JP6770701B2 - Power storage element - Google Patents

Description

The present invention relates to a power storage element.

Conventionally, as a power storage element, a polymer battery using carbon having a pore diameter of 0.01 to 5 μm and a total volume of 0.5 ml / g or more obtained by a mercury injection method as a negative electrode material (negative electrode active material) is known. (For example, Patent Document 1).

However, in the battery described in Patent Document 1, when the aluminum foil is adopted as the current collector of the electrode and the fluorine-containing electrolyte salt such as LiPF ₆ is adopted as the electrolyte salt, the oxide on the surface of the aluminum foil ( Since Al ₂ O ₃ ) is corroded by fluorine such as LiPF ₆ , the output durability may not always be sufficient.

Japanese Unexamined Patent Publication No. 2004-335302

An object of the present embodiment is to provide a power storage element having sufficient output durability.

The power storage element of the present embodiment includes an electrolytic solution containing an electrolyte salt containing fluorine and an electrode, and the electrode is an electrode base material made of aluminum and an active material arranged along the surface of the electrode base material. It has a layer and a porous intermediate layer arranged between the electrode base material and the active material layer, and the abundance ratio of AlF ₃ to Al ₂ O ₃ per unit volume on the surface of the electrode base material is , 0.7 or more and 1.0 or less.
That is, the storage element of the present embodiment includes an electrolytic solution containing an electrolyte salt containing fluorine and an electrode, and the electrodes are arranged along the surface of the electrode base material made of aluminum and the electrode base material. It has an active material layer and a porous intermediate layer arranged between the electrode base material and the active material layer, and has a peak representing Al ₂ O ₃ when the surface of the electrode base material is measured by XPS. The maximum intensity A and the maximum intensity B of the peak representing AlF ₃ satisfy the relational expression of 0.7 ≦ B / A ≦ 1.0.

In the power storage element having the above configuration, aluminum oxide (Al ₂ O ₃ ) is generated on the entire surface of the electrode base material before it is manufactured. In general, aluminum oxide (Al ₂ O ₃ ) is easily corroded by fluorine, which is an electrolyte salt containing fluorine. By the way, at the time of manufacturing, a part of the surface of the electrode base material comes into direct contact with the electrolytic solution that has entered the pores of the porous intermediate layer. When the surface of the electrode substrate is in contact with the electrolyte, the surface of the electrode substrate is corroded by fluorine, fluorides such as aluminum fluoride (AlF ₃₎ or AlO _x F _y may occur. When AlO _x F _y occurs, corrosion further progresses, the resistance between the electrode substrate and the active material layer is increased, the current collecting property is lowered between the electrode substrate and the active material layer. However, in a state where the electrolyte enters the pores by fluorine electrolyte salt in the electrolytic solution, only a portion of the oxygen (O) of the aluminum oxide (Al 2 _{O 3)} was fluorided to AlO _x F _y While the change is suppressed, aluminum oxide (Al ₂ O ₃ ) changes to aluminum fluoride (Al F ₃ ). That is, in the portion where the electrolytic solution that has entered the pores and the surface of the electrode base material are in contact with each other, aluminum oxide (Al) rather than a reaction in which only a part of oxygen (O) of aluminum oxide (Al ₂ O ₃ ) is replaced with fluorine The reaction in which all of the oxygen (O) of Al ₂ O ₃ ) is replaced with fluorine is dominant. In this way, when a part of the surface of the electrode base material and the electrolytic solution that has entered the pores of the intermediate layer come into contact with each other, a part of the surface of the electrode base material is corroded to generate AlF ₃ . AlF ₃ can suppress further corrosion from the inside of the aluminum electrode base material due to the fluorine of the electrolyte salt. On the other hand, on the surface of the electrode base material, Al ₂ O ₃ that does not fluorinate exists in a portion that is not in direct contact with the electrolytic solution that has entered the pores of the intermediate layer. Al ₂ O ₃ is as described above, but likely to be corroded by fluorine, part there are _Al 2 _{O 3} is not directly in contact with the electrolyte. Therefore, the portion where Al ₂ O ₃ is present is not easily corroded by the fluorine of the electrolyte salt. In the power storage element provided with an electrode including an aluminum electrode base material and an intermediate layer, a maximum intensity A representing the maximum value of the peak of Al ₂ O ₃ and a maximum intensity B representing the maximum value of the peak of Al F ₃ By satisfying the relational expression of 0.7 ≦ B / A ≦ 1.0, AlF ₃ can sufficiently suppress the progress of corrosion inward near the surface of the aluminum electrode base material. .. As a result, it is possible to prevent the resistance between the electrode base material and the active material layer from increasing due to the progress of corrosion and the decrease in current collecting property between the electrode base material and the active material layer. Therefore, the above-mentioned power storage element can have sufficient output durability.

In the above-mentioned power storage element, the peak pore diameter measured by measuring the pore distribution of the intermediate layer may be 0.5 μm or more and 2.5 μm or less. With such a configuration, in the above-mentioned power storage element, AlF ₃ is more reliably generated on the surface of the electrode base material made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer. As a result, it is possible to more sufficiently suppress the progress of corrosion inward near the surface of the aluminum electrode base material. Therefore, the above-mentioned power storage element can have more sufficient output durability.

In the above power storage element, the total volume of pore diameters of 0.5 μm or more and 20 μm or less measured by measuring the pore distribution of the intermediate layer is 0.5 mL / g or more and 2.0 mL / g or less per unit mass of the intermediate layer. May be good. With such a configuration, in the above-mentioned power storage element, AlF ₃ is more reliably generated on the surface of the electrode base material made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer. As a result, it is possible to more sufficiently suppress the corrosion of the electrode base material made of aluminum. Therefore, the above-mentioned power storage element can have more sufficient output durability.

According to this embodiment, it is possible to provide a power storage element having sufficient output durability.

FIG. 1 is a perspective view of a power storage element according to the present embodiment. FIG. 2 is a front view of the power storage element according to the same embodiment. FIG. 3 is a cross-sectional view taken along the line III-III of FIG. FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. FIG. 5 is a perspective view of a state in which a part of the power storage element according to the same embodiment is assembled, and is a perspective view of a state in which the liquid injection plug, the electrode body, the current collector, and the external terminal are assembled to the lid plate. is there. FIG. 6 is a diagram for explaining the configuration of the electrode body of the power storage element according to the embodiment. FIG. 7 is a cross-sectional view (VII-VII cross section of FIG. 6) of the superimposed positive electrode, negative electrode, and separator. FIG. 8 is a perspective view of a power storage device including a power storage element according to the same embodiment. FIG. 9 is a chart diagram schematically showing the results of XPS measurement of the metal foil surface of the positive electrode.

