JP2021051944A - Power storage element and manufacturing method thereof - Google Patents

Abstract

To suppress the deterioration of the volumetric energy density of a power storage element while ensuring the reliability of the power storage element.SOLUTION: A power storage element 1 includes an exterior body 7, an electrode body 5, and a tab 6. The exterior body 7 includes a first exterior material 40 and a second exterior material 50. The electrode body 5 is accommodated in an accommodation space 7a formed between the first exterior material 40 and the second exterior material 50, and includes a plurality of first electrodes 10 and a plurality of second electrodes 20 laminated in a first direction d1. The tab 6 is electrically connected to the electrode body 5 at a connection portion 8, passes between the first exterior material 40 and the second exterior material 50, and extends in a second direction d2 which is non-parallel to the first direction d1. A value of a ratio of a length of the connection portion 8 along the second direction d2 to the width of the connection portion 8 along a third direction d3 orthogonal to both the first direction d1 and the second direction d2 is 0.025 or more and 2.00 or less.SELECTED DRAWING: Figure 6

Description

The present invention relates to a power storage element and a method for manufacturing the power storage element.

As a power storage element, for example, as proposed in Patent Document 1, a laminated battery or a wound battery having an electrode body in which positive electrodes and negative electrodes are alternately laminated is widely used. In such a power storage element, an electrode body and an electrolytic solution are housed inside the exterior body. Tabs are connected to each of the positive electrode body and the negative electrode body in order to extract electric power from the electrode body. More specifically, the electrodes are connected to each other in the connection region at the end of each electrode of the electrode body, and in this connection region, the tab is connected to each electrode. The electrode body and the tab are electrically connected by, for example, welding at the connecting portion. Further, the tab extends from the connection region of the electrode body to the outside of the exterior body. By connecting an external device that requires electric power to each tab, electric power can be supplied to the device.

Japanese Patent Application Laid-Open No. 2015-513183

By the way, the connection between the electrode body and the tab may be peeled off. For example, when a force is applied to the tip of the tab to connect the tab to an external device, the force is transmitted to the connection with the electrode body, which is the base end of the tab, and as a result, the electrode body and the tab May peel off. In order to prevent such peeling between the electrode body and the tab, it is conceivable to increase the area of the joint portion between the electrode body and the tab. When the area of the connecting portion between the electrode body and the tab is increased, the connection strength between the electrode body and the tab can be increased, and the electrode body and the tab can be made difficult to peel off.

In order to increase the area of the connecting portion between the electrode body and the tab, it is conceivable to increase the length of the connecting portion between the electrode body and the tab in the extending direction of the tab. However, since the tab is connected to the connection region in which each electrode included in the electrode body is connected to each other, in order to increase the length of the connection portion along the extending direction of the tab, the length of the connection region should be increased. It needs to be taken long. The connection region of the electrode body is a region that does not contribute to the improvement of the capacity that the electrode body can supply. Therefore, if the length of the connection region is increased, the volumetric energy density of the power storage element deteriorates.

Alternatively, in order to increase the area of the connecting portion between the electrode body and the tab, it is conceivable to increase the length of the connecting portion between the electrode body and the tab in the direction orthogonal to the extending direction of the tab, that is, the width of the tab. However, when the width of the tab is increased, the portion where the tab and the exterior body come into contact with each other also becomes longer. The portion where the tab and the exterior body come into contact with each other is weaker in strength than the other portions, and is easily eroded by the gas generated inside the power storage element. Therefore, if the width of the tab is increased, the sealing of the exterior body is likely to be impaired.

In this way, the reliability of the power storage element is ensured by preventing the electrode body and the tab from peeling off and the outer body is maintained to be sealed, and the deterioration of the volumetric energy density of the power storage element is suppressed. It is difficult to make them compatible. The present invention has been made in consideration of such a point, and an object of the present invention is to suppress deterioration of the volumetric energy density of the power storage element while ensuring the reliability of the power storage element.

The power storage element of the present invention
An exterior body including the first exterior material and the second exterior material,
An electrode body including a plurality of first electrodes and a plurality of second electrodes stacked in a first direction and accommodated in a storage space formed between the first exterior material and the second exterior material.
It is provided with a tab that is electrically connected to the electrode body at a connection portion and that passes between the first exterior material and the second exterior material and extends in a second direction that is non-parallel to the first direction.
The value of the ratio of the length of the connecting portion along the second direction to the width of the connecting portion along the third direction orthogonal to both the first direction and the second direction is 0.025 or more. It is 2.00 or less.

In the power storage element of the present invention, the area of the connection portion ^{may be 80 mm 2} or more and 400 mm ² or less.

In the power storage element of the present invention, the length of the connection portion along the second direction may be 2 mm or more and 20 mm or less.

In the power storage element of the present invention, the width of the connection portion along the third direction may be 10 mm or more and 80 mm or less.

In the power storage element of the present invention, the width of the tab along the third direction may be constant.

In the power storage element of the present invention, the width of the tab along the third direction may be the same as the width of the electrode body along the third direction.

In the power storage element of the present invention
The first electrode has a first electrode current collector and a first electrode active material layer provided on at least one surface of the first electrode current collector and containing the first electrode active material.
The first electrode active material layer may contain lithium iron phosphate.

In the electricity storage device of the present invention, the area of the electrode body in plan view, may be 80 cm ² or more 4700Cm ² or less.

In the power storage element of the present invention, the thickness of the electrode body along the first direction may be 0.25 mm or more and 9.5 mm or less.

In the power storage element of the present invention, the first exterior material and the second exterior material may be joined at a joint located at an edge portion.

The method for manufacturing a power storage element of the present invention is any of the above-mentioned methods for manufacturing a power storage element.
A step of electrically connecting an electrode body including a plurality of first electrodes and a plurality of second electrodes laminated in the first direction and a tab extending in the second direction non-parallel to the first direction at a connecting portion. With
The electrode body and the tab are the ratio of the length of the connecting portion along the second direction to the width of the connecting portion along the third direction orthogonal to both the first direction and the second direction. The connection is made so that the value of is 0.025 or more and 2.00 or less.

According to the present invention, it is possible to suppress deterioration of the volumetric energy density of the power storage element while ensuring the reliability of the power storage element.

FIG. 1 is a perspective view showing a power storage element. FIG. 2 is a plan view showing a power storage element. FIG. 3 is a cross-sectional view taken along the line III-III of FIG. FIG. 4 is a plan view showing the electrode body. FIG. 5 is a plan view showing an electrode body without an insulating sheet. FIG. 6 is an enlarged view showing the connection portion between the electrode body and the tab. FIG. 7 is a view showing a modified example of the electrode body, and is a plan view of the electrode body excluding the insulating sheet.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale, aspect ratio, etc. are appropriately changed from those of the actual product and exaggerated for the sake of ease of understanding.

It should be noted that the terms such as "parallel", "orthogonal", and "same", and the values of length and angle, etc., which specify the shape and geometric conditions and their degrees, which are used in the present specification, are strictly defined. Without being bound by meaning, we will interpret it including the range in which similar functions can be expected.

1 to 6 are diagrams for explaining an embodiment of a power storage element according to the present invention. FIG. 1 is a perspective view showing a specific example of a power storage element. Further, FIG. 2 shows the power storage element 1 in a plan view. In the present specification, the plan view means observing a flat plate-shaped or flat-shaped member from the normal direction of the sheet surface of the member. Specifically, in the present embodiment, it means observing the target member from the first direction d1. As shown in FIGS. 1 and 2, the power storage element 1 is connected to the exterior body 7, the electrode body 5 and the electrolytic solution housed in the storage space 7a formed by the exterior body 7, and the exterior body 5. It has a tab 6 extending from the inside of the body 7 to the outside. FIG. 3 is a cross-sectional view taken along the line III-III of the power storage element 1 of FIG. As shown in FIG. 3, the electrode body 5 has a plurality of first electrodes 10 and a plurality of second electrodes 20 laminated in the first direction d1.

