Method for manufacturing a secondary battery

Abstract

This invention provides a method for manufacturing a secondary battery that improves the liquid injection performance of a high-capacity secondary battery as a whole. The method disclosed herein is for manufacturing a secondary battery comprising a flat wound electrode body formed by winding a positive electrode and a negative electrode separated by a spacer, and a battery casing housing a plurality of wound electrode bodies. The method includes: an arrangement step in which a plurality of wound electrode bodies are arranged within the battery casing; a peeling step in which at least one of the positive and negative electrodes is peeled from the spacer; and a liquid injection step in which electrolyte is injected into the battery casing. In the peeling step, at least one of the positive and negative electrodes of each wound electrode body is peeled from the spacer such that a peeling region is formed in each of the plurality of wound electrode bodies.

Description

Technical Field

[0001] This invention relates to a method for manufacturing secondary batteries. Background Technology

[0002] Secondary batteries, such as lithium-ion secondary batteries, include, for example: a wound electrode body, which is formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode with a strip-shaped spacer between them; an outer casing having an opening and housing the wound electrode body and electrolyte; and a sealing plate that seals the opening of the outer casing. The secondary battery is constructed by sealing the outer casing and the sealing plate together. Patent Document 1 discloses a method for injecting electrolyte into a casing containing an electrode body.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-185899 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in recent years, in pursuit of further high capacity, research has been conducted on incorporating multiple wound electrode bodies within a single battery casing. Based on the inventors' in-depth research, it has been discovered that in cases where multiple wound electrode bodies are present within a single battery casing, electrolyte penetration between the individual wound electrode bodies can sometimes become uneven, resulting in reduced electrolyte fillability of the battery as a whole.

[0008] The present invention was made to solve the above-mentioned problems, and its object is to provide a method for manufacturing a high-capacity secondary battery with improved liquid filling performance as a whole battery.

[0009] Methods for solving problems

[0010] The method for manufacturing a secondary battery disclosed herein includes a flat wound electrode body formed by winding a positive electrode and a negative electrode separated by a spacer, and a battery casing housing a plurality of the wound electrode bodies. The method comprises: an arrangement step in which a plurality of the wound electrode bodies are arranged within the battery casing; a peeling step in which at least one of the positive and negative electrodes of each of the plurality of wound electrode bodies is peeled from the spacer; and an electrolyte injection step in which electrolyte is injected into the battery casing. In the peeling step, at least one of the positive and negative electrodes of each wound electrode body is peeled from the spacer such that a peeling region is formed in each of the plurality of wound electrode bodies.

[0011] As described above, in the stripping process, by stripping at least one of the positive and negative electrodes of each wound electrode body from the spacer in such a manner that a stripping region is formed in each of the plurality of wound electrode bodies, the electrolyte can easily and uniformly permeate the plurality of wound electrode bodies in the secondary battery containing the plurality of wound electrode bodies. Therefore, it is possible to manufacture a secondary battery with multiple wound electrode bodies and high capacity, and it is possible to suppress uneven permeation of the electrolyte into the plurality of wound electrode bodies, enabling the manufacture of a secondary battery with improved overall electrolyte fillability.

[0012] In one embodiment of the manufacturing method disclosed herein, an adhesive layer is formed on both surfaces of the spacer. Alternatively, in the embodiment where the adhesive layer is formed, the positive electrode may be bonded to the spacer using the adhesive layer, and the negative electrode may be bonded to the spacer using the adhesive layer during the configuration step. Furthermore, the spacer may comprise a porous substrate layer made of polyolefin resin, and the adhesive layer may comprise polyvinylidene fluoride (PVdF).

[0013] In a preferred embodiment of the manufacturing method disclosed herein, the width of the negative electrode may be 20 cm or more. Alternatively, the battery casing may include: a square outer body having a bottom wall, a pair of first side walls extending from the bottom wall and opposing each other, a pair of second side walls extending from the bottom wall and opposing each other, and an opening opposite the bottom wall; and a sealing plate sealing the opening. Furthermore, in the configuration step, the electrode body may be wound with its winding axis aligned along the orientation of the bottom wall.

[0014] In one embodiment of the manufacturing method disclosed herein, the manufacturing method of the secondary battery may also include an initial charging step in which the secondary battery is initially charged while under constrained conditions after the liquid injection step. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment.

[0016] Figure 2 This is a perspective view schematically showing one embodiment of a battery.

[0017] Figure 3 It is along Figure 2 A schematic longitudinal section view of line III-III.

[0018] Figure 4 It is along Figure 2 A schematic longitudinal section view of line IV-IV.

[0019] Figure 5 It is along Figure 2 A schematic cross-sectional view of the VV line.

[0020] Figure 6 This is a schematic perspective view of the electrode assembly mounted on the sealing plate.

[0021] Figure 7 It is a schematic perspective view of a wound electrode body with a positive second collector and a negative second collector installed.

[0022] Figure 8 This is a schematic diagram showing the structure of a wound electrode body according to one embodiment.

[0023] Figure 9 This is a schematic diagram showing the interface between the positive electrode, negative electrode, and spacer of a wound electrode body of a secondary battery according to one embodiment.

[0024] Figure 10 This is a schematic cross-sectional view illustrating the configuration process of one embodiment.

[0025] Explanation of reference numerals in the attached figures

[0026] 10 Battery casing

[0027] 14 Sealing plate (lid)

[0028] 15 injection holes

[0029] 16 sealing components

[0030] 20-wound electrode body

[0031] 22 positive plate

[0032] 24 negative electrode plate

[0033] 26 spacers

[0034] 26a Substrate layer

[0035] 26b Adhesive layer

[0036] 30 positive extremes

[0037] 40 negative extremes

[0038] 50 Positive Current Collector

[0039] 60 negative electrode current collector

[0040] 100 rechargeable batteries

[0041] 200 electrode assembly. Detailed Implementation

[0042] Hereinafter, some preferred embodiments of the technology disclosed herein will be described with reference to the accompanying drawings. Furthermore, matters necessary for the implementation of the invention other than those specifically mentioned in this specification (e.g., the general structure and manufacturing process of a battery not characterized by the present invention) can be understood as design matters for those skilled in the art based on prior art. The present invention can be implemented based on the disclosure herein and common technical knowledge in the art. Furthermore, the expression "A to B" indicating a range in this specification includes the meaning of A or more and B or less, and includes the meanings of "preferably larger than A" and "preferably smaller than B".

[0043] Furthermore, in this specification, "battery" refers to all energy storage devices capable of extracting electrical energy, encompassing both primary and secondary batteries. Additionally, in this specification, "secondary battery" refers to all energy storage devices capable of repeated charging and discharging, including so-called storage batteries (chemical batteries) such as lithium-ion secondary batteries and nickel-metal hydride batteries, as well as capacitors (physical batteries) such as electric double-layer capacitors.

[0044] Hereinafter, one embodiment of the method for manufacturing the secondary battery disclosed herein will be described. Figure 1 This is a flowchart illustrating a method for manufacturing a secondary battery according to this embodiment. Figure 1 As shown, the manufacturing method of the secondary battery disclosed herein includes: (1) an arrangement step S10 in which a plurality of wound electrode bodies are arranged in a battery casing; (2) a stripping step S20 in which at least one of the positive and negative electrodes of each of the plurality of wound electrode bodies is stripped from a spacer; and (3) an electrolyte injection step S30 in which electrolyte is injected into the battery casing. The manufacturing method of the secondary battery disclosed herein may also include an initial charging step of initially charging the secondary battery after the electrolyte injection step S30. The manufacturing method of the secondary battery disclosed herein is characterized in that: in the stripping step S20, at least one of the positive and negative electrodes of each of the plurality of wound electrode bodies is stripped from the spacer in such a way that a stripping region is formed in each of the plurality of wound electrode bodies. That is, in the manufacturing method disclosed herein, it is characterized in that: in the stripping step S20, at least one of the positive and negative electrodes of each of the plurality of wound electrode bodies is stripped from the spacer in such a way that a gap is formed between at least one of the positive and negative electrodes and the spacer in approximately the same proportion in each of the plurality of wound electrode bodies. Therefore, the manufacturing process can be the same as before, or additional steps can be included at any stage.

