JP2006338904A - Lithium primary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve flex resistance of a paper type lithium primary battery. <P>SOLUTION: This lithium primary battery 1A is provided with: a separator 9; a positive electrode active material layer 4 arranged on one-side surface side of the separator 9; a negative electrode active material layer 5 arranged on the other-side surface side of the separator; sheet-like frame members 2 and 3 surrounding the separator 9, the positive electrode active material layer 4 and the negative electrode active material layer 5; a positive electrode collector 6 attached to the frame member 2 for retaining the positive electrode active material layer 4 between the separator 9 and itself; and a negative electrode collector 7 attached to the frame member 3 for retaining the negative electrode active material layer 5 between the separator 9 and itself. The frame members 2 and 3 functioning as a sealing material are formed of a resin material having rubber elasticity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper-type lithium primary battery having flexibility.

Lithium primary batteries using lithium as a negative electrode are in demand mainly for low-load backup applications because of their extremely low self-discharge and stable characteristics for long-term storage. Among them, those disclosed in the following Patent Documents 1 and 2 are commonly called paper-type batteries, and demand for IC cards, active RFIDs, and the like is expected to increase.
Japanese Patent No. 2935427 JP-A-8-055627

  Among the test items for IC cards defined in ISO or JIS, there is an item for examining whether or not defects such as disconnection occur by bending the card. The same bending test is imposed on the battery built in the IC card.

  A paper-type lithium primary battery essentially has excellent flexibility and bending resistance, but is required to have bending resistance that can clear the bending test with a margin. Of course, a significant decrease in other properties such as water vapor barrier properties is not allowed. An object of this invention is to aim at the further improvement of the bending resistance of a paper-type lithium primary battery, maintaining other characteristics, such as water vapor | steam barrier property, to high level.

Means for Solving the Problems and Effects of the Invention

  In order to solve the above problems, a lithium primary battery of the present invention includes a separator, a positive electrode active material layer disposed on one surface side of the separator, and a negative electrode active material containing lithium disposed on the other surface side of the separator. A material layer, a sheet-like frame member surrounding the separator, the positive electrode active material layer and the negative electrode active material layer, and a frame member bonded to the frame member so as to close one opening of the frame member. A frame member comprising: a positive electrode current collector that holds the material layer; and a negative electrode current collector that is bonded to the frame member so as to close the other opening of the frame member and holds the negative electrode active material layer between the separator and the frame member. Is made of a material having rubber elasticity.

  In the present invention, the elasticity of the battery is improved by imparting rubber elasticity to the frame member. In other words, even when repeated folding operations are performed, seal breakage does not occur as long as the frame member is within a range in which it can be elastically deformed. Further, since the frame member has rubber elasticity, the stress generated in the metal current collector fixed to the frame member can be relaxed. Therefore, even when repeated bending operations are performed, plastic deformation of the current collector is suppressed, and large irregularities (wrinkles) are unlikely to occur in the current collector. Since the unevenness generated in the battery is transferred to the surface of the card and impairs the aesthetic appearance of the card, it is preferable that the unevenness is small.

As a material having rubber elasticity, a composite resin substantially composed of an elastomer and a resin (non-elastomer) having a higher water barrier property than the elastomer can be suitably used. In general terms regarding lithium primary batteries, it is known that lithium, which is a negative electrode active material, reacts with water to cause self-discharge of the negative electrode.
2Li + 2H ₂ O = 2LiOH + H ₂
Of course, the problem of self-discharge does not surface in a short period of several months. However, considering that one of the characteristics of a lithium primary battery is that it can exhibit stable performance even for long-term use over several years, the problem of moisture permeation into the battery cannot be avoided.

