Secondary battery and electronic device

Abstract

This invention provides a rechargeable battery suitable for portable information terminals or wearable devices. Additionally, it provides an electronic device with a novel structure having a variety of appearance shapes, and a rechargeable battery with a shape suitable for its shape. The rechargeable battery is sealed using a membrane with recesses or protrusions that mitigates stress on the membrane caused by applied external forces. A pattern is formed on the surface of the membrane, and the recesses or protrusions of the pattern are formed by pressing processes such as embossing.

Description

[Technical Field]

[0001] This invention relates to an object, method, or manufacturing method. Furthermore, this invention relates to a process, machine, manufacture, or composition of matter. Additionally, one aspect of this invention relates to a semiconductor device, display device, light-emitting device, energy storage device, imaging device, and a method for driving or manufacturing them. In particular, one aspect of this invention relates to an electronic device.

[0002] Note that in this specification, electronic device refers to all devices that have a secondary battery, including electro-optical devices with secondary batteries, information terminal devices with secondary batteries, vehicles with secondary batteries, etc. [Previous Technology]

[0003] In recent years, there has been active development of portable information terminals, represented by smartphones. Users expect portable information terminals, one of the electronic devices, to become lightweight and miniaturized.

[0004] Patent Document 1 discloses a goggle-type display device capable of communication and containing a CPU, as an example of a wearable device that allows users to view information anywhere without using their hands. The device disclosed in Patent Document 1 also falls within the scope of electronic devices.

[0005] Most wearable devices or portable information terminals are equipped with rechargeable and rechargeable batteries. Because wearable devices or portable information terminals are required to be lightweight and miniaturized, the capacity of the installed rechargeable batteries is limited, resulting in a limitation on their operating time. The rechargeable batteries installed in wearable devices or portable information terminals are required to be lightweight, miniaturized, and allow for long-term use.

[0006] Examples of secondary batteries include nickel-metal hydride batteries and lithium-ion secondary batteries. Among them, lithium-ion secondary batteries are increasingly being developed due to their ability to achieve high capacity and miniaturization.

[0007] Electrodes used as positive or negative electrodes in lithium-ion secondary batteries use lithium metal, carbon materials, alloy materials, etc.

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2005-157317 [Summary of the Invention]

[0009] One objective of this invention is to provide a secondary battery suitable for portable information terminals.

[0010] In addition, another objective of one aspect of the present invention is to provide a secondary battery suitable for wearable devices.

[0011] Furthermore, another object of one aspect of the present invention is to provide an electronic device having a wide variety of shapes and a secondary battery having a shape suitable for the electronic device. Additionally, another object of one aspect of the present invention is to provide a novel electronic device, a novel secondary battery, or a novel energy storage device.

[0012] Note that the description of these objectives does not preclude the existence of other objectives. One aspect of the present invention does not require achieving all of the above objectives. Furthermore, objectives other than those described above are clearly visible from the description, drawings, and claims, and objectives other than those described above can be extracted from the description, drawings, and claims.

[0013] When an electronic device is formed with a complex appearance, the housing is designed with a complex appearance, and electronic components (power supply, wiring, transistors, resistors, capacitors, etc.) are arranged in the space inside the housing. When the size and weight of the electronic device are not a major issue, the volume of the space inside the housing is relatively large, so the electronic components can be arranged more freely.

[0014] On the other hand, when electronic devices with complex shapes are small and require lightweight design, the volume of space inside the casing is small. Therefore, electronic components and their dimensions are selected and configured according to their volume. In this case, the smaller the size of the electronic components, the more expensive they are, which leads to an increase in manufacturing costs.

[0015] In addition, the capacity of a secondary battery tends to increase with the increase of its volume or weight. When a secondary battery is installed in a small electronic device, the size or configuration of the secondary battery is limited.

[0016] In addition, in vehicles with secondary batteries, such as electric vehicles or hybrid vehicles, it is necessary to increase the volume or weight of the secondary battery in order to extend the driving distance on each charge.

[0017] Therefore, by using deformable secondary batteries in electronic devices, secondary batteries and other electronic components can be efficiently arranged in the space inside the casing of the electronic device.

[0018] When a force is applied from the outside to deform the secondary battery, the force is applied from the outside to an object such as a membrane used for the outer packaging of the secondary battery, and the object is subjected to stress, and a part of it may be deformed or damaged.

[0019] One aspect of the present invention provides a secondary battery having a structure that mitigates strain caused by stress. Strain is a measure of deformation, representing the displacement of a point of matter within an object relative to a reference (initial) length of the object. One aspect of the present invention provides a secondary battery that suppresses the effects of strain (i.e., the measure of deformation) generated when an external force is applied to an allowable range.

[0020] One aspect of the invention disclosed in this specification is a secondary battery that is sealed using a membrane having concave or convex portions to mitigate membrane stress caused by the application of external forces.

[0021] Another aspect of the invention disclosed in this specification is a secondary battery that is sealed using a membrane having a pattern of recesses or convexities on a portion of its surface.

[0022] Another aspect of the invention disclosed in this specification is a secondary battery that is sealed by a first film having a pattern formed by recesses or convexities on a portion of its surface and a second film having a pattern formed by recesses or convexities on a portion of its surface that is different from the first film.

[0023] (1) Another aspect of the invention disclosed in this specification is a secondary battery that is sealed with a membrane comprising a region having a pattern of recesses or convexities and a region not having a pattern of recesses or convexities, the patterned region comprising a portion having a first thickness and a portion having a second thickness.

[0024] (2) Another aspect of the invention disclosed in this specification is a secondary battery sealed with a membrane comprising a region having a pattern of recesses or convexities and a region not having a pattern of recesses or convexities. The patterned region is formed by a portion having a first thickness and a portion having a second thickness. The portion having the first thickness includes recesses or convexities having a first pitch, and the portion having the second thickness includes recesses or convexities having a second pitch. Here, "pitch" refers to the distance between the bottom of a recess or the apex of a convexity and the bottom of a recess or the apex of a convexity adjacent to each other when viewed from above.

[0025] (3) Another aspect of the invention disclosed in this specification is the secondary battery described in (1) or (2), wherein there is a boundary between the area having a pattern of recesses or convexities and the area not having a pattern of recesses or convexities.

[0026] (4) Another aspect of the invention disclosed in this specification is a secondary battery that is sealed with a membrane comprising a first pattern having a recess or a convex portion, a portion having a first thickness and a portion having a second thickness, a second pattern having a recess or a convex portion, and a portion having a third thickness and a portion having a fourth thickness, wherein the first pattern is formed by the portion having the first thickness and the portion having the second thickness, and the second pattern is formed by the portion having the third thickness and the portion having the fourth thickness.

[0027] (5) Another aspect of the invention disclosed in this specification is a secondary battery that is sealed with a membrane comprising a first pattern having recesses or convexities, a portion having a first thickness and a portion having a second thickness, a second pattern having recesses or convexities, and a portion having a third thickness and a portion having a fourth thickness, the portion having the first thickness comprising recesses or convexities having a first pitch, and the portion having the third thickness comprising recesses or convexities having a second pitch.

[0028] (6) Another aspect of the invention disclosed in this specification is the secondary battery described in (4) or (5), wherein there is a boundary between a first pattern having a recess or a convex portion and a second pattern having a recess or a convex portion.

[0029] (7) Another aspect of the invention disclosed in this specification is a secondary battery comprising a first membrane and a second membrane for sealing, the first membrane comprising a region having a pattern of recesses or convexities, and the second membrane comprising a region not having a pattern of recesses or convexities, the patterned region being formed by a portion having a first thickness and a portion having a second thickness.

[0030] (8) Another aspect of the invention disclosed in this specification is a secondary battery comprising a first membrane and a second membrane for sealing, the first membrane comprising a region having a pattern of recesses or protrusions, the second membrane comprising a region not having a pattern of recesses or protrusions, the patterned region being formed by a portion having a first thickness and a portion having a second thickness, the portion having a first thickness comprising recesses or protrusions having a first pitch, and the portion having a second thickness comprising recesses or protrusions having a second pitch.

[0031] (9) Another aspect of the invention disclosed in this specification is the secondary battery described in (7) or (8), wherein at least a positive electrode active material layer, a negative electrode active material layer and an electrolyte are included between the first membrane and the second membrane.

[0032] (10) Another aspect of the invention disclosed in this specification is the secondary battery described in (2) or (8), wherein the first distance is different from the second distance.

[0033] (11) Another aspect of the invention disclosed in this specification is the secondary battery described in (2) or (8), wherein the depth of the recess or the height of the protrusion having a first distance and the depth of the recess or the height of the protrusion having a second distance are both less than half the thickness of the secondary battery.

[0034] (12) Another aspect of the invention disclosed in this specification is a secondary battery comprising a first membrane and a second membrane for sealing, the first membrane comprising a first pattern having a recess or a convex portion, and a portion having a first thickness and a portion having a second thickness, the second membrane comprising a second pattern having a recess or a convex portion, and a portion having a third thickness and a portion having a fourth thickness, the first pattern being formed by the portion having the first thickness and the portion having the second thickness, and the second pattern being formed by the portion having the third thickness and the portion having the fourth thickness.

[0035] (13) Another aspect of the invention disclosed in this specification is a secondary battery comprising a first membrane and a second membrane for sealing, the first membrane comprising a first pattern having a recess or a convex portion, and a portion having a first thickness and a portion having a second thickness, the second membrane comprising a second pattern having a recess or a convex portion, and a portion having a third thickness and a portion having a fourth thickness, the portion having a first thickness comprising a recess or a convex portion having a first pitch, and the portion having a third thickness comprising a recess or a convex portion having a second pitch.

[0036] (14) Another aspect of the invention disclosed in this specification is the secondary battery described in (12) or (13), wherein at least a positive electrode active material layer, a negative electrode active material layer and an electrolyte are included between the first membrane and the second membrane.

[0037] (15) Another aspect of the invention disclosed in this specification is the secondary battery described in (5) or (13), wherein the first pattern having a concave or convex portion includes a portion having a first thickness and a portion having a second thickness, and the second pattern having a concave or convex portion includes a portion having a third thickness and a portion having a fourth thickness.

[0038] (16) Another aspect of the invention disclosed in this specification is the secondary battery described in (5) or (13), wherein the depth of the recess or the height of the protrusion having a first distance and the depth of the recess or the height of the protrusion having a second distance are both less than half the thickness of the secondary battery.

[0039] In the above structure, the membrane pattern is a visible geometric pattern of intersecting diagonal lines in two directions. When a geometric pattern of intersecting diagonal lines in two directions is used, the stress caused by bending can be mitigated in at least two directions. Furthermore, the concave or convex portions of the pattern do not necessarily have to be arranged regularly; they can also be arranged irregularly. In the case of irregular arrangement of concave or convex portions, not only the stress caused by two-way bending can be mitigated, but also the stress caused by three-way irregular bending or twisting can be mitigated. Additionally, the membrane can include multiple regions with patterns varying depending on the location. For example, a membrane can have two patterns, such as a pattern in the central part of the membrane being different from the pattern at the ends, or a membrane can have three or more patterns. Alternatively, only the flexible portion of the membrane can have concave or convex portions, while the other portions are flat. There are no particular restrictions on the shape of the concave or convex portions of the membrane.

[0040] The concave or convex portions of the membrane can be formed using a pressing process (e.g., embossing). Embossing forms concave or convex portions on the membrane surface (or back side) to create a membrane seal that serves as part of the wall of a sealing structure, creating a closed space whose volume can be altered. This closed space can be considered as an accordion structure (also known as a corrugated structure) formed using a membrane with a pattern of concave or convex portions. The sealing structure using the membrane achieves waterproof and dustproof effects. Furthermore, embossing, not limited to one of the pressing processes, can also be used, employing methods that can form reliefs on a portion of the membrane. The above methods can also be combined, for example, embossing a membrane and other pressing processes. Additionally, embossing a membrane can be performed multiple times.

