JP6876883B1 - Power storage element and manufacturing method of power storage element - Google Patents

Abstract

The power storage element 1 is an electrode body housed in an exterior body 7 including a first exterior material 40 and a second exterior material 50, and an accommodation space 7a formed between the first exterior material 40 and the second exterior material 50. 5 and an electrolytic solution are provided. The electrode body 5 includes a plurality of negative electrodes 20Y and a plurality of positive electrodes 10X alternately laminated in the first direction d1. The negative electrode 20Y has a negative electrode current collector 21Y and a negative electrode active material layer 22Y provided on at least one surface of the negative electrode current collector 21Y and containing a negative electrode active material. The positive electrode 10X has a positive electrode current collector 11X and a positive electrode active material layer 12X provided on at least one surface of the positive electrode current collector 11X and containing a positive electrode active material. The AC ratio (WA / WC), which is the ratio value of the total weight WA of the negative electrode active material layer 22Y contained in the electrode body 5 to the total weight WC of the positive electrode active material layer 12X contained in the electrode body 5, is 0.45. More than 1.0 and less than 1.0. The actual volume VA of the negative electrode active material layer 22Y contained in the electrode body 5 is 50 cm3 or more and 150 cm3 or less. The accommodating space 7a has a volume capable of further accommodating a gas of 20 cm3 or more in addition to the electrolytic solution and the electrode body 5.

Description

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

As the power storage element, for example, as proposed in Japanese Patent Application Laid-Open No. 2009-545869 and Japanese Patent Application Laid-Open No. 2008-97940, a laminated battery or a winding element having an electrode body in which positive electrodes and negative electrodes are alternately laminated. Molded batteries are widely used. In such a power storage element, an electrode body and an electrolytic solution are housed inside the exterior body. When the positive electrode and the negative electrode of the electrode body are in contact with the electrolytic solution, ions such as lithium ions can move between the positive electrode and the negative electrode via the electrolytic solution. The movement of the ions can charge and discharge the power storage element.

By the way, gas may be generated inside the power storage element. The gas can be generated by decomposing the electrolytic solution on the electrode surface due to, for example, excessive charging or discharging. Since the gas stays inside the power storage element without reacting, if the power storage element is used for a long period of time, the gas accumulates inside the power storage element and the outer body of the power storage element swells. If an amount of gas that cannot be tolerated by the exterior body is generated inside the power storage element, the exterior body may be damaged, and problems such as an electrolytic solution flowing out from the inside of the power storage element may occur.

In response to such a problem, Japanese Patent Application Laid-Open No. 2009-545869 and Japanese Patent Application Laid-Open No. 2008-97940 propose that the accommodation space of the exterior body has a volume capable of accommodating gas. The accommodation space is required to have a sufficient volume so that the gas generated inside the power storage element can be accommodated in the accommodation space. However, if the volume of the accommodation space is made too large, the volumetric energy density of the power storage element deteriorates.

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 allowing the gas generated inside the power storage element to be housed in the storage space. ..

The first power storage element of the present invention is
An exterior body including the first exterior material and the second exterior material,
An electrode body and an electrolytic solution housed in a storage space formed between the first exterior material and the second exterior material are provided.
The electrode body includes a plurality of negative electrodes and a plurality of positive electrodes alternately laminated in the first direction.
The negative electrode has a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector and containing a negative electrode active material.
The positive electrode has a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector and containing a positive electrode active material.
Of the total weight W _A of the negative electrode active material layer included in the electrode body, AC ratio is a value of the ratio to the total weight W _C of the positive electrode active material layer included in the electrode body (W A _{/ W C)} is , 0.45 or more and less than 1.0,
_{The actual volume VA} of the negative electrode active material layer contained in the electrode body is 50 cm ³ or more and 150 cm ³ or less.
The accommodating space has a volume capable of further accommodating a gas of ^{20 cm 3} or more in addition to the electrolytic solution and the electrode body.

In the first power storage element of the present invention, the accommodating space may have a volume capable of further accommodating a gas of ^{60 cm 3 or more in addition to the electrolytic solution and the electrode body.}

The second power storage element of the present invention is
An exterior body including the first exterior material and the second exterior material,
An electrode body and an electrolytic solution housed in a storage space formed between the first exterior material and the second exterior material are provided.
The electrode body includes a plurality of negative electrodes and a plurality of positive electrodes alternately laminated in the first direction.
The negative electrode has a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material provided on the negative electrode current collector.
The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on the positive electrode current collector.
Of the total weight W _A of the negative electrode active material layer included in the electrode body, AC ratio is a value of the ratio to the total weight W _C of the positive electrode active material layer included in the electrode body (W A _{/ W C)} is , 0.45 or more and less than 1.0,
The ratio (V / V _A ) of the volume V of the gas that can be accommodated in addition to the electrolytic solution and the electrode body to the actual volume _VA of the negative electrode active material layer contained in the electrode body is 0. .133 or more and 2 or less.

