Method for manufacturing secondary batteries

Abstract

A purpose of the present invention is to automate at least part of a secondary battery production process. The present invention provides highly reliable a secondary battery. This secondary battery is produced by disposing a first electrode on a first outer body, disposing a separator on the first electrode, disposing a second electrode on the separator, dripping an electrolyte onto at least one of the first electrode, the separator, and the second electrode, disposing a resin layer on the first outer body, impregnating at least one of the first electrode, the separator, and the second electrode with the electrolyte, thereafter disposing a second outer body on the first outer body so as to cover the first electrode, the separator, and the second electrode and irradiating the resin layer with UV light under depressurization to cure at least a portion of the resin layer, and after the UV light irradiation, sealing the first electrode, the separator, and the second electrode under atmospheric pressure by using the first outer body and the second outer body.

Description

[Technical Field]

[0001] BACKGROUND OF THE INVENTION 1. Field of the Invention One embodiment of the present invention relates to a secondary battery and a manufacturing method thereof, or to a portable information terminal, a vehicle, or the like including a secondary battery, or to an apparatus for manufacturing a secondary battery.

[0002] One embodiment of the present invention is not limited to the above technical field, but examples of the technical field of one embodiment of the present invention include semiconductor devices, display devices, light-emitting devices, power storage devices, memory devices, electronic devices, lighting devices, driving methods thereof, and manufacturing methods thereof.

[0003] In this specification, the term "electronic device" refers to any device having a power storage device, and includes electro-optical devices having a power storage device, information terminal devices having a power storage device, and the like.

[0004] In this specification, the term "power storage device" refers to all elements and devices having a power storage function, including, for example, power storage devices such as lithium ion secondary batteries (also called secondary batteries), lithium ion capacitors, and electric double layer capacitors. [Background technology]

[0005] In recent years, there has been active development of various types of electricity storage devices, such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. Demand for high-power, high-energy-density lithium-ion secondary batteries, in particular, has rapidly expanded alongside the development of the semiconductor industry, and they are now essential to the modern information society as a rechargeable energy source, thanks to their high output and high energy density, and are used in a variety of applications, including mobile phones, smartphones, and laptop computers, as well as portable music players, digital cameras, medical devices, and next-generation clean-energy vehicles, such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs).

[0006] A lithium-ion secondary battery consists of a positive electrode containing a positive electrode active material such as lithium cobalt oxide (LiCoO2) or lithium iron phosphate (LiFePO4), a negative electrode containing a negative electrode active material such as graphite or other carbon materials that can absorb and release lithium, and an electrolyte containing an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC).

[0007] Furthermore, lithium ion secondary batteries are required to have high capacity, high performance, and safety in various operating environments.

[0008] Patent Document 1 discloses a manufacturing apparatus for a stacked battery that can improve the efficiency of manufacturing. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2017-117729 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of one embodiment of the present invention is to automate at least part of a manufacturing process of a secondary battery.

[0011] An object of one embodiment of the present invention is to provide a method for manufacturing a relatively large secondary battery.

[0012] An object of one embodiment of the present invention is to manufacture a secondary battery efficiently in a short time.An object of one embodiment of the present invention is to manufacture a secondary battery with a high yield.An object of one embodiment of the present invention is to provide a method for manufacturing a secondary battery with reduced manufacturing cost.

[0013] An object of one embodiment of the present invention is to provide a method for manufacturing a highly reliable secondary battery.An object of one embodiment of the present invention is to provide a method for manufacturing a highly safe secondary battery.

[0014] Note that the description of these problems does not preclude the existence of other problems. One embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than these can be extracted from the description in the specification, drawings, and claims. [Means for solving the problem]

[0015] One aspect of the present invention is a method for producing a secondary battery, which includes disposing a first electrode on a first exterior body, disposing a separator on the first electrode, disposing a second electrode on the separator, dripping an electrolyte onto at least one of the first electrode, the separator, and the second electrode, disposing a resin layer on the first exterior body, impregnating at least one of the first electrode, the separator, and the second electrode with the electrolyte, disposing a second exterior body on the first exterior body so as to cover the first electrode, the separator, and the second electrode, irradiating the resin layer with ultraviolet light under reduced pressure to at least partially cure the resin layer, irradiating the ultraviolet light, and then sealing the first electrode, the separator, and the second electrode with the first exterior body and the second exterior body under atmospheric pressure. One of the first electrode and the second electrode is a positive electrode and the other is a negative electrode.

[0016] The first exterior body preferably has a recess, and the first electrode, separator, and second electrode are preferably disposed in the recess.

[0017] Alternatively, one aspect of the present invention is a method for producing a secondary battery, which includes disposing multiple stacks on a first exterior housing, disposing a resin layer on the first exterior housing, disposing a second exterior housing on the first exterior housing so as to cover the multiple stacks, irradiating the resin layer with ultraviolet light under reduced pressure to at least partially cure the resin layer, irradiating with ultraviolet light, and then sealing the multiple stacks between the first exterior housing and the second exterior housing under atmospheric pressure. After sealing, the first exterior housing and the second exterior housing are separated to separate the stacks into individual secondary batteries. Each of the multiple stacks is formed by disposing a first electrode on the first exterior housing, disposing a separator on the first electrode, disposing a second electrode on the separator, and dripping an electrolyte onto at least one of the first electrode, the separator, and the second electrode. One of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0018] The first exterior body preferably has a plurality of recesses, and one of the plurality of laminates is preferably disposed in each of the plurality of recesses.

[0019] The resin layer is preferably disposed in a frame shape so as to surround the first electrode, the separator, and the second electrode.

[0020] The sealing may be performed by irradiating the resin layer with ultraviolet light to cure the resin layer. In this case, it is preferable that the area of ​​the resin layer irradiated with ultraviolet light during sealing is larger than the area irradiated with ultraviolet light under reduced pressure.

[0021] Alternatively, sealing may be performed by thermocompression bonding.

[0022] The second exterior body preferably has a function of transmitting ultraviolet light at least in the area overlapping with the resin layer.

[0023] The second exterior body preferably has a function of blocking ultraviolet light at least in the region that overlaps with at least one of the first electrode, the separator, and the second electrode.

[0024] It is preferable to have a step of connecting a first lead electrode to the first electrode and a step of connecting a second lead electrode to the second electrode before irradiating with ultraviolet light under reduced pressure.

[0025] The electrolyte preferably contains fluorine.

[0026] The electrolyte preferably comprises an ionic liquid.

[0027] One or both of the first electrode and the second electrode preferably includes graphene.

[0028] The first electrode preferably has a first active material layer on one or both surfaces of a first current collector.

[0029] The second electrode preferably has a second active material layer on one or both surfaces of a second current collector.

[0030] One aspect of the present invention is a manufacturing apparatus for a secondary battery in which a stack having one or more positive electrodes, separators, and negative electrodes is provided between a first exterior body and a second exterior body. The manufacturing apparatus includes a transfer chamber, a first processing chamber, and a second processing chamber. The transfer chamber functions to transfer a secondary battery being manufactured from the first processing chamber to the second processing chamber. The first processing chamber includes a first stage, an adsorption mechanism, an electrolyte dripping mechanism, and a sealing material supply mechanism. The first stage functions to support the secondary battery being manufactured. The adsorption mechanism functions to adsorb components constituting the stack and place them on the first exterior body. The electrolyte dripping mechanism functions to drip electrolyte onto the components constituting the stack. The sealing material supply mechanism functions to form a resin layer on the first exterior body. The second processing chamber includes a second stage, an exhaust mechanism, an exterior body support mechanism, and a first ultraviolet light irradiation mechanism. The second stage has a function of supporting the secondary battery in the process of being fabricated that has been transferred from the first processing chamber. The exhaust mechanism has a function of reducing the pressure inside the second processing chamber. The exterior body support mechanism has a function of supporting the second exterior body at a position facing the secondary battery in the process of being fabricated that has been transferred from the first processing chamber. The first ultraviolet light irradiation mechanism has a function of irradiating ultraviolet light onto at least a portion of the resin layer through the first exterior body or the second exterior body.

[0031] The suction mechanism preferably has a function of suctioning the first exterior body and placing it on the first stage.

[0032] The first processing chamber preferably has an inert gas supply mechanism. The inert gas supply mechanism preferably has a function of supplying an inert gas into the first processing chamber. The inert gas is preferably argon gas.

[0033] The manufacturing apparatus according to one embodiment of the present invention preferably further includes a third processing chamber. The third processing chamber includes a second ultraviolet light irradiation mechanism. The second ultraviolet light irradiation mechanism has a function of irradiating the resin layer with ultraviolet light via the first exterior body or the second exterior body. The area of ​​the resin layer irradiated with ultraviolet light by the second ultraviolet light irradiation mechanism is larger than the area irradiated with ultraviolet light by the first ultraviolet light irradiation mechanism. [Effects of the Invention]

[0034] According to one embodiment of the present invention, at least a part of the manufacturing process of a secondary battery can be automated.

[0035] According to one embodiment of the present invention, a method for manufacturing a relatively large secondary battery can be provided. When a large-capacity secondary battery is mounted, the number of mounted secondary batteries can be reduced compared to when a small secondary battery is mounted. By reducing the number of mounted secondary batteries, it becomes easier to control each battery, and the burden on the charge control circuit is reduced.

[0036] In the method for manufacturing a secondary battery according to one embodiment of the present invention, a sealing process for a plurality of secondary batteries can be performed at once, which significantly shortens the manufacturing process of the secondary batteries. Therefore, the manufacturing cost of the secondary batteries can be reduced. Furthermore, the secondary batteries can be manufactured efficiently and in a short time. Furthermore, the secondary batteries can be manufactured with a high yield.

[0037] According to one embodiment of the present invention, a method for manufacturing a highly reliable secondary battery can be provided.Furthermore, according to one embodiment of the present invention, a method for manufacturing a highly safe secondary battery can be provided.

[0038] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims. [Brief explanation of the drawings]

[0039] Fig. 1A is a cross-sectional view showing an example of a secondary battery, Fig. 1B is a top view illustrating the state after an electrolyte has been dropped onto an electrode, and Fig. 1C is a top view illustrating multiple panel cutting. FIG. 2 is a top view showing an example of a secondary battery manufacturing apparatus. FIG. 3 is a flow chart showing an example of a method for producing a secondary battery. 4A to 4D are cross-sectional views showing an example of a method for manufacturing a secondary battery. 5A to 5C are cross-sectional views showing an example of a method for manufacturing a secondary battery. 6A and 6B are perspective views showing an example of a method for producing a secondary battery. 7A and 7B are perspective views showing an example of a method for producing a secondary battery. 8A, 8B, and 8C are top views showing an example of a method for producing a secondary battery, a cross-sectional view showing an example of a secondary battery during production, and a top view showing an example of a secondary battery during production. 9A and 9B are top views showing an example of a method for producing a secondary battery. FIG. 10 is a top view showing an example of a method for producing a secondary battery. FIG. 11 is a top view showing an example of a method for producing a secondary battery. FIG. 12 is a diagram illustrating the crystal structure of the positive electrode active material. FIG. 13 is a diagram illustrating the crystal structure of the positive electrode active material. 14A to 14C are diagrams showing an example of the external appearance of a secondary battery. 15A and 15B are diagrams showing an example of the external appearance of a secondary battery. 16A to 16C are diagrams showing an example of a method for manufacturing a secondary battery. Fig. 17A is a perspective view showing an example of a battery pack, Fig. 17B is a block diagram showing an example of a battery pack, and Fig. 17C is a block diagram showing an example of a vehicle having a motor. 18A to 18D are diagrams showing an example of a transportation vehicle. 19A and 19B are diagrams illustrating an example of a power storage device. 20A to 20E are diagrams showing an example of an electronic device. DETAILED DESCRIPTION OF THE INVENTION

[0040] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes can be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0041] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and repeated explanations thereof will be omitted. In addition, when referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be assigned.

[0042] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0043] It should be noted that the terms "film" and "layer" can be interchangeable depending on the circumstances. For example, the term "conductive layer" can be changed to the term "conductive film." Or, for example, the term "insulating film" can be changed to the term "insulating layer."

[0044] (Embodiment 1) In this embodiment, a method for manufacturing a secondary battery of one embodiment of the present invention will be described with reference to FIGS.

[0045] In the process of manufacturing a secondary battery, a laminate having a positive electrode, a separator, and a negative electrode is often placed in a can or bag-shaped exterior, and then an electrolyte solution is injected and sealed. This method may require a long time for the electrolyte to penetrate into the positive and negative electrodes. This method may also result in insufficient impregnation of the electrolyte into the positive and negative electrodes. This method may also result in the risk of lithium ions diffusing outward from the injection port. This method also tends to require a large number of steps. It may also be difficult to accurately control the amount of electrolyte injected. Accurately providing the required amount of electrolyte for a secondary battery can lead to mass production of secondary batteries with uniform characteristics.

[0046] In a method for manufacturing a secondary battery according to one embodiment of the present invention, a first electrode is disposed on a first outer casing, a separator is disposed on the first electrode, a second electrode is disposed on the separator, and an electrolyte is dropped onto at least one of the first electrode, the separator, and the second electrode. By dropping multiple drops of the electrolyte, the first electrode, the separator, or the second electrode can be uniformly or sufficiently impregnated with the electrolyte.

[0047] In a method for manufacturing a secondary battery according to one embodiment of the present invention, a frame-shaped resin layer is disposed on a first exterior body. A UV-curable resin is preferably used for the resin layer. A second exterior body is then disposed on the first exterior body so as to cover a stacked structure (hereinafter also referred to as a stack) of a first electrode, a separator, and a second electrode. The resin layer is then irradiated with UV light under reduced pressure (also referred to as a reduced-pressure atmosphere) to at least partially cure the resin layer. An exterior film is preferably used for each of the first exterior body and the second exterior body.

[0048] After at least a portion of the resin layer is cured under an atmosphere reduced in pressure from atmospheric pressure, the secondary battery being fabricated is exposed to atmospheric pressure (also referred to as atmospheric pressure atmosphere or normal pressure), whereby the first and second exterior bodies are pressurized by atmospheric pressure. This maintains a reduced pressure state in the space surrounded by the first and second exterior bodies and the frame-shaped resin layer. This prevents impurities from being mixed into the secondary battery.

[0049] Furthermore, the dropped electrolyte can be widely permeated into the components in a short time by being exposed from a reduced pressure atmosphere to an atmospheric pressure atmosphere. Therefore, the time required for the electrolyte to permeate the surfaces and even the interiors of the positive and negative electrodes can be shortened. Furthermore, the electrolyte can be sufficiently impregnated into the interiors of the positive and negative electrodes.

[0050] The lead electrodes (also called lead wiring or lead terminals) functioning as terminals for external extraction are intended to protrude outside the exterior of the package. The lead electrodes are provided to lead the positive or negative electrode of the secondary battery to the outside of the exterior of the package.

[0051] In a method for manufacturing a secondary battery according to one embodiment of the present invention, the laminate is then sealed with a first exterior body and a second exterior body under atmospheric pressure. For example, in the case of a thin (laminated) secondary battery, the outer peripheries of the first exterior body and the second exterior body (four sides as viewed from above when the secondary battery has a thin rectangular parallelepiped shape) are sealed without gaps. Examples of sealing methods that can be used include irradiating the resin layer with light such as ultraviolet light, and thermocompression bonding of the exterior body.

[0052] In this specification, sealing refers to isolating a certain sealed area from the outside air, and in a secondary battery, sealing refers to surrounding the laminate and its periphery as the sealed area and isolating the sealed area from the outside air with an exterior body. After sealing, the edges of the exterior body are folded to increase the sealing strength and prevent the intrusion of impurities from the outside or the release of gases from the inside.

[0053] The process of curing the resin layer by irradiating it with light under reduced pressure or atmospheric pressure does not require exposing the secondary battery to high temperatures, thereby suppressing deterioration of the secondary battery and improving the reliability of the secondary battery.

[0054] In a method for manufacturing a secondary battery according to one embodiment of the present invention, at least the steps from forming a laminate on a first outer casing to curing a resin layer under reduced pressure can be performed continuously in a single device, thereby preventing impurities from being mixed into the secondary battery.

