JP4170192B2 - Absorption sheet for battery and battery using the absorption sheet - Google Patents

Description

  The present invention relates to the technical field of batteries, and more particularly, to a technique for preventing leakage of electrolyte solution inside the battery.

  Reference numeral 200 in FIG. 8 indicates a general secondary battery pack.

  In the secondary battery pack 200, a plurality of secondary batteries 202 are arranged inside a case 201, and each secondary battery 202 is connected in series by a lead 203 and formed on a wiring board 204. Connected to electrical circuit.

  In the secondary battery 202, an electrolyte solution containing a nonaqueous solvent as a main component and an electrolyte dissolved therein is disposed, and a positive electrode sheet and a negative electrode sheet sandwich a separation sheet between the electrolyte solution. What is wound in a roll shape is immersed, and when the output voltage drops due to discharge, the output voltage is recovered by charging.

Since the electrolyte solution may leak from the secondary battery 202, an electrolyte absorber 205 is disposed between the secondary batteries 202, and a positive electrode 207 is disposed as shown in FIG. An electrolyte absorbing sheet 206 is disposed on the surface. A small amount of liquid leakage is absorbed by the absorbent sheet 206, exceeding the absorption capacity of the absorbent sheet 206, and the overflow is absorbed by the absorbent body 205.
Japanese Patent Application No. 2003-039776

  However, in the prior art absorbent sheet 206, the electrolyte may overflow even if there is sufficient capacity to absorb the electrolyte, and if the overflowed electrolyte contacts the wiring substrate 204, an electrical failure will be caused. Is desired.

In order to solve the above-mentioned problem, the invention described in claim 1 has a substrate made of cloth and a polymer absorber disposed on the substrate, and absorbs a non-aqueous solvent having a solubility parameter value of 18 to 23. A ring-shaped absorbent sheet, wherein the polymer absorbent has a solubility parameter value in which a value obtained by subtracting the solubility parameter value of the non-aqueous solvent is −1.0 to 8.0. Ri from homopolymers formed, the non-aqueous solvent as a main component, an electrolyte in which an electrolyte is dissolved, a absorbent sheet that is used in a non-aqueous electrolyte secondary battery using the electrolytic solution.
The invention according to claim 2 is the absorbent sheet according to claim 1, wherein the absorbent sheet has a cut surface formed at a position between the outer periphery and the inner periphery of the ring.
The invention according to claim 3 is the absorbent sheet according to claim 1 or 2, wherein the cut surface is formed by cutting.
The invention according to claim 4 is the absorbent sheet according to claim 1, wherein the cut surface is formed by punching the absorbent sheet.
The invention according to claim 5 is the absorbent sheet according to any one of claims 1 to 4, wherein the absorbent sheet is formed with a ring-shaped protrusion along the inner periphery of the ring.
The invention according to claim 6 is a cylindrical container serving as a first electrode, an electrolytic solution disposed in the container, and a second electrode insulated from the first electrode, wherein the container 6. A projection protruding from one bottom surface, a vent hole formed through a wall surface of the projection, and the absorbent sheet according to any one of claims 1 to 5, which absorbs the electrolytic solution. In the battery, the absorbent sheet is formed in a ring shape and is fitted into the protrusion so that the protrusion protrudes from a hole in the center of the ring, and the absorbent sheet does not block the gas vent hole in that state. The electrolyte solution is a battery having a solubility parameter value of 18-23.
The invention according to claim 7 is the battery according to claim 6, wherein the absorbent sheet is formed with a ring-shaped protrusion along the inner periphery of the ring, the protrusion being around the protrusion. The battery is fitted in the recess.

  Since the rate of absorbing the electrolytic solution is high, the electrolytic solution is unlikely to overflow from the absorbent sheet 206.

Reference numeral 2 in FIG. 3 shows a battery (here, a secondary battery) of an example of the present invention.
In the present invention, one of the positive electrode and the negative electrode is described as a first electrode, and the other is described as a second electrode.