Hereinafter, an embodiment of the power storage element according to the present invention will be described with reference to FIGS. 1 to 7. The power storage element includes a primary battery, a secondary battery, a capacitor, and the like. In the present embodiment, a rechargeable secondary battery will be described as an example of the power storage element. The name of each component (each component) of the present embodiment is that of the present embodiment, and may be different from the name of each component (each component) in the background technology.

The power storage element 1 of the present embodiment is a non-aqueous electrolyte secondary battery. More specifically, the power storage element 1 is a lithium ion secondary battery that utilizes the electron transfer generated by the movement of lithium ions. This type of power storage element 1 supplies electrical energy. The power storage element 1 is used alone or in a plurality. Specifically, the power storage element 1 is used alone when the required output and the required voltage are small. On the other hand, when at least one of the required output and the required voltage is large, the power storage element 1 is used in the power storage device 100 in combination with the other power storage element 1. In the power storage device 100, the power storage element 1 used in the power storage device 100 supplies electrical energy.

As shown in FIGS. 1 to 7, the power storage element 1 includes an electrode body 2 including a positive electrode 11 and a negative electrode 12, a case 3 accommodating the electrode body 2, and an external terminal 7 arranged outside the case 3. It is provided with an external terminal 7 that is electrically connected to the electrode body 2. Further, the power storage element 1 has a current collector 5 or the like that conducts the electrode body 2 and the external terminal 7 in addition to the electrode body 2, the case 3, and the external terminal 7.

The electrode body 2 is formed by winding a laminated body 22 in which a positive electrode 11 and a negative electrode 12 are laminated in a state of being insulated from each other by a separator 4.

The positive electrode 11 is composed of a metal foil 111 (positive electrode base material), an active material layer 112 arranged so as to cover the surface of the metal foil 111 and containing an active material, and a metal foil 111 (positive electrode base material) and an active material layer 112. It has a porous intermediate layer 113 arranged between them. In this embodiment, the intermediate layer 113 overlaps both surfaces of the metal foil 111, respectively. The active material layer 112 overlaps one surface of each intermediate layer 113. The active material layer 112 is arranged on both sides of the metal foil 111 in the thickness direction, and similarly, the intermediate layer 113 is arranged on both sides of the metal foil 111 in the thickness direction. The thickness of the positive electrode 11 is usually 40 μm or more and 150 μm or less.

The metal foil 111 is strip-shaped. The metal foil 111 of the positive electrode 11 of the present embodiment is made of aluminum. In this embodiment, the metal foil 111 is an aluminum foil. The positive electrode 11 has an uncoated portion (a portion where the positive electrode active material layer is not formed) 115 of the positive electrode active material layer 112 at one end edge portion in the width direction, which is the lateral direction of the band shape.

Aluminum oxide (Al ₂ O ₃ ) is formed on at least a part of the surface of the metal foil 111. Such aluminum oxide is produced by oxidizing the aluminum on the surface by oxygen in the air.

The abundance ratio of AlF ₃ to Al ₂ O ₃ per unit volume on the surface of the metal foil 111 is 0.7 or more and 1.0 or less. That is, when the surface of the metal foil 111 is measured by XPS, the maximum intensity A of the peak representing Al ₂ O ₃ and the maximum intensity B of the peak representing Al F ₃ are 0.7 ≦ B / A ≦ 1.0. Satisfy the relational expression of. Specifically, the maximum intensity A of the peak having a maximum value between 74.3 eV and 75.3 eV and the maximum intensity B of the peak having a maximum value between 76.0 eV and 78.0 eV are 0.7 ≦. The relational expression of B / A ≦ 1.0 is satisfied. Note that the maximum intensity A represents the maximum value of the peak of _Al 2 _{O 3,} maximum intensity B represents the maximum value of the peak of AlF _3. XPS measurement is performed under the measurement conditions described in the examples. The value of B / A may be 0.75 ≦ B / A ≦ 0.85. The B / A value can be increased, for example, by increasing the peak pore diameter measured by measuring the pore distribution of the intermediate layer 113. On the other hand, the B / A value can be reduced, for example, by reducing the peak pore diameter measured by measuring the pore distribution of the intermediate layer 113. On the surface of the metal foil 111, it is considered that there is a so-called sea-island structure in which Al ₂ O ₃ spreads continuously and Al F ₃ is scattered.

The positive electrode active material layer 112 contains a particulate active material, a particulate conductive auxiliary agent, and a binder. In the positive electrode active material layer 112, the content of the active material is usually 88% by mass or more and 95% by mass or less, the content of the conductive auxiliary agent is 2.5% by mass or more and 6.0% by mass or less, and the binder The content is 2.5% by mass or more and 6.0% by mass or less. The thickness of the positive electrode active material layer 112 is usually 10 μm or more and 50 μm or less.

The basis weight of the positive electrode active material layer 112 is usually 5 mg / cm ² or more and 15 mg / cm ² or less. The density of the positive electrode active material layer 112 is usually 1.9 g / cm ³ or more and 2.8 g / cm ³ or less. The basis weight and density are the densities of one layer arranged so as to cover one surface of the metal foil 111. The porosity of the positive electrode active material layer 112 is usually 33% or more and 55% or less.

The active material of the positive electrode 11 is a compound that can occlude and release lithium ions. The average particle size D50 of the active material of the positive electrode 11 is usually 3 μm or more and 8 μm or less.

The active material of the positive electrode 11 is, for example, a lithium metal oxide. Specifically, the active material of the positive electrode, for _example, Li p _MeO t (Me represents one or more transition metal) complex oxide represented by _{(Li p Co s O 2,} Li p Ni q O _{2, Li p Mn r O 4} , Li p Ni q Co s Mn r O 2 , etc.), _{or, Li t Me u (XO v} ) w (Me represents one or more transition metals, X is e.g. P, Si, B, a polyanion compounds represented by the representative of the _{V) (Li t Fe u PO} 4, Li t Mn u PO 4, Li t Mn u SiO 4, Li t Co u PO 4 F , etc.).

