Graphene

Abstract

To provide a novel graphene, or a novel graphene compound, or an electrode with high output, or a novel electrode, or a secondary battery with low degradation, or a secondary battery with high safety. [Solution] The graphene has pores composed of multi-membered rings of 9 or more members, each composed of carbon atoms. In addition, one or more carbon atoms constituting the multi-membered rings are terminated with fluorine.

Description

[Technical Field]

[0001] This invention relates to a secondary battery using a negative electrode active material and a method for manufacturing the same; or a secondary battery using a positive electrode active material and a method for manufacturing the same; or a secondary battery using graphene and a method for manufacturing the same; or electronic devices such as portable information terminals, vehicles, etc., that have a secondary battery.

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

[0003] In this specification, "electronic equipment" refers to all devices that have an energy storage device, and all electro-optical devices with an energy storage device, information terminal devices with an energy storage device, etc., are considered electronic equipment.

[0004] In this specification, the term "energy storage device" refers to all elements and devices that have an energy storage function. For example, this includes energy storage devices such as lithium-ion secondary batteries (also called secondary batteries), lithium-ion capacitors, and electric double-layer capacitors. [Background technology]

[0005] In recent years, there has been a great deal of development on various energy storage devices, including lithium-ion secondary batteries, lithium-ion capacitors, and air batteries. In particular, lithium-ion secondary batteries, with their high output and high energy density, are seeing rapidly expanding demand in conjunction with the development of the semiconductor industry. They are used in mobile information terminals such as mobile phones, smartphones, and notebook computers, as well as portable music players, digital cameras, medical equipment, and next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), and plug-in hybrid vehicles (PHV). As a rechargeable energy source, they have become indispensable to today's information society.

[0006] Regarding lithium-ion secondary batteries, research has been conducted on the crystal structure of the positive electrode active material (Non-Patent Document 1).

[0007] In addition, for the improvement of the cycle characteristics and the increase in capacity of lithium-ion secondary batteries, the improvement of the negative electrode with a coating has been studied (Patent Document 1).

[0008] Fluorine has a high electronegativity, and various studies have been conducted on its reactivity. Non-Patent Document 2 describes the reaction of compounds containing fluorine.

[0009] Silicon-based materials have a high capacity and are used as the active material of secondary batteries. Silicon materials can be characterized by the chemical shift values obtained from NMR spectra (Patent Document 2).

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

[0012] One aspect of the present invention aims to provide a novel graphene. Alternatively, one aspect of the present invention aims to provide a novel graphene compound. Alternatively, one aspect of the present invention aims to provide an electrode having high output. Alternatively, one aspect of the present invention aims to provide a novel electrode.

[0013] Alternatively, one aspect of the present invention aims to provide a novel method for producing graphene. Alternatively, one aspect of the present invention aims to provide a novel method for producing graphene compounds. Alternatively, one aspect of the present invention aims to provide a novel method for producing electrodes.

[0014] Alternatively, one aspect of the present invention aims to provide a secondary battery that undergoes less degradation. Alternatively, one aspect of the present invention aims to provide a secondary battery that is highly safe. Alternatively, one aspect of the present invention aims to provide a novel secondary battery.

[0015] Alternatively, one aspect of the present invention aims to provide a novel material, active material particles, secondary battery, energy storage device, or a method for producing the same.

[0016] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. It is possible to extract other problems from the description, drawings, and claims. [Means for solving the problem]

[0017] One aspect of the present invention is graphene having pores composed of multi-membered rings of 9 or more members, each composed of carbon atoms.

[0018] Furthermore, in the graphene described above, it is preferable that one or more carbon atoms constituting the multi-membered ring are terminated with fluorine.

[0019] Furthermore, in the analysis of the above graphene by Raman spectroscopy, 1580 cm⁻¹ -1 Or the first peak observed in its vicinity, and 1360cm -1 Preferably, it has a second peak observed near or in the vicinity of the first peak.

[0020] Alternatively, one aspect of the present invention comprises active material particles and graphene, wherein the graphene has pores composed of multi-membered rings of 9 or more members made up of carbon atoms, and the graphene is an electrode covering at least a portion of the surface of the active material particles.

[0021] Furthermore, in the graphene of the electrode described above, it is preferable that one or more carbon atoms constituting the multi-membered ring are terminated with fluorine.

[0022] Furthermore, in the above electrode, graphene was analyzed by Raman spectroscopy at 1580 cm⁻¹. -1 Or the first peak observed in its vicinity, and 1360cm -1 Preferably, it has a second peak observed near or in the vicinity of the first peak.

[0023] Furthermore, in the above configuration, it is preferable that the active material particles are positive electrode active material particles.

[0024] Furthermore, in the above configuration, it is preferable that the active material particles are negative electrode active material particles.

[0025] Alternatively, one aspect of the present invention is a secondary battery having the electrode and electrolyte described in any one of the above.

[0026] Alternatively, one aspect of the present invention is an electronic device having the secondary battery described above.

[0027] Alternatively, one aspect of the present invention is a vehicle having the secondary battery described above. [Effects of the Invention]

[0028] According to one aspect of the present invention, a novel graphene can be provided. Furthermore, according to one aspect of the present invention, a novel graphene compound can be provided. Furthermore, according to one aspect of the present invention, an electrode having high output can be provided. Furthermore, according to one aspect of the present invention, a novel electrode can be provided.

[0029] Furthermore, according to one aspect of the present invention, a novel method for producing graphene can be provided. Furthermore, according to one aspect of the present invention, a novel method for producing graphene compounds can be provided. Furthermore, according to one aspect of the present invention, a novel method for producing electrodes can be provided.

[0030] Furthermore, according to one aspect of the present invention, a secondary battery with less degradation can be provided. Furthermore, according to one aspect of the present invention, a secondary battery with high safety can be provided. Furthermore, according to one aspect of the present invention, a novel secondary battery can be provided.

[0031] Furthermore, according to one aspect of the present invention, novel materials, active material particles, secondary batteries, energy storage devices, or methods for producing the same can be provided.

[0032] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0033] [Figure 1] Figures 1A, 1B, and 1C show examples of cross-sections of electrodes. [Figure 2] Figures 2A and 2B show examples of cross-sections of electrodes. [Figure 3] Figure 3 is a diagram illustrating the crystal structure of the positive electrode active material. [Figure 4] Figure 4 is a diagram illustrating the crystal structure of the positive electrode active material. [Figure 5] Figure 5 is a phase diagram. [Figure 6] Figures 6A and 6B show an example of the manufacturing method. [Figure 7] Figure 7 shows an example of a method for manufacturing an electrode according to one aspect of the present invention. [Figure 8] Figures 8A and 8B illustrate an example of a method for producing a positive electrode active material according to one embodiment of the present invention. [Figure 9] Figure 9 illustrates an example of a method for producing a positive electrode active material according to one aspect of the present invention. [Figure 10] Figure 10 illustrates an example of a method for producing a positive electrode active material according to one embodiment of the present invention. [Figure 11] Figure 11 illustrates an example of a method for producing a positive electrode active material according to one aspect of the present invention. [Figure 12] Figures 12A and 12B are examples of cross-sectional views of a secondary battery. [Figure 13] Figures 13A and 13B show examples of the external appearance of a secondary battery. [Figure 14] Figures 14A and 14B illustrate the method for manufacturing a secondary battery. [Figure 15] Figures 15A and 15B illustrate the method for manufacturing a secondary battery. [Figure 16] Figure 16 shows an example of the appearance of a secondary battery. [Figure 17] Figure 17 is a top view showing an example of a secondary battery manufacturing apparatus. [Figure 18]Figure 18 is a cross-sectional view showing an example of a method for manufacturing a secondary battery. [Figure 19] Figures 19A to 19C are perspective views showing an example of a method for manufacturing a secondary battery. Figure 19D is a cross-sectional view corresponding to Figure 19C. [Figure 20] Figures 20A to 20F are perspective views showing an example of a method for manufacturing a secondary battery. [Figure 21] Figure 21 is a cross-sectional view showing an example of a secondary battery. [Figure 22] Figure 22A shows an example of a secondary battery. Figures 22B and 22C show an example of a method for fabricating a laminate. [Figure 23] Figures 23A to 23C show an example of a method for manufacturing a secondary battery. [Figure 24] Figures 24A and 24B are cross-sectional views showing an example of a laminate. Figure 24C is a cross-sectional view showing an example of a secondary battery. [Figure 25] Figures 25A and 25B show an example of a secondary battery. Figure 25C shows the inside of a secondary battery. [Figure 26] Figures 26A to 26C show an example of a secondary battery. [Figure 27] Figure 27A is a perspective view showing an example of a battery pack. Figure 27B is a block diagram showing an example of a battery pack. Figure 27C is a block diagram showing an example of a vehicle with a motor. [Figure 28] Figures 28A to 28E show examples of transport vehicles. [Figure 29] Figure 29A shows an electric bicycle, Figure 29B shows the secondary battery of an electric bicycle, and Figure 29C illustrates an electric motorcycle. [Figure 30] Figures 30A and 30B show an example of an energy storage device. [Figure 31] Figures 31A to 31E show examples of electronic devices. [Figure 32] Figures 32A to 32H illustrate an example of an electronic device. [Figure 33]Figures 33A to 33C illustrate an example of an electronic device. [Figure 34] Figure 34 illustrates an example of an electronic device. [Figure 35] Figures 35A to 35C illustrate an example of an electronic device. [Figure 36] Figures 36A to 36C show examples of electronic devices. [Figure 37] Figure 37 is an optical microscope image. [Figure 38] Figures 38A, 38B, and 38C show the evaluation results of Raman spectroscopy. [Figure 39] Figure 39 shows the Raman spectrum. [Figure 40] Figure 40 shows the TEM image. [Figure 41] Figures 41A and 41B are FFT filtered images of the TEM images. [Figure 42] Figures 42A and 42B are FFT filtered images of the TEM images. Figure 42C is a TEM image obtained by calculation. [Figure 43] Figure 43A shows the STEM image. Figure 43B shows the EDX analysis results. [Modes for carrying out the invention]

[0034] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and its form and details can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the embodiments described below.

[0035] Furthermore, in this specification, crystal planes and directions are indicated by Miller indices. In crystallography, crystal planes and directions are indicated by a superscript bar above the number, but in this specification, due to limitations in patent application notation, a minus sign (-) may be placed before the number instead of a bar above it. In addition, individual orientations indicating directions within a crystal are indicated by [ ], collective orientations indicating all equivalent directions are indicated by < >, individual planes indicating crystal planes are indicated by ( ), and collective planes having equivalent symmetry are indicated by {}.

[0036] In this specification, segregation refers to the phenomenon in which a certain element (e.g., B) is spatially non-uniformly distributed in a solid composed of multiple elements (e.g., A, B, C).

[0037] In this specification, the surface layer of particles such as active material is, for example, preferably within 50 nm from the surface, more preferably within 35 nm, and even more preferably within 20 nm. Surfaces formed by cracks and fissures may also be considered the surface. The region deeper than the surface layer is called the interior.

[0038] Furthermore, in this specification, the charge depth when all insertable and detachable lithium is inserted into the positive electrode active material is defined as 0, and the charge depth when all insertable and detachable lithium in the positive electrode active material has been detached is defined as 1.

[0039] In this specification, charging refers to the movement of lithium ions from the positive electrode to the negative electrode within the battery, and the movement of electrons from the positive electrode to the negative electrode in the external circuit. For positive electrode active material, the release of lithium ions is referred to as charging. Furthermore, positive electrode active material with a charging depth of 0.7 to 0.9 may be referred to as positive electrode active material charged with high voltage.

[0040] Similarly, discharge refers to the movement of lithium ions from the negative electrode to the positive electrode within the battery, and the movement of electrons from the negative electrode to the positive electrode in the external circuit. For positive electrode active materials, the insertion of lithium ions is called discharge. Furthermore, a positive electrode active material with a charge depth of 0.06 or less, or a positive electrode active material that has been discharged to 90% or more of its charge capacity from a state where it was charged at a high voltage, is considered a sufficiently discharged positive electrode active material.

[0041] Furthermore, in this specification, a non-equilibrium phase change refers to a phenomenon that causes a nonlinear change in a physical quantity. For example, a non-equilibrium phase change is thought to occur around the peak in the dQ / dV curve obtained by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV), indicating a significant change in the crystal structure.

[0042] A secondary battery has, for example, a positive electrode and a negative electrode. The positive electrode is composed of a positive electrode active material. The positive electrode active material is, for example, a substance that performs a reaction that contributes to the charge and discharge capacity. However, the positive electrode active material may also contain a portion of substances that do not contribute to the charge and discharge capacity.

[0043] In this specification, the positive electrode active material of one aspect of the present invention may be expressed as a positive electrode material, a positive electrode material for secondary batteries, etc. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a compound. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composition. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composite.

[0044] The discharge rate is the relative ratio of the discharge current to the battery capacity, and is expressed in units of C. For a battery with a rated capacity of X (Ah), the current equivalent to 1C is X (A). If the battery is discharged with a current of 2X (A), it is said to have been discharged at 2C, and if it is discharged with a current of X / 5 (A), it is said to have been discharged at 0.2C. Similarly, the charge rate is also expressed in the same way: if the battery is charged with a current of 2X (A), it is said to have been charged at 2C, and if it is charged with a current of X / 5 (A), it is said to have been charged at 0.2C.

[0045] Constant current charging refers to a method of charging while maintaining a constant charging rate. Constant voltage charging refers to a method of charging while maintaining a constant voltage once the upper voltage limit is reached. Constant current discharging refers to a method of discharging while maintaining a constant discharge rate.

[0046] (Embodiment 1) This embodiment describes graphene and electrodes according to one aspect of the present invention.

[0047] Graphene according to one aspect of the present invention has pores composed of multi-membered rings made of carbon. Preferably, the multi-membered rings are 9-membered or more. Examples of multi-membered rings with 9 or more members include 12-membered rings, 18-membered rings, and 22-membered rings.

[0048] In one aspect of the present invention, the pores in graphene are preferably formed by mixing a material that will become graphene as a first material, a compound having a halogen as a second material, and a compound that undergoes a eutectic reaction with the second material as a third material, and then heating the mixture. For example, graphene oxide can be used as the material that will become graphene.

[0049] Furthermore, graphene according to one embodiment of the present invention preferably has a halogen. Preferably, one or more carbon atoms constituting the multi-membered ring are terminated with a halogen atom. Fluorine is particularly preferred as the halogen.

[0050] Graphene according to one aspect of the present invention preferably has a functional group. Examples of functional groups that graphene according to one aspect of the present invention may have include a hydroxyl group, an epoxy group, and a carboxyl group. Furthermore, the functional group that graphene according to one aspect of the present invention may be bonded to the carbon atoms constituting the multi-membered ring that graphene according to one aspect of the present invention may have.

[0051] Graphene according to one aspect of the present invention has a sheet-like shape. Graphene has a two-dimensional structure formed of six-membered carbon rings. In other words, graphene is a sheet having a two-dimensional structure formed of six-membered carbon rings, and graphene according to one aspect of the present invention has pores in a part of the sheet that are composed of multi-membered carbon rings.

[0052] An electrode according to one aspect of the present invention comprises active material particles and graphene. Preferably, the graphene covers at least a portion of the surface of the active material particles.

[0053] An electrode according to one aspect of the present invention comprises an active material particle and a plurality of graphenes. At least a portion of the surface of the active material particle may be covered by the plurality of graphenes. The plurality of graphenes may have overlapping regions and non-overlapping regions. By overlapping portions of the plurality of graphenes, a sheet with a larger area can be formed. For example, a first graphene has a first region that overlaps with the active material particle and a second graphene. The first region is located on the surface of the active material particle. The first region is sandwiched between the active material particle and the second graphene. By overlapping the second graphene on the first region of the first graphene, for example, portions of the first graphene and the second graphene can be overlapped. Furthermore, the first graphene and the second graphene may have bonds in the overlapping regions. Also, they may attract each other by intermolecular forces in the overlapping regions.

[0054] The graphene is provided so as to adhere to the surface of the active material particles. Preferably, the graphene has a region that is in surface contact with the active material particles. Furthermore, it is preferable that the graphene is provided so as to adhere to the surface of the active material.

[0055] Furthermore, an electrode according to one aspect of the present invention comprises a plurality of active material particles and graphene. Preferably, the graphene covers at least a portion of the surface of each of the plurality of active material particles. It is also preferable that the graphene clings to the plurality of active material particles.

[0056] Furthermore, an electrode according to one aspect of the present invention comprises a plurality of active material particles and a plurality of graphene. The plurality of graphene have overlapping regions, thereby forming a sheet with a larger area. Preferably, the sheet covers at least a portion of the surface of each of the plurality of active material particles. It is also preferable that the sheet clings to the plurality of active materials.

[0057] Furthermore, in an electrode according to one embodiment of the present invention, graphene forms a bag-like region. The bag-like region may be composed of multiple graphenes. For example, multiple graphenes can form a bag-like region by having overlapping regions. Multiple active material particles are enclosed within the bag-like region.

[0058] In one embodiment of the present invention, multiple graphenes can form a three-dimensional conductive path. In another embodiment of the present invention, multiple graphenes may form a three-dimensional network structure.

[0059] An electrode according to one aspect of the present invention comprises, for example, a current collector and an active material layer. The active material layer is provided on the current collector. The active material layer comprises an active material and graphene. The active material layer may also have a binder.

[0060] As the current collector, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, and alloys thereof, which have high conductivity and do not alloy with carrier ions such as lithium, can be used. Also, an aluminum alloy added with elements for improving heat resistance such as silicon, titanium, neodymium, scandium, molybdenum, etc. can be used. Further, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as sheet, net, punching metal, expanded metal, etc. The current collector preferably has a thickness of 10 μm or more and 30 μm or less.

[0061] In addition, as the current collector used for the negative electrode, it is preferable to use a material that does not alloy with carrier ions such as lithium.

[0062] A titanium compound may be provided by laminating on the above-described metal element as the current collector. As the titanium compound, for example, titanium nitride, titanium oxide, titanium nitride in which a part of nitrogen is substituted with oxygen, titanium oxide in which a part of oxygen is substituted with nitrogen, and titanium oxynitride (TiO z N w , 0 < z < 2, 0 < w < 1) can be selected singly, or two or more can be mixed or laminated and used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material and the metal in the active material layer formed on the current collector can be suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there may be a concern about the oxidation reaction between the oxygen in graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed.

[0063] In one embodiment of the present invention, the strength of the active material layer can be increased by distributing multiple graphene particles within the electrode so as to spread three-dimensionally and cover the active material. By increasing the strength of the active material layer, for example, the collapse of the active material layer can be suppressed. Furthermore, by having a portion of each of the multiple graphene particles in contact with the current collector, for example, the peeling of the active material layer from the current collector can be suppressed. Within the electrode, the graphene may function as a conductive agent that provides conductive paths, as well as as a binder that increases the strength of the active material layer and the electrode.

[0064] In the longitudinal section of the active material layer, sheet-like graphene is dispersed approximately uniformly within the internal region of the active material layer. Multiple graphene particles are formed to partially cover multiple granular active materials or to adhere to the surfaces of multiple granular active materials, thus being in surface contact with each other. Here, the longitudinal section of the active material layer refers, for example, to a surface approximately perpendicular to the current collector.

[0065] Here, multiple graphene particles can bond together to form a three-dimensional conductive path. This three-dimensional conductive path formed by the bonding of multiple graphene particles will be referred to as a graphene net below. When the active material is coated with a graphene net, the graphene net can also function as a binder that bonds the active material particles together. Therefore, the amount of binder can be reduced or eliminated, thereby increasing the ratio of the active material to the electrode volume and electrode weight. In other words, the charge and discharge capacity of the secondary battery can be increased.

[0066] The active material layer can be prepared, for example, using graphene oxide and an active material. In the preparation of the active material layer, it is preferable to mix graphene oxide with the active material to form a layer that will become the active material layer, and then reduce the graphene oxide to obtain graphene. In other words, it is preferable that the completed active material layer has reduced graphene oxide. In the preparation of the active material layer, by using graphene oxide, which has extremely high dispersibility in polar solvents, the graphene oxide can be uniformly dispersed in a slurry containing graphene oxide and the active material. Therefore, in the prepared active material layer, graphene can be dispersed approximately uniformly within the internal region of the active material layer. By volatilizing and removing the solvent from the dispersion medium containing uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene remaining in the active material layer partially overlaps and is dispersed to the extent that it is in surface contact with each other, thereby forming a three-dimensional conductive path. The reduction of graphene oxide may be performed, for example, by heat treatment or by using a reducing agent. The slurry is, for example, a mixture of the raw materials for the active material layer and a solvent.

[0067] Alternatively, a spray-drying device can be used to pre-cover at least a portion of the surface of the active material with graphene, which is a conductive agent, to form a coating. Then, the active materials with the graphene coatings can be electrically connected with graphene to form conductive paths.

[0068] In this specification, graphene may include, for example, graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multigraphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multigraphene oxide, graphene quantum dots, etc. Graphene refers to a material having carbon, having a plate-like or sheet-like shape, and having a two-dimensional structure formed by six-membered carbon rings. This two-dimensional structure formed by six-membered carbon rings may also be called a carbon sheet. Graphene may have functional groups. Furthermore, graphene preferably has a bent shape. Graphene may also be rolled up to resemble carbon nanofibers.

[0069] In this specification, graphene oxide refers to, for example, a material having carbon and oxygen, having a sheet-like structure, and having functional groups, particularly epoxy groups, carboxyl groups, or hydroxyl groups.

[0070] In this specification, reduced graphene oxide refers to, for example, a material having carbon and oxygen, having a sheet-like shape, and possessing a two-dimensional structure formed by a six-membered carbon ring. It may also be called a carbon sheet. Reduced graphene oxide can function as a single sheet, but multiple sheets may be stacked. It is preferable that reduced graphene oxide has a portion in which the carbon concentration is greater than 80 atomic%, and the oxygen concentration is between 2 atomic% and 15 atomic%. By having at least one or both of these carbon and oxygen concentrations, it can function as a highly conductive material even in small amounts.

[0071] In some cases, pores can be created in graphene by reducing graphene oxide.

[0072] Furthermore, the ends of the graphene may be terminated with halogen atoms, particularly fluorine.