  The battery 2 in FIG. 1 has a cylindrical container 3 made of a first electrode. The container 3 can be comprised by the container main body 3a and the cylinder 3b currently fixed to the upper part of this container main body 3, for example.

  Inside the container 3 is a battery body 4 having a non-aqueous solvent as a main component, an electrolyte solution in which an electrolyte is dissolved, and a laminate of a positive electrode sheet, a separation sheet, and a negative electrode sheet immersed in the electrolyte solution. Has been placed.

  A support plate 8 is disposed on the battery body 4, and a second electrode 5 is disposed on the support plate 8.

  The 2nd electrode 5 and the support plate 8 have the flat plate parts 11 and 12, respectively, and the center of each flat plate part 11 and 12 is bulged in one direction, and the protrusions 13 and 14 are formed.

  The protrusions 13 and 14 are directed in opposite directions, and the outer peripheral portions of the flat plate portions 11 and 12 are fixed to the open end portion of the container 3 by the insulating gasket 9 with the flat plate portions 11 and 12 being in close contact with each other.

  The protrusion 11 of the support plate 8 is directed toward the battery body 4, the protrusion 12 of the second electrode 5 is directed outward, and the positive or negative electrode sheet inside the battery body 4 is protruded from the support plate 8 by the lead 17. 11 is connected.

  Since the support plate 8 and the flat plate portions 11 and 12 of the second electrode 5 are in close contact and are electrically connected, the protrusion 13 of the second electrode 5 is electrically connected to the positive or negative electrode sheet of the battery body 4. Connected. The other sheet inside the battery main body 4 is electrically connected to the container 3 so that a voltage appears between the container 3 as the first electrode and the second electrode 5. In general, the container 3 is a negative electrode and the second electrode 5 is a positive electrode.

  The code | symbol 51 of FIG. 3 has shown the absorption sheet of this invention.

  The absorbent sheet 51 is ring-shaped and has an electrode hole 41 penetrating in the thickness direction at the center position. Here, the absorbent sheet 51 is composed of an absorbent resin layer 100 described later. The absorbent resin layer 100 is a material that absorbs the electrolytic solution disposed inside the battery body 4.

  A plan view of the absorbent sheet 51 is shown in FIG.

  The container 3 is a bottomed cylinder, and the shape of the absorbent sheet 51 is a disk having a slightly smaller diameter than the opening of the container 3, and a circular electrode hole 41 penetrating in the thickness direction is formed at the center. Has a circular ring shape.

  And the notch 42 which penetrates the thickness direction toward the inner periphery from the outer periphery is formed.

  The absorbent sheet 51 is formed with a protrusion 40 formed of a ring-shaped protrusion along the electrode hole 41. The protrusion 40 is made of a material that absorbs the electrolytic solution.

  The protrusion 13 of the second electrode 5 is cylindrical, and the electrode hole 41 is formed to be slightly larger than the diameter of the protrusion 13, and the absorbent sheet 51 is attached to the second electrode 5 as shown in FIG. When covered, the protrusion 13 protrudes from the electrode hole 41. FIG. 4 shows this state, and the outer peripheral portion of the absorbent sheet 51 is placed on the upper end of the container 3.

  The upper end portion of the container 3 protrudes upward from the flat plate portion 11 of the second electrode 5 and is bent inward, and between the bent portion and the inward bent portion below the upper end portion. The outer peripheral portions of the flat plate portions 11 and 12 are sandwiched with an insulating gasket 9 interposed therebetween.

  Since the upper end portion of the container 3 protrudes upward from the flat plate portion 11 of the second electrode 5, a ring-shaped depression is formed around the protrusion 13.

  The protrusion 40 of the absorbent sheet 51 is formed in a size that fits into a ring-shaped depression, and as a result, the surface area and thickness of the absorbent sheet 51 increase by the amount the protrusion 40 is formed. Yes.

  A plurality of gas vent holes 15 penetrating the protrusion 13 in the thickness direction are formed on the side surface of the protrusion 13, and the thickness of the absorbent sheet 51 is formed so as not to block the gas vent hole 15.