  For example, in the case of a coin-type lithium primary battery, airtightness inside the battery is maintained by a caulking structure of a metal container, so that the problem of water vapor permeation is not much considered. However, if a structure such as the lithium primary battery of the present invention is adopted, the possibility of moisture entering the battery through the frame member serving as a sealing material cannot be completely denied. Therefore, the water vapor barrier property of the frame member is preferably as high as possible. On the other hand, it is known that certain types of resins such as polypropylene and polyethylene terephthalate have excellent water vapor barrier properties. On the other hand, as a general theory, elastomers are inferior in water vapor barrier properties to polypropylene and the like. Therefore, if the frame member is composed of a composite resin in which the content ratio of the elastomer and the resin having excellent water vapor barrier properties such as polypropylene is appropriately adjusted, the flexibility of the battery can be improved while maintaining sufficient water vapor barrier properties. Is possible.

In a preferred embodiment, the lithium primary battery is a paper-type lithium primary battery having a rectangular shape in plan view, and has a size that can be built in an IC card defined in JIS X6301. The length of the frame member parallel to the long side direction or the short side direction of the lithium primary battery is W (mm), the thickness of the frame member is d (mm), and the elastic limit of the composite resin material constituting the frame member is k, when the volume content of the elastomer contained in the composite resin material is 100 * J (%), the lithium primary battery of the present invention satisfies the following inequality. However, “k” is the elastic limit of the elastomer. “L” represents the length of the short side of the IC card specified in JIS X6301. “H” represents the amount of bending in the short side direction of the IC card under the test conditions defined in JIS X6321. “T” represents the thickness of the IC card.
J> [{1 + W ² / ((L ² / (4h−t + d)) (L ² / (4h−t−d)))}} ^1/2 −1] / k

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view of a lithium primary battery which is an embodiment of a thin battery according to the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. The primary lithium battery 1A is rectangular and plate-shaped as a whole, and includes frame members 2 and 3, a positive electrode active material layer 4, a positive electrode current collector 6, a negative electrode active material layer 5, a negative electrode current collector 7, and a separator 9. The positive electrode current collector 6 and the negative electrode current collector 7 are fixed to the frame members 2 and 3 so as to close the openings of the frame members 2 and 3, respectively, and also serve as an exterior material of the lithium primary battery 1A. Further, the positive electrode current collector 6 and the negative electrode current collector 7 have power extraction portions 6t and 7t, respectively. The power extraction portions 6t and 7t extend outward from the frame members 2 and 3 in a plane orthogonal to the thickness direction of the lithium primary battery 1A. The frame members 2 and 3 functioning as a sealing material are sheet-like parts having a shape like a window frame, and are thin resins having rubber elasticity for the purpose of improving the flexibility and bending resistance of the lithium primary battery 1A. It consists of

  As shown in FIG. 2, the frame members 2 and 3 include a positive electrode side frame member 2 and a negative electrode side frame member 3. The positive electrode side frame member 2 and the negative electrode side frame member 3 are bonded to each other on the facing surfaces. An active material filling chamber 10 is formed by the frame members 2 and 3, the positive electrode current collector 6 and the negative electrode current collector 7, and the separator 9, the positive electrode active material layer 4 and the negative electrode active material layer 5 are accommodated in the active material filling chamber 10. As a result, the battery body 14 is formed. The inside of the active material filling chamber 10 is an atmosphere depressurized from the atmospheric pressure. Further, the positive electrode current collector 6 is bonded to the positive electrode side frame member 2 and the negative electrode current collector 7 is bonded to the negative electrode side frame member 3 so as to be located on the side opposite to the separator 9. Thereby, the seal part 11 which maintains the airtightness of the active material filling chamber 10 is formed. By fixing the peripheral edge portion 9k of the separator 9 to the negative electrode side frame member 3, the active material filling chamber 10 is divided into a positive electrode side where the positive electrode active material layer 4 is arranged and a negative electrode side where the negative electrode active material layer 5 is arranged. It is divided. In the active material filling chamber 10, the positive electrode active material layer 4 is held between the positive electrode current collector 6 and the separator 9, and the negative electrode active material layer 5 is held between the negative electrode current collector 7 and the separator 9. Yes.