[0073] When graphene is analyzed using Raman spectroscopy, a peak called the G band may be observed. The G band is located at 1580 cm⁻¹ in the Raman spectrum. -1 It refers to a peak in or near that location. The observation of the G band suggests the presence of carbon sp2 bonds. In addition, if graphene has defects such as pores, a peak called the D band may be observed. The D band is at 1360 cm⁻¹ in the Raman spectrum. -1 It refers to a peak in the vicinity of that peak.

[0074] A ratio of D-band peak intensity to G-band peak intensity (D / G) of less than 1 suggests, for example, a low defect density in graphene. Conversely, if graphene has defects such as pores, the D / G ratio may be greater than 1, for example, between 1 and 3, or between 1 and 2.

[0075] ToF-SIMS may allow observation of the bonds that constitute the pores in graphene, or the functional groups that bond to the atoms that make up the pores. TEM observation may also allow observation of the pores in graphene.

[0076] When graphene is observed using high-resolution TEM images, pores composed of multi-membered rings may be observed.

[0077] In one embodiment of the present invention, it is preferable that pores composed of multi-membered rings are observed by TEM observation. Furthermore, in one embodiment of the present invention, it is particularly preferable that pores composed of multi-membered rings of 9 or more members are observed by TEM observation.

[0078] Graphene can be observed, for example, by FFT filtering of a TEM image. An FFT filtering image is an image obtained by applying an FFT (Fast Fourier Transform) to a TEM image, and then applying an IFFT (Inverse Fast Fourier Transform) to that image.

[0079] An electrode according to one aspect of the present invention can be suitably used in lithium-ion secondary batteries. In the electrode according to one aspect of the present invention, the graphene has pores, which allows lithium ions, which are carrier ions, to pass through the pores. Therefore, even when graphene covers the surface of the active material, it does not hinder the insertion and removal of lithium from the active material, and excellent secondary battery characteristics can be achieved. For example, it is preferable that the graphene has pores composed of multi-membered rings of 9 or more members, as lithium ions can easily pass through the pores. In multi-membered rings with fewer than 9 members, when lithium ions pass through the pores, the distance between the carbon atoms constituting the pores and the lithium ions is small, which may result in a high barrier energy for lithium ions to pass through the pores.

[0080] In multi-membered rings with nine or more members, the distance between the carbon atoms constituting the pore and the lithium ion is moderately large, which can lead to energy stability and a lower barrier energy for lithium ions to pass through the pore. Furthermore, halogens, especially fluorine, have high electronegativity and tend to carry a negative charge. Therefore, when the carbon atoms constituting the pore are terminated by halogens, an interaction occurs as positively charged lithium ions approach, stabilizing the energy and lowering the barrier energy for lithium ions to pass through the pore.

[0081] Halogens, particularly fluorine, can form hydrogen bonds with hydrogen atoms. In one embodiment of the present invention, graphene contains halogens, and if the active material has hydrogen-terminated regions or regions terminated by functional groups having hydrogen atoms, hydrogen bonds can be formed, allowing the graphene to adhere to the active material.

[0082] An electrode according to one aspect of the present invention can be used as the positive and negative electrodes of a secondary battery. A secondary battery according to one aspect of the present invention has a positive electrode having graphene according to one aspect of the present invention and a negative electrode having graphene according to one aspect of the present invention.

[0083] When using an electrode according to one embodiment of the present invention as a positive electrode, a positive electrode active material may be used as the active material. When using an electrode according to one embodiment of the present invention as a negative electrode, a negative electrode active material may be used as the active material.

[0084] <Example of an electrode> Figure 1A is a schematic cross-sectional view showing an electrode according to one embodiment of the present invention. The electrode 570 shown in Figure 1A can be applied to the positive and negative electrodes of a secondary battery. The electrode 570 includes at least a current collector 571 and an active material layer 572 formed in contact with the current collector 571.

[0085] Figures 1B, 1C, 2A, and 2B are enlarged views of the rectangular region 570b enclosed by the dashed line in Figure 1A. The active material layer 572 comprises an electrolyte 581, particles 582, and graphene 583.

[0086] The active material layer 572 shown in Figure 1B has particles 582 covered with graphene 583. In Figure 1B, the graphene 583 may also cover the surface of multiple particles 582.

[0087] In the active material layer 572 shown in Figure 1C, a portion of the surface of the particles 582 is covered with graphene 583. In some cases, the graphene 583 may also cover the surface of multiple particles 582. Furthermore, the graphene 583 is distributed to form a three-dimensional conductive path within the electrode.

[0088] In the active material layer 572 shown in Figure 2A, multiple particles 582 are aggregated. Of these aggregated particles 582, some are covered by graphene 583. Furthermore, the graphene 583 is distributed to form a three-dimensional conductive path within the electrode.

[0089] In the active material layer 572 shown in Figure 2B, multiple graphenes 583 form a three-dimensional network structure, and particles 582 are arranged between the multiple graphenes 583.

[0090] The particles 582 preferably function as an active material. A material that functions as an active material can be used as the particles 582. Alternatively, it is preferable that the particles 582 have, for example, a material that functions as an active material. In this specification, particles 582 are referred to as active material particles. Various materials can be used as particles 582. Materials that can be used as particles 582 will be described later.

[0091] The active material layer 572 has graphene 583. Graphene 583 can function as a conductive agent.

[0092] Furthermore, it is preferable that the active material layer 572 contains carbon-based materials such as carbon black, graphite, carbon fiber, or fullerene in addition to graphene. For example, acetylene black (AB) can be used as carbon black. For example, natural graphite or artificial graphite such as mesocarbon microbeads can be used as graphite. These carbon-based materials have high conductivity and can function as conductive agents in the active material layer. These carbon-based materials may also function as active materials. Figures 1B and 1C show an example in which the active material layer 572 contains acetylene black 584.

[0093] Examples of carbon fibers that can be used include mesophase pitch carbon fibers and isotropic pitch carbon fibers. Carbon nanofibers and carbon nanotubes can also be used. Carbon nanotubes can be fabricated, for example, by vapor deposition.

[0094] The active material layer may also contain one or more conductive materials selected from metal powders such as copper, nickel, aluminum, silver, and gold, metal fibers, and conductive ceramic materials.

[0095] The content of the conductive additive relative to the total amount of the active material layer is preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%. Furthermore, when the active material layer contains graphene and graphene oxide is used as the material for the graphene, the content of graphene oxide relative to the total amount of the active material, graphene oxide, and binder in the slurry for forming the active material layer is preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%.

[0096] Unlike granular conductive agents such as carbon black, which make point contact with the active material, graphene enables surface contact with low contact resistance. Therefore, it is possible to improve the electrical conductivity between granular active material and graphene with a smaller amount than with conventional conductive agents. Consequently, the ratio of active material in the active material layer can be increased. This, in turn, can increase the discharge capacity of secondary batteries.

[0097] Furthermore, because the graphene in one aspect of the present invention allows lithium to pass through easily, it can increase the charge and discharge rate of the secondary battery.

[0098] Particulate carbon-containing compounds such as carbon black and graphite, and fibrous carbon-containing compounds such as carbon nanotubes, readily enter minute spaces. These minute spaces refer, for example, to regions between multiple active materials. By combining carbon-containing compounds that readily enter minute spaces with sheet-like carbon-containing compounds such as graphene, which can impart conductivity across multiple particles, the electrode density can be increased, forming excellent conductive paths. Furthermore, by having an electrolyte according to one aspect of the present invention, the operational stability of the secondary battery can be enhanced. In other words, a secondary battery according to one aspect of the present invention combines high energy density with stability, making it effective as an in-vehicle secondary battery. Increasing the number of secondary batteries increases the vehicle's weight, which in turn increases the energy required to move it, thus shortening the driving range. By using high-density secondary batteries, the driving range can be extended without significantly changing the total weight of a vehicle equipped with the same weight of secondary batteries.

[0099] Furthermore, as the capacity of a vehicle's secondary battery increases, more power is required for charging. Therefore, to complete charging in a short time, it is desirable to charge under high-rate charging conditions. In addition, regenerative charging, which temporarily generates electricity when the vehicle brakes are applied and then charges the battery, is carried out under high-rate charging conditions, so good rate characteristics are required for vehicle secondary batteries.

[0100] Because graphene has high conductivity, its proportion in the electrode can be reduced. Therefore, the surface area of ​​the conductive agent in the electrode can be reduced, thereby suppressing the decomposition of the electrolyte. Decomposition of the electrolyte can be particularly pronounced at high temperatures. Therefore, a secondary battery using an electrode according to one embodiment of the present invention can suppress degradation at high temperatures. Furthermore, because graphene has high conductivity, the secondary battery can operate at high output even at low temperatures. Therefore, by using an electrode according to one embodiment of the present invention, a secondary battery for automotive use with a wide operating temperature range can be obtained. In addition, by using an ionic liquid as the electrolyte, the decomposition of the electrolyte at high temperatures can be suppressed, resulting in a secondary battery that can operate at high temperatures.

[0101] Furthermore, the secondary battery according to one embodiment of the present invention can be miniaturized due to its high energy density, and rapid charging is possible due to its high conductivity. Therefore, the configuration of the secondary battery according to one embodiment of the present invention is also effective in portable information terminals.

[0102] The active material layer 572 preferably has a binder (not shown). The binder binds or fixes, for example, the electrolyte and the active material. The binder can also bind or fix the electrolyte and a carbon-based material, the active material and a carbon-based material, multiple active materials to each other, multiple carbon-based materials, etc.

[0103] It is preferable to use materials such as polystyrene, methyl polyacrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose as binders.

[0104] Polyimides possess excellent thermal, mechanical, and chemical stability. Furthermore, when polyimides are used as a binder, dehydration and cyclization (imidization) reactions are performed. These reactions can be carried out, for example, by heat treatment. In one embodiment of the present invention, when graphene having oxygen-containing functional groups is used as the graphene and polyimides as the binder, the heat treatment can also reduce the graphene, simplifying the process. Due to its excellent heat resistance, the heat treatment can be performed at temperatures of, for example, 200°C or higher. By performing the heat treatment at temperatures of 200°C or higher, the reduction reaction of graphene can be sufficiently carried out, further improving the conductivity of the electrode.

[0105] Fluorine-containing polymer materials, specifically polyvinylidene fluoride (PVDF), can be used. PVDF is a resin with a melting point in the range of 134°C to 169°C, and is a material with excellent thermal stability.

[0106] Furthermore, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer as a binder. Fluororubber can also be used as a binder.

[0107] Furthermore, it is preferable to use a water-soluble polymer as the binder. Examples of water-soluble polymers include polysaccharides. One or more polysaccharides can be selected from cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, as well as starch. It is even more preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0108] You may use a combination of several of the binders mentioned above.

[0109] Furthermore, graphene 583 is flexible and pliable, and can cling to particles 582 like natto (fermented soybeans). For example, particles 582 can be likened to soybeans, and graphene 583 to a sticky component, such as polyglutamic acid. By arranging graphene 583 between materials such as the electrolyte, multiple active materials, and multiple carbon-based materials in the active material layer 572, not only is a good conductive path formed within the active material layer 572, but these materials can also be bound or fixed using graphene 583. For example, by forming a three-dimensional network structure, a structure with arranged polygons, such as a honeycomb structure with hexagons arranged in a matrix, using multiple graphene 583s, and arranging materials such as the electrolyte, multiple active materials, and multiple carbon-based materials in the network, the graphene can form a three-dimensional conductive path, and the detachment of the electrolyte from the current collector can be suppressed. In addition, in the above-mentioned structure with arranged polygons, polygons with different numbers of sides may be mixed together. Therefore, graphene 583 may function as both a conductive agent and a binder in the active material layer 572.

[0110] The particle 582 can have various shapes, such as rounded shapes or angular shapes. Furthermore, in the cross-section of the electrode, the particle 582 can have various cross-sectional shapes, such as circles, ellipses, curved shapes, polygons, etc. For example, Figure 2A shows an example where the cross-sectional shape of the particle 582 is rounded, but the cross-sectional shape of the particle 582 may also have angular shapes. Alternatively, it may have both rounded and angular parts.

[0111] <An example of a negative electrode active material> When electrode 570 is the negative electrode, particles having a negative electrode active material can be used as particle 582. It is preferable to use a material that can react with carrier ions of a secondary battery, a material that can insert and remove carrier ions, a material that can alloy with a metal that becomes a carrier ion, a material that can dissolve and precipitate a metal that becomes a carrier ion, etc., as the negative electrode active material.

[0112] As the negative electrode active material, silicon can be used. The electrode 570 preferably uses particles having silicon as the particles 582.

[0113] Also, as the negative electrode active material, a metal or a compound having one or more elements selected from tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium can be used. Examples of alloy-based compounds using such elements include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc.

[0114] Also, impurities such as phosphorus, arsenic, boron, aluminum, gallium, etc. may be added to silicon as impurity elements, and a material with reduced resistance may be used. Also, a silicon material pre-doped with lithium may be used. Examples of pre-doping methods include mixing silicon with lithium fluoride or lithium carbonate and annealing, mechanical alloying of lithium metal and silicon, etc. Also, after forming as an electrode, it may be combined with an electrode such as lithium metal and doped with lithium by a charge-discharge reaction, and then, a secondary battery may be fabricated by combining an electrode that becomes a counter electrode (for example, a positive electrode with respect to a pre-doped negative electrode) using the doped electrode.

[0115] For example, silicon nanoparticles can be used as the particles 582. The average diameter of the silicon nanoparticles is, for example, preferably 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0116] The silicon nanoparticles may have crystallinity. Also, the silicon nanoparticles may have a crystalline region and an amorphous region.

[0117] Examples of materials having silicon include SiO zA material represented by (where z is preferably less than 2, and more preferably between 0.5 and 1.6) can be used.

[0118] As a material containing silicon, for example, a form having multiple crystal grains within a single particle can be used. For example, a form having one or more silicon crystal grains within a single particle can be used. Furthermore, the single particle may have silicon oxide surrounding the silicon crystal grain. Furthermore, the silicon oxide may be amorphous. It may also be a particle in which graphene is attached to a secondary silicon particle.

[0119] Furthermore, as silicon-containing compounds, for example, Li2SiO3 and Li4SiO4 can be used. Li2SiO3 and Li4SiO4 may be crystalline or amorphous, respectively.

[0120] The analysis of silicon-containing compounds can be performed using NMR, XRD, Raman spectroscopy, SEM, TEM, EDX, etc.

[0121] Furthermore, carbon-based materials such as graphite, easily graphitizable carbon, poorly graphitizable carbon, carbon nanotubes, carbon black, and graphene can be used as the negative electrode active material.

[0122] Furthermore, as the negative electrode active material, for example, an oxide having one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0123] Multiple metals, materials, compounds, etc., as described above can be used in combination as the negative electrode active material.

[0124] Examples of negative electrode active materials include SnO, SnO2, titanium dioxide (TiO2), and lithium titanium oxide (Li4Ti5O2). 12 ), lithium-graphite intercalation compound (Li z Oxides such as C6, niobium pentoxide (Nb2O5), tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used.

[0125] Furthermore, as the negative electrode active material, a Li3N type structure is used, which is a lithium and transition metal binitride. 3-z M z N (M = Co, Ni, Cu, z is between 0 and 3) can be used. For example, Li 2.6 Co 0.4 N3 is preferable because it exhibits a large charge / discharge capacity (900mAh / g).

[0126] When lithium and transition metal binitrides are used as the negative electrode material, it is preferable that they be combined with lithium-ion-free materials such as V2O5 and Cr3O8 as the positive electrode material. Even when a lithium-ion-containing material is used as the positive electrode material, lithium and transition metal binitrides can be used as the negative electrode material by removing the lithium ions contained in the positive electrode material beforehand.

[0127] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not undergo alloying reactions with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may be used as the negative electrode active material. Other materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, Cr2O3, and CoS 0.89 Examples include sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3. Since the potential of these fluorides is high, they may also be used as positive electrode materials.

[0128] Furthermore, although particle 582 may undergo volume changes during charging and discharging, by arranging a fluorine-containing electrolyte between multiple particles 582 within the electrode, the material becomes more fluid even when volume changes occur during charging and discharging, suppressing crack formation and dramatically improving cycle characteristics. It is important that fluorine-containing organic compounds are present between the multiple active materials that make up the electrode.

[0129] <Example of positive electrode active material> When the electrode 570 is a positive electrode, particles 582 having a positive electrode active material can be used as the particles. Examples of the positive electrode active material include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, compounds such as LiFePO4, LiFeO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2 can be mentioned.

[0130] In addition, a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 as the positive electrode active material is preferably mixed with lithium nickelate (LiNiO2 or LiNi 1-z Mj z O2 (0 < z < 1) (Mj = Co, Al, etc.)). By adopting such a configuration, the characteristics of the secondary battery can be improved.

[0131] In addition, as the positive electrode active material, the composition formula Li a Mn b Mk c O dA lithium manganese composite oxide can be used, which can be represented as follows: Here, the element Mk is preferably a metallic element selected from lithium and manganese, or silicon or phosphorus, and more preferably nickel. Furthermore, when measuring the entire particle of the lithium manganese composite oxide, <a / (b+c)<2、かつc>it is preferable that the discharge is 0 0 and 0.26 ≤ (b+c) / d < 0.5. The composition of metals, silicon, phosphorus, etc., of the entire particle of the lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle of the lithium manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectroscopy). In addition, it can be determined by using molten gas analysis and valence evaluation of XAFS (X-ray absorption fine structure) analysis in combination with ICP-MS analysis. Lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may also contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0132] ​Furthermore, as the positive electrode active material, particles having multiple positive electrode active materials as listed above may be used. For example, one of the positive electrode active materials listed above and another may be used to form particles having a structure in which at least a portion of one positive electrode active material is covered by the other. Such particles having a structure in which at least a portion of one is covered by the other are sometimes called positive electrode active material composites. As for the composite treatment, one or more of the following composite treatments can be performed: composite treatments using mechanical energy such as mechanochemical methods, mechanofusion methods, and ball milling methods; composite treatments using liquid-phase reactions such as coprecipitation methods, hydrothermal methods, and sol-gel methods; and composite treatments using gas-phase reactions such as barrel sputtering, ALD (Atomic Layer Deposition), vapor deposition, and CVD (Chemical Vapor Deposition). It is also preferable to perform a heat treatment after the composite treatment. Note that the composite treatment is sometimes called a surface coating treatment or coating treatment.

[0133] Furthermore, positive electrode active material particles may form secondary particles. For example, in the structures shown in Figures 1B and 1C, particle 582 may be replaced with secondary particles formed by the positive electrode active material particles.

[0134] [Structure of the positive electrode active material] Materials having a layered rock salt-type crystal structure, such as lithium cobalt oxide (LiCoO2), are known to have high discharge capacity and are excellent as positive electrode active materials for secondary batteries. Examples of materials having a layered rock salt-type crystal structure include composite oxides represented by LiMO2. Element M is, for example, one or more elements including a transition metal. Alternatively, element M may include, for example, one or more metals including cobalt, and further, one or more elements selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0135] Alternatively, a positive electrode active material according to one aspect of the present invention comprises lithium, element M, and additive element X. Examples of additive element X include magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, zinc, titanium, yttrium, nickel, aluminum, cobalt, manganese, vanadium, iron, chromium, niobium, hafnium, silicon, sulfur, phosphorus, boron, arsenic, chlorine, and fluorine.

[0136] It is known that the Jahn-Teller effect in transition metal compounds differs in strength depending on the number of electrons in the d orbitals of the transition metal.

[0137] In nickel-containing compounds, distortion can easily occur due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged at high voltages, there is a concern that the crystal structure may collapse due to distortion. In LiCoO2, the effect of the Jahn-Teller effect is suggested to be smaller, and it may have better resistance to high-voltage charging and discharging, making it preferable.

[0138] Here, the composition of the lithium composite oxide represented by LiMO2 is not limited to Li:M:O=1:1:2. Examples of lithium composite oxides represented by LiMO2 include lithium cobaltate, lithium nickel-cobalt-manganate, lithium nickel-cobalt-aluminate, and lithium nickel-cobalt-manganate.

[0139] Using cobalt as element M in an amount of 75 atomic% or more, preferably 90 atomic% or more, and more preferably 95 atomic% or more, offers many advantages, such as being relatively easy to synthesize, easy to handle, and having excellent cycle properties.

[0140] On the other hand, using nickel as element M in an amount of 33 atomic% or more, preferably 60 atomic% or more, and more preferably 80 atomic% or more, may result in lower raw material costs compared to cases with a high cobalt content, and may also increase the charge / discharge capacity per unit weight, which is preferable.

[0141] Furthermore, if nickel is used as element M in an amount of 33 atomic% or more, preferably 60 atomic% or more, and more preferably 80 atomic% or more, the particle size may become smaller. Therefore, for example, it is preferable that the third particle described above contains 33 atomic% or more, preferably 60 atomic% or more, nickel as element M, and more preferably 80 atomic% or more.

[0142] Furthermore, the presence of nickel along with cobalt as element M can suppress the displacement of the layered structure composed of octahedra of cobalt and oxygen. This is preferable, as it can lead to a more stable crystal structure, especially in the charged state at high temperatures. This is because nickel can easily diffuse into the interior of lithium cobalt oxide, and while it may be present at the cobalt sites during discharge, it can be cation-mixed and positioned at the lithium sites during charging. Nickel present at the lithium sites during charging is thought to function as pillars supporting the layered structure composed of octahedra of cobalt and oxygen, contributing to the stabilization of the crystal structure.

[0143] Furthermore, element M does not necessarily have to include manganese, nickel, or cobalt.

[0144] During charging, lithium is released from the surface of the particles, so the lithium concentration in the surface layer of the particles tends to be lower than in the interior, making the crystal structure more prone to collapse.

[0145] A particle according to one aspect of the present invention comprises lithium, element M, and oxygen. Furthermore, the particle according to one aspect of the present invention includes a lithium composite oxide represented as LiMO2. Additionally, the particle according to one aspect of the present invention has one or more elements selected from magnesium, fluorine, aluminum, and nickel in its surface layer. By having one or more of these elements in the surface layer of the particle according to one aspect of the present invention, structural changes associated with charging and discharging can be reduced in the surface layer of the particle, and crack formation can be suppressed. Furthermore, irreversible structural changes in the surface layer of the particle can be suppressed, and capacity reduction associated with repeated charging and discharging can be suppressed. It is also preferable that the concentration of these elements in the surface layer is higher than the concentration of these elements in the entire particle. Furthermore, in one aspect of the present invention, the particle may have a structure in which, for example, in the lithium composite oxide, some of the atoms are substituted with one or more elements selected from magnesium, fluorine, aluminum, and nickel in the surface layer.

