JP7568528B2 - Electrochemical Cell - Google Patents

Description

The present invention relates to an electrochemical cell.

2. Description of the Related Art Lithium-ion secondary batteries, electrochemical capacitors, and other electrochemical cells have traditionally been widely used as power sources for small devices such as smartphones, wearable devices, and hearing aids.
In recent years, a so-called laminate-type electrochemical cell has been known as this type of electrochemical cell, which uses a laminate film for an exterior body that houses an electrode assembly inside. This laminate-type electrochemical cell is known as an electrochemical cell that is small in size, has a high degree of freedom in shape, and can be further increased in capacity.

For example, Patent Document 1 listed below discloses an electrochemical cell including an electrode assembly and an exterior body that has a first laminate member and a second laminate member and that houses the electrode assembly.
The exterior body includes a housing portion that houses the electrode body, and a sealing portion that is bent along the outer periphery of the housing portion. The sealing portion is formed by bending the welded portion, which welds the first laminate member and the second laminate member together, using a molding die so that the welded portion fits the outer periphery of the housing portion.

JP 2018-85214 A

In this type of laminate-type electrochemical cell, a three-layer laminate structure is often used in which the first and second laminate members are laminated such that a metal layer, such as aluminum, is used as an intermediate layer and both sides of this metal layer are covered with resin layers (such as polypropylene or nylon). As a result, the ends of the first and second laminate members are exposed to the outside, and the exposed parts of the metal layer are likely to come into contact with, for example, an external negative electrode terminal.

For example, in the electrochemical cell described in the above-mentioned conventional Patent Document 1, the sealing portion of the exterior part is folded so as to fit the outer periphery of the housing part, and therefore, at the end of the sealing portion, the metal layers constituting the first laminate member and the second laminate member are exposed to the outside and are easily brought into contact with an external negative electrode terminal or the like.
Under such circumstances, for example, if the resin layers constituting the first laminate member and the second laminate member are damaged or scratched for some reason, the electrolyte may come into contact with the metal layer inside the electrochemical cell. In this state, if the metal layer in contact with the negative electrode terminal or the like falls below the reduction potential with respect to the lithium or the like in the electrolyte, an alloying reaction of the metal layer (for example, an alloying reaction of aluminum with lithium) may occur.

If an alloying reaction occurs in the metal layer, it may cause inconveniences such as the alloy precipitated in needle-like form penetrating through the resin layer on the outside of the metal layer, or the metal layer expanding due to the alloying reaction and damaging the resin layer on the outside of the metal layer, making it difficult to maintain the airtightness of the exterior body.

In order to prevent the above-mentioned inconveniences, it is conceivable to attach an insulating seal to the electrochemical cell so as to cover and conceal the metal layer exposed to the outside at the end of the sealing part, for example in the coin-shaped electrochemical cell described in the above-mentioned conventional Patent Document 1.
However, in this case, in order to adequately cover and hide the metal layer, the outer diameter of the insulating seal needs to be made larger than the outer diameter of the electrochemical cell, which increases the radial dimension of the electrochemical cell, resulting in a new problem that it becomes difficult to reduce the diameter of the electrochemical cell.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a laminate-type electrochemical cell that can suppress external contact with the metal layer and can be made smaller, leading to further improvement in volumetric efficiency.
The volumetric efficiency refers to the ratio of the volume of the electrodes to the volume of the entire battery, that is, "electrode partial volume/total battery volume."

(1) The electrochemical cell of the present invention comprises an electrode body having a positive electrode and a negative electrode, and an exterior body having a first laminate member and a second laminate member and housing the electrode body therein, the first laminate member and the second laminate member being formed of a laminate film having a metal layer and a resin layer covering both sides of the metal layer, the exterior body being formed by arranging the first laminate member and the second laminate member in the battery axial direction with the electrode body sandwiched therebetween, and the exterior body comprises a housing portion housing the electrode body therein, and the first laminate member and The second laminate members are joined together in an overlapping state, and a sealing portion seals the inside of the storage portion. The storage portion has a top wall portion and a bottom wall portion that face each other in the battery axis direction with the electrode body sandwiched therebetween, and a cylindrical peripheral wall portion that surrounds the electrode body from the outside in the radial direction. The sealing portion is bent toward the top wall portion along the peripheral wall portion and is formed in a cylindrical shape that surrounds the peripheral wall portion from the outside in the radial direction over the entire circumference, and the tip side of the sealing portion is deformed so as to curve radially inward as it approaches the tip edge.

According to the electrochemical cell of the present invention, the first laminate member and the second laminate member are formed of a laminate film having a metal layer and a resin layer, and therefore the first laminate member and the second laminate member can be joined by, for example, heat welding to form a sealing portion with high sealing properties (adhesion). In addition, since the sealing portion is folded along the peripheral wall portion, it is possible to effectively prevent disturbances such as dust and moisture from entering the housing portion from the outside through the gap between the first laminate member and the second laminate member. Therefore, an electrochemical cell with stable operational reliability can be obtained.
Furthermore, since the exterior body is constructed using the first and second laminate members formed of thin laminate films, the thickness of the peripheral wall and the sealing portion themselves can be thin, making it easy to reduce the diameter of the electrochemical cell.

In particular, the tip side of the sealing portion bent along the peripheral wall toward the top wall is deformed so as to be curved radially inward toward the tip edge. This allows the tip side of the sealing portion formed by joining the first laminate member having a metal layer and the second laminate member having a metal layer to be forcibly curved radially inward around the entire circumference of the sealing portion. Therefore, it is possible to make it difficult for the metal layers of the first laminate member and the second laminate member to be exposed to the outside at the tip edge of the sealing portion. Therefore, it is possible to suppress contact with the metal layer from the outside compared to the conventional method. Therefore, it is possible to suppress various inconveniences (e.g., alloying of the metal layer) caused by contact between the metal layer and the outside (e.g., the negative electrode terminal) from occurring, and it is possible to obtain an electrochemical cell with improved operating reliability over a long period of time.

Furthermore, since external contact with the metal layer can be suppressed, there is no need to cover the metal layer using, for example, a conventional insulating seal having an outer diameter larger than the outer diameter of the electrochemical cell. This allows the electrochemical cell to be made smaller in size and diameter, which contributes to improving the volume ratio of the electrode body to the overall volume of the electrochemical cell. This can also lead to improved volumetric efficiency.

(2) The sealing portion may contact the peripheral wall portion from the outside in the radial direction.

In this case, since the sealing portion is in contact with the peripheral wall portion from the outside in the radial direction, the sealing portion can be configured to surround the peripheral wall portion without leaving an annular gap between the sealing portion and the peripheral wall portion. Therefore, the diameter of the entire electrochemical cell can be further reduced by the amount that the gap can be omitted. In particular, since the diameter of the entire electrochemical cell can be reduced without changing the size of the storage portion, the volume ratio of the electrode body to the volume of the entire electrochemical cell can be further improved. This can lead to a further improvement in volumetric efficiency.

(3) The exterior body may be provided with an insulating protective member that covers at least the leading edge of the sealing portion.

In this case, the protective member can be used to cover the leading edge of the sealing portion, so that the metal layer itself, which is configured to be less likely to be exposed to the outside, can be further concealed. This effectively prevents the metal layer from coming into contact with the outside (e.g., the negative electrode terminal).

(4) The protective member may be a protective sheet that overlaps the top wall portion and whose outer peripheral edge side covers and encases the tip edge.

In this case, the leading edge of the sealing portion can be covered by a simple method of simply fixing the protective sheet by adhesion or the like so that it overlaps the top wall portion of the storage portion. In particular, as described above, since the leading end side of the sealing portion is deformed so as to be curved radially inward, the leading edge can be adequately covered even if the outer diameter of the protective sheet is formed smaller than the outer diameter of the electrochemical cell. Therefore, even when a protective sheet is used, it is possible to suppress any impact on the miniaturization of the electrochemical cell.

