JP2004039271A - Sealing structure of battery encapsulating case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of battery performance caused by wrinkles by containing occurrence of the wrinkles of the encapsulating case housing the generating element. <P>SOLUTION: A recessed part 20 nearly similar to the outside shape of the generating element 11 is formed on one hand of a laminate film 12 covering the both faces of a rectangular generating element 11, and the generating element 11 is housed in this recessed part 20. When the mutually opposing faces at the periphery of the laminate film are jointed and sealed, insulating spacers 30, 30-for filling the spaces between the corner parts C1a, C2a, C3a, C4a of the generating element 11 opposed to these corner parts are arranged inside the corner parts C1, C2, C3, C4 of the recessed part 20. Thereby, when the laminate films are sealed in a reduced pressure state, the shape of the recessed part 20 is maintained, and occurrence of the wrinkles at the corner parts C1, C2, C3, C4 of the laminate film 12 is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sealing structure for a battery outer case, in which a laminate film is used for the exterior of a power generation element of a battery, and its peripheral edge is joined and sealed by heat welding or the like.
[0002]
[Prior art]
In recent years, air pollution by automobile exhaust gas has become a global problem, and electric cars powered by electricity and hybrid cars that run with a combination of an engine and a motor have attracted attention and are installed in these. The development of a high-output type battery having a high energy density and a high output density occupies an important industrial position.
[0003]
Such a high-power battery is, for example, a lithium-ion battery. In this case, a cylindrical battery wound with a separator interposed between a positive electrode plate and a negative electrode plate, or a flat positive electrode plate and a negative electrode plate, Are stacked with a separator interposed therebetween.
[0004]
In the latter type, the flat and rectangular power generating elements are sandwiched on both sides by a pair of laminated films, and their peripheral edges are joined by heat welding to seal the electrolyte together with the power generating elements. In this case, for example, as disclosed in Japanese Patent Application Laid-Open No. 2000-200555, a concave portion for accommodating a power generating element is formed in one laminated film, and the power generating element is stored in the concave portion together with the electrolytic solution, and the other laminated film is formed. After that, the peripheral edges are heat-welded to form an exterior case.
[0005]
[Problems to be solved by the invention]
By the way, when the power generation element is sealed with a pair of laminate films, the separator between the positive electrode plate and the negative electrode plate is efficiently impregnated with the electrolytic solution, and in order to suppress a volume change due to swelling of the power generation element, The periphery of the laminate film is joined while the inside of the outer case is decompressed.
[0006]
However, in this case, the laminated film hardly adheres particularly to the portion corresponding to the corner of the power generating element, and wrinkles are generated in the laminated film corresponding to the corner. This wrinkle generation is necessary because it is necessary to have an extra space volume between the laminate film and the power generation element in anticipation of gas generation due to decomposition of the electrolyte solution and gas generation due to chemical change of moisture entering the inside. When the pressure is reduced, the slack of the surplus portion gathers at the corner, and wrinkles are likely to be generated at the corner.
[0007]
When wrinkles occur in the laminate film in this manner, there is a possibility that a crack is caused in the aluminum foil layer inside the laminate film to cause early deterioration of battery performance.
[0008]
Therefore, an object of the present invention is to prevent the deterioration of battery performance due to wrinkles by suppressing the occurrence of wrinkles in an outer case that houses a power generating element.
[0009]
[Means for Solving the Problems]
The sealing structure of the battery outer case of the present invention includes a laminate film having a metal layer and a resin layer covering both surfaces of a polygonal power generation element in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, and the laminate film A concave portion substantially similar to the outer shape of the power generating element is formed on at least one surface of the laminate film, and the opposing surfaces of the peripheral edge of the laminate film are joined and sealed while accommodating the power generating element in the concave portion. In the sealed structure of the battery outer case, a spacer is provided inside a corner of the recess to fill a space between the corner of the power generating element and the corner of the recess facing the corner of the recess.
[0010]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the sealing structure of the battery exterior case of this invention, a spacer is arrange | positioned inside the corner part of the recessed part of the laminated film which accommodates a power generation element, and the space between the corner part of the power generation element facing the corner part of a recessed part Since the portion is filled, the spacer can maintain the shape of the concave portion even when a surplus space volume is provided between the laminate film and the power generation element and the laminate films are sealed under reduced pressure.
