Method for manufacturing a secondary battery

Abstract

One embodiment of the present invention enables the achievement of a production method that is capable of automating the production of a secondary battery. Another embodiment of the present invention enables the achievement of a production method that is capable of efficiently producing a secondary battery in a short time. Another embodiment of the present invention enables the achievement of a production method that is capable of producing a secondary battery with high yield. Another embodiment of the present invention enables the achievement of a production method for the cases where a relatively large-sized secondary battery is produced. According to the present invention, after dropping an electrolyte on at least one of a positive electrode, a separator and a negative electrode so as to impregnate the at least one of a positive electrode, a separator and a negative electrode with the electrolyte, the pressure is reduced so as to seal a multilayer body of the positive electrode, the separator and the negative electrode by means of an outer package film. After arranging a plurality of multilayer bodies on an outer package film, dropping an electrolyte on the multilayer bodies and sealing the multilayer bodies at a reduced pressure, the outer package film may be divided so as to separate secondary batteries individually.

Description

Technical Field

[0001] The present invention relates to a secondary battery and a method for manufacturing the same. Alternatively, the present invention relates to a portable information terminal, a vehicle, etc. having a secondary battery.

[0002] One aspect of the present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, a manufacture, or a composition of matter. One aspect of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, or a method for manufacturing the same.

[0003] In this specification, the electronic device refers to all devices having a power storage device, and all electro-optical devices having a power storage device, information terminal devices having a power storage device, etc. are electronic devices.

[0004] In this specification, the power storage device refers to all elements and devices having a power storage function. For example, it includes power storage devices (also referred to as secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

Background Art

[0005] In recent years, various power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been actively developed. In particular, lithium ion secondary batteries with high output and high energy density are rapidly expanding in demand along with the development of the semiconductor industry, such as portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV), and have become indispensable in modern information society as a rechargeable energy supply source.

[0006] A lithium-ion secondary battery is composed 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 a carbon material like graphite capable of occluding and releasing lithium, and an electrolyte containing an organic solvent such as ethylene carbonate (EC) or diethyl carbonate (DEC).

[0007] In addition, high capacity, high performance, and safety in various operating environments are required for lithium-ion secondary batteries.

[0008] Patent Document 1 discloses a manufacturing apparatus for a laminated battery capable of improving manufacturing efficiency.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object is to realize a manufacturing method capable of automating the production of secondary batteries. Another object is to realize a manufacturing method capable of efficiently and quickly manufacturing secondary batteries. Another object is also to realize a manufacturing method capable of producing secondary batteries with a high yield.

[0011] Or, another object is to realize a manufacturing method for manufacturing relatively large-sized secondary batteries.

[0012] Or, another object is to provide a manufacturing method for secondary batteries with reduced manufacturing costs.

[0013] Or, another object is to provide a manufacturing method for secondary batteries with high safety or reliability.

[0014] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention does not need to solve all of these problems. Note that it is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0015] Conventionally, a secondary battery is often manufactured by putting a laminate of a positive electrode, a separator, and a negative electrode into a can or a bag-shaped exterior body, then injecting an electrolyte, and then sealing it. In the conventional method, there is a risk that lithium ions easily diffuse outward from the injection port. Also, in the conventional method, the number of steps tends to increase, and it may be difficult to accurately adjust the amount of the electrolyte to be injected. It can be said that accurately providing the amount of electrolyte required for the secondary battery leads to mass production of secondary batteries having uniform characteristics.

[0016] One of the inventions disclosed in this specification is to uniformly impregnate by dropping a plurality of electrolytes onto any one or more of the positive electrode, the separator, and the negative electrode. Then, the laminate of the positive electrode, the separator, and the negative electrode is sandwiched between exterior films, and the outer peripheral edge (the four sides when viewed from above in the case where the three-dimensional shape of the secondary battery is a thin rectangular parallelepiped) is sealed without a gap. Here, mainly an example of a thin battery (also called a laminate type) is shown. Note that terminals for external extraction (such as lead-out wiring or lead electrodes (also called lead terminals)) are made to protrude outside the exterior film. The lead terminal is provided to lead out the positive electrode or the negative electrode of the secondary battery to the outside of the exterior film. Note that when sealing, it is preferably performed under reduced pressure at a pressure lower than at least atmospheric pressure in order not to mix impurities.

[0017] When dropping a plurality of electrolytes, they are dropped one or more times at a uniform pitch with respect to the plane of the surface to be dropped. As the dropping method, any one of a dispensing method, a spraying method, an inkjet method, etc. can be used. The dispensing method is a method using a liquid metering and discharging device, and a fixed amount can be dropped from a nozzle. By using a plurality of liquid metering and discharging devices, the manufacturing time can also be shortened. Dropping can also be performed at regular distance intervals by relatively moving the nozzle or the object to be dropped (any one or more of the positive electrode, the separator, and the negative electrode). If the dropping amount to one location with a certain nozzle diameter is 0.01 cc, by dropping at n (n>1) locations, an electrolyte amount of 0.01 cc×n can be impregnated, so the dropping point or the total dropping amount can be precisely controlled. Dropping at n (n>1) locations with respect to the plane, for example, in the case of the positive electrode, compared with dropping only at one point of the positive electrode, dropping at a plurality of locations of the positive electrode can shorten the time for impregnating the entire positive electrode, and the manufacturing time can be shortened.

[0018] Also, it is preferable to appropriately adjust the viscosity of the electrolyte dropped from a nozzle or the like. If the viscosity of the entire electrolyte is in the range of 10 mPa·s or more and 95 mPa·s or less at room temperature (25°C), it can be dropped from the nozzle. For viscosity measurement, a rotational viscometer (TVE-35L manufactured by Toki Sangyo Co., Ltd.) is used.

[0019] As the electrolyte to be dropped, an organic solvent or an ionic liquid can be used.

[0020] Also, it is preferable to seal under reduced pressure after dropping the electrolyte. Therefore, when continuously dropping and sealing, it is preferable to use the same chamber or a plurality of connected chambers. For example, after dropping the electrolyte in the first chamber, without exposing it to the atmosphere, it is transported to the second chamber, the inside of the second chamber is depressurized, and then the laminate is sealed with an exterior film in the second chamber, so that impurities such as dust do not mix in, which is preferable. Or the dropping of the electrolyte and the sealing with the exterior film may be continuously performed in the same chamber, and the secondary battery can be efficiently manufactured.

[0021] The chamber for sealing is connected to a vacuum evacuation treatment chamber, and it can be evacuated to a vacuum, and after evacuation, an inert gas can be introduced to make it atmospheric pressure. As the vacuum evacuation treatment chamber, a magnetic levitation type turbo molecular pump, a cryopump, or a dry pump is provided. Thereby, the achievable vacuum degree of the chamber for sealing can be set to about 10 -5 Pa to 10 -6 Pa, and furthermore, the reverse diffusion of impurities from the pump side and the exhaust system can be controlled. In order to prevent impurities from being introduced into the apparatus, as the gas to be introduced, an inert gas such as nitrogen or a noble gas is used. These gases introduced into the apparatus are those purified to a high purity by a gas purifier before being introduced into the apparatus.

[0022] Under reduced pressure, the ionic liquid hardly volatilizes even in a high vacuum, so it is preferable. Also, as the electrolyte, a mixture of an ionic liquid and an organic solvent may be used. When an organic solvent is included as the electrolyte, the degree of vacuum in the chamber is set to a lower vacuum than about 5×10 -1 Pa.

[0023] The configuration of the invention disclosed in this specification is to drop an electrolyte onto any one or more of a positive electrode, a negative electrode, and a separator, impregnate any one or more of the positive electrode, the negative electrode, and the separator with the electrolyte, then reduce the pressure, and seal the laminate of the positive electrode, the separator, and the negative electrode with an exterior film.

[0024] In addition, by using a large-area exterior film, a large number of secondary batteries can be manufactured at once. For example, for large-area exterior films with sizes 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, 1150 mm × 1300 mm, a method for efficiently manufacturing a plurality of secondary batteries from a single large-area exterior film can be provided. Furthermore, a method for manufacturing a secondary battery suitable for mass production using large-area exterior films with sizes such as 1500 mm × 1800 mm, 1800 mm × 2000 mm, 2000 mm × 2100 mm, 2200 mm × 2600 mm, 2600 mm × 3100 mm is provided.

[0025] Regarding the configuration related to other manufacturing methods disclosed in this specification, it is a method for manufacturing a secondary battery in which a plurality of laminates are arranged on an exterior film, a plurality of electrolytes are dropped onto the laminates, sealed under reduced pressure, and then the exterior film is cut to separate the secondary batteries individually. The laminate is at least a laminate of two or more of a positive electrode, a separator, and a negative electrode. Note that the cutting of the exterior film can be performed using a laser beam or the like.

[0026] When using a film (also called a laminate film) including a laminate of a metal foil (such as aluminum, stainless steel, etc.) and a resin (heat-sealable resin) as the exterior film, a lighter and thinner secondary battery than a secondary battery using a metal can can be manufactured. A metal foil having an adhesive layer on one or both surfaces is used. A seal area is formed by performing thermocompression bonding in a state where the first adhesive layer of the first laminate film and the second adhesive layer of the second laminate film are adhered so that the first adhesive layer and the second adhesive layer are on the inside. Also, it is not limited to thermocompression bonding, and a sealing material may be drawn in the seal area using a thermosetting resin or an ultraviolet curable resin or the like.

[0027] The sealing area shall be in a frame shape or a closed-loop shape. A laminate of a positive electrode, a separator, and a negative electrode is disposed and sealed within the area surrounded by the sealing area. Therefore, the area of the region surrounded by the sealing area shall be at least larger than the area of the positive electrode of the secondary battery.

[0028] The film used for the exterior body of the secondary battery is a single-layer film selected from a metal film (such as aluminum, stainless steel, nickel steel, gold, silver, copper, titanium, nichrome, iron, tin, tantalum, niobium, molybdenum, zirconium, zinc, etc., which is a metal or alloy such as a metal foil), a plastic film made of an organic material, a hybrid material film containing an organic material (such as an organic resin or fiber) and an inorganic material (such as ceramic), or a carbon-containing inorganic film (such as a carbon film or a graphite film), or a laminated film composed of a plurality of these.

[0029] Also, the sealing structure of the secondary battery is configured such that a single rectangular exterior film is bent at the center, and among the four corners, two ends sandwiching the bending portion are overlapped, and the four sides are fixed with an adhesive layer to be closed. With such a configuration, the laminate of the positive electrode, the separator, and the negative electrode is housed so as to be wrapped by the exterior film. Alternatively, two exterior films are overlapped, and the four sides of the exterior film are fixed with an adhesive layer to be closed. Also, in this specification, after sealing with the exterior film, it may be referred to as an exterior body instead of an exterior film.

[0030] When using two exterior films, the manufacturing method also has characteristics. Its configuration is as follows: place the positive electrode on the first exterior film, drop the first electrolyte onto the positive electrode, place the separator on the positive electrode, drop the second electrolyte onto the separator, place the negative electrode on the separator, drop the third electrolyte onto the negative electrode, place the laminate of the positive electrode, separator, and negative electrode under reduced pressure, and seal it using the first exterior film and the second exterior film with the laminate sandwiched therebetween. Sealing means blocking a certain sealed area from the outside air. In a secondary battery, the laminate and its periphery are regarded as the sealed area, and the outside of the sealed area is surrounded by one or two exterior films to block it from the outside air, which is defined as sealing. Also, after sealing, the ends of the exterior film are bent to increase the sealing strength and prevent the intrusion of impurities from the outside or the release of gas from the inside.

