Lithium-ion secondary battery, electric vehicle

Abstract

To reduce graphene oxide with high reaction efficiency under mild conditions to improve cycle characteristics and rate characteristics of a storage battery in manufacturing of an electrode for a storage battery containing graphene as a conductive agent.SOLUTION: A method for manufacturing an electrode for a storage battery includes producing a paste containing an active material, a binder, graphene oxide, and a solvent, applying the paste to a current collector, evaporating the solvent contained in the paste to form an active material layer, immersing the active material layer in a liquid containing alcohol, taking out the active material layer from the liquid, and reducing graphene oxide by heating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One aspect of the present invention relates to an electrode for a storage battery, a manufacturing method thereof, a storage battery, and an electronic device. .

[0002] Note that one embodiment of the present invention is not limited to the above technical field. One aspect of the present invention relates to a process, a machine, a method of manufacture, or a method of manufacture. It is related to the fact or composition of matter. More specifically, the technical field of one embodiment of the present invention disclosed in this specification is a semiconductor device, a display device, A device, a light-emitting device, a power storage device, a storage device, a driving method thereof, or a manufacturing method thereof is one example. It can be mentioned as follows. [Background technology]

[0003] In recent years, mobile phones, smartphones, electronic book terminals (e-books), portable game consoles, and other mobile devices have With the rapid spread of portable electronic devices, there is a demand for smaller and larger capacity secondary batteries, which are the driving power source for these devices. There is a growing demand for lithium-ion batteries with high energy density and high thermal conductivity as secondary batteries for portable electronic devices. Non-aqueous secondary batteries, such as lithium-ion secondary batteries, have become popular due to their large capacity. It is being utilized.

[0004] Lithium-ion secondary batteries have been widely adopted due to their high energy density among non-aqueous secondary batteries. Lithium-ion secondary batteries are made of lithium cobalt oxide (LiCoO2) and lithium The positive electrode contains an active material such as lithium iron phosphate (LiFePO4), and the negative electrode contains a material that stores lithium ions. The negative electrode contains an active material such as graphite that can release carbon dioxide, and the negative electrode contains ethylene carbonate or diethyl carbonate. Dissolve an electrolyte composed of a lithium salt such as LiBF4 or LiPF6 in an organic solvent such as toluene It is composed of a non-aqueous electrolyte or the like. Charging and discharging of the lithium ion secondary battery is carried out in the secondary battery Lithium ions move between the positive electrode and the negative electrode through the non-aqueous electrolyte, and lithium ions are inserted into and desorbed from the active materials of the positive electrode and the negative electrode This is done by doing so.

[0005] In the positive electrode or the negative electrode, in order to bind the active material to the active material and the active material layer to the current collector, a binder (also referred to as a binder) is mixed in. Since the binder is generally a polymer organic compound such as insulating polyvinylidene fluoride (PVdF), its electrical conductivity is extremely low. Therefore, if the ratio of the binder is increased with respect to the amount of the active material, the ratio of the amount of the active material in the electrode relatively decreases As a result, the discharge capacity of the secondary battery decreases. Therefore, by mixing a conductive aid such as acetylene black (AB) or graphite (carbon) particles, the electrical conductivity between the active materials or between the active material layer and the current collector is improved. This enables the provision of an active material layer with high electrical conductivity (see Patent Document 1).

[0006] Therefore, electrodes containing graphene as a conductive aid have been developed. Patent Document 2 discloses a method for manufacturing an electrode having a step of reducing GO (also abbreviated as Graphene Oxide) after mixing GO, an active material, and a binder. By this manufacturing method, it is possible to provide an active material layer having high electrical conductivity with a small amount of conductive aid.

[0007] In addition, electrodes containing graphene as a conductive aid have been developed. Patent Document 2 discloses a method for manufacturing an electrode having a step of reducing GO (also abbreviated as Graphene Oxide) after mixing GO, an active material, and a binder. Rough graphene (also referred to as GO (abbreviation of Graphene Oxide)), an active material, and After mixing the binder, a method for manufacturing an electrode having a step of reducing GO is disclosed. By this manufacturing method, it is possible to provide an active material layer having high electrical conductivity with a small amount of conductive aid.

Prior Art Documents

Patent Documents

[0008] ​​​​ Patent Document 1 Japanese Patent Application Laid-Open No. 2002-110162 Patent Document 2 Japanese Patent Application Laid-Open No. 2014-7141 Summary of the Invention Problems to be Solved by the Invention

[0009] In order to improve the performance of a storage battery having an electrode containing graphene as a conductive assistant, there is a demand for the development of a method for manufacturing an electrode capable of sufficiently reducing graphene oxide.

[0010] Therefore, one aspect of the present invention aims to increase the reaction efficiency of the reaction for reducing graphene oxide. Another aspect of the present invention aims to provide a method for manufacturing an electrode for a storage battery with a small internal resistance.

[0011] Another aspect of the present invention aims to reduce graphene oxide under mild reaction conditions. Another aspect of the present invention aims to reduce damage to the active material layer due to the reduction reaction.

[0012] Another aspect of the present invention aims to increase the discharge capacity of the storage battery. Another aspect of the present invention aims to improve the cycle characteristics of the storage battery. Another aspect of the present invention aims to improve the rate characteristics of the storage battery.

[0013] Or, one aspect of the present invention aims to provide a novel electrode, a novel method for manufacturing an electrode, or a novel power storage device, etc. Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention solves all of these problems. ​​​​​​​It is not necessary. Also, in one aspect of the present invention, it is intended to solve at least one of the above problems. . Other problems among these will become clear on their own from the descriptions in the specification, drawings, claims, etc. It is possible to extract other problems among these from the descriptions in the specification, drawings, claims, etc. .

Means for Solving the Problems

[0014] One aspect of the present invention is a method for manufacturing an electrode for a storage battery, which includes preparing a paste having an active material, a binder, graphene oxide, and a solvent, applying the paste to a current collector, evaporating the solvent contained in the paste to form an active material layer, impregnating the active material layer with a liquid containing alcohol, taking out the active material layer from the liquid, and heating it. Or, one aspect of the present invention is a method for manufacturing an electrode for a storage battery, which includes preparing a paste having an active material, a binder, graphene oxide, a conductive auxiliary agent, and a solvent, applying the paste to a current collector, evaporating the solvent contained in the paste to form an active material layer, impregnating the active material layer with a liquid containing alcohol, taking out the active material layer from the liquid, and heating it. Or, one aspect of the present invention is a method for manufacturing an electrode for a storage battery, which includes preparing a paste having an active material, a binder, graphene oxide, a conductive auxiliary agent, and a solvent, applying the paste to a current collector, evaporating the solvent contained in the paste to form an active material layer, impregnating the active material layer with a liquid containing alcohol, taking out the active material layer from the liquid, and heating it.

[0015] Also, in one aspect of the present invention, in each of the above configurations, the alcohol is preferably methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol.

[0016] Also, one aspect of the present invention is an electrode for a storage battery having a current collector and an active material layer, wherein the active material layer is in contact with the current collector, and the active material layer has an active material, a binder, graphene, and a second conductive auxiliary agent.

[0017] ​ It is an electrode.

[0018] Also, one aspect of the present invention has a first electrode and a second electrode, and the first electrode is an electrode for a storage battery having the above structure. The first electrode can function as either a positive electrode or a negative electrode, and the second electrode is a storage battery having a function that can function as the other of the positive electrode or the negative electrode.

[0019] Also, one aspect of the present invention is an electronic device characterized by mounting the storage battery having the above structure, a display panel, operation keys, a speaker, and a microphone.

Advantages of the Invention

[0020] According to one aspect of the present invention, the reaction efficiency of the reaction for reducing graphene oxide can be increased. Also, according to one aspect of the present invention, a method for manufacturing an electrode for a storage battery with a small internal resistance can be provided.

[0021] Also, according to one aspect of the present invention, graphene oxide can be reduced under mild reaction conditions. Also, according to one aspect of the present invention, damage to the active material layer due to the reduction reaction can be reduced.

[0022] Also, according to one aspect of the present invention, the cycle characteristics of the storage battery can be improved. Also, according to one aspect of the present invention, the rate characteristics of the storage battery can be improved.

[0023] Also, according to one aspect of the present invention, a novel electrode, a method for manufacturing a novel electrode, or a novel storage device can be provided. Note that the description of these effects does not prevent the existence of other effects. Note that one aspect of the present invention does not necessarily have all of these effects. Oh, other effects will be obvious from the descriptions in the specification, drawings, claims, etc. Therefore, it is possible to extract other effects from the descriptions in the specification, drawings, claims, etc.

Brief Description of Drawings

[0024]

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Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments will be described with reference to the drawings. However, the embodiments can be implemented in many different ways, and it is easily understood by those skilled in the art that the form and details can be variously changed without departing from the spirit and its scope. Therefore, the present invention is not construed as being limited to the description of the following embodiments.

[0026] In the configuration of the invention described below, the same part or the part having the same function is commonly used with the same reference numeral among different drawings, and the repeated description thereof is omitted. Also, when referring to the same function, the hatch pattern may be the same and may not be particularly labeled.

[0027] In each drawing described in this specification, the size of each component such as the thickness and area of the film, layer, substrate, etc. may be exaggerated for the sake of clarity of the description. Therefore, not necessarily each component is limited to its size, nor is it limited to the relative size between each component. ​

[0028] In addition, in this specification and the like, ordinal numbers such as first and second are used for convenience and do not indicate the order of processes or the order of lamination. Therefore, for example, " the first" can be appropriately replaced with " the second" or " the third" and so on for explanation. Also, the ordinal numbers described in this specification

[0029] (Embodiment 1) In this embodiment, an electrode for a storage battery according to an aspect of the present invention will be described with reference to FIGS. 2 and 3 FIG. 2(A) shows a perspective view of the electrode, FIG. 2(B) shows a plan view of the active material layer, and FIGS. 2(C) and 3 show a longitudinal sectional view of the active material layer.

[0030] FIG. 2(A) is a perspective view of the electrode 200. In FIG. 2(A), the electrode 200 is shown in a rectangular sheet shape, but the shape of the electrode 200 is not limited to this, and any shape can be appropriately selected . In FIG. 2(A), the active material layer 202 is formed only on one surface of the current collector 201 , but the active material layer 202 may be formed on both surfaces of the current collector 201. Also, the active material layer 20 2 does not need to be formed on the entire surface of the current collector 201, and a non-coated area such as an area for connecting to a tab is appropriately provided .

[0031] For the current collector 201, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, etc , and alloys thereof, which have high conductivity and do not alloy with carrier ions such as lithium , can be used. Also, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molyb denum to improve heat resistance can be used Alternatively, it may be formed of a metal element that reacts with silicon to form a silicide. Silicon Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium , vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nick el, etc. The current collector 201 can be appropriately used in a shape such as foil, plate (sheet), net, punching metal , expanded metal, etc. The current collector 201 preferably has a thickness of 10 μm or more and 30 μm or less. An undercoat layer may be provided on the surface of the current collector 201 using graphene or the like.

[0032] FIGS. 2(B) and 2(C) are schematic diagrams showing the top surface and the longitudinal cross-section of the active material layer 202, respectively . The active material layer 202 includes graphene 204 as a conductive aid, granular active material 203 , and a binder (also referred to as a binder. Not shown). The active material layer 202 may have a conductive aid other than graphene (also referred to as a second conductive aid. Not shown).

[0033] As shown in the top view of the active material layer 202 shown in FIG. 2(B), a plurality of granular active materials 203 are covered by a plurality of graphene 204. A single sheet-like graphene 204 is connected to a plurality of granular active materials 203. In particular, since graphene 204 is sheet-like, it can make surface contact so as to wrap a part of the surface of the granular active material 203. Different from granular conductive aids such as acetylene black that make point contact with the active material, graphene 204 enables low-contact-resistance surface contact. Therefore, without increasing the amount of the conductive aid, the electrical conductivity between the granular active material 203 and graphene 204 can be improved.

[0034] In addition, the multiple graphene sheets 204 are in surface contact with each other. This is because graphene oxide with extremely high dispersibility in a polar solvent is used in the formation of the graphene 204. By volatilizing and removing the solvent from the dispersion containing uniformly dispersed graphene oxide and reducing the graphene oxide to form graphene, the graphene 204 remaining in the active material layer 202 partially overlaps and is dispersed to such an extent that they are in surface contact with each other, thereby forming an electrical conduction path. In the top view of the active material layer 202 shown in Fig. 2(B), the graphene 204 does not necessarily overlap with other graphene only on the surface of the active material layer 202. A part of the graphene 204 is provided between the active material layers 202. Also, since the graphene 204 is an extremely thin film (sheet) composed of a single layer or a stack of carbon molecules, a part of its surface covers and contacts the surface of the individual granular active materials 203 as if tracing it, and the part not in contact with the active material 203 bends, forms wrinkles, or is stretched and taut between the multiple granular active materials 203. In the longitudinal cross-section of the active material layer 202, as shown in Fig. 2(C), sheet-like graphene 204 is dispersed approximately uniformly inside the active material layer 202. In Fig. 2(C), the graphene 204 is schematically represented by a thick line, but in reality, it is a thin film having a thickness of a single layer or multiple layers of carbon molecules. Similar to the description of the top surface of the active material layer 202, since the multiple graphene sheets 204 are formed so as to wrap or cover the multiple granular active materials 203, they are in surface contact with each other. Also, by being in surface contact with each other, the multiple graphene sheets 204 form an electrical conduction path.

[0035]

[0036] The graphene 204 forms an electrical conduction network. Further, FIG. 2(C) is enlarged in a schematic view shown in FIG. 3. The graphene 204 coats the surfaces of a plurality of granular active materials 203 and the graphene 204s also contact each other to form a network.

[0037] As shown in FIGS. 2(B), 2(C) and 3, the plurality of sheet-like graphenes 204 are three-dimensionally dispersed inside the active material layer 202, and they are in surface contact with each other to form a three-dimensional electrical conduction network. Further,

[0038] each graphene 204 coats the plurality of granular active materials 203 and is in surface contact with them.

[0039] In this specification, the graphene includes single-layer graphene or multi-layer graphene of 2 layers or more and 100 layers or less. The single-layer graphene refers to a sheet of a one-atom layer carbon molecule having π bonds. Further, the graphene oxide refers to a compound in which the above graphene is oxidized. When reducing the graphene oxide to form graphene, not all of the oxygen contained in the graphene oxide needs to be desorbed, and some oxygen may remain in the graphene. By the manufacturing is 1 atomic % or more and 20 atomic % or less, preferably 3 atomic % or more and 10 atomic % or less of the entire graphene. As described above, the plurality of sheet-like graphenes 204 are three-dimensionally dispersed inside the active material layer 202, and by contacting each other in a face-to-face manner, they form a three-dimensional electrical conductivity network. Therefore, by reducing graphene oxide with high reaction efficiency, the internal resistance of the active material layer 202 and the electrode 200 can be reduced. As a result, in a storage battery using the electrode 200, the rate characteristics can be improved. Graphene oxide can be produced using an oxidation method called the Hummers method. The Hummers method adds a sulfuric acid solution of potassium permanganate, hydrogen peroxide water, etc. to graphite powder and causes an oxidation reaction to produce a mixed solution containing graphite oxide. Functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups are bonded to the carbon of the graphite oxide. For this reason, the interlayer distance of the plurality of graphene is longer compared to graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. Graphene oxide may also be formed by appropriately adjusting the amount of an oxidizing agent such as potassium permanganate. For example, by increasing the amount of the oxidizing agent with respect to the graphite powder, graphene oxide is obtained. As described above, the plurality of sheet-like graphenes 204 are three-dimensionally dispersed inside the active material layer 202, and by contacting each other in a face-to-face manner, they form a three-dimensional electrical conductivity network. Therefore, by reducing graphene oxide with high reaction efficiency, the internal resistance of the active material layer 202 and the electrode 200 can be reduced. As a result, in a storage battery using the electrode 200, the rate characteristics can be improved.

[0040] Graphene oxide can be produced using an oxidation method called the Hummers method. The Hummers method adds a sulfuric acid solution of potassium permanganate, hydrogen peroxide water, etc. to graphite powder and causes an oxidation reaction to produce a mixed solution containing graphite oxide. Functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups are bonded to the carbon of the graphite oxide. For this reason, the interlayer distance of the plurality of graphene is longer compared to graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained. The carbon of the graphite oxide has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups bonded thereto. Therefore, the interlayer distance of the plurality of graphene is longer than that of graphite, and it becomes easier to form thin flakes by separating the layers. Next, by applying ultrasonic vibration to the mixed solution containing graphite oxide, the graphite oxide with a long interlayer distance is cleaved, separating the graphene oxide and producing a mixed solution containing graphene oxide. Then, by removing the solvent from the mixed solution containing graphene oxide, powdery graphene oxide can be obtained.

[0041] Graphene oxide may also be formed by appropriately adjusting the amount of an oxidizing agent such as potassium permanganate. For example, by increasing the amount of the oxidizing agent with respect to the graphite powder, graphene oxide is obtained. ​The oxidation degree of graphene (the atomic number ratio of oxygen to carbon) can be increased. Therefore, when manufacturing the amount of the oxidizing agent relative to the graphite powder used as the raw material may be determined according to the amount of the produced graphene oxide.

[0042] Note that the production of graphene oxide is not limited to the Hummers method using a sulfuric acid solution of potassium permanganate. For example, the Humm ers method using nitric acid, potassium chlorate, sodium nitrate, etc., or a method for producing graphene oxide other than the Hummers method may be appropriately used.

[0043] In addition, the thinning of the oxidized graphite may be performed by adding ultrasonic vibration, irradiating with microwaves or radio waves, or irradiating with thermal plasma, or applying physical stress.

[0044] The produced graphene oxide has epoxy groups, carbonyl groups, carboxyl groups, hydroxyl groups, etc. In a polar solvent typified by NMP (also referred to as N-methylpyrrolidone, 1-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone, etc.), since the oxygen of the functional group is negatively charged, while interacting with the polar solvent, different graphene oxides repel each other and are less likely to aggregate. Therefore, in a polar solvent, graphene oxide is likely to be uniformly dispersed.

[0045] In addition, the length of one side of the graphene oxide (also referred to as the flake size) is 50 nm or more and 100 μm or less, preferably 800 nm or more and 20 μm or less. By adjusting the flake size of the graphene oxide, the flake size of the graphene in the active material layer can be controlled. When the flake size of the graphene is smaller than the average particle size of the granular active material 203, complex It becomes difficult to achieve surface contact with the active material 203 in terms of quantity, and it also becomes difficult to connect the graphene to each other, making it difficult to improve the electrical conductivity of the active material layer 202.

[0046] The binder constructs a network in the active material layer 202 and binds the active material 203 to the active material 203, the active material 203 to the graphene 204, the graphene 204 to the graphene 204 , and the active material layer 202 to the current collector 201. When manufactured using the method for manufacturing an electrode described in Embodiment 2, the network constructed by the binder can be made stronger. Therefore, the binding between the active material 203 and the active material 203, the active material 203 and the graphene 204, the graphene 204 and the graphene 204, and the active material layer 202 and the current collector 201 can be made stronger.

