Positive electrode and method for manufacturing positive electrode

Abstract

Provided are a positive electrode having a high active material density, and a method for manufacturing a positive electrode having a high active material density. The positive electrode contains: a plurality of lithium iron phosphate particles having a median diameter D50 in a particle size distribution of 300 nm-3 μm or less; and a plurality of lithium manganese iron phosphate particles having a median diameter D50 in a particle size distribution of 30-100 nm. The lithium manganese iron phosphate particles are represented by LiMn1-xFexPO4, where x is a number greater than 0 and smaller than 0.5.

Description

Positive electrode, method for manufacturing the positive electrode

[0001] One aspect of the present invention relates to a secondary battery. Another aspect of the present invention relates to a positive electrode of a secondary battery. Another aspect of the present invention relates to a positive electrode active material of a secondary battery. The present invention is not limited to the above fields, but also relates to semiconductor devices, display devices, light-emitting devices, energy storage devices, lighting devices, electronic devices, vehicles, and methods for manufacturing the same. The above-mentioned semiconductor devices, display devices, light-emitting devices, energy storage devices, lighting devices, electronic devices, and vehicles can be supplied with the secondary battery of the present invention as a necessary power source. For example, the above-mentioned electronic devices include information terminal devices equipped with a secondary battery. Furthermore, the above-mentioned energy storage devices include stationary energy storage devices.

[0002] In recent years, demand for high-power, high-capacity lithium-ion rechargeable batteries (also known as lithium-ion batteries) has expanded rapidly, and they have become an indispensable energy source for modern society as a reusable energy source.

[0003] To increase the capacity of lithium-ion secondary batteries, research is underway on increasing the capacity of the active material and increasing the density of the positive electrode active material layer (Patent Document 1).

[0004] WO2024 / 150082

[0005] One aspect of the present invention aims to provide a positive electrode with a high active material density, or a positive electrode with a low porosity, or a positive electrode for a secondary battery with high capacity and excellent charge-discharge cycle characteristics, or a positive electrode for a secondary battery with high capacity, or a positive electrode for a secondary battery with excellent charge-discharge cycle characteristics, or a positive electrode for a secondary battery with high capacity, or a positive electrode for a secondary battery with excellent charge-discharge characteristics, or a positive electrode for a secondary battery with high safety or reliability.

[0006] One aspect of the present invention aims to provide a method for producing a positive electrode with a high active material density. Alternatively, it aims to provide a method for producing a positive electrode with a low porosity. Alternatively, it aims to provide a method for producing a positive electrode for a secondary battery with high capacity and excellent charge-discharge cycle characteristics. Alternatively, one aspect of the present invention aims to provide a method for producing a high-capacity secondary battery. Alternatively, one aspect of the present invention aims to provide a method for producing a secondary battery with excellent charge-discharge characteristics. Alternatively, one aspect of the present invention aims to provide a method for producing a secondary battery that is safe or highly reliable.

[0007] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. It is possible to extract other problems from the description, drawings, and claims.

[0008] (1) One aspect of the present invention is a positive electrode comprising a plurality of lithium iron phosphate particles and a plurality of manganese iron lithium phosphate particles, wherein the median diameter D50 in the particle size distribution of the plurality of lithium iron phosphate particles is 300 nm or more and 3 μm or less, the median diameter D50 in the particle size distribution of the plurality of manganese iron lithium phosphate particles is 30 nm or more and 100 nm or less, and the total weight of the plurality of lithium iron phosphate particles is 70% or more of the total weight of the plurality of lithium iron phosphate particles and the plurality of manganese iron lithium phosphate particles.

[0009] (2) Alternatively, one aspect of the present invention is a positive electrode comprising a plurality of lithium iron phosphate particles and a plurality of manganese iron lithium phosphate particles, wherein the median diameter D50 in the particle size distribution of the plurality of lithium iron phosphate particles is 300 nm or more and 3 μm or less, the median diameter D50 in the particle size distribution of the plurality of manganese iron lithium phosphate particles is 30 nm or more and 100 nm or less, and the total weight of the plurality of manganese iron lithium phosphate particles is 70% or more of the total weight of the plurality of lithium iron phosphate particles and the plurality of manganese iron lithium phosphate particles.

[0010] (3) In (1) or (2) above, the lithium iron manganese phosphate particles are LiMn１−ｘ Fe ｘ PO ４ It is expressed as such, and it is preferable that x is a number greater than 0 and less than 0.5.

[0011] (4) In (3) above, it is preferable that each of the multiple lithium iron phosphate particles and the multiple lithium manganese iron phosphate particles each have a carbon coating layer.

[0012] (5) Or, in (3) above, it is preferable that there is a region in which one of the plurality of lithium iron phosphate particles and one of the plurality of lithium manganese iron phosphate particles are connected by a carbon coating layer.

[0013] (6) One aspect of the present invention is a method for producing a positive electrode, comprising the steps of: mixing lithium iron phosphate, lithium manganese iron phosphate, and a compound having carbon to produce a mixture; heating the mixture at a temperature of 600°C to 700°C for 2 to 20 hours to produce a carbon-coated composite; mixing the carbon-coated composite, a conductive material, a binder, and a solvent to produce a slurry; applying the slurry to aluminum foil; and removing the solvent.

[0014] (7) In (6) above, LiMn １−ｘ Fe ｘ PO ４ It is expressed as such, and it is preferable that x is a number greater than 0 and less than 0.5.

[0015] According to one aspect of the present invention, one aspect of the present invention can provide a positive electrode with a high active material density, or a positive electrode with a low porosity, or a positive electrode for a secondary battery with high capacity and excellent charge-discharge cycle characteristics, or one aspect of the present invention can provide a high-capacity secondary battery, or one aspect of the present invention can provide a secondary battery with excellent charge-discharge characteristics, or one aspect of the present invention can provide a safe or reliable secondary battery.

[0016] According to one aspect of the present invention, one aspect of the present invention can provide a method for producing a positive electrode with a high active material density. Alternatively, one aspect of the present invention can provide a method for producing a positive electrode with a low porosity. Alternatively, one aspect of the present invention can provide a method for producing a positive electrode for a secondary battery with high capacity and excellent charge-discharge cycle characteristics. Alternatively, one aspect of the present invention can provide a method for producing a high-capacity secondary battery. Alternatively, one aspect of the present invention can provide a method for producing a secondary battery with excellent charge-discharge characteristics. Alternatively, one aspect of the present invention can provide a method for producing a secondary battery that is safe or highly reliable.

[0017] 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.

[0018] Figure 1A is a cross-sectional view illustrating the internal structure of a secondary battery, Figure 1B is a cross-sectional view illustrating the positive electrode and electrolyte of a secondary battery, and Figure 1C is a cross-sectional view illustrating the positive electrode active material. Figure 2 is a diagram illustrating the method of manufacturing the positive electrode. Figure 3 is a diagram illustrating the method of manufacturing the positive electrode. Figure 4 is a diagram illustrating the method of manufacturing the positive electrode active material. Figure 5 is a diagram illustrating the method of manufacturing the positive electrode active material. Figure 6A is an exploded perspective view of a coin-type secondary battery, Figure 6B is a perspective view of a coin-type secondary battery, and Figure 6C is a cross-sectional perspective view thereof. Figure 7A shows an example of a cylindrical secondary battery. Figure 7B shows an example of a cylindrical secondary battery. Figure 7C shows an example of multiple cylindrical secondary batteries. Figure 7D shows an example of an energy storage system having multiple cylindrical secondary batteries. Figures 8A and 8B are diagrams illustrating examples of secondary batteries, and Figure 8C is a diagram showing the inside of a secondary battery. Figures 9A, 9B, and 9C are diagrams illustrating examples of secondary batteries. Figures 10A and 10B show the external appearance of a secondary battery. Figures 11A, 11B, and 11C illustrate a method for manufacturing a secondary battery. Figure 12A shows an example of a battery pack configuration, Figure 12B shows an example of a battery pack configuration, and Figure 12C shows an example of a battery pack configuration. Figure 13A is a perspective view of a battery pack showing one aspect of the present invention, Figure 13B is a block diagram of the battery pack, and Figure 13C is a block diagram of a vehicle having a battery pack. Figures 14A, 14B, 14C, and 14D illustrate an example of a transport vehicle. Figure 14E illustrates an example of an artificial satellite. Figures 15A and 15B illustrate an energy storage device according to one aspect of the present invention. Figure 16A shows an electric bicycle, Figure 16B shows a secondary battery for an electric bicycle, and Figure 16C illustrates a scooter. Figures 17A, 17B, 17C, and 17D illustrate an example of an electronic device. Figure 18A shows an example of a wearable device, Figure 18B shows a perspective view of a wristwatch-type device, and Figure 18C illustrates a side view of a wristwatch-type device.