(5) The protective member may be a shrink tube that covers the tip edge while surrounding the sealing portion from the radial outside.

In this case, the leading edge of the sealing portion can be covered by a simple method of simply shrinking the shrink tube. Even in this case, for example, by providing a shrink tube so as to surround the leading end side of the sealing portion mainly from the outside in the radial direction, it is possible to suppress the influence on the miniaturization of the electrochemical cell.
Furthermore, in this case, by adopting a configuration in which the sealing portion contacts the peripheral wall portion from the radial outside, it is still possible to reduce the size of the entire electrochemical cell even if, for example, a shrink tube is provided so as to surround the entire sealing portion from the radial outside.

(6) The protective member may be an insulating resin that covers the leading edge and fills the gap formed between the leading edge and the housing portion.

In this case, the leading edge of the sealing portion can be covered by a simple method of applying an insulating resin, for example, by dropping, to the leading edge and curing the insulating resin. In particular, since the leading edge can be covered with pinpoint accuracy, the metal layer at the leading edge can be reliably covered and concealed while effectively suppressing any adverse effect on the miniaturization of the electrochemical cell. Furthermore, since the process requires only a simple process of applying the insulating resin by dropping, the electrochemical cell is excellent in mass productivity and can easily be produced at low cost.
In this case, by adopting a configuration in which the sealing portion contacts the peripheral wall portion of the accommodating portion from the radially outside, it is easier to more reliably fill the gap formed between the tip edge and the accommodating portion (peripheral wall portion) using insulating resin.

According to the present invention, it is possible to provide a laminate-type electrochemical cell that can suppress contact with the metal layer from the outside and can be made compact, leading to further improvement in volumetric efficiency. Therefore, it is possible to suppress the occurrence of various inconveniences caused by contact between the metal layer and the outside, and to provide an electrochemical cell with improved operational reliability, and it is possible to provide a high-performance electrochemical cell with high volumetric capacity density by making it smaller in diameter and compact.

1 is a perspective view showing an embodiment of a secondary battery (electrochemical cell) according to the present invention. 2 is a longitudinal sectional view of the secondary battery taken along line AA shown in FIG. 1. 3 is an enlarged longitudinal sectional view of the secondary battery of a portion surrounded by a virtual circle B shown in FIG. 2. FIG. 3 is an exploded perspective view of the secondary battery shown in FIG. 2 . 5 is a longitudinal sectional view of the electrode body taken along line CC shown in FIG. 4. FIG. 6 is a development view of the positive electrode shown in FIG. 5 before being wound. FIG. 6 is a development view of the negative electrode shown in FIG. 5 before being wound. FIG. 2 is a perspective view showing a step during the manufacture of the secondary battery shown in FIG. 1, showing a pre-molded battery before the sealing portion is folded and molded. 9 is a perspective view of the pre-molded battery shown in FIG. 8 as seen from a different angle. 9 is a cross-sectional view showing a state in which the pre-molded battery shown in FIG. 8 is set in a first die of a molding die. 11 is a cross-sectional view showing a state in which the sealing portion of the pre-molded battery is sandwiched and fixed between a first mold and a second mold after the state shown in FIG. 10 . 12 is a cross-sectional view showing a state in which the punch portion is raised after the state shown in FIG. 11 . 13 is a cross-sectional view showing a state in which the sealing portion is bent and formed by utilizing the forming portion of the punch portion after the state shown in FIG. 12 . 14 is a cross-sectional view showing the state in which the molded battery in which the sealing portion has been folded and molded is removed from the molding die after the state shown in FIG. 13 . 15 is a cross-sectional view showing a state in which the molded battery is set in a die for drawing after the state shown in FIG. 14. FIG. 16 is a cross-sectional view showing a state in which the sealing portion of the molded battery is being drawn after the state shown in FIG. 15 . 17 is a cross-sectional view showing a state in which, after the state shown in FIG. 16, the upper end of the sealing portion of the post-drawing battery is curved using a curve-forming die. FIG. 18 is a cross-sectional view showing the state immediately before the battery is removed after being curved and the die for curve forming is released from the state shown in FIG. 17. FIG. FIG. 11 is a cross-sectional view showing a modified example of the secondary battery according to the present invention. FIG. 11 is a cross-sectional view showing another modified example of the secondary battery according to the present invention. FIG. 11 is a cross-sectional view showing still another modified example of the secondary battery according to the present invention. FIG. 11 is a cross-sectional view showing still another modified example of the secondary battery according to the present invention. FIG. 11 is a cross-sectional view showing still another modified example of the secondary battery according to the present invention.

Below, an embodiment of an electrochemical cell according to the present invention will be described with reference to the drawings. In this embodiment, a lithium ion secondary battery (hereinafter simply referred to as a secondary battery), which is a type of non-aqueous electrolyte secondary battery, will be used as an example of an electrochemical cell.

As shown in Figures 1 to 4, the secondary battery 1 of this embodiment is a so-called coin-type (button-type) battery, and mainly comprises an electrode body 2 having multiple electrodes, i.e., positive electrodes 10 and negative electrodes 20, stacked on top of each other along the battery axis O, and an exterior body 3 formed of a laminate film and housing the electrode body 2 therein. Note that in each drawing, the electrode body 2 is appropriately simplified.

In this embodiment, the axis that passes through the center of the electrode body 2 and extends in the up-down direction is referred to as the battery axis O. In addition, in a plan view seen from the battery axis O direction, the direction that intersects with the battery axis O is referred to as the radial direction, and the direction that goes around the battery axis O is referred to as the circumferential direction.
Furthermore, in explaining the configuration of the secondary battery 1, the direction along the battery axis O from the second electrode terminal plate 63, which functions as the external connection terminal for the negative electrode described later, to the first electrode terminal plate 62, which functions as the external connection terminal for the positive electrode, is referred to as the upward direction, and the opposite direction is referred to as the downward direction.

As shown in Figs. 4 and 5, the electrode assembly 2 is a so-called laminated electrode in which a positive electrode 10 and a negative electrode 20 are laminated with a separator (not shown) sandwiched therebetween.
The electrode body 2 is formed so that its outer shape is circular in a plan view. However, the outer shape of the electrode body 2 is not limited to this case and may be other shapes, such as an ellipse, an oval shape, or a diamond shape, and may be changed as appropriate.

In this embodiment, the positive electrode 10 and the negative electrode 20 are stacked alternately by being wound with the separator in between. However, this is not limited to this case, and for example, the positive electrode 10 and the negative electrode 20 may be stacked alternately by being folded in a zigzag shape from the direction in which they intersect each other. Furthermore, a so-called pellet-type electrode body having the positive electrode 10 and the negative electrode 20 on both sides of the separator may also be used.

The structure of the electrode body 2 will now be briefly described.
As shown in FIG. 6 , the positive electrode 10 includes a positive electrode collector 11 formed in a band shape extending along a first direction L1 in an unfolded state before being wound, and a positive electrode active material layer (not shown) formed on both sides of the positive electrode collector 11.

The positive electrode current collector 11 is formed in a thin sheet shape from a metal material such as aluminum or stainless steel, and includes a plurality of positive electrode bodies 12 and a plurality of positive electrode connection pieces 13. The positive electrode bodies 12 are formed in a disk shape and are arranged at intervals so as to be aligned in a line in the first direction L1. In the illustrated example, the number of positive electrode bodies 12 is eight. However, the number of positive electrode bodies 12 is not limited to eight and may be changed as appropriate.

The positive electrode connection pieces 13 are disposed between adjacent positive electrode bodies 12 in the first direction L1, and connect the adjacent positive electrode bodies 12 to each other. Therefore, in the illustrated example, the number of positive electrode connection pieces 13 is seven. Note that the width of the positive electrode connection pieces 13 in the second direction L2 perpendicular to the first direction L1 in a plan view is formed to be shorter than the width of the positive electrode bodies 12 in the second direction L2.

