JP2017157516A - Power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage element which can suppress the rise in internal resistance involved in charge and discharge.SOLUTION: A power storage element comprises: an electrolytic solution containing an electrolyte salt; and as electrodes, a positive electrode and a negative electrode. At least one electrode has: an electrode base material; an active material layer overlying the electrode base material and including active material particles; and a porous body including particles, formed to be porous by cavities among the particles, and overlying the active material layer. The porous body partially extends toward inside the active material layer further than the outermost active material particle of the active material layer.SELECTED DRAWING: None

Description

  The present invention relates to a power storage element such as a secondary battery.

  Conventionally, a nonaqueous secondary battery including an electrode group in which an electrode plate is wound with a separator interposed therebetween, an electrolytic solution, and an exterior body that encloses the electrode group and the electrolytic solution is known (for example, a patent) Reference 1).

  The battery electrode plate described in Patent Document 1 includes a positive or negative current collector, a mixture layer formed on the surface of the current collector and containing an active material, and a filler formed on the surface of the mixture layer. Including a surface layer. The penetration depth of the filler into the mixture layer is 1 μm or more and less than the average particle diameter of the active material.

  In the battery described in Patent Document 1, an increase in internal resistance due to charge / discharge may not be suppressed.

JP 2014-107172 A

  This embodiment makes it a subject to provide the electrical storage element which can suppress that internal resistance raises with charging / discharging.

The electricity storage device of this embodiment includes an electrolyte solution containing an electrolyte salt, a positive electrode and a negative electrode as electrodes, and at least one of the electrodes overlaps with the electrode base material, the electrode base material, and active material particles An active material layer including a porous body that includes particles and is formed porous by voids between the particles, and overlaps the active material layer, and a part of the porous body includes: It extends inward from the outermost active material particles of the active material layer.
In the electricity storage device having such a configuration, the porous body is impregnated with the electrolytic solution. Since a part of the porous body extends inward from the outermost active material particles of the active material layer, the porous material is not only applied to the active material particles on the surface of the active material layer but also to the inner active material particles. Through the process, the electrolytic solution is supplied. Thereby, the electrolytic solution is easily supplied into the active material layer. By supplying the electrolytic solution to the inside of the active material layer, even if charging and discharging are repeated with a relatively large current, uneven distribution of the electrolyte salt of the electrolytic solution does not easily occur in the active material layer. An increase in resistance can be suppressed.

  In the power storage device, the ratio of the area of the porous body to the total area of the active material layer and the porous body in the cross section in the thickness direction of the electrode may be 1/50 or more and 1/10 or less. When the ratio is 1/50 or more, the electrolytic solution that has passed through the porous body can be more reliably supplied to the active material layer. Therefore, it is possible to more sufficiently suppress the internal resistance from increasing. On the other hand, when such a ratio is 1/10 or less, it can suppress more reliably that the reaction accompanying charging / discharging in an active material layer is prevented by a porous body.

  The power storage device includes an electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and the electrode body is in a state where a laminate of the positive electrode, the negative electrode, and the separator is wound. In addition, the length of the electrode body in the winding axis direction may be twice or more the shortest length in the direction perpendicular to the winding axis direction of the electrode body. In the electrode body having such a configuration, the ratio of the lengths is twice or more, so that it is difficult for the electrolytic solution to enter the electrode body. However, as described above, the electrolytic solution is supplied to the active material layer by the portion extending inward of the porous body. Therefore, uneven distribution of the electrolyte salt of the electrolytic solution in the active material layer is suppressed. As described above, even in the electric storage element including the electrode body in which the electrolytic solution is not easily supplied to the inside, it is possible to suppress an increase in internal resistance.

  In the above electricity storage device, the electrode having a porous body may be at least a negative electrode.

  In the above electricity storage device, the active material particles of the negative electrode may be graphite particles. Graphite particles have a relatively small hardness and are easily expanded by charging. Therefore, the graphite particles swollen at the time of charging can prevent the electrolytic solution from moving through the active material layer, and the internal resistance can be increased. However, as described above, the electrolytic solution is supplied to the active material layer by the portion extending inward of the porous body. Thereby, even if an active material particle is a graphite particle, it can suppress that internal resistance raises similarly to the above.