[0047] When the electrode 200 is immersed in an electrolytic solution and charged and discharged repeatedly, the binder may absorb the electrolytic solution and expand. As a result, the entire active material layer 202 may expand or deform. These phenomena become prominent when the network of the binder in the active material layer 202 has been damaged during the manufacturing process of the electrode. As described above, sheet-like graphene 204 is three-dimensionally dispersed inside the active material layer 202, and these form a three-dimensional electrically conductive network by making surface contact with each other. Also, each graphene 204 covers a plurality of granular active materials 203 and makes surface contact. In such an active material layer 202, when expansion or deformation occurs, the plurality of graphene 204 that were in contact, or the graphene 204 and the active material 203 that were in contact will peel off, separate, or have a reduced contact area. There is a possibility of becoming so. Also, graphene 204 or the active material 203 may crack or break. Due to these factors, a part of the three-dimensional electrically conductive network formed in the active material layer 202 is disconnected, and when the performance of the electrode 200 deteriorates, problems such as a decrease in the discharge capacity of the battery or a decrease in potential occur due to repeated charge and discharge.

[0048] On the other hand, in the active material layer 202 of the electrode 200, which is one aspect of the present invention, as described above, a network of a strong binder is constructed. Therefore, even if the binder absorbs the electrolytic solution and swells, the entire active material layer 202 is difficult to expand or deform. Therefore, even when the electrode 200 is immersed in the electrolytic solution and the charge and discharge of the battery are repeated, in the active material layer 202, a plurality of graphenes 2 04, and the contacting graphene 204 and active material 203 are difficult to peel off, difficult to separate, or difficult to reduce the contact area. Also, graphene 204 and the active material 203 are difficult to crack or break. Therefore, the three-dimensional electrically conductive network is difficult to be disconnected, and the performance of the electrode 200 is difficult to deteriorate. Therefore, a battery using the electrode 200 is difficult to reduce the discharge capacity and difficult to reduce the potential even when charge and discharge are repeated. That is, the cycle characteristics of the storage battery can be improved.

[0049] As the binder, in addition to typical polyvinylidene fluoride (PVdF), polyimide, polytetra fluoroethylene, polyvinyl chloride, ethylene propylene diene polymer, styrene -butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate , polymethyl methacrylate, polyethylene, nitrocellulose, etc. can be used.

[0050] The active material 203 is a granular active material composed of secondary particles having an average particle size and a particle size distribution, which are obtained by mixing raw material compounds in a predetermined ratio, firing the mixture, and then crushing, granulating, and classifying it. Therefore, in FIGS. 2(B) and 2(C), the active material 203 is schematically shown as a sphere, but it is not limited to this shape.

[0051] When the electrode 200 is used as the positive electrode of the storage battery, as the active material 203, a material capable of inserting and extracting lithium ions can be used. For example, a lithium manganese composite oxide having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure can be used. Examples thereof include lithium manganese composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure.

[0052] Examples of the lithium-containing composite phosphate having an olivine-type structure include, for example, the general formula LiMPO4 (M is one or more of Fe(II), Mn(II), Co(II), Ni(II)). Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, LiCoP O4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is 1 or less, 0 < a < 1, 0 < b < 1), LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO 4, LiNi c Co d Mne PO4(c+d+e is less than 1, 0 <c<1、0<d<1、0 <e<1)、LiFe f Ni g Co h Mn i PO4(f+g+h+i is less than 1, 0 <f< 1, 0 <g<1、0<h<1、0<i<1)等が挙げられる。

[0053] In particular, LiFePO4 has the following features: safety, stability, high capacity density, high potential, and low initial oxidation (charging). It satisfies the requirements for an active material in a well-balanced manner, including the presence of lithium ions that can pass through. Therefore, it is preferable.

[0054] Examples of lithium-containing composite silicates having a layered rock salt type crystal structure include LiCoO 2, LiNiO2, LiMnO2, Li2MnO3, LiNi 0.8 Co 0.2 O2 etc. NiCo system (general formula: LiNi x Co 1-x O2(0 <x<1))、LiNi 0.5 M n 0.5 O2, etc. NiMn system (general formula: LiNi x Mn 1-x O2(0 <x<1))、 LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, etc. NiMnCo system (also called NMC. General formula LiNi x Mn y Co 1-x-y O2(x>0, y>0, x+y<1) Furthermore, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li2MnO3-Li Other examples include MO2 (M=Co, Ni, Mn).

[0055] In particular, LiCoO₂ is preferable because it has advantages such as a large capacity, being more stable in the atmosphere compared to LiNiO₂, and being thermally more stable than Li NiO₂.

[0056] Examples of lithium manganese composite oxides having a spinel-type crystal structure include, for example, LiMn ₂O₄, Li 1+x Mn 2-x O₄ (0 < x < 2), LiMn 2-x Al x O₄ (0 < x < 2), LiMn 1.5 Ni 0.5 O₄ and the like.

[0057] Mixing a small amount of lithium nickelate (LiNiO₂, LiNi M 1-x M x O₂ (0 < x < 1) (M = C o, Al, etc.)) with a lithium manganese composite oxide having a spinel-type crystal structure such as LiMn₂O₄ has advantages such as suppressing the elution of manganese and suppressing the decomposition of the electrolyte, and is preferable.

[0058] Also, as the positive electrode active material, a composite oxide represented by the general formula Li (2-j) MSiO₄ (M is one or more of Fe(II), Mn (II), Co(II), Ni(II), and j is 0 or more and 2 or less) can be used. Representative examples of the general formula Li MSiO₄ include Li (2-j) MSiO₄, Li ( 2-j) FeSiO₄, Li (2-j) NiSiO₄, Li (2-j) CoSiO₄, L i (2-j) MnSiO₄, Li (2-j) Fe k Ni l SiO₄, Li (2-j) Fe k Co l SiO₄, Li (2-j)Fe k Mn l SiO4, Li (2-j) Ni k Co l SiO4, Li (2-j) Ni k Mn l SiO4 (k + l is 1 or less, 0 < k < 1, 0 < l <1), Li (2-j) Fe m Ni n Co q SiO4, Li (2-j) Fe m Ni n Mn q SiO4, Li (2-j) Ni m Co n Mn q SiO4 (m + n + q is 1 or less, 0 < m <1, 0 < n < 1, 0 < q < 1), Li (2-j) Fe r Ni s Co t Mn u SiO4( r + s + t + u is 1 or less, 0 < r < 1, 0 < s < 1, 0 < t < 1, 0 < u < 1), etc. can be mentioned among others.

[0059] Also, as the positive electrode active material, A x M2(XO4)3 (A = Li, Na, Mg, M = Fe, M n, Ti, V, Nb, Al, X = S, P, Mo, W, As, Si) represented by the general formula of the sodium silicon type compound can be used. Examples of the sodium silicon type compound include Fe2(MnO4) 3, Fe2(SO4)3, Li3Fe2(PO4)3, etc. Also, as the positive electrode active material Li2MPO4F, Li2MP2O7, Li5MO4 (M = Fe, Mn) represented by the general formula of the compound, perovskite type fluoride such as FeF3, metal chalcogenide (sulfide, selenide, telluride) such as TiS2, MoS2, etc., inverse spinel such as LiMVO4 ​ Lithium vanadium-containing composite oxides having a crystal structure of the type, vanadium oxide-based compounds ( V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. It can be used.

[0060] The particle size of the positive electrode active material is preferably, for example, 5 nm or more and 100 μm or less.

[0061] In addition, the positive electrode active material is Li x Mn y M z O w Lithium manganese complex represented by An oxide may also be used. Here, the element M is selected from among elements other than lithium and manganese. It is preferable to use a metal element, silicon, or phosphorus, and more preferably nickel. Also, x / (y+z) is 0 or more and less than 2, z is greater than 0, and (y+z) / w It is preferable that the ratio is 0.26 or more and less than 0.5. It refers to an oxide containing at least lithium and manganese, and does not contain chromium, cobalt, aluminum, etc. nium, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, At least one element selected from the group consisting of titanium, niobium, silicon, phosphorus, etc. The lithium manganese composite oxide may have a layered rock salt type crystal structure. In addition, the lithium manganese composite oxide is preferably a layered rock salt type crystal. The lithium manganese may have a crystal structure or a spinel crystal structure. The composite oxide preferably has an average particle size of, for example, 5 nm or more and 50 μm or less.

[0062] In addition, the carrier ions are alkali metal ions other than lithium ions, and alkaline earth metal ions. In the case of the Group I ion, as the positive electrode active material, in the above lithium compound and lithium manganese composite oxide, instead of lithium, an alkali metal (for example, sodium, potassium, etc.), an alkaline earth metal (for example, calcium, strontium, barium, beryllium, magnesium, etc.) may be used.

[0063] When the electrode for a storage battery to be manufactured is used as the negative electrode of the storage battery, as the active material 203, a material capable of performing charge and discharge reactions by alloying / dealloying reactions with lithium can be used.

[0064] As a material capable of performing charge and discharge reactions by alloying / dealloying reactions with lithium, for example, carbon - based materials can be mentioned. Examples of carbon - based materials include graphite, graphitizable carbon (soft carbon), non - graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon black, etc.

[0065] Examples of graphite include artificial graphite such as mesocarbon microbeads (MCMB), coke - based artificial graphite, pitch - based artificial graphite, etc., and natural graphite such as spherical natural graphite.

[0066] Graphite shows a potential as low as that of lithium metal (0.1 V or more and 0.3 V or less vs. Li / Li ) when lithium ions are inserted into graphite (when a lithium - graphite intercalation compound is formed). + As a result, a lithium - ion secondary battery can exhibit a high operating voltage. Furthermore, graphite has advantages such as a relatively high capacity per unit volume, small volume expansion, low cost, and high safety compared to lithium metal, and is thus preferable.

[0067] ​​​​​​​Also, as a material capable of performing charge and discharge reactions through alloying and dealloying reactions with lithium there are materials containing at least one of, for example, Ga, Si, Al, Ge, Sn, Pb, Sb, Bi, Ag, Zn, Cd, I n, etc. Such elements have a larger capacity compared to carbon. In particular, silicon has a high theoretical capacity of 4200 mAh / g. Materials using such elements include, for example, Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn 3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb , SbSn, etc.

[0068] Also, as the negative electrode active material, oxides such as SiO, SnO, SnO2, titanium dioxide, lithium titanate compounds, lithium-graphite intercalation compounds, niobium pentoxide, tungsten oxide, molybdenum oxide, etc. can be used.

[0069] Also, as the negative electrode active material, Li3N-type structured Li Li 3-x M x N (M = Co, Ni, Cu), which is a complex nitride of lithium and a transition metal, can be used. For example, a lithium-ion secondary battery using Li 2.6 Co 0.4 N shows a large charge and discharge capacity (900 mAh / g, 1890 mAh / cm 3 ) and is thus preferable.

[0070] When using a complex nitride of lithium and a transition metal, since the negative electrode active material contains lithium ions, it can be preferably combined with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions as the positive electrode active material ​ By previously desorbing lithium ions contained in the positive electrode active material, a complex nitride of lithium and a transition metal can be used as the negative electrode active material.

[0071] 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 such as cobalt oxide, nickel oxide, and iron oxide that do not undergo an alloying reaction with lithium may be used as the negative electrode active material. As materials in which a conversion reaction occurs, further, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, 0.89 FeP2, and phosphides such as CoP3, and fluorides such as FeF3 and BiF3 can also be used.

[0072] The granular active material 203 preferably has an average primary particle size of 500 nm or less, preferably 50 nm or more and 500 nm or less when measured with a laser diffraction particle size distribution analyzer. In order to make surface contact with a plurality of the granular active material 203, the graphene 204 preferably has a side length of 50 nm or more and 100 μm or less, more preferably 800 nm or more and 20 μm or less.

[0073] In addition, the active material layer 202 may contain a second conductive aid. Graphene has a flaky shape and is likely to be arranged in a direction substantially parallel to the surface of the current collector 201 in the active material layer 202. When the active material layer 202 contains graphene and a second conductive aid, the three-dimensional network of electrical conduction constructed by the active material and graphene can be reinforced and made into a more complex shape. This can suppress the disconnection of the electrical conduction path in the active material layer 202 during the use of the power storage device. This can be achieved. Also, even if the thickness of the active material layer 202 is increased, the electrical conduction path can be made less likely to be disconnected.

[0074] As the second conductive aid, for example, natural graphite, artificial graphite such as mesocarbon microbeads, carbon fibers, etc. can be used. Also, metal powders such as copper, nickel, aluminum, silver, gold, metal fibers, conductive ceramic materials, etc. can be used.

[0075] As the carbon fibers, for example, carbon fibers such as mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers can be used. Also, as the carbon fibers, carbon nanofibers, carbon nanotubes, etc. can be used. Also, as the carbon fibers, vapor-grown carbon fibers ( VGCF:Vapor-Grown Carbon Fiber) (registered trademark) can be used. The representative values of VGCF (registered trademark) are: fiber diameter 150 nm, fiber length 10 μm or more and 20 μm or less, true density 2 g / cm 3 , specific surface area 13 m 2 / g. Note that the fiber diameter refers to , when observed with a SEM (Scanning Electron Microscope), a cross-section perpendicular to the fiber axis from an image taken two-dimensionally is taken as the cut surface, and the diameter of the true circle circumscribing this cut surface is what is meant. Also, the true density refers to the density calculated using only the volume occupied by the substance itself as the volume for density calculation. Also, the specific surface area refers to the surface area per unit mass or the surface area per unit volume of the object.

[0076] VGCF (registered trademark) having a needle-like shape has excellent electrical properties of having high conductivity and has excellent physical properties such as high mechanical strength. Therefore, by using VGCF (registered trademark) as a conductive aid, the electrical contact points and contact areas between the active materials can be increased.

[0077] In addition, a granular material can also be used as the conductive aid. Representative examples of the granular material include acetylene black with a diameter of 3 nm or more and 500 nm or less, and carbon black such as Ketjen black (registered trademark).

[0078] Flaky, needle-shaped, or fibrous conductive aids serve to connect the active materials and suppress the deterioration of the battery. In addition, these materials also function as a structure for maintaining the shape of the active material layer 202 or as a buffer material. The fact that they also function as a structure for maintaining the shape of the active material layer 202 or as a buffer material means that when the expansion and contraction of the active material are repeated or when the secondary battery is bent, peeling between the current collector and the active material is less likely to occur. In addition, instead of the above materials, carbon black such as acetylene black and Ketjen black (registered trademark) can be used, but using VGCF (registered trademark) is preferable because the strength for maintaining the shape of the active material layer 202 can be increased. When the strength for maintaining the shape of the active material layer 202 is increased, deterioration due to deformation such as bending of the secondary battery can be prevented.

[0079] The active material layer 202 shown above preferably contains 80 wt% or more and 95 wt% or less of the active material 203, 0.1 wt% or more and 8 wt% or less of graphene, and 1 w t% or more and 10 wt% or less of the binder, based on the total weight of the active material layer 202. In addition, the active material layer 202 is the first When having the second conductive aid, the total weight of graphene and the second conductive aid is preferably 0.1 wt% or more and 8 wt% or less with respect to the total weight of the active material layer 202.

[0080] As shown in this embodiment, graphene 20 4 having an average particle size larger than that of the granular active material 203 is dispersed in the active material layer 202 so as to be in surface contact with one or more other adjacent graphenes 204 and is in surface contact so as to wrap a part of the surface of the granular active material 203, thus providing a battery electrode including an active material layer with a high filling amount and high density using a small amount of a conductive aid. This can be achieved.

[0081] This embodiment can be implemented in appropriate combination with other embodiments.

[0082] (Embodiment 2) In this embodiment, a method for manufacturing an electrode 200 including an active material layer 202 using the active material, conductive aid, and binder exemplified in Embodiment 1 will be described with reference to FIG. 1.

[0083] First, a paste having an active material, a binder, graphene oxide, and a solvent is prepared (step S101). The paste may contain a second conductive aid. Hereinafter, an example of the method for preparing the paste will be shown. First, graphene oxide is dispersed in a solvent. When the weight of graphene oxide is less than 0.2 wt% with respect to the paste (the total weight of the active material, graphene oxide, and binder), the conductivity decreases when the active material layer 202 is formed. Also, when the weight of graphene oxide exceeds 16 wt%, the viscosity of the paste increases, although it depends on the particle size of the active material. Also, after applying the paste to the current collector 201, a step of evaporating the solvent contained in the paste During this process, convection occurs in the paste due to heating, and the light and thin graphene oxide moves or aggregates, which may cause the active material layer 202 to crack or the active material layer 202 to peel off from the current collector 201. Therefore, the weight of the graphene oxide is preferably 0.2 wt% or more and 16 wt% or less based on the paste. Note that since the graphene oxide is reduced by a subsequent heat treatment process to become graphene and its weight is approximately halved, the weight ratio of graphene in the active material layer 202 is 0.1 wt% or more and 8 wt% or less. When the active material layer 202 cracks or peels off from the current collector 201, it may cause problems in the performance of the battery. Therefore, it is necessary to control the weight of graphene oxide to ensure the stability of the active material layer 202. In addition, the use of a polar solvent as the solvent can improve the dispersion of graphene oxide in the paste. For example, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or a mixture of two or more of them can be used. Among them, NMP is particularly preferred because it can disperse graphene oxide well.

[0084] Next, an active material is added. The average particle size of the primary particles of the active material is preferably 50 nm or more and 500 nm or less. Using an active material with an appropriate particle size can improve the performance of the battery. Then, kneading (kneading in a high-viscosity state) is performed on these mixtures to loosen the aggregation of graphene oxide and the active material. In addition, since the oxygen of the functional group of graphene oxide is negatively charged in a polar solvent, it is difficult for different graphene oxides to aggregate with each other. Moreover, graphene oxide has a strong interaction with the active material. Therefore, graphene oxide can be more uniformly dispersed in the active material layer.

[0085] Next, an active material is added. The average particle size of the primary particles of the active material is preferably 50 nm or more and 500 nm or less. Using an active material with an appropriate particle size can improve the performance of the battery.

[0086] Next, kneading (kneading in a high-viscosity state) is performed on these mixtures to loosen the aggregation of graphene oxide and the active material. In addition, since the oxygen of the functional group of graphene oxide is negatively charged in a polar solvent, it is difficult for different graphene oxides to aggregate with each other. Moreover, graphene oxide has a strong interaction with the active material. Therefore, graphene oxide can be more uniformly dispersed in the active material layer. This can improve the performance of the battery. Finally, the mixture is formed into a desired shape to obtain the final product.

[0087] Next, a binder is added to these mixtures. The amount of the binder may be set according to the amounts of graphene oxide and the active material and may be added in an amount of 1 wt% or more and 5 wt% or less with respect to the paste . By adding the binder in a state where the graphene oxide is uniformly dispersed so as to be in surface contact with a plurality of active material particles, the active material and the graphene oxide can be bound while maintaining the dispersed state. Also, depending on the ratio of the active material and the graphene oxide, it may not be necessary to add a binder, but when a binder is added, the strength of the electrode can be improved . .

[0088] Next, a solvent is added to these mixtures and kneaded until a predetermined viscosity is obtained, whereby a paste can be produced. By producing the paste in the above steps, a paste with a uniform kneaded state of graphene oxide, the active material, and the binder can be produced .