[0045] 1. Structure of a secondary battery

[0046] Here, we will first explain the structure of the secondary battery 100, which is the object of manufacture, and then explain each process. Figure 2It is a 3D diagram of a secondary battery 100. Figure 3 It is along Figure 2 A schematic longitudinal section view of line III-III. Figure 4 It is along Figure 2 A schematic longitudinal section view of line IV-IV. Figure 5 It is along Figure 2 A schematic cross-sectional view of the VV line. Figure 6 This is a schematic perspective view of the electrode assembly mounted on the sealing plate. Figure 7 It is a schematic perspective view of a wound electrode body with a positive second collector and a negative second collector installed. Figure 8 This is a schematic diagram showing the structure of the wound electrode body 20. In the following description, the reference numerals L, R, F, Rr, U, and D in the figures represent left, right, front, back, top, and bottom, respectively, and the reference numerals X, Y, and Z in the figures represent the short side direction, the long side direction orthogonal to the short side direction, and the up-down direction of the secondary battery 100, respectively. However, these are merely directions for ease of explanation and do not impose any limitation on the arrangement of the secondary battery 100.

[0047] like Figures 2-4 As shown, the secondary battery 100 manufactured in the method disclosed herein includes a battery casing 10, an electrode assembly 200 having multiple wound electrode bodies 20, a positive terminal 30, a negative terminal 40, a positive current collector 50, and a negative current collector 60. Although not shown in the figures, the secondary battery 100 also includes an electrolyte. The secondary battery 100 is a lithium-ion secondary battery.

[0048] (1) Battery casing

[0049] The battery casing 10 serves as a frame for housing the electrode assembly 200. Here, the battery casing 10 has a flat, bottomed cuboid shape (square). The material of the battery casing 10 can be the same as conventionally used materials and is not particularly limited. The battery casing 10 is preferably made of metal, and more preferably of aluminum, aluminum alloy, iron, or iron alloy. Figure 3 As shown, the battery casing 10 includes an outer body 12 with an opening 12h and a sealing plate (cover) 14 that seals the opening 12h. Preferably, when the battery casing 10 houses the electrode assembly 200, it has a slight dimensional allowance (gap) in the thickness direction (short side direction X) of the outer body 12. This ensures that when the positive electrode plate 22 and negative electrode plate 24 of each of the plurality of wound electrode bodies 20 are peeled from the spacer 26 in the peeling process S20 described later, space can be ensured for increasing the thickness (length in the short side direction X) of the electrode assembly 200.

[0050] like Figure 2As shown, the outer casing 12 includes a bottom wall 12a, a pair of long side walls 12b extending from the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the bottom wall 12a and facing each other. The bottom wall 12a is generally rectangular in shape. The bottom wall 12a is opposite to the opening 12h. The area of ​​the short side walls 12c is smaller than the area of ​​the long side walls 12b.

[0051] The sealing plate 14 is installed on the outer casing 12 to seal the opening 12h of the outer casing 12. The sealing plate 14 is opposite to the bottom wall 12a of the outer casing 12. The sealing plate 14 is approximately rectangular in shape when viewed from above. Figure 3 As shown, the sealing plate 14 is provided with an injection hole 15, an vent valve 17, and two terminal outlet holes 18 and 19. The terminal outlet holes 18 and 19 are respectively located at both ends of the sealing plate 14 in the long side direction Y. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal outlet holes 18 and 19 each have an inner diameter large enough to allow the positive terminal 30 and negative terminal 40 installed before the sealing plate 14 to pass through. The injection hole 15 is used to inject electrolyte in the injection process described later. The injection hole 15 is sealed by the sealing member 16. The vent valve 17 is configured to break when the pressure inside the battery housing 10 reaches a predetermined value, venting the gas inside the battery housing 10 to the outside.

[0052] (2) Electrolyte

[0053] As described above, the secondary battery 100 includes an electrolyte. The electrolyte can be the same as conventional electrolytes and is not particularly limited. The electrolyte may be, for example, a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent may include carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. Preferably, the non-aqueous solvent includes chain carbonates and cyclic carbonates. The supporting salt may be, for example, a fluorinated lithium salt such as LiPF6. The electrolyte may also contain additives as needed.

[0054] (3) Electrode terminals

[0055] The positive terminal 30 and the negative terminal 40 are respectively fixed to the sealing plate 14. The positive terminal 30 is located on one side of the long side Y direction of the sealing plate 14. Figure 2 , Figure 3 (Left side). The positive terminal 30 is electrically connected to the plate-shaped positive electrode external conductive member 32 on the outside of the battery casing 10. The positive terminal 30 is preferably made of metal, for example, more preferably aluminum or an aluminum alloy. On the other hand, the negative terminal 40 is disposed on the other side of the sealing plate 14 in the long side direction Y ( Figure 2 , Figure 3(Right side). The negative terminal 40 is electrically connected to the plate-shaped negative external conductive member 42 on the outside of the battery casing 10. The negative terminal 40 is preferably made of metal, for example, more preferably copper or a copper alloy. The negative terminal 40 may also be constructed by joining and integrating two conductive members. For example, the portion connected to the negative current collector 60 described later may be made of copper or a copper alloy, and the portion exposed on the outer surface of the sealing plate 14 may be made of aluminum or an aluminum alloy. In addition, metals with excellent conductivity (aluminum, aluminum alloy, copper, copper alloy, etc.) can also be appropriately used in the electrode current collectors (positive current collector 50 and negative current collector 60).

[0056] The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are components that provide busbars when multiple secondary batteries 100 are electrically connected to each other. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are preferably made of metal, for example, more preferably aluminum or an aluminum alloy. However, the positive electrode external conductive member 32 and the negative electrode external conductive member 42 are not essential and can be omitted in other embodiments.

[0057] (4) Electrode collector

[0058] like Figures 3-6 As shown, in the secondary battery 100 of this embodiment, a plurality of (three in this case) wound electrode bodies 20 are housed within the battery casing 10. While detailed construction will be described later, each wound electrode body 20 is provided with a positive electrode tab group 23 and a negative electrode tab group 25. The aforementioned positive terminal 30 is connected to the positive electrode tab group 23 of each of the plurality of wound electrode bodies 20 via a positive current collector 50. Specifically, the positive current collector 50 is housed inside the battery casing 10. Figure 3 and Figure 6 As shown, the positive electrode current collector 50 includes: a first positive electrode current collector 51, which is a plate-shaped conductive member extending along the inner side of the sealing plate 14 in the long side direction Y; and a plurality of second positive electrode current collectors 52, which are plate-shaped conductive members extending along the vertical direction Z. Furthermore, the lower end 30c of the positive terminal 30 is inserted into the battery casing 10 through the terminal lead-out hole 18 of the sealing plate 14 and connected to the first positive electrode current collector 51 (see reference). Figure 3 On the other hand, such as Figures 5-7 As shown, the secondary battery 100 has a number of positive electrode second current collectors 52 corresponding to the number of wound electrode bodies 20. Each positive electrode second current collector 52 is connected to a positive electrode tab group 23 of each of the plurality of wound electrode bodies 20. Furthermore, the positive electrode tab group 23 of each of the plurality of wound electrode bodies 20 is bent so that the positive electrode second current collector 52 faces one side 20e of the wound electrode body 20. As a result, the upper end of the positive electrode second current collector 52 is electrically connected to the positive electrode first current collector 51.

