JP6981085B2 - How to manufacture a secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery. In particular, the present invention relates to a method for manufacturing a secondary battery including an electrode assembly including an electrode laminated structure.

Since the secondary battery is a so-called storage battery, it can be repeatedly charged and discharged, and is used for various purposes. For example, secondary batteries are used in mobile devices such as mobile phones, smartphones and notebook computers.

The secondary battery is composed of at least a positive electrode, a negative electrode and a separator between them. The positive electrode is composed of a positive electrode material layer and a positive electrode current collector, and the negative electrode is composed of a negative electrode material layer and a negative electrode current collector. In the electrode assembly of the secondary battery, a plurality of such positive electrodes and negative electrodes are laminated via a separator and housed in an exterior body.

Japanese Unexamined Patent Publication No. 2014-12456 Japanese Patent Application Laid-Open No. 2015-536024

The inventor of the present application noticed that there is a problem to be overcome with the conventional secondary battery, and found that it is necessary to take measures for that. Specifically, the inventor of the present application has found that there are the following problems.

The electrode assembly having a planar laminated structure has an electrode laminated structure in which electrode layers of a positive electrode and a negative electrode are stacked on each other via a separator. In order to obtain such an electrode assembly, it is not easy to obtain the accuracy of laminating after going through the laminating process.

Specifically, when laminating the electrode assembly, it may be required to reduce the laminating misalignment at a high level on the order of microns in order to obtain a desired secondary battery. Here, for the outermost layer of the electrode assembly, an element different from most of the other electrode assembly elements in terms of lamination may be used, and it is preferable to consider matters peculiar to the outermost layer. Was found by the inventor of the present application. For example, unlike double-sided electrodes, which can occupy most of the electrode assembly, single-sided electrodes are used in the outermost layer to increase energy density, or metal sheets are used in the outermost layer to suppress heat generation during short circuits. It may be done.

The present invention has been made in view of such a problem. That is, a main object of the present invention is to provide a technique for manufacturing a secondary battery, which is particularly suitable for laminating the outermost layer of an electrode assembly.

The inventor of the present application has attempted to solve the above-mentioned problems by dealing with it in a new direction, rather than dealing with it as an extension of the prior art. As a result, we have invented a technology for manufacturing a secondary battery that achieves the above-mentioned main purpose.

The present invention is a method for manufacturing a secondary battery including an electrode assembly including an electrode laminated structure.
A metal layer is used as the outermost layer in the electrode assembly,
A secondary battery in which an image of a metal layer is taken when the metal layer is laminated on an electrode assembly precursor that does not yet contain at least the outermost layer as a configuration of the electrode assembly, and the position of the outermost layer is detected through the image pickup. A manufacturing method is provided.

The present invention provides a stacking technique that is particularly suitable for the outermost layer of the electrode assembly. Therefore, it becomes easy to obtain a desired secondary battery.

In particular, when a single-sided electrode is used as the outermost layer of the electrode assembly, the stacking deviation is further reduced, so that the desired high energy density can be easily achieved in the obtained secondary battery. Further, when the metal sheet is used for the outermost layer for suppressing heat generation at the time of short circuit, it becomes easy to suppress or avoid deterioration of the shape accuracy of the electrode assembly due to it.

Schematic cross-sectional view for explaining an electrode assembly having a two-dimensional laminated structure. Schematic diagram for explaining the manufacturing method of the present invention Schematic diagram to explain the laminating process with clearer outermost layer edges Schematic diagram for explaining a laminating process using an electrode current collector in a single-sided electrode as the outermost metal layer. Schematic diagram for explaining a laminating process using a metal foil of a single-sided electrode having a shine surface and a matte surface as an outermost metal layer. Schematic diagram for explaining the laminating process using a metal sheet as the outermost metal layer Schematic diagram for explaining the mode in which the outermost metal layer causes halation.

Hereinafter, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described in more detail. Although explanations will be given with reference to the drawings as necessary, the various elements in the drawings are merely schematically and exemplary for the purpose of understanding the present invention, and the appearance, dimensional ratio, etc. may differ from the actual ones. ..

The "plan view (or plan view)" described directly or indirectly in the present specification is the stacking direction of the electrode material layers constituting the secondary battery (thickness direction of the battery, the electrode assembly, or the electrode material layer). It is based on the form when the object is grasped from the outside along the line. Further, the “cross-sectional view (or cross-sectional view)” described directly or indirectly in the present specification is along the stacking direction of the electrode material layers constituting the secondary battery (thickness direction of the battery or the electrode material layer). It is based on a virtual cross section of an object.

Further, the vertical direction and the horizontal direction used directly or indirectly in the present specification correspond to the vertical direction and the horizontal direction in the figure, respectively. Unless otherwise specified, the same sign or symbol shall indicate the same member or the same meaning.