[0019] The following describes embodiments for carrying out the present invention with reference to drawings and other illustrations. However, the present invention is not limited to the following embodiments. It is possible to modify the embodiments for carrying out the invention without departing from the spirit of the present invention.

[0020] The positions, sizes, and ranges of each component shown in the drawings may not represent their actual positions, sizes, and ranges in order to facilitate understanding. Furthermore, some components may be omitted from the drawings to avoid clutter. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings.

[0021] In this specification, the ordinal numbers "first," "second," etc., are used for convenience only and do not limit the number of components or the order of components (for example, process order or stacking order). Also, the ordinal numbers attached to components in one part of this specification may not be the same as the ordinal numbers attached to those components in other parts of this specification or in the claims.

[0022] In this specification, the term "particle" is not limited to spherical shapes (circular cross-sections), but may also refer to individual particles with elliptical, rectangular, trapezoidal, triangular, rounded quadrilateral, or asymmetrical cross-sections, and individual particles may also have irregular shapes.

[0023] In this specification, a lithium-ion secondary battery refers to a battery that uses lithium ions as carrier ions; however, the carrier ions in this invention are not limited to lithium ions. For example, alkali metal ions or alkaline earth metal ions can be used as carrier ions in this invention, and specifically, sodium ions, etc., can be applied. In this case, the present invention can be understood by substituting sodium ions, etc., for lithium ions. Furthermore, when there are no limitations on the carrier ions, the term "secondary battery" may be used.

[0024] In this specification, secondary particles refer to particles formed by the aggregation of primary particles. Primary particles refer to particles that do not have visible grain boundaries. Single particles refer to particles that do not have visible grain boundaries. Single crystals refer to crystals in which grain boundaries do not exist within the particles, while polycrystalline crystals refer to crystals in which grain boundaries exist within the particles. Polycrystalline crystals can also be described as aggregates of multiple crystallites, and grain boundaries can be described as interfaces between two or more crystallites. In polycrystalline crystals, it is preferable that the orientation of the crystallites is aligned.

[0025] In this specification, the phrase "A and / or B" may be used, but this is just one example of how A alone, B alone, or A and B may be included.

[0026] (Embodiment 1) This embodiment describes a battery according to one aspect of the present invention.

[0027] [Battery] A battery according to one aspect of the present invention comprises a positive electrode, a negative electrode, and an electrolyte. If the electrolyte contains an electrolyte solution, a separator is provided between the positive electrode and the negative electrode. Furthermore, an outer casing is provided to surround the positive electrode, the negative electrode, and the electrolyte.

[0028] This embodiment primarily describes the positive electrode and positive electrode active material of a battery according to one aspect of the present invention. The method for producing the positive electrode active material of the battery is described in Embodiment 2, and the details of the remaining components of the lithium-ion battery according to one aspect of the present invention are described in Embodiment 3.

[0029] Figure 1A is a schematic cross-sectional view illustrating the internal structure of a lithium-ion battery 10. The lithium-ion battery 10 has a positive electrode 11, a negative electrode 12, and a separator 13. The positive electrode 11 has a positive electrode current collector 21 and a positive electrode active material layer 22 on the positive electrode current collector 21, and the negative electrode 12 has a negative electrode current collector 31 and a negative electrode active material layer 32. As shown in the figure, the positive electrode active material layer 22 and the negative electrode active material layer 32 face each other with the separator 13 in between. Although not shown in Figure 1A, the electrolyte is contained in the voids of the positive electrode active material layer 22, the voids of the separator 13, and the voids of the negative electrode active material layer 32.

[0030] Although Figure 1A shows one positive electrode 11, one negative electrode 12, and one separator 13, the lithium-ion battery according to one embodiment of the present invention is not limited to this structure. It may also have a structure with two positive electrodes 11, two negative electrodes 12, and two separators 13, and even more electrodes may be stacked. Furthermore, instead of the stacked structure shown in Figure 1A, a wound structure may also be used.

[0031] Figure 1B is an enlarged view of area A, which is enclosed by a dashed line in Figure 1A.

[0032] The positive electrode active material layer 22 comprises a first positive electrode active material 100, a second positive electrode active material 200, and a conductive material 41. Although not shown in the figures, in addition to the first positive electrode active material 100, the second positive electrode active material 200, and the conductive material 41, it may also have a binder.

[0033] Furthermore, the voids in the positive electrode active material layer 22 are preferably filled with electrolyte 51, as shown in the figure. For example, it is preferable that 60% or more of the voids in the positive electrode active material layer 22 are filled with electrolyte 51, more preferably 70% or more, more preferably 80% or more, more preferably 90% or more, more preferably 95% or more, and most preferably 99% or more. Note that the voids in the positive electrode active material layer 22 refer to the regions in the positive electrode active material layer 22 other than the solid components (positive electrode active material, conductive material, etc.).

[0034] [Positive Electrode] The positive electrode 11 has a positive electrode current collector 21 and a positive electrode active material layer 22, and the positive electrode active material layer 22 has positive electrode active material. The positive electrode active material in the positive electrode active material layer 22 is a particle group having a plurality of first particles and a plurality of second particles. In other words, the positive electrode active material layer 22 has a first positive electrode active material 100 as a plurality of first particles and a second positive electrode active material 200 as a plurality of second particles. Alternatively, the positive electrode active material in the positive electrode active material layer 22 can be said to be a particle group in which the first positive electrode active material 100 and the second positive electrode active material 200 are mixed.

[0035] The particle size of the first positive electrode active material 100 is preferably larger than the particle size of the second positive electrode active material 200. Specifically, the particle size of the first positive electrode active material 100 (median diameter D50 in the particle size distribution) is preferably 3 to 100 times larger than the particle size of the second particle, and more preferably 3 to 10 times larger.

[0036] A laser diffraction particle size analyzer can be used to measure particle size. However, if the sample contains many particles smaller than 1 μm, the major axis of the particle cross-section may be measured by analysis using an SEM (Scanning Electron Microscope) or TEM. As a method for measuring D50 from analysis using an SEM or TEM, for example, 20 or more particles can be measured, a cumulative curve can be created, and the particle size at which the cumulative amount accounts for 50% can be defined as D50. Similarly, D10 is the particle size at which the cumulative amount accounts for 10% in the cumulative curve of the particle size distribution measurement results, and D90 is the particle size at which the cumulative amount accounts for 90% in the cumulative curve of the particle size distribution measurement results.

[0037] <First Positive Electrode Active Material> The first positive electrode active material 100 has the function of taking in and releasing lithium ions during charging and discharging. The first positive electrode active material 100 used in one aspect of the present invention can be made of a material with excellent charge / discharge capacity, high safety and reliability. As the first positive electrode active material 100, for example, lithium iron phosphate (LiFePO) obtained by the method for producing the positive electrode active material described in Embodiment 2 may be used. ４ ) can be used. In other words, a plurality of lithium iron phosphate particles (also called a group of lithium iron phosphate particles) can be used as the first positive electrode active material 100. The median diameter D50 of the first positive electrode active material 100 is preferably 100 nm or more and 10 μm or less, and more preferably 300 nm or more and 3 μm or less. Furthermore, it is preferable that the first positive electrode active material 100 has a carbon coating layer on its particle surface by performing a carbon coating treatment.