[0055] One of the first electrode and the second electrode is a positive electrode and the other is a negative electrode. The laminate may be formed by laminating the positive electrode, separator, and negative electrode in this order, or the negative electrode, separator, and positive electrode in this order. The separator is used to prevent short-circuiting between the positive electrode and the negative electrode. When a configuration is adopted in which multiple positive electrodes and negative electrodes are laminated to increase the capacity of the secondary battery, a single common separator may be folded to reduce the number of parts.

[0056] In a method for manufacturing a secondary battery according to one embodiment of the present invention, a plurality of stacks may be disposed on a first exterior housing. In this case, the resin layer may be a single frame-shaped resin layer that surrounds all of the stacks, or multiple frame-shaped resin layers that surround one or more stacks. For example, one frame-shaped resin layer may be formed for each stack. A second exterior housing is disposed on the first exterior housing so as to cover the plurality of stacks. Then, ultraviolet light is irradiated onto the resin layer under reduced pressure, and the plurality of stacks are sealed between the first exterior housing and the second exterior housing under atmospheric pressure. After sealing, the first exterior housing and the second exterior housing are separated to separate the secondary batteries each having the stack.

[0057] Although the above example illustrates the use of an ultraviolet light-curable resin as the material for the resin layer, one embodiment of the present invention is not limited to this. The resin layer may be made of various curable adhesives, such as a photocurable resin (also referred to as a photocurable adhesive) such as an ultraviolet light-curable resin, a thermosetting resin (also referred to as a thermosetting adhesive), a reactive curable adhesive, or an anaerobic adhesive. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. Materials with high gas barrier properties, such as epoxy resin, are particularly preferred. Two-component resins may also be used.

[0058] When using various photocurable resins, at least a portion of the resin layer can be cured by irradiating the resin layer with light under reduced pressure. This maintains the reduced pressure state in the space surrounded by the first exterior body, the second exterior body, and the frame-shaped resin layer even when the secondary battery being manufactured is exposed to atmospheric pressure. This prevents impurities from being mixed into the secondary battery. Using a photocurable resin eliminates the need to expose the secondary battery to high temperatures when curing the resin layer, thereby suppressing deterioration of the secondary battery and enabling the manufacture of a highly reliable secondary battery.

[0059] Furthermore, when using a thermosetting resin, it is preferable to perform thermocompression bonding or welding under reduced pressure. This maintains the reduced pressure state in the space surrounded by the first and second exterior bodies and the frame-shaped resin layer even when the secondary battery being manufactured is exposed to atmospheric pressure. This prevents impurities from being mixed into the secondary battery. Using a thermosetting resin eliminates the need for a light irradiation device, which can potentially reduce the cost of installing the device.

[0060] Furthermore, when thermocompression bonding or welding is performed under reduced pressure, the step of forming a resin layer may not be necessary. For example, by using thermocompression bonding or welding with the resin (such as a thermoplastic film material) on the inner surface of the exterior film, the reduced pressure state in the space surrounded by the first exterior body, the second exterior body, and the frame-shaped resin layer may be maintained at atmospheric pressure. This reduces the number of steps in the production of secondary batteries.

[0061] When a plurality of secondary batteries are individually sealed under reduced pressure, the sealing step under atmospheric pressure can be omitted.

[0062] An example of a secondary battery of one embodiment of the present invention will be described with reference to FIG. 1A.

[0063] 1A includes an outer casing 509a, an outer casing 509b, and a laminate 512 disposed between the outer casings 509a and 509b. The laminate 512 includes a positive electrode 503, a negative electrode 506, and a separator 507. In the laminate 512, the positive electrode 503 and the negative electrode 506 overlap each other, and the separator 507 is disposed between the positive electrode 503 and the negative electrode 506.

[0064] The positive electrode 503 includes a positive electrode current collector 501 and a positive electrode active material layer 502. In this embodiment, an example is shown in which the positive electrode active material layer 502 is provided on both surfaces of the positive electrode current collector 501. Note that the positive electrode active material layer 502 may be provided on only one surface of the positive electrode current collector 501.

[0065] The negative electrode 506 includes a negative electrode current collector 504 and a negative electrode active material layer 505. In this embodiment, an example is shown in which the negative electrode active material layer 505 is provided on both surfaces of the negative electrode current collector 504. Note that the negative electrode active material layer 505 may be provided on only one surface of the negative electrode current collector 504.

[0066] The positive electrode active material layer 502 and the negative electrode active material layer 505 are preferably disposed so as to face each other with a separator 507 sandwiched therebetween. Fig. 1A shows an example in which the secondary battery 500 has four pairs of positive electrode active material layers 502 and negative electrode active material layers 505 facing each other with a separator 507 sandwiched therebetween. The number of pairs of positive electrode active material layers 502 and negative electrode active material layers 505 is not particularly limited and can be, for example, 1 to 50 pairs.

[0067] In the secondary battery of one embodiment of the present invention, the electrolyte can be uniformly or sufficiently impregnated into one or more of the positive electrode 503, the negative electrode 506, and the separator 507 by dropping multiple drops of the electrolyte.

[0068] 1B shows an example in which multiple drops of electrolyte 515a are dropped onto a positive electrode 503. A secondary battery electrode has an active material layer on a current collector, and the active material layer contains an active material, a conductive material, a binder, and the like, with gaps between them. The dropped electrolyte moves from the dropping position into the gaps in the active material layer, and is uniformly impregnated with the electrolyte, ideally without any voids.

[0069] In FIG. 1B, droplets of electrolyte 515a are shown at 140 locations (20 rows x 7 columns) at equal intervals on the positive electrode 503, but the number and locations of the droplets are not particularly limited and may be determined appropriately by the practitioner. When using one nozzle, it is preferable to sequentially scan the droplet positions while checking them with an imaging mechanism (an imaging element such as a CCD element). Furthermore, when droplets are simultaneously dropped from multiple nozzles, this is preferable because it shortens the drop processing time.

[0070] It is preferable to measure out the electrolyte when dropping so that the amount dropped each time is the same. For example, it is preferable to drop the electrolyte using a pipette (such as a micropipette).

[0071] As shown in FIG. 1C , multiple laminates 512 can be arranged on an outer casing 509b to form multiple panels. Multiple laminates are arranged on a single large outer casing, secondary batteries are fabricated, and then the resulting laminate is divided into multiple panels in a plane to form multiple secondary batteries. Multiple laminates can shorten the time required to fabricate one secondary battery. By performing multiple laminates using the method for fabricating a secondary battery according to one embodiment of the present invention, the characteristics of multiple secondary batteries can be easily made uniform, and secondary batteries can be fabricated with a high yield.

[0072] For example, using a large-area exterior film for exterior body 509a and exterior body 509b allows for the production of many secondary batteries at once. For example, it is preferable to use a large-area exterior film having a size such as 320 mm × 400 mm, 370 mm × 470 mm, 550 mm × 650 mm, 600 mm × 720 mm, 680 mm × 880 mm, 1000 mm × 1200 mm, 1100 mm × 1250 mm, or 1150 mm × 1300 mm. This allows for efficient production of multiple secondary batteries from a single large-area exterior film. Furthermore, large-area exterior films having a size such as 1500 mm × 1800 mm, 1800 mm × 2000 mm, 2000 mm × 2100 mm, 2200 mm × 2600 mm, or 2600 mm × 3100 mm can also be used. The exterior body can also be referred to as a packaging material.

[0073] 1C also shows an example of the arrangement of the resin layers. For example, resin layers 518 may be provided at the four corners of exterior body 509b, and multiple frame-shaped resin layers 513 may be provided to surround one laminate 512. For example, resin layer 518 may be cured under reduced pressure, and then frame-shaped resin layer 513 may be cured under atmospheric pressure. If resin layer 518 is cured under reduced pressure, the reduced pressure state of the space surrounded by two exterior bodies and frame-shaped resin layer 513 is maintained under atmospheric pressure, even if frame-shaped resin layer 513 is not yet cured.

[0074] [Secondary battery manufacturing equipment example] FIG. 2 shows an example of a manufacturing apparatus that can be used to manufacture the secondary battery of one embodiment of the present invention.

[0075] 2 includes a material input chamber 301, a transfer chamber 302, a processing chamber 303, a processing chamber 304, a processing chamber 305, and a material removal chamber 306. Each chamber can be configured to be connected to various exhaust mechanisms depending on the intended use.

[0076] Each chamber can be configured to be connected to various gas supply mechanisms depending on the intended use. In order to prevent impurities from entering the manufacturing apparatus 300, it is preferable to supply an inert gas to the manufacturing apparatus 300. It is preferable that the gas supplied to the inside of the manufacturing apparatus 300 is highly purified by a gas purifier before being introduced into the manufacturing apparatus 300.

[0077] The component input chamber 301 is a chamber for inputting the positive electrode 503, the separator 507, the negative electrode 506, the outer casing 509a, the outer casing 509b, and the like into the manufacturing apparatus 300.

[0078] The transfer chamber 302 functions as a delivery chamber for transferring materials and the like from one of the material input chamber 301, the processing chamber 303, the processing chamber 304, the processing chamber 305, and the material removal chamber 306 to another. For example, a secondary battery being fabricated can be transferred from the processing chamber 303 to the processing chamber 304. The transfer chamber 302 includes a transfer mechanism 320.

[0079] The processing chamber 303 has a function of arranging the positive electrode 503, the separator 507, and the negative electrode 506 in layers on the exterior body 509b, and a function of forming a resin layer on the exterior body 509b.

[0080] The processing chamber 303 includes a stage, an adsorption mechanism, an electrolyte dropping mechanism, and a sealing material supply mechanism.

[0081] The stage has a function of supporting the secondary battery during fabrication.

[0082] The suction mechanism has a function of suctioning the members constituting the stack (positive electrode 503, separator 507, or negative electrode 506) and disposing them on the exterior body 509b. The suction mechanism may further have a function of suctioning the exterior body 509b (or a temporary support substrate on which the exterior body 509b is disposed) and disposing it on the stage.

[0083] The electrolyte dropping mechanism has a function of dropping an electrolyte onto the members that make up the stack.

[0084] The sealing material supply mechanism has a function of forming a resin layer on the exterior body 509b, for example, a function of supplying ultraviolet light curable resin.

[0085] The processing chamber 303 further has holders for accommodating the plurality of positive electrodes 503, the plurality of separators 507, and the plurality of negative electrodes 506. When necessary, these members are carried to the stage or in the vicinity thereof by a transport mechanism such as a robot arm or a robot hand. Alternatively, a suction mechanism may directly suction the members on the holders.

[0086] The processing chamber 303 preferably has an inert gas supply mechanism. The inert gas supply mechanism preferably has a function of supplying an inert gas into the processing chamber 303. As the inert gas, nitrogen or a rare gas can be used, and argon gas is preferable.

[0087] The processing chamber 304 has a function of curing the resin layer under reduced pressure. In this embodiment, an example will be described in which an ultraviolet light curable resin is used for the resin layer. That is, the processing chamber 304 has a function of irradiating the resin layer with ultraviolet light under reduced pressure.

[0088] The processing chamber 304 includes a stage, an exhaust mechanism, an exterior support mechanism, and an ultraviolet light irradiation mechanism.

[0089] The stage has a function of supporting the secondary battery being fabricated after being transported from the processing chamber 303 .

[0090] The exhaust mechanism has a function of reducing the pressure inside the processing chamber 304. Examples of the exhaust mechanism include a dry pump, a rotary pump, and a diaphragm pump. Examples of the exhaust mechanism include an exhaust mechanism equipped with a pump having an adsorption means, such as a cryopump, a sputter ion pump, or a titanium sublimation pump, and an exhaust mechanism equipped with a turbomolecular pump and a cold trap.

[0091] The processing chamber 304 can be evacuated to a vacuum, and preferably has a function of introducing an inert gas to atmospheric pressure after evacuation. Note that the processing chamber 303 also preferably has this function. It is also preferable that the other chambers of the manufacturing apparatus 300 each have this function.

[0092] For example, the processing chamber 304 can achieve an ultimate vacuum of about 0.1 Pa, and furthermore, can control the back diffusion of impurities from the pump side and the exhaust system.

[0093] The exterior body support mechanism has a function of supporting the exterior body 509a (or the temporary support substrate on which the exterior body 509a is arranged) at a position facing the secondary battery in the process of fabrication that is transported from the processing chamber 303. As the exterior body support mechanism, for example, one or more of an adsorption mechanism, an electrostatic mechanism, a weak adhesion mechanism, etc. can be used.

[0094] The processing chamber 304 has an ultraviolet light irradiation mechanism that irradiates ultraviolet light onto at least a part of the resin layer through the exterior body 509a or the exterior body 509b.

[0095] After the manufacturing apparatus 300 drips the electrolyte in the processing chamber 303, it can harden the resin layer under reduced pressure in the processing chamber 304 without exposing it to the atmosphere. This makes it possible to prevent impurities from entering the secondary battery being manufactured. Furthermore, the manufacturing apparatus 300 can seal the secondary battery in the processing chamber 305 without exposing it to the atmosphere. In this way, by performing the processes continuously in one apparatus, it is possible to improve the reliability of the secondary battery.

[0096] The processing chamber 305 has a sealing function.

[0097] For example, when sealing is performed by irradiating ultraviolet light, the processing chamber 305 has an ultraviolet light irradiation mechanism. In this case, the ultraviolet light irradiation mechanism of the processing chamber 305 may be the same as or different from that of the processing chamber 304. The processing chamber 305 may be in an atmospheric pressure atmosphere.

[0098] For example, when sealing is performed by thermocompression bonding, the processing chamber 305 has a thermocompression bonding mechanism. The processing chamber 305 can be set to an atmospheric pressure atmosphere or a reduced pressure atmosphere.

[0099] In the method for manufacturing a secondary battery according to one embodiment of the present invention, even when the resin layer is cured under reduced pressure in the treatment chamber 304 and then exposed to atmospheric pressure, the reduced pressure state of the space surrounded by the outer casing 509 a, the outer casing 509 b, and the frame-shaped resin layer is maintained. Even when thermocompression bonding is performed under atmospheric pressure, a highly reliable secondary battery can be manufactured.

[0100] Alternatively, the processing chamber 305 may not be provided, and after the processing in the processing chamber 304 is completed, the material may be transported to a material removal chamber 306 and removed to the outside of the manufacturing apparatus 300. Then, sealing may be performed outside the manufacturing apparatus 300.

[0101] The component removal chamber 306 is a chamber for removing the fabricated secondary battery to the outside of the manufacturing apparatus 300.

[0102] [Example of secondary battery manufacturing method] Next, a method for manufacturing a secondary battery according to one embodiment of the present invention will be described with reference to FIGS. 3 to 5. FIG. 3 is a flowchart illustrating the method for manufacturing a secondary battery according to one embodiment of the present invention. FIGS. 4 and 5 are cross-sectional views illustrating the method for manufacturing a secondary battery according to one embodiment of the present invention, and correspond to the cross-sectional views taken along the two-dot chain line AB in FIG. 1C. Note that in some steps, an example of the manufacturing method using the above-described manufacturing apparatus 300 will be described.

[0103] <Step S00> In step S00, the process starts.

[0104] <Step S01> In step S01, the exterior body 509b is placed on the stage 331 of the processing chamber 303. To facilitate the transportation and placement of the exterior body 509b, the exterior body 509b may be temporarily fixed to a temporary support substrate or the like (in other words, fixed in a detachable manner) and then placed on the stage 331. It is preferable to use an exterior film as the exterior body 509b.

[0105] <Step S02> In step S02, the positive electrode 503 is placed on the exterior body 509b (FIG. 4A). The positive electrode 503, the exterior body 509b, the stage 331, and the like are placed in the chamber of the processing chamber 303, but for simplicity, the inner walls of the chamber and the like are not shown here.

[0106] The stage 331 may be movable back and forth, left and right, or up and down. Fixing mechanisms for fixing components placed on the stage 331 include chucks such as mechanical chucks, suction chucks, and electrostatic chucks. For example, a porous chuck may be used. Furthermore, components may be fixed to an adhesive sheet, a suction table, a heater table, a spinner table, or the like.

