WO2017158986A1

WO2017158986A1 - Battery cell

Info

Publication number: WO2017158986A1
Application number: PCT/JP2016/088762
Authority: WO
Inventors: 健人高橋
Original assignee: Ｎｅｃエナジーデバイス株式会社
Priority date: 2016-03-15
Filing date: 2016-12-26
Publication date: 2017-09-21
Also published as: JPWO2017158986A1

Abstract

The purpose of the present invention is to provide a battery cell having long-term reliability and high energy density per volume using a film-like exterior material for the exterior body. The battery cell 1 according to the present invention has a battery element 6 housed in the film-like exterior material 4 comprising a laminated film having at least a barrier layer 12 and a thermally-welded resin layer 13. The battery cell 1 is characterized in that: the film-like exterior material 4 includes a seal portion 16 wherein opposing thermally-welded resin layers 13 have been thermally-welded to one another; the seal portion 16 includes, at an end portion on the battery element 6 side, a portion in which the thickness increases in the direction from the battery element 6 side to the outer side of the film-like exterior material 4, and, at an end portion on the outer side of the film-like exterior material 4, a portion in which the thickness increases in the direction from the outer edge to the battery element 6 side; and, except within 0.5 mm of the outer end portion of the film-like exterior material 4, the minimum thickness of the seal portion 16 is 40 or greater if 100 is the thickness of 132 thermally-welded resin layers.

Description

Battery cell

The present invention relates to a battery cell in which a power generation element is housed in a film-shaped exterior material and has high energy density and confidentiality.

Lithium ion batteries with large capacity density and mass density are installed not only for portable devices such as mobile phones and digital cameras, but also for electric bicycles, electric motorcycles, electric cars and the like. With the diversification of battery applications, battery weight reduction and design freedom are required.

As a battery exterior body, a film-like exterior material in which a metal container, aluminum foil, etc. and a synthetic resin film are laminated is used. However, as a battery that satisfies the above requirements, a film-like exterior that is lightweight and has a high degree of freedom in shape. The demand for battery cells using materials is increasing.

The battery cell is hermetically sealed so that a power generation element including a positive electrode and a negative electrode is covered with a film-shaped packaging material, and the positive electrode terminal and the negative electrode terminal are led out of the film-shaped packaging material. Battery film-like packaging material has the role of preventing leakage of electrolyte inside and moisture intrusion into the battery, but this sealing part affects the reliability of the battery. Yes.

For example, in Patent Document 1, by providing a non-welded portion inside the heat-welded portion of the film-shaped exterior material, the occurrence of a notch-like portion due to the protrusion of the resin is prevented, and the peel strength is reduced. It has been proposed to prevent this.

On the other hand, in Patent Document 2, in order to push out the electrolyte attached to the sealing part to the outside of the sealing part, the part where one side used for the injection of the electrolyte corresponds to the inner part of the battery is shorter, and the part corresponding to the outer side of the battery A technique of pressing so that the interval becomes wider has been proposed.

JP 2005-332726 A JP 2010-244930 A

In the structure of Patent Document 1, it is necessary to enlarge the accommodating part by the amount of space divided for the second resin part protruding to the accommodating part side, or to reduce the volume of the power generation element, and lower the energy density. Yes.

Further, in the structure of Patent Document 2, the thickness on the outer side of the heat seal portion is increased, and moisture easily enters from the outside. On the other hand, if the thickness of the heat seal portion outside is reduced to increase the peel strength of the heat seal portion, the thickness of the welded portion on the power generation element side, which is the inside of the heat seal portion, is further reduced, and the resin to the power generation element side is reduced. Protrusion becomes prominent.

The present invention solves the above-described problems, and the battery cell according to the present invention is housed in a film-shaped exterior material made of a laminate film in which the battery element is provided with at least a barrier layer and a resin layer. In the battery cell, the film-shaped packaging material includes a sealing portion that is heat-welded with the resin layers facing each other, and the sealing portion is a film-shaped packaging material from the battery element side at the end on the battery element side. The outer edge of the film-shaped packaging material includes the portion whose thickness increases in the direction from the outer edge to the battery element side, and the outer edge of the film-shaped packaging material is within 0.5 mm. The minimum thickness of the sealing portion to be removed is 40 or more when the thickness of two resin layers is 100.

