdFeB magnetic powder (manufactured by Aichi Steel Corporation, MF-15P) was added to parts by weight of the mixed solution to prepare a filler dispersion. The filler dispersion was vigorously stirred for 5 minutes using a stirring blade at a rotation speed of 1000 rpm so that bubbles were taken into the reaction system. Thereafter, 34.5 parts by weight of polyol C (polyoxypropylene glycol using glycerol as an initiator, OH number 84, functional group number 3, manufactured by Asahi Glass Co., Ltd., EX-2030) was added, and secondary stirring was performed for 3 minutes. A cell-dispersed urethane composition containing a magnetic filler was prepared.

  The cell-dispersed urethane composition was dropped onto a release-treated PET film having a 1.2 mm spacer and adjusted to a thickness of 1.2 mm with a nip roll. Then, it hardened at 80 degreeC for 1 hour, and obtained the polyurethane resin foam containing a magnetic filler. The obtained foam was magnetized at 2.0 T with a magnetizing device (manufactured by Electronic Magnetic Industry Co., Ltd.) to obtain a magnetic polyurethane resin foam. The formulation and production conditions are shown in Table 2. Here, regarding the item “Attaching the polymer matrix layer” in Table 2, “large bubble diameter” means that the side with the larger average bubble diameter (the other side in the above-described embodiment) is the Hall element (the opposite side to the unit cell). ) Means that the side having the smaller average bubble diameter (one side in the above-described embodiment) is attached to the unit cell. The opposite is true for “small bubble size”.

Examples 2 to 8 and Comparative Examples 1 and 2
Based on the formulation and production conditions in Table 2, a magnetic polyurethane resin foam was obtained in the same manner as in Example 1.

(Measurement of bubble content)
Specific gravity was measured according to JIS Z-8807-1976, and the bubble content was calculated from this value and the specific gravity value of the non-foamed material. The specific gravity measurement was made by cutting the produced magnetic polyurethane resin foam into a size of 40 mm × 75 mm as a measurement sample, and allowed to stand for 16 hours in an environment of a temperature of 23 ± 2 ° C. and a humidity of 50 ± 5%. (Sartorius, LA-230S) was used.

(Measurement of average bubble diameter and average opening diameter)
The cross section of the produced magnetic polyurethane resin foam was observed at a magnification of 100 using a scanning electron microscope (SEM) (manufactured by Hitachi Science Systems, S-3500N), and image analysis software (Mitani) Using a trading company, WinROOF, the bubble diameter (diameter) and the opening diameter (diameter) in an arbitrary range were measured, and the average bubble diameter and the average opening diameter were calculated.

(Measurement of average bubble diameter difference)
The cross section of the produced magnetic polyurethane resin foam was observed at a magnification of 70 times using a scanning electron microscope (SEM) (S-3500N, manufactured by Hitachi Science Systems Co., Ltd.). 3 straight lines are drawn (see FIG. 3), and the average length of the line segments passing through the bubbles on each straight line is calculated as the average bubble diameter for each straight line. A value obtained by subtracting the minimum value from the maximum value of the average bubble diameter was determined.

(Measurement of closed cell ratio)
The produced magnetic polyurethane resin foam was cut into a size of 20 mm × 20 mm and measured using an air comparison type hydrometer 930 type (manufactured by Beckman). The closed cell ratio was calculated by the following formula based on the counter value and sample volume value obtained by measurement.
Closed cell ratio (%) = (counter value / sample volume value) × 100

(Evaluation of sensor characteristics)
The produced magnetic polyurethane resin foam was cut into a size of 5 mm × 30 mm and attached to a 1.44 Ah unit cell (size: 90 mm long × 30 mm wide × 4 mm thick). As shown in FIG. 4, the unit cell (unit cell 2) is accommodated in an acrylic resin casing 15 having an inner space thickness T of 5.0 mm, and a 1.0 mm gap G3 provided therebetween is accommodated. A magnetic polyurethane resin foam (polymer matrix layer 3) was disposed. The casing was installed in a vibration testing machine, and a vibration test was performed by applying a sine wave having a vibration frequency of 200 Hz and an amplitude of 0.8 mm (total amplitude of 1.6 mm). The sine wave was applied for 3 hours from three directions perpendicular to each other.