[0146] The positive electrode active material will be explained using Figures 3 and 4.

[0147] In this specification, the layered rock salt crystal structure belonging to space group R-3m, which is found in composite oxides containing lithium and transition metals such as cobalt, refers to a crystal structure that has a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, thereby enabling two-dimensional diffusion of lithium. Defects such as vacancies in cations or anions may be present. Furthermore, strictly speaking, the layered rock salt crystal structure may have a distorted lattice structure of the rock salt crystal.

[0148] Furthermore, in this specification, a rock salt-type crystal structure refers to a cubic crystal structure having a space group Fm-3m and other similar structures, in which cations and anions are arranged alternately. Note that cation or anion deficiencies may be present.

[0149] The approximate agreement of crystal orientation in two regions can be determined from TEM (Transmission Electron Microscope) images, STEM (Scanning Transmission Electron Microscope) images, HAADF-STEM (High-angle Annular Dark Field Scanning TEM) images, ABF-STEM (Annular Bright-Field Scanning Transmission Electron Microscope) images, etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as a basis for determination. In high-resolution TEM images, contrast originating from crystal planes can be obtained. Due to electron diffraction and interference, for example, when an electron beam is incident perpendicular to the c-axis of a layered rock salt composite hexagonal lattice, contrast originating from the (0003) plane is obtained as a repetition of bright bands (bright strips) and dark bands (dark strips). Therefore, in a TEM image, if the angle between bright fringes is between 0 and 5 degrees, or between 0 and 2.5 degrees, it can be determined that the crystal planes roughly coincide, i.e., the crystal orientation roughly coincides. Similarly, if the angle between dark fringes is 5 degrees or less, or 2.5 degrees or less, it can also be determined that the crystal orientation roughly coincides.

[0150] The positive electrode active material produced according to one aspect of the present invention can reduce the displacement of the CoO2 layer during repeated high-voltage charging and discharging. Furthermore, it can reduce volume changes. Therefore, the compound can achieve excellent cycle characteristics. In addition, the compound can adopt a stable crystal structure in a high-voltage charged state. Therefore, when the compound is maintained in a high-voltage charged state, short circuits may be less likely to occur. In such cases, safety is further improved, which is preferable.

[0151] In this compound, the difference in crystal structure and volume per unit number of transition metal atoms between a fully discharged state and a high-voltage charged state is small.

[0152] Figure 3 shows an example of the crystal structure of the positive electrode active material before and after charging and discharging. The positive electrode active material shown in Figure 3 preferably has a layered rock salt type crystal structure that belongs to space R-3m in the discharge state. In addition, the surface layer of the positive electrode active material may have crystals that contain titanium, magnesium, and oxygen, and have a structure different from the layered rock salt type structure, in addition to or instead of the region represented by the layered rock salt type structure. For example, it may have crystals that contain titanium, magnesium, and oxygen and have a spinel structure.

[0153] The theoretical capacity of a positive electrode active material refers to the amount of electric charge that would be generated if all of the insertable and removeable lithium in the positive electrode active material were to be removed. For example, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 274 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g.

[0154] Furthermore, the extent to which insertable and detachable lithium remains in the positive electrode active material is determined by x in the composition formula, for example, Li x x in CoO2, or Li x Indicated by x in MO2. Li in this specification. x CoO2 contains Li as appropriate. x This can be interpreted as MO2. In the case of the positive electrode active material in a secondary battery, x can be expressed as x = (theoretical capacity - charging capacity) / theoretical capacity. For example, when a secondary battery using LiCoO2 as the positive electrode active material is charged at 219.2 mAh / g, Li 0.2 It can be expressed as CoO2 or x=0.2. x A small x in CoO2 means, for example, 0.1 <x≦0.24をいう。

[0155] When properly synthesized lithium cobalt oxide, before being used as the positive electrode, approximately satisfies the stoichiometric ratio, it is LiCoO2 and the lithium occupancy rate x=1 at the lithium site is 1. Similarly, a secondary battery that has finished discharging is also LiCoO2 and can be said to have x=1. Discharge completion here refers to the state where, for example, with a current of 100mA / g, the voltage falls below 2.5V (counter electrode lithium). In lithium-ion secondary batteries, when the lithium occupancy rate at the lithium site becomes x=1 and no more lithium can be added, the voltage drops sharply. At this point, discharge can be said to have finished. Generally, in lithium-ion secondary batteries using LiCoO2, the discharge voltage drops sharply before reaching 2.5V, so discharge is considered to have finished under the above conditions.

[0156] A charging depth of 0 refers to, for example, the state where x = 1 in the above example. Furthermore, an increasing charging depth refers to, for example, a decrease in the value of x in the above example.

[0157] Li x The charging and / or discharging capacities used to calculate x in CoO2 should preferably be measured under conditions with little or no influence from short circuits and / or electrolyte decomposition. For example, data from secondary batteries that have experienced a sudden change in capacity, which may be attributed to a short circuit, should not be used to calculate x.

[0158] The crystal structure at charge depth 0 (discharge completed) in Figure 3 is R-3m(O3), the same as in Figure 4. On the other hand, the positive electrode active material shown in Figure 3 has a crystal structure different from the H1-3 type crystal structure when it is sufficiently charged, for example, when x is 0.24 or less, for example, around 0.2 or around 0.12. This structure has a space group R-3m, and the symmetry of the CoO2 layer is the same as that of the O3 type. Therefore, this structure is referred to as the O3' type crystal structure in this specification. In the diagram of the O3' type crystal structure shown in Figure 3, it is stated that when x=0.2, lithium can be present at any lithium site with a probability of about 20%, but this is not limited to this. It may be present only at certain lithium sites. Furthermore, in both the O3 type crystal structure and the O3' type crystal structure, it is preferable that magnesium is present dilutely between the CoO2 layers, i.e., at the lithium sites. In addition, halogens such as fluorine may be present randomly and dilutely at the oxygen sites.

[0159] In the O3' type crystal structure, the space group is R-3m, and ions such as cobalt and magnesium occupy the 6-coordinate positions of oxygen. Light elements such as lithium may occupy the 4-coordinate positions of oxygen.

[0160] Furthermore, the O3' type crystal structure can be described as a crystal structure similar to the CdCl2 type crystal structure, although it has Li randomly placed between layers. This crystal structure similar to the CdCl2 type is observed when lithium nickelate is charged to a depth of charge of 0.94 (Li 0.06 Although its crystal structure is similar to that of NiO2, it is known that pure lithium cobaltate, or layered rock salt-type cathode active materials containing a large amount of cobalt, do not usually adopt this crystal structure.

[0161] The anions in layered rock salt crystals and rock salt crystals adopt a cubic close-packed structure (face-centered cubic lattice structure). It is also presumed that the anions in O3'-type crystals adopt a cubic close-packed structure. Therefore, when layered rock salt crystals and rock salt crystals are in contact, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned. However, the space group of layered rock salt crystals and O3'-type crystals is R-3m, which is different from the space group Fm-3m of rock salt crystals (the space group of typical rock salt crystals). Therefore, the Miller indices of the crystal planes that satisfy the above conditions differ between layered rock salt crystals and O3'-type crystals and rock salt crystals. In this specification, when the orientation of the cubic close-packed structure composed of anions is aligned in layered rock salt crystals, O3'-type crystals, and rock salt crystals, it is sometimes said that the crystal orientations are roughly the same.

[0162] In the positive electrode active material shown in Figure 3, the change in crystal structure when charged at high voltage and a large amount of lithium is released is further suppressed compared to the positive electrode active material shown in Figure 4. For example, as shown by the dotted line in Figure 3, there is almost no displacement of the CoO2 layer in these crystal structures.

[0163] More specifically, the positive electrode active material shown in Figure 3 exhibits high structural stability even at high charging voltages. For example, even at charging voltages where the H1-3 type crystal structure is formed in Figure 4, such as a voltage of approximately 4.6V relative to the lithium metal potential, the positive electrode active material shown in Figure 3 can maintain the R-3m(O3) crystal structure. Furthermore, even at even higher charging voltages, such as 4.65V to 4.7V relative to the lithium metal potential, there is a region in the positive electrode active material shown in Figure 3 where an O3' type crystal structure can be adopted. If the charging voltage is further increased above 4.7V, an H1-3 type crystal may be observed in the positive electrode active material shown in Figure 3. Moreover, even at lower charging voltages (for example, when the charging voltage is between 4.5V and 4.6V relative to the lithium metal potential), the positive electrode active material in Figure 3 may still adopt an O3' type crystal structure. Furthermore, in the case of a secondary battery, if graphite is used as the negative electrode active material, the voltage of the secondary battery will be lower than the voltage based on the potential of lithium metal by the amount of the potential of graphite. The potential of graphite is approximately 0.05V to 0.2V relative to the potential of lithium metal. Therefore, even when the voltage of a secondary battery using graphite as the negative electrode active material is between 4.3V and 4.5V, the positive electrode active material shown in Figure 3 can maintain the R-3m(O3) crystal structure, and there is a region where the O3' type crystal structure can be adopted even when the charging voltage is increased, for example, when the secondary battery voltage is above 4.5V and below 4.6V. Moreover, even at lower charging voltages, for example, when the secondary battery voltage is between 4.2V and 4.3V, the positive electrode active material shown in Figure 3 may be able to adopt the O3' type crystal structure.

[0164] Therefore, in the positive electrode active material shown in Figure 3, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0165] The crystal structure shown in Figure 4 has R-3m(O3) attached to it, which represents Li xThis is the crystal structure of lithium cobalt oxide with x=1 in CoO2. In this crystal structure, lithium occupies octahedral sites, and there are three CoO2 layers in a unit cell. For this reason, this crystal structure is sometimes called the O3 type crystal structure. The CoO2 layer is defined as a structure in which octahedral structures, in which oxygen is 6-coordinated to cobalt, are continuous in a plane with shared edges. This is sometimes referred to as a layer consisting of octahedra of cobalt and oxygen.

[0166] The lithium cobalt oxide shown in Figure 4 is known to have a crystal structure that belongs to the monoclinic space group P2 / m when x = approximately 0.5, as the symmetry of lithium increases. This structure has one CoO2 layer in the unit cell. For this reason, it is sometimes called the O1 type or monoclinic O1 type.

[0167] Furthermore, the positive electrode active material at x=0 has a crystal structure of the trigonal space group P-3m1, and also has one CoO2 layer in the unit cell. For this reason, this crystal structure is sometimes called O1 type or trigonal O1 type. In addition, the trigonal structure is sometimes converted to a composite hexagonal lattice and called hexagonal O1 type.

[0168] Furthermore, when x = approximately 0.12, the lithium cobalt oxide shown in Figure 4 has a crystal structure with space group R-3m. This structure can be described as a structure in which the trigonal O1 type CoO2 structure and the R-3m(O3) LiCoO2 structure are alternately stacked. For this reason, this crystal structure is sometimes called the H1-3 type crystal structure. Note that because actual lithium insertion and removal can be uneven, the H1-3 type crystal structure is experimentally observed from approximately x = 0.25. In reality, the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell compared to other structures. However, in this specification, etc., the H1-3 type crystal structure is sometimes shown with the c axis of the unit cell set to half in order to facilitate comparison with other crystal structures.

[0169] As an example, in the H1-3 type crystal structure, as described in Non-Patent Literature 1, the coordinates of cobalt and oxygen in the unit cell can be represented as Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are oxygen atoms, respectively. The unit cell that should be used to represent the crystal structure of the positive electrode active material can be determined, for example, by Rietveld analysis of the XRD pattern. In this case, the unit cell that yields the smallest GOF (goodness of fit) value should be adopted.

[0170] The positive electrode active material shown in Figure 3 is Li x The change in crystal structure between the discharge state where x is 1 and the state where x is 0.24 or less in CoO2 is even smaller compared to Figure 4. More specifically, the displacement of the CoO2 layer between the state where x is 1 and the state where x is 0.24 or less can be reduced. In addition, the change in volume when compared per cobalt atom can be reduced.

[0171] Furthermore, in the positive electrode active material shown in Figure 3, the difference in volume per unit number of cobalt atoms between the discharged state R-3m(O3) and the O3'-type crystal structure is 2.5% or less, more specifically 2.2% or less, and typically 1.8%.

[0172] In the O3' type crystal structure, the coordinates of cobalt and oxygen in the unit cell can be expressed as Co(0,0,0.5), O(0,0,x), and within the range of 0.20≦x≦0.25. The lattice constant of the unit cell is preferably 0.2797≦a≦0.2837(nm) for the a axis, more preferably 0.2807≦a≦0.2827(nm), and typically a=0.2817(nm). For the c axis, it is preferably 1.3681≦c≦1.3881(nm), more preferably 1.3751≦c≦1.3811(nm), and typically c=1.3781(nm).

[0173] Magnesium, randomly and dilutely present between CoO2 layers, i.e., at lithium sites, has the effect of suppressing the displacement of the CoO2 layers when charged at high voltage. Therefore, the presence of magnesium between CoO2 layers makes it easier for an O3' type crystal structure to form.

[0174] However, if the heat treatment temperature is too high, cation mixing occurs, increasing the likelihood of magnesium entering the cobalt site. Magnesium present in the cobalt site may have little effect in maintaining the R-3m structure during high-voltage charging. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium.

[0175] Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobalt oxide before the heat treatment to distribute magnesium throughout the particles. Adding a halogen compound lowers the melting point of lithium cobalt oxide. Lowering the melting point makes it easier to distribute magnesium throughout the particles at a temperature at which cation mixing is less likely to occur. Furthermore, if a fluorine compound is present, it can be expected that the corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte will be improved.

[0176] Furthermore, if the magnesium concentration is increased beyond the desired value, the effect on stabilizing the crystal structure may decrease. This is thought to be because magnesium will enter not only the lithium sites but also the cobalt sites. The number of magnesium atoms in the positive electrode active material produced according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times or less the number of cobalt atoms, more preferably greater than 0.01 times and less than 0.04 times, and even more preferably about 0.02 times. The magnesium concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, or it may be based on the value of the raw material composition during the process of producing the positive electrode active material.

[0177] The number of nickel atoms in the positive electrode active material is preferably 7.5% or less of the number of cobalt atoms, preferably 0.05% to 4%, and more preferably 0.1% to 2%. The nickel concentration shown here may be the value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, for example, or it may be based on the value of the raw material composition during the manufacturing process of the positive electrode active material.

[0178] <Particle size> If the particle size of the positive electrode active material is too large, problems arise such as difficulty in lithium diffusion and excessive roughness of the surface of the active material layer when coated onto the current collector. On the other hand, if it is too small, problems arise such as difficulty in supporting the active material layer when coating onto the current collector and excessive reaction with the electrolyte. Therefore, the average particle size (D50: also called the median diameter) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[0179] <Analysis method> Whether a positive electrode active material exhibits an O3'-type crystal structure when charged at high voltage can be determined by analyzing the high-voltage charged positive electrode using XRD, electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. XRD is particularly preferable because it can analyze the symmetry of transition metals such as cobalt in the positive electrode active material with high resolution, compare the crystallinity and crystal orientation, analyze the periodic distortion of the lattice and crystallite size, and obtain sufficient accuracy even when measuring a positive electrode obtained by disassembling a secondary battery.

[0180] As mentioned above, a key characteristic of positive electrode active materials is that their crystal structure changes little between the high-voltage charged state and the discharged state. Materials in which the crystal structure that changes significantly from the discharged state accounts for 50 wt% or more when charged at high voltage are undesirable because they cannot withstand high-voltage charging and discharging. It is also important to note that simply adding impurity elements may not result in the desired crystal structure. For example, even if both materials are lithium cobalt oxide containing magnesium and fluorine, when charged at high voltage, there are cases where the O3' type crystal structure accounts for 60 wt% or more, and cases where the H1-3 type crystal structure accounts for 50 wt% or more. Furthermore, at a given voltage, the O3' type crystal structure may account for almost 100 wt%, and if the voltage is further increased, the H1-3 type crystal structure may emerge. Therefore, it is preferable to analyze the crystal structure of positive electrode active materials using XRD or similar methods. By using XRD or similar measurements in combination, even more detailed analysis can be performed.

[0181] However, positive electrode active materials in a high-voltage charged or discharged state may undergo changes in their crystal structure when exposed to air. For example, they may change from an O3' type crystal structure to an H1-3 type crystal structure. Therefore, it is preferable to handle all samples in an inert atmosphere such as an argon-containing atmosphere.

[0182] The positive electrode active material shown in Figure 4 is lithium cobalt oxide (LiCoO2) without the addition of doping element X. The crystal structure of lithium cobalt oxide shown in Figure 4 changes depending on the charging depth.

[0183] As shown in Figure 4, lithium cobalt oxide at charge depth 0 (discharge state) has a region with a crystal structure of space group R-3m, and there are three CoO2 layers in the unit cell. For this reason, this crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer refers to a structure in which octahedral structures, in which oxygen atoms are coordinated to cobalt in a 6-coordinate manner, are continuous in a plane with shared edges.

[0184] Furthermore, at a charge depth of 1, it has a crystal structure of space group P-3m1, with one CoO2 layer present in the unit cell. For this reason, this crystal structure is sometimes called an O1 type crystal structure.

[0185] Furthermore, lithium cobalt oxide at a charge depth of approximately 0.8 has a crystal structure with space group R-3m. This structure can be described as a structure in which CoO2 structures such as P-3m1(O1) and LiCoO2 structures such as R-3m(O3) are alternately stacked. For this reason, this crystal structure is sometimes called the H1-3 type crystal structure. In reality, the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell compared to other structures. However, in Figure 4 and other parts of this specification, the H1-3 type crystal structure is shown with the c-axis halved to make it easier to compare with other structures.

[0186] As an example, the H1-3 type crystal structure can be represented by the coordinates of cobalt and oxygen in a unit cell as follows: Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are oxygen atoms, respectively. Thus, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygen atoms. On the other hand, the O3' type crystal structure in one embodiment of the present invention is preferably represented by a unit cell using one cobalt and one oxygen atom. This indicates that the symmetry between cobalt and oxygen differs between the O3' type crystal structure and the H1-3 type structure, and that the O3' type crystal structure shows less variation from the O3 structure compared to the H1-3 type structure. The choice of which unit cell is preferable to represent the crystal structure of the positive electrode active material can be made, for example, by selecting the unit cell that results in a smaller GOF (good of fitness) value in Rietveld analysis of the XRD pattern.

[0187] When high-voltage charging occurs, such as when the charging voltage is 4.6V or higher relative to the oxidation-reduction potential of lithium metal, or when deep charging occurs, such as when the charging depth is 0.8 or higher, and when this charging and discharging cycle is repeated, lithium cobalt oxide undergoes repeated changes in its crystal structure (i.e., non-equilibrium phase changes) between the H1-3 type crystal structure and the R-3m(O3) structure in the discharged state.

[0188] However, these two crystal structures exhibit a significant displacement of the CoO2 layer. As shown by the dotted line and double-headed arrow in Figure 4, in the H1-3 type crystal structure, the CoO2 layer is significantly shifted from R-3m(O3). Such dynamic structural changes can negatively affect the stability of the crystal structure.

[0189] Furthermore, the volume difference is also significant. When comparing the same number of cobalt atoms, the volume difference between the H1-3 type crystal structure and the O3 type crystal structure in the discharged state is more than 3.0%.

[0190] In addition, the H1-3 type crystal structure, which consists of continuous CoO2 layers such as P-3m1(O1), is likely to be unstable.

[0191] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to break down. This breakdown of the crystal structure leads to a deterioration of the cycle characteristics. This is thought to be because the breakdown of the crystal structure reduces the number of sites where lithium can exist stably, and also makes it more difficult for lithium to be inserted and removed.

[0192] <An example of a graphene fabrication method> The following is an example of a method for producing graphene according to one aspect of the present invention.

[0193] Graphene 583 can be produced by mixing a material that will become graphene as material 801 and a halogen-containing compound as material 802, and then performing a heat treatment. For example, graphene oxide can be used as material 801.

[0194] In addition to material 802, a material that undergoes a eutectic reaction with material 802 may be mixed as material 803. Furthermore, it is preferable that the eutectic point resulting from the eutectic reaction is lower than at least one of the melting points of material 802 and material 803. The decrease in melting point due to the eutectic reaction may make material 802 and material 803 more likely to react with material 801 during heat treatment. Also, during heat treatment, material 802 and material 803 may more easily cover the surface of material 801, thereby improving the coverage.

[0195] Furthermore, by using compounds containing a metal whose ions function as carrier ions in the reaction of a secondary battery as material 802 and material 803, if the negative electrode active material contains the metal, it may be possible to contribute to charging and discharging as a carrier ion. A detailed example of a manufacturing method using material 801, material 802, and material 803 will be described later with reference to Figure 6.

[0196] As material 803, for example, a compound having oxygen and carbon can be used. For example, a carbonate can be used as a compound having oxygen and carbon. Alternatively, for example, an organic compound can be used as a compound having oxygen and carbon.

[0197] Alternatively, a hydroxide may be used as material 803.

[0198] Carbonates, hydroxides, etc., are preferred because many of them are inexpensive and highly safe materials. Furthermore, carbonates, hydroxides, etc., may form eutectic points with halogen-containing compounds, which is also preferable.

[0199] Let's give a more specific example regarding materials 802 and 803. When lithium fluoride is used as material 802, when it is mixed with material 801 and heated, the lithium fluoride may not melt easily, and the reaction with material 801 may not occur easily. In such cases, by using a compound that undergoes a eutectic reaction with lithium fluoride as material 803, the reaction between the fluorine contained in lithium fluoride and material 801 becomes easier due to the eutectic reaction between lithium fluoride and material 803.

[0200] As an example of material 803 that undergoes a eutectic reaction with lithium fluoride, we will describe lithium carbonate.

