Carbon materials

Abstract

To provide a carbon material with excellent properties. Or, to provide an electrode with excellent properties. Or, to provide a novel carbon material. Or, to provide a novel electrode. [Solution] A graphene compound having pores, wherein the graphene compound has a plurality of carbon atoms and one or more fluorine atoms, and the pores are formed by the plurality of carbon atoms and one or more fluorine atoms. The pore has a cyclic region composed of a plurality of carbon atoms and one or more fluorine atoms terminated at the cyclic region, and the cyclic region is preferably an 18-membered ring or more.

Description

[Technical Field]

[0001] This invention relates to graphene and methods for producing the same; or to secondary batteries and methods for producing the same; or to mobile devices including vehicles having secondary batteries, and to portable information terminals.

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

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

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

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

[0006] In addition to their stability, high capacity is crucial for secondary batteries. Silicon-based materials have high capacity and are used as active materials in secondary batteries. Silicon materials can be characterized by chemical shift values ​​obtained from NMR spectra (Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-156355 [Overview of the project] [Problems that the invention aims to solve]

[0008] Secondary batteries used in mobile vehicles such as electric vehicles and hybrid vehicles need to have increased capacity in order to extend their driving range.

[0009] Furthermore, power consumption in mobile devices is increasing due to their multi-functionality. Additionally, there is a demand for smaller and lighter rechargeable batteries used in mobile devices. Therefore, there is a need for higher capacity rechargeable batteries for mobile devices.

[0010] The electrodes of a secondary battery are composed of materials such as active material, conductive agent, and binder. The higher the proportion of materials that contribute to charge and discharge capacity, such as the active material, the higher the capacity of the secondary battery can be. By having a conductive agent in the electrodes, the conductivity of the electrodes is increased, and excellent output characteristics can be obtained. Also, during the charging and discharging of a secondary battery, the active material repeatedly expands and contracts, which can cause the active material to collapse, short circuits in the conductive paths, etc. in the electrodes. In such cases, the presence of a conductive agent or binder in the electrodes can suppress the collapse of the active material and short circuits in the conductive paths. On the other hand, by using a conductive agent or binder, the proportion of active material decreases, which may reduce the capacity of the secondary battery.

[0011] One aspect of the present invention aims to provide a carbon material having excellent properties. Or, one aspect of the present invention aims to provide an electrode having excellent properties. Or, one aspect of the present invention aims to provide a novel carbon material. Or, one aspect of the present invention aims to provide a novel electrode.

[0012] Or, one aspect of the present invention aims to provide a robust negative electrode. Or, one aspect of the present invention aims to provide a robust positive electrode. Or, one aspect of the present invention aims to provide a highly conductive negative electrode. Or, one aspect of the present invention aims to provide a highly conductive positive electrode.

[0013] Or, one aspect of the present invention aims to provide a secondary battery with less degradation. Or, one aspect of the present invention aims to provide a highly safe secondary battery. Or, one aspect of the present invention aims to provide a novel secondary battery.

[0014] One aspect of the present invention also aims to provide a novel substance, active material particles, or a method for producing them.

[0015] Note that the description of these problems does not prevent the existence of other problems. Note that one aspect of the present invention does not need to solve all of these problems. Note that it is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

[0016] Graphene compounds such as graphene enable surface contact with low contact resistance, and thus can improve the electrical conductivity between granular active materials and graphene compounds with a smaller amount than ordinary conductive agents. Therefore, in an electrode, the ratio of the active material can be increased. As a result, the discharge capacity of the secondary battery can be increased.

[0017] In addition, the graphene compound can wrap around the active material like natto. By arranging the graphene compound across a plurality of active materials, electrolytes, etc., not only can a good conductive path be formed within the electrode, but these materials can also be bound or fixed. For example, a three-dimensional network structure can be constituted by the graphene compound, and by arranging an electrolyte, a plurality of active material materials, etc. in the network, the graphene compound forms a three-dimensional conductive path and can suppress the dropout of the active material from the electrode. Therefore, the graphene compound can function as a conductive agent and also as a binder within the electrode.

[0018] As used herein, the graphene compound includes graphene, multi-layer graphene, multi-graphene, 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 substance that has carbon, has a flat plate shape, sheet shape, etc., and has a two-dimensional structure formed by carbon six-membered rings. The two-dimensional structure formed by the carbon six-membered rings may also be referred to as a carbon sheet. The graphene compound may have a functional group. Also, the graphene compound preferably has a bent shape. Further, the graphene compound may be curled up to be like a carbon nanofiber.

[0019] Within the electrode, the graphene compound can wrap around the active material. The active material has a region covered by the graphene compound.

[0020] The graphene compound according to one aspect of the present invention preferably has pores in a part of the carbon sheet. In the graphene compound according to one aspect 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 desorption of carrier ions become easier on the surface of the active material covered by the graphene compound, and the rate characteristics of the secondary battery can be improved. The pores provided in a part of the carbon sheet may be called voids, defects or gaps.

[0021] Here, it is preferable that the pores in the carbon sheet of the graphene compound are small enough to suppress a decrease in conductivity.

[0022] A graphene compound according to one aspect of the present invention preferably has pores provided by a plurality of carbon atoms and one or more fluorine atoms terminating the carbon atoms. Furthermore, a graphene compound according to one aspect of the present invention preferably has a plurality of carbon atoms and one or more fluorine atoms, wherein the plurality of carbon atoms are preferably cyclically bonded, and one or more of the cyclically bonded plurality of carbon atoms are preferably terminated by the fluorine.

[0023] Fluorine has high electronegativity and readily carries a negative charge. When positively charged lithium ions approach, an interaction occurs, stabilizing the energy and lowering the barrier energy for lithium ions to pass through the pores. Therefore, because the pores of graphene compounds contain fluorine, lithium ions can easily pass through even small pores, making it possible to create graphene compounds with excellent conductivity.

[0024] A graphene compound according to one aspect of the present invention has a region in which 7 or more, preferably 18 or more, and more preferably 22 or more carbon atoms are cyclically bonded, and one or more of the cyclically bonded carbon atoms are terminated with fluorine. Furthermore, a graphene compound according to one aspect of the present invention may have two or more regions in which 18 or more, more preferably 22 or more carbon atoms are cyclically bonded.

[0025] A graphene compound according to one aspect of the present invention has pores composed of multi-membered rings consisting of 7 or more carbon-based rings, preferably 18 or more, and more preferably 22 or more, wherein one or more carbon atoms in the multi-membered rings are terminated with fluorine.

[0026] A graphene compound according to one aspect of the present invention has a ring composed of carbon, the size of which the ring has a diameter of 0.6 nm or more, preferably 0.7 nm or more, more preferably 0.75 nm or more, and even more preferably 0.8 nm or more, in terms of a circle. Furthermore, a graphene compound according to one aspect of the present invention may have a plurality of the above-mentioned rings composed of carbon. In the graphene compound according to one aspect of the present invention, lithium ions can pass through the above-mentioned ring.

[0027] One aspect of the present invention is a graphene compound having pores, wherein the graphene compound has a plurality of carbon atoms and one or more fluorine atoms terminating the carbon atoms, and pores are formed by the plurality of carbon atoms and one or more fluorine atoms.

[0028] Furthermore, in the above configuration, the pore has a cyclic region composed of multiple carbon atoms and one or more fluorine atoms terminated in the cyclic region, and it is preferable that the cyclic region is an 18-membered ring or more.

[0029] Furthermore, in the above configuration, it is preferable that lithium ions can pass through the cyclic region.

[0030] Furthermore, in the above configuration, it is preferable that the change in stabilization energy when lithium ions pass through the pores is 1 eV or less.

[0031] Furthermore, in the above configuration, the stabilization energy is preferably determined by the Nudged Elastic Band method.

[0032] Alternatively, one aspect of the present invention is a secondary battery having an electrode having graphene as described in any of the above, an active material, and an electrolyte.

[0033] Alternatively, one aspect of the present invention is a mobile body having the secondary battery described above.

[0034] Alternatively, one aspect of the present invention is an electronic device having the secondary battery described above. [Effects of the Invention]

[0035] A carbon material with excellent properties can be provided. Furthermore, according to one aspect of the present invention, an electrode with excellent properties can be provided. Furthermore, according to one aspect of the present invention, a novel carbon material can be provided. Furthermore, according to one aspect of the present invention, a novel electrode can be provided.

[0036] Furthermore, according to one aspect of the present invention, a robust negative electrode can be provided. Furthermore, according to one aspect of the present invention, a robust positive electrode can be provided. Furthermore, according to one aspect of the present invention, a highly conductive negative electrode can be provided. Furthermore, according to one aspect of the present invention, a highly conductive positive electrode can be provided.

[0037] Furthermore, according to one aspect of the present invention, a secondary battery with less degradation can be provided. Furthermore, according to one aspect of the present invention, a secondary battery with high safety can be provided. Furthermore, according to one aspect of the present invention, a novel secondary battery can be provided.

[0038] Furthermore, according to one aspect of the present invention, novel materials, active material particles, or methods for producing them can be provided.

[0039] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0040] [Figure 1] Figure 1A shows an example of a cross-section of a secondary battery. Figure 1B shows an example of a cross-section of the negative electrode. [Figure 2] Figure 2 shows an example of a cross-section of the negative electrode. [Figure 3] Figure 3 is a schematic cross-sectional view of multilayer graphene and the active material. [Figure 4] Figures 4A, 4B, and 4C show examples of graphene compounds. [Figure 5] Figures 5A, 5B, and 5C show examples of graphene compounds. [Figure 6] Figures 6A, 6B, and 6C illustrate the pores present in graphene compounds. [Figure 7] Figures 7A and 7B show examples of graphene compounds. [Figure 8] Figures 8A and 8B show examples of graphene compounds. [Figure 9] Figures 9A and 9B show examples of graphene compounds. [Figure 10] Figures 10A and 10B show examples of graphene compounds. [Figure 11] Figures 11A and 11B show examples of graphene compounds. [Figure 12] Figures 12A and 12B show examples of graphene compounds. [Figure 13] Figures 13A and 13B show examples of graphene compounds. [Figure 14] Figure 14 shows an example of a graphene compound. [Figure 15] Figures 15A and 15B show the energy calculation results. [Figure 16] Figure 16 illustrates the crystal structure of the positive electrode active material. [Figure 17] Figure 17 illustrates the crystal structure of the positive electrode active material. [Figure 18] Figure 18 shows an example of a cross-section of a secondary battery. [Figure 19] Figure 19A is an exploded perspective view of a coin-type rechargeable battery, Figure 19B is a perspective view of a coin-type rechargeable battery, and Figure 19C is a cross-sectional perspective view thereof. [Figure 20]Figures 20A and 20B show examples of cylindrical secondary batteries, and Figures 20C and 20D show examples of energy storage systems having multiple cylindrical secondary batteries. [Figure 21] Figures 21A and 21B illustrate examples of secondary batteries, while Figure 21C shows the inside of a secondary battery. [Figure 22] Figures 22A, 22B, and 22C illustrate examples of secondary batteries. [Figure 23] Figures 23A and 23B show the external appearance of a secondary battery. [Figure 24] Figures 24A, 24B, and 24C illustrate the method for manufacturing a secondary battery. [Figure 25] Figure 25A is a perspective view showing the battery pack, Figure 25B is a block diagram of the battery pack, and Figure 25C is a block diagram of a vehicle with a motor. [Figure 26] Figures 26A to 26D illustrate an example of a transport vehicle. [Figure 27] Figures 27A and 27B illustrate the energy storage device. [Figure 28] Figures 28A to 28D illustrate an example of an electronic device. [Figure 29] Figures 29A and 29B show examples of graphene compounds. [Figure 30] Figures 30A and 30B show the energy calculation results. [Figure 31] Figures 31A to 31G show examples of graphene compounds. [Modes for carrying out the invention]

[0041] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and its form and details can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the embodiments described below.

[0042] (Embodiment 1) This embodiment describes a secondary battery and electrodes, etc., according to one aspect of the present invention.

[0043] One aspect of the present invention is a secondary battery having a positive electrode and a negative electrode. Examples of secondary batteries include lithium-ion batteries.

[0044] <Example of an electrode> Figure 1A is a schematic cross-sectional view showing an electrode according to one embodiment of the present invention. The electrode 570 shown in Figure 1A can be applied to the positive and negative electrodes of a secondary battery. The electrode 570 includes at least a current collector 571 and an active material layer 572 formed in contact with the current collector 571.

[0045] Figure 1B is an enlarged view of the area enclosed by the dashed line in Figure 1A. As shown in Figure 1B, the active material layer 572 has an electrolyte 581 and an active material 582. Various materials can be used as the active material 582. Materials that can be used as the active material 582 will be described later. Furthermore, it is preferable to use particles as the active material.

[0046] The active material layer 572 preferably contains carbon-based materials such as graphene compounds, carbon black, graphite, carbon fibers, and fullerenes, and is particularly preferably a graphene compound. For example, acetylene black (AB) can be used as carbon black. For example, natural graphite, artificial graphite such as mesocarbon microbeads, etc., can be used as graphite. These carbon-based materials have high conductivity and can function as conductive agents in the active material layer. These carbon-based materials may also function as active materials. Figure 1B shows an example in which the active material layer 572 contains graphene compounds 583 and AB584.

[0047] As carbon fibers, for example, mesophase pitch carbon fibers and isotropic pitch carbon fibers can be used. Alternatively, carbon nanofibers and carbon nanotubes can also be used. Carbon nanotubes can be fabricated, for example, by vapor deposition.

[0048] The active material layer may also contain one or more conductive materials selected from metal powders such as copper, nickel, aluminum, silver, and gold, metal fibers, and conductive ceramic materials.

[0049] The content of the conductive agent relative to the total amount of the active material layer is preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%.

[0050] Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene compounds enable surface contact with low contact resistance. Therefore, a smaller amount of graphene compound can improve the electrical conductivity between the granular active material and the graphene compound compared to conventional conductive materials. Consequently, the ratio of the active material in the active material layer can be increased. This, in turn, can increase the discharge capacity of the secondary battery.

[0051] Furthermore, since the graphene compound according to one embodiment of the present invention has excellent lithium permeability, it can increase the charge and discharge rate of secondary batteries.

[0052] Particulate carbon-containing compounds such as carbon black and graphite, and fibrous carbon-containing compounds such as carbon nanotubes, readily penetrate minute spaces. By combining carbon-containing compounds that readily penetrate minute spaces with sheet-like carbon-containing compounds such as graphene, which can impart conductivity across multiple particles, the electrode density can be increased, and excellent conductive paths can be formed. Furthermore, by having an electrolyte according to one aspect of the present invention in a secondary battery, the stability of the secondary battery's operation can be improved. In other words, a secondary battery according to one aspect of the present invention can combine high energy density and stability, making it effective as a secondary battery for vehicles. Increasing the number of secondary batteries increases the weight of the vehicle, which in turn increases the energy required to move it, thus shortening the driving range. By using high-density secondary batteries, the driving range can be maintained without significantly changing the total weight of a vehicle equipped with the same weight of secondary batteries.

