Method for manufacturing a secondary battery

Abstract

This invention provides a more efficient method for manufacturing a highly reliable secondary battery. The method disclosed herein is for manufacturing a secondary battery comprising an electrode body and a battery casing housing the electrode body. The electrode body includes a positive electrode, a negative electrode, and a spacer disposed between the positive and negative electrodes, with adhesive layers formed on both surfaces of the spacer. The manufacturing method includes: a placement step, in which an electrode body, in which the positive electrode and the spacer are bonded by the adhesive layers, and the negative electrode and the spacer are bonded by the adhesive layers, are placed within the battery casing; a peeling step, in which at least one of the positive and negative electrodes is peeled from the spacer within the electrode body; and an electrolyte injection step, after the peeling step, in which electrolyte is injected into the battery casing.

Description

Technical Field

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

[0002] Generally, secondary batteries such as lithium-ion batteries include: an electrode body having a positive electrode and a negative electrode; an outer casing having an opening and housing the electrode body and electrolyte; and a sealing plate sealing 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 the 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, there has been a trend towards larger electrode bodies from the perspective of increasing battery capacity. According to the results of the inventors' research, it has been found that the electrolyte injection time is longer for larger electrode bodies compared to the past, making it difficult to uniformly penetrate the entire electrode body with electrolyte.

[0008] This invention was made to solve the above-mentioned problems, and its purpose is to provide a more efficient method for manufacturing highly reliable secondary batteries.

[0009] Methods for solving problems

[0010] The method for manufacturing a secondary battery disclosed herein is as follows: the secondary battery includes an electrode body and a battery casing housing the electrode body; the electrode body includes a positive electrode, a negative electrode, and a spacer disposed between the positive electrode and the negative electrode; an adhesive layer is formed on both surfaces of the spacer; and the method comprises: a placement step in which the electrode body, wherein 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, are placed in the battery casing; a peeling step in which at least one of the positive electrode and the negative electrode is peeled from the spacer in the electrode body; and an electrolyte injection step in which, after the peeling step, electrolyte is injected into the battery casing.

[0011] As described above, the stripping process separates at least one of the positive and negative electrodes from the spacer. This allows for electrolyte injection in a shorter time during the electrolyte filling process. Furthermore, it suppresses uneven electrolyte penetration into the electrode body. By suppressing uneven electrolyte penetration into the electrode body, it is possible to suppress the degradation of battery characteristics caused by poor coating formation, lithium deposition, etc. Therefore, based on this structure, a more efficient method for manufacturing highly reliable secondary batteries can be achieved.

[0012] In one embodiment of the manufacturing method disclosed herein, the stripping step includes: a heat treatment in which the temperature of the electrode body is heated to 80°C or higher; and a first decompression treatment in which, while the temperature of the electrode body is 80°C or higher, pressure is reduced within the battery casing. In the first decompression treatment, the pressure within the battery casing is reduced to below 1 kPa at a rate of 30 kPa / min or higher, based on an absolute pressure reference.

[0013] According to this structure, at least one of the positive and negative electrodes can be properly separated from the spacer.

[0014] In one embodiment of the manufacturing method disclosed herein, the electrode body is a flat wound electrode body formed by winding the strip-shaped positive electrode and the strip-shaped negative electrode with the strip-shaped spacer in between, wherein the width of the negative electrode is 20 cm or more.

[0015] In electrode bodies with such relatively large negative electrodes, the electrolyte injection takes a particularly long time and there is a tendency for the electrolyte to become unevenly permeated. Therefore, the technique disclosed herein is particularly effective.

[0016] In one embodiment of the manufacturing method disclosed herein, 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 that seals the opening. Furthermore, in the configuration step, the electrode bodies may be wound with the winding axis of the electrode bodies aligned along the orientation of the bottom wall. Alternatively, in the configuration step, a plurality of electrode bodies may be configured within the battery casing.

[0017] In one embodiment of the manufacturing method disclosed herein, the method for manufacturing the secondary battery may further include a pressurization step that increases the pressure within the battery casing after the stripping step and before the liquid injection step. Alternatively, the liquid injection step may include a second depressurization process that reduces the pressure within the battery casing after the pressurization step. Additionally, the method for manufacturing the secondary battery may include an initial charging step that performs an initial charge while the secondary battery is constrained after the liquid injection step.