In the examples shown in FIGS. 1 and 2, the power storage element 1 has a thin flat shape in the first direction d1 which is the thickness direction as a whole, and is short of the second direction d2 which is the longitudinal direction. It extends in the third direction d3, which is the direction. The first direction d1, the second direction d2, and the third direction d3 are non-parallel to each other, and in the illustrated example, they are orthogonal to each other. The plan view of the power storage element 1 shown in FIG. 2 means observation from a direction along the first direction d1, as in the plan view of the electrode body 5 in FIGS. 4 and 5 which will be referred to later. ..

In the plan view of the power storage element 1 shown in FIG. 2, the size of the power storage element 1, more specifically, the size of the exterior body 7 of the power storage element 1, that is, the area of the power storage element 1 in a plan view is, for example, 100 cm ² or more and 5000 ^{cm 2.} It can be as follows. Further, the length of the outer circumference of the power storage element 1 can be set to, for example, 40 cm or more and 300 cm or less. The thickness of the power storage element 1, that is, the length along the first direction d1, can be set to 0.3 mm or more and 10 mm or less. The weight of the power storage element 1 can be, for example, 0.06 kg or more and 4.00 kg or less. The illustrated exterior body 7 has a rectangular shape in a plan view. The length along the long side parallel to the second direction d2 of the exterior body 7 can be 10 cm or more and 100 cm or less. The length along the long side parallel to the third direction d3 of the exterior body 7 can be 10 cm or more and 50 cm or less.

The power storage element 1 having such a large and flat shape can be installed even in a narrow space having a limited height. Further, the flat power storage element 1 can be bent and curved. Further, the large and flat power storage elements 1 can be easily laminated. By stacking a plurality of power storage elements 1 to form a unit, a large-capacity power storage element unit can be easily formed. In addition, the heat dissipation of the power storage element unit can be made excellent.

Hereinafter, an example in which the power storage element 1 is a laminated lithium ion secondary battery will be described. In this example, the first electrode 10 constitutes the positive electrode 10X, and the second electrode 20 constitutes the negative electrode 20Y. However, as can be understood from the description of the action and effect described below, the embodiment described here is not limited to the lithium ion secondary battery, and the first electrode 10 and the second electrode 20 are used. It can be widely applied to the power storage element 1 formed by alternately stacking in the first direction d1. Further, the power storage element 1 is not limited to the laminated battery, and may be, for example, a wound battery. Even when the power storage element 1 is a wound battery, the first electrode 10 and the second electrode 20 are laminated in the first direction d1.

Hereinafter, each component of the power storage element 1 will be described.

First, the electrode body 5 will be described. As shown in FIG. 3, the electrode body 5 includes a positive electrode 10X (first electrode 10) and a negative electrode 20Y (second electrode 20) alternately laminated along the first direction d1, and a positive electrode 10X and a negative electrode 20Y. It has an insulating sheet 30 arranged between them. In the illustrated example, the insulating sheet 30 is arranged on the onemost side and the othermost side of the electrode body 5, in other words, also between the electrode body 5 and the exterior body 7. The electrode body 5 includes, for example, a plate-shaped positive electrode 10X and a negative electrode 20Y in total of 20 or more. The electrode body 5 has an overall flat shape, is thin in the first direction d1, and extends in the second direction d2 and the third direction d3, which are non-parallel to the first direction d1. The size of the electrode body 5, that is, to the area in plan view, for example, 80 cm ² or more 4700Cm ² or less. Further, the thickness of the electrode body 5, that is, the length of the electrode body 5 along the first direction d1 can be set to, for example, 0.25 mm or more and 9.5 mm or less.

FIG. 4 is a plan view of the electrode body 5. FIG. 5 is a plan view showing the electrode body 5 shown in FIG. 4 with the insulating sheet 30 removed. In the non-limiting example shown in FIGS. 4 and 5, the positive electrode 10X and the negative electrode 20Y are plate-shaped electrodes having a substantially rectangular outer contour. The second direction d2, which is non-parallel to the first direction d1, is the longitudinal direction of the positive electrode 10X and the negative electrode 20Y, and the third direction d3, which is orthogonal to both the first direction d1 and the second direction d2, is the positive electrode 10X and the negative electrode 20Y. It is the short side direction (width direction) of. As shown in FIGS. 3 and 4, the positive electrode 10X and the negative electrode 20Y are arranged so as to be offset in the second direction d2. More specifically, the plurality of positive electrodes 10X are arranged closer to one side in the second direction d2, and the plurality of negative electrodes 20Y are arranged closer to the other side in the second direction d2. As shown in FIG. 4, the positive electrode 10X and the negative electrode 20Y overlap with the first direction d1 at the center in the second direction d2.

In the examples shown in FIGS. 4 and 5, the negative electrode 20Y extends from the positive electrode 10X to one side and the other side of the third direction d3. The thickness of the positive electrode 10X and the negative electrode 20Y, that is, the lengths of the positive electrode 10X and the negative electrode 20Y along the first direction d1 can be set to, for example, 80 μm or more and 250 μm or less. The lengths of the positive electrode 10X and the negative electrode 20Y along the longitudinal direction, that is, the second direction d2 can be set to, for example, 95 mm or more and 950 mm or less. The length (width) of the positive electrode 10X and the negative electrode 20Y along the lateral direction, that is, the third direction d3 can be set to, for example, 95 mm or more and 450 mm or less.

Next, the positive electrode 10X (first electrode 10) will be described. As shown in FIG. 3, the positive electrode 10X (first electrode 10) includes a positive electrode current collector 11X (first electrode current collector 11) and a positive electrode active material layer provided on the positive electrode current collector 11X. It has 12X (first electrode active material layer 12). In the lithium ion secondary battery, the positive electrode 10X occludes lithium ions during discharging and releases lithium ions during charging.

As shown in FIG. 3, the positive electrode current collector 11X has a first surface 11a and a second surface 11b facing each other as main surfaces. The positive electrode active material layer 12X is formed on both surfaces of the first surface 11a and the second surface 11b of the positive electrode current collector 11X. Specifically, when the first surface 11a or the second surface 11b of the positive electrode current collector 11X is located on the outermost side of the electrode plates 10 and 20 included in the electrode body 5 in the stacking direction d1, the positive electrode current collector is collected. The positive electrode active material layer 12X is not provided on the outermost surface of the electric body 11X. Except for the presence or absence of the positive electrode active material layer 12X depending on the position of the positive electrode current collector 11X, the plurality of positive electrode bodies 10X included in the electrode body 5 have positive electrode active material layers 12X on both sides of the positive electrode current collector 11X. They can be configured identically to each other.

The positive electrode current collector 11X and the positive electrode active material layer 12X can be produced by various manufacturing methods using various materials that can be applied to the power storage element 1 (lithium ion secondary battery). As an example, the positive electrode current collector 11X can be formed of a conductive metal such as copper, aluminum, titanium, nickel, stainless steel, especially aluminum foil. The thickness of the positive electrode current collector 11X is not particularly limited, but is preferably 1 μm or more and 50 μm or less, and more preferably 5 μm or more and 20 μm or less. When the thickness of the positive electrode current collector 11X is 1 μm or more and 50 μm or less, the positive electrode current collector 11X can be easily handled and the decrease in the volumetric energy density of the power storage element 1 can be suppressed. The positive electrode active material layer 12X contains, for example, a positive electrode active material, a conductive auxiliary agent, and a binder serving as a binder. The positive electrode active material layer 12X is produced by applying a positive electrode slurry obtained by dispersing a positive electrode active material, a conductive auxiliary agent and a binder in a solvent onto a material forming the positive electrode current collector 11X and solidifying the positive electrode active material layer 12X. obtain.

