JP2017201589A - Electricity storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electricity storage element having sufficient output durability.SOLUTION: An electricity storage element includes an electrolyte containing a fluorine-containing electrolyte salt and an electrode. The electrode includes; an electrode base material made of aluminum; an active material layer disposed along a surface of the electrode base material; and a porous intermediate layer disposed between the electrode base material and the active material layer. The maximum strength A of a peak representing AlOand the maximum strength B of a peak representing AlFin the XPS measurement for the surface of the electrode base material satisfy a relational expression: 0.7≤B/A≤1.0.SELECTED DRAWING: None

Description

  The present invention relates to a power storage element.

  Conventionally, a polymer battery using carbon having a total volume of pores of 0.01 to 5 μm obtained by mercury porosimetry as a negative electrode material (negative electrode active material) as a negative electrode material (negative electrode active material) is known as a storage element. (For example, patent document 1).

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

JP 2004-335302 A

  This embodiment makes it a subject to provide the electrical storage element which has sufficient output durability.

The electricity storage device of the present embodiment includes an electrolytic solution containing an electrolyte salt containing fluorine and an electrode, and the electrode is an aluminum electrode base material and an active material disposed along the surface of the electrode base material A porous intermediate layer disposed between the electrode base material and the active material layer, and the 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 electricity storage device of this embodiment includes an electrolyte solution containing an electrolyte salt containing fluorine and an electrode, and the electrode is disposed along the surface of the electrode substrate made of aluminum and the electrode substrate. An active material layer and a porous intermediate layer disposed between the electrode base material and the active material layer, and a peak representing Al ₂ O ₃ when the surface of the electrode base material is subjected to XPS measurement. The maximum intensity A and the maximum intensity B of the peak representing AlF ₃ satisfy the relational expression 0.7 ≦ B / A ≦ 1.0.

In the electricity storage device having the above configuration, aluminum oxide (Al ₂ O ₃ ) is generated on the entire surface of the electrode base material before being manufactured. In general, aluminum oxide (Al ₂ O ₃ ) is easily corroded by fluorine of an electrolyte salt containing fluorine. By the way, at the time of manufacture, a part of the surface of the electrode base material comes into direct contact with the electrolytic solution entering the pores of the porous intermediate layer. When the surface of the electrode base material comes into contact with the electrolytic solution, the surface of the electrode base material is corroded by fluorine, and fluorides such as aluminum fluoride (AlF ₃ ) and AlO _x F _y may be generated. When AlO _x F _y is generated, the corrosion further proceeds, the resistance between the electrode base material and the active material layer is increased, and the current collecting property is reduced between the electrode base material and the active material layer. However, in a state where the electrolytic solution enters the pores, only a part of oxygen (O) of aluminum oxide (Al ₂ O ₃ ) is fluorided to AlO _x F _y by fluorine of the electrolyte salt in the electrolytic solution. While the change is suppressed, aluminum oxide (Al ₂ O ₃ ) changes to aluminum fluoride (AlF ₃ ). That is, in the surface and has a contact portion of the electrolyte and the electrode substrate that has entered the pores, than the reaction in which only a portion of the oxygen (O) of the aluminum oxide (Al 2 _{O 3)} is replaced with fluorine, aluminum oxide ( A reaction in which all of oxygen (O) in Al ₂ O ₃ ) is replaced by fluorine is dominant. In this way, when a part of the surface of the electrode base material comes into contact with the electrolyte solution that has entered the pores of the intermediate layer, a part of the surface of the electrode base material is corroded to produce AlF ₃ . AlF ₃ can suppress further progress of corrosion into the inside of the aluminum electrode base material by fluorine of the electrolyte salt. On the other hand, on the surface of the electrode base material, Al ₂ O ₃ that does not become fluoride exists in a portion that is not in direct contact with the electrolyte 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 fluorine of the electrolyte salt. In the above electric storage element including an electrode including an aluminum electrode base material and an intermediate layer, the maximum intensity A representing the maximum value of the peak of Al ₂ O ₃ and the maximum intensity B representing the maximum value of the peak of AlF ₃ Satisfying the relational expression 0.7 ≦ B / A ≦ 1.0, AlF ₃ can sufficiently suppress the progress of corrosion in the vicinity of the surface of the electrode base made of aluminum. . Thereby, it can suppress that resistance between an electrode base material and an active material layer becomes high by progress of corrosion, and current collection property falls between an electrode base material and an active material layer. Therefore, the above electricity storage element can have sufficient output durability.