  When gas is generated inside the battery body 4 and the safety plate 7 is bent or broken due to gas pressure, the gas vent hole 15 passes through the hole 16 of the support plate 8 and is formed from the internal space formed by the protrusions 13 and 14. Gas is released through.

  Here, the surface of the absorbent sheet 51 is located below the through hole 15 and the entire through hole 15 is exposed. However, the through hole 15 may be partially covered with the absorbent sheet 51.

  FIG.5 (b)-(d) is a top view of the 2nd-4th example of the absorption sheet of this invention.

  In the absorbent sheet 51 of the first example, the end portion of the cut 42 is exposed to the outer periphery. However, in the absorbent sheet 52 of the second example, the end portion of the cut 43 is exposed to the inner periphery, from the inner periphery toward the outer periphery. (Fig. 5 (b)).

  The absorbent sheet 53 of the third example has both the cuts 42 of the first example and the cuts 43 of the second example, and the cuts 42 and 43 are arranged alternately (FIG. 5 (c)).

  In the first to third examples of the absorbent sheets 51 to 53, the cuts 42 and 43 are arranged radially, whereas in the fourth example of the absorbent sheet 54, the cuts 44 are arranged in parallel (FIG. 5). (d)).

  Although each notch 42-44 has penetrated the thickness direction of the absorption sheets 51-54, it does not necessarily need to penetrate and the opening part of a notch should just appear on the surface.

  FIGS. 6A to 6C show fifth to seventh examples of absorbent sheets 55 to 57 in which cut surfaces are formed by punching. In the fifth example of absorbent sheet 55, circular punched 45 is formed. (FIG. 6 (a)) In the absorbent sheet 56 of the sixth example, wedge-shaped punching 46, 46 is applied to the outer periphery and the inner periphery, and is formed into a gear shape (FIG. 6 (b)).

  Further, in the absorbent sheet 57 of the seventh example, an elongated punching 48 is formed.

  These punchings 45 to 48 penetrate through the thickness direction of the respective absorbent sheets 55 to 57, but do not necessarily penetrate and include a hollow shape whose surface is excavated.

  Similarly to the absorbent sheet 51 of the first example, the absorbent sheets 52 to 57 of the second to seventh examples can also be disposed on the second electrode 5 with the protrusions 13 protruding.

  Moreover, a protrusion can also be formed in the absorption sheets 52 to 57 of the second to seventh examples and can be fitted into the recesses.

  Reference numeral 60 in FIG. 1 is a secondary battery pack using the secondary battery 2, and a plurality of the secondary batteries 2 are arranged inside the case 61.

  Each secondary battery 2 is connected in series by a lead 63 and is connected to an electric circuit formed on the wiring board 64. When each secondary battery 2 is discharged and the output voltage is lowered, charging is performed. The output voltage is restored.

  When there is a liquid leak from each secondary battery 2, the absorption speed of the absorbent sheets 51 to 57 is fast. Therefore, when a small amount of liquid leaks, the absorbent sheets 51 to 57 absorb and do not leak to the outside of the secondary battery 2. It is like that.

  Between each secondary battery 2, the absorber 1 comprised by the same material as the absorption layer of the absorption sheets 51-57 is arrange | positioned.

  The absorbent body 1 has a cylindrical shape, and its volume is larger than that of the absorbent sheets 51 to 57. Therefore, the electrolytic solution that has a large amount of liquid leakage and cannot be absorbed by the absorbent sheets 51 to 57 is absorbed by the absorbent body 1.

  Although the above has been described by taking a secondary battery as an example, the present invention is also effective for liquid leakage of a non-chargeable battery.

  Moreover, even if it is methods other than cutting and punching, such as excavation, if the cut surface which increases the surface area of an absorption sheet is formed, it will be contained in the absorption sheet of this invention.

  As will be described later, the absorbent sheet of the present invention also includes a sheet having a multilayer structure in which an electrolyte absorber is formed on a layer such as a cloth, a nonwoven fabric, or a resin film.