  As shown in FIG. 2, the opening of the positive electrode side frame member 2 is wider than the opening of the negative electrode side frame member 3, and the frame members 2 and 3 have a stepped shape in the active material filling chamber 10. Specifically, the inner peripheral edge 2 h of the opening of the positive electrode side frame member 2 is positioned outside the inner peripheral edge 3 h of the opening of the negative electrode side frame member 3 in the in-plane direction. And the separator 9 is being fixed to the opening peripheral part 3a of the negative electrode side frame member 3 located inside the positive electrode side frame member 2. FIG. Further, the outer peripheral edge 9 h of the separator 9 is located between the inner peripheral edge 2 h of the opening of the positive electrode side frame member 2 and the inner peripheral edge 3 h of the opening of the negative electrode side frame member 3. The entire main surface 2 p of the positive electrode side frame member 2 that forms the boundary with the negative electrode side frame member 3 is an adhesive surface with the negative electrode side frame member 3. The “in-plane direction” is a direction orthogonal to the thickness direction of the lithium primary battery 1A.

Before describing the frame members 2 and 3 in detail, other components will be described.
The positive electrode active material layer 4 includes, for example, 60% by mass or more and 70% by mass or less of a positive electrode active material, 1% by mass or more and 5% by mass or less of a conductive auxiliary agent, and 25% by mass or more and 35% by mass or less of an electrolytic solution. It consists of a positive electrode composite. As the positive electrode active material, a transition metal oxide powder that forms a composite oxide with lithium such as MnO ₂ can be used. A carbon material such as acetylene black can be used for the conductive assistant. As the electrolytic solution, a lithium salt dissolved in an organic solvent such as dimethoxyethane (DME), ethylene carbonate (EC), or propylene carbonate (PC) can be used.

  The negative electrode active material layer 5 is composed of a lithium foil. It is also possible to use lithium alloy foil (for example, lithium-aluminum alloy) instead of lithium foil. The masses of the positive electrode active material layer 4 and the negative electrode active material layer 5 are adjusted such that the battery capacity of the positive electrode is larger than the battery capacity of the negative electrode. This prevents the lithium foil forming the negative electrode active material layer 5 from remaining after complete discharge.

  As the material for the current collectors 6 and 7 and the lead terminals 6t and 7t, a material selected from a group of highly conductive metals consisting of copper, copper alloy, stainless steel, aluminum, aluminum alloy, nickel and nickel alloy is preferably used. can do. In particular, stainless steel is preferable because it is excellent in workability, corrosion resistance, and economy. In order to obtain long-term stability, it is important that the current collector does not elute into the electrolyte. Considering this point, stainless steel is preferable because it is excellent in corrosion resistance. For example, SUS301, SUS304, SUS316, SUS316L, which are typical as austenitic stainless steel, and SUS631, which is typical as precipitation hardened stainless steel, are also excellent in spring properties, and their use is recommended.

  The separator 9 is a thin film that separates the positive electrode and the negative electrode and sufficiently penetrates the electrolyte, and has a porous and multilayer structure. Specifically, a nonwoven fabric made of a resin such as polyethylene or polypropylene can be used. In the present embodiment, a polyethylene porous sheet is used for the separator 9.

For example, when designing the lithium primary battery 1A for an ISO standard IC card, the thickness of each component is preferably adjusted within the following range.
・ Positive electrode active material layer 4 30 μm or more and 300 μm or less ・ Negative electrode active material layer 5 10 μm or more and 150 μm or less ・ Positive electrode side frame member 2 30 μm or more and 200 μm or less (the negative electrode side frame member 3 can have the same thickness)
Positive electrode current collector 6: 10 μm or more and 100 μm or less (the negative electrode current collector 7 may have the same thickness)
・ Separator 9: 10 μm or more and 60 μm or less

Next, the frame members 2 and 3 will be described in detail.
As shown in FIG. 3, the positive electrode current collector 6 is fixed to the positive electrode side frame member 2 via the adhesive layer 12. Similarly, the negative electrode current collector 7 is fixed to the negative electrode side frame member 3 via the adhesive layer 13. The adhesive layers 12 and 13 are made of hot-melt adhesive such as ethylene vinyl acetate (EVA), ethylene / methacrylic acid copolymer (EMAA), acid-modified polyethylene (PE-a), and acid-modified polypropylene (PP-a). Is a layer. In general, the material of a card-type simple storage medium such as an IC card is typically vinyl chloride, and the temperature applied during card manufacture is relatively high at 110 ° C. to 140 ° C. Therefore, the adhesive layers 12 and 13 should also have a reasonably high melting point, for example, acid-modified polypropylene is preferable.