[0059] On the other hand, the negative terminal 40 is connected to the negative electrode tabs 25 of each of the plurality of wound electrode bodies 20 via the negative electrode current collector 60. The connection structure on the negative side is substantially the same as the connection structure on the positive side described above. Specifically, the negative electrode current collector 60 includes: a first negative electrode current collector 61, which is a plate-shaped conductive member extending along the inner side of the sealing plate 14 in the long side direction Y; and a plurality of second negative electrode current collectors 62, which are plate-shaped conductive members extending along the vertical direction Z (see reference). Figure 3 and Figure 6 Furthermore, the lower end 40c of the negative terminal 40 is inserted into the battery casing 10 through the terminal lead-out hole 19 and connected to the negative first current collector 61 (see reference). Figure 3 On the other hand, multiple negative electrode second current collectors 62 are respectively connected to the negative electrode tabs 25 of each of the multiple wound electrode bodies 20 (see reference). Figures 5-7 Furthermore, the negative electrode tab assembly 25 is bent so that the second negative electrode current collector 62 faces the other side 20g of the wound electrode body 20. Thus, the upper end of the second negative electrode current collector 62 is electrically connected to the first negative electrode current collector 61.

[0060] (5) Insulating components

[0061] Furthermore, the secondary battery 100 is equipped with various insulating components to prevent electrical conduction between the electrode assembly 200 and the battery casing 10. Specifically, an external insulating component 92 (see reference 42) is sandwiched between the positive electrode external conductive component 32 (the negative electrode external conductive component 42) and the outer surface of the sealing plate 14. Figure 2 and Figure 3 This prevents the positive electrode external conductive member 32 and the negative electrode external conductive member 42 from conducting with the sealing plate 14. Additionally, gaskets 90 are installed in the terminal lead-out holes 18 and 19 of the sealing plate 14 (see reference). Figure 3 This prevents the positive terminal 30 (or negative terminal 40) inserted into the terminal lead-out holes 18 and 19 from conducting with the sealing plate 14. Furthermore, an internal insulating member 94 is disposed between the positive first current collector 51 (or negative first current collector 61) and the inner surface of the sealing plate 14. This internal insulating member 94 has a plate-shaped base 94a sandwiched between the positive first current collector 51 (or negative first current collector 61) and the inner surface of the sealing plate 14. This prevents the positive first current collector 51, the negative first current collector 61, and the sealing plate 14 from conducting with each other. Moreover, the internal insulating member 94 has a protrusion 94b protruding from the inner surface of the sealing plate 14 toward the electrode assembly 200 (see reference). Figure 3 and Figure 4Therefore, the movement of the electrode assembly 200 in the vertical Z direction can be restricted, and direct contact between the electrode assembly 200 and the sealing plate 14 can be prevented. Furthermore, the materials of each of the above-mentioned insulating components are not particularly limited, as long as they have the predetermined insulating properties. For example, synthetic resin materials such as polyolefin resins (e.g., polypropylene (PP), polyethylene (PE)) and fluorine resins (e.g., perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE)) can be used.

[0062] Furthermore, multiple wound electrode bodies 20 are held by electrode body retainers 29 made of insulating resin sheets (see reference). Figure 4 The electrode assembly 200 is housed inside the battery casing 10 in a covered state. This prevents direct contact between the electrode assembly 200 and the outer casing 12. The electrode holder 29 can be prepared, for example, by bending an insulating resin sheet made of a resin material such as polyethylene (PE) into a bag or box shape. The thickness of the resin sheet constituting the electrode holder 29 is not particularly limited, but can be around 0.2 mm. Preferably, the electrode holder 29 has a slight dimensional margin (gap) when housing multiple (here, three) wound electrodes. Alternatively, it is preferable to be made of a soft material. Therefore, even if the thickness increases slightly in the peeling process S20 described later, where each of the multiple wound electrodes 20 has a peeling area formed, the electrode holder 29 will not be damaged.

[0063] (6) Electrode assembly

[0064] like Figure 4 As shown, the electrode assembly 200 has three wound electrode bodies 20. However, the number of wound electrode bodies disposed inside an outer casing 12 is not particularly limited, as long as there are two or more. The electrode assembly 200 is disposed inside the outer casing 12 with the winding axis WL of each wound electrode body along the orientation of the bottom wall 12a (i.e., the orientation where the winding axis WL is parallel to the long side direction Y). In other words, the wound electrode bodies 20 are disposed inside the outer casing 12 with the winding axis WL parallel to the bottom wall 12a and orthogonal to the short side wall 12c. The end face of the wound electrode body 20 (in other words, the stacked surface of the positive electrode plate 22 and the negative electrode plate 24) is... Figure 8 The end face of the long side direction Y) is opposite to the short sidewall 12c. That is, the "winding axis direction" in the following description is the same as the long side direction Y in the figure.

[0065] like Figure 8 As shown, the wound electrode body 20 has a positive electrode plate 22 and a negative electrode plate 24. The wound electrode body 20 is a flat electrode body formed by stacking strip-shaped positive electrode plate 22 and strip-shaped negative electrode plate 24 separated by strip-shaped spacers 26 and wound around a winding shaft WL.

[0066] like Figure 4 As shown, the wound electrode body 20 has a pair of curved portions 20r with a curved outer surface and a flat portion 20f with a flat surface connecting the pair of curved portions 20r. The pair of curved portions 20r are respectively opposed to the bottom wall 12a and the sealing plate 14. One side ( Figure 4 The curved portion 20r (on the upper side) is indirectly opposed to the sealing plate 14 via the positive electrode first current collector 51, the negative electrode first current collector 61, and the internal insulating member 94. The other side ( Figure 4 The curved portion 20r on the lower side is indirectly opposed to the bottom wall 12a via the electrode holder 29.

[0067] From the viewpoint of increasing battery capacity and effectively utilizing space when installed in vehicles, it is preferable that the length of the wound electrode body 20 in the winding axis direction is longer and the height of the wound electrode body 20 (length in the vertical Z direction) is lower. On the other hand, in a wound electrode body 20 with a longer length and lower height in the winding axis direction, the electrolyte is difficult to penetrate to the central part in the winding axis direction, and the penetration is prone to become uneven. Therefore, the technical effects disclosed herein can be more appropriately utilized. The length of the wound electrode body 20 in the winding axis direction is preferably 20 cm or more, and more preferably 25 cm or more. The height H1 of the wound electrode body 20 (refer to...) Figure 4 Preferably, the height is 12 cm or less, and more preferably 10 cm or less. Furthermore, the height of the wound electrode body 20 refers to its length in the vertical direction perpendicular to the winding axis direction and the thickness direction (short side direction X) of the wound electrode body 20.

[0068] like Figure 8 As shown, the positive electrode plate 22 is a strip-shaped component. The positive electrode plate 22 has a positive electrode core 22c and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed to at least one surface of the positive electrode core 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode core 22c is strip-shaped. The positive electrode core 22c is made of conductive metals such as aluminum, aluminum alloy, nickel, and stainless steel. The positive electrode core 22c is a metal foil, specifically an aluminum foil. Furthermore, the average thickness of the positive electrode core 22c is not particularly limited. For example, it is preferably 2μm to 30μm, more preferably 2μm to 20μm, and even more preferably 5μm to 15μm.

[0069] At one end of the positive electrode core 22c along the long side direction Y ( Figure 8 Multiple positive electrode tabs 22t are provided at the left end. The multiple positive electrode tabs 22t are positioned towards the long side Y ( Figure 8The positive electrode tabs 22t protrude from the left side of the positive electrode plate 22. Multiple positive electrode tabs 22t protrude in the long side direction Y compared to the spacer 26. The multiple positive electrode tabs 22t are spaced apart (intermittently) along the long side direction of the positive electrode plate 22. However, the positive electrode tabs 22t can also be located at the end on the opposite side of the long side direction Y. Figure 8 The positive electrode tab 22t can be located at either end of the positive electrode core 22c, or at either end of the positive electrode core 22c along the long side (Y). The positive electrode tab 22t is part of the positive electrode core 22c and is made of metal foil (aluminum foil). At least a portion of the positive electrode tab 22t lacks the positive electrode active material layer 22a and the positive electrode protective layer 22p, exposing the positive electrode core 22c.