  The protrusion 40 is not limited to a ring-shaped protrusion, and may be constituted by a plurality of protrusions.

  Next, the material and laminated structure of the absorbent sheets 51 to 57 will be described.

  As shown in FIG. 7A, an eighth example of the absorbent sheet 101 including the absorbent resin layer 100 formed in a sheet shape can be used for the absorbent sheet of the present invention.

  In addition, as shown in FIG. 7B, the ninth example absorbent sheet 102 having a support 112 and an absorbent resin layer 100 formed on one side of the support 112 can be used. In the ninth absorbent sheet 102, the cut surface is not only formed on the absorbent resin layer 100 but also formed on both the absorbent resin layer 100 and the support 112.

  Further, as shown in FIG. 7C, the tenth includes a support 112, an absorbent resin layer 100 formed on the surface of the support 112, and an adhesive layer 113 formed on the back surface of the support 112. An example absorbent sheet 103 can be used. When the absorbent sheet 103 of the tenth example is used, the absorbent sheet 103 can be adhered by attaching the adhesive layer 113 to the inner wall of the battery case, so the absorbent sheet 103 can be easily installed inside the battery case. Can do. The adhesive which comprises the adhesion layer 103 is not specifically limited, A well-known adhesive can be used.

  In the absorbent sheet 103 of the tenth example, the cut surface is formed only on the absorbent resin layer 100, the case where the cut surface is formed on the absorbent resin layer 100 and the support 112, and the absorbent resin layer 100 and the support 112. And may be formed on the adhesive layer 103.

  Moreover, as shown in FIG.7 (d), the absorption sheet 105 (eleventh example absorption sheet) which provided the protrusion part 105 on the absorptive resin layer 100 side of the absorption sheet 102 of the ninth example is also in this invention. included.

  As the support 102 that can be used in the absorbent sheet of the present invention, a resin film, for example, a plastic film such as polypropylene, that does not allow permeation of the electrolyte of a secondary battery mainly composed of a nonaqueous solvent can be used. In addition to the resin film, a fibrous sheet capable of absorbing and holding the nonaqueous solvent can be used. As the fibrous sheet, cloth, paper, nonwoven fabric made of plastic fiber such as polypropylene, or the like can be used. It is preferable to form the support with such a fibrous sheet because the absorption rate of the nonaqueous solvent can be increased.

  In particular, when the adhesive layer 103 is disposed on one side of the absorbent sheet 103 as in the above-described tenth example of the absorbent sheet 103, the absorbent resin layer is more than the absorbent sheets 101 and 102 of the eighth and ninth examples. Since the area in contact with the non-aqueous solvent becomes small, it is preferable to use a fibrous sheet for the support 112 in order to maintain the absorbability of the non-aqueous solvent.

  As the liquid-absorbent resin layer 100 used in the absorbent sheet of the present invention, a monomer composition containing a monofunctional monomer component (A) that is a film-forming component and a polyfunctional monomer component (B) that is a crosslinking component. It is possible to use a polymer film formed by polymerizing by irradiating with ultraviolet rays and forming into a sheet shape. As the monofunctional monomer component (A), a homopolymer that dissolves in a non-aqueous solvent of a non-aqueous electrolyte secondary battery is used. What contains the monofunctional monomer (a) which can be formed can be used.

  In this invention, it is preferable to use the monofunctional monomer (a) which can form the homopolymer which melt | dissolves in the nonaqueous solvent of a nonaqueous electrolyte secondary battery as a monofunctional monomer component (A). This is because when only a monofunctional monomer that forms a homopolymer that does not dissolve in such a non-aqueous solvent is used as the monofunctional monomer component (A), the resulting resin layer has insufficient liquid absorbency. Because.

  Here, the fact that the homopolymer is dissolved in the non-aqueous solvent means that 30 parts by weight of the non-aqueous solvent (particularly, a mixed solvent containing at least one of dimethyl carbonate, propylene carbonate and ethylene carbonate described later, preferably an equal volume mixed solvent) is used. On the other hand, when 1 part by weight of the homopolymer is immersed at room temperature (about 23 ° C.) for 24 hours, it means that the mass of the homopolymer is reduced by 10% or more.

