Method for manufacturing battery cell

Abstract

The present invention provides a method for manufacturing a battery cell capable of reducing energy loss associated with heating when manufacturing a dry electrode body by heating and bonding a self-supporting electrode film and an electrode foil. A method for manufacturing a battery cell (10) provided with a dry electrode body (3) in which a self-supporting electrode film (1) having an electrode active material (11), a conductive material (12), and binders (13, 14), and an electrode foil (2) having an undercoat layer (2P) formed on the upper surface (21) thereof are sandwiched and pressed by a press roll (7), and the electrode foil (2) and the electrode film (1) are bonded with each other via the undercoat layer. The method includes: a heating step (S1) in which at least one of bonding surfaces (HM (HM1, HM2)) on which a self-supporting electrode film and an electrode foil are bonded is heated to a desired temperature; and a bonding step (S2) in which, after the heating step, the self-supporting electrode film and the electrode foil are bonded by being pressed by a press roll (7).

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing battery cells for hybrid electric vehicles, electric vehicles, and the like. Background Technology

[0002] In conventional battery cell manufacturing methods, the electrode body is formed by coating an electrode foil with a paste-like solution made by mixing electrode active materials, conductive materials as additives, and binders using a solvent, followed by drying. However, this method suffers from the problem that the drying process, which involves evaporating the solvent, takes a significant amount of time. If the heating temperature during the drying process is rapidly increased to shorten this time, uneven distribution of the binder occurs due to solvent convection, and problems such as easy peeling of the electrode active material layer from the electrode foil also arise.

[0003] Therefore, the development of solvent-free dry electrode bodies has attracted attention in recent years. For example, Patent Document 1 discloses a method in which a self-supporting film containing an electrode active material, a conductive material, and a binder containing a fibrous polymer is bonded to an electrode foil coated with a base coating by applying pressure through a heated laminating roller, thereby manufacturing a dry electrode body.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2023-517975 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in the above method, pressure is applied by heated opposing rollers during the bonding of the self-supporting electrode film and the electrode foil. Therefore, the roller temperature is only transferred to the bonding surface of the self-supporting electrode film and electrode foil when they pass between each other, making it difficult to heat the bonding surface to the required temperature. Consequently, the roller temperature needs to be raised to a level exceeding the required temperature and maintained, resulting in significant energy loss.

[0009] This disclosure was made in view of the problem, and its objective is to provide a method for manufacturing a battery cell that can reduce the energy loss caused by heating during the manufacture of a dry electrode body by heating and bonding a self-supporting electrode film and an electrode foil.

[0010] Solution for solving the problem

[0011] (1) One aspect of the present disclosure for solving the above-mentioned problem is a method for manufacturing a battery cell, the battery cell comprising a dry electrode body, the dry electrode body being formed by pressing a self-supporting electrode film having an electrode active material, a conductive material and an adhesive and an electrode foil having a base coating formed on its upper surface by a pressure roller and bonding them together via the base coating, wherein the method for manufacturing the battery cell comprises: a heating step of heating at least one of the bonding surfaces of the self-supporting electrode film and the electrode foil to a desired temperature; and a bonding step of bonding the self-supporting electrode film and the electrode foil together by pressing them together by the pressure roller after the heating step.

[0012] (2) In the manufacturing method of the battery cell described in (1), preferably, the undercoating layer contains graphite particles as a conductive material, and in the heating process, the bonding surface of the electrode foil is heated by irradiating the undercoating layer with a laser.

[0013] (3) In the method for manufacturing a battery cell described in (1) or (2), preferably, it includes: a coating step of coating the base layer onto the electrode foil; and a drying step of drying the base layer coated in the coating step, wherein the drying step also serves as the heating step of heating the bonding surface of the electrode foil to a desired temperature.

[0014] (4) In any one of (1) to (3) the method for manufacturing a battery cell, it is preferable that the pressure roller has a roller control section for controlling the gap between the rollers to be constant. Attached Figure Description

[0015] Figure 1 This is a side view of a battery cell formed by a method of manufacturing a battery cell according to an embodiment of the present disclosure.

[0016] Figure 2 yes Figure 1 The flowchart shown is part of the manufacturing process of the battery cell, and is a process diagram of the manufacturing of the dry electrode.

[0017] Figure 3 It is a schematic representation Figure 2 A schematic cross-sectional view of the manufacturing process of the dry electrode shown.