[0038] <Second Positive Electrode Active Material> Similar to the first positive electrode active material 100, the second positive electrode active material 200 has a function of taking in lithium ions and a function of releasing them in association with charge and discharge. As a mode of the present invention, the second positive electrode active material 200 can use a material having a high charge-discharge voltage, high safety, and high reliability. For example, as the second positive electrode active material 200, lithium manganese iron phosphate (LiMn １−ｘ Fe ｘ PO ４ , where x is a number greater than 0 and less than 0.5) can be used. In other words, a plurality of lithium manganese iron phosphate particles (also referred to as a particle group of lithium manganese iron phosphate) can be used as the second positive electrode active material 200. The median diameter D50 of the second positive electrode active material 200 is preferably 10 nm or more and 300 nm or less, and more preferably 30 nm or more and 100 nm or less. Further, it is preferable that the second positive electrode active material 200 has a carbon coating layer on the surface of its particles by performing a carbon coating treatment.

[0039] Furthermore, the first positive electrode active material 100 and the second positive electrode active material 200 may each have their own carbon coating layer, but as shown in Figure 1C, they may also have a shared carbon coating layer. Specifically, the first positive electrode active material 100 and the second positive electrode active material 200 may have a region (also called an integrated region, a connected region, etc.) to which they are connected by the carbon coating layer 150. Specifically, one of a plurality of lithium iron phosphate particles and one of a plurality of lithium manganese iron phosphate particles may have a region to which they are connected by the carbon coating layer 150. Also, although Figure 1C shows a configuration in which one first positive electrode active material 100 and one second positive electrode active material 200 are connected by the carbon coating layer 150, the configuration is not limited to this, and one or both of the first positive electrode active material 100 and the second positive electrode active material 200 may be multiple. A positive electrode active material having a first positive electrode active material 100 and a second positive electrode active material 200 connected by the carbon coating layer 150 described above can be called a carbon-coated composite. The carbon coating layer is preferably 1 nm to 100 nm, more preferably 1 nm to 10 nm, and even more preferably 1 nm to 5 nm.

[0040] When a particle group in which the first positive electrode active material 100 and the second positive electrode active material 200 are mixed is used in the positive electrode active material layer 22, the density in the positive electrode active material layer 22 is (g / cm³). ３ This is preferable because it improves [the following].

[0041] Furthermore, when prioritizing charge-discharge cycle characteristics for the lithium-ion battery 10, it is preferable to use the first positive electrode active material 100 as the main constituent material of the positive electrode active material layer 22. It is preferable that the weight of the first positive electrode active material 100 accounts for 50% or more of the total weight of the positive electrode active material in the positive electrode active material layer 22, more preferably 60% or more, and even more preferably 70% or more. Specifically, for example, when using a mixture of multiple lithium iron phosphate particles (first positive electrode active material 100) and multiple lithium manganese iron phosphate particles (second positive electrode active material 200), it is preferable that the total weight of the multiple lithium iron phosphate particles accounts for 50% or more of the total weight of the multiple lithium iron phosphate particles and the multiple lithium manganese iron phosphate particles, more preferably 60% or more, and even more preferably 70% or more. In this case, a battery with a high density of the positive electrode active material layer 22 and high charge-discharge cycle characteristics can be obtained.

[0042] Alternatively, when output characteristics are important for the lithium-ion battery 10, it is preferable to use the second positive electrode active material 200 as the main constituent material of the positive electrode active material layer 22, and it is preferable that the weight of the second positive electrode active material 200 accounts for 50% or more of the total weight of the positive electrode active material in the positive electrode active material layer 22, more preferably 60% or more, and even more preferably 70% or more. Specifically, for example, when using a mixture of multiple lithium iron phosphate particles (first positive electrode active material 100) and multiple lithium manganese iron phosphate particles (second positive electrode active material 200), it is preferable that the total weight of the multiple lithium manganese iron phosphate particles accounts for 50% or more of the total weight of the multiple lithium iron phosphate particles and the multiple lithium manganese iron phosphate particles, more preferably 60% or more, and even more preferably 70% or more. In this case, the density of the positive electrode active material layer 22 is high, and a battery with high output characteristics can be obtained.

[0043] An example of a method for manufacturing the positive electrode 11 will be explained using Figures 2 and 3. As explained above, the positive electrode 11 has a positive electrode active material layer 22, and the positive electrode active material layer 22 is made of the first positive electrode active material 100 (LiFePO ４ ) and the second positive electrode active material 200 (LiMn １−ｘ Fe ｘ PO４ ) and have.

[0044] [Method for manufacturing a positive electrode 1] Figure 2 shows a first positive electrode active material 100 (carbon coated LiFePO) having a carbon coating layer. ４ ) and a second positive electrode active material 200 (carbon-coated LiMn) having a carbon coating layer １−ｘ Fe ｘ PO ４ This is a flowchart illustrating the method for manufacturing the positive electrode 11A using ).

[0045] In step S111 of Figure 2, the first positive electrode active material 100 is lithium iron phosphate (carbon-coated LiFePO) having a carbon coating layer. ４ ) is prepared. Also, in step S112, as the second positive electrode active material 200, manganese iron lithium phosphate (carbon coated LiMn) having a carbon coating layer is prepared. １−ｘ Fe ｘ PO ４ Prepare the following: In step S113, prepare the conductive material. In step S114, prepare the binder. In step S115, prepare the solvent. Note that the binder can be used after being pre-mixed with a portion of the solvent.

[0046] Next, in step S121 of Figure 2, the carbon-coated LiFePO prepared in steps S111 to S115 ４ And, carbon-coated LiMn １−ｘ Fe ｘ PO ４ The conductive material, binder, and solvent are mixed to obtain a mixture 101 in step S122. The mixture 101 is sometimes called a slurry. A slurry is a liquid material used to form an active material layer on a positive electrode current collector. The slurry is also sometimes called an electrode slurry or an active material slurry, and a positive electrode slurry is used when forming a positive electrode active material layer, while a negative electrode slurry is sometimes used when forming a negative electrode active material layer.

[0047] A rotating / revolving type agitator can be used for mixing. However, the mixing method is not limited to the above method, and any known mixing method can be used as appropriate. Furthermore, ultrasonic treatment may be performed to improve the dispersibility of the conductive material during mixing. The ultrasonic treatment can be performed at a frequency of 25 kHz to 40 kHz.

[0048] <Binder> As a binder, it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, or ethylene-propylene-diene copolymer. Fluororubber can also be used as a binder.

[0049] Furthermore, it is preferable to use a water-soluble polymer as the binder. Examples of water-soluble polymers include polysaccharides. Examples of polysaccharides include cellulose derivatives such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, diacetylcellulose, and regenerated cellulose, or starch. It is even preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0050] Alternatively, it is preferable to use materials such as polystyrene, methyl polyacrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, or nitrocellulose as the binder.

[0051] You may use a combination of several of the binders mentioned above.

[0052] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For instance, rubber materials have excellent adhesive and elastic properties, but their viscosity can be difficult to adjust when mixed with a solvent. In such cases, it is preferable to mix them with a material with particularly excellent viscosity-modifying properties. As a material with particularly excellent viscosity-modifying properties, a water-soluble polymer may be used. As a water-soluble polymer with particularly excellent viscosity-modifying properties, the aforementioned polysaccharides, such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, and diacetylcellulose, cellulose derivatives such as regenerated cellulose, or starch can be used.

[0053] Furthermore, cellulose derivatives such as carboxymethylcellulose can be made more soluble by using salts such as sodium or ammonium salts of carboxymethylcellulose, thereby increasing their effectiveness as viscosity modifiers. Increased solubility also improves the dispersibility with active materials or other components when preparing electrode slurries. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0054] Water-soluble polymers stabilize viscosity by dissolving in water, allowing for stable dispersion of active materials and other materials used as binders, such as styrene-butadiene rubber, in aqueous solutions. Furthermore, their functional groups are expected to facilitate stable adsorption to the surface of the active material. Additionally, cellulose derivatives such as carboxymethylcellulose often possess functional groups like hydroxyl or carboxyl groups, and these functional groups allow the polymers to interact with each other, resulting in a broad coverage of the active material surface.

[0055] When a binder covers or is in contact with the surface of the active material, it is expected to act as a passivation film, suppressing the decomposition of the electrolyte. Here, a "passivation film" is a film that does not conduct electricity, or has extremely low electrical conductivity. For example, when a passivation film is formed on the surface of the active material, the decomposition of the electrolyte can be suppressed at the battery reaction potential. Furthermore, it is even more desirable for the passivation film to suppress electrical conductivity while still allowing lithium ions to conduct.