[0031] In the above configuration, the first electrolyte, the second electrolyte, and the third electrolyte may use the same material or different materials. Also, in each of the above configurations, the laminate may be laminated in the order of the positive electrode, separator, and negative electrode, or may be laminated in the order of the negative electrode, separator, and positive electrode. Also, the separator is used to prevent the short circuit between the positive electrode and the negative electrode. When adopting a configuration of stacking laminates to increase the capacity, in order to reduce the number of parts, it may be configured to use a single common separator by folding.

[0032] For the adhesive layer (also called the heat-sealing layer), a thermoplastic film material, a thermosetting adhesive, or an anaerobic adhesive, a photocurable adhesive such as an ultraviolet-curable adhesive, or a reaction-curable adhesive can be used. As the material of these adhesives, an epoxy resin, an acrylic resin, a silicone resin, or a phenolic resin can be used.

[0033] In addition, as the current collector such as the positive current collector or the negative current collector, metals such as stainless steel, gold, platinum, zinc, iron, nickel, copper, aluminum, titanium, tantalum, etc., and alloys thereof, etc., materials with high conductivity and that do not alloy with carrier ions such as lithium ions can be used. Further, an aluminum alloy added with elements for improving heat resistance such as silicon, titanium, neodymium, scandium, molybdenum, etc. can be used. Further, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. In addition, the current collector can appropriately use shapes such as foil shape, plate shape (sheet shape), net shape, cylindrical shape, coil shape, punched metal shape, expanded metal shape, etc. The current collector is preferably one with a thickness of 10 μm or more and 30 μm or less.

[0034] As described above, examples of the thin battery (laminate type) have been mainly described, but it is not particularly limited, and it is also possible to apply it to a wound type. In the case of the wound type, the electrolyte may be dropped onto the wound body, or it may be dropped before making the wound body, that is, before winding. The wound body refers to a body formed by stacking a strip-shaped positive electrode, a strip-shaped separator, and a strip-shaped negative electrode in this order and winding them while stacked.

Advantages of the Invention

[0035] Since the number of sealing steps of the secondary battery is small, the manufacturing process of the secondary battery can be significantly shortened. Therefore, a method for manufacturing a secondary battery with reduced manufacturing cost can be provided. Or, a manufacturing method capable of efficiently manufacturing the secondary battery in a short time can be realized. Or, a manufacturing method capable of automating the manufacturing of the secondary battery can be realized. Or, a manufacturing method capable of manufacturing the secondary battery with a high yield can be realized.

[0036] Alternatively, it is possible to realize a manufacturing method for manufacturing a relatively large-sized secondary battery. When mounting a large-capacity secondary battery, the number of large-sized secondary batteries to be mounted can be reduced compared to the number of small-sized secondary batteries to be mounted. If the number of large-sized secondary batteries to be mounted can be reduced, individual control becomes easier, and the burden on the charge control circuit is reduced.

[0037] Alternatively, since the secondary battery obtained by the manufacturing method disclosed in this specification can be firmly sealed by a single sealing process, it can be made into a secondary battery with high safety or reliability.

Brief Description of the Drawings

[0038] FIG. 1A is a schematic cross-sectional view of a secondary battery showing one aspect of the present invention, FIG. 1B is a top view after dropping the electrolyte, and FIG. 1C is an example of a top view when performing multi-faceted chamfering. FIG. 2 is a flow chart for explaining an example of a manufacturing method of a secondary battery according to one aspect of the present invention. FIGS. 3A, 3B, 3C, 3D, and 3E are cross-sectional views for explaining an example of a manufacturing method of a secondary battery according to one aspect of the present invention. FIG. 4 is a diagram for explaining the crystal structure of a positive electrode active material. FIG. 5 is a diagram for explaining the crystal structure of a positive electrode active material. FIGS. 6A, 6B, and 6C are diagrams showing the appearance of a secondary battery. FIGS. 7A and 7B are diagrams showing the appearance of a secondary battery. FIGS. 8A, 8B, and 8C are diagrams for explaining a manufacturing method of a secondary battery. FIG. 9A is a perspective view showing a battery pack, FIG. 9B is a block diagram of the battery pack, and FIG. 9C is a block diagram of a vehicle having a motor. FIGS. 10A to 10D are diagrams for explaining an example of a transport vehicle. FIGS. 11A and 11B are diagrams for explaining an electric storage device. FIGS. 12A, 12B, 12C, 12D, and 12E are perspective views of an electronic device showing one aspect of the present invention.

Embodiments for Carrying Out the Invention

[0039] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that its form and details can be variously changed. Further, the present invention is not to be construed as being limited to the description of the embodiments shown below.

[0040] (Embodiment 1) In this embodiment, a secondary battery according to an aspect of the present invention, a method for manufacturing the same, and the like will be described.

[0041] An example of a secondary battery according to an aspect of the present invention will be described with reference to FIG. 1A.

[0042] The secondary battery 500 shown in FIG. 1A includes an exterior body 509 and a laminate 512 disposed inside the exterior body 509. 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 are superimposed, and the separator 507 is disposed therebetween.

[0043] The positive electrode 503 includes a positive electrode current collector 501 and a positive electrode active material layer 502 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 side of the positive electrode current collector 501.

[0044] The negative electrode 506 includes a negative electrode current collector 504 and a negative electrode active material layer 505 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 side of the negative electrode current collector 504.

[0045] 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 the separator 507 therebetween. FIG. 1A shows an example in which the secondary battery has four sets of the positive electrode active material layer 502 and the negative electrode active material layer 505 facing each other with the separator 507 therebetween.

[0046] The positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, the tab region.

[0047] In the plurality of positive electrode current collectors 501, for example, the respective tab regions are arranged in an overlapping manner. The overlapping tab regions and the positive electrode lead electrode may be overlapped and joined using ultrasonic welding or the like. Also, in the plurality of negative electrode current collectors 504, for example, the respective tab regions are arranged in an overlapping manner. 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 may be appropriately selected by the implementer and may be before or after sealing.

[0048] In the secondary battery according to one aspect of the present invention, the electrolyte can be uniformly impregnated by dropping a plurality of droplets of the electrolyte onto any one or more of the positive electrode, the negative electrode, and the separator. FIG. 1B shows an example in which a plurality of droplets of the electrolyte are dropped onto the negative electrode. The negative electrode has a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer has a negative electrode active material, a conductive material, a binder, or the like, and has a gap therebetween. The dropped electrolyte moves from the dropping position to the gaps in the negative electrode active material layer, and it is preferable to make the state in which the electrolyte is uniformly impregnated, ideally a state without voids. In FIG. 1B, droplets of the electrolyte 515c are shown at 140 positions (7 columns × 20 rows) at equal intervals on the negative electrode, but it is not particularly limited and may be appropriately determined by the implementer. When using one nozzle, it may be sequentially scanned while confirming the dropping position with a CCD or the like. When droplets are dropped simultaneously from a plurality of nozzles, the processing time of dropping can be shortened, which is preferable.

[0049] A secondary battery according to one aspect of the present invention is produced by dropping a plurality of electrolyte droplets onto any one or more of a positive electrode, a negative electrode, and a separator to uniformly impregnate them, and then sandwiching a laminate 512 of the positive electrode, the separator, and the negative electrode with an exterior film serving as an exterior body, and sealing the outer peripheral edge (the four sides when viewed from above in the case where the appearance of the secondary battery is a thin rectangular parallelepiped) without any gaps. For example, in the seal region 513 shown in FIG. 1B, the outer peripheral edge may be sealed. The sealing can be performed even under atmospheric pressure, and in that case, it is performed in an inert atmosphere such as argon gas or nitrogen gas. Sealing under reduced pressure is preferable because impurities or air are less likely to enter the sealed region surrounded by the exterior film. In the present embodiment, the sealing is performed in a chamber at a pressure of about 4×10 4 Pa.

[0050] Also, as shown in FIG. 1C, multi-sided taking can be performed by arranging a plurality of laminates 512 on the exterior film. Multi-sided taking refers to a method of producing a plurality of secondary batteries by arranging a plurality of laminates on one large exterior film, producing a secondary battery, and then dividing the laminates planar by planar. By performing multi-sided taking, the production time per secondary battery can be shortened.

[0051] FIG. 2 is a flow chart for explaining a method of manufacturing a secondary battery according to one aspect of the present invention. FIG. 3 is a cross-sectional view for explaining a method of manufacturing a secondary battery according to one aspect of the present invention, and corresponds to the two-dot chain line A-B shown in FIG. 1C.

[0052] An example of a method of manufacturing a secondary battery according to one aspect of the present invention will be described along the flow shown in FIG. 2.

[0053] In step S000, the process is started.

[0054] In step S001, the positive electrode is arranged. The positive electrode is arranged on the exterior film 509b that will become the exterior body 509. The exterior film 509b is arranged on the stage 516. Although the positive electrode, the exterior film, and the stage are all arranged inside the chamber, for simplicity, the inner wall of the chamber etc. are not illustrated here.

[0055] Next, in step S002, the electrolyte is dropped. Fig. 3A shows a state where the positive electrode 503 is arranged on the exterior film 509b and the electrolyte 515a is dropped from the nozzle 514. By moving the nozzle 514, as shown in Fig. 3B, the electrolyte 515a can be dropped over the entire surface of the positive electrode 503. Alternatively, by moving the stage 516, the electrolyte 515a may be dropped over the entire surface of the positive electrode 503.

[0056] Next, in step S003, the separator 507 is arranged so as to overlap on the positive electrode 503. Next, in step S004, the electrolyte 515b is dropped on the separator 507. Fig. 3C shows a state where the electrolyte 515b is dropped on the separator.

[0057] Next, in step S005, the negative electrode is arranged so as to overlap on the positive electrode 503 and the separator 507. Next, in step S006, the electrolyte 515c is dropped. Fig. 3D shows a state where the electrolyte 515c is dropped on the negative electrode.

[0058] After step S006, the laminate of the positive electrode, the separator, and the negative electrode can be further laminated. For example, after step S006, by laminating the separator, the positive electrode, the separator, the negative electrode, the separator, and the positive electrode in order, the laminate 512 shown in Fig. 1A can be produced. After arranging the positive electrode, the negative electrode, and the separator respectively, it is preferable to drop the electrolyte.

[0059] In addition, in the step of disposing the positive electrode, the negative electrode, and the separator, it may not be necessary to drop the electrolyte. For example, the electrolyte may be dropped only in the step of disposing the positive electrode and the negative electrode. Alternatively, for example, the electrolyte may be dropped only in the step of disposing the separator.

[0060] Next, in step S007, the outer film 509b is sealed under reduced pressure. FIG. 3E shows a state in which the outer film 509b is sealed.

[0061] Through the above steps, in step S008, the process is terminated.

[0062] (Embodiment 2) In this embodiment, an example of a secondary battery according to an aspect of the present invention will be described.

[0063] <Configuration Example 1 of Secondary Battery> Hereinafter, a secondary battery in which a positive electrode, a negative electrode, and an electrolytic solution are wrapped in an exterior body will be described as an example.

[0064] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer has a positive electrode active material and may have the conductive material and the binder described above.

[0065] [Negative Electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer has a negative electrode active material and may have the conductive material and the binder described above.

[0066] [Current Collector] As the positive electrode current collector and the negative electrode current collector, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, and alloys thereof, which have high conductivity and do not alloy with carrier ions such as lithium, can be used. The current collector can appropriately use shapes such as a sheet shape, a net shape, a punching metal shape, and an expanded metal shape. It is preferable to use a current collector having a thickness of 10 μm or more and 30 μm or less.