[0018] Figure 4 yes Figure 3 A schematic cross-sectional view of part A shown. Detailed Implementation

[0019] <Overall Description of This Battery Cell>

[0020] Below, please refer to the attached diagram ( Figures 1-4This describes in detail the overall structure of the battery cell (hereinafter also referred to as "this battery cell") formed by the manufacturing method of the battery cell according to the above-disclosed technology. Figure 1 A side view showing a battery cell formed by a method of manufacturing a battery cell according to an embodiment of the present disclosure. Figure 2 express Figure 1 The flowchart shown is part of the manufacturing method of the battery cell, illustrating the manufacturing process of the dry electrode. Figure 3 Indicative of Figure 2 A schematic cross-sectional view of the manufacturing process of the dry electrode shown. Figure 4 express Figure 3 A schematic cross-sectional view of part A is shown. Furthermore... Figure 1 The X direction represents the long side direction (axial direction) of the main body of the housing, the Y direction represents the short side direction of the main body of the housing, and the Z direction represents the width direction of the short side face of the main body of the housing. In addition, the X direction is also the width direction of the electrode foil, the Y direction is also the long side direction of the electrode foil, and the Z direction is also the stacking direction of the electrode foil.

[0021] like Figures 1-4 As shown, the battery cell 10 is a battery cell 10 having a dry electrode body 3. The dry electrode body 3 is formed by pressing a self-supporting electrode film 1 having an electrode active material 11, a conductive material 12 and adhesives 13 and 14 with a pressure roller 7 and an electrode foil 2 having a base coating 2P formed on its upper surface 21 and bonding it together with the base coating 2P.

[0022] Here, the self-supporting electrode film 1 is formed by applying shear force to a mixture comprising, for example, electrode active material 11, conductive material 12, and binders 13 and 14, to create an electrode film of a predetermined thickness capable of self-support, and includes binder 14 which is fibrousized by shear force. The conductive material 12 can be, for example, carbon nanotubes (CNTs) or carbon black (CB). The binders 13 and 14 can be, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF). Furthermore, the base coating 2P comprises conductive material 2P1 such as graphite particles and binder 2P2, which are mixed with a suitable solvent and coated onto the electrode foil 2. The binder 2P2 can be, for example, polyvinylidene fluoride (PVDF) or styrene-butadiene rubber (SBR), and can be either a thermoplastic resin or a thermosetting resin. Additionally, in the dry electrode body 3, the positive electrode dry electrode body 3a and the negative electrode dry electrode body 3b are stacked with a separator 4 in between.

[0023] like Figure 1As shown, the battery cell 10 includes a battery casing 6 for housing the dry electrode 3. The battery casing 6 comprises a rectangular cylindrical body 61 with rectangular openings 611 at both ends along its long side (X direction) and a flat cover 62 that seals the openings 611. The positive electrode current collector 5a, connected to the tab TB of the positive dry electrode 3a, and the negative electrode current collector 5b, connected to the tab TB of the negative dry electrode 3b, are fixed to the cover 62 via an insulating material 5Z. The insulating material 5Z can be, for example, polyphenylene sulfide (PPS) resin.

[0024] Furthermore, the battery casing 6 is not necessarily limited to the above-described structure. For example, the battery casing 6 may also be a structure having a bottomed cylindrical casing body 61 with an opening 611 at one end in the long side direction (X direction) and a flat cover 62 that seals the opening 611. Additionally, the casing body 61 may also be cylindrical. Both the casing body 61 and the cover 62 are made of aluminum, but are not necessarily limited to this; for example, they may also be made of stainless steel.

[0025] This battery cell 10 can be applied to various battery cells; here, a lithium-ion secondary battery is used as an example. In this case, the positive electrode foil 2a can, for example, be an aluminum foil with a thickness of about 10 to 15 μm, and the electrode active material 11a can, for example, be a lithium transition metal oxide (LiNi). 1／3 Co 1／3 Mn 1／3 (O2, LiNiO2, etc.). Additionally, the negative electrode foil 2b can be, for example, a copper foil with a thickness of about 10-15 μm, and the electrode active material 11b can be, for example, graphite, hard carbon, soft carbon, etc. The positive electrode current collector 5a can be an aluminum plate, and the negative electrode current collector 5b can be a copper plate. Furthermore, the separator SP can be, for example, a porous sheet material such as polypropylene or polyethylene.

[0026] <Manufacturing Method of This Battery Cell>

[0027] Below, please refer to the attached diagram ( Figures 1-4 This section details the manufacturing method of the battery cell. Specifically, as... Figures 1-4As shown, the manufacturing method of this battery cell is a method for manufacturing battery cell 10. The battery cell 10 includes a dry electrode body 3, which is formed by pressing a self-supporting electrode film 1 having electrode active material 11, conductive material 12, and adhesives 13 and 14 onto an electrode foil 2 having a base coating 2P formed on its upper surface 21 using pressure rollers 7, and then bonding them together via the base coating 2P. The manufacturing method of this battery cell includes: a heating step S1 in which at least one of the bonding surfaces HM (HM1, HM2) of the self-supporting electrode film 1 and the electrode foil 2 is heated to a desired temperature; and a bonding step S2 in which, after the heating step S1, the self-supporting electrode film 1 and the electrode foil 2 are bonded together by pressing them together using pressure rollers 7. The opposing cylindrical rollers 71 and 72 of the pressure rollers 7 rotate in opposite directions R1 and R2 at the same circumferential speed. Here, a pressurizing device 73 is installed to pressurize the roller 71 that abuts against the electrode foil 2 with a specified clamping pressure P against the roller 71 that abuts against the self-supporting electrode film 1.