[0070] like Figure 8 As shown, the positive electrode active material layer 22a is arranged in a strip shape along the long side of the strip-shaped positive electrode core 22c. The positive electrode active material layer 22a contains a positive electrode active material (e.g., a lithium transition metal composite oxide such as a lithium nickel cobalt manganese composite oxide) capable of reversibly absorbing and releasing charge carriers. When the total solid content of the positive electrode active material layer 22a is set to 100% by mass, the positive electrode active material can also occupy approximately 80% by mass or more, typically 90% by mass or more, for example, 95% by mass or more. The positive electrode active material layer 22a can also contain any components other than the positive electrode active material, such as conductive materials, binders, and various additives. For example, carbon materials such as acetylene black (AB) can be used as conductive materials. For example, polyvinylidene fluoride (PVdF) can be used as a binder.

[0071] like Figure 8 As shown, the positive electrode protective layer 22p is disposed at the boundary between the positive electrode core 22c and the positive electrode active material layer 22a in the long side direction Y. Here, the positive electrode protective layer 22p is disposed at one end of the positive electrode core 22c in the long side direction Y. Figure 8 (The left end). However, the positive electrode protective layer 22p can also be provided at both ends in the long side direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains inorganic filler (e.g., alumina). When the total solid content of the positive electrode protective layer 22p is set to 100% by mass, the inorganic filler can also occupy approximately 50% by mass or more, typically 70% by mass or more, for example, 80% by mass or more. The positive electrode protective layer 22p can also contain any component other than the inorganic filler, such as conductive materials, binders, various additives, etc. The conductive materials and binders can also be the same as those exemplified as those that can be included in the positive electrode active material layer 22a.

[0072] like Figure 8As shown, the negative electrode plate 24 is a strip-shaped component. The negative electrode plate 24 has a negative electrode core 24c and a layer 24a of negative electrode active material fixed to at least one surface of the negative electrode core 24c. The negative electrode core 24c is strip-shaped. The negative electrode core 24c is made of conductive metals such as copper, copper alloy, nickel, or stainless steel. The negative electrode core 24c is, in this case, a metal foil, specifically a copper foil.

[0073] At one end of the negative electrode core 24c along the long side direction Y ( Figure 8 Multiple negative electrode tabs 24t are provided at the right end of the negative electrode plate 24. These multiple negative electrode tabs 24t protrude in the long side direction Y compared to the spacer 26. The multiple negative electrode tabs 24t are spaced apart (intermittently) along the long side direction of the negative electrode plate 24. The negative electrode tabs 24t are positioned on one side in the long side direction Y (…). Figure 8 (The right side) protrudes. However, the negative electrode tab 24t can also be located at the other end in the long side direction Y ( Figure 8 The negative electrode tab 24t can be located at either end of the negative electrode core 24c, or at either end of the negative electrode core 24c along the long side Y. The negative electrode tab 24t is part of the negative electrode core 24c and is made of metal foil (copper foil). A negative electrode active material layer 24a is present in a portion of the negative electrode tab 24t. At least a portion of the negative electrode tab 24t lacks the negative electrode active material layer 24a, exposing the negative electrode core 24c.

[0074] like Figure 8 As shown, the negative electrode active material layer 24a is arranged in a strip shape along the long side of the strip-shaped negative electrode core 24c. The negative electrode active material layer 24a contains a negative electrode active material (such as a carbon material like graphite) capable of reversibly absorbing and releasing charge carriers. When the total solid content of the negative electrode active material layer 24a is set to 100% by mass, the negative electrode active material can also account for approximately 80% by mass or more, typically 90% by mass or more, for example, 95% by mass or more. The negative electrode active material layer 24a can also contain any components other than the negative electrode active material, such as binders, dispersants, and various additives. As a binder, rubbers such as styrene-butadiene rubber (SBR) can be used, for example. As a dispersant, cellulose-based materials such as carboxymethyl cellulose (CMC) can be used, for example.

[0075] Preferably, the width W1 of the main body portion of the negative electrode plate 24, excluding the negative electrode tab 24t, is 20 cm or more. The width W1 of the main body portion of the negative electrode plate 24 is preferably 20 cm or more and 45 cm or less, more preferably 25 cm or more and 35 cm or less. In a battery with such a relatively large main body portion, high capacity can be achieved, and on the other hand, electrolyte is less likely to penetrate into the interior of the wound electrode body 20. Therefore, the technical effects disclosed herein can be further realized. Furthermore, the width of the main body portion of the negative electrode plate refers to the length in the short side direction of the strip-shaped negative electrode plate.

[0076] like Figure 8 As shown, the wound electrode body 20 includes two spacers 26. Each spacer 26 is a component that insulates the positive electrode active material layer 22a of the positive electrode plate 22 from the negative electrode active material layer 24a of the negative electrode plate 24. The spacers 26 constitute the outer surface of the wound electrode body 20. Figure 9 This diagram schematically shows the interface of the positive electrode plate 22, the negative electrode plate 24, and the spacer 26 of the wound electrode body 20. In this embodiment, the spacer 26 has a strip-shaped substrate layer 26a and adhesive layers 26b disposed on both surfaces of the substrate layer 26a. In this embodiment, one adhesive layer 26b of the spacer 26 is bonded to the positive electrode plate 22, and the other adhesive layer 26b is bonded to the negative electrode plate 24. This suppresses the flat portion 20f of the wound electrode body 20 (see reference 20f). Figure 4 The electrode expands in the thickness direction (short side direction X), and in the configuration process S10 described later, even for an electrode body assembly 200 having multiple wound electrode bodies 20, insertion into the battery housing 10 becomes easy.

[0077] The thickness t1 of spacer 26 (refer to) Figure 9 For example, it is preferably 5μm or more and 40μm or less, more preferably 8μm or more and 30μm or less, and even more preferably 12μm or more and 20μm or less. Furthermore, as... Figure 9 As shown, the "thickness t1 of spacer 26" in this specification refers to the total thickness of the substrate layer 26a and the adhesive layer 26b. Unless otherwise specified, it indicates the thickness before stamping.

[0078] The substrate layer 26a can be used without particular limitation in substrate layers used in conventionally known secondary battery spacers. For example, the substrate layer 26a is preferably a porous sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP). The thickness t2 of the substrate layer 26a (refer to...) Figure 9 The thickness of the substrate layer 26a is not particularly limited, but is preferably 4 μm or more and 35 μm or less, more preferably 8 μm or more and 25 μm or less, and even more preferably 10 μm or more and 20 μm or less. Furthermore, the porosity of the substrate layer 26a is preferably 20% to 70%, more preferably 30% to 60%. This allows the charge carrier to move appropriately between the positive electrode plate 22 and the negative electrode plate 24. Moreover, unless otherwise specified, "thickness of substrate layer 26a" and "porosity of substrate layer 26a" in this specification refer to the thickness and porosity before the stamping process.

[0079] like Figure 9As shown, in this embodiment, the adhesive layer 26b is a layer disposed on both sides of the substrate layer 26a. The adhesive layer 26b contains an adhesive and inorganic particles. Furthermore, the adhesive layer 26b can have the same structure on the side opposite the positive electrode plate 22 and the side opposite the negative electrode plate 24, or it can have different structures.

[0080] Furthermore, the spacer 26 preferably comprises a porous substrate layer 26a made of polyolefin resin, with adhesive layers 26b on both surfaces. The adhesive layer 26b preferably comprises polyvinylidene fluoride (PVdF). Alternatively, other layers may be disposed between the adhesive layer 26b and the substrate layer 26a.

[0081] As the adhesive included in the adhesive layer 26b, conventionally known resin materials with certain adhesive properties can be used without particular limitation. Thermoplastic resins are preferred as the adhesive for the adhesive layer 26b, such as fluorinated resins like polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE); polyester resins like polyethylene terephthalate; polyamide resins; polyimide resins; and acrylic resins. Furthermore, the adhesive layer 26b may also contain two or more of the above-mentioned adhesive resins. Moreover, among the above-mentioned adhesive resins, PVdF is preferred because it can more appropriately exert its adhesive properties relative to the electrode plate. When the adhesive layer 26b is set to 100% by mass, the content of the adhesive included in the adhesive layer 26b is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The upper limit of the adhesive content contained in adhesive layer 26b is not particularly limited, but it can be, for example, less than 50% by mass, less than 45% by mass, or less than 40% by mass. By keeping the adhesive contained in adhesive layer 26b within the above range, appropriate adhesive properties can be achieved.