[0041] There are various types of structures for secondary batteries; here, a structure using a membrane as the outer packaging is adopted. The membrane is required to have high water resistance and high gas resistance. The membrane used for the outer packaging is selected from metal films (films of metals or alloys that can form metal foils, such as aluminum, stainless steel, nickel steel, gold, silver, copper, titanium, nickel-chromium alloys, iron, tin, tantalum, niobium, molybdenum, zirconium, and zinc), plastic films formed of organic materials, mixed material films containing organic materials (organic resins or fibers, etc.) and inorganic materials (ceramics, etc.), single-layer films containing carbon inorganic films (carbon films, graphite films, etc.), or laminated films composed of multiple such films. Metal films are easy to emboss, and when concave or convex portions are formed by embossing, the surface area of ​​the film exposed to external gases increases, thus improving heat dissipation.

[0042] In addition, when sealing a secondary battery, a rectangular membrane is folded in the center and the two ends are overlapped, and the three sides are fixed with an adhesive layer to seal it, or two membranes are overlapped and the four sides of the ends of the membrane are fixed with an adhesive layer to seal it.

[0043] The adhesive layer can be made of thermoplastic film materials, thermosetting adhesives, or anaerobic adhesives, UV-curing adhesives, and other light-curing adhesives or reactive curing adhesives. Materials used as these adhesives include epoxy resins, acrylic resins, silicone resins, phenolic resins, etc.

[0044] When the adhesive layer and the membrane are bonded together to form a sealing structure, compression is performed so that the depth of the concave portion or the height of the convex portion at the compressed end of the membrane is different from that at the center of the membrane. By making the depth of the concave portion or the height of the convex portion at the end of the membrane lower than that at the center of the membrane, the effects of strain can be suppressed to an acceptable range.

[0045] When the central portion of the membrane has a concave or convex portion, and the pressed ends do not have a concave or convex portion, the secondary battery can expand significantly even if the internal structure of the secondary battery expands in the central portion. Therefore, it has the effect of preventing the secondary battery from rupturing. However, since the ends do not have a concave or convex portion, the flexibility and stress mitigation effect at the ends are lower than in the central portion. In other words, providing a concave or convex portion at the ends of the membrane also helps to suppress the effects of strain within an acceptable range.

[0046] Furthermore, "forming an electronic device into a complex shape" can be interpreted in several ways. One interpretation is to give the electronic device a fixed, complex shape, such as a curved shape. In fixing the shape of the electronic device, the secondary battery is bent once and the bent shape is fixed. Furthermore, electronic devices with complex shapes can be divided into electronic devices that do not deform when subjected to external force and electronic devices that deform. Another interpretation is that electronic devices with simple shapes deform when subjected to external force. When the electronic device deforms when force is applied, it is preferable that the secondary battery also deforms each time force is applied.

[0047] Another aspect of the invention disclosed in this specification is an electronic device comprising: a housing having a curved surface therein; and a secondary battery having a curved surface, wherein the outer casing of the secondary battery has a film having a pattern formed by recesses or convexities on a portion of its surface.

[0048] In addition, another aspect of the invention disclosed in this specification is an electronic device comprising: a housing; and a secondary battery in contact with a portion of the housing, wherein the outer casing of the secondary battery has a film having a pattern formed by recesses or convexities on a portion of its surface, and the portion of the housing is deformable.

[0049] In the above structure, the outer casing of the secondary battery can be deformed within a radius of curvature of 10 mm or more and 150 mm or less, preferably 30 mm or more and 150 mm or less. One or two membranes are used as the outer casing of the secondary battery. When the secondary battery has a laminated structure and its cross-section is made into an arc shape by bending the secondary battery, the electrodes and electrolyte are held by the two curved surfaces of the membranes.

[0050] Here, the radius of curvature of the surface of the outer packaging body will be explained with reference to Figures 1A to 1C. In the plane 1701 of the truncated surface 1700 in Figure 1A, a portion of the curve 1702 contained in the surface 1700 is approximated as a circular arc, the radius of which is taken as the radius of curvature 1703, and the center of the circle as the center of curvature 1704. Figure 1B shows a top view of the surface 1700. Figure 1C shows a cross-sectional view of the surface 1700 truncated along the plane 1701. When the surface is truncated along the plane, the radius of curvature of the curve in the cross-section varies depending on the angle relative to the plane of the surface or the angle at which the truncation is performed. In this specification, the minimum radius of curvature is defined as the radius of curvature of the surface.

[0051] When a secondary battery, in which electrodes and electrolyte 1805 are sandwiched between two membranes serving as the outer packaging, is bent, the radius of curvature 1802 of the membrane 1801, which is closer to the center of curvature 1800 of the secondary battery, is smaller than the radius of curvature 1804 of the membrane 1803, which is farther from the center of curvature 1800 (Fig. 2A). When the secondary battery is bent so that its cross-section is arc-shaped, the membrane surface farther from the center of curvature 1800 is subjected to tensile stress (Fig. 2B). When a pattern formed by concave or convex portions is formed on the surface of the outer packaging, even if tensile stress is applied as described above, the effect of strain can be suppressed within an acceptable range. Therefore, the secondary battery can be deformed within a range where the radius of curvature of the outer packaging near the center of curvature is 10 mm or more, preferably 30 mm or more.

[0052] In addition, the cross-sectional shape of the secondary battery is not limited to a simple arc shape, but can also be a part of which is an arc shape as shown in Figure 2C.

[0053] In the cross-section when the secondary battery is bent, the outer surface is stretched and the inner surface is compressed, that is, the outer surface stretches and the inner surface contracts.

[0054] By giving the outer packaging film an appropriate pattern formed by recesses or convexities, concerns can be reduced about the film deteriorating or being damaged when bending the secondary battery, which could lead to electrolyte leakage.

[0055] When a part of a device such as a watch comes into contact with a part of a user's body (wrist or arm, etc.), the user will feel a lighter weight than the actual weight even when wearing the device. By using a flexible secondary battery in an electronic device that has an appearance shape that follows the curve of a part of the user's body, the secondary battery can be configured in a way that fits the shape of the electronic device.

[0056] When a user moves the part of their body on which the electronic device is worn, even if the electronic device has a curved surface that follows a part of the body, the user will feel uncomfortable and find the electronic device annoying, and may also experience pressure. Therefore, by deforming at least a part of the electronic device according to the movement of the body, the user can avoid feeling uncomfortable, and a flexible secondary battery can be installed in the deformable part of the electronic device.

[0057] The external shape of an electronic device is not limited to curved or complex shapes; it can also be a simple shape. For example, in the interior of an electronic device with a simple external shape, the number or size of components that can be built into the electronic device largely depends on the volume of the space formed by the outer casing of the electronic device. By placing the flexible secondary battery in the gap between the components other than the secondary battery, the space formed by the outer casing of the electronic device can be effectively utilized, and miniaturization can also be achieved.

[0058] Note that wearable devices, within their scope, include wearable input terminals such as wearable cameras, wearable microphones, and wearable sensors; wearable output terminals such as wearable displays and wearable speakers; and wearable input / output terminals that combine these functions. Furthermore, wearable devices, within their scope, also include devices for controlling various devices, calculating or processing data, a typical example being a wearable computer with a CPU. Additionally, wearable devices, within their scope, also include devices for storing, transmitting, and receiving data, typical examples being portable information terminals and memory.

[0059] One aspect of the present invention enables the realization of a novel structure for a secondary battery. Furthermore, it enables the realization of novel energy storage devices.

[0060] Since the shape of the secondary battery can be freely designed, for example, by using a secondary battery with a curved surface, the flexibility of the entire device can be improved, and devices with a wide variety of designs can be realized. In addition, by placing the secondary battery inside the curved surface of the device along the curved surface of the device, the space inside the device can be effectively utilized without creating unnecessary space inside the device with a curved surface.

[0061] Therefore, it is possible to realize electronic devices with novel structures.

[0062] Note that the description of these effects does not preclude the existence of other effects. Note that one aspect of the present invention does not necessarily require all of the above-described effects. Furthermore, effects other than these are clearly visible from the description in the specification, drawings, claims, etc., and these effects can be extracted from the description in the specification, drawings, claims, etc. [Simplified Explanation of the Diagram]

[0063] Figures 1A to 1C are diagrams illustrating the radius of curvature of the surface;

[0063] Figures 2A to 2C are diagrams illustrating the center of curvature;

[0063] Figures 3A to 3C are top views illustrating one aspect of the present invention;

[0063] Figures 4A and 4B are top views illustrating one aspect of the present invention;

[0063] Figures 5A to 5F are diagrams illustrating an embossing process according to one aspect of the present invention;

[0063] Figures 6A to 6F are top views, cross-sectional views and schematic diagrams illustrating one aspect of the present invention;

[0063] Figures 7A to 7C are top views and cross-sectional views illustrating one aspect of the present invention;

[0063] Figures 8A to 8D are cross-sectional views illustrating a secondary battery according to one embodiment of the present invention;

[0063] Figures 9A to 9C are cross-sectional views illustrating a secondary battery according to one embodiment of the present invention;

[0063] Figures 10A and 10B are top views illustrating one aspect of the present invention;

[0063] Figures 11A to 11E are top views illustrating one aspect of the present invention;

[0063] Figures 12A to 12C are perspective views and cross-sectional views illustrating one aspect of the present invention;

[0063] Figures 13A to 13C are perspective views and cross-sectional views illustrating one aspect of the present invention;

[0063] Figures 14A to 14H are diagrams illustrating an electronic device having a flexible secondary battery;

[0063] Figures 15A to 15C are diagrams illustrating the electronic device;

[0063] Figures 16A and 16B are diagrams illustrating a vehicle with a secondary battery;

[0063] Figures 17A to 17C are cross-sectional views and photographs showing Embodiment 1;

[0063] Figure 18 is a graph showing the data on frictional force in Example 1;

[0063] Figures 19A to 19D are diagrams illustrating Embodiment 2;

[0063] Figure 20 is a diagram illustrating Embodiment 2;

[0063] Figures 21A to 21C are photographs showing Embodiment 2;

[0063] Figures 22A and 22B are diagrams illustrating Embodiment 3;

[0063] Figures 23A and 23B are diagrams illustrating Embodiment 3 and Embodiment 4;

[0063] Figure 24 is a graph showing the data of the load test in Example 3;

[0063] Figures 25A and 25B are graphs showing the data of the load test in Example 4.

Implementation Method

[0064] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that the manner and details of the present invention can be varied in many ways. Furthermore, the present invention should not be construed as being limited only to the description of the embodiments shown below.

[0065] "Electrical connection" includes the case of connection by means of "element having a certain electrical function". Here, there are no particular restrictions on "element having a certain electrical function" as long as it can transmit and receive electrical signals between the connected parts.

[0066] For ease of understanding, the positions, dimensions, and extents of the constituent elements shown in the drawings, etc., do not necessarily represent their actual positions, dimensions, and extents. Therefore, the disclosed invention is not necessarily limited to the positions, dimensions, and extents disclosed in the drawings, etc.

[0067] Ordinal numbers such as “first,” “second,” and “third” are added to avoid confusion among the constituent elements.

[0068] In addition, depending on the situation or state, the "film" and "layer" can be interchanged. For example, sometimes the "conductive layer" can be replaced with the "conductive film". In addition, sometimes the "insulating film" can be replaced with the "insulating layer".

[0069] Implementation Method 1

[0069] In this embodiment, an example of embossing the membrane surface and using a patterned membrane to manufacture a lithium-ion secondary battery is shown with reference to Figures 3A to 9C.

[0070] First, a sheet made of a flexible substrate is prepared. The sheet is a laminate, using a metal film with an adhesive layer (also called a heat-sealing layer) provided on one or both of its surfaces. The adhesive layer uses a hot-melt adhesive resin film containing polypropylene or polyethylene, etc. In this embodiment, the sheet is a metal sheet with a nylon resin provided on the surface of an aluminum foil and an acid-resistant polypropylene film and a polypropylene film laminate provided on the back side. The film 10 shown in FIG. 3A is prepared by cutting this sheet.