  After the vibration test, the Hall element (EQ-430L, manufactured by Asahi Kasei Electronics Co., Ltd.) is attached to the upper surface of the housing, and the single battery is overcharged from the fully charged (4.3V) state to 2.88 Ah (2C). The time until the magnetic flux density reached a predetermined value (0.5 gauss / sec) was measured, and the average time (min) obtained by performing this test five times was defined as the sensor sensitivity. It shows that sensor sensitivity is so high that time until magnetic flux density reaches a predetermined value is short. Further, the difference (minute) between the longest and shortest of the measured times was used as an indicator of stability. It shows that it is excellent in stability of a sensor characteristic, so that this difference is small. The results are shown in Table 2.

  In Comparative Example 1, it is considered that the sensitivity of the sensor was low because the polymer matrix layer, which is a non-foamed material, was hard and an excessive load was applied during compression. In Comparative Example 2, although the hardness of the polymer matrix layer is lower than that in Comparative Example 1, it is considered that the sensor sensitivity was low because the compressed polymer matrix layer was entirely deformed. On the other hand, in Examples 1-8, the comparatively excellent sensor sensitivity was shown and stability was also excellent. As for sensor sensitivity, if the above measurement time exceeds 45,46 minutes, there is a risk of ignition, but in any of the examples, sensing could be performed in less time. In Examples 4 and 5, although the sensor sensitivity or stability was slightly lower, both were usable levels.

DESCRIPTION OF SYMBOLS 1 Battery module 2 Single cell 3 Polymer matrix layer 4 Detection part 11 Case 30 Air bubble

Claims (10)

In a deformation detection sensor for a sealed secondary battery,
A polymer matrix layer to be attached to an object to be detected, and a detection unit;
The polymer matrix layer is a foam containing dispersed fillers that change the external field according to deformation of the polymer matrix layer, and the detection unit detects the change of the external field. A deformation detection sensor for a sealed secondary battery. The polymer matrix layer contains a magnetic filler as the filler,
The deformation detection sensor for a sealed secondary battery according to claim 1, wherein the detection unit detects a change in a magnetic field as the external field.   The deformation detection sensor for a sealed secondary battery according to claim 1 or 2, wherein the foam has a bubble content of 20 to 80% by volume.   The deformation detection sensor for a sealed secondary battery according to any one of claims 1 to 3, wherein the foam has an average cell diameter of 50 to 300 µm.   The deformation detection sensor for a sealed secondary battery according to any one of claims 1 to 4, wherein the polymer matrix layer has an average bubble diameter difference of 20 µm or more in a thickness direction.   The sealed secondary battery according to any one of claims 1 to 5, wherein an average bubble diameter on one side of the polymer matrix layer attached to the object to be detected is smaller than an average bubble diameter on the other side. Deformation detection sensor.   The closed-cell secondary battery deformation detection sensor according to any one of claims 1 to 6, wherein the foam has a closed cell ratio of 5 to 70%.   A sealed secondary battery to which the deformation detection sensor according to any one of claims 1 to 7 is attached. In a method for detecting deformation of a sealed secondary battery,
A polymer matrix layer is attached to an object to be detected, and the polymer matrix layer is a foam containing dispersed fillers that change the external field according to deformation of the polymer matrix layer,
A method for detecting deformation of a sealed secondary battery, comprising: detecting a change in the external field accompanying deformation of the polymer matrix layer, and detecting deformation of the sealed secondary battery based on the change.   The sealed secondary battery according to claim 9, wherein an average bubble diameter on one side in the thickness direction of the polymer matrix layer is smaller than an average bubble diameter on the other side, and the one side is attached to the object to be detected. Deformation detection method.

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