Lithium-ion secondary battery

Abstract

To increase the efficiency of the reaction of reducing graphene oxide under a mild condition, and improve the cycle characteristics and rate characteristics of a storage battery in the manufacturing of a storage battery electrode containing graphene as a conductive auxiliary agent.SOLUTION: In a manufacturing method of a storage battery electrode, a first mixture including an active material, a graphene oxide, and a solvent is formed, a reducing agent is added to the first mixture, the graphene oxide is reduced to make a second mixture, a binder is mixed with the second mixture to prepare a third mixture, the third mixture is applied to a current collector, and the solvent is evaporated to form an active material layer.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. An electrolyte made of a lithium salt such as LiBF4 or LiPF6 is dissolved in an organic solvent such as ethanol. The charge and discharge of a lithium-ion secondary battery is Lithium ions move between the positive and negative electrodes through the non-aqueous electrolyte, and lithium is absorbed into the active material of the positive and negative electrodes. This is achieved by the insertion and desorption of ions.

[0005] The positive electrode or the negative electrode is provided with a binder for bonding the active material to the active material and the active material layer to the current collector. The binder is an insulating material called polyvinylidene fluoride (PV Generally, polymer organic compounds such as fluorine, fluorine-containing polymers, etc. are used, which have extremely low electrical conductivity. When the ratio of the binder to the amount of material is increased, the ratio of the amount of active material in the electrode decreases relatively. As a result, the discharge capacity of the secondary battery decreases.

[0006] Therefore, conductive additives such as acetylene black (AB) and graphite particles are mixed This improves the electrical conductivity between the active materials or between the active material layer and the current collector. This makes it possible to provide an active material layer with high electrical conductivity (see Patent Document 1).

[0007] In addition, an electrode containing graphene as a conductive additive has been developed. Graphene oxide (GO), active material, and bond A method for manufacturing an electrode is disclosed that includes a step of reducing GO after mixing an adhesive. According to the manufacturing method of the present invention, it is possible to provide an active material layer having high electrical conductivity with a small amount of conductive additive. can. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2002-110162 A [Patent Document 2] JP 2014-7141 A Summary of the Invention [Problem to be solved by the invention]

[0009] To improve the performance of batteries that have graphene as a conductive additive, There is a need to develop a manufacturing method for electrodes that can reduce ions. In order to facilitate this, there is a demand for simplifying the manufacturing method of the electrodes.

[0010] In view of the above, one embodiment of the present invention is to provide a storage battery electrode capable of efficiently reducing graphene oxide. Another object of the present invention is to provide a method for manufacturing a cathode having a low internal resistance. Another object of the present invention is to provide a method for manufacturing an electrode for a storage battery. Another object of the present invention is to improve the cycle characteristics of a storage battery. The objective is to improve the performance of the device.

[0011] Further, one embodiment of the present invention provides a method for manufacturing a storage battery electrode including graphene as a conductive additive. Another object of one embodiment of the present invention is to reduce graphene oxide under mild conditions. Another object of the present invention is to provide a method for manufacturing a storage battery electrode, The objective is to simplify the manufacturing method of a storage battery.

[0012] Another object of one embodiment of the present invention is to provide a storage battery electrode having a uniform thickness. Another object of one embodiment of the present invention is to provide a storage battery electrode and a storage battery having high strength. do.

[0013] Alternatively, one aspect of the present invention is a novel electrode, a novel storage battery, or a novel method for producing an electrode. The objective of the present invention is to provide the following. Note that the description of these objectives may be omitted. However, it is not necessary for one embodiment of the present invention to achieve all of these objects. In addition, one aspect of the present invention is to solve at least one of the above problems. Problems other than these will be obvious from the description, drawings, claims, etc. Other issues can be extracted from the description, drawings, claims, etc. It is possible to do so. [Means for solving the problem]

[0014] According to one embodiment of the present invention, a first mixture containing an active material, graphene oxide, and a solvent is formed. adding a reducing agent to the first mixture to form a second mixture; and mixing a binder with the second mixture. combining the first and second mixtures to form a third mixture, applying the third mixture to a current collector, and allowing the solvent to evaporate. This is a method for producing an electrode for a storage battery, in which an active material layer is formed by:

[0015] In addition, one aspect of the present invention is a method for manufacturing the above-mentioned semiconductor device by heating the semiconductor device at a temperature of room temperature or higher and 100° C. or lower. and evaporating the solvent by the above-mentioned method.

[0016] Another embodiment of the present invention includes a current collector and an active material layer. The active material layer includes an active material and a graphite. The electrode for a storage battery includes a conductive additive having laphene, a binder, and a reducing agent.

[0017] Another embodiment of the present invention includes a current collector and an active material layer. The active material layer includes an active material and a graphite. Battery electrode comprising a conductive additive having laphene, a binder, and an oxidized derivative of a reducing agent It is.

[0018] In addition, one embodiment of the present invention includes a first electrode and a second electrode, and the first electrode is The electrodes are configured as follows: the first electrode has a function of acting as either a positive electrode or a negative electrode; The two electrodes are storage batteries that have the function of acting as either the positive or negative electrode.

[0019] Another embodiment of the present invention is a storage battery having the above structure, a display panel, a light source, an operation key, a speaker, and a display panel. It is an electronic device equipped with a microphone and a.

[0020] In each of the above configurations, the reducing agent is ascorbic acid, hydrazine, dimethylhydrazine, hydrazine, Hydroquinone, sodium borohydride (NaBH4), lithium aluminum hydride (Li AlH4) or N,N-diethylhydroxylamine. preferable. Effect of the Invention

[0021] According to one embodiment of the present invention, graphene oxide contained in an active material layer can be efficiently reduced. According to one embodiment of the present invention, a network of three-dimensional electrical conduction paths can be formed in the active material layer. By virtue of the above-mentioned effects, one embodiment of the present invention provides a device having a low internal resistance. In addition, one embodiment of the present invention can provide a storage battery having improved cycle characteristics. Furthermore, one embodiment of the present invention can improve the rate characteristics of a storage battery. do.

[0022] In addition, according to one embodiment of the present invention, a method for manufacturing an electrode including graphene as a conductive additive is simplified. According to one embodiment of the present invention, graphene oxide can be reduced under mild conditions. By virtue of the above-described effects, one embodiment of the present invention is a method for manufacturing an electrode. The method of manufacturing the pond can be simplified.

[0023] In addition, according to one embodiment of the present invention, the mixture for forming the active material layer is prevented from becoming strongly basic. In addition, according to one embodiment of the present invention, aggregation of the active material in the active material layer can be suppressed. In addition, one aspect of the present invention is to suppress the gelation of the binder. Due to the above-mentioned effects, one embodiment of the present invention provides a semiconductor device having an active material layer with a uniform thickness. Another embodiment of the present invention is to provide an electrode and a storage battery having high strength. can be provided.

[0024] According to one embodiment of the present invention, a novel electrode, a novel storage battery, or a method for manufacturing a novel electrode is provided. The description of these effects does not preclude the existence of other effects. It is to be noted that one embodiment of the present invention does not necessarily have all of these effects. Effects other than those mentioned above are obvious from the description, drawings, claims, etc. Effects other than these will be extracted from the description in the specification, drawings, claims, etc. It is possible. [Brief description of the drawings]

[0025] [Figure 1] 5A to 5C are diagrams illustrating a manufacturing method of a storage battery electrode. [Diagram 2] FIG. 4 is a diagram illustrating a storage battery electrode. [Diagram 3] FIG. 4 is a diagram illustrating a storage battery electrode. [Figure 4] FIG. 1 is a diagram illustrating a coin-type storage battery. [Diagram 5]FIG. 1 is a diagram illustrating a laminated storage battery. [Figure 6] FIG. 1 is a diagram illustrating a laminated storage battery. [Figure 7] FIG. 1 is a diagram illustrating a cylindrical storage battery. [Figure 8] 1A and 1B are diagrams illustrating an example of an electrical device. [Figure 9] 1A and 1B are diagrams illustrating an example of an electrical device. [Figure 10] 1A and 1B are diagrams illustrating an example of an electrical device. [Figure 11] FIG. 1 is a block diagram illustrating one embodiment of the present invention. [Figure 12] FIG. 1 is a conceptual diagram illustrating one embodiment of the present invention. [Figure 13] FIG. 1 is a circuit diagram illustrating one embodiment of the present invention. [Figure 14] FIG. 1 is a circuit diagram illustrating one embodiment of the present invention. [Figure 15] FIG. 1 is a conceptual diagram illustrating one embodiment of the present invention. [Figure 16] FIG. 1 is a block diagram illustrating one embodiment of the present invention. [Figure 17] 1 is a flowchart illustrating one embodiment of the present invention. [Figure 18] FIG. [Figure 19] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the embodiments will be described with reference to the drawings. It is possible to carry out the present invention in various forms without departing from the spirit and scope of the present invention. It will be readily understood by those skilled in the art that various modifications may be made to the details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments.

[0027] In the configuration of the invention described below, the same parts or parts having similar functions are referred to as the same parts. The same reference numerals are used in common among different drawings, and the repeated explanations are omitted. When referring to a function, the same hatch pattern may be used and no particular reference number may be given.

[0028] In each figure described in this specification, each component such as a film, layer, substrate, etc., thickness, region, etc. The dimensions of the individual components may be exaggerated for clarity of illustration. The size of each component is not limited, nor is the relative size between each component limited. do not have.

[0029] In this specification, ordinal numbers such as 1st, 2nd, etc. are used for convenience. It does not indicate the order of steps or the order of layers. " can be appropriately replaced with "second" or "third" etc. The ordinal numbers described in the specification and the ordinal numbers used to specify one aspect of the present invention are There may be cases where they do not match.

[0030] (Embodiment 1) In this embodiment, a battery electrode according to one embodiment 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 FIG. 3 shows a vertical cross-sectional view of the active material layer.

[0031] Fig. 2(A) is a perspective view of an electrode 200. In Fig. 2(A), the electrode 200 is in the form of a rectangular sheet. However, 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. However, the active material layer 202 may be formed on both sides of the current collector 201. 2 does not need to be formed on the entire surface of the current collector 201, and may be formed on non-coated areas such as areas for connecting to a tab. Set up appropriate areas.

[0032] The current collector 201 may be made of any of a variety of metals, including stainless steel, gold, platinum, zinc, iron, copper, aluminum, and titanium. Metals and their alloys, which are highly conductive and do not alloy with carrier ions such as lithium Materials that can be used include silicon, titanium, neodymium, scandium, molybdenum, etc. Aluminum alloys containing elements that improve heat resistance, such as tin, can be used. Alternatively, it may be formed of a metal element that reacts with silicon to form a silicide. Metal elements that react with to form silicides include zirconium, titanium, and hafnium. , vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel The current collector 201 may be in the form of a foil, a plate (sheet), a mesh, a punched metal, or the like. The current collector 201 may have a thickness of 10 mm or more. It is preferable to use a graphite film having a thickness of 30 μm or more. An undercoat layer may be provided using a material such as a tungsten carbide.

[0033] 2B and 2C are schematic diagrams showing the top surface and vertical cross section, respectively, of the active material layer 202. The active material layer 202 is made of graphene 204 as a conductive additive and granular active material 203. and a binder (not shown). The conductive additive may contain a conductive additive other than the conductive additive (also called a second conductive additive, not shown).

[0034] As shown in the top view of the active material layer 202 in FIG. 2B, the active material particles 203 are The graphene 204 is covered with a single sheet of graphene. In particular, since the graphene 204 is in a sheet shape, the particles are connected to each other. The surface of the active material 203 can be brought into surface contact with the active material 203 so as to wrap a part of the surface of the active material 203. Unlike granular conductive additives such as acetylene black, graphene 204 has low contact resistance. Since it allows surface contact, it is possible to use granular active material without increasing the amount of conductive additive. The electrical conductivity between 203 and graphene 204 can be improved.

[0035] In addition, the graphenes 204 are also in surface contact with each other. This is because graphene oxide, which has extremely high dispersibility in polar solvents, is used. The solvent is removed from the mixture containing the reduced graphene oxide by evaporation, and the reduced graphene oxide is In order to convert the graphene back into graphene, the graphene 204 remaining in the active material layer 202 is partially overlapped. The particles are dispersed to such an extent that they come into surface contact with each other. Thus, a path for electrical conduction is formed.

[0036] In the top view of the active material layer 202 shown in FIG. 2B, the graphene 204 is not necessarily an active material. The graphene 204 does not overlap with other graphene only on the surface of the layer 202. The portion is provided between the active material layers 202. The graphene 204 is a single layer of carbon molecules or Since it is an extremely thin film (sheet) composed of these layers, the individual granular active material 203 The surface of the active material 203 is covered with the conductive layer 204 and is in contact with the conductive layer 204. The loosened portion is bent, wrinkled, or stretched between the multiple granular active materials 203. The condition is as follows.

[0037] In the vertical cross section of the active material layer 202, as shown in FIG. 2(C), In FIG. 2(C), the graphene 204 is uniformly dispersed in the sheet shape. The phenanthrene 204 is shown in bold in schematic form, but in reality it has a single or multiple layer thickness of carbon molecules. As in the description of the upper surface of the active material layer 202, a plurality of graphenes 20 4 is formed so as to encase or cover a plurality of granular active materials 203. In addition, the graphenes 204 are also in surface contact with each other, forming multiple The graphene 204 forms an electrical conduction network. An enlarged schematic diagram is shown in FIG. 3. Grafts are attached to the surfaces of multiple granular active materials 203. As the graphene 204 covers the surface, the graphene also comes into contact with each other to form a network. is doing.

