JP7652003B2 - Manufacturing method of power storage device - Google Patents

Description

This disclosure relates to a method for manufacturing an electricity storage device.

Patent Document 1 describes a liquid injection process and an impregnation process using a secondary battery manufacturing device. The battery cell that is the subject of this liquid injection process and impregnation process is housed in a container with a coil that is formed by winding a positive electrode plate and a negative electrode plate in a spiral shape with a separator interposed therebetween. In this liquid injection process, the battery cell is first placed in the chamber of the pressure reducing device. Here, an electrolyte injection nozzle is abutted against the electrolyte injection hole of the battery cell, and the electrolyte supply unit and the pressure reducing device are connected.

JP 2013-197035 A

In the manufacturing device of Patent Document 1, when the pressure inside the battery cell is atmospheric pressure, the pressure inside the chamber is reduced by a pressure reducing device, making the pressure outside the battery cell lower than the pressure inside the battery cell in the chamber, and the battery cell container expands due to the pressure difference. This makes it possible to inject a predetermined amount of electrolyte to be impregnated into the coil into the expanded container.

However, in the manufacturing device of Patent Document 1, although the battery cell container expands due to the pressure difference, no pressure difference occurs inside and outside the space between the positive and negative electrodes that make up the coil, making it difficult for voids to form. Therefore, even if a specified amount of electrolyte can be accommodated in the expanded container, it still takes a long time for the electrolyte to penetrate into the positive and negative electrodes.

The present disclosure aims to provide a method for manufacturing an electricity storage device that can shorten the time required for electrolyte impregnation.

The method for manufacturing the electric storage device according to the present disclosure includes a preparation step for preparing a battery element including a first electrode including a first current collector and a first active material layer provided on the first current collector, a second electrode including a second current collector and a second active material layer provided on the second current collector, the second electrode being laminated on the first electrode such that the first active material layer and the second active material layer face each other, and a sealing body that is joined to the first current collector and the second current collector so as to surround the first active material layer and the second active material layer and forms a sealed space between the first current collector and the second current collector, an expansion step for expanding the sealed space by increasing the pressure inside the sealed space to a pressure outside the sealed space after the preparation step, an injection step for injecting an electrolyte into the sealed space while the sealed space is expanded after the expansion step, and an impregnation step for reducing the pressure inside the sealed space to a pressure outside the sealed space after the injection step.

In this manufacturing method, first, a battery element is prepared in which a sealed space including an active material layer is formed between a first electrode and a second electrode. Then, the sealed space is expanded by using a pressure difference, and an electrolyte is injected into the expanded sealed space. In this manner, in this manufacturing method, the electrolyte is injected in a state in which the gap between the first electrode and the first active material layer and the second electrode and the second active material layer is expanded, so that the electrolyte is more likely to wet and spread over a wider area of the first active material layer and the second active material layer. Therefore, the time required for the electrolyte to be impregnated is shortened. Furthermore, in this manufacturing method, after the injection, the pressure inside the sealed space is relatively low, so that the expansion of the sealed space is released and the gap between the first active material layer and the second active material layer is reduced. Therefore, the impregnation of the electrolyte that was placed in the gap into the first active material layer and the second active material layer is promoted. As described above, according to this manufacturing method, the time required for the electrolyte to be impregnated can be shortened.

In the manufacturing method of the electricity storage device according to the present disclosure, in the expansion step, the battery element is placed in the chamber, and the pressure inside the sealed space is reduced to a first pressure lower than atmospheric pressure, and the pressure inside the chamber is reduced to a second pressure lower than the first pressure, and in the impregnation step, the pressure inside the chamber may be increased to a third pressure higher than the first pressure. In this case, in the injection step and the impregnation step, the pressure inside the sealed space is made lower than atmospheric pressure. This suppresses the inhibition of the penetration and impregnation of the electrolyte solution due to air bubbles remaining inside the sealed space. As a result, it is possible to more reliably shorten the time required for impregnation of the electrolyte solution.

The manufacturing method of the electricity storage device according to the present disclosure includes a discharge step of discharging a portion of the electrolyte solution after the impregnation step so that the amount of electrolyte solution in the sealed space is a specified amount, and in the injection step, an amount of electrolyte solution exceeding the specified amount may be injected into the sealed space. In this case, injecting a larger amount of electrolyte solution can promote the wetting and spreading of the electrolyte solution. In addition, discharging a portion of the electrolyte solution (e.g., an excess amount) in the discharge step prevents the excess electrolyte solution from interfering with the battery reaction during use.

In the manufacturing method of the electricity storage device according to the present disclosure, in the discharge step, a constraining pressure is applied to the sealed space in order from the constraining point farthest from the discharge port to the constraining point closest to the discharge port among a plurality of constraining points arranged toward the discharge port of the electrolyte in the sealed space, and a portion of the electrolyte is discharged from the discharge port, and the pitch between adjacent constraining points may be narrower toward the discharge port. In this case, excess electrolyte can be discharged more reliably.