The above electricity storage element may have a peak pore diameter of 0.5 μm or more and 2.5 μm or less by measuring the pore distribution of the intermediate layer. With such a configuration, in the above electricity storage element, AlF ₃ is more reliably generated on the surface of the electrode base made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer. Thereby, it can suppress more fully that corrosion progresses inside near the surface of the electrode base material made from aluminum. Therefore, the above electricity storage element can have more sufficient output durability.

In the above electricity storage device, the total volume of pore diameters of 0.5 μm or more and 20 μm or less measured by pore distribution in the intermediate layer is 0.5 mL / g or more and 2.0 mL / g or less per unit mass of the intermediate layer. Also good. With such a configuration, in the above electricity storage element, AlF ₃ is more reliably generated on the surface of the electrode base made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer. Thereby, it can suppress more fully that the aluminum electrode base material is corroded. Therefore, the above electricity storage element can have more sufficient output durability.

  According to the present embodiment, a power storage element having sufficient output durability can be provided.

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

  Hereinafter, an embodiment of a power storage device according to the present invention will be described with reference to FIGS. Examples of the power storage element include a primary battery, a secondary battery, and a capacitor. In the present embodiment, a chargeable / dischargeable secondary battery will be described as an example of a power storage element. In addition, the name of each component (each component) of this embodiment is a thing in this embodiment, and may differ from the name of each component (each component) in background art.

  The electricity storage device 1 of the present embodiment is a nonaqueous electrolyte secondary battery. More specifically, the electricity storage element 1 is a lithium ion secondary battery that utilizes electron movement that occurs in association with movement of lithium ions. This type of power storage element 1 supplies electric energy. The electric storage element 1 is used singly or in plural. Specifically, the storage element 1 is used as a single unit when the required output and the required voltage are small. On the other hand, power storage element 1 is used in power storage device 100 in combination with other power storage elements 1 when at least one of a required output and a required voltage is large. In the power storage device 100, the power storage element 1 used in the power storage device 100 supplies electric energy.

  As shown in FIGS. 1 to 7, the storage element 1 includes an electrode body 2 including a positive electrode 11 and a negative electrode 12, a case 3 that houses the electrode body 2, and an external terminal 7 that is disposed outside the case 3. And an external terminal 7 that is electrically connected to the electrode body 2. In addition to the electrode body 2, the case 3, and the external terminal 7, the power storage element 1 includes a current collector 5 that electrically connects the electrode body 2 and the external terminal 7.

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

  The positive electrode 11 includes a metal foil 111 (positive electrode base material), an active material layer 112 disposed so as to cover the surface of the metal foil 111 and containing an active material, and the metal foil 111 (positive electrode base material) and the active material layer 112. And a porous intermediate layer 113 disposed therebetween. In the present embodiment, the intermediate layer 113 overlaps both surfaces of the metal foil 111, respectively. The active material layer 112 overlaps with one surface of each intermediate layer 113. The active material layers 112 are disposed on both sides of the metal foil 111 in the thickness direction, and similarly, the intermediate layers 113 are disposed 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 has a strip shape. The metal foil 111 of the positive electrode 11 of this embodiment is made of aluminum. In the present embodiment, the metal foil 111 is an aluminum foil. The positive electrode 11 has an uncovered portion (a portion where the positive electrode active material layer is not formed) 115 of the positive electrode active material layer 112 at one edge portion in the width direction, which is the short direction of the band shape.