The third power storage element of the present invention is
An exterior body including the first exterior material and the second exterior material,
An electrode body and an electrolytic solution housed in a storage space formed between the first exterior material and the second exterior material are provided.
The electrode body includes a plurality of negative electrodes and a plurality of positive electrodes alternately laminated in the first direction.
The negative electrode has a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material provided on the negative electrode current collector.
The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on the positive electrode current collector.
The total weight W _A of the negative electrode active material layer included in the electrode _body, the total weight W _C of the positive electrode active material layer included in the electrode _body, the actual volume V _A of the negative electrode active material layer included in the electrode body , And the volume V of the gas that the accommodating space can accommodate in addition to the electrolytic solution and the electrode body satisfies the following relationship.
_{0.04 <V / V A × W} A / W C <1.2

In the first to third power storage elements of the present invention
The first exterior material and the second exterior material are joined at a joint portion.
The distance between the joint portion and the electrode body in a plan view may be 3 mm or more and less than 15 mm.

In the first to third power storage elements of the present invention, at least one of the surface roughness Ra _C of the positive electrode active material layer and the surface roughness Ra _A of the negative electrode active material layer may be 100 nm or more.

In the first to third power storage elements of the present invention, in a plan view, the length of the negative electrode in the direction orthogonal to the direction in which the negative electrode is the shortest with respect to the length of the negative electrode in the direction in which the negative electrode is the shortest. The ratio may be 1.5 or more.

In the first to third power storage elements of the present invention, the positive electrode active material layer may contain lithium iron phosphate.

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

In the first to third power storage elements of the present invention, the first exterior material and the second exterior material may be joined at a joint portion on the peripheral edge.

According to the present invention, it is possible to suppress deterioration of the volumetric energy density of the power storage element while allowing the gas generated inside the power storage element to be housed in the storage space.

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 a cross-sectional view taken along the line VI-VI of FIG. FIG. 7 is a diagram for explaining an example of a method for manufacturing a power storage element. FIG. 8 is a diagram for explaining an example of a method for manufacturing a power storage element.

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

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

1 to 8 are diagrams for explaining one embodiment of the 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 non-parallel to both the first direction d1 and the second direction d2, is the positive direction 10X and the negative electrode. It is the short side direction (width direction) of 20Y. 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, for example, 80 μm or more and 250 μm or less in the longitudinal direction, that is, the positive electrode 10X along the second direction d2. The length of the negative electrode 20Y and the negative electrode 20Y 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. Here, in a plan view, the length of the negative electrode 20Y in the direction orthogonal to the direction in which the negative electrode 20Y is the shortest (second direction d2) with respect to the length of the negative electrode 20Y in the direction in which the negative electrode 20Y is the shortest (third direction d3). The ratio of the electrodes is preferably 1.5 or more, and more preferably 2.0 or more.

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 provided on the positive electrode current collector 11X. It has a positive electrode active material layer 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 coating a positive electrode slurry formed by dispersing a positive electrode active material, a conductive auxiliary agent, and a binder in a solvent on a material forming the positive electrode current collector 11X and solidifying the positive electrode active material layer 12X. Can be done. Such a positive electrode active material layer 12X is formed including voids.

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 or 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. 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) provided on the negative electrode current collector 21Y and containing a negative electrode active material. It has a material layer 22) and. 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 slurry for a negative electrode onto a material forming the negative electrode current collector 21Y and solidifying it. Such a negative electrode active material layer 22Y is formed including voids.

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. 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 in 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.

The power storage element 1 supplies electric power by reacting the electrode active material and the electrolytic solution at the electrodes. Therefore, the amount of electric power that can be supplied by the power storage element 1 is proportional to the amount of the positive electrode active material layer 12X and the amount of the negative electrode active material layer 22Y. The total weight W _C of the positive electrode active material layer 12X contained in the electrode body 5 of the storage element 1 is preferably 10g or more, the total weight W _A of the negative electrode active material layer 22Y is preferably 6g or more. Further, in order to effectively prevent the precipitation of lithium on the negative electrode, it is preferable that the negative electrode active material layer 22Y has a sufficient amount with respect to the positive electrode active material layer 12X. Specifically, the total weight _{W A} of the negative electrode active material layer 22Y, AC ratio is a value of the ratio to the total weight _{W C} of the positive electrode active material layer 12X _(W A / W _C) is 0.45 or more 1. It is less than 0, preferably 0.50 or more and less than 1.0. The total weight W _A of the total weight W _C and the anode active material layer 22Y of the positive electrode active material layer 12X can be obtained by the following method. When measuring the weights of the positive electrode active material layer 12X and the negative electrode active material layer 22Y formed on the positive electrode 10X and the negative electrode 20Y in the power storage element, the positive electrode current collector 11X and the negative electrode collection are taken from the weights of the positive electrode 10X and the negative electrode 20Y. It is obtained by subtracting the weight of only the electric body 21Y. As a more specific procedure, first, the exterior body 7 of the power storage element 1 is incised to take out the electrode body 5, then the positive electrode 10X, the negative electrode 20Y, and the insulating sheet 30 are peeled off one by one, and the positive electrode 10X and the negative electrode 20Y are separated. Wash with a solvent such as diethyl carbonate and dry. Next, the weights of the positive electrode 10X and the negative electrode 20Y are measured. Then, the positive electrode active material layer 12X and the negative electrode active material layer 22Y are wiped off with a solvent such as N-methylpyrrolidone or water to make only the positive electrode current collector 11X and the negative electrode current collector 21Y, which are dried and weighed. Finally, it can be obtained by subtracting the weights (measured values) of the positive electrode current collector 11X and the negative electrode current collector 21Y from the weights (measured values) of the positive electrode 10X and the negative electrode 20Y.