[0018] Alternatively, the spacer may comprise: a porous substrate layer made of polyolefin resin; and the adhesive layer formed on both surfaces of the substrate layer and comprising polyvinylidene fluoride (PVdF). Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a method for manufacturing a secondary battery according to one embodiment.

[0020] Figure 2 This is a perspective view schematically showing one embodiment of a battery.

[0021] Figure 3 It is along Figure 2 A schematic longitudinal section view of line III-III.

[0022] Figure 4 It is along Figure 2 A schematic longitudinal section view of line IV-IV.

[0023] Figure 5 It is along Figure 2 A schematic cross-sectional view of the VV line.

[0024] Figure 6 It is a schematic perspective view of the electrode body installed on the sealing plate.

[0025] Figure 7 It is a perspective view schematically showing an electrode body with a positive second collector and a negative second collector installed.

[0026] Figure 8 This is a schematic diagram showing the structure of an electrode body according to one embodiment.

[0027] Figure 9 This is a schematic diagram showing the interface between the positive electrode, negative electrode, and spacer of the electrode body of a secondary battery according to one embodiment.

[0028] Figure 10 This is another implementation method with Figure 4 The corresponding diagram.

[0029] Figure 11This is a schematic cross-sectional view illustrating the configuration process of another embodiment.

[0030] Explanation of reference numerals in the attached figures

[0031] 10 Battery casing

[0032] 12 outer body

[0033] 14 Sealing plate (lid)

[0034] 15 injection holes

[0035] 16 sealing components

[0036] 17 Exhaust Valve

[0037] 20 electrode body

[0038] 22 positive plate

[0039] 24 negative electrode plate

[0040] 26 spacers

[0041] 26a Substrate layer

[0042] 26b Adhesive layer

[0043] 30 positive extremes

[0044] 40 negative extremes

[0045] 50 Positive Current Collector

[0046] 60 negative electrode current collector

[0047] 100 rechargeable batteries

[0048] 200 secondary batteries. Detailed Implementation

[0049] 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".

[0050] 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.

[0051] 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 method for manufacturing a secondary battery disclosed herein includes: (1) a placement step S10 in which an electrode body is disposed within a battery casing; (2) a stripping step S20 in which at least one of the positive and negative electrodes of the electrode body is separated from a spacer; and (3) an electrolyte injection step S30 in which electrolyte is injected into the battery casing. The method for manufacturing a secondary battery disclosed herein may also include a pressurization step after the stripping step S20 and before the electrolyte injection step S30, which increases the pressure within the battery casing. Furthermore, the method for manufacturing a secondary battery disclosed herein may also include an initial charging step after the electrolyte injection step S30, which performs an initial charge on the secondary battery. The method for manufacturing a secondary battery disclosed herein is characterized by having the aforementioned stripping step S20; other manufacturing processes may be the same as conventional methods. Additionally, other steps may be further included at any stage.

[0052] 1. Structure of a secondary battery

[0053] Here, we will first explain the structure of the secondary battery 100, which is the object of manufacture, and then explain each process. Figure 2 This is a 3D diagram of a secondary battery (model 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 It is a schematic perspective view of the electrode body installed on the sealing plate. Figure 7 It is a perspective view schematically showing an electrode body with a positive second collector and a negative second collector installed.

[0054] Figure 8This is a schematic diagram showing the structure of the 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.

[0055] like Figure 2 and Figure 3 As shown, the secondary battery 100 manufactured using the method disclosed herein includes a battery casing 10, an electrode body 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.

[0056] (1) Battery casing

[0057] The battery casing 10 is a frame that houses the electrode body 20. 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.

[0058] like Figure 2 As 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.

[0059] 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 3As 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.

[0060] (2) Electrolyte

[0061] 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.

[0062] (3) Electrode terminals

[0063] 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).

[0064] 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.