Aluminum oxide (Al ₂ O ₃ ) is generated on at least a part of the surface of the metal foil 111. Such aluminum oxide is produced by oxidation of 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 subjected to XPS measurement, the maximum intensity A of the peak representing Al ₂ O ₃ and the maximum intensity B of the peak representing AlF ₃ are 0.7 ≦ B / A ≦ 1.0. Is satisfied. Specifically, the maximum intensity A of a peak having a maximum value between 74.3 eV and 75.3 eV and the maximum intensity B of a peak having a maximum value between 76.0 eV and 78.0 eV are 0.7 ≦ The relational expression B / A ≦ 1.0 is satisfied. The maximum intensity A represents the maximum value of the Al ₂ O ₃ peak, and the maximum intensity B represents the maximum value of the AlF ₃ peak. 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 value of B / A can be increased, for example, by increasing the peak pore diameter by measuring the pore distribution of the intermediate layer 113. On the other hand, the value of B / A can be reduced, for example, by reducing the peak pore diameter by the pore distribution measurement of the intermediate layer 113. It is considered that a so-called sea-island structure in which Al ₂ O ₃ spreads continuously and AlF ₃ is scattered is present on the surface of the metal foil 111.

  The positive electrode active material layer 112 includes a particulate active material, a particulate conductive aid, and a binder. In the positive electrode active material layer 112, the content of the active material is usually 88% by mass to 95% by mass, the content of the conductive auxiliary agent is 2.5% by mass to 6.0% by mass, Content is 2.5 mass% or more and 6.0 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 the density are densities in 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 diameter 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. Note 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.

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

  The conductive additive of the positive electrode active material layer 112 is a carbonaceous material containing 98% by mass or more of carbon. Examples of the carbonaceous material include ketjen black (registered trademark), acetylene black, and graphite. The positive electrode active material layer 112 of this embodiment has acetylene black as a conductive additive.

  The intermediate layer 113 includes a particulate conductive additive and a binder (binder). Note that the intermediate layer 113 does not include a positive electrode active material. The intermediate layer 113 is formed to be porous by a gap between the conductive assistants. The intermediate layer 113 has conductivity because it includes a conductive additive. The intermediate layer 113 serves as an electron path between the metal foil 111 and the positive electrode active material layer 112, and maintains electrical conductivity therebetween. The conductivity of the intermediate layer 113 is usually higher than the conductivity of the active material layer 112.

  The intermediate layer 113 is disposed between the metal foil 111 and the positive electrode active material layer 112. The intermediate layer 113 containing a binder (binder) has sufficient adhesion to the metal foil 111. The intermediate layer 113 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 measured by pore distribution measurement of the intermediate layer 113 is not less than 0.5 μm and not more than 2.5 μm. Such a peak pore diameter may be 0.67 μm or more and 2.20 μm or less. The pore distribution is measured by a mercury intrusion method (JIS R1655: 2003). The peak pore diameter is the pore diameter at the site where the peak is highest in the obtained pore distribution.

  The total volume of pore diameters of 0.5 μm or more and 20 μm or less by pore distribution measurement 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 not less than 0.78 mL / g and not more than 1.61 mL / g. The total pore diameter volume is determined by obtaining the pore distribution by the mercury intrusion method (JIS R1655: 2003) and reading the total pore diameter volume in the range of 0.5 μm to 20 μm.

The conductive aid of the intermediate layer 113 is a carbonaceous material containing 98% by mass or more of carbon. The electric conductivity of the carbonaceous material is usually 10 ⁻⁶ S / m or more. Examples of the carbonaceous material include ketjen black (registered trademark), acetylene black, and graphite. The intermediate layer 113 of this embodiment has acetylene black as a conductive additive. The average particle diameter D50 of the conductive assistant is usually 20 nm or more and 150 nm or less. The average particle diameter D50 of the conductive assistant can be measured using a laser diffraction type particle diameter measuring apparatus.

  Examples of the binder for the intermediate layer 113 include polyvinylidene fluoride (PVdF), a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, 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), 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 additive and contains 50% by mass or more and 80% by mass or less of a binder. The intermediate layer 113 may include a curing agent such as pyromellitic acid.

  The negative electrode 12 includes 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 overlaid on both surfaces of the metal foil 121. The metal foil 121 has a strip shape. The metal foil 121 of the negative electrode of this embodiment is, for example, a copper foil. The negative electrode 12 has a non-covered 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 short direction of the belt shape. In addition, 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 includes a particulate active material and a binder. The negative electrode active material layer 122 is disposed so as to face the positive electrode 11 with the separator 4 interposed therebetween. 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 negative electrode active material 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 has an alloying reaction with carbon materials such as graphite and amorphous carbon (non-graphitizable carbon and graphitizable carbon), or lithium ions such as silicon (Si) and tin (Sn). The resulting material. The active material of the negative electrode of this embodiment is amorphous carbon. More specifically, the negative electrode active material is non-graphitizable carbon. The average particle diameter D50 of the active material of the negative electrode 12 is usually 1 μm or more and 10 μm or less.

