Electrode, negative electrode active material, negative electrode, secondary battery, moving object, electronic device, method for manufacturing negative electrode active material, and method for manufacturing

Abstract

Provided is a negative electrode having little deterioration. In addition, a novel negative electrode is provided. Also provided is a power storage device with little deterioration. In addition, a novel power storage device is provided. The electrode includes silicon, graphite, and a graphene compound, silicon particles having a particle diameter of 1 [mu] m or less adhere to graphite particles having a particle diameter of 10 or more times the particle diameter of the silicon particles, and the graphene compound is in contact with the graphite particles so as to cover the silicon particles.

Description

Technical Field

[0001] One aspect of the present invention relates to an electrode and a method for manufacturing the same. In addition, one aspect of the present invention relates to an active material included in the electrode and a method for manufacturing the same. In addition, one aspect of the present invention relates to a secondary battery and a method for manufacturing the same. In addition, one aspect of the present invention relates to a moving body such as a vehicle including a secondary battery, a portable information terminal, an electronic device, and the like.

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

[0003] Note that in this specification, an electronic device refers to all devices having a power storage device, such as an electro-optical device having a power storage device and an information terminal device having a power storage device.

[0004] It should be noted that in this specification, a power storage device refers to all elements and devices having a power storage function. For example, power storage devices such as lithium-ion secondary batteries (also referred to as secondary batteries), lithium-ion capacitors, and electric double-layer capacitors are included in the category of power storage devices. Background Art

[0005] In recent years, research and development of various power storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and air batteries have been increasingly active. In particular, with the development of the semiconductor industry for portable information terminals such as mobile phones, smartphones, notebook personal computers, portable music players, digital cameras, medical devices, and new-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV), the demand for high-output, high-energy-density lithium-ion secondary batteries has increased dramatically, and they have become essential in modern information society as an energy supply source that can be repeatedly charged. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-216751 [Patent Document 2] Japanese PCT International Application Translation No. 2019-522886 Summary of the Invention Technical Problem to be Solved by the Invention

[0007] In order to extend the driving distance, secondary batteries for mobile bodies such as electric vehicles and hybrid vehicles need to increase their capacity.

[0008] In addition, in portable terminals and the like, as they become more multifunctional, their power consumption increases. In addition, secondary batteries for portable terminals and the like are required to be miniaturized and lightweight. Therefore, secondary batteries for portable terminals are also required to have a high capacity.

[0009] In addition to stability, it is important for secondary batteries to have a high capacity. Alloy materials such as silicon-based materials have a high capacity and are thus expected to be used as active materials for secondary batteries. However, alloy materials with a high charge-discharge capacity undergo volume changes during charge and discharge, resulting in problems such as pulverization and detachment of the active material, and sufficient cycle characteristics cannot be obtained.

[0010] In order to solve the problems of the above alloy materials, the compounding of alloy materials with graphite or carbon materials has been studied. In Patent Document 1, there is a description of a composite material in which a coating layer made of carbon is formed on the surface of a porous particle core formed by bonding silicon-containing particles and carbon-containing particles. In Patent Document 2, there is a description of composite particles containing silicon (Si), lithium fluoride (LiF), and a carbon material. However, in any of the above documents, the problems such as pulverization and detachment of the active material caused by the expansion of the alloy material during charge and discharge still cannot be fully solved.

[0011] For example, the electrode of a secondary battery is composed of materials such as an active material, a conductive agent, and a binder. The higher the ratio of materials such as the active material that contribute to the charge-discharge capacity, the higher the capacity of the secondary battery can be increased. By including a conductive agent in the electrode, the conductivity of the electrode can be improved and good output characteristics can be obtained. In addition, when the active material repeatedly expands and contracts during the charge and discharge of the secondary battery, peeling of the active material and blockage of the conduction path sometimes occur in the electrode. In this case, by including a conductive agent and a binder in the electrode, peeling of the active material and blockage of the conduction path can be suppressed. On the other hand, when using a conductive agent and a binder, the ratio of the active material decreases, and sometimes the capacity of the secondary battery decreases.

[0012] One of the objectives of one aspect of the present invention is to provide an electrode having excellent characteristics. In addition, one of the objectives of one aspect of the present invention is to provide an active material having excellent characteristics. In addition, one of the objectives of one aspect of the present invention is to provide a novel electrode.

[0013] In addition, one of the objectives of one embodiment of the present invention is to provide a negative electrode with high mechanical strength. In addition, one of the objectives of one embodiment of the present invention is to provide a positive electrode with high mechanical strength. In addition, one of the objectives of one embodiment of the present invention is to provide a negative electrode with high capacity. In addition, one of the objectives of one embodiment of the present invention is to provide a positive electrode with high capacity. In addition, one of the objectives of one embodiment of the present invention is to provide a negative electrode with less deterioration. In addition, one of the objectives of one embodiment of the present invention is to provide a positive electrode with less deterioration.

[0014] In addition, one of the objectives of one embodiment of the present invention is to provide a secondary battery with less deterioration. In addition, one of the objectives of one embodiment of the present invention is to provide a secondary battery with high safety. In addition, one of the objectives of one embodiment of the present invention is to provide a secondary battery with high energy density. In addition, one of the objectives of one embodiment of the present invention is to provide a novel secondary battery.

[0015] Note that the description of the above objectives does not preclude the existence of other objectives. Note that one embodiment of the present invention does not need to achieve all of the above objectives. In addition, objectives other than the above can be extracted from the descriptions in the specification, drawings, and claims. Means for Solving Technical Problems

[0016] An electrode according to one embodiment of the present invention includes particles and a flaky material. The particles include first particles and second particles. The particle size of the first particles and the flaky material is larger than that of the second particles. The electrode includes a region where the second particles are located between the first particles and the flaky material, and the electrode includes a region where the first particles are in contact with the flaky material.

[0017] In addition, an electrode according to one embodiment of the present invention includes particles and a flaky material. The particles include first particles and second particles. The particle size of the first particles and the flaky material is larger than that of the second particles, and the flaky material includes a region in contact with the first particles in a manner of covering, coating, or winding the second particles located on the surface of the first particles.

[0018] Preferably, the flaky material includes a first region terminated by hydrogen atoms. The first region is, for example, a region composed of an atom bondable to hydrogen and a hydrogen atom bonded to the atom. In addition, the first region is, for example, a region containing a plurality of atoms bondable to hydrogen.

[0019] The hydrogen atoms contained in the first region and the oxygen atoms contained in the functional groups terminating the surfaces of the first particles or the second particles can form hydrogen bonds.

[0020] The sheet material can be bent in a manner close to the particle due to intermolecular forces and wind around the particle through hydrogen bonds. In addition, the sheet material preferably includes a plurality of regions terminated by hydrogen atoms on the sheet surface.

[0021] In addition, the first region may also be terminated by a functional group containing oxygen. Examples of the functional group containing oxygen include a hydroxyl group, an epoxy group, a carboxyl group, etc. The hydrogen atoms contained in the hydroxyl group, the carboxyl group, etc. can form hydrogen bonds with the oxygen atoms contained in the functional group terminating the particle. In addition, the oxygen atoms contained in the hydroxyl group, the epoxy group, and the carboxyl group can form hydrogen bonds with the hydrogen atoms contained in the functional group terminating the particle.

[0022] In addition, in the case where the sheet material includes a second region terminated by fluorine atoms, the fluorine atoms contained in the second region can form hydrogen bonds with the hydrogen atoms contained in the functional group terminating the particle. Thereby, the sheet material can wind around the particle more easily.

[0023] In addition, the first region sometimes includes pores formed on the sheet surface. The pores are constituted by, for example, a plurality of atoms bonded in a ring shape and atoms terminating the plurality of atoms. In addition, the plurality of atoms may also be terminated by a functional group.

[0024] The particles included in the electrode of one embodiment of the present invention are preferably used as an active material, for example. As the particles included in the electrode of one embodiment of the present invention, a material used as an active material can be used. In addition, the particles included in the electrode of one embodiment of the present invention preferably contain a material used as an active material, for example. In addition, the sheet material included in the electrode of one embodiment of the present invention is preferably used as a conductive agent, for example. In one embodiment of the present invention, the conductive agent can wind around the active material due to hydrogen bonds, thereby enabling an electrode with high conductivity to be achieved.

[0025] In addition, the first particles included in the electrode of one embodiment of the present invention are preferably used as a first active material, and the second particles are preferably used as a second active material. The first particles are preferably an active material with a relatively small volume change during charge and discharge, and their particle size is preferably 10 times or more the particle size of the second particles, for example. In addition, the sheet material included in the electrode of one embodiment of the present invention is preferably used as a conductive agent, for example. In one embodiment of the present invention, the sheet material can contact the first particles in a manner of covering, coating, or winding the second particles located on the surface of the first particles, thereby enabling an electrode with high conductivity to be achieved.

[0026] In addition, the sheet-like material can prevent the exfoliation of the active material in the electrode by winding the active material. In addition, the sheet-like material can also wind multiple active materials. When a material with a large volume change during charge and discharge, such as silicon, is used as the active material, the adhesion between the active material and the conductive agent, between multiple active materials, etc. may gradually weaken due to repeated charge and discharge, resulting in the exfoliation of the active material in the electrode. In one embodiment of the present invention, when silicon is used as the second particle, it can be in contact with the first particle in a manner of covering, coating, or winding the second particle on the surface of the first particle with a small volume change during charge and discharge. Thus, the exfoliation of the active material in the electrode can be suppressed even during repeated charge and discharge, and a highly reliable electrode with stable characteristics can be achieved. The theoretical capacity of silicon is very high, reaching more than 4000 mAh / g, so the energy density of the secondary battery can be increased. By using an active material with a small volume change during charge and discharge and a material containing silicon as the first particle and the second particle in one embodiment of the present invention, a highly reliable secondary battery with high energy density and stable characteristics even during repeated charge and discharge can be achieved.

[0027] The second particle in one embodiment of the present invention contains silicon atoms terminated with hydroxyl groups. In addition, the particle in one embodiment of the present invention contains silicon, and at least a part of the surface is terminated with hydroxyl groups. In addition, the particle in one embodiment of the present invention is a silicon compound with at least a part of the surface terminated with hydroxyl groups. In addition, the particle in one embodiment of the present invention is silicon with at least a part of the surface terminated with hydroxyl groups.

[0028] In addition, the first particle in one embodiment of the present invention preferably contains a first material, and the second particle preferably contains a second material.

[0029] In addition, in the above structure, the first material is preferably one or more selected from graphite, graphitizable carbon, non-graphitizable carbon, carbon nanotubes, carbon black, and graphene.

[0030] In addition, in the above structure, the second material preferably contains a metal or compound containing one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium.

[0031] As the material having a sheet-like shape, a graphene compound is preferably used. As the graphene compound, for example, graphene in which carbon atoms are terminated with atoms or functional groups other than carbon in the thin film plane is preferably used.

[0032] Graphene has a structure in which its edges are terminated with hydrogen. In addition, the thin sheet of graphene has a two-dimensional structure formed by carbon 6-membered rings. When defects or pores are formed in this two-dimensional structure, the carbon atoms near the defects or the carbon atoms constituting the pores may sometimes be terminated with various functional groups or atoms such as hydrogen atoms and fluorine atoms.

[0033] In one embodiment of the present invention, by forming defects or pores in graphene and using hydrogen atoms, fluorine atoms, functional groups containing hydrogen atoms or fluorine atoms, oxygen-containing functional groups, etc. to terminate the carbon atoms near the defects or the carbon atoms constituting the pores, graphene can be wound around the particles included in the electrode. In addition, the number of defects or pores formed in graphene is preferably such that the conductivity of the entire graphene is not severely damaged. Here, the atoms constituting the pores refer to, for example, the atoms around the opening, the atoms at the end of the opening, etc.

[0034] The graphene compound of one embodiment of the present invention has pores formed by polycyclic rings composed of 7-membered rings or more of carbon, preferably 18-membered rings or more, and more preferably 22-membered rings or more. In addition, one of the carbon atoms of the polycyclic ring is terminated by a hydrogen atom. Further, in one embodiment of the present invention, one of the carbon atoms of the polycyclic ring is terminated by a hydrogen atom, and another one is terminated by a fluorine atom. In addition, in one embodiment of the present invention, the number of carbon atoms terminated by fluorine in the polycyclic ring is less than 40% of the number of carbon atoms terminated by hydrogen atoms.

[0035] The graphene compound of one embodiment of the present invention has pores formed by a plurality of carbon atoms bonded in a ring and atoms or functional groups, etc. that terminate the plurality of carbon atoms. One or more of the plurality of carbon atoms bonded in a ring may also be substituted by group 13 elements such as boron, group 15 elements such as nitrogen, and group 16 elements such as oxygen.

[0036] In the graphene compound of one embodiment of the present invention, the carbon atoms other than the edges are preferably terminated by hydrogen atoms, fluorine atoms, functional groups containing hydrogen atoms or fluorine atoms, oxygen-containing functional groups, etc. Further, for example, in the graphene compound of one embodiment of the present invention, the carbon atoms are preferably terminated by hydrogen atoms, fluorine atoms, functional groups containing hydrogen atoms or fluorine atoms, oxygen-containing functional groups, etc. near the center of the surface of the graphene.

[0037] One embodiment of the present invention is an electrode including: a first active material; a second active material; and a graphene compound, wherein the first active material contains silicon with a particle size of 1 μm or less, the second active material contains graphite larger than the first active material, the first active material is located on the surface of the second active material, and the graphene compound is in contact with the first active material and the second active material.

[0038] In any of the above-described electrodes, the graphene compound preferably contacts the second active material in a manner covering the first active material.

[0039] In any of the above-described electrodes, the graphene compound preferably contacts the second active material in a manner winding around the first active material.

[0040] In any of the above-described electrodes, preferably, the first active material is located between the second active material and the graphene compound.

[0041] In any of the above-described electrodes, preferably, the size of the second active material is 10 times or more the size of the first active material.

[0042] In any of the above-described electrodes, silicon preferably contains amorphous silicon.

[0043] In any of the above-described electrodes, preferably, the graphene compound includes pores and contains a plurality of carbon atoms and one or more hydrogen atoms. The one or more hydrogen atoms respectively terminate any of the plurality of carbon atoms, and the pores are formed by the plurality of carbon atoms and the one or more hydrogen atoms.

[0044] In addition, one aspect of the present invention is a secondary battery including: any of the above-described electrodes; and an electrolyte.

[0045] In addition, one aspect of the present invention is a moving body including any of the above-described secondary batteries.

[0046] In addition, one aspect of the present invention is an electronic device including any of the above-described secondary batteries.

[0047] In addition, one aspect of the present invention is a method for manufacturing an electrode for a lithium ion secondary battery, including: a first step of manufacturing a first mixture by mixing silicon and a solvent; a second step of manufacturing a second mixture by mixing the first mixture and graphite; a third step of manufacturing a third mixture by mixing the second mixture and a graphene compound; a fourth step of manufacturing a fourth mixture by mixing the third mixture, a polyimide precursor, and a solvent; a fifth step of coating the fourth mixture on a metal foil; a sixth step of drying the fourth mixture; and a seventh step of heating the fourth mixture to manufacture an electrode. The heating is performed in a reduced-pressure environment, and the graphene compound is reduced and the polyimide precursor is imidized by heating.

[0048] In addition, in the above structure, preferably, the graphene compound contains graphene oxide, and the size of the graphite is 10 times or more the size of the silicon. Advantages of the Invention

[0049] According to one aspect of the present invention, an electrode having excellent characteristics can be provided. In addition, according to one aspect of the present invention, a novel electrode can be provided.

[0050] In addition, according to one aspect of the present invention, a negative electrode with high mechanical strength can be provided. In addition, according to one aspect of the present invention, a positive electrode with high strength can be provided. In addition, according to one aspect of the present invention, a negative electrode with less deterioration can be provided. In addition, according to one aspect of the present invention, a positive electrode with less deterioration can be provided. In addition, according to one aspect of the present invention, a negative electrode with less deterioration can be provided. In addition, according to one aspect of the present invention, a positive electrode with less deterioration can be provided.

[0051] In addition, according to one aspect of the present invention, a secondary battery with less deterioration can be provided. In addition, according to one aspect of the present invention, a secondary battery with high safety can be provided. In addition, according to one aspect of the present invention, a secondary battery with high energy density can be provided. In addition, according to one aspect of the present invention, a novel secondary battery can be provided.

[0052] Note that the description of these effects does not preclude the existence of other effects. In addition, one aspect of the present invention does not necessarily have all of the above effects. In addition, there are obviously effects other than the above effects in the descriptions of the specification, drawings, claims, etc., and effects other than the above effects can be obtained from the descriptions of the specification, drawings, claims, etc. Brief Description of the Drawings

[0053] Figure 1A and Figure 1B is a diagram showing an example of a cross section of an electrode, Figure 1C is a perspective view of particles. Figure 2A and Figure 2B is a diagram showing the shape change of particles during charge and discharge. Figure 3A and Figure 3B show an example of a model of a graphene compound. Figure 4 is a diagram showing an example of a manufacturing method of an electrode according to one aspect of the present invention. Figure 5 is a diagram for explaining the crystal structure of a positive electrode active material. Figure 6 is a diagram for explaining the crystal structure of a positive electrode active material. Figure 7 is a diagram showing an example of a cross section of a secondary battery. Figure 8A is an exploded perspective view of a coin-type secondary battery, Figure 8B is a perspective view of a coin-type secondary battery, Figure 8C is a cross-sectional perspective view thereof. Figure 9A and Figure 9B are examples of cylindrical secondary batteries,Figure 9C is an example of a plurality of cylindrical secondary batteries, Figure 9D is an example of a power storage system including a plurality of cylindrical secondary batteries. Figure 10A and Figure 10B is a diagram illustrating an example of a secondary battery, Figure 10C is a diagram showing the state inside the secondary battery. Figure 11A , Figure 11B and Figure 11C is a diagram illustrating an example of a secondary battery. Figure 12A and Figure 12B is a diagram showing the appearance of the secondary battery. Figure 13A , Figure 13B and Figure 13C is a diagram illustrating a method of manufacturing a secondary battery. Figure 14A is a perspective view showing a battery pack, Figure 14B is a block diagram of the battery pack, Figure 14C is a block diagram of a vehicle including an engine. Figures 15A to 15D is a diagram illustrating an example of a transport vehicle Figure 16A and Figure 16B is a diagram illustrating a power storage device. Figures 17A to 17D is a diagram illustrating an example of an electronic device. Figure 18A and Figure 18B shows a SEM image. Figure 19A and Figure 19B shows a SEM image. Figure 20A and Figure 20B shows a SEM image. Figure 21A and Figure 21B shows a SEM image. Figure 22A and Figure 22B is a diagram showing a cycle characteristic. Figure 23 is a diagram showing the relationship between the electrode ratio and the cycle characteristic. Mode for Carrying Out the Invention

[0054] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and those of ordinary skill in the art can easily understand the fact that its mode and details can be changed into various forms. In addition, the present invention should not be construed as being limited only to the content described in the following embodiments.