  According to the present embodiment, it is possible to provide a power storage device in which an increase in internal resistance is suppressed.

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 schematic diagram of a negative electrode cross section of the energy storage device according to the same embodiment. FIG. 9 is a perspective view of a power storage device including the power storage element according to the embodiment. FIG. 10 is an observation image obtained by observing a cross section of the negative electrode of the battery of the example cut in the thickness direction with a scanning electron microscope. FIG. 11 is an observation image obtained by observing a cross section obtained by cutting the negative electrode of the battery of the comparative example in the thickness direction with a scanning electron microscope.

  Hereinafter, an embodiment of a power storage device according to the present invention will be described with reference to FIGS. Examples of power storage elements include secondary batteries and capacitors. 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 8, 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) and an active material layer 112 that is disposed along the surface of the metal foil 111 and includes an active material. In the present embodiment, the active material layer 112 is disposed on each side of the metal foil 111 and overlaps both surfaces of the metal foil 111. The thickness of the positive electrode 11 is usually 40 μm or more and 150 μm or less.

  The metal foil 111 of the positive electrode 11 has a strip shape. The metal foil 111 of the positive electrode 11 of this embodiment is, for example, an aluminum foil. As shown in FIG. 7, the positive electrode 11 has an uncovered portion of the positive electrode active material layer 112 (a portion where the positive electrode active material layer is not formed) at one edge in the width direction, which is the short direction of the band shape. 115.

  The positive electrode active material layer 112 includes an active material, a conductive additive, and a binder. For example, the positive electrode active material layer 112 includes 88% by mass to 91.5% by mass of the active material, 4.5% by mass to 9% by mass of the conductive additive, and 3% by mass to 4.5% by mass of the binder. % Or less. Note that the thickness of the positive electrode active material layer 112 is usually 10 μm or more and 50 μm or less.

  The active material of the positive electrode 11 is a compound that can occlude and release lithium ions. The active material of the positive electrode 11 is particulate. The average particle diameter D50 of the active material of the positive electrode 11 is usually 3 μm or more and 20 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 a Me b (XO c} ) d (Me represents one or more transition metals, X is e.g. Polyanion compounds represented by P, Si, B, and V) (Li _a Fe _b PO ₄ , Li _a Mn _b PO ₄ , Li _a Mn _b SiO ₄ , Li _a Co _b PO ₄ F, and the like).

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 2 _{/ 3} Mn _1/6 O ₂ , LiNi _1/6 Co _1/6 Mn _2/3 O ₂ , LiNi _3/5 Co _1/5 Mn _1/5 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.

  Examples of the conductive auxiliary for the positive electrode active material layer 112 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 negative electrode 12 includes a metal foil 121 (negative electrode base material), a negative electrode active material layer 122 formed on the metal foil 121, and a porous body 123 formed on the negative electrode active material layer 122. 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 an uncoated portion 125 of the negative electrode active material layer 122 (a portion where the negative electrode active material layer is not formed) at one end edge 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 active material particles 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 binder ratio may be 1% by mass or more and 10% by mass or less with respect to the total mass of the active material particles of the negative electrode and the binder.

  The active material particles 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 particles of the negative electrode 12 are particles of carbon materials such as graphite and amorphous carbon (non-graphitizable carbon and graphitizable carbon), or lithium ions such as silicon (Si) and tin (Sn) and alloys. It is a particle of a material that causes a chemical reaction. The active material particles of the negative electrode of the present embodiment are graphite particles.

  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.

