Lithium ion secondary battery

Abstract

To reduce graphene oxide with good reaction efficiency in a moderate condition in manufacture of an electrode for a storage battery including graphene as a conduction assistant, and thereby improve the cycle characteristics and rate characteristics of the storage battery.SOLUTION: There is provided a method for manufacturing an electrode for a storage battery including: manufacturing a paste having an active material, a binder, graphene oxide, and a solvent; applying the paste to a collector; evaporating the solvent contained in the paste to form an active material layer; immersing the active material layer in a liquid having alcohol; and taking out the active material layer from the liquid and heating the active material layer to reduce the graphene oxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to a storage battery electrode, 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 fields. One aspect relates to a process, a machine, a method of manufacture. It relates to the 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, device, light emitting device, power storage device, storage device, driving method thereof, or manufacturing method thereof, for 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 become With the rapid spread of mobile electronic devices, there is a need to make the secondary batteries that drive them smaller and with larger capacities. As a secondary battery used in portable electronic devices, it has high energy density and Non-aqueous secondary batteries, such as lithium-ion secondary batteries, are widely used because of their large capacity. It is being used.

[0004] Lithium-ion secondary batteries are widely used 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 lithium ion storage material. The negative electrode contains an active material such as graphite that can release carbon dioxide, and the negative electrode contains an active material such as ethylene carbonate or diethyl carbonate. An electrolyte consisting 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 performed by Lithium ions move between the positive and negative electrodes through the non-aqueous electrolyte, and lithium is released 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 polyvinylidene fluoride (PV Generally, polymer organic compounds such as dF 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 in. 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 (also known as GO (short for graphene oxide)), an active material, and A method for manufacturing an electrode is disclosed that includes a step of reducing GO after mixing with a binder. This manufacturing method provides an active material layer having high electrical conductivity with a small amount of conductive additive. can be done. [Prior art documents] [Patent documents]

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

[0009] In order to improve the performance of a storage battery having an electrode containing graphene as a conductive additive, There is a need to develop a method for manufacturing electrodes that can reduce graphene oxide.

[0010] Therefore, one embodiment of the present invention aims to improve the reaction efficiency of the reduction reaction of graphene oxide. Another aspect of the present invention is to provide a method for producing a storage battery electrode having low internal resistance. The goal is to

[0011] Another object of one embodiment of the present invention is to reduce graphene oxide under mild reaction conditions. Another object of one embodiment of the present invention is to reduce damage to an active material layer due to a reduction reaction. .

[0012] Another object of one embodiment of the present invention is to increase the discharge capacity of a storage battery. An object of one embodiment of the present invention is to improve the cycle characteristics of a storage battery. An object of the present invention is to improve the rate characteristics of a storage battery.

[0013] Another embodiment of the present invention is a novel electrode, a novel electrode manufacturing method, or a novel power storage device. The objective of the project is to provide a facility for the provision of such equipment. It should be noted that one embodiment of the present invention solves all of these problems. In addition, one aspect of the present invention is intended to solve at least one of the above problems. Problems other than these will be obvious from the description, drawings, claims, etc. It is not possible to extract other issues from the description, drawings, claims, etc. is possible. [Means for solving the problem]

[0014] One embodiment of the present invention is a paste including an active material, a binder, graphene oxide, and a solvent. The paste is applied to a current collector, and the solvent contained in the paste is evaporated to form an active material. a layer formed on the active material layer, the active material layer being impregnated with a liquid containing alcohol, and the active material layer being removed from the liquid This is a manufacturing method for storage battery electrodes, in which the electrodes are removed and heated.

[0015] Alternatively, one embodiment of the present invention is a conductive film including an active material, a binder, graphene oxide, a conductive additive, and a solvent. and a paste having the above-mentioned formula (1) is prepared, the paste is applied to a current collector, and the solvent contained in the paste is The solvent is evaporated to form an active material layer, and the active material layer is impregnated with a liquid containing alcohol. The active material layer is removed from the solution and heated.

[0016] In addition, one aspect of the present invention is the method for producing the liquid crystal display device according to the present invention. , 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl A method for manufacturing storage battery electrodes that are alcohol or tert-butyl alcohol is preferred.

[0017] Another embodiment of the present invention is a battery including a current collector and an active material layer, the active material layer being in contact with the current collector, The active material layer is a storage battery layer having an active material, a binder, graphene, and a second conductive additive. It is an electrode.

[0018] Another embodiment of the present invention includes a first electrode and a second electrode, and the first electrode has the above structure. The first electrode can be operated as either a positive electrode or a negative electrode. The first electrode has a function of being able to operate as the positive electrode or the negative electrode, and the second electrode has a function of being able to operate as the other of the positive electrode or the negative electrode. It is a storage battery having the following.

[0019] Another embodiment of the present invention is a storage battery having the above structure, a display panel, an operation key, a speaker, or is an electronic device characterized by being equipped with a microphone and. [Effects of the Invention]

[0020] According to one embodiment of the present invention, the reaction efficiency of the reaction for reducing graphene oxide can be increased. Furthermore, one aspect of the present invention provides a method for producing a storage battery electrode having low internal resistance. This can be done.

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

[0022] According to one embodiment of the present invention, the cycle characteristics of a storage battery can be improved. According to one embodiment of the present invention, the rate characteristics of a storage battery can be improved.

[0023] According to one embodiment of the present invention, a novel electrode, a novel electrode manufacturing method, or a novel power storage device It should be noted that the description of these effects does not preclude the existence of other effects. It should be noted that one embodiment of the present invention does not necessarily have all of these effects. Effects other than these will become apparent from the description, drawings, claims, etc. It is possible to extract other effects from the description, drawings, claims, etc. It is Noh. [Brief explanation of the drawings]

[0024] [Figure 1] 1A to 1C are diagrams illustrating a method for manufacturing a storage battery electrode. [Figure 2] FIG. 2 is a diagram illustrating a storage battery electrode. [Figure 3] FIG. 2 is a diagram illustrating a storage battery electrode. [Figure 4] FIG. 1 is a diagram illustrating a coin-type storage battery. [Figure 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] FIG. 1 illustrates an example of an electrical device. [Figure 9] FIG. 1 illustrates an example of an electrical device. [Figure 10] FIG. 1 illustrates 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. 10 is a diagram illustrating the cycle characteristics of a half cell. [Figure 19] FIG. 10 is a diagram illustrating the rate characteristics of a half cell. [Figure 20]FIG. 10 is a diagram illustrating the rate characteristics of a half cell. [Figure 21] FIG. 1 is a diagram illustrating the cycle characteristics of a full cell. [Figure 22] 13C NMR spectrum of graphene oxide. [Figure 23] Cross-sectional SEM image of the electrode. [Figure 24] Cross-sectional SEM image of the electrode. [Figure 25] FIG. 10 is a diagram illustrating the rate characteristics of a half cell. [Figure 26] FIG. 10 is a diagram illustrating the cycle characteristics of a half cell. [Figure 27] FIG. 1 is a diagram illustrating the cycle characteristics of a full cell. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments will be described with reference to the drawings. It is possible to implement the present invention in various ways without departing from the spirit and scope of the present invention. It will be readily apparent to 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.

[0026] In the configuration of the invention described below, the same parts or parts having similar functions are designated by the same reference numerals. The same reference numerals are used in common among different drawings, and the repeated explanations thereof will be omitted. When referring to a function, the hatch pattern may be the same and no particular symbol may be added.

[0027] In each drawing 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. The size of each component is not limited, and the relative sizes between each component are not limited. do not have.

[0028] In this specification, ordinal numbers such as first, second, etc. are used for convenience. It does not indicate the order of processes or the order of lamination. " can be appropriately replaced with "second" or "third" etc. The ordinal numbers described in the specification and the like and the ordinal numbers used to identify one aspect of the present invention are There may be cases where they do not match.

[0029] (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. 2(C) shows a plan view of the active material layer. 3 shows a vertical cross-sectional view of the active material layer.

[0030] 2(A) is a perspective view of the 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 selected as appropriate. 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, but may be formed on non-coated areas such as areas for connecting with tabs. Set up appropriate areas.

[0031] The current collector 201 may be made of stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, or other metals. Metals and their alloys have high conductivity and do not alloy with carrier ions such as lithium. Materials that can be used include silicon, titanium, neodymium, scandium, and molybdenum. Aluminum alloys containing elements that improve heat resistance, such as arsenic, 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 and 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, The current collector 201 may have a shape such as an expanded metal. It is preferable to use a graphite film having a thickness of 30 μm or more. An undercoat layer may be provided using a coating agent or the like.

[0032] 2(B) and 2(C) are schematic diagrams showing the top surface and vertical cross section of the active material layer 202, respectively. 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).

[0033] 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 form, the particles are connected to the active material 203. The surface of the active material 203 can be brought into surface contact with the active material 203 so as to wrap around a part of the surface. Unlike granular conductive additives such as acetylene black, graphene 204 has low contact resistance. Since it allows for 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.

[0034] In addition, the plurality of graphenes 204 are in surface contact with each other. This is because graphene oxide, which has extremely high dispersibility in polar solvents, is used. The solvent is evaporated from the dispersion containing the graphene oxide, and the graphene oxide is reduced. To form graphene, the graphene 204 remaining in the active material layer 202 is partially overlapped. They are dispersed to the extent that they come into surface contact with each other, forming electrical conduction paths.

[0035] 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 graphene 204 is a single layer of carbon molecules. Since it is an extremely thin film (sheet) made up of these layers, it is possible to separate the individual granular active material203 The surface of the active material 203 is covered with the conductive layer 204 and is in contact with the conductive layer 204. The thin part is bent, wrinkled, or stretched between the plurality of granular active materials 203. The condition is as follows:

[0036] 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 dispersed uniformly. Although the phenanthrene 204 is shown in bold, it actually has a thickness of a single layer or multiple layers 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 wrap 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. The granules 203 are attached to the surfaces of the active material particles 203. The graphene 204 covers the surface and contacts with each other to form a network. is formed.

[0037] As shown in FIGS. 2B, 2C, and 3, the sheet-like graphenes 204 are They are three-dimensionally dispersed inside the active material layer 202 and are in surface contact with each other. The graphene 2 04 covers and is in surface contact with a plurality of granular active material 203.

[0038] The graphene 204 is formed by heating in the method for producing a storage battery electrode described in the second embodiment. Therefore, it is formed by reducing graphene oxide.

[0039] In this specification, graphene refers to single-layer graphene or multi-layer graphene with 2 to 100 layers. Single-layer graphene is a single-atom layer of carbon molecules with π bonds. Graphene oxide refers to a compound obtained by oxidizing the graphene. 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 the method for producing a storage battery electrode described in Form 2, graphene oxide can be reduced with high reaction efficiency. When oxygen is contained in graphene, the oxygen ratio can be calculated by XPS ( When measured using X-ray photoelectron spectroscopy 1 atomic % to 20 atomic % of the entire graphene, preferably 3 atomic % As mentioned above, the sheet-like multiple gratings are The laphenes 204 are dispersed three-dimensionally inside the active material layer 202, and these laphenes are The surface contact with the surface forms a three-dimensional electrically conductive network. By reducing graphene with high reaction efficiency, the inside of the active material layer 202 and the electrode 200 As a result, in a storage battery using the electrode 200, The rate characteristics can be improved.