[0038] As shown in FIG. 2B, FIG. 2C, and FIG. 3, a plurality of sheet-like graphenes 204 are They are three-dimensionally dispersed inside the active material layer 202 and come into surface contact with each other. The graphene 2 forms a three-dimensional electrically conductive network. 04 covers and is in surface contact with a plurality of granular active material 203 .

[0039] The graphene 204 is formed by the method for producing a storage battery electrode described in the second embodiment. The graphene oxide is formed by reducing the graphene oxide using the above-mentioned method. In the manufacturing method, a reducing agent is used when forming the active material layer 202. The reducing agent may remain in the catalyst 02. The reducing agent may be the same as that used to reduce graphene oxide. Therefore, the active material layer 202 is formed by oxidizing the reducing agent. It may contain derivatives (hereinafter referred to as oxidized derivatives of the reducing agent).

[0040] The presence of a reducing agent or an oxidized derivative of a reducing agent in the active material layer 202 can be confirmed by EDX (Energy Dispersion X-ray spectroscopy). y Dispersive X-ray spectrometry) analysis, XPS(X -ray Photoelectron Spectroscopy), or ToF-S IMS(Time-of-Flight Secondary Ion Mass Sp The detection can be performed by analytical means such as spectrometry.

[0041] Reducing agents include ascorbic acid, hydrazine, dimethylhydrazine, hydroquinone, and water. Sodium borohydride (NaBH4), lithium aluminum hydride (LiAlH4), or N,N-diethylhydroxylamine, or their derivatives can be used. In particular, ascorbic acid and hydroquinone are more effective than hydrazine and sodium borohydride. Since the reducing power is weak, it is highly safe and is easy to use industrially.

[0042] The reducing agent is converted into an oxidized derivative of the reducing agent by a reaction that reduces graphene oxide. As an example, let us explain the redox reaction of ascorbic acid. Therefore, when ascorbic acid is used as a reducing agent, In the present embodiment, dehydroascorbic acid remains in the active material layer 202 as an oxidized derivative of the reducing agent. In addition, the present invention is not limited to the case where ascorbic acid is used as a reducing agent, and the oxidative induction of the reducing agent may be used. The body may remain in the active material layer 202 .

[0043] Graphene is a carbon material with a crystalline structure in which the hexagonal skeleton of carbon is extended in a planar fashion. Graphene is an atomic surface of a graphite crystal, and has electrical and mechanical properties. Due to its extraordinary mechanical and chemical properties, graphene is expected to be used for high-mobility field effect transistors, highly sensitive sensors, highly efficient solar cells, and next-generation transparent conductive films It is attracting attention as it is expected to be applied in various fields such as the following.

[0044] In this specification, graphene refers to single-layer graphene or multi-layer graphene having 2 to 100 layers. Single-layer graphene is a single atomic layer of carbon molecules with π bonds. Graphene oxide refers to a sheet of the above-mentioned graphene oxidized compound. In addition, when graphene is formed by reducing graphene oxide, It is possible that not all of the oxygen contained in the graphene is released, and some of the oxygen remains in the graphene. By using the method for producing a storage battery electrode described in the second embodiment, it is possible to reduce graphene oxide. The reaction efficiency of the original reaction can be increased. In addition, when oxygen is contained in graphene, oxygen The ratio of is 2 atomic % or more of the graphene as measured by XPS. ic% or less, preferably 3 atomic% to 10 atomic%. As described above, the sheet-like graphenes 204 are three-dimensionally arranged inside the active material layer 202. These nanoparticles are dispersed in a uniform manner, and when they come into contact with each other, they form a three-dimensional electrically conductive network. Therefore, by increasing the reaction efficiency of the reduction reaction of graphene oxide, The internal resistance of the active material layer 202 and the electrode 200 can be reduced.

[0045] Graphene oxide can be produced using an oxidation method called the Hummers process. The Hummers process involves adding a solution of potassium permanganate in sulfuric acid, water peroxide, and graphite powder to the Add water or other substances to cause an oxidation reaction and produce a mixture containing graphite oxide. The oxidation of carbon in graphite results in the formation of epoxy groups, carbonyl groups, and carboxyl groups. As a result, the distance between the layers of multiple graphene is reduced. Compared to the phytoplankton, it is longer and easier to separate the layers and form thin films. By applying ultrasonic vibration to a mixture containing graphite, graphite oxide with a long interlayer distance is produced. The graphene oxide is separated by cleavage, and a mixture containing the graphene oxide is prepared. By removing the solvent from the mixture containing graphene oxide, a powder-like Graphene oxide can be obtained.

[0046] Graphene oxide is formed by appropriately adjusting the amount of oxidizing agent such as potassium permanganate. For example, by increasing the amount of oxidizing agent relative to the graphite powder, the graphite oxide The degree of oxidation of the benzene (ratio of the number of oxygen atoms to the number of carbon atoms) can be increased. The amount of oxidant relative to the graphite powder used as raw material is determined according to the amount of graphene oxide. Just do that.

[0047] The graphene oxide was prepared using a Hummers method using a sulfuric acid solution of potassium permanganate. The present invention is not limited to the Humm method, which uses nitric acid, potassium chlorate, or sodium nitrate. A method for producing graphene oxide other than the ers method or the Hummers method may be used as appropriate.

[0048] In addition, graphite oxide can be flaked by adding ultrasonic vibrations, microwaves, radio waves, or This may be achieved by irradiation with thermal plasma or application of physical stress.

[0049] The graphene oxide produced contains epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups. In a polar solvent, graphene oxide has oxygen atoms in these functional groups. Since the graphene oxide has a negative charge, it interacts with polar solvents. Since the atoms repel each other and do not easily aggregate, in a polar solvent, graphene oxide is uniformly dispersed. Easy to disperse.

[0050] In addition, the length of one side of graphene oxide (also called the flake size) is 50 nm or more and 100 nm or less. The graphene oxide flakes are preferably 800 nm or more and 20 μm or less. By adjusting the size of the graphene flakes, it is possible to control the size of the graphene flakes in the active material layer. When the flake size of the graphene is larger than the average particle size of the granular active material 203, This makes it easier for the graphene to come into surface contact with the active material 203 and to connect the graphenes to each other. Therefore, it is effective in improving the electrical conductivity of the active material layer 202.

[0051] The active material 203 is made by mixing raw materials in a predetermined ratio, sintering the mixture, and then sintering the mixture by a suitable method. A granular active material consisting of secondary particles that have been crushed, granulated, and classified and have an average particle size and particle size distribution. For this reason, in FIG. 2(B) and FIG. 2(C), the active material 203 is shown diagrammatically as a sphere. However, the shape is not limited to this.

[0052] When the electrode 200 is used as a positive electrode of a storage battery, the active material 203 is lithium ion. Materials that allow insertion and removal of lithium ions can be used. For example, lithium manganese composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure and the like can be mentioned.

[0053] Examples of lithium-containing composite phosphates 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)). Typical examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, Li CoPO4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, Li Fe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4 (a + b is less than 1, 0 < a < 1, 0 < b < 1), LiFe Ni c Ni d Co e PO4, LiFe c Ni d Mn e PO4, LiNi c Co d Mn e 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), etc. can be mentioned.

[0054] In particular, LiFePO4 has 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.

[0055] 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).

[0056] In particular, LiCoO2 has a large capacity, is more stable in air than LiNiO2, and It is preferred because it has advantages such as being more thermally stable than NiO2.

[0057] Examples of lithium manganese composite oxides having a spinel crystal structure include LiMn 2O4, Li 1+x Mn 2-x O4(0 <x<2)、LiMn 2-x Al x O4(0 <x <2), LiMn 1.5 Ni0.5 Examples include O4.

[0058] A small amount of lithium manganese composite oxides with a spinel-type crystal structure, such as LiMn2O4, Lithium nickel oxide (LiNiO2 or LiNi 1-x M x O2(0 <x<1)(M=C Mixing it with ZnO, Al, etc., suppresses the elution of manganese and the decomposition of the electrolyte. There are advantages and it is preferable.

[0059] In addition, the positive electrode active material is a compound having the general formula Li (2-j) MSiO4 (M is Fe(II), Mn (II), Co(II), Ni(II), or more, j is 0 to 2 The general formula Li (2-j) A typical example of MSiO4 is 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. are mentioned.

[0060] 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 can be used. Examples of the NASICON 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, perovskite type fluorides such as FeF3, metal chalcogenides (sulfides, selenides, tellurides) such as TiS2, MoS2, lithium vanadium-containing composite oxides having an inverse spinel type crystal structure such as LiMVO4, vanadium oxide-based compounds( V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. can be used.

[0061] The particle size of the positive electrode active material is preferably, for example, 5 nm or more and 100 μm or less.

[0062] Also, as the positive electrode active material, the composition formula Li x Mn y M zO 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 greater than or equal to 0 and less than 2, and z is greater than 0, and (y+z) It is preferable that / w is 0.26 or more and less than 0.5. The oxide refers to an oxide containing at least lithium and manganese, and is not limited to chromium, cobalt, Aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium At least one selected from the group consisting of copper, titanium, niobium, silicon, phosphorus, etc. The lithium manganese composite oxide may have a layered rock salt type crystal structure. The lithium manganese composite oxide preferably has a layered rock salt structure. The lithium arsenide may have a crystalline structure of the arsenide type or a crystalline structure of the spinel type. The average particle size of the calcium carbonate composite oxide is preferably 5 nm or more and 50 μm or less. It is.

[0063] In addition, the carrier ion is an alkali metal ion or an alkaline earth ion other than the lithium ion. In the case of metal ions, the positive electrode active material is the above-mentioned lithium compound and lithium manganese complex acid. In the hydride, an alkali metal (e.g., sodium or potassium) is substituted for lithium. or alkaline earth metals (e.g., calcium, strontium, barium, beryllium , magnesium, etc.) may also be used.

[0064] In addition, when the battery electrode to be manufactured is used as a negative electrode of a battery, the active material 203 is The material used is capable of carrying out charge / discharge reactions through alloying / de-alloying reactions with lithium. It is possible.

[0065] Materials that can undergo charge-discharge reactions through alloying and dealloying reactions with lithium include: Carbon-based materials include graphite, graphitizable carbon (soft carbon), etc. ), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon Black, etc.

[0066] Graphite includes mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch. These include artificial graphite such as spheroidized artificial graphite, and natural graphite such as spheroidized natural graphite.

[0067] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), It has a low potential similar to that of lithium metal (0.1 to 0.3 V vs. Li / Li + This allows the lithium-ion secondary battery to exhibit a high operating voltage. Graphite has a relatively high capacity per unit volume, small volume expansion, is inexpensive, and is a lithium It is preferable since it has advantages such as higher safety compared to metals.

[0068] In addition, it is a material that can undergo charge-discharge reactions by alloying and dealloying reactions with lithium. Other examples include Ga, Si, Al, Ge, Sn, Pb, Sb, Bi, Ag, Zn, Materials containing at least one of Cd, In, etc. can be used. Compared to carbon, silicon has a large capacity, and the theoretical capacity of silicon is 4200mAh / g. Examples of materials using such elements include Mg2Si, Mg2Ge, Mg2Sn, and S nS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3S n, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, Co Examples include Sb3, InSb, and SbSn.

[0069] In addition, the negative electrode active material is SiO, SnO, SnO2, titanium dioxide, lithium titanate. oxide, lithium-graphite intercalation compound, niobium pentoxide, tungsten oxide or molybdenum oxide For example, oxides such as tantalum can be used.

[0070] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 The lithium-ion secondary battery using N has a large charge / discharge capacity (900mAh / g , 1890mAh / cm 3 ), which is preferred.

[0071] When a composite nitride of lithium and transition metals is used, the negative electrode active material contains lithium ions, The positive electrode active material is made of V2O5, Cr3O8, etc., which do not contain lithium ions. In addition, when a material containing lithium ions is used as the positive electrode active material, However, by first removing the lithium ions contained in the positive electrode active material, As the lithium-transition metal nitride, a complex nitride of lithium and a transition metal can be used.

[0072] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. For example, Lithium oxide (LiO), cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not undergo an alloying reaction with the negative electrode active material may be used. Further materials in which the reaction occurs include Fe2O3, CuO, Cu2O, RuO2, and Cr2O. 3rd order oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, G Nitrides such as e3N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3 Fluorides such as the following can also be used.

[0073] The average particle size of the primary particles of the granular active material 203 is measured using, for example, a laser diffraction particle size distribution measuring device. When measured by the method described above, the diameter is 500 nm or less, preferably 50 nm to 500 nm. In order to make surface contact with the plurality of particles of the active material 203, the graphene 204 is preferably The length of the side is 50 nm or more and 100 μm or less, more preferably 800 nm or more and 20 μm or less. It would be good to have one.

[0074] The binder contained in the active material layer 202 is typically polyvinylidene fluoride (P VdF), polyimide, polytetrafluoroethylene, polyvinyl chloride, ethylene propylene diene polymer, styrene-butadiene rubber, acrylonitrile-butadiene Energized rubber, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene or Nitrocellulose or the like can be used.

[0075] The active material layer 202 may further include a second conductive assistant. When the active material layer has a second conductive additive, the three-dimensional network of electrical conduction in the active material layer is more Therefore, the charge in the active material layer 202 during use of the power storage device can be easily removed. The second conductive additive can be, for example, a tantalum oxide. Natural graphite, artificial graphite such as mesocarbon microbeads, or carbon fiber can be used. In addition, metal powder or metal fibers such as copper, nickel, aluminum, silver, and gold can be used. A conductive ceramic material or the like can be used.