  The porous body 123 overlaps one surface of the negative electrode active material layer 122. The porous body 123 covers the negative electrode active material layer 122 while being in contact with the negative electrode active material layer 122. The porous body 123 is disposed so as to cover the outer surface of the negative electrode active material layer 122 that overlaps the metal foil 111. The porous body 123 includes particles having a hardness higher than that of the active material particles of the negative electrode 12. The hardness of the particles is measured according to ISO 14577-1. As the measuring instrument, for example, a product name “DUH-211” manufactured by Shimadzu Corporation and a product name “Nano Indenter G200” manufactured by Keysight Technologies can be used. In the present embodiment, such particles are insulating particles having electrical insulating properties. The porous body 123 further includes a binder.

The porous body 123 is formed to be porous by voids between insulating particles so that Li ions and the like can move inside. The insulating particles contain 95% by mass or more of an insulating material having an electric conductivity of less than 10 ⁻⁶ S / m.

  The porous body 123 is disposed so as to overlap the outer surface of the negative electrode active material layer 122. The porous body 123 includes a layered portion 123a that extends along the outer surface of the negative electrode active material layer 122, and an intrusion portion 123b that enters between the active material particles from a part of the layered portion 123a and enters the active material layer. .

  The porous body 123 usually contains 30% by mass or more and 99% by mass or less of insulating particles. The porous body 123 is preferably contained in an amount of 50% by mass to 98% by mass.

  The porous body 123 usually contains 1% by mass or more and 10% by mass or less of a binder. The electrical insulation of the porous body 123 is higher than the electrical insulation of the negative electrode active material layer 122. The electrical conductivity of the porous body 123 is lower than the electrical conductivity of the negative electrode active material layer 122.

  The average particle diameter D50 of the insulating particles is usually 0.1 μm or more and 1 μm or less. The insulating particles are smaller than the active material particles of the negative electrode 12. The average particle diameter D50 of the active material particles of the negative electrode 12 may be 5 to 200 times the average particle diameter D50 of the insulating particles. The average particle diameter D50 of each particle is obtained by measurement using a laser diffraction / scattering type particle size distribution measuring apparatus. The average particle diameter D50 is obtained by a laser scattering method or by a particle volume standard. In addition, when measuring the average particle diameter D50 of the insulating particles of the manufactured battery, the electrode (the negative electrode 12) is taken out, and the solvent (N-methylpyrrolidone or the negative electrode active material layer 122 or the porous body 123 is dissolved in the binder. Immerse in water, etc.) to dissolve the binder. Undissolved material is separated by filtration and dried. Thereafter, the active material particles and the insulating particles are separated using a centrifuge or a specific gravity gradient tube. The separated active material particles and insulating particles are dispersed in a measurement solvent by ultrasonic treatment. The average particle diameter D50 is obtained by measuring the particle size frequency distribution of the active material particles and the insulating particles using a particle size distribution measuring device.

Examples of the insulating particles include oxide particles, nitride particles, ionic crystal particles, covalently bonded crystal particles, clay particles, mineral resource-derived substances, or particles of these artificial substances. Examples of the oxide particles (metal oxide particles) include particles such as iron oxide, SiO ₂ , Al ₂ O ₃ , TiO ₂ , BaTiO ₂ , ZrO, and alumina-silica composite oxide. Examples of the nitride particles include particles such as aluminum nitride and silicon nitride. Examples of the ionic crystal particles include particles of calcium fluoride, barium fluoride, barium sulfate, and the like. Examples of the covalently bonded crystal particles include particles such as silicon and diamond. Examples of the clay particles include particles such as talc and montmorillonite. Examples of particles of mineral resource-derived substances or those artificial substances include particles of boehmite (alumina hydrate), zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica, and the like. A fired body obtained by firing a natural mineral containing a hydrate (for example, the above-mentioned clay or mineral resource-derived substance) can also be employed. In this embodiment, the insulating particles are Al ₂ O ₃ particles.

  Examples of the binder for the porous body 123 include polyacrylonitrile, polyvinylidene fluoride (PVdF), a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, Examples include sphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, or polycarbonate.