[0056] <Conductive Materials> Conductive materials, also called conductivity imparters or conductivity enhancers, are typically made of carbon. By attaching conductive materials between multiple active materials, the multiple active materials are electrically connected to each other, increasing conductivity. Note that "attachment" does not only refer to physical contact between the active materials and the conductive material, but also includes cases where covalent bonds are formed, bonds are formed by van der Waals forces, the conductive material covers a portion of the surface of the active material, the conductive material fits into surface irregularities of the active material, or where they are electrically connected even without physical contact.

[0057] The active material layers, such as the positive electrode active material layer and the negative electrode active material layer, preferably contain a conductive material.

[0058] As conductive materials, one or more of the following can be used: carbon black such as acetylene black and furnace black; graphite such as artificial graphite and natural graphite; carbon fibers such as carbon nanofibers and carbon nanotubes; and graphene compounds.

[0059] As carbon fibers, for example, mesophase pitch carbon fibers and isotropic pitch carbon fibers can be used. Alternatively, carbon nanofibers or carbon nanotubes can be used. Carbon nanotubes can be fabricated, for example, by vapor deposition.

[0060] 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 defined as a material having carbon, having a plate-like or sheet-like shape, and possessing a two-dimensional structure formed by a six-membered carbon ring. This two-dimensional structure formed by a 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. Graphene compounds may also be rolled up to resemble carbon nanofibers.

[0061] The content of conductive material relative to the total amount of active material layer is preferably 1 wt% to 10 wt%, and more preferably 1 wt% to 5 wt%.

[0062] 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 battery.

[0063] Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes, readily penetrate minute spaces. These minute spaces refer, for example, to regions between multiple active materials. By combining a carbon-containing compound that readily penetrates minute spaces with a sheet-like carbon-containing compound such as graphene, which can impart conductivity across multiple particles, the electrode density can be increased, and excellent conductive paths can be formed. A battery obtained by the manufacturing method according to one embodiment of the present invention can have high capacity density and stability, making it effective as an in-vehicle battery.

[0064] Next, in step S123 of Figure 2, the current collector is prepared.

[0065] <Current Collector> As the current collector, materials with high conductivity such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used. It is preferable to use aluminum foil as the positive electrode current collector. In addition, aluminum alloys to which elements such as iron, silicon, titanium, neodymium, scandium, and molybdenum have been added can be used. The current collector can be in any shape as appropriate, such as foil, plate, sheet, mesh, perforated metal, or expanded metal. It is preferable to use a current collector with a thickness of 5 μm or more and 30 μm or less. In addition, a current collector having a coating layer (also called an undercoat layer or anchor coat layer) on its surface to improve conductivity and / or adhesion can be used.

[0066] Next, in step S131, the mixture 101 is applied (also called coating) onto the current collector prepared in step 123. For coating, the slot die method, gravure method, blade method, and combinations thereof can be used. A continuous coating machine may also be used for coating.

[0067] Next, as shown in step S132 of Figure 2, drying is performed to remove the solvent from the mixture 101 coated above. The drying method is not particularly limited and can be performed by methods such as forced-air drying, reduced-pressure (vacuum) drying, or infrared drying. After drying in step S132, it is preferable to perform the pressing treatment shown in step S133 in order to reduce the voids in the active material layer. The pressing treatment can be performed using a roll press device, and it is preferable that the rolls of the roll press device are heated to a temperature such that the binder softens. The temperature of the rolls can be, for example, 80°C to 150°C.

[0068] After the above process, the positive electrode 11A can be obtained as shown in step S140 of Figure 2.

[0069] [Method for manufacturing the positive electrode 2] Figure 3 shows the first positive electrode active material 100 (LiFePO) without a carbon coating layer. ４ ) and a second positive electrode active material 200 (LiMn) that does not have a carbon coating layer １−ｘ Fe ｘ PO ４This is a flowchart illustrating the method for manufacturing the positive electrode 11B using ) and . In the explanation of the method for manufacturing the positive electrode 11B, steps similar to those for manufacturing the positive electrode 11A can be found in the explanation in Figure 2.

[0070] Steps S211 to S225 shown in Figure 3 describe the process of mixing a first positive electrode active material 100 without a carbon coating layer and a second positive electrode active material 200 without a carbon coating layer, and then applying a carbon coating layer. Through the above process, a composite of the first positive electrode active material 100 and the second positive electrode active material 200 having a carbon coating layer (referred to as a carbon-coated composite 202) is produced. Steps S230 to S260 describe the method for producing a positive electrode 11B having the carbon-coated composite 202.

[0071] In step S211 of Figure 3, the first positive electrode active material 100 is lithium iron phosphate (LiFePO) without a carbon coating layer. ４ ) is prepared. Also, in step S212, as the second positive electrode active material 200, manganese iron lithium (LiMn) phosphate without a carbon coating layer is prepared. １−ｘ Fe ｘ PO ４ Prepare the following:

[0072] As a carbon source, compounds containing carbon can be used, such as sugars including glucose and sucrose, polysaccharides including starch and cellulose, synthetic resins including polyvinyl alcohol (PVA) and polyacrylic acid. Carbon black including acetylene black, graphene, graphene oxide, and graphite can also be used. A combination of several of these can also be used.

[0073] In addition to the above, when using a planetary rotary mill device such as a ball mill for mixing, a mixing medium is prepared (step S214). For example, zirconia balls can be used as the mixing medium. Also, when wet mixing is used, a solvent is prepared (step S215). For example, dehydrated acetone can be used as the solvent.

[0074] Next, in step S221, the first positive electrode active material 100, the second positive electrode active material 200, and the carbon source are mixed. The mixing can be carried out wet, for example, using a ball mill. For example, zirconia balls with a diameter of 3 mm can be used as the mixing medium, dehydrated acetone can be used as the solvent, and the mixture can be mixed at 300 rpm for 2 hours while cooling using a planetary rotating ball mill apparatus.

[0075] Next, in step S222, if wet mixing was performed, the solvent is dried, or if a mixing medium was used, the mixture is sieved to remove the mixing medium, thereby obtaining the mixture 201 in step S223. For example, the mixture can be recovered by drying it in a ventilated drying oven and then sieving it through a 300 μm sieve.

[0076] Next, in step S224, the mixture 201 is heated. The heating temperature is preferably 500°C to 900°C, more preferably 600°C to 700°C, and most preferably around 650°C. The heating time is preferably 1 hour to 60 hours, more preferably 2 hours to 20 hours, and most preferably around 10 hours. If the heating temperature is too low and / or the heating time is too short, the carbon source may not be sufficiently carbonized. On the other hand, if the heating temperature is too high and / or the heating time is too long, sintering may proceed too much, causing the particles to become too large and reducing productivity.

[0077] During heating, it is preferable to use an inert or reducing atmosphere, such as a nitrogen or argon atmosphere. The reaction chamber may be depressurized and then filled (purged) with an inert atmosphere to prevent the atmosphere from entering or leaving the reaction chamber, or a constant flow of atmosphere may be maintained.

[0078] For the heating furnace, for example, a muffle furnace, roller hearth kiln, rotary kiln, etc., can be used. For the container that holds the material to be heated, an aluminum oxide crucible or an aluminum oxide setter (also called a sheath) can be used. It is preferable to cover the crucible or setter before heating to prevent the material from volatilizing. Mullite-cordierite may also be used as the material for the crucible and setter.

[0079] For example, mixture 201 can be placed in a crucible made of 99.9% pure aluminum oxide, covered, and heated in a muffle furnace under a nitrogen flow atmosphere at 350°C for 10 hours.

[0080] Next, in step S225, the heated material is sieved. For example, it can be sieved using a sieve with a mesh size of 53 μm. The carbon-coated composite 202 is obtained through the above steps (step S230). In the subsequent steps, the slurry is prepared by mixing, coated, dried, and pressed, similar to steps S112 to S133 of the positive electrode 11A shown in Figure 2.

[0081] Next, in steps S231, S232, and S233 of Figure 3, the conductive material, binder, and solvent are prepared in the same manner as in steps S113, S114, and S115 of Figure 2.