[0053] Furthermore, as the capacity of a vehicle's secondary battery increases, more power is required for charging, making it desirable to complete the charging process in a short time. In addition, regenerative charging, which involves temporarily generating electricity when the vehicle brakes are applied and then charging the battery, is performed under high-rate charging conditions, so good rate characteristics are required for vehicle secondary batteries.

[0054] In the active material layer 572 shown in Figure 1B, multiple graphene compounds 583 are arranged so that their faces face to face, and the active material 582 is located between the multiple graphene compounds 583. Alternatively, as shown in the active material layer 572 in Figure 2, the graphene compounds may be arranged in a three-dimensional network.

[0055] By using an electrolyte according to one aspect of the present invention, a secondary battery for automotive use having a wide temperature range can be obtained.

[0056] Furthermore, the secondary battery according to one embodiment of the present invention can be miniaturized due to its high energy density, and rapid charging is possible due to its high conductivity. Therefore, the configuration of the secondary battery according to one embodiment of the present invention is also effective in portable information terminals.

[0057] The active material layer 572 preferably has a binder (not shown). The binder binds or fixes, for example, the electrolyte and the active material. The binder can also bind or fix the electrolyte and a carbon-based material, the active material and a carbon-based material, multiple active materials to each other, multiple carbon-based materials, etc.

[0058] It is preferable to use a flame-retardant or non-flammable polymer material as the binder. For example, a fluorine-containing polymer material such as fluoropolymer, specifically polyvinylidene fluoride (PVDF), can be used. PVDF is a resin with a melting point in the range of 134°C to 169°C and is a material with excellent thermal stability. Other binders that can be used include polyamide resin, polycarbonate resin, polyvinyl chloride resin, and polyphenylene oxide resin.

[0059] In this specification, "non-flammable" refers to the property of a polymer material that does not ignite at all when ignited with a flame, according to combustion test standards such as the UL94 standard or the JIS oxygen index (OI). Furthermore, "flame-retardant" refers to the property of a polymer material that hardly undergoes any chemical reaction when ignited with a flame, according to combustion test standards such as the UL94 standard or the JIS oxygen index (OI).

[0060] Furthermore, the graphene compound 583 can adhere to the active material 582 like natto (fermented soybeans). For example, the active material 582 can be likened to soybeans, and the graphene compound 583 to a sticky component. By arranging the graphene compound 583 between the electrolyte, multiple active materials, multiple carbon-based materials, etc., present in the active material layer 572, not only is a good conductive path formed within the active material layer 572, but these materials can also be bound or fixed using the graphene compound 583. For example, by forming a three-dimensional network structure with multiple graphene compounds 583 and arranging the electrolyte, multiple active materials, multiple carbon-based materials, etc., in the network, the graphene compound 583 can form a three-dimensional conductive path, and the detachment of the electrolyte from the current collector can be suppressed. Therefore, the graphene compound 583 may function as both a conductive agent and a binder in the active material layer 572.

[0061] The active material 582 can have various shapes, such as rounded shapes or angular shapes. Furthermore, in the cross-section of the electrode, the active material 582 can have various cross-sectional shapes, such as circles, ellipses, curved shapes, polygons, etc. For example, Figure 1B shows an example where the cross-section of the active material 582 has a rounded shape, but the cross-section of the active material 582 may also have angular shapes, as shown in Figure 2, for example. Alternatively, part of it may be rounded and part of it may have angular shapes.

[0062] <Graphene compound> In this specification, graphene compounds include graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multigraphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multigraphene oxide, graphene quantum dots, etc. A graphene compound is a material having carbon, having a plate-like or sheet-like shape, and having a two-dimensional structure formed by a six-membered carbon ring. The two-dimensional structure formed by the six-membered carbon ring may also be called a carbon sheet. Graphene compounds may have functional groups. Furthermore, graphene compounds preferably have a bent shape. Furthermore, graphene compounds may be rolled up to resemble carbon nanofibers.

[0063] In this specification, graphene oxide refers to a material having carbon and oxygen, having a sheet-like structure, and possessing functional groups, particularly epoxy groups, carboxyl groups, or hydroxyl groups.

[0064] An electrode according to one aspect of the present invention preferably has a graphene compound having pores. The graphene compound according to one aspect of the present invention has a region in which 7 or more, preferably 18 or more, more preferably 22 or more carbon atoms are bonded in a ring, and one or more of the cyclically bonded carbon atoms are terminated with fluorine. Furthermore, the graphene compound according to one aspect of the present invention may have two or more regions in which 18 or more, more preferably 22 or more carbon atoms are bonded in a ring.

[0065] A graphene compound according to one aspect of the present invention has pores composed of multi-membered rings consisting of 7 or more carbon-based rings, preferably 18 or more, and more preferably 22 or more, wherein one or more carbon atoms in the multi-membered rings are terminated with fluorine.

[0066] In this specification, reduced graphene oxide refers to a material having carbon and oxygen, having a sheet-like shape, and possessing a two-dimensional structure formed by a six-membered carbon ring. It may also be called a carbon sheet. Reduced graphene oxide can function as a single sheet, but multiple sheets may be laminated together. It is preferable that reduced graphene oxide has a portion where the carbon concentration is greater than 80 atomic%, and the oxygen concentration is between 2 atomic% and 15 atomic%. By having such carbon and oxygen concentrations, it can function as a highly conductive material even in small quantities. It is also preferable that reduced graphene oxide has a G / D intensity ratio of 1 or more in the Raman spectrum. Reduced graphene oxide with such an intensity ratio can function as a highly conductive material even in small quantities.

[0067] In some cases, pores can be created in graphene compounds by reducing graphene oxide.

[0068] Alternatively, a material in which the ends of graphene are terminated with fluorine may be used.

[0069] In the longitudinal section of the active material layer, sheet-like graphene compounds are dispersed approximately uniformly within the internal region of the active material layer. Multiple graphene compounds are formed to partially cover multiple granular active materials or to adhere to the surfaces of multiple granular active materials, and thus are in surface contact with each other.

[0070] Here, multiple graphene compounds can bond together to form a mesh-like graphene compound sheet (also called a graphene compound net or graphene net). When the active material is coated with the graphene net, the graphene net can also function as a binder that binds the active materials together. Therefore, the amount of binder can be reduced, or even eliminated altogether, thereby improving the ratio of active material to electrode volume and electrode weight. In other words, the charge and discharge capacity of the secondary battery can be increased.

[0071] Here, it is preferable to use graphene oxide as the graphene compound, mix it with the active material to form a layer that will become the active material layer, and then reduce it. In other words, it is preferable that the completed active material layer has reduced graphene oxide. By using graphene oxide, which has extremely high dispersibility in polar solvents, for the formation of the graphene compound, the graphene compound can be dispersed approximately uniformly within the internal region of the active material layer. By volatilizing and removing the solvent from the dispersion medium containing the uniformly dispersed graphene oxide and reducing the graphene oxide, the graphene compounds remaining in the active material layer partially overlap and are dispersed to the extent that they are in surface contact with each other, thereby forming three-dimensional conductive paths. The reduction of graphene oxide may be carried out, for example, by heat treatment or by using a reducing agent.

[0072] Furthermore, by using a spray-drying device beforehand, a graphene compound, which is a conductive material, can be formed as a coating to cover the entire surface of the active material, and then the active material particles can be electrically connected with the graphene compound to form conductive paths.

[0073] Furthermore, the active material layer may be made by mixing the graphene compound with the material used to form the graphene compound. For example, particles used as a catalyst when forming the graphene compound may be mixed together with the graphene compound. Examples of catalysts used when forming the graphene compound include silicon dioxide (SiO2, SiO2). x Examples of particles include those having (x<2), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, germanium, etc. The particles preferably have a D50 of 1 μm or less, and more preferably 100 nm or less.

[0074] If the graphene compound has multiple layers, such as multilayer graphene or modified multilayer graphene, pores may be provided in each layer. An example is shown in the schematic diagram of Figure 3. During charging and discharging, lithium ions move in the plane of the graphene compound 202, and when they reach the pores 204, if the electrode 201 (active material in the case of a secondary battery) in contact with the graphene compound 202 is at a negative potential, the ions move to the lower layer of graphene compound. On the other hand, if the electrode 201 is at a positive potential, the ions move to the upper layer of graphene compound.

[0075] Furthermore, while Figure 3 and other diagrams illustrate lithium ions as single ions for simplification, in reality, it is not a single lithium ion, but rather an aggregate of multiple lithium ions that moves within the active material. Additionally, the solvent is thought to solvate, for example, these aggregates of lithium ions. This is a concept not found in conventional literature or books (including textbooks), and represents a new solvation model discovered by the inventors. Moreover, depending on the fluorine-containing electrolyte used, the manner of solvation may differ depending on the number of fluorine atoms bonded.

[0076] [Calculation] Energy calculations were performed for a layered graphene structure, and for a layered structure of graphene with pores.

[0077] The structure of graphene with pores is shown in Figures 4A, 4B, 4C, 5A, 5B, and 5C.

[0078] In Figure 4A, graphene has a pore composed of 18 carbon atoms bonded in a ring. Six of the 18 carbon atoms are bonded to hydrogen. Figure 4A has an 18-membered carbon ring, and six of the carbon atoms constituting the 18-membered ring are each terminated by hydrogen. Figure 4A has a structure in graphene where one 6-membered ring has been removed, and the carbon atoms that were bonded to the removed 6-membered ring are terminated by hydrogen.

[0079] In Figure 4B, graphene has pores formed by 22 carbon atoms bonded in a ring. Of the 22 carbon atoms, 8 are bonded to hydrogen. Figure 4B has a 22-membered carbon ring, and 8 of the carbon atoms constituting the 22-membered ring are each terminated by hydrogen. Figure 4B shows a structure in graphene where two linked 6-membered rings have been removed, and the carbon atoms that were bonded to the removed 6-membered rings are terminated by hydrogen.

[0080] In Figure 4C, graphene has a pore composed of 24 carbon atoms bonded in a ring. Of the 24 carbon atoms, 9 are bonded to hydrogen. Figure 4C has a 24-membered carbon ring, and each of the 9 carbon atoms constituting the 24-membered ring is terminated by hydrogen. Figure 4C shows a structure in graphene where three linked 6-membered rings have been removed, and the carbon atoms that were bonded to the removed 6-membered rings have been terminated by hydrogen.

[0081] In Figure 5A, graphene has a pore composed of 18 carbon atoms bonded in a ring. Six of these 18 carbon atoms are bonded to fluorine. Figure 5A has an 18-membered carbon ring, and six of the carbon atoms constituting the 18-membered ring are each terminated with fluorine. Figure 5A has a structure in graphene where one 6-membered ring has been removed, and the carbon atoms that were bonded to the removed 6-membered ring are terminated with fluorine.

[0082] In Figure 5B, graphene has a pore composed of 22 carbon atoms bonded in a ring. Of the 22 carbon atoms, 8 are bonded to fluorine. Figure 5B has a 22-membered carbon ring, and each of the 8 carbon atoms constituting the 22-membered ring is terminated with fluorine. Figure 5B has a structure in graphene where two linked 6-membered rings have been removed, and the carbon atoms that were bonded to the removed 6-membered rings have been terminated with fluorine.

[0083] In Figure 5C, graphene has a pore composed of 24 carbon atoms bonded in a ring. Of the 24 carbon atoms, 9 are bonded to fluorine. Figure 5C has a 24-membered carbon ring, and each of the 9 carbon atoms constituting the 24-membered ring is terminated with fluorine. Figure 5C has a structure in graphene where three linked 6-membered rings have been removed, and the carbon atoms that were bonded to the removed 6-membered rings are terminated with fluorine. In Figure 5C, the three removed 6-membered rings are linked together, for example, as in phenalene.

[0084] Figure 6A is used to explain the size of the 18-membered ring in graphene. In Figure 6A, a circle is drawn containing the carbon atoms that are closest to the center of the pore among the carbon atoms that make up the 18-membered ring. The diameter of the circle was approximately 0.595 nm. Although the lattice distortion is extremely small in the configuration shown in Figure 6A, etc., in actual graphene compounds, the distances between atoms may change due to distortion.

[0085] The area of ​​an 18-membered ring is approximately equivalent to the area of ​​seven 6-membered rings. The size of the ring can also be expressed as its diameter, for example, by converting the area formed by the ring into a circle. The area of ​​a 6-membered ring is, for example, 0.0524 nm when the structural distortion is extremely small. 2 It is approximately as follows: The diameter of the 18-membered ring, converted to a circle, is approximately 0.68 nm.

[0086] Figure 6B is used to explain the size of the 18-membered ring in graphene. In Figure 6B, an ellipse is drawn containing the carbon atoms that are closest to the center of the pore among the carbon atoms that make up the 22-membered ring. The major axis of the ellipse was approximately 0.817 nm, and the minor axis was approximately 0.640 nm.

[0087] The area of ​​a 22-membered ring is approximately equivalent to the area of ​​10 6-membered rings. The diameter of the 22-membered ring, when converted to a circle, is approximately 0.82 nm.

[0088] Figure 6C is used to explain the size of the 24-membered ring in graphene. In Figure 6C, a circle is drawn containing the carbon atoms that are closest to the center of the pore among the carbon atoms that make up the 24-membered ring. Note that the 24-membered ring has a structure that extends further below the circle. The distance between the carbon atom located at the center of the circle and the carbon atom closest to the center of the pore among the five carbon atoms that extend below the circle was approximately 0.815 nm.

[0089] The area of ​​a 24-membered ring is approximately equivalent to the area of ​​12 6-membered rings. The diameter of the 24-membered ring, when converted to a circle, is approximately 0.89 nm.

[0090] <Quantum Mechanics> The structure was optimized using quantum mechanical calculations. Atomic relaxation calculations were performed using the first-principles electronic state simulation package VASP (Vienna ab initio simulation package). The functional used was GGA+U (DFT-D2), the pseudopotential was PAW, and the cutoff energy was set to 600 eV. The k-point grid was 1×1×1.

[0091] First, we optimized the structures of structure G-1, which consists of six layers of graphene with a total of 432 carbon atoms, and structure G-2, which consists of four layers of graphene with a total of 648 carbon atoms, using quantum molecular dynamics calculations. Structure G-2 has fewer graphene layers than structure G-1, but the area of ​​graphene per unit cell is larger.

[0092] Subsequently, pores were introduced into the optimized structures G-1 and G-2. Specifically, one 18-membered, 22-membered, or 24-membered ring, terminated with hydrogen or fluorine, was added to the middle layer of the stacked graphene layers.

[0093] Next, in each structure with a pore, one lithium ion was placed at position [a], position [b], position [c], or position [d], and the structure was optimized using quantum molecular dynamics calculations. The initial value of position [a] (the position where the ion is placed before the calculation) is below the center of the pore and at a height midway between adjacent graphene layers. The initial value of position [b] is above the center of the pore and at a height midway between adjacent graphene layers. Position [c] is further from the pore than position [b], and position [d] is further from the pore than position [c]. For details on each position, please refer to the diagram described later.

[0094] The energy calculations for position [a] were performed for both the structure with a hole in structure G-1 and the structure with a hole in structure G-2. The energy calculations for position [b] were performed for the structure with a hole in structure G-1. The energy calculations for position [c] and position [d] were performed for the structure with a hole in structure G-2.