[0055] In the drawings, for the sake of clear illustration, the sizes, thicknesses of layers, or regions are sometimes exaggerated. Therefore, the present invention is not limited to the dimensions in the drawings.

[0056] In addition, in this specification and the like, for convenience, ordinal numbers such as first, second, etc. are added, and they do not indicate the process order or the stacking order. Therefore, for example, "first" can be appropriately replaced with "second" or "third", etc. for explanation. In addition, the ordinal numbers described in this specification and the like are sometimes inconsistent with the ordinal numbers used to specify one mode of the present invention.

[0057] (Embodiment 1) In this embodiment, an electrode, an active material, a conductive agent, etc. of one mode of the present invention will be described.

[0058] <An example of an electrode> Figure 1A is a schematic cross-sectional view showing an electrode of one mode of the present invention. Figure 1A The electrode 570 shown can be applied to the positive electrode and / or negative electrode included in 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.

[0059] Figure 1B is Figure 1A an enlarged view of the region surrounded by a dashed line in Figure 1B As shown, the active material layer 572 includes first particles 581, second particles 582, a graphene compound 583, and an electrolyte 584. The graphene compound 583 has a sheet shape. Figure 1C is a schematic view showing a case where the graphene compound 583 contacts the first particles 581 in such a manner as to cover, coat, or wind the second particles 582 located on the surface of the first particles 581. As the first particles 581 and the second particles 582, materials used as active materials can be used. In addition, at least the second particles 582 preferably contain materials used as active materials. In addition, the graphene compound 583 included in the electrode 570 is preferably used as a conductive agent. In one mode of the present invention, when the graphene compound 583 is used as a conductive material, the active material can be wound by hydrogen bonds, thereby enabling an electrode with high conductivity to be achieved.

[0060] As the first particles 581 and the second particles 582, various materials can be used. When the particles of one mode of the present invention are used as the first particles 581 and the second particles 582, as Figure 1B and Figure 1C shown, the affinity between the first particles 581 and the second particles 582 and the graphene compound 583 is improved, as Figure 1B andFigure 1C As shown, the graphene compound 583 can contact the first particle 581 in a manner that covers, coats, or winds around the second particle 582 located on the surface of the first particle 581. As the particles of one aspect of the present invention, for example, particles containing a functional group containing oxygen or fluorine in the surface layer portion or particles having a region terminated with a functional group containing oxygen or fluorine atoms on the surface can be used. The graphene compound 583 can wind around the first particle 581 and the second particle 582, thereby enabling an electrode with high conductivity to be achieved. The state of contact in a winding manner can also be said to be a state of contact in a close contact manner rather than at a point. In addition, it can also be said to be a state of contact along the particle surface. In addition, it can also be said to be a state of surface contact with a plurality of particles. The materials that can be used as the first particle 581 and the second particle 582 will be described later.

[0061] A case where an active material with a large volume change during charge and discharge is used as the second particle 582 will be described with reference to FIG. 2. Figure 2A The following is shown: including the first particle 581, the second particle 582, and the graphene compound 583 as a sheet material, and the graphene compound 583 contacts the first particle 581 in a manner that covers, coats, or winds around the second particle 582 located on the surface of the first particle 581. The second particle 582 is located between the first particle 581 and the graphene compound 583, and thus it can also be said that the graphene compound 583 contacts the first particle 581 and the second particle 582. Figure 2B Shows Figure 2A The case where the volume of the second particle 582 shown increases due to charging or discharging. Since the graphene compound 583 contacts the first particle 581 in a manner that covers, coats, or winds around the second particle 582 located on the surface of the first particle 581, even if the volume of the second particle 582 increases due to charging or discharging, the electrical connection between the second particle 582 and the first particle 581 can be maintained. In addition, exfoliation of the active material of the electrode can be suppressed.

[0062] When the graphene compound 583 contacts the active material in a manner that winds around the active material such as the first particle 581 and the second particle 582, the contact area between the graphene compound 583 and the active material increases, and the conductivity of electrons migrating through the graphene compound 583 is improved. In addition, when the volume change of the active material due to charge and discharge is large, by making the graphene compound 583 contact the active material in a manner that winds around the active material, detachment of the active material can be effectively prevented, and these effects are more significant when the graphene compound contacts the active material in a tightly wound manner. Here, preferably, the pore size of the graphene compound 583 is sufficient for Li ions to pass through, and the number of pores is large enough not to block the electron conductivity of the graphene compound 583.

[0063] Here, an example of using the graphene compound 583 as the sheet material is shown. However, the sheet material is not limited to the graphene compound 583, and other sheet-like highly electron-conductive materials can also be used.

[0064] In addition to the graphene compound 583, the active material layer 572 may also include carbonaceous materials such as carbon black, graphite, carbon fiber, and fullerene. As the carbon black, for example, acetylene black (AB) etc. can be used. As the graphite, for example, natural graphite, artificial graphite such as mesocarbon microbeads etc. can be used. These carbonaceous materials have high conductivity and thus can be used as conductive agents in the active material layer. In addition, these carbonaceous materials can also be used as active materials.

[0065] As the carbon fiber, for example, mesophase pitch-based carbon fiber, isotropic pitch-based carbon fiber etc. can be used. As the carbon fiber, carbon nanofiber or carbon nanotube etc. can be used. For example, carbon nanotubes can be manufactured by a vapor growth method etc.

[0066] In addition, the active material layer may also contain, as a conductive agent, metal powders, metal fibers, conductive ceramic materials etc. selected from copper, nickel, aluminum, silver, gold etc.

[0067] Relative to the total solid weight of the active material layer, the content of the conductive agent is preferably 0.5 wt% or more and 10 wt% or less, more preferably 0.5 wt% or more and 5 wt% or less.

[0068] Different from granular conductive agents such as carbon black that form point contact with the active material, the graphene compound 583 can form a surface contact with low contact resistance. Therefore, the conductivity between the granular active material and the graphene compound can be improved with less graphene compound 583 than general conductive agents. Thus, the ratio of the active material in the active material layer can be increased. Thereby, the discharge capacity of the secondary battery can be increased.

[0069] In addition, the graphene compound 583 of one embodiment of the present invention has excellent lithium permeability, so the charge-discharge rate of the secondary battery can be improved.

[0070] Particulate carbon-containing compounds such as carbon black and graphite, and fibrous carbon-containing compounds such as carbon nanotubes are likely to enter minute spaces. Minute spaces refer to, for example, regions between multiple active materials. By using a combination of a carbon-containing compound that easily enters minute spaces and a sheet-like carbon-containing compound such as graphene that can impart conductivity to multiple particles, the density of the electrode can be increased and a good conduction path can be formed. In addition, by including an electrolyte according to one embodiment of the present invention in a secondary battery, the operating stability of the secondary battery can be improved. That is to say, a secondary battery according to one embodiment of the present invention can have both a high energy density and stability, and is very effective as a secondary battery for vehicle use. When the number of secondary batteries increases and the vehicle weight increases, the energy required for movement increases, so the cruising range becomes shorter. By using a high-density secondary battery, the cruising range can be extended even when the weight of the secondary batteries mounted on the vehicle is the same, that is, when the total weight of the vehicle is the same.

[0071] Since more charging power is required when the capacity of the secondary battery of a vehicle is increased, it is preferable to complete charging in a short time. In addition, since charging is performed under high-rate charging conditions during so-called regenerative charging in which electricity is generated temporarily when the vehicle brakes and used for charging, the secondary battery of the vehicle requires excellent rate characteristics.

[0072] By using an electrolyte according to one embodiment of the present invention, a secondary battery for vehicle use having a wide operating temperature range can be obtained.

[0073] In addition, a secondary battery according to one embodiment of the present invention can be miniaturized due to its high energy density, and can be rapidly charged due to its high conductivity. Therefore, the structure of a secondary battery according to one embodiment of the present invention is also very effective in a portable information terminal.

[0074] The active material layer 572 preferably includes a binder (not shown). The binder binds or fixes, for example, the electrolyte and the active material. In addition, the binder can bind or fix the electrolyte and the carbonaceous material, the active material and the carbonaceous material, multiple active materials to each other, multiple carbonaceous materials, etc.

[0075] As the binder, materials such as polystyrene, polymethyl acrylate, polymethyl methacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly(ethylene oxide) (PEO), poly(propylene oxide), polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, and nitrocellulose are preferably used.

[0076] Polyimide has very excellent and stable properties in terms of heat, mechanics, and chemistry. In addition, when polyimide is used as an adhesive, dehydration reaction and cyclization (imidation) reaction occur. These reactions can be caused, for example, by heat treatment. If graphene containing an oxygen-containing functional group is used as a graphene compound in an electrode according to one embodiment of the present invention, and polyimide is used as an adhesive, the graphene compound can be reduced by this heat treatment, thereby simplifying the process. In addition, because of its high heat resistance, for example, the heat treatment can be carried out at a heating temperature of 200 °C or higher. By carrying out the heat treatment at a heating temperature of 200 °C or higher, the reduction reaction of the graphene compound can be sufficiently caused, thereby further improving the conductivity of the electrode.

[0077] As the adhesive, a fluoropolymer which is a fluorine-containing polymer material can be used. Specifically, polyvinylidene fluoride (PVDF) etc. PVDF is a resin having a melting point in the range of 134 °C or higher and 169 °C or lower, and has excellent thermal stability.

[0078] In addition, styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer and other rubber materials are preferably used as the adhesive. Fluororubber can also be used as the adhesive.

[0079] In addition, for example, a water-soluble polymer is preferably used as the adhesive. As the water-soluble polymer, for example, polysaccharides etc. can also be used. As the polysaccharides, cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, regenerated cellulose, or starch etc. can be used. It is more preferable to use these water-soluble polymers and the above rubber materials in combination.

[0080] As the adhesive, a plurality of the above materials can also be used in combination.

[0081] In addition, the graphene compound 583 is flexible and can wrap around the second particle 582 like natto. Further, for example, the second particle 582 can be likened to soybeans and the graphene compound 583 can be likened to a viscous component such as polyglutamic acid. By disposing the graphene compound 583 among materials such as the electrolyte included in the active material layer 572, multiple active materials such as the second particle 582, and multiple carbonaceous materials, not only can a good conduction path be formed in the active material layer 572, but the graphene compound 583 can also be used to bind or fix these materials. Further, for example, by forming a three-dimensional mesh structure or a structure in which polygons such as hexagons are arranged in a polygonal arrangement and arranging materials such as the electrolyte, multiple active materials, and multiple carbonaceous materials in a mesh pattern, the graphene compound 583 can not only form a three-dimensional conduction path but also suppress the detachment of the electrolyte from the current collector. Further, in the above-described polygonal arrangement structure, polygons having different numbers of sides can also be arranged in a mixed manner. Therefore, the graphene compound 583 is sometimes used as a conductive agent and as an adhesive in the active material layer 572.

[0082] The first particle 581 and the second particle 582 can have various shapes such as a rounded shape, a shape having corners, etc. Further, in the cross-section of the electrode, the first particle 581 and the second particle 582 can have various cross-sectional shapes, and for example, can have a circular shape, an elliptical shape, a figure having a curve, a polygon, etc. For example, Figure 1B and Figure 1C Examples showing that the cross-sections of the first particle 581 and the second particle 582 have a rounded shape are shown, but the cross-sections of the first particle 581 and the second particle 582 can also have corners. Further, a part thereof can have a rounded shape and a part can have corners.

[0083] <Graphene Compound> The graphene compound in this specification and the like includes graphene, multi-layer graphene, multigraphene, graphene oxide, multi-layer graphene oxide, multi-graphene oxide, reduced graphene oxide, reduced multi-layer graphene oxide, reduced multi-graphene oxide, graphene quantum dots, etc. The graphene compound refers to a compound containing carbon and having a two-dimensional structure formed by carbon 6-membered rings and having a flat plate shape, a sheet shape, etc. Further, the two-dimensional structure formed by carbon 6-membered rings can also be referred to as a carbon sheet. The graphene compound can also have a functional group containing oxygen. Further, the graphene compound preferably has a curved shape. Further, the graphene compound can also be curled like a carbon nanofiber.

[0084] Further, in this specification and the like, graphene oxide is, for example, a graphene compound containing carbon and oxygen and having a sheet shape and including functional groups, particularly epoxy groups, carboxyl groups, or hydroxyl groups.

[0085] In the present specification and the like, the reduced graphene oxide contains, for example, carbon and oxygen, has a flaky shape, and has a two-dimensional structure formed by carbon 6-membered rings. In addition, the reduced graphene oxide may also be referred to as a carbon sheet. One layer of the reduced graphene oxide can function, but a laminated structure may also be adopted. The reduced graphene oxide preferably has a portion where the carbon concentration is greater than 80 atomic% and the oxygen concentration is 2 atomic% or more and 15 atomic% or less. By having such a carbon concentration and oxygen concentration, a small amount of the reduced graphene oxide can also function as a conductive agent with high conductivity. In addition, the intensity ratio G / D of the G band to the D band in the Raman spectrum of the reduced graphene oxide is preferably 1 or more. The reduced graphene oxide having such an intensity ratio can function as a conductive agent with high conductivity even in a small amount.

[0086] By reducing graphene oxide, pores can sometimes be formed in the reduced graphene.

[0087] In addition, as the graphene compound, a material in which the ends of graphene are terminated with fluorine can also be used.

[0088] In the longitudinal section of the active material layer, the flaky graphene compound is substantially uniformly dispersed in the internal region of the active material layer. Since a plurality of graphene compounds are formed in such a manner as to cover a part of a plurality of granular active materials or to adhere to the surfaces of a plurality of granular active materials, the plurality of graphene compounds form a surface contact with the plurality of granular active materials.

[0089] Here, by binding a plurality of graphene compounds to each other, a mesh-like graphene compound thin sheet (hereinafter referred to as a graphene compound network or a graphene network) can be formed. When the graphene network covers the active material, the graphene network can be used as an adhesive for binding the active materials to each other. Therefore, the amount of the adhesive can be reduced or the adhesive can be not used, whereby the ratio of the active material in the electrode volume and the electrode weight can be increased. That is, the charge-discharge capacity of the secondary battery can be improved.

[0090] Here, preferably, graphene oxide is used as the graphene compound, the graphene oxide and the active material are mixed to form a layer that will become the active material layer, and then the graphene oxide is reduced. That is, the completed active material layer preferably contains the reduced graphene oxide. By using graphene oxide having extremely high dispersibility in a polar solvent when forming the active material layer containing the graphene compound, the graphene compound can be substantially uniformly dispersed in the internal region of the active material layer.

[0091] After applying a dispersion liquid in which graphene oxide is substantially uniformly dispersed in a solvent onto a current collector and removing the solvent by volatilization, the graphene oxide is reduced to manufacture the active material layer. The graphene compound contained in the active material layer partially overlaps. Thus, if the reduced graphene oxide is dispersed in a face-to-face contact manner with each other, a three-dimensional conduction path can be formed. In addition, the reduction of graphene oxide can also be carried out, for example, by heat treatment or using a reducing agent.

[0092] In addition, by previously covering the surface of the active material with a graphene compound, a conductive coating film is formed on the surface of the active material, and the active materials are electrically connected to each other using the graphene compound, whereby a conduction path can be formed.

[0093] The graphene compound of one embodiment of the present invention preferably has pores in a part of the carbon sheet. In the graphene compound of one embodiment of the present invention, by providing pores through which carrier ions such as lithium ions can pass in a part of the carbon sheet, the insertion and extraction of carrier ions can be easily performed on the surface of the active material covered with the graphene compound, whereby the rate characteristics of the secondary battery can be improved. The pores provided in a part of the carbon sheet are sometimes referred to as voids, defects or gaps.

[0094] The graphene compound of one embodiment of the present invention preferably has pores formed by a plurality of carbon atoms and one or more fluorine atoms. In addition, the plurality of carbon atoms are preferably bonded in a ring, and one or more of the plurality of carbon atoms bonded in a ring are preferably terminated by the fluorine. Fluorine has a high electronegativity and is easily negatively charged. When a positively charged lithium ion approaches, an interaction occurs and the energy becomes stable, thereby reducing the barrier energy for the lithium ion to pass through the pore. Therefore, by including fluorine in the pores of the graphene compound, lithium ions can easily pass through smaller pores, and a graphene compound with good conductivity can be achieved. In addition, one or more of the plurality of carbon atoms bonded in a ring can also be terminated by hydrogen.

[0095] Figure 3A and Figure 3B An example of the structure of the graphene compound including pores is shown.

[0096] Figure 3A The shown structure includes a 22-membered ring, and 8 carbons among the carbons constituting the 22-membered ring are all terminated by hydrogen. In addition, Figure 3A it can also be said to have the following structure: two 6-membered rings connected in graphene are removed, and the carbons bonded to the removed 6-membered rings are terminated by hydrogen.