[0065] (4) Electrode collector

[0066] like Figures 3-6 As shown, in the secondary battery 100 of this embodiment, an electrode body 20 is housed within the battery casing 10. While a detailed structure will be described later, the 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 the electrode body 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 second positive electrode current collector 52, which is a plate-shaped conductive member 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 Additionally, such as Figures 5-7 As shown, the second positive current collector 52 is connected to the positive electrode tab assembly 23 of the electrode body 20. Furthermore, the positive electrode tab assembly 23 of the electrode body 20 is bent so that the second positive current collector 52 and one side 20e of the electrode body 20 face each other. Thus, the upper end of the second positive current collector 52 is electrically connected to the first positive current collector 51.

[0067] On the other hand, the negative terminal 40 is connected to the negative electrode tab assembly 25 of the electrode body 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 surface of the sealing plate 14 in the long side direction Y; and a second negative electrode current collector 62, which is a plate-shaped conductive member 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 Additionally, such as Figures 5-7As shown, the second negative current collector 62 is connected to the negative electrode tab assembly 25 of the electrode body 20. Furthermore, the negative electrode tab assembly 25 is bent so that the second negative current collector 62 faces the other side 20g of the electrode body 20. Thus, the upper end of the second negative current collector 62 is electrically connected to the first negative current collector 61.

[0068] (5) Insulating components

[0069] Furthermore, the secondary battery 100 is equipped with various insulating components to prevent conductivity between the electrode body 20 and the battery casing 10. Specifically, an external insulating component 92 (see reference 42) is sandwiched between the positive electrode external conductive component 32 (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 body 20 (see reference). Figure 3 and Figure 4 This restricts the movement of the electrode body 20 in the vertical Z direction and prevents the electrode body 20 from directly contacting the sealing plate 14. Furthermore, the electrode body 20 is held in place by an electrode body retainer 29 made of an insulating resin sheet (see [reference]). Figure 4 The electrode 20 is contained within the battery casing 10 in a covered state. This prevents direct contact between the electrode 20 and the outer casing 12. Furthermore, the materials of the aforementioned insulating components are not particularly limited, as long as they possess 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.

[0070] (6) Electrode body

[0071] Figure 8 This is a schematic diagram showing the structure of the electrode body 20. (As shown) Figure 8As shown, the electrode body 20 has a positive electrode plate 22 and a negative electrode plate 24. Here, the electrode body 20 is a flat wound 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.

[0072] The electrode body 20 is disposed inside the outer casing 12 with its winding axis WL aligned along the bottom wall 12a (i.e., with the winding axis WL parallel to the long side direction Y). In other words, the electrode body 20 is disposed inside the outer casing 12 with its winding axis WL parallel to the bottom wall 12a and orthogonal to the short side wall 12c. The end face of the electrode body 20 (in other words, the laminated surface of the positive electrode plate 22 and the negative electrode plate 24) is... Figure 8 The end face of the long side in the Y direction is opposite to the short sidewall 12c.

[0073] like Figure 4 As shown, the 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. However, the electrode body 20 may also be a stacked electrode body formed by stacking multiple square (typically rectangular) positive electrodes and multiple square (typically rectangular) negative electrodes in an insulated state. The height (length in the vertical direction Z) H1 of the electrode body 20 is preferably 12 cm or less, more preferably 10 cm or less. Furthermore, the height of the electrode body 20 refers to the length in the vertical direction perpendicular to the thickness direction (short side direction X) of the electrode body 20.

[0074] 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.

[0075] 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 8 The 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.

[0076] 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.

[0077] 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.

[0078] like Figure 8 As 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.

[0079] 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.

[0080] 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.

[0081] Preferably, the width W1 of the main body of the negative electrode plate 24, excluding the negative electrode tab 24t (refer to...) Figure 8 The width W1 of the main body 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, high capacity can be achieved, and on the other hand, electrolyte is less likely to penetrate into the interior of the electrode body 20. Therefore, the technical effects disclosed herein can be further realized. Furthermore, the width of the main body of the negative electrode plate refers to the length in the short side direction of the strip-shaped negative electrode plate.

[0082] like Figure 8 As shown, the electrode body 20 includes two spacers 26. Each spacer 26 is a component that insulates the positive active material layer 22a of the positive electrode plate 22 from the negative active material layer 24a of the negative electrode plate 24. The spacers 26 constitute the outer surface of the electrode body 20. Figure 9This diagram schematically shows the interface between the positive electrode plate 22, the negative electrode plate 24, and the spacer 26 of the 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 electrode body 20 (see reference). Figure 4 The electrode body 20 expands in the thickness direction (short side direction X), making it easier to insert in the configuration process S10 described later.