[0040] Graphene oxide can be produced using an oxidation method called the Hummers method. The Hummers method involves adding a solution of potassium permanganate in sulfuric acid and water peroxide to graphite powder. Add water or other substances to cause an oxidation reaction and create a mixture containing graphite oxide. The carbon of the thiol group has functional groups such as epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups. As a result, the distance between multiple graphene layers becomes longer than that of graphite. This facilitates separation of the layers and thinning of the particles. By applying ultrasonic vibrations, graphite oxide with a long interlayer distance is cleaved, and graphene oxide is formed. The graphene oxide is then separated and a mixture containing the graphene oxide is prepared. Powdered graphene oxide is obtained by removing the solvent from the mixture containing graphene. can be done.

[0041] 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 oxidized graphite Therefore, the degree of oxidation of the benzene (ratio of oxygen atoms to carbon atoms) can be increased. The amount of oxidizer relative to the graphite powder used as raw material is determined according to the amount of graphene oxide. Just do that.

[0042] Graphene oxide was prepared using a Hummers method using a sulfuric acid solution of potassium permanganate. The method is not limited to the Humm method, for example, using nitric acid, potassium chlorate, or sodium nitrate. A method for forming graphene oxide other than the ers method or the Hummers method may be used as appropriate.

[0043] In addition, graphite oxide can be thinned by adding ultrasonic vibrations, microwaves, radio waves, or The heating may be performed by irradiating thermal plasma or applying physical stress.

[0044] The graphene oxide produced contains epoxy groups, carbonyl groups, carboxyl groups, and hydroxyl groups. Graphene oxide is a polymer that can be used in a wide range of applications, including NMP (N-methylpyrrolidone, 1-methyl-2-pyrrolidone). In polar solvents such as methylpyrrolidone, N-methyl-2-pyrrolidone, etc. The oxygen in the functional group is negatively charged, so it interacts with polar solvents while reacting with different oxidation states. Graphene repels each other and is difficult to aggregate. Therefore, in polar solvents, graphene oxide This helps the fen to disperse evenly.

[0045] The length of one side of graphene oxide (also called flake size) is 50 nm or more and 100 The graphene oxide flakes are preferably 800 nm or more and 20 μm or less. By adjusting the size, it is possible to control the size of the graphene flakes in the active material layer. When the size of the graphene flakes is smaller than the average particle size of the granular active material 203, It becomes difficult for the graphene to come into surface contact with the active material 203 and to connect with each other. Therefore, it becomes difficult to improve the electrical conductivity of the active material layer 202.

[0046] The binder forms a network in the active material layer 202 and binds the active material 203 Active material 203, active material 203 and graphene 204, graphene 204 and graphene 204 and functions to bond the active material layer 202 and the current collector 201 together. When the electrode is manufactured using this manufacturing method, the network constructed by the binder becomes stronger. Therefore, the active material 203 and the active material 203, the active material 203 and the graphene 204, graphene 204 and graphene 204, and bonding between the active material layer 202 and the current collector 201 It can make the garment stronger.

[0047] When the electrode 200 is immersed in an electrolyte and repeatedly charged and discharged, the binder absorbs the electrolyte and expands. This may cause the entire active material layer 202 to expand or deform. These phenomena occur when the binder network in the active material layer 202 is As described above, the inside of the active material layer 202 The graphene sheets 204 are dispersed three-dimensionally, and they come into surface contact with each other. The graphene 2 forms a three-dimensional electrically conductive network. The active material layer 202 covers and is in surface contact with a plurality of granular active material 203. When expansion or deformation occurs in the graphene 204, the graphene 204 may be in contact with each other. The graphene 204 and the active material 203 that were in contact with each other are peeled off, separated, or the contact area is small. In addition, the graphene 204 or the active material 203 may crack or break. These factors may cause the tertiary structure formed in the active material layer 202 to When part of the original electrically conductive network is broken and the performance of the electrode 200 is reduced, Repeated discharges can lead to problems such as a decrease in the discharge capacity of the battery or a decrease in potential.

[0048] On the other hand, in the active material layer 202 of the electrode 200 according to one embodiment of the present invention, as described above, Therefore, the binder absorbs the electrolyte and swells. However, the active material layer 202 as a whole is unlikely to expand or deform. Even if the battery is immersed in the solution and repeatedly charged and discharged, the active material layer 202 04, and the graphene 204 and the active material 203 that are in contact with each other are difficult to peel off or separate. In addition, the graphene 204 and the active material 203 are Therefore, the three-dimensional electrically conductive network is not broken. Therefore, the battery using the electrode 200 is less likely to deteriorate during charging and discharging. Even if the cycle is repeated, the discharge capacity is not likely to decrease and the potential is not likely to decrease. This can improve the driving characteristics.

[0049] The binders include the typical polyvinylidene fluoride (PVdF), as well as polyimide and polytetrafluoroethylene. Fluoroethylene, polyvinyl chloride, ethylene propylene diene polymer, styrene Acrylonitrile-butadiene rubber, acrylonitrile-butadiene rubber, fluororubber, polyvinyl acetate , polymethyl methacrylate, polyethylene, nitrocellulose, etc. can be used. .

[0050] The active material 203 is made by mixing raw material compounds in a predetermined ratio, baking the mixture, and then baking the mixture by an appropriate means. 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 schematically as a sphere. However, the shape is not limited to this.

[0051] When the electrode 200 is used as a positive electrode of a storage battery, the active material 203 is lithium ion. Materials that allow ions to be inserted and removed can be used. For example, olivine-type crystal structures, Lithium manganese composite oxide having a layered rock salt type crystal structure or a spinel type crystal structure etc.

[0052] Examples of lithium-containing complex phosphates having an olivine structure include those represented by the general formula LiMPO4 (M is one or more of Fe(II), Mn(II), Co(II), and Ni(II) Representative examples of the general formula LiMPO4 include LiFePO4, LiNiPO4, and LiCoP O4, LiMnPO4, LiFe a Ni b PO4, LiFe a Co b PO4, LiFe a Mn b PO4, LiNi a Co b PO4, LiNi a Mn b PO4(a+b is less than 1, 0 <a<1、0<b<1)、LiFe c Ni d Co e PO4, LiFe c Ni d Mn e PO 4. LiNi c Co d Mne PO4 (where c + d + e is less than or equal to 1, 0 < c < 1, 0 < d < 1, 0 < e < 1), LiFe f Ni g Co h Mn i PO4 (where f + g + h + i is less than or equal to 1, 0 < f < 1, 0 < g < 1, 0 < h < 1, 0 < i < 1) and the like can be mentioned.

[0053] In particular, LiFePO4 satisfies well the requirements for an active material, such as safety, stability, high capacity density, high potential, and the presence of lithium ions that are extracted during initial oxidation (charging). Therefore, it is preferable.

[0054] Examples of lithium-containing complex silicates having a layered rock salt crystal structure include, for example, LiCoO 2, LiNiO2, LiMnO2, Li2MnO3, LiNi 0.8 Co 0.2 O2 and the like NiCo-based (general formula: LiNi x Co 1-x O2 (0 < x < 1)), LiNi 0.5 M n 0.5 O2 and the like of NiMn-based (general formula: LiNi x Mn 1-x O2 (0 < x < 1)), LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 and the like of NiMnCo-based (also referred to as NMC. General formula is LiNi x Mn y Co 1-x-y O2 (x > 0, y > 0, x + y < 1)) can be mentioned. Furthermore, Li(Ni 0.8 Co 0.15 Al 0.05 )O2, Li2MnO3 - Li MO2 (M = Co, Ni, Mn) and the like can also be mentioned.

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

[0056] Examples of lithium manganese composite oxides having a spinel-type 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 Ni 0.5 Examples include O4.

[0057] A small amount of lithium manganese composite oxides with a spinel-type crystal structure, such as LiMn2O4, Lithium nickel oxide (LiNiO2 and LiNi 1-x M x O2(0 <x<1)(M=C Mixing with o, Al, etc.) can suppress the elution of manganese and the decomposition of the electrolyte. It is advantageous and desirable.

[0058] In addition, the positive electrode active material is a compound of the general formula Li (2-j) MSiO4 (M is Fe(II), Mn (II), Co(II), Ni(II), or more, j is 0 or more and 2 or less) 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. can be mentioned.

[0059] Also, as the positive electrode active material, A x M2(XO4)3 (A = Li, Na, Mg, M = Fe, M n, Ti, V, Nb, Al, X = S, P, Mo, W, As, Si) represented by the general formula of the NASICON-type compound 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, etc., inverse spinels such as LiMVO4 etc. Lithium vanadium-containing composite oxides having a crystalline structure of the type, vanadium oxide-based compounds ( V2O5, V6O 13 , LiV3O8, etc.), manganese oxides, organic sulfur compounds, etc. It can be used.

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

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

[0062] In addition, the carrier ions are alkali metal ions other than lithium ions, and alkaline earth metal ions. In the case of metal ions, the positive electrode active material is the lithium compound and the lithium manganese composite oxide. In some cases, instead of lithium, an alkali metal (such as sodium or potassium) is used. Alkaline earth metals (e.g., calcium, strontium, barium, beryllium, magnesium) Nesium, etc.), may also be used.

[0063] When the produced storage battery electrode is used as a negative electrode of a storage battery, the active material 203 is The material used is capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium. It is possible.

[0064] Examples of materials that can undergo charge-discharge reactions through alloying and dealloying reactions with lithium include For example, carbon-based materials can be mentioned. Carbon-based materials include graphite, easily graphitizable carbon (soft carbon), carbon), non-graphitizable carbon (hard carbon), carbon nanotubes, graphene, carbon -Bon Black, etc.

[0065] 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.

[0066] When lithium ions are inserted into graphite (when lithium-graphite intercalation compounds are formed), It exhibits 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 because it has advantages such as higher safety compared to metals.

[0067] In addition, materials that can undergo charge-discharge reactions through alloying and dealloying reactions with lithium are For example, Ga, Si, Al, Ge, Sn, Pb, Sb, Bi, Ag, Zn, Cd, I Such elements have a higher capacity than carbon. In particular, silicon has a high theoretical capacity of 4200mAh / g. The materials used include, for example, Mg2Si, Mg2Ge, Mg2Sn, SnS2, and V2Sn. 3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb , SbSn, etc.

[0068] In addition, the negative electrode active material is SiO, SnO, SnO2, titanium dioxide, lithium titanate oxides, lithium-graphite intercalation compounds, niobium pentoxide, tungsten oxide, molybdenum oxide, etc. The oxides of the following can be used.

[0069] 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 ) is preferred.

[0070] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0071] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. transition metals that do not undergo alloying reactions with lithium, such as cobalt oxide, nickel oxide, and iron oxide The oxide may be used as the negative electrode active material. , Fe2O3, CuO, Cu2O, RuO2, Cr2O3 and other oxides, CoS 0.89 , Sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N and Ge3N4, NiP2, Phosphides such as FeP2 and CoP3, and fluorides such as FeF3 and BiF3 can also be used. do.

[0072] 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, the thickness is 500 nm or less, preferably 50 nm or more and 500 nm or less. In order to make surface contact with a plurality of the particles of the active material 203, the graphene 204 The side length 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.