[0011]
For this reason, it is possible to prevent or effectively suppress the occurrence of wrinkles in the laminate film, and particularly to suppress the occurrence of wrinkles concentrated on corners, thereby preventing damage to the metal foil layer in the laminate film, Battery performance can be prevented from deteriorating.
[0012]
In addition, since the wrinkles of the laminate film can be suppressed as described above, the quality of each battery can be stabilized.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0014]
1 to 5 show one embodiment of a battery outer case sealing structure according to the present invention. 1 is a plan view of the battery, FIG. 2 is an enlarged sectional view taken along line AA in FIG. 1, FIG. 3 is an exploded perspective view showing a state in which a power generating element is assembled into a concave portion of a laminate film, and FIG. FIG. 5 (a) is an upper perspective view of the spacer, and FIG. 5 (b) is a lower perspective view of the spacer.
[0015]
The battery 10 to which the sealed structure of the battery outer case of the present embodiment is applied has a laminated electrode 11 as a power generating element disposed between central portions of a pair of laminated films 12 and 13 as shown in FIGS. The pair of laminated films 12 and 13 cover the laminated electrode 11 on both sides (in the drawing, front and back directions).
[0016]
As shown in FIG. 2, the laminated electrode 11 is configured by sequentially laminating a plurality of positive plates 11A, 11A,... And negative plates 11B, 11B, respectively, with separators 11C, 11C. Each of the positive plates 11A, 11A,... Is connected to a positive electrode tab 14 through a positive electrode lead 11D, 11D, and each negative electrode plate 11B, 11B is connected to a negative electrode tab 15 through a negative electrode lead 11E, 11E. The positive electrode tab 14 and the negative electrode tab 15 are pulled out from the joint 16 of the laminate films 12 and 13.
[0017]
The laminated electrode 11 formed as a laminated structure has a flat rectangular shape with a predetermined thickness, and is housed together with an electrolytic solution in a concave portion 20 formed in one laminated film 12 as shown in FIG. The outer case 17 is formed by disposing the other laminated film 13 so as to cover the concave portion 20 and heat-sealing the peripheral edges of both the laminated films 12 and 13 under reduced pressure conditions to seal them. .
[0018]
FIG. 3 shows one laminate film 12 shown in FIG. 2 upside down, and the battery 10 is assembled in this upside down state.
[0019]
The battery 10 thus configured is, for example, a lithium ion secondary battery. In this case, as the positive electrode active material of the positive electrode forming the positive electrode plates 11A, 11A,. Specifically, the general formula LiNi _1-x MxO ₂ (where 0.01 ≦ x ≦ 0.5, and M is Fe, Co, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V , Ti, Mg, Ca, and Sr).
[0020]
The positive electrode can also contain a positive electrode active material other than the lithium nickel composite oxide. As the positive electrode active material other than the lithium nickel composite oxide, for example, a general formula LiyMn _2-z M′zO ₄ (provided that 0.9 ≦ y ≦ 1.2, 0.01 ≦ z ≦ 0.5, and M 'Is at least one of Fe, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti, Mg, Ca, and Sr.) Things. Also, a general formula LiCo _1-x MxO ₂ (where 0.01 ≦ x ≦ 0.5, and M is Fe, Ni, Mn, Cu, Zn, Al, Sn, B, Ga, Cr, V, Ti , Mg, Ca, and Sr) may be contained.
[0021]
Lithium nickel composite oxide, lithium manganese composite oxide and lithium cobalt composite oxide, for example, a carbonate such as lithium, nickel, manganese, and cobalt are mixed according to the composition, and the mixture is heated to 600 ° C. to 1000 ° C. in an oxygen-containing atmosphere. It is obtained by firing in a temperature range. The starting materials are not limited to carbonates, and can be synthesized from hydroxides, oxides, nitrates, organic acid salts, and the like.
[0022]
The average particle size of the positive electrode active material such as a lithium nickel composite oxide and a lithium manganese composite oxide is preferably 30 μm or less.
[0023]
As the negative electrode active material forming the negative electrode plate 11B, 11B, a ... a specific surface area to use a 0.05 m ² / g or more, a range of ^2m 2 / g. By setting the content in this range, formation of SEI (Solid Electrolyte Interface) on the surface of the negative electrode can be sufficiently suppressed.