In the manufacturing method of the energy storage device according to the present disclosure, in the expansion process, the amount of expansion of the sealed space may be restricted using restraining plates arranged to sandwich the battery element in the stacking direction of the first electrode and the second electrode. In this case, it is possible to control the amount of expansion of the sealed space in the expansion process.

The present disclosure provides a method for manufacturing an electricity storage device that can shorten the time required for electrolyte impregnation.

FIG. 1 is a schematic cross-sectional view showing an electricity storage device according to an embodiment. 5 is a schematic diagram showing one step of a method for manufacturing an electricity storage device according to the present embodiment. FIG. 5A to 5C are schematic diagrams illustrating a process of a method for manufacturing an electricity storage device according to the present embodiment. 5 is a schematic diagram showing one step of a method for manufacturing an electricity storage device according to the present embodiment. FIG. 5 is a schematic diagram showing one step of a method for manufacturing an electricity storage device according to the present embodiment. FIG. 5 is a schematic diagram showing one step of a method for manufacturing an electricity storage device according to the present embodiment. FIG.

Embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicate descriptions will be omitted.

Figure 1 is a schematic cross-sectional view showing an embodiment of a power storage device. The power storage device 1 shown in Figure 1 is a power storage module used in batteries for various vehicles such as forklifts, hybrid cars, and electric cars. The power storage device 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. The power storage device 1 may be an electric double layer capacitor. In this embodiment, the power storage device 1 is a lithium-ion secondary battery.

The energy storage device 1 includes a stack 5 formed by stacking a plurality of storage cells 2. Here, the stacking direction of the storage cells 2 is the Z-axis direction. Each storage cell 2 includes a positive electrode (first electrode) 11, a negative electrode (second electrode) 12, a separator 13, and a first seal member (sealing body) 14. The positive electrode 11 includes a first current collector 20 and a positive electrode active material layer (first active material layer) 22 provided on one surface 20a of the first current collector 20. The first current collector 20 is, for example, a rectangular plate, and the positive electrode 11 is, for example, a rectangular electrode.

The negative electrode 12 includes a second current collector 21 and a negative electrode active material layer (a second active material layer having a polarity different from that of the first active material layer) 23 provided on one surface 21a of the second current collector 21. The second current collector 21 is, for example, a rectangular plate, and the negative electrode 12 is, for example, a rectangular electrode. In one storage cell 2, the negative electrode 12 is stacked on the positive electrode 11 so that the negative electrode active material layer 23 faces the positive electrode active material layer 22. In this embodiment, the stacking direction of the positive electrode 11 and the negative electrode 12 coincides with the stacking direction of the storage cell 2 (Z-axis direction). Hereinafter, the stacking direction of the storage cell 2 and the stacking direction of the positive electrode 11 and the negative electrode 12 may be simply referred to as the "stacking direction". In this embodiment, the positive electrode active material layer 22 and the negative electrode active material layer 23 are both formed in a rectangular shape. The negative electrode active material layer 23 is formed to be slightly larger than the positive electrode active material layer 22, and in a plan view (when viewed from the stacking direction), the entire formation area of the positive electrode active material layer 22 is located within the formation area of the negative electrode active material layer 23.

The first current collector 20 has a second surface 20b opposite to the first surface 20a. The positive electrode active material layer 22 is not formed on the second surface 20b. The second current collector 21 has a second surface 21b opposite to the first surface 21a. The negative electrode active material layer 23 is not formed on the second surface 21b. The stack 5 is formed by stacking a plurality of storage cells 2 such that the second surface 20b of the first current collector 20 of one storage cell 2 and the second surface 21b of the second current collector 21 of another storage cell 2 are superimposed on each other.

As a result, in the stack 5, the multiple storage cells 2 are electrically connected in series. In the stack 5, the storage cells 2 adjacent to each other in the stacking direction form a pseudo bipolar electrode 10 with the first current collector 20 and the second current collector 21 in contact with each other as an electrode body. That is, one bipolar electrode 10 includes the first current collector 20, the second current collector 21, the positive electrode active material layer 22, and the negative electrode active material layer 23. At one end of the stacking direction, a positive electrode 11 is arranged as a terminal electrode. At the other end of the stacking direction, a negative electrode 12 is arranged as a terminal electrode. Here, the directions along the one side 20a, 21a and the other side 20b, 21b are the X-axis direction and the Y-axis direction.

Each of the first current collector 20 and the second current collector 21 (hereinafter, sometimes simply referred to as "current collector") is a chemically inactive electrical conductor for continuing to pass current to the positive electrode active material layer 22 and the negative electrode active material layer 23 during discharging or charging of the lithium ion secondary battery. Examples of materials that can be used to form the current collector include metal materials, conductive resin materials, conductive inorganic materials, etc. Examples of conductive resin materials include resins in which a conductive filler is added as necessary to a conductive polymer material or a non-conductive polymer material. The current collector may have multiple layers including one or more layers containing the above-mentioned metal material or conductive resin material. The surface of the current collector may be covered with a known protective layer. The surface of the current collector may be treated by a known method such as plating.