[0107] The stage 331 may have a heating mechanism. By heating the stage 331 during the process in the processing chamber 303, the electrolyte can be more quickly impregnated into the member.

[0108] 4A shows an example in which the positive electrode 503 is carried to a predetermined position while being held by a suction jig 333. Although only one suction jig 333 is shown in FIG. 4A, multiple suction jigs may be used. To facilitate alignment, the processing chamber 303 preferably has an alignment camera 332.

[0109] <Step S03> Next, in step S03, electrolyte 515a is dropped onto positive electrode 503. 4B and 4C show how electrolyte 515a is dropped onto positive electrode 503 from nozzle 334.

[0110] By moving the nozzle 334, the electrolyte 515a can be dropped over the entire surface of the positive electrode 503. Alternatively, the electrolyte 515a may be dropped over the entire surface of the positive electrode 503 by moving the stage 331.

[0111] When dropping multiple electrolyte droplets onto the surface, they are dropped onto the surface at a uniform interval in one or multiple batches. The dropping method can be any one of the following: dispensing, spraying, and inkjet printing. The dispensing method uses a constant-volume liquid dispenser, which dispenses a constant amount from a nozzle. Using multiple constant-volume liquid dispensers can also shorten manufacturing time. Dropping can also be performed at regular intervals by moving the nozzle or the object to be dropped (one or more of the positive electrode, separator, and negative electrode) relative to one another. If the amount of electrolyte dropped onto one location using a certain nozzle diameter is 0.01 cc, dropping onto n (n > 1) locations allows for 0.01 cc × n of electrolyte to be impregnated, thereby enabling precise control of the drop locations and total amount dropped. Dropping onto n (n > 1) locations on a flat surface, for example, in the case of a positive electrode, dropping onto multiple positive electrodes can shorten the time required to impregnate the entire positive electrode compared to dropping onto only one positive electrode, thereby shortening manufacturing time. The electrolyte can be dropped using the ODF (One Drop Fill) method.

[0112] It is also preferable to adjust the viscosity of the electrolyte dropped from a nozzle as needed. The electrolyte can be dropped from a nozzle as long as the viscosity of the entire electrolyte is within the range of 0.3 mPa·s to 1000 mPa·s at room temperature (25°C). For example, it is preferable to set the viscosity of the electrolyte to 10 mPa·s to 95 mPa·s. A rotary viscometer (for example, Toki Sangyo's TVE-35L) is used to measure the viscosity.

[0113] The electrolyte to be dropped can be an organic solvent (also called an organic electrolyte solution) or an ionic liquid.

[0114] The method for manufacturing a secondary battery according to this embodiment includes a step performed under reduced pressure. Ionic liquids are preferable because they hardly volatilize even under high vacuum. In addition, a mixture of an ionic liquid and an organic solvent may be used as the electrolyte. When an organic solvent is included as the electrolyte, the degree of vacuum in the processing chamber is 5×10 -1 It is desirable to have a vacuum lower than about Pa.

[0115] <Step S04> Next, in step S04, separator 507 is placed on positive electrode 503. Separator 507 is placed so as to overlap the entire surface of positive electrode 503. This prevents positive electrode 503 from coming into contact with negative electrode 506, which will be placed later, and causing a short circuit.

[0116] <Step S05> Next, in step S05, electrolyte 515b is dropped onto separator 507. Fig. 4D shows the state in which electrolyte 515b has been dropped onto separator 507. Electrolyte 515b can be dropped using nozzle 334 described above.

[0117] <Step S06> Next, in step S06, negative electrode 506 is placed on separator 507. Negative electrode 506 is placed so as to overlap separator 507 so as not to protrude from separator 507 when viewed from above. This makes it possible to prevent positive electrode 503 and placed negative electrode 506 from coming into contact with each other and causing a short circuit.

[0118] <Step S07> Next, in step S07, electrolyte 515c is dropped onto negative electrode 506. Fig. 5A shows electrolyte 515c dropped onto negative electrode 506. Electrolyte 515c can be dropped using nozzle 334 described above.

[0119] After step S07, a laminate of the positive electrode 503, the separator 507, and the negative electrode 506 can be further laminated. For example, after step S07, the separator 507, the positive electrode 503, the separator 507, the negative electrode 506, the separator 507, and the positive electrode 503 can be laminated in this order to produce the laminate 512 shown in FIG. 1A. It is preferable to drip an electrolyte every time after arranging any of the positive electrode 503, the negative electrode 506, and the separator 507.

[0120] Note that, although an example in which the positive electrode 503, separator 507, and negative electrode 506 are stacked in this order is shown in this embodiment, the present invention is not limited thereto. For example, the negative electrode 506, separator 507, and positive electrode 503 may be stacked in this order. Alternatively, the stacking may start from the separator 507, and for example, the stacking may be in the order of separator 507, positive electrode 503, separator 507, and negative electrode 506, or the stacking may be in the order of separator 507, negative electrode 506, separator 507, and positive electrode 503.

[0121] Note that in the method for manufacturing a secondary battery of one embodiment of the present invention, at least one of steps S03, S05, and S07 may be performed. That is, the electrolyte may be dropped onto at least one of the positive electrode 503, the negative electrode 506, and the separator 507. For example, the electrolyte may be dropped onto only the positive electrode 503 and the negative electrode 506. Alternatively, the electrolyte may be dropped onto only the separator 507. The electrolytes dropped onto the positive electrode 503, the negative electrode 506, and the separator 507 may be the same material, or some or all of them may be different materials.

[0122] <Step S08> Next, in step S08, a resin layer is formed on exterior body 509b. Fig. 1C shows an example in which frame-shaped resin layer 513 and resin layers 518 at the four corners are formed. Fig. 5B shows how resin 517 is ejected from nozzle 335 onto exterior body 509b.

[0123] The resin layer may be formed on exterior body 509b at any time before step S09, and may be formed after step S01, for example.

[0124] After step S07 and before step S09, lead electrodes may be connected to the positive electrode 503 and the negative electrode 506, respectively.

[0125] The resin layer can be formed by, for example, any one of a dispensing method, a spraying method, an inkjet method, and the like.

[0126] The resin layer may be made of any of the above-mentioned adhesives. Alternatively, if a resin layer that forms an exterior body is used, this step may not be necessary.

[0127] As the material for the resin layer, it is preferable to use a photocurable resin, and it is particularly preferable to use an ultraviolet light curable resin.

[0128] In addition, since the material of the resin layer may be mixed into the electrolyte, which may reduce the reliability of the secondary battery, it is preferable to form the resin layer so that the electrolyte and the resin layer do not come into contact with each other, thereby improving the reliability of the secondary battery.

[0129] <Step S09> Next, in step S09, at least a portion of the resin layer is irradiated with ultraviolet light under reduced pressure.

[0130] Specifically, the exterior body 509a is placed on the exterior body 509b so as to cover the positive electrode 503, the separator 507, and the negative electrode 506, and the resin layer is irradiated with ultraviolet light under reduced pressure to harden at least a portion of the resin layer.

[0131] Here, an example is shown in which resin layer 518 provided on the four corners of exterior body 509b is hardened. As a result, when the secondary battery being fabricated is exposed to atmospheric pressure, exterior bodies 509a and 509b are pressurized by atmospheric pressure. Then, the reduced pressure state of the space surrounded by exterior bodies 509a, 509b, and frame-shaped resin layer 513 is maintained. Therefore, it is possible to prevent impurities from entering the secondary battery being fabricated from the outside.

[0132] Under reduced pressure, the area of ​​the secondary battery that can be irradiated with ultraviolet light may be limited. Therefore, in the method for manufacturing a secondary battery according to one embodiment of the present invention, a part of the resin layer may be cured under reduced pressure so that the reduced pressure state inside the secondary battery can be maintained even under atmospheric pressure. This allows the sealing process to be performed under atmospheric pressure.

[0133] Exterior body 509a transmits ultraviolet light at least in the area overlapping with resin layer 518.

[0134] In this embodiment, an example in which the resin layer is cured by irradiation with ultraviolet light is described, but one embodiment of the present invention is not limited thereto. For example, the resin layer may be cured by irradiation with light other than ultraviolet light. Alternatively, the resin layer may be cured by, for example, thermocompression bonding or welding (also referred to as fusion bonding or thermal adhesion). Examples of welding include high-frequency welding, thermal welding, and ultrasonic welding.

[0135] <Step S10> Next, in step S10, sealing is performed under atmospheric pressure.

[0136] Since the process in step S09 is performed under reduced pressure, the sealing process in step S10 can be performed under atmospheric pressure. The sealing process is preferably performed in an inert atmosphere such as an argon atmosphere or a nitrogen atmosphere.

[0137] For example, sealing can be performed by irradiating the frame-shaped resin layer 513 with ultraviolet light and curing it. In this way, it is preferable that the area of ​​the resin layer irradiated with ultraviolet light during sealing is larger than the area irradiated with ultraviolet light under reduced pressure. By performing sealing by light irradiation, it is not necessary to expose the secondary battery to high temperatures, so deterioration of the secondary battery can be suppressed and a highly reliable secondary battery can be manufactured.

[0138] Alternatively, sealing may be performed by thermocompression bonding or welding. For example, in a case where a single frame-shaped resin layer (see frame-shaped resin layer 521 shown in FIG. 9A, which will be described later) is provided to surround all of the multiple laminates in step S08, sealing is preferably performed by thermocompression bonding or welding.

[0139] FIG. 5C shows a state in which positive electrode 503, separator 507, and negative electrode 506 are sealed with exterior body 509a and exterior body 509b.

[0140] <Step S11> After the above steps, the process ends in step S11.

[0141] 1C, when multiple secondary batteries are fabricated on the exterior body 509b, these secondary batteries can be separated individually by dividing the exterior body 509a and the exterior body 509b. The exterior body can be divided using a laser beam or the like.

[0142] <Modifications of exterior body 509b> The exterior body 509b preferably has a recess. In this case, the positive electrode 503, the separator 507, and the negative electrode 506 are preferably disposed in the recess. Disposing them in the recess makes it easy to dispose the positive electrode 503, the separator 507, and the negative electrode 506 in desired positions, and also makes it possible to prevent these components from being displaced. This allows a highly reliable secondary battery to be manufactured.

[0143] FIG. 6A shows an example in which, in step S01, exterior body 509b having multiple recesses 509c is arranged.

[0144] It is preferable that one secondary battery can be produced per one recess 509c, and therefore the shape of the recess (width, length, depth, etc.) is preferably determined according to the shape of the secondary battery to be produced.

[0145] The recess is preferably formed in advance by press working or the like. The depth of the recess is preferably the same as or greater than the thickness of the laminate. When viewed from above, the area of ​​the bottom of the recess is preferably greater than the area of ​​the positive electrode. Also, when viewed from above, the area of ​​the bottom of the recess is preferably greater than the area of ​​the negative electrode. Also, when viewed from above, the area of ​​the bottom of the recess is preferably greater than the area of ​​the laminate. The recess preferably has a space inside which the positive electrode and the negative electrode, at least the regions excluding the tab regions, can be placed.

[0146] FIG. 6B shows an example in which one positive electrode 503 is placed in each recess in step S02.

[0147] Similarly, in step S04, one separator 507 is placed per recess, and in step S06, one negative electrode 506 is placed per recess. This allows one laminate 512 to be placed in one recess (FIG. 7A). Note that in FIG. 7A, one positive electrode 503, one separator 507, and one negative electrode 506 are illustrated as the laminate 512, but the configuration of the laminate 512 is not limited to this. The laminate 512 may have multiple positive electrodes 503, multiple separators 507, and multiple negative electrodes 506.

[0148] Fig. 8A shows a top view of laminated body 512 placed in recess 509c of exterior body 509b. Fig. 8B shows a cross-sectional view taken along dashed line AB in Fig. 8A.

[0149] As shown in FIGS. 8A and 8B, a positive electrode 503, a separator 507, and a negative electrode 506 are stacked and arranged in the recess 509c. FIG. 8B shows an example in which the laminate 512 has three positive electrodes 503, four separators, and two negative electrodes 506. The thickness of the laminate 512 is preferably equal to or less than the depth of the recess 509c. This makes it possible to particularly prevent the laminate 512 and the components constituting the laminate 512 from shifting from their desired positions.

[0150] Positive electrode 503 has a region (hereinafter referred to as tab region) where positive electrode current collector 501 is partially exposed. Negative electrode 506 has a region where negative electrode current collector 504 is partially exposed, that is, a tab region.

[0151] In the multiple positive electrode current collectors 501, for example, the tab regions are arranged so as to overlap each other. The overlapping tab regions and the positive electrode lead electrode may be overlapped and joined using ultrasonic welding or the like. In the multiple negative electrode current collectors 504, for example, the tab regions are arranged so as to overlap each other. The overlapping tab regions and the negative electrode lead electrode may be overlapped and joined using ultrasonic welding or the like. The timing of joining using ultrasonic welding or the like can be appropriately selected by the practitioner, and may be before or after sealing.

[0152] Furthermore, while FIG. 8A shows an example in which the tab regions of the positive electrode 503 and the negative electrode 506 are entirely contained within the recess 509c, as shown in FIG. 8C, the tab regions may have portions that extend outside the recess 509c.

[0153] <Modifications of exterior body 509a> As described above, the exterior body 509a transmits ultraviolet light at least in the region overlapping with the resin layer. The exterior body 509a preferably blocks ultraviolet light at least in the region overlapping with at least one of the positive electrode 503, the separator 507, and the negative electrode 506. The exterior body 509a preferably blocks ultraviolet light, particularly in the region overlapping with the laminate 512. This can prevent ultraviolet light from being irradiated onto the laminate 512, thereby preventing deterioration of the secondary battery.

[0154] FIG. 7B shows an example in which step S09 uses an exterior body 509a having an ultraviolet light-transmitting region 529a and an ultraviolet light-shielding region 529b. The ultraviolet light-shielding region 529b is arranged so as to overlap with a recess in the exterior body 509b. In a top view, the width and length of the ultraviolet light-shielding region 529b are preferably equal to or greater than those of the recess in the exterior body 509b. This configuration can particularly prevent ultraviolet light from irradiating the laminate 512, thereby improving the reliability of the secondary battery. The ultraviolet light-transmitting region 529a may transmit visible light.

[0155] 7B, resin layer 518 overlaps ultraviolet light transmitting region 529a of package 509a. Resin layer 518 is irradiated with ultraviolet light through ultraviolet light transmitting region 529a of package 509a, thereby curing resin layer 518.

[0156] <Top surface layout of resin layer> Next, an example of the top surface layout of a resin layer provided on exterior body 509b will be described.

[0157] 9A and 9B, a positive electrode (positive electrode active material layer 502 and positive electrode current collector 501), a separator 507, and a negative electrode (negative electrode active material layer 505 and negative electrode current collector 504) are arranged in a recess 509c of an outer casing 509b. A positive electrode lead electrode 510 is joined to the positive electrode current collector 501, and a negative electrode lead electrode 511 is joined to the negative electrode current collector 504.

[0158] FIG. 9A shows an example in which a frame-shaped resin layer 521 is provided along the four sides of the outer casing 509b. In this case, in step S09, ultraviolet light is preferably irradiated onto the frame-shaped resin layer 521 under reduced pressure to harden at least a portion of the frame-shaped resin layer 521. Then, in step S10, thermocompression bonding is preferably performed to seal the outer casing 509b. As described above, the frame-shaped resin layer 521 is preferably provided near the edge of the outer casing 509b or in an outer portion sufficiently away from the region where the secondary battery is formed. This prevents the material of the resin layer from being mixed into the electrolyte. When the resin layer is provided over the lead electrodes, it is preferable to use a resin material with high insulation properties to prevent electrical conduction between the lead electrodes. Alternatively, it is preferable to form a protective layer between the lead electrodes and the resin layer so that the resin layer does not come into contact with the lead electrodes.

[0159] 10 shows an example of the top surface layout of the sealing area 525 formed by thermocompression bonding. One sealing area 525 is provided for one secondary battery.

[0160] Exterior body 509a is bonded to exterior body 509b (not shown) by frame-shaped resin layer 521 and sealing region 525. An example in which the above-described configuration having ultraviolet light transmitting region 529a and ultraviolet light blocking region 529b is applied to exterior body 509a is shown.