Here, for example, when sealing the sealing portion by thermal welding, the sealing is performed so that the thickness increases from the battery element side of the sealing portion toward the outer side of the film-shaped exterior material on the battery element side. It stops, and it cut | disconnects so that a sealing part outer side edge part may be crushed in the edge part outside a film-form exterior material.

According to the battery cell of the present invention, on the battery element side of the sealing portion, the resin of the heat-welded resin layer is formed into a film by forming a portion where the sealing thickness increases from the battery element side toward the outer side. In addition to preferentially protruding outside the exterior material, the sealing thickness is as much as the outer edge while removing the resin protrusion outside the film-like exterior material generated during the welding on the outside of the film-like exterior material of the sealing portion. By forming a smaller portion, it is possible to reduce the resin protrusion on the battery element side of the sealing portion and to suppress moisture intrusion from the outside.

Moreover, according to the battery cell which concerns on this invention, it is possible to make a battery element large and to make the shape of a film-shaped exterior material small, since the protrusion part of the resin of the battery element side end of a sealing part becomes small. Therefore, the energy density per volume can be increased, and by suppressing the ingress of moisture from the outside, it is possible to inhibit the invaded moisture from being decomposed and expanded into a gas, thereby preventing the film-like exterior material from cracking.

In addition, according to the battery cell of the present invention, the protruding portion of the resin formed inside the battery can be reduced, and moisture entry from the outside can also be suppressed. As a result, the energy density per volume is high and long-term A battery cell having excellent reliability can be provided.

It is a figure explaining an example of a battery cell, and is a top view. It is a figure explaining the sealing part of a battery cell. It is a figure which illustrates typically an example of the manufacturing method of the battery cell 1 which concerns on embodiment of this invention. It is a figure which illustrates typically an example of the manufacturing method of the battery cell 1 which concerns on other embodiment of this invention. It is a figure which supplements description of an Example. It is a figure which shows the variation of the heating member shape which can be used at the manufacturing process of the battery cell 1 which concerns on embodiment of this invention.

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view illustrating an example of the battery cell 1.

FIG. 2 is a plan view for explaining a battery cell 1 in which a power generation element 6 is housed in a film-shaped exterior member 4 together with an electrolyte (not shown) and the like, and is joined to each of a positive electrode extraction terminal and a negative electrode extraction terminal extracted from the power generation element 6. The positive electrode terminal 2 and the negative electrode terminal 3 are provided.

The positive electrode terminal 2 and the negative electrode terminal 3 are protruded from the film-shaped exterior material 4 and are thermally welded and sealed around the film-shaped exterior material 4.

FIG. 1 shows an example in which the power generation element is stored by two films provided with a storage section for the power generation element, and all the surroundings of both members are sealed. However, the present invention is not limited to this. After storing the power generation element in a storage portion formed by deforming a part of the exterior material 4 by press molding, the other end side of the film-shaped exterior material is bent and overlaid on the storage portion of the power generation element and sealed. The positive electrode terminal and the negative electrode terminal may be taken out.

Further, it is also possible to use a film-shaped exterior material that is sealed after a power generation element is housed in a member processed into a cylindrical shape or an envelope shape.

1 is not limited to the case where the positive electrode terminal 2 and the negative electrode terminal 3 are taken out from the same side as in the example described with reference to FIG. It may be taken out from the side.

In addition, the power generation element is a laminate in which a plurality of positive electrodes, separators, and negative electrodes are sequentially laminated, or a belt-like separator, a belt-like positive electrode, a belt-like negative electrode, and a belt-like separator are sequentially laminated and wound. The wound body etc. which were made can also be used.

FIG. 2 is a diagram schematically showing a cross section taken along the line A-A ′ and the structure around it in the heat-welded portion located at the periphery of the battery cell 1 shown in FIG. 1. FIG. 2A is a schematic diagram showing a sealed state of the battery cell 1 according to the present invention, and FIG. 2B is a schematic diagram showing a sealed state of a conventional general battery cell.

The film-shaped packaging material 4 that houses the battery element 6 includes a surface protective layer 11 that protects the outer surface, a barrier layer 12 such as a metal barrier layer that blocks the permeation of gas, and prevents the electrolyte from penetrating. It is the structure containing the heat welding resin layer 13 which heat-welds.