  The thickness (thickness of the thinnest portion) of the layered portion 123 a of the porous body 123 is usually 1/10 or more of the thickness of the separator 4. The thickness of the layered portion 123a (thickness of the thinnest portion) is 1/5 or more and 3/5 or less of the diameter (major axis) of the active material particles inside the layered portion 123a. The thickness of the layered portion 123a (the thickness of the thinnest portion) is usually 0.1 μm or more and 10 μm or less. The thickness of the layered portion 123a is obtained from an observation image obtained by observing a cross section in the thickness direction of the negative electrode 12 with an electron microscope.

  The intrusion portion 123 b of the porous body 123 extends inward beyond the outermost active material particles of the negative electrode active material layer 122. Specifically, the intrusion portion 123 b extends inward of the outermost active material particles in the thickness direction of the negative electrode active material layer 122. The intrusion portion 123b extends while bending from a part of the layered portion 123a toward the metal foil 121. Intrusion portion 123b has a straight portion and a bent portion. That is, the intrusion part 123b bends in the middle of the intrusion direction and approaches the metal foil 121 while being bent. The intrusion portion 123b penetrates into the negative electrode active material layer 122 through between the active material particles.

  The penetration depth of the penetration portion 123b is at least half the thickness of the negative electrode active material layer 122. The penetration depth of the penetration portion 123b is preferably 3/5 or more and 4/5 or less of the thickness of the negative electrode active material layer 122. The penetration depth is determined as follows. That is, first, at least 50 locations selected at random along the surface of the metal foil 121 are selected in the electron microscope observation image of the cross section of the negative electrode 12. In each location, the distance from the metal foil surface to the outermost part of the outermost active material particles in the thickness direction is measured. A value obtained by averaging the measured values is taken as the thickness of the negative electrode active material layer 122. On the other hand, the base point of the penetration depth is a portion separated from the surface of the metal foil by the thickness of the negative electrode active material layer 122 obtained as described above. The front end point of the penetration depth is a portion that is closest to the surface of the metal foil in a state where a plurality of insulating particles are gathered. The distance in the thickness direction between the base point and the tip point is defined as the penetration depth.

  In the cross section in the thickness direction of the negative electrode 12, the ratio of the area of the porous body 123 to the total area of the negative electrode active material layer 122 and the porous body 123 is 1/50 or more and 1/10 or less. The area ratio is determined as follows. Specifically, in the electron micrograph image of the cross section in the thickness direction of the negative electrode 12, the region is partitioned by a length twice the thickness of the negative electrode active material layer 122 (direction perpendicular to the thickness direction). The areas of the negative electrode active material layer 122 and the porous body 123 are determined. Each area is obtained by image processing. In the image processing, in order to analyze the electron microscope observation image of the cross section, the contrast is adjusted and binarized, and the negative electrode active material layer 122 and the porous body 123 are distinguished. And an area is calculated | required with analysis software and the ratio of said area is determined.

  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 length of the electrode body 2 in the winding axis direction is at least twice as long as the shortest length in the direction perpendicular to the winding axis direction of the electrode body 2. In this embodiment, as shown in FIG. 4 etc., the shape of the electrode body 2 is flat. In such a flat electrode body 2, the length of the electrode body 2 in the winding axis direction (the width of the band-shaped laminate 22 before winding) is the thickness of the electrode body 2 (the length in the Y-axis direction described later). ) Is twice or more. Such a length ratio is usually 5 times or less.

  The separator 4 has a strip shape. The separator 4 includes at least a separator base material 41. The separator base material 41 is formed of a porous material. In the present embodiment, the separator 4 has only the separator base material 41.

  The separator substrate 41 is configured to be porous by, for example, a woven fabric, a nonwoven fabric, or a porous film. Examples of the material of the separator substrate 41 include a polymer compound, glass, and ceramic. 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 includes an organic solvent and an electrolyte salt. 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 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.

  In the case 3, the electrode body 2 is accommodated in contact with the inner surface of the case body 31. Since the electrode body 2 repeats expansion and contraction with charge and discharge, the electrode body 2 is compressed from the outside by the inner surface of the case body 31 when the electrode body 2 expands.