[0089] Next, the paste is applied to one or both sides of the current collector 201 (step S102). As a method for applying the paste to the current collector , coating methods such as a roll coating method using an applicator roll, a screen printing method, a doctor blade method, a spin coating method, and a bar coating method can be applied .

[0090] Next, the solvent contained in the paste applied to the current collector 201 is evaporated to form an active material layer (step S103). The solvent is evaporated by heating at a temperature of 40°C or higher and 170°C or lower, preferably 60°C or higher and 100°C or lower for 1 minute or more and 10 hours or less. The current collector 201 may be heated together with the paste. The atmosphere is not particularly limited .

[0091] ​​In the active material layer produced by evaporating the solvent contained in the paste, the binder constructs a network structure that binds the active material and graphene oxide.

[0092] Next, the active material layer is immersed in a liquid containing alcohol (step S104). The current collector may be immersed in the liquid together with the active material layer. The temperature of the liquid is preferably equal to or higher than the melting point and equal to or lower than the boiling point of the liquid containing alcohol, and more preferably 40°C or higher and 70°C or lower. The time may be 1 minute or longer and 1 hour or shorter. The temperature of the liquid is preferably equal to or higher than the melting point and equal to or lower than the boiling point of the liquid containing alcohol, and more preferably 40°C or higher and 70°C or lower. The time may be 1 minute or longer and 1 hour or shorter. The temperature of the liquid is preferably equal to or higher than the melting point and equal to or lower than the boiling point of the liquid containing alcohol, and more preferably 40°C or higher and 70°C or lower. The time may be 1 minute or longer and 1 hour or shorter. The time may be 1 minute or longer and 1 hour or shorter.

[0093] Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol. Using an alcohol with a low boiling point is preferable because it is easy to evaporate. Also, using an alcohol with high reducibility is preferable because it facilitates the reduction of graphene oxide. Therefore, it is more preferable to use ethanol, 1-propanol, 1-butanol, or the like.

[0094] The liquid containing alcohol may contain water or a stabilizer. The liquid may also be a mixed liquid of two or more alcohols, or a mixed liquid with an organic solvent other than alcohol. The liquid containing alcohol may contain water or a stabilizer. The liquid may also be a mixed liquid of two or more alcohols, or a mixed liquid with an organic solvent other than alcohol. The liquid containing alcohol may contain water or a stabilizer. The liquid may also be a mixed liquid of two or more alcohols, or a mixed liquid with an organic solvent other than alcohol.

[0095] At this time, when the active material layer is immersed in a solution containing a reducing agent (also referred to as a reducing solution), graphene oxide can be reduced in this step. Examples of the reducing agent include ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, sodium borohydride (NaBH4), At this time, when the active material layer is immersed in a solution containing a reducing agent (also referred to as a reducing solution), graphene oxide can be reduced in this step. Examples of the reducing agent include ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, sodium borohydride (NaBH4), At this time, when the active material layer is immersed in a solution containing a reducing agent (also referred to as a reducing solution), graphene oxide can be reduced in this step. Examples of the reducing agent include ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, sodium borohydride (NaBH4), At this time, when the active material layer is immersed in a solution containing a reducing agent (also referred to as a reducing solution), graphene oxide can be reduced in this step. Examples of the reducing agent include ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, sodium borohydride (NaBH4), Examples include etc.

[0096] As the solvent of the reducing solution, a polar solvent can be used. For example, water, methanol, ethanol amine, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N- methylpyrrolidone (NMP), or any one or a mixture of two or more of dimethyl sulfoxide (DMSO) can be used.

[0097] However, when reducing graphene oxide using a reducing solution, unexpected damage may be caused to the active material layer. For example, the reducing agent may react with materials other than graphene oxide contained in the active material layer. In addition, compounds generated by the reduction of the solvent by the reducing agent may react with the materials contained in the active material layer. There is a possibility of reaction.

[0098] In addition, when using a reducing solution, depending on the nature of the reducing agent, the solution may become acidic or basic. Therefore, it is necessary to add a pH adjuster to adjust the pH of the solution, but the process becomes complicated. In addition, it may be difficult to keep the pH of the solution constant. If the pH of the solution cannot be kept constant, the materials contained in the active material layer may be damaged. For example, if the reducing solution is acidic, the active material layer contains materials that are unstable to acids or easily react with acids. In this case, it is likely to be damaged. Also, for example, if the reducing solution is basic, the active material layer contains materials that are unstable to bases or easily react with bases. In this case, it is likely to be damaged. In addition, by using a strong reducing agent as described above, unexpected reactions or damage may occur in the active material layer. Note that active materials that are unstable to acids include , for example, the positive electrode active material can be mentioned. Also, as a binder that easily reacts with a base, for example , PVdF and the like can be mentioned.

[0099] Also, when the active material layer is immersed in a reducing solution, the binder contained in the active material layer absorbs the solvent and expands or deforms. When the solvent of the reducing solution is water, since the molecules are small, it is easily absorbed by the binder Also, when the solvent is an aprotic polar solvent such as NMP, it has a high affinity with a binder such as PVdF and is therefore easily absorbed by the binder. Therefore, when the solvent of the reducing solution is water or NMP etc. , the phenomenon of the binder expanding or deforming becomes prominent. When the binder expands or deforms , the network structure of the binder that binds the active material and graphene oxide in the active material layer may be cut or broken. Also, when the binder expands or deforms at this time, the active material layer may expand. When graphene oxide is reduced in a state where the active material layer has expanded , it may be difficult to construct a three-dimensional network of electrical conduction in the active material layer . Or, even when graphene oxide is reduced in a state where the active material layer has swollen and a three-dimensional network of electrical conduction is constructed in the active material layer , in the subsequent step of evaporating the solvent, since the active material layer shrinks, the network structure of electrical conduction may be damaged.

[0100] Due to the factors described above, when the damaged active material layer is immersed in an electrolyte etc., the active material layer expands or deforms, so the network of electrical conduction formed in the active material layer is easily cut.

[0101] On the other hand, in the above step S104, after immersing the active material layer in a liquid having alcohol and then adding Since graphene oxide is reduced by heating, there is no need to immerse the active material layer in a reducing solution. Alcohol promotes the reduction of graphene oxide, which is an easily reduced substance. However, for materials used as active materials and binders, it is necessary to promote reduction and reaction. Therefore, the active material layer is not easily damaged. Since coal is neutral, the active material layer does not contain any materials that are unstable to acids or bases, or that are acid or base sensitive. Even if the active material layer contains materials that react easily with acids and bases, it is not easily damaged by acids or bases. In addition, since there is no need to adjust the pH of the liquid containing alcohol, step S 104 can be said to be simple.

[0102] In addition, the binder does not easily absorb alcohol, or does not easily swell even if it absorbs alcohol. Therefore, it is possible to prevent the binder from absorbing the solvent and expanding. Before graphene is reduced, the network structure built by the binder is cut or destroyed. In addition, the active material layer can be prevented from expanding or shrinking before and after the reduction of graphene oxide. This prevents the graphene from shrinking. This prevents the three-dimensional network of the conductor from being destroyed due to the expansion or contraction of the active material layer. Cut.

[0103] Next, the active material layer is removed from the alcohol-containing liquid and heated to reduce the graphene oxide. At this time, the current collector may be heated together with the active material layer. The temperature is not particularly limited. The temperature is from room temperature to 200°C, preferably from 60°C to 170°C. More preferably, the temperature is 80°C or higher and 150°C or lower, and the heating time is 1 hour or higher and 30 hours or lower. Thereby, graphene oxide is reduced and the alcohol contained in the active material layer is evaporated. In this step, since the alcohol promotes the reduction of graphene oxide by heating, the reaction efficiency of the reaction for reducing graphene oxide can be increased. Thereby, an electrode with a small internal resistance can be fabricated. In this step, since the alcohol promotes the reduction of graphene oxide by heating, the reaction efficiency of the reaction for reducing graphene oxide can be increased. Thereby, an electrode with a small internal resistance can be fabricated. As shown in this embodiment, according to one aspect of the present invention, graphene oxide can be reduced without subjecting the active material layer to the treatment of immersing it in a reducing solution. That is, graphene oxide can be reduced under mild reaction conditions. Therefore, damage to the active material layer due to the reduction reaction can be reduced. Thereby, an electrode in which the electrical conduction path is not easily cut even when immersed in an electrolyte can be fabricated. Also, since the alcohol promotes the reduction of graphene oxide by heating, the reaction efficiency of the reaction for reducing graphene oxide by heating can be increased. Thereby, an electrode with a small internal resistance can be manufactured. Therefore, by fabricating a storage battery using the method for manufacturing an electrode described in this embodiment, the cycle characteristics of the storage battery can be improved. Also, the rate characteristics of the storage battery can be improved.

[0104] As shown in this embodiment, according to one aspect of the present invention, graphene oxide can be reduced without subjecting the active material layer to the treatment of immersing it in a reducing solution. That is, graphene oxide can be reduced under mild reaction conditions. Therefore, damage to the active material layer due to the reduction reaction can be reduced. Thereby, an electrode in which the electrical conduction path is not easily cut even when immersed in an electrolyte can be fabricated. Also, since the alcohol promotes the reduction of graphene oxide by heating, the reaction efficiency of the reaction for reducing graphene oxide by heating can be increased. Thereby, an electrode with a small internal resistance can be manufactured. Therefore, by fabricating a storage battery using the method for manufacturing an electrode described in this embodiment, the cycle characteristics of the storage battery can be improved. Also, the rate characteristics of the storage battery can be improved. In addition, in this embodiment, one aspect of the present invention has been described. Or, in other embodiments, one aspect of the present invention is described.

[0105] However, one aspect of the present invention is not limited to these. That is, in this embodiment and other embodiments, since various aspects of the invention are described, one aspect of the present invention is not limited to a specific aspect. For example, as one aspect of the present invention, an example in which graphene is applied to an electrode for a storage battery is shown, but one aspect of the present invention is not limited to this. That is, in this embodiment and other embodiments, since various aspects of the invention are described, one aspect of the present invention is not limited to a specific aspect. For example, as one aspect of the present invention, an example in which graphene is applied to an electrode for a storage battery is shown, but one aspect of the present invention is not limited to this. It is not limited thereto. In some cases, or depending on the situation, graphene or graphene oxide is used as an electrode for a supercapacitor, which is a capacitor with a very large capacitance, used as an oxygen reduction electrode catalyst, used as a material for a dispersion liquid with lower friction than lubricating oil, used as a transparent electrode for display devices, solar cells, etc., used as a gas barrier material, used as a polymer material with high mechanical strength and low weight, used as a material for a highly sensitive nanosensor for detecting uranium and plutonium contained in radioactive contaminated water, used as a material for removing radioactive substances, and so on. Or for example, in some cases, or depending on the situation, as one aspect of the present invention, graphene may not be applied to the electrode for a storage battery. This embodiment can be implemented in appropriate combination with other embodiments. (Embodiment 3) In this embodiment, the structure of a storage battery using the electrode for a storage battery manufactured by the manufacturing method shown in Embodiment 2 will be described with reference to FIGS. 4 to 7.

[0106] This embodiment can be implemented in appropriate combination with other embodiments.

[0107] (Embodiment 3) In this embodiment, the structure of a storage battery using the electrode for a storage battery manufactured by the manufacturing method shown in Embodiment 2 will be described with reference to FIGS. 4 to 7. Referring to FIGS. 4 to 7, the structure of the storage battery will be described.

[0108] (Coin-type storage battery) FIG. 4(A) is an external view of a coin-type (single-layer flat type) storage battery, and FIG. 4(B) is a cross-sectional view thereof. It is a sectional view.

[0109] The coin-type storage battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 3 02 that also serves as a negative electrode terminal, which are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 includes a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact therewith. It is formed from. Further, the negative electrode 307 is provided so as to be in contact with the negative electrode current collector 308 and is formed by the negative electrode active material layer 309 provided thereon. Between the positive electrode active material layer 306 and the negative electrode active material layer 309 there are a separator 310 and an electrolytic solution (not shown).

[0110] At least one of the positive electrode 304 or the negative electrode 307 can be manufactured using the method for manufacturing an electrode for a storage battery according to one aspect of the present invention shown in Embodiment 2.

[0111] The configuration of the positive electrode active material layer 306 or the negative electrode active material layer 309 when the manufacturing method of the electrode for a storage battery shown in Embodiment 2 is not used is shown for either the positive electrode 304 or the negative electrode 307.

[0112] The positive electrode active material layer 306 may have, in addition to the positive electrode active material, a binder (binder) for enhancing the adhesion of the positive electrode active material, a conductive auxiliary agent for enhancing the conductivity of the positive electrode active material layer 306, and the like.

[0113] As the positive electrode active material, the binder, and the conductive auxiliary agent, the materials described in Embodiment 1 can be used.

[0114] The negative electrode active material layer 309 may have, in addition to the negative electrode active material, a binder (binder) for enhancing the adhesion of the negative electrode active material, a conductive auxiliary agent for enhancing the conductivity of the negative electrode active material layer 309, and the like.

[0115] As the negative electrode active material, the binder, and the conductive auxiliary agent, the materials described in Embodiment 1 can be used.

[0116] Further, a film such as an oxide may be formed on the surface of the negative electrode active material layer 309. The film formed by the decomposition of the electrolytic solution or the like during charging releases the amount of charge consumed during its formation. is unable to do so and forms an irreversible capacity. In contrast, by providing a film such as an oxide in advance on the surface of the negative electrode active material layer 309, the generation of the irreversible capacity can be suppressed or prevented. .

[0117] For the film that coats such a negative electrode active material layer 309, an oxide film of any one of niobium, titanium, vanadium, tantalum, tungsten, zirconium, molybdenum, hafnium, chromium, aluminum or silicon, or an oxide film containing any one of these elements and lithium can be used. Such a film is a sufficiently dense film compared to the film formed on the surface of the negative electrode by the decomposition products of the conventional electrolyte. surface by the decomposition products of the conventional electrolyte. surface by the decomposition products of the conventional electrolyte.

[0118] For example, niobium pentoxide (Nb2O5) has a low electrical conductivity of 10 -9 S / cm and exhibits high insulation. Therefore, the niobium oxide film inhibits the electrochemical decomposition reaction of the electrolyte or the like that occurs due to the contact between the negative electrode active material and the electrolyte during charging. On the other hand, the lithium diffusion coefficient of niobium oxide is 10 cm -9 / sec, and it has high lithium ion conductivity. 2 Therefore, it is possible to permeate lithium ions. Also, silicon oxide or aluminum oxide may be used. oxide may be used.

[0119] For the formation of the film that coats the negative electrode active material layer 309, for example, the sol-gel method can be used. The sol-gel method is a method in which a solution composed of a metal alkoxide, a metal salt, etc. is made into a gel that has lost its fluidity by a hydrolysis reaction or a polycondensation reaction, and this gel is fired to form a thin film. Since the sol-gel method is a method for forming a thin film from a liquid phase, the raw materials are homogeneous at the molecular level. It can be mixed therewith. Therefore, by adding a negative electrode active material such as graphite to the raw material of the metal oxide film at the solution stage, the active material can be easily dispersed in the gel. In this way, a film can be formed on the surface of the negative electrode active material layer 309. By using this film, a decrease in the capacity of the power storage body can be prevented. Substances can be added to easily disperse the active material in the gel. In this way, a film can be formed on the surface of the negative electrode active material layer 309. By using this film, a decrease in the capacity of the power storage body can be prevented.

[0120] The separator 310 can be made of an insulator having pores, such as cellulose (paper), polypropylene, or polyethylene. As the electrolyte, in addition to an electrolyte containing a supporting electrolyte, a solid electrolyte or a gel electrolyte obtained by gelling a part of the electrolyte can be used.

[0121] As the electrolyte, in addition to an electrolyte containing a supporting electrolyte, a solid electrolyte or a gel electrolyte obtained by gelling a part of the electrolyte can be used. As the electrolyte, in addition to an electrolyte containing a supporting electrolyte, a solid electrolyte or a gel electrolyte obtained by gelling a part of the electrolyte can be used.

[0122] Materials having carrier ions can be used as the supporting electrolyte. Representative examples of the supporting electrolyte include lithium salts such as LiPF6, LiClO4, LiAsF6, LiBF4, LiCF3SO3, Li(CF3SO2)2N, and Li(C2F5SO2)2N. These electrolytes may be used alone or in any combination and ratio of two or more. Li(CF3SO2)2N, and Li(C2F5SO2)2N. These electrolytes may be used alone or in any combination and ratio of two or more. Li(CF3SO2)2N, and Li(C2F5SO2)2N. These electrolytes may be used alone or in any combination and ratio of two or more. These electrolytes may be used alone or in any combination and ratio of two or more.

[0123] When the carrier ion is an alkali metal ion or an alkaline earth metal ion other than a lithium ion, as the electrolyte, in the above lithium salts, an alkali metal (such as sodium or potassium) or an alkaline earth metal (such as calcium, strontium, barium, beryllium, magnesium, etc.) may be used instead of lithium. barium, beryllium, magnesium, etc.) may be used instead of lithium. barium, beryllium, magnesium, etc.) may be used instead of lithium.

[0124] As the solvent of the electrolyte, a material in which carrier ions can move can be used.As the solvent of the electrolyte, an aprotic organic solvent is preferred. Representative examples of aprotic organic solvents include ethylene carbonate (EC), propylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran, etc., and one or more of these can be used. In addition, by using a polymer material that gels as the solvent of the electrolyte, the safety against leakage and the like is enhanced. Also, the battery can be made thinner and lighter. Representative examples of the polymer materials that gel include silicone gel, acrylic gel, acrylonitrile gel, polyethylene oxide-based gel, polypropylene oxide-based gel, fluorine-based polymer gel, etc. In addition, by using one or more ionic liquids (especially room temperature molten salts) that are flame-retardant and low-volatile as the solvent of the electrolyte, even if the internal temperature of the battery rises due to internal short circuit, overcharging, etc., the battery can be prevented from bursting or catching fire. Ionic liquids consist of cations and anions. Examples of the organic cations that make up the ionic liquid include quaternary ammonium cations, tertiary sulfonium cations, and aliphatic onium cations such as quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anions that make up the ionic liquid include monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate, or perfluoroalkylphosphate.

[0125] Alternatively, instead of the electrolytic solution, a solid electrolyte having an inorganic material such as a sulfide-based or oxide-based material, or a solid electrolyte having a polymer material such as P EO (polyethylene oxide)-based can be used. When using a solid electrolyte, it is not necessary to install a separator or a spacer. Also, since the entire battery can be solidified, there is no risk of leakage and the safety is significantly improved. For the positive electrode can 301 and the negative electrode can 302, metals such as nickel, aluminum, and titanium, alloys of the metal, alloys of the metal and other metals (e.g., stainless steel, etc.), laminates of the metal, laminates of the metal and the alloy mentioned above (e.g., stainless steel / aluminum, etc.), laminates of the metal and other metals (e.g., nickel / iron / nickel, etc.) that have corrosion resistance against liquids such as electrolytic solution during charge and discharge of the secondary battery can be used. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0126] These negative electrode 307, positive electrode 304, and separator 310 are impregnated with the electrolyte, and as shown in FIG. 4(B), with the positive electrode can 301 facing down, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are laminated in this order, and the positive electrode can 301 and the negative electrode can 302 are crimped via the gasket 303 to manufacture a coin-type storage battery 300.