[0161] The seal area 525 is provided to surround the positive electrode, the separator, and the negative electrode. The positive electrode lead electrode 510 and the negative electrode lead electrode 511 each have a sealing layer 519 at a position overlapping the seal area 525. This allows the lead electrodes and the exterior body to be fixed to each other, as well as to each other, thereby improving the reliability of the secondary battery.

[0162] 9B shows an example in which one frame-shaped resin layer 513 is provided for one recess 509c. Specifically, frame-shaped resin layer 513 is provided on exterior body 509b so as to surround recess 509c. In this case, in step S09, it is preferable to irradiate frame-shaped resin layer 513 with ultraviolet light under reduced pressure to at least partially cure frame-shaped resin layer 513. In particular, it is preferable to cure at least a portion of each of the plurality of frame-shaped resin layers 513.

[0163] Then, in step S10, it is preferable to irradiate the entire frame-shaped resin layer 513 with ultraviolet light under atmospheric pressure, thereby curing the entire frame-shaped resin layer 513.

[0164] Alternatively, in step S10, thermocompression bonding may be performed to seal the resin layer 513. At this time, part of the frame-shaped resin layer 513 may remain uncured.

[0165] Furthermore, in step S09, if each of the plurality of frame-shaped resin layers 513 is cured under reduced pressure to individually seal the secondary batteries, step S10 does not need to be performed.

[0166] 11 shows an example of the top surface layout of sealing area 525 formed by thermocompression bonding. One sealing area 525 is provided for one secondary battery. It is preferable that sealing area 525 is provided inside frame-shaped resin layer 513. Note that in FIG. 11, exterior body 509a is not shown.

[0167] The seal area 525 is provided to surround the positive electrode, the separator, and the negative electrode. The positive electrode lead electrode 510 and the negative electrode lead electrode 511 each have a sealing layer 519 at a position overlapping the seal area 525. This allows the lead electrodes and the exterior body to be fixed to each other, as well as to each other, thereby improving the reliability of the secondary battery.

[0168] When a film (also called a laminate film) including a laminate of metal foil (aluminum, stainless steel, etc.) and resin (thermally adhesive resin) is used as the exterior body 509a and the exterior body 509b, a thin secondary battery can be manufactured that is lighter than a secondary battery using a metal can. The metal foil has an adhesive layer (also called a heat seal layer) on one or both sides. The first adhesive layer of the first laminate film and the second adhesive layer of the second laminate film are bonded together by thermocompression bonding in a state where the first adhesive layer and the second adhesive layer are on the inside, thereby forming the seal region 525. Furthermore, the seal region 525 may be formed by other means than thermocompression bonding, such as using a thermosetting resin.

[0169] The adhesive layer can be made of a thermoplastic film material, a heat-curing adhesive, an anaerobic adhesive, a light-curing adhesive such as an ultraviolet light-curing adhesive, or a reaction-curing adhesive. The adhesive material can be an epoxy resin, an acrylic resin, a silicone resin, or a phenolic resin.

[0170] The sealing area 525 is in the shape of a frame or a closed loop. A laminate including the positive electrode 503, the separator 507, and the negative electrode 506 is disposed and sealed within the area surrounded by the sealing area 525. Therefore, the area of ​​the area surrounded by the sealing area 525 is set to be at least larger than the area of ​​the positive electrode 503 of the secondary battery.

[0171] The film used for the exterior body of the secondary battery may be a single layer film selected from metal films (metals or alloys that can be used as metal foil, such as aluminum, stainless steel, nickel steel, gold, silver, copper, titanium, nichrome, iron, tin, tantalum, niobium, molybdenum, zirconium, and zinc), plastic films made of organic materials, hybrid material films containing organic materials (such as organic resins or fibers) and inorganic materials (such as ceramics), and carbon-containing inorganic films (such as carbon films and graphite films), or a laminate film made of two or more of these.

[0172] The secondary battery's sealing structure is such that two exterior bodies are stacked and the four sides of the exterior bodies are fixed with an adhesive layer to seal them. Alternatively, one rectangular exterior body is folded in the center, and two of the four corners that sandwich the bent part are stacked, and the four sides are fixed with an adhesive layer to seal them. With this configuration, the stack of the positive electrode, separator, and negative electrode is housed in a manner that is wrapped in the exterior body.

[0173] Although an example of a thin battery (laminated type) has been mainly described in this embodiment, the shape of a battery manufactured by the method for manufacturing a secondary battery according to one embodiment of the present invention is not particularly limited, and the battery can also be applied to a wound type. In the case of a wound type, the electrolyte may be dripped onto the wound body, or may be dripped before the wound body is manufactured, i.e., before winding. The wound body refers to a body in which a strip-shaped positive electrode, a strip-shaped separator, and a strip-shaped negative electrode are stacked in this order and wound while still stacked.

[0174] As described above, in the method for manufacturing a secondary battery according to one embodiment of the present invention, in the step of stacking a positive electrode, a separator, and a negative electrode to form a stack, multiple drops of an electrolyte are dropped onto at least one of the positive electrode, the separator, and the negative electrode, thereby allowing the electrolyte to be uniformly or sufficiently impregnated into the positive electrode, the separator, or the negative electrode.

[0175] Furthermore, in the method for manufacturing a secondary battery according to one embodiment of the present invention, the space surrounded by the exterior body and the frame-shaped resin layer can be reduced in pressure by, for example, curing the resin layer under reduced pressure. This can prevent impurities from being mixed into the secondary battery. Furthermore, when the battery is exposed from a reduced-pressure atmosphere to an atmospheric-pressure atmosphere, the dropped electrolyte penetrates widely in a short time. This reduces the time it takes for the electrolyte to penetrate the surfaces and even the interiors of the positive and negative electrodes. Furthermore, the electrolyte can be sufficiently impregnated into the interiors of the positive and negative electrodes. Furthermore, subsequent sealing can be performed under atmospheric pressure, broadening the options for sealing methods.

[0176] This embodiment mode can be combined with other embodiment modes as appropriate. In addition, in this specification, when a plurality of configuration examples are shown in one embodiment mode, the configuration examples can be combined as appropriate.

[0177] (Embodiment 2) In this embodiment, components and materials of a secondary battery according to one embodiment of the present invention will be described.

[0178] [Positive electrode] The positive electrode includes a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer may further include one or both of a conductive material and a binder.

[0179] [Negative electrode] The negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes a negative electrode active material. The negative electrode active material layer may further include one or both of a conductive material and a binder.

[0180] [Current collector] The positive electrode current collector and the negative electrode current collector can be made of a material that has high conductivity and does not alloy with carrier ions such as lithium ions, such as metals such as stainless steel, gold, platinum, zinc, iron, nickel, copper, aluminum, titanium, and tantalum, and alloys thereof.

[0181] Alternatively, an aluminum alloy containing an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum, may be used. Alternatively, one or both of the positive electrode current collector and the negative electrode current collector may be formed of a metal element that reacts with silicon to form a silicide. Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel.

[0182] The current collector can appropriately use shapes such as foil, plate (sheet), net, cylindrical, coil, punched metal, expanded metal, etc. It is preferable to use a current collector with a thickness of 10 μm or more and 30 μm or less.

[0183] A titanium compound may be laminated on the above-mentioned metal as the current collector. Examples of the titanium compound include titanium nitride, titanium oxide, titanium nitride in which a part of nitrogen is substituted by oxygen, titanium oxide in which a part of oxygen is substituted by nitrogen, and titanium oxynitride (TiO x N y , 0 < x < 2, 0 < y < 1). One or more selected therefrom can be used by mixing or laminating. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material of the active material layer formed on the current collector and the metal is suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there may be a concern about the oxidation reaction between the oxygen of graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed.

[0184] [Conductive material] Active material layers such as the positive electrode active material layer and the negative electrode active material layer preferably have a conductive material (also referred to as a conductive agent or a conductive auxiliary). As the conductive material, it is preferable to have a carbon-based material such as a graphene compound, carbon black, graphite, carbon fiber, fullerene, etc., and particularly preferable to have a graphene compound. As carbon black, for example, acetylene black (AB) etc. can be used. As graphite, for example, natural graphite, artificial graphite such as mesocarbon microbeads, etc. can be used. In addition, these carbon-based materials may function as an active material.

[0185] Examples of carbon fibers that can be used include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. Carbon nanofibers and carbon nanotubes can also be used as carbon fibers. Carbon nanotubes can be produced by vapor phase growth, for example.

[0186] The active material layer may also contain, as a conductive material, a metal powder such as copper, nickel, aluminum, silver, or gold, or metal fibers, a conductive ceramic material, or the like.

[0187] The content of the conductive material relative to the total amount of the active material layer is preferably 1 wt % or more and 10 wt % or less, and more preferably 1 wt % or more and 5 wt % or less.

[0188] Unlike granular conductive materials such as carbon black, which form point contacts with the active material, graphene compounds enable surface contact with low contact resistance. Therefore, the electrical conductivity between the granular active material and the graphene compound can be improved with a smaller amount than with conventional conductive materials. This allows the ratio of the active material in the active material layer to be increased, thereby increasing the discharge capacity of the secondary battery.

[0189] Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes, easily enter microscopic spaces. Microscopic spaces refer to, for example, the regions between multiple active materials. By combining a carbon-containing compound that easily enters microscopic spaces with a sheet-like carbon-containing compound such as graphene, which can impart conductivity across multiple particles, the density of the electrode can be increased and an excellent conductive path can be formed. A secondary battery obtained by a manufacturing method according to one embodiment of the present invention can be stable and is effective as an in-vehicle secondary battery. Increasing the number of secondary batteries complicates control. Using large secondary batteries reduces the number of secondary batteries and the burden on the charge control circuit.

[0190] [Binder] The active material layer preferably contains a binder. The binder binds or fixes, for example, the electrolyte and the active material. The binder can also bind or fix the electrolyte and a carbon-based material, the active material and another carbon-based material, multiple active materials together, multiple carbon-based materials, etc.

[0191] As the binder, it is preferable to use materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose.

[0192] Polyimide has excellent thermal, mechanical and chemical stability.

[0193] Fluorine-containing polymer materials, specifically polyvinylidene fluoride (PVDF), can be used. PVDF is a resin with a melting point between 134°C and 169°C, and is a material with excellent thermal stability.

[0194] Furthermore, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. As the binder, fluororubber can also be used.

[0195] Furthermore, it is preferable to use, for example, a water-soluble polymer as the binder. Examples of the water-soluble polymer that can be used include polysaccharides. Examples of the polysaccharide that can be used include cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0196] The binder may be used in combination with two or more of the above.

[0197] <Graphene compounds> In this specification and the like, graphene compounds include graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multi-graphene oxide, graphene quantum dots, and the like. Graphene compounds contain carbon, have a shape such as a plate or sheet, and have a two-dimensional structure formed by six-membered carbon rings. The two-dimensional structure formed by six-membered carbon rings may also be called a carbon sheet. Graphene compounds may have functional groups. Furthermore, graphene compounds preferably have a curved shape. Furthermore, graphene compounds may be rolled up to resemble carbon nanofibers.

[0198] In this specification and the like, graphene oxide refers to, for example, a material that contains carbon and oxygen, has a sheet shape, and has a functional group, in particular, an epoxy group, a carboxy group, or a hydroxy group.

[0199] In this specification, reduced graphene oxide refers to, for example, a material containing carbon and oxygen, having a sheet-like shape, and having a two-dimensional structure formed by six-membered carbon rings. It may also be called a carbon sheet. Although a single sheet of reduced graphene oxide can function, multiple sheets may also be stacked. Reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic % and the oxygen concentration is 2 atomic % to 15 atomic %. By achieving these carbon and oxygen concentrations, reduced graphene oxide can function as a highly conductive material even in small amounts. Furthermore, reduced graphene oxide preferably has an intensity ratio G / D between the G band and the D band in a Raman spectrum of 1 or more. Reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small amounts.

[0200] By reducing graphene oxide, it may be possible to provide holes in the graphene compound.

[0201] Alternatively, a material in which the ends of graphene are terminated with fluorine may be used.

[0202] In the longitudinal cross section of the active material layer, the sheet-like graphene compound is dispersed substantially uniformly in the inner region of the active material layer. The plurality of graphene compounds are formed so as to partially cover the plurality of granular active material particles or to be attached to the surfaces of the plurality of granular active material particles, and are in surface contact with each other.

[0203] Here, a mesh-like graphene compound sheet (hereinafter referred to as a graphene compound net or graphene net) can be formed by bonding multiple graphene compounds together. When an active material is covered with a graphene net, the graphene net can also function as a binder that bonds the active materials together. Therefore, the amount of binder can be reduced or can be eliminated, thereby improving the ratio of the active material to the electrode volume or weight. In other words, the charge / discharge capacity of a secondary battery can be increased.

[0204] Here, it is preferable to use graphene oxide as the graphene compound, mix it with an active material to form a layer that will become an active material layer, and then reduce it. That is, the completed active material layer preferably contains reduced graphene oxide. By using graphene oxide, which has extremely high dispersibility in a polar solvent, to form the graphene compound, it is possible to substantially uniformly disperse the graphene compound in the internal region of the active material layer. Since the solvent is volatilized and removed from the dispersion medium containing the uniformly dispersed graphene oxide and the graphene oxide is reduced, the graphene compound remaining in the active material layer partially overlaps and is dispersed to such an extent that it is in surface contact with each other, thereby forming a three-dimensional conductive path. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or using a reducing agent.

[0205] Furthermore, by using a spray dryer in advance, a graphene compound, which is a conductive material, can be formed as a coating that covers the entire surface of the active material, and the active material can be electrically connected to each other by the graphene compound to form a conductive path.

[0206] Furthermore, a material used in forming the graphene compound may be mixed with the graphene compound and used in the active material layer. For example, particles used as a catalyst in forming the graphene compound may be mixed with the graphene compound. Examples of catalysts used in forming the graphene compound include silicon oxide (SiO2, SiO x Examples of suitable particles include particles having one or more of the following: (x<2), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, and germanium. The particles preferably have an average particle diameter (D50: also referred to as median diameter) of 1 μm or less, and more preferably 100 nm or less.

[0207] [Negative electrode active material] As the negative electrode active material, it is preferable to use a material capable of reacting with carrier ions of a secondary battery, a material capable of inserting and desorbing carrier ions, a material capable of alloying with a metal that becomes a carrier ion, a material capable of dissolving and precipitating a metal that becomes a carrier ion, or the like.

[0208] An example of the negative electrode active material will be described below.

[0209] The negative electrode active material may be a metal or compound containing one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium. Examples of alloy compounds using such elements include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn.

[0210] Alternatively, a material may be used in which one or more impurity elements selected from phosphorus, arsenic, boron, aluminum, and gallium are added to silicon to reduce its resistance. Alternatively, a silicon material pre-doped with lithium may be used. Pre-doping methods include mixing silicon with lithium fluoride, lithium carbonate, or the like and annealing the mixture, or mechanical alloying of lithium metal and silicon. After forming an electrode, the material may be combined with an electrode such as lithium metal to dope lithium through a charge-discharge reaction. The doped electrode may then be combined with a counter electrode (e.g., a positive electrode for a pre-doped negative electrode) to produce a secondary battery.

[0211] The negative electrode active material may be, for example, silicon nanoparticles, which preferably have an average diameter of 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0212] The silicon nanoparticles may be crystalline, or may have a crystalline region and an amorphous region.

[0213] Examples of silicon-containing materials include SiO x (x is preferably smaller than 2, more preferably 0.5 or more and 1.6 or less) can be used.

[0214] As the negative electrode active material, a carbon-based material such as graphite, graphitizable carbon, non-graphitizable carbon, carbon nanotubes, carbon black, and a graphene compound can be used.

[0215] Furthermore, as the negative electrode active material, an oxide containing one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0216] In addition, as the negative electrode active material, SnO, SnO2, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), and other oxides can be used.

[0217] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, Li3N-type 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 is preferable because it exhibits a large charge / discharge capacity (900 mAh / g).