[0201] Figure 5 is a phase diagram showing the relationship between the ratio of LiF and Li2CO3 and temperature. Figure 5 is based on data from FACT Salt Phase Diagrams. As shown in Figure 5, the melting point of LiF is approximately 850°C, but the melting point can be lowered by mixing it with Li2CO3. Therefore, for example, at the same heating temperature, using a mixture of LiF and Li2CO3 makes it easier to dissolve compared to using LiF alone, thus facilitating the reaction with material 801. Furthermore, the heating temperature can be lowered.

[0202] Furthermore, by using a eutectic reaction, the affinity with the surface of material 801 can be increased. For example, when graphene is used as material 801, the CH bonds in graphene may have low affinity for fluorine, for instance. The eutectic reaction between LiF and Li2CO3 improves the affinity between the CH bonds and the fluorine-containing material, thereby increasing reactivity.

[0203] Furthermore, at point P shown in Figure 5, the molar amount of LiF [LiF / (Li2CO3+LiF)] relative to the total molar amounts of LiF and Li2CO3 is approximately 0.48, resulting in the lowest melting point. In other words, if the molar ratio of LiF to Li2CO3 is LiF:Li2CO3=a1:(1-a1), the melting point can be made lowest by setting a1 to a value around 0.48. The temperature at point P is approximately 615°C.

[0204] For example, a1 is preferably greater than 0.2, and more preferably 0.3 or greater. In particular, by setting a1 to a value greater than 0.48, the fluorine content of graphene can be increased. However, if the fluorine content is too high, the coating properties may deteriorate due to an increase in the melting point. For example, a1 is preferably less than 0.9, and more preferably 0.8 or less.

[0205] An example of a method for producing graphene according to one embodiment of the present invention will be explained using the flowchart shown in Figure 6A.

[0206] In step S21, material 801 is prepared. Material 801 is a raw material for graphene according to one embodiment of the present invention. Material 801 is, for example, graphene before fluorine addition. Material 801 is, for example, graphene before reduction. Here, graphene oxide is used as material 801.

[0207] In step S22, a halogen-containing compound is prepared as material 802. As the halogen-containing compound, a halogen compound having metal A1 can be used. As metal A1, one or more selected from lithium, magnesium, aluminum, sodium, potassium, calcium, barium, lanthanum, cerium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, titanium, vanadium, and niobium can be used. As the halogen compound, for example, fluoride or chloride can be used. The halogen contained in the halogen-containing compound is denoted as element Z. Examples of Z include fluorine, chlorine, etc.

[0208] Here, we will use lithium fluoride as an example.

[0209] In step S23, a compound having oxygen and carbon is prepared as material 803. As the compound having oxygen and carbon, for example, a carbonate having metal A2 can be used. As metal A2, for example, one or more selected from lithium, magnesium, aluminum, sodium, potassium, calcium, barium, lanthanum, cerium, chromium, manganese, iron, cobalt, and nickel can be used.

[0210] For this example, we will use lithium carbonate.

[0211] Next, in step S31, material 801, material 802, and material 803 are mixed, the mixture is collected in step S32, and the mixture 804 is obtained in step S33.

[0212] Material 802 and material 803 are preferably mixed in the ratio (material 802):(material 803)=a1:(1-a1)[unit is moles], where a1 is preferably greater than 0.2 and less than 0.9, and more preferably between 0.3 and 0.8.

[0213] Furthermore, it is preferable to mix material 801 and material 802 in a ratio of (material 801):(material 802)=1:b1 [unit is moles], where b1 is preferably 0.001 or more and 0.2 or less.

[0214] Next, in step S51, the mixture 804 is heated.

[0215] Heating under a reducing atmosphere is preferable because it suppresses oxidation of the surface of material 801. For example, the reducing atmosphere can be a nitrogen atmosphere or a noble gas atmosphere. Alternatively, a mixture of two or more gases from nitrogen and noble gases may be used. Furthermore, heating may be carried out under reduced pressure.

[0216] When the melting point of material 802 is expressed as M2[K], the heating temperature is preferably higher than (M2-550)[K] and lower than (M2+50)[K], and more preferably between (M2-400)[K] and M2[K].

[0217] Furthermore, solid-phase diffusion is more likely to occur in compounds at temperatures above the Tammann temperature. For example, the Tammann temperature is 0.757 times the melting point for oxides. Therefore, for example, it is preferable that the heating temperature is 0.757 times or higher than the eutectic point, or a temperature near it.

[0218] Furthermore, as a typical example of material 802, lithium fluoride shows a rapid increase in evaporation rate above its melting point. Therefore, for example, it is preferable that the heating temperature be below the melting point of material 802.

[0219] The eutectic points of material 802 and material 803 are M 23 When expressed as [K], the heating temperature is, for example, (M 23 It is preferable that it is higher than (M2+50)[K] and lower than (M 23 It is preferable that the temperature is between (M2 + 20) [K] and M 23 It is preferable that it is higher than [K] and lower than (M2+10)[K], (M 23 It is more preferable that the temperature is between 0.8)[K] and M2[K], 23 It is more preferable that the value is between [K] and M2[K].

[0220] When lithium fluoride is used as material 802 and lithium carbonate as material 803, the heating temperature is preferably, for example, greater than 350°C and less than 900°C, more preferably between 390°C and 850°C, even more preferably between 520°C and 910°C, even more preferably between 570°C and 860°C, and even more preferably between 610°C and 860°C.

[0221] The heating time is preferably between 1 hour and 60 hours, and more preferably between 3 hours and 20 hours.

[0222] Next, in step S52, the heated mixture is recovered, and in step S53, graphene 583 is obtained. The graphene 583 produced in the example shown here is, for example, fluorine-added graphene. The graphene 583 produced in the example shown here is, for example, reduced graphene oxide, which is fluorine-added graphene.

[0223] By following the steps described above, graphene according to one embodiment of the present invention can be obtained.

[0224] <An example of a particle preparation method> Alternatively, as shown in Figure 6B, particles 582 may be used in step S24, and in step S31b, particles 582 may be added to materials 801, 802, and 803 and mixed, the mixture may be recovered in step S32b, and a mixture 804b may be obtained in step S33b. By using the flow shown in Figure 6B, graphene-coated particles can be produced. Steps S31b and S32b can be replaced with steps S31 and S32, respectively.

[0225] In step S51b, the mixture 804b is heated, in step S52b, the heated mixture is recovered, and in step S53b, graphene-coated particles 582 (hereinafter, particles 582b) are obtained. Steps S51b and S52b can be replaced with steps S51 and S52, respectively. In step S53b, along with particles 582b, particles 582 not covered with graphene and graphene not covering particles 582 may also be obtained. Particles 582b are, for example, particles 582 covered with graphene to which fluorine has been added. Alternatively, particles 582b are, for example, graphene-coated particles 582 that contain fluorine.

[0226] <Method for fabricating electrodes> Figure 7 is a flowchart showing an example of a method for manufacturing an electrode according to one aspect of the present invention.

[0227] First, in step S71, particles 582 are prepared. Here, silicon-containing particles are prepared. Alternatively, particles 582b, whose preparation method is described above, may be used instead of particles 582.

[0228] Next, in step S72, the solvent is prepared. As the solvent, one or more of the following can be used: water, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0229] Next, in step S73, the particles 582 prepared in step S71 and the solvent prepared in step S72 are mixed, the mixture is recovered in step S74, and the mixture E-1 is obtained in step S75. A kneader or the like can be used for mixing. For example, a rotary-orbit mixer can be used as a kneader.

[0230] Next, in step S80, material 584b, which will later become graphene, is prepared. Here, graphene oxide can be used as material 584b. Alternatively, graphene 583 prepared using the flow shown in Figure 6 may be used.

[0231] Next, in step S81, mixture E-1 and material 584b prepared in step S80 are mixed, and in step S82, the mixture is recovered to obtain mixture E-2 (step S86). Note that solid kneading (kneading at high viscosity) may be performed during mixing. If solid kneading is performed, after solid kneading, solvent may be added to lower the viscosity and further mixing may be performed.

[0232] Next, in step S87, the binder is prepared. Any of the materials described above can be used as the binder. Here, polyimide is used. In step S87, a precursor of the material to be used as the binder may be prepared. For example, a precursor of polyimide is prepared.

[0233] Next, in step S88, the mixture E-2 is mixed with the binder or binder precursor prepared in step S87. Then, in step S89, the viscosity is adjusted. Specifically, for example, a solvent of the same type as the solvent prepared in step S72 is prepared and added to the mixture obtained in step S88. By adjusting the viscosity, it may be possible to adjust, for example, the thickness, density, etc. of the electrode obtained in the later step S97.

[0234] Next, the mixture whose viscosity was adjusted in step S89 is mixed in step S90 and recovered in step S91 to obtain mixture E-3 (step S92). The mixture E-3 obtained in step S92 is called, for example, a slurry.

[0235] Next, in step S93, the current collector is prepared.

[0236] Next, in step S94, the mixture E-3 is applied to the current collector prepared in step S93. For application, a slot die method, gravure coating, blade coating, or a combination thereof can be used. A continuous coating machine may also be used for application.

[0237] Next, in step S95, a first heating is performed. The solvent evaporates during the first heating. The first heating is preferably performed in a temperature range of 50°C to 200°C, preferably 60°C to 150°C.

[0238] For example, the material can be heated on a hot plate in an air atmosphere at a temperature between 30°C and 70°C for at least 10 minutes, and then heated again in a reduced-pressure environment at a temperature between room temperature and 100°C for at least 1 to 10 hours.

[0239] Alternatively, heat treatment may be performed using a drying oven or the like. If a drying oven is used, for example, heat treatment should be performed at a temperature of 30°C to 120°C for 30 seconds to 2 hours.

[0240] Alternatively, the temperature may be increased stepwise. For example, after performing a heat treatment at 60°C or lower for 10 minutes or less, a heat treatment may be further performed at a temperature of 65°C or higher for 1 minute or more.

[0241] Next, in step S96, the second heating is performed. When polyimide is used as the binder, it is preferable that a cyclization addition reaction of the polyimide occurs due to the second heating. Also, a dehydration reaction of the polyimide may occur due to the second heating. Alternatively, a dehydration reaction of the polyimide may occur due to the first heating. Further, a cyclization reaction of the polyimide may occur during the first heating. Additionally, it is preferable that a reduction reaction of the material 584b occurs during the second heating.

[0242] In step S97, an electrode having an active material layer provided on a current collector is obtained. The electrode obtained in step S97 is an electrode having graphene.

[0243] The thickness of the thus-formed active material layer is, for example, preferably 5 μm or more and 300 μm or less, more preferably 10 μm or more and 150 μm or less. Also, the active material loading amount of the active material layer is, for example, preferably 2 mg / cm 2 above and 50 mg / cm 2 below.

[0244] The active material layer may be formed on both sides of the current collector, or may be formed on only one side. Alternatively, it may have a region where the active material layer is partially formed on both sides.

[0245] After volatilizing the solvent from the active material layer, pressing may be performed by a compression method such as a roll pressing method and a flat pressing method. Heat may be applied during pressing.

[0246] By fabricating an electrode using the manufacturing method according to one embodiment of the present invention, a three-dimensional conductive path using multiple graphenes can be formed within the active material layer of the electrode. Furthermore, multiple graphenes can be arranged in a mesh-like structure within the electrode.

[0247] <About graphene> Here, graphene according to one embodiment of the present invention can be obtained in step S53 in Figure 6A, step S53b in Figure 6B, and step S97 in Figure 7. The graphene obtained in each step may have different fluorine concentrations and pore frequencies. Also, the graphene obtained in each step may have different oxygen concentrations.

[0248] At least a portion of the graphene according to one embodiment of the present invention obtained in step S53b of Figure 6B covers, for example, particle 582.

[0249] The graphene according to one embodiment of the present invention obtained in step S97 of Figure 7 is contained within the electrode. Furthermore, at least a portion of the graphene according to one embodiment of the present invention obtained in step S97 of Figure 7 covers, for example, particle 582. Furthermore, a plurality of the graphene according to one embodiment of the present invention obtained in step S97 of Figure 7 constitute a three-dimensional structure within the electrode.

[0250] This embodiment can be used in appropriate combination with other embodiments.

[0251] (Embodiment 2) This embodiment shows an example of a method for producing a positive electrode active material according to one aspect of the present invention.

[0252] The following is an example of a method for producing a material having a layered rock salt-type crystalline structure and represented as LiMO2. Metal M contains metal Me1. Metal Me1 is one or more metals including cobalt. In addition to metal Me1, metal M may also contain metal X. Metal X is one or more metals selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0253] [Method for preparing positive electrode active material 1] <Step S11> In step S11 of Figure 8A, a lithium source and a transition metal source are prepared as lithium and transition metal materials. In the drawing, the transition metal source is shown as an Me1 source.

[0254] For example, lithium carbonate, lithium fluoride, etc., can be used as lithium sources.

[0255] As a transition metal source, at least one of manganese, cobalt, and nickel can be used. For example, as a transition metal source, only cobalt may be used, only nickel may be used, both cobalt and manganese may be used, both cobalt and nickel may be used, or all three may be used: cobalt, manganese, and nickel.

[0256] Furthermore, it is preferable to use a high-purity material as the transition metal source during synthesis. Specifically, the purity of the material should be 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99.999%) or higher. By using a high-purity material, the capacity of the secondary battery can be increased and / or the reliability of the secondary battery can be improved.

[0257] In addition, it is preferable that the transition metal source has high crystallinity. For example, it is preferable that the transition metal source has single crystal grains. The crystallinity of the transition metal source can be evaluated from, for example, TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. Furthermore, X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as criteria for evaluating the crystallinity of the transition metal source. Note that the above evaluation of crystallinity can be applied not only to the transition metal source but also to the evaluation of the crystallinity of primary or secondary particles.

[0258] Furthermore, when using metals capable of forming layered rock salt-type composite oxides, it is preferable to use a mixing ratio of cobalt, manganese, and nickel within a range that allows for a layered rock salt-type crystal structure. Alternatively, an additive element X may be added to these transition metals within a range that allows for a layered rock salt-type crystal structure. An example of the process of adding additive element X is shown in Figure 8B. In step S11, a lithium source, a transition metal source, and an additive element X source are prepared, and then step S12 is carried out.

[0259] As the additive element X, one or more can be selected from magnesium, calcium, zirconium, lanthanum, barium, titanium, yttrium, nickel, aluminum, cobalt, manganese, vanadium, iron, chromium, niobium, copper, potassium, sodium, zinc, chlorine, fluorine, hafnium, silicon, sulfur, phosphorus, boron, and arsenic. In addition to the above elements, bromine and beryllium may also be used as additive element X. However, since bromine and beryllium are toxic to living organisms, it is preferable to use the additive element X described above.

[0260] Furthermore, as a transition metal source, oxides, hydroxides, etc., of the above-mentioned metals exemplified as transition metals can be used. As a cobalt source, for example, cobalt oxide, cobalt hydroxide, etc., can be used.

[0261] Furthermore, manganese oxide, manganese hydroxide, etc., can be used as manganese sources. Nickel oxide, nickel hydroxide, etc., can be used as nickel sources. Aluminum oxide, aluminum hydroxide, etc., can be used as aluminum sources.

[0262] <Step S12> Next, as step S12, the above lithium source and transition metal source are crushed and mixed. The crushing and mixing can be performed either dry or wet. In particular, it is preferable to perform the crushing using dehydrated acetone with a purity of 99.5% or more and a moisture content suppressed to 10 ppm or less. In this specification and the like, the term described as "crushing" may be read as "grinding". Also, for mixing, for example, a ball mill or a bead mill can be used. When using a ball mill, it is preferable to use zirconia balls as the media, for example. Further, when using a ball mill or a bead mill, etc., in order to suppress contamination from the media or materials, it is preferable to set the peripheral speed to 100 mm / s or more and 2000 mm / s or less. For example, it may be carried out at a peripheral speed of 838 mm / s (rotation speed 400 rpm, ball mill diameter 40 mm). Also, by using the above dehydrated acetone in the crushing and mixing, impurities that may be mixed into the material can be reduced.

[0263] <Step S13> Next, as step S13, the material mixed above is heated. The heating temperature in this step is preferably carried out at 800 °C or more and less than 1100 °C, more preferably at 900 °C or more and 1000 °C or less, and even more preferably about 950 °C. If the temperature is too low, there is a risk that the decomposition and melting of the lithium source and transition metal source will be insufficient. On the other hand, if the temperature is too high, there is a risk of defects due to, for example, lithium evaporating from the lithium source and / or the metal used as the transition metal source being excessively reduced. For example, when cobalt is used as the transition metal, a defect where cobalt becomes divalent may occur.

[0264] The heating time can be, for example, 1 hour to 100 hours, and preferably 2 hours to 20 hours. Heating is preferably carried out in an atmosphere with little water, such as dry air (for example, with a dew point of -50°C or lower, more preferably -80°C or lower). For example, heating may be carried out in an atmosphere with a dew point of -93°C. Furthermore, heating is preferable in an atmosphere where the impurity concentrations of CH4, CO, CO2, and H2 are each 5 ppb (parts per billion) or less, as this suppresses the incorporation of impurities into the material.

[0265] Furthermore, for example, when heating at 1000°C for 10 hours, it is preferable to raise the temperature at 200°C / h and the flow rate of dry air at 10 L / min. After that, the heated material can be cooled to room temperature. For example, it is preferable to set the cooling time from the specified temperature to room temperature to 10 hours or more and 50 hours or less. However, cooling to room temperature in step S13 is not essential.

[0266] Furthermore, the crucible used during heating in step S13 is preferably made of a material that does not easily release impurities. For example, a crucible made of alumina with a purity of 99.9% may be used.

[0267] Furthermore, when collecting the material after heating in step S13, it is preferable to transfer it from the crucible to a mortar before collection, as this prevents impurities from contaminating the material. It is also preferable that the mortar be made of a material that does not easily release impurities. Specifically, it is preferable to use a mortar made of alumina with a purity of 90% or higher, preferably 99% or higher. Note that the same conditions as in step S13 can be applied to the heating processes described later, other than step S13.

[0268] <Step S14> By the above steps, a positive electrode active material 100 according to one embodiment of the present invention can be produced (step S14). The positive electrode active material 100 may be represented as a composite oxide (LiMO2) having lithium, a transition metal, and oxygen. However, the positive electrode active material according to one embodiment of the present invention only needs to have the crystal structure of a lithium composite oxide represented as LiMO2, and its composition is not strictly limited to Li:M:O=1:1:2.

[0269] By using a high-purity material as the transition metal source during synthesis, and by producing the positive electrode active material in a process that minimizes the inclusion of impurities during synthesis, it is possible to obtain a material with a low impurity concentration, in other words, a highly purified material. Furthermore, the positive electrode active material obtained by such a method of producing positive electrode active material is a material with high crystallinity. In addition, the positive electrode active material obtained by the method of producing positive electrode active material according to one aspect of the present invention can increase the capacity of a secondary battery and / or improve the reliability of a secondary battery.

[0270] [Method for preparing positive electrode active material 2] Next, another example of a method for producing a positive electrode active material according to one aspect of the present invention will be explained with reference to Figure 9.

[0271] In Figure 9, steps S11 to S14 are performed in the same manner as in Figure 8A to prepare a composite oxide (LiMO2) having lithium, a transition metal, and oxygen.

[0272] In addition, a pre-synthesized composite oxide may be used as step S14. In this case, steps S11 to S13 can be omitted. When preparing a pre-synthesized composite oxide, it is preferable to use a high-purity material. The purity of the material should be 99.5% or higher, preferably 99.9% or higher, and more preferably 99.99% or higher.

[0273] A heating step may be included between step S14 and the next step S20. This heating can, for example, smooth the surface of the composite oxide. For example, the heating can be carried out under the same atmosphere and temperature conditions as in step S33, but for a shorter processing time than in step S33. A smooth surface means that there are few irregularities, the surface is generally rounded, and the corners are also rounded. Furthermore, a state in which there are few foreign substances adhering to the surface is also called smooth. Foreign substances are thought to be a cause of irregularities, so it is preferable that they do not adhere to the surface.

[0274] <Step S20> As step S20 in Figure 9, a source of additive element X is prepared. The materials described above can be used as the source of additive element X. In addition, multiple elements may be used as additive element X. Addition of additive element X can be carried out using methods such as solid-phase methods, liquid-phase methods including sol-gel methods, sputtering methods, vapor deposition methods, CVD (chemical vapor deposition), and PLD (pulsed laser deposition).

[0275] Here, we prepare a magnesium source (Mg source) and a fluorine source (F source) as the additive element X source. Alternatively, a lithium source may be prepared in conjunction with the magnesium and fluorine sources.

[0276] For example, magnesium fluoride, magnesium oxide, magnesium hydroxide, magnesium carbonate, etc., can be used as magnesium sources.

[0277] Examples of fluorine sources that can be used include lithium fluoride (LiF), magnesium fluoride (MgF2), aluminum fluoride (AlF3), titanium fluoride (TiF4), cobalt fluoride (CoF2, CoF3), nickel fluoride (NiF2), zirconium fluoride (ZrF4), vanadium fluoride (VF5), manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride (ZnF2), calcium fluoride (CaF2), sodium fluoride (NaF), potassium fluoride (KF), barium fluoride (BaF2), cerium fluoride (CeF2), lanthanum fluoride (LaF3), and sodium aluminum hexafluoride (Na3AlF6). Furthermore, the fluorine source is not limited to a solid; for example, fluorine (F2), carbon fluoride, sulfur fluoride, oxygen fluoride (OF2, O2F2, O3F2, O4F2, O2F), etc., may be used and mixed in the atmosphere during the heating process described later. Multiple fluorine sources may also be used in combination. Among these, lithium fluoride is preferred because it has a relatively low melting point of 848°C and is easily melted during the heating process described later.

[0278] For example, lithium fluoride and lithium carbonate can be used as lithium sources. In other words, lithium fluoride can be used as both a lithium source and a fluorine source. Similarly, magnesium fluoride can be used as both a fluorine source and a magnesium source.