[0082] Subsequently, in step S241 of Figure 3, the carbon-coated composite 202, conductive material, binder, and solvent are mixed, and the following steps S242 to S253 are carried out. Steps S242 to S253 of Figure 3 may be carried out in the same manner as steps S122 to S133 of Figure 2.

[0083] Through the above process, the positive electrode 11B can be obtained as shown in step S260 of Figure 3. The method for manufacturing the positive electrode 11B described in Figure 3 allows the first positive electrode active material 100 and the second positive electrode active material 200 to be carbon coated simultaneously, thus reducing the total number of steps compared to the manufacturing method described in Figure 2. Furthermore, by using the method for manufacturing the positive electrode 11B described in Figure 3, as shown in Figure 1C, the carbon coating layer 150 creates a region where the first positive electrode active material 100 and the second positive electrode active material 200 are integrated. This reduces the area in contact between the first positive electrode active material 100 and the second positive electrode active material 200 via a binder or the like, improving the overall conductivity of the positive electrode active material layer 22.

[0084] In addition, in the method for manufacturing the positive electrode 2, the first positive electrode active material 100 (LiFePO) does not have a carbon coating layer. ４) and a second positive electrode active material 200 (LiMn) that does not have a carbon coating layer １−ｘ Fe ｘ PO ４ A method for producing a material using ) and a carbon coating layer after mixing them has been described. The present invention is not limited to this embodiment, and either one or both of the first positive electrode active material 100 and the second positive electrode active material 200 may be positive electrode active materials having a carbon coating layer, and a carbon coating layer may be further provided after mixing them.

[0085] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0086] (Embodiment 2) In this embodiment, an example of a method for producing a first positive electrode active material 100 and a second positive electrode active material 200, which are positive electrode active materials of a battery according to one aspect of the present invention, will be described.

[0087] [Method for producing the first positive electrode active material 100] The first positive electrode active material 100 is preferably produced using a liquid-phase method, such as a hydrothermal method. The method for producing the first positive electrode active material 100 will be explained with reference to Figure 4.

[0088] In step S301 of Figure 4, a lithium source (Li source) is prepared. Also, in step S302, a phosphoric acid source is prepared.

[0089] Lithium sources can be prepared by dissolving lithium compounds in a solvent. Examples of lithium compounds include lithium hydroxide monohydrate (LiOH·H). ２ O), lithium chloride (LiCl), lithium carbonate (Li ２ CO ３ ), lithium acetate (CH ３ COOLi), lithium oxalate ((COOLi) ２ One or more of the following can be used: ), or water can be used as the solvent for dissolving the lithium compound.

[0090] A phosphoric acid source can be prepared by dissolving a phosphorus compound in a solvent. Examples of phosphorus compounds include orthophosphoric acid (H2). ３ PO ４ Phosphates such as ) or diammonium hydrogen phosphate ((NH ４ )２ HPO ４ ), or ammonium dihydrogen phosphate (NH ４ H ２ PO ４ One or more of the following ammonium hydrogen phosphates can be used: ) etc. Water can be used as the solvent for dissolving the phosphorus compound.

[0091] Next, in step S303 of Figure 4, the lithium source and the phosphoric acid source are mixed to obtain the mixture 301 of step S310. The mixing in step S303 can be carried out in an atmosphere such as air or an inert gas. For example, nitrogen can be used as the inert gas. Here, as an example, the lithium source prepared in step S301 and the phosphoric acid source prepared in step S302 are mixed in an atmospheric environment.

[0092] Alternatively, instead of mixing an aqueous solution of the lithium source and an aqueous solution of the phosphoric acid source to form the mixture 301 in step S310 of Figure 4, ３ PO ４ Li ２ HPO ４ , LiH ２ PO ４ A compound having solid phosphorus and lithium may be prepared and added to the solvent to form the mixture 301 of step S310.

[0093] Next, in step S311 of Figure 4, an iron source (Fe source) is prepared.

[0094] An iron source can be prepared by dissolving an iron compound in a solvent. Iron(II) compounds can be used as the iron compound. Water can be used as the solvent for dissolving the iron compound.

[0095] A typical example of an iron(II) compound is iron chloride tetrahydrate (FeCl ２ 4H ２ O), iron sulfate heptahydrate (FeSO ４ 7H ２ O), iron acetate (Fe(CH) ３ COO) ２ ) and others.

[0096] Next, as step 312 in Figure 4, the mixture 301 from step S310 and the Fe source are mixed to obtain the mixture 302 from step 320.

[0097] In the mixing of step 312 in Figure 4, it is preferable that the mixing ratio of the lithium source, phosphate source, and iron source be such that the atomic ratio of lithium, iron, and phosphorus is 1:1:1.

[0098] As a mixing method for step S312 in Figure 4, the mixture 302 of step 320 can be prepared by dropping a small amount of Fe source onto the mixture 301 of step S310 placed in a container. During mixing, it is desirable that the solution in the container and the solution used for mixing be stirred, and N ２ It is desirable to remove dissolved oxygen by bubbling.

[0099] Alternatively, as a mixing method in step S312 of Figure 4, the mixture 301 from step S310 can be added dropwise in small amounts to the Fe source in a container to prepare the mixture 302 from step 320. During mixing, it is desirable that the solution in the container and the solution used for mixing be stirred, and N ２ It is desirable to remove dissolved oxygen by bubbling.

[0100] Here, in step S312 of Figure 4, the concentration of the mixture 302 in step 320 can be adjusted by adding a solvent. For example, in step S312, the mixture 301 from step S310, the Fe source, and the solvent can be mixed to prepare the mixture 302 in step 320.

[0101] Next, in step S321 of Figure 4, the mixture 302 from step 320 is placed in a heat-resistant and pressure-resistant container such as an autoclave, and then heated at a temperature of 100°C to 350°C, more preferably greater than 100°C and less than 200°C, and a pressure of 0.11 MPa to 100 MPa, more preferably 0.11 MPa to 2 MPa, for 0.5 hours to 24 hours, more preferably 1 hour to 10 hours, and even more preferably 1 hour to less than 5 hours, and then cooled. Subsequently, in step S322, the solution in the heat-resistant and pressure-resistant container is filtered and washed with water. Next, in step S323, after drying, it is recovered to obtain the composite oxide 303 from step S330.

[0102] Composite oxide 303 is lithium iron phosphate (LiFePO) belonging to space group Pnm. ４ It is preferable that the median diameter D50 is 100 nm or more and 10 μm or less, and more preferably 300 nm or more and 3 μm or less. Therefore, if the particle size of the composite oxide 303 obtained in step S330 is larger than the above range, it is preferable to reduce the particle size by grinding, classification, etc. The composite oxide 303 produced in the above process can be called the first positive electrode active material 100 without a carbon coating layer, and is the lithium iron phosphate (LiFePO) without a carbon coating layer prepared in step S211 in Figure 3. ４ It can be used as ).

[0103] In the subsequent steps (steps S331 to S340 in Figure 4), a carbon coating layer is applied to the particle surface of the composite oxide 303.

[0104] Next, in step S331 of Figure 4, a carbon source is prepared. In addition to the carbon source, it is preferable to prepare a mixing medium for mixing (step S332) and a solvent (step S333).

[0105] As a carbon source, compounds containing carbon can be used, such as sugars including glucose and sucrose, polysaccharides including starch and cellulose, synthetic resins including polyvinyl alcohol (PVA) and polyacrylic acid. Carbon black including acetylene black, graphene, graphene oxide, and graphite can also be used. A combination of several of these can also be used.

[0106] Next, in step S334 of Figure 4, the composite oxide 303 and the carbon source are mixed. The mixing can be done wet, for example, using a ball mill. For example, 3 mm diameter zirconia balls can be used as the mixing medium, dehydrated acetone as the solvent, and the mixture can be mixed at 300 rpm for 2 hours while cooling using a planetary rotating ball mill apparatus.

[0107] Next, in step S335 of Figure 4, if wet mixing was performed, the solvent is dried, or if a mixing medium was used, the mixing medium is removed by sieving to obtain the mixture 304 of step S336.