[0067] It is preferable to use a material that does not alloy with carrier ions such as lithium for the negative electrode current collector.

[0068] A titanium compound may be provided by laminating on the metal shown above as the current collector. As the titanium compound, for example, titanium nitride, titanium oxide, titanium nitride in which part of nitrogen is substituted with oxygen, titanium oxide in which part of oxygen is substituted with nitrogen, and titanium oxynitride (TiO x N y , where 0 < x < 2 and 0 < y < 1), one selected therefrom, or two or more may be mixed or laminated and used. 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.

[0069] Active material layers such as the positive electrode active material layer and the negative electrode active material layer preferably have a conductive material. 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 preferably 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. Incidentally, these carbon-based materials may function as an active material.

[0070] As the carbon fiber, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fiber, carbon nanofibers or carbon nanotubes can be used. Carbon nanotubes can be produced, for example, by a vapor phase growth method or the like.

[0071] The active material layer may also contain metal powders or metal fibers such as copper, nickel, aluminum, silver, and gold, or conductive ceramic materials as the conductive material.

[0072] The content of the conductive material with respect 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.

[0073] Unlike granular conductive materials such as carbon black that make point contact 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 that of ordinary conductive materials. Thus, the ratio of the active material in the active material layer can be increased. Thereby, the discharge capacity of the secondary battery can be increased.

[0074] Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes easily enter minute spaces. The minute spaces refer to, for example, the regions between a plurality of active materials. By combining a carbon-containing compound that easily enters minute spaces with a sheet-like carbon-containing compound such as graphene that can impart conductivity over a plurality of particles, the density of the electrode can be increased and an excellent conductive path can be formed. The secondary battery obtained by the manufacturing method of one aspect of the present invention can have stability and is effective as a secondary battery for in-vehicle use. Increasing the number of secondary batteries makes control complicated. By using a large-sized secondary battery, the number of secondary batteries can be reduced and the burden on the charge control circuit can be alleviated.

[0075] The active material layer preferably has a binder (not shown). The binder binds or fixes, for example, an electrolyte and an active material. The binder can also bind or fix an electrolyte and a carbon-based material, an active material and a carbon-based material, a plurality of active materials, a plurality of carbon-based materials, etc.

[0076] As the binder, it is preferable to use materials such as polystyrene, methyl polyacrylate, methyl polymethacrylate (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, nitrocellulose, etc.

[0077] Polyimide has very excellent thermal, mechanical, and chemical stability properties.

[0078] As the binder, a fluoropolymer which is a polymer material having fluorine, specifically polyvinylidene fluoride (PVDF), etc. can be used. PVDF is a resin having a melting point in the range of 134°C or higher and 169°C or lower, and is a material with excellent thermal stability.

[0079] Also, as the binder, 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. Also, fluororubber can be used as the binder.

[0080] In addition, as the binder, it is preferable to use, for example, a water-soluble polymer. As the water-soluble polymer, for example, polysaccharides can be used. As the polysaccharides, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, or starch can be used. Further, it is more preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0081] The binder may be used in combination of a plurality of the above.

[0082] <Graphene compound> In this specification and the like, the graphene compound includes graphene, multi-layer graphene, multi-graphene, graphene oxide, multi-layer graphene oxide, multi-oxidized graphene, reduced graphene oxide, reduced multi-layer graphene oxide, reduced multi-oxidized graphene, graphene quantum dots, etc. The graphene compound refers to a substance having carbon, having a flat or sheet-like shape, and having a two-dimensional structure formed by carbon six-membered rings. The two-dimensional structure formed by the carbon six-membered rings may be referred to as a carbon sheet. The graphene compound may have a functional group. Further, the graphene compound preferably has a bent shape. Also, the graphene compound may be rounded to be like a carbon nanofiber.

[0083] In this specification and the like, graphene oxide refers to, for example, a substance having carbon and oxygen, having a sheet-like shape, and having a functional group, particularly an epoxy group, a carboxy group or a hydroxy group.

[0084] In this specification and the like, the reduced graphene oxide refers to, for example, a material that contains carbon and oxygen, has a sheet-like shape, and has a two-dimensional structure formed by carbon six-membered rings. It may also be referred to as a carbon sheet. The reduced graphene oxide can function alone, or multiple sheets may be stacked. The reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic% and the oxygen concentration is 2 atomic% or more and 15 atomic% or less. By setting such carbon and oxygen concentrations, it can function as a highly conductive material even in small amounts. Also, the reduced graphene oxide preferably has an intensity ratio G / D of the G band and the D band in the Raman spectrum of 1 or more. The reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small amounts.

[0085] By reducing graphene oxide, pores may be formed in the graphene compound.

[0086] Alternatively, a material in which the ends of graphene are terminated with fluorine may be used.

[0087] In the longitudinal section of the active material layer, sheet-like graphene compounds are dispersed substantially uniformly in the internal region of the active material layer. Since the plurality of graphene compounds are formed so as to partially cover the plurality of granular active materials or adhere onto the surfaces of the plurality of granular active materials, they are in surface contact with each other.

[0088] Here, by bonding the plurality of graphene compounds to each other, a network-like graphene compound sheet (hereinafter referred to as a graphene compound net or a graphene net) can be formed. When the active material is covered with the graphene net, the graphene net can also function as a binder that binds the active materials to each other. Therefore, the amount of the binder can be reduced or it can be omitted, so that the ratio of the active material in the electrode volume or the electrode weight can be improved. That is, the charge and discharge capacity of the secondary battery can be increased.

[0089] Here, it is preferable to use graphene oxide as the graphene compound, mix it with the active material to form a layer that becomes the active material layer, and then reduce it. That is, it is preferable that the completed active material layer has reduced graphene oxide. By using graphene oxide, which has extremely high dispersibility in a polar solvent, for the formation of the graphene compound, the graphene compound can be dispersed almost uniformly in the internal region of the active material layer. In order to volatilize and remove the solvent from the dispersion medium containing uniformly dispersed graphene oxide and reduce the graphene oxide, the graphene compounds remaining in the active material layer partially overlap and are dispersed to the extent of surface contact with each other, so that a three-dimensional conductive path can be formed. Note that the reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent.

[0090] Also, in advance, by using a spray dryer, the entire surface of the active material can be covered to form a coating of the graphene compound, which is a conductive material, and further, the active materials can be electrically connected to each other by the graphene compound to form a conductive path.

[0091] Also, together with the graphene compound, the materials used for forming the graphene compound may be mixed and used for the active material layer. For example, the particles used as a catalyst when forming the graphene compound may be mixed with the graphene compound. Examples of the catalyst used when forming the graphene compound include particles having silicon oxide (SiO2, SiO x (x < 2)), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, germanium, etc. It is preferable that the D50 of the particles is 1 μm or less, and more preferably 100 nm or less.

[0092] <An example of the negative electrode active material> As the negative electrode active material, it is preferable to use a material capable of reacting with the carrier ions of the secondary battery, a material capable of inserting and desorbing carrier ions, a material capable of alloying reaction with a metal serving as a carrier ion, a material capable of dissolving and depositing a metal serving as a carrier ion, and the like.

[0093] An example of the negative electrode active material will be described below.

[0094] As the negative electrode active material, a metal or a compound having one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. Examples of alloy-based compounds using such elements include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, and the like.

[0095] In addition, a material in which impurities such as phosphorus, arsenic, boron, aluminum, and gallium are added to silicon to reduce the resistance may be used. Also, a lithium pre-doped silicon material may be used. Examples of the pre-doping method include mixing lithium fluoride, lithium carbonate, etc. with silicon and annealing, mechanical alloying of lithium metal and silicon, and the like. Further, after forming as an electrode, it is combined with an electrode such as lithium metal and doped with lithium by a charge-discharge reaction, and then a secondary battery may be fabricated by combining an electrode serving as a counter electrode (for example, a positive electrode with respect to a pre-doped negative electrode) using the doped electrode.

[0096] For example, silicon nanoparticles can be used as the negative electrode active material. The average diameter of the silicon nanoparticles is, for example, preferably 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.

[0097] The silicon nanoparticles may have crystallinity. Further, the silicon nanoparticles may have a crystalline region and an amorphous region.

[0098] Examples of the material containing silicon include SiO xA material represented by (x is preferably less than 2, more preferably not less than 0.5 and not more than 1.6) can be used.

[0099] As the negative electrode active material, for example, carbon-based materials such as graphite, graphitizable carbon, non-graphitizable carbon, carbon nanotubes, carbon black, and graphene compounds can be used.

[0100] In addition, as the negative electrode active material, for example, an oxide having one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0101] As the negative electrode active material, a plurality of the above-described metals, materials, compounds, etc. can be used in combination.

[0102] As the negative electrode active material, for example, SnO, SnO2, titanium dioxide (TiO2), lithium titanate (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), and other oxides can be used.

[0103] In addition, as the negative electrode active material, Li 3-x M x N (M = Co, Ni, Cu), which is a complex nitride of lithium and a transition metal and has an Li3N-type structure, can be used. For example, Li 2.6 Co 0.4 N3 exhibits a large charge-discharge capacity (900 mAh / g) and is preferable.

[0104] When a complex nitride of lithium and a transition metal is used as the negative electrode material, it is preferably combined with a material such as V2O5 or Cr3O8 that does not contain lithium ions as the positive electrode material. Even when a material containing lithium ions is used as the positive electrode material, a complex nitride of lithium and a transition metal can be used as the negative electrode material by previously desorbing the lithium ions contained in the positive electrode material.

[0105] In addition, a material in which a conversion reaction occurs 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), may be used as the negative electrode active material. The conversion reaction further occurs in oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS 0.89 , 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. Since the potential of the above fluorides is high, they may be used as the positive electrode material.

[0106] <An example of the positive electrode 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.

[0107] It is preferable to use a positive electrode active material having a layered crystal structure as the positive electrode active material of one aspect of the present invention.

[0108] Examples of the layered crystal structure include a layered rock salt-type crystal structure. Examples of the lithium-containing material having a layered rock salt-type crystal structure include LiM x O y (where x > 0 and y > 0, more specifically, for example, y = 2 and 0.8 < x < 1.2). 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.

[0109] LiM x O y Examples of the lithium-containing material represented by include LiCoO2, LiNiO2, LiMnO2, etc. Also, examples of the lithium-containing material represented by LiM x O y include, for example, LiNi x Co1 -xNiCo-based represented by O2(0 < x < 1), LiNi x Mn 1-x NiMn-based represented by O2(0 < x < 1), etc. can be mentioned.

[0110] Also, as a lithium-containing material represented by LiMO2, for example, LiNi x Co y Mn z NiCoMn-based (also referred to as NCM) represented by O2(x > 0, y > 0, 0.8 < x + y + z < 1.2) can be mentioned. 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. Or as an example, x, y, and z preferably satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0111] Also, as a lithium-containing material having a layered rock salt-type crystal structure, for example, Li2MnO3, Li2MnO3-LiMeO2 (Me is Co, Ni, Mn), etc. can be mentioned.

[0112] In a positive electrode active material having a layered crystal structure represented by the above lithium-containing material, a secondary battery with a high lithium content per volume and a high capacity per volume may be realized. In such a positive electrode 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, when the crystal structure collapses during charge and discharge, high-speed charging or high-speed discharging may be inhibited.

[0113] A lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 as a positive electrode active material is preferably mixed 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.