[0218] The use of a lithium-transition metal complex nitride as the negative electrode material is preferable because it can be combined with a lithium-ion-free positive electrode material such as V2O5 or Cr3O8. Even when a material containing lithium ions is used as the positive electrode material, the lithium-transition metal complex nitride can be used as the negative electrode material by first removing the lithium ions contained in the positive electrode material.

[0219] In addition, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not undergo an alloying reaction with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), can be used as the negative electrode active material. Materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, and CoS 0.89 This phenomenon also occurs with sulfides such as 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 the above fluorides have high potentials and may therefore be used as positive electrode materials.

[0220] As the negative electrode active material, a combination of two or more of the above-described metals, materials, compounds, etc. can be used.

[0221] [Cathode active material] Examples of the positive electrode active material include lithium-containing materials having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure.

[0222] In the secondary battery of one embodiment of the present invention, a positive electrode active material having a layered crystal structure is preferably used.

[0223] An example of the layered crystal structure is a layered rock salt type crystal structure. An example of a lithium-containing material having a layered rock salt type crystal structure is LiM x O yA lithium-containing material represented by (x > 0 and y > 0, more specifically, for example, y = 2, and 0.8 < x < 1.2) can be used. Here, M is a metal element, preferably one or more selected from cobalt, manganese, nickel, and iron. Alternatively, M is, for example, two or more selected from cobalt, manganese, nickel, iron, aluminum, titanium, zirconium, lanthanum, copper, and zinc.

[0224] LiM x O y Examples of the lithium-containing material represented by include LiCoO2, LiNiO2, LiMnO2, etc. Also, LiNi x Co 1-x O2 (0 < x < 1) represented by NiCo-based, LiM x O y Examples of the lithium-containing material represented by include NiMn-based represented by LiNi x Mn 1-x O2 (0 < x < 1), etc.

[0225] Also, examples of the lithium-containing material represented by LiMO2 include NiCoMn-based (also referred to as NCM) represented by LiNi x Co y Mn z O2 (x > 0, y > 0, 0.8 < x + y + z < 1.2). Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, x, y, and z preferably satisfy x:y:z = 1:1:1 or values in the vicinity thereof. Alternatively, as an example, x, y, and z preferably satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Alternatively, as an example, x, y, and z preferably satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Alternatively, as an example, x, y, and z preferably satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Alternatively, as an example, x, y, and z preferably satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0226] In addition, examples of the lithium-containing material having a layered rock salt-type crystal structure include Li2MnO3, Li2MnO3-LiMeO2 (Me is Co, Ni, Mn), and the like.

[0227] In a cathode active material having a layered crystal structure represented by the above lithium-containing material, there may be a case where a secondary battery with a high lithium content per volume and a high capacity per volume can be realized. In such a cathode active material, the amount of lithium desorbed per volume during charging is also large, and in order to perform stable charge and discharge, stabilization of the crystal structure after desorption is required. Also, rapid charge or rapid discharge may be inhibited due to the collapse of the crystal structure during charge and discharge.

[0228] It is preferable to mix a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 as the cathode active material with lithium nickelate (LiNiO2 or LiNi 1-x M x O2 (0 < x < 1) (M = Co, Al, etc.)). By adopting such a configuration, the characteristics of the secondary battery can be improved.

[0229] In addition, as the cathode active material, the composition formula is Li a Mn b M c O dA lithium-manganese composite oxide that can be expressed by the formula (1) can be used. Here, element M is preferably a metal element selected from among lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire lithium-manganese composite oxide particle, <a / (b+c)<2、c>it is preferable that the composition be 0 0 during discharge and satisfy 0.26≦(b+c) / d<0.5. The composition of metals, silicon, phosphorus, etc. in the entire lithium-manganese composite oxide particle can be measured using, for example, an inductively coupled plasma mass spectrometer (ICP-MS). The oxygen composition in the entire lithium-manganese composite oxide particle can be measured using, for example, energy dispersive X-ray spectroscopy (EDX). In addition, the composition can be determined by valence evaluation using fusion gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. The lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, phosphorus, and the like.

[0230] <Structure of positive electrode active material> Materials with a layered rock-salt crystal structure, such as lithium cobalt oxide (LiCoO2), are known to have high discharge capacity and are excellent as positive electrode active materials for secondary batteries. Examples of materials with a layered rock-salt crystal structure include composite oxides represented by LiMO2. The metal M includes the metal Me1. The metal Me1 is one or more metals including cobalt. The metal M may also include a metal in addition to the metal Me1. The metal is one or more metals selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0231] The amount of lithium remaining in the positive electrode active material that can be inserted or removed is determined by the x in the composition formula, for example, Li x x in CoO2, or Li x In this specification, Li​x CoO2 is appropriately Li x In the case of the positive electrode active material in a secondary battery, x can be expressed as charge capacity / theoretical capacity. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2mAh / g, Li 0.8 CoO2 or x=0.8. x The x in CoO2 is small, for example, 0.1 <x≦0.24をいう。

[0232] It is known that the strength of the Jahn-Teller effect in transition metal compounds varies depending on the number of electrons in the d orbital of the transition metal.

[0233] In compounds containing nickel, distortion may occur easily due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged so that x becomes small, there is a concern that the crystal structure may collapse due to distortion. In LiCoO2, it is suggested that the influence of the Jahn-Teller effect is small, and Li x When x in CoO2 is small, the charge / discharge durability may be better, which is preferable.

[0234] The positive electrode active material will be described with reference to FIGS.

[0235] <Crystal structure> <Li x When x in CoO2 is 1≫ The positive electrode active material according to one embodiment of the present invention is in a discharged state, i.e., Li x When x = 1 in CoO2, it is preferable for the layered rock-salt complex oxide to have a layered rock-salt crystal structure belonging to the space group R-3m. Layered rock-salt complex oxides have high discharge capacity, two-dimensional lithium ion diffusion paths, and are suitable for lithium ion insertion / extraction reactions, making them excellent cathode active materials for secondary batteries. Therefore, it is particularly preferable for the interior, which accounts for most of the volume of the cathode active material, to have a layered rock-salt crystal structure. Figure 12 shows the layered rock-salt complex oxide crystal structure, labeled R-3m O3.

[0236] The surface layer is the area where lithium ions are first released during charging, and is prone to have a lower lithium concentration than the interior. In addition, the atoms on the surface of the positive electrode active material in the surface layer can be said to have some of their bonds broken. Therefore, the surface layer is prone to becoming unstable, and is a region where deterioration of the crystal structure is likely to begin. On the other hand, if the surface layer can be made sufficiently stable, Li x Even when x in CoO2 is small, for example, 0.24 or less, the layered structure consisting of the internal transition metal M and oxygen octahedra can be made less likely to break. Furthermore, the displacement of the internal transition metal M and oxygen octahedra can be suppressed.

[0237] In order to give the surface layer a stable composition and crystal structure, the surface layer preferably contains an additive element A, and more preferably contains a plurality of additive elements A. Furthermore, the surface layer preferably has a higher concentration of one or more selected from the additive elements A than the interior. Furthermore, it is preferable that the one or more selected from the additive elements A contained in the positive electrode active material have a concentration gradient. Furthermore, it is more preferable that the distribution of the additive element A in the positive electrode active material differs depending on the additive element A. For example, it is more preferable that the depth from the surface of the concentration peak differs depending on the additive element A. Here, the concentration peak refers to the maximum concentration value in the surface layer or within 50 nm from the surface.

[0238] For example, some of the additive elements A, such as magnesium, fluorine, titanium, silicon, phosphorus, boron, and calcium, preferably have a concentration gradient that increases from the inside toward the surface. Elements having such a concentration gradient will be referred to as additive elements X.

[0239] For example, magnesium, one of the added elements X, is divalent, and magnesium ions are more stable at the lithium site than at the transition metal M site in the layered rock salt crystal structure, so they tend to enter the lithium site. The presence of magnesium at an appropriate concentration at the lithium site in the surface layer makes it easier to maintain the layered rock salt crystal structure. This is presumably because the magnesium present at the lithium site functions as a pillar supporting the CoO2 layers. The presence of magnesium also makes it easier to maintain the Lix When x in CoO2 is, for example, 0.24 or less, the release of oxygen from the surrounding magnesium can be suppressed. The presence of magnesium is also expected to increase the density of the positive electrode active material. Furthermore, a high magnesium concentration in the surface layer is expected to improve corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte.

[0240] At an appropriate concentration, magnesium does not adversely affect the intercalation and deintercalation of lithium during charging and discharging, providing the above benefits. However, excessive magnesium may adversely affect the intercalation and deintercalation of lithium. Furthermore, it may have a reduced effect on stabilizing the crystal structure. This is thought to be due to magnesium occupying the transition metal M site in addition to the lithium site. In addition, unnecessary magnesium compounds (e.g., oxides and fluorides) that do not substitute for either the lithium site or the transition metal M site may segregate on the surface of the positive electrode active material and become resistance components in the secondary battery. Furthermore, as the magnesium concentration in the positive electrode active material increases, the discharge capacity of the positive electrode active material may decrease. This is thought to be due to excessive magnesium occupancy in the lithium site, reducing the amount of lithium contributing to charging and discharging.

[0241] Therefore, it is preferable that the amount of magnesium contained in the entire positive electrode active material is appropriate. For example, the number of magnesium atoms is preferably 0.001 to 0.1 times the number of cobalt atoms, more preferably more than 0.01 to less than 0.04 times, and even more preferably about 0.02 times. The amount of magnesium contained in the entire positive electrode active material referred to here may be a value obtained by performing elemental analysis of the entire positive electrode active material using, for example, GD-MS, ICP-MS, etc., or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material.

[0242] Furthermore, aluminum, one of the additive elements A, can exist in the transition metal M site in the layered rock salt crystal structure. Because aluminum is a typical trivalent element and its valence does not change, lithium around the aluminum is less likely to move during charging and discharging. Therefore, the aluminum and its surrounding lithium function as pillars, suppressing changes in the crystal structure. Aluminum also suppresses the elution of the surrounding transition metal M, improving continuous charging durability. Furthermore, because the Al-O bond is stronger than the Co-O bond, it can suppress the release of oxygen around the aluminum. These effects improve thermal stability. Therefore, having aluminum as the additive element A can improve safety when used in secondary batteries. It can also be used as a positive electrode active material whose crystal structure is less likely to collapse even after repeated charging and discharging.

[0243] On the other hand, an excess of aluminum may adversely affect the intercalation and deintercalation of lithium.

[0244] Therefore, it is preferable that the aluminum content of the entire positive electrode active material is an appropriate amount. For example, the number of aluminum atoms contained in the entire positive electrode active material is preferably 0.05% to 4% of the number of cobalt atoms, preferably 0.1% to 2% and more preferably 0.3% to 1.5%. Alternatively, 0.05% to 2% is preferable. Alternatively, 0.1% to 4% is preferable. The amount contained in the entire positive electrode active material here may be, for example, a value obtained by performing elemental analysis of the entire positive electrode active material using GD-MS, ICP-MS, or the like, or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material.

[0245] For example, it is preferable that the crystal structure continuously changes from the inside of the layered rock salt type toward the surface and surface layer portion having characteristics of the rock salt type or both the rock salt type and the layered rock salt type.Alternatively, it is preferable that the orientation of the rock salt type or the surface layer portion having characteristics of both the rock salt type and the layered rock salt type is approximately the same as that of the inside of the layered rock salt type.

[0246] In this specification, the layered rock-salt crystal structure belonging to the space group R-3m, which is possessed by a composite oxide containing lithium and a transition metal M such as cobalt, refers to a crystal structure having a rock-salt ion arrangement in which cations and anions are alternately arranged, and in which the transition metal M and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as vacancies of cations or anions may also be present. Furthermore, strictly speaking, the layered rock-salt crystal structure may have a structure in which the lattice of the rock-salt crystal is distorted.

[0247] The rock salt crystal structure is a cubic crystal structure, such as that of the space group Fm-3m, in which cations and anions are arranged alternately. Note that cation or anion defects are also acceptable.

[0248] Furthermore, the presence of both the characteristics of layered rock salt type and rock salt type crystal structures can be determined by electron diffraction, TEM (Transmission Electron Microscope) images, cross-sectional STEM (Scanning Transmission Electron Microscope) images, etc.

[0249] The anions in layered rock salt crystals and rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure). It is estimated that the anions in the O3' crystals (also called pseudospinel crystals), which will be described later, also have a cubic close-packed structure. Therefore, when layered rock salt crystals and rock salt crystals come into contact, there are crystal faces where the cubic close-packed structure composed of anions is aligned.

[0250] Alternatively, it can be explained as follows: Anions on the {111} plane of the cubic crystal structure have a triangular lattice. Layered rocksalt has a space group of R-3m and a rhombohedral structure, but to make the structure easier to understand, it is generally expressed as a compound hexagonal lattice, and the (000l) plane of the layered rocksalt has a hexagonal lattice. The triangular lattice of the cubic {111} plane has the same atomic arrangement as the hexagonal lattice of the (000l) plane of the layered rocksalt. The compatibility of the two lattices can be said to be the alignment of the cubic close-packed structure.

[0251] However, the space group of the layered rock salt type crystal and the O3' type crystal is R-3m, which is different from the space group Fm-3m of the rock salt type crystal (the space group of a general rock salt type crystal), and therefore the Miller indices of the crystal planes that satisfy the above conditions are different between the layered rock salt type crystal and the O3' type crystal and the rock salt type crystal. In this specification, when the orientations of the cubic close-packed structures formed by anions in the layered rock salt type crystal, the O3' type, and the rock salt type crystal are aligned, it may be said that the crystal orientations are approximately the same.

[0252] The fact that the crystal orientations of the two regions roughly match can be determined from TEM images, STEM images, HAADF-STEM (High-angle Annular Dark Field Scanning TEM) images, ABF-STEM (Annular Bright-Field Scanning Transmission Electron Microscopy) images, electron diffraction, FFT of TEM images, STEM images, etc. XRD (X-ray diffraction), neutron diffraction, etc. can also be used as materials for determination.

[0253] Figure 13 shows R-3m O3 and Li xThis shows the crystal structure of lithium cobalt oxide with x=1 in CoO2. In this crystal structure, lithium occupies octahedral sites, and there are three CoO2 layers in the unit cell. For this reason, this crystal structure is sometimes called an O3-type crystal structure. Note that a CoO2 layer is an octahedral structure in which cobalt is coordinated with six oxygen atoms, and these structures are connected in a plane with edge sharing. This is sometimes called a layer consisting of octahedra of cobalt and oxygen.

[0254] Conventional lithium cobalt oxide is known to have a crystal structure that belongs to the monoclinic space group P2 / m when the symmetry of lithium increases when x is around 0.5. This structure has one CoO2 layer in the unit cell. For this reason, it is sometimes called the O1 type or monoclinic O1 type.

[0255] When x = 0, the positive electrode active material has a trigonal space group P-3m1 crystal structure, with one CoO2 layer in each unit cell. This crystal structure is sometimes called the O1 type or trigonal O1 type. The trigonal structure may also be converted to a composite hexagonal lattice, which is sometimes called the hexagonal O1 type.

[0256] Furthermore, conventional lithium cobalt oxide (LiCOO) with x = 0.12 or so has a crystal structure of the space group R-3m. This structure can be described as a structure in which a trigonal O1-type CoO2 structure and an R-3m O3-type LiCoO2 structure are alternately stacked. Therefore, this crystal structure is sometimes referred to as the H1-3-type crystal structure. Because actual lithium insertion and extraction can be uneven, the H1-3-type crystal structure is experimentally observed from x = 0.25 or so. Furthermore, the H1-3-type crystal structure actually has twice the number of cobalt atoms per unit cell compared to other structures. However, in Figure 13 and other parts of this specification, the c-axis of the H1-3-type crystal structure is shown as half the unit cell to facilitate comparison with other crystal structures.

[0257] For example, the coordinates of cobalt and oxygen in the unit cell of the H1-3 crystal structure can be expressed as Co(0, 0, 0.42150±0.00016), O1(0, 0, 0.27671±0.00045), and O2(0, 0, 0.11535±0.00045). O1 and O2 are oxygen atoms. The unit cell that should be used to represent the crystal structure of the positive electrode active material can be determined, for example, by Rietveld analysis of XRD. In this case, the unit cell that results in the smallest GOF (goodness of fit) value should be used.