[0108] Next, in step S337 of Figure 4, the mixture 304 is heated. The heating temperature is preferably 500°C to 900°C, more preferably 600°C to 700°C, and most preferably around 650°C. The heating time is preferably 1 hour to 60 hours, more preferably 2 hours to 20 hours, and most preferably around 10 hours. If the heating temperature is too low and / or the heating time is too short, the carbon source may not be sufficiently carbonized. On the other hand, if the heating temperature is too high and / or the heating time is too long, sintering may progress too much, the secondary particles may become too large, and productivity may decrease.

[0109] During heating, it is preferable to use an inert or reducing atmosphere, such as a nitrogen or argon atmosphere. The reaction chamber may be depressurized and then filled (purged) with an inert atmosphere to prevent the atmosphere from entering or leaving the reaction chamber, or a constant flow of atmosphere may be maintained.

[0110] For the heating furnace, for example, a muffle furnace, roller hearth kiln, rotary kiln, etc., can be used. For the container that holds the material to be heated, an aluminum oxide crucible or an aluminum oxide setter (also called a sheath) can be used. It is preferable to cover the crucible or setter before heating to prevent the material from volatilizing. Mullite-cordierite may also be used as the material for the crucible and setter.

[0111] For example, the mixture 304 can be placed in a crucible made of 99.9% pure aluminum oxide, covered, and heated in a muffle furnace under a nitrogen flow atmosphere at 650°C for 10 hours.

[0112] Next, in step S338 of Figure 4, the heated material is sieved. For example, it can be sieved using a sieve with a mesh size of 53 μm. The first positive electrode active material 100 is obtained through the above steps (step S340).

[0113] In the above process, a first positive electrode active material 100 having a carbon coating layer can be produced. The first positive electrode active material 100 having a carbon coating layer produced above is used in step S111 of Figure 2 to prepare a carbon-coated LiFePO ４ It is preferable to use it as such.

[0114] Although Figure 4 illustrates an example of producing the positive electrode active material by a hydrothermal method, the present invention is not limited to this. The first positive electrode active material 100 can be produced not only by the hydrothermal method, but also by methods such as the solid-phase method, flux method, and solvothermal method.

[0115] [Method for producing the second positive electrode active material 200] The second positive electrode active material 200 is preferably produced using a solid-phase method. The method for producing the second positive electrode active material 200 will be explained with reference to Figure 5.

[0116] First, as shown in Figure 5, a lithium source (Li source) is prepared in step S411, a manganese source (Mn source) in step S412, an iron source (Fe source) in step S413, and a phosphoric acid source in step S414. It is also preferable to prepare a mixing medium (step S415) and a solvent (step S416) for mixing.

[0117] As the lithium source, for example, lithium carbonate, lithium hydroxide, lithium oxide, lithium phosphate (Li ３ PO ４ ), lithium acetate and its hydrates (CH ３ CO ２ Li, Li(CH ３ COO)·2H ２ O), lithium oxalate (Li ２ C ２ O ４ ), lithium nitrate (LiNO ３ ), lithium chloride (LiCl), lithium sulfate (Li ２ SO ４ ), lithium fluoride (LiF) and other lithium compounds can be used.

[0118] As the manganese source, for example, manganese carbonate, manganese oxide (MnO, Mn ３ O ４ , Mn<\ ２ O ３ , MnO ２ , MnO ３ etc.), manganese hydroxide, manganese phosphate (MnPO ４ ), manganese acetate and its hydrates (Mn(OCOCH ３ ), <\\ ２ Mn(CH ３ COO ３ ·2H ２ O, Mn(CH ３ COO ２ ·4H ２ O), manganese oxalate (MnC ２ O ４ ·2H[[ID=6'4]] ２ O), manganese nitrate and its hydrates (Mn(NO ３ ), ２ Mn(NO ３ ), ２ ·4H ２ O, Mn(NO ３ ), ２ ·6H ２ O)), manganese chloride (MnCl ２ ·4H ２ O), manganese sulfate and its hydrates (MnSO ４ ), MnSO ４・H ２ O, MnSO ４ 4H ２ O, MnSO ４ ・5H ２ O, MnSO ４ 7H ２ O,) Manganese fluoride (MnF ２ MnF ３ Manganese compounds such as ) can be used.

[0119] As an iron source, for example, iron carbonate (FeCO3) ３ ), iron oxide (FeO, Fe ３ O ４ Fe ２ O ３ ), iron hydroxide, iron phosphate (FePO ４ ・2H ２ O, FePO ４ ・5H ２ O), iron acetate (Fe(CH) ３ CO ２ ) ２ ), iron oxalate hydrate (Fe(C) ２ O ４ )・2H ２ O, Fe ２ (C ２ O ４ ) ３ 6H ２ O), iron nitrate hydrate (Fe(NO) ３ ) ３ 9H ２ O, Fe (NO ３ ) ３ 6H ２ O), iron chloride and its hydrate (FeCl ２ FeCl ２ 4H ２ OFeCl ３ FeCl ３ 6H ２ O), iron sulfate and its hydrate (FeSO4) ４ FeSO ４ ・H ２ O, FeSO ４ 4H ２ O, FeSO ４ ・5H ２ O, FeSO ４ 7H ２ O), iron fluoride and its hydrate (FeF２ FeF ２ 4H ２ O, FeF ３ FeF ３ 3H ２ Iron compounds such as O) can be used.

[0120] For example, ammonium dihydrogen phosphate (NH₄) can be used as a source of phosphate. ４ H ２ PO ４ ), diammonium hydrogen phosphate ((NH ４ ) ２ HPO ４ ), lithium dihydrogen phosphate (LiH ２ PO ４ Phosphate compounds such as ) can be used.

[0121] It should be noted that the lithium, manganese, iron, and phosphate sources do not necessarily have to be separate; compounds that serve multiple purposes can be used. For example, lithium dihydrogen phosphate can serve as both a lithium and phosphate source.

[0122] For example, lithium carbonate is used as the lithium source, manganese carbonate as the manganese source, iron(II) oxalate dihydrate as the iron source, and ammonium dihydrogen phosphate as the phosphate source, Li:Mn:Fe:Mg:PO ４ The weights can be weighed so that the ratio is 1:0.59:0.4:0.01:1 (molar ratio).

[0123] In addition to the above, when using a planetary rotary mill device such as a ball mill for mixing, a mixing medium must be prepared. For example, zirconia balls can be used as the mixing medium. Also, when wet mixing is used, a solvent must be prepared. For example, dehydrated acetone can be used as the solvent.

[0124] Next, in step S417 of Figure 5, the lithium source, manganese source, iron source, and phosphate source are mixed. The mixing can be done wet, for example, using a ball mill. For example, 3 mm diameter zirconia balls can be used as the mixing medium, dehydrated acetone as the solvent, and the mixture can be mixed at 300 rpm for 2 hours while cooling using a planetary ball mill apparatus.

[0125] Next, in step S418 of Figure 5, if wet mixing is performed, the solvent is dried, or if a mixing medium is used, the mixing medium is removed by sieving to obtain the mixture 401 of step S420. For example, the mixture can be recovered by drying it in a ventilated drying oven and then sieving it through a 300 μm sieve.

[0126] Next, in step S421 of Figure 5, the mixture 401 is heated. The heating temperature is preferably 250°C to 450°C, more preferably 300°C to 400°C, and most preferably around 350°C. The heating time is preferably 1 hour to 60 hours, more preferably 2 hours to 20 hours, and most preferably around 10 hours. If the heating temperature is too low and / or the heating time is too short, the reaction may not be completed, such as by not completing the evaporation of the hydrate and / or carbon dioxide. On the other hand, if the heating temperature is too high and / or the heating time is too long, fuel costs for heating will increase, and productivity may decrease.

[0127] During heating, it is preferable to use an inert or reducing atmosphere, such as a nitrogen or argon atmosphere. The reaction chamber may be depressurized and then filled (purged) with an inert atmosphere to prevent the atmosphere from entering or leaving the reaction chamber, or a constant flow of atmosphere may be maintained.

[0128] For the heating furnace, for example, a muffle furnace, roller hearth kiln, rotary kiln, etc., can be used. For the container that holds the material to be heated, an aluminum oxide crucible or an aluminum oxide setter (also called a sheath) can be used. It is preferable to cover the crucible or setter before heating to prevent the material from volatilizing. Mullite-cordierite may also be used as the material for the crucible and setter.