[0024]
When the specific surface area of the negative electrode active material is less than 0.05 m ² / g, the place where lithium can enter and exit is too small, so that the lithium doped in the negative electrode active material during charging is discharged from the negative electrode active material during discharging. It is not sufficiently undoped, and the charge / discharge efficiency decreases. On the other hand, when the specific surface area of the negative electrode active material exceeds 2 m ² / g, formation of SEI on the negative electrode surface cannot be controlled.
[0025]
As the negative electrode active material, any material can be used as long as it is capable of doping and undoping lithium with a potential with respect to lithium of 2.0 V or less, and specifically, a non-graphitizable carbon material, Organic polymer made by firing artificial graphite, natural graphite, pyrolytic graphite, coke such as pitch coke, needle coke, petroleum coke, graphite, glassy carbon, phenolic resin and furan resin at appropriate temperature It is possible to use a carbonaceous material such as a compound fired body, carbon fiber, activated carbon, and carbon black.
[0026]
In addition, a metal capable of forming an alloy with lithium and an alloy thereof can also be used. Specifically, lithium is doped with lithium at a relatively low potential such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, and tin oxide. In addition to oxides and nitrides thereof to be dedoped, nitrides thereof, group 3B typical elements, elements such as Si and Sn, or MxSi, MxSn (where M represents one or more metal elements excluding Si or Sn). ) Can be used. Among these, it is particularly preferable to use Si or a Si alloy.
[0027]
Further, as the electrolytic solution, in addition to a liquid prepared by dissolving an electrolyte salt in a non-aqueous solvent, a polymer gel electrolyte in which a solution in which the electrolyte salt is dissolved in a non-aqueous solvent is held in a polymer matrix, Is also good.
[0028]
When a polymer gel electrolyte is used as the non-aqueous electrolyte, a polymer material to be used includes polyvinylidene fluoride, polyacrylonitrile, and the like.
[0029]
As the non-aqueous solvent, any non-aqueous solvent used so far in this type of non-aqueous electrolyte secondary battery can be used, such as propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, and diethyl carbonate. Dimethyl carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like. One of these non-aqueous solvents may be used alone, or two or more of them may be used in combination.
[0030]
In particular, the non-aqueous solvent preferably contains an unsaturated carbonate, and specifically, preferably contains vinylene carbonate, ethyleneethylidene carbonate, ethylene isopropylidene carbonate, propylidene carbonate, and the like. Among them, it is most preferable to contain vinylene carbonate. By containing unsaturated carbonate as the non-aqueous solvent, it is considered that an effect due to the properties of SEI generated in the negative electrode active material (function of the protective film) is obtained, and the overdischarge resistance is further improved.
[0031]
Further, the unsaturated carbonate is preferably contained in the electrolyte at a ratio of 0.05% by weight or more and 5% by weight or less, particularly preferably at a ratio of 0.5% by weight or more and 3% by weight or less. Is most preferred. By setting the content of the unsaturated carbonate in the above range, a non-aqueous secondary battery having a high initial discharge capacity and a high energy density can be obtained.
[0032]
The electrolyte salt is not particularly limited as long as it is a lithium salt exhibiting ion conductivity. For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, and the like can be used. One of these electrolyte salts may be used alone, or two or more thereof may be used in combination.
[0033]
By the way, the concave portion 20 formed in the one laminated film 12 is formed in a rectangular shape substantially similar to the outer shape of the laminated electrode 11, and the opening area of the concave portion 20 is formed slightly larger than the outer shape of the laminated electrode 11. Thus, an appropriate gap is provided between the inner side surface 20a of the concave portion 20 and the outer peripheral edge of the laminated electrode 11.
[0034]
The depth D of the concave portion 20 (see FIG. 3) is substantially equal to the thickness of the laminated electrode 11, and the concave portion 20 has corners C1a, C2a, C3a, and C4a of the rectangular laminated electrode 11. Are provided. Four corners C1, C2, C3, and C4 corresponding to are provided.
[0035]
As shown in FIG. 4, the laminated films 12 and 13 are formed of a nylon layer α as a resin layer, an adhesive layer β, an aluminum foil layer γ as a metal layer, and PE (Polyethylene) or PP (polypropylene) layer δ.
[0036]
Here, in the present embodiment, inside the corners C1, C2, C3, and C4 of the recess 20, the corners C1a, C2a, and C3a of the laminated electrode 11 facing the corners C1, C2, C3, and C4. , C4a, and insulating spacers 30, 30,...