[Structure of the secondary battery manufactured by the present invention]
A secondary battery can be obtained by the manufacturing method of the present invention. The term "secondary battery" as used herein refers to a battery that can be repeatedly charged and discharged. Therefore, the secondary battery obtained by the manufacturing method of the present invention is not excessively bound by its name, and may include, for example, a power storage device.

The secondary battery according to the present invention includes an electrode assembly having an electrode laminated structure in which electrode constituent layers including a positive electrode, a negative electrode, and a separator are laminated. FIG. 1 schematically illustrates an electrode assembly. As shown in the figure, the positive electrode 1 and the negative electrode 2 are stacked via the separator 3 to form an electrode constituent layer 10, and at least one such electrode constituent layer 10 is laminated to form an electrode assembly. There is. In a secondary battery, such an electrode assembly is enclosed in an exterior body together with an electrolyte (for example, a non-aqueous electrolyte).

The positive electrode is composed of at least a positive electrode material layer and a positive electrode current collector. In the positive electrode, a positive electrode material layer is provided on at least one surface of the positive electrode current collector, and the positive electrode material layer contains a positive electrode active material as an electrode active material. For example, each of the plurality of positive electrodes in the electrode assembly may be provided with a positive electrode material layer on both sides of the positive electrode current collector, or may be provided with a positive electrode material layer on only one side of the positive electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, the positive electrode may be provided with positive electrode material layers on both sides of the positive electrode current collector.

The negative electrode is composed of at least a negative electrode material layer and a negative electrode current collector. In the negative electrode, a negative electrode material layer is provided on at least one surface of the negative electrode current collector, and the negative electrode material layer contains a negative electrode active material as an electrode active material. For example, each of the plurality of negative electrodes in the electrode assembly may be provided with a negative electrode material layer on both sides of the negative electrode current collector, or may be provided with a negative electrode material layer on only one side of the negative electrode current collector. .. From the viewpoint of further increasing the capacity of the secondary battery, the negative electrode may be provided with negative electrode material layers on both sides of the negative electrode current collector.

The electrode active materials contained in the positive and negative electrodes, that is, the positive electrode active material and the negative electrode active material, are substances that are directly involved in the transfer of electrons in the secondary battery, and are the main substances of the positive and negative electrodes that are responsible for charge / discharge, that is, the battery reaction. be. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", and such ions are transferred between the positive electrode and the negative electrode. The electrons are transferred and charged and discharged. The positive electrode material layer and the negative electrode material layer are particularly preferably layers that can occlude and release lithium ions. That is, it is preferable that the non-aqueous electrolyte secondary battery is a non-aqueous electrolyte secondary battery in which lithium ions move between the positive electrode and the negative electrode via the non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging / discharging, the secondary battery obtained by the production method of the present invention corresponds to a so-called lithium ion battery, and the positive electrode and the negative electrode have layers capable of occluding and discharging lithium ions.

Since the positive electrode active material of the positive electrode material layer is made of, for example, granules, it is preferable that the positive electrode material layer contains a binder (also referred to as a binder) for sufficient contact between particles and shape retention. Further, a conductive auxiliary agent may be contained in the positive electrode material layer in order to facilitate the transfer of electrons that promote the battery reaction. Similarly, when the negative electrode active material of the negative electrode material layer is composed of, for example, granules, it is preferable that the negative electrode active material contains a binder for sufficient contact between particles and shape retention, and facilitates the transfer of electrons that promote the battery reaction. A conductive auxiliary agent may be contained in the negative electrode material layer. As described above, since the form is composed of a plurality of components, the positive electrode material layer and the negative electrode material layer can also be referred to as a positive electrode mixture layer and a negative electrode mixture layer, respectively.

The positive electrode active material is preferably a substance that contributes to the occlusion and release of lithium ions. From this point of view, the positive electrode active material is preferably, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese and iron. That is, such a lithium transition metal composite oxide is preferably contained as a positive electrode active material in the positive electrode material layer of the secondary battery obtained by the production method of the present invention. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium iron phosphate, or a part of the transition metal thereof replaced with another metal. Such a positive electrode active material may be contained as a single species, but may be contained in combination of two or more species. Although it is merely an example, in the secondary battery obtained by the production method of the present invention, the positive electrode active material contained in the positive electrode material layer may be lithium cobalt oxide.

The binder obtained contained in the cathode material layer, is not particularly limited, polyvinylidene mold Niri Den, bi Niri Den fluoride - hexafluoropropylene copolymer, bi Niri Den fluoride - tetra fluorothiazol Ren copolymerization At least one selected from the group consisting of coalesced and polytetrafluoroethylene and the like can be mentioned. The conductive auxiliary agent that can be contained in the positive electrode material layer is not particularly limited, but is limited to carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon nanotubes and vapor phase growth. At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. For example, the binder of the positive electrode material layer may be polyvinylidene fluoride, and the conductive auxiliary agent of the positive electrode material layer may be carbon black. Although only an example, the binder and the conductive auxiliary agent of the positive electrode material layer may be a combination of polyvinylidene fluoride and carbon black.