[0076] Examples of carbon fibers include mesophase pitch-based carbon fibers and isotropic pitch-based carbon fibers. Carbon fibers can be used. Carbon fibers include carbon nanofibers and carbon Carbon fibers such as vapor grown carbon fibers ( Uses VGCF (Vapor-Grown Carbon Fiber) (registered trademark) The typical value of VGCF (registered trademark) is a fiber diameter of 150 nm and a fiber length of 10 μm or less. Upper 20μm or less, true density 2g / cm 3 , specific surface area 13m 2 / g. The fiber diameter is , and observed with a SEM (Scanning Electron Microscope), From the two-dimensionally captured image, a cross section perpendicular to the fiber axis is taken as a cut surface. The true density is the diameter of a circle that circumscribes the volume of the substance itself. The specific surface area refers to the density that is used for the calculation of the volume. This refers to the surface area per unit of volume or surface area per unit of volume.

[0077] VGCF (registered trademark) has a needle-like shape and is highly conductive, making it an excellent electrical material. It has excellent physical properties, such as high mechanical strength and low temperature resistance. By using ZnO (registered trademark) as a conductive additive, the contact points and contact area between active materials are increased. It is possible to do so.

[0078] In addition, a granular material may be used as the conductive assistant. Representative examples of the granular material include The diameter is 3 nm to 500 nm, and the registered trademark is acetylene black and Ketjen black. Carbon black such as carbon black (Titanium dioxide) can be used.

[0079] Flake, needle, or fiber-shaped conductive additives serve to connect the active materials together and prevent battery deterioration. In addition, these materials are used as a structure that maintains the shape of the active material layer 202 or as a material that reduces the It also functions as a shock absorbing material. This function means that the active material expands and contracts repeatedly, and that the secondary battery does not expand or contract when it is bent. In addition, instead of the above materials, acetone is used. Carbon black such as ethylene black or Ketjenblack (registered trademark) can also be used. However, when VGCF (registered trademark) is used, the strength required to maintain the shape of the active material layer 202 is not sufficient. This is preferable because the strength required to maintain the shape of the active material layer 202 is large. This makes it possible to prevent deterioration of the secondary battery due to deformation such as bending.

[0080] The active material layer 202 described above has an active material 203 of 80% by weight based on the total weight of the active material layer 202. wt% or more but not exceeding 95wt%, graphene is 0.1wt% or more but not exceeding 8wt%, and binder is 1w It is preferable that the content of the active material layer 202 is t% or more and 10 wt% or less. In the case where the active material layer has a second conductive additive, the total weight of the graphene and the second conductive additive is It is preferable that the content of 202 is 0.1 wt % or more and 8 wt % or less with respect to the total weight of 202.

[0081] As shown in this embodiment, the graphene 20 having an average particle size larger than that of the granular active material 203 is 4 are in contact with one or more of the adjacent graphenes 204 in the active material layer 202. The particles are dispersed to the extent that they can be touched, and are in surface contact with the particles so as to envelop a part of the surface of the granular active material 203. This allows the provision of a storage battery electrode that contains a highly packed and highly densified active material layer using a small amount of conductive additive. It is possible.

[0082] Note that one embodiment of the present invention has been described in this embodiment. An embodiment of the present invention will be described below. However, the embodiment of the present invention is not limited to these. That is, various inventive aspects are described in this and other embodiments. Therefore, one embodiment of the present invention is not limited to a specific embodiment. In the above example, graphene is applied to a storage battery electrode. In some cases or depending on the situation, graphene or graphene oxide may be used. Phenol is being used as an electrode for supercapacitors, which are capacitors with extremely high capacitance. It is used as an electrode catalyst for oxygen reduction, and as a material for dispersions with lower friction than lubricating oil. They are used as transparent electrodes for display devices and solar cells, and as gas barrier materials. It is used as a lightweight polymer material with high mechanical strength, and is also used to remove radioactive contaminated water. It can be used as a material for highly sensitive nanosensors to detect uranium and plutonium in Or it can be used as a material to remove radioactive materials. In some cases, or depending on the situation, as one embodiment of the present invention, graphene may be used in a storage battery. The above-mentioned requirements do not necessarily have to be applied to the electrodes used.

[0083] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0084] (Embodiment 2) In this embodiment, the active material, the conductive additive, and the binder exemplified in the first embodiment are used to form an active material. A method of manufacturing an electrode 200 including a layer 202 will be described with reference to FIG.

[0085] First, an active material, graphene oxide, and a solvent are kneaded to form a first mixture (step At this time, a second conductive additive may be added. As the conductive assistant, the materials described in the first embodiment can be used.

[0086] A polar solvent can be used as the solvent for forming the mixture. For example, methanol , ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DM F), N-methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO) One or a mixture of two or more of these can be used. In particular, NMP is effective in removing graphene oxide. This is preferable because it can be dispersed.

[0087] Next, the first mixture is kneaded (kneaded in a high viscosity state) to obtain graphene oxide and The graphene oxide can be functionalized in a polar solvent. Because the oxygen in the group is negatively charged, different graphene oxides are less likely to aggregate with each other. , the active material and graphene oxide can be dispersed more uniformly.

[0088] Next, a reducing agent is added to the first mixture and mixed to reduce graphene oxide to produce a second mixture. The reducing agent is dissolved in a small amount of solvent and then added to the first mixture (step S102). By adding the graphene oxide to the mixture, it becomes easier to mix. The graphene oxide can be obtained by reducing the oxygen. Some oxygen may remain in the graphene rather than being released.

[0089] As the reducing agent, the material described in the first embodiment can be used.

[0090] The solvent used to dissolve the reducing agent should have a high solubility for the reducing agent and a low boiling point. For example, water, methanol, ethanol, or the like may be used.

[0091] The mixture to which the reducing agent has been added is heated to a temperature of 30°C or higher and 200°C or lower, preferably 50°C or higher and 100°C or lower. Heating can promote the reduction reaction of graphene oxide. The atmosphere is not particularly limited.

[0092] Note that graphene oxide was obtained by heating a mixture containing graphene oxide without adding a reducing agent. However, it is not possible to sufficiently reduce graphene oxide by heating. Therefore, the heat resistance of the material or device used to fabricate the electrode must be high. Due to temperature restrictions, graphene oxide cannot be heated to a high enough temperature, and reduction is insufficient. On the other hand, in one embodiment of the present invention, by adding a reducing agent, the reaction can be carried out at a high temperature. Therefore, the graphene oxide can be reduced without the need for the step S102. The method can increase the efficiency of the graphene oxide reduction reaction under mild conditions. It can be said that.

[0093] The weight of the reducing agent is 5 wt % or more with respect to the weight of the graphene oxide contained in the first mixture. The weight of the reducing agent used in step S101 should be 500 wt% or less. This may be changed depending on the degree of oxidation of the graphene oxide.

[0094] Here, when a high-density active material is used, the density of the active material layer 202 may become high. Examples of suitable active materials include those with the formula Li x Mn y M z O w Lithium manganese represented by Complex oxides, LiCoO2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 NiMnCo such as O2 When a reduction treatment of the graphene oxide is performed after the active material layer 202 is formed, In some cases, the graphene oxide cannot be sufficiently reduced. The reason for this is that there are very few voids, and the reducing agent does not penetrate deep into the active material. It is possible.

[0095] On the other hand, in one embodiment of the present invention, as shown in step S102, The graphene oxide is reduced by adding a reducing agent to the first mixture. By adding the base agent, the reducing agent is distributed widely throughout the mixture, so that the reducing agent contained in the second mixture Graphene oxide can be reduced with high reaction efficiency. In step 4, an active material layer 202 is formed in which graphene oxide is reduced with high reaction efficiency. can be done.

[0096] In addition, compared to the case where graphene oxide is reduced at each electrode after the electrode is fabricated, Adding a reducing agent to the mixture in step 1 to reduce graphene oxide is much easier than adding a reducing agent to the mixture in step 2 to reduce graphene oxide. In other words, one aspect of the present invention is to simplify the process. This method can be said to be capable of improving productivity and mass production.

[0097] In addition, when a basic active material is used as the active material, the second mixture may become basic. In this case, in the subsequent step S103, PVdF is added to the second mixture. If the temperature is too high, the PVdF may gel, making it difficult to uniformly knead the third mixture. On the other hand, even when a basic active material is used as the active material, in step S102 Adding an acid as a reducing agent can prevent the second mixture from becoming too basic. Therefore, in the subsequent step S103, gelation of PVdF can be suppressed. Therefore, the third mixture can be uniformly kneaded. Since it is possible to form an active material layer in which the active material is uniformly distributed, it is possible to prepare an electrode having a uniform thickness. In addition, it is possible to fabricate electrodes that are strong and not easily broken by, for example, external impacts. It is possible.

[0098] As an example of an active material having basicity, the composition formula Li x Mn y M z O w Lithium, represented by Manganese composite oxide and the like.

[0099] Acids that can be used as reducing agents include, for example, ascorbic acid and hydroquinone. Some examples include:

[0100] In addition, when an active material or a binder that is unstable to acid is used, in step S102 It is more preferable to use a base as the reducing agent. Examples of active materials that are unstable to acids include For example, LiCoO2, LiFePO4, etc. are listed. In addition, binders that are unstable to acids Examples of the reducing agent include SBR. Examples of the hydrazine include hydrazine, dimethylhydrazine, sodium borohydride, and N, N-diethylhydroxylamine and the like.

[0101] In this way, in one embodiment of the present invention, an acid is used as a reducing agent to reduce an active material having basicity. The material is combined with a binder that gels in a strong basic mixture to produce a uniform thickness. It is possible to fabricate electrodes with high strength. In addition, by using a base as a reducing agent, It is also possible to prepare an electrode using an active material or binder that is unstable to acid. By applying one embodiment, the range of materials and combinations of materials to be used for the active material and binder can be expanded. However, this is preferable.

[0102] Here, the second mixture is heated at 20° C. or higher and 80° C. or lower under a reduced pressure atmosphere for 5 minutes or longer and 10 hours or shorter. Alternatively, the solvent added together with the reducing agent may be removed by heating at 40° C.

[0103] Next, a binder is added to the second mixture, which is then kneaded to form a third mixture (also called a paste). As the binder, the material described in the first embodiment is used. It is possible.

[0104] Next, the third mixture is applied to a current collector, and the solvent is evaporated to form an active material layer. More specifically, the third mixture and the current collector are heated at 20° C. or higher for 1 Heat the mixture at 70°C or less for 1 minute to 10 hours to evaporate the solvent contained in the third mixture. In this way, the active material layer can be formed. The atmosphere is not particularly limited.

[0105] Through the above steps, an active material layer 202 in which the active material 203 and the graphene 204 are uniformly dispersed is obtained. After this step, the electrode 200 can be fabricated. A pressurizing step may be carried out.

[0106] As described in this embodiment, the first mixture containing the active material, the graphene oxide, and the solvent By adding a reducing agent and heating the mixture, graphene oxide can be reduced under mild conditions. In addition, the efficiency of the reaction for reducing graphene oxide can be increased. The second mixture containing phene was used to prepare a third mixture, which was then applied to a current collector and the solvent was allowed to evaporate. By this, an electrode containing graphene as a conductive additive can be produced under mild conditions. It is also possible to produce electrodes with a uniform thickness. It is possible to fabricate an electrode that is not easily damaged by external impact. By producing a storage battery using the electrode manufacturing method described above, the cycle characteristics of the storage battery can be improved. In addition, the manufacturing method of the storage battery can be simplified. In addition, it is possible to manufacture a storage battery that is strong and is not easily destroyed by, for example, an external impact. It is possible.

[0107] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0108] (Embodiment 3) In this embodiment, a storage battery electrode manufactured by the manufacturing method shown in the second embodiment is used. The structure of the storage battery will be described with reference to FIGS.

[0109] (Coin cell battery) FIG. 4(A) is an external view of a coin-type (single-layer flat) storage battery, and FIG. 4(B) is a cross-sectional view of the battery. FIG.

[0110] The coin-type storage battery 300 is made up of a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. 02 is insulated and sealed by a gasket 303 made of polypropylene or the like. The electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector. The negative electrode 307 is formed by a negative electrode current collector 308 and a The positive electrode active material layer 306 and the negative electrode active material layer 309 are formed. Between them, there is a separator 310 and an electrolyte (not shown).

[0111] At least one of the positive electrode 304 and the negative electrode 307 may be the same as that of the embodiment of the present invention described in Embodiment 2. The storage battery electrode can be produced using the above-mentioned method for producing the storage battery electrode.

[0112] Either the positive electrode 304 or the negative electrode 307 is formed by the method for manufacturing the storage battery electrode shown in the second embodiment. 3 shows the structure of a positive electrode active material layer 306 or a negative electrode active material layer 309 in the case where no such method is used.

[0113] The positive electrode active material layer 306 contains a positive electrode active material and a binder (binder) for improving the adhesion of the positive electrode active material. The positive electrode active material layer 306 may contain an indium ion (indium ion), a conductive assistant for increasing the conductivity of the positive electrode active material layer 306, or the like.

[0114] The materials described in the first embodiment are used as the positive electrode active material, the binder, and the conductive additive. can be done.

[0115] The negative electrode active material layer 309 contains, in addition to the negative electrode active material, a binder (binder) for improving the adhesion of the negative electrode active material. The negative electrode active material layer 309 may contain an indium ion, a conductive assistant for increasing the conductivity of the negative electrode active material layer 309, or the like.

[0116] The materials described in the first embodiment are used as the negative electrode active material, the binder, and the conductive additive. can be done.

[0117] In addition, a coating 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 electrolyte releases the charge consumed during its formation. In contrast, a film of oxide or the like is applied to the negative electrode active material in advance, resulting in irreversible capacity. By providing it on the surface of the layer 309, the occurrence of irreversible capacity can be suppressed or prevented. .