[0037]
The spacers 30 are formed of a synthetic resin, and as shown in FIGS. 5A and 5B, the outer faces opposing the inner side faces 20a, 20a on both sides of the corners C1, C2, C3, C4 inside the recess 20 respectively. It is provided with side surfaces 31 and 32 and an installation surface 33 facing the bottom surface 20 b inside the concave portion 20, respectively, and is generally formed in a substantially triangular prism shape.
[0038]
Then, as shown by a two-dot chain line in FIG. 5B, the corners C1, C2, C3 of the outer surfaces 31, 32 start from the ridge line R1 where the outer surfaces 31, 32 intersect with the installation surface 33. The curved surface S is formed over the ridge line R2 corresponding to C4. That is, the edges of the outer surfaces 31 and 32 on the side of the bottom surface 20b in the recess 20 are formed in a convex curved shape.
[0039]
In this embodiment, as shown in FIG. 5A, the peripheral side surface of the spacer 30 having a triangular shape in plan view includes the outer side surfaces 31 and 32 and a slope 34 between the outer side surfaces 31 and 32. However, the slope 34 side is cut into a triangular shape (cut portion 36) except for a mounting portion 35 on which the corners C1a, C2a, C3a, and C4a of the laminated electrode 11 are mounted.
[0040]
Thereby, the spacer 30 forms the L-shape along the outer surfaces 31 and 32 by forming the cut-out portion 36, and the placing portion 35 is provided on the bottom side of the L-shaped spacer 30. Shape.
[0041]
Therefore, when assembling the battery 10 of the present embodiment, as shown in FIG. 3, the outer surfaces 31 and 32 are attached to the four corners C1, C2, C3, and C4 of the concave portion 20 formed in the one laminated film 12. Are arranged along the inner side surface 20 a of the recess 20, and the spacer 30 is arranged such that the installation surface 33 is installed on the bottom surface 20 b of the recess 20.
[0042]
Then, while aligning the corners C1a, C2a, C3a, and C4a of the laminated electrode 11 with the cut portion 36 of each spacer 30, the four corners of the laminated electrode 11 are placed on the placement portion 35 of the cut portion 36, and the concave portion 20 is formed. Housed inside. In this state, the concave portion 20 is covered with the other laminated film 13, and the peripheral portions of both laminated films 12, 13 are thermally welded under reduced pressure. The injection of the electrolytic solution is performed, for example, after performing heat welding while leaving only a part of the peripheral edge of the laminated films 12 and 13, and then through an opening of this part.
[0043]
With the above configuration, in the sealed structure of the battery outer case 17 of the present embodiment, when the laminated electrode 11 is stored in the concave portion 20 of the laminate film 12, the corners C1, C2, C3, C4 of the concave portion 20 are stored. The spaces between the corners C1a, C2a, C3a, and C4a of the laminated electrode 11 can be filled by the spacers 30, 30,.
[0044]
For this reason, when providing an extra space volume between the laminated films 12 and 13 and the laminated electrode 11 to seal the laminated films 12 and 13 under reduced pressure, the spacer 30 is supported by the laminated electrode 11. In order to maintain the distance between the spacers 30 in the retracted state, it is possible to prevent the surface of the recess 20 from shrinking and to maintain the shape of the recess 20.
[0045]
For this reason, generation of wrinkles in the laminated film 12 can be prevented or effectively suppressed, and in particular, concentration of wrinkles on the corners of the concave portion 20 can be suppressed, so that the aluminum foil layer γ of the laminated film 12 (FIG. 4) ) Can be prevented from being damaged and battery performance can be prevented from deteriorating.
[0046]
In addition, since the wrinkles of the laminate film 12 can be suppressed as described above, the quality of each battery can be stabilized. In particular, the shape and size of the spacer 30 and the location where the spacer 30 is installed with the laminated electrode 11 are defined in advance. This can reduce variations in the shape of the battery 10 (including the wrinkles of the laminate film 12) after sealing under reduced pressure and variations in battery reliability.
[0047]
By the way, the spacer 30 of the present embodiment has a curved surface S from the ridge line R1 where the outer surfaces 31 and 32 intersect with the installation surface 33 to the ridge line R2 corresponding to the corners C1, C2, C3 and C4 of the recess 20. Is formed, when the corners C1, C2, C3, and C4 of the concave portion 20 are contracted by the reduced pressure, the laminated film 12 of the contracted portion is smoothly deformed along the curved surface S to be extremely bent or deep. The generation of wrinkles can be reliably prevented.