[0083] 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.

[0084] 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.

[0085] like Figure 9 As 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] 2. Manufacturing method of secondary batteries

[0093] 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 herein. As mentioned above, the manufacturing method of the secondary battery disclosed herein is characterized by having a stripping step S20, and other manufacturing processes are not particularly limited thereto.

[0094] (1) Configuration process S10

[0095] The configuration step S10 is the process of arranging the electrode body 20 as described above inside the battery casing 10. Specifically, first, the electrode body 20, the battery casing 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 body 20 is inserted into the battery casing 10. Here, the case where the electrode body 20 is a wound electrode body will be described, but the electrode body 20 can also be a stacked electrode body as described above.

[0096] (a) Winding process

[0097] In the winding process, the positive electrode plate 22 and the negative electrode plate 24 are stacked and wound together via two spacers 26 to prepare the electrode body 20. More specifically, a laminated body is fabricated by sequentially stacking the strip-shaped spacer 26, the strip-shaped negative electrode plate 24, the strip-shaped spacer 26, and the strip-shaped positive electrode plate 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 20 protrudes. Then, the laminated body is wound to form a cylindrical body. The number of windings is preferably adjusted appropriately, taking into account the performance of the target electrode body 20, manufacturing efficiency, etc. For example, the number of windings of the positive electrode plate 22 in the electrode body 20 is preferably 10 to 60 times, more preferably 30 to 40 times.

[0098] (b) Stamping process

[0099] In the stamping process, a flat electrode body 20 is prepared by stamping the cylindrical body prepared above. The stamping process can be carried out at room temperature or under heating (for example, around 40°C to 80°C). When the wound cylindrical body is stamped, due to the residual elasticity in the bent portion 20r of the formed electrode body 20, the thickness expansion of the flat portion 20f may occur. If springback occurs, it may be difficult to accommodate it into the battery housing 10 in the configuration 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 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 the adhesive layer 26b to the negative electrode plate 24, and springback can be suppressed. Therefore, the electrode body 20 can be smoothly positioned at the desired location during the configuration process.

[0100] (c) Configuration processing

[0101] In the configuration process, the electrode body 20 prepared above is housed within the battery casing 10. First, as... Figure 6 As shown, a combined assembly consisting of a positive current collector 50, a negative current collector 60, and a sealing plate 14 is prepared to be installed on the electrode body 20. First, the second positive current collector 52 is joined to the positive electrode tab assembly 23 of the electrode body 20, and the second negative current collector 62 is joined to the negative electrode tab assembly 25. Next, the sealing plate 14 is positioned above the electrode body 20, and as shown... Figure 5The positive electrode tab assembly 23 of the electrode body 20 is bent so that the positive second current collector 52 faces one side 20e of the electrode body 20. This connects the positive first current collector 51 and the positive second current collector 52. Similarly, the negative electrode tab assembly 25 of the electrode body 20 is bent so that each negative second current collector 62 faces the other side 20g of the electrode body 20. This connects the negative first current collector 61 and the negative second current collector 62. As a result, the electrode body 20 is mounted on the sealing plate 14 via the positive current collector 50 and the negative current collector 60.

[0102] The electrode body 20, which is installed on the sealing plate 14, is housed in the electrode body holder 29 (see reference). Figure 4 Next, the electrode body 20, covered by the electrode body retainer 29, is inserted into the outer casing 12. It is preferable to insert the winding shaft WL in such a way that it is positioned inside the outer casing 12 along the bottom wall 12a (i.e., the winding shaft WL is parallel to the long side direction Y). This allows for efficient heating of the electrode body 20 during the heat treatment described later. Then, the opening 12h is sealed by joining the sealing plate 14 at its edge. This completes the preparation of a battery assembly in which the electrode body 20 is disposed within the battery casing 10.

[0103] Furthermore, 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. Additionally, the outer casing 12 and the sealing plate 14 are preferably sealed by welding, for example. The welding of the outer casing 12 and the sealing plate 14 can be performed, for example, by laser welding.