[0127]

[0128] (Laminated-type storage battery) FIG. 5 shows an external view of a laminated-type storage battery 500. Also, FIGS. 6(A) and 6(B) show the cross-sections A1 - A2 and B1 - B2 shown by the dashed line in FIG. 5. The laminated-type storage battery 500 includes a positive electrode 503 having a positive electrode current collector 501 and a positive electrode active material layer 502, and a negative electrode current collector ​​​​​​​​​A negative electrode 506 having a body 504 and a negative electrode active material layer 505, a separator 507, an electrolytic solution 5 08, and an exterior body 509. A separator 507 is disposed between the positive electrode 503 and the negative electrode 506 . Further, the electrolytic solution 508 is injected into the region surrounded by the exterior body 509 .

[0129] In the laminated battery 500 shown in FIG. 5, the positive electrode current collector 501 and the negative electrode current collector 50 4 also serve as terminals for obtaining electrical contact with the outside. Therefore, a part of the positive electrode current collector 501 and the negative electrode current collector 504 is arranged to be exposed outside from the exterior body 509

[0130] In the laminated battery 500, the exterior body 509 is provided with, for example, a flexible metal thin film made of a material such as polyethylene, polypropylene , polycarbonate, ionomer, polyamide, etc. on a film, and aluminum , stainless steel, copper, nickel, etc. A laminated film having a three-layer structure in which an insulating synthetic resin film such as a polyamide-based resin or a polyester-based resin is provided as the outer surface of the exterior body is provided on the metal thin film . By adopting such a three-layer structure , permeation of the electrolytic solution and gas is blocked, insulation is ensured, and at the same time, it has resistance to the electrolytic solution .

[0131] (Cylindrical battery) Next, an example of a cylindrical battery will be described with reference to FIG. 7. The cylindrical battery 600 has a positive electrode cap (battery lid) 601 on the upper surface as shown in FIG. 7(A), and a battery can (outer can) 602 on the side surface and the bottom surface . The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610

[0132] ​FIG. 7(B) is a diagram schematically showing a cross section of a cylindrical storage battery. Inside a hollow cylindrical battery can 6 02, a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 interposed therebetween to form a battery element. Although not shown, the battery element is wound around a center pin One end of the battery can 602 is closed and the other end is open. The battery can 602 is made of nickel, aluminum a metal such as titanium, an alloy of the metal, an alloy of the metal and another metal (for example, stainless steel, etc.), a laminate of the metal, a laminate of the metal and the above-described alloy (for example, stainless steel / aluminum, etc.), a laminate of the metal and another metal (for example, nickel / iron / nickel steel, etc.), which has corrosion resistance against liquids such as electrolytic solution during charge and discharge of the secondary battery Inside the battery can 602, the battery element around which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609 Also, the inside of the battery can 602 where the battery element is provided is filled with a non-aqueous electrolytic solution (not shown). The non-aqueous electrolytic solution can be the same as that used in coin-type or laminate-type storage batteries

[0133] The positive electrode 604 and the negative electrode 606 may be manufactured in the same manner as the positive electrode and negative electrode of the coin-type storage battery described above. However, since the positive electrode and negative electrode used in the cylindrical storage battery are wound, they are different in that active materials are formed on both sides of the current collector A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604 and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. The positive electrode terminal 60 3 and the negative electrode terminal 607 can both be made of a metal material such as aluminum. The positive electrode terminal 60 3 is connected to the safety valve mechanism 612, and the negative electrode terminal 607 is connected to the bottom of the battery can 602, respectively, with a resistor connected therebetween ​It is welded. The safety valve mechanism 612 is electrically connected to the positive electrode cap 601 via a PTC element (Positive Temperature Coefficient) 611. When the internal pressure of the battery rises above a predetermined threshold value, the safety valve mechanism 612 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604. Further, the PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it restricts the current amount due to the increase in resistance to prevent abnormal heat generation. For the PTC element, barium titanate (BaTi O3)-based semiconductor ceramics or the like can be used.

[0134] In this embodiment, coin-type, laminate-type, and cylindrical storage batteries are shown as storage batteries, but storage batteries of various shapes such as other sealed storage batteries and square storage batteries can be used. Further, a structure in which a plurality of positive electrodes, negative electrodes, and separators are stacked, or a structure in which a positive electrode, a negative electrode, and a separator are wound may be used.

[0135] For the positive electrode or the negative electrode of the coin-type storage batteries 300, 500, and 600 shown in this embodiment, an electrode manufactured by the method for manufacturing an electrode for a storage battery according to one aspect of the present invention is used. Therefore, the discharge capacity of the coin-type storage batteries 300, 500, and 600 can be increased.

[0136] In this embodiment, one aspect of the present invention has been described. However, one aspect of the present invention is not limited to these. That is, in this embodiment, various aspects of the invention are described, so one aspect of the present invention is not limited to a specific aspect. For example, as one aspect of the present invention ​​​​​However, an example of the case where it is applied to a lithium-ion secondary battery has been shown, but one aspect of the present invention is not limited thereto. Depending on the case or situation, one aspect of the present invention may be applied to various secondary batteries, for example, lead-acid batteries, lithium-ion polymer secondary batteries, nickel-metal hydride batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, or silver oxide-zinc batteries, primary batteries, capacitors, or lithium-ion capacitors, etc. It may also be applied to solid batteries or air batteries, etc. Or for example, depending on the case or situation, one aspect of the present invention may not be applied to a lithium-ion secondary battery. This embodiment can be implemented in appropriate combination with other embodiments. A storage battery using the electrode for a storage battery according to one aspect of the present invention can be used as a power source for various electric appliances driven by electric power. Specific examples of electric appliances using the storage battery using the electrode for a storage battery according to one aspect of the present invention include display devices such as televisions and monitors, lighting devices, desktop or notebook personal computers, word processors, image playback devices that play still images or moving images stored on recording media such as DVDs (Digital Versatile Discs), portable CD players, radios, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless telephone handsets, transceivers, mobile phones, car phones, portable game machines, calculators, portable information terminals, electronic notebooks, electronic book terminals, electronic translators, voice input devices, video cameras

[0137]

[0138] (Embodiment 4)

[0139] ​​​​​​​​​​​​​​La, digital still cameras, toys, electric shavers, high-frequency heating devices such as microwave ovens, electric rice cookers, washing machines, vacuum cleaners, water heaters, fans, hair dryers, air conditioners, air-conditioning equipment such as humidifiers and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, freezers, refrigerator-freezers, DNA storage freezers, flashlights, chain saws and other power tools, smoke detectors, medical devices such as dialysis machines, etc. Further, induction lamps, signal machines, belt conveyors, elevators, escalators, industrial robots, power storage systems and industrial equipment such as energy storage devices for load leveling and smart grids. Also, mobile bodies propelled by electric motors using power from storage batteries are also included in the category of electrical equipment as well. As the above mobile bodies, for example, electric vehicles (EVs), hybrid vehicles (HEVs) having both an internal combustion engine and an electric motor, plug-in hybrid vehicles (PHEVs), these tracked vehicles obtained by changing the tire wheels of these to endless tracks, motorized bicycles including electric assist bicycles, self motorcycles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, airplanes rockets, artificial satellites, space exploration vehicles and planetary exploration vehicles, spaceships, etc. can be mentioned.

[0140] Note that as a main power source for supplying almost all of the power consumption, the above electrical equipment can use a storage battery using an electrode for a storage battery according to one aspect of the present invention. Alternatively, when the supply of power from the above main power source or commercial power source stops, the above electrical equipment can use a storage battery using an electrode for a storage battery according to one aspect of the present invention as an uninterruptible power supply that can supply power to the electrical equipment. Alternatively, the above electrical equipment can supply power to the electrical equipment from the above main power source or commercial power source ​​​​​As an auxiliary power source for supplying power to an electrical device in parallel with the power supply, a storage battery using an electrode for a storage battery according to an aspect of the present invention can be used.

[0141] Fig. 8 shows a specific configuration of the above electrical device. In Fig. 8, the display device 700 is an example of an electrical device using a storage battery 704 using an electrode for a storage battery according to an aspect of the present invention. Specifically the display device 700 corresponds to a display device for receiving TV broadcasts, and includes a housing 701, a display unit 70 2, a speaker unit 703, a storage battery 704, etc. The storage battery 704 using an electrode for a storage battery according to an aspect of the present invention is provided inside the housing 701. The display device 700 can receive power supply from a commercial power source, or can use the power stored in the storage battery 704. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, by using the storage battery 704 using an electrode for a storage battery according to an aspect of the present invention as an uninterruptible power supply the display device 700 can be used.

[0142] The display unit 702 can use a light-emitting device having a light-emitting element such as a liquid crystal display device or an organic EL element in each pixel, an electrophoretic display device, a DMD (Digital Micromirror Devic e), a PDP (Plasma Display Panel), an FED (Field E mission Display), etc., a semiconductor display device.

[0143] Note that the display device includes all display devices for information display, such as for personal computers and advertising displays, in addition to those for receiving TV broadcasts.

[0144] In Fig. 8, the installed lighting device 710 uses an electrode for a storage battery according to an aspect of the present invention This is an example of an electrical device using the storage battery 713. Specifically, the lighting device 710 includes a housing 7 11, a light source 712, a storage battery 713, etc. In FIG. 8, an example is illustrated where the storage battery 713 is provided inside the ceiling 714 on which the housing 711 and the light source 712 are installed. However, the storage battery 713 may be provided inside the housing 711. The lighting device 710 can receive power supply from a commercial power source, or can also use the power stored in the storage battery 713. Therefore, even when power supply from the commercial power source cannot be received due to a power outage or the like, by using the storage battery 713 using the electrode for a storage battery according to one aspect of the present invention as an uninterruptible power supply, the lighting device 710 can be used. Note that in FIG. 8, a built-in type lighting device 710 provided on the ceiling 714 is illustrated. However, the storage battery using the electrode for a storage battery according to one aspect of the present invention can be used not only for the ceiling 714 but also for, for example, a built-in type lighting device provided on a side wall 71 5, a floor 716, a window 717, etc., and can also be used for a desktop type lighting device or the like.

[0145] In addition, as the light source 712, an artificial light source that artificially obtains light using power can be used. Specifically, an incandescent bulb, a discharge lamp such as a fluorescent lamp, a light emitting element such as an LED or an organic EL element can be cited as an example of the above artificial light source.

[0146]

[0147] In FIG. 8, an air conditioner having an indoor unit 720 and an outdoor unit 724 is an example of an electrical device using a storage battery 723 using an electrode for a storage battery according to one aspect of the present invention. Specifically, the indoor unit 720 includes a housing 721, an air outlet 722, a storage battery 723, etc. In FIG. 8, Although the example shows the case where the storage battery 723 is provided in the indoor unit 720, the storage battery 723 may be provided in the outdoor unit 724. Alternatively, the storage battery 723 may be provided in both the indoor unit 720 and the outdoor unit 724. The air conditioner can receive power supply from the commercial power supply and can also use the power stored in the storage battery 723. In particular , when the storage battery 723 is provided in both the indoor unit 720 and the outdoor unit 724, even when power supply cannot be received from the commercial power supply due to a power outage or the like , by using the storage battery 723 using the electrode for storage battery according to one aspect of the present invention as an uninterruptible power supply, the use of the air conditioner becomes possible .

[0148] Note that in FIG. 8, a separate type air conditioner composed of an indoor unit and an outdoor unit is exemplified , but it is also possible to use a storage battery using the electrode for storage battery according to one aspect of the present invention in an integrated type air conditioner having the functions of the indoor unit and the outdoor unit in one housing .

[0149] In FIG. 8, the electric refrigerator 730 is an example of an electric device using a storage battery 734 using the electrode for storage battery according to one aspect of the present invention. Specifically, the electric refrigerator 730 includes a housing 7 31, a refrigerator door 732, a freezer door 733, a storage battery 734, etc. In FIG. 8, the storage battery 734 is provided inside the housing 731. The electric refrigerator 730 can receive power supply from the commercial power supply and can also use the power stored in the storage battery 734 . Therefore, even when power supply cannot be received from the commercial power supply due to a power outage or the like, by using the storage battery 734 using the electrode for storage battery according to one aspect of the present invention as an uninterruptible power supply , the use of the electric refrigerator 730 becomes possible . ​​

[0150] Among the above-mentioned electrical appliances, high-frequency heating devices such as microwave ovens, electric rice cookers, etc. The equipment requires high power for a short period of time. Therefore, the equipment supplements the power that cannot be supplied by commercial power sources. A storage battery using the storage battery electrode according to one embodiment of the present invention is used as an auxiliary power source for This can prevent the commercial power breaker from tripping when electrical equipment is in use.

[0151] In addition, during periods when electrical equipment is not being used, especially during periods when the total amount of power that can be supplied by the commercial power supplier is low, During times when the proportion of electricity actually used (called the electricity usage rate) is low, By storing electricity in the pond, it is possible to prevent the power usage rate from increasing outside the above-mentioned time periods. For example, in the case of an electric refrigerator-freezer 730, when the temperature is low, the refrigerator compartment door 732 and the freezer During the night when the room door 733 is not opened or closed, power is stored in the storage battery 734. During the daytime when the temperature rises and the refrigerator door 732 and the freezer door 733 are opened and closed, By using the storage battery 734 as an auxiliary power source, it is possible to keep the power usage rate low during the day.

[0152] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0153] (Embodiment 5) Next, a portable information terminal, which is an example of an electrical device, will be described with reference to FIG.

[0154] 9(A) and 9(B) show a tablet terminal 800 that can be folded in two. 8 shows the tablet terminal 800 in an open state. The tablet terminal 800 includes a housing 801, a display unit 802a, and a display 802b, a display mode changeover switch 803, a power switch 804, a power saving mode changeover switch It has a replacement switch 805 and an operation switch 807.

[0155] The display unit 802a can have a part as the area 808a of the touch panel, and data can be input by touching the displayed operation key 809. In the display unit 802a, as an example, a configuration in which half of the area has only a display function and the other half has a touch panel function is shown, but it is not limited to this configuration. All of the area of the display unit 802a may have a touch panel function. For example, the entire surface of the display unit 802a can be made to display keyboard buttons to serve as a touch panel, and the display unit 802b can be used as a display screen.

[0156] Also, in the display unit 802b, similar to the display unit 802a, a part of the display unit 802b can be made into the area 808b of the touch panel. Also, by touching the position where the keyboard display switching button 810 of the touch panel is displayed with a finger or a stylus, etc., the keyboard buttons can be displayed on the display unit 802b.

[0157] Also, simultaneous touch input can be performed on the area 808a of the touch panel and the area 808b of the touch panel.

[0158] Also, the display mode switching switch 803 can select switching of the display orientation such as vertical display or horizontal display, switching between black and white display and color display, etc. The power saving mode switching switch 805 can optimize the display brightness according to the amount of external light detected by the optical sensor built in the tablet type terminal during use. The tablet type terminal has only an optical sensor. ​​​​​​​​​​​​​In addition, other detection devices such as sensors for detecting inclination, such as gyroscopes and acceleration sensors, may be incorporated. It may be made to do so.

[0159] Also, FIG. 9(A) shows an example in which the display areas of the display unit 802b and the display unit 802a are the same. However, it is not particularly limited, and one size and the other size may be different, and the display quality may also be different. For example, one may be a display panel that can perform a higher-definition display than the other. It may be good too.

[0160] FIG. 9(B) shows a closed state, and the tablet-type terminal 800 includes a housing 801, a solar cell 8 11, a charge / discharge control circuit 850, a battery 851, and a DCDC converter 852. Note that in FIG. 9(B), as an example of the charge / discharge control circuit 850, a configuration having a battery 851 and a DCDC converter 852 is shown, and the battery 851 has a storage battery using an electrode for a storage battery according to one aspect of the present invention described in the above embodiment. It has a storage battery using an electrode for a storage battery according to one aspect of the present invention described in the above embodiment.

[0161] Note that since the tablet-type terminal 800 is foldable in two, the housing 801 can be closed when not in use. Therefore, since the display units 802a and 802b can be protected, it is possible to provide a tablet-type terminal 800 that is excellent in durability and reliability from the viewpoint of long-term use. It is possible to provide a tablet-type terminal 800 that is excellent in durability and reliability from the viewpoint of long-term use. It can be done.

[0162] In addition, the tablet-type terminal shown in FIGS. 9(A) and 9(B) also has functions such as displaying various information ( still images, moving images, text images, etc.), functions of displaying a calendar, date, or time on a display unit, touch input functions for touch input operations or editing of information displayed on the display unit, functions of controlling processing by various software (programs), and the like. It has functions of displaying a calendar, date, or time on a display unit, touch input functions for touch input operations or editing of information displayed on the display unit, functions of controlling processing by various software (programs), and the like. It has functions such as a touch input function for touch input operations or editing of information displayed on the display unit, functions of controlling processing by various software (programs), and the like. It is possible.

[0163] Power can be supplied to the touch panel, display unit, video signal processing unit, etc. by the solar cell 811 mounted on the surface of the tablet terminal. Note that the solar cell 811 can be provided on one or both sides of the housing 801, and can be configured to efficiently charge the battery 851. In addition, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). FIG. 9(C) shows the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. Note that the solar cell 811 is shown as an example of a power generation means, but is not particularly limited, and the pressure

[0164] Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B). Moreover, the configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9(B) will be described using the block diagram shown in FIG. 9(C). In FIG. 9(C), the solar cell 811, battery 851, DCDC converter 852, converter 853, switches SW1 to SW3, and display unit 802 are shown. The battery 851, DCDC converter 852, converter 853, and switches SW1 to SW3 correspond to the locations of the charge / discharge control circuit 850 shown in FIG. 9(B).

[0165] First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851. First, an example of the operation when power is generated by the solar cell 811 due to external light will be described. The power generated by the solar cell is stepped up or down by the DCDC converter 852 to a voltage for charging the battery 851. When the power from the solar cell 811 is used for the operation of the display unit 802, switch SW1 is turned on, and the converter 853 steps up or down the voltage to the voltage required for the display unit 802. When the display unit 802 is not displaying, SW1 can be turned off and SW2 can be turned on to charge the battery 851.

[0166] Note that the solar cell 811 is shown as an example of a power generation means, but is not particularly limited, and the pressure Batteries using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the device may be configured to transmit and receive power wirelessly (contactlessly). This can be combined with a non-contact power transmission module that charges by transmitting power, or other charging methods. It may also be composed of.

[0167] In addition, a storage battery using the storage battery electrode according to one aspect of the present invention described in the above embodiment is provided. It goes without saying that the electrical device is not particularly limited to the one shown in FIG. 9 so long as it is provided.

[0168] (Embodiment 6) Furthermore, an example of a moving object, which is an example of an electrical device, will be described with reference to FIG.

[0169] The storage battery described in the previous embodiment can be used as the control battery. The battery can be charged by external power supply using plug-in technology or wireless power supply. In addition, if the moving object is an electric rail vehicle, it can be driven by power supply from overhead lines or conductive rails. It can be charged by pressing the

[0170] 10(A) and (B) show an example of an electric vehicle. The electric vehicle 860 has a battery. The power of the battery 861 is output by a control circuit 862. The force is adjusted and supplied to the driving device 863. The control circuit 862 includes a ROM (not shown), It is controlled by a processing unit 864 having a RAM, a CPU, etc.