[0129] For example, mixture 401 can be placed in a crucible made of 99.9% pure aluminum oxide, covered, and heated in a muffle furnace under a nitrogen flow atmosphere at 350°C for 10 hours.

[0130] Next, in step S422 of Figure 5, the heated material is sieved. In this embodiment, a sieve with a mesh size of 300 μm is used. The composite oxide 402 is obtained through the above steps (step S430).

[0131] The composite oxide 402 is preferably manganese iron lithium phosphate belonging to space group Pnm. The median diameter D50 is preferably 10 nm to 300 nm, and more preferably 30 nm to 100 nm. Therefore, if the particle size of the composite oxide 402 obtained in step S430 is larger than the above range, it is preferable to reduce the particle size by grinding, classification, or the like.

[0132] The composite oxide 402 produced in the above process can be described as a second positive electrode active material 200 without a carbon coating layer, and is the same as the lithium iron manganese phosphate (LiMn) without a carbon coating layer prepared in step S212 of Figure 3. １−ｘ Fe ｘ PO ４ It can be used as ).

[0133] In the subsequent steps (steps S431 to S440 in Figure 5), a carbon coating layer is applied to the particle surface of the composite oxide 402.

[0134] Next, as step S431 in Figure 5, a carbon source is prepared. In addition to the carbon source, it is preferable to prepare a mixing medium for mixing (step S432) and a solvent (step S433).

[0135] As a carbon source, compounds containing carbon can be used, such as sugars including glucose and sucrose, polysaccharides including starch and cellulose, synthetic resins including polyvinyl alcohol (PVA) and polyacrylic acid. Carbon black including acetylene black, graphene, graphene oxide, and graphite can also be used. A combination of several of these can also be used.

[0136] For information regarding the mixed medium and solvent, refer to the descriptions in steps S415 and 416 of Figure 5.

[0137] Next, in step S434 of Figure 5, the composite oxide 402 and the carbon source are mixed. The mixing can be done wet, for example, using a ball mill. For example, 3 mm diameter zirconia balls can be used as the mixing medium, dehydrated acetone as the solvent, and the mixture can be mixed at 300 rpm for 2 hours while cooling using a planetary ball mill apparatus.

[0138] Next, in step S435 of Figure 5, if wet mixing was performed, the solvent is dried, and if a mixing medium was used, the mixture is sieved to remove the mixing medium, thereby obtaining the mixture 403 of step S435. For details on sieving, refer to the description in step S418.

[0139] Next, in step S437 of Figure 5, the mixture 403 is heated. The heating temperature is preferably 500°C to 900°C, more preferably 600°C to 700°C, and most preferably around 650°C. The heating time is preferably 1 hour to 60 hours, more preferably 2 hours to 20 hours, and most preferably around 10 hours. If the heating temperature is too low and / or the heating time is too short, the carbon source may not be sufficiently carbonized. On the other hand, if the heating temperature is too high and / or the heating time is too long, sintering may progress too much, causing the particles to become too large and reducing productivity.

[0140] The atmosphere during heating, the heating furnace, and the container can be described in step S421.

[0141] For example, mixture 403 can be placed in a crucible made of 99.9% pure aluminum oxide, covered, and heated in a muffle furnace under a nitrogen flow atmosphere at 650°C for 10 hours.

[0142] Next, in step S438 of Figure 5, the heated material is sieved. For example, it can be sieved using a sieve with a mesh size of 53 μm. The second positive electrode active material 200 is obtained through the above steps (step S440).

[0143] The second positive electrode active material 200 can be produced through the above process.

[0144] Although Figure 5 illustrates an example of producing a positive electrode active material by a solid-phase method, the present invention is not limited to this. The second positive electrode active material 200 can be produced not only by the solid-phase method but also by methods such as the hydrothermal method and the sol-gel method.

[0145] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0146] (Embodiment 3) In this embodiment, each element constituting the battery will be described.

[0147] [Positive Electrode] The positive electrode comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer contains a positive electrode active material and may further contain at least one of a conductive material and a binder. The positive electrode and positive electrode active material can be those described in Embodiment 1 and Embodiment 2.

[0148] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a negative electrode active material, a conductive material, and a binder.

[0149] <Negative electrode active material> For example, lithium metal, alloy materials, or carbon materials can be used as the negative electrode active material.

[0150] Furthermore, the negative electrode active material can be an element capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium. For example, a material containing at least one of silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc., can be used. Such elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Compounds containing these elements may also be used. For example, SiO, Mg ２ Si, Mg ２ Ge, SnO, SnO ２ Mg ２ Sn, SnS ２ , V ２ Sn ３ FeSn ２ CoSn ２ Ni ３ Sn２ ,Cd ６ Sn ５ Ag ３ Sn, Ag ３ Sb, Ni ２ MnSb, CeSb ３ LaSn ３ La ３ Co ２ Sn ７ CoSb ３ Examples include InSb and SbSn. For example, compounds of Si, SiO, or SiC with Ti may also be used. Here, elements capable of undergoing charge-discharge reactions through alloying and de-alloying reactions with lithium, and compounds containing such elements, are sometimes referred to as alloying materials.

[0151] In this specification, "SiO" refers to silicon monoxide, for example. Alternatively, SiO refers to SiO ｘ It can also be expressed as follows. Here, x preferably has a value of 1 or a value in the vicinity of 1. For example, x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.

[0152] Carbon materials such as graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon fibers (carbon nanotubes), graphene, and carbon black can be used.

[0153] Examples of graphite include artificial graphite and natural graphite. Examples of artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, spheroidal graphite having a spherical shape can be used as artificial graphite. For example, MCMB may have a spherical shape and is therefore preferable. Furthermore, it is relatively easy to reduce the surface area of ​​MCMB, which may also be preferable. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0154] Graphite exhibits a potential as low as lithium metal (0.05V to 0.3V vs. Li / Li) when lithium ions are inserted into it (during the formation of lithium-graphite intercalation compounds). ＋This allows lithium-ion batteries using graphite to exhibit a high operating voltage. Furthermore, graphite is preferable because it has advantages such as a relatively high capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0155] Furthermore, titanium dioxide (TiO) is used as the negative electrode active material. ２ ), lithium titanium oxide (Li ４ Ti ５ O １２ ), lithium-graphite intercalation compound (Li ｘ C ６ ), niobium pentoxide (Nb ２ O ５ ), tungsten oxide (WO ２ ), molybdenum oxide (MoO ２ Oxides such as those listed above can be used.

[0156] Furthermore, as the negative electrode active material, a complex nitride of lithium and a transition metal, Li ３ Li with an N-type structure ３−ｘ M ｘ N (M = Co, Ni, Cu) can be used. For example, Li ２．６ Co ０．４ N has a large discharge capacity (900 mAh / g, 1890 mAh / cm²). ３ ) indicates a preference.

[0157] When a lithium-transition metal binitride is used, the negative electrode active material contains lithium ions, so the positive electrode active material does not contain lithium ions. ２ O ５ , Cr ３ O ８ It is preferable that it be combined with materials such as the above. Furthermore, even when a material containing lithium ions is used as the positive electrode active material, a lithium-transition metal complex nitride can be used as the negative electrode active material by desorbing the lithium ions contained in the positive electrode active material beforehand.

[0158] Furthermore, materials that undergo a conversion reaction can also be used as the negative electrode active material. For example, transition metal oxides that do not form alloys with lithium, such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO), may be used as the negative electrode active material. As for materials that undergo a conversion reaction, Fe ２ O ３ ,CuO,Cu ２ O, RuO ２ , Cr ２ O ３ Oxides such as CoS ０．８９ , sulfides such as NiS and CuS, Zn ３ N ２ ,Cd ３ N, Ge ３ N ４ Nitrides such as NiP ２ FeP ２ CoP ３ Phosphates such as FeF ３ BiF ３ Examples of fluorides include the following.

[0159] Furthermore, another form of the negative electrode is one that does not have negative electrode active material at the end of battery manufacturing. For example, a negative electrode without negative electrode active material may have only a negative electrode current collector at the end of battery manufacturing, in which lithium ions that detach from the positive electrode active material during battery charging deposit as lithium metal on the negative electrode current collector, forming a negative electrode active material layer. Batteries using such a negative electrode are sometimes called negative electrode-free (anode-free) batteries or negative electrode-less (anode-less) batteries.