[0095] The structure used in the calculations will be explained using Figures 7A to 14. The position [m] shown in each figure will be explained later.

[0096] Figure 7A shows the positions [a] and [b] in a structure G-1 with an 18-membered ring terminated by 6 fluorine atoms. Figure 7A is a view from the a-axis direction. Figure 7B shows the pore-containing layer as viewed from the c-axis direction.

[0097] Figure 8A shows the positions [c] and [d] in a structure where an 18-membered ring is provided in structure G-2 and terminated with 6 fluorine atoms. Figure 8A is a view from the a-axis direction. Figure 8B shows a view of the pore-containing layer from the c-axis direction.

[0098] Figure 9A shows the positions [a] and [b] in a structure G-1 with a 22-membered ring terminated by 8 fluorine atoms. Figure 9A is a view from the a-axis direction. Figure 9B shows the pore-containing layer as viewed from the c-axis direction.

[0099] Figure 10A shows the positions [c] and [d] in a structure where a 22-membered ring is provided in structure G-2 and terminated with 8 fluorine atoms. Figure 10A is a view from the a-axis direction. Figure 10B shows a view of the pore-containing layer from the c-axis direction.

[0100] Figure 11A shows the positions [a] and [b] in a structure G-1 with a 24-membered ring terminated by 9 fluorine atoms. Figure 11A is a view from the a-axis direction. Figure 11B shows the pore-containing layer as viewed from the c-axis direction.

[0101] Figure 12A shows the positions [c] and [d] in a structure where a 24-membered ring is provided in structure G-2 and terminated with 9 fluorine atoms. Figure 12A is a view from the a-axis direction. Figure 12B shows a view of the pore-containing layer from the c-axis direction.

[0102] Figure 13A shows positions [a] and [b] in a structure where an 18-membered ring is provided on structure G-1 and terminated with hydrogen. Figure 13A is a view from the a-axis direction.

[0103] Figure 13B shows positions [a] and [b] in a structure where a 22-membered ring is provided on structure G-1 and terminated with hydrogen. Figure 13B is a view from the a-axis direction.

[0104] Figure 14 shows positions [a] and [b] in a structure G-1 with a 24-membered ring terminated with hydrogen. Figure 14 is a view from the a-axis direction.

[0105] Next, the path and energy changes of the lithium ion as it moves from position [a] through the pore to position [b] were calculated using the Nudged Elastic Band (NEB) method. Seven intermediate points were created by giving continuous coordinate changes between the initial point [a] and the final point [b] of the path, and the position and energy were optimized using NEB calculations. The position [m] shown in the aforementioned figure is an intermediate point among the seven points in the path between position [a] and position [b] determined by the NEB method.

[0106] The energy results obtained by the NEB method are shown in Figures 15A and 15B. The energy at each potential point is based on the energy at potential [a] as the reference point (0 eV).

[0107] Figure 15A shows the relationship between lithium ion position and stabilization energy in multilayer graphene with hydrogen-terminated 18-membered rings, multilayer graphene with hydrogen-terminated 22-membered rings, and multilayer graphene with hydrogen-terminated 24-membered rings, respectively. Figure 15B shows the relationship between lithium ion position and stabilization energy in multilayer graphene with 6 fluorine-terminated 18-membered rings, multilayer graphene with 8 fluorine-terminated 22-membered rings, and multilayer graphene with 9 fluorine-terminated 24-membered rings, respectively.

[0108] In multilayer graphene having hydrogen-terminated 18-membered, 22-membered, and 24-membered rings, it was suggested that an energy barrier of 1.0 eV or more exists in the path from position [a] to position [b], suggesting that the energy is maximum inside the pore. Furthermore, it was suggested that the energy is higher in the 18-membered ring compared to the 22-membered and 24-membered rings. This is thought to be because the smaller pore size brings the lithium ions and hydrogen closer together, resulting in interatomic repulsion.

[0109] On the other hand, in multilayer graphene having 18-membered, 22-membered, and 24-membered rings terminated with fluorine, the energy was lower in the path from position [a] to position [b] compared to the hydrogen-terminated case, suggesting that lithium ions can easily pass through the graphene layer. Furthermore, at positions [a] and [b], which are above and below the pore, the energy was lower than at positions [c] and [d], which are further from the pore, indicating a tendency for the entire system to be stabilized. This suggests that lithium ions tend to remain near the pore. These effects are thought to occur because fluorine has high electronegativity and easily becomes negatively charged, so positively charged lithium ions approach it, causing interactions and stabilization.

[0110] In graphene, it was suggested that lithium ions could easily pass through the pores, which are formed by the bonding of multiple carbon atoms and terminated with fluorine.

[0111] [Calculation 2] Next, we varied the proportion of fluorine-terminated rings in the multi-membered rings of graphene and performed structural optimization and energy calculations.

[0112] As structures for calculations, the following structures were prepared by adding a 24-membered ring to the structure G-2 shown above: a structure terminated with 9 hydrogen atoms, a structure terminated with 1 fluorine atom and 8 hydrogen atoms, a structure terminated with 2 fluorine atoms and 7 hydrogen atoms, a structure terminated with 3 fluorine atoms and 6 hydrogen atoms, a structure terminated with 4 fluorine atoms and 5 hydrogen atoms, a structure terminated with 6 fluorine atoms and 3 hydrogen atoms, and a structure terminated with 9 fluorine atoms.

[0113] In each of the prepared structures, lithium ions were placed in five different positions (position 1, position 2, position 3, position 4, and position 5) as shown in Figures 29(A) and (B), and the structure was optimized using quantum molecular dynamics calculations. In the figures, the numbers 1, 2, 3, 4, and 5 are indicated by circles. Figure 29(A) shows a top view of structure G-2, and Figure 29(B) shows a cross-sectional view of structure G-2.

[0114] Figures 29(A) and (B) show examples of structures in which a 24-membered ring is terminated with nine hydrogen atoms, but the lithium ions were also placed in the same five possible positions in other structures.

[0115] Figures 30(A) and (B), and Table 1 show the results of energy calculations for each structure. In Figures 30(A) and (B), the horizontal axis represents the position of the lithium ion, and the vertical axis represents the stabilization energy.

[0116] Furthermore, in Figures 30(A), (B), and Table 1, a structure terminated with 9 hydrogen atoms is denoted as F: 0, a structure terminated with 1 fluorine atom and 8 hydrogen atoms as F: 1, a structure terminated with 2 fluorine atoms and 7 hydrogen atoms (see Figure 31(A)) as F: 2, among the structures terminated with 3 fluorine atoms and 6 hydrogen atoms, the structure shown in Figure 31(B) is F: 3, the structure shown in Figure 31(C) is F: 3-V, a structure terminated with 4 fluorine atoms and 5 hydrogen atoms (see Figure 31(D)) is F: 4, a structure terminated with 5 fluorine atoms and 4 hydrogen atoms (see Figure 31(E)) is F: 5, among the structures terminated with 6 fluorine atoms and 3 hydrogen atoms, the structure shown in Figure 31(F) is F: 6, the structure shown in Figure 31(G) is F: 6-V, and a structure terminated with 9 fluorine atoms is F: 9.

[0117] [Table 1]

[0118] Table 2 shows the energy barriers obtained from the results in Table 1. The energy barrier was determined as the difference between the maximum and minimum stabilization energies at each of the five positions of the lithium ion.

[0119] [Table 2]

[0120] When the 24-membered ring does not contain a fluorine-terminated carbon atom, the energy at position 2 is high, suggesting that lithium ions have difficulty passing through the pores formed by the 24-membered ring.

[0121] Furthermore, it is suggested that increasing the number of fluorine-terminated carbon atoms in the 24-membered ring from one to four reduces the absolute value of the energy at position 2, lowers the energy barrier, and makes it easier for lithium ions to pass through the pores formed by the 24-membered ring.

[0122] Furthermore, the low energy at position 1 suggests that the state is stabilized at position 1 due to the interaction between fluorine and lithium. In a 24-membered ring, the lowest energy is at position 1 in the structure where the three fluorine-terminated carbon atoms are located close together (F:3-V).

[0123] When the number of fluorine-terminated carbon atoms is increased to five or more, the magnitude of the energy barrier and the change in energy at position 1 slow down with increasing carbon atoms. Furthermore, when the number of fluorine-terminated carbon atoms is increased to six or more, the energy at position 2 becomes negative and its absolute value increases, suggesting that lithium ions are trapped and it becomes difficult for them to pass through the pore.

[0124] Furthermore, when comparing the case with 4 fluorine-terminated carbon atoms and the case with 5 fluorine-terminated carbon atoms, a decreasing trend is observed in the energy at position 2.

[0125] Based on the above, it can be said that the number of fluorine-terminated carbon atoms is preferably five or less.

[0126] Furthermore, in structure (F:3-V), the energy change is small at positions 2, 3, 4, and 5. From this, it is possible that among the structures listed above, structure (F:3-V) is the structure through which lithium ions can pass most easily through the pores formed by the 24-membered ring. Therefore, it can be said that it is most preferable for lithium to permeate through the pores of graphene when 33% of the terminal groups of the 24-membered ring are terminated with fluorine.

[0127] On the other hand, it is considered difficult to control the positions of the three carbon atoms terminated by fluorine. The arrangement of fluorine terminations at the edges of an actual graphene sheet is likely to be random. Therefore, for the terminal groups of a 24-membered ring, it is preferable to have a configuration in which 33% to 67% are terminated by fluorine, such that the absolute value of the barrier at position 2 is approximately 0.3 eV, and more preferably a configuration in which 44% to 56% are terminated by fluorine, such that the absolute value of the barrier at position 2 is approximately 0.2 eV.

[0128] <An example of a negative electrode active material> When electrode 570 is the negative electrode, a negative electrode active material can be used as the active material. It is preferable to use a material as the negative electrode active material that can react with carrier ions of a secondary battery, a material that can insert and remove carrier ions, a material that can alloy with metals that become carrier ions, a material that can dissolve and precipitate metals that become carrier ions, etc.

[0129] Furthermore, as the negative electrode active material, for example, a metal, material, or compound having one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium can be used. Examples of alloy materials using such elements include Mg2Si, Mg2Ge, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, and the like.

[0130] Furthermore, silicon may be made to have lower resistance by adding impurity elements such as phosphorus, arsenic, boron, aluminum, and gallium.

[0131] The negative electrode active material is preferably in the form of particles. For example, silicon nanoparticles can be used as the negative electrode active material. The average diameter of the silicon nanoparticles is preferably 5 nm or more and less than 1 μm, more preferably 10 nm or more and 300 nm or less, and even more preferably 10 nm or more and 100 nm or less.

[0132] Silicon nanoparticles may be crystalline. Furthermore, silicon nanoparticles may have both crystalline and amorphous regions.

[0133] For example, a material containing silicon is SiO x A material represented by (where x is preferably less than 2, and more preferably between 0.5 and 1.6) can be used.

[0134] As a material containing silicon, for example, a form having multiple crystal grains within a single particle can be used. For example, a form having one or more silicon crystal grains within a single particle can be used. Furthermore, the single particle may have silicon oxide surrounding the silicon crystal grain. Furthermore, the silicon oxide may be amorphous.

[0135] Furthermore, as silicon-containing compounds, for example, Li2SiO3 and Li4SiO4 can be used. Li2SiO3 and Li4SiO4 may be crystalline or amorphous, respectively.

[0136] The analysis of silicon-containing compounds can be performed using NMR, XRD, Raman spectroscopy, etc.

[0137] Furthermore, carbon-based materials such as graphite, easily graphitizable carbon, poorly graphitizable carbon, carbon nanotubes, carbon black, and graphene compounds can be used as the negative electrode active material.

[0138] Further, as the negative electrode active material, for example, an oxide having one or more elements selected from titanium, niobium, tungsten, and molybdenum can be used.

[0139] As the negative electrode active material, a plurality of combinations of the above-described metals, materials, compounds, etc. can be used.

[0140] As the negative electrode active material, for example, SnO, SnO2, titanium dioxide (TiO2), lithium titanate (Li4Ti5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5), tungsten oxide (WO2), molybdenum oxide (MoO2), etc. can be used.

[0141] Further, as the negative electrode active material, Li 3-x M x N (M = Co, Ni, Cu) having a Li3N-type structure, which is a complex nitride of lithium and a transition metal, can be used. For example, Li 2.6 Co 0.4 N3 exhibits a large charge-discharge capacity (900 mAh / g) and is preferable.

[0142] When using a complex nitride of lithium and a transition metal, since lithium ions are contained in the negative electrode active material, it is preferable to combine it with materials such as V2O5 and Cr3O8 that do not contain lithium ions as the positive electrode active material. Even when using a material containing lithium ions for the positive electrode active material, by previously desorbing the lithium ions contained in the positive electrode active material, a complex nitride of lithium and a transition metal can be used as the negative electrode active material.

[0143] Further, a material in which a conversion reaction occurs can also be used as the negative electrode active material. For example, transition metal oxides such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO) that do not undergo an alloying reaction with lithium may be used as the negative electrode active material. As materials in which a conversion reaction occurs, further, oxides such as Fe2O3, CuO, Cu2O, RuO2, and Cr2O3, CoS 0.89Examples include sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3. Since the potential of the above fluorides is high, they may also be used as positive electrode active materials.

[0144] Furthermore, while the negative electrode active material may undergo volume changes during charging and discharging, arranging a fluorine-containing electrolyte between multiple negative electrode active materials within the negative electrode makes it easier for the electrolyte to slide even when volume changes occur during charging and discharging, thus suppressing cracking and dramatically improving cycle characteristics. It is important that a fluorine-containing organic compound is present between the multiple active materials that make up the negative electrode.

[0145] In one embodiment of the present invention, the negative electrode active material preferably has fluorine in its surface layer.

[0146] In secondary batteries, irreversible reactions, such as those between electrodes and electrolytes, can reduce charge-discharge efficiency. This decrease in efficiency is particularly noticeable during the initial charge-discharge cycle.

[0147] In one embodiment of the present invention, the presence of a halogen on the surface of the negative electrode active material can suppress a decrease in charge-discharge efficiency. It is believed that the presence of a halogen on the surface of the negative electrode active material in one embodiment of the present invention suppresses the reaction with the electrolyte on the surface of the active material. Furthermore, in one embodiment of the present invention, at least a portion of the surface of the negative electrode active material may be covered by a region containing halogen. This region may be, for example, in the form of a film.

[0148] The surface layer is, for example, the region within 50 nm from the surface, more preferably within 35 nm, and even more preferably within 20 nm. The region deeper than the surface layer is called the interior.

[0149] Furthermore, if the negative electrode active material in one embodiment of the present invention has a halogen on its surface, the solvent solvated with carrier ions in the electrolyte may be more easily desorbed from the surface of the negative electrode active material. This easier desorption of the solvated solvent may enable the secondary battery to achieve excellent performance at high charge-discharge rates. It is preferable to use a material terminated with a halogen as the negative electrode active material. For example, a material in which silicon is terminated with a halogen such as fluorine can be used as the negative electrode active material.