The outer edge of the positive electrode connection piece 13 is formed in an inwardly recessed arc shape in a plan view, and is provided so as to be smoothly connected to the arc-shaped outer edge of the positive electrode main body 12. However, the outer edge of the positive electrode connection piece 13 does not necessarily have to be arc-shaped, and may be formed, for example, in a straight line.
In particular, the dimension of each positive electrode connection piece 13 along the first direction L1 is larger for the positive electrode connection piece 13 disposed closer to the outer periphery of the electrode body 2 in the wound state. As a result, the distance between a pair of adjacent positive electrode bodies 12 in the first direction L1 in the unfolded state is larger for the positive electrode connection pieces 13 disposed closer to the outer periphery in the wound state.

Of the multiple positive electrode bodies 12, the positive electrode body 12 located at one end position in the first direction L1 (i.e., the positive electrode body 12 located at the outermost circumference when wound) has a positive electrode terminal tab 14 formed so as to extend further outward in the first direction L1.
In this embodiment, the positive electrode body 12 located at the other end position in the first direction L1 is referred to as the first tier positive electrode body 12, and the positive electrode bodies 12 on the other tier are referred to as the second tier, third tier, fourth tier, fifth tier, sixth tier, seventh tier, and eighth tier in order toward the positive electrode body 12 on which the positive electrode terminal tab 14 is formed. Therefore, the positive electrode body 12 on which the positive electrode terminal tab 14 is formed corresponds to the eighth tier positive electrode body 12.

The positive electrode active material layer is formed on both sides of the positive electrode current collector 11 except for the positive electrode terminal tab 14. The positive electrode active material layer contains a positive electrode active material, a conductive assistant, a binder, a thickener, and the like, and is formed of a composite metal oxide such as lithium cobalt oxide or lithium nickel oxide.
Examples of the conductive assistant include carbon blacks, carbon materials, and metal fine powders. Examples of the binder include resin materials such as polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE). Examples of the thickener include resin materials such as carboxymethyl cellulose (CMC).

As shown in FIG. 7 , the negative electrode 20 includes a negative electrode current collector 21 formed in a band shape extending along a first direction L1 in an unfolded state before being wound, and a negative electrode active material layer (not shown) formed on both sides of the negative electrode current collector 21.
The negative electrode current collector 21 is formed in a thin sheet shape using a metal material such as copper, nickel, or stainless steel, and includes a plurality of negative electrode bodies 22 and a plurality of negative electrode connection pieces 23. The negative electrode bodies 22 are formed in a disk shape similar to the positive electrode bodies 12, and are arranged at intervals so as to be aligned in a line in the first direction L1. In the illustrated example, the number of negative electrode bodies 22 is eight, corresponding to the number of positive electrode bodies 12. However, the number of negative electrode bodies 22 is not limited to eight, and may be changed appropriately in accordance with the number of positive electrode bodies 12.

The negative electrode connection pieces 23 are disposed between the negative electrode bodies 22 adjacent to each other in the first direction L1, and connect the adjacent negative electrode bodies 22 to each other. Therefore, in the illustrated example, the number of negative electrode connection pieces 23 is seven. Note that the width of the negative electrode connection pieces 23 in the second direction L2 perpendicular to the first direction L1 in a plan view is formed to be shorter than the width of the negative electrode bodies 22 in the second direction L2.

The outer edge of the negative electrode connection piece 23 is formed in an arc shape recessed inward in a plan view, and is provided so as to be smoothly connected to the arc-shaped outer edge of the negative electrode main body 22. However, the outer edge of the negative electrode connection piece 23 does not necessarily have to be arc-shaped, and may be formed, for example, in a straight line.
In particular, the dimension of each negative electrode connection piece 23 along the first direction L1 is larger for the negative electrode connection piece 23 disposed closer to the outer periphery of the electrode body 12 in the wound state. As a result, the distance between a pair of negative electrode bodies 22 adjacent to each other in the first direction L1 in the deployed state is larger for the negative electrode connection pieces 23 disposed closer to the outer periphery in the wound state.

Of the multiple negative electrode bodies 22, the negative electrode body 22 located at one end position in the first direction L1 (i.e., the negative electrode body 22 located at the outermost circumference in the wound state) has a negative electrode terminal tab 24 formed so as to extend further outward in the first direction L1.
In this embodiment, the negative electrode body 22 located at the other end position in the first direction L1 is referred to as the first tier negative electrode body 22, and the negative electrode bodies 22 in the order from the first tier to the negative electrode body 22 on which the negative electrode terminal tab 24 is formed are referred to as the second tier, third tier, fourth tier, fifth tier, sixth tier, seventh tier, and eighth tier negative electrode body 22. Therefore, the negative electrode body 22 on which the negative electrode terminal tab 24 is formed corresponds to the eighth tier negative electrode body 22.

The negative electrode 20 configured as described above has an external shape similar to that of the positive electrode 10 described above. However, the external size of the positive electrode 10 is slightly smaller (one size smaller) than the external size of the negative electrode 20.

The negative electrode active material layer is formed on both sides of the negative electrode current collector 21 except for the negative electrode terminal tab 24. The negative electrode active material layer contains a negative electrode active material, a conductive assistant, a binder, a thickener, and the like, and is formed of a carbon material such as graphite.
Examples of the conductive assistant include carbon blacks, carbon materials, and metal fine powders. Examples of the binder include resin materials such as polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE). Examples of the thickener include resin materials such as carboxymethyl cellulose (CMC).

The positive electrode 10 and the negative electrode 20 configured as described above are wound with the separator therebetween, as described above, so that they are stacked alternately.
Specifically, the positive electrode 10 shown in FIG. 6 and the negative electrode 20 shown in FIG. 7 are arranged along the first direction L1 so that the positive terminal tab 14 and the negative terminal tab 24 are arranged on opposite sides to each other, and then the first layer of the positive electrode body 12 and the first layer of the negative electrode body 22 are overlapped. Next, the positive electrode 10 and the negative electrode 20 are repeatedly wound in the same direction, starting from the first layer of the positive electrode body 12 and the negative electrode body 22 that are overlapped with each other. This allows the positive electrode body 12 and the negative electrode body 22 to be stacked alternately in the direction of the battery axis O, and the electrode body 2 shown in FIG. 5 can be obtained. Note that the separator is not shown in FIG. 5.

As shown in FIG. 5, the electrode body 2 obtained by the above-mentioned winding has the eighth-stage positive electrode body 12 on which the positive electrode terminal tab 14 is formed located in the topmost stage, and the eighth-stage negative electrode body 22 on which the negative electrode terminal tab 24 is formed located in the bottommost stage. Therefore, the electrode body 2 is housed in the exterior body 3 with the positive electrode terminal tab 14 facing upward and the negative electrode terminal tab 24 facing downward.

In the electrode body 2 shown in FIG. 5, when the positive electrode 10 is focused on, the positive electrode 10 is wound so that the positive electrode bodies 12 are arranged parallel to each other in the direction of the battery axis O in the order of the eighth stage, the sixth stage, the fourth stage, the second stage, the first stage, the third stage, the fifth stage, and the seventh stage from top to bottom. In contrast, when the negative electrode 20 is focused on, the negative electrode 20 is wound so that the negative electrode bodies 22 are arranged parallel to each other in the direction of the battery axis O in the order of the seventh stage, the fifth stage, the third stage, the first stage, the second stage, the fourth stage, the sixth stage, and the eighth stage from top to bottom.

As shown in FIGS. 1 to 4, the exterior body 3 includes a first laminating member 30 and a second laminating member 40 formed of a laminate film.
The exterior body 3 is formed by arranging a first laminate member 30 and a second laminate member 40 in the direction of the battery axis O with the electrode body 2 sandwiched therebetween, and includes a housing section 50 that houses the electrode body 2 therein, and a sealing section 51 in which the first laminate member 30 and the second laminate member 40 are joined to each other in an overlapping state, sealing the inside of the housing section 50. As a result, the exterior body 3 houses the electrode body 2 in a sealed state inside the housing section 50. The inside of the housing section 50 is filled with an electrolyte solution (electrolyte solution) not shown.