The weight per unit area (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 include a conductive additive such as ketjen black (registered trademark), acetylene black, or 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 where they are insulated by the separator 4. That is, in the electrode body 2 of the present embodiment, the stacked body 22 of the positive electrode 11, the negative electrode 12, and the separator 4 is wound. The separator 4 is a member having insulating properties. The separator 4 is disposed between the positive electrode 11 and the negative electrode 12. Thereby, in the electrode body 2 (specifically, the laminated body 22), the positive electrode 11 and the negative electrode 12 are insulated from each other. The separator 4 holds the electrolytic solution in the case 3. Thereby, at the time of charging / discharging of the electrical storage element 1, lithium ion moves between the positive electrode 11 and the negative electrode 12 which are laminated | stacked alternately on both sides of the separator 4. FIG.

  The separator 4 has a strip shape. The separator 4 has a porous separator base material. The separator 4 of this embodiment has only a separator base material. The separator 4 is disposed 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 comprised porous by the textile fabric, the nonwoven fabric, or a porous film, for example. Examples of the material for the separator substrate include polymer compounds, glass, and ceramics. Examples of the polymer compound include polyesters such as polyacrylonitrile (PAN), polyamide (PA), and polyethylene terephthalate (PET), polyolefins (PO) such as polypropylene (PP) and polyethylene (PE), and cellulose. .

  The width of the separator 4 (the dimension of the strip shape in the short direction) is slightly larger than the width of the negative electrode active material layer 122. The separator 4 is disposed between the positive electrode 11 and the negative electrode 12 that are stacked in a state of being displaced in the width direction so that the positive electrode active material layer 112 and the negative electrode active material layer 122 overlap. At this time, as shown in FIG. 6, the non-covered portion 115 of the positive electrode 11 and the non-covered portion 125 of the negative electrode 12 do not overlap. That is, the uncovered 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 non-covered portion 125 of the negative electrode 12 extends from the region where the positive electrode 11 and the negative electrode 12 overlap in the width direction ( It protrudes in a direction opposite to the protruding direction of the non-covering portion 115 of the positive electrode 11. The electrode body 2 is formed by winding the stacked positive electrode 11, negative electrode 12, and separator 4, that is, the stacked body 22. The portion where only the uncovered portion 115 of the positive electrode 11 or the uncovered portion 125 of the negative electrode 12 is stacked constitutes the uncoated stacked portion 26 in the electrode body 2.

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

  The uncoated laminated portion 26 configured as described above is provided on each electrode of the electrode body 2. That is, the non-coated laminated portion 26 in which only the non-coated portion 115 of the positive electrode 11 is laminated constitutes the non-coated laminated portion of the positive electrode 11 in the electrode body 2 and the non-coated laminated layer in which only the non-coated 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 includes a case main body 31 having an opening and a cover plate 32 that closes (closes) the opening of the case main body 31. The case 3 houses the electrolytic solution in the internal space together with the electrode body 2 and the current collector 5. Case 3 is formed of a metal having resistance to the electrolytic solution. The case 3 is made of an aluminum-based metal material such as aluminum or an aluminum alloy, for example. The case 3 may be formed of a metal material such as stainless steel and nickel, or a composite material obtained by bonding a resin such as nylon to aluminum.

The electrolytic solution is a non-aqueous electrolytic solution. The electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte salt is LiClO ₄ , LiBF ₄ , LiPF ₆ or the like. The electrolytic solution of this embodiment is obtained by dissolving 0.5 to 1.5 mol / L 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 anion component of the electrolyte salt contains fluorine. The anionic component can react with a small amount of moisture in the battery to give a slight amount of hydrofluoric acid. The surface of the metal foil 111 is corroded by the 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 peripheral edge of the opening of the case main body 31 and the peripheral edge of the rectangular lid plate 32 in an overlapping state. The case 3 has an internal space defined by the case main body 31 and the lid plate 32. In this embodiment, the opening peripheral part of the case main body 31 and the peripheral part of the cover plate 32 are joined by welding.
In the following, as shown in FIG. 1, the long side direction of the cover plate 32 is the X-axis direction, the short side direction of the cover plate 32 is the Y-axis direction, and the normal direction of the cover plate 32 is the Z-axis direction.