[0150] In one embodiment of the present invention, the negative electrode active material preferably contains fluorine as a halogen. When the negative electrode active material is measured by X-ray photoelectron spectroscopy, the concentration of fluorine is preferably 1 atomic% or more relative to the sum of the concentrations of fluorine, oxygen, lithium, and carbon.

[0151] Fluorine has high electronegativity, and the presence of fluorine on the surface of the negative electrode active material may have the effect of facilitating the removal of the solvated solvent from the surface of the negative electrode active material.

[0152] Furthermore, in addition to the negative electrode active material, the conductive agent in the negative electrode active material layer of one embodiment of the present invention may also be modified with fluorine. For example, it is preferable to include fluorine in carbon-based materials such as graphene compounds, carbon black, graphite, carbon fibers, and fullerenes. Carbon-based materials containing fluorine can also be called particulate or fibrous fluorinated carbon materials. When measuring carbon-based materials by X-ray photoelectron spectroscopy, the concentration of fluorine is preferably 1 atomic% or more relative to the sum of the concentrations of fluorine, oxygen, lithium, and carbon.

[0153] Fluorine modification of the negative electrode active material and conductive agent can be carried out, for example, by treatment with a fluorine-containing gas, heat treatment, plasma treatment in a fluorine-containing gas atmosphere, etc. As the fluorine-containing gas, for example, fluorine gas, lower fluorine hydrocarbon gases such as methane fluoride (CF4), etc. can be used.

[0154] Alternatively, as a fluorine modification to the negative electrode active material and the conductive agent, it may be immersed in, for example, a solution having hydrofluoric acid, boron tetrafluoride acid, phosphoric acid hexafluoride, etc., a solution containing a fluorine-containing ether compound, or the like.

[0155] By performing fluorine modification on the negative electrode active material and the conductive agent, it is expected that the structure is stabilized and side reactions are suppressed during the charge and discharge process of the secondary battery. By suppressing side reactions, the charge and discharge efficiency can be improved. In addition, it is possible to suppress a decrease in capacity accompanying repeated charge and discharge. Therefore, in the negative electrode of one aspect of the present invention, by using a fluorine-modified negative electrode active material and a conductive agent, an excellent secondary battery can be realized.

[0156] In addition, when the structures of the negative electrode active material and the conductive agent are stabilized, the conductive characteristics may be stabilized and high output characteristics can be realized.

[0157] The fluorine-containing material is stable, and by using it as a component of the secondary battery, stabilization of characteristics, long life, etc. can be realized. Therefore, it is preferably used for the separator and the exterior body. Details of the separator and the exterior body will be described later.

[0158] When the electrode 570 is a positive electrode, a negative electrode active material can be used as the active material. Examples of the positive electrode active material include composite oxides having an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. For example, compounds such as LiFePO4, LiFeO2, LiNiO2, LiMn2O4, V2O5, Cr2O5, and MnO2 can be mentioned.

[0159] <An example of the positive electrode active material> In addition, it is preferable to mix lithium nickelate (LiNiO2 or LiNi 1-x M x O2 (0 < x < 1) (M = Co, Al, etc.)) with a lithium-containing material having a spinel-type crystal structure containing manganese such as LiMn2O4 as the positive electrode active material. By adopting this configuration, the characteristics of the secondary battery can be improved.

[0160] Furthermore, as a positive electrode active material, the composition formula is Li a Mn b M c O d A lithium manganese composite oxide can be used, which can be represented as follows: Here, element M is preferably a metallic element selected from lithium and manganese, or silicon or phosphorus, and more preferably nickel. When measuring the entire particle of lithium manganese composite oxide, <a / (b+c)<2、かつc>it is preferable that the discharge is 0 0 and 0.26 ≤ (b+c) / d < 0.5. The composition of metals, silicon, phosphorus, etc., of the entire particle of lithium manganese composite oxide can be measured, for example, using ICP-MS (inductively coupled plasma mass spectrometer). The oxygen composition of the entire particle of lithium manganese composite oxide can be measured, for example, using EDX (energy dispersive X-ray spectrometry). It can also be determined by using valence evaluation of molten gas analysis and XAFS (X-ray absorption fine structure) analysis in combination with ICPMS analysis. Lithium manganese composite oxide refers to an oxide containing at least lithium and manganese, and may also contain at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon, and phosphorus.

[0161] [Structure of the positive electrode active material] Materials with a layered rock salt crystal structure, such as lithium cobalt oxide (LiCoO2), are known to have high discharge capacity and are excellent as positive electrode active materials for secondary batteries. Examples of materials with a layered rock salt crystal structure include composite oxides represented by LiMO2. Metal M contains metal Me1. Metal Me1 is one or more metals containing cobalt. In addition to metal Me1, metal M may also contain metal X. Metal X is one or more metals selected from magnesium, calcium, zirconium, lanthanum, barium, copper, potassium, sodium, and zinc.

[0162] ​It is known that the Jahn-Teller effect in transition metal compounds differs in strength depending on the number of electrons in the d orbitals of the transition metal.

[0163] In nickel-containing compounds, distortion can easily occur due to the Jahn-Teller effect. Therefore, when LiNiO2 is charged and discharged at high voltages, there is a concern that the crystal structure may collapse due to distortion. In LiCoO2, the effect of the Jahn-Teller effect is suggested to be smaller, and it may have better resistance to high-voltage charging and discharging, making it preferable.

[0164] The positive electrode active material will be explained using Figures 16 and 17.

[0165] A positive electrode active material manufactured according to one aspect of the present invention can reduce the displacement of the CoO2 layer during repeated high-voltage charging and discharging. Furthermore, it can reduce volume changes. Therefore, the positive electrode active material can achieve excellent cycle characteristics. In addition, the positive electrode active material can adopt a stable crystal structure in a high-voltage charged state. Therefore, when the positive electrode active material is maintained in a high-voltage charged state, short circuits may be less likely to occur. In such cases, safety is further improved, which is preferable.

[0166] In this positive electrode active material, the change in crystal structure and the difference in volume per unit number of transition metal atoms between a fully discharged state and a state charged with high voltage are small.

[0167] The positive electrode active material is preferably represented by a layered rock salt structure, and more preferably by a space R-3m. The positive electrode active material is a region containing lithium, metal Me1, oxygen, and metal X. An example of the crystal structure of the positive electrode active material before and after charging and discharging is shown in Figure 16. In addition to the region represented by the layered rock salt structure described in Figure 16 below, the surface layer of the positive electrode active material may have crystals containing titanium, magnesium, and oxygen, and represented by a structure different from the layered rock salt structure. For example, it may have crystals containing titanium, magnesium, and oxygen, and represented by a spinel structure.

[0168] The crystal structure at charge depth 0 (discharge state) in Figure 16 is R-3m(O3), the same as in Figure 17. On the other hand, the positive electrode active material shown in Figure 16 has a crystal structure different from the H1-3 type crystal structure when fully charged. This structure has a space group R-3m and is not a spinel type crystal structure, but ions such as cobalt and magnesium occupy the oxygen 6-coordinate positions, and the arrangement of cations has a symmetry similar to that of the spinel type. Furthermore, the symmetry of the CoO2 layer in this structure is the same as that of the O3 type. Therefore, this structure is referred to as the O3' type crystal structure or pseudo-spinel type crystal structure in this specification. Note that in the diagram of the O3' type crystal structure shown in Figure 16, lithium may be present at any lithium site with a probability of about 20%, but this is not limited to this. It may be present only at certain lithium sites. In addition, in both the O3 type crystal structure and the O3' type crystal structure, it is preferable that dilute magnesium is present between the CoO2 layers, i.e., at the lithium sites. Furthermore, halogens such as fluorine may be present at the oxygen site in a random and dilute manner.

[0169] Furthermore, in the O3' type crystal structure, light elements such as lithium may occupy the oxygen 4-coordinate position, and in this case as well, the ion arrangement exhibits a symmetry similar to that of the spinel type.

[0170] Furthermore, the O3' type crystal structure can be described as a crystal structure similar to the CdCl2 type crystal structure, although it has Li randomly placed between layers. This crystal structure similar to the CdCl2 type is observed when lithium nickelate is charged to a depth of charge of 0.94 (Li 0.06 Although its crystal structure is similar to that of NiO2, it is known that pure lithium cobaltate or layered rock salt-type cathode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0171] The anions in layered rock salt crystals and rock salt crystals adopt a cubic close-packed structure (face-centered cubic lattice structure). It is also presumed that the anions in O3'-type crystals adopt a cubic close-packed structure. When these are in contact, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned. However, the space group of layered rock salt crystals and O3'-type crystals is R-3m, which is different from the space group of rock salt crystals Fm-3m (the space group of a typical rock salt crystal) and Fd-3m (the space group of a rock salt crystal with the simplest symmetry). Therefore, the Miller indices of the crystal planes that satisfy the above conditions are different for layered rock salt crystals and O3'-type crystals and for rock salt crystals. In this specification, when the orientation of the cubic close-packed structure composed of anions is aligned in layered rock salt crystals, O3'-type crystals, and rock salt crystals, it is sometimes said that the crystal orientation is approximately the same.

[0172] In the positive electrode active material shown in Figure 16, the change in crystal structure when charged at high voltage and a large amount of lithium is released is suppressed compared to the comparative example described later. For example, as shown by the dotted line in Figure 16, there is almost no displacement of the CoO2 layer in these crystal structures.

[0173] More specifically, the positive electrode active material shown in Figure 16 exhibits high structural stability even at high charging voltages. For example, in Figure 17, at charging voltages that result in an H1-3 type crystal structure, such as around 4.6V relative to the lithium metal potential, an H1-3 type crystal structure is formed. However, the positive electrode active material of one embodiment of the present invention can maintain an R-3m(O3) crystal structure even at this charging voltage of around 4.6V. Furthermore, there is a region where an O3' type crystal structure can be adopted even at higher charging voltages, such as around 4.65V to 4.7V relative to the lithium metal potential. If the charging voltage is increased further above 4.7V, an H1-3 type crystal may finally be observed in the positive electrode active material of one embodiment of the present invention. Moreover, at lower charging voltages (for example, when the charging voltage is between 4.5V and 4.6V relative to the lithium metal potential), the positive electrode active material of one embodiment of the present invention may adopt an O3' type crystal structure. Furthermore, in the case of a secondary battery, if graphite is used as the negative electrode active material, for example, the voltage of the secondary battery will decrease by the amount of the graphite's potential compared to the above. The potential of graphite is approximately 0.05V to 0.2V, based on the potential of lithium metal. Therefore, for example, even when the voltage of a secondary battery using graphite as the negative electrode active material is between 4.3V and 4.5V, the positive electrode active material of one embodiment of the present invention can maintain the R-3m(O3) crystal structure. Moreover, there is a region where the O3' type crystal structure can be adopted even when the charging voltage is increased, for example, when the secondary battery voltage is above 4.5V and below 4.6V. Furthermore, even when the charging voltage is lower, for example, when the secondary battery voltage is between 4.2V and 4.3V, the positive electrode active material of one embodiment of the present invention may be able to adopt the O3' type crystal structure.

[0174] Therefore, in the positive electrode active material shown in Figure 16, the crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0175] Furthermore, in one embodiment of the present invention, the difference in volume per unit cell between the O3-type crystal structure with a charging depth of 0 and the O3'-type crystal structure with a charging depth of 0.8 is 2.5% or less, more specifically 2.2% or less.

[0176] Furthermore, the O3' type crystal structure can be represented by showing the coordinates of cobalt and oxygen in the unit cell as follows: Co(0,0,0.5), O(0,0,x), within the range of 0.20≦x≦0.25.

[0177] Magnesium, randomly and dilutely present between CoO2 layers, i.e., at lithium sites, has the effect of suppressing the displacement of the CoO2 layers when charged at high voltage. Therefore, the presence of magnesium between CoO2 layers makes it easier for an O3' type crystal structure to form.

[0178] However, if the heat treatment temperature is too high, cation mixing occurs, increasing the likelihood of magnesium entering the cobalt site. Magnesium present in the cobalt site may have little effect in maintaining the R-3m structure during high-voltage charging. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium.

[0179] Therefore, it is preferable to add a halogen compound such as a fluorine compound to lithium cobalt oxide before the heat treatment to distribute magnesium throughout the particles. Adding a halogen compound lowers the melting point of lithium cobalt oxide. Lowering the melting point makes it easier to distribute magnesium throughout the particles at a temperature at which cation mixing is less likely to occur. Furthermore, if a fluorine compound is present, it can be expected that the corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte will be improved.

[0180] Furthermore, if the magnesium concentration is increased beyond the desired value, the effect on stabilizing the crystal structure may decrease. This is thought to be because magnesium will enter not only the lithium sites but also the cobalt sites. The number of magnesium atoms in the positive electrode active material produced according to one aspect of the present invention is preferably 0.001 times or more and 0.1 times the number of cobalt atoms, more preferably greater than 0.01 and less than 0.04, and even more preferably around 0.02. The magnesium concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, or it may be based on the value of the raw material composition during the process of producing the positive electrode active material.

[0181] The number of nickel atoms in the positive electrode active material is preferably 7.5% or less of the number of cobalt atoms, preferably 0.05% to 4%, and more preferably 0.1% to 2%. The nickel concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, or a value based on the raw material composition during the manufacturing process of the positive electrode active material.

[0182] <Particle size> If the particle size of the positive electrode active material is too large, problems arise such as difficulty in lithium diffusion and excessive roughness of the surface of the active material layer when coated onto the current collector. On the other hand, if it is too small, problems arise such as difficulty in supporting the active material layer when coating onto the current collector and excessive reaction with the electrolyte. Therefore, the average particle size (D50: also called the median diameter) is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 40 μm or less, and even more preferably 5 μm or more and 30 μm or less.

[0183] <Analysis method> Whether a positive electrode active material exhibits an O3'-type crystal structure when charged at high voltage can be determined by analyzing the high-voltage charged positive electrode using XRD, electron diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), etc. XRD is particularly preferable because it can analyze the symmetry of transition metals such as cobalt in the positive electrode active material with high resolution, compare the crystallinity and crystal orientation, analyze the periodic distortion of the lattice and crystallite size, and obtain sufficient accuracy even when measuring a positive electrode obtained by disassembling a secondary battery.

[0184] As mentioned above, a key characteristic of positive electrode active materials is that their crystal structure changes little between the high-voltage charged state and the discharged state. Materials in which the crystal structure that changes significantly from the discharged state accounts for 50 wt% or more when charged at high voltage are undesirable because they cannot withstand high-voltage charging and discharging. It is also important to note that simply adding impurity elements may not result in the desired crystal structure. For example, even if both materials are lithium cobalt oxide containing magnesium and fluorine, when charged at high voltage, there are cases where the O3' type crystal structure accounts for 60 wt% or more, and cases where the H1-3 type crystal structure accounts for 50 wt% or more. Furthermore, at a given voltage, the O3' type crystal structure may account for almost 100 wt%, and if the voltage is further increased, the H1-3 type crystal structure may emerge. Therefore, it is preferable that the crystal structure of positive electrode active material 811 be analyzed by XRD or the like. By using this in combination with XRD or the like, more detailed analysis can be performed.