As the positive electrode active material, for example, a _{lithium metallic acid compound represented by the general formula LiM x} O _y (where M is a metal and x and y are composition ratios of metal M and oxygen O) is used. Specific examples of the lithium metal acid compound include lithium cobalt oxide, lithium nickel oxide, lithium manganate and the like. Alternatively, as the positive electrode active material, a _{lithium metal phosphate compound represented by the general formula LiMPO 4} (where M is a metal) may be used. Specific examples of the metallic lithium phosphate compound include lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, and the like. Further, as the positive electrode active material, a material using a plurality of metals other than lithium may be used, and an NCM (nickel cobalt manganese) oxide, an NCA (nickel cobalt aluminum) oxide, or the like, which is called a ternary system, is used. You may. As the positive electrode active material, one of these substances may be used alone, or two or more of these substances may be used in combination, but lithium iron phosphate is preferable. When the positive electrode active material contained in the positive electrode active material layer 12X is lithium iron phosphate, it can be a long-life power storage element having excellent cycle characteristics. That is, the power storage element 1 can be used for a long period of time. The positive electrode active material is not particularly limited, but its average particle size is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less. The average particle size means the particle size (D50) when the volume integration is 50% in the particle size distribution obtained by the laser diffraction / scattering method. The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 98.5% by mass or less, more preferably 60% by mass or more and 98% by mass or less, based on the total amount of the positive electrode active material layer.

Specific examples of the binder serving as a positive electrode binder include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), and fluorine-containing resins such as polytetrafluoroethylene (PTFE). Acrylic resins such as polymethyl acrylate (PMA) and polymethyl methacrylate (PMMA), polyvinyl acetate, polyimide (PI), polyamide (PA), polyvinylidene chloride (PVC), polyether nitrile (PEN), polyethylene (PE) , Polypropylene (PP), Polyacrylonitrile (PAN), Acrylonitrile-butadiene rubber, Styrene butadiene rubber (SBR), Poly (meth) acrylic acid, Carboxymethyl cellulose (CMC), Hydroxyethyl cellulose, Polyvinyl alcohol and the like. These binders may be used alone or in combination of two or more. Further, carboxymethyl cellulose and the like may be used in the form of a salt such as a sodium salt. Among these, a fluorine-containing resin is preferable, and polyvinylidene fluoride is more preferable. The content of the binder in the positive electrode active material layer 12X is preferably 0.5% by mass or more, more preferably 0.5% by mass or more and 20% by mass or less, based on the total amount of the positive electrode active material layer 12X. , 1.0% by mass or more and 10% by mass or less is more preferable.

As the conductive auxiliary agent, a material having higher conductivity than the positive electrode active material and the negative electrode active material is used. Specifically, carbon black such as Ketjen black and acetylene black (AB), carbon nanotubes, carbon such as rod-shaped carbon, etc. Materials and the like can be mentioned. The conductive auxiliary agent may be used alone or in combination of two or more. When the positive electrode active material layer contains a conductive auxiliary agent, the content of the conductive auxiliary agent is preferably 0.5% by mass or more and 15% by mass or less based on the total amount of the positive electrode active material layer, and is 1.0. It is more preferably mass% or more and 9 mass% or less.

The positive electrode active material layer 12X may contain an optional component other than the positive electrode active material, the conductive auxiliary agent, and the binder as long as the effects of the present invention are not impaired. However, the total content of the positive electrode active material, the conductive auxiliary agent, and the binder in the total mass of the positive electrode active material layer 12X is preferably 90% by mass or more, and more preferably 95% by mass or more. The thickness of the positive electrode active material layer 12X (the thickness of each of the positive electrode active material layers 12X when there are a plurality of layers) is not particularly limited, but is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 80 μm or less.

As shown in FIG. 5, the positive electrode current collector 11X (first electrode current collector 11) has a first connection region a1 and a first electrode region b1. The positive electrode active material layer 12X (first electrode active material layer 12) is laminated only in the first electrode region b1 of the positive electrode current collector 11X. Therefore, the first connection region a1 is a portion of the positive electrode current collector 11X of the electrode body 5 that does not contribute to the supply of electric power. The first connection region a1 and the first electrode region b1 are arranged in the second direction d2. The first connection region a1 is located on one side (left side in FIG. 5) in the second direction d2 from the first electrode region b1. That is, the first connection region a1 is located at the end of the second direction d2. As shown in FIG. 5, the plurality of positive electrode current collectors 11X are bonded to each other by resistance welding, ultrasonic welding, bonding with tape, fusion, etc. in the first connection region a1, and are electrically connected to each other. There is.

In the illustrated example, one tab 6 is electrically connected to the positive electrode current collector 11X in the first connection region a1. The tab 6 extends from the electrode body 5 in the second direction d2. On the other hand, as shown in FIG. 5, the first electrode region b1 is located inside the region of the negative electrode 20Y facing the negative electrode active material layer 22Y, which will be described later. The width of the positive electrode 10X along the third direction d3 is narrower than the width of the negative electrode 20Y along the third direction d3. By arranging the first electrode region b1 in this way, it is possible to prevent the precipitation of lithium from the negative electrode active material layer 22Y.

Next, the negative electrode 20Y (second electrode 20) will be described. The negative electrode 20Y (second electrode 20) includes a negative electrode current collector 21Y (second electrode current collector 21) and a negative electrode active material layer 22Y (second electrode active material layer 22) provided on the negative electrode current collector 21Y. And have. In the lithium ion secondary battery, the negative electrode 20Y emits lithium ions at the time of discharging and occludes the lithium ions at the time of charging.

As shown in FIG. 3, the negative electrode current collector 21Y has a first surface 21a and a second surface 21b facing each other as main surfaces. The negative electrode active material layer 22Y is formed on at least one of the first surface 21a and the second surface 21b of the negative electrode current collector 21Y. Specifically, when the first surface 21a or the second surface 21b of the negative electrode current collector 21Y is located on the outermost side of the electrode plates 10 and 20 included in the electrode body 5 in the stacking direction d1, the negative electrode current collector The negative electrode active material layer 22Y is not provided on the outermost surface of the electric body 21Y. Except for the presence or absence of the negative electrode active material layer 22Y depending on the position of the negative electrode current collector 21Y, the plurality of negative electrode bodies 20Y included in the electrode body 5 are a pair of negative electrode active material layers provided on both sides of the negative electrode current collector 21Y. It has 22Y and can be configured identically to each other.

The negative electrode current collector 21Y and the negative electrode active material layer 22Y can be produced by various manufacturing methods using various materials that can be applied to the power storage element 1 (lithium ion secondary battery). As an example, the negative electrode current collector 21Y is formed of a conductive metal such as copper, aluminum, titanium, nickel, or stainless steel, particularly copper foil. The thickness of the negative electrode current collector 21Y is not particularly limited, but is preferably 1 μm or more and 50 μm or less, and more preferably 5 μm or more and 20 μm or less. When the thickness of the negative electrode current collector 21Y is 1 μm or more and 50 μm or less, the negative electrode current collector 21Y can be easily handled and the decrease in the volumetric energy density of the power storage element 1 can be suppressed. The negative electrode active material layer 22Y contains, for example, a negative electrode active material made of a carbon material and a binder that functions as a binder. The negative electrode active material layer 22Y is formed by dispersing, for example, a negative electrode active material composed of carbon powder or graphite powder, a composite of a tin compound and silicon and carbon, lithium or the like, and a binder such as polyvinylidene fluoride in a solvent. It can be produced by applying a negative electrode slurry on a material forming the negative electrode current collector 21Y and solidifying it.

As the negative electrode active material, a carbon material is preferable, and graphite is more preferable. As the negative electrode active material, these substances may be used alone or in combination of two or more. The negative electrode active material is not particularly limited, but its average particle size is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less. The content of the negative electrode active material in the negative electrode active material layer 22Y is preferably 50% by mass or more and 98.5% by mass or less, more preferably 60% by mass or more and 98% by mass or less, based on the total amount of the negative electrode active material layer 22Y.

Specific examples of the binder serving as the negative electrode binder are the same as those of the positive electrode binder, and these binders may be used alone or in combination of two or more. Further, carboxymethyl cellulose and the like may be used in the form of a salt such as a sodium salt. Among these, a fluorine-containing resin is preferable, and polyvinylidene fluoride is more preferable. The content of the binder in the negative electrode active material layer 22Y is preferably 0.5% by mass or more, more preferably 0.5% by mass or more and 20% by mass or less, based on the total amount of the negative electrode active material layer 22Y. , 1.0% by mass or more and 10% by mass or less is more preferable.