The negative electrode active material is preferably a substance that contributes to the occlusion and release of lithium ions. From this point of view, the negative electrode active material is preferably, for example, various carbon materials, oxides, lithium alloys, or the like.

Examples of various carbon materials for the negative electrode active material include graphite (natural graphite, artificial graphite), hard carbon, soft carbon, and diamond-like carbon. In particular, graphite is preferable because it has high electron conductivity and excellent adhesion to a negative electrode current collector. As the oxide of the negative electrode active material, at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, lithium oxide and the like can be mentioned. The lithium alloy of the negative electrode active material may be any metal that can be alloyed with lithium, for example, Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, It may be a binary, ternary or higher alloy of a metal such as La and lithium. It is preferable that such an oxide is amorphous as its structural form. This is because deterioration due to non-uniformity such as grain boundaries or defects is less likely to occur. Although it is merely an example, in the secondary battery obtained by the manufacturing method of the present invention, the negative electrode active material of the negative electrode material layer may be artificial graphite.

The binder that can be contained in the negative electrode material layer is not particularly limited, but is at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide-based resin, and polyamide-imide-based resin. Can be mentioned. For example, the binder contained in the negative electrode material layer may be styrene-butadiene rubber. The conductive auxiliary agent that can be contained in the negative electrode material layer is not particularly limited, but is limited to carbon black such as thermal black, furnace black, channel black, ketjen black and acetylene black, graphite, carbon nanotubes and vapor phase growth. At least one selected from carbon fibers such as carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives can be mentioned. The negative electrode material layer may contain a component derived from the thickener component (for example, carboxylmethyl cellulose) used at the time of manufacturing the battery.

Although only an example, the negative electrode active material and the binder in the negative electrode material layer may be a combination of artificial graphite and styrene-butadiene rubber.

The positive electrode current collector and the negative electrode current collector used for the positive electrode and the negative electrode are members that contribute to collecting and supplying electrons generated by the active material due to the battery reaction. Such a current collector may be a sheet-shaped metal member and may have a perforated or perforated form. For example, the current collector may be a metal foil, a punching metal, a net, an expanded metal, or the like. The positive electrode current collector used for the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel and the like, and may be, for example, an aluminum foil. On the other hand, the negative electrode current collector used for the negative electrode is preferably made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel and the like, and may be, for example, a copper foil.

The separator used for the positive electrode and the negative electrode is a member provided from the viewpoint of preventing a short circuit due to contact between the positive and negative electrodes and retaining an electrolyte. In other words, it can be said that the separator is a member that allows ions to pass through while preventing electronic contact between the positive electrode and the negative electrode. Preferably, the separator is a porous or microporous insulating member and has a film morphology due to its small thickness. Although only an example, a microporous film made of polyolefin may be used as a separator. In this respect, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or polypropylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of a "microporous membrane made of PE" and a "microporous membrane made of PP". The surface of the separator may be covered with an inorganic particle coat layer, an adhesive layer, or the like. The surface of the separator may have adhesiveness. In the present invention, the separator should not be particularly bound by its name, and may be a solid electrolyte having the same function, a gel-like electrolyte, insulating inorganic particles, or the like.

In the secondary battery obtained by the production method of the present invention, an electrode assembly composed of an electrode constituent layer including a positive electrode, a negative electrode and a separator is enclosed in an exterior together with an electrolyte. When the positive electrode and the negative electrode have a layer capable of occluding and releasing lithium ions, the electrolyte is preferably an "non-aqueous" electrolyte such as an organic electrolyte / organic solvent (that is, the electrolyte is a non-aqueous electrolyte). preferable). In the electrolyte, metal ions emitted from the electrodes (positive electrode / negative electrode) are present, and therefore, the electrolyte assists the movement of the metal ions in the battery reaction.

A non-aqueous electrolyte is an electrolyte containing a solvent and a solute. As a specific solvent for the non-aqueous electrolyte, a solvent containing at least carbonate is preferable. Such carbonates may be cyclic carbonates and / or chain carbonates. Although not particularly limited, the cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC). be able to. Examples of the chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) and dipropyl carbonate (DPC). Although only an example, a combination of cyclic carbonates and chain carbonates may be used as the non-aqueous electrolyte, and for example, a mixture of ethylene carbonate and diethyl carbonate is used. Further, as a specific non-aqueous electrolyte solute, for example, Li salts such as _{LiPF 6} and / or LiBF _{4 are preferably used.}

A metal sheet may be used for the electrode assembly of the secondary battery in order to suppress heat generation at the time of short circuit. For example, a metal sheet may be used to form the outermost metal layer of the electrode assembly. The metal sheet may be a metal foil containing at least one selected from the group consisting of aluminum, copper, stainless steel, nickel and the like.