[0279] In this embodiment, lithium fluoride (LiF) is prepared as the fluorine source, and magnesium fluoride (MgF2) is prepared as both the fluorine source and the magnesium source. Mixing lithium fluoride (LiF) and magnesium fluoride (MgF2) in a molar ratio of approximately LiF:MgF2 = 65:35 yields the highest effect in lowering the melting point (Non-Patent Literature 2). On the other hand, if the amount of lithium fluoride is too high, there is a concern that the lithium will be in excess and the cycle characteristics will deteriorate. Therefore, the molar ratio of lithium fluoride (LiF) to magnesium fluoride (MgF2) is preferably LiF:MgF2 = k:1 (0 ≤ k ≤ 1.9), more preferably LiF:MgF2 = k:1 (0.1 ≤ k ≤ 0.5), and even more preferably LiF:MgF2 = k:1 (k = 0.33 or its vicinity). In this specification, "nearby" means a value greater than 0.9 times and less than 1.1 times the value.

[0280] Furthermore, if the following mixing and crushing steps are carried out wet, a solvent should be prepared. It is preferable to use a protic solvent that does not react easily with lithium, such as ketones like acetone, alcohols like ethanol and isopropanol, ethers, dioxane, acetonitrile, or N-methyl-2-pyrrolidone (NMP).

[0281] Next, the above materials are mixed and crushed. Mixing can be done dry or wet, but wet mixing is preferred because it allows for finer crushing. For mixing, for example, a ball mill or a bead mill can be used. When using a ball mill, it is preferable to use zirconia balls as the media. The conditions for the ball mill or bead mill can be the same as those in step S12.

[0282] Next, the materials crushed and mixed as described above are recovered to obtain the additive element X source. Since this additive element X source is formed from multiple materials, it may also be referred to as a mixture.

[0283] The above mixture preferably has a median diameter (D50) of 600 nm to 20 μm, and more preferably 1 μm to 10 μm. When the mixture is finely powdered in this way, it is easier to uniformly adhere the mixture to the surface of the composite oxide particles when it is mixed with lithium, a transition metal, and oxygen in a later process. When the mixture is uniformly adhered to the surface of the composite oxide particles, it is preferable because it is easier to distribute halogen and magnesium evenly near the surface of the composite oxide particles after heating. If there are regions near the surface that do not contain halogen and magnesium, it may be difficult to form the above-mentioned O3' type crystal structure in the charged state.

[0284] The above examples illustrate a method of mixing two types of materials, but the method is not limited to this. For example, a source of additive element X may be prepared by mixing four types of materials (magnesium source (Mg source), fluorine source (F source), nickel source (Ni source), and aluminum source (Al source)). Alternatively, a source of additive element X may be prepared using a single material, i.e., one type of material. Nickel sources can include nickel oxide, nickel hydroxide, etc. Aluminum sources can include aluminum oxide, aluminum hydroxide, etc.

[0285] <Step S31> Next, in step S31 of Figure 9, the LiMO2 obtained in step S14 is mixed with the additive element X source. The ratio of the number of transition metal atoms M in the composite oxide having lithium, a transition metal, and oxygen to the number of magnesium atoms Mg in the additive element X is preferably M:Mg=100:y (0.1≦y≦6), and more preferably M:Mg=100:y (0.3≦y≦3).

[0286] The mixing in step S31 is preferably carried out under milder conditions than the mixing in step S12 in order to avoid destroying the particles of the composite oxide. For example, it is preferable to use conditions with a lower rotation speed or a shorter time than the mixing in step S12. Also, dry mixing is generally milder than wet mixing. For mixing, for example, a ball mill or a bead mill can be used. When using a ball mill, it is preferable to use zirconia balls as the media.

[0287] In this embodiment, the mixing is performed dry using a ball mill with zirconia balls with a diameter of 1 mm at 150 rpm for 1 hour. The mixing is carried out in a dry room with a dew point of -100°C or higher and -10°C or lower.

[0288] <Step S32> Next, in step S32 of Figure 9, the materials mixed above are collected to obtain mixture 903.

[0289] In this embodiment, a method of adding a mixture of lithium fluoride and magnesium fluoride to lithium cobalt oxide with few impurities is described, but the present invention is not limited to this. Instead of the mixture 903 in step S32, a starting material of lithium cobalt oxide to which a magnesium source and a fluorine source, etc., have been added and heated may be used. In this case, it is not necessary to separate the processes in steps S11 to S14 and steps S21 to S23, making it simpler and more productive.

[0290] Alternatively, lithium cobalt oxide with magnesium and fluorine added beforehand may be used. Using lithium cobalt oxide with magnesium and fluorine added makes the process up to step S32 easier to complete.

[0291] Alternatively, magnesium and fluorine sources may be added to lithium cobalt oxide that has already been treated with magnesium and fluorine.

[0292] <Step S33> Next, in step S33, the mixture 903 is heated in an oxygen-containing atmosphere. It is preferable to heat the mixture 903 in a way that prevents the particles from sticking together.

[0293] It is preferable that the additives be added uniformly and without bias across the entire surface of the particles. However, if the particles of mixture 903 stick together during heating, the additives may be added unevenly to only a portion of the surface. Furthermore, even if the surface of the particles is preferably smooth with few irregularities, if the particles stick together, the irregularities will increase, potentially leading to an increase in defects such as cracks and / or fissures. This is thought to be due to the effect of the adhesion of mixture 903 particles, which reduces the contact area with oxygen in the atmosphere and obstructs the diffusion pathway of the additives.

[0294] Furthermore, heating in step S33 may be performed using a rotary kiln. Heating with a rotary kiln can be performed while stirring, whether in a continuous or batch system. Alternatively, heating in step S33 may be performed using a roller hearth kiln.

[0295] The heating temperature in step S33 must be above the temperature at which the reaction between LiMO2 and the additive element X source proceeds. The temperature at which the reaction proceeds is simply the temperature at which elemental interdiffusion occurs between LiMO2 and the additive element X source. Therefore, it may be possible to set the temperature lower than the melting temperature of these materials. For example, in oxides, the melting temperature T m [K] 0.757 times (Tammann temperature T) d )Solid-phase diffusion occurs.Therefore, the heating temperature in step S33 should be, for example, 500°C or higher.

[0296] However, it is preferable that the heating temperature in step S33 be 742°C or higher, as this facilitates the reaction. For example, if LiF and MgF2 are used as the source of additive element X, the eutectic point of LiF and MgF2 is around 742°C, so it is preferable to set the heating temperature in step S33 to 742°C or higher.

[0297] Furthermore, when mixture 903 is prepared by mixing LiCoO2:LiF:MgF2 in a molar ratio of 100:0.33:1, an endothermic peak is observed around 830°C in differential scanning calorimetry (DSC measurement). Therefore, a heating temperature of 830°C or higher is more preferable.

[0298] A higher heating temperature is preferable because it facilitates the reaction, shortens the heating time, and increases productivity.

[0299] However, the heating temperature must be below the decomposition temperature of LiMO2 (1130°C in the case of LiCoO2). Furthermore, at temperatures near the decomposition temperature, there is a concern that a small amount of LiMO2 may decompose. For this reason, the heating temperature in step S33 is preferably less than 1130°C, more preferably 1000°C or less, even more preferably 950°C or less, and even more preferably 900°C or less.

[0300] Therefore, the heating temperature in step S33 is preferably 500°C to 1130°C, more preferably 500°C to 1000°C, even more preferably 500°C to 950°C, and even more preferably 500°C to 900°C. Also, it is preferably 742°C to 1130°C, more preferably 742°C to 1000°C, even more preferably 742°C to 950°C, and even more preferably 742°C to 900°C. Also, it is preferably 830°C to 1130°C, more preferably 830°C to 1000°C, even more preferably 830°C to 950°C, and even more preferably 830°C to 900°C.

[0301] Furthermore, when heating mixture 903, it is preferable to control the partial pressure of fluorine or fluoride in the atmosphere to an appropriate range.

[0302] In the manufacturing method described in this embodiment, some materials, such as LiF, which is a fluorine source, may function as a flux. This function allows the heating temperature to be lowered to below the decomposition temperature of LiMO2, for example, between 742°C and 950°C, enabling the distribution of additives such as magnesium near the surface and the production of a positive electrode active material with good properties.

[0303] However, since LiF is less dense than oxygen in its gaseous state, heating causes LiF to volatilize, reducing the amount of LiF in mixture 903. This weakens its function as a flux. Therefore, heating is necessary while suppressing the volatilization of LiF. Even if LiF is not used as a fluorine source, Li and F on the surface of LiMO2 may react to produce LiF, which may then volatilize. Therefore, even if a fluoride with a higher melting point than LiF is used, the same need to suppress volatilization is required.

[0304] Therefore, it is preferable to heat the mixture 903 in an atmosphere containing LiF, that is, to heat the mixture 903 while the partial pressure of LiF in the heating furnace is high. Such heating can suppress the volatilization of LiF in the mixture 903.

[0305] Furthermore, when heating with a rotary kiln, it is preferable to heat the mixture 903 by controlling the flow rate of the oxygen-containing atmosphere inside the kiln. For example, it is preferable to reduce the flow rate of the oxygen-containing atmosphere, or to purge the atmosphere first and then not allow the atmosphere to flow after introducing the oxygen atmosphere into the kiln.

[0306] When heating by roller hearth kiln, for example, the mixture 903 can be heated in an atmosphere containing LiF by placing a lid on the container containing the mixture 903.

[0307] Heating should preferably be carried out for an appropriate amount of time. The heating time varies depending on conditions such as the heating temperature, the size of the LiMO2 particles in step S14, and the composition. When the particles are small, a lower temperature or shorter time may be preferable than when the particles are large.

[0308] For example, if the average particle size (D50) of the composite oxide in step S14 of Figure 9 is about 12 μm, the heating temperature is preferably, for example, 600°C to 950°C. The heating time is preferably 3 hours or more, more preferably 10 hours or more, and even more preferably 60 hours or more.

[0309] On the other hand, if the average particle size (D50) of the composite oxide in step S14 is about 5 μm, the heating temperature is preferably, for example, 600°C to 950°C. The heating time is preferably, for example, 1 hour to 10 hours, and more preferably about 2 hours. The cooling time after heating is preferably, for example, 10 hours to 50 hours.

[0310] <Step S34> Next, the heated material is recovered to produce the positive electrode active material 100. At this time, it is preferable to further sift the recovered particles. By the above steps, a positive electrode active material 100 according to one embodiment of the present invention can be produced (step S34).

[0311] [Method for preparing positive electrode active material 3] Next, another example of a method for producing a positive electrode active material according to one aspect of the present invention will be explained with reference to Figure 10.

[0312] In Figure 10, steps S11 to S14 are performed in the same manner as in Figure 8A to prepare a composite oxide (LiMO2) having lithium, a transition metal, and oxygen.

[0313] In addition, a pre-synthesized composite oxide containing lithium, a transition metal, and oxygen may be used as step S14. In this case, steps S11 to S13 can be omitted.

[0314] As described in Figure 9, a heating step may be included between step S14 and step S20. This heating may be performed using the same atmosphere and temperature conditions as in step S33, but with a shorter processing time than in step S33.

[0315] <Step S20a> In step S20a of Figure 10, a source of additive element X1 is prepared. The additive element X1 source can be selected from the additive elements X described above. For example, one or more of magnesium, fluorine, and calcium can be suitably used as additive element X1. Addition of additive element X1 can be carried out using methods such as solid-phase methods, liquid-phase methods including sol-gel methods, sputtering methods, vapor deposition methods, CVD (chemical vapor deposition), and PLD (pulsed laser deposition).

[0316] Here, a magnesium source (Mg source) and a fluorine source (F source) are prepared as the first additive element X1. Next, referring to step S20 shown in Figure 9, the magnesium source and fluorine source are crushed, mixed, heated, etc. as appropriate to obtain the additive element source (X1 source).

[0317] Furthermore, steps S31 to S33 shown in Figure 10 can be manufactured using the same process as steps S31 to S33 shown in Figure 9.

[0318] <Step S34a> Next, the material heated in step S33 is recovered to produce a composite oxide.

[0319] <Step S40> In step S40 of Figure 10, a source of additive element X2 is prepared. The additive element X2 source can be selected from the additive element X described above. For example, one or more of nickel, titanium, boron, zirconium, and aluminum can be suitably used as additive element X2. In this embodiment, nickel and aluminum are used as additive element X2. Addition of additive element X2 can be carried out using methods such as solid-phase methods, liquid-phase methods including sol-gel methods, sputtering methods, vapor deposition methods, CVD (chemical vapor deposition), and PLD (pulsed laser deposition).

[0320] For step S40 shown in Figure 10, refer to step S20 shown in Figure 9, and perform grinding, mixing, heating, etc. as appropriate to obtain the additive element source (X2 source).

[0321] Furthermore, if there are multiple elements as the second additive element source, each may be prepared by independently grinding them. As a result, in step S40, multiple second additive element sources (X2 sources) are prepared independently.

[0322] Here, when using the sol-gel method for adding element X2, in addition to the element X2 source, a solvent for the sol-gel method is prepared. For example, a metal alkoxide can be used as the metal source for the sol-gel method, and an alcohol can be used as the solvent. For example, when adding aluminum, aluminum isopropoxide can be used as the metal source, and isopropanol (2-propanol) can be used as the solvent. For example, when adding zirconium, zirconium(IV) tetrapropoxide can be used as the metal source, and isopropanol can be used as the solvent.

[0323] <Steps S51 to S53> Next, step S51 in Figure 10 is a process of mixing the composite oxide prepared in step S34a with the additive element X2 source prepared in step S40. Step S51 in Figure 10 can be processed in the same way as step S31 shown in Figure 9. Step S52 in Figure 10 can be processed in the same way as step S32 shown in Figure 9. The material prepared in step S52 in Figure 10 is mixture 904. Mixture 904 is a material that contains the additive element X2 source added in step S40 in addition to the material of mixture 903. Step S53 in Figure 10 can be processed in the same way as step S33 shown in Figure 9.

[0324] <Step S54> Next, the heated material is recovered to produce the positive electrode active material 100. At this time, it is preferable to further sift the recovered particles. By the above steps, a positive electrode active material 100 according to one embodiment of the present invention can be produced (step S54).

[0325] As shown in Figure 10, by separating the processes for introducing the transition metal, additive element X1, and additive element X2, it is sometimes possible to change the depth profile of each element. For example, the concentration of additives can be increased near the surface compared to the interior of the particles. Also, using the number of atoms of the transition metal as a reference, the ratio of the number of atoms of the additive elements to this reference can be made higher near the surface than in the interior.

[0326] Furthermore, by using a high-purity material as the transition metal source during synthesis, employing a process that minimizes impurity contamination during synthesis, thoroughly eliminating impurity contamination from the transition metal source and during synthesis, and controlling the introduction of desired additive elements (additive element X, additive element X1, or additive element X2) into the positive electrode active material, it is possible to obtain a positive electrode active material in which the regions with low impurity concentrations and the regions with introduced additive elements are controlled. In addition, a positive electrode active material with high crystallinity can be obtained. Moreover, a positive electrode active material obtained by the method for producing a positive electrode active material according to one aspect of the present invention can increase the capacity of a secondary battery and / or improve the reliability of a secondary battery.

[0327] [Method for preparing positive electrode active material 4] Next, an embodiment of the present invention, which differs from methods 1 to 3 for producing the positive electrode active material, will be described.

[0328] As mentioned above, the composite oxide may be given an additive element X to the extent that it can take on a layered rock salt type crystal structure, and in Figure 11, steps S11 to S34a are carried out in the same manner as in Figure 10. In this manufacturing method 4, the step of adding the second additive element (X2) in two or more separate steps will be explained.

[0329] <Step S40a> In step S40a shown in Figure 11, one of the second additive element sources (hereinafter referred to as the X2a source) is prepared. The X2a source can be selected from the additive element X described in step S20 shown in Figure 9. For example, as the additive element X2a, one or more selected from nickel, titanium, boron, zirconium, and aluminum can be suitably used.

[0330] The addition of additive element X2a can be carried out using methods such as solid-phase methods, liquid-phase methods including sol-gel methods, sputtering, vapor deposition, CVD (chemical vapor deposition), or PLD (pulsed laser deposition).

[0331] Figure 11 illustrates the case where nickel is used as the additive element X2a.

[0332] In step S40a shown in Figure 11, referring to step S20 shown in Figure 9, a second additive element source (X2a source) can be obtained by performing appropriate steps such as grinding, mixing, and heating. For example, a nickel source can be obtained as the second additive element source (X2a source) using a solid-phase method.

[0333] Furthermore, if multiple sources of additive elements are prepared, each may be ground independently.

[0334] <Step S40b> The second additive element source (hereinafter referred to as the X2b source) can be obtained by step S40b shown in Figure 11. For example, the second additive element source (X2b source) can be obtained using the sol-gel method. Unlike step S40a, when using the sol-gel method, it is preferable to prepare the process independently. The process for preparing the second additive element source (X2b source) using the sol-gel method will now be described.

[0335] When using the sol-gel method, in addition to the second additive element (X2b), a solvent for the sol-gel method is prepared. For example, a metal alkoxide can be used as the metal source for the sol-gel method, and an alcohol can be used as the solvent. When an aluminum source is prepared, aluminum isopropoxide can be used as the aluminum alkoxide, and when a zirconium source is prepared, zirconium isopropoxide can be used as the zirconium alkoxide, and isopropanol can be used as the solvent.

[0336] Next, the aluminum alkoxide, zirconium alkoxide, and isopropanol are mixed (stirred). The sol-gel reaction may proceed at this stage, or it may proceed in the next step. If the sol-gel reaction is to proceed, heating may be done during mixing. In this way, a mixture (also called a mixed solution) containing the aluminum source and the zirconium source is prepared as the second additive element source (X2b source).

[0337] <Steps S51 to S53> Next, steps S51 to S53 shown in Figure 11 can be carried out under the same conditions as steps S31 to S33 shown in Figure 9. Through these steps, a positive electrode active material 100 according to one embodiment of the present invention can be produced in step S54. The sol-gel reaction can then be carried out in step S53.

[0338] This embodiment can be used in combination with other embodiments.

[0339] (Embodiment 3) In this embodiment, an example of a secondary battery according to one aspect of the present invention will be described using Figure 12A. The secondary battery has an outer casing (not shown), a positive electrode 503, a negative electrode 506, a separator 507, and an electrolyte containing a dissolved lithium salt or the like. The separator 507 is provided between the positive electrode 503 and the negative electrode 506.

[0340] The positive electrode 503 has a positive electrode active material. The positive electrode 503 also has a positive electrode active material layer 502 provided on the positive electrode current collector 501. The positive electrode active material layer 502 includes, for example, a positive electrode active material, a conductive agent, and a binder. As one aspect of the present invention, the electrode described in the previous embodiment can be used as the positive electrode.

[0341] The negative electrode 506 has a negative electrode active material. The negative electrode 506 also has a negative electrode active material layer 505 provided on the negative electrode current collector 504. The negative electrode active material layer 505 includes, for example, a negative electrode active material, a conductive agent, and a binder. As a negative electrode in one aspect of the present invention, the electrode described in the previous embodiment can be used.

[0342] [Electrolyte] The electrolyte preferably comprises a solvent and a salt of a metal that acts as a carrier ion. As the solvent for the electrolyte, an aprotic organic solvent is preferred. Examples include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, and one of these, or two or more of these, can be used in any combination and ratio.

[0343] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the secondary battery from rupturing or catching fire even if the internal temperature rises due to internal short circuits or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations used in electrolytes include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in electrolytes include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkyl borate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0344] Examples of salts to be dissolved in the above solvents include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B. 10 Cl 10 Li2B 12 Cl 12 Lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), and LiN(C2F5SO2)2 can be used individually or in any combination and ratio of two or more of these salts.

[0345] For secondary batteries, it is preferable to use a highly purified electrolyte with a low content of granular debris and elements other than the constituent elements of the electrolyte (hereinafter also simply referred to as "impurities"). Specifically, it is preferable that the weight ratio of impurities to the electrolyte be 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0346] Furthermore, additives such as vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the added material should be, for example, 0.1 wt% to 5 wt% relative to the total solvent. VC or LiBOB are particularly preferred because they readily form a good film.

[0347] A solution containing a solvent and a salt that acts as a carrier ion is sometimes called an electrolyte.

[0348] A polymer gel electrolyte, obtained by swelling a polymer with an electrolyte solution, may also be used.

[0349] Using polymer gel electrolytes enhances safety against leakage and other issues. Furthermore, it enables the secondary battery to be made thinner and lighter.

[0350] As the polymer to be gelled, silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide-based gels, polypropylene oxide-based gels, fluorine-based polymer gels, and the like can be used.

[0351] Examples of polymers that can be used include polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, and polyacrylonitrile. Copolymers containing these can also be used. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The resulting polymer may also have a porous structure.

[0352] Furthermore, solid electrolytes containing inorganic materials such as sulfides and oxides, or solid electrolytes containing polymeric materials such as PEO (polyethylene oxide), can be used as the electrolyte. When using a solid electrolyte, the installation of one or more separators and spacers becomes unnecessary. In addition, since the entire battery can be solidified, the risk of leakage is eliminated, dramatically improving safety.

[0353] [Separator] The separator 507 can be made of, for example, paper, nonwoven fabric, glass fiber, ceramics, etc. Alternatively, it can be made of nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyurethane, polypropylene, polyethylene, etc. It is preferable that the separator be processed into an envelope shape and arranged to enclose either the positive or negative electrode.

[0354] Furthermore, a polymer film made of, for example, polypropylene, polyethylene, or polyimide can be used for the separator 507. Polyimide has good wettability with ionic liquids and may be a more preferable material for the separator 507.

[0355] Polymer films containing polypropylene, polyethylene, etc., can be manufactured by dry or wet methods. The dry method involves stretching a polymer film containing polypropylene, polyethylene, polyimide, etc., while heating it, creating gaps between crystals and forming fine pores. The wet method involves mixing a solvent into the resin beforehand, forming it into a film, and then extracting the solvent to create pores.

[0356] Figure 12B (left) shows an enlarged view of region 507a as an example of separator 507 (fabricated by a wet process). In this example, a structure with multiple pores 587 is shown in the polymer film 588. Figure 12B (right) shows an enlarged view of region 507b as another example of separator 507 (fabricated by a dry process). In this example, a structure with multiple pores 585 is shown in the polymer film 586.

[0357] The diameter of the pores in the separator may differ between the surface of the side facing the positive electrode and the surface of the side facing the negative electrode after charging and discharging. In this specification, the surface of the separator is preferably, for example, an area within 5 μm, more preferably within 3 μm, from the surface.