[0185] However, positive electrode active materials in a high-voltage charged or discharged state may undergo changes in their crystal structure when exposed to air. For example, they may change from an O3' type crystal structure to an H1-3 type crystal structure. Therefore, it is preferable to handle all samples in an inert atmosphere such as an argon-containing atmosphere.

[0186] The positive electrode active material shown in Figure 17 is lithium cobalt oxide (LiCoO2) without the addition of metal X. The crystal structure of lithium cobalt oxide shown in Figure 17 changes depending on the depth of charge.

[0187] As shown in Figure 17, lithium cobalt oxide at charge depth 0 (discharge state) has a region with a crystal structure of space group R-3m, and there are three CoO2 layers in the unit cell. For this reason, this crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer refers to a structure in which octahedral structures, in which oxygen atoms are coordinated to cobalt in a 6-coordinate manner, are continuous in a plane with shared edges.

[0188] Furthermore, at a charge depth of 1, it has a crystal structure of space group P-3m1, with one CoO2 layer present in the unit cell. For this reason, this crystal structure is sometimes called an O1 type crystal structure.

[0189] Furthermore, lithium cobalt oxide at a charge depth of approximately 0.8 has a crystal structure with space group R-3m. This structure can be described as a structure in which CoO2 structures such as P-3m1(O1) and LiCoO2 structures such as R-3m(O3) are alternately stacked. For this reason, this crystal structure is sometimes called the H1-3 type crystal structure. In reality, the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell compared to other structures. However, in this specification, including Figure 17, the c-axis of the H1-3 type crystal structure is shown as half the unit cell for easier comparison with other structures.

[0190] As an example, the H1-3 type crystal structure can be represented by the coordinates of cobalt and oxygen in a unit cell as follows: Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are oxygen atoms, respectively. Thus, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygen atoms. On the other hand, the O3' type crystal structure in one embodiment of the present invention is preferably represented by a unit cell using one cobalt and one oxygen atom. This indicates that the symmetry between cobalt and oxygen differs between the O3' type crystal structure and the H1-3 type structure, and that the O3' type crystal structure shows less variation from the O3 structure compared to the H1-3 type structure. The choice of which unit cell should represent the crystal structure of the positive electrode active material can be determined, for example, by Rietveld analysis using XRD. In this case, the unit cell that yields the smallest GOF (goodness of fit) value should be selected.

[0191] When high-voltage charging occurs, such as when the charging voltage is 4.6V or higher relative to the oxidation-reduction potential of lithium metal, or when deep charging occurs, such as when the charging depth is 0.8 or higher, and when this charging and discharging cycle is repeated, lithium cobalt oxide undergoes repeated changes in its crystal structure (i.e., non-equilibrium phase changes) between the H1-3 type crystal structure and the R-3m(O3) structure in the discharged state.

[0192] However, these two crystal structures exhibit a large displacement of the CoO2 layer. As shown by the dotted line and arrow in Figure 17, in the H1-3 type crystal structure, the CoO2 layer is significantly shifted from R-3m(O3). Such dynamic structural changes can negatively affect the stability of the crystal structure.

[0193] Furthermore, the volume difference is also significant. When comparing the same number of cobalt atoms, the volume difference between the H1-3 type crystal structure and the O3 type crystal structure in the discharged state is more than 3.0%.

[0194] In addition, the H1-3 type crystal structure, which consists of continuous CoO2 layers such as P-3m1(O1), is likely to be unstable.

[0195] Therefore, repeated high-voltage charging and discharging causes the crystal structure of lithium cobalt oxide to break down. This breakdown of the crystal structure leads to a deterioration of the cycle characteristics. This is thought to be because the breakdown of the crystal structure reduces the number of sites where lithium can exist stably, and also makes it more difficult for lithium to be inserted and removed.

[0196] <Electrolyte> When using a liquid electrolyte in a secondary battery, for example, one of the following can be used as the electrolyte: ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., or two or more of these can be used in any combination and ratio.

[0197] Furthermore, by using one or more flame-retardant and non-volatile ionic liquids (room-temperature molten salts) as the solvent for the electrolyte, it is possible to prevent the secondary battery from rupturing and igniting even when internal temperature rises due to short circuits in the internal region of the secondary battery or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, as well as aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0198] A secondary battery according to one aspect of the present invention has, for example, one or more carrier ions selected from 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.

[0199] When lithium ions are used as carrier ions, the electrolyte, for example, contains a lithium salt. Examples of lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, and Li2B. 10 Cl 10 Li2B 12 Cl 12 LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc. can be used.

[0200] Furthermore, the electrolyte preferably contains fluorine. As a fluorine-containing electrolyte, for example, an electrolyte having one or more types of fluorinated cyclic carbonates and lithium ions can be used. Fluorinated cyclic carbonates can improve flammability and enhance the safety of lithium-ion secondary batteries.

[0201] As fluorinated cyclic carbonates, fluorinated ethylene carbonates such as monofluoroethylene carbonate (fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), and tetrafluoroethylene carbonate (F4EC) can be used. Note that DFEC has isomers such as cis-4,5 and trans-4,5. As an electrolyte, it is important to solvate lithium ions using one or more types of fluorinated cyclic carbonates and transport them within the electrolyte contained in the electrodes during charging and discharging in order to operate at low temperatures. By contributing to the transport of lithium ions during charging and discharging, rather than using fluorinated cyclic carbonates as small additives, low-temperature operation becomes possible. In secondary batteries, lithium ions move in clusters of several to several dozen ions.

[0202] By using fluorinated cyclic carbonates as the electrolyte, the desolvation energy required for lithium ions, which are solvated within the electrolyte contained in the electrodes, to enter the active material particles is reduced. If this desolvation energy can be reduced, lithium ions can be more easily inserted into the active material particles, or more easily desorbed from the negative electrode active material particles, even in the low-temperature range. Although lithium ions may move while remaining solvated, a hopping phenomenon may occur in which the coordinating solvent molecules are replaced. If the solvent is more easily desolvated from the lithium ions, movement due to the hopping phenomenon becomes easier, and thus the movement of lithium ions may become easier. There is a concern that the degradation of secondary batteries may occur because the decomposition products of the electrolyte during charging and discharging adhere to the surface of the active material. However, when the electrolyte contains fluorine, the electrolyte is fluid, and the decomposition products of the electrolyte are less likely to adhere to the surface of the active material. Therefore, the degradation of secondary batteries can be suppressed.

[0203] Solvated lithium ions may form clusters in the electrolyte and move within the negative electrode, between the positive and negative electrodes, within the positive electrode, etc.

[0204] An example of a fluorinated cyclic carbonate is shown below.

[0205] Monofluoroethylene carbonate (FEC) is represented by the following formula (1).

[0206] [ka]

[0207] Tetrafluoroethylene carbonate (F4EC) is represented by the following formula (2).

[0208] [ka]

[0209] Difluoroethylene carbonate (DFEC) is represented by the following formula (3).

[0210] [ka]

[0211] In this specification, electrolytes are a general term that includes solid, liquid, or semi-solid materials.

[0212] Degradation is prone to occur at interfaces within secondary batteries, such as the interface between the active material and the electrolyte. In one embodiment of the present invention, the presence of a fluorine-containing electrolyte prevents degradation, typically alteration of the electrolyte or increased viscosity of the electrolyte, that can occur at the interface between the active material and the electrolyte. Alternatively, a binder or graphene compound may be attached to or retained around the fluorine-containing electrolyte. This configuration makes it possible to maintain a state where the viscosity of the electrolyte is reduced, in other words, a free-flowing state of the electrolyte, thereby improving the reliability of the secondary battery. DFEC with two fluorine atoms bonded or F4EC with four fluorine atoms bonded have lower viscosity and are freer than FEC with one fluorine atom bonded, resulting in weaker coordination bonds with lithium. Therefore, the adhesion of highly viscous decomposition products to the active material particles can be reduced. When highly viscous decomposition products adhere to or cling to the active material particles, lithium ions become less able to move at the interface of the active material particles. Fluorine-containing electrolytes mitigate the formation of decomposition products on the surface of the active material (positive electrode active material or negative electrode active material) through solvation. Furthermore, by using fluorine-containing electrolytes, the formation and growth of dendrites can be prevented by preventing the adhesion of decomposition products.

[0213] Another characteristic is the use of an electrolyte containing fluorine as the main component, with the fluorine-containing electrolyte being 5% or more by volume, 10% or more by volume, preferably 30% to 100% by volume.

[0214] In this specification, the main component of the electrolyte refers to a component that accounts for 5% or more by volume of the total electrolyte of the secondary battery. Furthermore, "5% or more by volume of the total electrolyte of the secondary battery" here refers to the proportion of the total electrolyte measured during the manufacturing of the secondary battery. In addition, when a secondary battery is disassembled after its manufacture, it is difficult to quantify the proportion of each of the multiple types of electrolytes, but it is possible to determine whether a particular organic compound accounts for 5% or more by volume of the total electrolyte.

[0215] By using an electrolyte containing fluorine, a secondary battery capable of operating over a wide temperature range, specifically from -40°C to 150°C, preferably from -40°C to 85°C, can be realized.

[0216] Furthermore, additives such as vinylene carbonate, propanesultone (PS), tert-butylbenzene (TBB), lithium bis(oxalate)borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive should be, for example, 0.1% or more and less than 5% by volume relative to the total electrolyte.

[0217] In addition to the above, the electrolyte may also contain one or more aprotic organic solvents such as γ-butyrolactone, acetonitrile, dimethoxyethane, and tetrahydrofuran.

[0218] Furthermore, the presence of a polymer material that gels the electrolyte enhances safety against leakage and other issues. Typical examples of polymer materials that gel include silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide gels, polypropylene oxide gels, and fluorine-based polymer gels.

[0219] As the polymer material, one or more can be selected from polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing these. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the polymer formed may have a porous structure.

[0220] Furthermore, the above configuration is an example of a secondary battery using a liquid electrolyte, but is not particularly limited. For example, semi-solid-state batteries and all-solid-state batteries can also be fabricated.

[0221] In this specification, whether it is a secondary battery using a liquid electrolyte or a semi-solid battery, the layer placed between the positive and negative electrodes will be referred to as the electrolyte layer. The electrolyte layer of a semi-solid battery is a layer formed by film deposition and can be distinguished from the liquid electrolyte layer.

[0222] Furthermore, in this specification, a semi-solid battery refers to a battery having a semi-solid material in at least one of its components: the electrolyte layer, the positive electrode, and the negative electrode. Here, "semi-solid" does not mean that the solid material makes up 50% of the battery. "Semi-solid" means possessing solid properties, such as small volume change, while also having some liquid-like properties, such as flexibility. As long as these properties are met, the battery may consist of a single material or multiple materials. For example, a liquid material may be impregnated into a porous solid material.

[0223] Furthermore, in this specification, a polymer electrolyte secondary battery refers to a secondary battery having a polymer in the electrolyte layer between the positive and negative electrodes. Polymer electrolyte secondary batteries include dry (or intrinsic) polymer electrolyte batteries and polymer gel electrolyte batteries. Polymer electrolyte secondary batteries may also be called semi-solid batteries.

[0224] When a semi-solid battery is manufactured using the negative electrode according to one embodiment of the present invention, the semi-solid battery becomes a secondary battery with a large charge / discharge capacity. Furthermore, it can be a semi-solid battery with a high charge / discharge voltage. Alternatively, it can be a semi-solid battery that is safe or highly reliable.

[0225] Here, using Figure 18, we show an example of how to fabricate a semi-solid battery.

[0226] Figure 18 is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention. The secondary battery according to one embodiment of the present invention has 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. The secondary battery also has an electrolyte 576 between the negative electrode 570a and the positive electrode 570b.

[0227] Electrolyte 576 comprises a lithium-ion conductive polymer and a lithium salt.

[0228] In this specification, a lithium-ion conductive polymer is a polymer that has the conductivity of a cation such as lithium. More specifically, it is a polymer compound having a polar group to which a cation can coordinate. Preferably, the polar group is an ether group, ester group, nitrile group, carbonyl group, siloxane, etc.

[0229] Examples of lithium-ion conductive polymers that can be used include polyethylene oxide (PEO), derivatives having polyethylene oxide as the main chain, polypropylene oxide, polyacrylic acid esters, polymethacrylate esters, polysiloxanes, and polyphosphazenes.

[0230] The lithium-ion conductive polymer may be branched, crosslinked, or copolymerized. Its molecular weight is preferably, for example, 10,000 or more, and more preferably 100,000 or more.

[0231] In lithium-ion conductive polymers, lithium ions move while changing the polar groups they interact with through partial motion (also called segmental motion) of the polymer chains. For example, in PEO, lithium ions move while changing the oxygen groups they interact with through segmental motion of the ether chains. When the temperature is close to or higher than the melting or softening point of the lithium-ion conductive polymer, the crystalline region dissolves and the amorphous region increases, and the motion of the ether chains becomes more active, resulting in higher ionic conductivity. Therefore, when using PEO as a lithium-ion conductive polymer, it is preferable to perform charging and discharging at 60°C or higher.

[0232] According to Shannon et al., Acta A 32 (1976) 751, the radius of a monovalent lithium ion is 0.590 Å for 4-coordinate, 0.76 Å for 6-coordinate, and 0.92 Å for 8-coordinate. The radius of a divalent oxygen ion is 1.35 Å for 2-coordinate, 1.36 Å for 3-coordinate, 1.38 Å for 4-coordinate, 1.40 Å for 6-coordinate, and 1.42 Å for 8-coordinate. The distance between polar groups in adjacent lithium-ion conductive polymer chains is preferably greater than the distance at which lithium ions and the anions of the polar groups can stably exist while maintaining the above-mentioned ionic radii. Furthermore, it is preferable that the distance is such that sufficient interaction occurs between lithium ions and polar groups. However, as mentioned above, segmental motion occurs, so it is not necessary to always maintain a constant distance. It is sufficient if the distance is appropriate when lithium ions pass through.

[0233] Furthermore, as lithium salts, compounds can be used that contain lithium along with at least one of the following: phosphorus, fluorine, nitrogen, sulfur, oxygen, chlorine, arsenic, boron, aluminum, bromine, and iodine. For example, LiPF6, LiN(FSO2)2 (lithium bis(fluorosulfonyl)amide, LiFSA), LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 Li2B 12 Cl 12Lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2 (lithium bis(trifluoromethanesulfonyl)amide, LiTFSA), LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, and lithium bis(oxalate)borate (LiBOB) can be used individually or in any combination and ratio of two or more of these salts.

[0234] In particular, using LiFSA is preferable because it exhibits good low-temperature characteristics. Furthermore, LiFSA and LiTFSA are less reactive with water compared to LiPF6 and the like. Therefore, it is easier to control the dew point when fabricating electrodes and electrolyte layers using LiFSA. For example, they can be handled not only in an inert atmosphere such as argon with moisture removed as much as possible, and in a dry room with a controlled dew point, but also in a normal atmospheric atmosphere. This improves productivity, which is preferable. Moreover, using Li salts with high dissociability and plasticizing effects, such as LiFSA and LiTFSA, is particularly preferable when using lithium conduction utilizing the segmental motion of the ether chain, because it can be used over a wide temperature range.