  In FIG. 3, the frame members 2, 3 and the adhesive layers 12, 13 are shown in a distinguished form, but the adhesive layers 12, 13 may be configured to be included in the frame members 2, 3. . For example, by using a resin sheet with an adhesive in which an adhesive to be the adhesive layer 12 is applied to a resin sheet to be the positive electrode side frame member 2 or an adhesive film is bonded together, the frame members 2 and 3 are used. Adhesive layers 12 and 13 can be formed to join the current collectors 6 and 7 to each other. In addition, the hot melt adhesive is disposed on the outer peripheral portion of the current collectors 6 and 7, and the hot melt adhesive is melted and solidified at the time of battery assembly, whereby the frame members 2 and 3 and the current collector 6 are obtained. , 7 may be formed. In the present embodiment, the thickness of the positive electrode side frame member 2 and the thickness of the negative electrode side frame member 3 are set equal to each other, but may be adjusted to different thicknesses. Further, when the frame members 2 and 3 themselves are made of a material having adhesiveness to metal, it is not necessary to provide the adhesive layers 12 and 13 separately, and the frame members 2 and 3 and the current collectors 6 and 7 are not required. Can be directly bonded to each other.

  Next, the material of the frame members 2 and 3 will be described. As a material of the frame members 2 and 3, a composite resin containing an elastomer (rubber material) and a resin having a higher water vapor barrier property than the elastomer can be suitably used. If the rubber elasticity is simply applied, it is considered that all the frame members 2 and 3 may be made of an elastomer. However, the configuration is difficult to realize. The reason is as follows. Necessary characteristics for the frame members 2 and 3 are high water vapor barrier properties, moderate hydrogen permeability, high air (oxygen, nitrogen, carbon dioxide) barrier properties, and organic electrolyte vapors. High barrier properties, high redox resistance, excellent organic electrolyte resistance, easy molding into sheet material, heat fusion at a relatively low temperature (150 ° C.), insulating material Can be mentioned. It is not easy to obtain an elastomer having all such characteristics in a well-balanced manner at a low cost. For example, even butyl rubber, which is said to have a relatively high water vapor barrier, has a difference of about 10 times under room humidity and room temperature conditions as compared with polypropylene, which is one of the resins having the highest water vapor barrier. Further, an elastomer into which molecules having strong oxidizing power such as chlorosulfonated polyethylene are introduced may be deteriorated by the reducing power of the negative electrode of the lithium primary battery. In the case of having an unsaturated bond such as a diene rubber, there is a possibility of deterioration due to the oxidizing power of the positive electrode of the lithium primary battery. Because of such circumstances, it is preferable to select a composite resin containing an elastomer and another resin as a material for the frame members 2 and 3.

  The composite resin is a resin in which the properties that the elastomer lacks are supplemented with other resins. The type of elastomer contained in the composite resin is not particularly limited. For example, butadiene rubber, isoprene rubber, dimethylbutadiene rubber, haloprene rubber, polyalkylene sulfide, isobutylene-diene copolymer (butyl rubber), alkyl-siloxane condensate (silicone rubber) One or more kinds selected from the group consisting of fluorine rubber, urethane rubber, chlorosulfonated polyethylene, olefin rubber and vinyl rubber can be used. These elastomers are sometimes referred to as thermoplastic elastomers, as distinguished from crosslinked rubber. Moreover, it is also possible to use a resin imparted with rubber elasticity by stretching a part of plastic in a uniaxial direction, such as polyvinyl alcohol. In consideration of the characteristics required for the frame members 2 and 3, one of the most recommended elastomers is butadiene rubber.