The surface protective layer 11 may be made of a synthetic resin material that has a ductility that does not break during processing of the film-shaped exterior material 4 and that has a higher melting point or softening point than the heat-welded resin layer 13. Among these, a resin having sufficient ductility during processing and having a high melting point or softening point is preferable. Specific examples thereof include nylon and polyethylene terephthalate, and these may be combined.

As long as the barrier layer 12 has a ductility that prevents gas permeation and does not break during processing, various types of metal or metal oxide deposition layers, metal films, and the like can be used. A superior aluminum or aluminum alloy foil is desirable.

The heat-welded resin layer 13 is corrosion resistant to the electrolytic solution and has excellent adhesive strength at the time of heat-welding. Polyolefin-based synthetic resins such as polypropylene and polyethylene, modified polyolefin resins obtained by modifying these, or a plurality of them Can be used.

Further, the surface protective layer 11, the barrier layer 12, and the heat-welded resin layer 13 are not limited to being composed of only one layer, but may be a laminate of two or more layers. In the case where a plurality of layers are laminated, a plurality of layers having different characteristics may be laminated.

In the sealing portion 16 of the film-shaped exterior material 4, the heat-welded resin layer 13 reaches the melting point, and forms a weld layer 17a. In addition, a resin protrusion 17b that protrudes from the welded layer is formed on the storage portion side of the battery element 6 of the sealing portion 16.

In the battery cell 1 of the present invention, at the end of the battery element 6 side, in order to reduce the resin protrusion 17b, the battery element 1 includes a portion that increases in thickness from the battery element 6 side to the outer side of the film-shaped exterior material 4, In order to suppress the amount of moisture entering from the outer side of the outer packaging material 4 to the battery element 6 side, the outer end portion of the film-like outer packaging material 4 includes a portion where the thickness increases from the outer edge toward the battery element 6.

As a result, on the battery element 6 side, as shown in FIG. 2 (A), as compared to the sealed state shown in FIG. 2 (B), the resin protruding portion 17b is reduced, and the battery is not enlarged. Element 6 can be enlarged. Thereby, the energy density per unit volume of the battery cell 1 can be increased. The broken line shown in FIG. 2 (B) shows the area where the battery element 6 could not be accommodated by the resin protrusion, and the broken line shown in FIG. 2 (A) shows the case where the resin protrusion 17b was present. This is for schematically representing an end portion of the battery element 6.

FIG. 3 is a diagram schematically illustrating an example of the manufacturing method of the battery cell 1 according to the present invention described in FIG. As shown to FIG. 3 (A), it presses with the two heating members 21 from both surfaces of the sealing part 16, and it heats until the welding surface of the heat welding resin layer 13 will be in a molten state. At the time of heating, the heat-welded resin layer 13 in a molten state forms a resin protrusion 17b that protrudes to the storage portion side of the battery element 6 and a resin protrusion 17c that protrudes to the outer end of the film-like exterior material 4. In the present invention, in order to reduce the resin protrusion 17b, the heating member 21 is inclined so that the heating member 21 is sealed thicker on the outer side of the film-shaped exterior material 4 than the battery element 6 side.

Next, after removing the heating member 21, similarly, as shown in FIG. 3B, the region where the heating member 21 is in contact is cooled by two cooling members 22 from both sides. This is to prevent the welded layer 17a from crystallizing. When cooling is not performed or when cooling is too slow, crystallization of the welded layer 17a proceeds and a hard and brittle resin layer is formed, resulting in a decrease in corrosion resistance and insulation.

In the present invention, the resin thickness of the welding layer 17a on the battery element 6 side is reduced. Generally, when the resin thickness of the welding layer 17a is smaller than that when the resin thickness is large, the insulating property tends to be lowered. Therefore, in order to prevent a decrease in insulation, that is, to prevent crystallization of the resin on the battery element 6 side, the cooling member is securely applied to the film at the position corresponding to the thinnest part of the resin layer of the welding layer 17a on the battery element 6 side. It is preferable to contact. When polypropylene is used for the heat-welded resin layer 13, it is preferable to press the cooling member 22 before the temperature at the battery element 6 side end falls below 110 ° C.