[0071] A portion of the surface of film 10 (film 10a) is embossed, but film 10b is not embossed. Film 11 as shown in FIG. 3B is manufactured by performing the above processing. As shown in FIG. 3B, a visible pattern is formed by forming irregularities on the surface of film 11a, while no irregularities are formed on the surface of film 11b. Furthermore, there is a boundary between film 11a with irregularities and film 11b without irregularities. In FIG. 3B, film 11a is the portion of the surface of film 11 that is embossed, and film 11b is the portion of the surface of film 11 that is not embossed. The embossing of film 11a can either form the same irregularities across the entire surface, or it can form two or more different irregularities depending on the portion of film 11a. When two or more different irregularities are formed, there is a boundary between the different irregularities.

[0072] Alternatively, the entire surface of the membrane 10 shown in FIG. 3A can be embossed to manufacture the membrane 22 shown in FIG. 4A. The embossing of the membrane 22 can either form the same unevenness across the entire surface, or form two or more different unevennesses depending on a portion of the membrane 22. When two or more different unevennesses are formed, there are boundaries between the different unevennesses.

[0073] Here, an example is shown where embossing is performed after cutting the sheet, but there is no particular restriction on the order. Embossing can be performed first, and then the sheet can be cut to form the film shown in FIG. 3B. Alternatively, the sheet can be cut after being folded and heat-pressed.

[0074] The following describes one of the pressing processes, namely embossing.

[0075] Figures 5A to 5F are cross-sectional views illustrating an example of embossing. Note that embossing is a type of pressing process in which an embossing roller with raised or recessed surfaces is pressed onto a film, forming a texture on the film corresponding to the raised or recessed areas of the embossing roller. An embossing roller is a roller whose surface is engraved with a pattern.

[0076] Figure 5A shows an example of embossing one surface of a film.

[0077] In Figure 5A, a film 50 is sandwiched between an embossing roller 53 that contacts one surface of the film and a roller 54 that contacts another surface, and the film 50 is conveyed in the travel direction 60. Patterns can be formed on the film surface by pressure or heat, or by a combination of pressure and heat.

[0078] The method in Figure 5A is also known as one-side embossing, which can be performed by combining embossing roller 53 and roller 54 (metal roller or elastic roller (rubber roller, etc.)).

[0079] In Figure 5B, a film 51 with one surface embossed is sandwiched between embossing rollers 53 and 54, and is conveyed in the travel direction 60. The embossing roller 53 rotates in contact with the unembossed surface of the film 51, thereby embossing both surfaces of the film 51. As shown in this example, a film can also be embossed multiple times.

[0080] Figure 5C shows an enlarged cross-sectional view of a film 52 with embossed surfaces on both sides. H1 in the figure represents the thickness of a concave or convex portion of the film. H2 in the figure represents the thickness of the boundary portion between a concave portion and a convex portion adjacent to that concave portion, or the thickness of the boundary portion between a convex portion and a concave portion adjacent to that convex portion. The thickness is not uniform; H2 is smaller than H1.

[0081] In addition, Figure 5D shows other examples of embossing on both surfaces of the film.

[0082] In Figure 5D, a film 50 is sandwiched between an embossing roller 53 that contacts one surface of the film and an embossing roller 55 that contacts another surface, and the film 50 is conveyed in the travel direction 60.

[0083] The method shown in Figure 5D is also known as both-side embossing, which combines embossing rollers 53 and 55, which are paired by matching the concave portion of one embossing roller with the convex portion of another embossing roller, to perform embossing. In addition, a pattern is formed on the surface of the film 50 by a continuous series of raised and recessed embossing patterns.

[0084] In FIG. 5E, an embossing roller 53 as shown in FIG. 5D and an embossing roller 56 having protrusions formed by the embossing roller 53 at different distances are used. Here, the distance between the protrusions or the embossing distance refers to the distance between the tops of adjacent protrusions. For example, the distance P shown in FIG. 5E is referred to as the distance between the protrusions or the embossing distance. In FIG. 5E, a film 50 is sandwiched between the embossing roller 53 and the embossing roller 56, and the film 50 is conveyed in the travel direction 60. By changing the distance between the protrusions, the two surfaces of the film can be processed with different embossing distances.

[0085] In FIG5F, a film 50 is sandwiched between an embossing roller 57 in contact with one surface of the film and an embossing roller 58 in contact with the other surface, and the film 50 is conveyed in the travel direction 60.

[0086] Figure 5F refers to a tip-to-tip double-sided embossing process, in which an embossing roller 57 and an embossing roller 58 having the same pattern as the embossing roller 57 are combined for embossing. By making the phases of the convex and concave portions of the same embossing roller the same, almost identical patterns can be formed on the surface and back of the film 50. Alternatively, unlike Figure 5F, embossing can also be performed with the phases of the convex and concave portions of the same embossing roller different.

[0087] In addition, embossing plates can also be used, not limited to embossing rollers. Furthermore, embossing can also be formed in a part of the film, not limited to embossing.

[0088] In this embodiment, a pattern is formed by providing unevenness on two surfaces of a portion of the surface of the membrane 10 (membrane 10a) to manufacture the membrane 11, the membrane 11 is folded in the center and the two ends are overlapped, and the three sides are sealed with an adhesive layer.

[0089] Next, the membrane 11 is partially folded along the dashed line shown in FIG3B, resulting in the state shown in FIG6A.

[0090] Furthermore, as shown in FIG6B, a stack of a positive electrode current collector 12, an separator 13, and a negative electrode current collector 14 is prepared to constitute a secondary battery. A positive electrode active material layer 18 is formed on a portion of the surface of the positive electrode current collector 12, and a negative electrode active material layer 19 is formed on a portion of the surface of the negative electrode current collector 14. As current collectors such as the positive electrode current collector 12 and the negative electrode current collector 14, materials with high conductivity that do not alloy with carrier ions such as lithium ions, such as stainless steel, gold, platinum, zinc, iron, nickel, copper, aluminum, titanium, tantalum, etc., can be used. Additionally, aluminum alloys with added elements that improve heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, can also be used. Furthermore, metal elements that react with silicon to form silicates can also be used. Examples of metal elements that react with silicon to form silicates include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel. The current collector can be appropriately shaped as foil, plate (sheet), mesh, cylindrical, coil, perforated metal mesh, expanded metal mesh, etc. The thickness of the current collector is preferably 5 μm or more and 40 μm or less. For clarity, an example is shown of a combination consisting of a positive current collector 12 with a positive active material layer 18, an separator 13, and a negative current collector 14 with a negative active material layer 19, housed in an outer packaging. However, to increase the capacity of the secondary battery, multiple such combinations can be stacked and housed in an outer packaging.

[0091] Additionally, two lead electrodes 16 with sealing layers 15, as shown in FIG. 6C, are prepared. The lead electrodes 16, also called lead terminals, are provided for leading the positive or negative electrode of the secondary battery to the outside of the outer casing. In the lead electrodes, aluminum is used as the positive lead electrode, and nickel-plated copper is used as the negative lead electrode.

[0092] The positive lead electrode is electrically connected to the protrusion of the positive current collector 12 by ultrasonic soldering or the like. Additionally, the negative lead electrode is electrically connected to the protrusion of the negative current collector 14 by ultrasonic soldering or the like.

[0093] Furthermore, to leave one side for injecting electrolyte, the two sides of the membrane 11 are heat-pressed together to seal them (hereinafter, the shape of the membrane in this state will also be referred to as bag-shaped). During heat pressing, the sealing layer 15 provided on the lead electrode also melts, and the lead electrode and the membrane 11 are fixed together. Then, under reduced pressure or in an inert gas atmosphere, the desired amount of electrolyte is dripped into the bag-shaped membrane 11. Finally, the edges of the membrane 11 that were not heat-pressed are heat-pressed together to seal them.

[0094] The secondary battery 40 shown in FIG6D can be manufactured by the above steps.

[0095] The outer packaging of the obtained secondary battery 40 has a textured surface on the film 10. In addition, the area between the dashed line and the end in FIG6D is the heat-pressed area 17, and the surface of this area also has a textured surface. Although the texture of the heat-pressed area 17 is smaller than that of the central part, it can also mitigate the stress generated when the secondary battery is bent.

[0096] Additionally, Figure 6E shows an example of a cross section cut by the dashed line AB in Figure 6D.

[0097] As shown in FIG6E, the unevenness of the region of membrane 11a overlapping the positive current collector 12 is different from that of the hot-pressed region 17. In addition, as shown in FIG6E, the positive current collector 12, the positive active material layer 18, the separator 13, the negative active material layer 19, and the negative current collector 14 are sequentially stacked and sandwiched between the folded membranes 11. The ends of the membranes 11 are sealed with adhesive layers 30, and electrolyte 20 is provided in the other spaces inside the folded membranes 11.

[0098] Alternatively, the membrane 22 can be manufactured by forming a pattern on the entire surface of both surfaces of the membrane 10, in the same manner as described above, thereby manufacturing the secondary battery 40 shown in FIG. 7B. FIG. 7A shows the state of the membrane 22 folded by the dashed lines in FIG. 4A.

[0099] Figure 7C shows an example of a cross-section cut by the dashed line EF of the secondary battery 40 of Figure 7B, which is manufactured using membrane 22.

[0100] As shown in Figure 7C, the unevenness of the region of the membrane 22 overlapping the positive current collector 12 is different from that of the hot-pressed region 17. In addition, as shown in Figure 7C, the positive current collector 12, the positive active material layer 18, the separator 13, the negative active material layer 19, and the negative current collector 14 are sequentially stacked and sandwiched between the folded membrane 22. The ends of the membrane 22 are sealed with an adhesive layer 30, and the electrolyte 20 is provided in the other spaces inside the folded membrane 22.

[0101] Examples of positive electrode active materials used in the positive electrode active material layer 18 include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. Examples of positive electrode active materials include compounds such as LiFeO2, LiCoO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2.

[0102] In addition, composite materials (with the general formula LiMPO4, where M is one or more of Fe(II), Mn(II), Co(II), and Ni(II)) can be used. As typical examples of the general formula LiMPO4, lithium compounds such as LiFePO4, LiNiPO4, LiCoPO4, LiMnPO4, LiFeaNibPO4, LiFeaCobPO4, LiFeaMnbPO4, LiNiaCobPO4, LiNiaMnbPO4 (a + b ≤ 1, 0 < a < 1, 0 < b < 1), LiFecNidCoePO4, LiFecNidMnePO4, LiNicCodMnePO4 (c + d + e ≤ 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFefNigCohMniPO4 (f + g + h + i ≤ 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1) can be used.

[0103] In addition, composite materials with the general formula Li(2-j)MSiO4 (where M is one or more of Fe(II), Mn(II), Co(II), and Ni(II), 0 ≤ j ≤ 2) can also be used. As typical examples of the general formula Li(2-j)MSiO4, lithium compounds such as Li(2-j)FeSiO4, Li(2-j)NiSiO4, Li(2-j)CoSiO4, Li(2-j)MnSiO4, Li(2-j)FekNilSiO4, Li(2-j)FekColSiO4, Li(2-j)FekMnlSiO4, Li(2-j)NikColSiO4, Li(2-j)NikMnlSiO4 (k + l ≤ 1, 0 < k < 1, 0 < l < 1), Li(2-j)FemNinCoqSiO4, Li(2-j)FemNinMnqSiO4, Li(2-j)NimConMnqSiO4 (m + n + q ≤ 1, 0 < m < 1, 0 < n < 1, 0 < q < 1), Li(2-j)FerNisCotMnuSiO4 (r + s + t + u ≤ 1, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1) can be cited.

[0104] Furthermore, as the positive electrode active material, sodium nasicon type compounds represented by the general formula AxM2(XO4)3 (A=Li, Na, Mg, M=Fe, Mn, Ti, V, Nb, Al, X=S, P, Mo, W, As, Si, x2) can be used. Examples of sodium nasicon type compounds include Fe2(MnO4)3, Fe2(SO4)3, and Li3Fe2(PO4)3. In addition, as positive electrode active materials, the following can be used: compounds represented by the general formulas Li2MPO4F, Li2MP2O7, and Li5MO4 (M=Fe, Mn); perovskite fluorides such as NaFeF3 and FeF3; metal chalcogenides (sulfides, selenides, tellurides) such as TiS2 and MoS2; oxides with an anti-spinel crystal structure such as LiMVO4; vanadium oxides (V2O5, V6O13, LiV3O8, etc.); manganese oxides; and organic sulfur materials.