[0258] Li x When conventional lithium cobalt oxide is repeatedly charged and discharged so that x in CoO2 becomes 0.24 or less, the crystal structure changes repeatedly (i.e., a non-equilibrium phase change) between the H1-3 type crystal structure and the R-3m O3 structure in the discharged state.

[0259] However, these two crystal structures have a large misalignment of the CoO2 layers. As shown by the dotted lines and arrows in Figure 13, in the H1-3 crystal structure, the CoO2 layers are significantly misaligned from those in the R-3m O3 discharged state. Such dynamic structural changes can adversely affect the stability of the crystal structure.

[0260] Furthermore, the difference in volume between these two crystal structures is large: when compared per the same number of cobalt atoms, the difference in volume between the H1-3 crystal structure and the discharged R-3m O3 crystal structure exceeds 3.5%, typically 3.9% or more.

[0261] In addition, the H1-3 type crystal structure, which has continuous CoO2 layers like the trigonal O1 type, is likely to be unstable.

[0262] Therefore, when charging and discharging is repeated so that x becomes 0.24 or less, the crystal structure of conventional lithium cobalt oxide collapses. This collapse of the crystal structure causes a deterioration in cycle characteristics. This is because the collapse of the crystal structure reduces the number of sites where lithium can exist stably and makes it difficult for lithium to be inserted and extracted.

[0263] As shown by the dotted line in FIG. 12, there is almost no deviation in the CoO2 layer between the R-3m(O3) in the discharged state and the O3'-type crystal structure.

[0264] The difference in volume per the same number of cobalt atoms between R-3m(O3) in a discharged state and the O3'-type crystal structure is 2.5% or less, more specifically 2.2% or less, and typically 1.8%.

[0265] As described above, in the positive electrode active material according to one embodiment of the present invention, Li x When x in CoO2 is small, i.e., when a large amount of lithium is released, the change in crystal structure is suppressed compared to conventional positive electrode active materials. Furthermore, the change in volume is also suppressed when compared per the same number of cobalt atoms. Therefore, the positive electrode active material of one embodiment of the present invention is less likely to collapse in crystal structure even when repeatedly charged and discharged so that x is 0.24 or less. Therefore, the positive electrode active material of one embodiment of the present invention suppresses the decrease in charge / discharge capacity during charge / discharge cycles. Furthermore, because it can stably utilize more lithium than conventional positive electrode active materials, the positive electrode active material of one embodiment of the present invention has a large discharge capacity per weight and per volume. Therefore, by using the positive electrode active material of one embodiment of the present invention, a secondary battery with a high discharge capacity per weight and per volume can be fabricated.

[0266] The positive electrode active material is Li x It has been confirmed that when x in CoO2 is between 0.15 and 0.24, it may have an O3' type crystal structure, and it is also presumed that when x is between 0.24 and 0.27, it also has an O3' type crystal structure. However, the crystal structure is Li x Since it is affected not only by x in CoO2 but also by the number of charge / discharge cycles, charge / discharge current, temperature, electrolyte, etc., it is not necessarily limited to the above range of x.

[0267] Therefore, the positive electrode active material is Li x When x in CoO2 is more than 0.1 and not more than 0.24, the entire interior of the positive electrode active material does not have to have an O3'-type crystal structure, and may contain other crystal structures, or may be partially amorphous.

[0268] Also Li x To make the x in CoO2 small, it is generally necessary to charge at a high charging voltage. x A state in which x in CoO2 is small can be rephrased as a state in which the battery is charged at a high charging voltage. For example, when conventional positive electrode active materials are charged at a voltage of 4.6 V or higher relative to the potential of lithium metal in a 25°C environment under CC / CV charging, an H1-3 crystal structure appears. Therefore, a charging voltage of 4.6 V or higher relative to the potential of lithium metal can be considered a high charging voltage. Unless otherwise specified, charging voltages in this specification and elsewhere are expressed relative to the potential of lithium metal.

[0269] Therefore, in other words, the positive electrode active material of one embodiment of the present invention is preferable because it can maintain a crystal structure with R-3m O3 symmetry even when charged at a high charge voltage, for example, a voltage of 4.6 V or higher at 25° C. In other words, it is preferable because it can adopt an O3'-type crystal structure when charged at a higher charge voltage, for example, a voltage of 4.65 V or higher and 4.7 V or lower at 25° C.

[0270] Even in the case of a positive electrode active material, the H1-3 type crystal may be observed only when the charge voltage is further increased. Furthermore, as described above, since the crystal structure is affected by the number of charge / discharge cycles, the charge / discharge current, the electrolyte, etc., the positive electrode active material of one embodiment of the present invention may be able to adopt the O3' type crystal structure even when the charge voltage is lower, for example, even when the charge voltage is 4.5 V or higher but lower than 4.6 V at 25°C.

[0271] In addition, when graphite is used as the negative electrode active material in a secondary battery, the voltage of the secondary battery is lower than the above by the amount of the potential of the graphite. The potential of graphite is about 0.05 V to 0.2 V relative to the potential of lithium metal. Therefore, in the case of a secondary battery using graphite as the negative electrode active material, the same crystalline structure is maintained at a voltage obtained by subtracting the potential of graphite from the above voltage.

[0272] As shown in Figure 12, the lattice constant of the a-axis of the O3'-type crystal structure is 2.817 × 10-10 The lattice constants of the m and c axes are 13.781 × 10 -10 m.

[0273] In addition, the O3' type crystal structure can be expressed by the coordinates of cobalt and oxygen in the unit cell being Co(0,0,0.5), O(0,0,x), with 0.20≦x≦0.25.

[0274] <Particle size of positive electrode active material> If the particle size of the positive electrode active material is too large, problems such as difficulty in diffusing lithium and excessive roughness of the surface of the active material layer when applied to the current collector occur. On the other hand, if the particle size is too small, problems such as difficulty in supporting the active material layer when applied to the current collector and excessive reaction with the electrolyte occur. Therefore, D50 is preferably 1 μm to 100 μm, more preferably 2 μm to 40 μm, and even more preferably 5 μm to 30 μm. Alternatively, D50 is preferably 1 μm to 40 μm. Alternatively, D50 is preferably 1 μm to 30 μm. Alternatively, D50 is preferably 2 μm to 100 μm. Alternatively, D50 is preferably 2 μm to 30 μm. Alternatively, D50 is preferably 2 μm to 100 μm. Alternatively, D50 is preferably 2 μm to 30 μm. Alternatively, D50 is preferably 5 μm to 100 μm. Alternatively, D50 is preferably 5 μm to 40 μm.

[0275] <Analysis method> A certain positive electrode active material is Li x When x in CoO2 is small, whether or not the positive electrode active material of one embodiment of the present invention has an O3'-type crystal structure can be determined by Li x This can be determined by analyzing a positive electrode having a positive electrode active material with a small x in CoO2 using XRD, electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. XRD is particularly preferred because it can analyze the symmetry of transition metals such as cobalt contained in the positive electrode active material with high resolution, it can compare the level of crystallinity and the orientation of the crystals, it can analyze the periodic distortion of the lattice and the crystallite size, and it can obtain sufficient accuracy even when measuring a positive electrode obtained by disassembling a secondary battery.

[0276] As mentioned above, the positive electrode active material is Li xA characteristic of CoO2 is that there is little change in the crystal structure when x in CoO2 is 1 and when it is 0.24 or less. When charged at high voltage, materials in which the crystal structure that undergoes large changes when charged at high voltage accounts for 50% or more are not desirable because they cannot withstand high-voltage charging and discharging.

[0277] It should also be noted that simply adding an additional element A may not result in an O3'-type crystal structure. For example, even if lithium cobalt oxide with magnesium and fluorine or lithium cobalt oxide with magnesium and aluminum has something in common, depending on the concentration and distribution of the additional element A, the O3'-type crystal structure may not be obtained. x When x in CoO2 is 0.24 or less, the O3' type crystal structure accounts for 60% or more, and when the H1-3 type crystal structure accounts for 50% or more.

[0278] Furthermore, even in a positive electrode active material of one embodiment of the present invention, an H1-3 type or trigonal O1 type crystal structure may be formed if x is too small, such as 0.1 or less, or under conditions where the charge voltage exceeds 4.9 V. Therefore, to determine whether or not a positive electrode active material is one embodiment of the present invention, analysis of the crystal structure, such as XRD, and information such as the charge capacity or the charge voltage are required.

[0279] However, when positive electrode active materials with a small x or in a discharged state are exposed to air, their crystal structure may change. For example, they may change from an O3'-type crystal structure to an H1-3-type crystal structure. Therefore, it is recommended that all samples used for crystal structure analysis be handled in an inert atmosphere, such as an argon-containing atmosphere.

[0280] Furthermore, whether the distribution of the additive element A in a certain positive electrode active material is in the state described above can be determined by analysis using, for example, XPS, EDX, EPMA (electron probe microanalysis), or the like.

[0281] The crystalline structure of the surface layer, grain boundaries, etc. can be analyzed by electron beam diffraction of a cross section of the positive electrode active material.

[0282] [Electrolyte] When a liquid electrolyte (also referred to as electrolytic solution) is used in a secondary battery, for example, the electrolyte may be one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, and the like, or two or more of these may be used in any combination and ratio.

[0283] The electrolyte preferably contains fluorine. For example, an electrolyte containing one or more fluorinated cyclic carbonates and lithium ions can be used as the fluorine-containing electrolyte. The fluorinated cyclic carbonate improves non-flammability and can enhance the safety of the lithium ion secondary battery.

[0284] Fluorinated cyclic carbonates include fluorinated ethylene carbonates, such as monofluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), and tetrafluoroethylene carbonate (F4EC). DFEC includes isomers such as cis-4,5 and trans-4,5. For low-temperature operation, it is important to use one or more fluorinated cyclic carbonates as an electrolyte to solvate lithium ions and transport them within the electrolyte contained in the electrodes during charging and discharging. Using fluorinated cyclic carbonates not as a small additive but as a catalyst for lithium ion transport during charging and discharging enables low-temperature operation. Lithium ions move in clusters of several to several tens of ions within a secondary battery.

[0285] The use of a fluorinated cyclic carbonate in the electrolyte reduces the desolvation energy required for lithium ions solvated in the electrolyte contained in the electrode to enter active material particles. Reducing this desolvation energy facilitates insertion and desorption of lithium ions into active material particles, even at low temperatures. While lithium ions may migrate in a solvated state, they may also undergo a hopping phenomenon, in which the coordinated solvent molecules switch positions. When lithium ions are more easily desolvated, they may be more susceptible to hopping, which may facilitate lithium ion migration. There is a concern that electrolyte decomposition products may cling to the surface of the active material during charging and discharging of secondary batteries, causing deterioration of the secondary battery. However, when the electrolyte contains fluorine, the viscosity of the electrolyte is low, making it difficult for electrolyte decomposition products to adhere to the surface of the active material. This reduces secondary battery degradation.

[0286] A plurality of solvated lithium ions may form clusters in the electrolyte and move within the negative electrode, between the positive electrode and the negative electrode, within the positive electrode, etc.

[0287] An example of the structural formula of a fluorinated cyclic carbonate is shown below.

[0288] Monofluoroethylene carbonate (FEC) is represented by the following formula (1).

[0289] [ka]

[0290] Tetrafluoroethylene carbonate (F4EC) is represented by the following formula (2).

[0291] [ka]

[0292] Difluoroethylene carbonate (DFEC) is represented by the following formula (3).

[0293] [ka]

[0294] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the electrolyte solvent, it is possible to prevent either or both of the explosion and fire of the secondary battery even if a short circuit occurs in the internal region of the secondary battery or a temperature rise in the internal region occurs due to overcharging, etc. Ionic liquids are composed of cations and anions, including organic cations and anions. Examples of organic cations include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions include monovalent amide anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkylsulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, and perfluoroalkylphosphate anions.

[0295] As the ionic liquid having an imidazolium cation, for example, an ionic liquid represented by the following general formula (G1) can be used. In general formula (G1), R 1 represents an alkyl group having 1 to 4 carbon atoms, and R 2 ~R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 5 represents an alkyl group having 1 to 6 carbon atoms, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P. 5 A substituent may be introduced into the main chain of the polymer. Examples of the substituent to be introduced include an alkyl group and an alkoxy group.

[0296] [ka]

[0297] Examples of the cation represented by general formula (G1) include a 1-ethyl-3-methylimidazolium cation, a 1-butyl-3-methylimidazolium cation, a 1-methyl-3-(propoxyethyl)imidazolium cation, and a 1-hexyl-3-methylimidazolium cation.

[0298] As the ionic liquid having a pyridinium cation, for example, an ionic liquid represented by the following general formula (G2) may be used. In general formula (G2), R 6 represents an alkyl group having 1 to 6 carbon atoms, or a main chain composed of two or more atoms selected from C, O, Si, N, S, and P, and R 7 ~R 11 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 6 A substituent may be introduced into the main chain of the polymer. Examples of the substituent to be introduced include an alkyl group and an alkoxy group.

[0299] [ka]

[0300] As the ionic liquid having a quaternary ammonium cation, for example, ionic liquids represented by the following general formulas (G3) to (G6) can be used.

[0301] [ka]

[0302] In general formula (G3), R 28 ~R 31 each independently represents an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom.

[0303] [ka]

[0304] In general formula (G4), R 12 and R 17 each independently represents an alkyl group having 1 to 3 carbon atoms, and R 13 ~R 16 each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. An example of a cation represented by general formula (G4) is a 1-methyl-1-propylpyrrolidinium cation.

[0305] [ka]

[0306] In general formula (G5), R 18 and R 24 each independently represents an alkyl group having 1 to 3 carbon atoms, and R 19 ~R 23 each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the cation represented by general formula (G5) include an N-methyl-N-propylpiperidinium cation and a 1,3-dimethyl-1-propylpiperidinium cation.

[0307] [ka]

[0308] In general formula (G6), n and m are 1 or more and 3 or less. α is 0 or more and 6 or less; when n is 1, α is 0 or more and 4 or less; when n is 2, α is 0 or more and 5 or less; and when n is 3, α is 0 or more and 6 or less. β is 0 or more and 6 or less; when m is 1, β is 0 or more and 4 or less; when m is 2, β is 0 or more and 5 or less; and when m is 3, β is 0 or more and 6 or less. When α or β is 0, this indicates unsubstituted. This does not include cases where both α and β are 0. X or Y is a substituent, and represents a linear or side-chain alkyl group having 1 to 4 carbon atoms, a linear or side-chain alkoxy group having 1 to 4 carbon atoms, or a linear or side-chain alkoxyalkyl group having 1 to 4 carbon atoms.

[0309] As an ionic liquid having a tertiary sulfonium cation, for example, an ionic liquid represented by the following general formula (G7) can be used. In general formula (G7), R 25 ~R 27 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. 25 ~R 27 At least one of the above may have a main chain composed of two or more atoms selected from C, O, Si, N, S and P atoms.

[0310] [ka]

[0311] As the ionic liquid having a quaternary phosphonium cation, for example, an ionic liquid represented by the following general formula (G8) can be used. In general formula (G8), R 32 ~R 35 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. 32 ~R 35 At least one of the above may have a main chain composed of two or more atoms selected from C, O, Si, N, S and P atoms.

[0312] [ka]

[0313] A represented by general formula (G1) to general formula (G8) - As the anion, one or more of a monovalent amide anion, a monovalent methide anion, a fluorosulfonate anion, a perfluoroalkylsulfonate anion, a tetrafluoroborate anion, a perfluoroalkylborate anion, a hexafluorophosphate anion, and a perfluoroalkylphosphate anion can be used.

[0314] Monovalent amide anions include (C n F 2n+1 SO2)2N - (n is 0 or more and 3 or less), and the monovalent cyclic amide anion is (CF2SO2)2N - The monovalent methide anions include (C n F 2n+1 SO2)3C - (n is 0 or more and 3 or less), and the monovalent cyclic methide anion is (CF2SO2)2C - (CF3SO2) and the like can be used. As the fluoroalkylsulfonate anion, (C m F 2m+1 SO3) - (m is 0 or more and 4 or less). Fluoroalkylborate anions include {BF n (C m H k F 2m+1-k ) 4-n} - (n is 0 or more and 3 or less, m is 1 or more and 4 or less, k is 0 or more and 2m or less). Examples of the fluoroalkyl phosphate anion include {PF n (C m H k F 2m+1-k ) 6-n} - (n is 0 to 5, m is 1 to 4, k is 0 to 2m).