  The decrease in mass can be determined by comparing the mass after drying of the homopolymer pulled up from the non-aqueous solvent after immersion with the mass before immersion. When completely dissolved, the mass is reduced by 100%.

Such a monofunctional monomer (a) preferably has a value obtained by subtracting the solubility parameter value of the non-aqueous solvent to be applied from the solubility parameter value (SP value (J / cm ³ ) ^1/2 ). The thing which becomes 1.0-8.0, More preferably, 2.0-6.5 is selected. Outside this range, the homopolymer will not substantially dissolve in the non-aqueous solvent, and the resulting resin layer will tend to have insufficient liquid absorbency.

The solubility parameter can be calculated from the following Fedors equation (see RFFedors, Polym. Eng. Sci., 14 (2), p147, p472 (1947)). The solubility parameter of the monofunctional monomer is calculated for the repeating unit after polymerization. In the Fedors equation, “σ” is a solubility parameter, “V” is a molar volume (cm ³ / mol), and “Ecoh” is a binding energy (J / mol).
σ = (ΣEcoh / V) ^1/2

Here, as the monofunctional monomer (a), a mixed monofunctional monomer (a) using a monomer (a1) having a solubility parameter value of SP1 and n moles of a monomer (a2) having a solubility parameter value of SP2 is used. Is used, the solubility parameter SP (monomer) mix value is calculated from the following equation. The solubility parameter when three or more monofunctional monomers are used in combination can be calculated in the same manner.
SP (monomer) mix value = (SP1 × n + SP2 × m) / (n + m)

  Specific examples of such a monofunctional monomer (a) include imide acrylate (SP value = 27.6), N-vinyl-2-pyrrolidone (SP value 26.2), acryloylmorpholine (SP value = 25). , Benzyl acrylate (SP value = 22.9), phenoxyethyl acrylate (SP value = 22.6), N, N-diethylacrylamide (SP value = 20.6), methoxypolyethylene glycol acrylate (SP value = 19.6) ) And the like. Of these, benzyl acrylate and N-vinyl-2-pyrrolidone are preferable.

  Furthermore, tetrahydrofurfuryl acrylate (THFA) can also be used as the monofunctional monomer (a).

  On the other hand, the solubility parameter value of the non-aqueous solvent is preferably 17 to 28, more preferably 18 to 23. If it is out of this range, the cycle characteristics of the battery tend to deteriorate when used in a lithium battery.

  Examples of such nonaqueous solvents include carbonates such as dimethyl carbonate (SP value = 17.4), propylene carbonate (SP value = 20.8), and ethylene carbonate (SP value = 22.5). . These nonaqueous solvents may be used alone or in combination of two or more.

  A particularly preferred non-aqueous solvent is a mixed solvent (SP (solvent) mix value = 20.2) in which dimethyl carbonate, propylene carbonate, and ethylene carbonate are mixed in equal volumes. The solubility parameter of the mixed non-aqueous solvent can also be calculated according to the calculation method of the solubility parameter when a monofunctional monomer is used in combination based on the solubility parameter and the amount (number of moles) of each non-aqueous solvent.

The homopolymer of the monofunctional monomer (a) is preferably an ultraviolet polymerization initiator (for example, 2-hydroxy-2-methyl-1-phenylpropan-1-one) in 100 parts by weight of the monofunctional monomer (a). , bisacylphosphine phosphonic oxides, benzophenone and 2-methyl thioxanthone) were mixed with 0.1 to 5 parts by weight, the energy density of the mixture in the ultraviolet wavelength ^{250nm~350nm 100mJ / cm 2 ~2000mJ / cm} 2 Polymerized by irradiation with

  In this invention, what contains the monofunctional monomer (a) demonstrated above can be used for a monofunctional monomer component (A). When the amount of the monofunctional monomer (a) contained in the monofunctional monomer component (A) is too small, the liquid absorption amount of the non-aqueous solvent tends to decrease, so the monofunctional monomer (a) is contained in an amount of 20 mol% or more. It is preferable to use a monofunctional monomer component.