[0118] The coating for coating the negative electrode active material layer 309 may include niobium, titanium, vanadium, tungsten, etc. Ta, tungsten, zirconium, molybdenum, hafnium, chromium, aluminum or or silicon oxide film, or a film containing any one of these elements and lithium Such a coating can be formed on the negative electrode by the decomposition products of conventional electrolytes. This film is sufficiently dense compared to the coating formed on the surface.

[0119] For example, niobium pentoxide (Nb2O5) has an electrical conductivity of 10 -9 Low S / cm and high Therefore, the niobium oxide film is insulated from the negative electrode active material when it comes into contact with the electrolyte during charging. It inhibits the electrochemical decomposition reaction of electrolytes, etc. caused by the oxidation of niobium. The diffusion coefficient of 10 -9 cm 2 / sec, and has high lithium ion conductivity. Therefore, lithium ions can pass through. Minium may also be used.

[0120] The coating film for coating the negative electrode active material layer 309 can be formed by, for example, a sol-gel method. The sol-gel method is a process in which a solution of metal alkoxides and metal salts is subjected to hydrolysis and polymerization. This method involves creating a gel that has lost its fluidity through a condensation reaction, and then baking this gel to form a thin film. The sol-gel method is a method for forming a thin film from a liquid phase, so the raw materials are mixed homogeneously at the molecular level. For this reason, the raw material for the metal oxide film in the solution stage can be made of a negative electrode active material such as graphite. By adding the active material, it is possible to easily disperse the active material in the gel. A coating can be formed on the surface of the electrode active material layer 309. By using the coating, It can prevent loss of body volume.

[0121] The separator 310 may be made of a porous material such as cellulose (paper), polypropylene, or polyethylene. An insulator having the following structure can be used.

[0122] As the electrolyte, in addition to electrolyte containing a supporting electrolyte, solid electrolyte and electrolyte partially gelled are also used. A gel electrolyte can be used.

[0123] Materials that have carrier ions can be used as supporting electrolytes. Representative examples of supporting electrolytes Examples include LiPF6, LiClO4, LiAsF6, LiBF4, LiCF3SO3, Lithium salts include Li(CF3SO2)2N and Li(C2F5SO2)2N. These electrolytes may be used alone or in any combination and ratio of two or more. It's fine.

[0124] In addition, the carrier ion is an alkali metal ion other than the lithium ion, an alkaline earth metal ion, etc. In the case of ions, an alkali metal salt is used as an electrolyte instead of lithium in the lithium salt. Metals (e.g. sodium and potassium), alkaline earth metals (e.g. calcium, strontium Other suitable materials include tungsten, barium, beryllium, magnesium, etc.

[0125] In addition, a material in which carrier ions can move can be used as a solvent for the electrolyte. The solvent for the solution is preferably an aprotic organic solvent. Representative examples of aprotic organic solvents Examples include ethylene carbonate (EC), propylene carbonate, and dimethyl carbonate. diethyl carbonate (DEC), γ-butyrolactone, acetonitrile, dimeth- These include ethane, tetrahydrofuran, etc., and one or more of these can be used. In addition, by using a polymer material that gels as a solvent for the electrolyte, the electrolyte is less susceptible to leakage. This improves safety. It also makes it possible to make the storage battery thinner and lighter. Representative examples of materials are silicone gel, acrylic gel, acrylonitrile gel, and polyethylene gel. Styrene oxide gel, polypropylene oxide gel, fluorine polymer gel, etc. In addition, ionic liquids (especially those that are soluble at room temperature) that are flame-retardant and non-volatile are used as solvents for electrolytes. By using one or more molten salts, the internal temperature of the battery can be reduced due to internal short circuits, overcharging, etc. Even if the temperature rises, it is possible to prevent the battery from exploding or catching fire. Ionic liquids are made of cations and anions. The organic cations that make up the ionic liquid include quaternary ammonium cations, Aliphatic onium cations such as tertiary sulfonium cations and quaternary phosphonium cations and aromatic cations such as imidazolium cations and pyridinium cations. In addition, the anions that compose the ionic liquid include monovalent amide anions, monovalent methionine anions, and Anions of tides, fluorosulfonate anions, perfluoroalkylsulfonate anions Fluorophosphate, tetrafluoroborate, perfluoroalkylborate, hexafluorophosphate phosphate, or perfluoroalkyl phosphate.

[0126] In addition, instead of the electrolyte, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as EO (polyethylene oxide) can be used. When a solid electrolyte is used, the installation of a separator or spacer becomes unnecessary. Since the entire pond can be solidified, there is no risk of leakage, and safety is improved dramatically.

[0127] The positive electrode can 301 and the negative electrode can 302 are provided with a material that is resistant to liquids such as electrolyte during charging and discharging of the secondary battery. Metals such as nickel, aluminum, and titanium that are resistant to corrosion, alloys of such metals, and Alloys of metals with other metals (e.g., stainless steel, etc.), lamination of the metal, and the metal and the above Lamination with alloys (e.g. stainless steel, aluminum, etc.), lamination with the metal and other metals (For example, nickel, iron, nickel, etc.) can be used. The positive electrode can 301 is 04 and the negative electrode can 302 are electrically connected to the negative electrode 307, respectively.

[0128] The negative electrode 307, the positive electrode 304 and the separator 310 are impregnated with an electrolyte, and as shown in FIG. As shown, the positive electrode can 301 is placed downward, and the positive electrode 304, the separator 310, the negative electrode 307, and the negative electrode The cans 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are secured together with a gasket 303 interposed therebetween. The coin-type storage battery 300 is manufactured by crimping.

[0129] (Laminated battery) FIG. 5 shows an external view of a laminated type storage battery 500. In addition, FIG. 6(A) and FIG. 6(B) show The cross sections A1-A2 and B1-B2 are shown by dashed lines in FIG. 5. The 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 negative electrode active material layer 505 and a separator 507, and an electrolyte 506 are provided. 508 and an exterior body 509. A separator 507 is disposed between the positive electrode 503 and the negative electrode 506. In addition, an electrolyte solution 508 is poured into the area surrounded by the exterior body 509. There are.

[0130] In the laminated storage battery 500 shown in FIG. 5, a positive electrode current collector 501 and a negative electrode current collector 50 The positive electrode current collector 501 also serves as a terminal for electrical contact with the outside. A part of the negative electrode current collector 504 is disposed so as to be exposed to the outside from the exterior body 509 .

[0131] In the laminated storage battery 500, the exterior body 509 is made of, for example, polyethylene, polypropylene, On a membrane made of a material such as propylene, polycarbonate, ionomer or polyamide, A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper or nickel, is provided. On the metal thin film, an insulating material such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A laminate film having a three-layer structure with an insulating synthetic resin film can be used. The three-layer structure prevents electrolyte and gas from passing through, while also ensuring insulation. It also has electrolyte resistance.

[0132] (Cylindrical battery) Next, an example of a cylindrical storage battery will be described with reference to FIG. As shown in FIG. 7(A), the battery has a positive electrode cap (battery lid) 601 on the top surface, and The positive electrode cap and the battery can (outer can) 602 are disposed on the opposite sides. 2 is insulated by a gasket (insulating packing) 610.

[0133] FIG. 7(B) is a schematic diagram showing a cross section of a cylindrical storage battery. On the inside of 02, a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 sandwiched between them. Although not shown, the battery element is wound around a center pin. The battery can 602 is closed at one end and open at the other end. Nickel and aluminum, which have corrosion resistance against liquids such as electrolytes during charging and discharging of secondary batteries Metals such as aluminum and titanium, alloys of said metals, and alloys of said metals with other metals (e.g., stainless steel, Stainless steel, etc.), laminates of the metal, laminates of the metal and the alloys listed above (e.g., stainless steel, metals, aluminum, etc.), lamination of the metal with other metals (e.g. nickel, iron, nickel, etc.) Inside the battery can 602, a positive electrode, a negative electrode, and a separator are arranged. The battery element with the coil wound around it is sandwiched between a pair of opposing insulating plates 608 and 609 . The battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type or laminate-type storage batteries. Cut.

[0134] The positive electrode 604 and the negative electrode 606 are manufactured in the same manner as the positive electrode and the negative electrode of the coin-type storage battery described above. However, the positive and negative electrodes used in cylindrical storage batteries are wound, so active material is placed on both sides of the current collector. The positive electrode 604 is connected to a positive electrode terminal (positive electrode current collecting lead) 603. The negative electrode 606 is connected to a negative electrode terminal (negative electrode current collecting lead) 607. The positive electrode terminal 603 and the negative electrode terminal 607 can both be made of a metal material such as aluminum. The positive terminal 603 is connected to a safety valve mechanism 612, and the negative terminal 607 is connected to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coefficient) element. re Coefficient) 611 is electrically connected to the positive electrode cap 601. The safety valve mechanism 612 is a mechanism that releases the positive electrode cap when the internal pressure of the battery exceeds a predetermined threshold. The PTC element 611 cuts off the electrical connection between the positive electrode 601 and the positive electrode 604. is a thermal resistor whose resistance increases when the temperature rises. The PTC element is made of barium titanate (BaTi O3) based semiconductor ceramics, etc. can be used.

[0135] In this embodiment, the storage battery is a coin type, a laminate type, or a cylindrical type. However, other types of batteries, such as sealed batteries and rectangular batteries, can be used. In addition, a structure in which a positive electrode, a negative electrode, and a separator are laminated in multiple layers, The magnetic flux may have a structure in which the magnetic flux is wound.

[0136] The positive or negative electrodes of the coin-type storage battery 300, the storage battery 500, and the storage battery 600 shown in this embodiment The electrode is manufactured by the method for manufacturing a storage battery electrode according to one embodiment of the present invention. Therefore, the discharge capacity of the coin-type storage battery 300, storage battery 500, and storage battery 600 is It can be improved.

[0137] Note that in this embodiment, one embodiment of the present invention has been described. However, the present invention is not limited to these. In other words, various aspects of the invention are described in the present embodiment. Therefore, one embodiment of the present invention is not limited to a specific embodiment. In the above, an example of application to a lithium ion secondary battery has been shown, but one embodiment of the present invention is In some cases, or depending on the circumstances, one aspect of the present invention is to provide a variety of secondary Batteries, such as lead-acid batteries, lithium-ion polymer secondary batteries, nickel-metal hydride batteries, Nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries or acid batteries Silver-zinc storage batteries, primary batteries, capacitors, or lithium-ion capacitors, etc. It may also be applied to a solid-state battery or an air battery. In some cases or depending on the situation, one aspect of the present invention is applicable to lithium ion secondary batteries. It is not necessary to use it.

[0138] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0139] (Embodiment 4) A storage battery using the storage battery electrode according to one embodiment of the present invention can be used in various electric machines driven by electric power. It can be used as a power source for the device.

[0140] As a specific example of an electrical device using a storage battery including the storage battery electrode according to one embodiment of the present invention, Display devices such as TVs and monitors, lighting devices, desktop or notebook personal computers, Computers, word processors, DVDs (Digital Versatile Dis c) Image playback devices that play still or moving images stored on recording media such as portable C D player, radio, tape recorder, headphone stereo, stereo, table clock, wall-mounted Clocks, cordless telephone handsets, transceivers, mobile phones, car phones, portable game consoles, Calculators, personal digital assistants, electronic organizers, e-book readers, electronic translators, voice input devices, video cameras lasers, digital still cameras, toys, electric shavers, microwave ovens and other high-frequency heating devices, Rice cookers, electric washing machines, vacuum cleaners, water heaters, electric fans, hair dryers, air conditioners, Air conditioning equipment such as humidifiers and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric appliances Electric refrigerators, electric freezers, electric refrigerator-freezers, freezers for storing DNA, flashlights, chainsaws These include electric tools such as fire extinguishers, smoke detectors, and medical equipment such as dialysis machines. Units, conveyor belts, elevators, escalators, industrial robots, power storage systems , industrial equipment such as power storage devices for power leveling and smart grids. Vehicles propelled by electric motors using power from storage batteries are also included in the category of electrical equipment. The above-mentioned moving body may be, for example, an electric vehicle (EV), a vehicle that combines an internal combustion engine and an electric motor. Hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), Tracked vehicles that have tires replaced with tracks, motorized bicycles including electrically assisted bicycles, Two-wheeled motor vehicles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft Examples include aircraft, rockets, artificial satellites, space probes, planetary rovers, and spacecraft.

[0141] In addition, the above-mentioned electrical equipment is provided with a main power source for covering almost all of the power consumption, and Alternatively, the electrical device may be a storage battery using the storage battery electrode according to the above. When the power supply from the main power source or commercial power source is stopped, the power supply to the electrical equipment is As an uninterruptible power supply capable of performing the above-mentioned operation, a storage battery using the storage battery electrode according to one embodiment of the present invention is used. Alternatively, the electrical equipment may be connected to the mains or utility power supply. The present invention is used as an auxiliary power source for supplying power to electrical equipment in parallel with the supply of electric power. A storage battery using the storage battery electrode according to one aspect of the present invention can be used.

[0142] A specific configuration of the above-mentioned electrical device is shown in Fig. 8. In Fig. 8, a display device 700 is 7 is an example of an electrical device using a storage battery 704 that uses the storage battery electrode according to one embodiment of the present invention. In other words, 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 used is provided inside the housing 701. The display device 700 is powered by a commercial power source. It can be powered from a power source or can use the power stored in the battery 704. Therefore, even when power cannot be supplied from the commercial power source due to a power outage, this invention By using the storage battery 704 using the storage battery electrode according to one embodiment of the present invention as an uninterruptible power supply, The display device 700 becomes available for use.

[0143] The display unit 702 is a light-emitting device having light-emitting elements such as a liquid crystal display device or an organic EL element for each pixel. Device, electrophoretic display device, DMD (Digital Micromirror Device e), PDP (Plasma Display Panel), FED (Field E A semiconductor display device such as a mission display can be used.