[0171] The drive unit 863 is a DC motor or an AC motor alone, or a combination of a motor and an internal combustion engine. The processing device 864 is configured to receive operation information (acceleration , deceleration, stop, etc.) and information during driving (information such as uphill and downhill, load information applied to the drive wheels Based on the input information such as), it outputs a control signal to the control circuit 862. The control circuit 862 Adjusts the electrical energy supplied from the battery 861 according to the control signal of the processing device 864 And controls the output of the drive device 863. When an AC motor is installed, although not shown An inverter that converts DC to AC is also built-in.

[0172] The battery 861 can be charged by external power supply using plug-in technology. For example, it is charged from a commercial power supply through a power plug to the battery 861. Charging Can be performed by converting it to a DC constant voltage having a certain voltage value through a conversion device such as an AC / DC converter By mounting a storage battery using the electrode for a storage battery according to an aspect of the present invention as the battery 861, it can contribute to increasing the capacity of the battery, etc., and improving convenience Can be improved. Also, if the characteristics of the battery 861 are improved and the battery 861 itself can be made smaller and lighter It can contribute to reducing the weight of the vehicle, so the fuel efficiency can be improved . .

[0173] Of course, if the storage battery according to an aspect of the present invention is provided, it is not particularly limited to the electrical equipment shown above .

[0174] This embodiment can be implemented in appropriate combination with other embodiments.

[0175] (Embodiment 7) A battery control unit (Battery Management Unit: BMU) that can be used in combination with a battery cell including the material described in the above embodiment, and the battery Regarding the transistor suitable for the circuit constituting the control unit, reference will be made to FIGS. 11 to 17 for explanation. In this embodiment, the battery control unit of the power storage device having battery cells connected in series will be described. The battery control unit will be described.

[0176] When repeatedly charging and discharging a plurality of battery cells connected in series, the capacities (output voltages) will differ according to the variations in the characteristics among the battery cells. In the battery cells connected in series, the overall capacity during discharge depends on the battery cell with the smallest capacity. If there are variations in the capacity, the capacity during discharge will become smaller. Also, if charging is performed based on the battery cell with the smallest capacity, there is a risk of insufficient charging. On the other hand, if charging is performed based on the battery cell with the largest capacity, there is a risk of overcharging. Therefore, the battery control unit of the power storage device having battery cells connected in series has a function of equalizing the variations in the capacities among the battery cells, which can cause insufficient charging or overcharging. Circuit configurations for equalizing the variations in the capacities among the battery cells include the resistance method, the capacitor method, or the inductor method, etc. Here, as an example, a circuit configuration that can equalize the variations in the capacities by using a transistor with a small off-current will be described. As a transistor with a small off-current, a transistor (OS transistor) having an oxide semiconductor in the channel formation region is preferable. By using an OS transistor with a small off-current in the circuit configuration of the battery control unit of the power storage device, the amount of charge leaking from the battery cells can be reduced

[0177] and the decrease in capacity over time can be suppressed.

[0178]

[0179] ​​​​​​​​The oxide semiconductor used for the channel formation region is an In-M-Zn oxide (M is Ga, Sn, Y, Zr, La, Ce, or Nd). In the target used for forming the oxide semiconductor film, when the atomic ratio of the metal elements is In:M:Zn = x1:y1:z1, then 、 x1 / y1 is 1 / 3 or more and 6 or less, more preferably 1 or more and 6 or less, and z1 / y1 is 1 / 3 or more and 6 or less, more preferably 1 or more and 6 or less. By setting z1 / y1 to 1 or more and 6 or less, a CAAC-OS film is likely to be formed as the oxide semiconductor film.

[0180] Here, the CAAC-OS film will be described.

[0181] The CAAC-OS film is one of the oxide semiconductor films having a plurality of crystal parts oriented in the c-axis direction.

[0182] By observing the bright-field image and the composite analysis image of the diffraction pattern (also referred to as a high-resolution TEM image) of the CAAC-OS film with a transmission electron microscope (TEM: Transmission Electron Micro scope), a plurality of crystal parts can be confirmed. On the other hand, the boundaries between the clear crystal parts, that is, the grain boundaries (also referred to as grain boundaries), cannot be confirmed by the high-resolution TEM image. Therefore, it can be said that the CAAC-OS film is less likely to cause a decrease in electron mobility due to grain boundaries. When observing the high-resolution TEM image of the cross-section of the CAAC-OS film from a direction substantially parallel to the sample surface, it can be confirmed that the metal atoms are arranged in layers in the crystal parts. Each layer of the metal atoms reflects the unevenness of the surface (also referred to as the surface to be formed) or the upper surface of the CAAC-OS film for forming the film.

[0183] It has a shape and is arranged parallel to the formed surface or the upper surface of the CAAC-OS film.

[0184] On the other hand, when observing the high-resolution TEM image of the plane of the CAAC-OS film from a direction substantially perpendicular to the sample surface it can be confirmed that in the crystal part, the metal atoms are arranged in a triangular or hexagonal shape. However, no regularity is seen in the arrangement of the metal atoms between different crystal parts. However, no regularity is seen in the arrangement of the metal atoms between different crystal parts.

[0185] When performing structural analysis on the CAAC-OS film using an X-ray diffraction (XRD) device for example, in the out-of-plane method analysis of the CAAC-OS film having a crystal of InGaZnO4 peaks may appear in the vicinity of a diffraction angle (2θ) of about 31°. This peak is attributed to the (009) plane of the crystal of InGaZnO4 from which it can be confirmed that the crystal of the CAAC-OS film has c-axis orientation and the c-axis is oriented in a direction substantially perpendicular to the formed surface or the upper surface. from which it can be confirmed that the crystal of the CAAC-OS film has c-axis orientation and the c-axis is oriented in a direction substantially perpendicular to the formed surface or the upper surface. from which it can be confirmed that the crystal of the CAAC-OS film has c-axis orientation and the c-axis is oriented in a direction substantially perpendicular to the formed surface or the upper surface.

[0186] In addition, in the out-of-plane method analysis of the CAAC-OS film having a crystal of InGaZnO4 in addition to the peak at around 2θ of 31°, a peak may also appear at around 2θ of 36°. The peak at around 2θ of 36° indicates that a part of the CAAC-OS film contains crystals that do not have c-axis orientation. It is preferable that the CAAC-OS film shows a peak at around 2θ of 31° and does not show a peak at around 2θ of 36°. in addition to the peak at around 2θ of 31°, a peak may also appear at around 2θ of 36°. The peak at around 2θ of 36° indicates that a part of the CAAC-OS film contains crystals that do not have c-axis orientation. It is preferable that the CAAC-OS film shows a peak at around 2θ of 31° and does not show a peak at around 2θ of 36°. in addition to the peak at around 2θ of 31°, a peak may also appear at around 2θ of 36°. The peak at around 2θ of 36° indicates that a part of the CAAC-OS film contains crystals that do not have c-axis orientation. It is preferable that the CAAC-OS film shows a peak at around 2θ of 31° and does not show a peak at around 2θ of 36°. in addition to the peak at around 2θ of 31°, a peak may also appear at around 2θ of 36°. The peak at around 2θ of 36° indicates that a part of the CAAC-OS film contains crystals that do not have c-axis orientation. It is preferable that the CAAC-OS film shows a peak at around 2θ of 31° and does not show a peak at around 2θ of 36°.

[0187] The CAAC-OS film is an oxide semiconductor film with a low impurity concentration. Impurities are elements other than the main components of the oxide semiconductor film such as hydrogen, carbon, silicon, transition metal elements, etc. In particular, silicon Elements with a stronger binding force to oxygen than the metal elements constituting the oxide semiconductor film, such as, oxygen, will disrupt the atomic arrangement of the oxide semiconductor film and reduce the crystallinity by depriving the oxide semiconductor film of oxygen. In addition, heavy metals such as iron and nickel, argon, carbon dioxide, etc., have a large atomic radius (or molecular radius), so when they are contained inside the oxide semiconductor film, they will disrupt the atomic arrangement of the oxide semiconductor film and reduce the crystallinity. Note that impurities contained in the oxide semiconductor film may serve as carrier traps or carrier generation sources.

[0188] In addition, the CAAC-OS film is an oxide semiconductor film with a low density of defect levels. For example, oxygen deficiencies in the oxide semiconductor film may serve as carrier traps or may become carrier generation sources by capturing hydrogen.

[0189] Low impurity concentration and low defect level density (low oxygen deficiency) are referred to as high purity intrinsic or substantially high purity intrinsic. An oxide semiconductor film with high purity intrinsic or substantially high purity intrinsic has few carrier generation sources, so the carrier density can be lowered. Therefore, a transistor using the oxide semiconductor film is less likely to have an electrical characteristic in which the threshold voltage becomes negative ( also referred to as normally on).) In addition, an oxide semiconductor film with high purity intrinsic or substantially high purity intrinsic has few carrier traps. Therefore, a transistor using the oxide semiconductor film has small fluctuations in electrical characteristics and becomes a highly reliable transistor. Note that the charge trapped in the carrier trap of the oxide semiconductor film may take a long time to be released and may behave like a fixed charge. Therefore, the impurity concentration is ​Transistors using a high and high-defect level density oxide semiconductor film may have unstable electrical characteristics. There are cases where it becomes like this.

[0190] In addition, transistors using a CAAC-OS film have small fluctuations in electrical characteristics due to irradiation with visible light or ultraviolet light. The fluctuations are small.

[0191] Note that since an OS transistor has a larger bandgap than a transistor having silicon in a channel formation region (Si transistor), breakdown hardly occurs when a high voltage is applied. When battery cells are connected in series, a voltage of several hundred volts will be generated, but for the circuit configuration of a battery control unit applied to such battery cells in a power storage device, it is suitable to be composed of the aforementioned OS transistors. It hardly occurs. When connecting battery cells in series, a voltage of several hundred volts will be generated. In a power storage device, for the circuit configuration of a battery control unit applied to such battery cells, it is suitable to be composed of the aforementioned OS transistors. It is suitable to be composed of the OS transistors described above.

[0192] FIG. 11 shows an example of a block diagram of a power storage device. The power storage device 1000 shown in FIG. 11 includes a terminal pair 1001, a terminal pair 1002, a switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, a voltage conversion circuit 1007, and a battery unit 1008 including a plurality of battery cells 1009 connected in series. A terminal pair 1001, a terminal pair 1002, a switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, a voltage conversion circuit 1007, and a battery unit 1008 including a plurality of battery cells 1009 connected in series. A switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, a voltage conversion circuit 1007, and a battery unit 1008 including a plurality of battery cells 1009 connected in series. Connected in series.

[0193] In addition, in the power storage device 1000 of FIG. 11, the part composed of the terminal pair 1001, the terminal pair 1002, the switching control circuit 1003, the switching circuit 1004, the switching circuit 1005, the voltage conversion control circuit 1006, and the voltage conversion circuit 1007 can be called a battery control unit. A terminal pair 1001, a terminal pair 1002, a switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, a voltage conversion circuit 1007, and a battery unit 1008 including a plurality of battery cells 1009 connected in series. A switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, a voltage conversion circuit 1007, and a battery unit 1008 including a plurality of battery cells 1009 connected in series. It can be called a battery control unit.

[0194] The switching control circuit 1003 controls the operations of the switching circuit 1004 and the switching circuit 1005. Control. Specifically, the switching control circuit 1003 measures for each battery cell 1009 the voltage, and based on this voltage, determines the battery cells to be discharged (discharge battery cell group) and the battery cells to be charged (charge battery cell group).

[0195] Furthermore, the switching control circuit 1003 outputs a control signal S1 and a control signal S2 based on the determined discharge battery cell group and charge battery cell group. The control signal S1 is output to the switching circuit 1004. This control signal S1 is a signal for controlling the switching circuit 1004 to connect the terminal pair 1001 and the discharge battery cell group. Also, the control signal S2 is output to the switching circuit 1005. This control signal S2 is a signal for controlling the switching circuit 1005 to connect the terminal pair 1002 and the charge battery cell group.

[0196] Also, based on the configurations of the switching circuit 1004, the switching circuit 1005, and the transformer circuit 1007, the switching control circuit 1003 generates the control signal S1 and the control signal S2 such that terminals of the same polarity are connected between the terminal pair 1001 and the discharge battery cell group or between the terminal pair 1002 and the charge battery cell group.

[0197]

[0198] Details of the operation of the switching control circuit 1003 will be described.

[0198] First, the switching control circuit 1003 measures the voltage of each of the plurality of battery cells 1009. Then, the switching control circuit 1003 determines, for example, the battery cells 1009 with a voltage equal to or higher than a predetermined threshold as high-voltage battery cells (high-voltage cells), and the battery cells 1009 with a voltage lower than the predetermined threshold as low-voltage battery cells (low-voltage cells).

[0199] ​​Note that various methods can be used to determine the high-voltage cells and low-voltage cells. For example, the switching control circuit 1003 may determine whether each battery cell 1009 is a high-voltage cell or a low-voltage cell based on the voltage of the battery cell 1009 with the highest or lowest voltage among the plurality of battery cells 1009. In this case, the switching control circuit 1003 may determine whether each battery cell 1009 is a high-voltage cell or a low-voltage cell by determining whether the voltage of each battery cell 1009 is equal to or higher than a predetermined ratio with respect to the reference voltage. Thus, the switching control circuit 1003 can determine whether each battery cell 1009 is a high-voltage cell or a low-voltage cell based on this determination result. Then, the switching control circuit 1003 determines the discharge battery cell group and the charge battery cell group based on this determination result.

[0200] Note that among the plurality of battery cells 1009, high-voltage cells and low-voltage cells can coexist in various states. For example, in the case where high-voltage cells and low-voltage cells coexist, the switching control circuit 1003 sets the portion where the high-voltage cells are most continuously connected in series as the discharge battery cell group. In addition, the switching control circuit 1003 sets the portion where the low-voltage cells are most continuously connected in series as the charge battery cell group. Further, the switching control circuit 1003 may preferentially select the battery cell 1009 close to overcharge or overdischarge as the discharge battery cell group or the charge battery cell group.

[0201] Here, an operation example of the switching control circuit 1003 in the present embodiment will be described with reference to FIG. 12. FIG. 12 is a diagram for explaining the operation example of the switching control circuit 1003. For the sake of convenience of explanation, in FIG. 12, the case where four battery cells 1009 are connected in series will be described as an example.

[0202] ​​​​​First, in the example of FIG. 12(A), assuming that the voltages of battery cells a to d are voltage Va to voltage Vd, it shows a case where Va = Vb = Vc > Vd. That is, three consecutive high- voltage cells a to c and one low-voltage cell d are connected in series. In this case, the switching control circuit 1003 determines the three consecutive high-voltage cells a to c as the discharge battery cell group. Also, the switching control circuit 1003 determines the low-voltage cell d as the charge battery cell group.

[0203] Next, in the example of FIG. 12(B), it shows a case where Vc > Va = Vb >> Vd. That is, two consecutive low-voltage cells a and b, one high-voltage cell c, and one low-voltage cell d near over-discharge are connected in series. In this case, the switching control circuit 1003 determines the high-voltage cell c as the discharge battery cell group. Also, since the low-voltage cell d is near over-discharge, the switching control circuit 1003 preferentially determines the low-voltage cell d rather than the two consecutive low-voltage cells a and b as the charge battery cell group.

[0204] Finally, in the example of FIG. 12(C), it shows a case where Va > Vb = Vc = Vd. That is, one high-voltage cell a and three consecutive low-voltage cells b to d are connected in series. In this case, the switching control circuit 1003 determines the high-voltage cell a as the discharge battery cell group. Also, the switching control circuit 1003 determines the three consecutive low-voltage cells b to d as the charge battery cell group.

[0205] Based on the results determined as in the examples of FIGS. 12(A) to (C) above, the switching control circuit 1003 sets information indicating the discharge battery cell group that is the connection destination of the switching circuit 1004. ​​​The control signal S1 and the information indicating the rechargeable battery cell group which is the connection destination of the switching circuit 1005 are provided The defined control signal S2 is output to the switching circuit 1004 and the switching circuit 1005 respectively thereof.

[0206] The above is the explanation regarding the details of the operation of the switching control circuit 1003.

[0207] The switching circuit 1004, according to the control signal S1 output from the switching control circuit 1003 sets the connection destination of the terminal pair 1001 to the discharge battery cell group determined by the switching control circuit 1003 .

[0208] The terminal pair 1001 is composed of the paired terminals A1 and A2. The switching circuit 1004 connects one of the terminals A1 and A2 to the positive terminal of the battery cell 1009 located most upstream (higher potential side) in the discharge battery cell group, and the other to the negative terminal of the battery cell 1009 located most downstream (lower potential side) in the discharge battery cell group, thereby setting the connection destination of the terminal pair 1001. Note that the switching circuit 1004 can recognize the position of the discharge battery cell group using the information set in the control signal S1.

[0209] The switching circuit 1005, according to the control signal S2 output from the switching control circuit 1003 sets the connection destination of the terminal pair 1002 to the rechargeable battery cell group determined by the switching control circuit 1003 .

[0210] The terminal pair 1002 is composed of the paired terminals B1 and B2. The switching circuit 1005 connects one of the terminals B1 and B2 to the positive terminal of the battery cell located most upstream (higher potential side) in the rechargeable battery cell group, and the other to the negative terminal of the battery cell located most downstream (lower potential side) in the rechargeable battery cell group, thereby setting the connection destination of the terminal pair 1002. ​​​​One end is connected to the positive terminal of the battery cell 1009 located on the upstream (higher potential side), and the other end is connected to the negative terminal of the battery cell 1009 located on the most downstream (lower potential side) among the rechargeable battery cell group, thereby setting the connection destination of the terminal pair 1002. Note that the switching circuit 1005 can recognize the position of the rechargeable battery cell group using the information set in the control signal S2. By connecting to the negative terminal of the battery cell 1009 located on the most downstream (lower potential side), the connection destination of the terminal pair 1002 is set. Note that the switching circuit 1005 can recognize the position of the rechargeable battery cell group using the information set in the control signal S2. One end is connected to the positive terminal of the battery cell 1009 located on the upstream (higher potential side), and the other end is connected to the negative terminal of the battery cell 1009 located on the most downstream (lower potential side) among the rechargeable battery cell group, thereby setting the connection destination of the terminal pair 1002. Note that the switching circuit 1005 can recognize the position of the rechargeable battery cell group using the information set in the control signal S2. One end is connected to the positive terminal of the battery cell 1009 located on the upstream (higher potential side), and the other end is connected to the negative terminal of the battery cell 1009 located on the most downstream (lower potential side) among the rechargeable battery cell group, thereby setting the connection destination of the terminal pair 1002. Note that the switching circuit 1005 can recognize the position of the rechargeable battery cell group using the information set in the control signal S2.

[0211] Circuit diagrams showing configuration examples of the switching circuit 1004 and the switching circuit 1005 are shown in FIGS. 13 and 14. Circuit diagrams showing configuration examples of the switching circuit 1004 and the switching circuit 1005 are shown in FIGS. 13 and 14.