Next, as shown in FIG. 3C, each side of the outer periphery of the film-shaped packaging material 4 was thermally welded and sealed except for the side where the electrolytic solution was injected. After injecting the electrolytic solution from the electrolytic solution injection part, the electrolytic solution injection part was thermally welded and sealed in the same manner as other parts. Thereafter, the periphery of each side was cut into a predetermined shape to obtain a battery cell 1.

In the above-described cutting, when the thickness of the two layers other than the welded portion where no heat is applied is 100 in the heat-welded resin layer 13, the portion where the thickness of the welded layer 17a is greater than 95 is removed. Note that it is preferable to keep the original thickness of the heat-welded resin layer 13 other than the portion to be heat-welded because it prevents the electrolytic solution from reaching the barrier layer 12 and causing a short circuit.

As the thickness of the sealing portion 16 increases, moisture easily enters. However, if the thickness of the sealing portion 16 is too small, the insulating property is deteriorated. When the thickness of the two sheets in this part is 100, the thickness of the weld layer 17a is preferably 40 or more and 95 or less over the entire sealing part 16 excluding the outer end part 0.5 mm of the sealing part 16, more preferably Is 45 or more and 90 or less.

On the other hand, the outer edge of the sealing portion 16 may have the conductive barrier layer 12 exposed in the first place, so that insulation is not required and the thickness of the welded layer is smaller from the viewpoint of preventing moisture from entering. Is preferred. When the thickness of the two layers in the weld layer 13 other than the weld part where heat is not applied is 100, the thickness is 0 or more and 95 or less within 0.5 mm from the outer edge of the sealing part 16 to the battery element 6 side. Is preferred.

In order to make the end thin by cutting, a film-shaped outer packaging material 4 is prepared by preparing a cutting blade in which the angle of the cutting edge of the cutting blade, the angle of the belly of the cutting blade thicker than the cutting edge, and the frictional force are adjusted. It is possible to cut while reducing the thickness of the sealing outer edge.

The thickness of the heat-welded resin layer 13 is preferably 60 μm or more from the viewpoint of maintaining insulation, and preferably 200 μm or less from the viewpoint of sealing properties.

In addition, when the length of the sealing part 16 (or the width of the sealing part 16) from the battery element 6 side to the outer edge of the film-shaped exterior material 4 is short, the sealing performance between the battery element 6 and the outside is deteriorated. For this reason, the length of the sealing part 16 (or the width of the sealing part 16) is preferably at least 2 mm. From the viewpoint of airtightness, the longer the length of the sealing portion 16 (or the width of the sealing portion 16), the better. However, since the outer dimensions of the battery cell 1 increase accordingly, the viewpoint of energy efficiency per volume. It is not preferable.

Further, in order to increase the energy efficiency per volume by reducing the outer diameter dimension, when the sealing portion 16 of the film-shaped outer packaging material 4 is bent or bent so as to follow the battery element 6, The thickness is reduced, and the corresponding resin jumps out to the outer end portion of the film-shaped exterior material 4, that is, the outer diameter is increased. Therefore, it is preferable to perform the cutting after bending.

When heat sealing (heat welding) the film-shaped exterior material 4, for example, when a modified polyolefin is used for the heat welding resin layer 13, the melting point is about 120 to 160 ° C. Is preferably 180 to 220 ° C. On the other hand, for example, when a polyester film is used for the surface protective layer 11, the heating temperature at the time of sealing is preferably 200 ° C. or lower in order not to damage the surface protective layer 11.

FIG. 4 is a diagram for explaining another embodiment of the present invention. FIG. 2 is a view in which the battery cell shown in FIG. 1 of the present invention is partially cut away at A-A ′. It heats until it presses by the two heating members 23 from both surfaces of the sealing part 16 and the welding surface of the heat welding resin layer 13 will be in a molten state.

The heating member 23 is provided with an inclination so that the outer side of the film-shaped outer packaging material 4 is thicker than the battery element 6 side like the heating member 21, but unlike the heating member 21, the outer side of the film-shaped outer packaging material 4 is provided. A second slope is also provided so that the vicinity of the end is narrowly sealed. The battery of this embodiment can also obtain the product similar to the process of FIG. 3 without a cutting process by welding the outer edge part of the film film-shaped exterior material 4, ie, not providing the disposal part 25.