Further, since the actual volumes of the positive electrode active material layer 12X and the negative electrode active material layer 22Y are large, the region where the electrode active material layer and the electrolytic solution come into contact with each other can be expanded. As a result, electric power can be efficiently supplied from the power storage element 1. _{Specifically, the actual volume VA} of the negative electrode active material layer 22Y is 50 cm ³ or more and 150 cm ³ or less, preferably 65 cm ³ or more and 120 cm ³ or less. Here, the actual volume _{VA of the} negative electrode active material layer 22Y is the total volume excluding the voids contained in the negative electrode active material layer 22Y contained in the electrode body 5. For the actual volume _VA of the negative electrode active material layer 22Y, for example, the void volume (pore volume) in the negative electrode active material layer 22Y is obtained from the gas adsorption method and the BET conversion formula, and the apparent volume (area x thickness) is obtained. It is obtained by subtracting from.

The surface of the positive electrode 10X and the surface of the negative electrode 20Y are preferably rough. Specifically, it is preferable that at least one _{of the surface roughness Ra C} of the positive electrode 10X and the surface roughness _{Ra A} of the negative electrode 20Y is 100 nm or more. The surface roughness Ra means the arithmetic mean roughness in JIS B 0601-2001.

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 in 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.

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 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.

The accommodating space 7a can accommodate a certain amount or more of gas in addition to the electrode body 5 and the electrolytic solution. That is, the exterior body 7 that defines the accommodation space 7a can be deformed by a flexible material, and can be expanded by a certain amount or more by being deformed. For example, the gas is accommodated in the accommodation space 7a by deforming (expanding) the first exterior material 40 and the second exterior material 50 of the exterior body 7 forming the accommodation space 7a. Since the accommodation space 7a can accommodate more gas, the gas generated inside the power storage element 1, that is, in the accommodation space 7a can be accommodated in the accommodation space 7a without damaging the exterior body 7. it can. The volume V of the gas that can be accommodated in the accommodation space 7a is 20 cm ³ or more, preferably 40 cm ³ or more, and more preferably 80 cm ³ or more.

The volume of gas that can be accommodated is a volume that can be expanded without tearing, bursting, or damaging the exterior body. Therefore, the volume of gas that can be accommodated can be specified by preparing samples in which the exterior body is expanded by various volumes and confirming the presence or absence of tearing, rupture, damage, etc. in the exterior body of each sample. For example, in the exterior body 7 that forms the accommodation space 7a by joining the exterior materials facing each other as in the specific example described later, the volume at which the joined facing exterior materials can expand without peeling off. Means. The presence or absence of peeling of the facing exterior materials can be confirmed by cutting open the exterior body with a cutting tool such as scissors or a cutter and observing the inside of the exterior body.

Further, the ratio (V / _VA ) of the volume V of the gas that can be accommodated in the accommodation space 7a to the actual volume _VA of the negative electrode active material layer 22Y contained in the electrode body 5 is 0.133 or more and 2 or less. It is preferably 0.4 or more and 2 or less.

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 on the respective peripheral 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.

FIG. 6 shows a cross-sectional view of the power storage element 1 of FIG. 1 along the VI-VI line. As shown in FIG. 6, the joint portion 60 and the electrode body 5 are separated from each other. Since the joint portion 60 and the electrode body 5 are separated from each other, a gap for accommodating the gas in addition to the electrode body 5 and the electrolytic solution is formed in the accommodating space 7a. The distance between the joint portion 60 and the electrode body 5 in the plan view shown in FIGS. 2 and 6 in order to allow a sufficient amount of gas to be accommodated in the accommodation space 7a and to suppress deterioration of the volumetric energy density. L is preferably 3 mm or more and less than 15 mm, and more preferably 5 mm or more and less than 15 mm.

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. Includes the exit 47. 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 bulging portion, and the second exterior material 50 may include a bulging 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 sealing portion 4 of the tab 6 and the first sealant layer 42 and the second sealant layer 52 are welded to seal 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 formability, 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 have thermoplasticity. 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-film nylon or polyethylene terephthalate layers.

In the electricity storage device 1 of this embodiment includes the total weight W _A of the negative electrode active material layer 22Y contained in the electrode body _5, the total weight W _C of the positive electrode active material layer 12X contained in the electrode body _5, the electrode bodies 5 _{The actual volume VA} of the negative electrode active material layer 22Y and the volume V of the gas that the accommodating space 7a can accommodate in addition to the electrolytic solution and the electrode body 5 satisfy the following relationship (i), and are preferably as follows. The relationship (ii) is satisfied.
_{0.04 <V / V A × W} A / W C <1.2 ··· (i)
_{0.12 <V / V A × W} A / W C <1.2 ··· (ii)

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 pressure pressing, 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 pressure pressing, 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 an 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.