The current collector may have a form such as a foil, sheet, film, wire, rod, mesh, or clad material. The current collector may be a metal foil such as nickel foil, titanium foil, or stainless steel foil, in addition to aluminum foil or copper foil. From the viewpoint of ensuring mechanical strength, the current collector may be a stainless steel foil (e.g., SUS304, SUS316, SUS301, etc., as specified in JIS G 4305:2015). The current collector may be an alloy foil of the above metals. The first current collector 20 may be a foil including a substrate coated with an aluminum film. In this embodiment, the first current collector 20 is an aluminum foil, and the second current collector 21 is a copper foil. The second current collector 21 may be a foil including a substrate coated with a copper film. In the case of a foil-shaped current collector, the thickness may be within a range of 1 μm to 100 μm.

The positive electrode active material layer 22 includes a positive electrode active material capable of absorbing and releasing charge carriers such as lithium ions. As the positive electrode active material, any material that can be used as a positive electrode active material for a lithium ion secondary battery, such as a lithium composite metal oxide having a layered rock salt structure, a metal oxide having a spinel structure, or a polyanion-based compound, may be used. Two or more types of positive electrode active materials may be used in combination. In this embodiment, the positive electrode active material layer 22 includes an olivine-type lithium iron phosphate (LiFePO ₄ ) as a composite oxide.

The negative electrode active material layer 23 can be any element, alloy, or compound capable of absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active material include Li, carbon, metal compounds, elements that can be alloyed with lithium, or compounds thereof. Examples of carbon include natural graphite, artificial graphite, hard carbon (hardly graphitizable carbon), and soft carbon (easily graphitizable carbon). Examples of artificial graphite include highly oriented graphite and mesocarbon microbeads. Examples of elements that can be alloyed with lithium include silicon and tin. In this embodiment, the negative electrode active material layer 23 includes graphite as a carbon-based material.

Each of the positive electrode active material layer 22 and the negative electrode active material layer 23 (hereinafter, sometimes simply referred to as "active material layer") may further contain, as necessary, a conductive assistant, a binder, an electrolyte (polymer matrix, ion-conductive polymer, electrolyte solution, etc.), an electrolyte supporting salt (lithium salt) for increasing ion conductivity. The components contained in the active material layer or the blending ratio of the components and the thickness of the active material layer are not particularly limited, and conventionally known knowledge about lithium ion secondary batteries may be appropriately referred to. The thickness of the active material layer is, for example, 2 to 150 μm. To form the active material layer on the surface of the current collector, a conventionally known method such as a roll coating method may be used. In order to improve the thermal stability of the positive electrode 11 or the negative electrode 12, a heat-resistant layer may be provided on the surface (one side or both sides) of the current collector or on the surface of the active material layer. The heat-resistant layer contains, for example, inorganic particles and a binder, and may also contain additives such as a thickener.

The conductive assistant is added to increase the conductivity of the positive electrode 11 or the negative electrode 12. Therefore, the conductive assistant may be added if the conductivity of the positive electrode 11 or the negative electrode 12 is insufficient, and may not be added if the conductivity of the positive electrode 11 or the negative electrode 12 is sufficiently excellent. Examples of the conductive assistant include acetylene black, carbon black, graphite, etc.

The binder plays a role in binding the active material or conductive assistant to the surface of the current collector. Examples of binders include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins containing monomer units such as acrylic acid and methacrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers. These binders can be used alone or in combination. Examples of the solvent that can be used include water and N-methyl-2-pyrrolidone (NMP).

The separator 13 separates the positive electrode 11 and the negative electrode 12, preventing short circuits caused by contact between the two electrodes, while allowing charge carriers such as lithium ions to pass through. In one storage cell 2, the separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The separator 13 prevents short circuits between adjacent bipolar electrodes 10, 10 when the storage cells 2 are stacked.

The separator 13 is, for example, a porous sheet or nonwoven fabric containing a polymer that absorbs and retains an electrolyte. For example, a porous film made of polypropylene (PP) is used as a material constituting the separator 13. The material constituting the separator 13 may be a woven or nonwoven fabric made of polypropylene or methylcellulose. The separator 13 may have a single-layer structure or a multi-layer structure. The multi-layer structure may have, for example, a ceramic layer as a heat-resistant layer. Specifically, the electrolyte may be a liquid electrolyte (electrolytic solution) as a conventionally known material. The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent. As the non-aqueous solvent, known solvents such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers, etc. can be used. These materials may be used alone or in combination of two or more. As the electrolyte, known lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN(FSO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ can be used.

The first seal member 14 is formed at least between the first current collector 20 and the second current collector 21, and is bonded to both the first current collector 20 and the second current collector 21. The first seal member 14 contains an insulating material and prevents a short circuit by insulating between the first current collector 20 and the second current collector 21. In this embodiment, the first seal member 14 contains polyethylene, which is a resin, as an insulating material. In addition to polyethylene, examples of the resin material constituting the first seal member 14 include polystyrene, ABS resin, modified polypropylene, and AS resin.