[0028] Furthermore, in the manufacturing method of the battery cell 10, the pre-processes of the heating process S1 include an electrode film forming process for forming a self-supporting electrode film 1 and an electrode foil forming process for forming an electrode foil 2 coated with a base coating 2P. Additionally, the post-processes of the bonding process S2 include a battery assembly process where a dry electrode body 3, formed by stacking a positive electrode dry electrode body 3a and a negative electrode dry electrode body 3b across a separator 4, is placed in a battery casing 6 and sealed, and an adjustment process involving initial charging and aging. All of the above processes are known processes, therefore, their descriptions are omitted here.

[0029] As described above, before bonding the self-supporting electrode film 1 and the electrode foil 2 with the base coating 2P by clamping them together with the pressure roller 7, a heating step S1 is included, in which at least one of the bonding surfaces HM (HM1, HM2) of the self-supporting electrode film 1 and the electrode foil 2 is heated to a required temperature. Therefore, even without directly heating the pressure roller 7, the bonding surfaces HM of the self-supporting electrode film 1 and the electrode foil 2 can be heated to the required temperature for bonding. Compared with the case where the bonding surfaces HM of the self-supporting electrode film 1 and the electrode foil 2 are heated by the heated pressure roller 7, the energy loss of the heat energy required for this heating is less, and the required heat energy can be significantly reduced. Therefore, a method for manufacturing a battery cell 10 can be provided that reduces the energy loss caused by heating during the manufacturing of the dry electrode body 3 by heating and bonding the self-supporting electrode film 1 and the electrode foil 2.

[0030] Here, as Figure 2 , Figure 3As shown, in the heating process S1, the bonding surface HM1 of the self-supporting electrode film 1, which is horizontally conveyed toward the pressure roller 7, is heated by heating device 81, and the bonding surface HM2 of the electrode foil 2, which is horizontally conveyed toward the pressure roller 7 from the opposite side, is heated by another heating device 82. To uniformly heat both the self-supporting electrode film 1 and the undercoating layer 2P of the electrode foil 2, the heating devices 8 (81, 82) preferably irradiate each bonding surface HM1, HM2 with a uniformly diffused planar laser 8L. The planar laser 8L is formed, for example, when the laser 8L of a semiconductor laser passes through a special homogenizer such as a hexagonal grinding rod. Furthermore, the heating devices 8 (81, 82) are not necessarily limited to devices that irradiate a uniformly diffused planar laser 8L. For example, they could also be heating devices 8 (81, 82) that emit far-infrared rays from a planar heating element such as ceramic.

[0031] Furthermore, the heating temperature of the bonding surfaces HM1 and HM2 is preferably set within the operating temperature of the adhesives 13, 14, and 2P2 of the self-supporting electrode film 1 and the base coating 2P. For example, when the adhesive is polytetrafluoroethylene (PTFE), heating can be performed at approximately 250°C, and when the adhesive is polyvinylidene fluoride (PVDF), heating can be performed at approximately 150°C. In this case, such as Figure 4 As shown, the conductive material 2P1, such as graphite particles, of the base coating 2P is embedded in the gaps between the electrode active material 11 of the softened self-supporting electrode film 1, which can improve the conductivity and the anchoring effect.

[0032] Furthermore, when one of the bonding surfaces HM (HM1, HM2) of the self-supporting electrode film 1 and the electrode foil 2 is heated to the required temperature, the heat of the heated bonding surface HM is transferred to the other bonding surface HM when the self-supporting electrode film 1 and the electrode foil 2 are clamped by the pressure roller 7. This can also improve the conductivity of the self-supporting electrode film 1 and the electrode foil 2 in the bonded state and improve the anchoring effect.

[0033] In the manufacturing method of the battery cell 10, it is preferable that the undercoating 2P formed on the upper surface 21 of the electrode foil 2 contains graphite particles as a conductive material 2P1, and in the heating step S1, the bonding surface HM2 of the electrode foil 2 is heated by irradiating the undercoating 2P with laser 8L. More preferably, the weight ratio of graphite particles 2P1 in the undercoating 2P is about 80 to 90%. In this case, the light absorption rate of laser 8L relative to the undercoating 2P can be improved by the graphite particles 2P1, and the heat energy required to heat the electrode foil 2 can be further reduced.