[0235] In this specification, "binder" refers to a polymer compound mixed solely for the purpose of binding active materials, conductive materials, etc., onto a current collector. Examples include rubber materials such as polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, butadiene rubber, and ethylene-propylene-diene copolymer, as well as materials such as fluororubber, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, and ethylene-propylene-diene polymer.

[0236] Since lithium-ion conductive polymers are high-molecular-weight compounds, thoroughly mixing them and using them in the active material layer allows for the bonding of the active material and conductive material onto the current collector. Therefore, electrodes can be fabricated without the use of a binder. A binder is a material that does not contribute to the charge-discharge reaction. Consequently, the less binder used, the more materials that contribute to charge-discharge, such as the active material and electrolyte, can be increased. This allows for the creation of secondary batteries with improved discharge capacity or cycle characteristics.

[0237] The absence or very low amount of organic solvents makes it possible to create a secondary battery that is less prone to ignition and combustion, thus improving safety, which is desirable. Furthermore, if the electrolyte 576 is an electrolyte layer that has no organic solvents or very little organic solvents, it has sufficient strength to electrically insulate the positive and negative electrodes even without a separator. Since a separator is not required, a secondary battery with high productivity can be created. If the electrolyte 576 is an electrolyte layer containing inorganic fillers, the strength will be further increased, resulting in a secondary battery with even higher safety.

[0238] It is preferable that the electrolyte 576 is thoroughly dried in order to create an electrolyte layer that is free of or contains very little organic solvent. In this specification, a electrolyte layer is considered thoroughly dried if the weight change of the electrolyte layer after drying under reduced pressure at 90°C for 1 hour is within 5%.

[0239] Nuclear magnetic resonance (NMR), for example, can be used to identify materials such as lithium-ion conductive polymers, lithium salts, binders, and additives contained in secondary batteries. Analysis results from other methods such as 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), and liquid chromatography-mass spectrometry (LC / MS) may also be used as a basis for determination. It is preferable to suspend the active material layer in a solvent to separate the active material from other materials before subjecting it to analysis such as NMR.

[0240] Furthermore, in each of the above configurations, the negative electrode may be further enriched with a solid electrolyte material to improve flame retardancy. It is preferable to use an oxide-based solid electrolyte material.

[0241] Examples of oxide-based solid electrolytes include LiPON, Li2O, Li2CO3, Li2MoO4, Li3PO4, Li3VO4, Li4SiO4, and LLT(La 2 / 3-x Li 3x TiO3), LLZ(Li7La3Zr2O 12 Examples include lithium composite oxides and lithium oxide materials such as ).

[0242] LLZ is a garnet-type oxide containing Li, La, and Zr, and may also be a compound containing Al, Ga, or Ta.

[0243] Alternatively, polymer-based solid electrolytes such as PEO (polyethylene oxide) formed by coating methods may be used. Since such polymer-based solid electrolytes can also function as binders, using them can reduce the number of electrode components and lower manufacturing costs.

[0244] This embodiment can be used in appropriate combination with other embodiments.

[0245] (Embodiment 2) This embodiment describes an example of a secondary battery according to one aspect of the present invention.

[0246] <Example of a secondary battery configuration 1> The following explanation uses a secondary battery, in which the positive electrode, negative electrode, and electrolyte are enclosed in an outer casing, as an example.

[0247] [Negative electrode] As the negative electrode, the negative electrode shown in the previous embodiment can be used.

[0248] [Current collector] As the positive current collector and the negative current collector, metals such as stainless steel, gold, platinum, zinc, iron, copper, aluminum, titanium, and alloys thereof, materials with high conductivity and that do not alloy with carrier ions such as lithium, can be used. Further, an aluminum alloy added with elements such as silicon, titanium, neodymium, scandium, molybdenum to improve heat resistance can be used. Also, it may be formed of a metal element that reacts with silicon to form a silicide. Examples of the metal element that reacts with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, etc. The current collector can appropriately use shapes such as sheet-like, net-like, punching metal-like, expanded metal-like, etc. The current collector preferably has a thickness of 10 μm or more and 30 μm or less.

[0249] Note that it is preferable to use a material for the negative current collector that does not alloy with carrier ions such as lithium.

[0250] A titanium compound may be provided by laminating on the above-mentioned metal element as the current collector. As the titanium compound, for example, titanium nitride, titanium oxide, titanium nitride in which part of nitrogen is substituted by oxygen, titanium oxide in which part of oxygen is substituted by nitrogen, and titanium oxynitride (TiO x N y , 0 < x < 2, 0 < y < 1) can be selected, or two or more of them can be mixed or laminated and used. Among them, titanium nitride is particularly preferable because it has high conductivity and a high function of suppressing oxidation. By providing a titanium compound on the surface of the current collector, for example, the reaction between the material and the metal in the active material layer formed on the current collector can be suppressed. When the active material layer contains a compound having oxygen, the oxidation reaction between the metal element and oxygen can be suppressed. For example, when aluminum is used as the current collector and the active material layer is formed using graphene oxide described later, there may be a concern about the oxidation reaction between the oxygen in graphene oxide and aluminum. In such a case, by providing a titanium compound on aluminum, the oxidation reaction between the current collector and graphene oxide can be suppressed.

[0251] [Positive Electrode] The positive electrode has a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer has a positive electrode active material and may have a conductive material and a binder. As the positive electrode active material, the positive electrode active material produced using the production method described in the previous embodiment is used.

[0252] As the conductive material and the binder that the positive electrode active material layer can have, the same materials as the conductive material and the binder that the negative electrode active material layer can have can be used.

[0253] [Separator] A separator is disposed between the positive electrode and the negative electrode. As the separator, for example, fibers having cellulose such as paper, non-woven fabric, glass fiber, ceramics, or synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyurethane, etc. can be used. It is preferable that the separator is processed into a bag shape and disposed so as to wrap either the positive electrode or the negative electrode.

[0254] The separator is a porous material having holes with a size of about 20 nm, preferably holes with a size of 6.5 nm or more, and more preferably holes with a diameter of at least 2 nm. In the case of the semi-solid secondary battery described above, the separator can also be omitted.

[0255] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic-based material, a fluorine-based material, a polyamide-based material, or a mixture thereof. As the ceramic-based material, for example, aluminum oxide particles, silicon oxide particles, etc. can be used. As the fluorine-based material, for example, PVDF, polytetrafluoroethylene, etc. can be used. As the polyamide-based material, for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.

[0256] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging, and thus improving the reliability of secondary batteries. Coating with fluorine-based materials improves adhesion between the separator and electrodes, thereby improving output characteristics. Coating with polyamide materials, particularly aramid, improves heat resistance, thus enhancing the safety of secondary batteries.

[0257] For example, a polypropylene film may be coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, the side of the polypropylene film in contact with the positive electrode may be coated with a mixture of aluminum oxide and aramid, and the side in contact with the negative electrode may be coated with a fluorine-based material.

[0258] By using a multi-layered separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, thus increasing the capacity per unit volume of the secondary battery.

[0259] [Exterior] The outer casing of a secondary battery can be made from one or more materials selected from metal materials such as aluminum and resin materials. A film-like outer casing can also be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of materials such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer casing. Furthermore, it is preferable to use a fluororesin film as the film. Fluororesin films have high stability against acids, alkalis, organic solvents, etc., and suppress side reactions, corrosion, etc. associated with the reactions of the secondary battery, thereby realizing a superior secondary battery. Examples of fluororesin films include PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane: copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), FEP (perfluoroethylenepropene copolymer: copolymer of tetrafluoroethylene and hexafluoropropylene), and ETFE (ethylenetetrafluoroethylene copolymer: copolymer of tetrafluoroethylene and ethylene).

[0260] This embodiment can be used in appropriate combination with other embodiments.

[0261] (Embodiment 3) This embodiment describes examples of multiple shapes of secondary batteries having a positive or negative electrode, manufactured by the manufacturing method described in the previous embodiment.

[0262] [Coin-type rechargeable battery] An example of a coin-type rechargeable battery is described below. Figure 19A is an exploded perspective view of a coin-type (single-layer flat type) rechargeable battery, Figure 19B is a perspective view showing its external appearance, and Figure 19C is a cross-sectional perspective view showing its cross-section. Coin-type rechargeable batteries are mainly used in small electronic devices.

[0263] Figure 19A is a schematic diagram to show the overlapping (upper and lower relationships and positional relationships) of the components for clarity. Therefore, Figures 19A and 19B are not perfectly identical corresponding diagrams.

[0264] In Figure 19A, the positive electrode 304, separator 310, negative electrode 307, spacer 322, and washer 312 are stacked. These are sealed with the negative electrode can 302 and the positive electrode can 301. Note that the gasket for sealing is not shown in Figure 19A. The spacer 322 and washer 312 are used to protect the inside or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together. Stainless steel or insulating material is used for the spacer 322 and washer 312.

[0265] The positive electrode 304 is a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305.

[0266] To prevent a short circuit between the positive and negative electrodes, a separator 310 and a ring-shaped insulator 313 are arranged to cover the sides and top surfaces of the positive electrode 304, respectively. The separator 310 has a larger planar area than the positive electrode 304.

[0267] Figure 19B is a perspective view of the completed coin-type rechargeable battery.

[0268] The coin-type secondary battery 300 has a positive electrode casing 301, which also serves as the positive electrode terminal, and a negative electrode casing 302, which also serves as the negative electrode terminal, insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with it. Furthermore, the negative electrode 307 is not limited to a laminated structure, and lithium metal foil or a lithium-aluminum alloy foil may be used.

[0269] Furthermore, the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300 only need to have the active material layer formed on one side.

[0270] For the positive electrode can 301 and the negative electrode can 302, materials corrosion-resistant to the electrolyte can be used. For example, metals such as nickel, aluminum, titanium, or alloys of these metals, or alloys of these metals and other metals (such as stainless steel, etc.) can be used. Also, in order to prevent corrosion by the electrolyte, it is preferable to coat with nickel or aluminum, etc. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307 respectively.

[0271] Immerse these negative electrode 307, positive electrode 304, and separator 310 in the electrolyte. As shown in Fig. 19C, with the positive electrode can 301 facing downwards, stack the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 in this order, and crimp the positive electrode can 301 and the negative electrode can 302 through the gasket 303 to manufacture the coin-shaped secondary battery 300.

[0272] By making it a secondary battery, a coin-shaped secondary battery 300 with high capacity, high charge-discharge capacity, and excellent cycle characteristics can be obtained. In addition, when making it a secondary battery, the separator 310 between the negative electrode 307 and the positive electrode 304 can also be made unnecessary.

[0273] [Cylindrical secondary battery] An example of a cylindrical secondary battery will be described with reference to Fig. 20A. As shown in Fig. 20A, the cylindrical secondary battery 616 has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (outer can) 602 on the side surface and the bottom surface. The battery can (outer can) 602 is formed of a metal material and has excellent water permeation barrier property and gas barrier property. The positive electrode cap 601 and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

[0274] Fig. 20B is a diagram schematically showing a cross-section of the cylindrical secondary battery. The cylindrical secondary battery shown in Fig. 20B has a positive electrode cap (battery lid) 601 on the upper surface and a battery can (outer can) 602 on the side surface and the bottom surface. The positive electrode cap and the battery can (outer can) 602 are insulated by a gasket (insulating packing) 610.

[0275] Inside the hollow cylindrical battery can 602, a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 in between. Although not shown, the battery element is wound around a center pin. The battery can 602 is closed at one end and open at the other. The battery can 602 can be made of a material that is corrosion-resistant to the electrolyte. For example, metals such as nickel, aluminum, and titanium, or alloys of these metals, or alloys of these metals with other metals (e.g., stainless steel) can be used. Furthermore, it is preferable to coat the battery can 602 with nickel or aluminum to prevent corrosion by the electrolyte. Inside the battery can 602, the battery element in which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with an electrolyte (not shown). The electrolyte can be the same as that used in coin-type secondary batteries.

[0276] Since the positive and negative electrodes used in cylindrical storage batteries are wound, it is preferable to form the active material on both sides of the current collector.

[0277] 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 obtained.

[0278] A positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606. Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of metal materials such as aluminum. The positive electrode terminal 603 is resistance-welded to the safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the internal pressure of the battery rises above a predetermined threshold. The PTC element 611 is a thermal resistance element whose resistance increases when the temperature rises, and it prevents abnormal heat generation by limiting the amount of current through the increase in resistance. Barium titanate (BaTiO3) based semiconductor ceramics can be used for the PTC element.

[0279] Figure 20C shows an example of an energy storage system 615. The energy storage system 615 has a plurality of secondary batteries 616. The positive electrode of each secondary battery is in contact with a conductor 624 separated by an insulator 625 and is electrically connected. The conductor 624 is electrically connected to a control circuit 620 via wiring 623. The negative electrode of each secondary battery is also electrically connected to the control circuit 620 via wiring 626. The control circuit 620 can be a charge / discharge control circuit that performs charging and discharging, and a protection circuit that prevents overcharging or over-discharging. The control circuit 620 has the function of performing one or more of the following: charging control, discharging control, measuring charging voltage, measuring discharge voltage, measuring charging current, measuring discharge current, and measuring remaining charge using the integration of charge. The control circuit 620 also has the function of performing one or more of the following: overcharging detection, over-discharging detection, charging overcurrent detection, and discharge overcurrent detection. Preferably, the control circuit 620 also has the function of stopping charging, stopping discharging, changing charging conditions, and changing discharge conditions based on these detection results.

[0280] Figure 20D shows an example of an energy storage system 615. The energy storage system 615 has multiple secondary batteries 616, which are sandwiched between conductive plates 628 and 614. The multiple secondary batteries 616 are electrically connected to conductive plates 628 and 614 by wiring 627. The multiple secondary batteries 616 may be connected in parallel, in series, or connected in parallel and then in series. By configuring an energy storage system 615 with multiple secondary batteries 616, a large amount of power can be extracted.

[0281] Multiple secondary batteries 616 may be connected in parallel and then further connected in series.

[0282] A temperature control device may be provided between the multiple secondary batteries 616. When a secondary battery 616 overheats, it can be cooled by the temperature control device, and when a secondary battery 616 becomes too cold, it can be heated by the temperature control device. This makes the performance of the energy storage system 615 less susceptible to the influence of ambient temperature.

[0283] Furthermore, in Figure 20D, the energy storage system 615 is electrically connected to the control circuit 620 via wiring 621 and wiring 622. Wiring 621 is electrically connected to the positive terminals of the multiple secondary batteries 616 via conductive plate 628, and wiring 622 is electrically connected to the negative terminals of the multiple secondary batteries 616 via conductive plate 614.

[0284] [Example of a secondary battery structure] Examples of secondary battery structures will be explained using Figures 21 and 22.

[0285] The secondary battery 913 shown in Figure 21A has a wound body 950 with terminals 951 and 952 inside a housing 930. The wound body 950 is immersed in an electrolyte inside the housing 930. Terminal 952 is in contact with the housing 930, while terminal 951 is not in contact with the housing 930 due to the use of an insulating material or the like. In Figure 21A, the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and terminals 951 and 952 extend outside the housing 930. The housing 930 can be made of a metal material (e.g., aluminum) or a resin material.