The negative electrode active material layer 22Y may contain a conductive auxiliary agent. Specific examples of the conductive auxiliary agent include the same as in the case of the positive electrode active material layer 12X. The conductive auxiliary agent may be used alone or in combination of two or more. When the negative electrode active material layer contains a conductive auxiliary agent, the content of the conductive auxiliary agent is preferably 1% by mass or more and 30% by mass or less based on the total amount of the negative electrode active material layer, and is preferably 2% by mass or more and 25% by mass or more. It is more preferably mass% or less.

In the case of the positive electrode active material layer 12X, the negative electrode active material layer 22Y may contain any components other than the negative electrode active material, the conductive auxiliary agent, and the binder as long as the effects of the present invention are not impaired. And its content is also the same. The thickness of the negative electrode active material layer 22Y (when there are a plurality of negative electrode active material layers 22Y, the thickness of each) is not particularly limited, but is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 80 μm or less.

As shown in FIG. 5, the negative electrode current collector 21Y (second electrode current collector 21) has a second connection region a2 and a second electrode region b2. The negative electrode active material layer 22Y (second electrode active material layer 22) is laminated only on the second electrode region b2 of the negative electrode current collector 21Y. Therefore, the second connection region a2 is a portion of the negative electrode current collector 21Y of the electrode body 5 that does not contribute to the supply of electric power. The second connection region a2 and the second electrode region b2 are arranged in the second direction d2. The second connection region a2 is located on the other side (right side in FIG. 5) in the second direction d2 from the second electrode region b2. That is, the second connection region a2 is located at the end of the second direction d2. As shown in FIG. 5, the plurality of negative electrode current collectors 21Y are bonded to each other by resistance welding, ultrasonic welding, bonding with tape, fusion, etc. in the second connection region a2, and are electrically connected to each other. There is. In the illustrated example, a tab 6 other than the tab connected to the positive electrode current collector 11X is electrically connected to the negative electrode current collector 21Y in the second connection region a2. The tab 6 extends from the electrode body 5 to the other side of the second direction d2.

As described above, the first electrode region b1 of the positive electrode 10X is located inside the region facing the second electrode region b2 of the negative electrode 20Y (see FIG. 5). That is, the second electrode region b2 extends to a region including a region of the positive electrode 10X facing the positive electrode active material layer 12X. The width of the negative electrode 20Y along the third direction d3 is wider than the width of the positive electrode 10X along the third direction d3. In particular, the one-sided end portion 20a of the negative electrode 20Y in the third direction d3 is located on one side in the third direction d3 of the positive electrode 10X with respect to the one-sided end portion 10a in the third direction d3, and the negative electrode 20Y is the third. The other side end 20b in the three directions d3 is located on the other side in the third direction d3 with respect to the other side end 10b in the third direction d3 of the positive electrode 10X.

Next, the insulating sheet 30 will be described. The insulating sheet 30 is located, for example, between any two electrodes 10 and 20 adjacent to each other in the first direction d1. The insulating sheet 30 located between the positive electrode 10X (first electrode 10) and the negative electrode 20Y (second electrode 20) is separated so that the positive electrode 10X and the negative electrode 20Y do not come into contact with each other. The insulating sheet 30 arranged on the most one side and the most other side of the first direction d1 of the electrode body 5 forms a part of the surface of the electrode body 5, and the electrode body 5 does not come into contact with an external member. It is separated like this. The insulating sheet 30 has an insulating property and prevents a short circuit due to contact between the positive electrode 10X and the negative electrode 20Y.

In the example shown in FIGS. 4 and 5, the insulating sheet 30 has a rectangular shape extending in the second direction d2 and the third direction d3. Further, the insulating sheet 30 extends so as to cover the entire region of the positive electrode active material layer 12X of the positive electrode 10X and the entire region of the negative electrode active material layer 22Y of the negative electrode 20Y in a plan view.

The insulating sheet 30 preferably has a large ion permeability (air permeability), a predetermined mechanical strength, and durability against an electrolytic solution, a positive electrode active material, a negative electrode active material, and the like. As such an insulating sheet 30, for example, a porous body formed of an insulating material, a non-woven fabric, or the like can be used. More specifically, as the insulating sheet 30, a porous film made of a thermoplastic resin having a melting point of about 80 to 140 ° C. can be used. As the thermoplastic resin, a polyolefin-based polymer such as polypropylene or polyethylene, or polyethylene terephthalate can be adopted. An electrolytic solution is sealed together with the electrode body 5 in the accommodation space 7a of the exterior body 7. By impregnating the insulating sheet 30 made of a porous body or a non-woven fabric with the electrolytic solution, the electrode active material layers 12 and 22 of the electrodes 10 and 20 in which the insulating sheet 30 is arranged are maintained in contact with the electrolytic solution. To.

As an example, the insulating sheet 30 includes insulating fine particles and a binder for an insulating sheet, and the insulating fine particles are bound by a binder for an insulating sheet. The insulating fine particles are not particularly limited as long as they are insulating, and may be either organic particles or inorganic particles. Specific organic particles include, for example, crosslinked polymethyl methacrylate, crosslinked styrene-acrylic acid copolymer, crosslinked acrylonitrile resin, polyamide resin, polyimide resin, poly (lithium 2-acrylamide-2-methylpropanesulfonate), and the like. Examples thereof include particles composed of organic compounds such as polyacetal resin, epoxy resin, polyester resin, phenol resin, and melamine resin. Inorganic particles include silicon dioxide, silicon nitride, alumina, boehmite, titania, zirconia, boron nitride, zinc oxide, tin dioxide, niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), potassium fluoride, and foot. Examples thereof include particles composed of inorganic compounds such as lithium pentoxide, clay, zeolite, and calcium carbonate. Further, the inorganic particles may be particles composed of known composite oxides such as niobium-tantalum composite oxide and magnesium-tantalum composite oxide. One type of insulating fine particles may be used alone, or a plurality of types may be used in combination. The average particle size of the insulating fine particles is not particularly limited as long as it is smaller than the thickness of the insulating sheet 30, and is, for example, 0.001 μm or more and 1 μm or less, preferably 0.05 μm or more and 0.8 μm or less, and more preferably 0.1 μm or more and 0. It is 0.6 μm or less. The content of the insulating fine particles contained in the insulating sheet 30 is preferably 15% by mass or more and 95% by mass or less, more preferably 40% by mass or more and 90% by mass or less, still more preferably 60, based on the total amount of the insulating sheet 30. It is mass% or more and 85 mass% or less. When the content of the insulating fine particles is within the above range, the insulating sheet 30 can form a uniform porous structure and is provided with appropriate insulating properties. As the binder for the insulating sheet, the same type as the binder for the positive electrode described above can be used. The content of the binder for the insulating sheet in the insulating sheet 30 is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, and 15% by mass based on the total amount of the insulating sheet 30. More preferably 40% by mass or less.

Next, tab 6 will be described. The tab 6 functions as a terminal in the power storage element 1. As shown in FIGS. 3 to 5, one tab 6 (one side of the second direction d2) is electrically connected to the positive electrode 10X (first electrode 10) of the electrode body 5. Similarly, the tab 6 on the other side (the other side of the second direction d2) is electrically connected to the negative electrode 20Y (second electrode 20) of the electrode body 5. As shown in FIGS. 1 and 3, the pair of tabs 6 extend from the accommodation space 7a inside the exterior body 7 to the outside of the exterior body 7 in the second direction d2. The length of the portion extending to the outside of the exterior body 7 of the tab 6 along the second direction d2 is, for example, 10 mm or more and 25 mm or less.

As shown in FIG. 3, the tab 6 is between the first exterior material 40 and the second exterior material 50 of the exterior body 7, which will be described later, and more specifically, the first sealant layer 42 of the first exterior material 40. It passes between the second exterior material 50 and the second sealant layer 52.

The tab 6 can be formed in a plate shape or a strip shape using aluminum, copper, nickel, nickel-plated copper or the like. The thickness of the tab 6 is, for example, 0.1 mm or more and 1 mm or less. Further, the width of the tab 6, that is, the length of the tab 6 along the third direction d3 is constant.