[0358] The separator may have a multilayer structure. For example, a structure in which two types of polymer materials are layered may be used.

[0359] Furthermore, structures can be used in which a ceramic material, fluorine material, polyamide material, or a mixture thereof is coated onto a polymer film, such as polypropylene, polyethylene, or polyimide. Alternatively, structures can be used in which a ceramic material, fluorine material, polyamide material, or a mixture thereof is coated onto a nonwoven fabric. Polyimide is preferable as a coating material because of its good wettability with ionic liquids.

[0360] Examples of fluorine-based materials that can be used include PVDF and polytetrafluoroethylene.

[0361] Examples of polyamide materials that can be used include nylon and aramid (meta-aramid, para-aramid).

[0362] [Exterior] The outer casing of the secondary battery can be made of one or more materials selected from metal materials such as aluminum and resin materials. A film-like outer casing can also be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer casing.

[0363] This embodiment can be used in appropriate combination with other embodiments.

[0364] (Embodiment 4) This embodiment describes a method for manufacturing a secondary battery.

[0365] <Method 1 for manufacturing laminated rechargeable batteries> Here, an example of a method for manufacturing a laminate-type secondary battery, whose external view is shown in Figures 13A and 13B, will be explained using Figures 14A and 14B and Figures 15A and 15B. The secondary battery 500 shown in Figures 13A and 13B has a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511. As a cross-sectional view of the laminate-type secondary battery shown in Figure 13A, etc., for example, a structure in which the positive electrode, separator, and negative electrode are laminated and enclosed in an outer casing can be used, as shown in Figure 18, which will be described later.

[0366] First, prepare the positive electrode 503, the negative electrode 506, and the separator 507. Figure 14A shows an example of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode active material layer 502 on a positive electrode current collector 501. Preferably, the positive electrode 503 also has a tab region where the positive electrode current collector 501 is exposed. The negative electrode 506 has a negative electrode active material layer 505 on a negative electrode current collector 504. Preferably, the negative electrode 506 also has a tab region where the negative electrode current collector 504 is exposed.

[0367] Next, the negative electrode 506, separator 507, and positive electrode 503 are stacked. Figure 14B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. This can also be called a laminate consisting of a negative electrode, separator, and positive electrode.

[0368] Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For joining, ultrasonic welding, for example, may be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0369] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0370] Next, as shown in Figure 15A, the outer casing 509 is bent at the portion indicated by the dashed line. Then, the outer periphery of the outer casing 509 is joined. For joining, for example, heat sealing can be used. At this time, a region that is not joined (hereinafter referred to as the inlet 516) is provided on a part (or one side) of the outer casing 509 so that the electrolyte 508 can be inserted later.

[0371] Next, as shown in Figure 15B, the electrolyte 508 is introduced into the inside of the outer casing 509 through the inlet 516 provided in the outer casing 509. It is preferable to introduce the electrolyte 508 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet 516 is joined. In this way, a laminate-type secondary battery 500 can be manufactured.

[0372] In the above example, the positive lead electrode 510 and the negative lead electrode 511 were led out of the casing from the same side to create the secondary battery 500 shown in Figure 13A. Alternatively, the secondary battery 500 shown in Figure 13B can be created by leading the positive lead electrode 510 and the negative lead electrode 511 out of the casing from opposite sides.

[0373] <Method for manufacturing laminated rechargeable batteries, part 2> Next, an example of a method for manufacturing a laminate-type secondary battery 600, whose external view is shown in Figure 16, will be explained using Figures 17, 18, 19A to 19D, and 20A to 20F. The secondary battery 600 shown in Figure 16 has a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511. The outer casing 509 is sealed in region 514.

[0374] A laminate-type secondary battery 600 can be manufactured, for example, using the manufacturing apparatus shown in Figure 17. The manufacturing apparatus 670 shown in Figure 17 has a component input chamber 671, a transport chamber 672, a processing chamber 673, and a component removal chamber 676. Each chamber can be configured to be connected to various exhaust mechanisms depending on the application. Each chamber can also be configured to be connected to various gas supply mechanisms depending on the application. To suppress the entry of impurities into the manufacturing apparatus 670, it is preferable to supply an inert gas into the manufacturing apparatus 670. It is preferable that the gas supplied to the inside of the manufacturing apparatus 670 is purified to a high degree by a gas purifier before being introduced into the manufacturing apparatus 670. The component input chamber 671 is a chamber for inputting the positive electrode, separator, negative electrode, casing, etc. into the manufacturing apparatus 670. The transport chamber 672 has a transport mechanism 680. The processing chamber 673 has a stage and an electrolyte dropping mechanism. The component removal room 676 is a room for removing the manufactured secondary batteries from the manufacturing apparatus 670.

[0375] The procedure for manufacturing the laminate-type rechargeable battery 600 is as follows:

[0376] First, the outer casing 509b is placed on the stage 691 of the processing chamber 673, and then the positive electrode 503 is placed on the outer casing 509b (Figures 19A and 19B). Next, the electrolyte 515a is dropped onto the positive electrode 503 from the nozzle 694 (Figures 19C and 19D). Figure 19D is a cross-section corresponding to the dashed line AB in Figure 19C. Note that the stage 691 may be omitted in some cases to avoid making the drawings too complex. Any of the dropping methods can be used, such as the dispensing method, spray method, or inkjet method. In addition, the ODF (One Drop Fill) method can be used for dropping the electrolyte.

[0377] By moving the nozzle 694, the electrolyte 515a can be dropped over the entire surface of the positive electrode 503. Alternatively, the electrolyte 515a may be dropped over the entire surface of the positive electrode 503 by moving the stage 691.

[0378] It is preferable that the electrolyte is dispensed from a position where the shortest distance X from the bottom surface of the droplet is greater than 0 mm and less than or equal to 1 mm.

[0379] Furthermore, it is preferable to adjust the viscosity of the electrolyte being dispensed from the nozzle as appropriate. If the total viscosity of the electrolyte is within the range of 0.3 mPa·s to 1000 mPa·s at room temperature (25°C), it can be dispensed from the nozzle.

[0380] Furthermore, since the viscosity of the electrolyte changes with its temperature, it is preferable to appropriately adjust the temperature of the electrolyte being added dropwise. The temperature of the electrolyte is preferably above its melting point, below its boiling point, or below its flash point.

[0381] Next, the separator 507 is placed on the positive electrode 503 so as to overlap the entire surface of the positive electrode 503 (Figure 20A). Subsequently, the electrolyte 515b is dropped onto the separator 507 using the nozzle 694 (Figure 20B). After that, the negative electrode 506 is placed on the separator 507 (Figure 20C). The negative electrode 506 is placed overlapping the separator 507 so that it does not protrude from the separator 507 when viewed from above. Subsequently, the electrolyte 515c is dropped onto the negative electrode 506 using the nozzle 694 (Figure 20D). After that, the laminate 512 shown in Figure 18 can be fabricated by further stacking the laminate of the positive electrode 503, separator 507, and negative electrode 506. Next, the positive electrode 503, separator 507, and negative electrode 506 are sealed by the outer casings 509a and 509b (Figures 20E and 20F).

[0382] In Figure 18, the positive and negative electrodes are arranged such that the positive electrode active material layer and the negative electrode active material layer are sandwiched between a separator. In one embodiment of the present invention, it is preferable that the negative electrode active material layer has few or no regions that do not face the positive electrode active material layer. When the electrolyte is an ionic liquid and the negative electrode active material layer has regions that do not face the positive electrode active material layer, the charge and discharge efficiency of the secondary battery may decrease. Therefore, in one embodiment of the present invention, it is preferable that the edges of the positive electrode active material layer and the edges of the negative electrode active material layer are aligned as much as possible. Therefore, it is preferable that the areas of the positive electrode active material layer and the negative electrode active material layer are the same when viewed from above. Alternatively, it is preferable that the edges of the positive electrode active material layer are located inward from the edges of the negative electrode active material layer.

[0383] By arranging multiple laminates 512 on the outer casing 509b, multi-faceted processing can be achieved. After sealing the outer casings 509a and 509b with a region 514 so that each laminate 512 surrounds the active material layer, multiple secondary batteries can be individually separated by dividing them outside the region 514.

[0384] During sealing, first, a frame-shaped resin layer 513 is formed on the outer casing 509b. Next, at least a portion of the resin layer 513 is cured by irradiating it with light under reduced pressure. Then, sealing is performed in region 514 by thermocompression bonding or welding under atmospheric pressure. Alternatively, sealing may be performed only by thermocompression bonding or welding without the above-mentioned light irradiation sealing.

[0385] Although Figure 16 shows an example where the outer casing 509 is sealed on all four sides (sometimes called a four-sided seal), it may also be sealed on three sides (sometimes called a three-sided seal), as shown in Figures 13A and 13B.

[0386] Through the above process, a laminate-type secondary battery 600 can be manufactured.

[0387] <Other secondary batteries and their manufacturing methods 1> Figure 21 shows an example of a cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 550 shown in Figure 21 is manufactured by placing a single separator between the positive and negative electrodes while bending it.

[0388] In the laminate 550, a single separator 507 is folded multiple times so that it is sandwiched between the positive electrode active material layer 502 and the negative electrode active material layer 505. In Figure 21, since six layers each of positive electrodes 503 and negative electrodes 506 are laminated, the separator 507 is folded at least five times. In addition to being provided sandwiched between the positive electrode active material layer 502 and the negative electrode active material layer 505, the separator 507 may also be further folded so that multiple positive electrodes 503 and negative electrodes 506 are bundled together with tape or the like.

[0389] In one embodiment of the present invention, a method for manufacturing a secondary battery, the electrolyte can be dropped onto the positive electrode 503 after it has been placed. Similarly, the electrolyte can be dropped onto the negative electrode 506 after it has been placed. Furthermore, in one embodiment of the present invention, the electrolyte can be dropped onto the separator 507 before it has been folded, or after the separator 507 has been folded and placed on top of the negative electrode 506 or the positive electrode 503. By dropping the electrolyte onto at least one of the negative electrode 506, the separator 507, and the positive electrode 503, the electrolyte can be impregnated into the negative electrode 506, the separator 507, or the positive electrode 503.

[0390] The secondary battery 970 shown in Figure 22A has a laminate 972 inside the housing 971. Terminals 973b and 974b are electrically connected to the laminate 972. At least a portion of terminal 973b and at least a portion of terminal 974b are exposed to the outside of the housing 971.

[0391] As the laminate 972, a structure in which a positive electrode, a negative electrode, and a separator are laminated can be applied. Alternatively, as the laminate 972, a structure in which the positive electrode, negative electrode, and separator are wound can be applied, and so on.

[0392] For example, as the laminate 972, a laminate having a structure in which the separator is folded back, as shown in Figure 21, can be used.

[0393] An example of a method for manufacturing the laminate 972 will be explained using Figures 22B and 22C.

[0394] First, as shown in Figure 22B, a strip-shaped separator 976 is placed on top of the positive electrode 975a, and the negative electrode 977a is placed on top of the positive electrode 975a with the separator 976 in between. Then, the separator 976 is folded back and placed on top of the negative electrode 977a. Next, as shown in Figure 22C, the positive electrode 975b is placed on top of the negative electrode 977a with the separator 976 in between. In this way, by folding back the separator and arranging the positive and negative electrodes in order, a laminate 972 can be fabricated. A structure including a laminate fabricated in this way is sometimes called a "zigzag structure".

[0395] Next, an example of a method for manufacturing the secondary battery 970 will be explained using Figures 23A to 23C.

[0396] First, as shown in Figure 23A, the positive lead electrode 973a is electrically connected to the positive electrode of the laminate 972. Specifically, for example, tab regions can be provided on each of the positive electrodes of the laminate 972, and each tab region and the positive lead electrode 973a can be electrically connected by welding or the like. In addition, the negative lead electrode 974a is electrically connected to the negative electrode of the laminate 972.

[0397] One laminate 972 may be placed inside the housing 971, or multiple laminates 972 may be placed inside. Figure 23B shows an example in which two sets of laminates 972 are prepared.

[0398] Next, as shown in Figure 23C, the prepared laminate 972 is placed inside the housing 971, terminals 973b and 974b are attached, and the housing 971 is sealed. It is preferable to electrically connect the conductor 973c to each positive lead electrode 973a of the multiple laminates 972. It is also preferable to electrically connect the conductor 974c to each negative lead electrode 974a of the multiple laminates 972. Terminal 973b is electrically connected to the conductor 973c, and terminal 974b is electrically connected to the conductor 974c. The conductor 973c may have a conductive region and an insulating region. Similarly, the conductor 974c may have a conductive region and an insulating region.

[0399] A metal material (such as aluminum) can be used for the housing 971. Furthermore, when a metal material is used for the housing 971, it is preferable to coat the surface with resin or the like. Alternatively, a resin material can be used for the housing 971.

[0400] It is preferable to provide a safety valve or overcurrent protection element in the housing 971. The safety valve is a valve that releases gas when the inside of the housing 971 reaches a predetermined pressure in order to prevent the battery from rupturing.

[0401] <Other secondary batteries and their manufacturing methods 2> Figure 24C shows an example of a cross-sectional view of a secondary battery according to another embodiment of the present invention. The secondary battery 560 shown in Figure 24C is manufactured using the laminate 130 shown in Figure 24A and the laminate 131 shown in Figure 24B. Note that in Figure 24C, the laminate 130, laminate 131, and separator 507 are shown in part for clarity.

[0402] As shown in Figure 24A, the laminate 130 is constructed by stacking a positive electrode 503 having positive electrode active material layers on both sides of a positive electrode current collector, a separator 507, a negative electrode 506 having negative electrode active material layers on both sides of a negative electrode current collector, a separator 507, and a positive electrode 503 having positive electrode active material layers on both sides of a positive electrode current collector in this order.

[0403] As shown in Figure 24B, the laminate 131 is constructed by stacking a negative electrode 506 having negative electrode active material layers on both sides of the negative electrode current collector, a separator 507, a positive electrode 503 having positive electrode active material layers on both sides of the positive electrode current collector, a separator 507, and a negative electrode 506 having negative electrode active material layers on both sides of the negative electrode current collector in this order.

[0404] A method for manufacturing a secondary battery according to one aspect of the present invention can be applied when manufacturing a laminate. Specifically, when stacking the negative electrode 506, separator 507, and positive electrode 503 to manufacture the laminate, an electrolyte is dropped onto at least one of the negative electrode 506, separator 507, and positive electrode 503. By dropping multiple drops of the electrolyte, the negative electrode 506, separator 507, or positive electrode 503 can be impregnated with the electrolyte.

[0405] As shown in Figure 24C, the multiple laminates 130 and the multiple laminates 131 are covered by a wound separator 507.

[0406] Furthermore, in a method for manufacturing a secondary battery according to one aspect of the present invention, the electrolyte can be dropped onto the laminate 130 after the laminate 130 has been placed. Similarly, the electrolyte can be dropped onto the laminate 131 after the laminate 131 has been placed. In addition, the electrolyte can be dropped onto the separator 507 before it is folded, or after the separator 507 has been folded and stacked with the laminate. By dropping multiple drops of the electrolyte, the laminate 130, laminate 131, or separator 507 can be impregnated with the electrolyte.

[0407] <Other secondary batteries and their manufacturing methods 3> Another embodiment of the present invention, a secondary battery, will be described with reference to Figures 25 and 26. The secondary battery shown here can be called a wound-type secondary battery, etc.

[0408] The secondary battery 913 shown in Figure 25A has a wound body 950 with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, while terminal 951 is not in contact with the housing 930 due to the use of an insulating material or the like. In Figure 25A, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0409] Furthermore, as shown in Figure 25B, the housing 930 shown in Figure 25A may be formed from multiple materials. For example, in the secondary battery 913 shown in Figure 25B, housing 930a and housing 930b are bonded together, and the winding body 950 is provided in the area surrounded by housing 930a and housing 930b.

[0410] For the housing 930a, an insulating material such as organic resin can be used. In particular, by using a material such as organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by housing 930a is small, the antenna may be placed inside housing 930a. For housing 930b, for example, a metal material can be used.

[0411] Furthermore, the structure of the wound body 950 is shown in Figure 25C. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 in between, and the stacked sheets are wound up. Note that multiple stacks of the negative electrode 931, positive electrode 932, and separator 933 may be stacked.

[0412] In a method for manufacturing a secondary battery according to one aspect of the present invention, when stacking the negative electrode 931, separator 933, and positive electrode 932, an electrolyte is dropped onto at least one of the negative electrode 931, separator 933, and positive electrode 932. In other words, it is preferable to drop the electrolyte before rolling up the stacked sheet. By dropping multiple drops of the electrolyte, the negative electrode 931, separator 933, or positive electrode 932 can be impregnated with the electrolyte.

[0413] Alternatively, the secondary battery 913 may have a wound body 950a as shown in Figure 26A. The wound body 950a shown in Figure 26A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0414] The separator 933 has a wider width than the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Furthermore, it is preferable from a safety standpoint that the negative electrode active material layer 931a is wider than the positive electrode active material layer 932a. In addition, a wound body 950a of this shape is preferable because it offers good safety and productivity.

[0415] As shown in Figure 26B, the negative terminal 931 is electrically connected to terminal 951. Terminal 951 is electrically connected to terminal 911a. The positive terminal 932 is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0416] As shown in Figure 26C, the coiled body 950a and the electrolyte are covered by the housing 930, forming a secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc., in the housing 930. The safety valve is temporarily opened only when the internal pressure inside the housing 930 exceeds a predetermined level in order to prevent the battery from rupturing.

[0417] As shown in Figure 26B, the secondary battery 913 may have multiple windings 950a. By using multiple windings 950a, a secondary battery 913 with a larger charge and discharge capacity can be made.

[0418] This embodiment can be combined with other embodiments as appropriate.

[0419] (Embodiment 5) In this embodiment, an example of the application of a secondary battery according to one aspect of the present invention will be explained with reference to Figures 27 to 36.

[0420] [vehicle] First, we will show an example of applying a secondary battery according to one aspect of the present invention to an electric vehicle (EV).

[0421] Figure 27C shows a block diagram of a vehicle with a motor. The electric vehicle is equipped with a first battery 1301a, 1301b as the main secondary battery for propulsion, and a second battery 1311 that supplies power to the inverter 1312 that starts the motor 1304. The second battery 1311 is also called the cranking battery or starter battery. The second battery 1311 only needs to have high output, and does not require a large capacity, so the capacity of the second battery 1311 is smaller than that of the first batteries 1301a, 1301b.

[0422] For example, one or both of the first batteries 1301a and 1301b can be a secondary battery manufactured using a secondary battery manufacturing method according to one aspect of the present invention.

[0423] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack with multiple secondary batteries, a large amount of power can be extracted. Multiple secondary batteries may be connected in parallel, in series, or connected in parallel and then in series. Multiple secondary batteries are also called a battery pack.

[0424] Furthermore, the vehicle-mounted secondary battery has a service plug or circuit breaker that can cut off high voltage without using tools in order to interrupt power from multiple secondary batteries, and this is provided in the first battery 1301a.

[0425] Furthermore, the power from the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V (high-voltage) onboard components (electric power steering 1307, heater 1308, defogger 1309, etc.) via the DC-DC circuit 1306. If a rear motor 1317 is located on the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.

[0426] Furthermore, the second battery 1311 supplies power to 14V (low-voltage) in-vehicle components (audio 1313, power windows 1314, lights 1315, etc.) via the DC-DC circuit 1310.

[0427] Furthermore, the first battery 1301a will be explained using Figure 27A.

[0428] Figure 27A shows an example of a large battery pack 1415. One electrode of the battery pack 1415 is electrically connected to the control circuit unit 1320 by wiring 1421. The other electrode is electrically connected to the control circuit unit 1320 by wiring 1422. The battery pack may also be configured by connecting multiple secondary batteries in series.

[0429] Furthermore, the control circuit section 1320 may also use a memory circuit that includes a transistor made of an oxide semiconductor. A charging control circuit or battery control system having a memory circuit that includes a transistor made of an oxide semiconductor may be referred to as a BTOS (Battery operating system or Battery oxide semiconductor).

[0430] The control circuit unit 1320 detects the terminal voltage of the secondary battery and manages the charging and discharging state of the secondary battery. For example, to prevent overcharging, both the output transistor and the cutoff switch of the charging circuit can be turned off almost simultaneously.

[0431] Furthermore, an example of a block diagram of the battery pack 1415 shown in Figure 27A is shown in Figure 27B.

[0432] The control circuit unit 1320 includes a switch unit 1324 that includes at least a switch to prevent overcharging and a switch to prevent over-discharging, a control circuit 1322 that controls the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 sets the upper and lower voltage limits of the secondary battery used, and limits the upper limit of external current or the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the voltage range for which use is recommended, and if it goes outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge or overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch of the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0433] The switch unit 1324 can be configured by combining one or both of an n-channel transistor and a p-channel transistor. The switch unit 1324 is not limited to a switch having a Si transistor using single-crystal silicon, but can also be made of, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO zThe switch section 1324 may be formed using a power transistor having a gallium oxide (z is a real number greater than 0) or the like. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. Also, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost. That is, by stacking a control circuit section 1320 using OS transistors on the switch section 1324 and integrating them, it is possible to create a single chip. Since the volume occupied by the control circuit section 1320 can be reduced, miniaturization becomes possible.

[0434] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage) in-vehicle equipment, while the second battery 1311 supplies power to 14V (low-voltage) in-vehicle equipment. Lead-acid batteries are often used for the second battery 1311 due to their cost advantages.

[0435] This embodiment shows an example in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor.

[0436] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 or battery controller 1302. Alternatively, it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0437] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set the charging conditions according to the charging characteristics of the secondary battery being used and enable rapid charging.

[0438] Although not shown in the diagram, when an external charger is connected, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some cases, the charger may have a control circuit and may not use the functions of the battery controller 1302, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the connection cable or the charger's connection cable may also have a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. The ECU also uses a CPU or GPU.

[0439] Next, an example of implementing a secondary battery according to one aspect of the present invention in a vehicle, typically a transport vehicle, will be described.