  In addition to the monofunctional monomer (a), other monofunctional monomers can be added to the monofunctional manomer component (A) as long as the effects of the present invention are not impaired. Examples of other monofunctional monomers that can be added to the monofunctional monomer component (A) include hydroxyethyl acrylate (SP value = 29.6), acrylic acid (SP value = 28.7), and 2-ethylhexyl acrylate. (SP value = 18.9), lauryl acrylate (SP value = 18.7), or the like can be used.

  In the present invention, the polyfunctional monomer component (B) is a component for introducing a crosslinked structure into the liquid-absorbent resin layer 100, and a monomer having two or more acrylate residues in the chemical structure may be used. preferable. For example, hydroxypivalate neopentyl glycol diacrylate, polyethylene glycol diacrylate, bisphenol A diacrylate, and the like can be used.

  If the amount of the polyfunctional monomer component (B) in the monomer composition is too small, the shape retention of the liquid-absorbent resin layer 100 is not sufficient, and if it is too large, the non-aqueous solvent may not be sufficiently absorbed. Therefore, the crosslink density is preferably 0.0001 to 0.17, and more preferably 0.001 to 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 appropriately determined by the following formula.
Crosslink density = a × b / (b + c)

  As described above, the absorbent sheet of the present invention is obtained by applying a monomer composition containing the monofunctional monomer component (A) and the polyfunctional monomer component (B) on a release film such as a polyethylene terephthalate film, The coating film formed in the above is irradiated with ultraviolet rays to polymerize the monomer composition, and formed into a sheet shape. If it is peeled off from the release sheet after forming, the eighth example shown in FIG. An absorbent sheet 101 is obtained.

  As a method of producing the absorbent sheet 102 of the ninth example shown in FIG. 7B, the above-described monomer composition is applied on a support 112 made of a nonwoven fabric or the like to form a coating film, and the coating film is formed. There are a method of polymerizing the constituent monomer composition and forming the absorbent resin layer 100, and a method of laminating the sheet-like absorbent resin layer 100 and the support 112 shown in FIG.

  Moreover, as a method for producing the tenth example of the absorbent sheet 103 shown in FIG. 7C, an adhesive is applied on the absorbent resin layer 100 of the ninth example of the absorbent sheet 102 to form the adhesive layer 113. And a method of sticking the adhesive layer 113 formed into a sheet shape on the absorbent resin layer 100 of the absorbent sheet 102 of the ninth example.

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. As examples of the ultraviolet polymerization conditions, typically at 15 ° C. to 25 ° C., it includes conditions for irradiation with ultraviolet rays having a wavelength of 250nm~350nm at an energy density of ^{100mJ / cm 2 ~2000mJ / cm 2} .

  In addition, you may add a flame retardant (aluminum hydroxide, a melamine cyanurate, etc.) to the liquid absorbing resin layer 100 of the absorption sheet of this invention as needed. Thereby, a flame retardance can be provided to an absorption sheet.

Reference Example A homopolymer was formed by polymerizing a single type of monofunctional monomer, and the solubility of the homopolymer was examined as described below.

1 part by weight of a photopolymerization initiator (2-hydroxy-2-methyl-1-phenylpropan-1-one) is added to 100 parts by weight of a monofunctional monomer, and the resulting mixture is applied to a polyethylene terephthalate film with a roll coater. Polymerization was performed by irradiation with ultraviolet light having a wavelength of 365 nm at an energy density of 2000 mJ / cm ² . 1 part by weight of the resulting polymer film (homopolymer film) was immersed in 300 parts by weight of an equal volume mixture of dimethyl carbonate / propylene carbonate / ethylene carbonate (SP (solvent) mix value = 20.2) at 23 ° C. for 24 hours. Then, the mixture was filtered, and the solid matter remaining on the filter was dried at 100 ° C. for 1 hour, and the solubility (wt%) was calculated by the following calculation formula. The obtained results are shown in Table 1. In the formula, W ₁ is the mass of the polymer film before immersion, and W ₂ is the mass of the dry solid.
Solubility = ((W ₁ −W ₂ ) / W ₁ ) × 100

  Next, the characteristics of the absorbent sheet when the type of the monofunctional monomer component (A) and the blending amount of the monofunctional monomer and the polyfunctional monomer component (B) are changed will be described.