[0105] When the carrier ion is an alkali metal ion other than lithium ion or an alkaline earth metal ion, alkali metals (e.g., sodium, potassium, etc.) or alkaline earth metals (e.g., calcium, strontium, barium, beryllium, or magnesium, etc.) can be used instead of lithium as the positive electrode active material.

[0106] As the insulator 13, insulators such as cellulose (paper), polypropylene with pores, or polyethylene with pores can be used.

[0107] As an electrolyte for an electrolyte solution, a material containing lithium ions, which are capable of carrying mobile carrier ions, is used. Typical examples of electrolytes include lithium salts such as LiPF6, LiClO4, LiAsF6, LiBF4, LiCF3SO3, Li(CF3SO2)2N, and Li(C2F5SO2)2N. These electrolytes can be used alone or in combination of two or more materials in any ratio.

[0108] Furthermore, a material capable of carrying mobile ions is used as the solvent for the electrolyte. A non-protic organic solvent is preferred as the electrolyte solvent. Typical examples of non-protic organic solvents include one or more of ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), γ-butyrolactone, acetonitrile, ethylene glycol dimethyl ether, and tetrahydrofuran. In addition, when a gelled polymer material is used as the electrolyte solvent, safety against liquid leakage is improved. Furthermore, it enables the battery to be thinner and lighter. Typical examples of gelled polymer materials include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluoropolymer gel. Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room temperature molten salts) as the electrolyte solvent, even if the internal temperature rises due to internal short circuits, overcharging, etc., the battery can be prevented from rupture or catching fire. Ionic liquids are salts in a fluidized state with high ion mobility (conductivity). Furthermore, ionic liquids contain both cations and anions. Examples of ionic liquids include those containing ethylmethylimidazolium (EMI) cations or those containing N-methyl-N-propylpiperidinium (PP13) cations.

[0109] Furthermore, solid electrolytes made of inorganic materials such as sulfides or oxides, or solid electrolytes made of polymeric materials such as PEO (polyethylene oxide), can be used instead of the electrolyte. When using a solid electrolyte, there is no need to install separators or spacers. In addition, the entire battery can be solidified, so there is no concern about liquid leakage, and safety is significantly improved.

[0110] In addition, as the negative electrode active material layer 19, a material that can dissolve and precipitate lithium or insert and deintercalate lithium ions can be used, such as lithium metal, carbon materials, alloy materials, etc.

[0111] Lithium metal has a low redox potential (3.045V lower than the standard hydrogen electrode) and a high specific capacity per weight and volume (3860mAh / g and 2062mAh / cm3, respectively), making it a superior material.

[0112] As carbon materials, examples include graphite, graphitizing carbon (soft carbon), non-graphitizing carbon (hard carbon), carbon nanotubes, graphene, fullerene, carbon black, etc.

[0113] As graphite, there are artificial graphite such as mesophase carbon microspheres (MCMB), coke-based artificial graphite, pitch-based artificial graphite, or natural graphite such as spheroidized natural graphite.

[0114] When lithium ions are intercalated in graphite (during the formation of lithium-graphite intercalation compounds), graphite exhibits a low potential similar to that of lithium metal (above 0.1V and below 0.3V vs. Li / Li+). Therefore, lithium-ion secondary batteries can exhibit high operating voltages. Furthermore, graphite has the following advantages: higher capacity per unit volume; less volume expansion; lower cost; and higher safety than lithium metal, making it a superior choice.

[0115] As the negative electrode active material, alloy materials or oxides capable of charging and discharging reactions with lithium through alloying / dealloying reactions can also be used. When the carrier ion is lithium ion, examples of alloy materials include at least one of Al, Si, Ge, Sn, Pb, Sb, Bi, Ag, Au, Zn, Cd, In, and Ga. The capacity of this element is higher than that of carbon, especially silicon, whose theoretical capacity is significantly higher at 4200 mAh / g. Therefore, it is preferable to use silicon as the negative electrode active material. Examples of alloy materials using this element include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn. Note that SiO refers to silicon oxide powder, including a portion with high silicon content, and can also be represented as SiOy (2>y>0). For example, SiO within its scope includes materials containing one or more of Si2O3, Si3O4, and Si2O, as well as mixtures of Si powder and silicon dioxide (SiO2). Additionally, SiO sometimes contains other elements (carbon, nitrogen, iron, aluminum, copper, titanium, calcium, manganese, etc.). In other words, SiO refers to materials containing multiple types of Si, including single-crystal Si, amorphous Si, polycrystalline Si, Si2O3, Si3O4, Si2O, and SiO2. Furthermore, SiO is a colored material. SiO can be distinguished from colorless, transparent, or white SiOx. Note that when SiO is used as a material in secondary batteries, repeated charging and discharging can sometimes oxidize and deteriorate SiO into SiO2.

[0116] In addition, oxides such as SiO, SnO, SnO2, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O12), lithium-graphite intercalation compound (LixC6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2) and the like can be used as negative electrode active materials.

[0117] Furthermore, as the negative electrode active material, Li(3-x)MxN (M=Co, Ni, Cu) with a Li3N-type structure containing lithium and transition metal nitrides can be used. For example, Li2.6Co0.4N3 exhibits a large charge-discharge capacity (900mAh / g, 1890mAh / cm3), so it is preferred.

[0118] When using nitrides containing lithium and transition metals, lithium ions are included in the negative electrode active material. Therefore, it is preferable to combine them with materials such as V2O5 and Cr3O8, which do not contain lithium ions, as positive electrode active materials. Note that when using materials containing lithium ions as positive electrode active materials, lithium nitrides containing lithium and transition metals can also be used as negative electrode active materials by pre-intercalating and deintercalating the lithium ions contained in the positive electrode active material.

[0119] In addition, materials that induce the conversion reaction can also be used as negative electrode active materials. For example, transition metal oxides that do not alloy with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as negative electrode active materials. Other materials that induce the conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3; sulfides such as CoS0.89, NiS, and CuS; nitrides such as Zn3N2, Cu3N, and Ge3N4; phosphides such as NiP2, FeP2, and CoP3; and fluorides such as FeF3 and BiF3. Note that because the above-mentioned fluorides have high potentials, they can also be used as positive electrode active materials.

[0120] In addition, the negative electrode active material layer 19 may also include, in addition to the negative electrode active material mentioned above, an adhesive for improving the compactness of the active material and a conductive additive for improving the conductivity of the negative electrode active material layer 19.

[0121] For example, the structure of the secondary battery is as follows: the thickness of the separator 13 is approximately 15 μm or more and 30 μm or less; the thickness of the positive electrode current collector 12 is approximately 10 μm or more and 40 μm or less; the thickness of the positive electrode active material layer 18 is approximately 50 μm or more and 100 μm or less; the thickness of the negative electrode active material layer 19 is approximately 50 μm or more and 100 μm or less; and the thickness of the negative electrode current collector 14 is approximately 5 μm or more and 40 μm or less. The thickness of the membrane 11 is approximately 0.113 mm. Furthermore, the embossing depth of the membrane 11 is approximately 500 μm. When the embossing depth of the membrane 11 is 2 mm or more, the overall thickness of the secondary battery becomes too thick.

[0122] The larger the battery capacity per unit volume, the better. The larger the volume occupied by the battery portion in the overall secondary battery, the larger the battery capacity per unit volume. When the embossing depth is increased to make the overall thickness of the secondary battery thicker, the proportion of the battery portion in the battery per unit volume is smaller, and thus the battery capacity is also smaller.

[0123] The volume ratio of the battery portion in the overall secondary battery is preferably 50% or more. Figure 8A is a cross-section along line CD of the secondary battery shown in Figure 6D. Figure 9A is a cross-section along line GH of the secondary battery shown in Figure 7B. Figures 8A and 9A show the internal components 70 of the battery, the embossed film 71 covering the upper surface of the battery, the unembossed film 72 covering the lower surface of the battery, and the embossed film 72 covering the lower surface of the battery. For simplicity, the stacked structure of the positive current collector with a positive active material layer, the separator, and the negative current collector with a negative active material layer, along with the electrolyte, are shown together as the internal components 70 of the battery. Furthermore, in the diagram, T represents the thickness of the internal component 70 of the battery, t1 represents the total embossing depth and thickness of the embossed film 71 covering the upper surface of the battery, and t2 represents the thickness of the unembossed film 72 covering the lower surface of the battery, as well as the total embossing depth and thickness of the embossed film 72. In this case, the total thickness of the secondary battery is T + t1 + t2. Therefore, in order to set the proportion of the volume occupied by the internal component 70 of the secondary battery to be more than 50%, it is necessary to satisfy T > t1 + t2.

[0124] Note that only a portion of the adhesive layer 30 is shown in Figures 6E and 7C, but a layer made of polypropylene is disposed on the entire surface of the film, which is disposed on the side to be bonded, and the hot-pressed portion of this layer only becomes the adhesive layer 30.

[0125] Furthermore, Figures 6E and 7C show examples of pressing with the lower side of the fixed membrane 11b or membrane 22. In this case, the upper side of the membrane is significantly bent to form a step. Therefore, when multiple combinations of the above-mentioned stacks are provided between the folded membranes 11 or 22, for example, more than eight combinations of the above-mentioned stacks, the step becomes too large, and the membrane 11a or the upper membrane 22 may be subjected to excessive stress. In addition, there is a concern that the misalignment between the ends of the upper and lower membranes may increase. In this case, to prevent end misalignment, the lower membrane can also be stepped and pressed in the center to ensure uniform stress.

[0126] When a large misalignment occurs, there is a region where a portion of the end of one membrane does not overlap with the other membrane. This region can also be removed to align the end of the upper membrane with the end of the lower membrane, thus correcting the misalignment.

[0127] Here, the flow of current during charging of a secondary battery will be explained with reference to FIG6F. When a secondary battery using lithium as a carrier ion is considered as a closed circuit, the direction of lithium ion migration is the same as the direction of current flow. Note that in a secondary battery using lithium, since the anode and cathode are interchanged depending on whether it is charging or discharging, and the oxidation reaction and reduction reaction are interchanged, the electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. Therefore, in this specification, even when charging, discharging, supplying a reverse pulse current, and supplying a charging current, the positive electrode is referred to as the "positive electrode" or "+ electrode," and the negative electrode is referred to as the "negative electrode" or "- electrode." If the terms anode and cathode related to oxidation and reduction reactions are used, the anode and cathode will be interchanged during charging and discharging, which may cause confusion. Therefore, the terms anode and cathode are not used in this specification. If the terms anode and cathode are used, it will clearly indicate whether it is charging or discharging, and also indicate whether it is the corresponding positive electrode (+ electrode) or negative electrode (- electrode).

[0128] The two terminals shown in Figure 6F are connected to the charger to charge the secondary battery 40. As the charging of the secondary battery 40 progresses, the potential difference between the electrodes increases. In Figure 6F, electrons flow from one of the external terminals of the secondary battery 40 to the positive current collector 12; consequently, within the secondary battery 40, current flows from the positive current collector 12 to the negative current collector 14. The positive direction in Figure 6F represents the direction of current flow from the negative terminal to the other external terminal of the secondary battery 40. That is, the direction in which the charging current flows is the direction of the current.

[0129] In this embodiment, an example is shown where a rectangular membrane is folded in the center and the two ends are overlapped to form a seal. However, the shape of the membrane does not necessarily have to be rectangular. The shape of the membrane can also be any symmetrical shape other than a rectangle, such as a triangle, square, pentagon or other polygon, circle, star or the like.

[0130] In this embodiment, an example of a small battery for a portable information terminal, etc. is shown, but it is not limited thereto. One aspect of the present invention can also be applied to a large battery installed in a vehicle, etc.