On one side of the 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 by means such as ultrasonic welding, and on the other side in the second direction d2, the second Another tab 6 extending in the two directions d2 is electrically connected to the second electrode 20 by means such as ultrasonic welding.

Further, the first exterior material 40 and the second exterior material 50 are produced. The exterior materials 40 and 50 are 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. The first exterior material 40 is provided with a bulging portion 47, for example, by 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 is arranged so that the first sealant layer 42 faces the second exterior material 50, and the second exterior material 50 has the second sealant layer 52 facing the first exterior material 40. Arranged to be on the side. The first exterior material 40 and the second exterior material 50 are joined so as to surround the bulging portion 47 of the first exterior material 40 from three directions. That is, the first exterior material 40 and the second exterior material 50 are joined so as to open in one direction. Specifically, the three sides of the rectangular first exterior material 40 and the second exterior material 50 are joined. After that, the electrolytic solution is injected into the exterior body 7 from the opening direction to join the unbonded sides of the first exterior material 40 and the second exterior material 50. A temporary storage space 7b of the exterior body 7 is formed by joining all four sides of the rectangular first exterior material 40 and the second exterior material 50 to form a temporary joint portion 61. The electrode body 5 and the electrolytic solution are sealed in the temporary storage space 7b, and the temporary power storage element 2 is manufactured.

Next, the temporary power storage element 2 is charged. Charging is performed by passing a current between the tab 6 connected to the positive electrode 10X and the tab 6 connected to the negative electrode 20Y. When the temporary power storage element 2 is charged, gas is generated in the temporary storage space 7b of the exterior body 7. This gas is generated, for example, by electrolyzing impurities and the like contained in the electrolytic solution.

After that, the temporary power storage element 2 is aged. Aging is performed under various conditions depending on the purpose, but is typically performed by leaving it in a constant temperature environment (for example, 25 ° C. to 60 ° C.) for several days (for example, 24 hours or more). By aging, the performance of the power storage element 1 to be manufactured can be improved, and initial defects can be easily found. Even in aging, gas is generated in the temporary accommodation space 7b of the exterior body 7.

After aging, as shown in FIG. 8, a part of the exterior body 7 is cut off to provide an opening 65 in the exterior body 7. The gas generated inside the temporary storage element 2 is removed from the temporary storage space 7b through the opening 65.

Finally, the first exterior material 40 and the second exterior material 50 are joined, and more specifically, the first sealant layer 42 of the first exterior material 40 and the second sealant layer 52 of the second exterior material 50 are joined. , Form the joint 60. By forming the joint portion 60, the opening portion 65 does not ventilate the inside of the exterior body 7. The accommodating space 7a is partitioned by the joint portion 60, and the electrode body 5 and the electrolytic solution are sealed to the exterior body 7 in the accommodating space 7a. The power storage element 1 is manufactured by the above steps.

By the way, in the conventional power storage element, the accommodation space has a sufficient volume for accommodating the gas in order to accommodate the gas generated inside the exterior body. However, if the volume of the accommodation space is made too large, the volumetric energy density of the power storage element deteriorates. In order to suppress the deterioration of the volumetric energy density of the power storage element while allowing the gas generated inside the power storage element to be housed in the storage space, the volume of the storage space depends on the volume of gas that can be generated inside the power storage element. It is hoped that the decision will not be made too large.

In addition to the gas generated in the manufacturing process of the power storage element described above, gas may be generated when the electrolytic solution is decomposed on the electrode surface by, for example, charging or discharging when the power storage element is used. Specifically, for example, reduction decomposition of the electrolytic solution occurs at the negative electrode during charging, and gas may be generated. If the capacity of the positive electrode is excessive with respect to the capacity of the negative electrode, that is, if the amount of the positive electrode active material is excessive with respect to the amount of the negative electrode active material, lithium that cannot be occluded at the negative electrode is precipitated, and the precipitated lithium and the deposited lithium. Gas is likely to be generated by reacting with the electrolytic solution. That is, the easier it is for lithium to precipitate at the negative electrode, the easier it is for gas to be generated. Further, the larger the area where the negative electrode and the electrolytic solution contact and react, that is, the larger the actual volume of the negative electrode active material layer, the more likely it is that excessive charging or discharging occurs, and the lithium deposited on the negative electrode and the electrolytic solution come into contact with each other. Therefore, gas is likely to be generated.

In this embodiment, by sufficiently increasing the AC ratio is a positive electrode active value of the ratio to the total weight W _C of the material layer 12X of the total weight W _A of the negative electrode active material layer 22Y, lithium precipitation on the negative electrode 20Y It is effectively suppressed. That is, the generation of gas inside the power storage element 1 is suppressed. On the other hand, by not increasing the AC ratio too much, the non-functional negative electrode active material layer 22Y is reduced, and the deterioration of the volumetric energy density of the power storage element 1 is suppressed. Specifically, the total weight _{W A} of the negative electrode active material layer 22Y, AC ratio is a value of the ratio to the total weight _{W C} of the positive electrode active material layer 12X _(W A / W _C) is 0.45 or more 1. It is less than 0, preferably 0.50 or more and less than 1.0.