The exterior body of the secondary battery encloses the electrode assembly in which the electrode constituent layers including the positive electrode, the negative electrode, and the separator are laminated, but may be in the form of a hard case or may be in the form of a soft case. good. Specifically, the exterior body may be a hard case type corresponding to a so-called metal can, or may be a soft case type corresponding to a pouch made of a so-called laminated film.

[Characteristics of the manufacturing method of the present invention]
The manufacturing method of the present invention is characterized in the manufacturing process of the electrode assembly. In particular, the present invention is characterized by a laminating process of the outermost layers of the electrode assembly. Specifically, when the metal layer is laminated and arranged on the electrode assembly precursor that does not yet contain at least the outermost layer as the configuration of the electrode assembly, the metal layer is imaged, and the position of the outermost layer is detected through the image pickup.

As shown in FIG. 2, the metal layer 50 used as the outermost layer of the electrode assembly 100 is imaged by the image pickup means 60. That is, for laminating the metal layer 50, the metal layer 50 is imaged from the outside to detect the position, and the metal layer 50 is arranged with respect to the electrode assembly precursor 100'based on the information of the position detection. It is preferable that the metal layer 50 (hereinafter, also referred to as “outermost metal layer”) used as the outermost layer is imaged under illumination. That is, as shown in the figure, it is preferable to take an image of the outermost metal layer 50 while irradiating the outermost metal layer 50 with light using at least one irradiation light source 70.

In a broad sense, "imaging" as used herein means to photograph a metal layer as a subject from the outside in laminating an electrode assembly, and visually observe the laminating process of the outermost layer based on the position information of the obtained metal layer. It means to become. In a narrow sense, "imaging" is to photograph the outermost layer from above, especially when laminating the metal layer forming the outermost layer of the electrode assembly, and visualize the process of laminating the outermost layer through the obtained images and videos. It means that.

The image pickup means 60 is not particularly limited as long as it can visualize the stacking process of the outermost layer. For example, the image pickup means 60 may be a video camera, a digital camera, or the like. Specific examples of the imaging means include a CCD camera, a CMOS camera, an infrared camera, a near-infrared camera, a mid-infrared camera, an X-ray camera, and the like, and further, a laser microscope (laser microscope) and A laser interferometer or the like can also be mentioned.

In the imaging in the present invention, the process of laminating the outermost layer is visualized, and in particular, the position of the metal layer which is the outermost layer is detected. For the outermost layer of the electrode assembly, an element different from other components of the electrode assembly may be used. For example, a so-called double-sided electrode (an electrode having electrode material layers on both main surfaces of an electrode collector) is used as the main constituent electrode of the electrode assembly, while the outermost electrode of the electrode assembly is a so-called single-sided electrode. An electrode (an electrode having an electrode material layer provided only on one main surface of an electrode current collector) may be used to improve the energy density. In such a case, the electrode current collector in the single-sided electrode corresponds to the outermost layer of the electrode assembly. Further, a non-electrode element that does not form an electrode laminated structure may be used on the outermost side of the electrode assembly. For example, a metal sheet may be used as the outermost metal layer of the electrode assembly to suppress heat generation during an inconvenient short circuit.

When such a metal layer is used as the outermost layer of the electrode assembly, the metal layer imaged as a subject can be an image image different from the electrode material layer (positive electrode material layer / negative electrode material layer), and the stacking deviation is high. The inventor of the present application has found that in order to reduce the amount of the metal layer, it is necessary to grasp the edge of the metal layer more accurately. For example, in the metal layer used as the outermost layer, the edge of the outermost layer may be blurred due to the degree of light reflection and / or reflection of the irradiation light. Therefore, from this point of view, the present invention preferably detects the position of the outermost layer more accurately and stacks the outermost layer.

In particular, when the outermost metal layer is imaged under illumination, halation may occur due to the light from the irradiation light source, and it may be difficult to more accurately detect the position of the outermost metal layer in the image pickup image (FIG. 7). ). Therefore, the light intensity of the irradiation light source may be adjusted and / or the direction of light incident on the outermost metal layer may be adjusted so that halation does not occur.

In one preferred embodiment of the present invention, the main surface of the metal layer, which is the outermost exposed surface in the electrode assembly, is subjected to a treatment for changing the surface roughness. This is because halation is reduced particularly effectively and more accurate position detection of the outermost metal layer can be performed in the image pickup image. The main surface of the outermost metal layer, which is the outermost exposed surface, is the surface directly exposed to the light from the irradiation light source, and halation can be reduced more efficiently by changing the surface roughness of the surface. .. More specifically, by increasing the degree of surface roughness on the main surface of the metal layer to be the outermost exposed surface (that is, by making the main surface of the metal layer to be the outermost exposed surface rougher than the initial surface). ), Halation may be reduced more effectively. When the halation is reduced in this way, the outermost metal layer edge 51 becomes clearer in the image pickup image 80 for laminating the outermost metal layer 50 (see FIG. 3), and the position of the outermost metal layer 50 becomes more accurate. Detection can be brought about.