The accommodating portion 50 includes a top wall portion 55 and a bottom wall portion 56 which face each other in the direction of the battery axis O with the electrode body 2 therebetween, and an annular peripheral wall portion 57 which surrounds the electrode body 2 from the outside in the radial direction.
The sealing portion 51 is bent (upward) along the peripheral wall portion 57 toward the top wall portion 55, and is formed in a ring shape that surrounds the peripheral wall portion 57 from the radial outside around the entire circumference, and is in contact with the peripheral wall portion 57 from the radial outside.

The exterior body 3 having the housing portion 50 and the sealing portion 51 will be described in detail below.
2 and 3, the first laminate member 30 is a member that mainly covers the electrode body 2 from above, and includes a metal layer 31, and an inner resin layer 32 and an outer resin layer 33 that cover both sides of the metal layer 31. The inner resin layer 32 and the outer resin layer 33 are tightly bonded to both sides of the metal layer 31 by, for example, heat fusion or adhesion via a bonding layer (not shown). In each drawing, the metal layer 31, the inner resin layer 32, and the outer resin layer 33 are appropriately omitted from illustration.

The metal layer 31 is formed from a metal material suitable for blocking outside air and water vapor, such as stainless steel or aluminum.
The inner resin layer 32 is formed using a thermoplastic resin such as polyolefin polyethylene or polypropylene. As the polyolefin, any of the following materials can be used: high-pressure low-density polyethylene (LDPE), low-pressure high-density polyethylene (HDPE), inflation polypropylene (IPP) film, non-oriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, linear short-chain branched polyethylene (L-LDPE, metallocene catalyst type). In particular, polypropylene resin is preferable.
The outer resin layer 33 is formed using, for example, the above-mentioned polyolefin, polyester such as polyethylene terephthalate, nylon, or the like.

The first laminate member 30 is formed in a double-tubular shape with an upper end, and includes a top wall portion 35 that is circular in plan view and covers the electrode body 2 from above, a cylindrical peripheral wall portion 36 that extends downward from the outer periphery of the top wall portion 35 and surrounds the electrode body 2 from the outside in the radial direction, and a cylindrical first sealing portion 37 that is folded upward from the lower end of the peripheral wall portion 36 and surrounds the peripheral wall portion 36 from the outside in the radial direction.

The second laminate member 40 is a member that mainly covers the electrode body 2 from below, and has a metal layer 41, and an inner resin layer 42 and an outer resin layer 43 that cover both sides of the metal layer 41. The inner resin layer 42 and the outer resin layer 43 are each tightly joined to both sides of the metal layer 41 via a joining layer (not shown), for example, by heat fusion or adhesion.
The materials and the like of the metal layer 41, the inner resin layer 42, and the outer resin layer 43 are similar to those of the metal layer 31, the inner resin layer 32, and the outer resin layer 33 in the first laminate member 30. Moreover, in each drawing, illustration of the metal layer 41, the inner resin layer 42, and the outer resin layer 43 is appropriately omitted.

The second laminate member 40 is formed in a bottomed cylindrical shape with a bottom wall portion 45 that covers the electrode body 2 from below, and a cylindrical second sealing portion 46 that extends upward from the outer peripheral edge of the bottom wall portion 45 and further surrounds the first sealing portion 37 from the radial outside.

The exterior body 3 is formed by the first laminating member 30 and the second laminating member 40 configured as described above.
Specifically, the top wall portion 35 and the peripheral wall portion 36 of the first laminate member 30 function as the top wall portion 55 and the peripheral wall portion 57 of the storage portion 50, respectively. Additionally, the bottom wall portion 45 of the second laminate member 40 functions as the bottom wall portion 56 of the storage portion 50. Additionally, the first sealing portion 37 of the first laminate member 30 and the second sealing portion 46 of the second laminate member 40 function as the sealing portion 51.
Depending on the size of the electrode body 2 to be accommodated, the second laminate member 40 may be provided with a peripheral wall portion.

The first sealing portion 37 and the second sealing portion 46 functioning as the sealing portion 51 are integrally joined to each other, thereby sealing the inside of the storage portion 50 in an airtight state.
Specifically, the inner resin layer 32 in the first sealing portion 37 and the inner resin layer 42 in the second sealing portion 46 are integrally joined together by, for example, ultrasonic welding or heat welding. However, the joining method is not limited to ultrasonic welding or heat welding, and may be, for example, high-frequency welding or adhesion using an adhesive.

In this embodiment, the height position of the upper end portion 51a of the sealing portion 51 is set to be equal to the height position of the top wall portion 55 of the accommodation portion 50. As a result, the sealing portion 51 is formed without protruding above the top wall portion 55.
However, this is not limited to this case, and for example, the height position of the upper end portion 51 a of the sealing portion 51 may be formed to be located above or below the top wall portion 55 .

In particular, the first sealing portion 37 and the second sealing portion 46 are integrally joined to each other, then bent and molded by a molding die 70 described later, and then squeezed to reduce their diameter by a squeeze molding die 80 described later.
As a result, the sealing portion 51 formed by the first sealing portion 37 and the second sealing portion 46 is in intimate contact with the outer circumferential surface of the peripheral wall portion 57 over the entire circumference, being tightly pressed from the outside in the radial direction.

The connection between the lower end of the first sealing portion 37 and the lower end of the peripheral wall portion 36 functions as an inner fold 52 created by the drawing. The connection between the lower end of the second sealing portion 46 and the outer peripheral edge of the bottom wall portion 45 functions as an outer fold 53 created by the drawing.

Furthermore, the sealing portion 51 composed of the first sealing portion 37 and the second sealing portion 46 is deformed by the curved molding die 90 described later so that the upper end portion (tip portion) 51a side is curved radially inward around the entire circumference as it approaches the upper edge.
3, the upper end 51a side of the sealing portion 51 is forcibly curved and deformed so as to follow the curvature of the curved connection portion (R portion) 58 that connects the top wall portion 55 and the peripheral wall portion 57. In the illustrated example, the upper end 51a side of the sealing portion 51 is deformed so as to be slightly crushed, but it is sufficient if it is curved, and it does not matter whether it is crushed or not.

Furthermore, as shown in Figures 2 and 4, the secondary battery 1 of this embodiment includes a first electrode plate 60 and a second electrode plate 61, a first electrode terminal plate 62 and a second electrode terminal plate 63, a first sealant film 64 and a second sealant film 65.
The first electrode plate 60 , the second electrode plate 61 , the first electrode terminal plate 62 , the second electrode terminal plate 63 , the first sealant film 64 and the second sealant film 65 are housed together with the electrode body 2 inside the housing portion 50 in the exterior body 3 .

The first electrode plate 60, the first electrode terminal plate 62, and the first sealant film 64 are disposed between the electrode body 2 and the top wall portion 35 of the first laminate member 30. The second electrode plate 61, the second electrode terminal plate 63, and the second sealant film 65 are disposed between the electrode body 2 and the bottom wall portion 45 of the second laminate member 40.

The first electrode plate 60 is formed in a circular shape in a plan view, and is integrally connected to the positive electrode 10 of the electrode body 2. The first electrode plate 60 is formed from a metal material such as aluminum or stainless steel with a smaller diameter than the electrode body 2, and is disposed coaxially with the battery axis O.
The first electrode plate 60 is disposed so as to overlap the eighth stage positive electrode body 12 of the positive electrode 10 in the electrode body 2, and the positive electrode terminal tab 14 is welded, for example, by ultrasonic welding, to the lower surface facing the electrode body 2. In this way, the first electrode plate 60 is integrally connected to the positive electrode 10.