[0440] By mounting a secondary battery according to one aspect of the present invention in a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. Furthermore, secondary batteries can also be mounted in agricultural machinery such as electric tractors, motorized bicycles including electric assist bicycles, motorcycles, electric wheelchairs, electric carts, small or large vessels, submarines, aircraft such as fixed-wing or rotary-wing aircraft, rockets, satellites, space probes or planetary probes, and other transport vehicles. By using the method for manufacturing a secondary battery according to one aspect of the present invention, large secondary batteries can be produced. Therefore, a secondary battery according to one aspect of the present invention is suitably used in transport vehicles.

[0441] Figures 28A to 28E show a transport vehicle using a secondary battery according to one embodiment of the present invention. The automobile 2001 shown in Figure 28A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for driving. When a secondary battery is mounted on a vehicle, the secondary battery is installed in one or more locations. The automobile 2001 shown in Figure 28A has the battery pack 1415 shown in Figure 27A. The battery pack 1415 has a secondary battery module. Preferably, the battery pack 1415 further has a charge control device that is electrically connected to the secondary battery module. The secondary battery module has one or more secondary batteries.

[0442] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via a plug-in or contactless power supply method to the secondary battery it possesses. For charging, the charging method or connector specifications may be carried out appropriately using a prescribed method such as CHAdeMO® or Combo. The charging device may be a charging station installed in a commercial facility, or it may be a household power supply. For example, the secondary battery mounted on the automobile 2001 can be charged by an external power supply using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.

[0443] Although not shown in the diagram, the vehicle can also be charged by mounting a power receiving device on the vehicle and receiving power wirelessly from a ground-based power transmission device. In this wireless power supply method, charging can be performed not only when the vehicle is stopped but also while it is in motion by incorporating the power transmission device into the road or exterior wall. Furthermore, this wireless power supply method can be used to transmit and receive power between two vehicles. In addition, solar panels can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or in motion. For such wireless power supply, electromagnetic induction or magnetic resonance methods can be used.

[0444] Figure 28B shows a large transport vehicle 2002 equipped with an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 has a maximum voltage of 170V, achieved by connecting 48 cells in series, each consisting of four secondary batteries with a voltage of 3.5V to 4.7V. The secondary battery module of the battery pack 2201 has the same functions as Figure 28A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0445] Figure 28C shows, as an example, a large transport vehicle 2003 equipped with an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V, achieved by connecting more than 100 secondary batteries with voltages of 3.5V to 4.7V in series. Therefore, secondary batteries with small variation in characteristics are required. By using the secondary battery manufacturing method according to one aspect of the present invention, secondary batteries with stable battery characteristics can be manufactured, enabling low-cost mass production from a yield standpoint. Furthermore, since it has the same functions as Figure 28A except for differences such as the number of secondary batteries constituting the secondary battery module of the battery pack 2202, a further explanation is omitted.

[0446] Figure 28D shows an example of an aircraft 2004 having a fuel-burning engine. The aircraft 2004 shown in Figure 28D has landing gear for takeoff and landing, and can therefore be considered part of a transport vehicle. It has a battery pack 2203 which includes a secondary battery module formed by connecting multiple secondary batteries and a charging control device.

[0447] The secondary battery module of aircraft 2004 has a maximum voltage of 32V, for example, by connecting eight 4V secondary batteries in series. The secondary battery module of battery pack 2203 has the same functionality as Figure 28A, except for differences in the number of secondary batteries that make up the module, so a detailed explanation is omitted.

[0448] Figure 28E shows a transport vehicle 2005 for transporting cargo as an example. It has an electrically controlled motor and performs various tasks by receiving power from a secondary battery that constitutes the secondary battery module of the battery pack 2204. Furthermore, the transport vehicle 2005 is not limited to being driven and operated by a human; it can also be operated unmanned via CAN communication or the like. Although Figure 28E illustrates a forklift, it is not particularly limited, and a battery pack having a secondary battery according to one aspect of the present invention can be mounted on industrial machinery that can be operated via CAN communication or the like, such as automated transport machines, work robots, or small construction machinery.

[0449] Furthermore, Figure 29A shows an example of an electric bicycle using a secondary battery according to one embodiment of the present invention. The secondary battery according to one embodiment of the present invention can be applied to the electric bicycle 2100 shown in Figure 29A. The energy storage device 2102 shown in Figure 29B includes, for example, a plurality of secondary batteries and a protection circuit.

[0450] The electric bicycle 2100 is equipped with a power storage device 2102. The power storage device 2102 can supply electricity to a motor that assists the rider. The power storage device 2102 is also portable, and Figure 29B shows it detached from the bicycle. The power storage device 2102 also has multiple secondary batteries 2101 according to one aspect of the present invention built in, and the remaining battery level can be displayed on a display unit 2103. The power storage device 2102 also has a control circuit 2104 capable of charging control or abnormality detection of the secondary batteries, as exemplified in one aspect of the present invention. The control circuit 2104 is electrically connected to the positive and negative electrodes of the secondary batteries 2101. A small solid-state secondary battery may also be provided in the control circuit 2104. By providing a small solid-state secondary battery in the control circuit 2104, power can be supplied to hold data in the memory circuit of the control circuit 2104 for a long period of time. Furthermore, a synergistic effect on safety can be obtained by combining it with a secondary battery that uses the positive electrode active material 100 according to one aspect of the present invention as the positive electrode. A secondary battery and control circuit 2104 using a positive electrode active material 100 according to one aspect of the present invention can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0451] Figure 29C also shows an example of a motorcycle using a secondary battery according to one embodiment of the present invention. The scooter 2300 shown in Figure 29C is equipped with a power storage device 2302, side mirrors 2301, and turn signals 2303. The power storage device 2302 can supply electricity to the turn signals 2303. Furthermore, the power storage device 2302, which houses multiple secondary batteries using the positive electrode active material 100 according to one embodiment of the present invention as the positive electrode, can have a high capacity and contribute to miniaturization. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery.

[0452] Furthermore, the scooter 2300 shown in Figure 29C can accommodate the power storage device 2302 in the under-seat storage compartment 2304. The power storage device 2302 can be stored in the under-seat storage compartment 2304 even if the under-seat storage compartment 2304 is small.

[0453] [Buildings] Next, an example of implementing a secondary battery according to one aspect of the present invention in a building will be explained with reference to Figure 30.

[0454] The house shown in Figure 30A has a power storage device 2612 having a secondary battery with stable battery characteristics, and a solar panel 2610, which are manufactured using a secondary battery manufacturing method according to one aspect of the present invention. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611, etc. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The power obtained from the solar panel 2610 can be used to charge the power storage device 2612. The power stored in the power storage device 2612 can be used to charge the secondary battery of the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space above the floor can be used effectively. Alternatively, the power storage device 2612 may be installed on the floor.

[0455] The electricity stored in the energy storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or other reasons, electronic devices can be used by using the energy storage device 2612 as an uninterruptible power supply.

[0456] Figure 30B shows an example of the application of an energy storage device according to one aspect of the present invention. As shown in Figure 30B, a large energy storage device 791 obtained by the secondary battery manufacturing method according to one aspect of the present invention is installed in the underfloor space 796 of the building 799.

[0457] The energy storage device 791 is equipped with a control device 790, which is electrically connected by wiring to the distribution board 703, the energy storage controller 705 (also called the control device), the display unit 706, and the router 709.

[0458] Power is supplied from the commercial power supply 701 to the distribution panel 703 via the service drop connection section 710. Power is also supplied to the distribution panel 703 from the energy storage device 791 and the commercial power supply 701, and the distribution panel 703 supplies the supplied power to the general load 707 and the energy storage system load 708 via outlets (not shown).

[0459] General load 707 is, for example, an electrical device such as a television or a personal computer, and energy storage load 708 is, for example, an electrical device such as a microwave oven, refrigerator, or air conditioner.

[0460] The energy storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has the function of measuring the amount of electricity consumed by the general load 707 and the energy storage system load 708 during a day (for example, from 0:00 to 24:00). The measurement unit 711 may also have the function of measuring the amount of electricity consumed by the energy storage device 791 and the amount of electricity supplied from the commercial power supply 701. The prediction unit 712 has the function of predicting the amount of electricity demanded by the general load 707 and the energy storage system load 708 during the next day, based on the amount of electricity consumed by the general load 707 and the energy storage system load 708 during the day. The planning unit 713 has the function of planning the charging and discharging of the energy storage device 791 based on the amount of electricity demand predicted by the prediction unit 712.

[0461] The amount of electricity consumed by the general load 707 and the energy storage system load 708, as measured by the measurement unit 711, can be checked on the display unit 706. It can also be checked via the router 709 on electrical equipment such as televisions or personal computers. Furthermore, it can be checked via the router 709 on portable electronic devices such as smartphones or tablets. Additionally, the amount of electricity demand predicted by the forecasting unit 712 for each time period (or hourly) can be checked on the display unit 706, electrical equipment, and portable electronic devices.

[0462] [Electronic equipment] A secondary battery according to one aspect of the present invention can be used, for example, in either or both electronic devices and lighting devices. Examples of electronic devices include mobile phones, smartphones, or notebook computers, portable game consoles, portable music players, digital cameras, and digital video cameras.

[0463] The personal computer 2800 shown in Figure 31A includes a casing 2801, a casing 2802, a display unit 2803, a keyboard 2804, and a pointing device 2805, etc. A secondary battery 2807 is provided inside casing 2801, and a secondary battery 2806 is provided inside casing 2802. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 2807 may be electrically connected to the secondary battery 2807. A touch panel is also applied to the display unit 2803. As shown in Figure 31B, the personal computer 2800 can be used as a tablet terminal by removing casings 2801 and 2802, and using only casing 2802.

[0464] A large secondary battery obtained by the secondary battery manufacturing method according to one aspect of the present invention can be applied to either or both of secondary batteries 2806 and 2807. The shape of the secondary battery obtained by the secondary battery manufacturing method according to one aspect of the present invention can be freely changed by changing the shape of the casing. By shaping secondary batteries 2806 and 2807 to match the shape of the casings 2801 and 2802, for example, the capacity of the secondary battery can be increased, and the operating time of the personal computer 2800 can be extended. In addition, the personal computer 2800 can be made lighter.

[0465] Furthermore, a flexible display is applied to the display unit 2803 of the housing 2802. The secondary battery 2806 is a large secondary battery obtained by the secondary battery manufacturing method according to one aspect of the present invention. In the large secondary battery obtained by the secondary battery manufacturing method according to one aspect of the present invention, by using a flexible film for the outer casing, a bendable secondary battery can be made. As a result, as shown in Figure 31C, the housing 2802 can be folded for use. At this time, as shown in Figure 31C, a part of the display unit 2803 can also be used as a keyboard.

[0466] Furthermore, the housing 2802 can be folded so that the display unit 2803 faces inward, as shown in Figure 31D, or so that the display unit 2803 faces outward, as shown in Figure 31E.

[0467] One embodiment of the present invention can be applied to a flexible secondary battery and mounted in electronic devices. It can also be incorporated along curved surfaces of interior or exterior walls of houses and buildings, or interiors and exteriors of automobiles.

[0468] Figure 32A shows an example of a mobile phone. The mobile phone 7400 includes a display unit 7402 built into the housing 7401, as well as operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. The mobile phone 7400 also has a secondary battery 7407. By using a secondary battery according to one embodiment of the present invention for the secondary battery 7407, a lightweight and long-life mobile phone can be provided. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 7407 may be electrically connected to the secondary battery 7407.

[0469] Figure 32B shows the mobile phone 7400 in a bent state. When the mobile phone 7400 is deformed by an external force and the entire device is bent, the secondary battery 7407 located inside is also bent. Figure 32C shows the state of the bent secondary battery 7407 at that time. The secondary battery 7407 is a thin storage battery. The secondary battery 7407 is fixed in the bent state. The secondary battery 7407 has lead electrodes that are electrically connected to a current collector. For example, the current collector is made of copper foil, and a portion of it is alloyed with gallium to improve the adhesion with the active material layer that is in contact with the current collector, resulting in a configuration that ensures high reliability of the secondary battery 7407 when it is bent.

[0470] Figure 32D shows an example of a bangle-type display device. The portable display device 7100 comprises a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 7104 may be electrically connected to the secondary battery 7104. Figure 32E shows the state of the bent secondary battery 7104. When the secondary battery 7104 is worn on the user's arm in a bent state, the housing deforms, and the curvature of part or all of the secondary battery 7104 changes. The degree of curvature at any point in the curve is expressed as the radius of the corresponding circle, and the reciprocal of the radius of curvature is called the curvature. Specifically, part or all of the main surface of the housing or secondary battery 7104 changes within the range of radius of curvature of 40 mm to 150 mm. High reliability can be maintained if the radius of curvature on the main surface of the secondary battery 7104 is within the range of 40 mm to 150 mm. By using a secondary battery according to one aspect of the present invention in the secondary battery 7104 described above, a lightweight and long-lasting portable display device can be provided.

[0471] Figure 32F shows an example of a wristwatch-type personal information terminal. The personal information terminal 7200 includes a housing 7201, a display unit 7202, a band 7203, a buckle 7204, operation buttons 7205, input / output terminals 7206, and the like.

[0472] The 7200 personal digital assistant (PDCA) can run various applications such as mobile phone calls, email, document viewing and creation, music playback, internet communication, and computer games.

[0473] The display unit 7202 has a curved display surface, allowing it to display information along the curved surface. The display unit 7202 also features a touch sensor, allowing it to be operated by touching the screen with a finger or stylus. For example, touching the icon 7207 displayed on the display unit 7202 can launch an application.

[0474] The operation button 7205 can be assigned various functions, including time setting, power on / off, wireless communication on / off, silent mode activation / deactivation, and power saving mode activation / deactivation. For example, the functions of the operation button 7205 can be freely configured by the operating system built into the personal digital assistant 7200.

[0475] Furthermore, the 7200 portable information terminal is capable of performing standardized short-range wireless communication. For example, it can communicate with a wireless-enabled headset to enable hands-free calling.

[0476] Furthermore, the portable information terminal 7200 is equipped with an input / output terminal 7206, allowing it to directly exchange data with other information terminals via a connector. It can also be charged via the input / output terminal 7206. Note that charging may also be performed wirelessly without using the input / output terminal 7206.

[0477] The display unit 7202 of the portable information terminal 7200 has a secondary battery according to one aspect of the present invention. By using a secondary battery according to one aspect of the present invention, a lightweight and long-lasting portable information terminal can be provided. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. For example, the secondary battery 7104 shown in Figure 32E can be incorporated inside the housing 7201 in a curved state, or inside the band 7203 in a bendable state.

[0478] The portable information terminal 7200 preferably has sensors. Preferably, the sensors include, for example, a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, or an acceleration sensor.

[0479] Figure 32G shows an example of an armband-type display device. The display device 7300 has a display unit 7304 and a secondary battery according to one embodiment of the present invention. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. The display device 7300 may also be equipped with a touch sensor on the display unit 7304 and may function as a portable information terminal.

[0480] The display unit 7304 has a curved display surface, allowing it to display information along the curved surface. Furthermore, the display device 7300 can change its display status via standardized short-range wireless communication.

[0481] Furthermore, the display device 7300 is equipped with input / output terminals, allowing it to directly exchange data with other information terminals via connectors. It can also be charged via the input / output terminals. Note that charging may also be performed wirelessly without using the input / output terminals.

[0482] By using a secondary battery according to one aspect of the present invention as the secondary battery of the display device 7300, a lightweight and long-life display device can be provided.

[0483] Furthermore, an example of mounting a secondary battery with good cycle characteristics in an electronic device, according to one aspect of the present invention, will be explained using Figures 32H, 33, and 34.

[0484] By using a secondary battery according to one embodiment of the present invention as a secondary battery in electronic devices, it is possible to provide lightweight and long-lasting products. Examples of everyday electronic devices include electric toothbrushes, electric shavers, and electric beauty devices. For the secondary batteries in these products, there is a demand for a stick-shaped, small, lightweight, and high-capacity secondary battery that is easy for the user to hold.

[0485] Figure 32H is a perspective view of a device also known as a tobacco-containing smoking device (electronic cigarette). In Figure 32H, the electronic cigarette 7500 consists of an atomizer 7501 including a heating element, a secondary battery 7504 that supplies power to the atomizer, and a cartridge 7502 including a liquid supply bottle or a sensor. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 7504 may be electrically connected to the secondary battery 7504. The secondary battery 7504 shown in Figure 32H has external terminals so that it can be connected to a charging device. Since the secondary battery 7504 is the tip when held, it is desirable that its total length is short and its weight is light. A secondary battery according to one aspect of the present invention has high capacity and good cycle characteristics, so it is possible to provide a small and lightweight electronic cigarette 7500 that can be used for a long time over a long period of time.

[0486] Next, Figures 33A and 33B show an example of a foldable tablet terminal. The tablet terminal 7600 shown in Figures 33A and 33B includes a housing 7630a, a housing 7630b, a movable part 7640 connecting housings 7630a and 7630b, a display unit 7631 having display units 7631a and 7631b, switches 7625 to 7627, a fastener 7629, and an operation switch 7628. By using a flexible panel for the display unit 7631, a tablet terminal with a larger display area can be created. Figure 33A shows the tablet terminal 7600 in an open state, and Figure 33B shows the tablet terminal 7600 in a closed state.

[0487] Furthermore, the tablet terminal 7600 has a power storage unit 7635 inside the housings 7630a and 7630b. The power storage unit 7635 is provided across the housings 7630a and 7630b, passing through the movable part 7640.

[0488] The display unit 7631 can have all or part of its area designated as a touch panel area, and data can be entered by touching images, characters, input forms, etc., including icons, displayed in that area. For example, keyboard buttons may be displayed on the entire surface of the display unit 7631a on the housing 7630a side, and information such as characters and images may be displayed on the display unit 7631b on the housing 7630b side.

[0489] Alternatively, the display unit 7631b on the housing 7630b may be used to display a keyboard, while the display unit 7631a on the housing 7630a may be used to display information such as characters and images. Alternatively, the display unit 7631 may be used to display a touch panel keyboard display switching button, so that the keyboard is displayed on the display unit 7631 when the button is touched with a finger or stylus.

[0490] Furthermore, it is possible to simultaneously input touch input to the touch panel area of ​​the display unit 7631a on the housing 7630a and the touch panel area of ​​the display unit 7631b on the housing 7630b.

[0491] Furthermore, switches 7625 to 7627 may not only serve as an interface for operating the tablet terminal 7600, but also as an interface for switching various functions. For example, at least one of switches 7625 to 7627 may function as a switch to turn the tablet terminal 7600 on and off. Also, for example, at least one of switches 7625 to 7627 may have a function to switch the display orientation, such as portrait or landscape, or a function to switch between monochrome or color display. Also, for example, at least one of switches 7625 to 7627 may have a function to adjust the brightness of the display unit 7631. The brightness of the display unit 7631 can be optimized according to the amount of ambient light during use, as detected by the light sensor built into the tablet terminal 7600. Note that the tablet terminal may incorporate other detection devices in addition to the light sensor, such as a gyroscope, accelerometer, or other tilt detection sensors.

[0492] Furthermore, while Figure 33A shows an example where the display area of ​​the display unit 7631a on the housing 7630a side and the display unit 7631b on the housing 7630b side are approximately the same, the display areas of the display units 7631a and 7631b are not particularly limited, and the size of one may differ from the other, and the display quality may also differ. For example, one display panel may be capable of displaying a higher resolution than the other.

[0493] Figure 33B shows the tablet terminal 7600 in a folded state. The tablet terminal 7600 includes a housing 7630, a solar cell 7633, and a charge / discharge control circuit 7634 including a DC-DC converter 7636. Furthermore, a secondary battery according to one embodiment of the present invention is used as the energy storage body 7635.

[0494] As mentioned above, the tablet terminal 7600 is foldable, so when not in use, the casings 7630a and 7630b can be folded together. Folding protects the display unit 7631, thereby increasing the durability of the tablet terminal 7600. Furthermore, since the energy storage unit 7635 using a secondary battery according to one embodiment of the present invention has high capacity and good cycle characteristics, it is possible to provide a tablet terminal 7600 that can be used for a long period of time over a long period of time. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery in the energy storage unit 7635 may be electrically connected to the secondary battery.

[0495] In addition, the tablet terminal 7600 shown in Figures 33A and 33B may have functions such as displaying various information (still images, videos, text images, etc.), displaying a calendar, date, or time on the display unit, a touch input function for touch input operation or editing of the information displayed on the display unit, and a function for controlling processing by various software (programs).

[0496] The solar cell 7633 mounted on the surface of the tablet terminal 7600 can supply power to the touch panel, display unit, or video signal processing unit, etc. The solar cell 7633 can be installed on one or both sides of the housing 7630, allowing for an efficient configuration of charging the energy storage unit 7635. Using a lithium-ion battery as the energy storage unit 7635 offers advantages such as miniaturization.

[0497] Furthermore, the configuration and operation of the charge / discharge control circuit 7634 shown in Figure 33B will be explained with a block diagram in Figure 33C. Figure 33C shows the solar cell 7633, energy storage unit 7635, DC-DC converter 7636, converter 7637, switches SW1 to SW3, and display unit 7631, with the energy storage unit 7635, DC-DC converter 7636, converter 7637, and switches SW1 to SW3 corresponding to the charge / discharge control circuit 7634 shown in Figure 33B.

[0498] First, let's explain an example of operation when electricity is generated by the solar cell 7633 using ambient light. The power generated by the solar cell is boosted or stepped down by the DC-DC converter 7636 to obtain a voltage suitable for charging the energy storage unit 7635. When power from the solar cell 7633 is used to operate the display unit 7631, switch SW1 is turned on, and the converter 7637 boosts or steps down the voltage to the voltage required by the display unit 7631. When the display unit 7631 is not being used, switch SW1 is turned off, and switch SW2 is turned on to charge the energy storage unit 7635.

[0499] The solar cell 7633 is shown as an example of a power generation method, but it is not particularly limited, and the storage unit 7635 may be charged by other power generation methods such as piezoelectric elements or thermoelectric elements (Peltier elements). For example, a contactless power transmission module that transmits and receives power wirelessly (non-contact) to charge the storage unit, or a combination of other charging methods may be used.