Although only an example, the main surface of the metal layer to be the outermost exposed surface may be subjected to at least one selected from the group consisting of etching treatment, blast treatment, laser treatment and surface coating treatment. This is because the main surface of the metal, which is the outermost exposed surface, can be made rougher.

The etching process is a process of changing the surface roughness by bringing the etching solution into contact with the main surface of the metal layer which is the outermost exposed surface. As the etching solution, a solution containing an acid, an alkali, or the like may be used. The acid is preferably an inorganic acid and may be, for example, at least one selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid. On the other hand, the alkali may be a conventional one for etching treatment, and may be at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonia and the like.

The blasting process is a process of spraying an abrasive on the main surface of the metal layer, which is the outermost exposed surface, to change the surface roughness. As the blasting treatment, for example, sandblasting treatment / air blasting treatment may be performed. That is, an air blast process using ground particles or the like may be performed. Wet blasting may be performed.

The laser treatment is a treatment for changing the surface roughness by irradiating the main surface of the metal layer, which is the outermost exposed surface, with a laser. For example, as the laser, an excimer laser, a semiconductor laser, a YAG laser, a CO ₂ laser, a femtosecond laser, or the like may be used. In particular, an excimer laser or a UV-YAG laser is preferable in terms of less heat damage.

The surface coating treatment is a treatment for changing the surface roughness by applying a surface coating material to the main surface of the metal layer which is the outermost exposed surface. As the specific surface coating material, any suitable material may be used as long as it contributes to the change of the surface roughness of the metal layer by forming the coating layer or the coating film.

By making the surface of the outermost exposed surface rougher in this way, halation is reduced more effectively, and it becomes easier to grasp the edge of the outermost metal layer more accurately. That is, in the image / video obtained by imaging, the edge of the outermost metal layer can be grasped more accurately without inconveniently blurring the edge contour of the outermost metal layer, and the positioning for laminating the outermost metal layer can be more accurately performed. Can be carried out. Therefore, in the laminating process of the electrode assembly, the laminating deviation can be reduced at a high level on the order of microns (μm), and the laminating accuracy can be improved. Such improvement in stacking accuracy is particularly preferable in terms of increasing energy density and the like.

The lamination of the metal layer as the outermost layer will be described in detail. In the present invention, the means for laminating the outermost layers can be suitably controlled based on the information obtained by imaging, and the positioning for laminating the outermost layers can be performed more accurately. That is, where the edge contour of the outermost layer can be grasped more accurately through imaging, the outermost layer is in a state where the stacking means (for example, a suction pad tool) is more preferably controlled based on the information to reduce the stacking deviation. Can be placed on the electrode assembly precursor. In other words, the information obtained by imaging in the present invention is fed back to the stacking means (for example, a suction pad tool), and is suitably used for the stacking arrangement of the outermost layer. From such a viewpoint, the laminating device preferably includes means for controlling the laminating means such as a suction pad tool based on the information of the edge contour of the outermost layer obtained by the imaging means. For example, when carrying out the stacking arrangement of the outermost layer, the edge contour of the outermost layer is measured in real time through imaging, and the measured data is used in the stacking means. The stacking device is preferably provided with arithmetic means for constructing control data for stacking arrangement of the outermost layer based on the measured data. The control means itself represented by the arithmetic means may be configured by a computer, and may be configured by, for example, a computer including at least a CPU and a primary storage device unit, a secondary storage device unit, and the like.

In the present invention, halation is more effectively reduced by roughening the surface of the outermost exposed surface, so that such surface treatment can provide more accurate information about the edge contours of the outermost layer of the image. can. Specifically, regarding the surface treatment of the outermost exposed surface for reducing halation (that is, the surface treatment for adjusting the roughness applied to the main surface of the metal layer to be the outermost exposed surface), for example, the electrode material layer (positive electrode). It may be rougher than the surface roughness of the material layer / negative electrode material layer). That is, the main surface of the metal layer to be the outermost exposed surface is treated so that the roughness is larger than the surface roughness of the positive electrode material layer and / or the negative electrode material layer used in the electrode assembly precursor or the outermost electrode. It's okay. Since halation is less likely to occur with respect to the electrode material layer, it is possible to more reliably reduce halation of the outermost exposed surface by making it coarser than the surface of such an electrode material layer. In other words, the main surface of the metal layer, which is the outermost exposed surface, may be treated more coarsely so that the glossiness of the main surface is 200 or less. Alternatively, a metal layer originally having a glossiness of 200 or less on the main surface may be used, and the metal layers may be laminated and arranged so that the main surface having a glossiness of 200 or less is the outermost exposed surface. This is because, in the case of the outermost exposed surface having a glossiness of 200 or less, halation of the outermost exposed surface can be effectively reduced as well. The term "glossiness" as used herein refers to a material measured according to JIS Z 8741. More specifically, the glossiness "200" mentioned above substantially refers to a value measured by the measuring machine IG-331 manufactured by HORIBA.