In this embodiment, the first seal member 14 extends along the peripheral portion 20e of the first current collector 20 and the peripheral portion 21e of the second current collector 21. The first seal member 14 is a frame surrounding the positive electrode active material layer 22 and the negative electrode active material layer 23 when viewed from the stacking direction. The first seal member 14 is joined to the first current collector 20 and the second current collector 21. More specifically, the sealing body 4 has a rectangular frame shape in a plan view and is welded to the peripheral portion 20e of the first current collector 20 and the peripheral portion 21e of the second current collector 21. As a result, the first seal member 14 seals the space between the first current collector 20 and the second current collector 21 to form a sealed space S.

The sealed space S includes at least a part of the positive electrode active material layer 22, the negative electrode active material layer 23, and the separator 13. The sealed space S contains an electrolyte. The first seal member 14 prevents leakage of the electrolyte from the sealed space S. The first seal member 14 can also prevent moisture from entering the sealed space S from the outside of the storage device 1. The first seal member 14 can also prevent gas generated from the positive electrode 11 or the negative electrode 12 due to, for example, a charge/discharge reaction from leaking to the outside of the storage device 1. The separator 13 is embedded in the first seal member 14 at the edge 13e. Here, the first seal members 14 adjacent to each other along the stacking direction are spaced apart from each other. Therefore, when viewed from a direction intersecting the stacking direction (for example, the X-axis direction or the Y-axis direction), the side end surfaces of the first current collector 20 and the second current collector 21 are exposed between the adjacent first seal members 14.

The energy storage device 1 further includes a pair of positive and negative conductive plates provided at one end and the other end of the laminate 5 in the stacking direction. More specifically, a conductive plate 30 having a rectangular shape when viewed from the stacking direction is provided at one end of the laminate 5. A conductive plate 40 having a rectangular shape when viewed from the stacking direction is provided at the other end of the laminate 5. One surface 30a of the conductive plate 30 is in contact with the other surface 20b of the first current collector 20. One surface 40a of the conductive plate 40 is in contact with the other surface 21b of the second current collector 21.

Each of the conductive plates 30, 40 is made of a plate-shaped material with good electrical conductivity. The conductive plates 30, 40 may be made of the same material as the current collector. The thickness of the conductive plates 30, 40 may be greater than the thickness of the current collector used in the stack 5. Here, the conductive plates 30, 40 are smaller than the stack 5 (storage cell 2) when viewed from the stacking direction, and the outer edge of the conductive plates 30, 40 is located inside the inner surface 14a of the first seal member 14. However, the conductive plates 30, 40 may be larger than the stack 5 (storage cell 2) when viewed from the stacking direction (may be configured to be about the same). In this case, the conductive plates 30, 40 may protrude outward from the outer surface 14b of the first seal member 14 when viewed from the stacking direction. The inner surface 14a of the first seal member 14 is the surface of the first seal member 14 that faces the sealed space S, and the outer surface 14b of the first seal member 14 is the surface opposite the inner surface 14a.

The conductive plates 30, 40 described above may be used, for example, to provide terminals and charge and discharge the energy storage device 1 through the terminals. Alternatively, the conductive plates 30, 40 may be used to electrically connect a plurality of energy storage devices 1 by stacking the plurality of energy storage devices 1 via the conductive plates 30, 40. The conductive plates 30, 40 may have a cooling function for cooling the stack 5 (energy storage cells 2). In this case, the conductive plates 30, 40 may have flow paths extending in the in-plane direction, for example, and heat exchange may be performed between the conductive plates 30, 40 and the stack 5 by flowing a cooling fluid (e.g., air) through the flow paths.

The energy storage device 1 further includes a second seal member 50 provided on the outer surface of the laminate 5. The outer surface of the laminate 5 is composed of the outer surface 14b of the first seal member 14 and the side end surface of the current collector exposed between adjacent first seal members 14. The second seal member 50 is an insulating member that seals the laminate 5 as a whole. The second seal member 50 is provided on (in contact with) the outer surface 14b of the first seal member 14 and the side end surface of the current collector exposed between adjacent first seal members 14.

That is, the second seal member 50 enters between the adjacent first seal members 14, thereby sealing the side end surfaces (interfaces) of the first current collector 20 and the second current collector 21 between the adjacent storage cells 2. The second seal member 50 also extends from the conductive plate 30 to the conductive plate 40 in the stacking direction. The second seal member 50 may be in contact with only the outer surface 14b of the first seal member 14.

The second seal member 50 is in contact with one surface 30a of the conductive plate 30 at one end of the stack 5, and is in contact with one surface 40a of the conductive plate 40 at the other end of the stack 5. As a result, the second seal member 50 surrounds and seals the entire stack 5 including each of the storage cells 2. The second seal member 50 can be made of a material such as silicone rubber, polyolefin, or urethane rubber.