  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 current collectors 5 are disposed in the case 3 on the uncoated stacked portion 26 of the positive electrode 11 and the uncoated stacked portion 26 of the negative electrode 12, 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 electricity storage device 1 of the present embodiment, the electrode body 2 (specifically, the electrode body 2 and the current collector 5) housed in the bag-like insulating cover 6 is housed in the case 3.

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

  In said manufacturing method, the mixture containing an active material and a binder is apply | coated to an electrode base material (metal foil). In producing the negative electrode, a composition containing insulating particles is further applied to the mixture after application. The positive electrode, the separator, and the negative electrode are overlapped to form an electrode body. An electrode body is put in a case, and an electric storage element is assembled by putting an electrolytic solution in the case.

  In producing the positive electrode 11, first, the positive electrode active material layer 112 is formed by applying a mixture containing a positive electrode active material, a binder, and a solvent to both surfaces of the positive electrode metal foil 111. As a coating method for forming the positive electrode active material layer 112, a general method is employed.

  In preparation of the negative electrode 12, the porous body 123 is formed by apply | coating the composition containing an insulating particle, a binder, and a solvent to the outer surface of each negative electrode active material layer 122 formed similarly to the above. In detail, the mixture which reduced the content rate of the active material and the binder by increasing the content rate of a solvent amount is adjusted. By applying such a mixture to the metal foil 121 and volatilizing the solvent, the negative electrode active material layer 122 having a relatively large number of voids between particles of the negative electrode active material is formed. On the negative electrode active material layer 122 formed in this way, the composition for a porous body is applied, and the composition after the application is pressed. By pressing, a part of the insulating particles in the composition is allowed to enter the negative electrode active material layer 122. As a coating method and a pressing method for forming the porous body 123, a general method is adopted.

  In the formation of the electrode body 2, the laminate 22 in which the separator 4 is sandwiched between the positive electrode 11 and the negative electrode 12 is wound. 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. Then, the laminated body 22 is wound to form the electrode body 2.

  In assembling the power storage element, the electrode body 2 is inserted into the case main body 31 of the case 3, the opening of the case main 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.

  The present invention can be implemented in the following manner.

(1) An electrolyte solution containing an electrolyte salt, a positive electrode and a negative electrode as electrodes, and at least one of the electrodes is an electrode base material and an active material layer that overlaps the electrode base material and contains active material particles And a porous body that includes particles and is formed porous by voids between the particles and overlaps the active material layer, and a part of the porous body is the most of the active material layer. A power storage element extending inward from the outer active material particles.

(2) The electrical storage according to (1), wherein the ratio of the area of the porous body to the total area of the active material layer and the porous body in the cross section in the thickness direction of the electrode is 1/50 or more and 1/10 or less. element.
(3) An electrode body including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode is provided, and the electrode body is a state in which a laminate of the positive electrode, the negative electrode, and the separator is wound, The length in the winding axis direction of the body is at least twice as long as the shortest length in the direction perpendicular to the winding axis direction of the electrode body, in (1) or (2) The electricity storage device described.
(4) The electricity storage device according to any one of (1) to (3), wherein the electrode having a porous body is at least a negative electrode.
(5) The power storage element according to (4), wherein the negative electrode active material particles are graphite particles.

The electricity storage device 1 of the present embodiment configured as described above includes an electrolytic solution containing an electrolyte salt, and a positive electrode 11 and a negative electrode 12 as electrodes. At least the negative electrode is a negative electrode active material layer 122 including active material particles, a metal foil 121 overlapping one surface of the negative electrode active material layer 122, and a porous body 123 including particles having hardness higher than that of the active material particles. And a porous body 123 disposed so as to overlap the other surface of the negative electrode active material layer 122. A part of the porous body exists (extends) inside the outermost active material particles of the negative electrode active material layer 122. That is, a part of the porous body extends inward beyond the outermost active material particles of the negative electrode active material layer 122. Specifically, a part of the porous body 123 penetrates between the active material particles and penetrates into the negative electrode active material layer 122 and penetrates to the depth of at least half of the thickness of the negative electrode active material layer 122.
In such an electricity storage element 1, the porous body 123 is impregnated with an electrolytic solution. A part of the porous body 123 extends inward from the outermost active material particles of the negative electrode active material layer 122 and passes between the active material particles and enters the negative electrode active material layer 122. Also impregnated with electrolyte. Thereby, the electrolyte is easily supplied into the negative electrode active material layer 122. Since the electrolytic solution is supplied to the inside of the negative electrode active material layer 122, even when charging and discharging are repeated with a relatively large current, uneven distribution of the electrolyte salt of the electrolytic solution does not easily occur in the negative electrode active material layer 122. As a result, the increase in internal resistance can be suppressed.