  The other resin mixed with the elastomer is, for example, one selected from the group of polyolefin resins, polyester resins, polyurethane resins, polysiloxane resins, polyamide resins, AS resins, ABS resins, and fluorine resins. The above resins can be used. Although it does not ask | require in particular whether it is thermosetting or thermoplasticity, it should select in consideration of the characteristic requested | required of the frame members 2 and 3. FIG. Also, it is important for industrial production to be inexpensive. As one of the resins that satisfy these requirements in a well-balanced manner, a polyolefin resin such as polypropylene can be recommended.

  In addition, as a method of combining the elastomer and another resin, there are a method of copolymerizing the two, a method of crosslinking, a method of melting and mixing and dispersing each other. Also, mechanical machining with fine powder can be considered. That is, in the present specification, the term “composite resin” means not only a resin in which two or more kinds of resins are mixed, but also a copolymer of two or more kinds of resins, or two or more kinds of resins, unless otherwise specified. Meaning a resin crosslinked with a crosslinking agent such as sulfur.

  Next, the content ratio between an elastomer such as butadiene and another resin such as polypropylene will be described. The elasticity required for the frame members 2 and 3 varies depending on the dimensions of the lithium primary battery 1A. For this reason, it is not easy to uniquely define the above content ratio. For example, when the lithium primary battery 1A is specialized for JIS standard IC card applications, the elastomer content ratio is satisfied so as to satisfy the conditions described in the following model. By adjusting, sufficient bending resistance can be achieved.

  In the dynamic bending strength test defined in JIS X 6305 6.1, the IC card is deformed as shown in FIG. The battery 1A built in the IC card is bent into an arc shape together with the IC card. When the battery 1A is bent or twisted, the maximum strain is generated at the end of the battery 1A, that is, the seal portion 11 of the battery 1A. When the frame members 2 and 3 constituting the end portion of the battery 1A can elastically absorb the maximum strain, the battery 1A does not undergo plastic deformation even when bent as shown in FIG. 4 (= seal portion 11). ) Does not crack, that is, seal breakage does not occur. Further, when the bending load applied to the IC card is removed, it is difficult for wrinkles to remain on the exterior material (current collectors 6 and 7 in this embodiment).

  According to the dynamic bending strength test specified in JIS X 6305 6.1, bending is repeated 250 times for each of the long side direction and the short side direction of the IC card. Therefore, it is preferable that the strain or elongation at the end of the battery 1 </ b> A be within the elastic limit of the frame members 2 and 3.

As shown in FIG. 4, when the dynamic bending strength test defined in JIS X 6305 6.1 is performed, the IC card is deformed into a cross-sectional arc shape represented by points M, P, and N. If the length of an arc including three points M, P and N is L, the bending height of this arc is h, the bending angle is θ _A , and the radius of the circle forming the arc is r, the following simultaneous system The equation holds.
L = 2rθ _A (1)
h = r (1-cos θ _A ) (2)
In order to obtain the solution of the simultaneous equations, cos θ _A is approximated by the equation (3).
cos θ _A = 1− (1/2) θ _A ² (3)
Substituting equation (3) into equations (1) and (2) gives a solution.
θ _A = 4h / L (4)
r = L ² / (8h) (5)

JIS X 6301 4.3.3 specifies the folding height h of the IC card as h = 20 mm in the long side direction and h = 10 mm in the short side direction. Further, the length L of the arc including the point M, the point P and the point N in FIG. 4 is equal to the long side length L1 or the short side length L2 of the IC card, and L1 = 85.60 mm, L2 respectively. = 53.98 mm. When these numerical values are substituted into the equation (4), the angle θ _A (/ rad) and the radius r (/ mm) can be obtained as follows.
<Long side direction>
θ _A = 4h / L1 ≦ 4 * 20 / 85.60 = 0.935
r = L1 ² /(8h)=(85.60) ² /(8*20)=45.80
<Short side direction>
θ _A = 4h / L2 ≦ 4 * 10 / 53.98 = 0.711
r = L2 ² /(8h)=(53.98) ² /(8*10)=36.42