In addition, although this invention may be applied to any sealing part 16 of the periphery of the battery cell 1 shown in FIG. 1, the width | variety of the sealing part 16 of the edge | side where the positive electrode terminal 2 or the negative electrode terminal 3 was taken out Even if it is made smaller, the outer dimensions are not affected, and the sealing structure of the terminal portion is complicated.

Further, the shapes of the

heating members

21 and 23 that can be used when the battery cell 1 is manufactured in the present invention are not limited to those shown in FIGS. 3 and 4. FIG. 6 is a diagram showing variations of the heating member that can be used in the manufacturing process of the battery cell 1 according to the present invention.

Hereinafter, examples and comparative examples of the present invention will be described.
Example 1
(Preparation of positive electrode)
A positive electrode slurry was prepared by kneading lithium manganate (LiMn ₂ O ₄ ) powder, carbon black, and polyvinylidene fluoride together with NMP (N-methyl-pyrrolidone). The obtained positive electrode slurry was applied and dried on both surfaces of an aluminum foil having a thickness of 20 μm, and then the positive electrode surface was pressed with a roll to form a positive electrode active material layer on the aluminum foil.

Next, a rectangular positive electrode active material layer forming portion having a length of 105 mm × width 55 mm including a portion where the positive electrode active material layer is formed, and a positive electrode tab having a length of 15 mm × width 10 mm including a portion where the positive electrode active material layer is not formed The aluminum foil containing the part in which the positive electrode active material layer was formed was cut so that the positive electrode was produced.
(Preparation of negative electrode)
Graphite, carbon black, and polyvinylidene fluoride were kneaded with NMP to prepare a negative electrode slurry. The obtained negative electrode slurry was applied to and dried on both sides of a copper foil having a thickness of 10 μm, and then the negative electrode surface was pressed with a roll to form a negative electrode active material layer on the copper foil.

Next, similarly to the positive electrode, a negative electrode in which a negative electrode active material layer forming portion having a length of 109 mm and a width of 59 mm and a negative electrode tab having a length of 12 mm and a width of 10 mm were integrally formed was produced.
(Production of power generation elements)
The prepared positive electrode and negative electrode were laminated by alternately stacking 15 positive electrodes and 16 negative electrodes through a polypropylene separator having a length of 111 mm, a width of 59 mm, and a thickness of 25 μm so that the outermost layer becomes a negative electrode. A power generation element was produced.

A synthetic resin layer integrated with the film-shaped exterior material at the time of sealing was formed on a part of an aluminum foil having a length of 30 mm, a width of 10 mm, and a thickness of 200 μm as a positive electrode lead terminal for leading out of the film-shaped exterior material 4. It joined to the positive electrode tab of the positive electrode which laminated | stacked the aluminum lead terminal.

Similarly, a negative electrode tab in which a copper lead terminal in which a synthetic resin layer integrated with a film-like exterior material is formed on a copper foil having a length of 30 mm, a width of 10 mm, and a thickness of 200 μm as a negative electrode lead terminal is formed as a negative electrode lead terminal. Joined.
(Production of battery cells)
25 μm thick nylon as the surface protective layer 11, 40 μm aluminum foil as the barrier layer 12, and polypropylene having a random-block-random three-layer structure with a melting point of 145 ° C. and a softening point of 120 ° C. as a heat-welded resin layer 13 Two film-shaped exterior materials having a length of 180 mm and a thickness of 100 mm and a thickness of 115 μm, which are laminated in order, are prepared. Formed.

The power generation element 6 is housed in the produced recess, and the positive electrode lead terminal and the negative electrode lead terminal are led out of the film-shaped exterior material 4 from one side, and the side where the lead terminal is taken out and the two sides that are in contact with the side where the lead terminal is taken out Sealed to form a positive electrode terminal and a negative electrode terminal.

Next, using the side opposite to the side from which both electrode terminals were taken out as the injection side, an electrolyte containing LiPF ₆ as a lithium salt was injected into a mixed solvent composed of ethylene carbonate and diethyl carbonate, and finally the injection side Was sealed.

The terminal side was sealed by sandwiching two heating members having a width of 5 mm heated to 180 ° C. for 6 seconds so that the interval was 0.2 mm.

Thereafter, two cooling members having a width of 5.6 mm at 25 ° C. were sandwiched and cooled for 1.5 seconds so that the interval was 0.2 mm.