[0073] The active material layer 202 may also contain a second conductive additive. In the active material layer 202, the particles tend to be arranged in a direction substantially parallel to the surface of the current collector 201. When the active material layer 202 contains graphene and a second conductive additive, the active material and the graphene It reinforces the three-dimensional electrically conductive network that is being constructed, allowing it to take on more complex shapes. This prevents the electrical conduction path in the active material layer 202 from being disconnected during use of the electricity storage device. Furthermore, even if the thickness of the active material layer 202 is increased, the electrical conduction path is not cut off. It can be made less likely.

[0074] Examples of the second conductive additive include natural graphite and artificial graphite such as mesocarbon microbeads. Also, copper, nickel, aluminum, silver, gold, etc. can be used. Metal powder, metal fiber, conductive ceramic material, etc. can be used.

[0075] 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 nanotubes and the like can be used. In addition, vapor grown carbon fibers ( VGCF: Vapor-Grown Carbon Fiber (registered trademark) is used The typical values ​​for VGCF (registered trademark) are 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 , observed with a SEM (Scanning Electron Microscope), The cross section perpendicular to the fiber axis is taken from the two-dimensionally captured image, and this cross section The true density is the diameter of a circle that circumscribes the volume of the substance itself. The specific surface area is the density of the object per unit mass. This refers to the surface area per unit volume or the surface area per unit volume.

[0076] 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 high thermal conductivity. By using a conductive additive, the electrical contact points and contact area between active materials are reduced. can be increased.

[0077] Furthermore, a granular material can also be used as the conductive additive. Representative examples of the granular material include: Acetylene black and Ketjenblack (registered trademark) have a diameter of 3 nm to 500 nm. Carbon black such as carbon black (carbon black having a carbon black mark) can be used.

[0078] The conductive additives in the form of flakes, needles, or fibers connect the active materials together and prevent battery deterioration. In addition, these materials are used to form a structure that maintains the shape of the active material layer 202 or to form a flexible structure that It also functions as a structure that maintains the shape of the active material layer 202 or as a buffer material. This function means that the active material expands and contracts repeatedly, and the secondary battery is bent. As a result, peeling between the current collector and the active material is less likely to occur. Carbon black such as polyethylene black or Ketjenblack (registered trademark) can also be used. However, when VGCF (registered trademark) is used, the strength to maintain the shape of the active material layer 202 is insufficient. This is preferable because the strength required to maintain the shape of the active material layer 202 can be increased. This makes it possible to prevent deterioration of the secondary battery due to deformation such as bending.

[0079] The active material layer 202 described above has the active material 203 in an amount of 80% based on the total weight of the active material layer 202. wt% or more but not exceeding 95wt%, graphene at 0.1wt% or more but not exceeding 8wt%, binder at 1w It is preferable that the content of the active material layer 202 is t% or more and 10 wt% or less. When the second conductive additive is present, 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 based on the total weight of 202.

[0080] 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 each other so as to enclose a part of the surface of the granular active material 203. This allows the provision of storage battery electrodes containing highly packed and highly densified active material layers using a small amount of conductive additive. It is possible.

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

[0082] (Embodiment 2) In this embodiment, the active material, the conductive additive, and the binder exemplified in Embodiment 1 are used to form an active material. A method for fabricating an electrode 200 including a layer 202 will now be described with reference to FIG.

[0083] First, a paste containing an active material, a binder, graphene oxide, and a solvent is prepared (step The paste may contain a second conductive additive. An example of the manufacturing method is as follows. First, graphene oxide is dispersed in a solvent. The weight of graphene oxide is less than 0.2 wt% of the total weight of graphene oxide and binder. If the content is less than 100%, the conductivity of the active material layer 202 decreases when the active material layer 202 is formed. If the weight of exceeds 16 wt %, the viscosity of the paste will increase, although this will depend on the particle size of the active material. In addition, a process of applying the paste to the current collector 201 and then evaporating the solvent contained in the paste During this process, convection occurs in the paste due to heating, causing the light and thin graphene oxide to move or aggregate. By collecting the active material layer 202, the active material layer 202 may crack or peel off from the current collector 201. Therefore, the weight of graphene oxide should be 0. The content of graphene oxide is preferably 2 wt% or more and 16 wt% or less. As a result, the graphene in the active material layer 202 is reduced to graphene, and its weight is reduced by almost half. The weight ratio of the phenyl is 0.1 wt% or more and 8 wt% or less.

[0084] The solvent may be a polar solvent, such as methanol, ethanol, or acetone. ton, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpiperidin One or more of the following: propyl methacrylate (NMP), dimethyl sulfoxide (DMSO) A mixed solution can be used. NMP in particular is a good dispersant for graphene oxide. This is preferable because it can be done easily.

[0085] Next, an active material is added. The average particle size of the primary particles of the active material is 50 nm or more and 500 nm or less. It is recommended to use the following.

[0086] Next, these mixtures are kneaded (kneaded in a high viscosity state) to form graphene oxide and In addition, graphene oxide can dissolve the aggregation of the active material in a polar solvent. Because the oxygen in the functional group is negatively charged, different graphene oxides are less likely to aggregate with each other. In addition, graphene oxide has a strong interaction with the active material. The laphenes can be dispersed more uniformly.

[0087] Next, a binder is added to the mixture. The amount of the binder is determined based on the ratio of the graphene oxide and the active material. The amount can be set by adding 1 wt% to 5 wt% of the paste. The graphene oxide is uniformly dispersed so as to be in surface contact with multiple active material particles. By adding a binder, the active material and graphene oxide are dispersed together while maintaining their dispersion state. Depending on the ratio of the active material and graphene oxide, the binder can be used. Although it is not necessary to add a binder, adding a binder can improve the strength of the electrode. .

[0088] Next, a solvent is added to these mixtures until the desired viscosity is reached, and the mixture is kneaded to form a paste. By preparing the paste through the above steps, the oxidation graph A paste in which the active material, the binder, and the ethylenediamine dinitrate are kneaded together uniformly can be produced.

[0089] Next, the paste is applied to one or both surfaces of the current collector 201 (step S102). There are several ways to apply the paste to the body, including roll coating with an applicator roll, Applying coating methods such as lean printing, doctor blade, spin coating, and bar coating It is possible.

[0090] Next, the solvent contained in the paste applied to the current collector 201 is evaporated to form an active material layer. (Step S103) 40°C or higher and 170°C or lower, preferably 60°C or higher and 100°C or lower The solvent is evaporated by heating at a temperature of 1 minute to 10 hours. The current collector 201 may be heated in any atmosphere.

[0091] In the active material layer formed by evaporating the solvent contained in the paste, the binder A network structure is constructed that connects the material and graphene oxide.

[0092] Next, the active material layer is immersed in a liquid containing alcohol (step S104). The current collector may be immersed in a liquid. The temperature of the liquid is between the melting point and the boiling point of the alcohol-containing liquid. The temperature is preferably 40°C or higher and 70°C or lower, and the time is preferably 1 minute or higher and 1 hour or lower. It would be good to do so.

[0093] Examples of alcohols include methanol, ethanol, 1-propanol, and 2-propanol. alcohol, 1-butanol, 2-butanol, isobutyl alcohol, or tert-butyl alcohol Alcohol with a low boiling point is easy to evaporate. In addition, when a highly reducing alcohol is used, the reduction of graphene oxide can be easily performed. Therefore, ethanol, 1-propanol, 1-butanol, etc. are used. And more preferable.

[0094] The liquid containing alcohol may contain water, a stabilizer, etc. The above alcohols may be mixed, or may be mixed with organic solvents other than alcohols. may be.

[0095] At this time, when the active material layer is immersed in a solution containing a reducing agent (also referred to as a reducing solution), this step The graphene oxide can be reduced in the presence of ascorbic acid, hydroxybenzoic acid, and benzoic acid. hydrazine, dimethylhydrazine, hydroquinone, sodium borohydride (NaBH4), Lithium aluminum hydride (LiAlH4), or N,N-diethylhydroxylamine Examples include:

[0096] The solvent for the reducing solution may be a polar solvent, such as water, methanol, or ethanol. acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N- Either methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) or A mixture of two or more types can be used.

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

[0098] Furthermore, when a reducing solution is used, the solution may become acidic or basic depending on the nature of the reducing agent. Therefore, it becomes necessary to add a pH adjuster to adjust the pH of the solution, but this process becomes complicated. In addition, it may be difficult to maintain a constant pH of the solution. If the temperature is not maintained at the same level as the temperature of the active material layer, the materials contained in the active material layer may be damaged. If the solution is acidic, the active material layer may contain materials that are unstable to acids or that easily react with acids. Furthermore, if the reducing solution is basic, the active material layer may be easily damaged. They are susceptible to damage if they contain materials that are unstable to bases or that react with bases. In addition, by using a strong reducing agent such as those listed above, the following can be achieved in the active material layer: There is a possibility of unexpected reactions or damage. Active materials that are unstable in acid include: Examples of binders that easily react with bases include positive electrode active materials. , PVdF, etc.

[0099] In addition, when the active material layer is immersed in the reducing solution, the binder contained in the active material layer absorbs the solvent and expands. If the solvent of the reducing solution is water, the molecules are small and are easily absorbed by the binder. In addition, if the solvent is an aprotic polar solvent such as NMP, the affinity with the binder such as PVdF is low. Therefore, the solvent of the reducing solution is water or NMP, etc. If the binder expands or deforms, the phenomenon of the binder expanding or deforming becomes significant. When this happens, the network structure of the binder that binds the active material and graphene oxide in the active material layer becomes At this time, the binder may expand or deform, causing the active material to break or be damaged. The material layer may expand. If graphene oxide is reduced while the active material layer is in an expanded state, However, it may be difficult to construct a three-dimensional electrically conductive network in the active material layer. Alternatively, graphene oxide may be reduced while the active material layer is swollen, creating an electrically conductive layer in the active material layer. Even if a three-dimensional network is constructed, the active material layer is not formed in the subsequent solvent evaporation process. As the material shrinks, the electrical conduction network structure may be damaged.

[0100] When the active material layer damaged by the factors explained above is immersed in an electrolyte solution, the active material layer swells. As a result, the electrical conduction network formed in the active material layer is easily broken. It becomes easier.

[0101] On the other hand, in the above step S104, the active material layer is immersed in a liquid containing alcohol and then heated. Since graphene oxide is reduced by heating, there is no need to immerse the active material layer in a reducing solution. Alcohol promotes the reduction of graphene oxide, which is an easily reduced substance. However, for materials used as active materials, binders, etc., it is necessary to Therefore, the active material layer is less likely to be damaged. Since coal is neutral, it is difficult to add materials that are unstable to acids or bases to the active material layer. Even if the active material layer contains materials that are reactive with acids and bases, it is not easily damaged by acids or bases. In addition, since there is no need to adjust the pH of the alcohol-containing solution, step S 104 can be said to be simple.

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

[0103] Next, the active material layer is removed from the alcohol-containing liquid and heated to reduce the graphene oxide. At this time, the current collector may be heated together with the active material layer. The temperature is not particularly limited. The temperature is from room temperature to 200°C, preferably from 60°C to 170°C. More preferably, the temperature is 80°C or higher and 150°C or lower, and the heating time is 1 hour or higher and 30 hours or lower. This reduces the graphene oxide and evaporates the alcohol contained in the active material layer. In this step, alcohol promotes the reduction of graphene oxide by heating, so the oxidation This can increase the reaction efficiency of the graphene reduction reaction, thereby reducing the internal resistance. Small electrodes can be made.