In this embodiment, the active material of the positive electrode _{11, Li p Ni q Mn r Co} s O lithium-metal composite oxide represented by the chemical composition of the _t (where a 0 <p ≦ 1.3, q + r + s = 1 , 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, 0 ≦ s ≦ 1, and 1.7 ≦ t ≦ 2.3). It should be noted that 0 <q <1, 0 <r <1, and 0 <s <1.

Additional such _{Li p Ni q Mn r Co s} O lithium-metal composite oxide represented by the chemical composition of the _t, for _{example, LiNi 1/3 Co 1/3 Mn 1/3 O} 2, LiNi 1/6 Co 1 _{/ 6 Mn 2/3 O 2, LiCoO} 2 and the like.

The binder used for the positive electrode active material layer 112 is, for example, polyvinylidene fluoride (PVdF), a copolymer of ethylene and vinyl alcohol, polymethylmethacrylate, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic. Acid, styrene-butadiene rubber (SBR). The binder of this embodiment is polyvinylidene fluoride.

The conductive auxiliary agent of the positive electrode active material layer 112 is a carbonaceous material containing 98% by mass or more of carbon. The carbonaceous material is, for example, Ketjen Black (registered trademark), acetylene black, graphite and the like. The positive electrode active material layer 112 of the present embodiment has acetylene black as a conductive auxiliary agent.

The intermediate layer 113 contains a particulate conductive auxiliary agent and a binder (binding agent). The intermediate layer 113 does not contain the positive electrode active material. The intermediate layer 113 is formed porous by the gaps between the conductive auxiliary agents. Since the intermediate layer 113 contains a conductive auxiliary agent, it has conductivity. The intermediate layer 113 serves as an electron path between the metal foil 111 and the positive electrode active material layer 112, and maintains conductivity between them. The conductivity of the intermediate layer 113 is usually higher than that of the active material layer 112.

The intermediate layer 113 is arranged between the metal foil 111 and the positive electrode active material layer 112. The intermediate layer 113 containing the binder (binding agent) has sufficient adhesion to the metal foil 111. The intermediate layer 113 also has sufficient adhesion to the positive electrode active material layer 112.

The thickness of the intermediate layer 113 is usually 0.1 μm or more and 2.0 μm or less. The basis weight of the intermediate layer 113 is usually 0.02 mg / cm ² or more and 0.20 mg / cm ² or less. Such unit weight, may be 0.03 mg / cm ² or more 0.14 mg / cm ² or less.

The peak pore diameter of the intermediate layer 113 measured by measuring the pore distribution is 0.5 μm or more and 2.5 μm or less. Such a peak pore diameter may be 0.67 μm or more and 2.20 μm or less. The pore distribution is measured by the mercury intrusion method (JIS R1655: 2003). The peak pore diameter is the pore diameter of the portion having the highest peak in the obtained pore distribution.

The total volume of pore diameters of 0.5 μm or more and 20 μm or less measured by measuring the pore distribution of the intermediate layer 113 is 0.5 mL / g or more and 2.0 mL / g or less per unit mass of the intermediate layer. The total volume of such pore diameters may be 0.78 mL / g or more and 1.61 mL / g or less. The total volume of the pore diameter is determined by determining the pore distribution by the mercury intrusion method (JIS R1655: 2003) and reading the total volume of the pore diameter in the range of 0.5 μm or more and 20 μm or less.

The conductive auxiliary agent of the intermediate layer 113 is a carbonaceous material containing 98% by mass or more of carbon. The electrical conductivity of carbonaceous materials is usually ^10-6 S / m or higher. The carbonaceous material is, for example, Ketjen Black (registered trademark), acetylene black, graphite and the like. The intermediate layer 113 of the present embodiment has acetylene black as a conductive auxiliary agent. The average particle size D50 of the conductive auxiliary agent is usually 20 nm or more and 150 nm or less. The average particle size D50 of the conductive auxiliary agent can be measured by using a laser diffraction type particle size measuring device.

Examples of the binder of the intermediate layer 113 include polyvinylidene fluoride (PVdF), a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, and polysiloxane. Polyvinyl acetate, polymethyl methacrylate, polystyrene, polycarbonate, polyamide, polyimide, polyamideimide, polyethylene oxide (polyethylene glycol), polypropylene oxide (polypropylene glycol), polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polytetrafluoroethylene ( Examples thereof include synthetic polymer compounds such as PTFE), styrene-butadiene rubber (SBR), polyolefin, and nitrile-butadiene rubber. Examples of the binder of the intermediate layer 113 include natural polymer compounds such as chitosan and chitosan derivatives (for example, hydroxyethyl chitosan), and cellulose and cellulose derivatives (for example, carboxymethyl cellulose).

The intermediate layer 113 usually contains 20% by mass or more and 50% by mass or less of a carbonaceous material as a conductive auxiliary agent, and 50% by mass or more and 80% by mass or less of a binder. The intermediate layer 113 may contain a curing agent such as pyromellitic acid.

The negative electrode 12 has a metal foil 121 (negative electrode base material) and a negative electrode active material layer 122 formed on the metal foil 121. In the present embodiment, the negative electrode active material layer 122 is laminated on both sides of the metal foil 121, respectively. The metal foil 121 is strip-shaped. The negative electrode metal foil 121 of the present embodiment is, for example, a copper foil. The negative electrode 12 has an uncoated portion (a portion where the negative electrode active material layer is not formed) 125 of the negative electrode active material layer 122 at one edge portion in the width direction, which is the lateral direction of the band shape. The thickness of the negative electrode 12 is usually 40 μm or more and 150 μm or less.

The negative electrode active material layer 122 contains a particulate active material and a binder. The negative electrode active material layer 122 is arranged so as to face the positive electrode 11 via the separator 4. The width of the negative electrode active material layer 122 is larger than the width of the positive electrode active material layer 112. The thickness of the negative electrode active material layer 122 is usually 10 μm or more and 50 μm or less.

In the negative electrode active material layer 122, the ratio of the binder may be 5% by mass or more and 10% by mass or less with respect to the total mass of the active material of the negative electrode and the binder.