[0104] (2) Stripping process S20

[0105] The peeling process S20 is a process of peeling at least one of the positive electrode plate 22 and the negative electrode plate 24 of the electrode body 20 housed in the battery assembly prepared in the above-mentioned configuration process S10 from the spacer 26. Specifically, for the 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 positive electrode plate 22 and the negative electrode plate 24 are peeled from the spacer 26 by performing the heat treatment and the first depressurization treatment described later, thereby setting the electrode body 20 to a state where there is a peeling area. Here, in the peeling area, 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 peeling area can be determined based on the X-ray CT image of the cross section perpendicular to the winding axis at the center of the electrode body in the winding axis direction.

[0106] (a) Heat treatment

[0107] The heat treatment is used to soften the adhesive layer 26b of the spacer 26 described above, making it easier to peel the spacer 26 off from the positive electrode plate 22 and the negative electrode plate 24. The temperature of this heat treatment varies depending on the type of adhesive used in the adhesive layer 26b, and therefore cannot be generalized. However, it is preferable, for example, to maintain the temperature of the electrode body 20 at 80°C or higher. More preferably, the heat treatment is maintained at a temperature of 90°C or higher, and even more preferably, at a temperature of 100°C or higher. Excessive temperature may lead to undesirable side reactions inside the secondary battery 100, deteriorating battery characteristics, and is therefore not preferred. Therefore, it is preferable to maintain the temperature of the electrode body 20 at, for example, 130°C or lower, and more preferably, 120°C or lower. The heating rate is not particularly limited, but can be set, for example, to about 4 to 8°C / min.

[0108] 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 electrode body 20 at a temperature of 80°C or higher for at least 1 hour, and more preferably to maintain the electrode body 20 at a temperature of 90°C or higher for at least 1 hour.

[0109] The heating process can be carried out in any manner that meets the above conditions, and the heating method is not particularly limited. For example, the heating method can be implemented by mounting the battery assembly on a base-shaped heating plate with an internal electric heater. Alternatively, it can be implemented by placing the battery assembly in a constant temperature bath or similar container set to maintain a predetermined temperature.

[0110] (b) First decompression treatment

[0111] The first decompression treatment is a process used to decompress the interior of the battery assembly after the aforementioned heat treatment to a pressure 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. Based on the inventors' in-depth research, by setting the decompression rate of this treatment to be faster than before, it is possible to properly separate the positive electrode plate 22 and the negative electrode plate 24 from the spacer 26. While there is no intention to limit the technology disclosed herein, the reason for this effect is presumably as follows: When the interior of the battery assembly (i.e., the interior of the battery casing) is decompressed, the interior of the electrode body housed in the battery casing is also decompressed. Here, if the interior of the battery casing is decompressed at a rapid rate, the pressure inside the electrode body cannot keep up with the decompression rate of the battery casing, creating a pressure difference between the interior of the battery casing and the interior of the electrode body, causing the electrode body to expand. It can be presumed that through this expansion, the positive and negative electrode plates of the electrode body are separated from the spacer. That is, by setting the decompression rate to be faster and more rapid than before to depressurize the inside of the battery assembly, the positive electrode plate 22 and the negative electrode plate 24 can be properly separated from the spacer 26, and a separation region can be formed in the electrode body 20. This shortens the electrolyte injection time in the electrolyte injection process S30 described later. Furthermore, the central portion of the electrode body 20 is sufficiently impregnated with electrolyte. Therefore, the reduction in battery characteristics caused by insufficient electrolyte inside the electrode body and insufficient film formation on the negative electrode can be improved. In addition, batteries with higher reliability can be manufactured more efficiently.

[0112] As described above, the decompression rate in the first decompression process is set to a relatively fast rate to peel at least one of the positive electrode plate 22 and the negative electrode plate 24 of the electrode body 20 from the spacer 26. The decompression rate is preferably at least 30 kPa / min. More preferably, it is 40 kPa / min or more, and even more preferably 50 kPa / min or more. The upper limit of the decompression rate is not particularly limited, but it is preferably 500 kPa / min or less, more preferably 250 kPa / min or less, and even more preferably 100 kPa / min or less. Furthermore, the internal pressure of the battery assembly is preferably reduced to less than 1 kPa by absolute pressure, more preferably to less than 100 Pa, and even more preferably to less than 50 Pa. By performing the first decompression process under these conditions, the positive electrode plate 22 and the negative electrode plate 24 can be peeled from the spacer 26, and a peeled area can be appropriately formed in the electrode body 20.