[0104] As described in this embodiment, according to one embodiment of the present invention, the active material layer is immersed in a reducing solution. Graphene oxide can be reduced without any treatment. Therefore, the active material layer can be reduced by the reduction reaction. This reduces damage to the electrode, preventing the electrical conduction path from being cut off even when immersed in an electrolyte. It is possible to fabricate an electrode that is resistant to heat treatment and to prevent the reduction of graphene oxide. Coal promotes the reaction, which increases the efficiency of the graphene oxide reduction reaction by heating. This makes it possible to manufacture an electrode with low internal resistance. By manufacturing a storage battery using the electrode manufacturing method described in this embodiment, The cycle characteristics of the battery can be improved. can be done.

[0105] Note that one embodiment of the present invention has been described in this embodiment. However, the present invention is not limited to these. That is, in this and other embodiments, various aspects of the invention are described. Therefore, one embodiment of the present invention is not limited to a specific embodiment. In this example, graphene is applied to a storage battery electrode. In some cases or depending on the situation, graphene or graphite oxide may be used. Phenomena are being used as electrodes 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. They can be used as materials for highly sensitive nanosensors to detect uranium and plutonium in radioactive materials. It can be used as a material for removing radioactive materials. In some cases or depending on the situation, graphene may be used as a storage battery electrode in one embodiment of the present invention. It does not have to be applied to all poles.

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

[0107] (Embodiment 3) In this embodiment, the storage battery electrode manufactured by the manufacturing method shown in Embodiment 2 is used. The structure of the storage battery will be described with reference to FIGS.

[0108] (Coin-type 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.

[0109] The coin-type storage battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 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).

[0110] At least one of the positive electrode 304 and the negative electrode 307 may contain the same material as in the embodiment 1 of the present invention described in Embodiment 2. The electrode for a storage battery can be manufactured by the manufacturing method of the electrode for a storage battery according to the present invention.

[0111] Either the positive electrode 304 or the negative electrode 307 is formed by the method for manufacturing the storage battery electrode shown in Embodiment 2. 3 shows the structure of the positive electrode active material layer 306 or the negative electrode active material layer 309 when no such method is used.

[0112] The positive electrode active material layer 306 contains not only the positive electrode active material but also 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, a conductive additive, or the like for increasing the conductivity of the positive electrode active material layer 306.

[0113] The materials described in the first embodiment are used as the positive electrode active material, binder, and conductive additive. can be done.

[0114] The negative electrode active material layer 309 contains, in addition to the negative electrode active material, a binder (binder) for increasing the adhesion of the negative electrode active material. The negative electrode active material layer 309 may contain an indium ion, a conductive additive for increasing the conductivity of the negative electrode active material layer 309, or the like.

[0115] The materials described in the first embodiment are used as the negative electrode active material, binder, and conductive additive. can be done.

[0116] In addition, a coating of an oxide or the like 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 formed on the negative electrode active material in advance, and irreversible capacity is formed. By providing it on the surface of the layer 309, it is possible to suppress or prevent the occurrence of irreversible capacity. .

[0117] The coating that coats the negative electrode active material layer 309 may contain niobium, titanium, vanadium, tungsten, or the like. aluminum, tungsten, zirconium, molybdenum, hafnium, chromium, aluminum or or silicon oxide film, or a film containing 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.

[0118] For example, niobium pentoxide (Nb2O5) has an electrical conductivity of 10 -9 Low S / cm and high Therefore, the niobium oxide film prevents the negative electrode active material from coming into contact with the electrolyte during charging. On the other hand, the lithium ion of niobium oxide inhibits the electrochemical decomposition reaction of the electrolyte, etc. The diffusion coefficient of 10 -9 cm 2 / sec, which means it has high lithium ion conductivity. Therefore, lithium ions can pass through. Minium may also be used.

[0119] The film that covers the negative electrode active material layer 309 can be formed by, for example, a sol-gel method. The sol-gel method is a method in which a solution of metal alkoxide or metal salt is subjected to a hydrolysis reaction or is a method in which a gel that has lost its fluidity through a polycondensation reaction is formed, and this gel is baked to form a thin film. The sol-gel method is a method for forming thin films from a liquid phase, so the raw materials are homogeneous at the molecular level. Therefore, it is possible to mix anode active materials such as graphite into the raw material of the metal oxide film at the solution stage. By adding the substance, the active material can be easily dispersed in the gel. A coating can be formed on the surface of the negative electrode active material layer 309. By using the coating, This can prevent the capacity of the electricity storage unit from decreasing.

[0120] The separator 310 is made of a porous material such as cellulose (paper), polypropylene, polyethylene, etc. An insulator with holes may be used.

[0121] As the electrolyte, in addition to the electrolyte containing the supporting electrolyte, solid electrolyte and the electrolyte partially gelled are also used. A gel electrolyte can be used.

[0122] Materials with carrier ions can be used as supporting electrolytes. Typical examples of supporting electrolytes Examples include LiPF6, LiClO4, LiAsF6, LiBF4, LiCF3SO3, Lithium salts include Li(CF3SO2)2N and Li(C2F5SO2)2N. The electrolytes may be used alone or in any combination and ratio of two or more. Good too.

[0123] In addition, the carrier ions are alkali metal ions other than lithium ions, alkaline earth metal ions, etc. In the case of ions, the electrolyte is an alkali metal salt instead of lithium. Metals (e.g., sodium and potassium), alkaline earth metals (e.g., calcium, strontium) Other suitable materials include titanium, barium, beryllium, magnesium, etc.

[0124] In addition, a material in which carrier ions can move can be used as the solvent for the electrolyte. The solvent for the solution is preferably an aprotic organic solvent. Representative examples of aprotic organic solvents are: Examples include ethylene carbonate (EC), propylene carbonate, and dimethyl carbonate. diethyl carbonate (DEC), γ-butyrolactone, acetonitrile, dimethicone Examples of the methyl ether include methyl ethane and tetrahydrofuran, and one or more of these can be used. In addition, by using a polymer material that gels as a solvent for the electrolyte, it is possible to reduce leakage and other issues. This increases safety. It also makes it possible to make storage batteries thinner and lighter. Typical 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 by an internal short circuit or overcharging. 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 make up the ionic liquid include monovalent amide anions, monovalent methyl anions, and Thiol anions, fluorosulfonate anions, perfluoroalkylsulfonate anions Fluorocarbons, tetrafluoroborates, perfluoroalkylborates, hexafluorophosphates phosphate, or perfluoroalkyl phosphate.

[0125] In addition, instead of the electrolyte solution, 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, there is no need to install a separator or spacer. Since the entire pond can be solidified, there is no risk of leakage, dramatically improving safety.

[0126] The positive electrode can 301 and the negative electrode can 302 are made of a material that is resistant to liquids such as electrolytes during charging and discharging of the secondary battery. Metals such as nickel, aluminum, and titanium that are corrosion-resistant, alloys of these metals, and Alloys of metals with other metals (e.g., stainless steel, etc.), laminations of the metals, and the metals and the above-mentioned Lamination with alloys (e.g., stainless steel, aluminum, etc.), lamination of the metal with other metals A layer (e.g., nickel, iron, nickel, etc.) can be used. 304 and the negative electrode can 302 are electrically connected to the negative electrode 307, respectively.

[0127] 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 downwards, and the positive electrode 304, separator 310, negative electrode 307, and 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.

[0128] (Laminated battery) FIG. 5 shows an external view of a laminated storage battery 500. In addition, FIGS. 6(A) and 6(B) show The cross sections A1-A2 and B1-B2 are shown by dashed lines in Figure 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 substrate 504 and a negative electrode active material layer 505, a separator 507, and an electrolyte 508 are provided. 508 and an outer casing 509. A separator 507 is disposed between the positive electrode 503 and the negative electrode 506. An electrolyte 508 is poured into the area surrounded by the exterior body 509. There are.

[0129] In the laminated storage battery 500 shown in FIG. 5, a positive electrode current collector 501 and a negative electrode current collector 50 4 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 .

[0130] In the laminated storage battery 500, the exterior body 509 is made of, for example, polyethylene, polypropylene, etc. Al is applied to 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 applied, and the metal On the thin film, an insulating synthetic resin 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 a film can be used. This prevents the permeation of electrolyte and gas, ensures insulation, and is also electrolyte-resistant. It has sexuality.

[0131] (cylindrical storage battery) Next, an example of a cylindrical storage battery will be described with reference to FIG. 7. 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 (external can) 602 are are insulated from each other by a gasket (insulating packing) 610.

[0132] FIG. 7(B) is a schematic diagram showing a cross section of a cylindrical storage battery. Inside the 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 are corrosion-resistant to liquids such as electrolytes during charging and discharging of secondary batteries. Metals such as aluminum and titanium, alloys of these metals, alloys of these metals with other metals (e.g., silicon 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, 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 laminated storage batteries. Cut.

[0133] 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, since the positive and negative electrodes used in cylindrical storage batteries are wound, active materials are 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 3 and the negative electrode terminal 607 can both be made of a metal material such as aluminum. The positive terminal 603 is connected to the 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. The positive electrode cap 601 is electrically connected to the positive electrode cap 601 via a re coefficient 611. The safety valve mechanism 612 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 resistance element whose resistance increases when the temperature rises, and the amount of current increases as the resistance increases. The PTC element is made of barium titanate (BaTi O3) based semiconductor ceramics, etc. can be used.

[0134] In this embodiment, the storage battery may be a coin type, a laminate type, or a cylindrical type. However, other types of batteries such as sealed batteries and rectangular batteries can also be used. In addition, there are also structures in which a plurality of positive electrodes, negative electrodes, and separators are stacked, and structures in which a plurality of positive electrodes, negative electrodes, and separators are stacked. The structure may be such that the motor is wound around the core.

[0135] 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 aspect 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 increased.

[0136] Note that in this embodiment, one embodiment of the present invention has been described. 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 this example, an example in which the present invention is applied to a lithium ion secondary battery has been shown. In some cases, or depending on the circumstances, one aspect of the present invention is to 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 circumstances, one aspect of the present invention is applicable to lithium ion secondary batteries. It may not be necessary to use it.

[0137] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0138] (Fourth embodiment) A storage battery using a 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 devices.

[0139] As a specific example of an electrical device using a storage battery including a 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, Computer, word processor, DVD (Digital Versatile Disk) c) Image playback devices that play still images or videos 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, electric Rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air conditioners, Humidifiers, dehumidifiers and other air conditioning equipment, dishwashers, dish dryers, clothes dryers, futon dryers, electric appliances Electric refrigerators, electric freezers, electric refrigerator-freezers, freezers for DNA storage, flashlights, chainsaws These include power tools such as fire extinguishers, smoke detectors, and medical equipment such as dialysis machines. Units, belt conveyors, elevators, escalators, industrial robots, power storage systems , industrial equipment such as power storage devices for power leveling and smart grids. Mobile 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 with tires and wheels replaced with endless tracks, motorized bicycles including electrically assisted bicycles, Motorized two-wheeled vehicles, electric wheelchairs, golf carts, small or large ships, submarines, helicopters, aircraft Examples include aircraft, rockets, satellites, space probes, planetary probes, and spacecraft.

[0140] The electrical equipment is powered by a power supply according to one embodiment of the present invention. Alternatively, the electrical device may be a storage battery using the above-mentioned storage battery electrode. 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-described functions, 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 main power supply or commercial power supply. The present invention is applicable to an auxiliary power supply for supplying power to an electrical device in parallel with the supply of power. A storage battery using the storage battery electrode according to one aspect of the present invention can be used.