<Test pieces 1-6, C1-3>
Monofunctional monomers listed in Tables 2 and 3, hydroxypivalate neopentyl glycol diacrylate as the polyfunctional monomer, and 2-hydroxy-2-methyl-1-phenylpropan-1-one as the polymerization initiator Are mixed with the blending amounts shown in Tables 2 and 3, and applied onto a polyethylene terephthalate film by a roll coater method, and polymerized by irradiating ultraviolet rays having a wavelength of 365 nm at an energy density of 2000 mJ / cm ^2. The film | membrane was peeled from the polyethylene terephthalate film and the test pieces 1-6 and C1-3 which are a single layer absorption sheet were obtained.

  Here, benzyl acrylate, N-vinyl-2-pyrrolidone, and acrylic acid were used as monofunctional monomers.

  Each test piece 1 to 6 and C1 to 3 was immersed in a large-capacity mixed solvent of dimethyl carbonate / propylene carbonate / ethylene carbonate (SP (solvent) mix value = 20.2) at 23 ° C., and after 2 hours. While visually observing the shape of each test piece 1-6, C1-3, it pulled up from the mixed solvent, wiped off the mixed solvent on the surface immediately, measured the weight, and calculated swelling magnification. The obtained results are shown in Table 2. In addition, the SP value (SP (monomer) value) of the monofunctional monomer, the SP value difference with the solvent (ΔSP value), the crosslinking density of the liquid-absorbent resin layer of the absorbent sheet, and the shape after immersion are also shown in Table 2 and Table. 3 shows.

  From the results of Table 2 and Table 3, the test piece 1 has a swelling ratio of 10 times, and also maintains the film shape even after the nonaqueous solvent is absorbed and swollen. It can be seen that when the liquid leakage occurs, it is useful as an electrolyte solution absorbing member for absorbing the electrolyte solution.

  Moreover, although the test pieces 2-6 have shown the performance of the level which is practically satisfactory as an electrolyte solution absorption member, when the crosslinking density fell from the result of the test piece 2, it absorbed the nonaqueous solvent and swollen. It can be seen that the later shape tends to change from a film shape to a gel shape. On the contrary, it can be seen from the results of the test piece 3 and the test piece 6 that the swelling ratio tends to decrease as the crosslinking density increases. From the results of the test piece 4, it can be seen that good results can be obtained even when N-vinyl-2-pyrrolidone is used instead of benzyl acrylate as the monofunctional monomer. From the result of the test piece 5, it can be seen that when a monofunctional monomer in which the homopolymer does not dissolve in the non-aqueous solvent is used in combination, the swelling ratio tends to decrease.

  On the other hand, it can be seen from the result of the test piece C1 that when no polyfunctional monomer is used, the liquid-absorbing resin layer is dissolved in the non-aqueous solvent and cannot be used as the electrolytic solution-absorbing member. From the result of test piece C2, when the SP value of the monofunctional monomer is too large and the homopolymer does not substantially dissolve in the non-aqueous solvent, the swelling ratio is too small to be used as an electrolyte solution absorbing member. I understand. On the contrary, from the result of the test piece 3, even when the SP value of the monofunctional monomer is too small and the homopolymer does not substantially dissolve in the non-aqueous solvent, the swelling ratio is too small and the electrolyte solution absorbing member It turns out that it cannot be used.