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

  The cover plate 32 has a gas discharge valve 321 that can discharge 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 liquid injection hole is sealed (closed) by a liquid injection stopper 326. The liquid filling tap 326 is fixed to the case 3 (the cover plate 32 in the example of the present embodiment) by welding.

  The external terminal 7 is a part that is electrically connected to the external terminal 7 of another power storage element 1 or an external device. 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 aluminum alloy, or a copper-based metal material such as copper or 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 extending along the lid plate 32. Specifically, the external terminal 7 has a rectangular plate shape when viewed in the Z-axis direction.

  The current collector 5 is disposed 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 connected to the electrode body 2 through the clip member 50 so as to be energized. That is, the electrical storage element 1 includes a clip member 50 that connects the electrode body 2 and the current collector 5 so as to allow energization.

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

  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 electricity storage device 1 of the present embodiment, the electrode body 2 (specifically, the electrode body 2 and the current collector 5) housed in a bag-like insulating cover 6 that insulates the electrode body 2 and the case 3 is the case 3. Housed inside.

  Next, the manufacturing method of the electrical storage element 1 of the said embodiment is demonstrated.

  In the manufacturing method of the electrical storage element 1, the mixture containing an active material is apply | coated to metal foil (electrode base material), an active material layer is formed, and an electrode (the positive electrode 11 and the negative electrode 12) is produced. Note that in the production of the positive electrode 11, the active material layer 112 is formed after the intermediate layer 113 containing the conductive additive is formed on the metal foil 111. Next, the positive electrode 11, the separator 4, and the negative electrode 12 are overlapped to form the electrode body 2. Subsequently, the electrode body 2 is put in the case 3 and the electrolytic solution is put in the case 3 to assemble the power storage element 1.

  In preparation of an electrode (positive electrode 11), the composition for intermediate | middle layers containing a conductive support agent, a binder, and a solvent is apply | coated to both surfaces of metal foil, respectively, for example, by drying a composition at 100-160 degree | times, The intermediate layer 113 is formed. Further, the positive electrode active material layer 112 is formed by applying a mixture containing an active material, a binder, and a solvent to each intermediate layer. By adjusting the coating amount, the weight per unit area 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 employed. The applied 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 pressing 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. Note that the negative electrode is similarly formed without forming the intermediate layer.

  In the formation of the electrode body 2, the electrode body 2 is formed by winding a laminate 22 in which the separator 4 is 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 overlapped so that the positive electrode active material layer 112 and the negative electrode active material layer 122 face each other through the separator 4, thereby forming the laminate 22. Subsequently, the stacked body 22 is wound to form the electrode body 2.

  In assembling the electricity storage element 1, the electrode body 2 is inserted into the case body 31 of the case 3, the opening of the case body 31 is closed with the cover plate 32, and the electrolytic solution is injected into the case 3. When closing the opening of the case main body 31 with the cover plate 32, the electrode body 2 is inserted into the case main body 31, the positive electrode 11 and the one external terminal 7 are electrically connected, and the negative electrode 12 and the other external terminal 7 are connected to each other. In the conductive state, the opening of the case body 31 is closed with the lid plate 32. When the electrolytic solution is injected into the case 3, the electrolytic solution is injected into the case 3 from the injection hole of the cover plate 32 of the case 3.