[0141] 8 shows a specific configuration of the above-mentioned electrical device. In FIG. 8, a display device 700 is a display device according to the present invention. 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. The power can be supplied from a power source or can be stored in the battery 704. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or other reason, this invention By using the storage battery 704 using the storage battery electrode according to one embodiment as an uninterruptible power supply, The display device 700 becomes available for use.

[0142] The display unit 702 may be a liquid crystal display device, a light emitting device having a light emitting element such as an organic EL element in each pixel, or the like. Device, electrophoretic display, DMD (Digital Micromirror Device) e), PDP (Plasma Display Panel), FED (Field E A semiconductor display device such as a mission display can be used.

[0143] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0144] In FIG. 8, a stationary lighting device 710 uses a storage battery electrode according to one embodiment of the present invention. Specifically, the lighting device 710 is an example of an electrical device that uses a storage battery 713. 8, the storage battery 713 is disposed in the housing 711 and 7 illustrates a case in which the light source 712 is installed inside a ceiling 714. The storage battery 713 may be provided inside the housing 711. The lighting device 710 is It is possible to receive power from a power source or use power stored in a storage battery 713. Therefore, even when power cannot be supplied from the commercial power source 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.

[0145] Although FIG. 8 illustrates a fixed lighting device 710 provided on the ceiling 714, In a storage battery using a storage battery electrode according to one embodiment of the present invention, the side wall 71 is not necessarily provided with a ceiling 714. 5. It can also be used in a fixed lighting device installed on the floor 716, window 717, etc. It can also be used as a tabletop lighting device.

[0146] The light source 712 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, 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.

[0147] 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 Alternatively, the air conditioner 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 air conditioner is supplied with power from a commercial power source. The power can be supplied by the power supply or can be stored in the battery 723. If both the indoor unit 720 and the outdoor unit 724 are provided with a storage battery 723, the The electrode for a storage battery according to one embodiment of the present invention can be used even when power cannot be supplied from a commercial power source. By using a storage battery 723 as an uninterruptible power supply, it is possible to use an air conditioner. It becomes Noh.

[0148] Note that 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 the functions of both the indoor unit and the outdoor unit 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 analyzer.

[0149] 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 power source or use 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, one aspect of the present invention can be used. By using the storage battery 734 using the storage battery electrodes according to the present invention as an uninterruptible power supply, Warehouse 730 will be available for use.

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

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

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

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

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

[0155] A part of the display unit 802a can be used as a touch panel area 808a, and the displayed operation Data can be input by touching the operation key 809. 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, it 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 function as a touch panel, and the display unit 802b is used as a display screen. It is possible.

[0156] Similarly to the display unit 802a, the display unit 802b can also be touched by touching a part of the display unit 802b. The area 808b of the touch panel can be used as a 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.

[0157] 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.

[0158] A display mode changeover switch 803 is used to change the display orientation between portrait and landscape. You can select between black and white and color display. The Touch 805 detects external light during use using a light sensor built into the tablet device. The tablet device has a light sensor that can adjust the display brightness to suit the amount of light. In addition, it also incorporates other detection devices such as gyro, acceleration sensor, etc. to detect tilt. It is also acceptable to do so.

[0159] FIG. 9A shows an example in which the display area of ​​the display unit 802b is the same as that of the display unit 802a. There is no particular limitation on the size of the image, and the size of one image may be different from the other image. For example, one of the display panels may be capable of displaying a higher resolution image than the other. Good too.

[0160] FIG. 9B shows the tablet terminal 800 in a closed state, and the tablet terminal 800 includes a housing 801, a solar cell 802, and a battery 803. 11, includes a charge / discharge control circuit 850, a battery 851, and a DC / DC 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 also includes a storage battery using the storage battery electrode according to one embodiment of the present invention described above.

[0161] The tablet terminal 800 can be folded in half, so when not in use, the housing 801 can be closed. Therefore, the display units 802a and 802b can be protected, and the display units 802a and 802b can be To provide a tablet terminal 800 that is highly durable and reliable from the viewpoint of long-term use. This can be done.

[0162] In addition, the tablet terminals shown in Fig. 9(A) and Fig. 9(B) can also display various information ( Functions that display still images, videos, text images, etc., 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 can have functions such as the ability to control processing by various software (programs), etc. can.

[0163] 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 processing unit, etc. The battery 851 can be efficiently charged by providing the charger 801 on one or both sides. It can be concluded that

[0164] The configuration and operation of the charge / discharge control circuit 850 shown in FIG. 9B are shown in FIG. 9C. 9C shows a solar cell 811, a battery 851, and a , DC-DC converter 852, converter 853, switches SW1 to SW3, display unit 8 02, battery 851, DC / DC converter 852, converter 8 53, the switches SW1 to SW3 correspond to the charge / discharge control circuit 850 shown in FIG. 9(B). This is the location.

[0165] First, an example of operation when 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 voltage is increased or decreased by the converter 852. When power from 811 is used, switch SW1 is turned on and the converter 853 is turned on. The voltage is increased or decreased to the voltage required for the display unit 802. When not displaying, turn SW1 off and SW2 on to charge the battery 851. The configuration may be such that:

[0166] The solar cell 811 is shown as an example of a power generating means, but is not particularly limited thereto. Other power generation methods such as piezoelectric elements (piezoelectric elements) and thermoelectric elements (Peltier elements) For example, the power may be transmitted and received wirelessly (contactlessly). It is possible to combine a non-contact power transmission module that charges by transmitting power to the battery, or other charging methods. It may also be composed.

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

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

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

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

[0171] The drive unit 863 is a DC motor or an AC motor alone, or a combination of a motor and an internal combustion engine. The processing device 864 is configured to receive operation information (acceleration , deceleration, stopping, etc.) and driving information (uphill and downhill slopes, load information on the drive wheels, etc.) The control circuit 862 outputs a control signal based on the input information such as The control signal from the processing unit 864 adjusts the electrical energy supplied from the battery 861. In case an AC motor is installed, the output of the drive unit 863 is controlled by adjusting the speed. However, it also has a built-in inverter that converts direct current to alternating current.

[0172] 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 can be formed by using a storage battery electrode according to one embodiment of the present invention. By installing a storage battery using this technology, it is possible to contribute to increasing the battery capacity, improving convenience. In addition, the improvement of the characteristics of the battery 861 allows the battery 861 If the device itself can be made smaller and lighter, it will contribute to reducing the vehicle's weight, thereby improving fuel efficiency. .

[0173] Note that the present invention is not limited to the above-described electrical 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.

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

[0175] (Embodiment 7) A battery system that can be used in combination with a battery cell containing the material described in the above embodiment Battery Management Unit (BMU), and the battery For transistors suitable for the circuits constituting the control unit, please refer to Figures 11 to 17. In this embodiment, a battery of a power storage device having battery cells connected in series will be described. The control unit will now be described.

[0176] When multiple battery cells connected in series are repeatedly charged and discharged, the characteristics between the battery cells change. The capacity (output voltage) varies depending on the variation in the The overall discharge capacity depends on the battery cell with the smallest capacity. Also, if charging is performed based on a battery cell with a small 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.

[0177] Therefore, the battery control unit of the power storage device having battery cells connected in series is It has the function of equalizing the capacity variations between battery cells, which can cause overcharging. The circuit configuration to equalize the capacitance variation between the resistors, capacitors, or inductors can be used. There are other methods such as a transistor with a small off-state current, but here we use a transistor with a small off-state current to reduce the capacitance variation. An example of a circuit configuration that can be aligned will be described below.

[0178] 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 for power storage devices. By using this in the circuit configuration of the battery control unit of the device, the amount of charge leaking from the battery cell can be reduced. This makes it possible to suppress the decrease in capacity over time.

[0179] 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 upper limit is 6 or less, a CAAC-OS film is easily formed as the oxide semiconductor film.

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

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

[0182] Transmission Electron Microscope (TEM) A bright-field image and a combined analysis image of the diffraction pattern of the CAAC-OS film were obtained by using a microscope. By observing the TEM image, multiple crystalline regions can be identified. On the other hand, high-resolution TEM images also reveal clear boundaries between crystalline parts, 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.

[0183] 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 crystalline part. Each layer of metal atoms is The CAAC-OS film is formed on a surface (also called a surface to be formed) or on a surface that reflects the unevenness of the surface. The CAAC-OS film has a shape and is aligned parallel to the surface on which the film is formed or the upper surface.

[0184] 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 a triangular or hexagonal shape. However, there is no regularity in the arrangement of metal atoms between different crystal parts.

[0185] X-ray diffraction (XRD) was performed on the CAAC-OS film. For example, a CAAC-OS film with InGaZnO4 crystals was found by structural analysis using the device. 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. Therefore, 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.

[0186] 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 around 31°, a peak also appeared at 2θ around 36°. The peak at 2θ around 36° is due to the presence of c-axis orientation in part of the CAAC-OS film. The CAAC-OS film contains crystals that do not have a 2θ of around 31°. It is preferable that the peak is exhibited at 2θ of around 36° and that the peak is not exhibited at 2θ of around 36°.

[0187] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. These are elements 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 constitute the oxide semiconductor film, such as fluorine, 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 (or molecular radius) is large, and when it is contained inside the oxide semiconductor film, The impurities contained in the oxide semiconductor film are likely to disturb the atomic arrangement and cause a decrease in crystallinity. Objects can act as carrier traps or carrier sources.

[0188] The CAAC-OS film is an oxide semiconductor film with a low density of defect states. Oxygen vacancies in the semiconductor film can become carrier traps or trap hydrogen, It can be a source of carrier generation.

[0189] Low impurity concentration and low defect level density (low oxygen vacancies) are called high purity intrinsic or The term "substantially highly purified intrinsic" refers to a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film. Since there are fewer carrier generation sources, the carrier density can be reduced. The transistor using the oxide semiconductor film has electrical characteristics ( It is also called normally-on.) It is rare for it to become a high-purity intrinsic or substantially high-purity The intrinsic oxide semiconductor film has few carrier traps. Transistors using this film have little fluctuation in electrical characteristics and are highly reliable. Note that it takes time for the charges trapped in the carrier traps in the oxide semiconductor film to be released. The impurity concentration is high and the charge is stable for a long time, so the charge may behave like a fixed charge. Therefore, a transistor using an oxide semiconductor film with a high density of defect states has unstable electrical characteristics. This may occur.

[0190] In addition, transistors using CAAC-OS films show improved electrical characteristics when irradiated with visible light or ultraviolet light. The fluctuation is small.

[0191] Note that an OS transistor is a transistor having silicon in a channel formation region (Si transistor). Since the band gap is larger than that of a semiconductor (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. 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 transistor using an OS transistor.

[0192] 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.

[0193] In addition, in the power storage device 1000 of FIG. 11, the terminal pair 1001 and the terminal pair 1002 are connected to each other. 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 the battery control unit. It is possible.

[0194] The switching control circuit 1003 controls the operations 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 (discharge battery cell group) and the battery cells to be charged (charge battery group) are selected. Determine the pond cell group.

[0195] Furthermore, the switching control circuit 1003 controls the determined discharging battery cell group and charging battery cell group. The control signal S1 and the control signal S2 are output based on the group. 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 This control signal S2 is output to the switching circuit 1005. This is a signal that controls the switching circuit 1005 to connect the groups.