A monomer composition was prepared under the same conditions as the above test piece 1 except that tetrahydrofurfuryl acrylate (THFA) was used as a monofunctional acrylate instead of benzyl acrylate, and ultraviolet irradiation was performed under the same conditions as the above test piece 1. The monomer composition was polymerized to obtain an absorbent resin layer 100 having a thickness of 150 μm. The absorbent resin layer 100 and the support 112 made of a nonwoven fabric were laminated and then processed to obtain the absorbent sheet 53 of the example having the shape shown in FIG. The area of the planar shape of the absorbent sheet 53 was 1.63 cm ² .

  Apart from this, an absorbent sheet of a comparative example was produced under the same conditions as in the example except that there were no cuts 42 and 43.

  The secondary sheet which has the same non-aqueous solvent as the main component which stuck the absorption sheet of these Examples and a comparative example on the plate plated with nickel, and measured the expansion coefficient of the said test pieces 1-6 and C1-3. After being immersed in the battery electrolyte for 10 minutes, it was pulled up, immediately wiped off the surface electrolyte, the weight of the absorbent sheet was measured, and the swelling factor was calculated. The swelling factor of the comparative example was 4.3 times. In contrast, the absorbent sheet 53 of the example had a swelling ratio of 7.5 times, and the result of the swelling ratio was about 1.75 times that of the comparative example.

  From these results, it was confirmed that the absorption sheet 53 of the present invention has an extremely high absorption rate compared to the conventional one.

Battery pack using the secondary battery of the present invention Drawing for demonstrating the state which mounts the absorption sheet of this invention Drawing (1) for demonstrating the absorption sheet of this invention, and the internal structure of a secondary battery using the same Drawing (2) for demonstrating the internal structure of the absorption sheet of this invention, and a secondary battery using the same (a)-(d): The top view of the absorption sheet of a 1st example-a 4th example (a) to (c): Plan views of the absorbent sheets of the fifth to seventh examples (a)-(d): Top view of the absorption sheet of 8th example-11th example Battery pack using a conventional secondary battery The figure for demonstrating the absorption sheet of a prior art, and a secondary battery using the same

Explanation of symbols

2 ... Batteries 41-44 ... Incision 40 ... Projection 45-48 ... Punching 51-57 ... Absorbing sheet

Claims (7)

A substrate made of cloth;
Having a polymer absorber disposed on the substrate;
A ring-shaped absorbent sheet capable of absorbing a non-aqueous solvent having a solubility parameter value of 18 to 23,
The absorbent polymer, a value obtained by subtracting the solubility parameter value of the non-aqueous solvent, Ri consists homopolymer of the monofunctional monomer having a solubility parameter value as a -1.0～8.0,
The non-aqueous solvent as a main component, and an electrolytic solution in which an electrolyte is dissolved, the absorbent sheet that is used in a non-aqueous electrolyte secondary battery using the electrolytic solution.   The said absorption sheet is an absorption sheet of Claim 1 in which the cut surface was formed in the position between an outer periphery of a ring.   The absorbent sheet according to claim 1, wherein the cut surface is formed by cutting.   The absorbent sheet according to claim 1, wherein the cut surface is formed by punching the absorbent sheet.   The absorbent sheet according to any one of claims 1 to 4, wherein the absorbent sheet is formed with a ring-shaped protrusion along the inner periphery of the ring. A cylindrical container serving as a first electrode;
An electrolyte solution disposed in the container;
A protrusion that protrudes from one bottom surface of the container, the second electrode being insulated from the first electrode;
A vent hole formed through the wall of the protrusion;
A battery having the absorbent sheet according to any one of claims 1 to 5, which absorbs the electrolytic solution,
The absorbent sheet is formed in a ring shape, fitted into the protrusion so that the protrusion protrudes from a hole in the center of the ring, and in that state, the absorbent sheet is formed to a thickness that does not block the vent hole,
The electrolyte solution has a solubility parameter value of 18 to 23. The battery according to claim 6, wherein a ring-shaped protrusion is formed along the inner periphery of the ring on the absorbent sheet.
The protrusion is a battery fitted in a recess around the protrusion.

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