Such a second seal member 50 can be formed, for example, by stacking a plurality of storage cells 2 to form a stack 5, arranging conductive plates 30, 40 on both ends of the stack 5, and then applying the uncured material to the outer surface of the stack 5 and curing it. When the second seal member 50 is formed by applying a molten material to the first seal member 14, the material constituting the second seal member 50 can be a material with a melting point lower than that of the material constituting the first seal member 14 in order to reduce the thermal effect on the first seal member 14 when the second seal member 50 is formed.

Next, a method for manufacturing an energy storage device according to one embodiment will be described. Figures 2 to 6 are schematic diagrams showing a step in the method for manufacturing an energy storage device. Note that in Figure 3 and subsequent figures, a schematic cross section of the configuration related to the energy storage cell is shown, but hatching may be omitted to avoid complication. Also, in Figure 3 and subsequent figures, for the same purpose, separator 13 may be omitted from battery element 2A shown in Figure 2.

In this manufacturing method, first, as shown in FIG. 2, a battery element 2A is prepared (step S101: preparation step). The battery element 2A is different from the above-mentioned storage cell 2 in that the electrolyte is not contained in the sealed space S. That is, the battery element 2A has a positive electrode 11, a separator 13, a negative electrode 12 laminated on the positive electrode 11 via the separator 13, and a first seal member 14 joined to the first current collector 20 and the second current collector 21 to form the sealed space S. In this manufacturing method, the storage cell 2 is manufactured by disposing the electrolyte in the sealed space S of the battery element 2A. For this purpose, the battery element 2A is provided with a liquid injection member 60 that penetrates the first seal member 14 and reaches the sealed space S from the outside. The liquid injection member 60 is provided with an openable and closable valve 61. The liquid injection member 60 is made of a cylindrical resin member that communicates between the inside and outside of the sealed space S. The configuration of the liquid injection member 60 is not limited to this, and it may be a hole that penetrates the first seal member 14 and communicates between the inside and outside of the sealed space S, and the valve 61 may not be provided.

3, the battery element 2A prepared in step S101 is placed in the chamber P1 of the liquid injection device P (step S102: expansion step). The vacuum pump P2 is connected to the chamber P1 via lines L1 and L2. The lines L1 and L2 are provided with vacuum regulators P3 and P4 between the chamber P1 and the vacuum pump P2, respectively. The line L1 is connected to the liquid injection member 60 of the battery element 2A via a valve 61. The line L1 is provided with a switching valve P5 between the chamber P1 (valve 61) and the vacuum regulator P3, and the switching valve P5 is connected to a tank P6 that stores the electrolyte R. Therefore, in the liquid injection device P, it is possible to switch between a state in which the vacuum pump P2 is connected to the sealed space S and a state in which the tank P6 of the electrolyte R is connected to the sealed space S by controlling the switching valve P5. In addition, in the liquid injection device P, it is also possible to close the line L1 at the switching valve P5 by closing the switching valve P5.

Next, as shown in FIG. 4(a), a process of expanding the sealed space S is carried out. A pair of constraint plates H are arranged in the chamber P1 to regulate the amount of expansion of the sealed space S. When the battery element 2A is arranged in the chamber P1, the battery element 2A is arranged between the constraint plates H. At this time, the pair of constraint plates H are positioned to sandwich the battery element 2A in the stacking direction of the positive electrode 11 and the negative electrode 12, and the distance between them is appropriately maintained by members such as bolts and nuts provided across the pair of constraint plates H.

Next, in this state, the pressure inside the sealed space S is made higher than the pressure outside the sealed space S, thereby expanding the sealed space S (step S102: expansion step). As an example, in this step S102, the sealed space S is evacuated using line L1 and vacuum pump P2, thereby reducing the pressure inside the sealed space S to a first atmospheric pressure lower than atmospheric pressure. At the same time, the chamber P1 is evacuated using line L2 and vacuum pump P2, thereby reducing the pressure inside the space T (inside chamber P1) outside the battery element 2A to a second atmospheric pressure lower than the first atmospheric pressure. This creates a pressure difference between the inside and outside of the sealed space S, causing the sealed space S to expand.

At this time, since the first current collector 20 and the second current collector 21 are joined and fixed to the first seal member 14 at their peripheral portions, the sealed space S expands so that the distance Dc between the surface 22s of the positive electrode active material layer 22 and the surface 23s of the negative electrode active material layer 23 becomes relatively large (expanded compared to before expansion) at the center portion of the first current collector 20 and the second current collector 21. The amount of expansion of the sealed space S at this time is restricted to a constant amount according to the distance between the restraining plates H because the first current collector 20 and the second current collector 21 come into contact with the restraining plates H and further deformation is inhibited.

Next, while the sealed space S is in an expanded state, the line L1 is switched to the tank P6 side by the switching valve P5, and the electrolyte R is injected into the sealed space S via the line L1 and the injection member 60 as shown in FIG. 4(b) (step S103, injection step). The tank P6 is previously stored with the amount of electrolyte R to be injected into the sealed space S, and the inside of the tank P6 is set to, for example, atmospheric pressure. As a result, when the line L1 is switched to the tank P6 side, substantially the entire amount of electrolyte R stored in the tank P6 can be injected into the sealed space S.