The first electrode terminal plate 62 is made of a metal material such as nickel and has a circular shape in plan view with a smaller diameter than the first electrode plate 60, and is disposed so as to overlap the upper surface of the first electrode plate 60 facing the first laminate member 30. The first electrode terminal plate 62 is integrally fixed to the upper surface of the first electrode plate 60 by welding such as resistance welding. The first electrode terminal plate 62 functions as an external connection terminal for the positive electrode 10.

A first through hole 35a, which is circular in plan view and exposes the first electrode terminal plate 62 to the outside, is formed in the top wall portion 35 of the first laminate member 30. The first through hole 35a is formed to penetrate vertically through the center of the top wall portion 35 and is formed coaxially with the battery axis O.

The first sealant film 64 is formed in a ring shape surrounding the first electrode terminal plate 62 from the radially outside, and is arranged coaxially with the battery axis O between the first electrode terminal plate 62 and the top wall portion 35 of the first laminate member 30 while surrounding the first electrode terminal plate 62.
The first sealant film 64 is heat-welded to the inner resin layer 32 of the top wall portion 35 of the first laminate member 30 and to the upper surface of the first electrode plate 60. As a result, the first electrode plate 60 is heat-welded to the top wall portion 35 of the first laminate member 30 via the first sealant film 64.
The first sealant film 64 is formed of a thermoplastic resin, such as polyolefin polyethylene or polypropylene, or polypropylene reinforced with nonwoven fabric.

Since the first electrode plate 60, the first electrode terminal plate 62, and the first sealant film 64 are formed as described above, the entire surface of the first electrode terminal plate 62 is exposed upward through the first through hole 35a.

As shown in Figures 2 and 4, the second electrode plate 61, the second electrode terminal plate 63, and the second sealant film 65 are formed and arranged in the same manner as the first electrode plate 60, the first electrode terminal plate 62, and the first sealant film 64 described above.

The second electrode plate 61 is formed in a circular shape in a plan view, and is integrally connected to the negative electrode 20 in the electrode body 2. The second electrode plate 61 is formed with a smaller diameter than the electrode body 2 from a metal material such as copper, and is arranged coaxially with the battery axis O. The second electrode plate 61 is arranged overlapping the negative electrode body 22 in the eighth stage of the negative electrode 20 in the electrode body 2, and the negative electrode terminal tab 24 is welded to the upper surface facing the electrode body 2, for example by ultrasonic welding. In this way, the second electrode plate 61 is integrally connected to the negative electrode 20.

The second electrode terminal plate 63 is made of a metal material such as nickel and has a circular shape in plan view with a smaller diameter than the second electrode plate 61, and is disposed on the underside of the second electrode plate 61 facing the second laminate member 40. The second electrode terminal plate 63 is integrally fixed to the underside of the second electrode plate 61 by welding such as resistance welding. The second electrode terminal plate 63 functions as an external connection terminal for the negative electrode.

A second through hole 45a, which is circular in plan view and exposes the second electrode terminal plate 63 to the outside, is formed in the bottom wall portion 45 of the second laminate member 40. The second through hole 45a is formed so as to penetrate vertically through the center of the bottom wall portion 45 and is formed coaxially with the battery axis O.

The second sealant film 65 is formed in a ring shape surrounding the second electrode terminal plate 63 from the radially outside, and is arranged coaxially with the battery axis O between the second electrode terminal plate 63 and the bottom wall portion 45 of the second laminate member 40 while surrounding the second electrode terminal plate 63.
The second sealant film 65 is heat-welded to the inner resin layer 42 of the bottom wall portion 45 of the second laminate member 40 and to the lower surface of the second electrode plate 61. As a result, the second electrode plate 61 is heat-welded to the bottom wall portion 45 of the second laminate member 40 via the second sealant film 65.
Like the first sealant film 64, the second sealant film 65 is made of a thermoplastic resin such as polyolefin polyethylene or polypropylene, or polypropylene reinforced with nonwoven fabric.

Since the second electrode plate 61, the second electrode terminal plate 63, and the second sealant film 65 are formed as described above, the entire surface of the second electrode terminal plate 63 is exposed downward through the second through hole 45a.

Furthermore, the secondary battery 1 of this embodiment is provided with an insulating protective sheet (protective member in the present invention) 5 that covers at least the upper edge of the sealing portion 51 of the exterior body 3, as shown in FIGS.
The protective sheet 5 is, for example, a polyimide tape or a PET tape having a PET (polyethylene terephthalate) film base coated with an adhesive, and is formed in a ring shape in a plan view. The protective sheet 5 is fixed by adhesion or the like so as to overlap the top wall portion 35 of the first laminating member 30, and the outer peripheral edge portion 5a side covers and coats the upper edge of the sealing portion 51.
As a result, the protective sheet 5 serves to cover and conceal the metal layers 31 , 41 of the first laminating member 30 and the second laminating member 40 on the upper end portion 51 a side of the sealing portion 51 .

Furthermore, the inner peripheral edge 5b side of the protective sheet 5 protrudes radially inward from the first through hole 35a formed in the top wall portion 35 of the first laminate member 30, and is also folded back downward. As a result, the inner peripheral edge 5b side of the protective sheet 5 covers and protects the inner surface of the first through hole 35a from the radial inside all around. Therefore, the protective sheet 5 plays a role of covering and concealing the metal layer 31 of the first laminate member 30 at the first through hole 35a.

In the illustrated example, the inner peripheral edge 5b side of the protective sheet 5 is folded downward to block the inner peripheral surface of the first through hole 35a from the inside in the radial direction, but this is not limited to this case, and it is not necessary to fold the inner peripheral edge 5b side of the protective sheet 5 downward. However, since the metal layer 31 of the first laminate member 30 can be covered and concealed in the first through hole 35a, it is preferable to fold the inner peripheral edge 5b side of the protective sheet 5 downward.

(Secondary battery manufacturing method)
Next, a method for manufacturing the secondary battery 1 configured as described above, in which the sealing portion 51 is bent and drawn, and then the upper end portion 51a of the sealing portion 51 is curved, will be described.
First, as shown in Figures 8 and 9, the electrode body 2 is accommodated in the accommodation portion 50 of the outer casing 3 and filled with an electrolyte solution, and then a process is performed in which the first sealing portion 37 and the second sealing portion 46 are joined together by ultrasonic welding or the like.

As a result, the first sealing portion 37 and the second sealing portion 46 are joined together to obtain a pre-molded battery 1A having a sealing portion 51 formed in an annular shape.
At this stage, the first electrode terminal plate 62 has its entire surface exposed upward through the first through-hole 35a, and the second electrode terminal plate 63 has its entire surface exposed downward through the second through-hole 45a.

Next, a process of bending and molding the sealing portion 51 is carried out using a molding die 70 shown in FIG.
The molding die 70 includes a first die 71 that supports the pre-molded battery 1A, a second die 72 that is arranged above the first die 71 and is capable of moving toward and away from the first die 71 in the direction of the battery axis O, and a punch portion 73 that is capable of moving relatively in the direction of the battery axis O with respect to the first die 71 and the second die 72.

The first mold 71 has a first molding hole 71a formed therein, which penetrates the first mold 71 in the direction of the battery axis O. The first molding hole 71a is formed in a circular shape in a plan view, and is disposed coaxially with the battery axis O. The upper surface of the first mold 71 serves as a mounting surface 75 on which the sealing portion 51 is supported.
The second mold 72 is formed with a second molding hole 72a penetrating the second mold 72 in the direction of the battery axis O. The second molding hole 72a is formed in a circular shape in a plan view with the same diameter as the first mold 71, and is disposed coaxially with the battery axis O. The lower surface of the second mold 72 serves as a pressing surface 76 that can press the sealing portion 51 from above between the lower surface 72 and the mounting surface 75.