[0500] Figure 34 shows an example of another electronic device. In Figure 34, the display device 8000 is an example of an electronic device using a secondary battery 8004 according to one aspect of the present invention. Specifically, the display device 8000 corresponds to a display device for receiving TV broadcasts and has a housing 8001, a display unit 8002, a speaker unit 8003, a secondary battery 8004, etc. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 8004 may be electrically connected to the secondary battery 8004. The secondary battery 8004 according to one aspect of the present invention is provided inside the housing 8001. The display device 8000 can receive power from a commercial power source or use power stored in the secondary battery 8004. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the display device 8000 can be used by using the secondary battery 8004 according to one aspect of the present invention as an uninterruptible power supply.

[0501] The display unit 8002 can use semiconductor display devices such as liquid crystal displays, light-emitting devices equipped with light-emitting elements such as organic EL elements in each pixel, electrophoretic displays, DMDs (Digital Micromirror Devices), PDPs (Plasma Display Panels), and FEDs (Field Emission Displays).

[0502] Furthermore, the term "display device" includes all information display devices, such as those for receiving TV broadcasts, personal computers, and advertising displays.

[0503] In Figure 34, the fixed-type lighting device 8100 is an example of an electronic device using a secondary battery 8103 according to one aspect of the present invention. Specifically, the lighting device 8100 includes a housing 8101, a light source 8102, a secondary battery 8103, etc. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 8103 may be electrically connected to the secondary battery 8103. In Figure 34, the case in which the secondary battery 8103 is installed inside the ceiling 8104 on which the housing 8101 and light source 8102 are installed is illustrated, but the secondary battery 8103 may also be installed inside the housing 8101. The lighting device 8100 can receive power from a commercial power source or use power stored in the secondary battery 8103. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the lighting device 8100 can be used by using the secondary battery 8103 according to one aspect of the present invention as an uninterruptible power source.

[0504] Although Figure 34 illustrates a fixed lighting device 8100 installed on the ceiling 8104, the secondary battery according to one aspect of the present invention can also be used in fixed lighting devices installed on surfaces other than the ceiling 8104, such as the side wall 8105, floor 8106, window 8107, etc., or in tabletop lighting devices, etc.

[0505] Furthermore, the light source 8102 can be an artificial light source that artificially generates light using electricity. Specifically, examples of the above artificial light sources include incandescent light bulbs, discharge lamps such as fluorescent lamps, LEDs, and / or light-emitting elements such as organic EL elements.

[0506] In Figure 34, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is an example of an electronic device using a secondary battery 8203 according to one aspect of the present invention. Specifically, the indoor unit 8200 has a housing 8201, an air outlet 8202, a secondary battery 8203, etc. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 8203 may be electrically connected to the secondary battery 8203. In Figure 34, the case in which the secondary battery 8203 is provided in the indoor unit 8200 is illustrated, but the secondary battery 8203 may also be provided in the outdoor unit 8204. Alternatively, the secondary battery 8203 may be provided in both the indoor unit 8200 and the outdoor unit 8204. The air conditioner can receive power from a commercial power source or it can use power stored in the secondary battery 8203. In particular, when both the indoor unit 8200 and the outdoor unit 8204 are equipped with secondary batteries 8203, even when power cannot be supplied from the commercial power source due to a power outage or the like, the air conditioner can be used by using the secondary battery 8203 according to one aspect of the present invention as an uninterruptible power supply.

[0507] Although Figure 34 illustrates a separate-type air conditioner consisting of an indoor unit and an outdoor unit, the secondary battery according to one aspect of the present invention can also be used in an integrated-type air conditioner that has the functions of both the indoor and outdoor units in a single housing.

[0508] In Figure 34, the electric refrigerator-freezer 8300 is an example of an electronic device using a secondary battery 8304 according to one aspect of the present invention. Specifically, the electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator door 8302, a freezer door 8303, a secondary battery 8304, etc. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 8304 may be electrically connected to the secondary battery 8304. In Figure 34, the secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 can receive power from a commercial power source or use power stored in the secondary battery 8304. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, the electric refrigerator-freezer 8300 can be used by using the secondary battery 8304 according to one aspect of the present invention as an uninterruptible power source.

[0509] Furthermore, among the electronic devices mentioned above, high-frequency heating devices such as microwave ovens and electric rice cookers require high power in a short period of time. Therefore, by using a secondary battery according to one aspect of the present invention as an auxiliary power source to supplement the power that cannot be supplied by the commercial power supply, it is possible to prevent the commercial power supply circuit breaker from tripping when the electronic device is in use.

[0510] Furthermore, by storing power in the secondary battery during periods when electronic devices are not in use, particularly during periods when the proportion of the total amount of power supplied by the commercial power source that is actually used (referred to as the power usage rate) is low, it is possible to suppress the increase in the power usage rate outside of these periods. For example, in the case of the electric refrigerator-freezer 8300, power is stored in the secondary battery 8304 at night when the temperature is low and the refrigerator door 8302 and freezer door 8303 are not opened or closed. Then, during the daytime when the temperature is high and the refrigerator door 8302 and freezer door 8303 are opened and closed, the secondary battery 8304 can be used as an auxiliary power source, thereby keeping the daytime power usage rate low.

[0511] According to one aspect of the present invention, the cycle characteristics of a secondary battery can be improved, thereby enhancing its reliability. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be created, thereby improving the characteristics of the secondary battery and thus making the secondary battery itself smaller and lighter. Therefore, by incorporating a secondary battery according to one aspect of the present invention into the electronic device described in this embodiment, it is possible to create an electronic device that has a longer lifespan and is lighter.

[0512] Figure 35A shows an example of a wearable device. Wearable devices use rechargeable batteries as a power source. Furthermore, in order to enhance splash resistance, water resistance, or dust resistance when used by users in daily life or outdoors, there is a demand for wearable devices that can be charged wirelessly in addition to wired charging with exposed connectors.

[0513] For example, a secondary battery according to one aspect of the present invention can be mounted in a spectacle-type device 9000 as shown in Figure 35A. The spectacle-type device 9000 has a frame 9000a and a display unit 9000b. By mounting the secondary battery in the temple portion of the curved frame 9000a, a lightweight spectacle-type device 9000 with good weight balance and long continuous use time can be made. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0514] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the headset-type device 9001. The headset-type device 9001 has at least a microphone section 9001a, a flexible pipe 9001b, and an earphone section 9001c. The secondary battery can be provided in the flexible pipe 9001b or in the earphone section 9001c. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0515] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in a device 9002 that can be directly attached to the body. The secondary battery 9002b can be provided within the thin housing 9002a of the device 9002. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 9002b may be electrically connected to the secondary battery 9002b. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0516] Furthermore, a secondary battery according to one aspect of the present invention can be mounted on a device 9003 that can be attached to clothing. The secondary battery 9003b can be provided within the thin housing 9003a of the device 9003. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 9003b may be electrically connected to the secondary battery 9003b. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0517] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the belt-type device 9006. The belt-type device 9006 has a belt portion 9006a and a wireless power supply / receiving portion 9006b, and a secondary battery can be mounted inside the belt portion 9006a. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0518] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the wristwatch-type device 9005. The wristwatch-type device 9005 has a display unit 9005a and a belt unit 9005b, and the secondary battery can be provided in either the display unit 9005a or the belt unit 9005b. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery may be electrically connected to the secondary battery. By incorporating a secondary battery according to one aspect of the present invention, a configuration that can accommodate space saving due to miniaturization of the housing can be realized.

[0519] The display unit 9005a can display not only the time, but also various other information such as incoming emails and / or phone calls.

[0520] Furthermore, since the wristwatch-type device 9005 is a wearable device that is worn directly on the wrist, it may be equipped with sensors to measure the user's pulse, blood pressure, etc. It can accumulate data on the user's exercise level and health, and manage their health.

[0521] Figure 35B shows a perspective view of the wristwatch-type device 9005 after it has been removed from the arm.

[0522] A side view is also shown in Figure 35C. Figure 35C shows a secondary battery 913 according to one embodiment of the present invention built inside. The secondary battery 913 is located in a position overlapping with the display unit 9005a, and is small and lightweight.

[0523] Figure 36A shows an example of a cleaning robot. The cleaning robot 9300 has a display unit 9302 located on the top surface of the housing 9301, multiple cameras 9303 located on the sides, a brush 9304, operation buttons 9305, a secondary battery 9306, and various sensors. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 9306 may be electrically connected to the secondary battery 9306. Although not shown, the cleaning robot 9300 is equipped with wheels, a suction port, etc. The cleaning robot 9300 is self-propelled, can detect dirt 9310, and can suck up the dirt from a suction port located on the bottom surface.

[0524] For example, the cleaning robot 9300 can analyze images captured by the camera 9303 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that could become entangled in the brush 9304, such as wiring, the rotation of the brush 9304 can be stopped. The cleaning robot 9300 is equipped with a secondary battery 9306 according to one aspect of the present invention and a semiconductor device or electronic component. By using the secondary battery 9306 according to one aspect of the present invention in the cleaning robot 9300, the cleaning robot 9300 can be made into a highly reliable electronic device with a long operating time.

[0525] Figure 36B shows an example of a robot. The robot 9400 shown in Figure 36B is equipped with a secondary battery 9409, an illuminance sensor 9401, a microphone 9402, an upper camera 9403, a speaker 9404, a display unit 9405, a lower camera 9406 and an obstacle sensor 9407, a movement mechanism 9408, a computing device, etc. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 9409 may be electrically connected to the secondary battery 9409.

[0526] Microphone 9402 has the function of detecting the user's voice and ambient sounds. Speaker 9404 has the function of emitting sound. Robot 9400 can communicate with the user using microphone 9402 and speaker 9404.

[0527] The display unit 9405 has the function of displaying various types of information. The robot 9400 can display the user's desired information on the display unit 9405. The display unit 9405 may be equipped with a touch panel. The display unit 9405 may also be a detachable information terminal, and by installing it in a fixed position on the robot 9400, charging and data transfer can be made possible.

[0528] The upper camera 9403 and lower camera 9406 have the function of imaging the area around the robot 9400. In addition, the obstacle sensor 9407 can detect the presence or absence of obstacles in the direction of travel when the robot 9400 moves forward using the movement mechanism 9408. The robot 9400 can recognize its surrounding environment and move safely using the upper camera 9403, lower camera 9406 and obstacle sensor 9407.

[0529] The robot 9400 is equipped with a secondary battery 9409 according to one aspect of the present invention and a semiconductor device or electronic components inside. By using the secondary battery according to one aspect of the present invention in the robot 9400, the robot 9400 can be made into an electronic device with a long operating time and high reliability.

[0530] Figure 36C shows an example of an aircraft. The aircraft 9500 shown in Figure 36C has a propeller 9501, a camera 9502, and a secondary battery 9503, and has the capability to fly autonomously. To enhance safety, a protection circuit to prevent overcharging and / or over-discharging of the secondary battery 9503 may be electrically connected to the secondary battery 9503.

[0531] For example, image data captured by camera 9502 is stored in electronic component 9504. Electronic component 9504 can analyze the image data and detect the presence or absence of obstacles during movement. Furthermore, electronic component 9504 can estimate the remaining battery level from the change in the storage capacity of secondary battery 9503. The aircraft 9500 is equipped with a secondary battery 9503 according to one aspect of the present invention. By using a secondary battery according to one aspect of the present invention in the aircraft 9500, the aircraft 9500 can be made into an electronic device with a long operating time and high reliability.

[0532] This embodiment can be implemented in appropriate combination with other embodiments. [Examples]

[0533] In this example, graphene according to one embodiment of the present invention was fabricated and its physical properties were evaluated.

[0534] <Graphene fabrication> Fluorine-containing graphene was fabricated by referring to the flow chart shown in Figure 6.

[0535] In step S21, graphene oxide was prepared as material 801. In step S22, lithium fluoride was used as material 802. In step S23, lithium carbonate was used as material 803.

[0536] In step S31, 0.25 g of graphene oxide, 0.0125 g of lithium fluoride, and 0.0125 g of lithium carbonate were mixed, recovered in step S32, and mixture 804 was obtained in step S33.

[0537] In step S51, heating was performed. The heating conditions were 850°C for 10 hours under a nitrogen atmosphere.

[0538] In step S52, the heated mixture was recovered, and in step S53, graphene 583 was obtained. The graphene 583 obtained in this example will hereafter be referred to as sample Sm1.

[0539] <Raman spectroscopy> Using a NRS-5500 spectrometer manufactured by JASCO Corporation, Japan, the Raman spectrum of sample Sm1 was obtained. The excitation wavelength was set to 532 nm. The measurement was carried out in an air atmosphere at room temperature.

[0540] An optical microscope photograph of sample Sm1 is shown in Fig. 37. In the Raman spectrum, the in-plane distribution of the peak intensity of the D band is shown in Fig. 38A, the in-plane distribution of the peak intensity of the G band is shown in Fig. 38B, and the ratio of the peak intensity of the D band to the peak intensity of the G band (D-band peak intensity / G-band peak intensity) is shown in Fig. 38C. Also, the Raman spectrum of an arbitrary location of sample Sm1 is shown in Fig. 39.

[0541] The observation of the G band (G-band) suggested the sp2 bonding of carbon, indicating that the obtained sample Sm1 has graphene. Also, the observation of the D band (D-band) suggested that the obtained graphene has defects.

[0542] <TEM observation> Next, TEM observation of sample Sm1 was performed. For the observation, a JEM-ARM200F manufactured by JEOL Ltd., Japan was used. The acceleration voltage was set to 80 kV. The obtained TEM image is shown in Fig. 40. Also, the FFT filtering images of the region 91 indicated by a square in Fig. 40 are shown in Figs. 41A and 42A. Fig. 41B is an enlarged view of the region surrounded by a square in Fig. 41A, and Fig. 42B is an enlarged view of the region surrounded by a square in Fig. 42A.

[0543] The FFT filtering image refers to an image obtained by performing IFFT processing on an image obtained by performing FFT processing on a TEM image.

[0544] As shown in Fig. 41B, the presence of a 7-membered ring was suggested.

[0545] As shown in Fig. 42B, the presence of a 12-membered ring was suggested. The presence of the 12-membered ring was suggested by consideration using an image obtained by first-principles calculation.

[0546] Figure 42C shows the TEM image of graphene with a 12-membered ring, obtained by calculation. The structure of graphene with a 12-membered ring was determined by first-principles calculations using a plane-wave basis and pseudopotential. GGA-PBE was used as the exchange-correlation functional. Based on the graphene structure obtained by first-principles calculations, the image when the electron beam optical system was defocused from the focal position was calculated using the aperture radius, convergence angle, and spherical aberration coefficient of the electron beam optical system. The acceleration voltage was 80kV and the objective aperture radius was 6nm. -1 The convergence angle was set to 0.3 mrad, and the defocus value was set to -10 nm.

[0547] The graphene obtained in this embodiment according to one aspect of the present invention is suggested to have multi-membered rings of 7 or more members, and is also suggested to have pores composed of 12-membered rings.

[0548] <edx> Next, we performed STEM imaging and EDX analysis on sample Sm1.

[0549] A JEOL JEM-ARM200F microscope was used for STEM observation and EDX analysis. The acceleration voltage was set to 80kV. A JEOL JED-2300T EDX analyzer was used. Figure 43A shows the STEM image of region 92 shown in Figure 40. Figure 43B shows the EDX surface analysis image corresponding to the observation area shown in Figure 43A. When the spectra were analyzed in regions A and B, indicated by squares in the figures, fluorine was detected in both regions. Furthermore, fluorine was also detected in other regions, suggesting that fluorine is widely distributed within the surface. [Explanation of Symbols]

[0550] 91: Region, 92: Region, 100: Positive electrode active material, 130: Laminate, 131: Laminate, 500: Secondary battery, 501: Positive electrode current collector, 502: Positive electrode active material layer, 503: Positive electrode, 504: Negative electrode current collector, 505: Negative electrode active material layer, 506: Negative electrode, 507: Separator, 507a: Region, 507b: Region, 508: Electrolyte, 509: Outer casing, 509a: Outer casing, 509b: Outer casing, 510: Positive electrode lead electrode, 511: Negative electrode lead electrode, 512: Laminate, 513: Resin layer, 514: Region, 515a: Electrolyte, 515b: Electrolyte, 515c: Electrolyte, 516: Inlet, 550 :Laminate, 560:Secondary battery, 570:Electrode, 570b:Region, 571:Current collector, 572:Active material layer, 581:Electrolyte, 582:Particle, 582b:Particle, 583:Graphene, 584:Acetylene black, 584b:Material, 585:Pore, 586:Pore, Polymer film, 587:Pore, 588:Pore, Polymer film, 600:Secondary battery, 670:Manufacturing equipment, 671:Material input chamber, 672:Transportation chamber, 673:Processing chamber, 676:Material removal chamber, 680:Transportation mechanism, 691:Stage, 694:Nozzle, 701:Commercial power supply, 703:Distribution board, 705:Energy storage controller, 70 6: Display unit, 707: General load, 708: Energy storage system load, 709: Router, 710: Service drop connection section, 711: Measurement section, 712: Prediction section, 713: Planning section, 790: Control device, 791: Energy storage device, 796: Underfloor space section, 799: Building, 801: Material, 802: Material, 803: Material, 804: Mixture, 804b: Mixture, 903: Mixture, 904: Mixture, 911a: Terminal, 911b: Terminal, 913: Secondary battery, 930: Housing, 930a: Housing, 930b: Housing, 931: Negative electrode, 931a: Negative electrode active material layer, 932: Positive electrode, 932a: Positive electrode active material layer, 933: Se Separator, 950: wound body, 950a: wound body, 951: terminal, 952: terminal, 970: secondary battery, 971: housing, 972: laminate, 973a: positive lead electrode, 973b: terminal, 973c: conductor, 974a: negative lead electrode, 974b: terminal, 974c: conductor, 975a: positive electrode, 975b: positive electrode, 976: separator, 977a: negative electrode, 1301a: battery, 1301b: battery, 1302: battery controller, 1303: motor controller, 1304: motor, 1305: gear, 1306: DC-DC circuit, 1307: electric power steering,1308: Heater, 1309: Defogger, 1310: DC-DC circuit, 1311: Battery, 1312: Inverter, 1313: Audio, 1314: Power windows, 1315: Lights, 1316: Tires, 1317: Rear motor, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1325: External terminals, 1326: External terminals, 1415: Battery pack, 1421: Wiring, 1422: Wiring, 2001: Automobile, 2002: Transport vehicle, 2003: Transport vehicle, 2004: Aircraft, 2005: Transport vehicle, 21 00: Electric bicycle, 2101: Secondary battery, 2102: Energy storage device, 2103: Display unit, 2104: Control circuit, 2201: Battery pack, 2202: Battery pack, 2203: Battery pack, 2204: Battery pack, 2300: Scooter, 2301: Side mirror, 2302: Energy storage device, 2303: Turn signal light, 2304: Under-seat storage, 2603: Vehicle, 2604: Charging device, 2610: Solar panel, 2611: Wiring, 2612: Energy storage device, 2800: Personal computer, 2801: Enclosure, 2802: Enclosure, 2803: Display unit, 2804: Keyboard, 2 805: Pointing device, 2806: Rechargeable battery, 2807: Rechargeable battery, 7100: Portable display device, 7101: Housing, 7102: Display unit, 7103: Operation buttons, 7104: Rechargeable battery, 7200: Portable information terminal, 7201: Housing, 7202: Display unit, 7203: Band, 7204: Buckle, 7205: Operation buttons, 7206: Input / output terminal, 7207: Icon, 7300: Display device, 7304: Display unit, 7400: Mobile phone, 7401: Housing, 7402: Display unit, 7403: Operation buttons, 7404: External connection port, 7405: Speaker, 7 406: Microphone, 7407: Rechargeable battery, 7500: Electronic cigarette, 7501: Atomizer, 7502: Cartridge, 7504: Rechargeable battery, 7600: Tablet terminal, 7625: Switch, 7627: Switch, 7628: Operation switch, 7629: Fastener, 7630: Housing, 7630a: Housing, 7630b: Housing, 7631: Display unit, 7631a: Display unit, 7631b: Display unit, 7633: Solar cell, 7634: Charge / discharge control circuit, 7635: Energy storage unit, 7636: DC-DC converter, 7637: Converter, 7640: Movable part, 8000: Display device,8001: Enclosure, 8002: Display unit, 8003: Speaker unit, 8004: Rechargeable battery, 8100: Lighting device, 8101: Enclosure, 8102: Light source, 8103: Rechargeable battery, 8104: Ceiling, 8105: Side wall, 8106: Floor, 8107: Window, 8200: Indoor unit, 8201: Enclosure, 8202: Air outlet, 8203: Rechargeable battery, 8204: Outdoor unit, 8300: Electric refrigerator / freezer, 830 1: Enclosure, 8302: Door for refrigerator compartment, 8303: Door for freezer compartment, 8304: Rechargeable battery, 9000: Glasses-type device, 9000a: Frame, 9000b: Display unit, 9001: Headset-type device, 9001a: Microphone unit, 9001b: Flexible pipe, 9001c: Earphone unit, 9002: Device, 9002a: Enclosure, 9002b: Rechargeable battery, 9003: Device Chair, 9003a: Housing, 9003b: Rechargeable battery, 9005: Wristwatch-type device, 9005a: Display unit, 9005b: Belt unit, 9006: Belt-type device, 9006a: Belt unit, 9006b: Wireless power supply / receiving unit, 9300: Cleaning robot, 9301: Housing, 9302: Display unit, 9303: Camera, 9304: Brush, 9305: Operation buttons, 9306: Rechargeable battery Battery, 9310: Garbage, 9400: Robot, 9401: Illuminance sensor, 9402: Microphone, 9403: Upper camera, 9404: Speaker, 9405: Display unit, 9406: Lower camera, 9407: Obstacle sensor, 9408: Movement mechanism, 9409: Rechargeable battery, 9500: Flying object, 9501: Propeller, 9502: Camera, 9503: Rechargeable battery, 9504: Electronic component,< / edx>

Claims

[Claim 1] It has a pore composed of a multi-membered ring of 9 or more members made up of carbon atoms, The graphene in which one or more of the carbon atoms constituting the multi-membered ring are terminated with fluorine, The aforementioned graphene was found to have a temperature of 1580 cm⁻¹ by Raman spectroscopy analysis. －１ Or the first peak observed in its vicinity, and 1360 cm －１ or has a second peak observed in its vicinity, The ratio of the intensity of the second peak to the intensity of the first peak is 1 or more and 3 or less. Graphene.

Images