A seal portion 4 is provided on the tab 6. The seal portion 4 surrounds the tab 6 from the periphery at the intermediate portion of the tab 6 in the second direction d2. The seal portion 4 is welded to the exterior body 7 and seals between the tab 6 and the exterior body 7. The sealing portion 4 effectively prevents contact between the tab 6 and the exterior body 7, particularly contact between the tab 6 and the exterior body 7 with the metal layer 41 of the first exterior material 40. Examples of the material of the sealing portion 4 include polypropylene, modified polypropylene, low-density polyethylene, ionomer, ethylene-vinyl acetate copolymer and the like. The thickness of the seal portion 4 can be, for example, 0.05 mm or more and 0.4 mm or less.

As shown in FIGS. 3 to 5, the tab 6 is electrically connected to the electrode body 5 by contacting the electrode body 5 at the connecting portion 8. More specifically, the portion of one tab 6 located on one side in the second direction d2 located on the other side in the second direction d2 is first connected to the positive electrode 10X (first electrode 10) at the one connecting portion 8. It is connected in the area a1. The portion of the other tab 6 located on the other side in the second direction d2 located on one side in the second direction d2 is connected to the negative electrode 20Y (second electrode 20) in the other connection portion 8 in the second connection region a2. are doing.

FIG. 6 shows an enlarged connection portion 8 in which one of the tabs 6 and the positive electrode 10X (first electrode 10) of the electrode body 5 are connected. In FIG. 6, the connecting portion 8 is shown by diagonal lines. The value of the ratio of the length L along the second direction d2 of the connecting portion 8 shown in FIG. 6 to the width W along the third direction d3 is 0.025 or more and 2.00 or less, preferably 0. It is 100 or more and 1.00 or less, and more preferably 0.10 or more and 0.80 or less. The area of the connecting portion 8 ^{is preferably 80 mm 2} or more and 400 mm ² or less, and ^{more preferably 120 mm 2} or more and 250 mm ² or less. In the illustrated example, the connecting portion 8 is rectangular. Therefore, the area of the connecting portion 8 is the product of the length L along the second direction d2 and the width W along the third direction d3. The length L of the connecting portion 8 along the second direction d2 is preferably 2 mm or more and 20 mm or less, and more preferably 4 mm or more and 10 mm or less. Further, the width W of the connecting portion 8 along the third direction d3 is preferably 10 mm or more and 80 mm or less, and more preferably 10 mm or more and 40 mm or less.

Next, the exterior body 7 will be described. The exterior body 7 is a package for sealing the electrode body 5 and the electrolytic solution. As shown in FIG. 3, the exterior body 7 forms an accommodation space 7a for accommodating the electrode body 5. The exterior body 7 houses the electrode body 5 and the electrolytic solution in the storage space 7a inside the outer body 7 and seals the outer body 7.

The accommodation space 7a has a size equal to or larger than the size of the electrode body 5 so that the electrode body 5 can be accommodated. On the other hand, in order to increase the volumetric energy density of the power storage element 1, the accommodation space 7a is preferably small. Here, the volumetric energy density means the amount of electric power (capacity) that can be supplied by the power storage element per volume occupied by the power storage element. Therefore, it is preferable that the exterior body 7 is in contact with the electrode body 5 housed in at least in the first direction d1. The accommodation space 7a is formed so as to have a shape that matches the shape of the electrode body 5 to be accommodated. In the illustrated example, the accommodation space 7a has a substantially rectangular parallelepiped shape. The accommodation space 7a has, for example, a length along the first direction d1 of 0.25 mm or more and 9.5 mm or less, a length along the second direction d2 of 95 mm or more and 990 mm or less, and a third direction d3. The length along the line is 95 mm or more and 490 mm or less.

Further, the exterior body 7 has a first exterior material 40 and a second exterior material 50. As is well shown in FIG. 2, the accommodation space 7a is formed by joining the first exterior material 40 and the second exterior material 50 at the joints 60 located at the respective edges. .. In particular, in the example shown in FIG. 2, the first exterior material 40 and the second exterior material 50 are arranged so as to face each other and are joined at the joint portion 60. The first exterior material 40 and the second exterior material 50 may be joined by, for example, an adhesive layer having adhesiveness, or may be joined by welding. When bonded by an adhesive layer, the adhesive layer preferably has insulating properties, chemical resistance, thermoplasticity, etc. in addition to adhesiveness, for example, polypropylene, modified polypropylene, low density polyethylene, ionomer, ethylene. -A vinyl acetate copolymer or the like can be used. The thickness of the first exterior material 40 and the second exterior material 50 can be, for example, 0.1 mm or more and 0.3 mm or less.

The first exterior material 40 and the second exterior material 50 may be separate members, but may be integrated members. That is, the first exterior material 40 and the second exterior material 50 may be a part of one sheet-shaped member and a part of the other. In this case, the accommodation space is formed by joining the first exterior material 40 and the second exterior material 50 at a portion (edge portion) other than the portion where the first exterior material 40 and the second exterior material 50 are connected. 7a is formed.

As is well shown in FIG. 3, the first exterior material 40 bulges from the peripheral edge of the first exterior material 40 in order to form a storage space 7a having a sufficient size for accommodating the electrode body 5. The exit 47 is included. The bulging portion 47 is surrounded by the peripheral edge of the first exterior material 40 and bulges in a direction away from the second exterior material 50. The bulging portion 47 is located at the central portion of the first exterior material 40. On the other hand, in the illustrated example, the second exterior material 50 does not include a bulging portion and is flat.

However, not limited to the illustrated example, the first exterior material 40 does not include a bulge portion, and the second exterior material 50 may include a bulge portion for forming the accommodation space 7a. Furthermore, both the first exterior material 40 and the second exterior material 50 may include a bulge for forming the accommodation space 7a.

In the example shown in FIG. 3, the first exterior material 40 includes a first metal layer 41 and a first sealant layer 42 laminated on the first metal layer 41. Similarly, the second exterior material 50 includes a second metal layer 51 and a second sealant layer 52 laminated on the second metal layer 51. The first sealant layer 42 is provided on the side of the first exterior material 40 facing the second exterior material 50. The second sealant layer 52 is provided on the side of the second exterior material 50 facing the first exterior material 40. That is, the first exterior material 40 and the second exterior material 50 are arranged so that the first sealant layer 42 of the first exterior material 40 and the second sealant layer 52 of the second exterior material 50 face each other.

Further, in the illustrated example, the first exterior material 40 is provided on the surface of the first metal layer 41, that is, on the surface opposite to the surface on which the first sealant layer 42 of the first metal layer 41 is laminated. It further includes a first insulating layer 43 having an insulating property. Further, in the illustrated example, the second exterior material 50 is provided on the surface of the second metal layer 51, that is, on the surface of the second metal layer 51 opposite to the surface on which the second sealant layer 52 is laminated. A second insulating layer 53 having an insulating property is further included. As shown in FIG. 3, in the second direction d2, the tab 6 passes between the first sealant layer 42 of the first exterior material 40 and the second sealant layer 52 of the second exterior material 50. The seal portion 4 provided on the tab 6 and the first sealant layer 42 and the second sealant layer 52 are welded to seal between the tab 6 and the exterior body 7.

The first metal layer 41 and the second metal layer 51 preferably have high gas barrier properties and molding processability, and for example, aluminum foil, stainless steel foil, or the like can be used. The first sealant layer 42 and the second sealant layer 52 prevent the electrode body 5 housed in the storage space 7a from being electrically connected to the first metal layer 41 and the second metal layer 51. The first sealant layer 42 and the second sealant layer 52 are thermoplastic. The first exterior material 40 and the second exterior material 50 can be joined by welding by the first sealant layer 42 and the second sealant layer 52 having thermoplasticity. As the first sealant layer 42 and the second sealant layer 52, for example, polypropylene or the like can be used. The first insulating layer 43 and the second insulating layer 53 prevent the external conductor from being electrically connected to the first metal layer 41 and the second metal layer 51. The first insulating layer 43 and the second insulating layer 53 are, for example, thin nylon layers.

Next, an example of a method for manufacturing the power storage element 1 having the above-described configuration will be described.

First, a positive electrode 10X is produced as the first electrode 10. In order to form the positive electrode active material layer 12X of the positive electrode 10X, first, a composition for the positive electrode active material layer containing the positive electrode active material, the binder for the positive electrode, and the solvent is prepared. The composition for the positive electrode active material layer may contain other components such as a conductive additive to be blended if necessary. The positive electrode active material, the binder for the positive electrode, the conductive auxiliary agent and the like are as described above. The composition for the positive electrode active material layer is a slurry.