The punch portion 73 is positioned below the first mold 71 and is capable of rising relative to the first mold 71 and the second mold 72, thereby entering the first molding hole 71a and the second molding hole 72a from below.
The punch portion 73 includes a cylindrical punch portion body 77 having an outer diameter smaller than the inner diameters of the first molding hole 71a and the second molding hole 72a, and an annular molding portion 78 formed to protrude upward from the upper surface of the punch portion body 77. The molding portion 78 has an inner diameter equal to the outer diameter of the storage portion 50 and an outer diameter smaller than the outer diameter of the punch portion body 77. The protruding length of the molding portion 78 (length along the direction of the battery axis O) is equal to the height of the storage portion 50.

When bending the sealing portion 51 using the molding die 70 configured as described above, first, as shown in FIG. 10, the pre-molded battery 1A is placed on the first die 71 with the first electrode terminal plate 62 facing the punch portion 73. This places the storage portion 50 in the first molding hole 71a, and the annular sealing portion 51 is placed on the placement surface 75.

Next, as shown in FIG. 11, the second mold 72 is moved from above toward the first mold 71, and the second mold 72 is overlapped with the first mold 71 in the direction of the battery axis O with the sealing portion 51 between them. This allows the sealing portion 51 to be sandwiched and fixed between the mounting surface 75 of the first mold 71 and the pressing surface 76 of the second mold 72.

12, the punch portion 73 is moved upward from below the first die 71 relative to the combined first die 71 and second die 72. This allows the punch portion 73 to enter the first molding hole 71a and then move further upward, so that the molding portion 78 can come into contact with the sealing portion 51 from below.
Then, by further upward movement of the punch portion 73, as shown in Figure 13, the sealing portion 51 can be lifted by utilizing the molding portion 78, and the sealing portion 51 can be bent and molded into a cylindrical shape by utilizing the inner surface of the second molding hole 72a and the outer surface of the molding portion 78.

In addition, the upper edge of the punch body 77 moves above the lower edge of the second forming hole 72a, so that the sealing portion 51 can be cut between the upper and lower edges, and the portion of the sealing portion 51 that is sandwiched between the placement surface 75 and the pressing surface 76 can be cut off.

As a result, a molded battery 1B can be obtained in which the sealing portion 51 is bent into a cylindrical shape so as to surround the housing portion 50, as shown in FIG.
However, since the sealing portion 51 of this molded battery 1B is formed by bending it using the molding portion 78 of the punch 73, an annular gap S is defined between the storage portion 50 and the sealing portion 51.

Next, a process is performed in which the sealing portion 51 is drawn radially inward using a drawing die 80 shown in FIG. 15 to fill the annular gap S described above.
The die 80 for drawing comprises a drawing die 81, a first movable jig 82 arranged so as to be movable relative to the drawing die 81 in the direction of the battery axis O, and a second movable jig 83 arranged so as to be movable relative to the drawing die 81 in the direction of the battery axis O and capable of moving toward the first movable jig 82 in the direction of the battery axis O.

The drawing die 81 is formed with a choke hole 81a penetrating the drawing die 81 along the direction of the battery axis O. The choke hole 81a is formed in a circular shape in a plan view, and is disposed coaxially with the battery axis O. The inner diameter of the choke hole 81a corresponds to the outer diameter of the accommodation portion 50 plus twice the thickness of the sealing portion 51.
Furthermore, a cross-sectionally tapered mounting surface 81b is formed around the entire periphery of the opening edge of the drawing hole 81a on the upper end surface of the drawing die 81. Using this mounting surface 81b, the molded battery 1B can be placed and set on the drawing die 81 from above with the first electrode terminal plate 62 facing upward.

The first movable jig 82 is formed in a cylindrical shape with an outer diameter smaller than the inner diameter of the throttling hole 81a and smaller than the outer diameter of the storage section 50, and is arranged coaxially with the battery axis O. The first movable jig 82 is arranged inside the throttling hole 81a while being located below the molded battery 1B, and its upper surface is a flat first abutment surface 82a that can contact the bottom wall portion 56 of the storage section 50 from below.

The second movable jig 83 is formed in a cylindrical shape with an outer diameter equal to that of the first movable jig 82, and is arranged coaxially with the battery axis O. The second movable jig 83 is arranged so as to be located above the molded battery 1B, and its lower surface is a flat second abutment surface 83a that can contact the top wall portion 55 of the storage section 50 from above.

The second movable jig 83 moves downward so as to approach the molded battery 1B and the first movable jig 82, thereby pressing the molded battery 1B downward and fixing the molded battery 1B by clamping it between the first movable jig 82 with a predetermined stress.
16 , the first movable jig 82 and the second movable jig 83 are capable of moving downward together with respect to the drawing die 81 so as to press the molded battery 1B into the drawing hole 81a while keeping the molded battery 1B fixed. This allows the sealing portion 51 to be draw-formed as described below, and a draw-formed battery 1C with the sealing portion 51 drawn can be obtained.

After the molded battery 1B is pushed into the drawing hole 81a to form the drawn battery 1C, the first movable jig 82 and the second movable jig 83 can move upward relative to the drawing die 81 so as to push the drawn battery 1C up from inside the drawing hole 81a while maintaining the drawn battery 1C in a fixed state.

When performing drawing of the sealing portion 51 using the drawing die 80 configured as described above, as shown in FIG. 15, the molded battery 1B is placed on the mounting surface 81b of the drawing die 81, and then the second movable jig 83 is moved downward so as to approach the molded battery 1B and the first movable jig 82. This allows the molded battery 1B to be pushed into the drawing hole 81a using the second movable jig 83, and the molded battery 1B can be sandwiched and fixed between the first contact surface 82a of the first movable jig 82 and the second contact surface 83a of the second movable jig 83.

Then, while maintaining the molded battery 1B fixed by the first movable jig 82 and the second movable jig 83, as shown in FIG. 16, the first movable jig 82 and the second movable jig 83 are moved downward relative to the drawing die 81, causing the molded battery 1B to enter the drawing hole 81a. This allows the molded battery 1B to be moved downward inside the drawing hole 81a while the sealing portion 51 is drawn using the inner surface of the drawing hole 81a.

As a result, an external force can be applied to the sealing portion 51 such that the entire sealing portion 51 shrinks radially inward, and the entire sealing portion 51 can be drawn. This fills the annular gap S described above, and the sealing portion 51 can be brought into close contact with the peripheral wall portion 57 of the storage portion 50 from the radially outer side. This makes it possible to obtain a drawn battery 1C in which the sealing portion 51 is drawn.

Next, a process of forming the upper end portion 51a of the sealing portion 51 so as to be curved radially inward is carried out using a curve forming die 90 shown in FIG.
The curved forming die 90 includes a curved die 91 in an annular shape that radially surrounds the second movable jig 83 from the outside. The curved die 91 is arranged coaxially with the battery axis O and is arranged to be movable in the direction of the battery axis O relative to the second movable jig 83. The first movable jig 82 and the second movable jig 83 also function as components that constitute the curved forming die 90.

The inner diameter of the curved die 91 is set to be the same as the inner diameter of the drawing die 81. Furthermore, on the inner peripheral surface of the curved die 91, an annular forming groove 92 that opens downward is formed.
The inner diameter of the forming groove 92 is the same as the outer diameter of the sealing portion 51 that is in close contact with the peripheral wall portion 57 from the outside in the radial direction. Therefore, it is possible to insert the sealing portion 51 of the drawn-molded battery 1C from below into the forming groove 92. Of the wall surfaces that define the forming groove 92, the connection portion between the inner surface facing radially inward and the upper wall surface facing downward is a curved forming surface 92a that is smoothly curved around the entire circumference of the curved mold 91.

The following describes a case where the upper end 51a side of the sealing portion 51 is curved radially inward using the curved forming die 90 configured as described above. When performing the above-mentioned drawing, the curved die 91 moves downward in conjunction with the second movable jig 83 as shown in FIG. 16, and is positioned in contact with the drawing die 81 from above.