[0286] Furthermore, as shown in Figure 21B, the housing 930 shown in Figure 21A may be formed from multiple materials. For example, in the secondary battery 913 shown in Figure 21B, housing 930a and housing 930b are bonded together, and the winding body 950 is provided in the area surrounded by housing 930a and housing 930b.

[0287] For the housing 930a, an insulating material such as organic resin can be used. In particular, by using a material such as organic resin on the surface where the antenna is formed, shielding of the electric field by the secondary battery 913 can be suppressed. If the shielding of the electric field by housing 930a is small, the antenna may be placed inside housing 930a. For housing 930b, for example, a metal material can be used.

[0288] Furthermore, the structure of the wound body 950 is shown in Figure 21C. The wound body 950 has a negative electrode 931, a positive electrode 932, and a separator 933. The wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the separator 933 in between, and the stacked sheets are wound up. Note that multiple stacks of the negative electrode 931, positive electrode 932, and separator 933 may be stacked.

[0289] Alternatively, the secondary battery 913 may have a wound body 950a as shown in Figure 22. The wound body 950a shown in Figure 22A has a negative electrode 931, a positive electrode 932, and a separator 933. The negative electrode 931 has a negative electrode active material layer 931a. The positive electrode 932 has a positive electrode active material layer 932a.

[0290] By using the negative electrode structure obtained in Embodiment 1, i.e., an electrolyte containing fluorine, as the negative electrode 931, a secondary battery 913 with high capacity, high charge / discharge capacity, and excellent cycle characteristics can be obtained.

[0291] The separator 933 has a wider width than the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Furthermore, it is preferable from a safety standpoint that the negative electrode active material layer 931a is wider than the positive electrode active material layer 932a. A wound body 950a of this shape is also preferable due to its good safety and productivity.

[0292] As shown in Figures 22A and 22B, the negative electrode 931 is electrically connected to terminal 951. Terminal 951 is electrically connected to terminal 911a. The positive electrode 932 is electrically connected to terminal 952. Terminal 952 is electrically connected to terminal 911b.

[0293] As shown in Figure 22C, the coiled body 950a and electrolyte are covered by the housing 930, forming a secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc., in the housing 930. The safety valve is a valve that opens when the inside of the housing 930 reaches a predetermined pressure in order to prevent the battery from rupturing.

[0294] As shown in Figure 22B, the secondary battery 913 may have multiple windings 950a. By using multiple windings 950a, a secondary battery 913 with a larger charge / discharge capacity can be made. Other elements of the secondary battery 913 shown in Figures 22A and 22B can be referenced from the description of the secondary battery 913 shown in Figures 21A to 21C.

[0295] <Laminated rechargeable battery> Next, an example of a laminate-type secondary battery is shown in Figures 23A and 23B, which show an example of its external appearance. Figures 23A and 23B show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead electrode 510, and a negative electrode lead electrode 511.

[0296] Figure 24A shows the external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 has a positive electrode current collector 501, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. The positive electrode 503 also has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). The negative electrode 506 has a negative electrode current collector 504, and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. The negative electrode 506 also has a region where the negative electrode current collector 504 is partially exposed, i.e., the tab region. The area and shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 24A.

[0297] <Method for manufacturing laminated rechargeable batteries> Here, an example of a method for manufacturing a laminate-type secondary battery, whose external view is shown in Figure 23A, will be explained using Figures 24B and 24C.

[0298] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. Figure 24B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using 5 sets of negative electrodes and 4 sets of positive electrodes is shown. This can also be called a laminate consisting of negative electrodes, separators, and positive electrodes. Next, the tab regions of the positive electrode 503 are joined together, and the positive electrode lead electrode 510 is joined to the tab region of the outermost positive electrode. For joining, ultrasonic welding, for example, can be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0299] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0300] Next, as shown in Figure 24C, the outer casing 509 is folded along the dashed line. Then, the outer periphery of the outer casing 509 is joined. For joining, for example, heat sealing may be used. At this time, a region that is not joined (hereinafter referred to as an inlet) is provided on a part (or one side) of the outer casing 509 so that the electrolyte 508 can be inserted later. It is preferable to use a film for the outer casing 509 that has excellent water permeability barrier properties and gas barrier properties. Furthermore, the outer casing 509 can be made into a laminated structure, and high water permeability barrier properties and gas barrier properties can be achieved by making one of the intermediate layers a metal foil (for example, aluminum foil).

[0301] Next, the electrolyte 508 (not shown) is introduced into the inside of the outer casing 509 through an inlet provided in the outer casing 509. It is preferable to introduce the electrolyte 508 under reduced pressure or an inert atmosphere. Finally, the inlet is sealed. In this way, a laminate-type secondary battery 500 can be manufactured.

[0302] By using the negative electrode structure obtained in Embodiment 1, i.e., an electrolyte containing fluorine, as the negative electrode 506, a secondary battery 500 can be made that has high capacity, high charge / discharge capacity, and excellent cycle characteristics.

[0303] This embodiment can be used in appropriate combination with other embodiments.

[0304] (Embodiment 4) A secondary battery according to one aspect of the present invention can be mounted on a moving object such as an automobile, train, or aircraft, as shown below. This embodiment shows an example different from Figure 20D, which is a cylindrical secondary battery. Figure 25C shows an example of applying the secondary battery to an electric vehicle (EV).

[0305] Electric vehicles are equipped with a first battery 1301a and 1301b as the main secondary battery for propulsion, and a second battery 1311 that supplies power to the inverter 1312 that starts the motor 1304. The second battery 1311 is also called the cranking battery (starter battery). The second battery 1311 only needs to be able to output power, and does not require a large capacity, so the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0306] The internal structure of the first battery 1301a may be a wound type as shown in Figure 21A, or a stacked type as shown in Figures 23A and 23B.

[0307] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack with multiple secondary batteries, a large amount of power can be extracted. Multiple secondary batteries may be connected in parallel, in series, or connected in parallel and then in series. Multiple secondary batteries are also called a battery pack.

[0308] Furthermore, in the vehicle-mounted secondary battery, a service plug or circuit breaker that can cut off high voltage without using tools is provided in order to interrupt the power from multiple secondary batteries, and this is installed in the first battery 1301a.

[0309] Furthermore, the power from the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V onboard components (electric power steering 1307, heater 1308, defogger 1309, etc.) via the DC-DC circuit 1306. If a rear motor 1317 is located on the rear wheels, the first battery 1301a is used to rotate the rear motor 1317.

[0310] Furthermore, the second battery 1311 supplies power to 14V automotive components (audio 1313, power windows 1314, lights 1315, etc.) via the DC-DC circuit 1310.

[0311] Furthermore, the first battery 1301a will be explained using Figure 25A.

[0312] Figure 25A shows an example where nine rectangular secondary batteries 1300 are arranged in a single battery pack 1415. In this example, nine rectangular secondary batteries 1300 are connected in series, with one electrode fixed by an insulating fixing part 1413 and the other electrode fixed by an insulating fixing part 1414. While this embodiment shows an example of fixing with fixing parts 1413 and 1414, the batteries may also be housed in a battery housing box (also called a casing). Since vehicles are expected to be subjected to vibrations or shaking from external sources (such as the road surface), it is preferable to fix multiple secondary batteries using fixing parts 1413 and 1414 or a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421, and the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0313] Furthermore, the control circuit unit 1320 may also use a memory circuit that includes a transistor made of an oxide semiconductor. A charging control circuit or battery control system having a memory circuit that includes a transistor made of an oxide semiconductor may be referred to as a BTOS (Battery operating system or Battery oxide semiconductor).

[0314] The control circuit unit 1320 detects the terminal voltage of the secondary battery and manages the charging and discharging state of the secondary battery. For example, to prevent overcharging, both the output transistor and the cutoff switch of the charging circuit can be turned off almost simultaneously.

[0315] Furthermore, an example of a block diagram of the battery pack 1415 shown in Figure 25A is shown in Figure 25B.

[0316] The control circuit unit 1320 includes at least a switch to prevent overcharging, a switch unit 1324 including a switch to prevent over-discharging, a control circuit 1322 that controls the switch unit 1324, and a voltage measurement unit for the first battery 1301a. The control circuit unit 1320 sets upper and lower voltage limits for the secondary battery used, and limits the upper limit of external current and the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the recommended voltage range for use, and if it falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0317] The switch section 1324 can be constructed by combining n-channel and p-channel transistors. The switch section 1324 is not limited to switches using Si transistors made of single-crystal silicon, but may also be formed using power transistors made of, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (gallium oxide; x is a real number greater than 0), etc. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. Also, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost. That is, by stacking a control circuit section 1320 using OS transistors on the switch section 1324 and integrating them, it is possible to create a single chip. This allows for miniaturization as the occupied volume of the control circuit section 1320 can be reduced.

[0318] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage) onboard equipment. Lead-acid batteries are often used for the second battery 1311 due to their cost advantages. Lead-acid batteries have the disadvantage of higher self-discharge and being more susceptible to degradation due to a phenomenon called sulfation compared to lithium-ion secondary batteries. Using a lithium-ion secondary battery for the second battery 1311 offers the advantage of being maintenance-free, but after long-term use, for example more than three years, there is a risk of abnormalities occurring that could not be detected at the time of manufacture. In particular, if the second battery 1311, which starts the inverter, becomes inoperable, it will be impossible to start the motor even if the first batteries 1301a and 1301b have remaining capacity. To prevent this, if the second battery 1311 is a lead-acid battery, power is supplied from the first battery to the second battery to keep it constantly charged to a full state.

[0319] This embodiment shows an example in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311. A lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor may be used as the second battery 1311.

[0320] Furthermore, the regenerative energy from the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged the second battery 1311 via the control circuit unit 1321 from either the motor controller 1303 or the battery controller 1302, or from the battery controller 1302 via the control circuit unit 1320. Alternatively, the first battery 1301a is charged from the battery controller 1302 via the control circuit unit 1320, or from the battery controller 1302 to the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0321] The battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b. The battery controller 1302 can set the charging conditions according to the charging characteristics of the secondary battery being used and enable rapid charging.

[0322] Although not shown in the diagram, when connected to an external charger, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some chargers, a control circuit is provided, and the functions of the battery controller 1302 may not be used, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the charger's outlet or connection cable may also have a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. In addition, a CPU or GPU is used as the ECU.

[0323] Next, we will describe an example in which a secondary battery, which is one aspect of the present invention, is implemented in a vehicle, typically a transport vehicle.

[0324] Furthermore, by mounting the secondary battery shown in either Figure 20D or Figure 25A onto a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV) can be realized. Secondary batteries can also be mounted on agricultural machinery, motorized bicycles including electric-assist bicycles, motorcycles, electric wheelchairs, electric carts, small or large vessels, submarines, aircraft such as fixed-wing or rotary-wing aircraft, rockets, satellites, space probes or planetary probes, and other transport vehicles. A secondary battery according to one embodiment of the present invention can be a high-capacity secondary battery. Therefore, a secondary battery according to one embodiment of the present invention is suitable for miniaturization and weight reduction, and can be suitably used in transport vehicles.

[0325] Figures 26A to 26D illustrate a transport vehicle using one embodiment of the present invention. The automobile 2001 shown in Figure 26A is an electric vehicle that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as power sources for driving. When a secondary battery is mounted on the vehicle, one or more examples of the secondary battery shown in Embodiment 4 are installed in one location. The automobile 2001 shown in Figure 26A has a battery pack 2200, and the battery pack has a secondary battery module in which multiple secondary batteries are connected. Furthermore, it is preferable to have a charging control device electrically connected to the secondary battery module.

[0326] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via one or more methods, such as a plug-in method and a contactless power supply method, to the secondary battery of the automobile 2001. When charging, the charging method and connector specifications may be carried out as appropriate using a prescribed method such as CHAdeMO (registered trademark) or Combo. The secondary battery may be a charging station installed in a commercial facility or a household power supply. For example, the secondary battery installed in the automobile 2001 can be charged by supplying power from an external source using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC / DC converter.

[0327] Although not shown in the diagram, the vehicle can also be charged by mounting a power receiving device on the vehicle and supplying power wirelessly from a ground-based power transmission device. In this wireless power supply method, by incorporating power transmission devices into one or both of the road and / or a wall, charging can be performed not only when the vehicle is stopped but also while it is in motion. Furthermore, this wireless power supply method can be used to transmit and receive power between two vehicles. In addition, solar panels can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or in motion. For such wireless power supply, one or more of the electromagnetic induction method and the magnetic resonance method can be used.

[0328] Figure 26B shows a large transport vehicle 2002 equipped with an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 has a maximum voltage of 170V, achieved by connecting 48 cells in series, each consisting of four secondary batteries with a voltage of 3.5V to 4.7V. The secondary battery module of the battery pack 2201 has the same functions as Figure 26A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0329] Figure 26C shows, as an example, a large transport vehicle 2003 equipped with an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V, achieved by connecting more than 100 secondary batteries with voltages between 3.5V and 4.7V in series. Therefore, secondary batteries with small variation in characteristics are required. By using a secondary battery with the negative electrode structure described in Embodiment 1, that is, a structure in which an electrolyte containing fluorine is contained within the negative electrode, it is possible to manufacture secondary batteries with stable battery characteristics, enabling low-cost mass production from a yield standpoint. Furthermore, since it has the same functions as Figure 26A except for differences in the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the explanation is omitted.

[0330] Figure 26D shows an aircraft 2004 having a fuel-burning engine as an example. The aircraft 2004 shown in Figure 26D has wheels for takeoff and landing, and can therefore be considered part of a transport vehicle. It has a battery pack 2203 which includes a secondary battery module formed by connecting multiple secondary batteries and a charging control device.

[0331] The secondary battery module of aircraft 2004 has a maximum voltage of 32V, for example, by connecting eight 4V secondary batteries in series. The secondary battery module of battery pack 2203 has the same functionality as Figure 26A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0332] This embodiment can be used in appropriate combination with other embodiments.

[0333] (Embodiment 5) In this embodiment, an example of implementing a secondary battery, which is one aspect of the present invention, in a building will be explained using Figures 27A and 27B.

[0334] The house shown in Figure 27A has a power storage device 2612 having a secondary battery, which is one embodiment of the present invention, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611, etc. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The electricity obtained from the solar panel 2610 can be used to charge the power storage device 2612. The electricity stored in the power storage device 2612 can be used to charge the secondary battery of the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space above the floor can be used effectively. Alternatively, the power storage device 2612 may be installed on the floor.

[0335] The electricity stored in the energy storage device 2612 can also supply power to other electronic devices in the house. Therefore, even when power cannot be supplied from the commercial power source due to a power outage or the like, electronic devices can be used by using the energy storage device 2612 according to one aspect of the present invention as an uninterruptible power supply.

[0336] Figure 27B shows an example of an energy storage device 700 according to one aspect of the present invention. As shown in Figure 27B, an energy storage device 791 according to one aspect of the present invention is installed in the underfloor space 796 of the building 799.

[0337] The energy storage device 791 is equipped with a control device 790, which is electrically connected by wiring to the distribution board 703, the energy storage controller 705 (also called the control device), the display unit 706, and the router 709.