_{Further, in the present embodiment, by not increasing the actual volume VA} of the negative electrode active material layer 22Y too much, the region where the negative electrode active material layer and the electrolytic solution come into contact with each other is suppressed, and the precipitation of lithium in the negative electrode 20Y is effective. Is suppressed. That is, the generation of gas inside the power storage element 1 is suppressed. On the other hand, since the actual volume _VA of the negative electrode active material layer 22Y is sufficiently large, it is possible to efficiently supply electric power from the power storage element 1. Specifically, it is 50 cm ³ or more and 150 cm ³ or less, preferably 65 cm ³ or more and 120 cm ³ or less.

When the present inventors have confirmed, using the electricity storage device 1 has a total area S _A of such AC ratio and the negative electrode active material layer 22Y for a long period of time, the gas generated in the interior of the storage element 1 The volume was 20 cm ³ or less. ^{Therefore, the storage space 7a inside the power storage element 1 can further store a gas of 20 cm 3} or more in addition to the electrolytic solution and the electrode body 5, so that even if the power storage element 1 is used for a long period of time, it can be used. The gas generated inside the power storage element 1 can be accommodated. That is, damage to the exterior body 7 of the power storage element 1 can be suppressed.

Further, when the present inventors have confirmed, the volume of gas generated in such AC ratio and manufacturing process of the electricity storage device 1 has a total area S _A of the anode active material layer 22Y is a in 40 cm ³ or less It was. Therefore, the storage space 7a inside the power storage element 1 ^{can further store a gas of 40 cm 3} or more in addition to the electrolytic solution and the electrode body 5, so that the gas generated in the manufacturing process of the power storage element 1 is removed. The gas generated inside the power storage element 1 can be accommodated even if it cannot be completely closed. That is, damage to the exterior body 7 of the power storage element 1 can be further suppressed.

Further, the storage space 7a inside the power storage element 1 can further store ^{a gas of 80 cm 3} or more in addition to the electrolytic solution and the electrode body 5, so that the gas generated in the manufacturing process of the power storage element 1 is removed. Even if the power storage element 1 is used for a long period of time without being completely exhausted, the gas generated inside the power storage element 1 can be accommodated. That is, damage to the exterior body 7 of the power storage element 1 can be further suppressed. In this way, the volume of the gas that can be accommodated in the storage space 7a is determined according to the volume of the gas that can be generated inside the power storage element 1, so that the gas generated inside the power storage element 1 is stored in the storage space 7a. It is possible to suppress deterioration of the volumetric energy density of the power storage element 1 while making it accommodable.

_{Further, as described above, the larger the actual volume VA} of the negative electrode active material layer 22Y, the easier it is for gas to be generated inside the power storage element 1. That is, gas tends to be generated inside the power storage element 1 in proportion to _{the actual volume VA} of the negative electrode active material layer 22Y. By increasing or decreasing the volume V of the gas that can be accommodated in the accommodation space 7a according to the actual volume _VA of the negative electrode active material layer 22Y, more specifically, the volume V of the gas that can be accommodated in the accommodation space 7a is the negative electrode. increases with the increase in actual volume V _a of the active material layer 22Y, that decreases with decreasing actual volume V _a of the anode active material layer 22Y, and more specifically, the housing space 7a is capable of accommodating _{Since the volume V of the gas is proportional to the actual volume VA} of the negative electrode active material layer 22Y, the volume V of the gas that can be accommodated in the accommodation space 7a is sufficient to accommodate the gas generated inside the power storage element 1. It is possible to suppress the deterioration of the volumetric energy density without becoming too large while increasing the size. Specifically, the ratio actual volume _{V A} of the negative electrode active material layer 22Y for accommodating space 7a is contained in the electrode body 5 volume V can accommodate gas (V / _{V A)} is a 0.133 to 2 Yes, preferably 0.4 or more and 2 or less. By satisfying such a relationship, the volume energy of the power storage element 1 can be accommodated in the storage space 7a with respect to _{the actual volume VA} of the arbitrary negative electrode active material layer 22Y. Deterioration of density can be suppressed.