[0144] In addition, display devices are used for TV broadcast reception, personal computers, advertising displays, etc. , all display devices for displaying information are included.

[0145] In FIG. 8, a stationary lighting device 710 uses a storage battery electrode according to one embodiment of the present invention. This is an example of an electrical device using a storage battery 713. 8, the storage battery 713 is disposed in the housing 711 and 7, the light source 712 is provided inside a ceiling 714. The storage battery 713 may be provided inside the housing 711. The lighting device 710 is It can receive power from a power source, or use the power stored in the storage battery 713. Therefore, even if the power supply from the commercial power source cannot be received due to a power outage, this The storage battery 713 using the storage battery electrode according to one embodiment of the present invention is used as an uninterruptible power supply. , the lighting device 710 becomes available for use.

[0146] In addition, FIG. 8 illustrates a lighting device 710 that is installed on a ceiling 714. In the storage battery using the storage battery electrode according to one embodiment of the present invention, in addition to the ceiling 714, for example, the side wall 71 5. It can also be used in a fixed lighting device installed on a floor 716, a window 717, etc. It can also be used as a tabletop lighting device.

[0147] The light source 712 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent light bulbs, fluorescent lamps and other discharge lamps, and light-emitting elements such as LEDs and organic EL elements An example of the artificial light source is a lamp.

[0148] In FIG. 8, an air conditioner having an indoor unit 720 and an outdoor unit 724 is 1 is an example of an electrical device using a storage battery 723 that uses a storage battery electrode according to one embodiment. The indoor unit 720 includes a housing 721, an air outlet 722, a storage battery 723, and the like. Although the storage battery 723 is illustrated as being provided in the indoor unit 720, the storage battery 723 is Alternatively, the cooling fan 722 may be provided in both the indoor unit 720 and the outdoor unit 724. The air conditioner may be provided with a storage battery 723. The power can be supplied from the power source or can be stored in the battery 723. In the case where a storage battery 723 is provided in both the indoor unit 720 and the outdoor unit 724, in the event of a power outage, The storage battery electrode according to one embodiment of the present invention can be used even when power cannot be supplied from a commercial power source. By using the storage battery 723 as an uninterruptible power source, it is possible to use an air conditioner. It becomes Noh.

[0149] In addition, Figure 8 shows an example of a separate type air conditioner consisting of an indoor unit and an outdoor unit. However, it is an integrated air conditioner that has both the indoor and outdoor functions in a single housing. A storage battery using a storage battery electrode according to one embodiment of the present invention can also be used in the scanner.

[0150] In FIG. 8, an electric refrigerator-freezer 730 is a storage battery using a storage battery electrode according to one embodiment of the present invention. This is an example of an electric device using a battery 734. Specifically, the electric refrigerator-freezer 730 has a housing 7 31, a refrigerator door 732, a freezer door 733, a storage battery 734, etc. A battery 734 is provided inside the housing 731. The electric refrigerator-freezer 730 is powered by a commercial power source. It can receive power from the battery 734 or use the power stored in the battery 734. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention can be used in one embodiment. By using a storage battery 734 using the storage battery electrodes according to the present invention as an uninterruptible power source, Warehouse 730 will be available for use.

[0151] 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.

[0152] 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.

[0153] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0154] (Embodiment 5) Next, a portable information terminal, which is an example of an electrical device, will be described with reference to FIG.

[0155] 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 The switch 805 and the operation switch 807 are provided.

[0156] A part of the display unit 802a can be used as a touch panel area 808a, and the displayed operation By touching the operation keys 809, data can be input. For example, half of the area has a display function and the other half has a touch function. Although the display unit 802a has a configuration having a panel function, the present invention is not limited to this configuration. For example, the entire surface of the display unit 802a may have a touch panel function. The keyboard buttons are displayed on the display unit 802b to serve as a touch panel, and the display unit 802b is used as a display screen. It is possible.

[0157] Similarly to the display unit 802a, when a part of the display unit 802b is touched, The area 808b of the touch panel can be used as the keyboard display switch. By touching the position where the replacement button 810 is displayed with a finger or a stylus, the display unit 80 Keyboard buttons can be displayed on 2b.

[0158] In addition, when the area 808a of the touch panel and the area 808b of the touch panel are touched at the same time, You can also input it.

[0159] A display mode changeover switch 803 is used to change the display orientation between portrait and landscape. You can switch between black and white and color display. The Touch 805 is a tablet-type device that detects the amount of external light that is being used by the device using a built-in light sensor. The brightness of the display can be adjusted according to the amount of light. In addition, it also has other detection devices such as gyro, acceleration sensor, etc. that detect tilt. It may be allowed.

[0160] FIG. 9A shows an example in which the display area of ​​the display portion 802b is the same as that of the display portion 802a. is not particularly limited, one size may be different from the other, and the quality of the display may be For example, one of the display panels may be capable of displaying a higher resolution image than the other. Good too.

[0161] FIG. 9B shows the tablet terminal 800 in a closed state. The tablet terminal 800 includes a housing 801 and a solar cell 802. 11, includes a charge / discharge control circuit 850, a battery 851, and a DCDC converter 852. In FIG. 9B, a battery 851 and a DC / DC converter are used as an example of the charge / discharge control circuit 850. The battery 851 is the same as that in the above embodiment. The present invention includes a storage battery using the storage battery electrode according to one embodiment of the present invention described above.

[0162] In addition, since the tablet terminal 800 can be folded in half, when the housing 801 is closed, Therefore, the display unit 802a and the display unit 802b can be protected, and the display unit 802a and the display unit 802b can be protected. To provide a tablet terminal 800 having excellent durability and excellent reliability from the viewpoint of long-term use. This can be done.

[0163] In addition, the tablet terminals shown in Figs. 9(A) and 9(B) can store various information ( Functions for displaying still images, videos, text images, etc., and for displaying calendars, dates, or times, etc. A function to display information on the display unit, and a touch input device to operate or edit the information displayed on the display unit by touch input. It has the ability to control processing by various software (programs), etc. can.

[0164] The solar cell 811 attached to the surface of the tablet terminal supplies power to the touch panel, display, and The solar cell 811 can supply the power to a display unit, a video signal processor, or the like. The battery 851 can be efficiently charged by providing a charger on one or both sides of the battery 801. It can be said that it is completed.

[0165] The configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9B are shown in FIG. FIG. 9C shows a solar cell 811, a battery 851, and a , a DC-DC converter 852, a converter 853, switches SW1 to SW3, a display unit 8 02, battery 851, DCDC converter 852, converter 8 53, switches SW1 to SW3 correspond to the charge / discharge control circuit 850 shown in FIG. This is the location.

[0166] First, an example of operation in which power is generated by solar cell 811 using external light will be described. The power generated by the solar cell is converted to a voltage to charge the battery 851. The converter 852 steps up or steps down the voltage. When power from 811 is used, switch SW1 is turned on and the converter 853 is The voltage is increased or decreased to a voltage required for the display unit 802. When not displaying, turn SW1 off and SW2 on to charge the Battery 851. It is sufficient to adopt a configuration in which the above-mentioned

[0167] Although the solar cell 811 is shown as an example of a power generating means, it is not particularly limited and may be any type of power generating means. 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.

[0168] 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.

[0169] (Embodiment 6) Furthermore, an example of a moving object, which is an example of an electrical device, will be described with reference to FIG.

[0170] 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, the electric current from the overhead wire or conductive rail (conductive rail) can be It can be charged by supplying electricity.

[0171] 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, and the like.

[0172] 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, stopping, etc.) and driving information (uphill, downhill, etc., load information on the drive wheels Based on the input information, the control circuit 862 outputs a control signal to the control circuit 862. The control signal from the processing unit 864 adjusts the electric energy supplied from the battery 861. In the case where an AC motor is installed, the output of the drive unit 863 is controlled by adjusting the speed of the drive unit 863. However, it also has a built-in inverter that converts direct current to alternating current.

[0173] The Battery 861 can be charged by an external power supply using plug-in technology. For example, the battery 861 can be charged from a commercial power source through a power plug. It is converted into a constant DC voltage with a constant voltage value through a conversion device such as an AC / DC converter. The battery 861 may be a storage battery electrode according to one embodiment of the present invention. By installing a storage battery using this technology, it will be possible to contribute to increasing the battery capacity and improve convenience. In addition, the improvement of the characteristics of the battery 861 allows the battery 861 to be If the vehicle itself can be made smaller and lighter, it will contribute to reducing the vehicle's weight, improving fuel efficiency. .

[0174] Note that the present invention is not limited to the above-described electric devices as long as the storage battery according to one embodiment of the present invention is included. Needless to say, that is not the case.

[0175] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0176] (Embodiment 7) A battery cell including the material described in the above embodiment (for example, the battery cell described in the third embodiment) A battery control unit (Battery Manager) that can be used in combination with the A battery control unit (BMU) and a circuit suitable for the circuit constituting the battery control unit The transistor will be described with reference to FIGS. A battery control unit for a power storage device having battery cells connected in a series will be described.

[0177] When multiple battery cells connected in series are repeatedly charged and discharged, the characteristics between the battery cells The capacity (output voltage) varies depending on the variation in the The total discharge capacity depends on the battery cells with smaller capacity. Also, if charging is performed based on a battery cell with a smaller capacity, the charging In addition, if charging is performed based on the battery cell with the larger capacity, it may result in overcharging. There is a risk that this may happen.

[0178] Therefore, the battery control unit of the power storage device having battery cells connected in series is It has the function of aligning the capacity variation between battery cells, which can cause overcharging. The circuit configuration for aligning the capacitance variation between the resistors, capacitors, or inductors can be used. There are other methods such as the transistor method, but here we use a transistor with a small off-current to reduce the variation in capacitance. An example of a circuit configuration that can be made uniform will be described below.

[0179] As a transistor with low off-state current, a transistor having an oxide semiconductor in a channel formation region is OS transistors with low off-state current are preferred. By using this in the circuit configuration of the battery control unit of the device, the amount of charge leaking from the battery cell is reduced. This makes it possible to suppress the capacity from decreasing over time.

[0180] The oxide semiconductor used in the channel formation region is In-M-Zn oxide (M is Ga, Sn, Y, Zr, La, Ce, or Nd) is used to form an oxide semiconductor film. In the target, if the atomic ratio of metal elements is In:M:Zn=x1:y1:z1, 、 x1 / y1 is 1 / 3 or more and 6 or less, and further 1 or more and 6 or less, and z1 / y1 is 1 It is preferable that z1 / y1 is 1 or more and 6 or less, and more preferably 1 or more and 6 or less. When the content is 6 or less, a CAAC-OS film is easily formed as the oxide semiconductor film.

[0181] Here, the CAAC-OS film will be described.

[0182] The CAAC-OS film is one of oxide semiconductor films having a plurality of crystal parts aligned along the c-axis.

[0183] Transmission Electron Microscope (TEM) A bright-field image and a combined diffraction pattern of the CAAC-OS film were obtained by using a microscope. By observing the TEM image, multiple crystalline regions can be confirmed. On the other hand, the high-resolution TEM image also shows clear boundaries between crystals, i.e., grain boundaries. Therefore, the CAAC-OS film is It can be said that the decrease in electron mobility caused by grain boundaries is unlikely to occur.

[0184] When a high-resolution TEM image of the cross section of the CAAC-OS film was observed from a direction approximately parallel to the sample surface, It can be seen that the metal atoms are arranged in layers in the crystal part. Each layer of metal atoms is The CAAC-OS film is formed on the surface (also called the surface on which the film is formed) or on the upper surface. The CAAC-OS film has a shape similar to that of the crystalline silicon film, and is aligned parallel to the surface on which the CAAC-OS film is formed or the upper surface.

[0185] On the other hand, a high-resolution TEM image of the plane of the CAAC-OS film was observed from a direction approximately perpendicular to the sample surface. It was confirmed that the metal atoms in the crystals were arranged in triangular or hexagonal shapes. However, there is no regularity in the arrangement of metal atoms between different crystal parts.

[0186] X-ray diffraction (XRD) was performed on the CAAC-OS film. For example, a CAAC-OS film with InGaZnO4 crystals was In the out-of-plane analysis, a peak was observed at a diffraction angle (2θ) of approximately 31°. This peak is attributed to the (009) plane of the InGaZnO4 crystal. From this, it can be seen that the crystals of the CAAC-OS film have a c-axis orientation, and the c-axis is approximately aligned on the surface on which the film is formed or on the upper surface. You can see that it is oriented vertically.

[0187] In addition, the out-of-plane method of CAAC-OS film with InGaZnO4 crystals In the analysis by , in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ of around 36° may be due to the c-axis orientation in some parts of the CAAC-OS film. The CAAC-OS film contains crystals that do not have a 2θ of around 31°. It is preferred that the spectrum exhibits a peak and does not exhibit a peak at 2θ of around 36°.

[0188] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The impurities include hydrogen, carbon, and The elements are other than the main components of the oxide semiconductor film, such as silicon and transition metal elements. The elements that bond to oxygen more strongly than the metal elements that form the oxide semiconductor film, such as arsenic, are oxidized. By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disrupted, reducing its crystallinity. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide have an atomic radius of Since the molecular radius is large, when the cation is contained in the oxide semiconductor film, the The impurities in the oxide semiconductor film may cause the atomic arrangement to be disturbed, which may result in a decrease in crystallinity. Objects can act as carrier traps or carrier generation sources.

[0189] The CAAC-OS film is an oxide semiconductor film having a low density of defect states. Oxygen vacancies in the semiconductor film can become carrier traps or trap hydrogen, It can be a carrier source.