[0212] In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009. In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009. In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009. In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009. In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009. In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and a bus 1012. The bus 1011 is connected to the terminal A1. Also, the bus 1012 is connected to the terminal A2. One of the sources or drains of the plurality of transistors 1010 is alternately connected to the buses 1011 and 1012 every other one. Also, the other of the sources or drains of the plurality of transistors 1010 is connected between two adjacent battery cells 1009.

[0213] Among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most upstream is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery unit 1008. Also, among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008. Among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most upstream is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery unit 1008. Also, among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008. Among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most upstream is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery unit 1008. Also, among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008. Among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008. Among the plurality of transistors 1010, the other of the source or drain of the transistor 1010 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008.

[0214] The switching circuit 1004 applies the control signal S1 to the gates of the plurality of transistors 1010. Accordingly, one of the plurality of transistors 1010 connected to bus 1011 and one of the plurality of transistors 1010 connected to bus 1 012 are each turned on to connect the discharge battery cell group and the terminal pair 1001. As a result, the positive terminal of the battery cell 1009 located most upstream in the discharge battery cell group is connected to either terminal A1 or A 2 of the terminal pair. Also, the negative terminal of the battery cell 1009 located most downstream in the discharge battery cell group is connected to the other of terminals A1 and A2 of the terminal pair, that is, the terminal not connected to the positive terminal .. It is preferable to use an OS transistor for the transistor 1010. Since the OS transistor has a small off-current, it is possible to reduce the amount of charge leaking from battery cells not belonging to the discharge battery cell group and suppress the decrease in capacity over time. Also, the OS transistor is less likely to break down due to dielectric breakdown when a high voltage is applied. Therefore, even when the output voltage of the discharge battery cell group is large, the battery cell 1009 to which the non-conducting transistor 1010 is connected and the terminal pair 1001 can be kept in an insulated state. ..

[0215] .. .. .. .. .. ..

[0216] Also, in FIG. 13, the switching circuit 1005 includes a plurality of transistors 1013, a current control switch 1014, a bus 1015, and a bus 1016. Buses 1015 and 10 16 are arranged between the plurality of transistors 1013 and the current control switch 1014. One of the source or drain of the plurality of transistors 1013 is connected to the buses 1015 and 1016 alternately, one by one .. .. The other of the source or drain is connected between two adjacent battery cells 1009 respectively. It is.

[0217] Among the plurality of transistors 1013, the other of the source or drain of the transistor 1013 located at the most upstream is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery unit 1008. Also, among the plurality of transistors 1013, the other of the source or drain of the transistor 1013 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008.

[0218] For the transistor 1013, it is preferable to use an OS transistor in the same manner as the transistor 1010. Since the OS transistor has a small off - current, it can reduce the amount of charge leaked from battery cells that do not belong to the rechargeable battery cell group and suppress the capacity reduction over time. Also, the OS transistor is less likely to cause dielectric breakdown when a high voltage is applied. Therefore, even if the voltage for charging the rechargeable battery cell group is large, the battery cell 1009 to which the transistor 1013 in the non - conducting state is connected and the terminal pair 1002 can be insulated.

[0219] The current control switch 1014 has a switch pair 1017 and a switch pair 1018. One end of the switch pair 1017 is connected to the terminal B1. Also, the other end of the switch pair 1017 branches into two switches, one switch is connected to the bus 1015, and the other switch is connected to the bus 1016. One end of the switch pair 1018 is connected to the terminal B2. Also, the other end of the switch pair 1018 branches into two switches, one switch is connected to the bus 1015, and the other One switch is connected to bus 1015, and the other switch is connected to bus 1016. .

[0220] The switches included in switch pair 1017 and switch pair 1018 preferably use OS transistors, similar to transistor 1010 and transistor 1013.

[0221] Switching circuit 1005 controls the combination of the on / off states of transistor 1013 and current control switch 1014 according to control signal S2, thereby connecting the rechargeable battery cell group to terminal pair 1002.

[0222] Switching circuit 1005 connects the rechargeable battery cell group to terminal pair 100 2 as follows, for example.

[0223] Switching circuit 1005 turns on the transistor 1013 connected to the positive terminal of battery cell 1009, which is located most upstream in the rechargeable battery cell group, according to the control signal S2 applied to the gates of the plurality of transistors 1013. Also, switching circuit 1005 turns on the transistor 1013 connected to the negative terminal of battery cell 1009, which is located most downstream in the rechargeable battery cell group, according to the control signal S2 applied to the gates of the plurality of transistors 1013.

[0224] The polarity of the voltage applied to terminal pair 1002 can vary depending on the discharge battery cell group connected to terminal pair 1001 and the configuration of transformer circuit 1007. Also, in order to allow current to flow in the charging direction of the rechargeable battery cell group, it is necessary to connect terminals of the same polarity between terminal pair 1002 and the rechargeable battery cell group. Therefore, current control switch 1014 is controlled by control signal S2 ​ The switch pairs 1017 and 10 18 are controlled to switch their connection destinations according to the polarity of the voltage applied to the terminal pair 1002, respectively.

[0225] As an example, a state will be described in which a voltage is applied to the terminal pair 1002 such that the terminal B1 is the positive electrode and the terminal B2 is the negative electrode. At this time, when the lowermost battery cell 1009 of the battery unit 1008 is a rechargeable battery cell group, the switch pair 1017 is controlled by the control signal S2 to be connected to the positive electrode terminal of the battery cell 1009. That is, the switch connected to the bus 1016 of the switch pair 1017 is turned on, and the switch connected to the bus 101 5 of the switch pair 1017 is turned off. On the other hand, the switch pair 1018 is controlled by the control signal S2 to be connected to the negative electrode terminal of the battery cell 1009. That is, the switch connected to the bus 1015 of the switch pair 1018 is turned on, and the switch connected to the bus 101 6 of the switch pair 1018 is turned off. In this way, terminals with the same polarity are connected between the terminal pair 1002 and the rechargeable battery cell group. And the direction of the current flowing from the terminal pair 1002 is controlled to be the direction of charging the rechargeable battery cell group. 1002 and the rechargeable battery cell group, terminals with the same polarity are connected to each other. And the direction of the current flowing from the terminal pair 1002 is controlled to be the direction of charging the rechargeable battery cell group. is controlled.

[0226] Also, the current control switch 1014 may be included in the switching circuit 1004 instead of the switching circuit 1005. In this case, the current control switch 1014 controls the polarity of the voltage applied to the terminal pair 1002 by controlling the polarity of the voltage applied to the terminal pair 1001 according to the control signal S1. 04. In this case, the current control switch 1014 controls the polarity of the voltage applied to the terminal pair 1002 by controlling the polarity of the voltage applied to the terminal pair 1001 according to the control signal S1. Accordingly, the polarity of the voltage applied to the terminal pair 1002 is controlled. And the current control switch 1014 controls the direction of the current flowing from the terminal pair 100 2 to the rechargeable battery cell group. 2 to the rechargeable battery cell group.

[0227] FIG. 14 is a circuit diagram showing a configuration example of the switching circuit 1004 and the switching circuit 1005, which is different from that of FIG. 13.

[0228] In FIG. 14, the switching circuit 1004 includes a plurality of transistor pairs 1021, a bus 1024 and a bus 1025. The bus 1024 is connected to the terminal A1. Also, the bus 1025 is connected to the terminal A2. One end of each of the plurality of transistor pairs 1021 branches into a transistor 1022 and a transistor 1023, respectively. One of the source or drain of the transistor 1022 is connected to the bus 1024. Also, one of the source or drain of the transistor 1023 is connected to the bus 1025. Also, the other ends of the plurality of transistor pairs are connected between two adjacent battery cells 1009, respectively. Note that, among the plurality of transistor pairs 1021, the other end of the transistor pair 1021 located at the most upstream is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery unit 1008. Also, among the plurality of transistor pairs 1021, the other end of the transistor pair 1021 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery unit 1008. terminal.

[0229] The switching circuit 1004 switches the conduction / non-conduction states of the transistor 1022 and the transistor 1023 according to the control signal S1, thereby switching the connection destination of the transistor pair 1021 to either the terminal A1 or the terminal A2. Specifically, if the transistor 1 022 is in the conduction state, the transistor 1023 is in the non-conduction state, and the transistor pair 1021 is connected to the terminal A1. If the transistor 1022 is in the non-conduction state, the transistor 1023 is in the conduction state, and the transistor pair 1021 is connected to the terminal A2. ​​​The connection destination of 1021 is terminal A1. On the other hand, if transistor 1023 is in the conducting state, transistor 1022 will be in the non-conducting state, and the connection destination of transistor pair 1021 is terminal A2 will be. Which of transistor 1022 and transistor 1023 is in the conducting state is determined by control signal S1.

[0230] To connect terminal pair 1001 and the discharge battery cell group, two transistor pairs 1021 are used required. Specifically, based on control signal S1, the connection destinations of the two transistor pairs 1021 are respectively determined, whereby the discharge battery cell group and terminal pair 1001 are connected. The connection destinations of each of the two transistor pairs 1021 are controlled by control signal S1 such that one is terminal A1 and the other is terminal A2.

[0231] Switching circuit 1005 has a plurality of transistor pairs 1031, bus 1034, and bus 10 35. Bus 1034 is connected to terminal B1. Also, bus 1035 is connected to terminal B2. One end of each of the plurality of transistor pairs 1031 branches into transistor 1032 and transistor 1033 respectively. One of the source or drain of transistor 1032 is connected to bus 1034. Also, one of the source or drain of transistor 103 3 is connected to bus 1035. Also, the other end of each of the plurality of transistor pairs 1031 is connected between two adjacent battery cells 1009 respectively. Note that among the plurality of transistor pairs 1031, the other end of the transistor pair 1 031 located at the most downstream is connected to the negative terminal of the battery cell 1009 located at the most downstream of battery unit 1008 ​Among the plurality of transistor pairs 1031, the transistor pair 1031 located at the most upstream The other end of is connected to the negative terminal of the battery cell 1009 located at the most upstream of the battery unit 1008 and is.

[0232] The switching circuit 1005 switches the conduction / non - conduction states of the transistor 1032 and the transistor 1033, thereby switching the connection destination of the transistor pair 1031 to either the terminal B1 or the terminal B2. Specifically, if the transistor 1032 is in the conduction state, the transistor 1033 is in the non - conduction state, and the connection destination of the transistor pair 1031 is the terminal B1. Conversely, if the transistor 1033 is in the conduction state, the transistor 1032 is in the non - conduction state, and the connection destination of the transistor pair 1031 is the terminal B2 . Whether the transistor 1032 or the transistor 1033 is in the conduction state is determined by the control signal S2.

[0233] To connect the terminal pair 1002 and the rechargeable battery cell group, two transistor pairs 1031 are used . Specifically, based on the control signal S2, the connection destinations of the two transistor pairs 1031 are respectively determined, whereby the rechargeable battery cell group and the terminal pair 1002 are connected. The connection destinations of the two transistor pairs 1031 are controlled by the control signal S2 such that one becomes the terminal B1 and the other becomes the terminal B2.

[0234] Also, the connection destinations of the two transistor pairs 1031 are determined by the polarity of the voltage applied to the terminal pair 1002. Specifically, when a voltage such that the terminal B1 is the positive electrode and the terminal B2 is the negative electrode is applied to the terminal pair 1002, the upstream transistor pair 1031 is​​​ Therefore, the transistor 1032 is turned on and the transistor 1033 is turned off. On the other hand, the downstream transistor pair 1031 is controlled by the control signal S2. The transistor 1033 is controlled to be in a conductive state and the transistor 1032 is controlled to be in a non-conductive state. It is controlled by the signal S2. Also, the voltage at terminal B1 becomes negative and the voltage at terminal B2 becomes positive. When a voltage is applied to terminal pair 1002, the upstream transistor pair 1031 The control circuit 1034 controls the transistor 1033 so that the transistor 1033 is in a conducting state and the transistor 1032 is in a non-conducting state. On the other hand, the downstream transistor pair 1031 is controlled by the transistor A control signal S2 is supplied to the transistor 1032 so that the transistor 1032 is in a conducting state and the transistor 1033 is in a non-conducting state. In this way, the same The terminals with polarity are connected to each other. The direction of the current flowing from the terminal pair 1002 is the charging direction. The battery cell group is controlled in a charging direction.

[0235] The transformer control circuit 1006 controls the operation of the transformer circuit 1007. , the number of battery cells 1009 included in the discharge battery cell group and the number of battery cells 1009 included in the charge battery cell group Based on the number of cells 1009, a transformer signal S3 is generated to control the operation of the transformer circuit 1007. The converted signal is output to the transformer circuit 1007.

[0236] The number of battery cells 1009 included in the discharge battery cell group is equal to the number of battery cells 1009 included in the charge battery cell group. If the number of the battery cells 1009 is larger than the number of the battery cells 1009, an excessively large charging voltage is applied to the charging battery cell group. Therefore, the transformer control circuit 1006 is The voltage conversion circuit 1007 is controlled so as to step down the discharge voltage (Vdis) within the range where the cell group can be charged. A voltage conversion signal S3 for controlling is output.

[0237] Also, when the number of battery cells 1009 included in the discharge battery cell group is less than or equal to the number of battery cells 1009 included in the charge battery cell group, it is necessary to secure the charging voltage required to charge the charge battery cell group. Therefore, the voltage conversion control circuit 1006 outputs a voltage conversion signal S3 for controlling the voltage conversion circuit 1007 so as to step up the discharge voltage (Vdis) within the range where an excessive charging voltage is not applied to the charge battery cell group. 07.

[0238] Note that the voltage value for the excessive charging voltage can be determined in consideration of product specifications and the like of the battery cells 1009 used in the battery unit 1008. Also, the voltage stepped up and down by the voltage conversion circuit 1007 is applied to the terminal pair 1002 as the charging voltage (Vcha).

[0239] Here, an operation example of the voltage conversion control circuit 1006 in the present embodiment will be described with reference to FIGS. 15(A) to (C). FIGS. 15(A) to (C) are conceptual diagrams for explaining an operation example of the voltage conversion control circuit 1006 corresponding to the discharge battery cell group and the charge battery cell group described in FIGS. 12(A) to (C). Note that FIGS. 15(A) to (C) show the battery control unit 1041. The battery control unit 1041 includes a terminal pair 1001, a terminal pair 1002, a switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, a voltage conversion control circuit 1006, and a voltage conversion circuit 1007.

[0240] In the example shown in FIG. 15(A), as described in FIG. 12(A), three consecutive high voltages Cells a to c and one low-voltage cell d are connected in series. In this case, as described with reference to Fig. 12(A ), the switching control circuit 1003 determines the high-voltage cells a to c as the discharge battery cell group and determines the low-voltage cell d as the charge battery cell group. Then, the voltage conversion control circuit 1006 calculates the conversion ratio N from the discharge voltage (Vdis ) to the charge voltage (Vcha) based on the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. s) to the charge voltage (Vcha). It is preferable that the voltage conversion control circuit 1006 makes the conversion ratio N about 1 to 10% larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. At this time, the charge voltage is higher than the voltage of the charge battery cell group.

[0241] Note that when the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. It is preferable that the voltage conversion control circuit 1006 makes the conversion ratio N about 1 to 10% larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. At this time, the charge voltage is higher than the voltage of the charge battery cell group. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. When the number of battery cells 1009 included in the discharge battery cell group is larger than the number of battery cells 1009 included in the charge battery cell group, if the discharge voltage is directly applied to the terminal pair 1002 without voltage conversion, there is a possibility that an excessive voltage will be applied to the battery cells 1009 included in the charge battery cell group via the terminal pair 1002. Therefore, in the case shown in Fig. 15(A), it is necessary to step down the charge voltage (Vcha) applied to the terminal pair 1002 to be lower than the discharge voltage. Further, in order to charge the charge battery cell group, the charge voltage needs to be larger than the total voltage of the battery cells 1009 included in the charge battery cell group. Therefore, the voltage conversion control circuit 1006 sets the conversion ratio N to be larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference.

[0242] The voltage conversion control circuit 1006 sets the conversion ratio N to be about 1 to 10% larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. At this time, the charge voltage is higher than the voltage of the charge battery cell group. The voltage conversion control circuit 1006 sets the conversion ratio N to be about 1 to 10% larger than the ratio of the number of battery cells 1009 included in the charge battery cell group to the number of battery cells 1009 included in the discharge battery cell group when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. Although it increases, actually the charging voltage becomes equal to the voltage of the rechargeable battery cell group. However, the transformer The conversion control circuit 1006 makes the voltage of the rechargeable battery cell group equal to the charging voltage according to the conversion ratio N and causes a current to flow through the rechargeable battery cell group for charging. This current becomes the value set in the conversion control circuit 1006.

[0243] In the example shown in FIG. 15(A), since the number of battery cells 1009 included in the discharge battery cell group is 3 and the number of battery cells 1009 included in the rechargeable battery cell group is 1, the conversion control circuit 1006 calculates a value slightly larger than 1 / 3 as the conversion ratio N. Then, the conversion control circuit 1006 steps down the discharge voltage according to the conversion ratio N and outputs a conversion signal S3 for converting it into a charging voltage to the conversion circuit 1007. Then, the conversion circuit 1007 converts the stepped-down charging voltage according to the conversion signal S3 and applies it to the terminal pair 1002. And the charging voltage applied to the terminal pair 1002 charges the battery cell 1009 included in the rechargeable battery cell group.

[0244] Also, in the examples shown in FIGS. 15(B) and 15(C), similarly to FIG. 15(A), the conversion ratio N is calculated. In the examples shown in FIGS. 15(B) and 15(C), since the number of battery cells 1009 included in the discharge battery cell group is less than or equal to the number of battery cells 1009 included in the rechargeable battery cell group, the conversion ratio N becomes greater than 1. Therefore, in this case, the conversion control circuit 1006 outputs a conversion signal S3 for stepping up the discharge voltage and converting it into a charging voltage.

[0245] The conversion circuit 1007 converts the discharge voltage applied to the terminal pair 1001 into a charging voltage based on the conversion signal S3. Then, the conversion circuit 1007 applies the converted charging voltage to the terminal pair 100 Apply it to 2. Here, the transformer circuit 1007 electrically insulates between the terminal pair 1001 and the terminal pair 1002. This prevents a short circuit due to the difference in the absolute voltage of the negative terminal of the battery cell 1009 located at the most downstream in the discharge battery cell group and the absolute voltage of the negative terminal of the battery cell 1009 located at the most downstream in the charge battery cell group. Further, as described above, the transformer circuit 1007 converts the discharge voltage, which is the total voltage of the discharge battery cell group, into a charge voltage based on the transformer signal S3. Moreover, the transformer circuit 1007 can use, for example, an isolated DC (Direct Current)-DC converter or the like. In this case, the transformer control circuit 1006 outputs a signal for controlling the on / off ratio (duty ratio) of the isolated DC-DC converter as the transformer signal S3, thereby controlling the charge voltage converted by the transformer circuit 1007. Note that isolated DC-DC converters include flyback, forward, RCC (Ringing Choke Converter), push-pull, half-bridge, and full-bridge types, etc. An appropriate type is selected according to the magnitude of the target output voltage. The configuration of the transformer circuit 1007 using an isolated DC-DC converter is shown in FIG. 16. The isolated DC-DC converter 1051 has a switch section 1052 and a transformer section 1053. The switch section 1052 is a switch that switches the on / off of the operation of the isolated DC-DC converter. For example, it is a MOSFET (Metal-Oxide-Semiconductor).