The active material of the negative electrode 12 can contribute to the electrode reaction of the charge reaction and the discharge reaction in the negative electrode 12. For example, the active material of the negative electrode 12 undergoes an alloying reaction with a carbon material such as graphite or amorphous carbon (non-graphitized carbon, easily graphitized carbon) or lithium ions such as silicon (Si) and tin (Sn). It is the material that is produced. The active material of the negative electrode of this embodiment is amorphous carbon. More specifically, the active material of the negative electrode is non-graphitized carbon. The average particle size D50 of the active material of the negative electrode 12 is usually 1 μm or more and 10 μm or less.

The basis weight (for one layer) of the negative electrode active material layer 122 is usually 2.5 mg / cm ² or more and 5.0 mg / cm ² or less.

The binder used for the negative electrode active material layer 122 is the same as the binder used for the positive electrode active material layer 112. The binder of this embodiment is polyvinylidene fluoride.

The negative electrode active material layer 122 may further have a conductive auxiliary agent such as Ketjen Black (registered trademark), acetylene black, and graphite.

In the electrode body 2 of the present embodiment, the positive electrode 11 and the negative electrode 12 configured as described above are wound in a state of being insulated by the separator 4. That is, in the electrode body 2 of the present embodiment, the laminated body 22 of the positive electrode 11, the negative electrode 12, and the separator 4 is wound. The separator 4 is a member having an insulating property. The separator 4 is arranged between the positive electrode 11 and the negative electrode 12. As a result, in the electrode body 2 (specifically, the laminated body 22), the positive electrode 11 and the negative electrode 12 are insulated from each other. Further, the separator 4 holds the electrolytic solution in the case 3. As a result, when the power storage element 1 is charged and discharged, lithium ions move between the positive electrode 11 and the negative electrode 12 which are alternately laminated with the separator 4 in between.

The separator 4 has a strip shape. The separator 4 has a porous separator base material. The separator 4 of the present embodiment has only a separator base material. The separator 4 is arranged between the positive electrode 11 and the negative electrode 12 in order to prevent a short circuit between the positive electrode 11 and the negative electrode 12.

The separator base material of the separator 4 is made porous by, for example, a woven fabric, a non-woven fabric, or a porous membrane. Examples of the material of the separator base material include polymer compounds, glass, and ceramics. Examples of the polymer compound include polyesters such as polyacrylonitrile (PAN), polyamide (PA) and polyethylene terephthalate (PET), polyolefins (PP) such as polypropylene (PP) and polyethylene (PE), and cellulose. ..

The width of the separator 4 (the dimension of the strip shape in the lateral direction) is slightly larger than the width of the negative electrode active material layer 122. The separator 4 is arranged between the positive electrode 11 and the negative electrode 12 which are overlapped with each other so that the positive electrode active material layer 112 and the negative electrode active material layer 122 are overlapped with each other in the width direction. At this time, as shown in FIG. 6, the uncoated portion 115 of the positive electrode 11 and the uncoated portion 125 of the negative electrode 12 do not overlap. That is, the uncoated portion 115 of the positive electrode 11 protrudes in the width direction from the region where the positive electrode 11 and the negative electrode 12 overlap, and the uncoated portion 125 of the negative electrode 12 protrudes in the width direction from the region where the positive electrode 11 and the negative electrode 12 overlap. It protrudes in the direction opposite to the protruding direction of the uncoated portion 115 of the positive electrode 11. The electrode body 2 is formed by winding the positive electrode 11, the negative electrode 12, and the separator 4, that is, the laminated body 22, in a laminated state. The uncoated laminated portion 26 in the electrode body 2 is formed by the portion where only the uncoated portion 115 of the positive electrode 11 or the uncoated portion 125 of the negative electrode 12 is laminated.

The uncoated laminated portion 26 is a portion of the electrode body 2 that is electrically connected to the current collector 5. The uncoated laminated portion 26 has two portions (divided uncoated laminated portion) with the hollow portion 27 (see FIG. 6) interposed therebetween in the winding center direction of the wound positive electrode 11, negative electrode 12, and separator 4. ) It is divided into 261.

The uncoated laminated portion 26 configured as described above is provided at each electrode of the electrode body 2. That is, the uncoated laminated portion 26 in which only the uncoated portion 115 of the positive electrode 11 is laminated constitutes the uncoated laminated portion of the positive electrode 11 in the electrode body 2, and only the uncoated portion 125 of the negative electrode 12 is laminated. The portion 26 constitutes an uncoated laminated portion of the negative electrode 12 in the electrode body 2.

The case 3 has a case main body 31 having an opening, and a lid plate 32 that closes (closes) the opening of the case main body 31. In the case 3, the electrolytic solution is housed in the internal space together with the electrode body 2 and the current collector 5. Case 3 is formed of a metal that is resistant to electrolytes. The case 3 is formed of, for example, an aluminum-based metal material such as aluminum or an aluminum alloy. The case 3 may be formed of a metal material such as stainless steel and nickel, or a composite material in which a resin such as nylon is adhered to aluminum.

The electrolytic solution is a non-aqueous electrolyte solution. The electrolytic solution is obtained by dissolving the electrolyte salt in an organic solvent. The organic solvent is, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Electrolyte salts are LiClO ₄ , LiBF ₄ , LiPF ₆ , and the like. The electrolytic solution of the present embodiment is obtained by dissolving 0.5 to 1.5 mol / L of LiPF ₆ in a mixed solvent in which propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are mixed at a predetermined ratio.

The electrolyte salt contains fluorine. Specifically, the anionic component of the electrolyte salt contains fluorine. The anionic component can react with a small amount of water in the battery to produce a small amount of hydrofluoric acid. The surface of the metal foil 111 is corroded by this hydrofluoric acid, and the corrosion can proceed. The progress of such corrosion is suppressed by aluminum fluoride.

The case 3 is formed by joining the opening peripheral edge of the case body 31 and the peripheral edge of the rectangular lid plate 32 in a superposed state. Further, the case 3 has an internal space defined by the case main body 31 and the lid plate 32. In the present embodiment, the peripheral edge of the opening of the case body 31 and the peripheral edge of the lid plate 32 are joined by welding.
In the following, as shown in FIG. 1, the long side direction of the lid plate 32 is the X-axis direction, the short side direction of the lid plate 32 is the Y-axis direction, and the normal direction of the lid plate 32 is the Z-axis direction.

The case body 31 has a square tube shape (that is, a bottomed square tube shape) in which one end in the opening direction (Z-axis direction) is closed. The lid plate 32 is a plate-shaped member that closes the opening of the case body 31.