Water or an organic solvent is used as the solvent in the positive electrode active material layer composition. Specific examples of the organic solvent include one or more selected from N-methylpyrrolidone, N-ethylpyrrolidone, dimethylacetamide, and dimethylformamide. Of these, N-methylpyrrolidone is preferred. The solid content concentration of the composition for the positive electrode active material layer is preferably 5% by mass or more and 75% by mass or less, and more preferably 20% by mass or more and 65% by mass or less.

The positive electrode active material layer 12X may be formed by a known method using the positive electrode active material layer composition. For example, the positive electrode active material layer composition may be applied onto the positive electrode current collector 11X. It can be formed by drying. Further, the positive electrode active material layer 12X may be formed by applying the composition for the positive electrode active material layer on a base material other than the positive electrode current collector 11X and drying it. Examples of the base material other than the positive electrode current collector 11X include a known release sheet. The positive electrode active material layer 12X formed on the base material preferably has an insulating sheet 30 formed on the positive electrode active material layer 12X, and then the positive electrode active material layer 12X is peeled off from the base material and placed on the positive electrode current collector 11X. It may be transferred. The positive electrode active material layer 12X formed on the positive electrode current collector 11X or the base material is preferably pressure-pressed. By pressurizing, it becomes possible to increase the electrode density. The pressure press may be performed by a roll press or the like.

Next, the negative electrode 20Y as the second electrode 20 is manufactured. In order to form the negative electrode active material layer 22Y of the negative electrode 20Y, first, a composition for the negative electrode active material layer containing the negative electrode active material, the binder for the negative electrode, and the solvent is prepared. The composition for the negative electrode active material layer may contain other components such as a conductive auxiliary agent to be blended if necessary. The negative electrode active material, the binder for the negative electrode, the conductive auxiliary agent and the like are as described above. The composition for the negative electrode active material layer is a slurry.

As the solvent in the negative electrode active material layer composition, the same solvent as in the positive electrode active material layer composition can be used, and the solid content concentration thereof is also the same.

The negative electrode active material layer 22Y may be formed by a known method using the negative electrode active material layer composition. For example, the negative electrode active material layer composition may be applied onto the negative electrode current collector 21Y. It can be formed by drying. Further, the negative electrode active material layer 22Y may be formed by applying the composition for the negative electrode active material layer on a base material other than the negative electrode current collector 21Y and drying it. Examples of the base material other than the negative electrode current collector 21Y include a known release sheet. The negative electrode active material layer 22Y formed on the base material preferably has an insulating sheet 30 formed on the negative electrode active material layer 22Y, and then the negative electrode active material layer 22Y is peeled off from the base material and placed on the negative electrode current collector 21Y. It may be transferred. The negative electrode active material layer 22Y formed on the negative electrode current collector 21Y or the base material is preferably pressure-pressed. By pressurizing, it becomes possible to increase the electrode density. The pressure press may be performed by a roll press or the like.

In addition, the insulating sheet 30 is manufactured. The composition for the insulating sheet of the insulating sheet 30 contains inorganic particles, a binder for the insulating sheet, and a solvent. The composition for an insulating sheet may contain other optional components to be blended as needed. Details of the inorganic particles, the binder for the insulating layer, and the like are as described above. The composition for the insulating sheet is a slurry. As the solvent, water or an organic solvent may be used, and the details of the organic solvent include those similar to those of the organic solvent in the positive electrode active material layer composition. The solid content concentration of the composition for an insulating sheet is preferably 5% by mass or more and 75% by mass or less, and more preferably 15% by mass or more and 50% by mass or less.

The insulating sheet 30 can be formed by applying the composition for an insulating sheet on the positive electrode active material layer 12X or the negative electrode active material layer 22Y and drying it. The method of applying the composition for an insulating sheet to the surface of the positive electrode active material layer 12X or the negative electrode active material layer 22Y is not particularly limited, and for example, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, or a bar coating method. , Gravure coating method, screen printing method and the like. The drying temperature is not particularly limited as long as the solvent can be removed, but is, for example, 40 ° C. or higher and 120 ° C. or lower, preferably 50 ° C. or higher and 90 ° C. or lower. The drying time is not particularly limited, but is, for example, 30 seconds or more and 20 minutes or less.

The first electrode 10 (positive electrode 10X), the insulating sheet 30, the second electrode 20 (negative electrode 20Y), and the insulating sheet 30 produced as described above are repeatedly laminated in this order. As a result, the plurality of first electrodes 10 and the second electrodes 20 are alternately laminated, and the insulating sheet 30 is arranged between the first electrode 10 and the second electrode 20. The first electrode 10, the insulating sheet 30, and the second electrode 20 may be laminated so that the electrode body 5 includes the first electrode 10 and the second electrode 20 in total of 20 or more.

The laminated first electrode 10, the insulating sheet 30, and the second electrode 20 are pressure-bonded to produce the electrode body 5. The specific method of crimping the first electrode 10, the insulating sheet 30, and the second electrode 20 may be performed by pressing with a press or the like. The pressing conditions may be such that the positive electrode active material layer 12X and the negative electrode active material layer 22Y are not compressed more than necessary. Specifically, the press temperature is 50 ° C. or higher and 130 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower, and the press pressure is, for example, 0.2 MPa or higher and 3 MPa or lower, preferably 0.4 MPa or higher and 1.5 MPa or lower. Is. The press time is, for example, 15 seconds or more and 15 minutes or less, preferably 30 seconds or more and 10 minutes or less.

Next, on one side of the produced electrode body 5 in the second direction d2, the tab 6 extending in the second direction d2 is electrically connected to the first electrode 10, and on the other side in the second direction d2, the second Another tab 6 extending in direction d2 is electrically connected to the second electrode 20. At this time, the plurality of first electrodes 10 included in the electrode body 5 may be electrically connected to each other in the first connection region a1. Further, the plurality of second electrodes 20 included in the electrode body 5 may be electrically connected to each other in the second connection region a2. The electrical connection between the tab 6 and the electrodes 10 and 20 and between the plurality of electrodes 10 and 20 can be achieved, for example, by welding a conductive material by ultrasonic bonding. In the present embodiment, the value of the ratio of the length L along the second direction d2 of the connecting portion 8 between the electrode body 5 and the tab 6 to the width W along the third direction is 0.025 or more. The electrode body 5 and the tab 6 are electrically connected so as to be 2.00 or less.

Further, the first exterior material 40 and the second exterior material 50 are prepared (manufactured). The exterior materials 40 and 50 can be produced by laminating, for example, metal layers 41 and 51 made of aluminum foil with sealant layers 42 and 52 made of, for example, polyethylene, polypropylene, or polyethylene terephthalate. The first exterior material 40 and the second exterior material 50 are formed in a flat plate shape. A bulging portion 47 may be formed on the first exterior material 40 by, for example, embossing.

After that, the electrode body 5 is arranged between the first exterior material 40 and the second exterior material 50. The first exterior material 40 and the second exterior material 50 are arranged so that the sides of the first sealant layer 42 and the second sealant layer 52 face each other. At this time, one tab 6 extends outward from between the first exterior material 40 and the second exterior material 50 on one side of the second direction d2, and the other tab 6 is the other of the second direction d2. In, it extends outward from between the first exterior material 40 and the second exterior material 50. After that, the first exterior material 40 and the second exterior material 50 are joined at the peripheral edge. The first exterior material 40 and the second exterior material 50 can be joined by welding the first sealant layer 42 and the second sealant layer 52. Welding of the first sealant layer 42 and the second sealant layer 52 can be realized, for example, by heating and pressurizing the first exterior material 40 and the second exterior material 50. The accommodation space 7a is formed by joining the first exterior material 40 and the second exterior material 50 at the (peripheral) joint portion 60 located at the edge portion. The electrolytic solution is injected into the accommodation space 7a.

By the above steps, the electrode body 5 and the electrolytic solution are accommodated in the accommodating space 7a formed by the bulging portion 47, and the power storage element 1 as shown in FIG. 1 is manufactured.