[0196] The switching control circuit 1003 also includes a switching circuit 1004, a switching circuit 1005, and Considering the configuration of the transformer circuit 1007, the terminal pair 1001 and the discharge battery cell group or 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. A signal S1 and a control signal S2 are generated.

[0197] The operation of the switching control circuit 1003 will now be described in detail.

[0198] First, the switching control circuit 1003 measures the voltage of each of the plurality of battery cells 1009. The switching control circuit 1003 then selects, for example, the battery cell 1009 with a voltage equal to or higher than a predetermined threshold. A high-voltage battery cell (high-voltage cell) is a battery cell 1009 with a voltage below a predetermined threshold. It is determined to be a battery cell (low voltage cell).

[0199] 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 can select the battery cell with the highest power among the plurality of battery cells 1009. The voltage of each battery cell 100 is determined based on the voltage of the battery cell 1009 with 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 determines whether the voltage of each battery cell 1009 is equal to or greater than a predetermined ratio of the 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. Then, based on the result of this determination, the switching control circuit 1003 switches between the discharging battery cell group and the charging battery cell group. Determine the pond cell group.

[0200] 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 controls the switching between high-voltage cells and low-voltage cells. The part with the most 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 cells are 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.

[0201] 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.

[0202] First, in the example of FIG. 12(A), if the voltages of the battery cells a to d are voltages Va to Vd, then , Va=Vb=Vc>Vd. In other words, 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. The switching control circuit 1003 also determines the low voltage cell d as the charging battery cell group. .

[0203] Next, the example of FIG. 12(B) 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 In this case, the switching control circuit 1003 is configured as follows: The high-voltage cell c is determined as the discharge battery cell group. Since the high-voltage cell d is close to over-discharge, it is the low-voltage cell a and b that are the two consecutive low-voltage cells. The pressure cell d is determined as the charging battery cell group with priority.

[0204] Finally, the example of FIG. 12(C) 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 determines whether to charge three consecutive low-voltage cells b to d. Determined as a battery cell group.

[0205] The switching control circuit 1003 determines the results as shown in the examples of FIGS. 12(A) to 12(C). 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 determined control signal S2 is sent to the switching circuit 1004 and the switching circuit 1005. Each is output.

[0206] The above is a detailed description of the operation of the switching control circuit 1003.

[0207] 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 it to the rule group.

[0208] The terminal pair 1001 is composed of a pair of terminals A1 and A2. In this case, 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 top of the discharge battery cell group. By connecting the negative terminal of the battery cell 1009 located further downstream (low potential side), The switching circuit 1004 sets the connection destination of the pair 1001. The position of the discharged battery cell group can be recognized using the obtained information.

[0209] The switching circuit 1005 is responsive to the 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 it to the rule group.

[0210] The terminal pair 1002 is composed of a pair of terminals B1 and B2. In this case, either one of the terminals B1 and B2 is connected to the most upstream (high voltage) of the charging battery cell group. The other end is connected to the positive terminal of the battery cell 1009 located at the top of the charging battery cell group. By connecting the negative terminal of the battery cell 1009 located further downstream (low potential side), The switching circuit 1005 sets the connection destination of the pair 1002. The position of the charging battery cell group can be recognized using the obtained information.

[0211] 13 and 14 are circuit diagrams showing examples of the configuration of the switching circuit 1004 and the switching circuit 1005. Shown in 4.

[0212] In FIG. 13, the switching circuit 1004 includes a plurality of transistors 1010 and a bus 1011. 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 plurality of transistors 1010 is connected to two adjacent It is connected between the battery cells 1009.

[0213] Among the plurality of transistors 1010, the transistor 1010 located at the most upstream position The other of the source and drain is connected to the positive electrode of the battery cell 1009 located at the most upstream of the battery section 1008. The transistor 1010 located at the most downstream side is connected to the terminal. The other of the source and drain of the transistor 1010 is located at the most downstream side of the battery section 1008. It is connected to the negative terminal of the battery cell 1009 .

[0214] The switching circuit 1004 controls the control signal S1 to be applied to the gates of the plurality of transistors 1010. In response, one of the plurality of transistors 1010 connected to the bus 1011 and the bus 1 1012 and one of the plurality of transistors 1010 connected to the By doing so, the discharge battery cell group and the terminal pair 1001 are connected. The positive terminal of the battery cell 1009 located at the most upstream position in the group of cells is 2. In addition, 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

[0215] The transistor 1010 is preferably an OS transistor. Since the off-state current of the capacitor is small, it reduces the amount of charge leaking from battery cells that do not belong to the discharge battery cell group. This prevents the capacitance from decreasing over time. Therefore, the output voltage of the discharged battery cell group is large. Even if the transistor 1010 is not electrically connected, the battery cell 1009 and the terminal pair 1001 can be insulated.

[0216] In addition, in FIG. 13, the switching circuit 1005 includes a plurality of transistors 1013 and a current control The bus 1015 and the bus 1016 are connected to the switch 1014 and the bus 1015. 16 is disposed between a plurality of transistors 1013 and a current control switch 1014. The source or drain of each of the plurality of transistors 1013 is alternately connected. 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. are.

[0217] Among the plurality of transistors 1013, the transistor 1013 located at the most upstream position The other of the source and drain is connected to 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 side of the battery section 1008. It is connected to the negative terminal of the battery cell 1009 .

[0218] The transistor 1013 is an OS transistor, similar to the transistor 1010. Since the OS transistor has a small off-state current, 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 prevents the capacity from decreasing over time. In addition, OS transistors are less likely to experience dielectric breakdown when high voltages are applied. A transistor 10 that is in a non-conducting state even when the voltage for charging the charging battery cell group is large. 13 can be connected to the battery cell 1009 and the terminal pair 1002 in an insulated state.

[0219] 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 branched by 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 by two switches, while The switch is connected to bus 1015 and the other switch is connected to bus 1016. .

[0220] The switches included in switch pair 1017 and switch pair 1018 are transistors 1010 Similarly to the transistor 1013, an OS transistor is preferably used.

[0221] 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.

[0222] The switching circuit 1005, for example, connects the charging battery cell group and the terminal pair 100 as follows. Connect 2.

[0223] 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 connected to the In response to the 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.

[0224] 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. and the configuration of the transformer circuit 1007. To allow current to flow in the opposite 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.

[0225] 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. At this time, the most downstream battery cell 1009 of the battery unit 1008 If the battery cell group is a charging battery cell group, the switch pair 1017 switches the battery cell group 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 101 of the switch pair 1017 is turned on. On the other hand, the switch pair 1018 is turned off by the control signal S2 , the negative terminal of the battery cell 1009 is connected to the negative terminal of the battery cell 1009. The switch connected to the bus 1015 of the switch pair 1018 is turned on, and The switch connected to the bus 1016 of the terminal pair 018 is turned off. Between 1002 and the charging battery cell group, terminals with the same polarity are connected. The direction of the current flowing from the slave pair 1002 is controlled so that it charges the charging battery cell group. will be done.

[0226] Also, the current control switch 1014 is connected to the switching circuit 1005, not the switching circuit 1006. 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 the current flowing to the charging battery cell group.

[0227] 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.

[0228] 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 branch is made up of a transistor 1022 and a transistor 1023. One of the source and drain of 1022 is connected to a bus 1024. One of the source and drain of the resistor 1023 is connected to the bus 1025. The other ends of the plurality of 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 position 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 side of the battery section 1008. is connected to the terminal.

[0229] The switching circuit 1004 switches between the transistor 1022 and the transistor 1023 in response to the control signal S1. 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 1022 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 conducting state, The transistor 1022 is in a non-conductive state, and the transistor pair 1021 is connected to the terminal A2. Which of the transistors 1022 and 1023 is turned on depends on the , determined by the control signal S1.

[0230] 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 terminal pairs 1001 and 2, the discharge battery cell group is connected to the terminal pair 1001. One of the transistor pairs 1021 is connected to terminal A1, and the other is connected to terminal A2 by the control signal S1.

[0231] The switching circuit 1005 includes a plurality of transistor pairs 1031 and a bus 1034 and a bus 1035. 35. Bus 1034 is connected to terminal B1. Bus 1035 has One end of each of the plurality of transistor pairs 1031 is connected to the terminal B1. The output of the transistor 1032 is branched off by the transistor 1033. One of the source and drain of the transistor 103 is connected to the bus 1034. One of the sources or drains of the transistors 3 is connected to the 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 most downstream transistor pair 1031 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.

[0232] The switching circuit 1005 switches between the transistor 1032 and the transistor 1033 in response to the control signal S2. 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 1032 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 conducting 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 turned on is controlled by is determined by control signal S2.

[0233] Two transistor pairs 1031 are used to connect the terminal pair 1002 to the charging battery cells. In detail, the connection destination of the two transistor pairs 1031 is determined based on the control signal S2. By determining the terminal pairs 1002 and the terminals 1003, the charging 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.

[0234] The two transistor pairs 1031 are connected to the terminal pair 1002. Specifically, terminal B1 is positive and terminal B2 is negative. When such a voltage is applied to the terminal pair 1002, the upstream transistor pair 1031 , the transistor 1032 is in a conducting state and the transistor 1033 is in a non-conducting state. 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 that makes the terminal B1 negative and the terminal B2 positive is When a voltage is applied to terminal pair 1002, the upstream transistor pair 1031 The control is performed 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 control signal S2. The control signal S2 is set to ON so that the transistor 1032 is in the ON state and the transistor 1033 is in the OFF state. In this way, the same voltage is applied between the terminal pair 1002 and the charging battery cells. The terminals with the same polarity are connected together. The direction of the current flowing from the terminal pair 1002 is the charging direction. The battery cells are controlled to charge.

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

[0236] The number of battery cells 1009 included in the discharge battery cell group is equal to the number of battery cells 1009 included in the charge battery cell group. If the number of battery cells is greater than the number of battery cells 1009, an excessively large charging voltage is applied to the charging battery cell group. Therefore, the voltage 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.

[0237] In addition, the number of battery cells 1009 included in the discharging battery cell group is equal to the number of battery cells 1009 included in the charging battery cell group. If the number of battery cells 1009 is less than or equal to the number of chargeable battery cells 1009, the chargeable battery cells 1009 are charged. Therefore, the voltage transformer control circuit 1006 controls the charging of the battery cell group. The transformer circuit 10 is configured to boost the discharge voltage (Vdis) within a range where an excessive charge voltage is not applied. 07.

[0238] The voltage value that constitutes the excessive charging voltage is the voltage of the battery cell 1009 used in the battery module 1008. This can be determined in consideration of product specifications, etc. Also, the voltage step-up and step-down are performed by the transformer circuit 1007. The voltage thus obtained is applied to the terminal pair 1002 as the charging voltage (Vcha).

[0239] Here, an example of the operation of the transformer control circuit 1006 in this embodiment is shown in FIGS. 15(A) to 15(C) 15(A) to (C) are the same as those described in FIGS. 12(A) to (C). An example of the operation of the voltage transformer control circuit 1006 corresponding to the power battery cell group and the charge battery cell group will be described. 15(A) to 15(C) are conceptual diagrams for illustrating the battery control unit 1041. The battery control unit 1041 is connected to the terminal pair 1001 and the 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.