[0097] Figure 3B The shown structure includes a 22-membered ring, 6 carbons among the 8 carbons constituting the 22-membered ring are terminated by hydrogen, and 2 carbons are terminated by fluorine. In addition, Figure 3B it can also be said to have the following structure: two 6-membered rings connected in graphene are removed, and the carbons bonded to the removed 6-membered rings are terminated by hydrogen or fluorine.

[0098] The interaction between the hydroxyl-terminated silicon and the graphene compound including pores is relatively large due to the formation of hydrogen bonds between the hydrogen contained in the hydroxyl group on the silicon surface and the hydrogen atoms or fluorine atoms contained in the graphene compound.

[0099] The graphene compound contains not only hydrogen but also fluorine. Thus, in addition to the hydrogen bond between the oxygen atom of the hydroxyl group and the hydrogen atom of the graphene compound, a hydrogen bond is also formed between the hydrogen atom of the hydroxyl group and the fluorine atom of the graphene compound. Therefore, it can be considered that the interaction between the silicon-containing particles and the graphene compound is stronger and more stable.

[0100] When graphene has pores, for example, it may be possible to observe the spectrum according to the characteristics caused by the pores through Raman spectroscopic mapping measurement. In addition, it may be possible to observe the bonds, functional groups, etc. constituting the pores through ToF-SIMS. In addition, it may be possible to analyze the vicinity of the pores, the periphery of the pores, etc. through TEM.

[0101] <Negative electrode active material> When the electrode 570 is a negative electrode, as the second particle 582, particles containing a negative electrode active material can be used. As the negative electrode active material, materials that can react with the carrier ions of the secondary battery, materials into which the carrier ions can be inserted and extracted, materials that can alloy with the metal used as the carrier ion, materials that can dissolve and precipitate the metal used as the carrier ion, etc. are preferably used.

[0102] An example of the negative electrode active material will be described below.

[0103] Silicon can be used as the negative electrode active material. In the electrode 570, as the second particle 582, particles containing silicon are preferably used.

[0104] In addition, as the negative electrode active material contained in the second particle 582, metals or compounds containing one or more elements selected from tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. As alloy compounds using such elements, for example, Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, and SbSn, etc. can be cited.

[0105] In addition, materials with reduced resistance achieved by adding impurity elements such as phosphorus, arsenic, boron, aluminum, gallium, etc. to silicon can also be used. In addition, silicon materials pre-doped with lithium can also be used. As methods of pre-doping, there are methods such as annealing by mixing lithium fluoride, lithium carbonate, etc. and silicon, and mechanical alloying between lithium metal and silicon. In addition, lithium doping can also be carried out by causing a charge-discharge reaction through combination with an electrode such as lithium metal after forming the electrode, and a secondary battery can be manufactured by combining the doped electrode and an electrode as a counter electrode (for example, relative to a pre-doped negative electrode, equivalent to a positive electrode).

[0106] As the second particles 582, for example, nano-silicon particles can be used. The average particle size of the nano-silicon particles 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 further preferably 10 nm or more and 100 nm or less.

[0107] The nano-silicon particles can have a spherical shape, a flattened spherical shape, or a rectangular parallelepiped shape with rounded corners. For example, taking D50 measured by laser diffraction particle size distribution measurement as the size of the nano-silicon particles is preferably 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and further preferably 10 nm or more and 100 nm or less. Here, D50 is the particle diameter at which the cumulative amount accounts for 50% in the cumulative particle amount curve of the particle size distribution measurement result, that is, the median. The measurement of the particle size is not limited to laser diffraction particle size distribution measurement. When it is below the measurement lower limit of laser diffraction particle size distribution measurement, the major axis of the particle cross-section can also be measured by analysis such as SEM or TEM.

[0108] The nano-silicon particles preferably contain amorphous silicon. In addition, the nano-silicon particles preferably contain polycrystalline silicon. The nano-silicon particles preferably contain amorphous silicon and polycrystalline silicon. In addition, the nano-silicon particles can also include a crystalline region and an amorphous region.

[0109] As the material containing silicon, for example, a material represented by SiO x (x is preferably less than 2, more preferably 0.5 or more and 1.6 or less) can be used.

[0110] As the material containing silicon, for example, a mode of containing multiple crystal grains in one particle can be adopted. For example, a mode of containing one or more silicon crystal grains in one particle can be adopted. In addition, the one particle can also contain silicon oxide around the silicon crystal grains. In addition, the silicon oxide can be amorphous. In addition, it can also be a particle surrounded by a graphene compound around silicon secondary particles.

[0111] In addition, as a silicon-containing compound, for example, Li2SiO3 and Li4SiO4 can be included. Li2SiO3 and Li4SiO4 can be either crystalline or amorphous.

[0112] The silicon-containing compound can be analyzed by NMR, XRD, Raman spectroscopy, SEM, TEM, EDX, etc.

[0113] As the first particles 581 included in the electrode 570, it is preferable to include graphite.

[0114] The first particles 581 are preferably used as the negative electrode active material, and more preferably a material with a small volume change during charge and discharge.

[0115] Regarding the volume change of the first particles 581 during charging or discharging, when the minimum volume during charging or discharging is 1, the maximum volume during charging or discharging is preferably 2 or less, more preferably 1.5 or less, and further preferably 1.1 or less.

[0116] The particle size of the first particles 581 is preferably larger than that of the second particles 582.

[0117] For example, the D50 of the first particles 581 measured by laser diffraction particle size distribution measurement is preferably 1.5 times or more and less than 1000 times that of the D50 of the second particles 582, more preferably 2 times or more and 500 times or less, and further preferably 10 times or more and 100 times or less. Here, D50 is the particle diameter at which the cumulative amount accounts for 50% in the cumulative particle amount curve of the particle size distribution measurement result, that is, the median. In addition, the measurement of the particle size is not limited to laser diffraction particle size distribution measurement, and the diameter of the particle cross-section can also be measured by analysis such as SEM or TEM.

[0118] In addition, as the first particles 581, for example, carbonaceous materials such as graphite, easily graphitizable carbon, hardly graphitizable carbon, carbon nanotubes, carbon black, and graphene compounds with a small volume change during charge and discharge can be used.

[0119] In addition, as the first particles 581, for example, oxides containing one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0120] As the first particles 581, a variety of the above-mentioned metals, materials, compounds, etc. can be combined.

[0121] For example, as the first particles 581, oxides such as SnO, SnO2, titanium dioxide (TiO2), lithium titanium oxide (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used.

[0122] In addition, materials that cause a conversion reaction can also be used for the first particles 581. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not alloy with lithium can be used for the first particles 581. As materials that cause a conversion reaction, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS 0.89 , sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3 can also be cited. In addition, since the above fluorides have a relatively high potential, these fluorides can also be used as the positive electrode material.

[0123] <Manufacturing method of electrode> Figure 4 It is a flowchart showing an example of a manufacturing method of an electrode according to one aspect of the present invention.

[0124] First, in step S61, particles containing silicon are prepared as the second particles 582. As the particles containing silicon, the particles described above as the second particles 582 can be used.

[0125] In step S62, a solvent is prepared. As the solvent, for example, any one or a mixture of two or more of water, methanol, ethanol, acetone, tetrahydrofuran (THF), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO) can be used.

[0126] Next, in step S63, the particles containing silicon prepared in step S61 and the solvent prepared in step S62 are mixed, the mixture is recovered in step S64, and mixture E-1 is obtained in step S65. A kneader or the like is used for the mixing. As the kneader, for example, a rotation revolution mixer or the like can be used.

[0127] Next, in step S72, particles containing graphite are prepared as the first particles 581. As the particles containing graphite, the particles described above as the first particles 581 can be used.

[0128] Next, in step S73, mixture E-1 and the particles containing graphite prepared in step S72 are mixed, the mixture is recovered in step S74, and mixture E-2 is obtained in step S75. A kneader or the like is used for the mixing. As the kneader, for example, a rotation revolution mixer or the like can be used.

[0129] Next, in step S80, a graphene compound is prepared.

[0130] Next, in step S81, the mixture E-2 and the graphene compound prepared in step S80 are mixed, and in step S82, the mixture is recovered. The recovered mixture is preferably in a state of high viscosity. When the viscosity of the mixture is high, dry thick mixing (mixing at high viscosity) can be performed in the next step S83.

[0131] Next, in step S83, dry thick mixing is performed. Dry thick mixing can be performed using, for example, a spatula or the like. By performing dry thick mixing, a mixture with good dispersibility of the graphene compound in which the silicon-containing particles and the graphene compound are well mixed can be formed.

[0132] Next, in step S84, the mixture subjected to dry thick mixing is mixed. For example, a kneader or the like can be used for the mixing. In step S85, the mixed mixture is recovered.

[0133] Preferably, the process of steps S83 to S85 is repeated n times for the mixture recovered in step S85. n is, for example, a natural number of 2 or more and 10 or less. In addition, when the mixture is in a dry state in the process of step S83, a solvent is preferably added. On the other hand, when too much solvent is added, the viscosity decreases and the effect of dry thick mixing is reduced.

[0134] After repeating steps S83 to S85 n times, mixture E-3 is obtained (step S86).

[0135] Next, in step S87, an adhesive is prepared. As the adhesive, the above materials can be used, and polyimide is particularly preferably used. Note that sometimes a precursor of the material for the adhesive is prepared in step S87. For example, a precursor of polyimide is prepared.

[0136] Next, in step S88, mixture E-3 and the adhesive prepared in step S87 are mixed. Then, in step S89, the viscosity is adjusted. Specifically, for example, a solvent of the same type as the solvent prepared in step S62 is prepared and added to the mixture obtained in step S88. By adjusting the viscosity, for example, the thickness, density, etc. of the electrode obtained in step S97 can sometimes be adjusted.

[0137] Next, in step S90, the mixture whose viscosity is adjusted in step S89 is mixed, and in step S91, the mixture is recovered to obtain mixture E-4 (step S92). The mixture E-4 obtained in step S92 is, for example, called a slurry.

[0138] Next, in step S93, a current collector is prepared.

[0139] Next, in step S94, the mixture E-4 is applied to the current collector prepared in step S93. The application can be carried out, for example, using a slot die method, a gravure method, a blade method, or a method combining them. In addition, the coating can also be carried out using a continuous coater or the like.

[0140] Next, in step S95, the first heating is performed. The solvent is volatilized by the first heating. The first heating is carried out in a temperature range of 40°C or higher and 200°C or lower, preferably 50°C or higher and 150°C or lower. Sometimes the first heating is referred to as drying.

[0141] For example, the first heating can be carried out by heating with a hot plate at a temperature of 30°C or higher and 70°C or lower for 10 minutes or more in an atmospheric atmosphere, and then heating at a temperature of room temperature or higher and 100°C or lower for 1 hour or more and 10 hours or less in a reduced-pressure environment.

[0142] Alternatively, a heat treatment can also be carried out using a drying furnace or the like. When using a drying furnace, for example, a heat treatment can be carried out at a temperature of 30°C or higher and 120°C or lower for 30 seconds or more and 2 hours or less.

[0143] Alternatively, the temperature can also be increased in stages. For example, a heat treatment can be carried out at a temperature of 60°C or lower for 10 minutes or less, and then a heat treatment can be carried out at a temperature of 65°C or higher for 1 minute or more.

[0144] Next, in step S96, the second heating is performed. When polyimide is used as the binder, it is preferable that the cycloaddition reaction of polyimide occurs by the second heating. In addition, sometimes the dehydration reaction of polyimide occurs by the second heating. Alternatively, the dehydration reaction of polyimide occurs by the first heating. In addition, the cyclization reaction of polyimide can also occur during the first heating. In addition, it is preferable that the reduction reaction of the graphene compound occurs during the second heating. Sometimes the second heating is referred to as imidization heat treatment, reduction heat treatment, or thermal reduction treatment.

[0145] The second heating is carried out in a temperature range of 150°C or higher and 500°C or lower, preferably 200°C or higher and 450°C or lower.

[0146] For example, the second heating is preferably carried out by heating for 1 hour or more and 10 hours or less in a reduced-pressure environment of 200°C or higher and 450°C or lower and 10 Pa or less, or in an inert atmosphere such as nitrogen or argon.

[0147] In step S97, an electrode having an active material layer provided on the current collector is obtained.

[0148] The thickness of the active material layer formed by the above steps is preferably, for example, 5 μm or more and 300 μm or less, more preferably 10 μm or more and 150 μm or less. In addition, the active material loading of the active material layer is preferably, for example, 2 mg / cm 2 or more and 50 mg / cm 2 or less.

[0149] The active material layer can be formed on both sides of the current collector, or can be formed only on one side of the current collector. Alternatively, it can also have regions where the active material layer is partially formed on both sides of the current collector.

[0150] After volatilizing the solvent from the active material layer, pressing can also be performed using a compression method such as a roll pressing method or a flat pressing method. Heating can also be performed during pressing.

[0151] <An example of the positive electrode active material> As the positive electrode active material, for example, a lithium-containing composite oxide having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure can be cited.

[0152] As the positive electrode active material of one embodiment of the present invention, a positive electrode active material having a layered crystal structure is preferably used.

[0153] As the layered crystal structure, for example, a layered rock salt-type crystal structure can be cited. As the lithium-containing composite oxide having a layered rock salt-type crystal structure, for example, LiM x O y (x > 0 and y > 0, more specifically, for example, y = 2 and 0.8 < x < 1.2) can be used to represent the lithium-containing composite oxide. Here, M is a metal element, preferably one or more selected from cobalt, manganese, nickel, and iron. In addition, M is, for example, two or more selected from cobalt, manganese, nickel, iron, aluminum, titanium, zirconium, lanthanum, copper, and zinc.

[0154] As the lithium-containing composite oxide represented by LiM x O y , for example, LiCoO2, LiNiO2, LiMnO2, etc. can be cited. In addition, as the NiCo type represented by LiNi x Co 1-x O2 (0 < x < 1), and the lithium-containing composite oxide represented by LiM x O y , for example, the NiMn type represented by LiNi x Mn 1-x O2 (0 < x < 1) can be cited.

[0155] In addition, as the lithium-containing composite oxide represented by LiMO2, for example, the one represented by Li Ni xCo y Mn z NiCoMn type (also denoted as NCM) represented by O2 (x > 0, y > 0, 0.8 < x + y + z < 1.2). Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, x, y, and z preferably satisfy x:y:z = 1:1:1 or values in the vicinity thereof. Or, as an example, x, y, and z preferably satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Or, as an example, x, y, and z preferably satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Or, as an example, x, y, and z preferably satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Or, as an example, x, y, and z preferably satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0156] In addition, as a lithium-containing composite oxide having a layered rock salt-type crystal structure, for example, Li2MnO3, Li2MnO3-LiMeO2 (Me is Co, Ni, Mn), etc. can be cited.

[0157] Among the above-mentioned positive electrode active materials having a layered crystal structure represented by a lithium-containing composite oxide, a secondary battery with a large lithium content per unit volume and a high capacity per unit volume can sometimes be achieved. Since the amount of lithium deintercalation per unit volume during charging is also large in such a positive electrode active material, in order to perform stable charge and discharge, stabilization of the crystal structure after deintercalation is required. In addition, sometimes the collapse of the crystal structure during charge and discharge hinders rapid charging and rapid discharging.

[0158] In addition, as the positive electrode active material, it is preferable to mix lithium nickelate (LiNiO2 or LiNi 1-x M x O2 (0 < x < 1) (M = Co, Al, etc.)) into a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4. By adopting this structure, the characteristics of the secondary battery can be improved.

[0159] In addition, as the positive electrode active material, one that can be represented by the composition formula Li a Mn b M c O dThe lithium-manganese composite oxide represented herein. Herein, the element M is preferably a metal element selected from metal elements other than lithium and manganese, or silicon or phosphorus, and more preferably nickel. Further, when measuring the whole particles of the lithium-manganese composite oxide, it is preferable that 0 < a / (b + c) < 2, c > 0 and 0.26 ≤ (b + c) / d < 0.5 are satisfied during discharging. It should be noted that regarding the composition of metals, silicon, phosphorus, etc. in the whole particles of the lithium-manganese composite oxide, for example, it can be measured by ICP-MS (Inductively Coupled Plasma Mass Spectrometer). Further, the composition of oxygen in the whole particles of the lithium-manganese composite oxide, for example, can be measured by EDX (Energy Dispersive X-ray Spectroscopy). Further, it can also be calculated by using valence evaluation of fusion gas analysis and XAFS (X-ray Absorption Fine Structure) analysis together with ICPMS analysis. Note that the lithium-manganese composite oxide means an oxide containing at least lithium and manganese, and may further 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, etc.

[0160] [Structure of positive electrode active material] Materials having a layered rock salt-type crystal structure such as lithium cobaltate (LiCoO2) have a high discharge capacity and have been considered as excellent positive electrode active materials for secondary batteries. As materials having a layered rock salt-type crystal structure, for example, composite oxides represented by LiMO2 can be cited. The metal M contains the metal Me1. The metal Me1 is one or more metals containing cobalt. In addition to the metal Me1, the metal M may further contain the metal X. The metal X is one or more metals selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0161] The magnitude of the Jahn-Teller effect of the transition metal compound is considered to change according to the number of electrons in the d orbit of the transition metal.

[0162] Compounds containing nickel sometimes tend to be distorted due to the Jahn-Teller effect. Thus, when LiNiO2 is charged at a high voltage, there is a concern that the crystal structure collapses due to the distortion. The negative impact of the Jahn-Teller effect of LiCoO2 is small, and sometimes the charge resistance at high voltage is more excellent, so it is preferable.

[0163] Refer to Figure 5 and Figure 6 illustrate the positive electrode active material.

[0164] The positive electrode active material produced in one embodiment of the present invention can reduce the deviation of the CoO₂ layer even when charged and discharged repeatedly at high voltages. Moreover, the volume change can be reduced. Therefore, the compound can achieve excellent cycle characteristics. In addition, the compound can have a stable crystal structure even in a charged state at high voltage. Thus, the compound is sometimes not likely to short-circuit when maintaining the charged state at high voltage. In this case, the stability is further improved, so it is preferred.