By the way, in the conventional power storage element, the connection between the electrode body and the tab at the electrical connection portion is easily peeled off. In order to prevent the electrode body and the tab from peeling off, it is conceivable to increase the area of the connecting portion to increase the connection strength between the electrode body and the tab. However, if the length in the second direction, which is the extension direction of the tab in the connection portion, is lengthened, the connection region that does not contribute to the power supply of the electrode body is lengthened, and the volumetric energy density of the power storage element deteriorates. .. On the other hand, if the length (width) of the tab in the third direction at the connection portion is increased, the portion where the tab and the exterior body come into contact with each other, that is, the seal portion provided on the tab becomes larger. The joint strength of the portion where the seal portion and the exterior material are joined is weaker than that of the portion where the exterior materials are joined to each other. Further, the seal portion is easily eroded by the gas generated inside the power storage element, specifically, hydrogen fluoride gas. The longer the seal portion, the more easily it is damaged. From these facts, from the viewpoint of ensuring the sealing property of the exterior body, it is desired that the width of the sealing portion is short. In this way, it is difficult to ensure the reliability of the power storage element, such as preventing the electrode body from peeling off from the tab and ensuring the sealability of the exterior body, and to suppress the deterioration of the volumetric energy density of the power storage element. It was.

On the other hand, in the power storage element 1 of the present embodiment, the value of the ratio of the length L of the connecting portion 8 along the second direction d2 to the width W of the connecting portion 8 along the third direction d3 is 0.025. It is 2.00 or less, more preferably 0.100 or more and 1.00 or less, and further preferably 0.10 or more and 0.80 or less. That is, the length L of the connecting portion 8 along the second direction d2 is long enough to increase the connection strength between the electrode body 5 and the tab 6, and short enough not to deteriorate the volumetric energy density of the power storage element 1. However, the width W of the connecting portion 8 along the third direction d3 is long enough to increase the connection strength between the electrode body and the tab, and the sealing portion 4 is shortened to the extent that the sealing of the exterior body is not impaired. There is. Therefore, the area of the connecting portion 8 can be made large enough to prevent the electrode body 5 and the tab 6 from peeling off, and the sealing of the exterior body 7 can be prevented from being impaired. Further, the volumetric energy density of the power storage element 1 is not excessively deteriorated. As described above, in the power storage element 1 of the present embodiment, it is possible to both ensure the reliability of the power storage element and suppress the deterioration of the volumetric energy density of the power storage element.

The area of the connecting portion 8 is 80 mm ² or more and 400 mm ² or less. Since the area of the connecting portion 8 is sufficiently large, the connection strength between the electrode body 5 and the tab 6 becomes high, and it is possible to make it difficult for the electrode body 5 and the tab 6 to be separated from each other. Further, the area of the connecting portion 8 is not too large, and the length L of the connecting portion 8 along the second direction d2 and the width W along the third direction d3 are not too long. Therefore, the area of the connecting portion 8 can be made large enough to prevent the electrode body 5 and the tab 6 from peeling off, and the sealing of the exterior body 7 can be prevented from being impaired. Further, the volumetric energy density of the power storage element 1 is not excessively deteriorated. That is, it is possible to both ensure the reliability of the power storage element and suppress the deterioration of the volumetric energy density of the power storage element.

Further, the length L of the connecting portion 8 along the second direction d2 is 2 mm or more and 20 mm or less. The length L of the connecting portion 8 along the second direction d2 is long enough to increase the connection strength between the electrode body 5 and the tab 6, and short enough not to deteriorate the volumetric energy density of the power storage element 1. .. Therefore, it is possible to both ensure the reliability of the power storage element and suppress the deterioration of the volumetric energy density of the power storage element.

Further, the width W of the connecting portion 8 along the third direction d3 is 10 mm or more and 80 mm or less. The width W of the connecting portion 8 along the third direction d3 is long enough to increase the connection strength between the electrode body and the tab, and the portion where the tab and the exterior body come into contact with each other so that the sealing of the exterior body is not impaired. Is shortened. Therefore, the reliability of the power storage element can be further ensured.

Further, the width of the tab 6 extends in the second direction d2 with a constant width. Here, the width of the tab as described in Patent Document 1 changes in the extending direction. Such tabs need to be provided by processing a thin plate-shaped metal so as to have a desired width. On the other hand, if the width of the tab 6 is constant as in the present embodiment, the tab 6 can be formed without such processing. That is, the tab 6 can be easily formed.

The first electrode active material layer 12 contains lithium iron phosphate as a positive electrode active material. In this case, the power storage element 1 can be used for a long period of time. If the power storage element 1 is used for a long period of time, gas is generated inside the power storage element 1 according to the period of use. Also, the area of the electrode body 5 in plan view, has a 80 cm ² or more 4700Cm ² or less. Since the electrode body 5 having a sufficiently large area in a plan view has a large area in contact between the electrolytic solution and the electrode, gas is likely to be generated inside the power storage element 1. The gas generated inside the power storage element 1 may erode the seal portion 4 and impair the sealing of the exterior body 7. In the power storage element 1 of the present embodiment, the width of the seal portion 4 is sufficiently short. Therefore, even if gas is generated inside the power storage element, the sealing of the exterior body 7 is not easily impaired. That is, the present embodiment having the effect that the sealing of the exterior body 7 is not easily impaired with respect to the power storage element 1 in which the first electrode active material layer 12 contains lithium iron phosphate as the positive electrode active material is particularly preferable. is there.

As described above, the power storage element 1 of the present embodiment is formed between the exterior body 7 including the first exterior material 40 and the second exterior material 50, and between the first exterior material 40 and the second exterior material 50. The electrode body 5 including the plurality of first electrodes 10 and the plurality of second electrodes 20 stacked in the first direction d1 and accommodated in the accommodation space 7a is electrically connected to the electrode body 5 at the connecting portion 8. A tab 6 that passes between the first exterior material 40 and the second exterior material 50 and extends in the second direction d2 that is non-parallel to the first direction d1 is provided, and is along the second direction d2 of the connecting portion 8. The value of the ratio of the length L to the width W along the third direction d3 orthogonal to both the first direction d1 and the second direction d2 of the connecting portion 8 is 0.025 or more and 2.00 or less. According to such a power storage element 1, the area of the connecting portion 8 is made large enough to prevent the electrode body 5 and the tab 6 from peeling off, and the sealing of the exterior body 7 is not impaired. Moreover, the volumetric energy density of the power storage element 1 can be prevented from being excessively deteriorated. in this way. While ensuring the reliability of the power storage element 1, deterioration of the volumetric energy density of the power storage element can be suppressed.

Although one embodiment has been described by a plurality of specific examples, these specific examples are not intended to limit one embodiment. The above-described embodiment can be implemented in various other specific examples, and various omissions, replacements, changes, additions, and the like can be made without departing from the gist thereof.

Hereinafter, an example of modification will be described with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-mentioned specific examples are used for the parts that can be configured in the same manner as the above-mentioned specific examples, and the same reference numerals are used, and duplicate explanations are given. Is omitted.

For example, as shown in FIG. 7, the width of the tab 6 along the third direction d3 may be the same as the width of the electrode body 5 along the third direction. Such a tab 6 can be provided, for example, by extending at least one of the plurality of electrodes 10 and 20 in the second direction d2. Such a tab 6 can be formed without a separate processing step. That is, the tab 6 can be easily formed. Further, if the tab is provided by processing, the tab may be cracked due to a notch during processing or the like. This crack can spread from the tab to the electrodes 10 and 20 via the connection. If the tab 6 is integrally formed with the electrodes 10 and 20 without processing as in this modification, such a crack is unlikely to occur. Therefore, the tab 6 can be provided with higher reliability.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
(Example 1)
<Manufacturing of power storage element>
A negative electrode slurry containing 98 parts by weight of graphite as a negative electrode active material, 1 part by weight of styrene-butadiene rubber as a binder, 1 part by weight of carboxymethyl cellulose as a thickener, and water as a solvent was prepared. This was applied on a 465 mm × 175 mm negative electrode current collector (material is Cu) with a bar coater, and the solvent water was volatilized by heating and drying to form a negative electrode active material layer having a size of 440 mm × 175 mm. Similarly, a negative electrode active material layer was formed on the opposite surface of the negative electrode current collector, and a negative electrode having negative electrode active material layers formed on both sides of the negative electrode current collector was obtained. This was repeated to obtain a total of 17 negative electrodes. At the end of the negative electrode in the second direction, there is a portion on both sides of which the negative electrode active material layer is not formed. As will be described later, the negative electrode current collector is welded in the portion.