Then, as explained above, after the drawn-formed battery 1C is obtained by drawing the sealing portion 51, as shown in FIG. 17, while the drawn-formed battery 1C is kept fixed by the first movable jig 82 and the second movable jig 83, the first movable jig 82 and the second movable jig 83 are moved upward relative to the drawing die 81 and the curved die 91, so that the drawn-formed battery 1C1B is pushed up from within the drawing hole 81a and inserted into the inside of the curved die 91 from below.

This allows the sealing portion 51 to be inserted into the molding groove 92 from below, and the sealing portion 51 can be molded to conform to the wall surface of the molding groove 92. In other words, the upper end portion 51a side of the sealing portion 51 can be forcibly molded to be curved along the curved molding surface 92a. As a result, the upper end portion 51a side of the sealing portion 51 can be curved radially inward. This allows the battery 1D to be obtained after bending.

After the above-mentioned curved shaping is performed, as shown in FIG. 18, the second movable jig 83 and the curved die 91 are moved upward relative to the first movable jig 82 and the drawing die 81 to separate them, and the curved battery 1D is removed. Finally, a protective sheet 5 is fixed to the curved battery 1D by adhesion or the like, thereby obtaining the secondary battery 1 shown in FIG. 1.

(Function of secondary battery)
2 , the first electrode terminal plate 62 fixed to the first electrode plate 60 is exposed to the outside, and the second electrode terminal plate 63 fixed to the second electrode plate 61 is exposed to the outside, so that the first electrode terminal plate 62 and the second electrode terminal plate 63 can each function as an external connection terminal. This makes it possible to use the secondary battery 1 by utilizing the first electrode terminal plate 62 and the second electrode terminal plate 63.

In particular, in the secondary battery 1 of this embodiment, the first laminate member 30 and the second laminate member 40 are formed of a laminate film having metal layers 31, 41, so that the sealing portion 51 can be configured with high sealing properties (adhesion) by joining the first laminate member 30 and the second laminate member 40, for example, by heat welding. In addition, since the sealing portion 51 is folded along the peripheral wall portion 57, it is possible to effectively prevent disturbances such as dust and moisture from entering the storage portion 50 from the outside through the gap between the first laminate member 30 and the second laminate member 40. Therefore, a secondary battery 1 with stable operational reliability can be obtained.

Furthermore, since the exterior body 3 is constructed using the first laminate member 30 and the second laminate member 40 formed from thin laminate films, the thickness of the peripheral wall portion 57 and the sealing portion 51 themselves can be thin. Therefore, it is easy to reduce the diameter of the secondary battery 1.
In addition, because the sealing portion 51 contacts the peripheral wall portion 57 from the outside in the radial direction, it is possible to arrange the sealing portion 51 so as to surround the peripheral wall portion 57 without leaving an annular gap portion S (see FIG. 15 ) between the sealing portion 51 and the peripheral wall portion 57. Therefore, since the gap portion S can be omitted, it is possible to reduce the overall diameter of the secondary battery 1 compared to the conventional case.
Moreover, since the diameter of the entire secondary battery 1 can be reduced without changing the size of the housing portion 50 that houses the electrode body 2, it is possible to improve the volume ratio of the electrode body 2 to the entire volume of the secondary battery 1. This leads to an improvement in volumetric efficiency.

Furthermore, the upper end 51a side of the sealing portion 51, which is bent along the peripheral wall portion 57 toward the top wall portion 55, is deformed so as to be curved radially inward. Therefore, at the upper edge of the sealing portion 51, it is possible to make it difficult for the metal layers 31, 41 of the first laminate member 30 and the second laminate member 40 to be exposed to the outside. Therefore, it is possible to suppress contact with the metal layers 31, 41 from the outside compared to the conventional case. Therefore, it is possible to suppress various inconveniences (e.g., alloying of the metal layers 31, 41, etc.) caused by contact between the metal layers 31, 41 and the outside (e.g., the negative electrode terminal) from occurring, and it is possible to obtain a secondary battery 1 with improved operating reliability over a long period of time.

Moreover, the protective sheet 5 fixed on the top wall 55 of the housing 50 covers and coats the upper edge of the sealing portion 51, so that the metal layers 31, 41 themselves, which are configured to be less likely to be exposed to the outside, can be further covered and concealed, so that the above-mentioned effects can be achieved even more effectively.
Furthermore, the outer diameter of the protective sheet 5 is formed to be the same as or smaller than the outer diameter of the secondary battery 1, so that even when the protective sheet 5 is used, the impact on the miniaturization of the secondary battery 1 can be suppressed.

Furthermore, the inner peripheral edge portion 5b side of the protective sheet 5 is used to cover and protect the entire circumference of the first through hole 35a of the top wall portion 35 of the first laminate member 30 from the inside in the radial direction. Therefore, the metal layer 31 of the first laminate member 30 is covered and hidden at the first through hole 35a, preventing it from being exposed to the outside.

As described above, the secondary battery 1 of this embodiment can suppress contact with the metal layers 31, 41 from the outside, and can be made into a laminate-type secondary battery 1 that can be made smaller and lead to further improvement in volumetric efficiency. Therefore, various inconveniences caused by contact between the metal layers 31, 41 and the outside can be suppressed, and the secondary battery 1 can be made into a secondary battery 1 with improved operational reliability, and the secondary battery 1 can be made into a high-performance secondary battery 1 with high volumetric capacity density by being made smaller in diameter and size.

Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. Examples of the embodiments and their variations include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of equivalents.

For example, in the above embodiment, a secondary battery 1 is used as an example of an electrochemical cell, but the present invention is not limited to this case, and the electrochemical cell may be, for example, a capacitor (such as a lithium ion capacitor) or a primary battery.

In addition, in the above embodiment, the second electrode plate 61 is made of copper, but it may be made of nickel, for example. In this case, it is also possible to omit the second electrode terminal plate 63. In other words, an electrode terminal plate is not necessarily required for the negative electrode side, and it does not have to be provided. In this case, the second electrode plate 61 itself can function as an external connection terminal for the negative electrode side.

In addition, in the above embodiment, the secondary battery 1 is circular in plan view, but the shape of the secondary battery 1 may be changed as appropriate. For example, the secondary battery may be oval in plan view, combining straight lines and semicircular sections. In this case, the shape of the electrode body 2 may be oval in plan view to correspond to the external shape of the secondary battery.

Furthermore, in the above embodiment, the peripheral wall portion 36 of the first laminating member 30 functions as the peripheral wall portion 57 of the storage portion 50, but the present invention is not limited to this case.
For example, as shown in FIG. 19 , the secondary battery 100 may be constructed such that the second laminate member 40 has a peripheral wall portion 47, and the peripheral wall portion 47 and the peripheral wall portion 36 of the first laminate member 30 form a peripheral wall portion 57 of the storage section 50.

In this case, the sealing portion 51 composed of the first sealing portion 37 and the second sealing portion 46 may be formed so as to surround the entire periphery of the peripheral wall portion 36 of the first laminating member 30 from the radial outside, and may be brought into contact with the peripheral wall portion 36 from the radial outside. Then, the upper end portion 51a side of the sealing portion 51 may be curved radially inward.
Even in the case of the secondary battery 100 configured in this manner, the same effects can be achieved.

Furthermore, in the above embodiment, the case where the sealing portion 51 contacts the peripheral wall portion 57 from the outside in the radial direction has been described as an example, but the present invention is not limited to this case. For example, a secondary battery may be used in which an annular gap portion S is provided between the peripheral wall portion 57 and the sealing portion 51. Even in this case, it is sufficient to curve the upper end portion 51a side of the sealing portion 51 toward the inside in the radial direction.
However, in terms of reducing the diameter and size of the secondary battery, it is preferable that the sealing portion 51 contacts the peripheral wall portion 57 from the outside in the radial direction as in the above embodiment.