Further, as described above, by sufficiently increasing the AC ratio is a positive electrode active value of the ratio to the total weight W _C of the material layer 12X of the total weight W _A of the negative electrode active material layer 22Y, deposition of lithium in the negative electrode 20Y Can be effectively suppressed, and the generation of gas inside the power storage element 1 can be suppressed. A volume V of the accommodation space 7a is capable of accommodating gas in the cathode active value of the ratio to the total weight W _C of the material layer 12X of the total weight W _A of actual volume V _A and the anode active material layer 22Y of the negative electrode active material layer 22Y More specifically, the volume V of the gas that can be accommodated in the accommodation space 7a _{increases as the actual volume VA} of the negative electrode active material layer 22Y increases and the AC ratio decreases. _{Then, as the actual volume VA} of the negative electrode active material layer 22Y decreases and the AC ratio increases, more specifically, the volume V of the gas that can be accommodated in the accommodation space 7a becomes the negative electrode active material layer. in addition to being proportional to the actual volume V _a of 22Y, it is inversely proportional to the AC ratio is a positive electrode active value of the ratio to the total weight W _C of the material layer 12X of the total weight W _a of the negative electrode active material layer 22Y As a result, the volume V of the gas that can be accommodated in the accommodation space 7a can be made large enough to accommodate the gas generated inside the power storage element 1, and the deterioration of the volume energy density can be suppressed without becoming too large. .. Specifically, the negative electrode active material layer 22Y contained total weight W _A of the negative electrode active material layer 22Y contained in the electrode body _5, the total weight W _C of the positive electrode active material layer 12X contained in the electrode body _5, the electrode bodies 5 The actual volume _{VA of} the above and the volume V of the gas that the accommodating space 7a can accommodate in addition to the electrolytic solution and the electrode body 5 are generated inside the power storage element 1 when the following relationship (i) is satisfied. It is possible to suppress deterioration of the volumetric energy density of the power storage element 1 while allowing the gas to be accommodated in the accommodation space 7a. Further, when the following relationship (ii) is satisfied, it is possible to further suppress the deterioration of the volumetric energy density of the power storage element 1 while allowing the gas generated inside the power storage element 1 to be housed in the storage space 7a.
_{0.04 <V / S A × W} A / W C <1.2 ··· (i)
_{0.12 <V / S A × W} A / W C <1.2 ··· (ii)

Further, in the power storage element 1 of the present embodiment, the distance L between the joint portion 60 and the electrode body 5 in a plan view is preferably 3 mm or more and less than 15 mm, and more preferably 5 mm or more and less than 15 mm. .. Since the joint portion 60 and the electrode body 5 are separated from each other, a volume V for accommodating the gas in addition to the electrode body 5 and the electrolytic solution can be formed in the accommodating space 7a. Further, since the joint portion 60 and the electrode body 5 are not too far apart from each other, it is possible to prevent the volume V from becoming too large and the volume energy density of the power storage element 1 from deteriorating.

Further, it is preferable that at least one _{of the surface roughness Ra C} of the positive electrode 10X and the surface roughness _{Ra A} of the negative electrode 20Y is 100 nm or more. Since the surface of each electrode is roughened, it is possible to form a path through which the gas generated on the surface of the electrode is discharged from the electrode body 5 to the outside. That is, the gas is easily removed from between the positive electrode 10X and the negative electrode 20Y.

Further, in a plan view, the length of the negative electrode 20Y in the direction orthogonal to the direction in which the negative electrode 20Y is the shortest (second direction d2) with respect to the length of the negative electrode 20Y in the direction in which the negative electrode 20Y is the shortest (third direction d3). The ratio of is preferably 1.5 or more, and more preferably 2.0 or more. When the negative electrode 20Y has such a shape, the shortest distance from an arbitrary position on the surface of the negative electrode 20Y to the outside of the electrode body 5 becomes short. Therefore, the gas generated at an arbitrary position on the surface of the negative electrode 20Y easily reaches the outside of the electrode body 5. That is, the gas generated on the surface of the negative electrode 20Y is easily discharged from the electrode body 5. By promoting the discharge of the gas from the electrode body 5, the contact between the electrolytic solution and the electrode in the electrode body 5 is less likely to be hindered by the gas. That is, the efficiency of the electric power supplied from the power storage element 1 is unlikely to deteriorate.

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. That is, the present implementation having the effect of enabling the gas generated inside the power storage element to be housed in the storage space 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. The form of is particularly suitable.

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 includes the electrode body 5 and the electrolytic solution housed in the accommodation space 7a, and the electrode body 5 includes a plurality of negative electrodes 20Y and a plurality of positive electrodes 10X alternately laminated in the first direction d1, and the negative electrode 20Y is a negative electrode body 20Y. It has a negative electrode current collector 21Y and a negative electrode active material layer 22Y provided on the negative electrode current collector 21Y and containing a negative electrode active material, and the positive electrode 10X is on the positive electrode current collector 11X and the positive electrode current collector 11X. the total weight of the provided having a positive electrode active material layer 12X containing a positive electrode active material, the total weight W _a of the negative electrode active material layer 22Y contained in the electrode body 5, the positive electrode active material layer 12X contained in the electrode body 5 W AC ratio is a value of ratio _{C (W} a / W _C) is less than 0.45 or more 1.0, the actual volume _{V a} of the negative electrode active material layer 22Y contained in the electrode body 5, 50 cm ³ It is 150 cm ³ or less, and the accommodating space 7a has a volume V capable of further accommodating a gas of ^{20 cm 3} or more in addition to the electrolytic solution and the electrode body 5. According to such a power storage element 1, the volume of gas that can be stored in the storage space 7a can be determined according to the volume of gas that can be generated inside the power storage element 1. Therefore, it is possible to suppress the deterioration of the volumetric energy density of the power storage element 1 while allowing the gas generated inside the power storage element 1 to be housed in the storage space 7a.