[0082] Furthermore, the positive electrode plate 22 and the negative electrode plate 24 are preferably bonded to the adhesive layer 26b by, for example, pressing. Pressing can be performed, for example, at room temperature or under heating conditions.

[0083] Inorganic particles can be, for example, ceramic particles containing ceramics as the main component, such as alumina, boehmite, aluminum hydroxide, titanium dioxide, magnesium carbonate, magnesium oxide, zirconium oxide, zinc oxide, iron oxide, cerium dioxide, and yttrium oxide. The content of inorganic particles in the adhesive layer 26b is preferably adjusted to achieve a predetermined adhesiveness relative to the positive electrode plate 22 (or negative electrode plate 24).

[0084] Furthermore, the adhesive layer 26b preferably has a three-dimensional mesh structure containing multiple voids. In this three-dimensional mesh structure, inorganic particles are preferably dispersed. For example, the adhesive layer 26b can be configured by randomly stacking multiple fibrous PVdFs in a manner having multiple voids to form a three-dimensional mesh structure, and dispersing inorganic particles such as alumina and boehmite inside the three-dimensional mesh structure.

[0085] The thickness t3 of the adhesive layer 26b is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. The thickness t3 of the adhesive layer 26b is not particularly limited, but is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. This allows for appropriate adhesion. Furthermore, the weight per unit area of ​​the adhesive layer 26b is preferably 1 g / m². 2 The above, more preferably 2g / m 2 The above is further preferred to be 2.5 g / m 2 That's all. Furthermore, the weight per unit area of ​​the adhesive layer 26b is preferably, for example, 8 g / m². 2 The preferred value is 6g / m 2 The following is a further preferred value: 5.5 g / m 2 The porosity of the adhesive layer 26b is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more. Furthermore, the porosity of the adhesive layer 26b is preferably 90% or less, more preferably 80% or less. Unless otherwise specified, "thickness of adhesive layer 26b" and "porosity of adhesive layer 26b" in this specification refer to the thickness and porosity before the stamping process.

[0086] 2. Manufacturing method of secondary batteries

[0087] The structure of the secondary battery 100, which is the subject of this invention, has been described above. Next, referring to... Figure 1 The manufacturing method of the secondary battery 100 will be described. As described above, the manufacturing method of the secondary battery disclosed herein is characterized in that: in the stripping step S20, at least one of the positive electrode plate 22 and the negative electrode plate 24 of each of the plurality of wound electrode bodies 20 is stripped from the spacer 26 in such a manner that a stripping area is formed in each of the plurality of wound electrode bodies 20. Other manufacturing processes may be the same as conventional ones.

[0088] (1) Configuration process S10

[0089] In the configuration step S10, the electrode assembly 200 described above is configured inside the battery housing 10. Specifically, first, the electrode assembly 200 (three wound electrode bodies 20), the battery housing 10 (outer body 12 and sealing plate 14), the positive terminal 30, the negative terminal 40, the positive current collector 50 (positive first current collector 51 and positive second current collector 52) and the negative current collector 60 (negative first current collector 61 and negative second current collector 62) are prepared. Then, the electrode assembly 200 is inserted into the battery housing 10.

[0090] (a) Winding process

[0091] In the winding process, the positive electrode 22 and the negative electrode 24 are stacked and wound together via two spacers 26 to prepare the wound electrode body 20. More specifically, a laminated body is fabricated by sequentially stacking the strip-shaped spacer 26, the strip-shaped negative electrode 24, the strip-shaped spacer 26, and the strip-shaped positive electrode 22 (see reference). Figure 8 At this point, the stacking position of each component along the long side Y is adjusted so that only the positive electrode tab 22t of the positive electrode plate 22 is positioned along one side of the long side Y. Figure 8 The side edge of the negative electrode plate 24 protrudes from the left side, and only the negative electrode tab 24t of the negative electrode plate 24 protrudes from the other side. Figure 8 The right side of the electrode body protrudes. Then, the laminated body is wound to form a cylindrical body. The number of windings is preferably adjusted appropriately considering the performance of the wound electrode body 20 and the manufacturing efficiency. As an example, the number of windings of the positive electrode plate 22 in the wound electrode body 20 is preferably 10 to 60 times, more preferably 30 to 40 times.

[0092] (b) Stamping process

[0093] In the stamping process, a flat-shaped wound electrode body 20 is prepared by stamping the cylindrical body prepared above. Stamping can be performed at room temperature or under heating (e.g., around 40°C to 80°C). During stamping of the wound cylindrical body, due to the residual elasticity in the bent portion 20r of the formed wound electrode body 20, a springback due to thickness expansion of the flat portion 20f may occur. The secondary battery 100 manufactured by the method disclosed herein has multiple wound electrode bodies 20; if springback occurs, it may be difficult to accommodate them into the battery casing 10 during the arrangement process described later. However, according to the technology disclosed herein, since the spacer 26 has an adhesive layer 26b, and the adhesive layer 26b has a predetermined adhesiveness, the result of stamping the wound electrode body 20 having the adhesive layer 26b is that the adhesive layer 26b of the spacer 26 can be more properly bonded to the positive electrode plate 22 and to the negative electrode plate 24, thus suppressing springback. Therefore, the electrode body assembly 200 having multiple wound electrode bodies 20 can be appropriately housed in the battery housing 10.

[0094] On the other hand, if the positive electrode plate 22, negative electrode plate 24, and adhesive layer 26b are over-bonded, it may be difficult to create a peeling area in each of the multiple wound electrode bodies 20 during the peeling process S20 described later. Therefore, the stamping pressure used to stamp the wound cylindrical body during the stamping process is preferably adjusted in such a way that an appropriate peeling area is formed in each of the wound electrode bodies 20 during the peeling process. Since the stamping pressure varies depending on the properties of the adhesive layer 26b (e.g., material, thickness), the size of the wound electrode body 20, etc., it cannot be generalized, but it can be, for example, around 50 kN to around 400 kN. As a result, the electrode body assembly 200 can be smoothly housed in the arrangement process S10, and a peeling area can be easily formed in each of the wound electrode bodies 20 during the peeling process S20.

[0095] (b) Configuration processing

[0096] In the configuration process, the electrode assembly 200 with multiple wound electrode bodies 20 prepared above is housed within the battery housing 10. First, as... Figure 6 As shown, an assembly of a positive current collector 50, a negative current collector 60, and a sealing plate 14 is prepared to be installed on the electrode assembly 200. The second positive current collector 52 is joined to the positive electrode tab assembly 23 wound around the electrode body 20, and the second negative current collector 62 is joined to the negative electrode tab assembly 25. Next, as... Figure 6As shown, multiple (three in this case) wound electrode bodies 20 are arranged side-by-side with their flat portions 20f facing each other. Then, a sealing plate 14 is placed above the multiple wound electrode bodies 20, and the positive electrode tabs 23 of each wound electrode body are bent so that each positive second current collector 52 faces one side 20e of the wound electrode body 20. This connects the positive first current collector 51 and the positive second current collector 52. Similarly, the negative electrode tabs 25 of each wound electrode body are bent so that each negative second current collector 62 faces the other side 20g of the wound electrode body 20. This connects the negative first current collector 61 and the negative second current collector 62. As a result, the electrode body assembly 200 is mounted on the sealing plate 14 via the positive current collector 50 and the negative current collector 60.