[0131] Note that this embodiment shows an application example of a lithium-ion secondary battery, but the invention is not limited to this. It can also be applied to a wide variety of secondary batteries, such as lead-acid batteries, lithium-ion polymer secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, silver-zinc oxide batteries, solid-state batteries, air batteries, etc. Furthermore, it can be applied to a wide variety of energy storage devices, such as primary batteries, capacitors, lithium-ion capacitors, etc. Moreover, it can also be applied to solar cells, light sensors, touch sensors, display devices, FPCs (flexible printed circuit boards), optical films (polarizing plates, retardation plates, prisms, light reflectors, light diffusers, etc.), etc.

[0132] Implementation Method 2

[0132] In this embodiment, referring to FIGS. 6A to 6F and FIGS. 8A to 8D, an example is shown of manufacturing two films 11a and 11b as shown in FIG. 3C and bonding the two films together to manufacture a secondary battery. Referring to FIGS. 7A to 7C and FIGS. 9A to 9C, an example is shown of manufacturing two films 23 and 24 as shown in FIG. 4B and bonding the two films together to manufacture a secondary battery.

[0133] Instead of using a flexible secondary battery alone, the flexible secondary battery is used in conjunction with an electronic device. Therefore, in many cases, once the shape of the secondary battery installed in the electronic device is determined, it is not necessary to change the shape of the secondary battery.

[0134] For example, if a secondary battery bent at a certain angle in a certain direction is installed in an electronic device, in many cases the shape of the secondary battery will be fixed in that bent state. Therefore, it is not necessary to restore the bent state to its original state. Furthermore, it is not necessary to bend the secondary battery in the opposite direction.

[0135] Therefore, when you want to bend a secondary battery, you only need to consider the stress applied when bending the secondary battery in only one direction.

[0136] Figure 8B shows a cross-section along line CD when the secondary battery is bent in one direction. This secondary battery is the same as the battery shown in Figure 6D, which is manufactured using the membrane shown in Figure 6A. Note that, for the sake of simplicity, the stacked structure of the positive current collector with the positive active material layer, the separator, and the negative current collector with the negative active material layer, as well as the electrolyte, are shown together as the internal components 70 of the battery.

[0137] When the secondary battery is bent as shown in FIG8B, the film 72 covering the lower surface of the secondary battery is subjected to compressive stress, while the film 71 covering the upper surface of the secondary battery is subjected to tensile stress. As shown in FIG8B, when a pattern formed by concave or convex portions is formed on the surface of the film 71, even if the film 71 is subjected to tensile stress as described above, the effect of strain can be suppressed within an acceptable range. Therefore, the secondary battery can be deformed within a range where the radius of curvature of the outer packaging near the center of curvature is 10 mm or more, preferably 30 mm or more.

[0138] Figure 9B shows a cross-section along line GH when the secondary battery is bent in one direction. This secondary battery is the same as the battery shown in Figure 7B, manufactured using the membrane shown in Figure 7A. Note that, for the sake of simplicity, the stacked structure of the positive current collector with the positive active material layer, the separator, and the negative current collector with the negative active material layer, as well as the electrolyte, are shown together as the internal components 70 of the battery.

[0139] FIG. 8B illustrates an example where the film 71 covering the upper surface of the secondary battery has only a pattern formed by recesses or convexities on its surface; however, the present invention is not limited to this. Embossing can also be performed not only on the film 71 but also on the film 72 on the lower surface of the secondary battery, which is subjected to compressive stress as shown in FIG. 9B. By having patterns formed by recesses or convexities on both films 71 and 72, the effects of strain can be further suppressed. Regarding the film 72 on the lower surface of the secondary battery subjected to compressive stress, it can have a geometric pattern of intersecting diagonal lines in two directions, or it can have a longitudinal stripe pattern 1301 as shown in FIG. 10A, or a transverse stripe pattern 1302 as shown in FIG. 10B.

[0140] The membrane 71 covering the upper surface of the secondary battery is subjected to compressive stress, thus it is preferable to apply an embossing process to its surface so that the membrane can be stretched more easily. By embossing with a narrower distance, the surface area of ​​the membrane is increased, thereby making the membrane easier to stretch when it is bent. Therefore, when the membrane is bent with a smaller radius of curvature, as shown in FIG8C or FIG9C, it is preferable to make the embossing distance of the membrane covering it narrower than the embossing distance of the membrane covering it shown in FIG8A or FIG9A.

[0141] In addition, in Figures 9A to 9C, a secondary battery is completed by sealing two films with optimized embossing depth and distance. However, it is also possible to perform embossing processes to optimize both tensile stress and compressive stress on one film. In this case, embossing to optimize tensile stress is performed on one half of the film, while embossing to optimize compressive stress is performed on the remaining half. Then, the film is bent along the boundary between the embossed areas optimized for tensile stress and the embossed areas optimized for compressive stress, and the end faces of the film are aligned to achieve a seal.

[0142] FIG8D is an enlarged view of the area surrounded by the dashed line of the membrane 72 shown in FIG8A and FIG9A. The membrane covering the lower surface of the secondary battery can be a membrane with multiple layers stacked as shown in FIG8D. For example, layers of a membrane 72a using polypropylene, a membrane 72b using aluminum, and a membrane 72c using nylon can be formed.

[0143] After preparing membrane 11a with optimized embossing depth and distance, and membrane 11b without embossing, or membranes 23 and 24 with optimized embossing depth and distance, a combination consisting of a stack of positive current collector 12, separator 13, and negative current collector 14 as shown in FIG. 6B is provided between the two membranes, similar to Embodiment 1. A positive active material layer 18 is formed on a portion of the surface of the positive current collector 12, and a negative active material layer 19 is formed on a portion of the surface of the negative current collector 14. Next, the lead electrode 16 is electrically connected to the protrusion of the positive current collector 12 by ultrasonic soldering or the like, and the lead electrode 16 is electrically connected to the protrusion of the negative current collector 14 by ultrasonic soldering or the like. In addition, in order to leave one side for injecting electrolyte, the three sides of the membrane are heat-pressed together to seal it. Under reduced pressure or in an inert gas atmosphere, the desired amount of electrolyte is dripped into the bag-shaped membrane. Finally, the edge of the membrane that was not heat-pressed is sealed by heat pressing to complete the secondary battery.

[0144] In this embodiment, the case in which the secondary battery is used when the shape of the secondary battery which is installed in an electronic device or the like is fixed in one direction is described. However, it is also possible to repeatedly bend and stretch the secondary battery which is bent in one direction.

[0145] Implementation Method 3

[0145] In this embodiment, an example of housing a combination of multiple layers in a folded membrane 11 will be described with reference to FIGS. 11A to 13C. Part of this combination is different from that in Embodiment 1.

[0146] The combination of layers shown in this embodiment can also be applied to the combination of layers stored between the embossed film 11a and the unembossed film 11b shown in Embodiment 2, and the combination of layers stored between the embossed film 23 and the film 24.

[0147] Figure 11A shows a top view of the positive current collector 12, Figure 11B shows a top view of the insulator 13, Figure 11C shows a top view of the negative current collector 14, Figure 11D shows a top view of the sealing layer 15 and the lead electrode 16, and Figure 11E shows a top view of the membrane 11.

[0148] In Figures 11A to 11E, the dimensions of the positive current collector, the negative current collector, and the isolator are approximately the same. The dimension of the area 21 surrounded by the dotted line in Figure 11E is approximately the same as the dimension of the isolator in Figure 11B. In addition, the area between the dashed line and the end in Figure 11E corresponds to the hot-pressed area 17.

[0149] Figure 12A shows an example in which a positive electrode active material layer 18 is provided on both surfaces of the positive electrode current collector 12. Specifically, the stacked structure is provided in sequence as follows: negative electrode current collector 14, negative electrode active material layer 19, separator 13, positive electrode active material layer 18, positive electrode current collector 12, positive electrode active material layer 18, separator 13, negative electrode active material layer 19, and negative electrode current collector 14. Figure 12B shows a cross-sectional view of this stacked structure cut off at plane 80.

[0150] In Figure 12A, an example using two insulators is shown, but it is also possible to fold one insulator and seal both ends of the insulator to form a bag shape, and house the positive current collector 12 therein. Positive active material layers 18 are formed on both surfaces of the positive current collector 12 housed in the bag-shaped insulator.

[0151] Alternatively, negative electrode active material layers 19 may be provided on both surfaces of the negative electrode current collector 14. Figure 12C shows an example of a secondary battery consisting of two negative electrode current collectors 14 having a negative electrode active material layer 19 on only one surface, sandwiching three negative electrode current collectors 14 having negative electrode active material layers 19 on both surfaces, four positive electrode current collectors 12 having positive electrode active material layers 18 on both surfaces, and eight separators 13. In this case, four pouch-shaped separators may be used instead of eight separators.

[0152] The capacity of the secondary battery can be increased by increasing the number of layers. In addition, the thickness of the secondary battery can be reduced by providing a positive active material layer 18 on the two surfaces of the positive current collector 12 and a negative active material layer 19 on the two surfaces of the negative current collector 14.

[0153] FIG13A shows a secondary battery formed in which a positive active material layer 18 is provided on only one surface of the positive current collector 12 and a negative active material layer 19 is provided on only one surface of the negative current collector 14. Specifically, a negative active material layer 19 is provided on one surface of the negative current collector 14, and an insulator 13 is stacked in contact with the negative active material layer 19. The surface of the insulator 13 that is not in contact with the negative active material layer 19 is in contact with the positive active material layer 18 formed on one surface of the positive current collector 12. The other surface of the positive current collector 12 is in contact with other positive current collectors 12 on one surface of which a positive active material layer 18 is formed. At this time, two positive current collectors 12 are arranged facing each other with the surfaces without the positive active material layer 18. Furthermore, the positive active material layer 19 formed on one surface of the positive current collector 14 is stacked in a manner that is in contact with the other insulators 13 formed thereon. Figure 13B shows a cross-sectional view of the stacked structure of Figure 13A cut off at a plane 90°.

[0154] Two insulators are used in Figure 13A, but the following structure can also be adopted: fold an insulator and seal its two ends to make the insulator into a bag shape, and sandwich two positive current collectors 12 with a positive active material layer 18 on one surface of the insulator between the bag-shaped insulator.

[0155] FIG13C shows a diagram of multiple stacked structures as shown in FIG13A. In FIG13C, the negative electrode current collector 14 is arranged such that the faces of the negative electrode current collector 14 without the negative electrode active material layer 19 are opposite to each other, and the positive electrode current collector 12 is arranged such that the faces of the positive electrode current collector 12 without the positive electrode active material layer 18 are opposite to each other. FIG13C shows the appearance of stacked 12 positive electrode current collectors 12, 12 negative electrode current collectors 14, and 12 separators 13.

[0156] Compared to the structure in which positive active material layers 18 are provided on both surfaces of the positive current collector 12 and negative active material layers 19 are provided on both surfaces of the negative current collector 14, the structure in which positive active material layers 18 are provided on only one surface of the positive current collector 12 and negative active material layers 19 are provided on only one surface of the negative current collector 14, and these layers are stacked together, results in a greater number of current collectors and thus a thicker secondary battery. However, the surfaces of the positive current collector 12 without positive active material layers 18 are opposite to the surfaces of other positive current collectors 12 without positive active material layers 18, and their metal surfaces are in contact with each other. Similarly, the surfaces of the negative current collector 14 without negative active material layers 19 are opposite to the surfaces of other positive current collectors 14 without negative active material layers 19, and their metal surfaces are in contact with each other. Because the metal surfaces are in contact with each other, they can easily slide against each other without generating significant friction. Therefore, when a secondary battery is bent, it is easy to bend because it slides on the internal metal surface of the secondary battery.

[0157] The protrusions of the positive current collector 12 and the negative current collector 14 are called tab portions. When the secondary battery is bent, the tab portions of the positive current collector 12 and the negative current collector 14 are easily cut off. This is because the tab portions have a protruding, elongated shape, so the root of the tab portion is easily subjected to stress.