The curvature radius r is smaller when the IC card is bent in the short side direction than when the IC card is bent in the long side direction. Therefore, when estimating the rubber elasticity required for the frame members 2 and 3 of the battery 1A, the bending of the IC card in the short side direction is assumed, and the built-in configuration of the battery 1A is as described in 2 of (a) and (b) below. It is necessary to consider the street.
(A) Built-in form in which the short side direction of the IC card is matched with the long-side direction of the battery 1A (b) Built-in form in which the short-side direction of the IC card is matched with the short-side direction of the battery 1A

As a result of employing the cosine approximation, an error of 5% at the maximum in the long side direction and 2% at the maximum in the short side direction occurs with respect to the angle θ _A and the radius r. This is required by the frame members 2 and 3. This is a sufficiently small error in discussing rubber elasticity. Further, vertical and horizontal dimensions of the battery 1A is smaller than the height and width of the IC card, the value of the angle theta _A becomes smaller. Therefore, since the error can be ignored, the above equations (4) and (5) are established.

As shown in FIGS. 4 and 5, the center point O is common to the outer arc and the inner arc of the battery 1 </ b> A. The outer arc of the IC card, the outer arc of the battery 1A, and the inner arc of the battery 1A are concentric arcs having an angle θ _A , an angle θ _B , and an angle θ _C , respectively. The length of the arc on the outside of the battery 1A and the length of the arc on the inside of the battery 1A are both the length W of the battery 1A. Since the thickness t of the IC card in the portion containing the battery 1A and the thickness d of the battery 1A are constant, the radii of the respective arcs have the following relationship. 4 and 5, all the stress generated in the battery 1A by the dynamic bending strength test of JIS 6305 is absorbed by the elongation of the end of the battery 1A.

IC card arc radius = r
IC card sheet thickness at battery built-in position = (t−d) / 2
Radius of arc outside the battery (OX) = r− (t−d) / 2 = (2r−t + d) / 2
Radius of arc inside the battery (OY) = (OZ) = r − {(t−d) / 2} −d = (2r−t−d) / 2

Referring to the enlarged view of FIG. 5, the end of the battery 1A, that is, the end of the frame members 2 and 3 is represented by a region XYZ surrounded by the points X, Y and Z, and the frame members 2 and 3 are thick. It is stretched from XY (= d) to (XZ). In other words, the length of the end faces of the frame members 2 and 3 in the schematic cross-sectional view of FIG. 5 changes from XY to XZ. The arc (YZ) is an arc having a radius (OY) and an angle (θ _C −θ _B ). A length W of the cells 1A, the outer bending angle theta _B of cells 1A, relates inner bending angle theta _C of cells 1A, the following equation is established.

W = 2 * (OX) * θ _B
W = 2 * (OZ) * θ _C
θ _B = W / (2 * (OX)) = W / (2r−t + d)
θ _C = W / (2 * (OZ)) = W / (2r−t−d)
θ _B −θ _C = (XY) * W / (2 * (OX) * (OZ))

(XZ) ² = (OX) ² + (OZ) ² -2 (OX) (OZ) cos (θ _C −θ _B )
= (OX) ² + (OZ) ² -2 (OX) (OZ) [1- (1/2) {(XY) * W / (2 * (OX) * (OZ))} ² ]
= (XY) ² {1 + W ² / (4 * (OX) * (OZ))}

Therefore, the ends of the frame members 2 and 3 when deformed by the bending test are expressed by the following equation.
(XZ) = (XY) {1 + W ² / (4 * (OX) * (OZ))} ^1/2
= D {1 + W ² / ((2r−t + d) (2r−t−d))} ^1/2