  Furthermore, the assembled electrical storage element 1 is charged by energizing an electric quantity that is 40 to 50% of the design capacity at a predetermined current value. By charging, aluminum fluoride is generated 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 is subjected to XPS measurement, the peak maximum intensity A representing Al ₂ O ₃ and the peak representing AlF ₃ are measured. The maximum intensity B satisfies the relational expression 0.7 ≦ B / A ≦ 1.0. That is, the maximum intensity A of a peak having a maximum value between 74.3 eV and 75.3 eV and the maximum intensity B of a 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. The maximum intensity A represents the maximum value of the Al ₂ O ₃ peak, and the maximum intensity B represents the maximum value of the AlF ₃ peak. 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 electricity storage device 1, aluminum oxide (Al 2 _{O 3)} is generated on the entire surface before the metal foil 111 to be produced. In general, aluminum oxide (Al ₂ O ₃ ) is easily corroded by fluorine of an electrolyte salt containing fluorine. By the way, at the time of manufacture, 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 comes into contact with the electrolytic solution, the surface of the metal foil 111 is corroded by fluorine, and fluorides such as aluminum fluoride (AlF ₃ ) and AlO _x F _y may be generated. When AlO _x F _y is generated, the corrosion further proceeds, the resistance between the electrode base material and the active material layer is increased, and the current collecting property is reduced between the electrode base material and the active material layer. However, in a state where the electrolytic solution enters the pores, only a part of oxygen (O) of aluminum oxide (Al ₂ O ₃ ) is fluorided to AlO _x F _y by fluorine of the electrolyte salt in the electrolytic solution. While the change is suppressed, aluminum oxide (Al ₂ O ₃ ) changes to aluminum fluoride (AlF ₃ ). That is, in the portion where the electrolyte solution entering the pores and the surface of the metal foil 111 are in contact with each other, the aluminum oxide (Al ₂ O ₃ ) rather than the reaction in which only a part of oxygen (O) in the aluminum oxide (Al ₂ O ₃ ) is replaced by fluorine. A reaction in which all of oxygen (O) in Al ₂ O ₃ ) is replaced by fluorine is dominant. Thus, when a part of the surface of the metal foil 111 and the electrolyte solution entering the pores of the intermediate layer 113 are in 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 progress of corrosion into the aluminum metal foil 111 due to fluorine of the electrolyte salt. On the other hand, on the surface of the metal foil 111, Al ₂ O ₃ that does not become fluoride exists in a portion that is not in direct contact with the electrolyte 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 fluorine of the electrolyte salt. In the power storage device 1 including the positive electrode 11 including the metal foil 111 made of aluminum and the intermediate layer 113, the maximum intensity A representing the maximum value of the Al ₂ O ₃ peak and the maximum value of the AlF ₃ peak are represented. By satisfying the relational expression 0.7 ≦ B / A ≦ 1.0 with respect to the maximum strength B, AlF ₃ is sufficient for the corrosion to progress in the vicinity of the surface of the aluminum metal foil 111. Can be suppressed. Thereby, it can suppress that resistance between an electrode base material and an active material layer becomes high by progress of corrosion, and current collection property falls between an electrode base material and an active material layer. Therefore, the power storage device 1 can have sufficient output durability even when left at a relatively high temperature.
That is, if the AlO _x F _y is generated on the surface of the metal foil 111 due to corrosion, the progress of corrosion to the inside cannot be suppressed by the AlO _x F _y . Thereby, a layer with 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 electricity storage device 1, the peak pore diameter measured by pore distribution measurement of the intermediate layer 113 of the positive electrode 11 is not less than 0.5 μm and not more than 2.5 μm. With such a configuration, AlF ₃ is more reliably generated on the surface of the metal foil 111 made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer 113. Thereby, it can suppress more fully that the metal foil 111 made from aluminum is corroded. Therefore, the power storage device 1 can have sufficient output durability.
Specifically, when the peak pore diameter is 0.5 μm or more, the electrolytic solution easily penetrates into the intermediate layer 113. Since the electrolyte solution easily permeates, gas is easily generated when the electrolyte solution is decomposed due to an abnormal reaction in the battery. Thereby, the volume of the intermediate layer 113 is easily expanded, and the intermediate layer 113 is easily 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 permeated the intermediate layer 113. be able to.

In the above electricity storage device 1, the total volume of pore diameters of 0.5 μm or more and 20 μm or less by pore distribution measurement 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. It is. With such a configuration, AlF ₃ is more reliably generated on the surface of the metal foil 111 made of aluminum by the fluorine-containing electrolyte salt that has entered the pores of the intermediate layer 113. Thereby, it can suppress more fully that the metal foil 111 made from aluminum is corroded. Therefore, the power storage device 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 can easily penetrate into the intermediate layer 113. Since the electrolyte solution easily permeates, gas is easily generated when the electrolyte solution is decomposed due to an abnormal reaction in the battery. Thereby, the volume of the intermediate layer 113 is easily expanded, and the intermediate layer 113 is easily 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, aluminum fluoride (AlF ₃₎ is formed on the surface of the metal foil 111 by the fluorine-containing electrolyte salt in the electrolytic solution that has permeated the intermediate layer 113. ) Can be generated more reliably. In addition, aluminum fluoride is more reliably generated from aluminum oxide when the size of the pores is moderately small. That is, generation of partially fluorinated aluminum oxide (for example, a compound represented by AlOxFy) is suppressed. The partially fluorinated aluminum oxide is difficult to stop the progress of the color of the metal foil 111 made of aluminum.