[0158] The structure in which a positive active material layer 18 is provided on only one surface of the positive current collector 12 and a negative active material layer 19 is provided on only one surface of the negative current collector 14, and these layers are stacked together, has surfaces where the positive current collectors 12 and the negative current collectors 14 contact each other. The frictional resistance is low on the surfaces where the current collectors contact each other, and these surfaces easily release stress caused by differences in the radius of curvature when the battery is deformed. In the structure in which a positive active material layer 18 is provided on only one surface of the positive current collector 12 and a negative active material layer 19 is provided on only one surface of the negative current collector 14, the total thickness of the joint is also increased. Therefore, compared to the structure in which a positive active material layer 18 is provided on both surfaces of the positive current collector 12 and a negative active material layer 19 is provided on both surfaces of the negative current collector 14, stress is dispersed, making it less likely for the joint to break.

[0159] With this stacked structure, all the positive current collectors 12 are fixed and electrically connected by ultrasonic soldering that can be bonded in one step. When the positive current collectors 12 are ultrasonically soldered while overlapping with the lead electrodes, the electrical connection can be achieved efficiently.

[0160] Ultrasonic soldering can be performed by applying pressure and ultrasonic waves at the same time by overlapping the connector with the connector of other positive current collectors.

[0161] Implementation Method 4

[0161] In this embodiment, an example of an electronic device equipped with a lithium-ion secondary battery obtained using any of Embodiments 1 and 2 is shown with reference to FIGS. 14A to 16B. It can also be used in combination with Embodiment 3.

[0162] The secondary battery obtained using any one of embodiments 1 to 3 is a thin outer packaging and a flexible film, thereby allowing the secondary battery to be attached to a support structure with a curved surface and deformed into the shape of a curved portion reflecting the region of the support structure with a large radius of curvature.

[0163] Examples of electronic devices that utilize flexible energy storage devices include, for instance, display devices such as head-mounted displays or goggle-type displays (also known as televisions or television receivers), personal computers such as desktop personal computers or laptop personal computers, monitors for computers, digital cameras, digital camcorders, digital photo frames, electronic notebooks, e-book readers, electronic translators, toys, voice input devices such as microphones, electric shavers, electric toothbrushes, high-frequency heating devices such as microwave ovens, electric rice cookers, washing machines, vacuum cleaners, water heaters, electric fans, hair dryers, humidifiers, dehumidifiers, air conditioning equipment such as air conditioners, dishwashers, dish dryers, clothes dryers, quilt dryers, refrigerators, electric freezers, electric refrigerated freezers, DNA preservation freezers, flashlights, power tools, smoke detectors, gas alarm devices, security alarms, industrial robots, hearing aids, pacemakers, X-ray imaging devices, and radiation measuring devices. Health care or medical equipment such as counters, electric massagers, dialysis devices, mobile phones (also known as mobile phones or mobile phone devices), portable game consoles, portable information terminals, lighting equipment, headphones, speakers, remote controls, clocks such as table clocks or wall clocks, cordless handsets, walkie-talkies, pedometers, calculators, portable or fixed audio playback devices such as digital audio players, and large game machines such as pinball machines, etc.

[0164] In addition, the flexible energy storage device can also be assembled along the curved surfaces of the inner or outer walls of a house or high-rise building, or the interior or exterior of a car.

[0165] Figure 14A shows an example of a mobile phone. In addition to the display unit 7402 assembled in the housing 7401, the mobile phone 7400 also includes operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. Furthermore, the mobile phone 7400 has a power storage device 7407.

[0166] Figure 14B shows the mobile phone 7400 in a bent state. When the mobile phone 7400 is deformed by an external force and bent as a whole, the energy storage device 7407 disposed inside it is also bent. Figure 14C shows the bent energy storage device 7407. The energy storage device 7407 is a laminated battery (also called a stacked battery or membrane-exposed battery). The energy storage device 7407 is fixed in the bent state. The energy storage device 7407 has lead electrodes 7408 that are electrically connected to the current collector 7409. For example, the film of the outer packaging of the energy storage device 7407 is embossed, so the reliability of the energy storage device 7407 in the bent state is high. Furthermore, the mobile phone 7400 may also have a SIM card slot or a connector for connecting USB devices such as USB memory.

[0167] Figure 14D shows an example of a flexible mobile phone. The bracelet-type mobile phone shown in Figure 14E can be realized by bending it into a shape that follows the forearm. The mobile phone 7100 includes a housing 7101, a display 7102, operation buttons 7103, and a power storage device 7104. Figure 14F shows the flexible power storage device 7104. When the power storage device 7104 is worn on the user's arm in a bent state, the housing deforms, and the curvature of part or all of the power storage device 7104 changes. Specifically, part or all of the housing or the main surface of the power storage device 7104 deforms within a radius of curvature of 10 mm or more and 150 mm or less. The power storage device 7104 has lead electrodes 7105 that are electrically connected to a current collector 7106. For example, because the surface of the film of the outer packaging of the power storage device 7104 is pressed to form multiple irregularities, high reliability can be maintained even if the curvature of the power storage device 7104 is changed multiple times. Additionally, the mobile phone 7100 may also include a SIM card slot or a connector for connecting USB devices such as USB memory. When the mobile phone shown in FIG14D is folded in the center, it can become the shape shown in FIG14G. Furthermore, as shown in FIG14H, when the mobile phone is further folded in the center with its ends overlapping to reduce its size, it can be reduced to a size that can be placed in a user's pocket. Thus, the mobile phone shown in FIG14D can be transformed into various shapes. In order to change the shape of the mobile phone, it is preferable that at least the housing 7101, the display 7102, and the power storage device 7104 are flexible.

[0168] Additionally, Figure 15A shows an example of a vacuum cleaner. By equipping the vacuum cleaner with a rechargeable battery, a cordless vacuum cleaner can be realized. Inside the vacuum cleaner, in order to ensure a dust collection space for storing the sucked-up debris, the smaller the space occupied by the power storage device 7604, the better. Therefore, it is useful to arrange a thin, flexible power storage device 7604 between the outer surface of the vacuum cleaner and the dust collection space.

[0169] The vacuum cleaner 7600 includes an operation button 7603 and a power storage device 7604. Additionally, Figure 15B shows a flexible power storage device 7604. The outer packaging film of the power storage device 7604 is embossed, thus ensuring high reliability of the power storage device 7604 in a bent state. The power storage device 7604 has a lead electrode 7601 electrically connected to the negative terminal and a lead electrode 7602 electrically connected to the positive terminal.

[0170] Additionally, in the energy storage device 7604, two lead electrodes are exposed in one short side of the outer casing. Figure 15C shows a flexible energy storage device 7605 with another structure. In the energy storage device 7605, the current collector or lead electrodes are exposed in both short sides of the outer casing. By embossing the film of the outer casing of the energy storage device 7605, it can be bent, thus improving reliability.

[0171] The thin-film energy storage device 7604 can be manufactured using the manufacturing method of the laminated secondary battery shown in Embodiments 1 to 3.

[0172] The slim battery storage device 7604 has a laminated structure and is fixed in a bent state. Furthermore, the vacuum cleaner 7600 has a display section 7606 for displaying the battery level and other parameters of the slim battery storage device 7604, and the display surface of this display section 7606 is also curved along the shape of the outer surface of the vacuum cleaner. Additionally, the vacuum cleaner has a cable for connecting to a socket; when the slim battery storage device 7604 is sufficiently charged, the cable can be unplugged from the socket and the vacuum cleaner can be used. Moreover, the slim battery storage device 7604 can also be charged wirelessly without using a cable.

[0173] Furthermore, by installing flexible energy storage devices on vehicles, next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), or plug-in hybrid electric vehicles (PHEVs) can be realized. In addition, flexible energy storage devices can also be installed on agricultural machinery, electric bicycles (including electric-assisted bicycles), motorcycles, electric wheelchairs, electric transport vehicles, small or large ships, submarines, fixed-wing aircraft and rotary-wing aircraft, as well as aircraft, rockets, artificial satellites, space probes, planetary probes, spacecraft, and other mobile bodies.

[0174] Figures 16A and 16B illustrate a vehicle using one aspect of the present invention. The automobile 8100 shown in Figure 16A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, the automobile 8100 is a hybrid vehicle that can appropriately use an electric motor or an engine as a power source for driving. When a laminated secondary battery is installed in the vehicle, a battery module accumulating multiple laminated secondary batteries is provided in one or more parts. By using one aspect of the present invention, the energy storage device itself can be miniaturized and lightweighted. For example, by placing an energy storage device with a curved surface inside the tire, a vehicle with a long driving range can be achieved. In addition, energy storage devices of various shapes can be placed in gaps within the vehicle, thus ensuring trunk or passenger space. The automobile 8100 includes an energy storage device. The energy storage device not only drives the electric motor but also supplies electricity to light-emitting devices such as headlights 8101 or interior lights (not shown).

[0175] In addition, the energy storage device can also supply power to display devices such as speedometers and tachometers in the vehicle 8100. Furthermore, the energy storage device can also supply power to semiconductor devices such as navigation systems in the vehicle 8100.

[0176] In the automobile 8200 shown in Figure 16B, power can be supplied from an external charging device using either a plug-in method or a contactless power supply method to charge the energy storage device installed in the automobile 8200. Figure 16B shows the charging of the energy storage device installed in the automobile 8200 using a ground-mounted charging device 8021 via a cable 8022. When charging, the charging method or connector specifications can be appropriately determined according to the specifications of CHAdeMO (a trademark registered in Japan) or the "Combined Charging System". The charging device 8021 can also be a charging station installed in a commercial facility or a power source in a home. For example, by using plug-in technology to supply power from an external source, the energy storage device installed in the automobile 8200 can be charged. The AC power can be converted into DC power using a conversion device such as an AC / DC converter for charging.

[0177] Additionally, although not shown in the figure, the receiving device can be installed in the vehicle and charged by non-contact power supply from a ground-based power transmission device. When using this non-contact power supply method, by assembling the power transmission device in the road or exterior wall, charging can be performed both when the vehicle is parked and while it is in motion. Furthermore, this non-contact power supply method can also be used for power transmission and reception between two vehicles. Moreover, solar cells can be installed on the exterior of the vehicle to charge the energy storage device when the vehicle is parked or in motion. Such non-contact power supply can be achieved using electromagnetic induction or magnetic field resonance.

[0178] According to one aspect of the present invention, the energy storage device can be configured more freely, and vehicle design can be carried out more efficiently. Furthermore, according to one aspect of the present invention, the characteristics of the energy storage device can be improved, and the energy storage device itself can be miniaturized and lightweight. If the energy storage device itself can be miniaturized and lightweight, it contributes to the lightweighting of the vehicle, thereby extending the driving range. Additionally, the energy storage device installed in the vehicle can also be used as a power supply source outside the vehicle. In this case, the use of commercial power sources during peak electricity demand periods can be avoided.

[0179] This embodiment can be freely combined with any one of embodiments 1 to 3.

[0180] In addition, the content described in one embodiment (or a part thereof) may be applied to, combined with or replaced by other content described in that embodiment (or a part thereof) and / or content described in one or more other embodiments (or a part thereof).

[0181] Note that the content described in the embodiments refers to the content illustrated using various diagrams in each embodiment or the content recorded in the text of the specification.

[0182] In addition, more diagrams can be formed by combining a diagram (or a part thereof) shown in one embodiment with other parts thereof, other diagrams (or a part thereof) shown in that embodiment and / or diagrams (or a part thereof) shown in one or more other embodiments.

[0183] Furthermore, an invention can be constructed that does not include content not specified in the drawings or text of the specification. Additionally, when a numerical range of a certain value is described (upper limit and lower limit, etc.), an invention can be constructed by arbitrarily narrowing that range or removing a portion of that range. Thus, for example, it can be stipulated that prior art is not included within the technical scope of one aspect of the present invention.

[0184] As a specific example, a circuit diagram showing a circuit including the first to fifth transistors is described. In this case, the invention can be defined as the case where the circuit does not include a sixth transistor. It can also be defined as the case where the circuit does not include a capacitor element. Furthermore, it can be defined as the case where the circuit does not include a sixth transistor having a specific connection structure. It can also be defined as the case where the circuit does not include a capacitor element having a specific connection structure. For example, it can be defined as the case where a sixth transistor, whose gate is connected to the gate of a third transistor, is not included. For example, it can be defined as the case where a capacitor element, whose first electrode is connected to the gate of a third transistor, is not included.