[0190] A material with a low impurity concentration and a low defect level density (few oxygen vacancies) is called a high-purity intrinsic or The term "substantially high-purity intrinsic" refers to a highly-purified intrinsic oxide semiconductor film. Since there are fewer carrier generation sources, the carrier density can be reduced. The transistor including the oxide semiconductor film has electrical characteristics in which the threshold voltage is negative ( Also called normally-on.) In addition, high purity intrinsic or substantially high purity The highly intrinsic oxide semiconductor film has few carrier traps. The transistors using the thin film have small fluctuations in electrical characteristics and are highly reliable. Note that it takes a certain time for charges trapped in the carrier traps in the oxide semiconductor film to be released. The time when the charge is released is long, and it may behave as if it is a fixed charge. A transistor using an oxide semiconductor film having a high density of defect states has unstable electrical characteristics. This may be the case.

[0191] In addition, the electrical characteristics of transistors using CAAC-OS films were improved by irradiation with visible light or ultraviolet light. The fluctuation is small.

[0192] Note that an OS transistor is a transistor having silicon in a channel formation region (a Si transistor). Since the band gap is larger than that of a conventional transistor, dielectric breakdown does not occur when a high voltage is applied. When battery cells are connected in series, a voltage of several hundred volts is generated, but The circuit configuration of the battery control unit applied to such a battery cell in the battery device includes the above-mentioned It is suitable to configure the semiconductor device using an OS transistor having the above structure.

[0193] FIG. 11 shows an example of a block diagram of a power storage device. A terminal pair 1001, a terminal pair 1002, a switching control circuit 1003, and a switching circuit 100 4, a switching circuit 1005, a transformer control circuit 1006, and a transformer circuit 1007 are connected in series. and a battery section 1008 including a plurality of connected battery cells 1009.

[0194] In addition, in the power storage device 1000 of FIG. 11, a terminal pair 1001 and a terminal pair 1002 are A switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, and a transformer control The part consisting of the circuit 1006 and the transformer circuit 1007 is called a battery control unit. It is possible.

[0195] A switching control circuit 1003 controls the operation of the switching circuits 1004 and 1005. Specifically, the switching control circuit 1003 controls the measured voltage of each battery cell 1009. Based on the voltage, the battery cells to be discharged (discharging battery cell group) and the battery cells to be charged (charging battery cell group) are selected. Determine the number of cells (pond cell group).

[0196] Furthermore, the switching control circuit 1003 controls the determined discharge battery cell group and charge battery cell group. Based on the group, the control signal S1 and the control signal S2 are output. This control signal S1 connects the terminal pair 1001 and the discharge battery cell group. The control signal S2 is a signal that controls the switching circuit 1004 to connect the The control signal S2 is output to the switching circuit 1005. This is a signal that controls the switching circuit 1005 to connect the group.

[0197] The switching control circuit 1003 includes a switching circuit 1004, a switching circuit 1005, and Considering the configuration of the transformer circuit 1007, between the terminal pair 1001 and the discharge battery cell group, or between the terminal Control is performed so that terminals of the same polarity are connected between the slave pair 1002 and the charging battery cell group. It generates a signal S1 and a control signal S2.

[0198] The operation of the switching control circuit 1003 will now be described in detail.

[0199] First, the switching control circuit 1003 measures the voltage of each of the multiple battery cells 1009. The switching control circuit 1003 then selects, for example, a battery cell 1009 having a voltage equal to or higher than a predetermined threshold. A high-voltage battery cell (high-voltage cell), a battery cell 1009 with a voltage below a predetermined threshold is treated as a low-voltage It is determined to be a battery cell (low voltage cell).

[0200] There are various methods for determining whether a cell is a high-voltage cell or a low-voltage cell. For example, the switching control circuit 1003 may select the most highly charged battery cell 1009. The voltage of each battery cell 100 is determined based on the voltage of the battery cell 1009 having the highest or lowest voltage. 9 may be a high-voltage cell or a low-voltage cell. In this case, the switching control circuit 1003 It is determined whether the voltage of each battery cell 1009 is equal to or higher than a predetermined ratio of a reference voltage. By doing so, it is possible to determine whether each battery cell 1009 is a high-voltage cell or a low-voltage cell. Based on the result of this determination, the switching control circuit 1003 switches the discharging battery cell group and the charging battery cell group. The pond cell group is determined.

[0201] In addition, among the multiple battery cells 1009, high voltage cells and low voltage cells are mixed in various states. For example, the switching control circuit 1003 may be configured to: The part with the largest number of high-voltage cells connected in series is the discharge battery cell group. The switching control circuit 1003 charges the part in which the most low-voltage cells are connected in series. The switching control circuit 1003 detects whether the battery cell is close to being overcharged or overdischarged. The battery cell group 1009 may be preferentially selected as a discharge battery cell group or a charge battery cell group. good.

[0202] An example of the operation of the switching control circuit 1003 in this embodiment will now be described with reference to FIG. FIG. 12 is a diagram for explaining an example of the operation of the switching control circuit 1003. For convenience of explanation, FIG. 12 shows an example in which four battery cells 1009 are connected in series. explain.

[0203] First, in the example of FIG. 12A, if the voltages of the battery cells a to d are voltages Va to Vd, In other words, the relationship of Va=Vb=Vc>Vd is satisfied when three consecutive high voltages The high-voltage cells a to c and one low-voltage cell d are connected in series. The control circuit 1003 determines three consecutive high-voltage cells a to c as a discharge battery cell group. In addition, the switching control circuit 1003 determines the low-voltage cell d as the charging battery cell group. .

[0204] Next, the example of FIG. 12B shows a case where the relationship is Vc>Va=Vb>>Vd. That is, between two consecutive low voltage cells a and b, one high voltage cell c, and one over-discharge The nearby low-voltage cell d is connected in series. In this case, the switching control circuit 1003 The high-voltage cell c is determined as the discharge battery cell group. The low-voltage cell d, which is close to being over-discharged, is not connected to the two low-voltage cells a and b, but to the charging battery cell. The group is determined as a priority.

[0205] Finally, the example of FIG. 12C shows a case where the relationship Va>Vb=Vc=Vd holds. 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. The switching control circuit 1003 also controls the charging of three consecutive low-voltage cells b to d. Determined as a battery cell group.

[0206] The switching control circuit 1003 determines the result as shown in the examples of FIGS. Based on this, information indicating the discharge battery cell group to which the switching circuit 1004 is connected is set. The control signal S1 and information indicating the rechargeable battery cell group to which the switching circuit 1005 is connected are set. The control signal S2 thus determined is sent to the switching circuit 1004 and the switching circuit 1005. Each is output.

[0207] The above is a detailed explanation of the operation of the switching control circuit 1003.

[0208] The switching circuit 1004 is responsive to a control signal S1 output from the switching control circuit 1003. The connection destination of the terminal pair 1001 is determined by the switching control circuit 1003. Set the rule group.

[0209] The terminal pair 1001 is composed of a pair of terminals A1 and A2. Either one of the terminals A1 and A2 is connected to the most upstream (high voltage) of the discharge battery cell group. The other end is connected to the positive terminal of the battery cell 1009 located at the lowest position in the discharge battery cell group. By connecting it to the negative terminal of the battery cell 1009 located further downstream (low potential side), The switch circuit 1004 is set to the connection destination of the pair 1001 by the control signal S1. The obtained information can be used to identify the position of the discharging battery cell group.

[0210] The switching circuit 1005 is responsive to a control signal S2 output from the switching control circuit 1003. The connection destination of the terminal pair 1002 is determined by the switching control circuit 1003. Set the rule group.

[0211] The terminal pair 1002 is composed of a pair of terminals B1 and B2. Either of these terminals B1 and B2 is connected to the most upstream (high voltage) of the charging battery cell group. The other terminal is connected to the positive terminal of the battery cell 1009 located at the lowest position in the charging battery cell group. By connecting it to the negative terminal of the battery cell 1009 located further downstream (low potential side), The switch circuit 1005 is set to the connection destination of the pair 1002 by the control signal S2. The position of the rechargeable battery cell group can be recognized using the obtained information.

[0212] FIG. 13 and FIG. 14 are circuit diagrams showing examples of the configuration of the switching circuit 1004 and the switching circuit 1005. Shown in 4.

[0213] In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010, a bus 1011, and The bus 1011 is connected to the terminal A1. 2 is connected to the terminal A2. One of them is alternately connected to the buses 1011 and 1012. The other of the sources or drains of the multiple transistors 1010 is connected to two adjacent It is connected between the battery cells 1009.

[0214] Among the multiple transistors 1010, the transistor 1010 located at the most upstream The other of the source and drain is the positive electrode of the battery cell 1009 located at the most upstream of the battery section 1008. In addition, the transistor located at the most downstream of the plurality of transistors 1010 is connected to the terminal. The other of the source and drain of the transistor 1010 is located at the most downstream of the battery section 1008. It is connected to the negative terminal of the battery cell 1009 .

[0215] The switching circuit 1004 is configured to control a control signal S1 to be applied to the gates of a plurality of transistors 1010. In response, one of the plurality of transistors 1010 connected to the bus 1011 and the bus 1012 and one of the plurality of transistors 1010 connected thereto are respectively in a conductive state. This connects the discharge battery cell group to the terminal pair 1001. The positive terminal of the battery cell 1009 located at the most upstream of the group of cells is 2. Also, the battery cell located most downstream in the discharge battery cell group is connected to either The negative terminal of the terminal 1009 is the other of the terminals A1 and A2 of the terminal pair, i.e., the positive terminal The terminal that is not connected to the

[0216] The transistor 1010 is preferably an OS transistor. Since the off-state current of the capacitor is small, the amount of charge leaking from the battery cells that do not belong to the discharge battery cell group is reduced. This suppresses the decrease in capacitance over time. Dielectric breakdown is unlikely to occur when voltage is applied. Therefore, the output voltage of the discharge battery cell group is large. However, the transistor 1010 that is in a non-conducting state is connected to the battery cell 1009 and the terminal pair. 1001 can be insulated.

[0217] In addition, in FIG. 13, the switching circuit 1005 includes a plurality of transistors 1013 and a current control The switch 1014, the bus 1015, and the bus 1016 are included. 16 is disposed between a plurality of transistors 1013 and a current control switch 1014. The source or drain of each of the transistors 1013 is alternately The plurality of transistors 1013 are connected to buses 1015 and 1016. The other of the source and drain is connected between two adjacent battery cells 1009. is.

[0218] Among the multiple transistors 1013, the transistor 1013 located at the most upstream The other of the source and drain is the positive electrode of the battery cell 1009 located at the most upstream of the battery section 1008. The transistor 1013 located at the most downstream side is connected to the terminal. The other of the source and drain of the transistor 1013 is located at the most downstream of the battery section 1008. It is connected to the negative terminal of the battery cell 1009 .

[0219] The transistor 1013 is an OS transistor, similar to the transistor 1010. Since the off-state current of the OS transistor is small, it is preferable that the OS transistor does not belong to the rechargeable battery cell group. This reduces the amount of charge leaking from the battery cell and suppresses the decrease in capacity over time. In addition, OS transistors are less susceptible to dielectric breakdown when high voltages are applied. A transistor 10 that is in a non-conducting state even if the voltage for charging the battery cell group is large. 13, the battery cell 1009 connected thereto and the terminal pair 1002 can be insulated from each other.

[0220] The current control switch 1014 includes a switch pair 1017 and a switch pair 1018. One end of the switch pair 1017 is connected to the terminal B1. The end is split into two switches, one of which is connected to the bus 1015 and the other The switch is connected to the bus 1016. One end of the switch pair 1018 is connected to the terminal B2. The other end of the switch pair 1018 is branched into two switches. The switch is connected to bus 1015 and the other switch is connected to bus 1016. .

[0221] The switches in switch pair 1017 and switch pair 1018 are transistors 1010 Like the transistor 1013, an OS transistor is preferably used.

[0222] The switching circuit 1005 switches the transistor 1013 and the current control By controlling the combination of on / off states of the switch 1014, the battery cell group and terminal pair 1002 are connected.

[0223] The switching circuit 1005, for example, connects the rechargeable battery cell group and the terminal pair 100 in the following manner. Connect 2.

[0224] The switching circuit 1005 is configured to control a control signal S2 to be applied to the gates of a plurality of transistors 1013. In response, the positive terminal of the battery cell 1009 located most upstream in the charging battery cell group is connected. The switching circuit 1005 turns on the transistor 1013 that is connected to the In response to a control signal S2 applied to the gate of the transistor 1013, A transistor 1013 connected to the negative terminal of the battery cell 1009 located most downstream is put into a conductive state.

[0225] The polarity of the voltage applied to the terminal pair 1002 is the polarity of the discharge battery cell group connected to the terminal pair 1001. The method of charging the rechargeable battery cell group may vary depending on the configuration of the transformer circuit 1007. To allow current to flow in the same direction, terminals of the same polarity must be connected between the terminal pair 1002 and the charging battery cells. Therefore, the current control switch 1014 is controlled by the control signal S2 as follows: Depending on the polarity of the voltage applied to terminal pair 1002, switch pair 1017 and switch pair 10 It is controlled to switch between each of the 18 connection destinations.

[0226] As an example, a voltage is applied to the terminal pair 1002 such that the terminal B1 is positive and the terminal B2 is negative. In this case, the most downstream battery cell 1009 of the battery unit 1008 is If the battery cell group is a charging battery cell group, the switch pair 1017 is turned on by the control signal S2. That is, the switch pair 1017 is controlled to be connected to the positive terminal of the switch 1009. The switch connected to the bus 1016 is turned on, and the bus 10 The switch connected to the control signal 1015 is turned off. S2 is controlled so as to be connected to the negative terminal of the battery cell 1009. Then, the switch of the switch pair 1018 connected to the bus 1015 is turned on. The switch connected to the bus 1016 of the pair 1018 is turned off. Between the terminal pair 1002 and the charging battery cell group, terminals having the same polarity are connected to each other. The direction of the current flowing from the terminal pair 1002 is set to the direction that charges the rechargeable battery cell group. It is controlled as follows.