[0315] Furthermore, as the monovalent amide anion, for example, one or more of a bis(fluorosulfonyl)amide anion and a bis(trifluoromethanesulfonyl)amide anion can be used.

[0316] The ionic liquid may also have one or more of a hexafluorophosphate anion and a tetrafluoroborate anion.

[0317] Hereafter, (FSO2)2N - The anion represented by the formula is the FSA anion, (CF3SO2)2N - The anion represented by the formula is sometimes referred to as the TFSA anion.

[0318] The secondary battery of one embodiment of the present invention includes, for example, lithium ions as carrier ions. The secondary battery of one embodiment of the present invention may also include, as carrier ions, alkali metal ions such as sodium ions and potassium ions, or alkaline earth metal ions such as calcium ions, strontium ions, barium ions, beryllium ions, and magnesium ions.

[0319] When lithium ions are used as carrier ions, the electrolyte contains, for example, a lithium salt, such as LiPF, LiClO, LiAsF, LiBF, LiAlCl, LiSCN, LiBr, LiI, LiSO, or LiB. 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. can be used.

[0320] In this specification, the term "electrolyte" is a general term that includes solid, liquid, or semi-solid materials.

[0321] Deterioration is likely to occur at interfaces present in secondary batteries, such as the interface between the active material and the electrolyte. In a secondary battery according to one embodiment of the present invention, the presence of a fluorine-containing electrolyte can prevent deterioration, typically electrolyte alteration or increased viscosity, that can occur at the interface between the active material and the electrolyte. Furthermore, a binder and a graphene compound may be attached to or retained by the fluorine-containing electrolyte. This configuration can maintain a reduced viscosity of the electrolyte, in other words, a smooth electrolyte, thereby improving the reliability of the secondary battery. DFEC, which has two fluorine atoms bonded, and F4EC, which has four fluorine atoms bonded, have lower viscosity, are smoother, and have weaker coordination bonds with lithium than FEC, which has one fluorine atom bonded. Therefore, adhesion of viscous decomposition products to active material particles can be reduced. Adhesion or adhesion of viscous decomposition products to active material particles can hinder the movement of lithium ions at the interfaces of the active material particles. Fluorine-containing electrolytes mitigate the formation of decomposition products on the surface of the active material (positive electrode active material or negative electrode active material) by solvating. Furthermore, the use of fluorine-containing electrolytes can prevent the formation and growth of dendrites by preventing the adhesion of decomposition products.

[0322] One of the characteristics of the secondary battery of one embodiment of the present invention is that it uses a fluorine-containing electrolyte as a main component, and the content of the fluorine-containing electrolyte is 5 vol% or more, 10 vol% or more, preferably 30 vol% or more and 100 vol% or less.

[0323] In this specification, the term "main component of the electrolyte" refers to 5% by volume or more of the total electrolyte of the secondary battery. Furthermore, "5% by volume or more of the total electrolyte of the secondary battery" refers to the percentage of the total electrolyte measured during the manufacture of the secondary battery. Furthermore, when disassembling a secondary battery after fabrication, it is difficult to quantify the percentage of each of multiple electrolytes, but it is possible to determine whether a certain type of organic compound accounts for 5% by volume or more of the total electrolyte.

[0324] By using an electrolyte containing fluorine, a secondary battery that can operate over a wide temperature range, specifically, from -40°C to 150°C, preferably from -40°C to 85°C, can be realized.

[0325] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), lithium bis(oxalato)borate (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1% by volume or more and less than 5% by volume of the entire electrolyte.

[0326] In addition to the above, the electrolyte may contain one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran.

[0327] Furthermore, the inclusion of a gelling polymer material in the electrolyte increases safety against leakage, etc. Typical examples of gelling polymer materials include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, and fluorine-based polymer gel.

[0328] Examples of polymeric materials that can be used include polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing these. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The polymer formed may also have a porous shape.

[0329] [Separator] A separator is placed between the positive electrode and the negative electrode. Examples of separators that can be used include those made of cellulose-containing fibers such as paper, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers made of nylon resin (polyamide), vinylon resin (polyvinyl alcohol-based fibers), polyester resin, acrylic resin, polyolefin resin, and polyurethane resin. The separator is preferably processed into a bag shape and placed so as to encase either the positive electrode or the negative electrode.

[0330] The separator is a porous material having pores on the order of 20 nm in size, preferably pores of 6.5 nm or larger in size, and more preferably pores of at least 2 nm in diameter.

[0331] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine-based material, a polyamide material, or a mixture of these. Examples of ceramic materials that can be used include aluminum oxide particles and silicon oxide particles. Examples of fluorine-based materials that can be used include PVDF and polytetrafluoroethylene. Examples of polyamide materials that can be used include nylon and aramid (meta-aramid, para-aramid).

[0332] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging and improving the reliability of secondary batteries. Coating with fluorine-based materials also improves adhesion between the separator and electrodes, improving output characteristics. Coating with polyamide materials, especially aramid, improves heat resistance, improving the safety of secondary batteries.

[0333] For example, both sides of a polypropylene film may be coated with a mixed material of aluminum oxide and aramid, or the surface of the polypropylene film that contacts the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface that contacts the negative electrode may be coated with a fluorine-based material.

[0334] When a separator with a multilayer structure is used, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, and therefore the capacity per volume of the secondary battery can be increased.

[0335] [Exterior body] The exterior body of a secondary battery can be, for example, a can-type housing made of a metal material such as aluminum, or a case-type housing made of a resin material. Alternatively, a film-like exterior body (also called an exterior film) can be used. For example, an exterior film can have a three-layer structure in which a flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is further provided on the metal thin film as the exterior body outer surface. This three-layer structure can block the permeation of electrolytes and gases, ensure insulation, and provide electrolyte resistance. By stacking the two interior surfaces of the exterior films facing each other and applying heat, the inner surface material melts, fusing the two exterior films together, creating a sealed structure.

[0336] It is also preferable to use a fluororesin film as the exterior film. Fluororesin films have high stability against acids, alkalis, organic solvents, etc., and can suppress side reactions, corrosion, etc. associated with reactions in secondary batteries, thereby realizing excellent secondary batteries. Examples of fluororesin films include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane: a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylenepropene copolymer: a copolymer of tetrafluoroethylene and hexafluoropropylene), and ETFE (ethylenetetrafluoroethylene copolymer: a copolymer of tetrafluoroethylene and ethylene).

[0337] This embodiment mode can be combined with other embodiment modes as appropriate.

[0338] (Embodiment 3) In this embodiment, a specific structural example of a secondary battery of one embodiment of the present invention will be described with reference to FIGS.

[0339] 14 and 15 are external views of an example of a secondary battery of one embodiment of the present invention.

[0340] 14A has a positive electrode 503, a negative electrode 506, a separator 507, and an exterior body 509. The exterior body 509 is sealed by a seal area 514. The positive electrode 503, the negative electrode 506, and the separator 507 are stacked and disposed inside the exterior body 509.

[0341] 14A, a positive electrode lead electrode 510 is joined to a positive electrode 503. The positive electrode lead electrode 510 is exposed to the outside of an outer casing 509. A negative electrode lead electrode 511 is joined to a negative electrode 506, and the negative electrode lead electrode 511 is exposed to the outside of the outer casing 509.

[0342] The joining of the lead electrodes will be described with reference to FIG.

[0343] 16A shows an external view of positive electrode 503. Positive electrode 503 has positive electrode current collector 501, and positive electrode active material layer 502 is formed on the surface of positive electrode current collector 501. Positive electrode 503 also has a tab region.

[0344] 16B shows an external view of a negative electrode 506. The negative electrode 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., a tab region. The area or shape of the tab regions of the positive electrode and negative electrode are not limited to the examples shown in FIGS. 16A and 16B.

[0345] FIG. 16C is a diagram illustrating the joining of lead electrodes. First, a negative electrode 506, a separator 507, and a positive electrode 503 are laminated. FIG. 16C shows the laminated negative electrode 506, separator 507, and positive electrode 503. Here, the laminate consisting of a negative electrode, a separator, and a positive electrode has five pairs of negative electrodes and four pairs of positive electrodes. The tab regions of the positive electrodes 503 are joined together, and a positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, ultrasonic welding, for example, can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and a negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode. The positive electrode lead electrode 510 and the negative electrode lead electrode 511 each have a sealing layer 519 (which can also be called a resin layer, etc.). By providing sealing layer 519, exterior body 509 and sealing layer 519 can be thermocompression bonded together, which can prevent gaps from occurring during sealing. It also makes it possible to fix lead electrodes and exterior body 509 together. A thermoplastic resin, such as polypropylene, can be used for sealing layer 519.

[0346] The external view shown in Fig. 14B shows an example in which the ends of two sides of the exterior body 509 are folded. By folding the ends of the exterior body 509, the strength of the exterior body 509 can be increased. For example, when an external force is applied to the secondary battery 500, or when gas or the like is generated inside the exterior body 509 and the secondary battery 500 expands, defects such as loosening of the seal can be suppressed. Fig. 14C also shows an example in which three sides are folded.

[0347] 14A to 14C show an example in which the positive electrode lead electrode 510 and the negative electrode lead electrode 511 are arranged on the same side, but the positive electrode lead electrode 510 and the negative electrode lead electrode 511 may be arranged on different sides, for example, on the upper and lower sides as shown in Fig. 15A. Fig. 15B shows an example in which the left and right sides of the exterior body 509 in Fig. 15A are folded.

[0348] This embodiment mode can be combined with other embodiment modes as appropriate.

[0349] (Fourth embodiment) In this embodiment, application examples of a secondary battery of one embodiment of the present invention will be described with reference to FIGS.

[0350] [Electric Vehicles] First, an example in which the secondary battery of one embodiment of the present invention is applied to an electric vehicle (EV) will be described.

[0351] 17C shows a block diagram of a vehicle having a motor. The electric vehicle is equipped with first batteries 1301a and 1301b as main driving secondary batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304. The second battery 1311 is also called a cranking battery (also called a starter battery). The second battery 1311 only needs to have high output, and does not need to have a large capacity, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0352] For example, a secondary battery manufactured using the method for manufacturing a secondary battery described in Embodiment 1 can be used for one or both of the first batteries 1301a and 1301b.

[0353] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack having multiple secondary batteries, it is possible to extract large amounts of power. The multiple secondary batteries may be connected in parallel, in series, or in series after being connected in parallel. A plurality of secondary batteries is also called a battery pack.

[0354] In addition, in a secondary battery for vehicle use, a service plug or circuit breaker that can cut off high voltage without using tools is provided in first battery 1301a in order to cut off power from multiple secondary batteries.

[0355] The power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V (high voltage) in-vehicle components (such as an electric power steering 1307, a heater 1308, and a defogger 1309) via a DC-DC circuit 1306. When a rear motor 1317 is provided for the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.

[0356] The second battery 1311 also supplies power via the DC-DC circuit 1310 to 14V (low voltage) in-vehicle components (such as an audio system 1313, a power window 1314, and lamps 1315).

[0357] The first battery 1301a will be described with reference to FIG. 17A.

[0358] FIG. 17A shows an example in which nine prismatic secondary batteries 1300 are used as one battery pack 1415. Furthermore, nine prismatic secondary batteries 1300 are connected in series, with one electrode fixed by fixing portion 1413 made of an insulator and the other electrode fixed by fixing portion 1414 made of an insulator. While this embodiment shows an example in which the batteries are fixed by fixing portions 1413 and 1414, they may also be housed in a battery housing box (also called a casing). Because it is expected that a vehicle will be subjected to external vibrations or shaking (such as from the road surface), it is preferable to fix multiple secondary batteries in a battery housing box or the like by fixing portions 1413 and 1414. Furthermore, one electrode is electrically connected to control circuit unit 1320 by wiring 1421. Furthermore, the other electrode is electrically connected to control circuit unit 1320 by wiring 1422.

[0359] A memory circuit including a transistor using an oxide semiconductor may be used for the control circuit unit 1320. A charge control circuit or a battery control system having a memory circuit including a transistor using an oxide semiconductor may be referred to as a battery operating system (BTOS) or a battery oxide semiconductor.

[0360] The control circuit 1320 detects the terminal voltage of the secondary battery and manages the charge / discharge state of the secondary battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.

[0361] FIG. 17B shows an example of a block diagram of the battery pack 1415 shown in FIG. 17A.

[0362] The control circuit unit 1320 includes a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 sets upper and lower voltage limits for the secondary battery used, and limits the upper limit of the current from the outside or the upper limit of the output current to the outside. The range between the lower and upper voltage limits of the secondary battery is the recommended voltage range. If the voltage falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging or overdischarging. For example, if the control circuit 1322 detects a voltage that could cause overcharging, it turns off the switch unit 1324 to cut off the current. A PTC element may also be provided in the charge / discharge path to provide a function for cutting off the current in response to a rise in temperature. The control circuit section 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0363] The switch unit 1324 can be configured by combining one or both of n-channel transistors and p-channel transistors. The switch unit 1324 is not limited to a switch having a Si transistor using single crystal silicon. For example, the switch unit 1324 may be formed of a power transistor having Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), or GaOx (gallium oxide; x is a real number greater than 0). Furthermore, memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, facilitating integration. Furthermore, OS transistors can be fabricated using the same manufacturing equipment as Si transistors, allowing for low-cost fabrication. That is, a control circuit unit 1320 using OS transistors can be stacked on the switch unit 1324 and integrated into a single chip. The volume occupied by the control circuit section 1320 can be reduced, which allows for miniaturization.

[0364] The first batteries 1301a and 1301b mainly supply power to high-voltage in-vehicle devices, and the second battery 1311 supplies power to low-voltage in-vehicle devices. A lead-acid battery is often used as the second battery 1311 because of its cost advantage.

[0365] In this embodiment, an example is shown in which lithium ion secondary batteries are used as both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead storage battery, an all-solid-state battery, or an electric double layer capacitor.

[0366] Furthermore, regenerated energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then charged into the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 or the battery controller 1302. Alternatively, the first battery 1301a is charged from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerated energy, it is desirable that the first batteries 1301a and 1301b be capable of being rapidly charged.

[0367] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set charging conditions according to the charging characteristics of the secondary battery used, and can perform rapid charging.

[0368] Although not shown, when an external charger is connected, the charger's outlet or the charger's connection cable is electrically connected to the battery controller 1302. The power supplied from the external charger is charged to the first batteries 1301a, 1301b via the battery controller 1302. Some chargers are provided with a control circuit, and although the function of the battery controller 1302 may not be used, it is preferable to charge the first batteries 1301a, 1301b via a control circuit unit 1320 to prevent overcharging. In some cases, the connection cable or the charger's connection cable is provided with a control circuit. The control circuit unit 1320 is also called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU includes a microcomputer. The ECU uses a CPU or a GPU.

[0369] Next, an example in which the secondary battery of one embodiment of the present invention is mounted on a vehicle, typically a transportation vehicle, will be described.

[0370] When a secondary battery of one embodiment of the present invention is installed in a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), and plug-in hybrid vehicles (PHVs) can be realized. Furthermore, the secondary battery can also be installed in transportation vehicles such as agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft or rotary-wing aircraft, rockets, artificial satellites, space probes or planetary probes, and spaceships. A large secondary battery can be obtained by using the manufacturing method of the secondary battery described in Embodiment 1. Therefore, the secondary battery of one embodiment of the present invention can be suitably used in transportation vehicles.

[0371] 18A to 18D show transportation vehicles using a secondary battery of one embodiment of the present invention. The automobile 2001 shown in FIG. 18A is an electric automobile that uses an electric motor as a power source for running. Alternatively, it is a hybrid automobile that can appropriately select and use an electric motor or an engine as a power source for running. When a secondary battery is installed in a vehicle, the secondary battery is installed in one location or multiple locations. The automobile 2001 shown in FIG. 18A includes a battery pack 2200, which includes a secondary battery module to which multiple secondary batteries are connected. It is preferable that the automobile further includes a charge control device electrically connected to the secondary battery module.