  In the electricity storage device 1, in the cross section in the thickness direction of the negative electrode 12, the ratio of the area of the porous body 123 to the total area of the negative electrode active material layer 122 and the porous body 123 is 1/50 or more and 1/10 or less. is there. When the ratio is 1/50 or more, the electrolytic solution that has passed through the porous body 123 can be more reliably supplied to the negative electrode active material layer 122. Therefore, it is possible to more sufficiently suppress the internal resistance from increasing. On the other hand, when the ratio is 1/10 or less, the porous body 123 can more reliably suppress the reaction accompanying the charge / discharge in the negative electrode active material layer 122.

  The power storage element 1 includes the electrode body 2 described above, and the length of the electrode body 2 in the winding axis direction is the shortest length in the direction perpendicular to the winding axis direction of the electrode body 2. In contrast, it is twice or more. In the electrode body 2 having such a configuration, the length ratio is twice or more, so that it is difficult for the electrolytic solution to enter the electrode body 2. However, the electrolyte solution is supplied to the negative electrode active material layer 122 as described above by the penetration portion 123 b of the porous body 123. Therefore, uneven distribution of the electrolyte salt of the electrolytic solution in the negative electrode active material layer 122 is suppressed. Thus, even if it is an electrical storage element provided with the electrode body 2 in which electrolyte solution is hard to be supplied inside, it can suppress that internal resistance raises.

  In the power storage device 1 described above, the active material particles of the negative electrode 12 are graphite particles. Graphite particles have a relatively small hardness and are easily expanded by charging. Therefore, the graphite particles swollen at the time of charging prevent the electrolytic solution from moving through the negative electrode active material layer 122, and the internal resistance can be increased. However, the electrolyte solution is supplied to the negative electrode active material layer 122 as described above by the penetration portion 123 b of the porous body 123. Thereby, even if an active material particle is a graphite particle, it can suppress that internal resistance raises.

  The power storage device 1 includes not only the porous separator 4 impregnated with the electrolytic solution but also the porous body 123 impregnated with the electrolytic solution. Therefore, not only the separator 4 but also the porous body 123 can more uniformly supply the electrolytic solution into the electrode body 2.

  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 separator 4 composed only of the separator base material 41 has been described in detail. However, in the present invention, the separator 4 overlaps the separator base material 41 and at least one surface of the separator base material 41. You may have an inorganic layer containing an insulating inorganic particle.

  In the above embodiment, the positive 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 positive electrode has a conductive layer containing a binder and a conductive additive, and the conductive layer However, it may be disposed between the metal foil and the active material layer.

  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, and other power storage elements 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. 9 (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) Preparation of positive electrode N-methyl-2-pyrrolidone (NMP), a conductive additive (acetylene black), a binder (PVdF) as a solvent, and an active material (LiNi _1/3 Co) having an average particle diameter D50 of 10 μm _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 assistant, binder, and active material were 5% by mass, 5% by mass, and 90% by mass, respectively. The prepared positive electrode mixture was applied to both surfaces of an aluminum foil (15 μm thickness) so that the application amount (weight per unit area) after drying was 8 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) was 30 μm.