[0114] In addition, a lithium manganese composite oxide represented by the composition formula Li a Mn b M c O d can be used. Here, the element M is preferably a metal element selected from those other than lithium and manganese, or silicon or phosphorus, and more preferably nickel. Further, when measuring the entire particle of the lithium manganese composite oxide, it is preferable to satisfy 0 < a / (b + c) < 2, c > 0, and 0.26 ≦ (b + c) / d < 0.5 during discharge. The composition of metals, silicon, phosphorus, etc. in the entire particle of the lithium manganese composite oxide can be measured using, for example, ICP-MS (inductively coupled plasma mass spectrometer). Also, the oxygen composition of the entire particle of the lithium manganese composite oxide can be measured using, for example, EDX (energy dispersive X-ray analysis method). Further, it can be obtained by using valence evaluation of melting gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. Note that 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, and phosphorus.

[0115] [Structure of Positive Electrode Active Material] Materials having a layered rock salt-type crystal structure such as lithium cobalt oxide (LiCoO2) are known to have a high discharge capacity and be excellent as a positive electrode active material for secondary batteries. Examples of materials having a layered rock salt-type crystal structure include composite oxides represented by LiMO2. Metal M includes metal Me1. Metal Me1 is one or more metals including cobalt. Further, in addition to metal Me1, metal M can further include metal X. Metal X is one or more metals selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0116] Also, the degree of remaining lithium that can be inserted and removed in the positive electrode active material is represented by x in the composition formula, for example, Li x in CoO2, or x in Li x MO2. Li x CoO2 in this specification can be appropriately read as Li x MO2. In the case of the positive electrode active material in a secondary battery, x = charge capacity / theoretical capacity can be set. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2 mAh / g, it can be said that Li 0.8 CoO2 or x = 0.8. A small x in Li x CoO2 means, for example, 0.1 < x ≤ 0.24.

[0117] In transition metal compounds, it is known that the strength of the Jahn-Teller effect varies depending on the number of electrons in the d orbitals of the transition metal.

[0118] In compounds having nickel, distortion may easily occur due to the Jahn-Teller effect. Therefore, when charging and discharging at a high voltage in LiNiO2, there is a concern that the crystal structure may collapse due to distortion. It is suggested that the influence of the Jahn-Teller effect is small in LiCoO2, and it may be more excellent in resistance to charging and discharging at a high voltage, which is preferable.

[0119] The positive electrode active material will be described with reference to FIGS. 4 and 5.

[0120] <Crystal structure> ≪Li x When x is 1 in CoO2≫ The positive electrode active material of one embodiment of the present invention is in a discharged state, that is, Li x When x = 1 in CoO2, it preferably has a layered rock salt-type crystal structure belonging to the space group R-3m. The layered rock salt-type composite oxide has a high discharge capacity, has a two-dimensional lithium ion diffusion path, is suitable for the insertion / desorption reaction of lithium ions, and is excellent as a positive electrode active material for secondary batteries. Therefore, in particular, it is preferable that the inside, which occupies most of the volume of the positive electrode active material, has a layered rock salt-type crystal structure. Fig. 4 shows the layered rock salt-type crystal structure with R-3m O3 attached.

[0121] The surface layer part is a region where lithium ions first depart during charging, and is a region where the lithium concentration is more likely to be lower than that inside. Also, the atoms on the surface of the positive electrode active material in the surface layer part can be said to be in a state where some bonds are broken. Therefore, the surface layer part is likely to become unstable and can be said to be a region where the deterioration of the crystal structure easily starts. On the other hand, if the surface layer part can be made sufficiently stable, even when x is small in Li x CoO2, for example, even when x is 0.24 or less, it is possible to make it difficult to break the layered structure composed of the inner transition metal M and oxygen octahedrons. Furthermore, it is possible to suppress the displacement of the layer composed of the inner transition metal M and oxygen octahedrons.

[0122] In order to make the surface layer part have a stable composition and crystal structure, the surface layer part preferably has an additive element A, and more preferably has a plurality of additive elements A. Also, it is preferable that the surface layer part has a higher concentration of one or more selected from the additive element A than the inside. Also, it is preferable that one or more selected from the additive element A that the positive electrode active material has have a concentration gradient. Also, it is more preferable that the distribution of the positive electrode active material is different depending on the additive element A. For example, it is more preferable that the depth from the surface of the concentration peak is different depending on the additive element A. Here, the concentration peak refers to the maximum value of the concentration within 50 nm or less from the surface layer part or the surface.

[0123] For example, some of the additive elements A, such as magnesium, fluorine, titanium, silicon, phosphorus, boron, calcium, etc., preferably have a concentration gradient that increases from the inside towards the surface. An element having such a concentration gradient will be referred to as additive element X.

[0124] For example, magnesium, which is one of the additive elements X, has a divalent charge. Since magnesium ions are more stable in the lithium sites than in the transition metal M sites in the layered rock salt-type crystal structure, they tend to enter the lithium sites. When magnesium is present at an appropriate concentration in the lithium sites of the surface layer, it becomes easier to maintain the layered rock salt-type crystal structure. This is presumably because the magnesium present in the lithium sites functions as a pillar supporting the CoO2 layers. Also, due to the presence of magnesium, x in the state where x in LiCoO2 is, for example, 0.24 or less, the oxygen detachment around magnesium can be suppressed. Also, due to the presence of magnesium, an increase in the density of the positive electrode active material can be expected. Further, when the magnesium concentration in the surface layer is high, an improvement in the corrosion resistance against hydrofluoric acid generated by the decomposition of the electrolyte can also be expected.

[0125] Magnesium can enjoy the above-mentioned merits without adversely affecting the insertion and extraction of lithium accompanying charge and discharge as long as it is at an appropriate concentration. However, if magnesium is excessive, it may have an adverse effect on the insertion and extraction of lithium. Furthermore, the effect on the stabilization of the crystal structure may become small. This is considered to be because magnesium starts to enter not only the lithium sites but also the transition metal M sites. In addition, unnecessary magnesium compounds (such as oxides and fluorides) that do not substitute for either the lithium sites or the transition metal M sites may segregate on the surface of the positive electrode active material, etc., and may become a resistance component of the secondary battery. Also, as the magnesium concentration of the positive electrode active material increases, the discharge capacity of the positive electrode active material may decrease. This is considered to be because too much magnesium enters the lithium sites, reducing the amount of lithium contributing to charge and discharge.

[0126] Therefore, it is preferable that the amount of magnesium in the entire positive electrode active material is appropriate. For example, the number of magnesium atoms is preferably 0.001 times or more and 0.1 times or less the number of cobalt atoms, more preferably more than 0.01 times and less than 0.04 times, and even more preferably about 0.02 times. The amount of magnesium in the entire positive electrode active material referred to here may be, for example, a value obtained by performing elemental analysis of the entire positive electrode active material using GD-MS, ICP-MS, etc., or may be based on the value of the raw material formulation in the process of producing the positive electrode active material.

[0127] In addition, aluminum, which is one of the additive elements Y, may be present at the transition metal M site in the layered rock salt type crystal structure. Since aluminum is a trivalent typical element and its valence does not change, lithium around aluminum is less likely to move even during charge and discharge. Therefore, aluminum and the lithium around it can function as pillars and suppress changes in the crystal structure. In addition, aluminum suppresses the elution of the surrounding transition metal M and has the effect of improving the continuous charge resistance. Also, since the Al-O bond is stronger than the Co-O bond, the detachment of oxygen around aluminum can be suppressed. Due to these effects, the thermal stability is improved. Therefore, when the additive element Y has aluminum, the safety when used in a secondary battery can be improved. Also, a positive electrode active material with a crystal structure that is difficult to collapse even when charge and discharge are repeated can be obtained.

[0128] On the other hand, if aluminum is excessive, it may have an adverse effect on the insertion and desorption of lithium.

[0129] Therefore, it is preferable that the amount of aluminum in the entire positive electrode active material is appropriate. For example, the number of aluminum atoms in the entire positive electrode active material is preferably 0.05% or more and 4% or less of the number of cobalt atoms, preferably 0.1% or more and 2% or less, and more preferably 0.3% or more and 1.5% or less. Or preferably 0.05% or more and 2% or less. Or preferably 0.1% or more and 4% or less. The amount referred to as the amount 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, etc., or may be based on the value of the raw material formulation in the process of producing the positive electrode active material.

[0130] For example, it is preferable that the crystal structure continuously changes from the inside of the layered rock salt type toward the surface and the surface layer having the characteristics of the rock salt type or both the rock salt type and the layered rock salt type. Or it is preferable that the orientation of the surface layer having the characteristics of both the rock salt type or both the rock salt type and the layered rock salt type is substantially consistent with the orientation inside the layered rock salt type.

[0131] In this specification and the like, the layered rock salt type crystal structure belonging to the space group R-3m of the composite oxide containing the transition metal M including lithium and cobalt means a crystal structure having a rock salt type ion arrangement in which cations and anions are alternately arranged, and lithium and the transition metal M are regularly arranged to form a two-dimensional plane, so that two-dimensional diffusion of lithium is possible. Note that there may be defects such as cation or anion deficiencies. Also, strictly speaking, the layered rock salt type crystal structure may be a structure in which the lattice of the rock salt type crystal is distorted.

[0132] The rock salt type crystal structure means a crystal structure of the cubic crystal system including the space group Fm-3m, and a structure in which cations and anions are alternately arranged. Note that there may be cation or anion deficiencies.

[0133] Also, having both the characteristics of the layered rock salt type and the rock salt type crystal structures can be determined by electron beam diffraction, TEM images, cross-sectional STEM images, and the like.

[0134] The anions of the layered rock salt type crystal and the rock salt type crystal take a cubic close-packed structure (face-centered cubic lattice structure). It is presumed that the anions of the O3' type crystal (also called a pseudo-spinel type crystal) described later also take a cubic close-packed structure. Therefore, when the layered rock salt type crystal and the rock salt type crystal are in contact, there is a crystal plane in which the orientations of the cubic close-packed structures composed of anions are aligned.

[0135] Alternatively, it can also be explained as follows. Anions on the {111} plane of the cubic crystal structure have a triangular lattice. The layered rock salt type has a space group of R-3m and a rhombohedral structure, but is generally represented by a composite hexagonal lattice for easy understanding of the structure, and the (000l) plane of the layered rock salt type 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 rock salt type. The alignment of the orientations of the cubic close-packed structures composed of anions in both can be said to have the same orientation.

[0136] However, since the space groups of the layered rock salt type crystal and the O3’ type crystal are 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), the Miller indices of the crystal planes satisfying the above conditions are different for the layered rock salt type crystal and the O3’ type crystal, and the rock salt type crystal. In this specification, in the case of the layered rock salt type crystal, the O3’ type, and the rock salt type crystal, when the orientations of the cubic close-packed structures composed of anions are aligned, it may be said that the crystal orientations are generally in agreement.

[0137] The approximate agreement of the crystal orientations in the two regions can be determined from TEM (Transmission Electron Microscope) images, STEM (Scanning Transmission Electron Microscope) 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 and STEM images, etc. XRD (X-ray Diffraction), neutron diffraction, etc. can also be used as materials for determination.

[0138] Figure 5 shows R-3m O3 with Li xIt shows the crystal structure of lithium cobaltate with x = 1 in CoO₂. In this crystal structure, lithium occupies octahedral sites, and there are three CoO₂ layers in the unit cell. Therefore, this crystal structure is sometimes called the O3-type crystal structure. Note that the CoO₂ layer refers to a structure in which octahedrons with cobalt coordinated by six oxygens are continuously arranged in a plane in a state of sharing edges. It is also sometimes called a layer composed of octahedrons of cobalt and oxygen.