If the limit of rubber elasticity of the frame members 2 and 3 exceeds the deformation amount of the elongation, even if the frame members 2 and 3 are bent, the frame members 2 and 3 are elastically restored to their original shapes. In other words, the following inequality may be satisfied.
(Elastic limit of frame member)> {(Thickness of end of frame member at the time of bending test) − (Initial thickness)} / (Initial thickness)

(Thickness of the end of the frame member at the time of the bending test) = (XZ),
(Elastic limit of frame member)> ((XZ) -d) / d
= {1 + W ² / ((2r−t + d) (2r−t−d))} ^1/2 −1
= {1 + W ² / ((L ² / (4h−t + d)) (L ² / (4h−t−d)))}} ^1/2 −1

  IC card length L, bending amount h (bending height), IC card thickness t, battery 1A length W (equal to the length of frame members 2 and 3), frame members 2 and 3 The elastic limit of the frame member can be derived by substituting the thickness d of the above into the above inequality.

  The “elastic limit” refers to the maximum elongation rate at which elastic deformation is allowed, that is, the value obtained by dividing the amount of elongation in a state where the object causing elastic deformation reaches the yield point by the initial length. To do. All the test conditions and the like described in this specification are based on room temperature (20 ° C.) and atmospheric pressure (1 atmosphere). Further, the yield point of the composite resin material constituting the frame members 2 and 3 is determined according to the tensile yield point strength test specified in ASTM D638, and the load and elongation applied to the test piece lose linearity. Define the point as the yield point.

  By selecting a composite resin material having an elastic limit that satisfies the above inequality, it is possible to produce a lithium primary battery 1A in which the frame members 2 and 3 do not undergo plastic deformation and seal failure hardly occurs. Further, from the capacity design of the battery 1A, the length W of the battery 1A (which is equal to the length of the long side or the short side of the frame members 2 and 3) and the thickness d of the frame members 2 and 3 are determined. Thus, the elastic limit required for the frame members 2 and 3 can be determined.

Further, it is assumed that the frame members 2 and 3 are made of a composite resin in which an elastomer and a polyolefin are mixed. In this case, the elasticity of the frame members 2 and 3 is a combination of the elasticity of the elastomer and the elasticity of the polyolefin, but the elasticity of the polyolefin is much smaller than the elasticity of the elastomer and can be ignored. If the elastic limit when the frame members 2 and 3 are made of an elastomer alone is k, and the volume content ratio of the elastomer in the actual frame members 2 and 3 is 100 * J (%), the frame members 2 and 3 The elastic limit is represented by k * J. Therefore, the lower limit of the parameter J that specifies the volume content ratio of the elastomer can be defined by the following equation (6).
J> [{1 + W ² / ((L ² / (4h−t + d)) (L ² / (4h−t−d)))}} ^1/2 −1] / k
(6)

On the other hand, the water vapor permeability Q of the frame members 2 and 3 is a combination of the water vapor permeability of the elastomer and the water vapor permeability of the polyolefin. When the water vapor permeability per unit volume of the elastomer is Q1, and the water vapor permeability per unit volume of the polyolefin is Q2,
Q = J * Q1 + (1-J) * Q2
It becomes.

In order to use a resin containing an elastomer having a low water vapor permeability as a material for the frame members 2 and 3, and to suppress a decrease in water vapor permeability, the width of the seal part is multiplied by m, and the thickness of the seal part is increased. 1 / n is sufficient (m and n are positive real numbers).
Q = m * n * Q2
m * n * Q2 = J * Q1 + (1-J) * Q2
J = (m * n-1) / {(Q1 / Q2) -1} (7)

  If the above expression (7) is larger than 1, the frame members 2 and 3 can be made of substantially only an elastomer. However, since the frame members 2 and 3 are made of an elastomer alone, there are large design restrictions such as dimensions, which cannot be easily adopted. Therefore, it is indispensable to use a composite resin as a material for the frame members 2 and 3 as in the present invention.

  For example, polypropylene is a typical example of a polyolefin resin that satisfies various requirements such as low cost, easy availability, low water vapor permeability, and easy processing. When polypropylene is used as the material of the frame members 2 and 3 of the paper-type lithium primary battery for IC card 1A defined by ISO or JIS, the thickness of the seal part 11 described in FIG. 2 is 100 μm to 500 μm, and the seal part 11 It is reasonable to set the width of about 2 mm.