[0097] The electrode assembly 200, which is installed on the sealing plate 14, is housed in the electrode holder 29 (see reference). Figure 4 Then, the electrode assembly 200, covered by the electrode holder 29, is inserted into the outer casing 12. At this time, it is preferable to insert the winding shaft WL in a manner that aligns with the bottom wall 12a (i.e., the winding shaft WL is parallel to the long side direction Y) inside the outer casing 12. Furthermore, it is preferable to arrange the lower end bend 20r of the wound electrode 20 in a manner that contacts the bottom wall 12a of the battery casing 10 via the electrode holder 29. This allows for efficient heating of the electrode assembly 200 during the heat treatment described later. While not particularly limited, if the electrode assembly 200 is relatively heavy, approximately 1 kg or more, for example, 1.5 kg or more, or even 2-3 kg, then... Figure 10 As shown, the electrode assembly 200 can be inserted into the outer body 12 in such a way that the long sidewall 12b of the outer body 12 intersects the direction of gravity (so that the outer body 12 is horizontal).

[0098] Then, the opening 12h is sealed by joining the sealing plate 14 to the edge of the opening 12h of the outer casing 12. For example, it is preferable to seal the opening 12h by welding the outer casing 12 to the sealing plate 14. The welding of the outer casing 12 to the sealing plate 14 can be performed, for example, by laser welding. Thus, a battery assembly in which the electrode assembly 200 is disposed within the battery casing 10 can be prepared.

[0099] (2) Stripping process S20

[0100] The peeling process S20 is a process of creating a peeling region in each of the plurality of wound electrode bodies 20 housed in the battery assembly prepared by the above-described configuration process S10. The peeling region is the area where the contact surface between at least one of the positive electrode plate 22 and the negative electrode plate 24 and the spacer 26 is peeled off. Specifically, for each wound electrode body 20 in a state where the positive electrode plate 22 and the spacer 26 are bonded together by the adhesive layer 26b and the negative electrode plate 24 and the spacer 26 are bonded together by the adhesive layer 26b, the heat treatment and the first depressurization treatment described later are performed. Thus, in each of the wound electrode bodies 20, a peeling region is created between at least one of the positive electrode plate 22 and the negative electrode plate 24 and the spacer 26.

[0101] Here, in the stripping region, it is preferable that a gap is formed between the positive electrode plate 22 or the negative electrode plate 24 and the spacer 26. The presence or absence of the stripping region can be determined based on an X-ray CT image of a section perpendicular to the winding axis WL at the center of the winding axis direction of the wound electrode body 20.

[0102] (a) Heat treatment

[0103] The heat treatment is used to soften the adhesive layer 26b of the spacer 26 of the wound electrode body 20 as described above, making it easier to peel the spacer 26 off from the positive electrode plate 22 and the negative electrode plate 24. In this heat treatment, it is preferable to heat uniformly so that the temperature of each wound electrode body 20 is approximately the same. This facilitates the formation of a peeling region in each of the wound electrode bodies 20. Since the heating temperature of the heat treatment varies depending on the type of adhesive used in the adhesive layer 26b, it cannot be generalized, but it is preferable to maintain the temperature of each wound electrode body 20 at 80°C or higher. For example, it is more preferable to maintain the temperature of each wound electrode body 20 at 90°C or higher, and even more preferable to maintain the temperature of each wound electrode body 20 at 100°C or higher. Excessive temperature is not preferred because it may lead to undesirable side reactions inside the secondary battery 100, deteriorating battery characteristics. Therefore, for the temperature of the heat treatment, it is preferable to maintain the temperature of each wound electrode body 20 at, for example, 130°C or below, and more preferably at 120°C or below. The heating rate is not particularly limited, but can be set to, for example, about 4 to 8°C / min.

[0104] Furthermore, since the heating treatment time varies depending on the size of the secondary battery 100, it cannot be generalized. However, it can be set to approximately 1 to 6 hours, or approximately 1.5 to 4 hours. As an example, it is preferable to maintain the temperature of each wound electrode 20 at 80°C or higher for at least 1 hour, and more preferably to maintain the temperature of each wound electrode 20 at 90°C or higher for at least 1 hour.

[0105] The heating process is only required to heat each of the wound electrode bodies 20 in a generally uniform manner, and the heating method is not particularly limited. For example, the heating can be carried out by mounting the battery assembly on a base-shaped heating plate with an internal electric heater. Alternatively, it can be carried out by placing the battery assembly in a constant temperature bath or similar environment set to maintain a predetermined temperature.

[0106] (b) First decompression treatment

[0107] The first decompression process is used to depressurize the internal pressure of the battery assembly after the above-mentioned heat treatment to a level lower than atmospheric pressure (i.e., the air pressure outside the battery assembly) to separate the positive electrode plate 22 and the negative electrode plate 24 from the spacer 26. In this first decompression process, by setting the decompression speed to be faster than before, a gap can be appropriately generated between the positive electrode plate 22 and the negative electrode plate 24 and the spacer 26 of each wound electrode body 20, and a separation area can be formed in each of the wound electrode bodies 20.

[0108] As described above, compared to the conventional method, the decompression rate in the first decompression process is set to a relatively fast rate, preferably at least 30 kPa / min or higher. The decompression rate is more preferably 40 kPa / min or higher, and even more preferably 50 kPa / min or higher. The upper limit of the decompression rate is not particularly limited, but is preferably 500 kPa / min or lower, more preferably 250 kPa / min or lower, and even more preferably 100 kPa / min or lower. Furthermore, the internal pressure of the battery assembly is preferably reduced to 1 kPa or lower by absolute pressure, more preferably to 100 Pa or lower, and even more preferably to 50 Pa or lower. By performing the first decompression process under these conditions, the positive electrode plate 22 and negative electrode plate 24 of each wound electrode body 20 can be peeled from the spacer 26, and a peeling area can be generated in each of the wound electrode bodies 20. Therefore, even when multiple wound electrode bodies 20 are housed in the battery casing 10, the electrolyte injection time in the electrolyte injection process S30 described later can be shortened. In addition, uneven electrolyte penetration between the wound electrode bodies can be suppressed. Therefore, it is possible to improve the electrolyte deficiency inside all the multiple wound electrode bodies 20 housed in the battery casing 10. In addition, it is possible to improve the degradation of battery characteristics caused by lithium deposition, etc., and to manufacture high-capacity and highly reliable batteries.

[0109] The duration of maintaining the aforementioned depressurization state is not particularly limited, but can be set, for example, for approximately 1 to 8 hours, or based on approximately 1 to 5 hours. Furthermore, the timing of initiating the first depressurization process is not particularly limited. From the viewpoint of forming a peeling region in each of the plurality of wound electrode bodies 20, it is preferable to begin the first depressurization process after the plurality of wound electrode bodies 20 have been heated substantially uniformly by heat treatment. Typically, the first depressurization process can begin approximately 2 hours after the start of the heat treatment, for example, approximately 4 hours after the start of the heat treatment.

[0110] The first decompression process can be implemented in any manner that satisfies the above conditions, and the means of decompression are not particularly limited. For example, decompression can be achieved by venting gas from inside the battery casing 10. For example, one side of the nozzle is installed in the injection hole 15 of the sealing plate 14, and the other side is connected to a vacuum pump. By operating the vacuum pump in this state, the gas inside the battery assembly can be vented from the injection hole 15, thereby decompressing the battery assembly.

[0111] (3) Pressurization process

[0112] The pressurization process involves pressurizing (restoring) the internal pressure of the battery assembly, which has been depressurized by the first depressurization treatment described above, to approximately atmospheric pressure. This pressurization process is not essential in the technology disclosed herein and can be appropriately omitted. For example, the liquid injection process S30 (more specifically, liquid injection treatment) described later can be performed after the first depressurization treatment described above. By performing this pressurization process after the stripping process S20 under the following conditions, the stripped area in each of the plurality of wound electrode bodies 20 can be maintained in an appropriate state.