[0139] Also, it is known that conventional lithium cobaltate has a crystal structure belonging to the monoclinic space group P2 / m with enhanced lithium symmetry when x is about 0.5. This structure has one CoO₂ layer in the unit cell. Therefore, it is sometimes called the O1-type or monoclinic O1-type.

[0140] Also, the cathode active material when x = 0 has a crystal structure of the trigonal space group P-3m1 and also has one CoO₂ layer in the unit cell. Therefore, this crystal structure is sometimes called the O1-type or trigonal O1-type. Also, when the trigonal crystal is converted into a composite hexagonal lattice, it is sometimes called the hexagonal O1-type.

[0141] Also, conventional lithium cobaltate when x is about 0.24 has a crystal structure of the space group R-3m. This structure can also be said to be a structure in which the structure of CoO₂ like the trigonal O1-type and the structure of LiCoO₂ like R-3m O3 are alternately stacked. Therefore, this crystal structure is sometimes called the H1-3 type crystal structure. In fact, in the H1-3 type crystal structure, the number of cobalt atoms per unit cell is twice that of other structures. However, in this specification including Fig. 5, for easy comparison with other crystal structures, it is shown in a figure with the c-axis of the H1-3 type crystal structure halved to that of the unit cell.

[0142] As shown by the dotted line in Fig. 4, there is almost no shift in the CoO₂ layer between the discharged state of R-3m (O3) and the O3'-type crystal structure.

[0143] Also, the volume difference per cobalt atom between R-3m(O3) in the discharged state and the O3'-type crystal structure is 2.5% or less, more specifically 2.2% or less, and typically 1.8%.

[0144] Thus, in the positive electrode active material of one aspect of the present invention, when x in Li x CoO2 is small, that is, when a large amount of lithium has been removed, the change in the crystal structure is suppressed more than that of the conventional positive electrode active material. Also, the change in volume when compared per the same number of cobalt atoms is suppressed. Therefore, the positive electrode active material is less likely to have its crystal structure collapse even when charge and discharge are repeated such that x becomes 0.24 or less. Therefore, the decrease in the charge-discharge capacity in the charge-discharge cycle of the positive electrode active material is suppressed. Also, since more lithium can be stably utilized than in the conventional positive electrode active material, the positive electrode active material has a large discharge capacity per unit weight and per unit volume. Therefore, by using the positive electrode active material, a secondary battery with a high discharge capacity per unit weight and per unit volume can be manufactured.

[0145] Note that the positive electrode active material may have an O3'-type crystal structure when x in Li x CoO2 is 0.15 or more and 0.24 or less, and it is presumed that it also has an O3'-type crystal structure when x exceeds 0.24 and is 0.27 or less. However, since the crystal structure is affected not only by x in Li x 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.

[0146] Therefore, when x in Li x CoO2 exceeds 0.1 and is 0.24 or less, not all of the inside of the positive electrode active material needs to have an O3'-type crystal structure. It may contain other crystal structures or a part thereof may be amorphous.

[0147] Also, to make x in Li x CoO2 small, generally, it is necessary to charge at a high charging voltage. Therefore, Li xThe state where x in CoO₂ is small can be rephrased as the state charged at a high charging voltage. For example, when charging at a voltage of 4.6 V or higher with respect to the potential of lithium metal in an environment of 25 °C by CC / CV charging, an H1-3 type crystal structure appears in the conventional cathode active material. Therefore, a charging voltage of 4.6 V or higher with respect to the potential of lithium metal can be referred to as a high charging voltage. Also, in this specification and the like, unless otherwise specified, the charging voltage is expressed with respect to the potential of lithium metal.

[0148] Therefore, it can be rephrased that the cathode active material according to one aspect of the present invention is preferable because it can maintain a crystal structure having the symmetry of R-3m O3 even when charged at a high charging voltage, for example, a voltage of 4.6 V or higher at 25 °C. Also, it can be rephrased that it is preferable because it can adopt an O3'-type crystal structure when charged at an even higher charging voltage, for example, a voltage of 4.65 V or higher and 4.7 V or lower at 25 °C.

[0149] When the charging voltage of the cathode active material is further increased, an H1-3 type crystal may be observed. Also, as described above, since the crystal structure is affected by the number of charge-discharge cycles, charge-discharge current, electrolyte, etc., when the charging voltage is lower, for example, even when the charging voltage is 4.5 V or higher and less than 4.6 V at 25 °C, the cathode active material according to one aspect of the present invention may adopt an O3'-type crystal structure.

[0150] In a secondary battery, for example, when using graphite as the anode active material, the voltage of the secondary battery decreases by the potential of graphite compared to the above. The potential of graphite is about 0.05 V to 0.2 V with respect to the potential of lithium metal. Therefore, in the case of a secondary battery using graphite as the anode active material, it has the same crystal structure at the voltage obtained by subtracting the potential of graphite from the above voltage.

[0151] <Particle size> If the particle size of the positive electrode active material of one embodiment of the present invention is too large, there are problems such as difficulty in lithium diffusion and the surface of the active material layer becoming too rough when coated on the current collector. On the other hand, if it is too small, there are also problems such as difficulty in supporting the active material layer during coating on the current collector and excessive progress of the reaction with the electrolyte. Therefore, the median diameter (D50) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less. Or preferably 1 μm or more and 40 μm or less. Or preferably 1 μm or more and 30 μm or less. Or preferably 2 μm or more and 100 μm or less. Or preferably 2 μm or more and 30 μm or less. Or preferably 5 μm or more and 100 μm or less. Or preferably 5 μm or more and 40 μm or less.

[0152] <Analysis method> Whether a certain positive electrode active material is a positive electrode active material of one embodiment of the present invention having an O3'-type crystal structure when x in Li x CoO2 is small can be determined by analyzing a positive electrode having a positive electrode active material with a small x in Li x CoO2 using XRD, electron beam diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc.

[0153] In particular, XRD is preferable in that it can analyze the symmetry of transition metals M such as cobalt in the positive electrode active material with high resolution, can compare the crystallinity and crystal orientation, can analyze the periodic strain of the lattice and the crystallite size, and sufficient accuracy can be obtained even by measuring the positive electrode obtained by disassembling the secondary battery as it is. Among XRDs, powder XRD can obtain diffraction peaks reflecting the internal crystal structure of the positive electrode active material that occupies most of the volume of the positive electrode active material.

[0154] As described above, the positive electrode active material of one embodiment of the present invention is characterized in that the change in the crystal structure is small when x in Li x CoO2 is 1 and when it is 0.24 or less. When charged at a high voltage, a material in which a crystal structure with a large change in the crystal structure occupies 50% or more is not preferable because it cannot withstand high-voltage charge and discharge.

[0155] Note that simply adding the additive element A may not result in the O3'-type crystal structure. For example, lithium cobaltate having magnesium and fluorine, or lithium cobaltate having magnesium and aluminum, although common in this regard, depending on the concentration and distribution of the additive element A, Li x x

[0156] Also, in the case of the positive electrode active material of one embodiment of the present invention, if x is too small, such as x being 0.1 or less, or under conditions where the charging voltage exceeds 4.9 V, an H1-3 type or trigonal O1 type crystal structure may occur. Therefore, in order to determine whether it is the positive electrode active material of one embodiment of the present invention, analysis of the crystal structure including XRD and information such as the charge capacity or charging voltage are required.

[0157] However, the positive electrode active material in a state where x is small may change its crystal structure when exposed to the atmosphere. For example, it may change from the O3'-type crystal structure to the H1-3 type crystal structure. Therefore, it is preferable to handle all samples for crystal structure analysis in an inert atmosphere such as an argon atmosphere.

[0158] Also, whether the distribution of the additive element A in a certain positive electrode active material is in the state as described above can be determined by analysis using, for example, XPS, energy dispersive X-ray spectroscopy (EDX), EPMA (electron probe microanalysis), or the like.

[0159] Also, the crystal structure of the surface layer portion, crystal grain boundaries, etc. can be analyzed by electron beam diffraction of the cross-section of the positive electrode active material.

[0160] As an example, the coordinates of cobalt and oxygen in the unit cell of the H1-3 type 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 respectively. Which unit cell 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, a unit cell with a smaller GOF (goodness of fit) value may be adopted.

[0161] Li x When charging and discharging are repeated such that x in CoO2 becomes 0.24 or less, conventional lithium cobaltate repeats a change in crystal structure (i.e., an unbalanced phase change) between the H1-3 type crystal structure and the R-3m O3 structure in the discharged state.

[0162] However, the shift of the CoO2 layers in these two crystal structures is large. As shown by the dotted lines and arrows in Fig. 5, in the H1-3 type crystal structure, the CoO2 layer is significantly shifted from the R-3m O3 in the discharged state. Such dynamic structural changes can have an adverse effect on the stability of the crystal structure.

[0163] Furthermore, the volume difference between these two crystal structures is also large. When compared per the same number of cobalt atoms, the volume difference between the H1-3 type crystal structure and the R-3m O3 type crystal structure in the discharged state exceeds 3.5%, typically 3.9% or more.

[0164] In addition, a structure in which the CoO2 layers are continuous, such as the trigonal O1 type, which the H1-3 type crystal structure has, is likely to be unstable.

[0165] Therefore, when charging and discharging are repeated such that x becomes 0.24 or less, the crystal structure of conventional lithium cobaltate collapses. The collapse of the crystal structure causes deterioration of the cycle characteristics. This is because when the crystal structure collapses, the sites where lithium can exist stably decrease, and it becomes difficult for lithium to be inserted and removed.

[0166] <Electrolyte> When a liquid electrolyte layer is used in a secondary battery, for example, as the electrolyte layer, 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, etc. can be used alone or in any combination and ratio of two or more of these.

[0167] Also, the electrolyte preferably contains fluorine. As the electrolyte containing fluorine, for example, an electrolyte having one or more fluorinated cyclic carbonates and lithium ions can be used. The fluorinated cyclic carbonate can improve the nonflammability and enhance the safety of the lithium-ion secondary battery.

[0168] As the fluorinated cyclic carbonate, fluorinated ethylene carbonate such as monofluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), tetrafluoroethylene carbonate (F4EC), etc. can be used. Note that DFEC has isomers such as cis-4,5 and trans-4,5. As the electrolyte, using one or more fluorinated cyclic carbonates to solvate lithium ions and transport them in the electrolyte contained in the electrode during charge and discharge is important for operating at low temperatures. When the fluorinated cyclic carbonate contributes to the transport of lithium ions during charge and discharge rather than as a small amount of additive, operation at low temperatures becomes possible. In the secondary battery, lithium ions move in clusters of several to several tens.

[0169] By using a fluorinated cyclic carbonate as an electrolyte, the energy required for desolvation when lithium ions solvated in the electrolyte enter the active material particles is reduced. If this desolvation energy can be reduced, lithium ions can be more easily inserted into or desorbed from the active material particles even in the low temperature range. Although lithium ions may move while remaining in a solvated state, a hopping phenomenon may occur where the coordinating solvent molecules are replaced. When lithium ions become more easily desolvated, movement due to the hopping phenomenon becomes easier, and in some cases, the movement of lithium ions becomes easier. There is a concern that decomposition products of the electrolyte during charge and discharge of the secondary battery may adhere to the surface of the active material, causing deterioration of the secondary battery. However, when the electrolyte contains fluorine, the electrolyte is dry, and it becomes difficult for the decomposition products of the electrolyte to adhere to the surface of the active material. Therefore, deterioration of the secondary battery can be suppressed.