[0227] Also, the current control switch 1014 is not the switching circuit 1005 but the switching circuit 10 04. In this case, the current control switch 1014 is By controlling the polarity of the voltage applied to the terminal pair 1001, The current control switch 1014 controls the polarity of the applied voltage. 2 controls the direction of current flowing to the charging battery cell group.

[0228] FIG. 14 shows a configuration example of the switching circuit 1004 and the switching circuit 1005, which is different from that shown in FIG. FIG.

[0229] In FIG. 14, the switching circuit 1004 includes a plurality of transistor pairs 1021 and a bus 1024. and a bus 1025. The bus 1024 is connected to the terminal A1. 1025 is connected to the terminal A2. Each of them is branched by a transistor 1022 and a transistor 1023. Either the source or drain of 1022 is connected to a bus 1024. Either the source or the drain of the resistor 1023 is connected to the bus 1025. The other ends of the transistor pairs are connected between two adjacent battery cells 1009. Among the plurality of transistor pairs 1021, the transistor located at the most upstream The other end of the pair 1021 is connected to the positive terminal of the battery cell 1009 located at the most upstream of the battery section 1008. In addition, among the plurality of transistor pairs 1021, the transistor located at the most downstream The other end of the resistor pair 1021 is connected to the negative electrode of the battery cell 1009 located at the most downstream of the battery section 1008. is connected to the terminal.

[0230] The switching circuit 1004 switches between the transistor 1022 and the transistor By switching the conductive / non-conductive state of 1023, the connection of the transistor pair 1021 is The connection destination is switched to either terminal A1 or terminal A2. If transistor 022 is conductive, transistor 1023 is non-conductive, and the transistor pair The connection destination of 1021 is terminal A1. On the other hand, if transistor 1023 is in a conductive state, The transistor 1022 is turned off, and the transistor pair 1021 is connected to the terminal A2. Whether the transistor 1022 or the transistor 1023 is in a conductive state depends on , determined by the control signal S1.

[0231] Two transistor pairs 1021 are used to connect the terminal pair 1001 to the discharge battery cell group. In detail, the connection destination of the two transistor pairs 1021 is determined based on the control signal S1. By determining the terminals 1001 and 1002, the discharge battery cell group is connected to the terminal pair 1001. One of the transistor pairs 1021 is connected to a terminal A1, and the other is connected to a terminal A2 by the control signal S1.

[0232] The switching circuit 1005 includes a plurality of transistor pairs 1031, a bus 1034 and a bus 1035. 35. The bus 1034 is connected to the terminal B1. The bus 1035 is One end of each of the transistor pairs 1031 is connected to the terminal B1. The output of the transistor 1032 is branched off by a transistor 1033. Either the source or the drain of the transistor 103 is connected to the bus 1034. Either the source or the drain of each of the transistors 3 is connected to a bus 1035. The other ends of the resistor pairs 1031 are connected between two adjacent battery cells 1009. Among the plurality of transistor pairs 1031, the transistor pair 1031 located at the most downstream The other end of the 031 is connected to the negative terminal of the battery cell 1009 located at the most downstream of the battery section 1008. Among the plurality of transistor pairs 1031, the most upstream transistor pair 1031 The other end is connected to the negative terminal of the battery cell 1009 located at the most upstream of the battery section 1008. There are.

[0233] The switching circuit 1005 switches between the transistor 1032 and the transistor By switching the conductive / non-conductive state of 1033, the connection of the transistor pair 1031 is The connection destination is switched to either terminal B1 or terminal B2. If transistor 032 is conductive, transistor 1033 is non-conductive, and the transistor pair The connection destination of 1031 is terminal B1. Conversely, if transistor 1033 is in a conductive state, The transistor 1032 is turned off, and the transistor pair 1031 is connected to the terminal B2. Whether the transistor 1032 or the transistor 1033 is in a conductive state depends on , determined by the control signal S2.

[0234] Two transistor pairs 1031 are used to connect the terminal pair 1002 to the charging battery cell group. In detail, the connection destination of the two transistor pairs 1031 is determined based on the control signal S2. By determining the terminals 1002 and 1003, the rechargeable battery cell group is connected to the terminal pair 1002. One of the transistor pairs 1031 is connected to a terminal B1, and the other is connected to a terminal B2 by the control signal S2.

[0235] The two transistor pairs 1031 are connected to terminal pairs 1002. Specifically, terminal B1 is the positive terminal and terminal B2 is the negative terminal. When such a voltage is applied to the terminal pair 1002, the upstream transistor pair 1031 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.

[0236] 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.

[0237] 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 transformer circuit 1007 is configured to step down the discharge voltage (Vdis) to a level that allows the cell group to be charged. It outputs a control transformer signal S3.

[0238] In addition, 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 battery cells 1009 is less than or equal to the number of chargeable battery cells 1009, the charge Therefore, the voltage conversion control circuit 1006 is configured to convert excess The transformer circuit 10 is configured to boost the discharge voltage (Vdis) to a level where an excessively high charging voltage is not applied. 07.

[0239] The voltage value that is considered as the excessive charging voltage is the voltage value of the battery cell 1009 used in the battery unit 1008. This can be determined in consideration of product specifications, etc. The resulting voltage is applied to terminal pair 1002 as a charging voltage (Vcha).

[0240] Here, an example of the operation of the transformer control circuit 1006 in this embodiment will be described with reference to FIGS. 15(A) to (C) are diagrams showing the radiation pattern described in FIG. 12(A) to (C). An example of the operation of the transformer control circuit 1006 corresponding to the power battery cell group and the rechargeable battery cell group will be described. 15(A) to (C) are conceptual diagrams illustrating a battery control unit 1041. The battery control unit 1041 is connected to a terminal pair 1001 and a terminal pair 1002. A switching control circuit 1003, a switching circuit 1004, a switching circuit 1005, and a transformer control It is composed of a circuit 1006 and a transformer circuit 1007.

[0241] In the example shown in FIG. 15(A), three consecutive high voltages are Cells a to c and one low-voltage cell d are connected in series. In this case, as shown in FIG. As explained above with reference to FIG. 1, the switching control circuit 1003 controls the high voltage cells a to c to discharge voltages. The low-voltage cell d is determined as the battery cell group, and the low-voltage cell d is determined as the charging battery cell group. The control circuit 1006 is based on the number of battery cells 1009 included in the discharge battery cell group. , the discharge voltage (Vdi s) to charging voltage (Vcha) is calculated.

[0242] 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. When the number of the battery cells 1009 is larger than the number of the discharge cells 1002, the discharge voltage is directly applied to the terminal pair 1002 without being transformed. When the voltage is applied to the battery cell 1009 included in the charging battery cell group, the voltage is applied to the battery cell 1009 via the terminal pair 1002. There is a possibility that an excessive voltage is applied. Therefore, in the case shown in FIG. In order to prevent this, the charging voltage (Vcha) applied to the terminal pair 1002 must be lower than the discharging voltage. Furthermore, in order to charge the battery cell group, the charging voltage must be The voltage of the battery cell 1009 must be greater than the total voltage of the battery cell 1009. 006 is the charging voltage when the number of battery cells 1009 included in the discharge battery cell group is used as a reference. The conversion ratio N is set to be larger than the ratio of the number of battery cells 1009 included in the battery cell group.

[0243] The voltage transformer control circuit 1006 determines the number of battery cells 1009 included in the discharge battery cell group as a reference. The conversion ratio N is set to 1 with respect to the ratio of the number of battery cells 1009 included in the charging battery cell group when At this time, the charging voltage is set to be equal to or greater than the voltage of the battery cell group. However, the charging voltage is actually equal to the voltage of the battery cells. The voltage conversion control circuit 1006 converts the voltage of the battery cells into the charging voltage according to the conversion ratio N. This current flows to charge the battery cell group. The value is set to 06.

[0244] In the example shown in FIG. 15(A), the number of battery cells 1009 included in the discharge battery cell group is three. Since the number of battery cells 1009 included in the charging battery cell group is one, the voltage transformation control circuit 1006 calculates a value slightly larger than 1 / 3 as the conversion ratio N. Then, the conversion control circuit 1006 is a transformer signal S3 which converts the discharge voltage into a charge voltage by stepping down the discharge voltage according to the conversion ratio N. The transformer circuit 1007 then outputs the transformed signal S3 to the transformer circuit 1007. The charging voltage applied to the terminal pair 1002 is then applied to the terminal pair 1002. The battery cell 1009 included in the charging battery cell group is charged by the charging voltage.

[0245] In the examples shown in FIG. 15(B) and FIG. 15(C), the conversion ratio N In the examples shown in FIG. 15(B) and FIG. 15(C), The number of battery cells 1009 included in the charging battery cell group is equal to or less than the number of battery cells 1009 included in the charging battery cell group. Therefore, the conversion ratio N is greater than 1. Therefore, in this case, the transformer control circuit 1006 is , and outputs a transformation signal S3 which boosts the discharge voltage and converts it into a charge voltage.

[0246] The transformer circuit 1007 adjusts the discharge voltage applied to the terminal pair 1001 based on the transformer signal S3. The transformer circuit 1007 then converts the converted charging voltage into a charging voltage. 2. Here, the transformer circuit 1007 applies a voltage between the terminal pair 1001 and the terminal pair 1002. This allows the transformer circuit 1007 to be connected to the lowest discharged battery cell group. The absolute voltage of the negative terminal of the battery cell 1009 located downstream and the most downstream of the charging battery cells This prevents a short circuit caused by a difference in absolute voltage between the negative terminal of the battery cell 1009 located at the opposite side. Then, as described above, the transformer circuit 1007 converts the total voltage of the discharge battery cell group into the total voltage of the discharge battery cell group based on the transformer signal S3. The discharge voltage, which is the measured voltage, is converted into a charge voltage.

[0247] The transformer circuit 1007 is, for example, an insulated DC (Direct Current)-DC In this case, the transformer control circuit 1006 may be an insulated DC- The signal that controls the on / off ratio (duty ratio) of the DC converter is the transformation signal S3. By outputting this, the charging voltage converted by the transformer circuit 1007 is controlled.

[0248] In addition, there are three types of isolated DC-DC converters: flyback type, forward type, RCC ( Ring Choke Converter, push-pull, half-blade There are various types of inverters, such as full-bridge inverter and ridge inverter, depending on the desired output voltage. The appropriate method is selected based on the result.

[0249] The configuration of a transformer circuit 1007 using an isolated DC-DC converter is shown in FIG. The C-DC converter 1051 includes a switch unit 1052 and a transformer unit 1053 . The switch unit 1052 is a switch for switching on / off the operation of the isolated DC-DC converter. For example, MOSFET (Metal-Oxide-Semiconductor tor Field-Effect Transistor) and bipolar transistors The switch unit 1052 is realized by using a transformer or the like. Based on the transformer signal S3 that controls the on / off ratio, the isolated DC-DC converter The switch unit 1051 periodically switches between the on and off states. Various configurations are possible depending on the type of isolated DC-DC converter used. 1053 converts the discharge voltage applied from the terminal pair 1001 into a charge voltage. The transformer section 1053 operates in conjunction with the on / off state of the switch section 1052. The discharge voltage is converted to a charge voltage according to the on / off ratio. This charge voltage is In the switching period of 2, the longer the on-state time, the larger the capacitance becomes. When a DC-DC converter of this type is used, the terminal pair 1001 and , and terminal pair 1002 can be insulated from each other.

[0250] The flow of processing performed by the power storage device 1000 in this embodiment will be described with reference to FIG. 7 is a flowchart showing a process flow of the power storage device 1000.

[0251] First, the power storage device 1000 acquires the voltage measured for each of the plurality of battery cells 1009 (step Step S1101). Then, the power storage device 1000 aligns the voltages of the multiple battery cells 1009. It is determined whether the start condition of the operation is satisfied (step S1102). For example, the difference between the maximum and minimum voltages measured for each of the plurality of battery cells 1009 is If this start condition is not met (step S1102: NO), since the voltages of the battery cells 1009 are in a balanced state. On the other hand, if the start condition is satisfied (step Step S1102: YES), the power storage device 1000 performs a process of making the voltages of the battery cells 1009 uniform. In this process, the power storage device 1000 performs a process based on the measured voltage of each cell. Then, it is determined whether each battery cell 1009 is a high-voltage cell or a low-voltage cell (step S1103 Then, the power storage device 1000 divides the discharge battery cell group and the charge battery cell group into two groups based on the result of the determination. Further, the power storage device 1000 determines a group of discharge A control signal S1 that sets the battery cell group as the connection destination of the terminal pair 1001, and A control signal S2 is generated to set the 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 a switching circuit The signal is output to the switching circuit 1004 and the switching circuit 1005. This connects the terminal pair 1001 to the discharge battery cell group, and the switching circuit 1005 The terminal pair 1002 and the discharge battery cell group are connected (step S1106). The device 1000 is configured to determine 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 battery cells 1009 included, a voltage transformation signal S3 is generated (step S1 107). The power storage device 1000 applies a voltage to the terminal pair 1001 based on the transformed signal S3. The applied discharge voltage is converted into a charge voltage and applied to the terminal pair 1002 (step S1108 This transfers the charge from the discharging battery cells to the charging battery cells.

[0252] In addition, in the flowchart of FIG. 17, multiple steps are listed in order, but each step The order in which the steps are executed is not limited to the order listed.