[0165] The crystal structure change of the crystal contained in the compound between the fully discharged state and the state charged at high voltage and the volume difference when compared per the same number of transition metal atoms are small.

[0166] The positive electrode active material is preferably represented by a layered rock salt-type structure, and this region is represented by the space R-3m. The positive electrode active material is a region containing lithium, metal Me1, oxygen, and metal X. Figure 5 An example of the crystal structure of the positive electrode active material before and after charge and discharge is shown. In addition, the surface layer portion of the positive electrode active material can be as follows: In addition to the region represented by the layered rock salt-type structure described below with reference to Figure 5 etc., its surface layer portion further includes a crystal containing titanium, magnesium, and oxygen and represented by a structure different from the layered rock salt-type structure; or, its surface layer portion includes a crystal containing titanium, magnesium, and oxygen and represented by a structure different from the layered rock salt-type structure instead of the region represented by the layered rock salt-type structure described below with reference to Figure 5 etc. For example, it may also include a crystal containing titanium, magnesium, and oxygen and represented by a spinel structure.

[0167] Figure 5 The crystal structure at a charge depth of 0 (discharge state) is the same R-3m (O3) as Figure 6 On the other hand, in the positive electrode active material shown in Figure 5 , when having a fully charged charge depth (for example, 0.8), it has a crystal different from the H1-3 type crystal structure. This structure is the space group R-3m, rather than a spinel-type crystal structure, but ions such as cobalt and magnesium occupy the oxygen six-coordination positions, and the arrangement of cations has a symmetry similar to that of the spinel type. In addition, the periodicity of the CoO₂ layer of this structure is the same as that of the O3 type. Therefore, in this specification, etc., this structure is referred to as the O3' type crystal structure or the pseudo-spinel type crystal structure. Therefore, the O3' type crystal structure can also be referred to as the pseudo-spinel type crystal structure. In addition, in order to illustrate the symmetry of cobalt atoms and oxygen atoms, in Figure 5In the figure showing the spinel - like crystal structure, the representation of lithium is omitted, but actually there is lithium, for example, at 20 at.% or less relative to cobalt between the CoO2 layers. In addition, in both the O3 - type crystal structure and the spinel - like crystal structure, it is preferable to have a small amount of magnesium at the lithium position, i.e., between the CoO2 layers. In addition, a small amount of halogens such as fluorine may be irregularly present at the oxygen position.

[0168] In addition, in the spinel - like crystal structure, light elements such as lithium sometimes occupy the oxygen four - coordination positions. In this case, the ion arrangement also has a symmetry similar to that of the spinel type.

[0169] In addition, it can be said that the spinel - like crystal structure, although it contains Li irregularly between the layers, also has a crystal structure similar to that of the CdCl2 - type crystal structure. It is known that the above - mentioned crystal structure similar to the CdCl2 - type, although similar to the crystal structure when lithium nickelate is charged to a charge depth of 0.94 (Li 0.06 NiO2), generally, pure lithium cobaltate or layered rock - salt - type positive electrode active materials containing a large amount of cobalt do not have the above - mentioned crystal structure.

[0170] The anions of the layered rock - salt - type crystal and the rock - salt - type crystal respectively form a cubic closest - packed structure (face - centered cubic lattice structure). It can be speculated that the anions in the spinel - like crystal also have a cubic closest - packed structure. When these crystals come into contact, there are crystal planes where the orientations of the cubic closest - packed structures formed by the anions are aligned. Note that the space groups of the layered rock - salt - type crystal and the spinel - like crystal are R - 3m, different from the space groups of the rock - salt - type crystal, Fm - 3m (the space group of a general rock - salt - type crystal) and Fd - 3m (the space group of a rock - salt - type crystal with the simplest symmetry). Therefore, the Miller indices of the crystal planes satisfying the above conditions are different between the layered rock - salt - type crystal and the spinel - like crystal and the rock - salt - type crystal. In this specification, sometimes the state where the orientations of the cubic closest - packed structures formed by the anions are the same in the layered rock - salt - type crystal, the spinel - like crystal, and the rock - salt - type crystal refers to the state where the crystal orientations are approximately the same.

[0171] Compared with the comparative examples described later, in Figure 5 the change in the crystal structure when the positive electrode active material shown is charged at a high voltage and a large amount of lithium is detached is further suppressed. For example, as shown by the dotted line in Figure 5 these crystal structures, there is almost no deviation of the CoO2 layer.

[0172] More specifically, in Figure 5In the positive electrode active material shown, the structural stability is high even at a high charging voltage. For example, in the comparative example, even at the charging voltage that forms the H1-3 type crystal structure, such as a voltage of about 4.6 V with respect to lithium metal, there is a region of the charging voltage that can maintain the crystal structure of R-3m (O3), and there is also a region at a higher charging voltage, such as a voltage of about 4.65 V to 4.7 V with respect to lithium metal, that can maintain the spinel-like crystal structure. When the charging voltage is further increased, the crystallization of the H1-3 type can be observed. For example, in the case of using graphite as the negative electrode active material of the secondary battery, there is a region of the charging voltage that can maintain the crystal structure of R-3m (O3) even at a voltage of the secondary battery of 4.3 V or more and 4.5 V or less, and there is also a region at a higher charging voltage, such as a voltage of 4.35 V or more and 4.55 V or less with respect to lithium metal, that can maintain the spinel-like crystal structure.

[0173] Therefore, in Figure 5 the positive electrode active material shown, even when charging and discharging are repeatedly performed at a high voltage, the crystal structure is not easily collapsed.

[0174] The coordinates of cobalt and oxygen in the unit cell of the spinel-like crystal structure can be expressed in the range of Co(0, 0, 0.5), O(0, 0, x) and 0.20 ≤ x ≤ 0.25, respectively.

[0175] In the CoO2 interlayer, that is, magnesium that is present in a small amount irregularly at the lithium position has the effect of suppressing the deviation of the CoO2 layer during charging at a high voltage. Thus, when magnesium is present in the CoO2 interlayer, it is easy to obtain the spinel-like crystal structure.

[0176] However, when the temperature of the heat treatment is too high, cation mixing occurs and the possibility of magnesium invading the cobalt position increases. Magnesium present at the cobalt position sometimes has a small effect of maintaining the R-3m structure during charging at a high voltage. Furthermore, when the heat treatment temperature is too high, there are also concerns about adverse effects such as cobalt being reduced to divalent, lithium evaporation or sublimation.

[0177] Then, it is preferable to add a halogen compound such as a fluorine compound to lithium cobaltate before performing the heat treatment for distributing magnesium over the entire surface layer portion of the particles. By adding the halogen compound, the melting point of lithium cobaltate is decreased. By decreasing the melting point, it is possible to easily distribute magnesium over the entire surface layer portion of the particles at a temperature at which cation mixing is not likely to occur. When a fluorine compound is also present, it is possible to expect an improvement in the corrosion resistance to hydrofluoric acid generated by the decomposition of the electrolyte.

[0178] Note that when the magnesium concentration is higher than the desired value, the effect of stabilizing the crystal structure sometimes becomes smaller. This is because magnesium not only invades the lithium sites but also the cobalt sites. The number of magnesium atoms contained in the positive electrode active material produced by one embodiment of the present invention is preferably 0.001 times or more and 0.1 times or less, more preferably more than 0.01 and less than 0.04, and further preferably about 0.02, based on the number of cobalt atoms. The magnesium concentration shown here can be, for example, a value obtained by elemental analysis of the entire particles of the positive electrode active material using ICP-MS or the like, or a value obtained based on the raw material formulation in the production process of the positive electrode active material.

[0179] The number of nickel atoms contained in the positive electrode active material is preferably 7.5% or less, more preferably 0.05% or more and 4% or less, and further preferably 0.1% or more and 2% or less, based on the number of cobalt atoms. The nickel concentration shown here can be, for example, a value obtained by elemental analysis of the entire particles of the positive electrode active material using ICP-MS or the like, or a value obtained based on the raw material formulation in the production process of the positive electrode active material.

[0180] <Particle size> When the particle size of the positive electrode active material is too large, there are problems such as difficulty in lithium diffusion; when coating on the current collector, the surface of the active material layer is too rough, etc. On the other hand, when the particle size of the positive electrode active material is too small, there are problems such as difficulty in holding the active material layer when coating on the current collector; excessive reaction with the electrolyte, etc. Therefore, the average particle diameter (D50: median particle diameter) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and further preferably 5 μm or more and 30 μm or less.

[0181] <Analysis method> In order to determine whether a certain positive electrode active material shows a pseudo-spinel type (also called O3' type) crystal structure when charged at a high voltage, it can be determined by analyzing the positive electrode charged at a high voltage using XRD, electron diffraction, neutron diffraction, electron spin resonance method (ESR), nuclear magnetic resonance method (NMR), etc. In particular, XRD is preferred because it has the following advantages: the symmetry of transition metals such as cobalt in the positive electrode active material can be analyzed with high resolution; the degree of crystallinity and the crystallographic orientation can be compared; the periodic distortion of the lattice and the grain size can be analyzed; sufficient accuracy can also be obtained when directly measuring the positive electrode obtained by disassembling the secondary battery, etc.

[0182] As described above, the positive electrode active material is characterized in that there is little change in the crystal structure between the state of charging at a high voltage and the discharging state. A material in which a crystal structure with a large change between charging and discharging at a high voltage accounts for 50 wt% or more is not preferred because it cannot withstand high-voltage charge and discharge. Note that sometimes the desired crystal structure cannot be achieved only by adding impurity elements. For example, in lithium cobaltate containing magnesium and fluorine, in the state of charging at a high voltage, some have a spinel-like crystal structure of 60 wt% or more, and some have an H1-3 type crystal structure of 50 wt% or more. In addition, when a specified voltage is used, the spinel-like crystal structure almost becomes 100 wt%, and sometimes an H1-3 type crystal structure is generated when the specified voltage is further increased. Therefore, the crystal structure of the positive electrode active material is preferably analyzed by XRD or the like. By combining with measurement methods such as XRD, more detailed analysis can be performed.

[0183] However, sometimes the crystal structure of the positive electrode active material in the state of charging at a high voltage or the discharging state changes when exposed to the atmosphere. For example, sometimes it changes from a spinel-like crystal structure to an H1-3 type crystal structure. Therefore, it is preferred that all samples be treated under an inert atmosphere such as an argon atmosphere.

[0184] Figure 6 The positive electrode active material shown is lithium cobaltate (LiCoO2) without the addition of metal X. Figure 6 The crystal structure of the lithium cobaltate shown changes according to the depth of charge.

[0185] As Figure 6 shown, lithium cobaltate with a charge depth of 0 (discharging state) includes a region having a crystal structure of space group R-3m and includes three CoO2 layers in the unit cell. Sometimes this crystal structure is called the O3 type crystal structure. Note that the CoO2 layer refers to a structure in which an octahedral structure formed by cobalt and six coordinated oxygen atoms maintains a state of sharing edges on a plane.

[0186] When the charge depth is 1, it has a crystal structure of space group P-3m1, and the unit cell includes one CoO2 layer. Sometimes this crystal structure is called the O1 type crystal structure.

[0187] When the charge depth is about 0.8, lithium cobaltate has a crystal structure belonging to space group R-3m. This structure can also be regarded as a structure in which a CoO2 structure such as P-3m1 (O1) and an LiCoO2 structure such as R-3m (O3) are alternately stacked. Sometimes this crystal structure is called the H1-3 type crystal structure. In fact, the number of cobalt atoms in each unit cell of the H1-3 type crystal structure is twice that of other structures. However, in as Figure 6In this specification, in order to facilitate comparison with other structures, the c-axis in the H1-3 type crystal structure is represented in a way of 1 / 2 of the unit cell.

[0188] As an example of the H1-3 type crystal structure, the coordinates of cobalt and oxygen in the unit cell can be represented by Co(0, 0, 0.42150 ± 0.00016), O1(0, 0, 0.27671 ± 0.00045), and O2(0, 0, 0.11535 ± 0.00045). Both O1 and O2 are oxygen atoms. In this way, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygens. On the other hand, as described later, it is preferable to represent the spinel-like crystal structure of one aspect of the present invention by a unit cell using one cobalt and one oxygen. This indicates that the difference between the spinel-like crystal structure and the H1-3 type crystal structure lies in the symmetry of cobalt and oxygen, and the spinel-like crystal structure has less change from the O3 structure than the H1-3 type crystal structure. For example, by using the Rietveld analysis of XRD, it can be judged which unit cell should be used to represent the crystal structure of the positive electrode active material. In this case, it is only necessary to select the unit cell with the smallest GOF (goodness of fit) value.

[0189] When high-voltage charging with a charging voltage of 4.6 V or more relative to the redox potential of lithium metal or deep charging and discharging with a charging depth of 0.8 or more are repeatedly performed, the crystal structure of lithium cobaltate repeatedly changes between the H1-3 type crystal structure and the structure belonging to R-3m (O3) in the discharged state (that is, non-equilibrium phase transition).

[0190] However, the deviation of the CoO2 layer of the above two crystal structures is relatively large. As Figure 6 shown by the dotted line and arrow in, in the H1-3 crystal structure, the CoO2 layer significantly deviates from R-3m (O3). Such dynamic structural changes will have an adverse effect on the stability of the crystal structure.

[0191] Moreover, the volume difference is also relatively large. When comparing per 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 3.0% or more.

[0192] In addition to the above, the structure in which the CoO2 layer is continuous, such as P-3m1 (O1), possessed by the H1-3 type crystal structure has a relatively high possibility of being unstable.

[0193] Therefore, when high-voltage charge and discharge are repeatedly performed, the crystal structure of lithium cobaltate will collapse. And the collapse of the crystal structure will cause the deterioration of the cycle characteristics. This is because the collapse of the crystal structure reduces the positions where lithium can stably exist, so it becomes difficult for lithium to be inserted and removed.

[0194] <Electrolyte> In addition, when using a liquid electrolyte layer as a secondary battery, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinyl chloride carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc. can be used as the electrolyte layer, or two or more of the above can be mixed in any combination and ratio for use.

[0195] In addition, by using one or more flame-retardant and low-volatility ionic liquids (room-temperature molten salts) as the solvent of the electrolyte, even if the internal area of the secondary battery is short-circuited or overcharged, etc., causing the temperature of the internal area to rise, the rupture or fire of the secondary battery can be prevented. Ionic liquids are composed of cations and anions, and contain organic cations and anions. As organic cations, aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations can be cited. In addition, as anions, monovalent amide anions, monovalent methylated anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions or perfluoroalkylphosphate anions, etc. can be cited.

[0196] The carrier ions of the secondary battery as one aspect of the present invention include, for example, any one or two or more of the following ions: alkali metal ions such as sodium ions and potassium ions, and alkaline earth metal ions such as calcium ions, strontium ions, barium ions, beryllium ions and magnesium ions.

[0197] When using lithium ions as carrier ions, for example, the electrolyte contains a lithium salt. For example, as the lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 、Li2B 12 Cl 12 、LiCF3SO3, LiC4F9SO3, Li C(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. can be used.

[0198] In addition, the electrolyte preferably contains fluorine. As a fluorine-containing electrolyte, for example, an electrolyte containing one or more fluorinated cyclic carbonates and lithium ions can be used. The fluorinated cyclic carbonate can improve the flame retardancy and the safety of the lithium ion secondary battery.

[0199] As the fluorinated cyclic carbonate, fluorinated ethylene carbonate can be used. For example, monofluoroethylene carbonate (fluorinated ethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), or tetrafluoroethylene carbonate (F4EC) can be used. In addition, as DFEC, there are isomers such as cis-4,5 and trans-4,5. From the viewpoint of operating at low temperatures, it is important to use one or more fluorinated cyclic carbonates to solvate lithium ions and transport the lithium ions in the electrolyte included in the electrodes during charge and discharge. By making the fluorinated cyclic carbonate contribute to the transport of lithium ions during charge and discharge and not acting as a small amount of additive, operation at low temperatures can be achieved. In the secondary battery, lithium ions migrate in clusters of several or dozens.

[0200] By using a fluorinated cyclic carbonate as the electrolyte, the desolvation energy required for the solvated lithium ions in the electrolyte included in the electrodes to enter the active material particles can be reduced. If this desolvation energy can be reduced, it becomes easy to intercalate lithium ions into the active material particles or deintercalate them from the active material particles even in the low temperature range. In addition, lithium ions sometimes migrate in a solvated state, and sometimes a hopping phenomenon occurs in which the solvent molecules coordinated with the lithium ions are exchanged. When the desolvation of lithium ions becomes easy, the migration using the hopping phenomenon sometimes becomes easy, and the migration of lithium ions becomes easy. Since the decomposition products of the electrolyte entangle the surface of the active material during charge and discharge of the secondary battery, deterioration of the secondary battery may occur. However, when the electrolyte contains fluorine, the electrolyte is not sticky, and the decomposition products of the electrolyte do not easily adhere to the surface of the active material. Therefore, deterioration of the secondary battery can be suppressed.

[0201] Sometimes multiple solvated lithium ions form clusters in the electrolyte, and the clusters migrate within the negative electrode, between the positive and negative electrodes, within the positive electrode, etc.

[0202] An example of the fluorinated cyclic carbonate is shown below.

[0203] Monofluoroethylene carbonate (FEC) is represented by the following formula (1).

[0204] [Chemical formula 1]

[0205] Vinyl tetrafluorocarbonate (F4EC) is represented by the following formula (2).

[0206] [Chemical formula 2]

[0207] Difluoro vinyl carbonate (DFEC) is represented by the following formula (3).

[0208] [Chemical formula 3]

[0209] In this specification, the electrolyte is a general term including solid electrolytes, liquid electrolytes, semi-solid gel electrolytes, etc.