Also, electric storage element 1 of the present embodiment, the negative electrode active of the total weight W _A material layer 22Y, the ratio of the values for the total weight W _C of the positive electrode active material layer 12X contained in the electrode body 5 included in the electrode body 5 AC ratio is _(W a / W _C) is less than 0.45 or more 1.0, accommodation space 7a of the volume V can accommodate gas in addition to the electrolyte and the electrode body 5, the electrode bodies 5 ratio actual volume _{V a} of the negative electrode active material layer 22Y included (V / _{V a)} is not more than 2 or 0.133. According to such a power storage element 1, the volume of gas that can be stored in the storage space 7a can be determined according to the volume of gas that can be generated inside the power storage element 1. Therefore, it is possible to suppress the deterioration of the volumetric energy density of the power storage element 1 while allowing the gas generated inside the power storage element 1 to be housed in the storage space 7a.

Furthermore, storage element 1 of the present embodiment, the total weight W _A of the negative electrode active material layer 22Y contained in the electrode body _5, the total weight W _C of the positive electrode active material layer 12X contained in the electrode body _5, the electrode bodies 5 _{The actual volume VA} of the negative electrode active material layer 22Y and the volume V of the gas that the accommodating space 7a can accommodate in addition to the electrolytic solution and the electrode body satisfy the following relationship.
_{0.04 <V / V A × W} A / W C <1.2
According to such a power storage element 1, the volume of gas that can be stored in the storage space 7a can be determined according to the volume of gas that can be generated inside the power storage element 1. Therefore, it is possible to suppress the deterioration of the volumetric energy density of the power storage element 1 while allowing the gas generated inside the power storage element 1 to be housed in the storage space 7a.

Aspects of the present invention are not limited to the above-described embodiments, but include various modifications that can be conceived by those skilled in the art, and the effects of the present invention are not limited to the above-mentioned contents. That is, various additions, changes and partial deletions are possible without departing from the conceptual idea and purpose of the present invention derived from the contents defined in the claims and their equivalents.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

As Examples 1 to 11 and Comparative Examples 1 and 2, the positive electrode active is the value of the ratio of the total weight W _C of the material layer AC ratio, the negative electrode active material layer included in the electrode body of the total weight W _A of the negative electrode active material layer Lithium ion secondary batteries (sheet-type laminated batteries) having different combinations of the actual volume _VA and the volume V of the gas that can be accommodated in addition to the electrolytic solution and the electrode body in the accommodating space were produced. In the lithium ion secondary batteries of Examples 8 and 9, the distance L between the joint and the electrode body in a plan view was changed. Along with this, in the lithium ion secondary batteries of Examples 8 and 9, the area of the electrode body and the aspect ratio of the negative electrode have changed. Further, in the lithium ion secondary batteries of Examples 4 to 7, the thickness of the electrode body was changed. Further, in the lithium ion secondary battery of Example 11, the surface roughness Ra _A of the negative electrode was changed.

The methods for manufacturing the lithium ion secondary batteries of Examples 1 to 11 and Comparative Examples 1 and 2 will be specifically described.

First, 100 parts by mass of a solid component containing a positive electrode active material, 5 parts by mass of carbon black as a conductive auxiliary agent, 5 parts by mass of polyvinylidene fluoride as a binder, and N-methylpyrrolidone (NMP) as a solvent are mixed. Then, a slurry having a solid content of 45% by mass was prepared. The positive electrode active material contains lithium iron phosphate. Then, this slurry was applied to an aluminum foil, pre-dried, and then vacuum dried at 120 ° C. The electrode was pressure-pressed at 4 kN and further punched to the dimensions of the electrode to prepare a positive electrode.

Further, 100 parts by mass of a solid component containing a negative electrode active material, 1.5 parts by mass of styrene-butadiene rubber as a binder, 1.5 parts by mass of sodium carboxymethyl cellulose as a thickener, and an aqueous solvent are mixed to solidify. A 50% by mass slurry was prepared. Then, this slurry was applied to the copper foil and dried at 100 ° C. The electrode was pressure-pressed at 2 kN and further punched to the dimensions of the electrode to prepare a negative electrode.

A lithium ion secondary battery laminated in a sheet shape was produced by laminating a positive electrode, a negative electrode, and a separator, injecting an electrolytic solution, and then sealing the battery. The lithium ion secondary batteries in Examples and Comparative Examples were manufactured in a dry box or a dry room.

Each of the prepared lithium ion secondary batteries of Examples 1 to 11 and Comparative Examples 1 and 2 was charged to 3.6 V at a current value of 1 C at 25 ° C. and then discharged to 2.5 V at a current value of 1 C. This charge / discharge cycle was repeated, and after repeating 1000 cycles, the thickness of the lithium ion secondary battery was measured at 5 points with a caliper. The thickness of the lithium ion secondary battery was measured at five points at equal intervals along the longitudinal direction of the lithium ion secondary battery. For the lithium ion secondary batteries of Examples 1 to 11 and Comparative Examples 1 and 2, the cycle characteristics were evaluated by the difference between the design thickness and the maximum value of the measured thickness. Lithium-ion batteries, which have a small change in thickness after repeated charge / discharge cycles, are evaluated to be resistant to repeated charge / discharge cycles and therefore have high cycle characteristics. Specifically, the difference between the design thickness and the thickness measured after repeating the charge / discharge cycle is A for less than 0.10 mm, B for 0.10 mm or more and less than 0.15 mm, and 0.20 mm for 0.15 mm or more. Less than was evaluated as C, and 0.20 mm or more was evaluated as D.