[0185] As another specific example, regarding a certain value, it may be stated that "a certain voltage is preferably 3V or higher and 10V or lower." In this case, for example, it may be defined as an invention excluding the case where the voltage is -2V or higher and 1V or lower. For example, it may be defined as an invention excluding the case where the voltage is 13V or higher. For example, it may be defined as an invention excluding the case where the voltage is 5V or higher and 8V or lower. For example, it may be defined as an invention excluding the case where the voltage is approximately 9V. For example, it may be defined as an invention excluding the case where the voltage is 3V or higher and 10V or lower but not 9V. Note that even if it is stated that "a certain value is preferably within a certain range" or "a certain value preferably satisfies a certain condition," it is not limited to this statement. In other words, the statement of "preferably," "mostly," etc., does not necessarily specify the value.

[0186] As another specific example, regarding a certain value, for example, it is stated that "a certain voltage is preferably 10V". In this case, for example, it can be defined as an inventive method excluding the case where the voltage is -2V or higher and 1V or lower. For example, it can be defined as an inventive method excluding the case where the voltage is 13V or higher.

[0187] As another specific example, regarding the properties of a certain substance, it may be stated that "a certain film is an insulating film." In this case, for example, a scenario where the insulating film is not an organic insulating film may be defined as an inventive method. For example, a scenario where the insulating film is not an inorganic insulating film may be defined as an inventive method. For example, a scenario where the film is not a conductive film may be defined as an inventive method. For example, a scenario where the film is not a semiconductor film may be defined as an inventive method.

[0188] As another specific example, regarding a certain laminated structure, it may be described as "a certain membrane is provided between membrane A and membrane B". In this case, for example, the case of a laminated membrane consisting of four or more layers excluding the membrane may be defined as an invention. For example, the case of excluding the case of a conductive membrane being provided between membrane A and the membrane may be defined as an invention.

[0189] Furthermore, even if the connection portions of all terminals of active elements (transistors, diodes, etc.) and passive elements (capacitors, resistors, etc.) are not specified in this specification, those skilled in the art can sometimes construct an inventive method. That is to say, it can be said that even if the connection portions are not specified, an inventive method is clearly defined. Moreover, when the content specifying the connection portions is described in this specification, it can sometimes be determined that an inventive method without specifying the connection portions is described in this specification. Especially when there may be multiple terminal connection portions, the connection portions of the terminals need not be limited to the specified portions. Therefore, sometimes by specifying only a portion of the connection portions of the terminals of active elements (transistors, diodes, etc.) and passive elements (capacitors, resistors, etc.), an inventive method can be constructed.

[0190] Furthermore, in this specification, etc., as long as at least one connection portion of a circuit is specified, a person skilled in the art can sometimes constitute an invention. Alternatively, as long as at least one function of a circuit is specified, a person skilled in the art can sometimes constitute an invention. That is to say, it can be said that as long as the function is specified, an inventive approach is clearly defined. Furthermore, it can sometimes be determined that an inventive approach with specified function is described in this specification, etc. Therefore, even if the function of a circuit is not specified, specifying the connection portion is considered an inventive approach and can constitute an inventive approach. Furthermore, even if the connection portion of a circuit is not specified, specifying its function is considered an inventive approach and can constitute an inventive approach.

[0191] Note that in this specification, a portion of the drawings or text shown in a particular embodiment can be taken to constitute a mode of the invention. Therefore, when drawings or text describing a particular part are provided, taking a portion of those drawings or text is also considered a mode of the disclosed invention, and thus can constitute a mode of the invention. Furthermore, it can be said that a mode of the invention is clearly defined. Therefore, for example, a portion of a drawing or text describing one or more of active elements (transistors, diodes, etc.), wiring, passive elements (capacitors, resistors, etc.), conductive layers, insulating layers, semiconductor layers, organic materials, inorganic materials, parts, devices, operating methods, manufacturing methods, etc., can be taken to constitute a mode of the invention. For example, M elements (M is an integer, M...) can be taken from a circuit diagram composed of N (N is an integer) circuit elements (transistors, capacitors, etc.). <n)電路元件(電晶體、電容元件等)來構成發明的一個方式。作為其他例子，可以從由n個(n是整數)層構成的剖面圖中取出m個(m是整數，m<n)層來構成發明的一個方式。再者，作為其他例子，可以從由n個(n是整數)要素構成的流程圖中取出m個(m是整數，m<n)要素來構成發明的一個方式。作為其他的例子，當從"a包括b、c、d、e或f”的記載中任意抽出一部分的要素時，可以構成"a包括b和e”、"a包括e和f”、"a包括c、e和f”或者"a包括b、c、d和e”等的發明的一個方式。

[0192] In this specification, etc., when at least one specific example is shown in the drawings or text illustrating a particular embodiment, those skilled in the art can easily understand that the general concept of that specific example is derived from it. Therefore, when at least one specific example is shown in the drawings or text illustrating a particular embodiment, the general concept of that specific example is also a mode of the disclosed invention, and can constitute a mode of the invention. Furthermore, it can be said that a mode of the invention is clearly defined.

[0193] Furthermore, in this specification and the like, at least the content shown in the drawings (or a portion thereof) is one aspect of the disclosed invention and can constitute one aspect of the invention. Therefore, even if a certain content is not described in the text, if that content is shown in the drawings, it can be said that that content is one aspect of the disclosed invention and can constitute one aspect of the invention. Similarly, a drawing that extracts a portion of the drawings is also one aspect of the disclosed invention and can constitute one aspect of the invention. Moreover, it can be said that one aspect of the invention is clearly defined.

[0193] Example 1

[0194] In this embodiment, the results of comparing the frictional force of an electrode with active material layers on both surfaces of the current collector with the frictional force of an electrode with active material layers on one surface of the current collector are explained using Figures 17A to 18.

[0195] First, in order to conduct a comparative experiment on friction, multiple electrodes were stacked on a glass plate and the electrodes between them were pulled out.

[0196] In the actual structure of a secondary battery, in the area surrounded by the outer packaging, a first current collector having a negative electrode active material layer on its surface, a second current collector having a positive electrode active material layer on its surface, and a third current collector having a negative electrode active material layer on its surface are arranged in a manner that partially overlaps, with a separator sandwiched between the first current collector and the second current collector. Additionally, a separator is also sandwiched between the second current collector and the third current collector.

[0197] In this embodiment, the same stacked body as the above-described structure used for secondary batteries was used in the experiment.

[0198] A first current collector, a second current collector, and a third current collector are stacked on a glass plate. When a load of 42 g / cm2 is applied to the stacked first current collector, second current collector, and third current collector, a digital push-pull force gauge (manufactured by AIKOH ENGINEERING CO.,LTD, Japan, RX-2) is used to pull out the current collector with a positive electrode active material layer on its surface in the horizontal direction of the paper to measure its maximum value.

[0199] Figure 17A shows a cross-sectional schematic diagram of a sample containing a negative electrode with active material disposed on one surface of a current collector. As shown in Figure 17A, a negative electrode active material layer 102a, a negative electrode current collector 103a, a negative electrode current collector 103b, a negative electrode active material layer 102b, an isolator 104, a positive electrode active material layer 105a, a positive electrode current collector 106, a positive electrode active material layer 105b, an isolator 104, a negative electrode active material layer 107a, a negative electrode current collector 108a, a negative electrode current collector 108b, and a negative electrode active material layer 107b are sequentially stacked on a glass plate 101. Furthermore, while maintaining an applied load 109, the positive electrode (positive electrode active material layer 105a, positive electrode current collector 106, and positive electrode active material layer 105b) clamped by a clip 120 is pulled out in the horizontal direction 110 towards the paper surface to measure the frictional force.

[0200] Figure 17B shows a cross-sectional schematic diagram of a sample containing a negative electrode with active material disposed on both surfaces of a current collector. As shown in Figure 17B, a negative electrode active material layer 102a, a negative electrode current collector 103, a negative electrode active material layer 102b, an isolator 104, a positive electrode active material layer 105a, a positive electrode current collector 106, a positive electrode active material layer 105b, an isolator 104, a negative electrode active material layer 107a, a negative electrode current collector 108, and a negative electrode active material layer 107b are sequentially stacked on a glass plate 101. Furthermore, while maintaining an applied load 109, the positive electrode (positive electrode active material layer 105a, positive electrode current collector 106, and positive electrode active material layer 105b) held by a clamp 120 is pulled out in the horizontal direction 110 towards the paper surface to measure the frictional force.

[0201] Furthermore, under the two conditions shown in FIG17A and FIG17B, the positive electrode is coated on both surfaces. Thus, the positive electrode includes a positive electrode active material layer 105a, a positive electrode current collector 106, and a positive electrode active material layer 105b.

[0202] Additionally, Figure 17C shows a photograph of a person conducting a comparative experiment on friction.

[0203] Furthermore, comparisons were also made under the two conditions shown in Figures 17A and 17B, with the laminate in a dry state and the laminate wetted by electrolyte. Measurements were performed three times under each condition, and the results are shown in Figure 18.

[0204] As shown in Figure 18, when the internal components of the secondary battery have the structure shown in Figure 17A, the secondary battery is prone to bending under both dry and wet conditions. This is because the metal surfaces are in contact with each other, and without significant friction, the surfaces in contact with each other are prone to sliding. Therefore, it can be seen that by including a negative electrode with an active material layer disposed on one surface of the current collector, the secondary battery can be easily bent.

[0204] Example 2

[0205] In this embodiment, the results of the following experiment are illustrated using Figures 19A to 21C. This experiment is an experiment in which the water resistance of a thin secondary battery is evaluated after bending it multiple times using the device shown in Figures 21A to 21C, in order to observe whether the outer packaging of the secondary battery is damaged due to the bending operation.

[0206] To determine whether the outer packaging was damaged, not only was it visually inspected, but the internal moisture content of the secondary battery was also measured using a Karl Fischer moisture meter. A sample was deemed to lack sufficient water resistance when the moisture content exceeded 100 ppm. When the outer packaging was severely damaged due to bending, resulting in cracks, moisture entered the interior through the cracks, thus increasing the internal moisture content.

[0207] As a Karl Fischer moisture analyzer, a device using the electrostatic titration method is used (manufactured by Kyoto Electric Industries, Ltd., MKC-610-DT).

[0208] First, 12 types of samples are manufactured. The shapes of the samples are as shown in Figures 19A to 20, with different lengths and widths. The number of layers between the samples is made so that the thickness of the samples is different and the radius of curvature when bent is also different, resulting in a total of 12 types of samples.

[0209] The above-described sample was manufactured using the same steps as those used in the secondary battery that employed the embossed film according to Embodiments 1 to 3 as the outer packaging. Note that propylene carbonate was used instead of the electrolyte in the space surrounded by the secondary battery's outer packaging, and moisture was detected in the propylene carbonate. Therefore, since the sample shown in this embodiment cannot be used as a secondary battery, it cannot be charged and discharged. However, if an electrolyte is used instead of propylene carbonate to manufacture the secondary battery, it can be charged and discharged. Table 1 shows the design capacity at this time.

[0210]

[0211] In addition, Table 2 shows the total thickness of each sample corresponding to the number of stacks of current collectors in the area surrounded by the outer packaging.

[0212]

[0213] Three of the twelve manufactured samples were bent 10,000 times using a bending tester. After the samples were kept in a container (thermostatic bath) with a pressure regulating mechanism at 120°C for 24 hours, the water content inside the samples was measured using a Karl Fischer moisture analyzer. Table 1 shows the measurement results. If at least one of the three samples had a water content exceeding 100 ppm, that condition was indicated as NG.

[0214] Figures 21A and 21B are photographs showing the process of bending a sample using a bending testing machine. The bending testing machine can be set with a radius of curvature. In this embodiment, the minimum bending radius of curvature is set to 30 mm, 40 mm, 60 mm and 100 mm respectively. Table 1 shows the results of bending tests on each sample.

[0215] As shown in Table 1, when the length of the battery is less than 75 mm and the thickness of the battery is less than 3.4 mm, even after the sample is bent and stretched 10,000 times, the outer packaging is less damaged and maintains water resistance.