[0170] Multiple solvated lithium ions may form clusters in the electrolyte and move within the negative electrode, between the positive and negative electrodes, within the positive electrode, etc.

[0171] An example of a fluorinated cyclic carbonate is shown below.

[0172] Monofluoroethylene carbonate (FEC) is represented by the following formula (1).

[0173]

Chemical formula

[0174] Tetrafluoroethylene carbonate (F4EC) is represented by the following formula (2).

[0175]

Chemical formula

[0176] Difluoroethylene carbonate (DFEC) is represented by the following formula (3).

[0177]

Chemical formula

[0178] In addition, by using one or more ionic liquids (room-temperature molten salts) that are flame-retardant and have low volatility as the electrolyte solvent, even if the internal region temperature of the secondary battery rises due to internal region short-circuiting, overcharging, etc., rupture or ignition of the secondary battery can be prevented. An ionic liquid consists of a cation and an anion and contains an organic cation and an anion. Examples of the organic cation 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 the anion include monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkylphosphate anions, etc.

[0179] As the ionic liquid having an imidazolium cation, for example, an ionic liquid represented by the following general formula (G1) can be used. In the general formula (G1), R 1 represents an alkyl group having 1 to 10 carbon atoms, and R 2 to 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 selected from the atoms C, O, Si, N, S, P. Further, substituents may be introduced into the main chain of R 5 . Examples of the substituents to be introduced include, for example, an alkyl group, an alkoxy group, etc.

[0180]

Chemical formula

[0181] As an example of the cation represented by the general formula (G1), 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-methyl-3-(propoxyethyl)imidazolium cation, 1-hexyl-3-methylimidazolium cation and the like can be mentioned.

[0182] As the ionic liquid having a pyridinium cation, for example, an ionic liquid represented by the following general formula (G2) may be used. In the general formula (G2), R 6 represents an alkyl group having 1 to 6 carbon atoms or a main chain composed of two or more selected from the atoms of C, O, Si, N, S, and P, and R 7 to R 11 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Further, a substituent may be introduced into the main chain of R 6 . Examples of the substituent to be introduced include an alkyl group and an alkoxy group.

[0183]

Chemical formula

[0184] As the ionic liquid having a quaternary ammonium cation, for example, ionic liquids represented by the following general formulas (G3), (G4), (G5) and (G6) can be used.

[0185]

Chemical formula

[0186] In the general formula (G3), R 28 to R 31 each independently represents any one of an alkyl group having 1 to 20 carbon atoms, a methoxy group, a methoxymethyl group, a methoxyethyl group, or a hydrogen atom.

[0187] [Chemistry]

[0188] In general formula (G4), R 12 and R 17 each independently represents an alkyl group having 1 to 3 carbon atoms. R 13 to R 16 each independently represents either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. As an example of the cation represented by general formula (G4), there is 1-methyl-1-propylpyrrolidinium cation and the like.

[0189] [Chemistry]

[0190] In general formula (G5), R 18 and R 24 each independently represents an alkyl group having 1 to 3 carbon atoms. R 19 to R 23 each independently represents either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. As an example of the cation represented by general formula (G5), there are N-methyl-N-propylpiperidinium cation, 1,3-dimethyl-1-propylpiperidinium cation and the like.

[0191] [Chemistry]

[0192] In the general formula (G6), n and m are each 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. Note that α or β being 0 means no substitution. Also, the case where both α and β are 0 is excluded. X or Y represents a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkoxyalkyl group having 1 to 4 carbon atoms as a substituent.

[0193] As the ionic liquid having a tertiary sulfonium cation, for example, an ionic liquid represented by the following general formula (G7) can be used. In the general formula (G7), R 25 to R 27 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Alternatively, as R 25 to R 27 a main chain composed of two or more selected from the atoms of C, O, Si, N, S, and P may be used.

[0194]

Chemical formula

[0195] 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 the general formula (G8), R 32 to R 35 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Alternatively, as R 32 to R 35 a main chain composed of two or more selected from the atoms of C, O, Si, N, S, and P may be used.

[0196]

Chemical formula

[0197] A represented by the general formulas (G1) to (G8) - can be one or more of a monovalent amide-based anion, a monovalent methide-based anion, a fluorosulfonic acid anion, a perfluoroalkylsulfonic acid anion, a tetrafluoroborate anion, a perfluoroalkylborate anion, a hexafluorophosphate anion, and a perfluoroalkylphosphate anion, etc.

[0198] Examples of the monovalent amide-based anion include (CnF 2n+1 SO2)2N - (n = 0 or more and 3 or less), and examples of the monovalent cyclic amide-based anion include (CF2SO2)2N - etc. can be used. Examples of the monovalent methide-based anion include (C n F 2n+1 SO2)3C - (n = 0 or more and 3 or less), and examples of the monovalent cyclic methide-based anion include (CF2SO2)2C - (CF3SO2), etc. can be used. Examples of the fluoroalkylsulfonic acid anion include (C m F 2m+1 SO3) - (m = 0 or more and 4 or less), etc. Examples of the fluoroalkylborate anion include {BF n (C m H k F 2m+1-k ) 4-n} - (n = 0 or more and 3 or less, m = 1 or more and 4 or less, k = 0 or more and 2m or less), etc. Examples of the fluoroalkylphosphate anion include {PF n (C m H k F 2m+1-k ) 6-n} - (n = 0 or more and 5 or less, m = 1 or more and 4 or less, k = 0 or more and 2m or less), etc.

[0199] Further, as the monovalent amide-based anion, for example, one or more of bis(fluorosulfonyl)amide anion and bis(trifluoromethanesulfonyl)amide anion can be used.

[0200] Further, the ionic liquid may have one or more of hexafluorophosphate anion and tetrafluoroborate anion.

[0201] Hereinafter, (FSO2)2N - The anion represented by is sometimes referred to as FSA anion, and the anion represented by (CF3SO2)2N - is sometimes referred to as TFSA anion.

[0202] The secondary battery according to one aspect of the present invention has, for example, alkali metal ions such as sodium ions and potassium ions, and alkaline earth metal ions such as calcium ions, strontium ions, barium ions, beryllium ions, and magnesium ions as carrier ions.

[0203] When lithium ions are used as carrier ions, for example, the electrolyte contains a lithium salt. Examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 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.

[0204] In the present specification, the electrolyte is a general term including solid, liquid, or semi-solid materials, etc.

[0205] Interfaces existing within a secondary battery, such as the interface between an active material and an electrolyte, are prone to degradation. In the secondary battery according to one aspect of the present invention, by having an electrolyte containing fluorine, it is possible to prevent degradation that may occur at the interface between the active material and the electrolyte, typically the alteration of the electrolyte or the increase in the viscosity of the electrolyte. Further, a configuration may be adopted in which a binder, a graphene compound, or the like clings to or is retained with respect to the electrolyte containing fluorine. By adopting such a configuration, it becomes possible to maintain a state in which the viscosity of the electrolyte is lowered, in other words, a state in which the electrolyte is smooth, and the reliability of the secondary battery can be improved. DFEC having two fluorines or F4EC having four bonds has a lower viscosity, is smoother, and has a weaker coordination bond with lithium compared to FEC having one fluorine bond. Therefore, it is possible to reduce the adhesion of decomposition products having a high viscosity to the active material particles. When decomposition products having a high viscosity adhere to or cling to the active material particles, it becomes difficult for lithium ions to move at the interface of the active material particles. The electrolyte containing fluorine alleviates the formation of decomposition products formed on the surface of the active material (positive electrode active material or negative electrode active material) by solvation. Further, by using an electrolyte containing fluorine, it is possible to prevent the generation and growth of dendrites by preventing the adhesion of decomposition products.

[0206] Another feature is to use an electrolyte containing fluorine as a main component, and the electrolyte containing fluorine is 5% by volume or more, 10% by volume or more, preferably 30% by volume or more and 100% by volume or less.

[0207] In this specification, the main component of the electrolyte refers to being 5% by volume or more of the entire electrolyte of the secondary battery. Further, 5% by volume or more of the entire electrolyte of the secondary battery here refers to the ratio occupied by the entire electrolyte measured during the manufacture of the secondary battery. Further, when decomposing the secondary battery after fabrication, it is difficult to quantify the proportion of each of the plurality of types of electrolytes, but it is possible to determine whether a certain type of organic compound is 5% by volume or more of the entire electrolyte.

[0208] By using an electrolyte containing fluorine, a secondary battery capable of operating within a wide temperature range, specifically, from -40°C to 150°C, preferably from -40°C to 85°C, can be realized.

[0209] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), lithium bis(oxalate) borate (LiBOB), and 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 based on the entire electrolyte.

[0210] In addition to the above, the electrolyte may have one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran.

[0211] Moreover, by having a polymer material that gels the electrolyte, the safety against leakage and the like is enhanced. Representative examples of the polymer material that gels include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, and gels of fluorine-based polymers.

[0212] As the polymer material, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Further, the formed polymer may have a porous shape.

[0213] 〔Separator〕 A separator is disposed between the positive electrode and the negative electrode. As the separator, for example, fibers having cellulose such as paper, non-woven fabric, glass fiber, ceramics, or synthetic fibers made of nylon resin (polyamide), vinylon resin (polyvinyl alcohol-based fiber), polyester resin, acrylic resin, polyolefin resin, polyurethane resin, etc. can be used. The separator is preferably processed into a bag shape and disposed so as to wrap either the positive electrode or the negative electrode.

[0214] The separator is a porous material having pores with a size of about 20 nm, preferably pores with a size of 6.5 nm or more, and more preferably pores with a diameter of at least 2 nm.

[0215] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0216] Coating with a ceramic-based material improves oxidation resistance, so it is possible to suppress deterioration of the separator during high-voltage charge and discharge and improve the reliability of the secondary battery. Also, coating with a fluorine-based material makes it easier for the separator and the electrode to adhere to each other, and the output characteristics can be improved. Coating with a polyamide-based material, especially aramid, improves heat resistance, so the safety of the secondary battery can be improved.

[0217] For example, a mixed material of aluminum oxide and aramid may be coated on both sides of a polypropylene film. Also, a mixed material of aluminum oxide and aramid may be coated on the surface of the polypropylene film that contacts the positive electrode, and a fluorine-based material may be coated on the surface that contacts the negative electrode.

[0218] When a separator having a multilayer structure is used, even if the overall thickness of the separator is thin, the safety of the secondary battery can be maintained, so that the capacity per unit volume of the secondary battery can be increased.

[0219] [Outer package] As the outer package of the secondary battery, for example, a can type using a metal material such as aluminum or a case type using a resin material can be used. Also, a film-like outer package can be used. As the film, for example, a flexible metal thin film such as aluminum, stainless steel, copper, nickel, etc. is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and further on the metal thin film, an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin is provided as the outer surface of the outer package. A three-layer structure film can be used. Also, it is preferable to use a fluororesin film as the film. The fluororesin film has high stability against acids, alkalis, organic solvents, etc., suppresses side reactions, corrosion, etc. associated with the reaction of the secondary battery, etc., and can realize an excellent secondary battery. Examples of the fluororesin film include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylene propene copolymer: copolymer of tetrafluoroethylene and hexafluoropropylene), ETFE (ethylene tetrafluoroethylene copolymer: copolymer of tetrafluoroethylene and ethylene), etc.

[0220] This embodiment can be used in appropriate combination with other embodiments.

[0221] (Embodiment 3) In this embodiment, a specific configuration example of the secondary battery described in the previous embodiment will be described.