[0338] Power is supplied from the commercial power supply 701 to the distribution panel 703 via the service drop connection section 710. Power is also supplied to the distribution panel 703 from the energy storage device 791 and the commercial power supply 701, and the distribution panel 703 supplies the supplied power to the general load 707 and the energy storage system load 708 via outlets (not shown).

[0339] General loads 707 are electronic devices such as televisions and personal computers, while energy storage loads 708 are electronic devices such as microwave ovens, refrigerators, and air conditioners.

[0340] The energy storage controller 705 includes a measurement unit 711, a prediction unit 712, and a planning unit 713. The measurement unit 711 has the function of measuring the amount of electricity consumed by the general load 707 and the energy storage system load 708 during a day (for example, from 0:00 to 24:00). The measurement unit 711 may also have the function of measuring the amount of electricity consumed by the energy storage device 791 and the amount of electricity supplied from the commercial power supply 701. The prediction unit 712 has the function of predicting the amount of electricity demanded by the general load 707 and the energy storage system load 708 during the next day, based on the amount of electricity consumed by the general load 707 and the energy storage system load 708 during the day. The planning unit 713 has the function of planning the charging and discharging of the energy storage device 791 based on the amount of electricity demand predicted by the prediction unit 712.

[0341] The amount of electricity consumed by the general load 707 and the energy storage system load 708, as measured by the measurement unit 711, can be checked on the display unit 706. It can also be checked on electronic devices such as televisions or personal computers via the router 709. Furthermore, it can be checked on mobile electronic devices such as smartphones or tablets via the router 709. Additionally, the amount of electricity demand predicted by the forecasting unit 712 for each time period (or hourly) can be checked on the display unit 706, electronic devices, and mobile electronic devices.

[0342] This embodiment can be used in appropriate combination with other embodiments.

[0343] (Embodiment 6) This embodiment describes an example of mounting a secondary battery, which is one aspect of the present invention, in an electronic device. Examples of electronic devices on which a secondary battery is mounted include television equipment (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, personal information terminals, sound playback devices, and large game machines such as pachinko machines. Personal information terminals include notebook personal computers, tablet terminals, e-books, and mobile phones.

[0344] Figure 28A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into the housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also has a secondary battery 2107. By incorporating the secondary battery 2107 using the negative electrode structure shown in Embodiment 1, that is, a structure in which a fluorine-containing electrolyte is contained within the negative electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0345] The mobile phone 2100 can run various applications such as making phone calls, sending emails, reading and creating documents, playing music, communicating on the internet, and playing computer games.

[0346] The operation button 2103 can be assigned various functions, including time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, and power saving mode activation / deactivation. For example, the function of the operation button 2103 can be freely configured by the operating system built into the mobile phone 2100.

[0347] Furthermore, the 2100 mobile phone is capable of performing standardized short-range wireless communication. For example, it can communicate with a wireless headset to enable hands-free calling.

[0348] Furthermore, the mobile phone 2100 is equipped with an external connection port 2104, which allows for direct data exchange with other information terminals via a connector. It can also be charged via the external connection port 2104. Note that charging may also be performed wirelessly without using the external connection port 2104.

[0349] The mobile phone 2100 preferably has sensors. Preferably, one or more sensors selected from, for example, a fingerprint sensor, a pulse sensor, and a body temperature sensor, a touch sensor, a pressure sensor, and an acceleration sensor, are installed.

[0350] Figure 28B shows an unmanned aerial vehicle 2300 having multiple rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 has a secondary battery 2301, a camera 2303, and an antenna (not shown), which are embodiments of the present invention. The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. The secondary battery using the negative electrode structure shown in Embodiment 1, that is, a structure having a fluorine-containing electrolyte in the negative electrode, has a high energy density and high safety, so it can be used safely for long periods of time over a long period of time and is suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0351] Figure 28C shows an example of a robot. The robot 6400 shown in Figure 28C is equipped with 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 and an obstacle sensor 6407, a movement mechanism 6408, a computing device, and the like.

[0352] Microphone 6402 has the function of detecting the user's voice and ambient sounds. Speaker 6404 has the function of emitting sound. Robot 6400 can communicate with the user using microphone 6402 and speaker 6404.

[0353] The display unit 6405 has the function of displaying various types of information. The robot 6400 can display the information desired by the user on the display unit 6405. The display unit 6405 may be equipped with a touch panel. The display unit 6405 may also be a detachable information terminal, and by installing it in a fixed position on the robot 6400, charging and data transfer can be made possible.

[0354] The upper camera 6403 and lower camera 6406 have the function of imaging the area around the robot 6400. In addition, the obstacle sensor 6407 can detect the presence or absence of obstacles in the direction of travel when the robot 6400 moves forward using the movement mechanism 6408. The robot 6400 can recognize its surrounding environment and move safely using the upper camera 6403, lower camera 6406 and obstacle sensor 6407.

[0355] The robot 6400 is equipped with a secondary battery 6409 according to one aspect of the present invention and a semiconductor device or electronic components in its internal region. The secondary battery using the negative electrode structure shown in Embodiment 1, that is, a structure having a fluorine-containing electrolyte in the negative electrode, has a high energy density and high safety, so it can be used safely for a long period of time over a long period of time and is suitable as the secondary battery 6409 to be mounted on the robot 6400.

[0356] Figure 28D shows an example of a cleaning robot. The cleaning robot 6300 has a display unit 6302 located on the top surface of the housing 6301, multiple cameras 6303 located on the sides, a brush 6304, operation buttons 6305, a secondary battery 6306, and various sensors. Although not shown, the cleaning robot 6300 is equipped with wheels, a suction port, etc. The cleaning robot 6300 is self-propelled, can detect dirt 6310, and can suck up the dirt from a suction port located on the bottom surface.

[0357] For example, the cleaning robot 6300 can analyze images captured by the camera 6303 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if the image analysis detects an object that could become entangled in the brush 6304, such as wiring, the rotation of the brush 6304 can be stopped. The cleaning robot 6300 is equipped with a secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or electronic component within its internal region. The secondary battery using the negative electrode structure shown in Embodiment 1, that is, a structure having a fluorine-containing electrolyte in the negative electrode, has high energy density and high safety, allowing for safe use over long periods of time, making it suitable as a secondary battery 6306 for the cleaning robot 6300.

[0358] This embodiment can be implemented in appropriate combination with other embodiments.

[0359] (Notes regarding the descriptions in this specification, etc.) Furthermore, in this specification, crystal planes and directions are indicated by Miller indices. In crystallography, crystal planes and directions are indicated by a superscript bar above the number, but in this specification, due to limitations in patent application notation, a minus sign (-) may be placed before the number instead of a bar above it. In addition, individual orientations indicating directions within a crystal are indicated by [ ], collective orientations indicating all equivalent directions are indicated by < >, individual planes indicating crystal planes are indicated by ( ), and collective planes having equivalent symmetry are indicated by {}.

[0360] In this specification, segregation refers to the phenomenon in which a certain element (e.g., B) is spatially non-uniformly distributed in a solid composed of multiple elements (e.g., A, B, C).

[0361] In this specification, the surface layer of particles such as active material is preferably a region within 50 nm from the surface, more preferably within 35 nm, and even more preferably within 20 nm. Surfaces formed by cracks or fissures may also be considered the surface. The region deeper than the surface layer is referred to as the interior.

[0362] In this specification, the layered rock salt crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, thereby enabling two-dimensional diffusion of lithium. Defects such as vacancies in cations or anions may be present. Furthermore, strictly speaking, a layered rock salt crystal structure may have a distorted lattice structure of the rock salt crystal.

[0363] In this specification, a rock salt-type crystal structure refers to a structure in which cations and anions are arranged alternately. However, deficiencies in cations or anions are acceptable.

[0364] Furthermore, in this specification, the O3' type crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure with a space group R-3m, which is not a spinel type crystal structure, but in which ions such as cobalt and magnesium occupy the oxygen 6-coordinate positions, and the arrangement of cations has a symmetry similar to that of a spinel type.

[0365] The general agreement of crystal orientation between two regions can be determined from TEM (transmission electron microscope) images, STEM (scanning transmission electron microscope) images, HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) images, ABF-STEM (annular bright-field scanning transmission electron microscope) images, etc. X-ray diffraction (XRD), electron diffraction, neutron diffraction, etc. can also be used as a basis for determination. In TEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientation of the cubic close-packed structure is aligned in layered rock salt crystals and rock salt crystals, it can be observed that the angle between the repetition of bright and dark lines between crystals is 5 degrees or less, more preferably 2.5 degrees or less. Note that light elements such as oxygen and fluorine may not be clearly visible in TEM images, etc., but in such cases, the agreement of orientation can be determined from the arrangement of metallic elements.

[0366] Furthermore, in this specification, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all of the insertable and detachable lithium present in the positive electrode active material has been detached. 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.

[0367] Furthermore, in this specification, the charging depth when all insertable and detachable lithium is inserted is defined as 0, and the charging depth when all insertable and detachable lithium in the positive electrode active material has been detached is defined as 1.

[0368] In this specification, charging refers to the movement of lithium ions from the positive electrode to the negative electrode within the battery, and the movement of electrons from the positive electrode to the negative electrode in the external circuit. For positive electrode active material, the release of lithium ions is referred to as charging. Furthermore, positive electrode active material with a charging depth of 0.7 to 0.9 may be referred to as positive electrode active material charged with high voltage.

[0369] Similarly, discharge refers to the movement of lithium ions from the negative electrode to the positive electrode within the battery, and the movement of electrons from the negative electrode to the positive electrode in the external circuit. For positive electrode active materials, the insertion of lithium ions is called discharge. Furthermore, a positive electrode active material with a charge depth of 0.06 or less, or a positive electrode active material that has been discharged to 90% or more of its charge capacity from a state where it was charged at a high voltage, is considered a sufficiently discharged positive electrode active material.

[0370] Furthermore, in this specification, a non-equilibrium phase change refers to a phenomenon that causes a nonlinear change in a physical quantity. For example, a non-equilibrium phase change is thought to occur around the peak in the dQ / dV curve obtained by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV), indicating a significant change in the crystal structure.

[0371] A secondary battery has, for example, a positive electrode and a negative electrode. The positive electrode is composed of a positive electrode active material. The positive electrode active material is, for example, a substance that performs a reaction that contributes to the charge and discharge capacity. However, the positive electrode active material may also contain a portion of substances that do not contribute to the charge and discharge capacity.

[0372] In this specification, the positive electrode active material of one aspect of the present invention may be expressed as a positive electrode material, a positive electrode material for secondary batteries, etc. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a compound. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composition. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composite.

[0373] The discharge rate is the relative ratio of the discharge current to the battery capacity, and is expressed in units of C. For a battery with a rated capacity of X (Ah), the current equivalent to 1C is X (A). If the battery is discharged with a current of 2X (A), it is said to have been discharged at 2C, and if it is discharged with a current of X / 5 (A), it is said to have been discharged at 0.2C. Similarly, the charge rate is also expressed in the same way: if the battery is charged with a current of 2X (A), it is said to have been charged at 2C, and if it is charged with a current of X / 5 (A), it is said to have been charged at 0.2C.

[0374] Constant current charging refers to a method of charging while maintaining a constant charging rate. Constant voltage charging refers to a method of charging while maintaining a constant voltage once the upper voltage limit is reached. Constant current discharging refers to a method of discharging while maintaining a constant discharge rate. [Explanation of symbols]

[0375] :201: Electrode, 202: Graphene compound, 204: Hole, 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: Ring-shaped 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 casing 510: Positive lead electrode, 511: Negative lead electrode, 570: Electrode, 570a: Negative electrode, 570b: Positive electrode, 571: Current collector, 571a: Negative current collector, 571b: Positive current collector, 572: Active material layer, 572a: Negative active material layer, 572b: Positive active material layer, 576: Electrolyte, 581: Electrolyte, 582: Active material, 583: Graphene compound, 584: Acetylene black (AB), 601: Positive cap, 602: Battery can, 603: Positive terminal, 604: Positive electrode, 605: Separator, 606: Negative electrode, 607: Negative terminal, 608: Insulating plate, 609: Insulating plate, 611: PT C element, 613: Safety valve mechanism, 614: Conductive plate, 615: Energy 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: Energy storage device, 701: Commercial power supply, 703: Distribution board, 705: Energy storage controller, 706: Display unit, 707: General load, 708: Energy storage system load, 709: Router, 710: Service drop mounting section, 711: Measurement section, 712: Prediction section, 713: Planning section, 790: Control device, 791: Energy storage device, 796: Underfloor space section, 7 99: Building, 811: Positive electrode active material, 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: Rectangular secondary battery, 1301a: Battery, 1301b: Battery, 1302: Battery controller, 1303: Motor controller, 1304: Motor, 1305: Gear, 1306: DC-DC circuit, 1307: Electric power steering,1308: Heater, 1309: Defogger, 1310: DC-DC circuit, 1311: Battery, 1312: Inverter, 1313: Audio, 1314: Power windows, 1315: Lights, 1316: Tires, 1317: Rear motor, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1325: External terminals, 1326: External terminal, 1413: Fixing part, 1414: Fixing part, 1415: Battery pack, 1421: Wiring, 1422: Wiring, 2001: Automobile, 2002: Transport vehicle, 2003: Transport vehicle, 2004: Aircraft, 2100: Mobile phone, 2101: Housing, 2102: Display unit, 2103: Operation buttons, 2104: External connection port, 2105: Speaker, 2106: Microphone, 2107: Rechargeable battery, 2200: Battery pack, 2201: Battery pack, 2202: Battery pack, 2203: Battery pack, 2300: Unmanned aerial vehicle, 2301: Rechargeable battery, 2302: Rotor, 2303: Camera, 2603: Vehicle, 2604: Charging device, 2610: Solar panel, 2611: Wiring, 2612: Energy storage device, 6300: Cleaning robot, 6301: Enclosure, 6302: Display unit, 6303: Camera, 6304: Brush, 6305: Operation button, 6306: Rechargeable battery, 6310: Dust, 6400: Robot, 6401: Illuminance sensor, 6402: Microphone, 6403: Upper camera, 6404: Speaker, 6405: Display unit, 6406: Lower camera, 6407: Obstacle sensor, 6408: Movement mechanism, 6409: Rechargeable battery,

Claims

1. A carbon material having a graphene compound with pores, The aforementioned hole is A cyclic region composed of multiple carbon atoms, It comprises one or more fluorine atoms terminated in the cyclic region, The aforementioned annular region is, It has 18 or more members in the ring, A carbon material in which, when measured by X-ray photoelectron spectroscopy, the concentration of fluorine is 1 atomic percent or more relative to the sum of the concentrations of fluorine, oxygen, lithium, and carbon.

2. A carbon material having a graphene compound in a sheet-like shape, The graphene compound has pores, The aforementioned hole is A cyclic region composed of multiple carbon atoms, It comprises one or more fluorine atoms terminated in the cyclic region, The aforementioned annular region is, It has 18 or more members in the ring, A carbon material in which, when measured by X-ray photoelectron spectroscopy, the concentration of fluorine is 1 atomic percent or more relative to the sum of the concentrations of fluorine, oxygen, lithium, and carbon.

Images