[0210] At the interface existing in the secondary battery, for example, at the interface between the active material and the electrolyte, deterioration is likely to occur. In the secondary battery according to one embodiment of the present invention, by including a fluorine-containing electrolyte, deterioration that may occur at the interface between the active material and the electrolyte can be prevented, typically deterioration of the electrolyte or an increase in the viscosity of the electrolyte. In addition, it may have a structure in which a binder or a graphene compound winds around the fluorine-containing electrolyte or a structure in which the fluorine-containing electrolyte holds a binder or a graphene compound. By having this structure, a state in which the viscosity of the electrolyte is reduced can be maintained. In other words, a non-sticky state of the electrolyte can be maintained, thereby improving the reliability of the secondary battery. Compared with FEC bonded to one fluorine, DFEC bonded to two fluorines and F4EC bonded to four fluorines have lower viscosities and are less sticky, and have a weaker coordination bond with lithium. Thus, attachment of high-viscosity decomposition products to the active material particles can be suppressed. When high-viscosity decomposition products attach to the active material particles or high-viscosity decomposition products wind around the active material particles, lithium ions are not easily migrated at the interface of the active material particles. The fluorine-containing electrolyte is solvated to mitigate the formation of decomposition products attached to the surface of the active material (positive electrode active material or negative electrode active material). In addition, by preventing the attachment of decomposition products by using a fluorine-containing electrolyte, the occurrence and growth of dendrites can be prevented.

[0211] In addition, using the fluorine-containing electrolyte as a main component is also one of the features. The fluorine-containing electrolyte is 5 vol.% or more, 10 vol.% or more, preferably 30 vol.% or more and 100 vol.% or less.

[0212] In this specification, the main component of the electrolyte refers to a component that accounts for 5 vol.% or more in the overall electrolyte of the secondary battery. Here, that the component accounts for 5 vol.% or more in the overall electrolyte of the secondary battery means the proportion of the component in the overall electrolyte measured during the manufacture of the secondary battery. In addition, when decomposing after manufacturing the secondary battery, it is difficult to quantify the ratios of various electrolytes, but it is possible to determine whether a certain organic compound accounts for 5 vol.% or more in the overall electrolyte.

[0213] By using an electrolyte containing fluorine, a secondary battery capable of operating within a wide temperature range can be realized. Specifically, a secondary battery capable of operating within a temperature range of -40°C or higher and 150°C or lower, preferably -40°C or higher and 85°C or lower can be realized.

[0214] In addition, additives such as vinylene carbonate, propanesultone (PS), tert-butylbenzene (TBB), lithium bis(oxalato)borate (LiBOB), or dinitrile compounds such as succinonitrile and adiponitrile can also be added to the electrolyte. The concentration of the additive can be set to, for example, 0.1 vol.% or more and less than 5 vol.% in the overall electrolyte.

[0215] In addition, the electrolyte may further contain one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, ethylene glycol dimethyl ether, and tetrahydrofuran in addition to the above.

[0216] In addition, by including a gelled polymer material in the electrolyte, the safety such as leakage resistance is improved. As typical examples of the gelled polymer material, silicone rubber, acrylic rubber, acrylonitrile rubber, polyethylene oxide-based rubber, polypropylene oxide-based rubber, fluoropolymer rubber, etc. can be cited.

[0217] As the polymer material, for example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing these can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. In addition, the formed polymer may also have a porous shape.

[0218] In addition, examples of secondary batteries using a liquid electrolyte are shown above, but it is not limited thereto. For example, semi-solid batteries and all-solid batteries can also be manufactured.

[0219] In this specification and the like, whether it is a secondary battery using a liquid electrolyte or a semi-solid battery, the layer disposed between the positive electrode and the negative electrode is referred to as the electrolyte layer. The electrolyte layer of the semi-solid battery can be said to be a layer formed by deposition, and this layer can be distinguished from the liquid electrolyte layer.

[0220] In addition, in this specification and the like, a semi-solid battery refers to a battery in which at least one of an electrolyte layer, a positive electrode, and a negative electrode contains a semi-solid material. Here, semi-solid does not mean that the proportion of the solid material is 50%. Semi-solid means having properties of a solid such as small volume change, and a part thereof has properties close to a liquid such as flexibility. When having the above properties, a single material or multiple materials can be used. For example, a material in which a liquid material is impregnated into a solid material having a porous shape can also be used.

[0221] In addition, in this specification and the like, a polymer electrolyte secondary battery refers to a secondary battery in which a polymer is contained in an electrolyte layer between a positive electrode and a negative electrode. The polymer electrolyte secondary battery includes a dry (or intrinsic) polymer electrolyte battery and a polymer gel electrolyte battery. In addition, the polymer electrolyte secondary battery can also be referred to as a semi-solid battery.

[0222] When manufacturing a semi-solid battery using the negative electrode of one embodiment of the present invention, the semi-solid battery becomes a secondary battery with a large charge-discharge capacity. In addition, it can become a semi-solid battery with a high charge-discharge voltage. In addition, a semi-solid battery with high safety or reliability can be achieved.

[0223] Here, use Figure 7 An example of manufacturing a semi-solid battery is shown.

[0224] Figure 7 It is a cross-sectional schematic view of a secondary battery of one embodiment of the present invention. The secondary battery of one embodiment of the present invention includes a negative electrode 570a and a positive electrode 570b. The negative electrode 570a includes at least a negative electrode current collector 571a and a negative electrode active material layer 572a formed in contact with the negative electrode current collector 571a, and the positive electrode 570b includes at least a positive electrode current collector 571b and a positive electrode active material layer 572b formed in contact with the positive electrode current collector 571b. In addition, the secondary battery includes an electrolyte 576 between the negative electrode 570a and the positive electrode 570b.

[0225] The electrolyte 576 contains a lithium ion conducting polymer and a lithium salt.

[0226] In this specification and the like, a lithium ion conducting polymer refers to a polymer having conductivity of cations such as lithium. More specifically, a lithium ion conducting polymer is a high molecular compound having a polar group with which a cation can coordinate. As the polar group, an ether group, an ester group, a nitrile group, a carbonyl group, a siloxane, etc. are preferably used.

[0227] As the lithium ion conducting polymer, for example, polyethylene oxide (PEO), a derivative having polyethylene oxide as a main chain, polypropylene oxide, polyacrylate, polymethacrylic acid, polysiloxane, polyphosphazene, etc. can be used.

[0228] The lithium ion conductive polymer can be either branched or crosslinked. In addition, the lithium ion conductive polymer can also be a copolymer. The molecular weight is preferably 10,000 or more, more preferably 100,000 or more.

[0229] In the lithium ion conductive polymer, the lithium ions migrate while replacing the polar groups with which they interact through the partial movement of the polymer chains (also called segmental movement). For example, in PEO, the lithium ions migrate while replacing the interacting oxygen through the segmental movement of the ether chains. When the temperature is near or higher than the melting point or softening point of the lithium ion conductive polymer, the crystalline regions dissolve and the amorphous regions increase, and the movement of the ether chains becomes active, thus increasing the ionic conductivity. Therefore, when using PEO as the lithium ion conductive polymer, it is preferable to charge and discharge at a temperature of 60 °C or higher.

[0230] According to the Shannon ionic radius (Shannon et al., Acta A 32 (1976) 751.), the radii of monovalent lithium ions in four-coordination, six-coordination, and eight-coordination are respectively and In addition, the radii of divalent oxygen ions in two-coordination, three-coordination, four-coordination, six-coordination, and eight-coordination are respectively and The distance between the polar groups of adjacent lithium ion conductive polymer chains is preferably at least the distance at which the lithium ions and the anions of the polar groups can stably exist while maintaining the above ionic radii. And this distance is preferably the distance at which the interaction between the lithium ions and the polar groups occurs sufficiently. Note that as described above, because of the segmental movement, it is not necessary to always maintain a fixed distance. As long as there is an appropriate distance when the lithium ions pass through.

[0231] In addition, as the lithium salt, for example, a compound containing lithium and at least one of phosphorus, fluorine, nitrogen, sulfur, oxygen, chlorine, arsenic, boron, aluminum, bromine, and iodine can be used. For example, LiPF6, LiN(FSO2)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 、Li2B 12 Cl 12, one or more of lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, and lithium bis(oxaloyl borate) (LiBOB).

[0232] When LiFSI is used, the low temperature characteristics are improved, so it is particularly preferred. In addition, LiFSI and LiTFSA are less likely to react with water than Li PF6 and the like. Therefore, it is easy to control the dew point when manufacturing electrodes and electrolyte layers using LiFSI. For example, in addition to inactive atmospheres such as argon that exclude moisture as much as possible and a drying chamber that controls the dew point, it can also be processed under a general atmospheric atmosphere. Therefore, productivity is improved, so it is preferred. In addition, when using Li salts such as LiFSI and LiTFSA that have high dissociation and plasticizing effects, lithium conduction through segmental movement of ether chains can be used in a wider temperature range, so it is particularly preferred.

[0233] In addition, in this specification, etc., a binder refers to a polymer compound mixed only for bonding active materials, conductive agents, etc. to a current collector, for example, a rubber material such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, butadiene rubber, ethylene-propylene-diene copolymer, fluororubber, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, ethylene-propylene-diene polymer, etc.

[0234] Since lithium ion conductive polymer is a high molecular compound, by fully mixing it and using it in the active material layer, the active material and the conductive agent can be bonded to the current collector. Therefore, even without using an adhesive, an electrode can be manufactured. The adhesive is a material that does not contribute to the charge and discharge reaction. Therefore, the less the adhesive, the more active materials, electrolytes, and other materials that contribute to charge and discharge can be added. Therefore, a secondary battery with improved discharge capacity or cycle characteristics can be realized.

[0235] When there is no organic solvent or very little organic solvent, a secondary battery that is not easy to cause ignition and fire can be realized, which improves safety, so it is preferred. In addition, when the electrolyte 576 is an electrolyte layer without organic solvent or with very little organic solvent, it is strong enough even without a separator to electrically insulate the positive electrode and the negative electrode. Because there is no need to use a separator, a secondary battery with high productivity can be realized. By making the electrolyte 576 an electrolyte layer including an inorganic filler, the strength is further improved, and a secondary battery with higher safety can be realized.

[0236] In order to make the electrolyte 576 an electrolyte layer with no or extremely little organic solvent, it is preferable to sufficiently dry the electrolyte layer. Note that in this specification, etc., a case where the weight change of the electrolyte layer during reduced-pressure drying at 90 °C for 1 hour is within 5% is equivalent to sufficient drying.

[0237] Note that in the identification of materials such as lithium-ion conductive polymers, lithium salts, binders, and additives included in the secondary battery, nuclear magnetic resonance (NMR) can be used, for example. In addition, the analysis results of Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), time-of-flight secondary ion mass spectrometry (TOF-SIMS), gas chromatography-mass spectrometry (GC / MS), pyrolysis gas chromatography-mass spectrometry (Py-GC / MS), liquid chromatography-mass spectrometry (LC / MS), etc. can also be used as the basis for judgment. It is preferable to suspend the active material layer in a solvent, separate the active material from other materials, and then perform analysis such as NMR.

[0238] In addition, in each of the above structures, the negative electrode may also contain a solid electrolyte material to improve flame retardancy. As the solid electrolyte material, an oxide-based solid electrolyte is preferably used.

[0239] Examples of the oxide-based solid electrolyte include LiPON, Li2O, Li2CO3, Li2MoO4, Li3PO4, Li3VO4, Li4SiO4, LLT (La 2 / 3-x Li 3x TiO3), LLZ (Li7La3Zr2O 12 ) and other lithium composite oxides and lithium oxide materials.

[0240] LLZ is a garnet-type oxide containing Li, La, and Zr, and may also be a compound further containing Al, Ga, or Ta.

[0241] In addition, a polymer-based solid electrolyte such as PEO (polyethylene oxide) formed by a coating method or the like can also be used. Since such a polymer-based solid electrolyte can also be used as a binder, the number of electrode components and manufacturing costs can be reduced when using a polymer-based solid electrolyte.

[0242] This embodiment can be used in appropriate combination with other embodiments.

[0243] (Embodiment 2) In this embodiment, an example of a secondary battery according to one aspect of the present invention will be described.

[0244] <Structural example of secondary battery> Hereinafter, a secondary battery in which a positive electrode, a negative electrode, and an electrolytic solution are surrounded by an outer package will be described as an example.

[0245] [Negative electrode] As the negative electrode, the negative electrode shown in the above-described embodiments can be used.

[0246] [Current collector] As the positive current collector and the negative current collector, materials such as metals and their alloys with high conductivity and not alloying with carrier ions such as lithium, such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, etc., can be used. In addition, as the positive current collector and the negative current collector, aluminum alloys added with elements for improving heat resistance such as silicon, titanium, neodymium, scandium, molybdenum, etc. can be used. In addition, metal elements that react with silicon to form silicides can also be used. As the metal elements that react with silicon to form silicides, there are zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. As the current collector, shapes such as sheet, mesh, punched metal mesh, drawn metal mesh, etc. can be appropriately used. The thickness of the current collector is preferably 10 μm or more and 30 μm or less.

[0247] In addition, as the negative current collector, a material that does not alloy with carrier ions such as lithium is preferably used.

[0248] As the current collector, a titanium compound can also be provided in a manner of being laminated on the above metal element. As the titanium compound, for example, one or more selected from titanium nitride, titanium oxide, titanium nitride in which a part of nitrogen is replaced by oxygen, titanium oxide in which a part of oxygen is replaced by nitrogen, and oxynitride titanium (TiO x N y , 0 < x < 2, 0 < y < 1) can be mixed or laminated and used. Among them, titanium nitride is particularly preferred because it has high conductivity and high oxidation inhibition function. By providing the titanium compound on the surface of the current collector, for example, the reaction between the material contained in the active material layer formed on the current collector and the metal can be inhibited. When the active material layer includes a compound containing oxygen, the oxidation reaction between the metal element and oxygen can be inhibited. For example, when aluminum is used as the current collector and graphene oxide described later is used to form the active material layer, there is a concern about the oxidation reaction between the oxygen contained in graphene oxide and aluminum. In this case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be inhibited.

[0249] [Positive electrode] The positive electrode includes a positive electrode active material layer and a positive current collector. The positive electrode active material layer includes a positive electrode active material and may also include a conductive agent and a binder. As the positive electrode active material, the positive electrode active material shown in the above-described embodiments is used.

[0250] As the conductive agent and the binder that can be included in the positive electrode active material layer, the same materials as those that can be included in the negative electrode active material layer can be used.

[0251] [Separator] A separator is disposed between the positive electrode and the negative electrode. As the separator, for example, the following materials can be used: fibers having cellulose such as paper, non-woven fabric, glass fiber, ceramic, or synthetic fibers including nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic resin, polyolefin, polyurethane, etc. Preferably, the separator is processed into a bag shape and disposed so as to surround either the positive electrode or the negative electrode.

[0252] The separator is a porous material having pores with a diameter of approximately 20 nm, preferably having pores with a diameter of 6.5 nm or more, and more preferably having pores with a diameter of at least 2 nm. In the case of the above semi-solid secondary battery, the separator can also be omitted.

[0253] The separator can have a multilayer structure. For example, a ceramic material, a fluorine material, a polyamide material, or a mixture thereof can be coated on an organic material film such as polypropylene or polyethylene. As the ceramic material, for example, alumina particles, silica particles, etc. can be used. As the fluorine material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide material, for example, nylon, aromatic polyamide (meta-aramid, para-aramid), etc. can be used.

[0254] By coating a ceramic material, the antioxidant property can be improved, thereby suppressing the deterioration of the separator during charge and discharge at a high voltage, and thus improving the reliability of the secondary battery. By coating a fluorine material, it is easy to make the separator in close contact with the electrode, and the output characteristics can be improved. By coating a polyamide material, especially aromatic polyamide, the heat resistance can be improved, thereby improving the safety of the secondary battery.

[0255] For example, a mixed material of alumina and aromatic polyamide can be coated on both sides of a polypropylene film. Alternatively, a mixed material of alumina and aromatic polyamide can be coated on the surface of the polypropylene film in contact with the positive electrode, and a fluorine material can be coated on the surface in contact with the negative electrode.

[0256] By adopting a separator with a multilayer structure, the safety of the secondary battery can be ensured even if the total thickness of the separator is small, so that the capacity per unit volume of the secondary battery can be increased.

[0257] [Outer packaging body] As the outer package included in the secondary battery, for example, a metal material such as aluminum and a resin material can be used. In addition, a film-shaped outer package can also be used. As the film, for example, a film having the following three-layer structure can be used: a metal film with excellent flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film such as a polyamide resin or a polyester resin can be provided on the metal film as the outer surface of the outer package. In addition, a fluororesin film is preferably used as the film. The fluororesin film has high stability against acids, alkalis, organic solvents, etc., and can suppress side reactions, corrosion, etc. caused by the reaction of the secondary battery, etc., to achieve an excellent secondary battery. As the fluororesin film, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy alkane: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylene-propene copolymer: copolymer of tetrafluoroethylene and hexafluoropropene), ETFE (ethylene-tetrafluoroethylene copolymer: copolymer of tetrafluoroethylene and ethylene), etc. can be cited.

[0258] This embodiment can be used in appropriate combination with other embodiments.

[0259] (Embodiment 3) In this embodiment, examples of various shapes of secondary batteries including a positive electrode or a negative electrode manufactured by the manufacturing method described in the above embodiment are described.

[0260] [Coin-type secondary battery] An example of a coin-type secondary battery is described. Figure 8A is an exploded perspective view of a coin-type (single-layer flat type) secondary battery, Figure 8B is an external view thereof, Figure 8C is a cross-sectional view thereof. The coin-type secondary battery is mainly used for small electronic devices.

[0261] To easily understand the overlapping relationship (upper-lower relationship and positional relationship) of the components, Figure 8A a schematic diagram is adopted. Therefore, Figure 8A it is not Figure 8B exactly the same as the

[0262] In Figure 8A , the positive electrode 304, the separator 310, the negative electrode 307, the spacer 322, and the gasket 312 are stacked. And the above components are sealed with the negative electrode can 302 and the positive electrode can 301. Note that in Figure 8AThe gasket for sealing is not shown. The spacer 322 and the washer 312 are used to protect the interior or fix the positions inside the cans when pressing the positive can 301 and the negative can 302. The spacer 322 and the washer 312 are made of stainless steel or insulating materials.