At this time, an amount of electrolyte R exceeding the specified amount for the storage cell 2 is injected into the sealed space S. The specified amount for the storage cell 2 is, for example, the amount of electrolyte R necessary for the storage cell 2 to exhibit the required capacity, and is, for example, an amount according to the volume and porosity of the positive electrode active material layer 22 and the negative electrode active material layer 23. However, the specified amount can include a reserve amount of electrolyte R when the storage cell 2 is operated. Here, the second current collector 21 and the negative electrode active material layer 23 are located vertically below the first current collector 20 and the positive electrode active material layer 22, and an amount of electrolyte R sufficient to immerse (wet) the entire surface 23s of the negative electrode active material layer 23 in the electrolyte can be injected into the sealed space S. This makes it possible to reliably spread the electrolyte R over the entire surface 22s of the positive electrode active material layer 22 facing the surface 32s of the negative electrode active material layer 23 when the expansion of the sealed space S is released in a later process.

In the next step, as shown in FIG. 5(a), the pressure inside the sealed space S is made lower than the pressure outside the sealed space S (step S104: impregnation step). More specifically, in this step S104, the switching valve P5 is closed and the pressure inside the chamber P1 (the pressure in the space T outside the sealed space S) is increased to a third pressure higher than the first pressure inside the sealed space S. As an example, while maintaining the sealed space S at a pressure lower than atmospheric pressure, the chamber P1 is opened to the atmosphere and the pressure in the space T outside the sealed space S is made atmospheric pressure. This generates a pressure difference between the inside and outside of the sealed space S, contracts the sealed space S (releases the expansion) and reduces the distance Dc. As a result, the electrolyte R is suitably brought into contact with both the surface 22s of the positive electrode active material layer 22 and the surface 23s of the negative electrode active material layer 23, and the impregnation of the electrolyte R proceeds. At this time, the air pressure in the sealed space S may be maintained at the first air pressure described above, or may be changed from the first air pressure within a range not exceeding the third pressure.

5(b), the battery element 2A is removed from the chamber P1, and the valve 61 provided on the liquid injection member 60 is closed. The line L1 is also disconnected from the liquid injection member 60. After that, the battery element 2A is left to stand (for example, for about one hour) until the electrolyte R is sufficiently impregnated into the positive electrode active material layer 22 and the negative electrode active material layer 23. As described above, in step S103, an amount of electrolyte R exceeding the specified amount is injected into the sealed space S. Therefore, after the impregnation of the electrolyte R is completed, an excess of electrolyte remains in the space of the sealed space S. The excess electrolyte here refers to an amount of electrolyte that further exceeds the reserve amount for using the storage cell 2.

In the next step, the valve 61 provided on the liquid injection member 60 is opened to drain the excess electrolyte. That is, after the impregnation of the electrolyte R is completed, at least a portion of the electrolyte R remaining in the space of the sealed space S is drained (step S105: draining step). At this time, a portion of the electrolyte R can be drained so that the amount of electrolyte R in the sealed space S becomes a specified amount. Note that, when using the storage cell 2, if there is no need to leave electrolyte in the space of the sealed space S as a reserve, the entire amount of electrolyte R remaining in the space may be drained.

As shown in (a) and (b) of FIG. 6, in this step S105, the battery element 2A is set in the restraining device 70. Note that (b) of FIG. 6 is a schematic diagram showing an enlarged area RA of (a) of FIG. 6. The restraining device 70 includes a plate-shaped support member 71 and a plurality of rod-shaped restraining members 72 arranged opposite the support member 71. The battery element 2A is arranged between the support member 71 and the restraining member 72 in a state where it is sandwiched between a pair of resin plates 81 and a pair of sponge layers 82. The restraining members 72 are arranged along one direction. In addition, the pitches H1 and H2 of the adjacent restraining members 72 are narrowed from one side to the other side in the one direction. Each of the restraining members 72 applies a restraining pressure to the battery element 2A toward the support member 71. Therefore, each of the restraining members 72 is a restraining point when applying a restraining pressure to the battery element 2A.

Here, the battery element 2A is set in the restraining device 70 so that the restraining members 72 arranged at a relatively narrow pitch H2 are positioned on the side of the liquid injection member 60 that functions as an outlet for the electrolyte R in the sealed space S. Then, in step S105, a restraining pressure is applied to the sealed space in order from the restraining point farthest from the liquid injection member 60 to the restraining point closest to the liquid injection member 60 among the multiple restraining points arranged toward the liquid injection member 60. This causes the electrolyte R to move through the separator 13 from the space S1 in the sealed space S separated from the liquid injection member 60 by the separator 13 toward the space S2 in the sealed space S that is directly connected to the liquid injection member 60, and is discharged from the liquid injection member 60. At this time, in the portion of the sealed space S close to the liquid injection member 60, pressure is required for the electrolyte R, which has been pushed in order from the restraint points farthest from the liquid injection member 60 in the space S1, to pass through the separator 13 toward the space S2. However, since this portion is restrained by the restraint members 72 arranged at a relatively narrow pitch H2, this pressure is applied appropriately, and the electrolyte R can be more reliably discharged. In step S105, the amount of electrolyte R discharged from the liquid injection member 60 or the weight of the battery element 2A that is reduced by the discharge of the electrolyte R is detected, and the restraint of the battery element 2A is controlled, so that an appropriate amount of electrolyte R can be discharged.