The side was sealed using a heating member having a shape as shown in FIG. d1 was 0.01 mm and d2 was 0.30 mm. As shown in FIG. 5 (B), the two heating members having a width of 7.5 mm heated to 180 ° C. were sandwiched and heated for 5 seconds so that the distance d3 was 0.2 mm, and sealed. Thereafter, two cooling bars having the same shape as the heating member and having a room temperature width of 7.5 mm were sandwiched and cooled for 3 seconds. The electrolyte solution was injected into the battery cell before injection prepared as described above from the injection side.

Thereafter, the injection side was heated to 200 ° C. and sandwiched by heating for 5 seconds so that the distance d3 between two heating bars (heating members) having a width of 7.5 mm was 0.2 mm. Thereafter, two cooling bars with a width of 7.5 mm at room temperature were sandwiched and cooled for 3 seconds to obtain a battery cell. A cross-sectional view of the sealing portion 16 of this battery cell is shown in FIG. FIG. 5C shows another form of heating member applied to the sealing portion 16 of the battery cell. The interval d4 was set to 0.2 mm.

Example 2
A battery cell was obtained in the same manner as in Example 1 except that the distance d3 between the heating bars was 0.21 mm during the thermal welding of the side and liquid injection sides.

Example 3
A battery cell was obtained in the same manner as in Example 1 except that the distance d3 between the heating bars was 0.22 mm during the thermal welding of the side and liquid injection sides.

Example 4
A battery cell was obtained in the same manner as in Example 1 except that the distance d3 between the heating bars was 0.17 mm during the thermal welding of the side and liquid injection sides.

Example 5
At the time of thermal welding of the side and the liquid injection side, welding was performed using the heating member of FIG. 3, and the other steps were performed in the same manner as in Example 1 by cutting the outer edge 1 mm of the battery cell sealing portion 16, thereby sealing. A battery cell having a thin outer edge of the stopper 16 was obtained.

Comparative Example 1
At the time of thermal welding of the side and liquid injection sides, the distance d3 between the heating bars was set to 0.16 mm, and the other steps were performed in the same manner as in Example 1 to obtain a battery cell. A cross-sectional view of the sealing portion 16 of this battery cell is shown in FIG.

Comparative Example 2
When heat-welding the side and liquid injection side, use the heating bar shape shown in Fig. 5 (C), set the heating bar interval d4 to 0.2 mm, and perform the other steps in the same manner as in Example 1. I got a cell.

Comparative Example 3
A battery cell was obtained in the same manner as in Example 1 except that the distance d3 between the heating bars was 0.23 mm during the thermal welding of the side and liquid injection sides. A cross-sectional view of the sealing portion 16 of this battery cell is shown in FIG.
However, compared to Example 1, the resin thickness is thicker. Details will be described later.

Table 1 shows the results of measuring the minimum sealing thickness, the maximum sealing thickness, the protrusion size, the peel strength, and the insulation resistance of Examples 1 to 5 and Comparative Example. The measurement of the minimum sealing thickness is based on the minimum thickness at a position where the distance from the power generation element side in the width direction of the sealing portion 16 is 2 mm, where moisture intrusion and resin protrusion are particularly likely to affect the element side. It is measured.

The minimum sealing thickness and the maximum sealing thickness in Table 1 are the thicknesses of two heat-welded resin layers, and the numbers in parentheses are the thicknesses of two heat-welded resin layers 13 in a portion not thermally welded. Represents the ratio to. In the part not heat-welded, it is necessary to prevent the electrolytic solution, the barrier layer 12 of the film-shaped exterior material 4 and the electrolytic solution from coming into contact with each other. Yes.

With respect to the size of the protruding portion 17b, in Example 4, since the pressure and heating were excessively performed until the thickness of the heat-welded resin layer 13 became too small, the protruding portion 17b was larger than in Examples 1 to 3, but the power generation It did not affect the containment of the elements. Note that the size L1 of the protrusion 17b in Examples 1 to 3, and 5 was 1.2 mm or less, and in Example 4, the maximum was 1.5 mm.