The lid plate 32 has a gas discharge valve 321 capable of discharging the gas in the case 3 to the outside. The gas discharge valve 321 discharges gas from the inside of the case 3 to the outside when the internal pressure of the case 3 rises to a predetermined pressure. The gas discharge valve 321 is provided at the center of the lid plate 32 in the X-axis direction.

The case 3 is provided with a liquid injection hole for injecting an electrolytic solution. The liquid injection hole communicates the inside and the outside of the case 3. The liquid injection hole is provided in the lid plate 32. The injection hole is sealed (closed) by the injection plug 326. The liquid injection plug 326 is fixed to the case 3 (lid plate 32 in the example of this embodiment) by welding.

The external terminal 7 is a portion electrically connected to the external terminal 7 of another power storage element 1 or an external device or the like. The external terminal 7 is formed of a conductive member. For example, the external terminal 7 is formed of a highly weldable metal material such as an aluminum-based metal material such as aluminum or an aluminum alloy, or a copper-based metal material such as copper or a copper alloy.

The external terminal 7 has a surface 71 to which a bus bar or the like can be welded. The surface 71 is a flat surface. The external terminal 7 has a plate shape that extends along the lid plate 32. Specifically, the external terminal 7 has a rectangular plate shape in the Z-axis direction.

The current collector 5 is arranged in the case 3 and is directly or indirectly connected to the electrode body 2 so as to be energized. The current collector 5 of the present embodiment is electrically connected to the electrode body 2 via the clip member 50. That is, the power storage element 1 includes a clip member 50 that connects the electrode body 2 and the current collector 5 so as to be energized.

The current collector 5 is formed of a conductive member. As shown in FIG. 3, the current collector 5 is arranged along the inner surface of the case 3. The current collector 5 is arranged on the positive electrode 11 and the negative electrode 12 of the power storage element 1, respectively. In the power storage element 1 of the present embodiment, the storage element 1 is arranged in the uncoated laminated portion 26 of the positive electrode 11 of the electrode body 2 and the uncoated laminated portion 26 of the negative electrode 12 in the case 3, respectively.

The current collector 5 of the positive electrode 11 and the current collector 5 of the negative electrode 12 are formed of different materials. Specifically, the current collector 5 of the positive electrode 11 is formed of, for example, aluminum or an aluminum alloy, and the current collector 5 of the negative electrode 12 is formed of, for example, copper or a copper alloy.

In the power storage element 1 of the present embodiment, the electrode body 2 (specifically, the electrode body 2 and the current collector 5) in a state of being housed in a bag-shaped insulating cover 6 that insulates the electrode body 2 and the case 3 is the case 3. It is housed inside.

Next, a method of manufacturing the power storage element 1 of the above embodiment will be described.

In the method for manufacturing the power storage element 1, a mixture containing an active material is applied to a metal foil (electrode base material) to form an active material layer, and electrodes (positive electrode 11 and negative electrode 12) are produced. In the production of the positive electrode 11, the intermediate layer 113 containing the conductive auxiliary agent is formed on the metal foil 111, and then the active material layer 112 is formed. Next, the positive electrode 11, the separator 4, and the negative electrode 12 are superposed to form the electrode body 2. Subsequently, the electrode body 2 is put into the case 3, and the electrolytic solution is put into the case 3 to assemble the power storage element 1.

In the production of the electrode (positive electrode 11), a composition for an intermediate layer containing a conductive auxiliary agent, a binder and a solvent is applied to both sides of the metal foil, and the composition is dried at, for example, 100 to 160 degrees. The intermediate layer 113 is formed. Further, the positive electrode active material layer 112 is formed by applying a mixture containing the active material, the binder and the solvent to each intermediate layer. By adjusting the coating amount, the basis weight of the intermediate layer 113 and the positive electrode active material layer 112 can be adjusted. As a coating method for forming the intermediate layer 113 and the positive electrode active material layer 112, a general method is adopted. The coated intermediate layer 113 and positive electrode active material layer 112 are roll-pressed at a predetermined temperature (for example, 80 to 150 ° C.) and a predetermined pressure. By adjusting the press pressure, the density of the intermediate layer 113 and the positive electrode active material layer 112 can be adjusted. After pressing, vacuum drying is performed at 80 to 140 ° C. for 12 to 24 hours. The negative electrode is also manufactured in the same manner without forming the intermediate layer.

In the formation of the electrode body 2, the electrode body 2 is formed by winding the laminated body 22 having the separator 4 sandwiched between the positive electrode 11 and the negative electrode 12. Specifically, the positive electrode 11, the separator 4, and the negative electrode 12 are superposed so that the positive electrode active material layer 112 and the negative electrode active material layer 122 face each other via the separator 4 to form the laminated body 22. Subsequently, the laminated body 22 is wound to form the electrode body 2.

In assembling the power storage element 1, the electrode body 2 is put into the case body 31 of the case 3, the opening of the case body 31 is closed with the lid plate 32, and the electrolytic solution is injected into the case 3. When closing the opening of the case body 31 with the lid plate 32, the electrode body 2 is inserted inside the case body 31, the positive electrode 11 and one external terminal 7 are made conductive, and the negative electrode 12 and the other external terminal 7 are connected. The opening of the case body 31 is closed with the lid plate 32 in a conductive state. When the electrolytic solution is injected into the case 3, the electrolytic solution is injected into the case 3 through the injection hole of the lid plate 32 of the case 3.

Further, the assembled power storage element 1 is charged by energizing an electric amount that is 40 to 50% of the design capacity at a predetermined current value. Charging produces aluminum fluoride on the surface of the metal foil 111. After charging, close the injection hole.