[0048]
Therefore, by providing the above-described curved surface S, the stress acting on the aluminum foil layer γ of the laminate film 12 is relaxed, the damage such as crack generation is reliably prevented, and the long-term reliability of the battery can be further improved. .
[0049]
Further, by providing the mounting portion 35 on the spacer 30, the work of setting the laminated electrode 11 in the concave portion 20 becomes easy.
[0050]
FIG. 6 shows a spacer 30a according to another embodiment of the present invention.
[0051]
The spacer 30 described in the above embodiment has a cutout portion 36 except for the mounting portion 35 as shown in FIGS. 5A and 5B, and is substantially L-shaped. 30a is substantially L-shaped by removing the mounting portion 35 from the spacer 30 shown in FIG. 5 and leaving the outer surfaces 31 and 32. In this case, the laminated electrode 11 is directly mounted on the bottom surface 20b of the recess 20.
[0052]
By the way, although the sealing structure of the battery outer case of the present invention has been described with reference to the above embodiments, various embodiments can be adopted without departing from the scope of the present invention.
[0053]
For example, since the laminated electrode 11 has a rectangular shape, the concave portion 20 has a rectangular shape with four corners. However, when the laminated electrode 11 has another polygonal shape, the concave portion 20 is substantially similar to the laminated electrode 11. And the number of spacers may be increased or decreased according to the polygonal shape.
[0054]
Regarding the shape of the spacer, the triangular prism may be simply formed without providing the deleted portion 36 on the inclined surface 34, and the corners C1, C2, C3, and C4 of the laminated electrode 11 may be brought into contact with the inclined surface 34 having the triangular prism shape. Good.
[0055]
Further, the recess 20 is formed in one of the laminate films 12, 13 sandwiching both sides of the laminated electrode 11. However, even if the recess 20 is formed in both the laminate films 12, 13, the present invention is not limited to this. The invention can be applied. In this case, spacers 30 or 30a are arranged at each corner of both recesses 20.
[0056]
Furthermore, the present invention is not limited to the lithium ion secondary battery as the battery 10 but may be applied to other batteries having the same configuration.
[Brief description of the drawings]
FIG. 1 is a plan view of a battery according to an embodiment of the present invention.
FIG. 2 is an enlarged sectional view taken along line AA in FIG.
FIG. 3 is an exploded perspective view showing a state in which a power generating element according to one embodiment of the present invention is assembled into a concave portion of a laminate film.
FIG. 4 is an enlarged sectional view of a portion B in FIG.
5A is an upper perspective view of a spacer, and FIG. 5B is a lower perspective view of the spacer.
6A and 6B show another embodiment of the present invention, wherein FIG. 6A is an upper perspective view of a spacer, and FIG. 6B is a lower perspective view of the spacer.
[Explanation of symbols]
10 Battery 11 Stacked electrode (power generation element)
11A Positive electrode plate 11B Negative electrode plate 11C Separator 12, 13 Laminate film 17 Outer case 20 Recess 20a Inner side surface 20b on both sides of corner portion Bottom surface 30, 30a of spacer 31, 32 Outer side surface 35 Mounting portion C1, C2, C3, C4 Recess Corners C1a, C2a, C3a, C4a of the power generating element S curved surface α nylon layer (resin layer)
γ Aluminum foil layer (metal layer)
δ PE / PP layer (resin layer)

Claims (3)

A laminate film having a metal layer and a resin layer covering both surfaces of a polygonal power generating element in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, and at least one surface of the laminated film outside the power generating element A sealing structure of a battery outer case in which a concave portion substantially similar in shape is formed, and the opposing surfaces of the peripheral edge of the laminate film are joined and sealed while accommodating the power generation element in the concave portion, A sealing structure for a battery outer case, wherein a spacer that fills a space between a corner of the power generation element and a corner of the power generation element facing the corner of the recess is arranged inside the corner. 2. The battery according to claim 1, wherein the spacer includes an outer surface facing the inner surface on both sides of the corner in the recess, and an edge of the outer surface on the bottom surface side of the recess has a convex curved shape. Sealing structure of the outer case. The sealing structure for a battery outer case according to claim 1, wherein the spacer includes a mounting portion for mounting the power generating element opposite to a bottom surface of the concave portion.

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