For Examples 1 to 11 and Comparative Examples 1 and 2, the positive electrode active is the value of the ratio of the total weight W _C of the material layer AC ratio, the negative electrode active material layer included in the electrode body of the total weight W _A of the negative electrode active material layer The actual volume _VA , the volume V of the gas that can be accommodated in addition to the electrolytic solution and the electrode body, and the ratio V / _VA , V / _VA and AC of the _{volume V to the actual volume VA of the negative electrode active material layer.} The product of the ratios, the distance L between the joint and the electrode body in the plan view, the area of the electrode body, and the length of the negative electrode in the direction in which the negative electrode is the shortest in the plan view in the direction orthogonal to the direction in which the negative electrode is the shortest. Table 1 below shows the evaluation results of the length ratio of the negative electrode (aspect ratio of the negative electrode), the thickness of the electrode body, the surface roughness Ra _{A of the negative electrode, and the cycle characteristics.}

Comparison with Example 1 to 11 and Comparative Examples 1 and 2 shown in Table 1, AC ratio is a value of the ratio to the total weight W _C of the positive electrode active material layer of the total weight W _A of the negative electrode active material layer It is understood that the cycle characteristics are improved when the value is 0.45 or more and less than 1.0. Further, from the comparison of Examples 4 to 6, the cycle characteristics are improved when the volume V of the gas that can be accommodated in addition to the electrolytic solution and the electrode body is 20 cm ³ or more, and the cycle characteristics are improved ^{when the accommodation space is 40 cm 3} or more. It is understood that it will improve further. Further, from the comparison between Example 2 and Example 10, it is understood that the cycle characteristics are improved _{when the V / V A is 2 or less.} Further, from the comparison between Example 5 and Example 11, it is understood that the cycle characteristics are further improved when _{the surface roughness Ra A of the negative electrode active material layer is 100 nm or more.}

1 Power storage element 5 Electrode body 6 Tab 7 Exterior body 7a Containment space 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 1st exterior material 50 2nd exterior material 60 Joint

Claims (10)

An exterior body including the first exterior material and the second exterior material,
An electrode body and an electrolytic solution housed in a storage space formed between the first exterior material and the second exterior material are provided.
The electrode body includes a plurality of negative electrodes and a plurality of positive electrodes alternately laminated in the first direction.
The negative electrode has a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector and containing a negative electrode active material.
The positive electrode has a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector and containing a positive electrode active material.
Of the total weight W _A of the negative electrode active material layer included in the electrode body, AC ratio is a value of the ratio to the total weight W _C of the positive electrode active material layer included in the electrode body (W A _{/ W C)} is , 0.45 or more and less than 1.0,
_{The actual volume VA} of the negative electrode active material layer contained in the electrode body is 50 cm ³ or more and 150 cm ³ or less.
The accommodating space is a power storage element having a volume capable of further accommodating a gas of ^{20 cm 3} or more in addition to the electrolytic solution and the electrode body. The power storage element according to claim 1, ^{wherein the accommodating space has a volume capable of further accommodating a gas of 40 cm 3} or more in addition to the electrolytic solution and the electrode body. An exterior body including the first exterior material and the second exterior material,
An electrode body and an electrolytic solution housed in a storage space formed between the first exterior material and the second exterior material are provided.
The electrode body includes a plurality of negative electrodes and a plurality of positive electrodes alternately laminated in the first direction.
The negative electrode has a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material provided on the negative electrode current collector.
The positive electrode has a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material provided on the positive electrode current collector.
Of the total weight W _A of the negative electrode active material layer included in the electrode body, AC ratio is a value of the ratio to the total weight W _C of the positive electrode active material layer included in the electrode body (W A _{/ W C)} is , 0.45 or more and less than 1.0,
The ratio (V / V _A ) of the volume V of the gas that can be accommodated in addition to the electrolytic solution and the electrode body to the actual volume _VA of the negative electrode active material layer contained in the electrode body is 0. A power storage element that is 133 or more and 2 or less. The first exterior material and the second exterior material are joined at a joint portion.
The power storage element according to any one of claims 1 to 3 , wherein the distance between the joint portion and the electrode body in a plan view is 3 mm or more and less than 15 mm. The power storage element according to any one of claims 1 to 4 , wherein at least one of the surface roughness Ra _C of the positive electrode active material layer and the surface roughness Ra _{A of the negative electrode active material layer is 100 nm or more.} In a plan view, the ratio of the length of the negative electrode in the direction orthogonal to the direction in which the negative electrode is the shortest to the length of the negative electrode in the direction in which the negative electrode is the shortest is 1.5 or more. The power storage element according to any one of 5 to 5. The power storage element according to any one of claims 1 to 6 , wherein the positive 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 7. The power storage element according to any one of claims 1 to 8 , wherein the thickness of the electrode body is 0.25 mm or more and 9.5 mm or less. The power storage element according to any one of claims 1 to 9 , wherein the first exterior material and the second exterior material are joined at a joint portion on a peripheral edge.

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