[0263] The laminated structure in which the positive electrode active material layer 306 is formed on the positive electrode current collector 305 is denoted as the positive electrode 304.

[0264] In order to prevent short - circuiting between the positive electrode and the negative electrode, the separator 310 and the annular insulator 313 are arranged so as to cover the side surface and the top surface of the positive electrode 304. The area of the separator 310 is larger than the area of the positive electrode 304.

[0265] Figure 8B It is a perspective view of the manufactured coin - type secondary battery.

[0266] In the coin - type secondary battery 300, the positive can 301 that also serves as the positive electrode terminal and the negative can 302 that also serves as the negative electrode terminal are insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by the positive electrode current collector 305 and the positive electrode active material layer 306 provided in contact therewith. In addition, the negative electrode 307 is formed by the negative electrode current collector 308 and the negative electrode active material layer 309 provided in contact therewith. In addition, the negative electrode 307 is not limited to the laminated structure, and a lithium metal foil or an alloy foil of lithium and aluminum can also be used.

[0267] In the positive electrode 304 and the negative electrode 307 for the coin - type secondary battery 300, the active material layers can be formed on one surface of the positive electrode and the negative electrode, respectively.

[0268] As the positive can 301 and the negative can 302, metals such as nickel, aluminum, and titanium that are corrosion - resistant to the electrolyte, alloys of these metals, or alloys of these metals and other metals (such as stainless steel, etc.) can be used. In addition, in order to prevent corrosion caused by the electrolyte, the positive can 301 and the negative can 302 are preferably covered with nickel and aluminum, etc. The positive can 301 is electrically connected to the positive electrode 304, and the negative can 302 is electrically connected to the negative electrode 307.

[0269] By impregnating these negative electrode 307, positive electrode 304, and separator 310 in the electrolyte, as Figure 8C shown, the positive can 301 is set below, and the positive electrode 304, separator 310, negative electrode 307, and negative can 302 are laminated in order, and the positive can 301 and the negative can 302 are pressed together with the gasket 303 in between to manufacture the coin - type secondary battery 300.

[0270] As a secondary battery, a coin - type secondary battery 300 with high capacity, high charge - discharge capacity, and excellent cycle characteristics can be manufactured.

[0271] [Cylindrical secondary battery] Next, an example of a cylindrical secondary battery will be described with reference to Figure 9A As shown in Figure 9A The top surface of the cylindrical secondary battery 616 includes a positive electrode cap (battery cap) 601, and its side surface and bottom surface include a battery can (outer can) 602. The battery can (outer can) 602 is formed of a metal material and has good water permeability barrier property and gas barrier property. The positive electrode cap 601 and the battery can (outer can) 602 are insulated by a gasket (insulating gasket) 610.

[0272] Figure 9B is a diagram schematically showing a cross section of the cylindrical secondary battery. Figure 9B The shown cylindrical secondary battery has a positive electrode cap (battery cap) 601 on its top surface, and a battery can (outer can) 602 on its side surface and bottom surface. The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating gasket) 610.

[0273] A battery element is provided inside the hollow cylindrical battery can 602. In this battery element, a strip-shaped positive electrode 604 and a strip-shaped negative electrode 606 are wound with a separator 605 interposed therebetween. Although not shown, the battery element is wound around a center pin. One end of the battery can 602 is closed and the other end is open. As the battery can 602, metals such as nickel, aluminum, and titanium, alloys of these metals, and alloys of these metals and other metals (such as stainless steel, etc.) that have corrosion resistance to the electrolyte can be used. In addition, in order to prevent corrosion caused by the electrolyte, the battery can 602 is preferably covered with nickel and aluminum, etc. Inside the battery can 602, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched by a pair of opposed insulating plates 608 and 609. In addition, an electrolyte (not shown) is injected into the inside of the battery can 602 in which the battery element is provided. As the electrolyte, the same electrolyte as that used in the coin-type secondary battery can be used.

[0274] Since the positive electrode and negative electrode for the cylindrical storage battery are wound, it is preferable that the active material is formed on both surfaces of the current collector.

[0275] By using the negative electrode obtained in Embodiment 1, a cylindrical secondary battery 616 with high capacity, high charge-discharge capacity, and excellent cycle characteristics can be manufactured.

[0276] The positive electrode 604 is connected to the positive terminal (positive current collector wire) 603, while the negative electrode 606 is connected to the negative terminal (negative current collector wire) 607. Both the positive terminal 603 and the negative terminal 607 can be made of a metal material such as aluminum. The positive terminal 603 is resistance-welded to the safety valve mechanism 613, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 and the positive electrode cap 601 are electrically connected through a PTC element (Positive Temperature Coefficient) 611. When the internal pressure of the battery rises above a specified threshold value, the safety valve mechanism 613 cuts off the electrical connection between the positive electrode cap 601 and the positive electrode 604. In addition, the PTC element 611 is a thermosensitive resistance element whose resistance increases when the temperature rises, and limits the current flow to prevent abnormal heating by increasing the resistance. As the PTC element, barium titanate (BaTiO3)-based semiconductor ceramics or the like can be used.

[0277] Figure 9C An example of the power storage system 615 is shown. The power storage system 615 includes a plurality of secondary batteries 616. The positive electrode of each secondary battery contacts a conductor 624 separated by an insulator 625 and the positive electrodes are electrically connected to each other. The conductor 624 is electrically connected to the control circuit 620 through a wiring 623. In addition, the negative electrode of each secondary battery is electrically connected to the control circuit 620 through a wiring 626. As the control circuit 620, a charge-discharge control circuit that performs charge and discharge or the like and a protection circuit that prevents overcharging and / or over-discharging can be used.

[0278] Figure 9D An example of the power storage system 615 is shown. The power storage system 615 includes a plurality of secondary batteries 616, and the plurality of secondary batteries 616 are sandwiched between a conductive plate 628 and a conductive plate 614. The plurality of secondary batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 through a wiring 627. The plurality of secondary batteries 616 can be connected in parallel, connected in series, or connected in parallel and then in series. By constructing the power storage system 615 including a plurality of secondary batteries 616, a large amount of power can be obtained.

[0279] In addition, the plurality of secondary batteries 616 can also be connected in parallel and then in series.

[0280] In addition, a temperature control device can also be included between the plurality of secondary batteries 616. When the secondary battery 616 is overheated, it can be cooled by the temperature control device, and when the secondary battery 616 is overcooled, it can be heated by the temperature control device. Therefore, the performance of the power storage system 615 is not easily affected by the external air temperature.

[0281] In addition, in Figure 9DIn this case, the power storage system 615 is electrically connected to the control circuit 620 via the wiring 621 and the wiring 622. The wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 via the conductive plate 628, and the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 via the conductive plate 614.

[0282] [Other structural examples of secondary batteries] The structural examples of the secondary battery will be described with reference to FIGS. 10 and 11.

[0283] Figure 10A The illustrated secondary battery 913 includes a wound body 950 provided with a terminal 951 and a terminal 952 inside a casing 930. The wound body 950 is immersed in an electrolyte inside the casing 930. The terminal 952 is in contact with the casing 930, and the terminal 951 is prevented from contacting the casing 930 by an insulating material or the like. Note that, for convenience, although the casing 930 is separately illustrated in Figure 10A in fact, the wound body 950 is covered with the casing 930, and the terminals 951 and 952 extend outside the casing 930. As the casing 930, a metal material (such as aluminum or the like) or a resin material can be used.

[0284] In addition, as Figure 10B shown, the casing 930 shown can also be formed of a plurality of materials. For example, in Figure 10A the secondary battery 913 shown in Figure 10B a casing 930a and a casing 930b are bonded, and a wound body 950 is provided in the region surrounded by the casing 930a and the casing 930b.

[0285] As the casing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an organic resin for the surface forming the antenna, the shielding of the electric field of the secondary battery 913 can be suppressed. In addition, if the electric field shielding caused by the casing 930a is small, an antenna can also be provided inside the casing 930a. As the casing 930b, for example, a metal material can be used.

[0286] Furthermore, Figure 10C shows the structure of the wound body 950. The wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is formed by overlapping the negative electrode 931 and the positive electrode 932 with each other with the separator 933 interposed therebetween to form a laminated sheet, and winding the laminated sheet. In addition, a plurality of laminations of the negative electrode 931, the positive electrode 932, and the separator 933 can also be laminated.

[0287] In addition, the secondary battery 913 including the wound body 950a shown in FIG. 11 can also be used. Figure 11AThe wound body 950a shown includes a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 includes a negative electrode active material layer 931a. The positive electrode 932 includes a positive electrode active material layer 932a.

[0288] By using an electrolyte containing fluorine for the negative electrode 931, a secondary battery 913 with a high charge-discharge capacity and excellent cycle characteristics can be manufactured.

[0289] The width of the separator 933 is greater than that of the negative electrode active material layer 931a and the positive electrode active material layer 932a, and the separator 933 is wound in a manner overlapping the negative electrode active material layer 931a and the positive electrode active material layer 932a. In addition, from the viewpoint of safety, it is preferable that the width of the negative electrode active material layer 931a is greater than that of the positive electrode active material layer 932a. In addition, the wound body 950a having the above shape has good safety and productivity, so it is preferable.

[0290] As Figure 11A and Figure 11B shown, the negative electrode 931 is electrically connected to the terminal 951. The terminal 951 is electrically connected to the terminal 911a. In addition, the positive electrode 932 is electrically connected to the terminal 952. The terminal 952 is electrically connected to the terminal 911b.

[0291] As Figure 11C shown, the wound body 950a and the electrolyte are covered by the casing 930 to form a secondary battery 913. The casing 930 is preferably provided with a safety valve, an overcurrent protection element, etc. The safety valve is a valve that opens the inside of the casing 930 at a specified pressure to prevent the battery from bursting.

[0292] As Figure 11B shown, the secondary battery 913 may also include a plurality of wound bodies 950a. By using a plurality of wound bodies 950a, a secondary battery 913 with a larger charge-discharge capacity can be realized. Regarding Figure 11A and Figure 11B shown other components of the secondary battery 913, reference can be made to the description of the secondary battery 913 shown in Figures 10A to 10C shown.

[0293] <Laminated secondary battery> Next, Figure 12A and Figure 12B are external views showing an example of a laminated secondary battery. Figure 12A and Figure 12B both show a positive electrode 503, a negative electrode 506, a separator 507, an outer packaging body 509, a positive electrode wire electrode 510, and a negative electrode wire electrode 511.

[0294] Figure 13AIt is an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 includes a positive electrode current collector 501, and a positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. In addition, the positive electrode 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter, referred to as the tab region). The negative electrode 506 includes a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, the tab region. The area and shape of the tab regions of the positive electrode and the negative electrode are not limited to Figure 13A the examples shown.

[0295] <Manufacturing method of a laminated secondary battery> Here, with reference to Figure 13B and Figure 13C an example of the manufacturing method of the laminated secondary battery whose appearance is shown in Figure 12A will be described.

[0296] First, stack the negative electrode 506, the separator 507, and the positive electrode 503. Figure 13B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example of using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. In addition, it can also be said to be a laminate composed of a negative electrode, a separator, and a positive electrode. Next, join the tab regions of the positive electrode 503 to each other, and join the positive electrode lead electrode 510 to the tab region of the outermost positive electrode. As the joining, for example, ultrasonic welding or the like can be used. Similarly, join the tab regions of the negative electrode 506 to each other, and join the negative electrode lead electrode 511 to the tab region of the outermost negative electrode.

[0297] Next, arrange the negative electrode 506, the separator 507, and the positive electrode 503 on the outer package 509.

[0298] Next, as Figure 13C shown, fold the outer package 509 along the part indicated by the dashed line. Then, join the outer peripheral portion of the outer package 509. As the joining, for example, thermocompression bonding or the like can be used. At this time, in order to inject the electrolyte 508 later, a region that is not joined to a part (or one side) of the outer package 509 (hereinafter, referred to as the inlet) is provided. The outer package 509 is preferably a film having good water permeation barrier properties and gas barrier properties. In addition, by making the outer package 509 have a laminated structure and using a metal foil (for example, aluminum foil) as one of the intermediate layers, high water permeation barrier properties and high gas barrier properties can be achieved.

[0299] Next, an electrolyte 508 (not shown) is introduced into the inside of the outer package 509 from an introduction port provided in the outer package 509. It is preferable to introduce the electrolyte 508 under a reduced pressure atmosphere or an inert gas atmosphere. Finally, the introduction port is joined. Thus, the laminated secondary battery 500 can be manufactured.

[0300] By using, for the negative electrode 506, an electrode obtained by closely winding and mixing a graphene compound, which is the negative electrode structure obtained in Embodiment 1, with particles containing silicon, a material containing a halogen, and a material containing oxygen and carbon and heating the mixture, a secondary battery 500 having a high capacity, a high charge-discharge capacity, and excellent cycle characteristics can be manufactured.

[0301] This embodiment can be used in appropriate combination with other embodiments.

[0302] (Embodiment 4) This embodiment shows an example different from the Figure 9D cylindrical secondary battery. Referring to Figure 14C shows an example for an electric vehicle (EV).

[0303] In an electric vehicle, there are provided first batteries 1301a and 1301b that are secondary batteries for main driving, and a second battery 1311 that supplies power to an inverter 1312 for starting an engine 1304. The second battery 1311 is also referred to as a cranking battery (also known as a starting battery). The second battery 1311 only needs to have a high output and does not need to have too large a capacity, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0304] The internal structure of the first battery 1301a can be either the Figure 10A shown wound type or the Figure 12A and Figure 12B shown stacked type.

[0305] In this embodiment, an example of connecting two batteries, the first batteries 1301a and 1301b, in parallel is shown, but three or more batteries can also be connected in parallel. In addition, as long as sufficient power can be stored in the first battery 1301a, the first battery 1301b can be omitted. By forming a battery pack from a plurality of secondary batteries, a larger amount of power can be taken out. The plurality of secondary batteries can be connected in parallel, in series, or in series after being connected in parallel. Sometimes a plurality of secondary batteries are referred to as a battery pack.

[0306] In order to cut off the power from a plurality of secondary batteries, an in-vehicle secondary battery includes a charging plug or a circuit breaker that can cut off high voltage without using tools, and it is provided in the first battery 1301a.

[0307] In addition, the power of the first batteries 1301a and 1301b is mainly used to rotate the engine 1304, and power is also supplied to 42V series vehicle components (such as an Electric Power Steering 1307, a heater 1308, a defroster 1309, etc.) through the DCDC circuit 1306. When the rear wheels include a rear-mounted engine 1317, the first battery 1301a is used to rotate the rear-mounted engine 1317.

[0308] In addition, the second battery 1311 supplies power to 14V series vehicle components (such as an audio 1313, power windows 1314, lights 1315, etc.) through the DCDC circuit 1310.

[0309] In addition, use Figure 14A to illustrate the first battery 1301a.

[0310] Figure 14A An example is shown in which nine rectangular secondary batteries 1300 are used as one battery pack 1415. In addition, the nine rectangular secondary batteries 1300 are connected in series, and one electrode is fixed using a fixing portion 1413 made of an insulator, and the other electrode is fixed using a fixing portion 1414 made of an insulator. In the present embodiment, an example of fixing using the fixing portions 1413 and 1414 is shown, but they may also be housed in a battery housing (also referred to as a casing). Assuming that the vehicle is subjected to vibration or shaking from the outside (such as a road surface), it is preferable to fix a plurality of secondary batteries using the fixing portions 1413 and 1414 and the battery housing. In addition, one electrode is electrically connected to the control circuit unit 1320 through a wiring 1421. In addition, the other electrode is electrically connected to the control circuit unit 1320 through a wiring 1422.

[0311] In addition, the control circuit unit 1320 may also use a storage circuit including a transistor using an oxide semiconductor. Sometimes a charge control circuit or a battery control system including a storage circuit using a transistor using an oxide semiconductor is referred to as BTOS (Battery operating system or Battery oxide semiconductor).

[0312] The control circuit unit 1320 detects the terminal voltage of the secondary battery and manages the charge and discharge state of the secondary battery. For example, in order to prevent overcharging, both the output transistor of the charging circuit and the cut-off switch can be turned off almost simultaneously.

[0313] In addition, Figure 14B shows Figure 14A an example of a block diagram of the battery pack 1415 shown.

[0314] The control circuit unit 1320 includes: a switch unit 1324 including at least a switch for preventing overcharging and a switch for preventing over-discharging; a control circuit 1322 for controlling the switch unit 1324; and a voltage measurement unit for the first battery 1301a. In the control circuit unit 1320, the upper limit voltage and the lower limit voltage of the secondary battery to be used are set, and the upper limit of the input current flowing from the outside and the upper limit of the output current flowing to the outside are set, etc. The range above the lower limit voltage and below the upper limit voltage of the secondary battery is the recommended voltage range. When the voltage is outside this range, the switch unit 1324 operates as a protection circuit. In addition, since the control circuit unit 1320 controls the switch unit 1324 to prevent over-discharging and / or overcharging, it can also be called a protection circuit. For example, when the control circuit 1322 detects a voltage that will cause overcharging, the current is blocked by closing the switch of the switch unit 1324. In addition, a function of blocking the current according to the rise in temperature can be set by providing a PTC element in the charge / discharge path. In addition, the control circuit unit 1320 includes an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0315] The switch unit 1324 can be configured by combining an n-channel transistor and a p-channel transistor. In addition to the switch including an Si transistor using single crystal silicon, for example, power transistors such as Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (gallium oxide; x is a real number greater than 0) can also be used to form the switch unit 1324. In addition, a storage element using an OS transistor can be freely arranged by laminating it on a circuit using an Si transistor, etc., so integration is easy to achieve. In addition, the OS transistor can be manufactured using the same manufacturing equipment as the Si transistor, so it can be manufactured at low cost. That is, by integrating the control circuit unit 1320 using an OS transistor on the switch unit 1324, the switch unit 1324 and the control circuit unit 1320 can be integrated in one chip. The volume occupied by the control circuit unit 1320 can be reduced, so miniaturization can be achieved.