In one preferred embodiment, the outermost metal layer is a metal foil forming an electrode laminated structure. More specifically, the outermost metal layer is a metal foil that contributes to battery capacity formation in the electrode assembly. For example, the electrode current collector foil of the positive electrode or the negative electrode is a metal foil forming an electrode laminated structure. When such a metal foil is used as the outermost metal layer, halation may occur and the edge of the outermost metal layer may be blurred as an image. Therefore, as described above, the light intensity of the irradiation light source may be adjusted and / or the direction of light incident on the outermost metal layer may be adjusted so that halation does not occur. Further, a treatment for changing the surface roughness of the metal foil to be the outermost metal layer (particularly the surface roughness of the outermost exposed surface of the metal foil) may be performed so that halation does not occur.

In one preferred embodiment of the present invention, the outermost metal layer is a so-called single-sided electrode metal foil. In such an embodiment, where the metal foil is used as the electrode current collector 52, the electrode laminated structure includes a single-sided electrode 55 in which the electrode material layer 54 is provided only on one main surface of the electrode current collector 52. The electrode current collector foil 52 in the single-sided electrode 55 serves as the outermost layer 50 of the electrode assembly 100 (see FIG. 4). The fact that the outermost metal layer is a metal foil of a single-sided electrode means that the outermost layer electrode of the electrode assembly is a single-sided electrode, but when the outermost layer electrode is a single-sided electrode, the outermost layer electrode is double-sided. The energy density per unit volume of the battery can be improved as compared with the case of the electrode. This is because, when the outermost layer electrode is a double-sided electrode, the outermost electrode material layer (the electrode material layer on the side not directly facing the inner electrode) cannot substantially effectively contribute to the battery capacity formation. be. That is, by using the outermost layer electrode as a single-sided electrode, it is possible to reduce the volume of the portion that cannot contribute effectively. In the present invention, while using such a single-sided electrode as the outermost layer electrode, it is possible to perform suitable imaging on the metal foil of the single-sided electrode and reduce the stacking deviation of the single-sided electrode. Therefore, in the manufacturing method according to the present invention, the effect of improving the energy density brought about by using the single-sided electrode as the outermost electrode can be more preferably achieved.

It is particularly preferable to use a single-sided negative electrode as the outermost layer electrode. That is, it is preferable that the single-sided electrode used as the outermost layer electrode of the electrode assembly is the negative electrode. As a result, the generation of so-called dendrites is further suppressed, so that the generation of heat generation and ignition due to overcurrent and the like is suppressed, and a secondary battery desirable from the viewpoint of safety is brought about. Specifically, in the laminating of single-sided electrodes obtained by applying a negative electrode electrode material (raw material containing a negative electrode active material) to one main surface of a negative electrode current collector and drying it, and then pressing the negative electrode, the negative electrode collection thereof. Suitable imaging of the electric body is performed, and the stacking deviation of the single-sided electrodes is reduced as much as possible.

When a single-sided electrode is used as the outermost layer electrode of the electrode assembly, a metal foil having different surface morphologies on both main surfaces facing each other may be used as the electrode current collector of the single-sided electrode. For example, in the manufacturing method of the present invention, the metal foil 52 of the single-sided electrode 55 has a shine surface and a matte surface as both main surfaces facing each other, so that the shine surface faces outward in the electrode assembly 100. The single-sided electrode 55 may be laminated and arranged on the electrode assembly precursor 100'(FIG. 5). In such a case, the single-sided electrode is arranged on the electrode assembly precursor while imaging the shine surface side of the metal foil of the single-sided electrode to detect the position. When the shine surface is the outermost exposed surface, the edge contour of the metal foil of the single-sided electrode may be inconveniently blurred in the image / video obtained by imaging. Therefore, in the present invention, it is preferable to more accurately detect the position of the metal foil of the single-sided electrode and stack the single-sided electrodes from the viewpoint. That is, as described above, the light intensity of the irradiation light source may be adjusted and / or the incident direction of the light on the metal foil of the single-sided electrode may be adjusted so as not to cause halation, and further. The metal foil of the single-sided electrode to be the outermost layer may be subjected to surface treatment for changing the surface roughness (that is, the surface roughness of the shine surface).

For example, a copper foil may be used as the electrode current collector of the negative electrode of the secondary battery. In such a case, the copper foil of the single-sided negative electrode has a shine surface and a matte surface as both main surfaces facing each other, and the single-sided negative electrode is laminated on the electrode assembly precursor so that the shine surface faces outward in the electrode assembly. It may be arranged. That is, the shine surface of the copper foil in the single-sided negative electrode is imaged to detect the position, and the single-sided negative electrode is arranged with respect to the electrode assembly precursor. An electrode material layer is formed on the matte surface of the electrode current collector foil. That is, in the single-sided electrode used as the outermost layer electrode of the electrode assembly, the electrode current collector foil and the electrode material layer are bonded to each other via the matte surface.