  In addition, the electrical storage element of this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment. Furthermore, a part of the configuration of an embodiment 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. However, in the present invention, the negative electrode may have an intermediate layer containing a binder and a conductive additive. .

  In the above embodiment, the electrodes in which the active material layers are disposed on both sides of the metal foil of each electrode have been described. However, in the electricity storage device of the present invention, the positive electrode 11 or the negative electrode 12 has the active material layer on one side of the metal foil. It may be provided only on the side.

  In the said embodiment, although the electrical storage element 1 provided with the electrode body 2 by which the laminated body 22 was wound was demonstrated in detail, the electrical storage element of this invention may be provided with the laminated body 22 which is not wound. Specifically, the 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 chargeable / dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been described. However, the type and size (capacity) of the power storage element 1 are arbitrary. is there. Moreover, although the lithium ion secondary battery was demonstrated as an example of the electrical storage element 1 in the said embodiment, it 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 as shown in FIG. 8 (a battery module when the power storage element is a battery). 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 nonaqueous electrolyte secondary battery (lithium ion secondary battery) was produced as shown below.

Example 1
(1) Production of positive electrode As a solvent, N-methyl-2-pyrrolidone (NMP), a conductive additive (acetylene black), a binder (hydroxyethyl chitosan), and a curing agent (pyromellitic acid) are mixed, A composition for the intermediate layer was prepared by kneading. After forming the intermediate layer (coating and drying), the composition was blended such that the composition was 33% by mass of the conductive additive, 34% by mass of the binder, and 33% by mass of the curing agent. The prepared composition for an intermediate layer was applied to both sides of an aluminum foil (15 μm thick) so that the coating amount after drying (weight per unit area) was 0.14 mg / cm ² and dried.
Next, N-methyl-2-pyrrolidone (NMP) as a solvent, a conductive additive (acetylene black), a binder (PVdF), and an active material (LiNi _1/3 Co _1/3 ) having an average particle diameter D50 of 5 μm. A mixture for Mn _1/3 O ₂ ) was mixed and kneaded to prepare a mixture for positive electrode. The blending amounts of the conductive assistant, binder, and active material were 4.5% by mass, 4.5% by mass, and 91% by mass, respectively. The prepared positive electrode mixture was applied to the intermediate layer so that the coating amount (weight per unit area) after drying was 9.0 mg / cm ² . After drying, a roll press was performed. Thereafter, 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) Production of Negative Electrode As the active material, particulate amorphous carbon (non-graphitizable carbon) having an average particle diameter D50 of 4 μm was used. Moreover, PVdF was used as the binder. The negative electrode mixture 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 negative electrode mixture was applied to both surfaces of a copper foil (thickness: 10 μm) so that the coating amount (weight per unit area) after drying was 4.0 mg / cm ² . After drying, roll pressing was performed and vacuum drying was performed to remove moisture 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 film 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, one prepared by the following method was used. As a non-aqueous solvent, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed in a volume of 1 part by volume, and LiPF ₆ was dissolved in this non-aqueous solvent so that the salt concentration was 1 mol / L. An electrolyte solution was prepared.

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

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

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

<XPS measurement of metal foil surface of battery positive electrode>
Each battery (after 2 hours of 2V, CCCV discharge) was disassembled in a gas 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 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 dried. The measurement sample thus prepared was stored so as not to be exposed to the atmosphere and subjected to XPS measurement.
XPS measurement was performed as follows. The binding energy was corrected based on the C—C 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 acceleration voltage of 15 kV. In addition, the schematic diagram of the chart which carried out XPS measurement of the Al2p spectrum is shown in FIG.