[0246] Also, the transformer circuit 1007 can use, for example, an isolated DC (Direct Current)-DC converter or the like. In this case, the transformer control circuit 1006 outputs a signal for controlling the on / off ratio (duty ratio) of the isolated DC-DC converter as the transformer signal S3 to control the charge voltage converted by the transformer circuit 1007. Outputting, by

[0247] Note that isolated DC-DC converters include flyback, forward, RCC ( Ringing Choke Converter), push-pull, half-bridge ridge, and full-bridge types, etc. An appropriate type is selected according to the magnitude of the target output voltage to be.

[0248] The configuration of the transformer circuit 1007 using an isolated DC-DC converter is shown in FIG. 16. The isolated DC-D C-DC converter 1051 has a switch section 1052 and a transformer section 1053. The switch section 1052 is a switch that switches the on / off of the operation of the isolated DC-DC converter, and for example, it is a MOSFET (Metal-Oxide-Semiconductor). a toroidal field-effect transistor, a bipolar transistor, or the like The switch unit 1052 is realized by using a transformer control circuit 1006 Based on the transformer signal S3 that is output from the transformer control circuit 1006 and controls the on / off ratio, the switch unit 1052 periodically switches between the on state and the off state of the isolated DC-DC converter 1051 Note that the switch unit 1052 can have various configurations depending on the type of isolated DC-DC converter used The transformer unit 1053 converts the discharge voltage applied from the terminal pair 1001 into a charging voltage Specifically, the transformer unit 1053 operates in conjunction with the on / off state of the switch unit 1052 and converts the discharge voltage into a charging voltage according to its on / off ratio This charging voltage increases as the time in the on state becomes longer during the switching period of the switch unit 1052 When using an isolated DC-DC converter, the terminal pair 1001 and the terminal pair 1002 can be insulated from each other inside the transformer unit 1053

[0249] The processing flow of the power storage device 1000 in this embodiment will be described with reference to FIG. 17. FIG. 17 is a flowchart showing the processing flow of the power storage device 1000

[0250] First, the power storage device 1000 acquires the voltages measured for each of the plurality of battery cells 1009 (step S1101). Then, the power storage device 1000 determines whether or not the start condition for the operation of equalizing the voltages of the plurality of battery cells 1009 is satisfied (step S1102). This start condition can be, for example, whether or not the difference between the maximum value and the minimum value of the voltages measured for each of the plurality of battery cells 1009 is equal to or greater than a predetermined threshold value If this start condition is not satisfied (step S1102), the process proceeds to step ​​​​​​S1102:NO), since the voltages of the respective battery cells 1009 are balanced, the power storage device 1000 does not execute the subsequent processing. On the other hand, when the start condition is satisfied (step S1102:YES), the power storage device 1000 executes a process of equalizing the voltages of the respective battery cells 1009. In this process, based on the measured voltage for each cell, the power storage device 1000 determines whether each battery cell 1009 is a high-voltage cell or a low-voltage cell (step S1103). Then, based on the determination result, the power storage device 1000 determines a discharge battery cell group and a charge battery cell group (step S1104). Furthermore, the power storage device 1000 generates a control signal S1 for setting the determined discharge battery cell group as the connection destination of the terminal pair 1001, and a control signal S2 for setting the determined charge battery cell group as the connection destination of the terminal pair 1002 (step S110 5). The power storage device 1000 outputs the generated control signal S1 and control signal S2 to the switching circuit 1004 and the switching circuit 1005, respectively. Then, the switching circuit 1004 connects the terminal pair 1001 to the discharge battery cell group, and the switching circuit 1005 connects the terminal pair 1002 to the charge battery cell group (step S1106). Also, the power storage device 1000 generates a voltage conversion signal S3 based on the number of battery cells 1009 included in the discharge battery cell group and the number of battery cells 1009 included in the charge battery cell group (step S1 107). Then, based on the voltage conversion signal S3, the power storage device 1000 converts the discharge voltage applied to the terminal pair 1001 into a charge voltage and applies it to the terminal pair 1002 (step S1108). As a result, the charge of the discharge battery cell group is transferred to the charge battery cell group.

[0251] ​​​​Also, in the flowchart of FIG. 17, although a plurality of steps are described in order, the execution order of each step is not limited to the described order. That is, the execution order of each step is not limited to the order of description.

[0252] As described above, according to the present embodiment, when moving charge from the discharge battery cell group to the charge battery cell group, it is not necessary to have a configuration such as a capacitor type that once accumulates the charge from the discharge battery cell group and then discharges it to the charge battery cell group. Thereby, the charge transfer efficiency per unit time can be improved. Further, by the switching circuit 1004 and the switching circuit 1005, among the discharge battery cell group and the charge battery cell group, the battery cells connected to the transformer circuit can be individually switched. That is, it is not necessary to have a configuration that once accumulates the charge from the discharge battery cell group and then discharges it to the charge battery cell group, such as a capacitor type. Thereby, the charge transfer efficiency per unit time can be improved. Further, by the switching circuit 1004 and the switching circuit 1005, among the discharge battery cell group and the charge battery cell group, the battery cells connected to the transformer circuit can be individually switched. That is, among the discharge battery cell group and the charge battery cell group, the battery cells connected to the transformer circuit can be individually switched. switched.

[0253] Furthermore, based on the number of battery cells 1009 included in the discharge battery cell group and the number of battery cells 1009 included in the charge battery cell group, the discharge voltage applied to the terminal pair 1001 is converted into a charge voltage and applied to the terminal pair 1002 by the transformer circuit 1007. Thereby, regardless of how the battery cells 1009 on the discharge side and the charge side are selected, charge transfer can be realized without problems. Furthermore, based on the number of battery cells 1009 included in the discharge battery cell group and the number of battery cells 1009 included in the charge battery cell group, the discharge voltage applied to the terminal pair 1001 is converted into a charge voltage and applied to the terminal pair 1002. Thereby, regardless of how the battery cells 1009 on the discharge side and the charge side are selected, charge transfer can be realized without problems. That is, regardless of how the battery cells 1009 on the discharge side and the charge side are selected, charge transfer can be realized without problems. can be achieved.

[0254] Furthermore, by using OS transistors for the transistor 1010 and the transistor 1013, the amount of charge leaked from the battery cells 1009 that do not belong to the charge battery cell group and the discharge battery cell group can be reduced. Thereby, a decrease in the capacity of the battery cells 1009 that do not contribute to charging and discharging can be suppressed. Also, the OS transistor has less variation in characteristics with respect to heat compared to the Si transistor. Thereby, even when the temperature of the battery cell 1009 rises, normal operations such as switching between the conducting state and the non-conducting state according to the control signals S1 and S2 can be performed. Furthermore, by using OS transistors for the transistor 1010 and the transistor 1013, the amount of charge leaked from the battery cells 1009 that do not belong to the charge battery cell group and the discharge battery cell group can be reduced. Thereby, a decrease in the capacity of the battery cells 1009 that do not contribute to charging and discharging can be suppressed. Also, the OS transistor has less variation in characteristics with respect to heat compared to the Si transistor. Thereby, even when the temperature of the battery cell 1009 rises, normal operations such as switching between the conducting state and the non-conducting state according to the control signals S1 and S2 can be performed. It is possible to do so.

[0255] This embodiment mode can be implemented in appropriate combination with other embodiment modes. EXAMPLES

[0256] Hereinafter, one embodiment of the present invention will be described in detail with reference to an example. The results of producing a positive electrode by the method shown in embodiment 2 will be described. The present invention is not limited to the above examples.

[0257] (Preparation of active material layer) The active material layer was prepared using LiFePO4 as the active material and graphene oxide as the raw material for the conductive additive. The materials used were PVDF as a binder, and NMP as a solvent. The mixture to which laphene was added was mixed with NMP as a solvent and kneaded. A mixture of graphene and LiFePO4 was added with PVdF (Kureha Corporation) as a binder solution. After adding NMP solution of 100% NMP (No. 7300), NMP was further added as a polar solvent. The paste was made by kneading. The mixing ratio of each was LiFePO4:Oxidation graph The ratio of PVDF to PVDF was 94.2:0.8:5 (by weight). The paste was applied to the current collector and heated at 65°C for 15 minutes and then at 75°C for 15 minutes under reduced pressure. The polar solvent contained in the paste was evaporated to form an active material layer. Aluminum was coated with carbon black to a thickness of about 1 μm. The loading of the paste is about 9mg / cm 2 The following describes the active material layer: The following shows how electrodes A to D and comparative examples E and F were prepared by performing different reduction treatments. .

[0258] (Fabrication of Electrode A) First, the active material layer and the current collector fabricated by the above procedure were immersed in ethanol (99. 5%) heated to 60 °C for 10 minutes. The active material layer and the current collector taken out from ethanol were heated at 1 00 °C for 10 hours under reduced pressure to reduce graphene oxide, thereby fabricating Electrode A.

[0259] (Fabrication of Electrode B) Similar to the fabrication of Electrode A, the active material layer and the current collector were immersed in ethanol at 60 °C and then heated at 150 °C for 10 hours to reduce graphene oxide, thereby fabricating Electrode B.

[0260] (Fabrication of Electrode C) Similar to the fabrication of Electrodes A and B, the active material layer and the current collector were immersed in ethanol at 60 °C and then heated at 1 70 °C for 10 hours to reduce graphene oxide, thereby fabricating Electrode C.

[0261] (Fabrication of Electrode D) Different from the fabrication of Electrodes A, B, and C, the active material layer and the current collector were immersed in ethanol at room temperature (25 °C) for 10 minutes and then heated at 100 °C for 10 hours under reduced pressure to fabricate Electrode D.

[0262] (Fabrication of Comparative Example E) For comparison, a positive electrode was fabricated by reducing graphene oxide only by heating without immersing the active material layer in ethanol. The positive electrode fabricated by heating the active material layer and the current collector at 170 °C for 10 hours was used as Comparative Example E. was fabricated and used as Comparative Example E.

[0263] (Fabrication of Comparative Example F) For comparison, a positive electrode was fabricated by reducing graphene oxide by immersing the active material layer in a solution containing a reducing agent. The solution containing the reducing agent was prepared by using L-ascorbic acid as the reducing agent as the reducing agent. An acid was used with lithium hydroxide as a pH adjuster. First, L-ascorbic acid and lithium hydroxide were dissolved in a water-NMP mixed solution (water:NMP = 1:9 (volume ratio)) so that their concentrations were 77 mM and 73 mM, respectively, to prepare a solution. This solution was immersed with the active material layer and the current collector, heated at 60 °C for 1 hour for reaction, washed, and then heated at 170 °C under reduced pressure to evaporate the solvent, thereby preparing Comparative Example F.

[0264] (Observation of cross-section of active material layer) For the fabricated Electrode A, SEM observation of the polished cross-section was performed using a cross-section polisher. Fig. 23 shows a cross-sectional SEM image of the active material layer of Electrode A at 30,000 times magnification.

[0265] As shown in Fig. 23, in the active material layer of Electrode A, the sheet-like graphene 902 is in contact with or covers the granular active material 901. Also, although not emphasized, the graphenes are in contact with each other. Therefore, it was found that a three-dimensional electrically conductive network was formed in the active material layer of Electrode A. Also, no particular damage was observed inside the active material layer. From this, it was found that by immersing the active material layer and the current collector in ethanol and then taking them out and heating, an electrode with less damage to the active material layer can be fabricated.

[0266] (Fabrication of half cell) Electrodes A, D and Comparative Examples E, F were incorporated into half cells as the positive electrodes, and the charge-discharge electrical characteristics of each cell were measured. A half cell refers to a cell of a lithium-ion secondary battery using an active material other than Li metal for the positive electrode and Li metal for the negative electrode. Lithium metal was used for the negative electrode, and the ​​​​​​​​​​​​​The plate is made of polypropylene (PP) and the electrolyte is ethylene carbonate (EC). Diethyl carbonate (DEC) was mixed with 6-fluorouracil in a volume ratio of 1:1. Lithium fluoride phosphate (LiPF6) was dissolved at a concentration of 1 mol / liter.

[0267] (Evaluation of cycle characteristics of half-cell) The half cells using electrodes A, D and comparative examples E and F were subjected to charge / discharge cycles at 25°C. The results of measuring the discharge capacity during charging are shown in Figure 18. In Figure 18, the vertical axis indicates the capacity (mAh / g), the horizontal axis is the number of cycles. The charge and discharge conditions were constant current and constant voltage for cycles 1 to 6. The charge rate was 0.2C, the charge rate was 0.2C, and the discharge rate was 0.2C. In the 36th test, the charge and discharge conditions were: constant current charge, charge rate 1C, constant current discharge, discharge rate It was 1C.

[0268] Here, we will explain the charge rate and discharge rate. A charge rate of 1C is the capacity x (Ah ) cell is charged at a constant current and the charging is completed in exactly one hour. = I(A), then a charging rate of 0.2C is I / 5(A), i.e. Similarly, a discharge rate of 1C means that the capacity of the battery is 1000mA. This is the current value at which a cell of quantity X (Ah) is discharged at a constant current and the discharge is completed in exactly one hour. Also, a discharge rate of 0.2C is I / 5(A), which is exactly 5 This refers to the current value at which discharge ends in time.

[0269] From Figure 18, the half-cells using electrodes A and D have almost the same discharge capacity. In addition, after the half cell using electrodes A and D, the comparative example E was used. The discharge capacity of the half-cell was high, and the half-cell using Comparative Example F had the smallest discharge capacity. Here, Electrodes A and D are electrodes obtained by reducing graphene oxide by heating after immersing them in ethanol. Comparative Example E is an electrode prepared by reducing graphene oxide by heating without immersing it in ethanol. Further, Comparative Example F is an electrode prepared by reducing graphene oxide by immersing it in a solution containing L-ascorbic acid. Therefore, it was found that when using an electrode obtained by reducing graphene oxide by heating, a half-cell with a larger discharge capacity is obtained than when using an electrode obtained by reducing graphene oxide by immersing it in a solution containing L-ascorbic acid. Also, it was found that by performing the operation of immersing in ethanol before heating, the discharge capacity of the half-cell can be increased.

[0270] Also, the discharge capacity of the half-cell using Comparative Example F decreased with an increase in the number of cycles, but it was found that the decrease in the discharge capacity was suppressed in the half-cells using Electrodes A and D. From this result, it became clear that the cycle characteristics of the half-cell are improved when using Electrodes A and D. Therefore, Electrodes A and D are electrodes with less damage to the active material layer, and it was found that the electrical conduction path in the active material layer is less likely to be interrupted because they are less likely to expand or deform.

[0271] (Evaluation of rate characteristics) Figures 19 and 20 show the discharge curves measured by changing the charge and discharge rate at 25 °C for the half-cells using Electrodes A and D and Comparative Examples E and F. The vertical axis represents voltage (V), and the horizontal axis represents discharge capacity (mAh / g (positive electrode weight)). The charging conditions were constant current constant voltage charging and a charging rate of 0. ​​​​​​​​​​​​​.2C, and the discharge condition is constant current discharge, and the discharge rates are 0.2C, 1C, 2C, 5C, 10C. FIG. 19(A) shows the discharge curve of the half-cell using electrode A. Also, FIG. 19(B) shows the discharge curve of the half-cell using electrode D. Also, FIG. 20(A) shows the ratio of the discharge curve of the half-cell using Comparative Example E. Also, FIG. 20(B) shows the discharge curve of the half-cell using Comparative Example F.

[0272] As can be seen by comparing FIGS. 19(A), (B) and FIGS. 20(A), (B), the slope near the end (end of discharge) of the discharge curve of the half-cell using Comparative Example F shown in FIG. 20(B ) was larger than that of the other half-cells.

[0273] From this result, it was found that the electrode with the highest conductivity, that is, the electrode that could reduce graphene oxide with the highest reaction efficiency, was Comparative Example F. Next, the conductivity of electrode A and electrode D was high, and it was found that Comparative Example E had the lowest conductivity. From this, it was found that by immersing the active material layer in a solution containing L-ascorbic acid and heating it after taking it out, graphene oxide could be reduced most efficiently. Also, it was shown that by immersing the active material layer in ethanol and heating it after taking it out, the efficiency of the reaction for reducing graphene oxide could also be increased.

[0274] (Measurement of current interruption method resistance) Next, electrode A and Comparative Example E were evaluated by measuring the current interruption method resistance. Here, the current interruption method resistance will be explained. When charging a battery and the charging is interrupted, a behavior of voltage drop can be observed. The cause of this voltage drop is the internal resistance of the battery. {( ​​​​​​​​​The ohmic component of the internal resistance of the half-cell incorporating electrode A and the half-cell incorporating Comparative Example E can be determined by the calculation formula: (voltage immediately after rest) - (voltage 3 seconds after rest) / current. The charging conditions are constant current constant voltage charging at a charging rate of 0.2C. The charging rest is performed every time the battery is charged to 8.5 mAh / g. At 25°C, the charging rest is performed while the battery is charged from 59.5 to 102 mAh / g, and the average value of the ohmic component of the internal resistance calculated during this period is obtained. The ohmic component of the internal resistance of the half-cell incorporating electrode A and the half-cell incorporating Comparative Example E can be determined. The charging conditions are constant current constant voltage charging at a charging rate of 0.2C. The charging rest is performed every time the battery is charged to 8.5 mAh / g. At 25°C, the charging rest is performed while the battery is charged from 59.5 to 102 mAh / g, and the average value of the ohmic component of the internal resistance calculated during this period is obtained. The charging rest is performed while the battery is charged from 59.5 to 102 mAh / g, and the average value of the ohmic component of the internal resistance calculated during this period is obtained.

[0275] The ohmic components of the internal resistance of the half-cell using electrode A and the half-cell using Comparative Example E were 32.6 Ω and 58.0 Ω, respectively. From these results, it was revealed that electrode A has a smaller ohmic component of the internal resistance than Comparative Example E. Therefore, it was suggested that by immersing the active material layer in ethanol and then taking it out and heating it, the efficiency of the reaction for reducing graphene oxide can be increased, and an electrode with a small ohmic component of the internal resistance can be fabricated. The ohmic components of the internal resistance of the half-cell using electrode A and the half-cell using Comparative Example E were 32.6 Ω and 58.0 Ω, respectively. From these results, it was revealed that electrode A has a smaller ohmic component of the internal resistance than Comparative Example E. Therefore, by immersing the active material layer in ethanol and then taking it out and heating it, the efficiency of the reaction for reducing graphene oxide can be increased, and an electrode with a small ohmic component of the internal resistance can be fabricated. The efficiency of the reaction for reducing graphene oxide can be increased, and an electrode with a small ohmic component of the internal resistance can be fabricated. It was suggested that an electrode with a small ohmic component of the internal resistance can be fabricated.