The "shine surface" and "matte surface" as used herein refer to a foil surface used in the field of metal foil. For example, when the copper foil of the single-sided negative electrode is an electrolytic copper foil and it is obtained by electrolytically precipitating copper on the surface of an electrolytic drum, the surface on which copper begins to precipitate in the precipitated electrolytic copper foil. That is, the surface in contact with the electrolytic drum is referred to as a shine surface, and the surface on which copper precipitation is completed is referred to as a matte surface. Typically, the "shine surface" is transferred with the streaky irregularities of the surface of the electrolytic drum, so that the copper fine particles can have a columnar arrangement morphology along substantially a certain direction, while the "matte surface" is. , Can have a columnar arrangement in which copper fine particles are randomly distributed.

In another preferred embodiment of the invention, the outermost metal layer may be the non-electrode element of the electrode assembly. For example, the metal sheet 90 that does not form an electrode laminated structure of the electrode assembly, which is used for suppressing heat generation at the time of an inconvenient short circuit, may be the outermost metal layer (FIGS. 6A and 6B). reference). That is, the metal sheet 90 may be used as a non-electrode element that does not form an electrode laminated structure, and the metal sheet 90 may be used as the outermost metal layer of the electrode assembly. As such a metal sheet, a copper sheet, an aluminum sheet, or the like may be used. For example, the metal sheet may be a metal foil similar to the current collector foil (for example, copper foil or aluminum foil).

When such a metal sheet is used as the outermost metal layer of the electrode assembly, the metal sheet is imaged to detect the position, and the metal sheet is arranged with respect to the electrode assembly precursor. Since the metal sheet can cause a phenomenon that the edge contour of the sheet is inconveniently blurred as an image / video obtained by imaging, it is possible to detect the position of the metal sheet more accurately and stack the metal sheets from this viewpoint. preferable. That is, as described above, for example, the light intensity of the irradiation light source may be adjusted and / or the incident direction of the light on the metal sheet may be adjusted so that halation does not occur. It is also preferable to perform a treatment for changing the surface roughness of the outermost metal sheet (that is, the surface roughness of the main surface of the outermost metal sheet in the electrode assembly).

When the metal sheet 90 is used as the outermost metal layer of the electrode assembly, the metal foil such as copper foil or aluminum foil may be used as it is as the metal sheet 90 as shown in FIG. 6 (A), or FIG. 6 (B). ) May be used, the metal sheet 90 provided with the additional sub-layer 94 on the lower side surface of the metal foil 92. Specifically, for example, a metal foil 92 having a sub-layer 94 containing alumina and a binder resin provided on the lower main surface may be used as a metal sheet 90 for suppressing heat generation at the time of short circuit. Further, when laminating such a metal sheet 90, a separator 96 may be interposed as shown in the figure.

The present invention can be embodied in various embodiments. For example, it is preferable to use a white jig as the jig used in the laminating process of the electrode assembly. When a double-sided electrode (an electrode having electrode material layers on both main surfaces of an electrode current collector) is used as an electrode of a main component of an electrode assembly, it is possible to more preferably stack such double-sided electrodes. Because. Specifically, since the positive electrode and the negative electrode of the double-sided electrode can exhibit black, the edge contour of the double-sided electrode becomes clearer and easier to grasp in the image / video obtained by imaging by using the white jig.

For example, as a pedestal for laminating the electrode assembly, a pedestal having a color different from that of the electrode material layer contained in the electrode assembly may be used. In particular, when the gantry as the base for lamination is white, both the positive electrode and the negative electrode are black, and the contrast with the positive electrode is stronger, so that the edge contour of the double-sided electrode can be more easily grasped. As a result, in the laminating process of the electrode assembly, it leads to reduction of laminating misalignment at a high level on the order of microns. As can be seen from this description, "having a different color from the electrode material layer contained in the electrode assembly" as used herein means a person skilled in the art of a secondary battery (particularly a person skilled in the art of laminating an electrode assembly). ) Refers to an aspect in which it can be usually determined that the color is different from that of the electrode material layer (positive electrode and / or negative electrode), and the electrode material layer and contrast are relatively high especially in the image / video obtained by the imaging means. , Refers to an embodiment having a color that contributes to grasping the contour of the electrode material layer. Further, the "white jig" referred to in the present specification is a jig that can be usually judged to be "white" as recognized by those skilled in the art of secondary batteries (particularly those skilled in the art of laminating electrode assemblies). It does not necessarily have to be a strict white color. For example, the gantry for laminating the electrode assembly may include alumite (particularly white alumite). As a result, the gantry used in the laminating process may exhibit a color different from that of the electrode material layer contained in the electrode assembly, and as a result, the edge contour of the double-sided electrode can be more easily grasped in the image / video obtained by imaging.