<Measurement of pore distribution in intermediate layer>
According to JIS R1655: 2003, pore distribution measurement was performed by a mercury intrusion method. Specifically, each battery (after 2 hours of 2 V and 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 process was performed at 80 degreeC until there was no mass change. Using the sample after the drying treatment, the pore distribution was measured with a pore distribution measuring device (“AutoPore IV 9500” manufactured by Micromeritics).
The peak pore size was read from the obtained pore distribution. Further, the total volume of pore diameters 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 standing test After adjusting the battery SOC to 85% (current value 1C, CCCV charging 3 hours), the battery was placed in a constant temperature bath at 65 ° C and left standing. After 60 days, the battery was taken out and DCR (output) measurement was performed at 25 ° C.
-DCR (output) measurement After adjusting the temperature of the battery to 25 ° C, it was charged to 55% SOC. Discharge was performed for 10 seconds at a current value of 12 C, and the voltage for the first second was read. Similarly, in the state of 55% SOC, discharging for 10 seconds at 18C, 24C, 30C, and 40C was performed, and the voltage for the first second was read at each current value. An IV plot was created from the obtained five points, and DCR was determined from the slope.
DCR increase rate [%] = (DCR after standing test / DCR before standing test) × 100-100

  When the surface of the electrode substrate (aluminum foil) is subjected to XPS measurement, the peak maximum intensity A having a maximum value between 74.3 eV and 75.3 eV and the maximum value between 76.0 eV and 78.0 eV are obtained. The battery of the example satisfying the relational expression of 0.7 ≦ B / A ≦ 1.0 with the peak maximum intensity B had sufficient output durability. On the other hand, the battery of the comparative example that does 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, the peak pore diameter is relatively large, and the ratio of the portion where the constituent material of the intermediate layer is in contact with the aluminum foil is considered to be relatively large. For example, if the basis weight is a predetermined amount or more, it is considered that aluminum oxide (Al ₂ O ₃ ) is appropriately changed to aluminum fluoride (AlF ₃ ) by the fluorine of the electrolyte salt of the electrolytic solution on the surface of the aluminum foil.
In order to set the value of B / A 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 the peak pore diameter increases when the blending ratio of the binder is increased, and the peak pore diameter decreases when the blending ratio of the binder is decreased. It is considered that the value of B / A can be adjusted by adjusting the blending ratio of the binder.
When the total volume of pore diameters of 0.5 to 20 μm of the intermediate layer is within the predetermined range, when aluminum oxide (Al ₂ O ₃ ) is more appropriately changed to aluminum fluoride (AlF ₃ ) Conceivable. In order to reduce the total volume of pore diameters, for example, it is conceivable to reduce the blending ratio of the binder in the intermediate layer, but aluminum oxide can be secured due to insufficient adhesion, while ensuring sufficient adhesion between the aluminum foil and the intermediate layer. In terms of suppressing the generation of the AlO _x F _y from (Al ₂ O ₃ ), the blending ratio of the binder is preferably not less than a predetermined ratio.

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

Claims (4)

An electrolyte solution containing an electrolyte salt containing fluorine, and an electrode;
The electrode includes an aluminum electrode base material, an active material layer disposed along the surface of the electrode base material, and a porous intermediate layer disposed between the electrode base material and the active material layer. And having
Wherein the surface of the electrode substrate, the presence ratio of AlF ₃ with respect to _Al 2 _{O 3} per unit volume is 0.7 to 1.0, the power storage device. An electrolyte solution containing an electrolyte salt containing fluorine, and an electrode;
The electrode includes an aluminum electrode base material, an active material layer disposed along the surface of the electrode base material, and a porous intermediate layer disposed between the electrode base material and the active material layer. And having
The peak maximum intensity A representing Al ₂ O ₃ and the peak maximum intensity B representing AlF ₃ when the surface of the electrode base material is subjected to XPS measurement are 0.7 ≦ B / A ≦ 1.0. A power storage element that satisfies the relational expression:   The power storage element according to claim 2, wherein a peak pore diameter measured by pore distribution measurement of the intermediate layer is not less than 0.5 μm and not more than 2.5 μm.   3. The total volume of pore diameters of 0.5 μm or more and 20 μm or less by pore distribution measurement 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. 3. The electricity storage device according to 3.