[0113] In the pressurization process, typically, it is sufficient to pressurize (restore) the internal pressure of the battery assembly to approximately atmospheric pressure. For example, it is preferable to pressurize to 5 kPa or more, and more preferably to 10 kPa or more. Furthermore, while the upper limit is not specifically limited, it is preferable to pressurize the internal pressure of the battery assembly to 200 kPa or less, and more preferably to 100 kPa or less. Regarding the pressurization (restore) rate at this time, it is preferable to pressurize relatively slowly to prevent the wound electrode body 20, which has been peeled off in the aforementioned peeling process S20, from re-adheding. Since the pressurization rate varies depending on the size of the battery assembly, etc., it cannot be generalized, but for example, the pressurization rate can be set to 5000 Pa / min or more and 80000 Pa / min or less.

[0114] When performing the pressurization process, any method that allows for controlled pressurization as described above is acceptable, and the pressurization method is not particularly limited. For example, one end of the nozzle can be installed in the injection hole 15 of the sealing plate 14, and the other end can be connected to a gas storage tank. By controlling the gas stored in the tank while introducing it into the interior of the battery assembly, the pressure can be increased (restored) to approximately atmospheric pressure. Here, the introduced gas can be the same as before, such as inert gases like nitrogen (N2) or dry air.

[0115] (4) Liquid injection process S30

[0116] The electrolyte injection process S30 is a process of injecting electrolyte into the interior of the battery assembly. In the technology disclosed herein, when each of the wound electrode bodies 20 has a peeled area formed by the peeling process S20 described above, by injecting electrolyte into the electrode body assembly 200 having the wound electrode bodies 20 in this state, the electrolyte injection time can be shortened and uneven penetration of electrolyte into the entire electrode body assembly 200 can be suppressed.

[0117] (a) Second decompression treatment

[0118] The second decompression treatment is a process of decompressing the interior of the battery assembly in order to properly perform the electrolyte injection treatment described later, after the pressurization process described above has been performed. This second decompression treatment is not essential in the technology disclosed herein and can be appropriately omitted. For example, the electrolyte injection treatment described later can be performed after the first decompression treatment described above (i.e., while maintaining the decompression state). Alternatively, the electrolyte injection treatment described later can be performed without performing the second decompression treatment after the pressurization process. By performing the second decompression treatment when the pressurization process has been performed, the electrolyte injection treatment can be performed while the battery assembly is under decompression. This shortens the electrolyte injection time. Furthermore, it is preferable because the electrolyte easily penetrates into the interior of the wound electrode body 20.

[0119] The second decompression process is not particularly limited; it only requires decompressing the internal pressure of the battery assembly in a manner that allows for appropriate liquid injection. For example, the internal pressure of the battery assembly can be reduced to approximately 5 to 50 kPa in absolute pressure. The duration of maintaining this decompression state can be set, for example, to approximately 100 to 400 seconds. Furthermore, the decompression rate can be set, for example, to a range of 1 kPa / min or higher and 800 kPa / min or lower. Moreover, the method of decompression in the second process is not particularly limited; the same method as the first decompression process described above can be used.

[0120] (b) Injection treatment

[0121] Electrolyte injection is a process of injecting electrolyte into the interior of the battery assembly. This injection can be performed under atmospheric pressure or under reduced pressure. Preferably, it is performed under reduced pressure. This allows for faster electrolyte injection. In the injection process, the electrolyte is injected in such a manner that it covers the entire winding of the electrode body 20. This injection process can appropriately utilize conventionally known electrolyte injection devices. Furthermore, the pressurizing gas used for pressurizing the electrolyte can be, as previously mentioned, inert gases such as nitrogen (N2) or dry air.

[0122] After the electrolyte is injected, the injection hole 15 of the sealing plate 14 of the battery assembly is sealed. The sealing of the injection hole 15 can be achieved by assembling a sealing member 16 that is adapted to the shape of the injection hole 15. Thus, a sealed secondary battery 100 can be constructed.

[0123] (5) Initial charging process

[0124] In the manufacturing method disclosed herein, it is preferable that the initial charging step can be performed after the liquid injection step S30 described above. More preferably, the initial charging step can be performed while the secondary battery 100 constructed above is constrained. The secondary battery 100 is constrained by the long sidewall 12b of the outer casing 12 along the short side direction X (see reference). Figure 2 The secondary battery 100 is subjected to a predetermined load. The initial charging conditions can be the same as before. For example, the secondary battery 100 can be subjected to approximately 1 to 5 cycles of charging and discharging within the battery drive voltage range at a charging rate of 0.1 to 2C under a constrained state. The secondary battery 100 can be manufactured as described above.

[0125] The manufacturing method disclosed herein can be preferably used, for example, in a high-capacity, sealed battery having multiple electrodes. Furthermore, the secondary battery 100 manufactured by this method can be used for various applications, such as being suitable as a power source (drive power supply) for an electric motor in a passenger car, truck, or other vehicle. The type of vehicle is not particularly limited; examples include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs). Additionally, the secondary battery 100 can be suitable for use in the construction of battery packs.

[0126] <Experimental Example>

[0127] The following describes test examples related to the present invention. Furthermore, the content of the test examples described below is not intended to limit the present invention.

[0128] 1. Configuration process

[0129] LiNi as a positive electrode active material powder 1 / 3 Co 1 / 3Mn 1 / 3 O2, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were weighed in a mass ratio of 97.5:1.5:1.0. These materials were dispersed in N-methylpyrrolidone (NMP) as a solvent to prepare a paste-like composition for forming a positive electrode active material layer. By coating this composition onto both sides of a strip-shaped positive electrode core (aluminum foil) and allowing it to dry, a strip-shaped positive electrode plate with a positive electrode active material layer on the positive electrode core was produced.

[0130] The natural graphite (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener were weighed in a mass ratio of 98.3:0.7:1.0. These materials were dispersed in ion-exchanged water as a solvent to prepare a paste-like composition for forming the negative electrode active material layer. By coating this composition onto both sides of a strip-shaped negative electrode core (copper foil) and allowing it to dry, a strip-shaped negative electrode plate with a negative electrode active material layer on the negative electrode core was produced.

[0131] Additionally, as spacers, spacers with an adhesive layer comprising alumina powder and polyvinylidene fluoride (PVdF) formed on the surface of a porous polyethylene (PE) substrate layer are used. Furthermore, spacers with two adhesive layers having different weights per unit area are prepared.

[0132] A laminate is fabricated by stacking the prepared strip-shaped positive electrode plate and strip-shaped negative electrode plate with the spacer provided above. This laminate is then wound to form a cylindrical body. Next, the wound laminate is stamped and flattened to create a flat wound electrode body. Three wound electrodes are fabricated following the same steps. The positive and negative terminals are connected to these three wound electrodes and placed in a battery casing with a liquid filling port. This creates an evaluation battery assembly in which multiple wound electrodes are housed within a battery casing.

[0133] 2. Observation of the stripping process and each wound electrode body

[0134] In this experiment, for the battery assembly prepared above, a stripping process was performed by changing the decompression speed of the first decompression treatment, followed by a pressurization process. Then, the presence or absence of stripping areas in each wound electrode body was confirmed.

[0135] (1) Example 1

[0136] First, the evaluation secondary battery assembly prepared above was subjected to heat treatment at a maximum temperature of 105°C. Next, four hours after the start of heating, a first decompression treatment was performed. This first decompression treatment was carried out at a decompression rate of 90 kPa / min, reducing the internal pressure of the evaluation battery assembly to 10 Pa absolute pressure, and maintaining the decompression for four hours. Following the first decompression treatment, a pressurization (pressure recovery) process was performed to restore the pressure to atmospheric pressure.

[0137] (2) Example 2

[0138] First, the aforementioned evaluation secondary battery assembly was subjected to heat treatment at a maximum temperature of 105°C. Next, a first depressurization treatment was performed 4 hours after the start of heating. The first depressurization treatment was performed under the same conditions as in Example 1. After the first depressurization treatment, a pressurization (pressure recovery) process was performed to atmospheric pressure. Furthermore, the unit area weight of the adhesive layer of the spacer used in Example 2 was smaller than that of the adhesive layer of the spacer in Example 1.