[0316] The first batteries 1301a and 1301b mainly supply power to 42V series (high voltage series) in-vehicle devices, while the second battery 1311 supplies power to 14V series (low voltage series) in-vehicle devices. In many cases, the second battery 1311 uses a lead-acid battery because of cost advantages.

[0317] This embodiment shows an example in which both the first battery 1301a and the second battery 1311 use lithium-ion secondary batteries. The second battery 1311 may also use a lead storage battery, an all-solid-state battery, or an electric double layer capacitor.

[0318] In addition, the regenerative energy generated by the rotation of the tire 1316 is transmitted to the engine 1304 through the transmission 1305, and is charged from the engine controller 1303 and the battery controller 1302 to the second battery 1311 through the control circuit unit 1321. In addition, it is charged from the battery controller 1302 to the first battery 1301a through the control circuit unit 1320. In addition, it is charged from the battery controller 1302 to the first battery 1301b through the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is preferable that the first batteries 1301a and 1301b can perform rapid charging.

[0319] The battery controller 1302 can set the charging voltage, charging current, etc. of the first batteries 1301a and 1301b. The battery controller 1302 sets the charging conditions according to the charging characteristics of the secondary battery used and performs rapid charging.

[0320] In addition, although not shown, when an electric vehicle is connected to an external charger, the socket of the charger or the connection cable of the charger is electrically connected to the battery controller 1302. The electric power supplied from the external charger is charged to the first batteries 1301a and 1301b through the battery controller 1302. In addition, some chargers are provided with a control circuit and do not use the functions of the battery controller 1302, but in order to prevent overcharging, it is preferable to charge the first batteries 1301a and 1301b through the control circuit unit 1320. In addition, sometimes the connection cable or the connection cable of the charger is provided with a control circuit. The control circuit unit 1320 is sometimes referred to as an ECU (Electronic Control Unit). The ECU is connected to the CAN (Controller Area Network) provided in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. In addition, the ECU includes a microcomputer. In addition, the ECU uses a CPU and a GPU.

[0321] Next, an example in which a secondary battery as one aspect of the present invention is installed in a vehicle, typically a transport vehicle, will be described.

[0322] In addition, when Figure 9D , Figure 14AWhen a secondary battery as shown in any of them is installed in a vehicle, new-generation clean energy vehicles such as a hybrid vehicle (HV), an electric vehicle (EV), or a plug-in hybrid vehicle (PHV) can be realized. In addition, the secondary battery can also be installed in transportation vehicles such as agricultural machinery, electric bicycles including electric assist bicycles, motorcycles, electric wheelchairs, electric karts, small or large ships, submarines, aerial vehicles such as fixed-wing aircraft or rotary-wing aircraft, rockets, artificial satellites, space probes or planetary probes, and spacecraft. The secondary battery of one aspect of the present invention can be a high-capacity secondary battery. Therefore, the secondary battery of one aspect of the present invention is suitable for miniaturization and light weight and can be suitable for use in transportation vehicles.

[0323] Figures 15A to 15D An example of a transportation vehicle using one aspect of the present invention is illustrated. Figure 15A The illustrated automobile 2001 is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, the automobile 2001 is a hybrid vehicle that can appropriately select an electric motor and an engine as power sources for driving. When the secondary battery is installed in a vehicle, the secondary battery can be provided in one or more parts. Figure 15A The illustrated automobile 2001 includes a battery pack 2200, and the battery pack includes a secondary battery module that connects a plurality of secondary batteries. In addition, a charge control device electrically connected to the secondary battery module is preferably further included.

[0324] In addition, in the automobile 2001, the secondary battery included in the automobile 2001 can be charged by supplying power from an external charging device by using a plug-in method or a non-contact power supply method or the like. When charging, as the charging method and the specifications of the connector and the like, it can be appropriately performed according to the specified methods such as CHAdeMO (registered trademark in Japan) or the Combined Charging System. As the secondary battery, a power source provided at a charging station in a commercial facility or at home can also be used. For example, by supplying power from the outside by using plug-in technology, the power storage device installed in the automobile 2001 can be charged. The alternating current power can be converted into direct current power by a conversion device such as an AC / DC converter for charging.

[0325] In addition, although not shown, the power receiving device can also be installed in a vehicle and charged by non-contact power supply from a power transmission device on the ground. When using the non-contact power supply method, by assembling the power transmission device on a road or an outer wall, charging can be performed not only while the vehicle is parked but also while it is moving. In addition, this non-contact power supply method can also be used to transmit and receive power between two vehicles. Furthermore, a solar cell can be provided outside the vehicle to charge the secondary battery while the vehicle is parked or moving. Such non-contact power supply can be achieved by means of electromagnetic induction or magnetic field resonance.

[0326] In Figure 15B , as an example of a transport vehicle, a large transport vehicle 2002 including an engine controlled by electricity is shown. The secondary battery module of the transport vehicle 2002 is, for example, a secondary battery module in which 48 units are connected in series with four secondary batteries of 3.5 V or more and 4.7 V or less as battery cells, and the maximum voltage is 170 V. Except for differences such as the number of secondary batteries constituting the secondary battery module, the battery pack 2201 has the same function as Figure 15A and thus the description thereof is omitted.

[0327] In Figure 15C as an example, a large transport vehicle 2003 including an engine controlled by electricity is shown. The secondary battery module of the transport vehicle 2003 is, for example, a secondary battery module in which 100 or more secondary batteries of 3.5 V or more and 4.7 V or less are connected in series, and the maximum voltage is 600 V. Therefore, secondary batteries with less characteristic non-uniformity are required. By using a secondary battery including an electrolyte containing fluorine in the negative electrode, a secondary battery with stable electrical characteristics can be manufactured, and mass production can be carried out at low cost from the perspective of the yield. In addition, except for differences such as the number of secondary batteries constituting the secondary battery module, the battery pack 2202 has the same function as Figure 15A and thus the description thereof is omitted.

[0328] In Figure 15D as an example, an aerial vehicle 2004 equipped with an engine that burns fuel is shown. Figure 15D The aerial vehicle 2004 shown includes landing and takeoff wheels, so it can be said that the aerial vehicle 2004 is a type of transport vehicle. In the aerial vehicle 2004, a plurality of secondary batteries are connected to form a secondary battery module, and a battery pack 2203 including the secondary battery module and a charge control device is included.

[0329] The secondary battery module of the aerial vehicle 2004, for example, has eight 4V secondary batteries connected in series, and its maximum voltage is 32V. Except for differences such as the number of secondary batteries of the secondary battery module constituting the battery pack 2203, it has the same function as Figure 15A and thus the description thereof is omitted.

[0330] This embodiment can be used in appropriate combination with other embodiments.

[0331] (Embodiment 5) In this embodiment, Figure 16A and Figure 16B an example of installing a secondary battery according to one aspect of the present invention in a building will be described.

[0332] Figure 16A The house shown includes a power storage device 2612 having a secondary battery according to one aspect of the present invention and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 through wiring 2611 or the like. In addition, the power storage device 2612 can be electrically connected to a ground-mounted charging device 2604. The power obtained from the solar panel 2610 can be charged into the power storage device 2612. In addition, the power stored in the power storage device 2612 can be charged into the secondary battery included in the vehicle 2603 through the charging device 2604. The power storage device 2612 is preferably provided in the under-floor space portion. By being provided in the under-floor space portion, the space above the floor can be effectively utilized. Alternatively, the power storage device 2612 can also be provided on the floor.

[0333] The power stored in the power storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power supply from a commercial power source cannot be received due to a power outage or the like, the electronic devices can be utilized by using the power storage device 2612 according to one aspect of the present invention as an uninterruptible power supply.

[0334] Figure 16B An example of a power storage device 700 according to one aspect of the present invention is shown. As Figure 16B shown, a power storage device 791 according to one aspect of the present invention is provided in the under-floor space portion 796 of a building 799.

[0335] A control device 790 is provided in the power storage device 791, and the control device 790 is electrically connected to a distribution board 703, a power storage controller 705 (also referred to as a control device), a display 706, and a router 709 through wiring.

[0336] Power is supplied from a commercial power source 701 to the distribution board 703 through an incoming line installation portion 710. In addition, power from the power storage device 791 and power from the commercial power source 701 are both supplied to the distribution board 703, and the distribution board 703 supplies the supplied power to a general load 707 and a power storage load 708 through sockets (not shown).

[0337] As the general load 707, for example, electronic devices such as a television and a personal computer can be cited. And as the power storage load 708, for example, electronic devices such as a microwave oven, a refrigerator, and an air conditioner can be cited.

[0338] The power storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has a function of measuring the power consumption of the general load 707 and the power storage load 708 in one day (such as from 0:00 to 24:00). In addition, the measurement unit 711 may also have a function of measuring the power amount of the power storage device 791 and the power amount supplied from the commercial power supply 701. In addition, the prediction unit 712 has a function of predicting the required power amount to be consumed by the general load 707 and the power storage load 708 on the next day based on the power consumption of the general load 707 and the power storage load 708 in one day. In addition, the planning unit 713 has a function of determining the charge-discharge plan of the power storage device 791 based on the required power amount predicted by the prediction unit 712.

[0339] The power amounts consumed by the general load 707 and the power storage load 708 measured by the measurement unit 711 can be confirmed using the display 706. In addition, it can also be confirmed using electronic devices such as a television and a personal computer through the router 709. Furthermore, it can also be confirmed using portable electronic terminals such as a smart phone and a tablet terminal through the router 709. In addition, the required power amount for each time period (or every hour) predicted by the prediction unit 712 can also be confirmed using the display 706, an electronic device, or a portable electronic terminal.

[0340] This embodiment can be used in appropriate combination with other embodiments.

[0341] (Embodiment 6) In this embodiment, an example of installing a secondary battery of one aspect of the present invention in an electronic device will be described. As the electronic device equipped with the secondary battery, for example, a television device (also referred to as a television or a television receiver), a display for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile telephone, a mobile phone device), a portable game machine, a portable information terminal, a sound reproduction device, a large game machine such as a pachinko machine, etc. can be cited. As the portable information terminal, a notebook personal computer, a tablet terminal, an e-book reader, a mobile phone, etc. can be cited.

[0342] Figure 17AAn example of a mobile phone is shown. In addition to the display unit 2102 mounted on the housing 2101, the mobile phone 2100 also includes operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, etc. In addition, the mobile phone 2100 includes a secondary battery 2107. By including a secondary battery 2107 having a structure in which an electrolyte containing fluorine is included in the negative electrode, a high capacity can be achieved, and a structure capable of saving space required for downsizing the housing can be achieved.

[0343] The mobile phone 2100 can execute various application programs such as mobile phone calls, emails, reading and writing of texts, music playback, network communication, computer games, etc.

[0344] In addition to time setting, the operation buttons 2103 can also have various functions such as a power switch, a switch for wireless communication, setting and canceling of a silent mode, setting and canceling of a power saving mode, etc. For example, by using the operating system installed in the mobile phone 2100, the functions of the operation buttons 2103 can be freely set.

[0345] In addition, the mobile phone 2100 can execute short-range wireless communication standardized for communication. For example, by communicating with a wireless headset, hands-free calling can be performed.

[0346] In addition, the mobile phone 2100 includes an external connection port 2104, and data can be directly sent to other information terminals or received from other information terminals through a connector. In addition, charging can also be performed through the external connection port 2104. In addition, the charging operation can also be performed using wireless power supply without using the external connection port 2104.

[0347] The mobile phone 2100 preferably includes sensors. As sensors, for example, it is preferable to install human body sensors such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, and an acceleration sensor.

[0348] Figure 17B An example of an unmanned aerial vehicle 2300 including a plurality of rotors 2302 is shown. The unmanned aerial vehicle 2300 is also referred to as a drone. The unmanned aerial vehicle 2300 includes a secondary battery 2301, a camera 2303, and an antenna (not shown) according to one embodiment of the present invention. The unmanned aerial vehicle 2300 can be remotely operated through the antenna. Since a secondary battery having a structure in which an electrolyte containing fluorine is included in the negative electrode has a high energy density and high safety, it can be safely used for a long time over a long period, and thus is suitable as a secondary battery installed in the unmanned aerial vehicle 2300.

[0349] Figure 17C An example of a robot is shown. Figure 17CThe illustrated robot 6400 includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6407, a moving mechanism 6408, an arithmetic unit, and the like.

[0350] The microphone 6402 has a function of detecting the voice of the user and surrounding sounds, etc. In addition, the speaker 6404 has a function of emitting sound. The robot 6400 can communicate with the user through the microphone 6402 and the speaker 6404.

[0351] The display unit 6405 has a function of displaying various information. The robot 6400 can display the information required by the user on the display unit 6405. A touch panel may also be installed on the display unit 6405. In addition, the display unit 6405 may be a detachable information terminal, and by setting it at a fixed position of the robot 6400, charging and data transmission and reception can be performed.

[0352] The upper camera 6403 and the lower camera 6406 have a function of photographing the surrounding environment of the robot 6400. In addition, the obstacle sensor 6407 can use the moving mechanism 6408 to detect whether there is an obstacle in the forward direction when the robot 6400 moves forward. The robot 6400 can use the upper camera 6403, the lower camera 6406, and the obstacle sensor 6407 to confirm the surrounding environment and move safely.

[0353] Inside the robot 6400, there are provided a secondary battery 6409 and a semiconductor device or an electronic component according to one aspect of the present invention. Since a secondary battery having a structure including an electrolyte containing fluorine in the negative electrode has a high energy density and high safety, it can be safely used for a long time over a long period, and thus is very suitable as the secondary battery 6409 installed in the robot 6400.

[0354] Figure 17D An example of a floor cleaning robot is shown. The floor cleaning robot 6300 includes a display unit 6302 disposed on the top surface of the housing 6301, a plurality of cameras 6303 disposed on the side surface, a brush 6304, an operation button 6305, a secondary battery 6306, various sensors, and the like. Although not shown, the floor cleaning robot 6300 also has wheels, a suction port, and the like. The floor cleaning robot 6300 can move autonomously, detect garbage 6310, and suck the garbage into the suction port provided below.

[0355] For example, the floor cleaning robot 6300 can determine whether there are obstacles such as walls, furniture, or steps by analyzing the images captured by the camera 6303. In addition, when an object such as a wire that may get entangled with the brush 6304 is detected through image analysis, the rotation of the brush 6304 can be stopped. Inside the floor cleaning robot 6300, there are a secondary battery 6306 and semiconductor devices or electronic components according to one aspect of the present invention. Since a secondary battery having a structure including an electrolyte containing fluorine in the negative electrode has a high energy density and high safety, it can be safely used for a long time over a long period, and thus is very suitable as the secondary battery 6306 installed in the floor cleaning robot 6300.

[0356] This embodiment can be implemented in appropriate combination with other embodiments.

[0357] (Notes on the descriptions in this specification, etc.) In this specification, etc., the crystal planes and orientations are represented by Miller indices. In crystallography, a bar is attached to the number to represent the crystal planes and orientations. However, in this specification, etc., due to the symbol limitations in patent applications, sometimes a negative sign (-) is attached in front of the number to represent the crystal planes and orientations, instead of attaching a bar to the number. In addition, "[]" represents an individual orientation showing the orientation within the crystal, "<>" represents a collective orientation showing all equivalent crystal directions, "()" represents an individual plane showing the crystal plane, and "{}" represents a collective plane having equivalent symmetry.

[0358] In this specification, etc., segregation refers to a phenomenon in which a certain element (for example, B) is unevenly distributed in space in a solid containing multiple elements (for example, A, B, C).

[0359] In this specification, etc., the "surface layer portion" of particles such as active materials is preferably a region within 50 nm from the surface, more preferably within 35 nm, and further preferably within 20 nm. The surface generated by cracks and fissures can also be referred to as the surface. A region deeper than the surface layer portion is referred to as the interior.

[0360] In this specification, etc., the layered rock salt-type crystal structure of a composite oxide containing lithium and a transition metal refers to the following crystal structure: having a rock salt-type ionic arrangement in which cations and anions are alternately arranged, and the transition metal and lithium are regularly arranged to form a two-dimensional plane, so that lithium can diffuse two-dimensionally therein. In addition, it may also include defects such as vacancies of cations or anions. Strictly speaking, the layered rock salt-type crystal structure is sometimes a structure formed by lattice deformation of a rock salt-type crystal.

[0361] In addition, in this specification, etc., the rock salt-type crystal structure refers to a structure in which cations and anions are alternately arranged. In addition, it may also include vacancies of cations or anions.

[0362] In addition, in this specification and the like, the pseudo-spinel type crystal structure of the composite oxide containing lithium and transition metals refers to the space group R-3m, that is: although it is not a spinel type crystal structure, ions such as cobalt and magnesium occupy the oxygen 6-coordination positions, and the cation arrangement has a similar symmetry to the spinel type crystal structure.

[0363] It is possible to judge that the crystal orientations of two regions are roughly the same based on TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle annular dark field-scanning transmission electron microscope) images, ABF-STEM (annular bright field scanning transmission electron microscope) images, etc. In addition, X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can be used as the judgment basis. In TEM images and the like, the arrangement of cations and anions is observed as a repetition of bright lines and dark lines. When the orientation of the cubic closest packing structure is the same in the layered rock salt type crystal and the rock salt type crystal, it is possible to observe that the angle formed by the repetition of bright lines and dark lines is 5 degrees or less, more preferably 2.5 degrees or less. Note that in TEM images and the like, it is sometimes impossible to clearly observe light elements such as oxygen and fluorine. In this case, the orientation consistency can be judged based on the arrangement of metal elements.

[0364] In addition, in this specification and the like, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all the lithium that can be intercalated and deintercalated in the positive electrode active material is deintercalated. 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.

[0365] In this specification and the like, the state of charge when all the lithium that can be intercalated and deintercalated is intercalated is denoted as 0, and the state of charge when all the lithium that can be intercalated and deintercalated in the positive electrode active material is deintercalated is denoted as 1.