Furthermore, in the above embodiment, the height position of the upper end 51a of the sealing portion 51 is set to be equal to the height of the top wall portion 55 of the storage portion 50, but this is not limited to this case. For example, the upper end 51a of the sealing portion 51 may be configured to be located above the top wall portion 55 of the storage portion 50, or the secondary battery 110 may be configured so that the upper end 51a of the sealing portion 51 is located below the top wall portion 55 of the storage portion 50, as shown in FIG. 20.

In particular, in the case of the secondary battery 110 shown in FIG. 20, the upper end 51a of the sealing portion 51 is located below the top wall portion 55, which is preferable because it further reduces the risk of the metal layers 31, 41 coming into contact with the outside. Therefore, it is also possible to omit the protective sheet 5.

Note that the protective sheet 5 is not essential to the present invention and may not be provided. In particular, when configured as shown in FIG. 20, the protective sheet 5 can be easily omitted. Furthermore, in the above embodiment, the protective sheet 5 is described as an example of a protective member, but the protective sheet 5 is not limited to the protective sheet 5.

For example, as shown in Fig. 21, a shrink tube 120 such as a heat shrink tube may be used as the protective member instead of the protective sheet 5. In the illustrated example, the shrink tube 120 is provided so as to surround the entire sealing portion 51 from the outside in the radial direction. Even in this case, the upper edge of the sealing portion 51 can be covered by a simple method of simply shrinking the shrink tube 120, so that the same effect can be achieved.
Even in this case, for example, by adopting a configuration in which the sealing portion 51 contacts the peripheral wall portion 57 from the radial outside, even if the shrink tube 120 is provided so as to surround the entire sealing portion 51 from the radial outside, it is still possible to reduce the size of the entire secondary battery 1. Note that the protective sheet 5 and the shrink tube 120 may be used together.

Furthermore, the protective member in this embodiment is not limited to the above-mentioned protective sheet 5 and shrink tube 120, but may be, for example, an insulating resin.
For example, the secondary battery 130 shown in Figure 22 has, instead of a protective sheet 5, an insulating resin 131 that covers the upper edge of the upper end portion 51a of the sealing portion 51 and fills a V-shaped gap K in vertical cross section that is formed between the upper edge of the upper end portion 51a and a connection portion 58 in the accommodating portion 50 (a curved R portion that connects the top wall portion 55 and the peripheral wall portion 57).
As a result, the insulating resin 131 serves to cover and conceal the metal layers 31 , 41 of the first laminating member 30 and the second laminating member 40 on the upper end portion 51 a side of the sealing portion 51 .

In the illustrated example, the insulating resin 131 is formed so as to fill the gap K all around and to bulge slightly above the top wall portion 55 in a vertical cross-sectional view. However, this is not limited to this case, and the insulating resin 131 may be formed, for example, so as to be flush with the upper surface of the top wall portion 55, or so as to be recessed below the top wall portion 55. In this way, the insulating resin 131 may fill the gap K in any shape as long as it can cover the upper edge of the upper end portion 51a and properly coat the metal layers 31 and 41.

The insulating resin 131 thus formed is formed, for example, by applying the resin by dropping into the gap K and then curing the resin. Note that the insulating resin 131 is not limited to a specific resin as long as it has insulating properties.
For example, the insulating resin 131 may be a thermosetting resin that can be hardened by cooling or the like after being applied by dropping or the like as a molten resin heated to or above its melting point.
Furthermore, a synthetic resin that can be hardened by cooling or the like after being applied by dropping or the like as a liquid resin dissolved in a solvent may be used as the insulating resin 131 .
Furthermore, the insulating resin 131 may be an ultraviolet-curable resin, which can be cured by applying a liquid resin by dropping or the like and then irradiating it with ultraviolet rays.

Examples of the thermosetting resin include acrylic thermosetting resin, polyimide thermosetting resin, epoxy thermosetting resin, etc. Examples of the ultraviolet-curable resin include epoxy ultraviolet-curable resin (epoxy potting material, etc.).
The method of applying the insulating resin 131 is not limited to a dropping method, and it is also possible to apply the insulating resin 131 using, for example, a dispenser.

According to the secondary battery 130 configured in this manner, the leading edge of the upper end 51a of the sealing portion 51 can be covered by a simple method of simply applying the insulating resin 131 to the gap K, for example, by dripping, and then curing the insulating resin 131. Therefore, the metal layers 31, 41 of the first laminate member 30 and the second laminate member 40 can be covered and hidden, and the same effect can be achieved.
In particular, since the leading edge at the upper end portion 51a can be covered with pinpoint precision, the metal layers 31, 41 can be reliably covered and concealed at the leading edge while effectively minimizing the impact on the miniaturization of the secondary battery 130.

Furthermore, the insulating resin 131 can be used to fill the gap K formed between the upper end 51a and the connection part 58 of the housing part 50, so that the upper end 51a can be fixed to the connection part 58. This makes it possible to effectively prevent, for example, the upper end 51a from peeling off, makes it easier to maintain the coating of the tip edge for a long period of time, and improves the quality of the secondary battery 130.
Furthermore, since the process requires only a simple step of applying the insulating resin 131 by dropping or the like, the secondary battery 130 is excellent in terms of mass productivity, and low-cost productivity can be easily achieved.

Even when insulating resin 131 is used, it is preferable to use the protective sheet 55 described above to cover and protect the entire inner periphery of the first through hole 35a formed in the top wall portion 55 from the inside in the radial direction. This allows the metal layer 31 in the first laminate member 30 to be covered and hidden in the first through hole 35a.

Furthermore, when using insulating resin 131, as shown in FIG. 23, it may be applied to a secondary battery 110 in which the upper end 51a of the sealing portion 51 is located below the top wall portion 55 of the storage portion 50. Even in this case, the same effect can be achieved.

O... battery axis 1, 100, 110, 130... secondary battery (electrochemical cell)
2: Electrode body 3: Exterior body 5: Protective sheet (protective member)
REFERENCE SIGNS LIST 10 Positive electrode 20 Negative electrode 30 First laminate member 40 Second laminate member 50 Storage section 51 Sealed section 51a Upper end (tip) of sealed section
55: Top wall portion 56: Bottom wall portion 57: Peripheral wall portion 120: Shrink tube (protective member)
131...insulating resin (protective member)

Claims (6)

an electrode assembly having a positive electrode and a negative electrode;
an exterior body having a first laminate member and a second laminate member and housing the electrode body therein;
The first laminating member and the second laminating member are formed of a laminating film having a metal layer and a resin layer covering both sides of the metal layer,
The exterior body is
a housing portion that is formed by disposing the first laminate member and the second laminate member in a battery axial direction with the electrode body therebetween and that houses the electrode body therein;
a sealing portion in which the first laminate member and the second laminate member are joined to each other in an overlapping state, and which seals the inside of the storage portion;
the housing portion includes a top wall portion and a bottom wall portion that face each other in the battery axis direction with the electrode body therebetween, and a cylindrical peripheral wall portion that surrounds the electrode body from the outside in the radial direction,
an electrochemical cell characterized in that the sealing portion is bent along the peripheral wall portion toward the top wall portion and formed into a cylindrical shape surrounding the peripheral wall portion from the radial outside over the entire circumference, and the tip side of the sealing portion is deformed so as to curve radially inward toward the tip edge. 2. The electrochemical cell of claim 1 ,
The sealing portion is in contact with the peripheral wall portion from the outside in the radial direction. 3. The electrochemical cell according to claim 1 or 2,
The electrochemical cell, wherein the exterior body is provided with an insulating protective member that covers at least the tip edge of the sealing portion. 4. The electrochemical cell of claim 3,
The protective member overlaps the top wall portion, and the outer peripheral edge side of the protective member is a protective sheet that covers and encases the tip edge. 4. The electrochemical cell of claim 3,
The electrochemical cell, wherein the protective member is a shrink tube that covers the tip edge while surrounding the sealing portion from the outside in the radial direction. 4. The electrochemical cell of claim 3,
The protective member is an insulating resin that covers the leading edge and fills a gap formed between the leading edge and the housing portion.

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