[0222] An example of an external view of a configuration example of a secondary battery according to an aspect of the present invention is shown in FIGS. 6 and 7.

[0223] The secondary battery shown in FIG. 6A 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 513. The positive electrode 503, the negative electrode 506, and the separator 507 are laminated and disposed inside the exterior body 509.

[0224] In FIG. 6A, a positive electrode lead electrode 510 is joined to the positive electrode 503. The positive electrode lead electrode 510 is exposed outside the exterior body 509. Also, a negative electrode lead electrode 511 is joined to the negative electrode 506, and the negative electrode lead electrode 511 is exposed outside the exterior body 509.

[0225] The joining of the lead electrodes will be described with reference to FIGS. 8A, 8B, and 8C.

[0226] FIG. 8A shows an external view of the positive electrode 503. The positive electrode 503 has a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. Also, the positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as a tab region).

[0227] FIG. 8B shows an external view of the 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. Also, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area or shape of the tab regions of the positive electrode and the negative electrode is not limited to the examples shown in FIGS. 8A and 8B.

[0228] FIG. 8C is a diagram for explaining the joining of the lead electrodes. First, the negative electrode 506, the separator 507, and the positive electrode 503 are laminated. FIG. 8C shows the laminated negative electrode 506, separator 507, and positive electrode 503. Here, the laminate composed of the negative electrode, the separator, and the positive electrode has five sets of negative electrodes and four sets of positive electrodes. The tabs of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For the joining, for example, ultrasonic welding or the like may be used. Similarly, the tabs of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0229] The external view shown in FIG. 6B shows an example in which the ends are folded at two sides of the side surface of the exterior body 509. 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, problems such as loosening of the seal can be suppressed. Further, FIG. 6C shows an example in which three sides are folded.

[0230] In FIGS. 6A, 6B, and 6C, an example is shown 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. 7A. FIG. 7B shows an example in which the left and right sides of the exterior body 509 are folded in FIG. 7A.

[0231] This embodiment can be used in appropriate combination with other embodiments.

[0232] (Embodiment 4) In this embodiment, an example in which a secondary battery is applied to an electric vehicle (EV) is shown.

[0233] As shown in FIG. 9C, in an electric vehicle, 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 are installed. The second battery 1311 is also called a cranking battery (starter battery). The second battery 1311 only needs to be able to output high power and does not require a large capacity so much, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0234] The first battery 1301a can use a secondary battery manufactured by using the method for manufacturing a secondary battery shown in Embodiment 1.

[0235] In this embodiment, an example is shown in which the first batteries 1301a and 1301b are connected in parallel, but they may be connected in parallel in three or more. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack having a plurality of secondary batteries, a large amount of power can be taken out. The plurality of secondary batteries may be connected in parallel, may be connected in series, or may be further connected in series after being connected in parallel. The plurality of secondary batteries are also called a battery set.

[0236] Also, in an in-vehicle secondary battery, in order to cut off the power from a plurality of secondary batteries, it has a service plug or a circuit breaker that can cut off a high voltage without using tools, and is provided in the first battery 1301a.

[0237] Also, the power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but supplies power to 42V in-vehicle components (such as an electric power steering 1307, a heater 1308, and a defroster 1309) via the DCDC circuit 1306. Even when the rear wheels have a rear motor 1317, the first battery 1301a is used to rotate the rear motor 1317.

[0238] Also, the second battery 1311 supplies power to 14V in-vehicle components (such as an audio 1313, a power window 1314, and lamps 1315) via the DCDC circuit 1310.

[0239] Also, the first battery 1301a will be described with reference to FIG. 9A.

[0240] FIG. 9A shows an example in which nine rectangular secondary batteries 1300 are used as one battery pack 1415. Also, the nine rectangular secondary batteries 1300 are connected in series, with one electrode fixed by a fixing portion 1413 made of an insulator and the other electrode fixed by a fixing portion 1414 made of an insulator. In the present embodiment, an example of fixing by the fixing portions 1413 and 1414 is shown, but it may also be configured to be housed in a battery housing box (also referred to as a casing). Since the vehicle is assumed to be subjected to vibrations or shakes from the outside (such as the road surface), it is preferable to fix a plurality of secondary batteries with a battery housing box or the like by the fixing portions 1413 and 1414. Also, one electrode is electrically connected to the control circuit portion 1320 by a wiring 1421. The other electrode is also electrically connected to the control circuit portion 1320 by a wiring 1422.

[0241] Further, the control circuit portion 1320 may use a memory circuit including a transistor using an oxide semiconductor. 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 BTOS (Battery operating system, or Battery oxide semiconductor).

[0242] The control circuit portion 1320 detects the terminal voltage of the secondary battery and manages the charge and discharge state of the secondary battery. For example, in order to prevent overcharging, both the output transistor of the charging circuit and the cutoff switch can be turned off almost simultaneously.

[0243] Also, FIG. 9B shows an example of the block diagram of the battery pack 1415 shown in FIG. 9A.

[0244] The control circuit unit 1320 includes at least a switch for preventing overcharge, a switch unit 1324 including a switch for preventing overdischarge, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The upper limit voltage and the lower limit voltage of the secondary battery to be used are set in the control circuit unit 1320, and the upper limit of the current from the outside or the upper limit of the output current to the outside is restricted. The range between the lower limit voltage and the upper limit voltage of the secondary battery is within the recommended voltage range for use. When it is outside this range, the switch unit 1324 operates and functions as a protection circuit. Also, since the control circuit unit 1320 controls the switch unit 1324 to prevent overdischarge or overcharge, it can also be called a protection circuit. For example, when the control circuit 1322 detects a voltage that is likely to result in overcharge, the switch of the switch unit 1324 is turned off to cut off the current. Further, a PTC element may be provided in the charge and discharge path to provide a function of cutting off the current in response to an increase in temperature. The control circuit unit 1320 also has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0245] The switch section 1324 can be configured by combining n-channel transistors or p-channel transistors. The switch section 1324 is not limited to a switch having an Si transistor using single-crystalline silicon. For example, the switch section 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), GaOx (gallium oxide; x is a real number greater than 0), or the like. Further, since a memory element using an OS transistor can be freely arranged by being stacked on a circuit using an Si transistor or the like, integration can be easily performed. Further, since the OS transistor can be manufactured using the same manufacturing apparatus as the Si transistor, it can be manufactured at low cost. That is, the control circuit section 1320 using the OS transistor can be stacked on the switch section 1324 and integrated into one chip. Since the occupied volume of the control circuit section 1320 can be reduced, miniaturization is possible.

[0246] The first batteries 1301a and 1301b mainly supply power to in-vehicle devices of the 42V system (high voltage system), and the second battery 1311 supplies power to in-vehicle devices of the 14V system (low voltage system). The second battery 1311 is often adopted because a lead-acid battery is advantageous in terms of cost.

[0247] In the present embodiment, an example in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311 is shown. The second battery 1311 may use a lead-acid battery, an all-solid-state battery, or an electric double layer capacitor.

[0248] In addition, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and is charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 or the battery controller 1302. Or it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Or it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b can be rapidly charged.

[0249] The battery controller 1302 can set the charging voltage, charging current, etc. of the first batteries 1301a and 1301b. The battery controller 1302 can set the charging conditions according to the charging characteristics of the secondary battery to be used and perform rapid charging.

[0250] Also, although not shown, when connecting to an external charger, the charger's plug or the charger's connection cable is electrically connected to the battery controller 1302. The power supplied from the external charger is used to charge the first batteries 1301a and 1301b via the battery controller 1302. Also, depending on the charger, a control circuit may be provided and in some cases, the functions of the battery controller 1302 may not be used, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. Also, in some cases, the connection cable or the charger's connection cable may be equipped with a control circuit. The control circuit unit 1320 may also be called an ECU (Electronic Control Unit). The ECU is connected to the CAN (Controller Area Network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. Also, the ECU includes a microcomputer. Also, the ECU uses a CPU or a GPU.

[0251] Next, an example of mounting a secondary battery, which is one aspect of the present invention, on a vehicle, typically a transportation vehicle, will be described.

[0252] In addition, when a secondary battery of one aspect of the present invention is mounted on a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. Further, secondary batteries can also be mounted on transportation vehicles such as agricultural machinery, motorized bicycles including electric assist bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing or rotary-wing aircraft, rockets, artificial satellites, space probes or planetary probes, and spaceships. By using the method for manufacturing a secondary battery shown in Embodiment 1, a large secondary battery can be obtained. Therefore, the secondary battery of one aspect of the present invention can be suitably used for transportation vehicles.

[0253] In FIGS. 10A to 10D, a transportation vehicle using one aspect of the present invention is illustrated. The automobile 2001 shown in FIG. 10A is an electric vehicle that uses an electric motor as a power source for running. Or, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for running. When mounting a secondary battery on a vehicle, the secondary battery is installed at one location or multiple locations. The automobile 2001 shown in FIG. 10A has a battery pack 2200, and the battery pack has a secondary battery module in which a plurality of secondary batteries are connected. Further, it preferably has a charge control device electrically connected to the secondary battery module.

[0254] In addition, the motor vehicle 2001 can be charged by receiving power supply from an external charging facility for the secondary battery of the motor vehicle 2001 by a plug-in method, a non-contact power supply method, or the like. When charging, the charging method, the connector standard, etc. may be appropriately carried out in a predetermined method such as CHAdeMO (registered trademark) or Combo. The secondary battery may be a charging station provided in a commercial facility or a household power supply. For example, by the plug-in technology, the power storage device mounted on the motor vehicle 2001 can be charged by an external power supply. Charging can be performed by converting AC power into DC power through a conversion device such as an AC-DC converter.

[0255] Also, although not shown, a power receiving device can be mounted on the vehicle, and power can be supplied non-contact from a power transmitting device on the ground for charging. In the case of this non-contact power supply method, by incorporating the power transmitting device into the road or the outer wall, charging can be performed not only while the vehicle is stopped but also while it is running. Also, using this non-contact power supply method, power can be transmitted and received between two vehicles. Furthermore, a solar cell may be provided on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or running. For such non-contact power supply, an electromagnetic induction method or a magnetic field resonance method can be used.

[0256] FIG. 10B 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 has, for example, four secondary batteries with a voltage of 3.5V or more and 4.7V or less as a cell unit, and a maximum voltage of 170V with 48 cells connected in series. Since it has the same functions as FIG. 10A except for the number of secondary batteries constituting the secondary battery module of the battery pack 2201 being different, the description is omitted.

[0257] FIG. 10C shows a large transport vehicle 2003 having a motor controlled electrically as an example. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V by connecting more than a hundred secondary batteries, for example, with voltages of 3.5V or more and 4.7V or less, in series. Therefore, secondary batteries with small characteristic variations are required. By using the method for manufacturing a secondary battery shown in Embodiment 1, a secondary battery having stable battery characteristics can be manufactured, and mass production at low cost is possible from the viewpoint of yield. Also, since it has the same functions as FIG. 10A except for the number of secondary batteries constituting the secondary battery module of the battery pack 2202 and the like, the description thereof is omitted.

[0258] FIG. 10D shows an aircraft 2004 having an engine that burns fuel as an example. Since the aircraft 2004 shown in FIG. 10D has wheels for takeoff and landing, it can also be said to be a part of a transport vehicle. It has a battery pack 2203 including a secondary battery module configured by connecting a plurality of secondary batteries and a charge control device.