[0366] In addition, in this specification and the like, charging means that in the battery, lithium ions migrate from the positive electrode to the negative electrode, and in the external circuit, electrons migrate from the positive electrode to the negative electrode. Charging of the positive electrode active material means deintercalation of lithium ions. In addition, sometimes the positive electrode active material with a state of charge of 0.7 or more and 0.9 or less is called the positive electrode active material charged at a high voltage.

[0367] Similarly, discharging means that in the battery, lithium ions migrate from the negative electrode to the positive electrode, and in the external circuit, electrons migrate from the negative electrode to the positive electrode. Discharging of the positive electrode active material means intercalation of lithium ions. In addition, the positive electrode active material with a state of charge of 0.06 or less or the positive electrode active material that has discharged 90% or more of the charge capacity from the state of being charged at a high voltage is called the fully discharged positive electrode active material.

[0368] In addition, in this specification and the like, a non-equilibrium phase transition refers to a phenomenon that causes a non-linear change in a physical quantity. For example, a non-equilibrium phase transition may occur near the peak of a dQ / dV curve obtained by differentiating the capacitance (Q) with respect to the voltage (V) (dQ / dV), resulting in a significant change in the crystal structure.

[0369] A secondary battery includes, for example, a positive electrode and a negative electrode. As a material constituting the positive electrode, a positive electrode active material can be cited. For example, a positive electrode active material is a substance that undergoes a reaction contributing to the capacitance during charge and discharge. In addition, the positive electrode active material may also include, in part, a substance that does not contribute to the capacitance during charge and discharge. As a material constituting the negative electrode, a negative electrode active material can be cited. For example, a negative electrode active material is a substance that undergoes a reaction contributing to the capacitance during charge and discharge. In addition, the negative electrode active material may also partially contain a substance that does not contribute to the capacitance during charge and discharge.

[0370] In this specification and the like, the positive electrode active material of one embodiment of the present invention is sometimes referred to as a positive electrode material or a positive electrode material for a secondary battery, etc. In addition, in this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a compound. In addition, in this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a composition. In addition, in this specification and the like, the positive electrode active material of one embodiment of the present invention preferably includes a composite.

[0371] In this specification and the like, the negative electrode active material of one embodiment of the present invention is sometimes referred to as a negative electrode material or a negative electrode material for a secondary battery, etc. In addition, in this specification and the like, the negative electrode active material of one embodiment of the present invention preferably includes a compound. In addition, in this specification and the like, the negative electrode active material of one embodiment of the present invention preferably includes a composition. In addition, in this specification and the like, the negative electrode active material of one embodiment of the present invention preferably includes a composite.

[0372] The discharge rate refers to the ratio of the current during discharge to the battery capacity and is expressed in units of C. In a battery with a rated capacity of X (Ah), a current equivalent to 1C is X (A). When discharging at a current of 2X (A), it can be said to be discharging at 2C, and when discharging at a current of X / 5 (A), it can be said to be discharging at 0.2C. In addition, the charging rate is the same. When charging at a current of 2X (A), it can be said to be charging at 2C, and when charging at a current of X / 5 (A), it can be said to be charging at 0.2C.

[0373] Constant current charging is, for example, a method of charging at a fixed charging rate. Constant voltage charging is, for example, a method of charging at a certain voltage after charging to the upper limit voltage. Constant current discharge is, for example, a method of discharging at a fixed discharge rate. [Examples]

[0374] In this example, a negative electrode according to one embodiment of the present invention was manufactured and the manufactured negative electrode was evaluated.

[0375] <Manufacturing of negative electrode> according to Figure 4 The negative electrode was manufactured by the process shown in the figure. As the particles containing silicon, nano silicon particles manufactured by ALD RICH were used. As the particles containing graphite, spherical graphite particles CGB-15 manufactured by Nippon Graphite Industries, Ltd. were used. As the graphene compound, graphene oxide was used. As the polyimide, a polyimide precursor manufactured by Toray Industries, Ltd. was used.

[0376] As negative electrodes, electrodes GS1, GS2, GS3, and GS4 were manufactured. The only difference between electrodes GS1 and GS4 was the electrode ratio shown in Table 1. Other than that, electrodes GS1 and GS4 were manufactured by the same method. The electrode ratio shown in Table 1 is the same as that in the manufacturing of electrodes GS1 and GS4. Figure 4 The weight ratio of the materials prepared in steps S61, S72, S80 and S87 is described in detail below.

[0377] [Table 1]

[0378] Prepare and mix nano-silicon particles and solvent ( Figure 4 Steps S61, S62, and S63 in the above method). NMP was used as a solvent. The mixture was mixed at 2000 rpm for 3 minutes using an auto-rotational mixer (Awatori Rentaro, manufactured by THINKY Co., Ltd.), and recovered to obtain a mixture E-1 ( Figure 4 Steps S64, S65 in the above description).

[0379] Next, spherical graphite particles are prepared and mixed with the mixture E-1 ( Figure 4 The mixture was mixed at 2000 rpm for 3 minutes and recovered to obtain a mixture E-2 ( Figure 4 Steps S74, S75 in the above description).

[0380] Next, the mixture E-2 and the graphene compound were repeatedly mixed while adding the solvent. Graphene oxide was prepared as the graphene compound. The mixture was mixed at 2000 rpm for 3 minutes using a rotary mixer and recovered ( Figure 4 Then, the recovered mixture was dry-mixed, NMP was appropriately added, and the mixture was mixed at 2000 rpm for 3 minutes using a rotary mixer to recover the mixture ( Figure 4Steps S83, S84, and step S85). Steps S83 to S85 are repeated five times, thereby obtaining mixture E-3( Figure 4 Step S86 therein).

[0381] Next, mix mixture E-3 and the precursor of polyimide( Figure 4 Step S88 therein). Mix for 3 minutes at 2000 rpm using a planetary mixer. Then, prepare NMP and add it to the mixture for viscosity adjustment( Figure 4 Step S89 therein), and then mix again (mix for 3 minutes at 2000 rpm using a planetary mixer, and perform this mixing twice), and recover, thereby obtaining mixture E-4 as a slurry( Figure 4 Steps S90, S91, and S92 therein).

[0382] Next, prepare a current collector and coat mixture E-4( Figure 4 Steps S93 and S94 therein). Prepare a copper foil provided with a base layer as the current collector, and use a doctor blade with a gap thickness of 100 μm to coat mixture E-3 as mixture E-4 on the copper foil. The thickness of the copper of the prepared copper foil is 18 μm, and a current collector provided with a carbon-containing outer layer is used as the base layer. Use AB as the raw material for the carbon-containing outer layer.

[0383] Next, perform a first heating on the copper foil coated with mixture E-4 at 50 °C for 1 hour( Figure 4 Step S95 therein). Then, perform a second heating at 400 °C for 5 hours under reduced pressure( Figure 4 Step S96 therein), thereby obtaining an electrode. By heating, graphene oxide is reduced, and thus the oxygen content decreases.

[0384] <sem> SEM observation of the surface of the fabricated electrode was carried out. This SEM observation was performed after the first heating. As the SEM, SU8030 manufactured by Hitachi High-Technologies Corporation was used. The acceleration voltage was 5 kV.

[0385] Figure 18A and Figure 18B Each is an observation image of the surface of electrode GS1. Figure 19A and Figure 19B Each is an observation image of the surface of electrode GS2. Figure 20A and Figure 20B Each is an observation image of the surface of electrode GS3. Figure 21A and Figure 21B Each is an observation image of the surface of electrode GS4. In the SEM image, the contrast of the nanosilicon particles is relatively bright.

[0386] Figure 18B It is a magnified view of the surface of graphite particles with a particle size of about 10 μm or more and 20 μm or less in electrode GS1. Nanosilicon particles with a particle size of about 50 nm or more and 250 nm or less exist on the surface of the graphite particles, and regions covered with graphene oxide and regions not covered with graphene oxide are observed.

[0387] Figure 19B It is a magnified view of the surface of graphite particles with a particle size of about 10 μm or more and 20 μm or less in electrode GS2. Nanosilicon particles with a particle size of about 50 nm or more and 250 nm or less exist on the surface of the graphite particles, and regions covered with graphene oxide and regions not covered with graphene oxide are observed. Compared with GS1, GS2 tends to have more regions covered with graphene oxide.

[0388] Figure 20B It is a magnified view of the surface of graphite particles with a particle size of about 10 μm or more and 20 μm or less in electrode GS3. Nanosilicon particles with a particle size of about 50 nm or more and 250 nm or less exist on the surface of the graphite particles, and regions covered with graphene oxide and regions not covered with graphene oxide are observed. Compared with GS2, GS3 tends to have more regions covered with graphene oxide.

[0389] Figure 21B It is a magnified view of the surface of graphite particles with a particle size of about 10 μm or more and 20 μm or less in electrode GS4. Nanosilicon particles with a particle size of about 50 nm or more and 250 nm or less exist on the surface of the graphite particles, and regions covered with graphene oxide and regions not covered with graphene oxide are observed. Compared with GS3, GS4 tends to have more regions covered with graphene oxide, and most of the nanosilicon is covered by multiple graphene oxides.

[0390] <Manufacture of Coin Battery> Next, CR2032 type (diameter 20 mm, height 3.2 mm) coin batteries are manufactured using the manufactured electrodes GS1 to GS4.

[0391] As the counter electrode, lithium metal is used. As the electrolyte, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) mixed at a volume ratio of EC:DEC = 3:7 is used, with lithium hexafluorophosphate (LiPF6) mixed at a concentration of 1 mol / L.

[0392] As the separator, a separator made of polypropylene with a thickness of 25 μm is used.

[0393] The positive electrode can and the negative electrode can are formed of stainless steel (SUS).

[0394] <Charge and Discharge Characteristics> The manufactured coin batteries are used to evaluate the charge and discharge characteristics. Note that in the manufactured coin batteries, lithium is occluded into the electrode during discharge and released from the electrode during charge.

[0395] As the discharge condition (lithium occlusion), constant voltage discharge (lower limit current density of 0.01C) is performed after constant current discharge (0.1C, lower limit voltage of 0.01V), and as the charge condition (lithium release), constant current charge (0.1C, upper limit voltage of 1V) is performed. Discharge and charge are carried out at 25°C. Figure 22A and Figure 22B Shows the change in capacity following the number of charge and discharge cycles. Table 2 shows the maximum charge capacity measured by the charge and discharge cycle test and the charge capacity retention rate after 40 cycles.

[0396] [Table 2]

[0397] Figure 23 Shows the electrode ratios of electrodes GS1 to GS4 and their characteristics, including plots of the GO / silicon ratio of electrodes GS1 to GS4 and the discharge capacity retention rate after 40 cycles. From this, it can be seen that when the silicon amount is 1, the ratio of graphene oxide in the electrode ratio during electrode manufacturing is preferably 0.05 or more, more preferably 0.10 or more, and further preferably 0.30 or more. In addition, the electrode ratios shown in Table 2 are the weight ratios of the materials prepared in steps S61, S72, and S80 during the manufacture of electrodes GS1 to GS4. Figure 4 of the materials prepared in steps S61, S72, and S80. [Symbol Explanation]

[0398] 300: Secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304: Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative electrode current collector, 309: Negative electrode active material layer, 310: Separator, 312: Washer, 313: Annular insulator, 322: Spacer, 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, 508: Electrolyte, 509: Outer packaging body, 510: Positive electrode wire electrode, 511: Negative electrode wire electrode, 570: Electrode, 570a: Negative electrode, 570b: Positive electrode, 571: Current collector, 571a: Negative electrode current collector, 571b: Positive electrode current collector, 572: Active material layer, 572a: Negative electrode active material layer, 572b: Positive electrode active material layer, 576: Electrolyte, 581: First particle, 582: Second particle, 583: Flaky material, 584: Electrolyte, 601: Positive electrode cover, 602: Battery can, 603: Positive terminal, 604: Positive electrode, 605: Separator, 606: Negative electrode, 607: Negative terminal, 608: Insulating plate, 609: Insulating plate, 611: PTC element, 613: Safety valve mechanism, 614: Conductive plate, 615: Power storage system, 616: Secondary battery, 620: Control circuit, 621: Wiring, 622: Wiring, 623: Wiring, 624: Conductor, 625: Insulator, 626: Wiring, 627: Wiring, 628: Conductive plate, 700: Power storage device, 701: Commercial power supply, 703: Distribution board, 705: Power storage controller, 706: Display, 707: General load, 708: Power storage load, 709: Router, 710: Lead wire installation part, 711: Measuring part, 712: Prediction part, 713: Planning part, 790: Control device, 791: Power storage device, 796: Underfloor space part, 799: Building, 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: Separator, 950: Winding body, 950a: Winding body, 951: Terminal, 952: Terminal, 1300: Square secondary battery, 1301a: Battery, 1301b: Battery, 1302: Battery controller, 1303: Engine controller, 1304: Engine, 1305: Transmission, 1306: DCDC circuit, 1307: Electric power steering system, 1308: Heater, 1309: Defroster, 1310: DCDC circuit, 1311: Battery, 1312: Inverter, 1313: Audio, 1314: Electric window, 1315: Lights,1316: Tire, 1317: Rear engine, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1325: External terminal, 1326: External terminal, 1413: Fixing section, 1414: Fixing section, 1415: Battery pack, 1421: Wiring, 1422: Wiring, 2001: Automobile, 2002: Transport vehicle, 2003: Transport vehicle, 2004: Aircraft, 2100: Mobile phone, 2101: Housing, 2102: Display section, 2103: Operation button, 2104: External connection port, 2105: Speaker, 2106: Microphone, 2107: Secondary battery, 2200: Battery pack, 2201: Battery pack, 2202: Battery pack, 2203: Battery pack, 2300: Unmanned aerial vehicle, 2301: Secondary battery, 2302: Rotor, 2303: Camera, 2603: Vehicle, 2604: Charging device, 2610: Solar panel, 2611: Wiring, 2612: Power storage device, 6300: Floor cleaning robot, 6301: Housing, 6302: Display section, 6303: Camera, 6304: Brush, 6305: Operation button, 6306: Secondary battery, 6310: Garbage, 6400: Robot, 6401: Illuminance sensor, 6402: Microphone, 6403: Upper camera, 6404: Speaker, 6405: Display section, 6406: Lower camera, 6407: Obstacle sensor, 6408: Moving mechanism, 6409: Secondary battery,< / sem>

Claims

1. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing silicon particles with a particle size of 1 μm or less, a second negative electrode active material containing graphite with a larger particle size than that of the silicon particles, graphene or a graphene compound, the silicon particles are in contact with the graphite, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material, the silicon particles have silicon oxide.

2. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing a silicon-containing compound with a particle size of 1 μm or less, a second negative electrode active material containing graphite with a larger particle size than that of the silicon-containing compound, graphene or a graphene compound, the silicon-containing compound is in contact with the graphite, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

3. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing SiOx with a particle size of 1 μm or less, a second negative electrode active material containing graphite with a larger particle size than that of the SiOx, graphene or a graphene compound, the x is less than 2, the SiOx is in contact with the graphite, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

4. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing a silicon-containing compound, a second negative electrode active material containing graphite, graphene or a graphene compound, the silicon-containing compound is in contact with the graphite, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

5. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing SiOx, a second negative electrode active material containing graphite, graphene or a graphene compound, the x is less than 2, the SiOx is in contact with the graphite, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

6. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, the negative electrode has a first negative electrode active material containing silicon particles with a particle size of 1 μm or less, a second negative electrode active material with a smaller volume change than that of the silicon particles, graphene or a graphene compound, the first negative electrode active material is in contact with the second negative electrode active material, and the graphene or the graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

7. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, The negative electrode has a first negative electrode active material containing a silicon-containing compound with a particle size of 1 μm or less, a second negative electrode active material with a smaller volume change compared to the silicon-containing compound, graphene or a graphene compound, The first negative electrode active material is in contact with the second negative electrode active material, and the graphene or graphene compound is in contact with the first negative electrode active material and the second negative electrode active material.

8. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, The negative electrode has a first negative electrode active material containing silicon particles with a particle size of 1 μm or less, a second negative electrode active material containing graphite with a larger particle size than the silicon particles, and a conductive agent, The silicon particles are in contact with the second negative electrode active material, During charging, lithium ions detached from the positive electrode active material of the positive electrode are inserted into the silicon particles of the negative electrode, presenting a charge-discharge state.

9. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, The negative electrode has a first negative electrode active material containing SiOx with a particle size of 1 μm or less, a second negative electrode active material containing graphite with a larger particle size than the SiOx, and a conductive agent, The x is less than 2, The SiOx is in contact with the second negative electrode active material, During charging, lithium ions detached from the positive electrode active material of the positive electrode are inserted into the SiOx of the negative electrode, presenting a charge-discharge state.

10. A lithium-ion secondary battery, which has a positive electrode, a negative electrode, an electrolyte, and a separator, wherein, The negative electrode has a first negative electrode active material containing SiOx, a second negative electrode active material containing graphite, and a conductive agent, The x is less than 2, The SiOx is in contact with the second negative electrode active material, During charging, lithium ions detached from the positive electrode active material of the positive electrode are inserted into the SiOx of the negative electrode, presenting a charge-discharge state.

11. The lithium-ion secondary battery according to any one of claims 1, 6, and 8, wherein, The silicon particles are polycrystalline silicon or amorphous silicon.

12. The lithium-ion secondary battery according to any one of claims 2, 4, and 7, wherein, The silicon-containing compound is Li2SiO3 or Li4SiO4.

13. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein, The negative electrode further has a binder.

14. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein, The particle size of the second negative electrode active material is 10 times or more larger than that of the first negative electrode active material.

15. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein, The size of the first negative electrode active material is 50 nm or more and 250 nm or less, The size of the second negative electrode active material is 10 μm or more and 20 μm or less.

16. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein, The negative electrode has a negative electrode current collector, The negative electrode current collector contains copper.

17. The lithium ion secondary battery according to any one of claims 1 to 10, wherein the graphene or graphene compound is in contact with the first negative electrode active material and the second negative electrode active material in a manner of covering, coating or winding them.

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