[0240] In the example shown in FIG. 15(A), three consecutive high voltages are applied as described in FIG. 12(A). Cells a to c and one low-voltage cell d are connected in series. In this case, as shown in FIG. ), 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. , based on the ratio of the number of battery cells 1009 included in the charging battery cell group, the discharge voltage (Vdi Calculate the conversion ratio N from the current (V) to the charging voltage (Vcha).

[0241] 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 voltage, the discharge voltage is directly applied to the terminal pair 1002 without being transformed. When the voltage is applied, a voltage is applied to the battery cell 1009 included in the charging battery cell group via the terminal pair 1002. There is a possibility that excessive voltage will be applied. Therefore, in the case shown in FIG. Therefore, 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 must be greater than the total voltage of the battery cells 1009 included. 006 is the charging voltage when the number of battery cells 1009 included in the discharging 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.

[0242] The transformer control circuit 1006 determines the number of battery cells 1009 included in the discharge battery cell group as a standard. When the conversion ratio N is 1, the ratio of the number of battery cells 1009 included in the charging battery cell group is At this time, the charging voltage is preferably set to be about 10% or more higher than the voltage of the charging battery cell group. However, the charging voltage is actually equal to the voltage of the charging battery cell group. The control circuit 1006 controls the voltage of the charging battery cells to be equal to the charging voltage according to the conversion ratio N. This current flows to charge the battery cell group. The set value will be used.

[0243] In the example shown in FIG. 15(A), the number of battery cells 1009 included in the discharge battery cell group is 3. 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 transformer control circuit 1006 is a transformer signal S3 that reduces the discharge voltage according to the conversion ratio N and converts it into a charge voltage. The transformer circuit 1007 then outputs the voltage 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.

[0244] In the examples shown in FIG. 15(B) and FIG. 15(C), as in FIG. 15(A), the conversion ratio N In the examples shown in FIG. 15(B) and FIG. 15(C), the 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 voltage transformation signal S3 that boosts the discharge voltage and converts it into a charge voltage.

[0245] The transformer circuit 1007 adjusts the discharge voltage applied to the terminal pair 1001 based on the transformer signal S3. The voltage transformer circuit 1007 then converts the converted charging voltage into a charging voltage. 2. Here, the transformer circuit 1007 connects the terminal pair 1001 and the terminal pair 1002. This allows the transformer circuit 1007 to be electrically isolated from 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 due to 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 sum of the discharging battery cell groups into the sum of the discharging battery cells based on the transformer signal S3. The discharge voltage, which is the measured voltage, is converted into the charge voltage.

[0246] The transformer circuit 1007 is, for example, an insulated DC (Direct Current)-DC In this case, the transformer control circuit 1006 may be an isolated DC- The signal that controls the on / off ratio (duty ratio) of the DC converter is the transformer signal S3. By outputting this, the charging voltage converted by the transformer circuit 1007 is controlled.

[0247] In addition, there are various types of isolated DC-DC converters, including flyback, forward, and RCC ( Ring Choke Converter type, push-pull type, half-block type There are various types of inverters, such as full-bridge and ridge types, depending on the magnitude of the desired output voltage. The appropriate method is selected based on the results.

[0248] The configuration of the 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 that switches the operation of the isolated DC-DC converter on and off. For example, MOSFET (Metal-Oxide-Semiconductor tor Field-Effect Transistor) and bipolar transistor 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 into a charge voltage according to the on / off ratio. In the switching period of 2, the longer the ON time, the larger the capacitance becomes. When a DC-DC converter of this type is used, the terminal pair 1001 and The terminal pairs 1002 may be isolated from each other.

[0249] The processing flow of the power storage device 1000 in this embodiment will be described with reference to FIG. 7 is a flowchart showing the flow of processing by the power storage device 1000.

[0250] 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 plurality of battery cells 1009. It is determined whether the start condition for 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 balanced. On the other hand, if the start condition is satisfied (step Step S1102: YES), the power storage device 1000 performs a process of aligning the voltages of the battery cells 1009. 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 based on the determination result. 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 that sets the battery cell group as the connection destination of the terminal pair 1001, and a control signal S3 that sets the battery cell group as the connection destination of the terminal pair 1001. 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 signals S1 and S2 to a switching circuit The signal is output to the switching circuit 1004 and the switching circuit 1005. The terminal pair 1001 and the discharge battery cell group are connected by this, 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. The voltage transform signal S3 is generated based on the number of battery cells 1009 included (step S1 107). Then, 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.

[0251] 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 in which they are listed.

[0252] 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 charging 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 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.

[0253] Furthermore, the number of battery cells 1009 included in the discharging 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 voltage applied to the terminal pair 1001. The discharge voltage is converted into a charge voltage and applied to the terminal pair 1002. No matter how the battery cells 1009 on the charge and discharge sides are selected, charge transfer can be achieved without any problems. can.

[0254] Furthermore, by using OS transistors for the transistors 1010 and 1013, As a result, leakage from the battery cells 1009 that do 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, OS transistors have the advantage over Si transistors in that they can suppress the decrease in capacitance. As a result, the temperature of the battery cell 1009 rises and However, normal operation, such as switching between conductive and non-conductive states according to the control signals S1 and S2, is also possible. It can be done.

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

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

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

[0258] (Preparation of electrode A) First, the active material layer and current collector prepared by the above procedure were placed in ethanol (99. The active material layer and the current collector were taken out of the ethanol and immersed in 1% ethanol for 10 minutes. The graphene oxide was reduced by heating at 00°C for 10 hours to prepare electrode A.

[0259] (Preparation of electrode B) In the same manner as in the preparation of electrode A, the active material layer and the current collector were immersed in ethanol at 60°C, and then The graphene oxide was reduced by heating at 0°C for 10 hours to prepare electrode B.

[0260] (Preparation of electrode C) As in the preparation of electrodes A and B, the active material layer and the current collector were immersed in ethanol at 60°C, and then The graphene oxide was reduced by heating at 70°C for 10 hours to prepare electrode C.

[0261] (Preparation of electrode D) Unlike the preparation of electrodes A, B, and C, the active material layer and current collector were placed in ethanol at room temperature (25°C). After immersion for 10 minutes, the electrode was heated at 100° C. for 10 hours under reduced pressure to prepare electrode D.

[0262] (Preparation of Comparative Example E) For comparison, graphene oxide was formed by heating only without immersing the active material layer in ethanol. The active material layer and current collector were heated at 170°C for 10 hours to produce a positive electrode that reduces A positive electrode was prepared from the above and designated as Comparative Example E.

[0263] (Preparation of Comparative Example F) For comparison, the active material layer was immersed in a solution containing a reducing agent to reduce the graphene oxide. The solution containing the reducing agent contained L-ascorbic acid. First, L-ascorbic acid and lithium hydroxide were used as a pH adjuster. The sodium was dissolved in a water-NMP mixture (water:NMP) to a concentration of 77 mM and 73 mM, respectively. P = 1:9 (volume ratio) to prepare a solution. After immersing the material in the solution, heating it to 60°C and reacting it for 1 hour, the material was washed and heated to 170°C under reduced pressure. The solvent was evaporated by the above procedure to prepare Comparative Example F.

[0264] (Observation of the cross section of the active material layer) For the prepared electrode A, the cross section polished with a cross-section polisher was observed using an SEM. FIG. 23 shows a cross-sectional SEM image of the active material layer of electrode A at 30,000 magnifications.

[0265] As shown in FIG. 23, in the active material layer of electrode A, sheet-like graphene 902 is The active material 901 is covered or in contact with the active material 901. Therefore, in the active material layer of electrode A, the three graphenes are in contact with each other. It was found that a multidimensional electrically conductive network was formed. No particular damage was observed in the area. After immersion, the electrode is removed and heated, resulting in an electrode with minimal damage to the active material layer. I realized that I could do this.

[0266] (Half-cell preparation) Electrodes A, D and comparative examples E, F were incorporated into half cells as positive electrodes, and the charge and discharge tests were carried out on each cell. 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. This shows a lithium-ion secondary battery cell that uses lithium metal. The battery is made of polypropylene (PP), and the electrolyte is ethylene carbonate (EC). Diethyl carbonate (DEC) was mixed with 6-fluoro-2-methyl-1,2-dichloro-2,2-dichloro ... Lithium fluoride phosphate (LiPF6) dissolved at a concentration of 1 mol / liter was used.

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

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

[0269] From Figure 18, the half-cells using electrodes A and D have almost the same discharge capacity, In addition, after the half cell using electrodes A and D, the comparative example E was used. The half-cell using Comparative Example F had the smallest discharge capacity. Here, electrodes A and D were immersed in ethanol and then heated to produce oxidized graphite. Comparative Example E is an electrode in which tetrachlorophene is reduced, and Comparative Example E is an electrode in which tetrachlorophene is reduced by heating without being immersed in ethanol. Comparative Example F is an electrode made by reducing graphene oxide. The electrode was made by reducing graphene oxide by immersing it in a solution containing acid. When an electrode in which graphene oxide was reduced by heating was used, a solution containing L-ascorbic acid was The discharge capacity was higher than when using an electrode in which graphene oxide was reduced by immersing it in a solution. Furthermore, by immersing the cells in ethanol before heating, It was found that the discharge capacity of the fuel cell can be increased.

[0270] In addition, the half cell using Comparative Example F had a decreased discharge capacity with increasing cycle number. It was found that the decrease in discharge capacity was suppressed in the half cells using electrodes A and D. These results clearly show that the use of electrodes A and D improves the cycle characteristics of the half-cell. Therefore, electrodes A and D are electrodes with little damage to the active material layer, and there is no expansion or deformation. It was found that this makes it difficult for the electrical conduction pathway within the active material layer to be broken.

[0271] (Evaluation of rate characteristics) 19 and 20 show the results of the half-cells using electrodes A and D and comparative examples E and F at 25°C. The graph shows the discharge curves measured by changing the charge / discharge rate. The vertical axis shows the voltage (V) and the horizontal axis shows the discharge The capacity (mAh / g (positive electrode weight)) is shown. The charging conditions were constant current and constant voltage charging, charging rate 0 .2C, discharge conditions are constant current discharge, discharge rate is 0.2C, 1C, 2C, 5C, 10C. Figure 19(A) shows the discharge curve of the half cell using electrode A. Fig. 19(B) shows the discharge curve of the half cell using electrode D. The discharge curve of the half cell using Comparative Example E is shown in FIG. 20(B). The discharge curves of the half cells are shown.

[0272] As can be seen by comparing Figures 19(A), (B) and Figures 20(A), (B), The slope of the discharge curve near the end (end of discharge) of the half cell using Comparative Example F shown in -It was bigger than Fussel.

[0273] From these results, it can be seen that the electrode has the highest conductivity, which means that graphene oxide is reduced most efficiently. The electrode that could be obtained was Comparative Example F, followed by Electrode A and Electrode D, which had the highest conductivity. It was found that Comparative Example E had the lowest conductivity. By immersing it in a solution containing acid and then heating it after removing it, graphite oxide is most efficiently produced. It was also found that the active material layer could be immersed in ethanol and removed. The efficiency of the graphene oxide reduction reaction can also be increased by heating after the reaction. It was shown that this was possible.

[0274] (Current-rest method resistance measurement) Next, Electrode A and Comparative Example E were evaluated by measuring the current-rest resistance. Explain the current rest resistance. When charging a battery, if you stop charging, the voltage will drop. The cause of this voltage drop is the internal resistance of the battery. The voltage immediately after resting (voltage after 3 seconds of resting) / current was calculated by incorporating electrode A. The ohmic components of the internal resistance of the half-cell incorporating the comparative example E and the half-cell incorporating the comparative example E were determined. The charging conditions are constant current and constant voltage charging, and a charging rate of 0.2C. Charging pauses are At 25°C, the battery was charged at 59.5-1 02mAh / g charging, the charging was paused and the internal resistance ohm component calculated during this period was The average value was calculated.