[0253] As described above, according to this embodiment, when transferring charges from the discharge battery cell group to the charge battery cell group, Like the capacitor method, the charge from the discharged battery cells is first stored and then transferred to the rechargeable battery cells. This eliminates the need for a structure that emits charge to a group of electrons. In addition, the switching circuit 1004 and the switching circuit 1005 can improve the efficiency. Therefore, among the discharge battery cell group and the charge battery cell group, the battery cells connected to the transformer circuit are individually can be switched to.

[0254] Furthermore, the number of battery cells 1009 included in the discharge battery cell group is calculated by the transformer circuit 1007. The number of battery cells 1009 included in the charging battery cell group is determined based on the number of battery cells 1009 included in the charging battery cell group. The discharge voltage is converted to a charge voltage and applied to the terminal pair 1002. Regardless of the selection of the battery cells 1009 on the charge and discharge sides, charge transfer can be achieved without any problems. can.

[0255] Furthermore, by using OS transistors for the transistors 1010 and 1013, As a result, leakage from the battery cell 1009 that does not belong to the charging battery cell group or the discharging battery cell group occurs. This reduces the amount of charge in the battery cell 1009 that does not contribute to charging or discharging. In addition, the OS transistor has a The change in characteristics due to heat is smaller than that of the conventional battery. However, normal operation, such as switching between conductive and non-conductive states according to the control signals S1 and S2, is performed. It is possible to do so.

[0256] This embodiment mode can be implemented in appropriate combination with other embodiment modes. EXAMPLES

[0257] 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.

[0258] (Synthesis of positive electrode active material) First, we synthesized a lithium manganese composite oxide as a positive electrode active material. Using i2CO3, MnCO3 and NiO, Li2CO3:MnCO3:NiO=0.84 The molar ratio of each of the components was 0.8062:0.318. Acetone was added to the powder, and the mixture was mixed in a ball mill to prepare a mixed powder.

[0259] Next, heating was carried out to evaporate acetone, and a mixed raw material was obtained.

[0260] Next, the mixed raw materials were placed in a crucible and fired to synthesize the material. The firing was carried out at 0°C for 10 hours. The firing atmosphere was air, and the gas flow rate was 10 L / min. It was decided.

[0261] Next, a crushing treatment was carried out to remove the sintering of the fired particles. Acetone was added to the mixture, and then the mixture was mixed in a ball mill.

[0262] Next, after the crushing treatment, heating is performed to evaporate acetone, and lithium having nickel is obtained. As a result, a manganese-manganese composite oxide was obtained.

[0263] (Preparation of electrode A) To prepare electrode A, lithium manganese composite oxide was used as the positive electrode active material and L-a was used as the reducing agent. Ascorbic acid, graphene oxide (GO) as the raw material for the conductive additive, and a Cetylene black (AB), PVdF as a binder, and NMP as a solvent were used. The lithium manganese composite oxide, GO, AB, and NMP were mixed to prepare a first mixture. Next, L-ascorbic acid dissolved in a small amount of water was added to the first mixture and kneaded. The GO was reduced by heating at 80°C for 1 hour to produce a second mixture. PVdF was added to the second mixture and kneaded to prepare a positive electrode paste. The mixture ratio of the positive electrode paste is lithium manganese composite oxide: graphene: AB: L-A. The weight ratio of each material was 89:0.5:4.5:1:5 (scorbic acid:PVdF). The amount of the material was adjusted. The positive electrode paste was applied to a current collector (aluminum) and heated at 250°C. The solvent in the positive electrode paste was evaporated by applying a 100% solvent to the current collector to produce electrode A. The loading of the positive electrode paste is 6 mg / cm 2 It was decided.

[0264] (Preparation of Comparative Example B) For comparison, comparative example B was prepared by reducing GO only by heating without using a reducing agent. First, the lithium manganese composite oxide, GO, AB, and NMP were mixed to obtain the first mixture. Next, PVdF was added to the first mixture and mixed to prepare a positive electrode. The mixture ratio of the positive electrode paste was lithium manganese composite oxide:GO. The amounts of each material were adjusted so that the ratio of AB to PVdF was 90:0.5:4.5:5. The positive electrode paste is applied to a current collector (aluminum) and heated to 250°C to evaporate the solvent. The positive electrode paste was then simultaneously reduced to prepare Comparative Example B. The dosage is 6mg / cm 2 It was decided.

[0265] (Preparation of half-cell) The prepared electrodes A and Comparative Example B were assembled into half cells, and the charge / discharge characteristics of each cell were measured. The half cell is a cell in which an active material other than Li metal is used for the positive electrode and Li is used for the negative electrode. The figure shows a lithium-ion secondary battery cell that uses lithium metal. The plate is made of polypropylene (PP) and the electrolyte is ethylene carbonate (EC). In a mixed solution of diethyl carbonate (DEC) and , lithium hexafluorophosphate (LiPF6) dissolved at a concentration of 1 mol / liter Used.

[0266] (Evaluation of cycle characteristics) The results of measuring the charge and discharge capacity are shown in FIG. 18. In FIG. 18, the vertical axis represents capacity (mAh / g). The horizontal axis represents the number of cycles. The charging conditions were constant current charging, charging rate 0.2C, and final voltage 4 The discharge conditions were constant current discharge, discharge rate 0.2C, and final voltage 2.0V. The number of cycles was measured up to 10. The cycle characteristics of the half cell prepared by the present invention are shown in FIG. 18(B). The cycle characteristics of the half cell are shown.

[0267] Here, the charge rate and discharge rate will be explained. A charge rate of 1C is a rate at which the cell is charged at a constant voltage. This is the current value at which charging is completed in exactly one hour. The theoretical capacity of the fuel cell is 150mAh / g, so 1C is 150mA / g. 0.2C is the current value at which the cell is charged at a constant current and charging is completed in exactly 5 hours. For the half-cell with the theoretical capacity mentioned above, it is 30mA / g. Similarly, a discharge rate of 1C is This is the current value at which the cell is discharged at a constant current and the discharge is completed in exactly one hour. In the half cell prepared in the example, 1C is 150mA / g and 0.2C is 30mA / g. be.

[0268] As can be seen from FIGS. 18(A) and (B), in the half cell using electrode A, Compared to the half cell using B, the decrease in capacity with increasing cycle number is suppressed. This shows that electrode A has higher electrical conductivity than comparative example B. During the preparation, a reducing agent is added, and the GO is reduced by heating before forming the positive electrode active material layer. The GO is reduced with high reaction efficiency, and a three-dimensional network of electrical conduction paths is formed in the active material layer. was presumed to have been constructed.

[0269] (Rate characteristic evaluation) FIG. 19 shows the discharge layer of the half cells fabricated by incorporating electrode A and comparative example B. The vertical axis shows the voltage (V) and the horizontal axis shows the charge / discharge capacity (mAh / g The charging conditions were constant current charging at a charge rate of 0.2C. The charge and discharge curves are shown when the rate is 0.2C. Also, FIG. 19(B) shows the discharge The charge and discharge curves at a rate of 0.5 C are shown. The charge and discharge curves at a rate of 1.0C are shown.

[0270] As shown in Figures 19(A), (B), and (C), the half cell incorporating Comparative Example B has a discharge layer. It was found that the discharge capacity and voltage decreased significantly with increasing the concentration of The half cell incorporating this has been found to be less susceptible to a decrease in discharge capacity and voltage even when the discharge rate is increased. Therefore, it is clear that electrode A has a smaller resistance than comparative example B. From this, it was found that the GO was reduced by a reducing agent before forming the positive electrode active material layer. This suggests that the efficiency of the GO reduction reaction can be increased.

[0271] (Current-rest method resistance measurement) Next, electrodes A and Comparative Example B were evaluated by performing current-rest resistance measurements. This section explains the current rest resistance. When charging a battery, if you pause charging, the voltage drops. The cause of this voltage drop is the internal resistance of the battery. The formula for calculating the voltage immediately after rest (voltage after 3 seconds of rest) / current is used to calculate the voltage. The ohmic components of the internal resistance of the half-cell incorporating Comparative Example B and the half-cell incorporating Comparative Example B were calculated and compared. The charging conditions were constant current charging, charging rate 0.2C. Charging pause was 15mA. The battery capacity was 195mAh / g and 210mAh. When the current reaches 225mAh / g, 240mAh / g, the current is stopped and the internal resistance is The results of calculating the ohmic components are shown in Table 1.

[0272] [Table 1]

[0273] From the results in Table 1, the half-cell incorporating electrode A exhibited a higher thermal conductivity than the half-cell incorporating comparative example B. It was found that the internal resistance ohmic component was smaller than that of Comparative Example B. Therefore, it was found that the resistance was small even when a reducing agent was used when preparing the positive electrode active material layer. By adding ZnO, the efficiency of the reaction to reduce GO can be increased, and the internal resistance ohmic component It was suggested that small electrodes could be fabricated. [Explanation of symbols]

[0274] S101 Step S102 Step S103 Step S104 Step 200 electrodes 201 Current collector 202 Active material layer 203 Active material 204 Graphene 300 Coin type battery 301 Positive electrode can 302 Anode can 303 Gasket 304 Positive electrode 305 Positive electrode current collector 306 Positive electrode active material layer 307 Negative electrode 308 Negative electrode current collector 309 Negative electrode active material layer 310 Separator 500 Battery 501 Positive electrode current collector 502 Positive electrode active material layer 503 Positive electrode 504 Negative electrode current collector 505 Negative electrode active material layer 506 negative electrode 507 Separator 508 Electrolyte 509 Exterior body 600 Battery 601 Positive electrode cap 602 Battery Can 603 Positive terminal 604 Positive electrode 605 Separator 606 negative electrode 607 Negative terminal 608 Insulating plate 609 Insulating plate 610 Gasket (insulating packing) 611 PTC element 612 Safety valve mechanism 700 Display device 701 Case 702 Display section 703 Speaker section 704 Storage battery 710 Lighting Equipment 711 Case 712 Light source 713 Storage battery 714 Ceiling 715 Side wall 716 Beds 717 Window 720 indoor unit 721 Case 722 Ventilator 723 Storage Battery 724 Outdoor unit 730 Electric refrigerator-freezer 731 Case 732 Refrigerator door 733 Freezer door 734 Storage Battery 800 tablet devices 801 Case 802 Display section 802a Display 802b display 803 Display mode change switch 804 Power Switch 805 Power saving mode switch 807 Operation Switch 808a Touch Panel Area 808b Touch Panel Area 809 Operation Key 810 Keyboard display switch button 811 Solar Cell 850 Charge / discharge control circuit 851 Battery 852 DC-DC Converter 853 Converter 860 Electric Vehicles 861 Battery 862 Control circuit 863 Drive Unit 864 Processing Equipment S1 Control signal S2 Control Signal S3 Transformer Signal 1000 Electricity 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. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material and a first multilayer graphene having a region covering the positive electrode active material, a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

2. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material and a first multilayer graphene having a region covering the positive electrode active material, The negative electrode has a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material and a second multilayer graphene having a region covering the negative electrode active material, a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

3. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, a first multilayer graphene having a region covering the positive electrode active material, and a third multilayer graphene having a region in contact with the first multilayer graphene, The negative electrode has a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, a second multilayer graphene having a region covering the negative electrode active material, and a fourth multilayer graphene having a region in contact with the second multilayer graphene, a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

4. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, a first multilayer graphene having a region covering the positive electrode active material, and a first conductive assistant having a needle-like, fibrous, or granular shape; a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

5. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, a first multilayer graphene having a region covering the positive electrode active material, and a first conductive assistant having a needle-like, fibrous, or granular shape; The negative electrode has a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, a second multilayer graphene having a region covering the negative electrode active material, and a second conductive assistant having a needle-like, fibrous, or granular shape; a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

6. A lithium ion secondary battery comprising a positive electrode and a negative electrode, The positive electrode has a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, a first multilayer graphene having a region covering the positive electrode active material, a third multilayer graphene having a region in contact with the first multilayer graphene, and a first conductive assistant having a needle-like, fibrous, or granular shape; The negative electrode has a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, a second multilayer graphene having a region covering the negative electrode active material, a fourth multilayer graphene having a region in contact with the second multilayer graphene, and a second conductive assistant having a needle-like, fibrous, or granular shape; a lithium ion secondary battery in which, when the positive electrode is incorporated into a half cell, the current is paused during constant current charging of the half cell, and the current pause resistance is measured using the difference between the voltage immediately after the current is paused and the voltage 3 seconds after the current is paused, the current pause resistance is 50.5 ohms or more and 82.6 ohms or less when the capacity at the time of pause is in the range of 195 mAh / g or more and 240 mAh / g or less.

7. 7. The lithium ion secondary battery according to claim 5, wherein the needle-shaped second conductive assistant is a vapor-grown carbon fiber.

8. 7. The lithium ion secondary battery according to claim 5 or 6, wherein the fibrous second conductive assistant is a carbon nanofiber or a carbon nanotube.

9. 7. The lithium ion secondary battery according to claim 5 or 6, wherein the granular second conductive assistant is carbon black.

10. 10. The lithium ion secondary battery according to claim 4, wherein the needle-shaped first conductive assistant is a vapor grown carbon fiber.

11. 10. The lithium ion secondary battery according to claim 4, wherein the fibrous first conductive assistant is a carbon nanofiber or a carbon nanotube.

12. 10. The lithium ion secondary battery according to claim 4, wherein the granular first conductive assistant is carbon black.

13. In any one of claims 2, 3, 5, and 6, The negative electrode active material of the lithium ion secondary battery comprises silicon.

14. In any one of claims 1 to 13, The positive electrode active material comprises Mn, Ni, and Co.

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