In the electricity storage device 1 of the present embodiment configured as described above, when the surface of the metal foil 111 of the positive electrode 11 was XPS measurement, the maximum intensity A of a peak representing the Al ₂ O _3, the peaks representing AlF ₃ The maximum strength B satisfies the relational expression of 0.7 ≦ B / A ≦ 1.0. That is, the maximum intensity A of the peak having a maximum value between 74.3 eV and 75.3 eV and the maximum intensity B of the peak having a maximum value between 76.0 eV and 78.0 eV are 0.7 ≦ B. The relational expression of / A ≦ 1.0 is satisfied. Maximum intensity A represents the maximum value of the peak of _Al 2 _{O 3,} maximum intensity B represents the maximum value of the peak of AlF _3. That is, the abundance ratio of AlF ₃ to Al ₂ O ₃ per unit volume in the vicinity of the surface of the metal foil 111 of the positive electrode 11 is 0.7 or more and 1.0 or less.
In the above-mentioned power storage element 1, aluminum oxide (Al ₂ O ₃ ) is formed on the entire surface of the metal foil 111 before it is manufactured. In general, aluminum oxide (Al ₂ O ₃ ) is easily corroded by fluorine, which is an electrolyte salt containing fluorine. By the way, at the time of production, a part of the surface of the metal foil 111 comes into direct contact with the electrolytic solution that has entered the pores of the porous intermediate layer 113. When the surface of the metal foil 111 is in contact with the electrolyte, the surface of the metal foil 111 is corroded by fluorine, fluorides such as aluminum fluoride (AlF ₃₎ or _AlO x _{F y} may occur. When AlO _x F _y occurs, corrosion further progresses, the resistance between the electrode substrate and the active material layer is increased, the current collecting property is lowered between the electrode substrate and the active material layer. However, in a state where the electrolyte enters the pores by fluorine electrolyte salt in the electrolytic solution, only a portion of the oxygen (O) of the aluminum oxide (Al 2 _{O 3)} was fluorided to AlO _x F _y While the change is suppressed, aluminum oxide (Al ₂ O ₃ ) changes to aluminum fluoride (Al F ₃ ). That is, in the portion where the electrolytic solution that has entered the pores and the surface of the metal foil 111 are in contact with each other, the reaction in which only a part of oxygen (O) of aluminum oxide (Al ₂ O ₃ ) is replaced with fluorine is more important than the reaction of aluminum oxide (Al). The reaction in which all of the oxygen (O) of Al ₂ O ₃ ) is replaced with fluorine is dominant. In this way, when a part of the surface of the metal foil 111 and the electrolytic solution that has entered the pores of the intermediate layer 113 come into contact with each other, a part of the surface of the metal foil 111 is corroded to generate AlF ₃ . .. AlF ₃ can suppress further corrosion of the inside of the aluminum metal foil 111 due to the fluorine of the electrolyte salt. On the other hand, on the surface of the metal foil 111, Al ₂ O ₃ that does not fluorinate exists in a portion that is not in direct contact with the electrolytic solution that has entered the pores of the intermediate layer 113. Al ₂ O ₃ is as described above, but likely to be corroded by fluorine, part there are _Al 2 _{O 3} is not directly in contact with the electrolyte. Therefore, the portion where Al ₂ O ₃ is present is not easily corroded by the fluorine of the electrolyte salt. In the power storage element 1 provided with the positive electrode 11 including the metal foil 111 made of aluminum and the intermediate layer 113, the maximum strength A representing the maximum value of the peak of Al ₂ O ₃ and the maximum value of the peak of Al F ₃ are represented. By satisfying the relational expression of 0.7 ≦ B / A ≦ 1.0 in relation to the maximum strength B, AlF ₃ is sufficient to prevent corrosion from proceeding inward near the surface of the metal foil 111 made of aluminum. Can be suppressed. As a result, it is possible to prevent the resistance between the electrode base material and the active material layer from increasing due to the progress of corrosion and the decrease in current collecting property between the electrode base material and the active material layer. Therefore, the power storage element 1 can have sufficient output durability even when left at a relatively high temperature.
That is, when the _AlO x _{F y} on the surface of the metal foil 111 due to corrosion will be generated, progress of corrosion to the inside is not prevented by the _AlO x _{F y.} As a result, a layer having poor conductivity can be formed near the surface of the metal foil 111. When such a layer is formed, the current collecting property of the metal foil 111 is lowered, and the output durability of the power storage element may be insufficient.

In the above-mentioned power storage element 1, the peak pore diameter measured by measuring the pore distribution of the intermediate layer 113 of the positive electrode 11 is 0.5 μm or more and 2.5 μm or less. With such a configuration, the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer 113 more reliably produces AlF _{3 on} the surface of the aluminum metal foil 111. As a result, it is possible to more sufficiently suppress the corrosion of the metal foil 111 made of aluminum. Therefore, the power storage element 1 can have sufficient output durability.
Specifically, when the peak pore diameter is 0.5 μm or more, the electrolytic solution easily permeates through the intermediate layer 113. As the electrolytic solution easily permeates, gas is likely to be generated when the electrolytic solution is decomposed due to an abnormal reaction in the battery. As a result, the volume of the intermediate layer 113 is likely to expand, and the intermediate layer 113 is likely to be peeled off from the metal foil 111. Therefore, it becomes easier to stop the abnormal reaction, and the safety of the battery can be further improved. On the other hand, when the peak pore diameter is 2.5 μm or less, aluminum fluoride (AlF ₃ ) is more reliably generated on the surface of the metal foil 111 by the fluorine-containing electrolyte salt in the electrolytic solution that has penetrated into the intermediate layer 113. be able to.

In the above-mentioned power storage element 1, the total volume of pore diameters of 0.5 μm or more and 20 μm or less measured by measuring the pore distribution of the intermediate layer 113 is 0.5 mL / g or more and 2.0 mL / g or less per unit mass of the intermediate layer 113. Is. With such a configuration, the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer 113 more reliably produces AlF _{3 on} the surface of the aluminum metal foil 111. As a result, it is possible to more sufficiently suppress the corrosion of the metal foil 111 made of aluminum. Therefore, the power storage element 1 can have sufficient output durability.
Specifically, when the total volume of the pore diameters is 0.5 mL / g or more, the electrolytic solution easily permeates through the intermediate layer 113. As the electrolytic solution easily permeates, gas is likely to be generated when the electrolytic solution is decomposed due to an abnormal reaction in the battery. As a result, the volume of the intermediate layer 113 is likely to expand, and the intermediate layer 113 is likely to be peeled off from the metal foil 111. Therefore, it becomes easier to stop the abnormal reaction, and the safety of the battery can be further improved. On the other hand, when the total volume of the pore diameters is 2.0 mL / g or less, the fluorine-containing electrolyte salt in the electrolytic solution permeating the intermediate layer 113 causes aluminum fluoride (AlF _{3) on} the surface of the metal foil 111. ) Can be generated more reliably. In addition, since the size of the pores is appropriately small, aluminum fluoride is more reliably produced from aluminum oxide. That is, the formation of partially fluorinated aluminum oxide (for example, the compound represented by AlOxFy) is suppressed. Partially fluorinated aluminum oxide makes it difficult to stop the progress of the color of the aluminum metal foil 111.