[0216] Figure 21C shows an external photograph of the bending testing machine 1100. A manufactured lithium-ion secondary battery 1200 is mounted on the upper part of the bending testing machine 1100. The lithium-ion secondary battery 1200 is sandwiched between two retaining plates 1101, and is thus indicated by a dashed line in Figure 21C. In the bending testing machine 1100, a cylindrical support body (not shown) with a radius of curvature of 40 mm, extending perpendicularly to the arm 1102 in the photograph, is provided directly below the central lithium-ion secondary battery 1200. The bending testing machine 1100 also has an arm 1102 extending in the left-right direction. The top end of the arm 1102 is mechanically connected to the retaining plates 1101. By rotating the top end of the arm 1102 upwards or downwards, the retaining plates 1101 can be bent or extended along the support body. A test was conducted to bend or extend the lithium-ion secondary battery 1200 while it was clamped between two retaining plates 1101. Thus, by rotating the tip of the arm 1102 upwards or downwards, the lithium-ion secondary battery 1200 can be bent or extended along the cylindrical support. Specifically, by rotating the tip of the arm 1102 downwards, the lithium-ion secondary battery 1200 can be bent or extended with a radius of curvature of 40 mm. By bending or extending the lithium-ion secondary battery 1200 while it is clamped by the two retaining plates 1101, unwanted forces other than bending or extending can be prevented from being applied to the lithium-ion secondary battery 1200. Furthermore, the force from bending or extending can be evenly applied to the entire lithium-ion secondary battery 1200.

[0216] Example 3

[0217] In this embodiment, the following results will be described with reference to Figures 22A to 23B: the results of measuring the load required when bending a secondary battery made of an electrode with an active material layer on one surface of the current collector and a secondary battery made of an electrode with active material layers on both surfaces of the current collector.

[0218] First, prepare a sample of a secondary battery made using an electrode with an active material layer on only one surface of the current collector and a sample of a secondary battery made using an electrode with an active material layer on both surfaces of the current collector.

[0219] The more specific structure of the above-mentioned secondary battery is as follows. Under the condition that the active material layer is coated on one surface, six positive electrode current collectors 1904 with a positive electrode active material layer 1905 on one surface, four negative electrode current collectors 1902 with a negative electrode active material layer 1903 on one surface and six separators 1906 are sandwiched between two negative electrode current collectors 1902 with a negative electrode active material layer 1903 on one surface.

[0220] With the active material layer coated on two surfaces, three positive current collectors 1904 with positive active material layers 1905 on both surfaces, two negative current collectors 1902 with negative active material layers 1903 on both surfaces, and six separators 1906 are sandwiched between two negative current collectors 1902 with negative active material layers 1903 on only one surface.

[0221] Figure 22A shows a cross-sectional schematic diagram of a sample with an active material layer coated on one surface. As shown in Figure 22A, the following layers are stacked sequentially from below the paper: negative electrode current collector 1902, negative electrode active material layer 1903, separator 1906, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode current collector 1904, positive electrode active material layer 1905, separator 1906, negative electrode active material layer 1903, negative electrode current collector 1902, negative electrode current collector 1902, negative electrode active material layer 1903, separator 1906, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode active material layer 1905, positive electrode active material layer 1906, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode active material layer 1905, positive electrode active material layer 1906, positive electrode active material layer 1905, positive electrode active material layer 1906, positive electrode active material layer 1904 ... A secondary battery with a thickness of approximately 2mm is manufactured by using a current collector 1904, a positive electrode active material layer 1905, an insulator 1906, a negative electrode active material layer 1903, a negative electrode current collector 1902, a negative electrode current collector 1902, a negative electrode active material layer 1903, an insulator 1906, a positive electrode active material layer 1905, a positive electrode current collector 1904, a positive electrode current collector 1904, a positive electrode active material layer 1905, an insulator 1906, a negative electrode active material layer 1903, and a negative electrode current collector 1902.

[0222] Figure 22B shows a cross-sectional schematic diagram of a sample with active material layers coated on both surfaces. As shown in Figure 22B, the following layers are stacked sequentially from below the paper: negative electrode current collector 1902, negative electrode active material layer 1903, separator 1906, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode active material layer 1905, separator 1906, negative electrode active material layer 1903, negative electrode current collector 1902, negative electrode active material layer 1903, separator 1906, positive electrode active material layer 1905, and positive electrode current collector. A secondary battery with a thickness of approximately 2 mm is manufactured by combining the following components: positive electrode active material layer 1904, positive electrode active material layer 1905, separator 1906, negative electrode active material layer 1903, negative electrode current collector 1902, negative electrode active material layer 1903, separator 1906, positive electrode active material layer 1905, positive electrode current collector 1904, positive electrode active material layer 1905, separator 1906, negative electrode active material layer 1903, and negative electrode current collector 1902.

[0223] Next, the sample is clamped using a curved fixture 1400, and a load is applied to the sample using a testing machine 1410 (EZ-graph, manufactured by Shimadzu Corporation). The fixture 1401 is moved towards the fixture 1402 at a displacement of 6 mm / min, from a state without bending until the radius of curvature of the sample is approximately 40 mm. Additionally, the sample is bent in the lead-out direction parallel to the lead electrode.

[0224] Figures 23A and 23B show schematic diagrams of a fixture 1400 with curved surfaces and a testing machine 1410. The fixture 1401, which contacts the inner diameter of the sample 1420 when it is bent, includes a protrusion with a radius of curvature of 40 mm, and the fixture 1402, which contacts the outer diameter of the sample 1420 when it is bent, includes a recess with a radius of curvature of 42 mm.

[0225] In Figures 23A and 23B, X1 represents the distance when the top surface of fixture 1401 is furthest from the top surface of fixture 1402, and X2 in Figure 23B represents the distance when the top surface of fixture 1401 is closest to the top surface of fixture 1402. Additionally, △X in Figure 23B represents the difference between X1 and X2, which is the actual distance that fixture 1401 moves.

[0226] Specifically, the battery is bent through the following steps. First, a jig 1401, which contacts the inner diameter of the sample when it is bent, and a jig 1402, which contacts the outer diameter of the sample when it is bent, are connected to a testing machine 1410. Then, a sample 1420 is placed on the jig 1402, which contacts the outer diameter. Next, a load is applied to the sample 1420, which is clamped by the jig 1400, in the direction of the arrow in FIG23A (compression direction) using the testing machine 1410. Following the above steps, as shown in FIG23B, the load required until the radius of curvature of the sample reaches 40 mm is measured.

[0227] Figure 24 shows the results of the load required to bend a sample manufactured under conditions where an active material layer is coated on one surface and a sample manufactured under conditions where an active material layer is coated on two surfaces to a radius of curvature of 40 mm. The solid line represents the results for a sample manufactured under conditions where an active material layer is coated on one surface, while the dashed line represents the results for a sample manufactured under conditions where an active material layer is coated on two surfaces. Note that the displacement represented by the horizontal axis represents the distance moved by the jig 1400 in contact with the inner diameter of the jig 1401 when the sample is bent, which is ΔX shown in Figure 23B. The displacement is 0 mm when the interval between the jigs 1400 is 40 mm and the sample is not bent, and the displacement is 40 mm when the contact area between the sample and the jig 1400 is at its maximum and the measurement ends. The displacement can also be referred to as displacement amount or moving distance, etc.

[0228] As shown in the graph of Figure 24, the load required to bend each sample at a certain displacement increases sharply. This is because the thinner parts, such as the junctions of the positive and negative electrodes, are bent first, followed by the thicker parts containing the active material layer.

[0229] As shown in Figure 24, when comparing a secondary battery manufactured using an electrode with an active material layer on only one surface of the current collector with a secondary battery manufactured using an electrode with an active material layer on both surfaces of the current collector, the secondary battery manufactured using an electrode with an active material layer on only one surface of the current collector can be bent with a smaller load than the secondary battery manufactured using an electrode with an active material layer on both surfaces of the current collector. This is because the metal surfaces are in contact with each other, and the surfaces in contact with each other are easy to slide without a large frictional force. Therefore, it can be seen that by coating an active material layer on one surface, the secondary battery can be easily bent.

[0229] Example 4

[0230] In this embodiment, the results of measuring the load required to bend thin secondary batteries with different thicknesses are explained.

[0231] First, three types of samples, A, B, and C, are manufactured, with two samples of each type. Sample A has 2 layers (1.5 mm thick), sample B has 6 layers (2.5 mm thick), and sample C has 10 layers (3.4 mm thick). Here, for example, 2 layers means including every two positive and two negative electrodes.

[0232] The number of layers in samples A, B, and C differs from that in Example 2, where the sample length is 75 mm and the sample width is 60 mm, but the other structures are manufactured in the same manner as those in Example 2. Table 3 shows the conditions for samples A, B, and C.

[0233]

[0234] Next, samples A, B, and C are clamped using a curved fixture 1400. A load is applied to samples A, B, and C using a testing machine 1410 (EZ-graph, manufactured by Shimadzu Corporation). The fixture 1401 is moved towards the fixture 1402 at a displacement of 6 mm / min, from a state without bending until the radius of curvature of samples A, B, and C is approximately 40 mm. Additionally, batteries A, B, and C are bent parallel to the lead-out direction of the lead electrodes.

[0235] The load was measured using the same testing machine and fixture as in Example 3.

[0236] Figure 25A shows the results of measuring the load required to bend samples A, B, and C to a radius of curvature of 40 mm. The solid line represents the results for sample A (2 layers, 1.5 mm thickness), the dashed line represents the results for sample B (6 layers, 2.5 mm thickness), and the dotted line represents the results for sample C (10 layers, 3.4 mm thickness). For clarity, Figure 25A also shows the results for one sample A, one sample B, and one sample C.

[0237] As shown in the graph of Figure 25A, the load required to bend each sample at a certain displacement increases sharply. This is because the thinner parts, such as the junctions of the positive and negative electrodes, are bent first, followed by the thicker parts containing the active material layer.

[0238] The points where the slope of the curves of samples A, B, and C in Figure 25A increases sharply (points with a slope of 6 N / mm or more) are set as the load values ​​required to bend the thicker portion containing the active material layer. In Figure 25B, the points where the slope of samples A, B, and C is 6 N / mm or more are plotted, with the sample thickness represented by the horizontal axis.

[0239] As can be seen from Figure 25B, the thicker the sample, the greater the load required to bend the sample, and more specifically, the greater the load required to bend the thicker portion containing the active material layer.

Claims

1. A secondary battery, comprising: a membrane folded with its two ends overlapping; the overlapping ends having regions bonded together by an adhesive layer; the region enclosed by the inner surface of the folded membrane and the adhesive layer comprising: two positive current collectors having a positive active material layer on only one side; two negative current collectors having a negative active material layer on only one side; two separators; and an electrolyte; the membrane having a stripe pattern formed by a plurality of recesses and a plurality of protrusions on its inner and outer surfaces, respectively; the plurality of recesses on the outer surface being disposed face-to-face with the plurality of protrusions on the inner surface; the plurality of protrusions on the outer surface being disposed face-to-face with the plurality of recesses on the inner surface; the inner surface having a first inner surface region and a second inner surface region bounded by a fold line; the outer surface having a first outer surface region and a second outer surface region bounded by the fold line; The membrane is folded such that the stripe pattern formed by the plurality of recesses and protrusions in the first inner surface region and the first outer surface region is parallel to the fold, and the stripe pattern formed by the plurality of recesses and protrusions in the second inner surface region and the second outer surface region has a geometric pattern of intersecting diagonal lines in two directions; among the plurality of recesses on the outer surface, the depth of the recess in the pressed area is shallower than the depth of the recess in the central part of the first outer surface region; among the plurality of protrusions on the outer surface, the height of the protrusion in the pressed area is lower than the height of the protrusion in the central part of the first outer surface region; the two positive current collectors are arranged face-to-face with the surfaces without the positive active material layer; one of the two positive current collectors with the positive active material layer is arranged face-to-face with one of the two negative current collectors with the negative active material layer, separated by one of the two separators; The other side of the two positive current collectors, which has the positive active material layer, is arranged face-to-face with the other side of the two negative current collectors, which has the negative active material layer, separated by the two insulators.

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