[0372] Furthermore, automobile 2001 can charge its secondary battery by receiving power supply from an external charging facility using a plug-in system, a contactless power supply system, or the like. Charging can be performed using a predetermined charging method or connector standard, such as CHAdeMO (registered trademark) or Combo, as appropriate. The secondary battery may be charged at a charging station provided in a commercial facility or from a household power source. For example, plug-in technology can be used to charge an electricity storage device mounted on automobile 2001 using an external power supply. Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.

[0373] Although not shown, a power receiving device can be mounted on a vehicle and power can be supplied contactlessly from a ground-based power transmitting device to charge the vehicle. In the case of this contactless power supply method, by incorporating a power transmitting device into the road or an exterior wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is moving. This contactless power supply method can also be used to transmit and receive power between two vehicles. Furthermore, a solar cell can be installed on the exterior of the vehicle to charge the secondary battery while the vehicle is stopped or moving. For such contactless power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0374] 18B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 is, for example, a four-cell unit of secondary batteries of 3.5V to 4.7V, with 48 cells connected in series for a maximum voltage of 170V. Apart from the number of secondary batteries constituting the secondary battery module of the battery pack 2201, the transport vehicle 2002 has the same functions as those shown in FIG. 18A, and therefore a description thereof will be omitted.

[0375] FIG. 18C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has, for example, a maximum voltage of 600 V, which is obtained by connecting in series one hundred or more secondary batteries with a voltage of 3.5 V or more and 4.7 V or less. Therefore, a secondary battery with little variation in characteristics is required. By using the method for manufacturing a secondary battery shown in embodiment 1, a secondary battery with stable battery characteristics can be manufactured, and mass production at low cost is possible from the viewpoint of yield. Furthermore, except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the same functions as those of FIG. 18A are provided, and therefore description thereof will be omitted.

[0376] As an example, Fig. 18D shows an aircraft 2004 having an engine that burns fuel. Since the aircraft 2004 shown in Fig. 18D has wheels for takeoff and landing, it can also be said to be part of a transportation vehicle, and has a battery pack 2203 that includes a secondary battery module formed by connecting multiple secondary batteries and the secondary battery module and a charge control device.

[0377] The secondary battery module of the aircraft 2004 has, for example, eight 4 V secondary batteries connected in series to produce a maximum voltage of 32 V. Other than the number of secondary batteries constituting the secondary battery module of the battery pack 2203, it has the same functions as those in FIG. 18A, and therefore a description thereof will be omitted.

[0378] [Buildings] Next, an example in which the secondary battery of one embodiment of the present invention is mounted in a building will be described with reference to FIG.

[0379] The house shown in FIG. 19A includes a power storage device 2612 including a secondary battery with stable battery characteristics obtained by using the manufacturing method of the secondary battery described in Embodiment 1, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611 or the like. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The power obtained by the solar panel 2610 can be charged to the power storage device 2612. The power stored in the power storage device 2612 can be charged to a secondary battery included in the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in an underfloor space. By installing the power storage device 2612 in the underfloor space, the space above the floor can be effectively utilized. Alternatively, the power storage device 2612 may be installed on the floor.

[0380] The power stored in the power storage device 2612 can be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the power storage device 2612 can be used as an uninterruptible power supply, allowing the use of electronic devices.

[0381] 19B illustrates an example of a power storage device 700 of one embodiment of the present invention. As illustrated in FIG. 19B, a large-sized power storage device 791 obtained by the method for manufacturing a secondary battery described in Embodiment 1 is installed in an underfloor space 796 of a building 799.

[0382] A control device 790 is installed in the power storage device 791, and the control device 790 is electrically connected to a distribution board 703, a power storage controller 705 (also called a control device), a display 706, and a router 709 by wiring.

[0383] Electric power is sent from commercial power source 701 to distribution board 703 via service line attachment section 710. Electric power is also sent to distribution board 703 from power storage device 791 and commercial power source 701, and distribution board 703 supplies the sent electric power to general load 707 and power storage load 708 via an outlet (not shown).

[0384] The general load 707 is, for example, an electrical appliance such as a television or a personal computer, and the power storage load 708 is, for example, an electrical appliance such as a microwave oven, a refrigerator, or an air conditioner.

[0385] The power storage controller 705 has a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the amount of power consumed by the general load 707 and the power storage load 708 during one day (for example, from midnight to midnight). The measurement unit 711 may also have a function of measuring the amount of power of the power storage device 791 and the amount of power supplied from the commercial power source 701. The prediction unit 712 has a function of predicting the amount of power demand to be consumed by the general load 707 and the power storage load 708 during the next day, based on the amount of power consumed by the general load 707 and the power storage load 708 during the previous day. The planning unit 713 has a function of creating a plan for charging and discharging the power storage device 791, based on the amount of power demand predicted by the prediction unit 712.

[0386] The amount of power consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed on the display 706. It can also be confirmed on an electrical device such as a television or a personal computer via the router 709. It can also be confirmed on a mobile electronic device such as a smartphone or a tablet via the router 709. The amount of power demand for each time period (or each hour) predicted by the prediction unit 712 can also be confirmed on the display 706, the electrical device, or the mobile electronic device.

[0387] [Electronic equipment] The secondary battery of one embodiment of the present invention can be used in, for example, one or both of an electronic device and a lighting device, including, for example, a mobile phone, a smartphone, a portable information terminal such as a laptop computer, a portable game console, a portable music player, a digital camera, and a digital video camera.

[0388] 20A includes a housing 2801, a housing 2802, a display unit 2803, a keyboard 2804, a pointing device 2805, and the like. A secondary battery 2807 is provided inside the housing 2801, and a secondary battery 2806 is provided inside the housing 2802. A touch panel is also applied to the display unit 2803. As shown in FIG. 20B, the housings 2801 and 2802 can be removed from the personal computer 2800, and the personal computer 2800 can be used as a tablet terminal using only the housing 2802.

[0389] A large secondary battery obtained by the method for manufacturing a secondary battery described in Embodiment 1 can be used as one or both of the secondary battery 2806 and the secondary battery 2807. The shape of the secondary battery obtained by the method for manufacturing a secondary battery described in Embodiment 1 can be freely changed by changing the shape of the exterior body. For example, by forming the secondary batteries 2806 and 2807 to match the shapes of the casings 2801 and 2802, the capacity of the secondary battery can be increased and the usage time of the personal computer 2800 can be extended. In addition, the weight of the personal computer 2800 can be reduced.

[0390] A flexible display is applied to the display portion 2803 of the casing 2802. A large-sized secondary battery obtained by the manufacturing method of a secondary battery described in Embodiment 1 is used as the secondary battery 2806. A large-sized secondary battery obtained by the manufacturing method of a secondary battery described in Embodiment 1 can be made into a bendable secondary battery by using a flexible film for the exterior body. Thus, as shown in FIG. 20C, the casing 2802 can be folded for use. In this case, part of the display portion 2803 can also be used as a keyboard, as shown in FIG. 20C.

[0391] The housing 2802 can be folded so that the display portion 2803 faces inward as shown in FIG. 20D, or so that the display portion 2803 faces outward as shown in FIG. 20E.

[0392] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0393] (Notes regarding the present specification) In this specification, crystal planes and directions are indicated by Miller indices. In crystallography, crystal planes and directions are indicated by a superscript bar after the number, but in this specification, due to limitations in application notation, a - (minus sign) may be placed before the number instead of a bar above it. Furthermore, individual directions indicating directions within a crystal are expressed with [ ], collective directions indicating all equivalent directions with < >, individual planes indicating crystal faces with ( ), and collective planes with equivalent symmetry with {}.

[0394] In this specification, the surface layer of particles of active material or the like is preferably, for example, a region within 50 nm from the surface, more preferably within 35 nm, and even more preferably within 20 nm. Surfaces formed by cracks or fissures may also be referred to as the surface. The region deeper than the surface layer is referred to as the interior.

[0395] In this specification, the layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock-salt type ion arrangement in which cations and anions are alternately arranged, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, allowing two-dimensional diffusion of lithium. Defects such as cation or anion deficiencies may also be present. Furthermore, strictly speaking, the layered rock-salt type crystal structure may have a distorted rock-salt type crystal lattice structure.

[0396] In this specification and the like, the rock salt type crystal structure refers to a structure in which cations and anions are arranged alternately, and it is also possible for there to be deficiencies of cations or anions.

[0397] In addition, in this specification and the like, the pseudospinel crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure that is in the space group R-3m and is not a spinel crystal structure, but in which ions of cobalt, magnesium, etc. occupy hexa-coordinated oxygen positions and the arrangement of cations has a symmetry similar to that of a spinel structure.

[0398] The general alignment of the crystal orientations of the two regions can be determined from TEM (transmission electron microscope), STEM (scanning transmission electron microscope), HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope), and ABF-STEM (annular bright-field scanning transmission electron microscope) images. XRD, electron diffraction, and neutron diffraction can also be used. In TEM images, the arrangement of cations and anions can be observed as repeated bright and dark lines. When the orientation of the cubic close-packed structure of the layered rock salt crystal and the rock salt crystal is aligned, the angle between the repeated bright and dark lines between the crystals can be observed to be less than 5 degrees, preferably less than 2.5 degrees. Light elements such as oxygen and fluorine may not be clearly visible in TEM images, but in such cases, the alignment of the orientations can be determined from the arrangement of metal elements.

[0399] In this specification, the theoretical capacity of a positive electrode active material refers to the amount of electricity when all of the intercalable lithium contained in the positive electrode active material is deintercalated. For example, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 274 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g.

[0400] In this specification and the like, the depth of charge when all intercalable / deintercalable lithium is intercalated is defined as 0, and the depth of charge when all intercalable / deintercalable lithium contained in the positive electrode active material is deintercalated is defined as 1.

[0401] In this specification, charging refers to the transfer of lithium ions from the positive electrode to the negative electrode within a battery and the transfer of electrons from the positive electrode to the negative electrode in an external circuit. Regarding a positive electrode active material, charging refers to the removal of lithium ions. A positive electrode active material with a charge depth of 0.7 to 0.9 is sometimes referred to as a positive electrode active material charged at a high voltage.

[0402] Similarly, discharging refers to the transfer of lithium ions from the negative electrode to the positive electrode within the battery and the transfer of electrons from the negative electrode to the positive electrode in an external circuit. For positive electrode active materials, discharging refers to the insertion of lithium ions. A fully discharged positive electrode active material is defined as a positive electrode active material with a charge depth of 0.06 or less, or a positive electrode active material that has been discharged to 90% or more of its charge capacity from a high-voltage charged state.

[0403] In this specification, a non-equilibrium phase change refers to a phenomenon that causes a non-linear change in a physical quantity. For example, a non-equilibrium phase change occurs around the peak in the dQ / dV curve obtained by differentiating capacitance (Q) with voltage (V), and it is believed that the crystal structure changes significantly.

[0404] A secondary battery has, for example, a positive electrode and a negative electrode. A material constituting the positive electrode is a positive electrode active material. The positive electrode active material is, for example, a substance that undergoes a reaction that contributes to the charge / discharge capacity. Note that the positive electrode active material may contain a substance that does not contribute to the charge / discharge capacity. [Explanation of symbols]

[0405] 300: manufacturing equipment, 301: material input chamber, 302: transfer chamber, 303: processing chamber, 304: processing chamber, 305: processing chamber, 306: material removal chamber, 320: transfer mechanism, 331: stage, 332: alignment camera, 333: suction jig, 334: nozzle, 335: nozzle, 500: secondary battery, 501: positive electrode current collector, 502: positive electrode active material layer, 503: positive electrode, 504: negative electrode current collector, 505: negative electrode active material layer, 506: negative electrode, 507: separator, 509a: exterior body, 509b: exterior body, 509c: recess, 509: exterior body, 510: positive electrode lead electrode, 511: negative electrode lead Electrode, 512: laminate, 513: resin layer, 514: sealing region, 515a: electrolyte, 515b: electrolyte, 515c: electrolyte, 517: resin, 518: resin layer, 519: sealing layer, 521: resin layer, 525: sealing region, 529a: ultraviolet light transmitting region, 529b: ultraviolet light blocking region, 700: power storage device, 701: commercial power source, 703: distribution board, 705: power storage controller, 706: display, 707: general load, 708: power storage system load, 709: router, 710: drop line attachment section, 711: measurement section, 712: prediction section, 713: planning section, 790: control device, 791: power storage device Electrical device, 796: underfloor space, 799: building, 1300: rectangular secondary battery, 1301a: first battery, 1301b: first battery, 1302: battery controller, 1303: motor controller, 1304: motor, 1305: gear, 1306: DCDC circuit, 1307: electric power steering, 1308: heater, 1309: defogger, 1310: DCDC circuit, 1311: second battery, 1312: inverter, 1313: audio, 1314: power window, 1315: lamps, 1316: tires, 1317: rear motor, 13 20: control circuit unit, 1321: control circuit unit, 1322: control circuit, 1324: switch unit, 1413: fixed unit, 1414: fixed unit, 1415: battery pack, 1421: wiring, 1422: wiring, 2001: automobile, 2002: transport vehicle, 2003: transport vehicle, 2004: aircraft, 2200: battery pack, 2201: battery pack, 2202: battery pack, 2203: battery pack, 2603: vehicle, 2604: charging device, 2610: solar panel, 2611: wiring, 2612: power storage device, 2800: personal computer, 2801: housing, 2802: housing,2803: display unit, 2804: keyboard, 2805: pointing device, 2806: secondary battery, 2807: secondary battery,

Claims

1. A first electrode is disposed on the first exterior body; disposing a separator on the first electrode; a second electrode disposed on the separator; dripping an electrolyte onto at least one of the first electrode, the separator, and the second electrode; a resin layer is disposed in a frame shape on the first exterior body so as to surround the first electrode, the separator, and the second electrode; After impregnating at least one of the first electrode, the separator, and the second electrode with the electrolyte, a second exterior body is disposed on the first exterior body so as to cover the first electrode, the separator, and the second electrode; irradiating the resin layer with ultraviolet light under reduced pressure to cure at least a portion of the resin layer; After the ultraviolet light irradiation, the first electrode, the separator, and the second electrode are sealed with the first exterior body and the second exterior body under atmospheric pressure; The method for producing a secondary battery, wherein one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode.

2. In claim 1, the first exterior body has a recess, The method for manufacturing a secondary battery, wherein the first electrode, the separator, and the second electrode are disposed in the recess.

3. In claim 1 or claim 2, the sealing is performed by irradiating the resin layer with ultraviolet light to harden the resin layer; The method for producing a secondary battery, wherein an area of ​​the resin layer irradiated with ultraviolet light during the sealing is larger than an area irradiated with ultraviolet light under reduced pressure.

4. In any one of claims 1 to 3, The method for producing a secondary battery, wherein the sealing is performed by thermocompression bonding.

5. In any one of claims 1 to 4, The method for producing a secondary battery, wherein the second exterior body has a function of transmitting ultraviolet light at least in a region overlapping with the resin layer.

6. In any one of claims 1 to 5, The method for manufacturing a secondary battery, wherein the second exterior body has a function of blocking ultraviolet light at least in an area overlapping with at least one of the first electrode, the separator, and the second electrode.

7. In any one of claims 1 to 6, a step of connecting a first lead electrode to the first electrode and a step of connecting a second lead electrode to the second electrode before irradiating ultraviolet light under reduced pressure.

8. In any one of claims 1 to 7, The method for producing a secondary battery, wherein the electrolyte contains fluorine.

9. In any one of claims 1 to 8, The method for producing a secondary battery, wherein the electrolyte contains an ionic liquid.

10. In any one of claims 1 to 9, The method for manufacturing a secondary battery, wherein one or both of the first electrode and the second electrode contain graphene.

11. In any one of claims 1 to 10, The method for producing a secondary battery, wherein the first electrode has a first active material layer on one or both surfaces of a first current collector.

12. In any one of claims 1 to 11, The second electrode has a second active material layer on one or both surfaces of a second current collector.

Images