[0113] 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, but from the viewpoint of properly peeling off the electrode body 20, it is preferable to begin the first depressurization process after the battery assembly has been sufficiently heated by the 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.

[0114] 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.

[0115] (3) Pressurization process

[0116] 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 under the following conditions, the state in which the stripped area is formed on the electrode body 20 can be maintained more appropriately.

[0117] In the pressurization process, typically, the internal pressure of the battery assembly is simply increased (restored) to approximately atmospheric pressure. For example, it is preferable to increase the pressure to 5 kPa or more, and more preferably to 10 kPa or more. Furthermore, while the upper limit is not specifically limited, the internal pressure of the battery assembly is preferably increased to 200 kPa or less, and more preferably to 100 kPa or less. Regarding the pressurization (restored) rate at this point, it is preferable to pressurize relatively slowly to prevent the electrode bodies 20, which were peeled off in the aforementioned peeling process, 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.

[0118] 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.

[0119] (4) Liquid injection process S30

[0120] The electrolyte injection process S30 is a process of injecting electrolyte into the interior of the battery assembly. In the technology disclosed herein, when the positive electrode plate 22 and negative electrode plate 24 are separated from the spacer 26 by the aforementioned stripping process S20, the electrolyte is injected into the electrode body 20 in this state, thereby shortening the electrolyte injection time and suppressing uneven penetration of the electrolyte into the electrode body 20.

[0121] (a) Second decompression treatment

[0122] 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 omitted appropriately. 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 preferred because the electrolyte can easily and uniformly penetrate the interior of the electrode body 20.

[0123] 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.

[0124] (b) Injection treatment

[0125] 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 a quantity that covers the entire 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.

[0126] 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.

[0127] (5) Initial charging process

[0128] 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.

[0129] The manufacturing method disclosed herein can be preferably used, for example, in high-capacity, sealed batteries with electrodes having a large area where electrolyte impregnation takes time. 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 electric motors in vehicles such as passenger cars and trucks. 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.

[0130] 3. Other implementation methods

[0131] The present invention has been described above with reference to some embodiments, but these embodiments are merely examples. The present invention can also be implemented in various other forms. Other embodiments of the technology disclosed herein will be described below.

[0132] The secondary battery 100 of the above embodiment has an electrode body 20 housed inside the battery casing 10. However, the technology disclosed herein is not limited to the above embodiment. For example, a secondary battery may also have multiple electrode bodies inside the battery casing.

[0133] Figure 10 Another embodiment of the secondary battery 200 and Figure 4 The corresponding diagram. The secondary battery 200, except for having multiple electrode bodies 20, can have the same structure as the secondary battery 100 described above. The number of electrode bodies housed in a battery casing 10 is not particularly limited; it can be three as shown in the diagram, or four or more. In the case of having multiple (here, three) electrode bodies 20, as... Figure 10 As shown, the flat portions 20f of each electrode body can be arranged side by side so that they are opposite each other.

[0134] When multiple electrode bodies 20 are located within a battery casing 10, the weight tends to be greater than that of a single electrode body. In cases where the weight is approximately 1 kg or more, for example, 1.5 kg or more, and further, 2 to 3 kg, in the aforementioned configuration step S10, if... Figure 11 As shown, the electrode body 20 can be inserted into the outer casing 12 in such a way that the long sidewall 12b of the outer casing 12 intersects the direction of gravity (making the outer casing 12 laterally). Furthermore, when multiple electrode bodies 20 are present within a battery casing 10, the above-described peeling process S20 can be performed by forming a peeling area on at least one electrode body 20.

[0135] <Experimental Example>

[0136] 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.

[0137] 1. Configuration process

[0138] To make LiNi as the 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.

[0139] 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.

[0140] Additionally, as a spacer, a spacer in which an adhesive layer comprising alumina powder and polyvinylidene fluoride (PVdF) is formed on both sides of a porous polyethylene (PE) substrate layer is used. Furthermore, spacers with two adhesive layers of different thicknesses are prepared for use.