[0275] The internal resistance ohmic components of the half-cell using electrode A and the half-cell using comparative example E are: The values ​​were 32.6Ω and 58.0Ω, respectively. From these results, it can be seen that electrode A has a higher internal resistance than comparative example E. Therefore, it was found that the ohmic component of the partial resistance was small. After that, the graphene oxide is removed and heated to increase the efficiency of the reduction reaction. It was suggested that it is possible to fabricate an electrode with a small ohmic component of internal resistance.

[0276] (Full cell preparation) Next, electrodes B, C, and comparative example E were each incorporated into a full cell, and the charge and discharge of each cell was The full cell is a cell in which both the positive and negative electrode materials are made of materials other than Li metal. The figure shows a lithium-ion secondary battery cell using graphite as the active material. The electrode is made of polypropylene (PP) for the separator, and the electrolyte is ethylene carbonate. A mixture of ethylenediaminetetraacetic acid (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1 was used. Lithium hexafluorophosphate (LiPF6) was dissolved in the solution at a concentration of 1 mol / L. was used.

[0277] (Evaluation of full cell cycle characteristics) Next, the discharge curves of the full cells using electrodes B, C, and comparative example E are shown in FIG. The conditions are for one cycle, constant current constant voltage charge, charge rate 0.2C, constant current discharge, The discharge rate is 0.2C, and after two cycles, the battery is charged at a constant current and the charge rate is 0. The discharge rate was 0.5C, constant current discharge, and 0.5C. In FIG. 21(A), the horizontal axis represents cycles. The vertical axis shows the number of discharges (cycles), and the vertical axis shows the discharge capacity of the secondary battery (mAh / g (weight of the positive electrode)). In 1(B), the horizontal axis indicates the number of cycles (times), and the vertical axis indicates the discharge capacity retention rate ( Here, the discharge capacity retention rate is the ratio of the discharge capacity (discharge) to the discharge capacity at the second cycle. (Capacity at first cycle ÷ Discharge capacity at second cycle × 100[%]) The results are for a full cell using electrode B, a full cell using electrode C, and a full cell using comparative example E. The results are denoted as B, C, and E, respectively.

[0278] As can be seen from Figure 21(A), the discharge capacity of the full cell using electrode C is the largest, followed by the full cell using electrode B. It was found that the full cell using Comparative Example E had the largest discharge capacity. This suggests that the reduction of graphene oxide during the production of the positive electrode It was found that the higher the heating temperature, the more the discharge capacity of the full cell can be improved. As shown in Figure 21(B), the discharge capacity retention rate is the least likely to decrease even when the number of cycles increases. is the full cell using electrode B, and the discharge capacity retention rate of the full cell using electrode C decreases next. It was found that Comparative Example E had the lowest discharge capacity retention rate. The lower the heating temperature during fabrication, the better the cycle characteristics of the full cell. This indicates that by reducing graphene oxide under mild reaction conditions, it is possible to obtain active materials. It was found that damage to the crust could be prevented. [Example]

[0279] In this example, in order to demonstrate that the reduction of graphene oxide is promoted by alcohol, We prepared samples of graphene oxide by heating it under various conditions and compared the degree of reduction.

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

[0281] Solids of Comparative Example 2, Comparative Example 3 and Sample 1 13 The C NMR spectrum is shown in Figure 22. Sample 1 In the spectrum, the peaks in the vicinity of 80 ppm to 50 ppm are higher than those in Comparative Examples 2 and 3. The peaks around 80 ppm to 50 ppm are due to the presence of graphene oxide. This is due to the carbon of the epoxy group and the carbon to which the hydroxyl group is bonded. It was found that Sample 1 contained fewer epoxy groups and hydroxyl groups than Comparative Examples 2 and 3. This suggests that the graphene contains many carbon-carbon double bonds. It was found that the reduction of laphene was promoted by alcohol. [Example]

[0282] In this example, a positive electrode was fabricated by the method using the second conductive additive shown in Embodiment 2. The results will be explained.

[0283] (Preparation of Electrode G and Electrode H) The active material layer was prepared using LiFePO4 as the active material and graphene oxide as the raw material for the conductive additive. As a second conductive additive, acetylene black (AB) or VGCF (registered The binder was PVdF, and the solvent was NMP. NMP was added to the O and the second conductive additive and the mixture was kneaded to prepare a mixture. The mixture was added with PVdF (No. 7300 manufactured by Kureha Corporation) in NMP solution and a second conductive agent. After the agent was added, NMP was further added and kneaded to prepare a paste.

[0284] The mixing ratio of the materials when preparing the paste was LiFePO4:GO:second conductive additive:PVdF= The weight ratio was 93.4:0.6:1:5. The paste prepared by the above method was applied to the current collector. The active material layer was then coated and heated under reduced pressure at 65°C for 15 minutes and then at 75°C for 15 minutes to evaporate the solvent. Formed.

[0285] The active material layer and current collector prepared by the above procedure were immersed in ethanol at 60°C, and then heated to 150°C. The GO was reduced by heating at RT for 10 hours to prepare an electrode.

[0286] The electrode prepared using VGCF (registered trademark) as the second conductive additive is referred to as electrode G. The electrode prepared using AB as the conductive additive was designated as electrode H.

[0287] An electrode prepared by the method for preparing electrode B described in Example 1 was designated as electrode B'.

[0288] (Observation of the cross section of the active material layer) The cross section of the prepared electrode G was polished with a cross-section polisher and observed using an SEM. In electrode G used for observation, the weight per unit area of ​​the active material layer was approximately 11 mg / cm 2 FIG. 24 shows an SEM image of a cross section of the active material layer of electrode G. 24(A) is a magnified view at 30,000 times, and FIG. 24(B) is a magnified view at 30,000 times.

[0289] In FIG. 24(A), a current collector 903 and an active material layer 904 were observed. 9, the active material layer 904 includes granular active material 901, graphene 902, and needle-like The conductive additive 905 was observed. The graphene 902 was roughly The conductive additive 905 is arranged obliquely relative to the surface of the current collector 903, as compared with the case where the conductive additive 905 is arranged parallel to the surface of the current collector 903. Therefore, the conductive additive 905 was disposed tilted relative to the surface of the current collector 903. It was speculated that this compensated for the vertical conductive path.

[0290] (Half-cell preparation) Next, electrodes G, H, and B' were incorporated into half cells as positive electrodes, and the same procedure as in Example 1 was carried out. The charge / discharge characteristics of each cell were measured under similar measurement conditions.

[0291] (Evaluation of rate characteristics) Figure 25(A) shows the half-cells using electrodes G, H, and B' at discharge rates of 1C and 2C. The graph shows the relationship between the discharge voltage and the weight of the active material layer of each electrode. The horizontal axis represents the unit discharge voltage [V] of the active material layer of the electrode G, H, or B' used. Weight per area [mg / cm 2 The charging conditions were constant current and constant voltage charging. The charge rate was 0.2 C, and the discharge condition was constant current discharge.

[0292] The average discharge voltage is the voltage measured from the start of discharge on the discharge curve shown in FIG. 25(B). This is the average voltage value up until just before the discharge voltage suddenly decreases.

[0293] In FIG. 25(A), in a half cell using electrode G, H, or B′, the active material layer As the weight of the electrode increased, the average discharge voltage decreased. The line showing the change in the average discharge voltage of the half-cell using electrode B' is the average of the half-cell using electrode B'. The slope was smaller than the straight line showing the change in discharge voltage.

[0294] From the above results, it is clear that the active material having VGCF (registered trademark) or AB as the second conductive additive It was found that the internal resistance of the layer is not likely to increase even if the weight increases. In the active material layer having the additive, the electrical conduction path has a more complex shape, so that the active material This is because the network is less likely to be cut even if the thickness of layer 202 is increased.

[0295] (Evaluation of half-cell cycle characteristics) FIG. 26 shows the stacking of the active material layers of the positive electrodes for the half cells using electrodes G, H, and B'. The graph shows the change in discharge voltage when charging and discharging with different amounts of charge and discharge. Voltage change [V] {Discharge voltage change [V] = (Average discharge voltage in the first cycle [V] )-(average discharge voltage at the 30th cycle [V])}, and the horizontal axis represents the electrode G used, Weight per unit area of ​​the active material layer of H or B' [mg / cm 2 ] as plot The discharge rate was set to 1C.

[0296] As can be seen from Figure 26, the average discharge voltage of the half-cell decreases as the weight of the active material layer increases, but the In the half cell using electrode G, the average discharge is lower than that in the half cell using electrode B'. This indicates that the voltage drop is suppressed. In the electrode containing the second conductive additive such as AB, the resistance does not increase even if the thickness of the active material layer increases. It was found that it was difficult to increase

[0297] (Full cell preparation) Next, in the same manner as in Example 1, electrodes G, H, and B' were assembled into full cells, and the The charge-discharge characteristics were measured.

[0298] (Evaluation of full cell cycle characteristics) The cycle characteristics of full cells using electrodes G, H, or B' were evaluated. The experimental conditions were as follows: The results are shown in Figure 27.

[0299] As can be seen from Figure 27, in the full cells using electrode G or electrode H, a sudden decrease in the charge immediately after the start of charging and discharging It was found that the decrease in discharge capacity can be suppressed. When electricity is applied, the active material layer absorbs the electrolyte and swells, cutting off the electrical conduction path. I found that I could prevent it from happening.

[0300] From the above results, it was found that by using the second conductive additive to prepare an electrode, the electrode was oriented perpendicular to the current collector. This strengthens the electrical conduction path, and even if the active material layer becomes thick, the resistance of the electrode is It was also found that the cycle characteristics could be improved. Understood. [Explanation of symbols]

[0301] S101 Step S102 Step S103 Step S104 Step S105 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 storage 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 board 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 Ventilation vent 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 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 Cells 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 901 Active material 902 Graphene 903 Current collector 904 Active material layer 905 Conductive additives S1 control signal S2 control signal S3 transformer signal 1000 Electricity storage device 1001 terminal pair 1002 terminal pairs 1003 Switching control circuit 1004 Switching circuit 1005 Switching circuit 1006 Transformer control circuit 1007 Transformer Circuit 1008 Battery section 1009 Battery Cells 1010 transistor 1011 Bus 1012 Bus 1013 Transistor 1014 Current Control Switch 1015 Bus 1016 Bus 1017 Switch Pairs 1018 Switch Pairs 1021 transistor pairs 1022 transistors 1023 transistors 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 having a current collector and an active material layer, the active material layer is in contact with the current collector, the active material layer includes first active material particles, second active material particles, first to third graphenes, and carbon black; the first graphene has a region in contact with the first active material particles and a region in contact with the second active material particles, the first graphene has a region arranged along a first direction substantially parallel to a surface of the current collector; the second graphene has a region in contact with the third graphene; the carbon black has a region in contact with the first active material particles and a region in contact with the second active material particles.

2. In claim 1, the carbon black has regions arranged along a second direction intersecting the first direction.

3. In claim 1 or claim 2, the first graphene is in surface contact with the first active material particles.

Images