[0259] The secondary battery module of the aircraft 2004 has a maximum voltage of 32V by connecting eight secondary batteries with a voltage of 4V in series. Since it has the same functions as FIG. 10A except for the number of secondary batteries constituting the secondary battery module of the battery pack 2203 and the like, the description thereof is omitted.

[0260] This embodiment can be used in appropriate combination with other embodiments.

[0261] (Embodiment 5) In this embodiment, an example of mounting a secondary battery, which is an aspect of the present invention, on a building will be described with reference to FIGS. 11A and 11B.

[0262] The house shown in Fig. 11A has a power storage device 2612 having a secondary battery with stable battery characteristics by using the method for manufacturing a secondary battery shown in Embodiment 1, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611 and the like. Also, the power storage device 2612 and a ground-mounted charging device 2604 may be electrically connected. The electric power obtained by the solar panel 2610 can be charged to the power storage device 2612. Further, the electric power stored in the power storage device 2612 can be charged to the secondary battery of the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space on the floor can be effectively utilized. Alternatively, the power storage device 2612 may be installed on the floor.

[0263] The electric power stored in the power storage device 2612 can also supply power to other electronic devices in the house. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, by using the power storage device 2612 as an uninterruptible power supply, the electronic devices can be used.

[0264] Fig. 11B shows an example of a power storage device 700 according to an aspect of the present invention. As shown in Fig. 11B, a large power storage device 791 obtained by the method for manufacturing a secondary battery shown in Embodiment 1 is installed in the underfloor space 796 of a building 799.

[0265] 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 referred to as a control device), a display 706, and a router 709 by wiring.

[0266] Electric power is sent from a commercial power source 701 to the distribution board 703 via a lead-in wire attachment part 710. Also, electric power is sent to the distribution board 703 from the power storage device 791 and the commercial power source 701, and the distribution board 703 supplies the sent electric power to a general load 707 and a power storage system load 708 via an outlet (not shown).

[0267] The general load 707 is an electrical device such as a television or a personal computer, and the power storage system load 708 is an electrical device such as a microwave oven, a refrigerator, or an air conditioner.

[0268] The power storage controller 705 includes 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 system load 708 during one day (for example, from 0:00 to 24:00). Further, the measurement unit 711 may 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 supply 701. Further, 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 system load 708 during the next day based on the amount of power consumed by the general load 707 and the power storage system load 708 during one day. Further, the planning unit 713 has a function of making a charge / discharge plan for the power storage device 791 based on the amount of power demand predicted by the prediction unit 712.

[0269] The amount of power consumed by the general load 707 and the power storage system load 708 measured by the measurement unit 711 can be confirmed by the display 706. Also, it can be confirmed in an electrical device such as a television or a personal computer via the router 709. Further, it can also be confirmed by a portable electronic terminal such as a smartphone or a tablet via the router 709. Also, the amount of power demand for each time period (or every hour) predicted by the prediction unit 712 can be confirmed by the display 706, the electrical device, and the portable electronic terminal.

[0270] This embodiment can be used in appropriate combination with other embodiments.

[0271] (Embodiment 6) The personal computer 2800 shown in FIG. 12A includes a housing 2801, a housing 2802, a display unit 2803, a keyboard 2804, a pointing device 2805, and the like. A secondary battery 2806 is provided inside the housing 2801, and a secondary battery 2807 is provided inside the housing 2802. A touch panel is applied to the display unit 2803. As shown in FIG. 12B, the personal computer 2800 can be used as a tablet terminal with only the housing 2802 by removing the housing 2801 and the housing 2802.

[0272] The large secondary battery obtained by the method for manufacturing a secondary battery shown in Embodiment 1 can be applied to the secondary battery 2807. The secondary battery obtained by the method for manufacturing a secondary battery shown in Embodiment 1 can increase the capacity of the secondary battery and extend the usage time of the personal computer 2800. In addition, the personal computer 2800 can be made lighter.

[0273] A flexible display is applied to the display unit 2803 of the housing 2802. A large secondary battery obtained by the method for manufacturing a secondary battery shown in Embodiment 1 is applied to the secondary battery 2807. In the large secondary battery obtained by the method for manufacturing a secondary battery shown in Embodiment 1, by using a film having flexibility for the exterior body, a secondary battery that can be bent can be obtained. Thereby, as shown in FIG. 12C, the housing 2802 can be bent and used. At this time, as shown in FIG. 12C, a part of the display unit 2803 can also be used as a keyboard.

[0274] Also, as shown in FIG. 12D, the housing 2802 can be folded so that the display unit 2803 is on the inside, or as shown in FIG. 12E, the housing 2802 can be folded so that the display unit 2803 is on the outside.

[0275] This embodiment can be used in appropriate combination with other embodiments.

[0276] (Supplementary Note Regarding the Description in this Specification, etc.) In addition, in this specification and the like, crystal planes and directions are indicated by Miller indices. In crystallography, the notations for crystal planes and directions have a bar above the numbers. However, in this specification and the like, due to the constraints of the application notation, instead of putting a bar above the numbers, a -(minus sign) may be attached before the numbers for expression. Also, individual orientations indicating directions within a crystal are represented by [ ], set orientations indicating all equivalent directions are represented by < >, individual planes indicating crystal planes are represented by ( ), and set planes having equivalent symmetries are represented by {}, respectively.

[0277] In this specification and the like, segregation refers to a phenomenon in a solid composed of a plurality of elements (for example, A, B, C) where a certain element (for example, B) is spatially non-uniformly distributed.

[0278] In this specification and the like, the surface layer part of particles such as active materials is preferably a region within 50 nm, more preferably within 35 nm, and even more preferably within 20 nm from the surface. A surface generated by a crack or a fissure may also be referred to as the surface. Also, a region deeper than the surface layer part is referred to as the interior.

[0279] In this specification and the like, 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 the transition metal and lithium are regularly arranged to form a two-dimensional plane, so that two-dimensional diffusion of lithium is possible. Note that there may be defects such as deficiencies of cations or anions. Also, strictly speaking, the layered rock salt-type crystal structure may be a structure in which the lattice of the rock salt-type crystal is distorted.

[0280] In addition, in this specification and the like, the rock salt-type crystal structure refers to a structure in which cations and anions are alternately arranged. Note that there may be deficiencies of cations or anions.

[0281] The approximate alignment of the crystal orientations of the two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction (XRD), electron beam diffraction, neutron beam diffraction, etc. can also be used as materials for determination. In TEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientations of the cubic close-packed structures in the layered rock salt-type crystal and the rock salt-type crystal are aligned, it can be observed that the angle formed by the repetition of bright and dark lines between the crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that in TEM images, etc., light elements such as oxygen and fluorine may not be clearly observable. In such cases, the alignment can be determined based on the arrangement of metal elements.

[0282] Also, in this specification, etc., the theoretical capacity of the positive electrode active material refers to the amount of electricity when all the insertable and removable lithium in the positive electrode active material has been removed. 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.

[0283] Also, in this specification, etc., the state of charge when all the insertable and removable lithium has been inserted is defined as 0, and the state of charge when all the insertable and removable lithium in the positive electrode active material has been removed is defined as 1.

[0284] Also, in this specification, etc., charging refers to moving lithium ions from the positive electrode to the negative electrode in the battery and moving electrons from the positive electrode to the negative electrode in the external circuit. For the positive electrode active material, removing lithium ions is called charging. Also, a positive electrode active material with a state of charge of 0.7 or more and 0.9 or less may be called a positively charged electrode active material charged at a high voltage.

[0285] Similarly, discharging means moving lithium ions from the negative electrode to the positive electrode in the battery and moving electrons from the negative electrode to the positive electrode in the external circuit. With respect to the positive electrode active material, inserting lithium ions is called discharging. Also, a positive electrode active material with a state of charge (SOC) of 0.06 or less, or a positive electrode active material that has been discharged by 90% or more of its capacity from a state of being charged at a high voltage, shall be referred to as a fully discharged positive electrode active material.

[0286] Also, in this specification and the like, non-equilibrium phase change shall refer to a phenomenon that causes a non-linear change in a physical quantity. For example, non-equilibrium phase changes occur before and after the peak in the dQ / dV curve obtained by differentiating the capacitance (Q) with respect to the voltage (V) (dQ / dV), and it is considered that the crystal structure changes significantly.

[0287] A secondary battery has, for example, a positive electrode and a negative electrode. As a material constituting the positive electrode, there is a positive electrode active material. The positive electrode active material is, for example, a material that undergoes a reaction contributing to the charge and discharge capacity. Note that the positive electrode active material may include, in part, a material that does not contribute to the charge and discharge capacity.

Explanation of Reference Signs

[0288] 500: Secondary battery, 501: Positive current collector, 502: Positive electrode active material layer, 503: Positive electrode, 504: Negative current collector, 505: Negative electrode active material layer, 506: Negative electrode, 507: Separator, 509: Outer package, 510: Positive electrode lead electrode, 511: Negative electrode lead electrode, 513: Seal area, 514: Nozzle, 515a, 515b, 515c: Electrolyte, 700: Power storage device, 701: Commercial power supply, 703: Distribution board, 705: Power storage controller, 706: Display, 707: General load, 708: Power storage system load, 709: Router, 710: Lead wire attachment part, 711: Measuring part, 712: Prediction part, 713: Planning part, 790: Control device, 791: Power storage device, 796: Underfloor space part, 799: Building, 1300: Square secondary battery, 1301a: Battery, 1301b: Battery, 1302: Battery controller, 1303: Motor controller, 1304: Motor, 1305: Gear, 1306: DC / DC circuit, 1307: Electric power steering, 1308: Heater, 1309: Defroster, 1310: DC / DC circuit, 1311: Battery, 1312: Inverter, 1313: Audio, 1314: Power window, 1315: Lamps, 1316: Tires, 1317: Rear motor, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1325: External terminal, 1326: External terminal, 1413: Fixing part, 1414: Fixing part, 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 part, 2804: Keyboard, 2805: Pointing device, 2806: Secondary battery, 2807: Secondary battery

Claims

1. A plurality of laminates are arranged on an exterior film, an electrolyte is dropped onto the laminate, after sealing under reduced pressure, the exterior film is cut to separately produce secondary batteries, which is a method for manufacturing secondary batteries. The laminate is at least two of a positive electrode, a separator, and a negative electrode in a method for manufacturing secondary batteries.

2. In Claim 1, the laminate is housed so as to be wrapped by the exterior film in a method for manufacturing secondary batteries.

3. In Claim 1 or Claim 2, the electrolyte contains fluorine in a method for manufacturing secondary batteries.

4. In any one of Claims 1 to 3, the electrolyte contains an ionic liquid in a method for manufacturing secondary batteries.

5. A positive electrode is disposed on a first exterior film, a first electrolyte is dropped onto the positive electrode, a separator is disposed on the positive electrode, a second electrolyte is dropped onto the separator, a negative electrode is disposed on the separator, a third electrolyte is dropped onto the negative electrode, the laminate of the positive electrode, the separator, and the negative electrode is disposed under reduced pressure, and the laminate is sandwiched and sealed using the first exterior film and a second exterior film in a method for manufacturing secondary batteries.

6. In any one of Claims 1 to 5, one or more of the positive electrode or the negative electrode contain graphene in a method for manufacturing secondary batteries.

7. In any one of Claims 1 to 6, the positive electrode has a positive electrode active material layer on one or both surfaces of a positive electrode current collector in a method for manufacturing secondary batteries.

8. The manufacturing method of a secondary battery according to any one of claims 1 to 7, wherein the negative electrode has a negative electrode active material layer on one surface or both surfaces of a negative electrode current collector.

Images