[0141] A laminated body, consisting of strip-shaped positive and negative electrode plates stacked together with spacers as described above, is fabricated. This laminated body is then wound to form a cylindrical shape. Next, the wound laminated body is stamped and flattened to create a flat, wound electrode body. The positive and negative terminals are connected to the fabricated wound electrode body and mounted on a battery casing with a liquid filling port. This results in the fabrication of an evaluation battery assembly.

[0142] 2. Peeling and pressurizing processes

[0143] In this experiment, for the battery assembly prepared above for evaluation, a stripping process was performed by changing the conditions of the heat treatment and the first depressurization treatment, followed by a pressurization process.

[0144] (1) Example 1

[0145] First, the evaluation battery assembly fabricated above was subjected to heat treatment. The heat treatment was performed at a heating rate of 5°C / min, a maximum temperature of 105°C, and a holding time at the maximum temperature of 3.5 hours. Next, four hours after the start of heating, a first decompression treatment was performed. This first decompression treatment was performed 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 4 hours. After the first decompression treatment, a pressurization (pressure recovery) process was performed to atmospheric pressure. Furthermore, the pressurization rate was set to 5000 Pa / min.

[0146] (2) Example 2

[0147] First, the battery assembly for evaluation prepared above was subjected to heat treatment. The heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first depressurization treatment was performed. The first depressurization treatment was performed under the same conditions as in Example 1. After the first depressurization treatment, a pressurization (pressure recovery) process to atmospheric pressure was performed. Furthermore, the pressurization rate was set to 80,000 Pa / min.

[0148] (3) Example 3

[0149] First, the battery assembly for evaluation prepared above was subjected to heat treatment. The heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first depressurization treatment was performed. After the first depressurization treatment, a pressurization process (pressure recovery) to atmospheric pressure was performed. The first depressurization treatment and the pressurization process were performed under the same conditions as in Example 1. Furthermore, the adhesive layer of the spacer in Example 3 was made thicker than that in Example 1.

[0150] (4) Example 4

[0151] First, the battery assembly for evaluation prepared above was subjected to heat treatment. Except that the maximum temperature was changed to 90°C, the heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first depressurization treatment was performed. After the first depressurization treatment, a pressurization process (pressure recovery) to atmospheric pressure was performed. The first depressurization treatment and the pressurization process were performed under the same conditions as in Example 1.

[0152] (5) Comparison Example 1

[0153] First, the battery assembly for evaluation prepared above was subjected to heat treatment. The heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first decompression treatment was performed. 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 under the same conditions as in Example 1.

[0154] (6) Comparison Example 2

[0155] First, the battery assembly for evaluation prepared above was subjected to heat treatment. The heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first decompression treatment was performed. The first decompression treatment was performed under the same conditions as in Example 1, except that the decompression rate was changed to 20 kPa / min. After the first decompression treatment, a pressurization (pressure recovery) process to atmospheric pressure was performed under the same conditions as in Example 1.

[0156] (7) Comparative Example 3

[0157] First, the battery assembly for evaluation prepared above was subjected to heat treatment. Except that the maximum temperature was changed to 60°C, the heat treatment was performed under the same conditions as in Example 1. Next, four hours after the start of heating, a first depressurization treatment was performed. After the first depressurization treatment, a pressurization process (pressure recovery) to atmospheric pressure was performed. The first depressurization treatment and the pressurization process were performed under the same conditions as in Example 1.

[0158] (8) Acquisition of X-ray CT images

[0159] 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 electrode body 20.

[0160] In the flat portion 20f of the electrode body 20, the distance D (μm) between the center of the thickness direction of one of the two adjacent positive electrode plates 22 in the stacking direction of the positive electrode plate 22 and the center of the thickness direction of the other positive electrode plate 22 is defined as the distance. The total thickness of all components existing between the aforementioned 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) is defined as the thickness T (μm). Then, it is determined that a peeling region exists in the portion where the distance D (μm) is 30 μm or more greater than the thickness T (μm). The results are shown in Table 1.