[0139] (3) Comparison Example 1

[0140] First, the evaluation secondary battery assembly prepared above was subjected to heat treatment at a maximum temperature of 105°C. Next, a first depressurization treatment was performed 4 hours after the start of heating. The first depressurization treatment was performed under the same conditions as in Example 1, except that the depressurization rate was changed to 10 kPa / min. After the first depressurization treatment, a pressurization process of pressurizing (pressure recovery) to atmospheric pressure was performed. Furthermore, the spacer used in Comparative Example 1 was the same as the spacer in Example 1.

[0141] (4) Comparison Example 2

[0142] First, the evaluation secondary battery assembly prepared above was subjected to heat treatment at a maximum temperature of 105°C. Next, a first decompression treatment was performed 4 hours after the start of heating. The first decompression treatment was performed under the same conditions as in Example 1, except that the decompression rate was changed to 10 kPa / min. After the first decompression treatment, a pressurization (pressure recovery) process to atmospheric pressure was performed. Furthermore, the unit area weight of the adhesive layer of the spacer used in Comparative Example 2 was smaller than that of the adhesive layer of the spacer in Example 1.

[0143] (5) Acquisition of X-ray CT images

[0144] In the central portion (central portion in the winding axis direction) of the wound electrode body prepared in each of the above embodiments and comparative examples, an X-ray CT apparatus (manufactured by Toshiba IT Control Systems Co., Ltd.) was used to take images of a section perpendicular to the winding axis, and X-ray CT images of each embodiment and comparative example were obtained. Then, in the X-ray CT images, it was confirmed whether there was a peeling area in the flat portion 20f of the wound electrode body 20. In the flat portion 20f of the wound electrode body 20, the distance between the center of the thickness direction of one of the positive electrode plates 22 and the center of the thickness direction of the other positive electrode plate 22 of two adjacent positive electrode plates 22 in the stacking direction of the positive electrode plate 22 was defined as the distance D (μm). The total thickness of each component existing between the two centers (the total thickness of half the thickness of one positive electrode plate 22, the thickness of one spacer 26, the thickness of the negative electrode plate 24, the thickness of the other spacer 26, and half the thickness of the other positive electrode plate 22) was defined as the thickness T (μm). Then, it was determined that there was a peeling region in the part where the distance D (μm) was more than 30 μm greater than the thickness T (μm).

[0145] The case where peeling areas are formed on all three wound electrode bodies is marked as "0". The case where no peeling area can be identified on any of the three wound electrode bodies is marked as "×". The results are shown in Table 1.

[0146] 3. Liquid injection process

[0147] The electrolyte injection process was performed on each embodiment and comparative example with modified stripping process conditions as described above. As the electrolyte used in the electrolyte injection process, an electrolyte containing LiPF6 as a supporting salt was prepared at a concentration of 1.1 mol / L in a mixed solvent comprising ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC = 3:4:3. In the electrolyte injection process, a second decompression treatment was performed to reduce the internal pressure of the evaluation battery assembly to 5 kPa, followed by the electrolyte injection process.

[0148] During the injection process, the time until the injection is completed was measured. The ratio of the injection times of each embodiment and each comparative example when the injection time of Comparative Example 2 is set to 1 is shown in Table 1.

[0149] Table 1

[0150]

[0151] 4. Test Results

[0152] It can be seen that, in the stripping process, the electrolyte injection time in Examples 1 and 2, where stripping regions are formed in all of the multiple wound electrode bodies, is very short compared to the comparative example. It can be inferred that this is because, by performing the first decompression treatment at a relatively fast decompression rate as described above, stripping regions are formed in each wound electrode body, thereby making it easier for the electrolyte to penetrate. Therefore, by forming a stripping region in each of the multiple wound electrode bodies in the stripping process, it is possible to manufacture a high-capacity secondary battery with improved electrolyte injection performance as a whole.

[0153] Furthermore, in the flat portion 20f of the wound electrode body 20, a unit is formed by combining one positive electrode active material layer 22a, one spacer 26, one negative electrode plate 24, the other spacer 26, and the other positive electrode active material layer 22a existing between the positive electrode cores 22c of two adjacent positive electrode plates 22 in the stacking direction. Preferably, three or more units are formed in the flat portion 20f of the wound electrode body 20, where at least one of the boundary surfaces between the positive electrode plate 22 and the spacer 26 and the negative electrode plate 24 and the spacer 26 exists within the unit; more preferably, five or more units are formed.

[0154] In a flat portion 20f of a wound electrode body 20, when the total number of layers of the positive electrode plate 22 is N, the unit with the stripping region preferably has a thickness of 0.1N or more, and more preferably 0.2N or more.

[0155] In the central portion of the winding axis direction of the winding electrode body 20, in a cross section perpendicular to the winding axis, the width of the peeling area is preferably 10 mm or more, more preferably 20 mm or more, and even more preferably 30 mm or more.

[0156] In the central portion of the winding axis direction of the wound electrode body 20, in a cross section perpendicular to the winding axis, when the width of the positive electrode plate 22 at the flat portion 20f of the wound electrode body 20 is set to width W2 (mm) and the width of the peeling area in a layer is set to width W3 (mm), W3 / W2 is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more.

[0157] Furthermore, among the plurality of wound electrode bodies 20, the number of units with peeling regions in the wound electrode body with the fewest units is designated as A, and the number of units with peeling regions in the wound electrode body with the most units is designated as B. In this case, the value of B / A is preferably 1 to 5. This allows for more effective suppression of uneven penetration of the electrolyte into the wound electrode body 20. Moreover, the value of B / A is more preferably 1 to 3, and even more preferably 1 to 2.

[0158] The present invention has been described in detail above, but the above description is merely illustrative. That is, the technology disclosed herein includes solutions obtained by various modifications and alterations to the above specific examples.

Claims

1. A method for manufacturing a secondary battery, the secondary battery comprising a flat wound electrode body formed by winding a positive electrode and a negative electrode with a spacer between them, and a battery casing housing a plurality of the wound electrode bodies, wherein, The method for manufacturing the secondary battery includes: The configuration process involves arranging a plurality of the wound electrode bodies within the battery housing. In the stripping process, at least one of the positive and negative electrodes of each of the plurality of wound electrode bodies is stripped from the spacer. as well as In the electrolyte injection process, electrolyte is injected into the battery casing. The stripping process sequentially includes a heat treatment that heats the wound electrode body and a decompression treatment that reduces pressure inside the battery casing. In the aforementioned decompression process, the decompression rate is made to be 30 kPa / min or higher. Here, in the stripping process, at least one of the positive and negative electrodes of each wound electrode body is stripped from the spacer in such a manner that a stripping region is formed in each of the plurality of wound electrode bodies.

2. The method for manufacturing a secondary battery according to claim 1, wherein, An adhesive layer is formed on both surfaces of the spacer.

3. The method for manufacturing a secondary battery according to claim 2, wherein, In the configuration process, the wound electrode body, in which the positive electrode and the spacer are bonded by the adhesive layer and the negative electrode and the spacer are bonded by the adhesive layer, is disposed in the battery housing.

4. The method for manufacturing a secondary battery according to claim 2 or 3, wherein, The spacer comprises a porous substrate layer made of polyolefin resin. The adhesive layer comprises polyvinylidene fluoride (PVdF).

5. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein, The width of the negative electrode is 20cm or more.

6. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein, The battery casing includes: A square outer casing having a bottom wall, a pair of first side walls extending from the bottom wall and opposing each other, a pair of second side walls extending from the bottom wall and opposing each other, and an opening opposite the bottom wall; as well as A sealing plate, which seals the opening. In the configuration process, the wound electrode body is configured with the winding axis of the wound electrode body facing the bottom wall.

7. The method for manufacturing a secondary battery according to any one of claims 1 to 3, wherein, Following the liquid injection step, the method for manufacturing the secondary battery includes an initial charging step for performing an initial charge of the secondary battery. The initial charging process is performed under constrained conditions on the secondary battery.

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