After that, activation and degassing are performed, and then the valve 61 is removed and the liquid injection member 60 is sealed to obtain the storage cell 2. The storage device 1 shown in FIG. 1 can be manufactured using the plurality of storage cells 2 thus obtained. That is, when manufacturing the storage device 1, first, the storage cells 2 are stacked in one direction to form the stack 5 (stacking process). Next, the stack 5 is sealed as a whole by providing a second sealing member 50 on the outer surface of the stack 5 (sealing process). Then, the conductive plates 30 and 40 are installed on both ends of the stack 5 in the stacking direction (installation process). This results in the storage device 1. In this way, the manufacturing method of the storage cell 2 described above can be included as part of the manufacturing method of the storage device 1.

As described above, in the manufacturing method of the storage device according to this embodiment, first, a battery element 2A is prepared in which a sealed space S including a positive electrode active material layer 22 and a negative electrode active material layer 23 is formed between the positive electrode 11 and the negative electrode 12. Then, the sealed space S is expanded by using a pressure difference, and the electrolyte solution R is injected into the expanded sealed space S. In this manner, in this manufacturing method, the electrolyte solution R is injected in a state in which the gap (e.g., distance Dc) between the positive electrode active material layer 22 and the negative electrode active material layer 23 is expanded, so that the electrolyte solution R is more likely to wet and spread over a wider area of the positive electrode active material layer 22 and the negative electrode active material layer 23. Thus, the time required for impregnation of the electrolyte solution R is shortened. Furthermore, in this manufacturing method, since the pressure inside the sealed space S is relatively low after injection, the expansion of the sealed space S is released and the gap (e.g., distance Dc) between the positive electrode active material layer 22 and the negative electrode active material layer 23 is reduced. This promotes the impregnation of the electrolyte solution R that was placed in the gap into the positive electrode active material layer 22 and the negative electrode active material layer 23. As described above, this manufacturing method can shorten the time required for the electrolyte solution R to be impregnated.

In the manufacturing method according to the present embodiment, in step S102 (expansion step), the battery element 2A is placed in the chamber P1, and the pressure inside the sealed space S is reduced to a first pressure lower than atmospheric pressure, and the pressure inside the chamber P1 is reduced to a second pressure lower than the first pressure. In step S104 (impregnation step), the pressure inside the chamber P1 is increased to a third pressure higher than the first pressure. Therefore, in steps S103 (pouring step) and S104, the pressure inside the sealed space S is made lower than atmospheric pressure. Therefore, the inhibition of the penetration and impregnation of the electrolyte solution R due to air bubbles remaining inside the sealed space S is suppressed. As a result, the time required for impregnation of the electrolyte solution R can be more reliably shortened.

The manufacturing method according to this embodiment also includes a step S105 (discharge step) of discharging a portion of the electrolyte solution R in the sealed space S after step S104. Then, in step S102, an amount of electrolyte solution R that exceeds the specified amount for the storage cell 2 is injected into the sealed space S. Therefore, by injecting a larger amount of electrolyte solution R, it is possible to promote the wetting and spreading of the electrolyte solution R. Also, by discharging a portion of the electrolyte solution R (e.g., an excess amount) in step S105, it is possible to prevent the excess electrolyte solution R from interfering with the battery reaction during use.

Here, when the energy storage device 1 is a non-aqueous secondary battery such as a lithium ion secondary battery, it is necessary to reduce the amount of moisture contained in the sealed space S as much as possible. For this reason, for example, in order to remove the moisture contained in the active material layer, the active material layer may be heated to evaporate the moisture, but there is a risk that moisture may remain in the active material layer. In contrast, by injecting an excess of electrolyte solution R into the sealed space S as described above and then discharging it, the moisture remaining in the positive electrode active material layer 22 and the negative electrode active material layer 23 can be mixed into the electrolyte solution R and removed. In particular, when the inside of the sealed space S is depressurized prior to the injection of the electrolyte solution R, the evaporation of moisture from the positive electrode active material layer 22 and the negative electrode active material layer 23 into the space of the sealed space S is promoted, which is more effective. According to one embodiment, it has been confirmed that the amount of moisture in the discharged electrolyte solution R increases by about five times compared to the amount of moisture in the electrolyte solution R before injection. In other words, the moisture can be removed from the inside of the sealed space S by the amount of increase.

In addition, in the manufacturing method according to this embodiment, in step S105, among the multiple constraint points (constraint members 72) arranged toward the liquid injection member 60, which is an outlet for the electrolyte in the sealed space S, a constraining pressure is applied to the sealed space S in order from the constraint point farthest from the liquid injection member 60 to the constraint point closest to the liquid injection member 60, thereby discharging a portion of the electrolyte R from the liquid injection member 60. At this time, the pitches H1, H2 between adjacent constraint points become narrower toward the liquid injection member 60. Therefore, the closer the liquid injection member 60 is, the greater the constraining pressure that can be applied, making it possible to more reliably discharge excess electrolyte R.