  On the other hand, one of the elastomers having the lowest water vapor permeability among readily available elastomers is a butadiene-based elastomer. However, even a butadiene-based elastomer has a water vapor permeability of 10 times or more compared to polypropylene. Further, considering that it is built in an IC card whose short side is defined to be about 54 mm, the upper limit of the width of the seal portion 11 (see FIG. 2) of the lithium primary battery 1A is about 6 mm. Further, in the lithium primary battery 1A according to the present invention, since the current collectors 6 and 7 are made of metal foil, the thickness of the seal portion 11 is taken into consideration in terms of preventing short circuit due to processing burr and ease of forming the seal portion 11. The practical lower limit is about 30 μm. Considering these restrictions comprehensively, it is desirable to limit the upper limit of the volume content of the elastomer to 100 * 8/9 (%).

The perspective view of the lithium primary battery concerning this invention. AA sectional drawing in FIG. The elements on larger scale of FIG. The conceptual diagram of the bending test imposed on an IC card. The elements on larger scale of FIG.

Claims (4)

A separator (9);
A positive electrode active material layer (4) disposed on one surface side of the separator (9);
A negative electrode active material layer (5) containing lithium disposed on the other surface side of the separator (9);
A sheet-like frame member (2, 3) surrounding the separator (9), the positive electrode active material layer (4) and the negative electrode active material layer (5);
A positive electrode current collector that is bonded to the frame member (2, 3) so as to block one opening of the frame member (2, 3) and holds the positive electrode active material layer (4) between the separator (9). Electric body (6),
A negative electrode collector that is bonded to the frame member (2, 3) so as to close the other opening of the frame member (2, 3) and holds the negative electrode active material layer (5) between the separator (9). Electric body (7),
The lithium primary battery (1A), wherein the frame member (2, 3) is made of a material having rubber elasticity.   2. The lithium primary battery (1 </ b> A) according to claim 1, wherein the material having rubber elasticity is substantially a composite resin composed of an elastomer and a resin having a higher moisture barrier property than the elastomer. An active material filling chamber (10) is formed between the positive electrode current collector (6) and the negative electrode current collector (7), and the separator (9) and the positive electrode active material are placed in the active material filling chamber (10). By accommodating the material layer (4) and the negative electrode active material layer (5), a battery body (14) is formed with the positive electrode current collector (6) and the negative electrode current collector (7) as exterior materials. And
An outer peripheral portion of the positive electrode current collector (6) is fixed to one surface side of the frame member (2, 3) with an adhesive (12), and an outer periphery of the negative electrode current collector (7) is fixed to the other surface side. A seal portion (11) in which the positive electrode current collector (6) and the negative electrode current collector (7) are arranged above and below the frame member (2, 3) by fixing the portion with an adhesive (13). The lithium primary battery (1A) according to claim 1 or 2, wherein is formed. The lithium primary battery (1A) is a rectangular paper-type lithium primary battery (1A) in a plan view, and has a dimension that can be incorporated in an IC card defined in JIS X6301.
The length of the frame member (2, 3) parallel to the long side direction or the short side direction of the lithium primary battery (1A) is W (mm), and the thickness of the frame member (2, 3) is d (mm). ), Where the elastic limit of the composite resin material constituting the frame member (2, 3) is k, and the volume content of the elastomer contained in the composite resin material is 100 * J (%), the following inequality is The lithium primary battery (1A) according to claim 2, which is satisfactory.
J> [{1 + W ² / ((L ² / (4h−t + d)) (L ² / (4h−t−d)))}} ^1/2 −1] / k
Where “k” is the elastic limit of the elastomer,
“L” is the length of the short side of the IC card specified in JIS X6301
“H” is the amount of bending in the short side direction of the IC card under the test conditions defined in JIS X6321;
“T” is the thickness of the IC card.

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