The power storage element of the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. In addition, some of the configurations of certain embodiments can be deleted.

In the above embodiment, the negative electrode in which the active material layer containing the active material is in direct contact with the metal foil has been described in detail, but in the present invention, the negative electrode may have an intermediate layer containing a binder and a conductive auxiliary agent. ..

In the above embodiment, the electrodes in which the active material layer is arranged on both side surfaces of the metal leaf of each electrode have been described, but in the power storage element of the present invention, the positive electrode 11 or the negative electrode 12 has the active material layer on one side of the metal leaf. It may be provided only on the side.

In the above embodiment, the power storage element 1 including the electrode body 2 in which the laminated body 22 is wound has been described in detail, but the power storage element of the present invention may include the laminated body 22 which is not wound. Specifically, the power storage element may include an electrode body in which a positive electrode, a separator, a negative electrode, and a separator each formed in a rectangular shape are stacked a plurality of times in this order.

In the above embodiment, the case where the power storage element 1 is used as a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) capable of charging and discharging has been described, but the type and size (capacity) of the power storage element 1 are arbitrary. is there. Further, in the above embodiment, the lithium ion secondary battery has been described as an example of the power storage element 1, but the present invention is not limited to this. For example, the present invention can be applied to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

The power storage element 1 (for example, a battery) may be used in a power storage device 100 (a battery module when the power storage element is a battery) as shown in FIG. The power storage device 100 includes at least two power storage elements 1 and a bus bar member 91 that electrically connects two (different) power storage elements 1 to each other. In this case, the technique of the present invention may be applied to at least one power storage element.

A non-aqueous electrolyte secondary battery (lithium ion secondary battery) was manufactured as shown below.

(Example 1)
(1) Preparation of positive electrode N-methyl-2-pyrrolidone (NMP) as a solvent, a conductive auxiliary agent (acetylene black), a binder (hydroxyethyl chitosan), and a curing agent (pyromellitic acid) are mixed and mixed. By kneading, a composition for the intermediate layer was prepared. The composition after forming the intermediate layer (after coating and drying) was 33% by mass of the conductive auxiliary agent, 34% by mass of the binder, and 33% by mass of the curing agent, respectively. The prepared composition for the intermediate layer was applied to both sides of the aluminum foil (thickness of 15 μm) so that the coating amount (weighting amount) after drying was 0.14 mg / cm ^2, and the mixture was dried.
Next, as a solvent, N-methyl-2-pyrrolidone (NMP), a conductive auxiliary agent (acetylene black), a binder (PVdF), and an active material having an average particle diameter D50 of 5 μm (LiNi _1/3 Co _1/3). Mn _1/3 O ₂ ) particles were mixed and kneaded to prepare a mixture for the positive electrode. The blending amounts of the conductive auxiliary agent, the binder, and the active material were 4.5% by mass, 4.5% by mass, and 91% by mass, respectively. The prepared mixture for the positive electrode was applied to the intermediate layer so that the coating amount (base weight) after drying was 9.0 mg / cm ² . After drying, a roll press was performed. Then, it was vacuum dried to remove moisture and the like. The thickness of the active material layer (for one layer) after pressing was 35 μm. The density of the active material layer was 2.57 g / cm ³ . The thickness of the intermediate layer after pressing was about 1 μm.

(2) Preparation of Negative Electrode As the active material, particulate amorphous carbon (non-graphitized carbon) having an average particle diameter D50 of 4 μm was used. Moreover, PVdF was used as a binder. The mixture for the negative electrode was prepared by mixing and kneading NMP as a solvent, a binder, and an active material. The binder was blended so as to be 7% by mass, and the active material was blended so as to be 93% by mass. The prepared mixture for the negative electrode was applied to both sides of the copper foil (10 μm thickness) so that the coating amount (weight) after drying was 4.0 mg / cm ² . After drying, a roll press was performed and vacuum dried to remove water and the like. The thickness of the active material layer (for one layer) was 35 μm. The density of the active material layer was 1.14 g / cm ³ .

(3) Separator A polyethylene microporous membrane having a thickness of 22 μm was used as the base material layer. The air permeability of the polyethylene microporous membrane was 100 seconds / 100 cc.

(4) Preparation of electrolytic solution As the electrolytic solution, the one prepared by the following method was used. As the non-aqueous solvent, a solvent obtained by mixing 1 part by volume of propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was used, and LiPF ₆ was dissolved in this non-aqueous solvent so that the salt concentration was 1 mol / L. An electrolyte was prepared.

(5) Arrangement of Electrode Body in Case Using the above positive electrode, the above negative electrode, the above electrolytic solution, the separator, and the case, a battery was manufactured by a general method.
First, a sheet-like material in which a separator was arranged between the positive electrode and the negative electrode and laminated was wound. Next, the wound electrode body was placed in the case body of the aluminum square battery case as a case. Subsequently, the positive electrode and the negative electrode were electrically connected to each of the two external terminals. Furthermore, a lid plate was attached to the case body. The above electrolytic solution was injected into the case through a liquid injection port formed on the lid plate of the case. Further, the assembled battery was charged by energizing an amount of electricity which is 50% of the design capacity at a current value of 0.5C. Finally, the case was sealed by sealing the injection port of the case.

(Examples 2 to 4)
A lithium ion secondary battery was manufactured in the same manner as in Example 1 except that the intermediate layer was prepared so as to have the configuration shown in Table 1.

(Comparative Examples 1 to 4)
A lithium ion secondary battery was manufactured in the same manner as in Example 1 except that the positive electrode was prepared so as to have the configuration shown in Table 1.

<XPS measurement of the metal foil surface of the positive electrode of the battery>
Each battery (2 V for 4 hours, after CCCV discharge) was disassembled in a gaseous atmosphere filled with an inert gas, and the positive electrode was taken out. The positive electrode active material layer and the intermediate layer were removed with a waste cloth impregnated with NMP or acetone. The aluminum metal foil was cut out to a size of 1 to 4 cm ² , washed with DMC, and then dried. The measurement sample thus prepared was stored so as not to be exposed to the atmosphere, and XPS measurement was performed.
The XPS measurement was performed as follows. The binding energy was corrected based on the CC bond peak position (284.8 eV) in the C1s spectrum. The measurement conditions were a monochromatic AlKα radiation source, an emission current of 1 mA, and an accelerating voltage of 15 kV. A schematic diagram of a chart obtained by XPS measurement of the Al2p spectrum is shown in FIG.