A positive electrode slurry containing 90 parts by weight of lithium iron phosphate as a positive electrode active material, 4 parts by weight of polyvinylidene fluoride as a binder, 6 parts by weight of carbon black as a conductive auxiliary agent, and N-methylpyrrolidone (NMP) as a solvent was prepared. .. This was applied on a 465 mm × 170 mm positive electrode current collector (material is Al) with a bar coater, and the NMP of the solvent was volatilized by heating and drying to form a positive electrode active material layer having a size of 430 mm × 170 mm. Therefore, the average area of the positive electrode active material layer was 73100 mm ² . Similarly, a positive electrode active material layer was formed on the plate facing the positive electrode current collector, and a positive electrode having positive electrode active material layers formed on both sides of the positive electrode current collector was obtained. This was repeated to obtain a total of 16 positive electrodes. At the end of the positive electrode in the second direction, there is a portion on both sides of which the positive electrode active material layer is not formed. As will be described later, the positive electrode current collector is welded in the portion.

Separately, 32 insulating sheets (material: polypropylene) having a size of 450 mm × 180 mm and two exterior materials (material: Al, having a polypropylene layer as a heat welding layer) having a size of 510 mm × 210 mm were prepared.

An electrode body was obtained by laminating 17 negative electrodes, 16 positive electrodes, and 32 insulating sheets in the order of negative electrode, insulating sheet, positive electrode, insulating sheet, negative electrode, and so on. In the second direction of the electrode body in a plan view, 17 negative electrode current collectors are located 15 mm away from one end of the insulating sheet, and 16 negative electrode current collectors are located 15 mm away from the other end of the insulating sheet. There was a second end of the positive electrode current collector. In a plan view (projection in the first direction), the positive electrode and the negative electrode were laminated so that the negative electrode active material layer contained the positive electrode active material layer.

Negative electrode tabs (material) with a length of 0.2 mm in the first direction, a length of 25 mm in the second direction, and a length of 10 mm in the third direction at the center of the 17 negative electrode current collectors (parts not coated with the positive electrode active material) in the third direction. Cu) is placed, and in the region of 8 mm in the second direction x 20 mm in the third direction (ratio of the length in the second direction to the length in the third direction: 0.4), a tab for the negative electrode and 17 negative electrode current collectors. The body was welded by ultrasonic welding to form a connecting portion. Further, in the center of the 16 positive electrode current collectors (the portion not coated with the positive electrode active material) in the third direction, a tab for the positive electrode having a length of 0.2 mm in the first direction, a length of 25 mm in the second direction, and a length of 10 mm in the third direction. (Material is Al), and in the area of 8 mm in the second direction x 20 mm in the third direction (ratio of the length in the second direction to the length in the third direction: 0.4), the positive electrode tab and 16 positive electrodes The current collector was welded by ultrasonic welding to form a connection portion.

Only one of the two exterior materials (first exterior material) is embossed to accommodate a length (depth) of 4.7 mm in the first direction, a length of 480 mm in the second direction, and a length of 190 mm in the third direction. A space was provided.

The unembossed exterior material (second exterior material) is placed on a flat surface, and the long side of the exterior material is the second direction of the electrode body, and the short side of the exterior material is the third direction of the electrode body. The electrode body was placed on the exterior material so that the center of the exterior material coincided with the center of the electrode body. From above, the embossed exterior material was placed so that the space provided by the embossing accommodated the electrode body. At this time, the negative electrode tab and the positive electrode tab passed between the two exterior materials and extended in the second direction.

15 mm from both ends of the two exterior materials in the second direction were welded in parallel with the third direction by heat welding. At this time, the negative electrode tab and the positive electrode tab were fixed between the two exterior materials. Next, 10 mm from one end of the two exterior materials in the third direction was welded by heat welding.

160 mL of an electrolytic solution (ethylene carbonate: diethyl carbonate = 3; 7, LiPF ₆ concentration 1 mol / L) was injected from the other end of the two exterior materials in the third direction. Next, the other ends of the two exterior materials in the third direction were welded by heat welding, and the electrode body and the electrolytic solution were sealed in the accommodation space.

The obtained power storage elements had a length of 4.9 mm in the first direction and a length of 574 mm in the second direction (of which 510 mm was the exterior body, 32 mm was the protruding portion of the negative electrode current collector, and 32 mm was the protruding portion of the positive electrode current collector). The length was 210 mm in three directions.

<Reliability test>
The peel strength between the negative electrode tab and the negative electrode current collector and the peeling test between the positive electrode tab and the positive electrode current collector were evaluated by a 90 ° peeling tester. The peeling speed at the time of the test was 5 cm / min. The obtained peel strength was 30 N / cm or more for both the negative electrode tab and the positive electrode tab, and sufficient reliability regarding connection was obtained.

<Volume energy density>
The current collector and the tab of each electrode are connected to each other over 8 mm in the second direction at the connecting portion. The length of the connecting portion in the second direction is sufficiently short, and therefore the length of the current collector of each electrode extending from the end portion of the insulating sheet is sufficiently short as 15 mm. Therefore, the length of the connection region that does not contribute to the supply of electric power is sufficiently shortened to suppress the deterioration of the volumetric energy density.

1 Power storage element 5 Electrode body 6 Tab 7 Exterior body 7a Storage space 8 Connection part 10 1st electrode 11 1st electrode current collector 12 1st electrode active material layer 20 2nd electrode 21 2nd electrode current collector 22 2nd electrode Active material layer 30 Insulation sheet 40 First exterior material 50 Second exterior material 60 Joint

Claims (10)

An exterior body including the first exterior material and the second exterior material,
An electrode body including a plurality of first electrodes and a plurality of second electrodes stacked in a first direction and accommodated in a storage space formed between the first exterior material and the second exterior material.
It is provided with a tab that is electrically connected to the electrode body at a connection portion and that passes between the first exterior material and the second exterior material and extends in a second direction that is non-parallel to the first direction.
The value of the ratio of the length of the connecting portion along the second direction to the width of the connecting portion along the third direction orthogonal to both the first direction and the second direction is 0.025 or more. A power storage element that is 2.00 or less. The power storage element according to claim 1, wherein the area of the connecting portion is 80 mm ² or more and 400 mm ^{2 or less.} The power storage element according to claim 1 or 2, wherein the length of the connection portion along the second direction is 2 mm or more and 20 mm or less. The power storage element according to any one of claims 1 to 3, wherein the width of the connection portion along the third direction is 10 mm or more and 80 mm or less. The power storage element according to any one of claims 1 to 4, wherein the width of the tab along the third direction is constant. The first electrode has a first electrode current collector and a first electrode active material layer provided on at least one surface of the first electrode current collector and containing the first electrode active material.
The power storage element according to any one of claims 1 to 5, wherein the first electrode active material layer contains lithium iron phosphate. Area of the electrode body in plan view is 80 cm ² or more 4700Cm ² or less, the electric storage device according to any one of claims 1 to 6. The power storage element according to any one of claims 1 to 7, wherein the thickness of the electrode body along the first direction is 0.25 mm or more and 9.5 mm or less. The power storage element according to any one of claims 1 to 8, wherein the first exterior material and the second exterior material are joined at a joint located at an edge portion. The method for manufacturing a power storage element according to any one of claims 1 to 9.
A step of electrically connecting an electrode body including a plurality of first electrodes and a plurality of second electrodes laminated in the first direction and a tab extending in the second direction non-parallel to the first direction at a connecting portion. With
The electrode body and the tab are the ratio of the length of the connecting portion along the second direction to the width of the connecting portion along the third direction orthogonal to both the first direction and the second direction. A method for manufacturing a power storage element, which is connected so that the value of is 0.025 or more and 2.00 or less.

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