[0276] (Fabrication of full cell) Next, electrode B, electrode C, and Comparative Example E were each incorporated into a full cell, and the charge-discharge electrical characteristics of each cell were measured. The full cell refers to a cell of a lithium-ion secondary battery using active materials other than Li metal for both the positive electrode material and the negative electrode material. For the negative electrode, an electrode using graphite as the active material was used, for the separator, polypropylene (PP) was used, and for the electrolyte, a mixed solution in which lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 mol / liter in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1 was used. The full cell refers to a cell of a lithium-ion secondary battery using active materials other than Li metal for both the positive electrode material and the negative electrode material. For the negative electrode, an electrode using graphite as the active material was used, for the separator, polypropylene (PP) was used, and for the electrolyte, a mixed solution in which lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 mol / liter in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1 was used. For the separator, polypropylene (PP) was used, and for the electrolyte, a mixed solution in which lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 mol / liter in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1 was used. The electrolyte is a mixed solution in which lithium hexafluorophosphate (LiPF6) is dissolved at a concentration of 1 mol / liter in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1. The electrolyte is a mixed solution in which lithium hexafluorophosphate (LiPF6) is dissolved at a concentration of 1 mol / liter in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1. was used.

[0277] (Evaluation of cycle characteristics of full cell)​ Next, the discharge curves of the full cells using electrodes B, C, and Comparative Example E are shown in FIG. 21. The charge-discharge conditions are as follows: when the number of cycles is 1, constant current constant voltage charging, charging rate 0.2C, constant current discharge, discharge rate 0.2C; and when the number of cycles is 2 or more, constant current charging, charging rate 0. 5C, constant current discharge, discharge rate 0.5C. In FIG. 21(A), the horizontal axis represents the number of cycles (times), and the vertical axis represents the discharge capacity (mAh / g (cathode weight)) of the secondary battery. In FIG. 2 (B), the horizontal axis represents the number of cycles (times), and the vertical axis represents the discharge capacity retention rate (%) of the secondary battery. Here, the discharge capacity retention rate is defined as the discharge capacity with respect to the discharge capacity in the second cycle (discharge capacity ÷ discharge capacity in the second cycle × 100 [%]). For convenience, in FIG. 21, the results of the full cell using electrode B, the full cell using electrode C, and the full cell using Comparative Example E are shown as B, C, and E, respectively.

[0278] From FIG. 21(A), it was found that the discharge capacity of the full cell using electrode C was the largest, followed by the full cell using electrode B. The full cell using Comparative Example E had the smallest discharge capacity. From this, it was found that the higher the heating temperature for reducing graphene oxide in the production of the cathode, the more the discharge capacity of the full cell could be improved. On the other hand, from FIG. 21(B), it was found that even as the number of cycles increased, the full cell using electrode B had the least decrease in the discharge capacity retention rate. Next, the full cell using electrode C had a relatively low decrease in the discharge capacity retention rate, and Comparative Example E had the lowest discharge capacity retention rate. Therefore, it was found that the lower the heating temperature in the production of the cathode, the more the cycle characteristics of the full cell could be improved. I see. From this, it was found that by reducing graphene oxide under mild reaction conditions, damage to the active material layer could be prevented.

Example

[0279] In this example, to explain that the reduction of graphene oxide is promoted by alcohol, samples obtained by heating graphene oxide under various conditions were prepared, and the degree of reduction was compared.

[0280] Sample 1 was prepared by dispersing graphene oxide in ethanol and heating it at 100 °C to evaporate the solvent. Also, Comparative Example 2 was prepared by heating graphene oxide under reduced pressure at 30 °C. Further, Comparative Example 3 was prepared by heating graphene oxide to 100 °C.

[0281] The solid 13 13C NMR spectra of Comparative Example 2, Comparative Example 3, and Sample 1 are shown in Fig. 22. In the spectrum of Sample 1, the peaks in the vicinity of 80 ppm to 50 ppm were significantly reduced compared to Comparative Examples 2 and 3. The peaks in the vicinity of 80 ppm to 50 ppm are derived from the carbon of the epoxy group of graphene oxide and the carbon to which the hydroxyl group is bonded. From this, it was found that Sample 1 has fewer epoxy groups and hydroxyl groups than Comparative Examples 2 and 3. Therefore, it was suggested that Sample 1 is graphene containing many carbon-carbon double bonds. Thus, it was found that the reduction of graphene oxide is promoted by alcohol.

Example

[0282] In this example, the results of fabricating the positive electrode by the method using the second conductive assistant shown in Embodiment 2 will be described.

[0283] (Fabrication of Electrodes G and H) For the fabrication of the active material layer, LiFePO4 was used as the active material, graphene oxide (GO) as the raw material of the conductive assistant, acetylene black (AB) or VGCF (registered trademark) as the second conductive assistant, PVdF as the binder, and NMP as the solvent. First, NMP was added to LiFePO4, GO and the second conductive assistant and kneaded to prepare a mixture. Next, an NMP solution of PVdF (No. 7300 manufactured by Kuraray Co., Ltd.) and the second conductive assistant were added to the mixture, and then NMP was further added and kneaded to prepare a paste. The mixing ratio of the materials during paste preparation was LiFePO4:GO:second conductive assistant:PVdF = 93.4:0.6:1:5 (by weight). The paste prepared by the above method was applied to the current collector and heated at 65 °C for 15 minutes and 75 °C for 15 minutes under reduced pressure to evaporate the solvent and form the active material layer. The active material layer and the current collector prepared by the above procedure were immersed in ethanol at 60 °C and then heated at 150 °C for 10 hours to reduce GO and fabricate the electrode. The electrode fabricated using VGCF (registered trademark) as the second conductive assistant was designated as electrode G, and the electrode fabricated using AB as the second conductive assistant was designated as electrode H. Also, the electrode fabricated using the method for fabricating electrode B described in Example 1 was designated as electrode B'.

[0284] The electrode G thus fabricated was subjected to SEM observation of the polished cross-section with a cross-section polisher. 93.4:0.6:1:5 (by weight). The paste prepared by the above method was applied to the current collector and heated at 65 °C for 15 minutes and 75 °C for 15 minutes under reduced pressure to evaporate the solvent and form the active material layer. The active material layer and the current collector prepared by the above procedure were immersed in ethanol at 60 °C and then heated at 150 °C for 10 hours to reduce GO and fabricate the electrode. The electrode fabricated using VGCF (registered trademark) as the second conductive assistant was designated as electrode G, and the electrode fabricated using AB as the second conductive assistant was designated as electrode H.

[0285] The active material layer and the current collector prepared by the above procedure were immersed in ethanol at 60 °C and then heated at 150 °C for 10 hours to reduce GO and fabricate the electrode. The electrode fabricated using VGCF (registered trademark) as the second conductive assistant was designated as electrode G, and the electrode fabricated using AB as the second conductive assistant was designated as electrode H.

[0286] The electrode fabricated using VGCF (registered trademark) as the second conductive assistant was designated as electrode G, and the electrode fabricated using AB as the second conductive assistant was designated as electrode H. The electrode fabricated using VGCF (registered trademark) as the second conductive assistant was designated as electrode G, and the electrode fabricated using AB as the second conductive assistant was designated as electrode H.

[0287] Also, the electrode fabricated using the method for fabricating electrode B described in Example 1 was designated as electrode B'.

[0288] (Observation of the Cross-Section of the Active Material Layer) For the fabricated electrode G, SEM observation of the polished cross-section was performed using a cross-section polisher. It was. In the electrode G used for observation, the weight per unit area of the active material layer was about 11 mg / cm 2 was used. Fig. 24 shows an SEM image of the cross section of the active material layer of the electrode G. Fig. 24(A) is a magnified view at 1 000 times, and Fig. 24(B) is a magnified view at 30,000 times.

[0289] In Fig. 24(A), the current collector 903 and the active material layer 904 were observed. Also, in Fig. 24(B ), the granular active material 901, graphene 902, and needle-like conductive assistant 905 contained in the active material layer 904 were observed. Compared with the graphene 902 being arranged substantially parallel to the surface of the current collector 903, the conductive assistant 905 was arranged obliquely to the surface of the current collector 903. From this, it was speculated that the conductive assistant 905 supplemented the conductive path in the direction perpendicular to the surface of the current collector 903.

[0290] (Fabrication of half cell) Next, using the electrodes G, H, and B' as the positive electrodes, they were incorporated into half cells respectively, and the charge-discharge characteristics of each cell were measured under the same measurement conditions as in Example 1.

[0291] (Evaluation of rate characteristics) Fig. 25(A) shows the relationship between the discharge voltage and the weight of the active material layer of each electrode at discharge rates of 1C and 2C for the half cells using the electrodes G, H, and B'. The vertical axis represents the average discharge voltage [V], and the horizontal axis represents the weight [mg / cm per unit area of the active material layer of the electrode G, H, or B' used, and is plotted. The charging condition was constant current constant voltage charging at a charging rate of 0.2C, and the discharging condition was constant current discharging. 2

[0292] Note that the average discharge voltage is the average of the voltage values from the start of discharge until just before the discharge voltage rapidly decreases in the discharge curve as shown in Fig. 25(B). It is the average of the voltage values from the start of discharge until just before the discharge voltage rapidly decreases.

[0293] In Fig. 25(A), in the half-cell using the electrodes G, H, or B´, as the weight of the active material layer increased, the average discharge voltage decreased. However, the slope of the straight line showing the change in the average discharge voltage of the half-cell using the electrodes G and H was smaller than the slope of the straight line showing the change in the average discharge voltage of the half-cell using the electrode B´. From the above results, it was found that the active material layer having VGCF (registered trademark) or AB as the second conductive assistant is less likely to increase its internal resistance even when its weight increases. This is because in the active material layer having the second conductive assistant, the electrical conduction path has a more complex shape, so that the network is less likely to be cut even when the thickness of the active material layer 202 is increased.

[0294] From the above results, it was found that the active material layer having VGCF (registered trademark) or AB as the second conductive assistant is less likely to increase its internal resistance even when its weight increases. This is because in the active material layer having the second conductive assistant, the electrical conduction path has a more complex shape, so that the network is less likely to be cut even when the thickness of the active material layer 202 is increased. From the above results, it was found that the active material layer having VGCF (registered trademark) or AB as the second conductive assistant is less likely to increase its internal resistance even when its weight increases. This is because in the active material layer having the second conductive assistant, the electrical conduction path has a more complex shape, so that the network is less likely to be cut even when the thickness of the active material layer 202 is increased. From the above results, it was found that the active material layer having VGCF (registered trademark) or AB as the second conductive assistant is less likely to increase its internal resistance even when its weight increases. This is because in the active material layer having the second conductive assistant, the electrical conduction path has a more complex shape, so that the network is less likely to be cut even when the thickness of the active material layer 202 is increased. From the above results, it was found that the active material layer having VGCF (registered trademark) or AB as the second conductive assistant is less likely to increase its internal resistance even when its weight increases. This is because in the active material layer having the second conductive assistant, the electrical conduction path has a more complex shape, so that the network is less likely to be cut even when the thickness of the active material layer 202 is increased.

[0295] (Evaluation of Cycle Characteristics of Half-Cell) Fig. 26 shows a graph representing the change in the discharge voltage when charge and discharge are performed while changing the weight of the active material layer of the positive electrode for the half-cells using the electrodes G, H, and B´. The vertical axis represents the change in the discharge voltage [V] {Change in discharge voltage [V] = (Average discharge voltage [V] in the first cycle) - (Average discharge voltage [V] in the 30th cycle)}, and the horizontal axis is plotted as the weight per unit area [mg / cm of the active material layer of the electrodes G, H, or B´ used. The discharge rate was 1C. H, or B´ used. The discharge rate was 1C. 2 of the active material layer of the electrodes G, H, or B´ used. The discharge rate was 1C.

[0296] From Fig. 26, as the weight of the active material layer increases, the average discharge voltage of the half-cell decreases, but the electric In the half-cell using the electrode G, it was found that the decrease in the average discharge voltage was suppressed compared to the half-cell using the electrode B'. From this, it was found that in the electrode containing the second conductive assistant such as VGCF (registered trademark) or AB, even when the thickness of the active material layer increased, the resistance was less likely to increase.

[0297] (Fabrication of full cell) Next, in the same manner as in Example 1, the electrodes G, H, and B' were incorporated into the full cell, and the charge-discharge characteristics of each cell were measured.

[0298] (Evaluation of cycle characteristics of full cell) The cycle characteristics of the full cell using the electrodes G, H, or B' were evaluated. The experiment was conducted under the same experimental conditions as in Example 1. The results are shown in Fig. 27.

[0299] From Fig. 27, it was found that in the full cell using the electrode G or the electrode H, it was possible to suppress the rapid decrease in the discharge capacity immediately after the start of charge and discharge. From this, it was found that by performing charge and discharge of the full cell, the swelling of the active material layer containing the electrolyte can prevent the electrical conduction path from being disconnected.

[0300] From the above results, by fabricating the electrode using the second conductive assistant, it was possible to strengthen the electrical conduction path in the direction perpendicular to the current collector, and it was found that even when the active material layer became thick, the resistance of the electrode could be reduced. Also, it was found that the cycle characteristics could be improved.

Description of reference numerals

[0301] S101 step S102 step S103 step Step S104 Step S105 Electrode 200 Current collector 201 Active material layer 202 Active material 203 Graphene 204 Coin-type battery 300 Positive electrode can 301 Negative electrode can 302 Gasket 303 Positive electrode 304 Positive electrode current collector 305 Positive electrode active material layer 306 Negative electrode 307 Negative electrode current collector 308 Negative electrode active material layer 309 Separator 310 Battery 500 Positive electrode current collector 501 Positive electrode active material layer 502 Positive electrode 503 Negative electrode current collector 504 Negative electrode active material layer 505 Negative electrode 506 Separator 507 Electrolyte 508 Outer package 509 Battery 600 Positive electrode cap 601 Battery can 602 Positive electrode terminal 603 Positive electrode 604 Separator 605 Negative electrode 606 Negative electrode terminal 607 Insulating plate 608 Insulating plate 609 Gasket (insulating packing) 610 PTC element 611 Safety valve mechanism 612 Display device 700 Housing 701 Display unit 702 Speaker unit 703 Battery 704 Lighting device 710 Housing 711 712 Light source 713 Storage battery 714 Ceiling 715 Side wall 716 Floor 717 Window 720 Indoor unit 721 Housing 722 Air outlet 723 Storage battery 724 Outdoor unit 730 Electric refrigerator-freezer 731 Housing 732 Door for refrigerator compartment 733 Door for freezer compartment 734 Storage battery 800 Tablet terminal 801 Housing 802 Display unit 802a Display unit 802b Display unit 803 Display mode changeover switch 804 Power switch 805 Power saving mode changeover switch 807 Operation switch 808a Touch panel area 808b Touch panel area 809 Operation key 810 Keyboard display changeover button 811 Solar cell 850 Charge-discharge control circuit 851 Battery 852 DCDC converter 853 Converter 860 Electric vehicle 861 Battery 862 Control circuit 863 Driving device 864 Processing device 901 Active material 902 Graphene 903 Current collector 904 Active material layer 905 Conductive aid S1 Control signal S2 control signal S3 transformer signal 1000 energy storage device 1001 terminal pair 1002 terminal pair 1003 switching control circuit 1004 switching circuit 1005 switching circuit 1006 transformer control circuit 1007 transformer circuit 1008 battery section 1009 battery cell 1010 transistor 1011 bus 1012 bus 1013 transistor 1014 current control switch 1015 bus 1016 bus 1017 switch pair 1018 switch pair 1021 transistor pair 1022 transistor 1023 transistor 1024 bus 1025 bus 1031 transistor pair 1032 transistor 1033 transistor 1034 bus 1035 bus 1041 battery control unit 1051 isolated DC-DC converter 1052 switch section 1053 transformer section S1101 step S1102 step S1103 step S1104 step S1105 step S1106 step S1107 step S1108 step

Claims

1. An electrode comprising a current collector and an active material layer, wherein the active material layer is in contact with the current collector, the active material layer includes active material particles, multi-layer graphene as a first conductive aid, and carbon black as a second conductive aid, the active material layer has a region where the first conductive aid is three-dimensionally dispersed, the flake size of the first conductive aid is larger than the average particle size of the active material particles, the first conductive aid has a region arranged along a first direction substantially parallel to the surface of the current collector, the second conductive aid has a region arranged along a second direction intersecting the first direction, a lithium-ion secondary battery.

2. An electrode comprising a current collector and an active material layer, wherein the active material layer is in contact with the current collector, the active material layer includes active material particles, multi-layer graphene as a first conductive aid, and carbon black as a second conductive aid, the active material layer has a region where the first conductive aid is three-dimensionally dispersed, the flake size of the first conductive aid is 800 nm or more and 20 μm or less, the first conductive aid has a region arranged along a first direction substantially parallel to the surface of the current collector, the second conductive aid has a region arranged along a second direction intersecting the first direction, a lithium-ion secondary battery.

3. An electrode comprising a current collector and an active material layer, wherein the active material layer is in contact with the current collector, the active material layer includes active material particles, multi-layer graphene as a first conductive aid, and carbon black as a second conductive aid, the flake size of the first conductive aid is 800 nm or more and 20 μm or less, The first conductive additive has a region arranged along a first direction substantially parallel to the surface of the current collector. The lithium ion secondary battery, wherein the second conductive additive has a region arranged along a second direction intersecting the first direction. **Claim 4** In claim 1, The lithium ion secondary battery, wherein the average particle diameter of the active material particles is measured by a laser diffraction particle size distribution measuring device. **Claim 5** In any one of claims 1 to 4, The lithium ion secondary battery, wherein a plurality of the active material particles form secondary particles. **Claim 6** An electric vehicle having a lithium ion secondary battery having a positive electrode and a negative electrode, and a control circuit, wherein the positive electrode has a current collector and an active material layer, the active material layer has active material particles, multilayer graphene as a first conductive additive, and carbon black as a second conductive additive, the active material layer has a region in which the first conductive additive is three-dimensionally dispersed, the flake size of the first conductive additive is larger than the average particle diameter of the active material particles, the first conductive additive has a region arranged along a first direction substantially parallel to the surface of the current collector, the electric vehicle, wherein the second conductive additive has a region arranged along a second direction intersecting the first direction. **Claim 7** An electric vehicle having a lithium ion secondary battery having a positive electrode and a negative electrode, and a control circuit, wherein the positive electrode has a current collector and an active material layer, the active material layer has active material particles, multilayer graphene as a first conductive additive, and carbon black as a second conductive additive, the active material layer has a region in which the first conductive additive is three-dimensionally dispersed, The flake size of the first conductive additive is 800 nm or more and 20 μm or less, The first conductive additive has a region arranged along a first direction substantially parallel to the surface of the current collector, The second conductive additive has a region arranged along a second direction intersecting the first direction, an electric vehicle.

8. An electric vehicle having a lithium-ion secondary battery having a positive electrode and a negative electrode, and a control circuit, The positive electrode has a current collector and an active material layer, The active material layer has active material particles, multilayer graphene as the first conductive additive, and carbon black as the second conductive additive, The flake size of the first conductive additive is 800 nm or more and 20 μm or less, The first conductive additive has a region arranged along a first direction substantially parallel to the surface of the current collector, The second conductive additive has a region arranged along a second direction intersecting the first direction, an electric vehicle.

9. In claim 6, The average particle size of the active material particles is measured by a laser diffraction particle size distribution measuring device, an electric vehicle.

10. In any one of claims 6 to 9, A plurality of the active material particles form secondary particles, an electric vehicle.

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