<Measurement of pore distribution in the intermediate layer>
According to JIS R1655: 2003, the pore distribution was measured by the mercury intrusion method. Specifically, each battery (2 V for 4 hours, after CCCV discharge) was disassembled in a low humidity atmosphere (dew point −20 ° C. or lower), and the positive electrode was taken out. The positive electrode was immersed in NMP, the active material layer was removed, and the intermediate layer and the metal foil attached to the intermediate layer were taken out. Then, the drying treatment was performed at 80 ° C. until the mass change disappeared. Using the sample after the drying treatment, the pore distribution was measured with a pore distribution measuring device (“AutoPore IV 9500” manufactured by Micromeritics Co., Ltd.).
The peak pore diameter was read from the obtained pore distribution. Moreover, the total volume of the pore diameter of 0.5 to 20 μm of the intermediate layer was determined. That is, the integrated pore volume in the range of 0.5 to 20 μm was read from the acquired measurement data.

<Evaluation of battery output durability>
-High temperature leaving test After adjusting the battery SOC to 85% (current value 1C, CCCV charging for 3 hours), the battery was placed in a constant temperature bath at 65 ° C. and left to stand. After 60 days, the battery was taken out and DCR (output) measurement was performed at 25 ° C.
-DCR (output) measurement After adjusting the battery temperature to 25 ° C, the battery was charged to 55% SOC. Discharge was performed for 10 seconds at a current value of 12C, and the voltage at the first second was read. Similarly, in a 55% SOC state, 10-second discharge was performed at 18C, 24C, 30C, and 40C, and the voltage at the first second was read at each current value. An IV plot was created from the obtained 5 points, and DCR was calculated from the slope.
DCR increase rate [%] = (DCR after neglect test / DCR before neglect test) × 100-100

When the surface of the electrode base material (aluminum foil) was measured by XPS, the maximum intensity A of the peak having a maximum value between 74.3 eV and 75.3 eV and the maximum value between 76.0 eV and 78.0 eV were obtained. The battery of the example in which the maximum intensity B of the peak having the maximum intensity B satisfies the relational expression of 0.7 ≦ B / A ≦ 1.0 had sufficient output durability. On the other hand, the batteries of the comparative examples that do not satisfy the above relational expression did not necessarily have sufficient output durability.

As the basis weight of the intermediate layer decreased, the peak pore diameter tended to decrease. When the basis weight is relatively large, it is considered that the peak pore diameter is relatively large, and the proportion of the portion where the constituent material of the intermediate layer is in contact with the aluminum foil is relatively large. For example, if the amount of grain is more than a predetermined amount, it is considered that aluminum oxide (Al ₂ O ₃ ) is appropriately changed to aluminum fluoride (AlF ₃ ) on the surface of the aluminum foil by the fluorine of the electrolyte salt of the electrolytic solution.
In order to keep the B / A value within the predetermined range as described above, for example, it is conceivable to adjust the blending ratio of the binder in the intermediate layer. It is considered that increasing the blending ratio of the binder increases the peak pore diameter, and decreasing the blending ratio of the binder reduces the peak pore diameter. It is considered that the B / A value can be adjusted by adjusting the blending ratio of the binder.
When the total volume of the pore diameter of 0.5 to 20 μm of the intermediate layer is within the predetermined range, the aluminum oxide (Al ₂ O ₃ ) is more reliably changed to aluminum fluoride (AlF ₃ ). Conceivable. In order to reduce the total volume of the pore diameter, for example, it is conceivable to reduce the blending ratio of the binder in the intermediate layer, but it is possible to secure sufficient adhesion between the aluminum foil and the intermediate layer, and aluminum oxide due to poor adhesion. _(Al 2 _{O 3)} from the viewpoint of suppressing that the _AlO x _{F y} occurs, the compounding ratio of the binder is preferably equal to or greater than a predetermined rate.

1: Power storage element (non-aqueous electrolyte secondary battery),
2: Electrode body,
26: Uncoated laminated part,
3: Case, 31: Case body, 32: Lid plate,
4: Separator,
5: Current collector, 50: Clip member,
6: Insulation cover,
7: External terminal, 71: Surface,
11: Positive electrode,
111: Metal leaf of positive electrode (positive electrode base material), 112: Positive electrode active material layer,
113: Intermediate layer,
12: Negative electrode,
121: Metal foil of negative electrode (negative electrode base material), 122: Negative electrode active material layer,
91: Bus bar member,
100: Power storage device.

Claims (3)

Contains an electrolytic solution containing an electrolyte salt containing fluorine and an electrode,
The electrode is an aluminum electrode base material, an active material layer arranged along the surface of the electrode base material, and a porous intermediate layer arranged between the electrode base material and the active material layer. And have
The surface of the electrode substrate, the presence ratio of AlF ₃ with respect to _Al 2 _{O 3} per unit volume state, and are 0.7 to 1.0,
A power storage element having a peak pore diameter measured by measuring the pore distribution of the intermediate layer, which is 0.5 μm or more and 2.5 μm or less . Contains an electrolytic solution containing an electrolyte salt containing fluorine and an electrode,
The electrode is an aluminum electrode base material, an active material layer arranged along the surface of the electrode base material, and a porous intermediate layer arranged between the electrode base material and the active material layer. And have
When the surface of the electrode base material is measured by XPS, the maximum intensity A of the peak representing Al ₂ O ₃ and the maximum intensity B of the peak representing Al F ₃ are 0.7 ≦ B / A ≦ 1.0. meet the relationship,
A power storage element having a peak pore diameter measured by measuring the pore distribution of the intermediate layer, which is 0.5 μm or more and 2.5 μm or less . The total volume of pore diameters of 0.5 μm or more and 20 μm or less measured by measuring the pore distribution of the intermediate layer is 0.5 mL / g or more and 2.0 mL / g or less per unit mass of the intermediate layer, claim 1 or 2. The power storage element according to 2 .