[0034] Furthermore, in the manufacturing method of this battery cell 10, it is preferable to, as follows: Figure 2 , Figure 3As shown, the process includes: a coating step S3 in which a base coating layer 2P is applied to the electrode foil 2; and a drying step S4 in which the base coating layer 2P applied in the coating step S3 is dried. The drying step S4 also serves as a heating step S1 in which the bonding surface HM2 of the electrode foil 2 is heated to the required temperature. Here, a coating device 9 for the base coating layer 2P is provided on the upstream side of the electrode foil 2 in the feed direction and adjacent to the heating device 82. By heating the bonding surface HM2 of the electrode foil 2, the heating device 82 can evaporate the solvent contained in the base coating layer 2P applied by the coating device 9 and heat the bonding surface HM2 of the electrode foil 2 to the required temperature for bonding. Therefore, the heating step S1 and the drying step S4 are both utilized.

[0035] In this case, the heat energy from drying the base coating 2P in the drying process S4 can be effectively utilized to heat the bonding surface HM, where the self-supporting electrode film 1 and the electrode foil 2 are bonded, to the required bonding temperature. Therefore, the heat energy required to heat the bonding surface HM can be further reduced. Furthermore, since the base coating 2P can be heated to the required bonding temperature for the self-supporting electrode film 1 and the electrode foil 2 in the drying process S4, the dry electrode body 3, formed by bonding the self-supporting electrode film 1 and the electrode foil 2, can be easily formed by subsequently pressing the self-supporting electrode film 1 and the electrode foil 2 together with the pressure roller 7. In this case, it is also unnecessary to temporarily store the electrode foil 2 with the base coating 2P formed on it.

[0036] Furthermore, in the manufacturing method of this battery cell 10, it is preferable to, as follows: Figure 3 As shown, the pressure roller 7 includes a roller control unit 72 that controls the gap d1 between the rollers 71 to be constant. Here, it includes: a pressure device 73 that applies pressure to one of the rollers 71 constituting the pressure roller 7 relative to the other roller 71; and a roller control unit 72 that calculates the gap d1 between the rollers 71 based on the amount of movement of the roller 71 by the pressure device 73 and controls the gap d1 to be constant.

[0037] In this case, by heating the bonding surface HM to the required temperature in the heating process S1, even if the temperature of the roller 71 rises and the roller diameter expands, the roller control unit 72 can issue a command to the pressure device 73 to keep the gap d1 between the rollers 71 constant. Therefore, the clamping pressure P of the pressure roller 7 relative to the self-supporting electrode film 1 and the electrode foil 2 can be maintained at a predetermined pressure. Thus, excessive elongation and breakage of the self-supporting electrode film 1 and the electrode foil 2 can be suppressed.

[0038] <Variation Example>

[0039] The embodiments described above are merely illustrative and do not limit the technology disclosed herein. Therefore, the technology disclosed herein can be modified and modified in various ways without departing from its spirit.

[0040] Explanation of reference numerals in the attached figures

[0041] 1 Self-supporting electrode film

[0042] 2. Electrode foil

[0043] 2P base coat

[0044] 2P1 conductive material, graphite particles

[0045] 3. Dry electrode body

[0046] 7. Pressure rollers

[0047] 8L laser

[0048] 10 battery cells

[0049] 11 Electrode active materials

[0050] 12 Conductive Materials

[0051] 13, 14 Adhesive

[0052] 21. Upper surface

[0053] 71 rolls

[0054] 72 Roller Control Section

[0055] HM, HM1, HM2 bonding surfaces

[0056] S1 Heating Process

[0057] S2 Pasting process

[0058] S3 Coating Process

[0059] S4 Drying process.

Claims

1. A method for manufacturing a battery cell, the battery cell comprising a dry electrode body, the dry electrode body being formed by pressing a self-supporting electrode film having electrode active material, conductive material and binder with pressure rollers and an electrode foil having a base coating formed on its upper surface, and then bonding them together via the base coating, wherein, The method for manufacturing the battery cell includes: A heating process that heats at least one of the bonding surfaces of the self-supporting electrode film and the electrode foil to a desired temperature; and The bonding process is performed after the heating process, in which the self-supporting electrode film and the electrode foil are pressed together by the pressure rollers.

2. The method for manufacturing a single battery cell according to claim 1, wherein, The base coating contains graphite particles as a conductive material. In the heating process, the bonding surface of the electrode foil is heated by irradiating the base coating with a laser.

3. The method for manufacturing a battery cell according to claim 1 or 2, wherein, The method for manufacturing the battery cell includes: The coating process of applying the base coating onto the electrode foil; and A drying process that dries the base coating applied in the coating process. The drying process also serves as the heating process for heating the bonding surface of the electrode foil to the required temperature.

4. The method for manufacturing a battery cell according to any one of claims 1 to 3, wherein, The pressure roller has a roller control section that controls the gap between the rollers to be constant.

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