Although the embodiments of the present invention have been described above, they merely exemplify typical examples. Therefore, those skilled in the art will easily understand that the present invention is not limited to this, and various aspects are conceivable.

The secondary battery according to the present invention can be used in various fields where storage is expected. Although only an example, secondary batteries are used in the fields of electricity, information, and communication where mobile devices are used (for example, the fields of mobile devices such as mobile phones, smart watches, smartphones, laptop computers, and digital cameras), homes, and so on. Small industrial applications (eg, power tools, golf carts, home / nursing / industrial robots), large industrial applications (eg, forklifts, elevators, bay port cranes), transportation systems (eg, hybrid vehicles) , Electric vehicles, buses, trains, electric assisted bicycles, electric two-wheeled vehicles, etc.), power system applications (for example, various power generation, road conditioners, smart grids, general household-installed power storage systems, etc.), and space / deep sea It can be used for various purposes (for example, in the fields of space explorers, submersible research vessels, etc.).

1 Positive electrode 2 Negative electrode 3 Separator 10 Electrode constituent layer 50 Metal layer as outermost layer 51 Outermost layer edge 52 Electrode current collector (for example, electrode current collector foil)
54 Electrode material layer 55 Single-sided electrode 60 Imaging means 70 Irradiation light source 90 Metal sheet 92 Metal foil constituting the metal sheet 94 Sub-layer constituting the metal sheet 96 Separator 100 Electrode assembly 100'Electrode assembly precursor

Claims (10)

A method of manufacturing a secondary battery having an electrode assembly including an electrode laminated structure.
A metal layer is used as the outermost layer in the electrode assembly, and the metal layer is used.
When the metal layer is laminated and arranged on an electrode assembly precursor that does not yet contain at least the outermost layer as a configuration of the electrode assembly, the metal layer is imaged, and the position of the outermost layer is detected through the image pickup. stomach,
A method for manufacturing a secondary battery, wherein the main surface of the metal layer, which is the outermost exposed surface of the electrode assembly, is subjected to a process of changing the surface roughness. The method for manufacturing a secondary battery according to claim 1, wherein the imaging of the metal layer is performed under illumination. The method for manufacturing a secondary battery according to claim 1 or 2, wherein the outermost metal layer is a metal foil forming the electrode laminated structure. The metal foil is used as an electrode current collector, and a single-sided electrode having an electrode material layer provided only on one main surface of the electrode current collector is included in the electrode laminated structure.
The method for manufacturing a secondary battery according to claim 3, wherein the electrode current collector in the single-sided electrode serves as the outermost layer of the electrode assembly. The method for manufacturing a secondary battery according to claim 4, wherein the single-sided electrode is a negative electrode. A metal sheet is used as a non-electrode element that does not form the electrode laminated structure.
The method for manufacturing a secondary battery according to claim 1 or 2, wherein the metal layer to be the outermost layer is the metal sheet. A method of manufacturing a secondary battery having an electrode assembly including an electrode laminated structure.
A metal layer is used as the outermost layer in the electrode assembly, and the metal layer is used.
When the metal layer is laminated and arranged on an electrode assembly precursor that does not yet contain at least the outermost layer as a configuration of the electrode assembly, the metal layer is imaged, and the position of the outermost layer is detected through the image pickup. ,
The outermost metal layer is a metal foil forming the electrode laminated structure, the metal foil is used as an electrode current collector, and an electrode material layer is provided only on one main surface of the electrode current collector. The single-sided electrode is included in the electrode laminated structure.
The single-sided electrode is a negative electrode, and the electrode current collector in the single-sided electrode is the outermost layer of the electrode assembly.
The metal foil has a shine surface and a matte surface as both main surfaces facing each other, and the one-sided electrode is laminated on the electrode assembly precursor so that the shine surface faces outward in the electrode assembly. A method of manufacturing a secondary battery to be arranged. The method for manufacturing a secondary battery according to claim 7, wherein the shine surface of the metal foil is imaged and the position is detected. A method of manufacturing a secondary battery having an electrode assembly including an electrode laminated structure.
A metal layer is used as the outermost layer in the electrode assembly, and the metal layer is used.
When the metal layer is laminated and arranged on an electrode assembly precursor that does not yet contain at least the outermost layer as a configuration of the electrode assembly, the metal layer is imaged, and the position of the outermost layer is detected through the image pickup. stomach,
A method for manufacturing a secondary battery , which uses a pedestal having a color different from that of the electrode material layer contained in the electrode assembly as a pedestal for laminating the electrode assembly. The method for manufacturing a secondary battery according to any one of claims 1 to 9, wherein a positive electrode capable of occluding and discharging lithium ions and a negative electrode are used as the electrodes of the electrode assembly.

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