In Comparative Example 1, due to being too thinly sealed, L1 was increased until the protruding portion 17b exceeded 1.5 mm, and the battery element 6 having the same shape as that of Example 1 could not be accommodated. In Comparative Example 2, since the shape of the overheating bar is flat, it is not possible to suppress the resin from protruding to the battery element 6 side, and the size of the protruding portion 17b is increased, so that the battery element 6 having the same shape as that of Example 1 is used. Could not be accommodated.

Regarding the peel strength, it was found that the adhesiveness between the heat-welded resin layers 13 tends to decrease when the sealing thickness is large. However, sufficient peel strength can be obtained by forming a portion that makes the sealing thickness 90 μm or less. Could get. In Comparative Example 3, the minimum thickness was large, that is, the sealing was performed in a state where the resin was not sufficiently adhered, and thus the peel strength was low. In addition, Example 3 was 6 N / mm, Example 2 was 4 N / mm, and Comparative Example 3 was less than 4 N / mm. In other examples, a peel strength of 7 N / mm or more could be obtained.

According to the battery cell 1 according to the present invention as described above, on the battery element 6 side of the sealing portion 16, heat is generated by forming a portion where the sealing thickness increases from the battery element 6 side toward the outer side. Not only the resin of the welded resin layer 13 protrudes preferentially to the outside of the film-shaped exterior material 4 but also the outside of the film-shaped exterior material 4 of the sealing portion 16 on the outside of the film-shaped exterior material 4 generated during the welding. By forming the portion where the sealing thickness becomes smaller toward the outer edge while removing the resin protruding portion, the resin protruding portion on the battery element 6 side of the sealing portion 16 can be reduced and moisture intrusion from the outside can be suppressed. .

Moreover, according to the battery cell 1 which concerns on this invention, since the protrusion part of the resin of the battery element 6 side end of the sealing part 16 becomes small, the battery element 6 is formed large and the shape of the film-form exterior material 4 is formed. Since the energy density per volume can be increased and the entry of moisture from the outside can be suppressed, the invaded moisture is decomposed to become a gas and expand to form a crack in the film-shaped exterior material 4. This can be suppressed.

Moreover, according to the battery cell 1 which concerns on this invention, the protrusion part 17b of the resin formed in the inside of a battery can be reduced, and also the moisture permeation from the outside can be suppressed, As a result, the energy density per volume is high. A battery cell with excellent long-term reliability can be provided.

The present invention relates to a battery cell such as a lithium ion battery, which has recently been installed not only for portable devices but also for electric motorcycles, electric cars, etc., and whose applications are rapidly expanding. Conventionally, in a battery cell using a film-like exterior material, problems such as space efficiency being reduced or peeling strength of the heat seal portion being lowered due to the protruding portion of the resin protruding when heat-sealing occurred. . On the other hand, in the battery cell according to the present invention, the resin protruding portion of the heat seal portion can be reduced, and further, moisture can be prevented from entering from the outside, thereby reducing deterioration of the battery cell. Therefore, a battery cell with high energy density per volume and excellent long-term reliability can be provided, and industrial applicability is very large.

DESCRIPTION OF SYMBOLS 1 ... Battery cell, 2 ... Positive electrode terminal, 3 ... Negative electrode terminal, 4 ... Film-form exterior material, 5 ... (Film-form exterior material periphery) sealing part, 6 ... -Battery element, 6a ... End part of sealing part side of battery element, 11 ... Surface protective layer, 12 ... Barrier layer, 13 ... Thermal welding resin layer, 16 ... Sealing part, 17a ... welding layer, 17b ... projection (resin that protrudes into the battery), 17c ... projection (resin that protrudes on the outer edge of the film-like exterior material), 21 ... heating member 22 ... cooling member, 23 ... heating member

Claims

In the battery cell, the battery element is housed in a film-shaped exterior material made of a laminate film that provides at least a barrier layer and a resin layer.
The film-shaped exterior material includes a sealing portion that is heat-welded with the resin layers facing each other, and the sealing portion is located at the end on the battery element side from the battery element side toward the outer side of the film-shaped exterior material. Including the part where the thickness increases, and the outer edge of the film-like exterior material includes the part where the thickness increases in the direction from the outer edge to the battery element side, excluding the outer edge of the film-like exterior material within 0.5 mm The battery cell is characterized in that the minimum thickness is 40 or more when the thickness of two resin layers is 100.
The battery cell according to claim 1, wherein the sealing portion has a width of 2 mm or more.