Furthermore, in the manufacturing method according to this embodiment, in step S102, the amount of expansion of the sealed space S is restricted using a pair of restraining plates H arranged to sandwich the battery element 2A in the stacking direction of the positive electrode 11 and the negative electrode 12. This makes it possible to control the amount of expansion of the sealed space S in step S102.

The above embodiment is one aspect of the method for manufacturing an energy storage device according to the present disclosure. Therefore, the method for manufacturing an energy storage device described above can be modified.

For example, in the above example, in step S102, the inside of the sealed space S is depressurized to a first atmospheric pressure, and the outside of the sealed space S (inside the chamber P1) is depressurized to a second atmospheric pressure lower than the first atmospheric pressure. However, in step S102, the inside of the sealed space S does not need to be depressurized because it is sufficient to create a pressure difference between the inside and outside of the sealed space S to expand the sealed space S.

In the above example, in step S103, the electrolyte R exceeds a specified amount and is injected into the sealed space S. However, a specified amount of the electrolyte R may be injected into the sealed space S. In this case, step S105 of discharging a portion of the electrolyte R is omitted.

Furthermore, in the above example, when carrying out step S102, the amount of expansion of the sealed space S is mechanically restricted by disposing the battery element 2A between a pair of restraining plates H, but the use of the restraining plates H is not essential.

In the above embodiment, the storage device 1 includes a plurality of independent storage cells 2 separated by the first current collector 20 and the second current collector 21, and the storage cells 2 are individually manufactured by injecting the electrolyte R into each of the battery elements 2A that are the basis of each storage cell 2. However, even if, for example, a positive electrode active material layer 22 and a negative electrode active material layer 23 are formed on both sides of a single current collector, and the first current collector 20 and/or the second current collector 21 are common between adjacent storage cells 2, and each storage cell 2 is not clearly separated, the storage device 1 can be manufactured with the storage cells 2 (in a stacked state) by injecting the electrolyte R into each of the sealed spaces S of the battery elements 2A by the above-mentioned manufacturing method in a stacked state of the plurality of battery elements 2A that are the basis of each storage cell 2.

1...electricity storage device, 2...electricity storage cell, 2A...battery element, 11...positive electrode (first electrode), 12...negative electrode (second electrode), 14...first seal member (sealing body), 20...first current collector, 21...second current collector, 22...positive electrode active material layer (first active material layer), 23...negative electrode active material layer (second active material layer), P1...chamber, S...sealed space, R...electrolyte.

Claims (5)

a preparation step of preparing a battery element including: a first electrode including a first current collector and a first active material layer provided on the first current collector; a second electrode including a second current collector and a second active material layer provided on the second current collector, the second electrode being stacked on the first electrode such that the first active material layer and the second active material layer face each other; and a sealant bonded to the first current collector and the second current collector so as to surround the first active material layer and the second active material layer, and forming a sealed space between the first current collector and the second current collector;
an expansion step of disposing the battery element in a chamber after the preparation step, and controlling a pressure in the chamber to be lower than a pressure inside the sealed space, thereby making the pressure inside the sealed space higher than a pressure outside the sealed space, thereby expanding the sealed space;
a liquid injection step of injecting an electrolyte into the sealed space while the sealed space is in a state in which the sealed space is expanded after the expansion step;
an impregnation step of controlling a pressure in the chamber to be higher than a pressure inside the sealed space after the liquid injection step, thereby making the pressure inside the sealed space lower than a pressure outside the sealed space;
A method for manufacturing an electricity storage device comprising the steps of: In the expansion step, a pressure inside the sealed space is reduced to a first pressure lower than atmospheric pressure, and a pressure inside the chamber is reduced to a second pressure lower than the first pressure,
In the impregnation step, the pressure in the chamber is increased to a third pressure higher than the first pressure.
A method for manufacturing the electricity storage device according to claim 1 . a discharge step of discharging a part of the electrolytic solution so that the amount of the electrolytic solution in the sealed space becomes a specified amount after the impregnation step,
In the injection step, the electrolyte solution is injected into the sealed space in an amount exceeding the specified amount.
A method for manufacturing the electricity storage device according to claim 1 or 2. In the discharge step, a constraining pressure is applied to the sealed space in order from a constraining point farthest from the discharge port to a constraining point closer to the discharge port among a plurality of constraining points arranged toward a discharge port of the electrolyte in the sealed space, thereby discharging a part of the electrolyte from the discharge port;
The pitch between adjacent constraint points becomes narrower toward the discharge port.
A method for manufacturing the electricity storage device according to claim 3. In the expansion step, an expansion amount of the sealed space is restricted by using restraining plates arranged to sandwich the battery element in a stacking direction of the first electrode and the second electrode.
A method for manufacturing the electricity storage device according to any one of claims 1 to 4.

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