(2) Production of negative electrode As the active material, particulate graphite (graphite) having an average particle diameter D50 of 10 μm was used. As the binder, carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) were used at a mass ratio of 1: 1. The negative electrode mixture was prepared by mixing and kneading water, a binder, and an active material as a solvent. The binder was blended so as to be 2% by mass in the active material layer, and the active material was blended so as to be 98% by mass. The prepared negative electrode mixture was applied to both sides of a copper foil (10 μm thick) so that the coating amount after drying (weight per unit area) was 4 mg / cm ² . After heat drying, moisture and the like were removed by vacuum drying. The thickness of the active material layer (for one layer) was 35 μm.
Further, a composition comprising 30 parts by mass of alumina particles (average particle size D50 is 0.5 μm), 0.9 part by mass of a binder (a copolymer having an acrylonitrile structure), and 69.1 parts by mass of a solvent (NMP). The product was applied so as to overlap each active material layer. Application was performed by a dry coating method (electrostatic coating method). The solvent was volatilized from the composition after coating, and roll pressing was performed at a linear pressure of 50 kg / cm. As a result, a porous body partially covering the active material layer while covering the active material layer was formed.

(3) Separator A polyethylene microporous film having a thickness of 22 μm was used as a separator substrate. 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 non-aqueous solvent, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, using a solvent were all mixed one part by volume in the non-aqueous solvent to dissolve the LiPF ₆ as the salt concentration of 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. Finally, the case was sealed by sealing the liquid injection port of the case.

(Example 2)
A lithium ion secondary battery was manufactured in the same manner as in Example 1 except that the linear pressure of the roll press was changed to 20 kg / cm.

(Comparative example)
Lithium ion secondary as in Example 1, except that the composition containing alumina particles was applied by a wet method (liquid coating method) and the composition containing alumina particles was not pressed after application. A battery was manufactured.

<Observation of negative electrode after production>
A cross section of the negative electrode of each battery cut in the thickness direction was observed with a scanning electron microscope. An observation image of the negative electrode of the battery of Example 1 is shown in FIG. In FIG. 10, a part of the porous body extends inward from the outermost active material particles of the active material layer. On the other hand, an observation image of the negative electrode of the battery of the comparative example is shown in FIG. In FIG. 11, the alumina particles constituting the porous body did not enter inside the outermost active material particles of the active material layer.

<Evaluation of battery internal resistance>
About each manufactured battery, the internal resistance value was calculated | required by remove | dividing the voltage drop amount immediately after starting discharge from full charge by a current value. Next, charging / discharging at 3 CA was repeated 100 cycles between 3.0 V and 4.2 V, and then the internal resistance value was determined by the same means.
The increase rate of the internal resistance of each battery before and after the cycle was 10% in Example 1, 15% in Example 2, and 50% in Comparative Example 1. The internal resistance value before the cycle was the same for all batteries.

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,
12: negative electrode,
121: negative electrode metal foil (negative electrode substrate), 122: negative electrode active material layer,
123: porous body,
91: Bus bar member,
100: Power storage device.

Claims (5)

Including an electrolytic solution containing an electrolyte salt, a positive electrode and a negative electrode as electrodes,
At least one of the electrodes is a porous body formed porous by an electrode base material, an active material layer that overlaps the electrode base material and contains active material particles, and a void between the particles. A porous body overlapping the active material layer,
A part of the porous body is an electricity storage element that extends inward from the outermost active material particles of the active material layer.   The ratio of the area of the said porous body with respect to the total area of the said active material layer and the said porous body in the cross section of the thickness direction of the said electrode is 1/50 or more and 1/10 or less. Power storage element. An electrode body including the positive electrode, the negative electrode, and a separator disposed between the positive electrode and the negative electrode;
The electrode body is a state in which a laminate of the positive electrode, the negative electrode, and the separator is wound,
The length in the winding axis direction of the electrode body is at least twice as long as the shortest length in the direction perpendicular to the winding axis direction of the electrode body. The electrical storage element as described in.   The electric storage element according to claim 1, wherein the electrode having the porous body is at least a negative electrode.   The power storage element according to claim 4, wherein the negative electrode active material particles are graphite particles.