[0161] 3. Liquid injection process

[0162] The electrolyte injection process was performed on each embodiment and comparative example where the conditions of the stripping process were modified as described above. As the electrolyte used in the electrolyte injection process, an electrolyte containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of EC:EMC:DMC = 3:4:3, with LiPF6 dissolved at a concentration of 1.1 mol / L as the supporting salt, was prepared. 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.

[0163] During the injection process, the time until the injection is completed is measured. The ratio of the injection times of each embodiment and each comparative example when the injection time of Comparative Example 1 is set to 1 is shown in Table 1.

[0164] Table 1

[0165]

[0166] 4. Test Results

[0167] It can be seen that in the stripping process, the electrolyte injection time of Examples 1-4, where the maximum temperature of the heat treatment is above 80°C and the decompression rate of the first decompression treatment is 30-100 kPa / min, is very short compared to the comparative example. It can be inferred that this is because, by performing the heat treatment and the first decompression treatment under the above conditions, the positive electrode plate and the spacer, as well as the negative electrode plate and the spacer, are stripped, resulting in an electrode body with a stripped area, thereby making it easier for the electrolyte to penetrate. Therefore, by having an appropriate stripping process, it is possible to manufacture a more efficient and reliable secondary battery.

[0168] Furthermore, in the flat portion 20f of the 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 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.

[0169] In the flat portion 20f of an electrode body 20, when the total number of layers of the positive electrode plate 22 is N, the unit with the stripping region is preferably formed to have a thickness of 0.1N or more, and more preferably 0.2N or more.

[0170] In the central portion of the electrode body 20 along the winding axis, 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.

[0171] In the central portion of the electrode body 20 along the winding axis, 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 electrode body 20 is set to width W2 (mm) and the width of the peeling region 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.

[0172] 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 an electrode body and a battery casing housing the electrode body, the electrode body comprising a positive electrode, a negative electrode, and a spacer disposed between the positive electrode and the negative electrode. An adhesive layer is formed on both surfaces of the spacer. in, The method for manufacturing the secondary battery includes: In the configuration process, the electrode body, in which the positive electrode and the spacer are bonded together by the adhesive layer and the negative electrode and the spacer are bonded together by the adhesive layer, is disposed within the battery casing. A stripping process, wherein at least one of the positive electrode and the negative electrode is stripped from the spacer in the electrode body; and In the electrolyte injection process, following the stripping process, electrolyte is injected into the battery casing. The stripping process includes: A heat treatment, wherein the electrode body is heated; and The first decompression treatment involves decompressing the contents of the battery casing after the heat treatment. In the first decompression process, the pressure inside the battery casing is reduced at a rate of 30 kPa / min or higher.

2. The method for manufacturing a secondary battery according to claim 1, wherein, In the heat treatment, the temperature of the electrode body is heated to above 80°C. In the first decompression process, when the temperature of the electrode body reaches above 80°C, the pressure inside the battery casing is reduced. In the first decompression process, the pressure inside the battery casing is reduced to below 1 kPa at a rate of 30 kPa / min or higher and based on an absolute pressure reference.

3. The method for manufacturing a secondary battery according to claim 1, wherein, The electrode body is a flat, wound electrode body formed by winding the strip-shaped positive electrode and the strip-shaped negative electrode together with the strip-shaped spacer in between. The width of the negative electrode is 20cm or more.

4. The method for manufacturing a secondary battery according to claim 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.

5. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein, In the configuration process, a plurality of electrode bodies are configured inside the battery casing.

6. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein, After the stripping process and before the liquid injection process, the method for manufacturing the secondary battery further includes a pressurization process that increases the pressure inside the battery casing.

7. The method for manufacturing a secondary battery according to claim 6, wherein, The liquid injection process includes a second decompression process that reduces the pressure inside the battery casing after the pressurization process.

8. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein, Following the liquid injection step, the method for manufacturing the secondary battery includes an initial charging step for performing an initial charge on the secondary battery. The initial charging process is performed under constrained conditions on the secondary battery.

9. The method for manufacturing a secondary battery according to any one of claims 1 to 4, wherein, The spacer includes: A porous substrate layer made of polyolefin resin; and The adhesive layer formed on both surfaces of the substrate layer and comprising polyvinylidene fluoride (PVdF).

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