[0160] When using a negative electrode without a negative electrode active material, a film may be provided on the negative electrode current collector to homogenize the deposition of lithium. As a film to homogenize the deposition of lithium, for example, a solid electrolyte having lithium ion conductivity can be used. As a solid electrolyte, sulfide-based solid electrolytes, oxide-based solid electrolytes, and polymer-based solid electrolytes can be used. Among these, polymer-based solid electrolytes are suitable as a film to homogenize the deposition of lithium because it is relatively easy to form a uniform film on the negative electrode current collector. Alternatively, as a film to homogenize the deposition of lithium, for example, a metal film that forms an alloy with lithium can be used. As a metal film that forms an alloy with lithium, for example, a magnesium metal film can be used. Since lithium and magnesium form a solid solution over a wide composition range, it is suitable as a film to homogenize the deposition of lithium.

[0161] Furthermore, when using a negative electrode without negative electrode active material, a negative electrode current collector with irregularities can be used. When using a negative electrode current collector with irregularities, the recesses in the negative electrode current collector become cavities where lithium is easily deposited during charging, thus suppressing the formation of dendrite-like shapes when lithium is deposited.

[0162] The conductive material and binder that the negative electrode active material layer can have can be the same materials as the conductive material and binder that the positive electrode active material layer can have.

[0163] <Negative electrode current collector> In addition to the same materials as the positive electrode current collector, copper, lithium, and other materials can also be used for the negative electrode current collector.

[0164] [Electrolyte] A secondary battery has an electrolyte containing carrier ions. In this specification, the electrolyte is not limited to one containing an organic solvent that is liquid at room temperature, but also includes solid electrolytes, and electrolytes containing both an organic solvent that is liquid at room temperature and a solid electrolyte that is solid at room temperature (semi-solid electrolytes) are also included. Note that a solution in which lithium salt is dissolved in an organic solvent that is liquid at room temperature is sometimes called an electrolyte solution.

[0165] <Organic solvents that are liquid at room temperature> Examples of organic solvents that are liquid at room temperature are described below.

[0166] The organic solvent, which is liquid at room temperature, is preferably an aprotic organic solvent. For example, one or more of the following can be used: 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 (EP), propyl propionate (PP), methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc.

[0167] By using one or more flame-retardant and low-volatility ionic liquids (room-temperature molten salts) as organic solvents that are liquid at room temperature, it is possible to prevent the battery cell from rupturing and igniting even if the internal temperature rises due to an internal short circuit or overcharging. Ionic liquids consist of cations and anions, and include organic cations and anions. Examples of organic cations used in organic solvents include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, or aromatic cations such as imidazolium cations and pyridinium cations. Examples of anions used in organic solvents include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkyl sulfonate anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkyl phosphate anions.

[0168] Furthermore, the lithium salt to be dissolved in the above organic solvent is, for example, LiPF ６ LiClO ４ LiAsF ６ LiBF ４ LiAlCl ４ , LiSCN, LiBr, LiI, Li ２SO ４ Li ２ B １０ Cl １０ Li ２ B １２ Cl １２ LiCF ３ SO ３ LiC ４ F ９ SO ３ LiC (CF ３ SO ２ ) ３ LiC(C ２ F ５ SO ２ ) ３ ,LiN(CF ３ SO ２ ) ２ ,LiN(C ４ F ９ SO ２ ) (CF ３ SO ２ ), and LiN(C ２ F ５ SO ２ ) ２ You may use one or more selected from the above.

[0169] <Additives> The above organic solvent may contain additives. Additives can suppress the reaction decomposition of the electrolyte that may occur on the positive or negative electrode surface when the secondary battery is operated at high voltage and / or high temperature. Examples of additives include vinylene carbonate (VC), propane sultone (PS), TerT-butylbenzene (TBB), fluoroethylene carbonate (FEC), and lithium bis(oxalate) borate (LiBOB). LiBOB is particularly preferred because it easily forms a good film. VC or FEC are preferred because they can form a good film on the negative electrode during aging or initial charging of the secondary battery, improving cycle characteristics.

[0170] The additive may include a compound shown in the following general formula (G1). The following general formula (G1) is a compound having two cyano groups and can be called a dinitrile compound.

[0171]

[0172] In the above general formula (G1), R represents a hydrocarbon having 1 to 5 carbon atoms. Preferably, in the above general formula (G1), R represents a hydrocarbon having 2 to 4 carbon atoms.

[0173] Examples of the above general formula (G1) include succinonitrile, glutaronitrile, or adiponitrile (ADN).

[0174] The structural formula (H1) of succinonitrile is shown below.

[0175]

[0176] The structural formula (H2) of glutaronitrile is shown below.

[0177]

[0178] The structural formula (H3) of adiponitrile is shown below.

[0179]

[0180] Furthermore, as a dinitrile compound, ethylene glycol bis(propionitrile) ether (EGBE), which has a hydrocarbon and an ether at the R position of the above general formula (G1), can be used. The structural formula (H4) of ethylene glycol bis(propionitrile) ether is shown below.

[0181]

[0182] One or more dinitrile compounds can be used as additives.

[0183] Furthermore, fluorobenzene may be added to the above organic solvent. The concentration of the additive should be, for example, 0.1 wt% to 5 wt% of the total electrolyte. PS or EGBE is preferable because it can form a good film on the positive electrode during charging and discharging, thereby improving cycle characteristics. FB is preferable because it improves the wettability of the organic solvent to the positive and negative electrodes. Dinitrile compounds are preferable because the nitrile groups are oriented toward the positive and negative electrodes, inhibiting oxidative decomposition of the organic solvent, thereby improving high-voltage resistance. Furthermore, when a current collector having copper is used in the negative electrode, dinitrile compounds are preferable because they can prevent the dissolution of copper during over-discharge. Considering the use of secondary batteries at high voltages, it is preferable to add nitrile compounds.

[0184] The electrolyte does not need to be liquid at room temperature; a semi-solid material called a polymer gel electrolyte may be used as the organic solvent. Using a polymer gel electrolyte enhances safety against leakage and other issues. It also allows for thinner and lighter battery cells.

[0185] As the polymer to be gelled, silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide-based gels, polypropylene oxide-based gels, fluorine-based polymer gels, and the like can be used.

[0186] Examples of polymers that can be used include polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing these. For example, PVDF-HFP, a copolymer of PVDF and hexafluoropropylene (HFP), can be used. The resulting polymer may also have a porous structure.

[0187] <Examples of organic solvents preferred for low-temperature applications> Examples of organic solvents preferred for low-temperature applications are described below.

[0188] A suitable organic solvent for low-temperature applications is one containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), where the total content of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is 100 vol%, and the volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate is x:y:100-x-y (where 5 ≤ x ≤ 35 and 0 < y < 65). More specifically, an organic solvent containing EC, EMC, and DMC in a volume ratio of EC:EMC:DMC = 30:35:35 can be used. Note that the above volume ratio may be the volume ratio before mixing the organic solvents, and the ambient temperature when mixing the organic solvents may be room temperature (typically 25°C).

[0189] EC is a cyclic carbonate with a high dielectric constant, which has the effect of promoting the dissociation of lithium salts. On the other hand, EC has high viscosity and a high freezing point (melting point) of 38°C, so when EC is used alone as an organic solvent, it is difficult to use in low-temperature environments. Therefore, the organic solvent specifically described in one aspect of the present invention further includes EMC and DMC, not just EC alone. EMC is a linear carbonate that has the effect of lowering the viscosity of the electrolyte and has a freezing point of -54°C. DMC is also a linear carbonate that has the effect of lowering the viscosity of the electrolyte and has a freezing point of -43°C. An electrolyte prepared using an organic solvent in which EC, EMC, and DMC having such physical properties are mixed, with the total content of these three organic solvents being 100 vol%, and the volume ratio at 25°C being x:y:100-x-y (where 5≦x≦35 and 0<y<65), has the characteristic of having a freezing point of -40°C or lower.

[0190] Conventional electrolytes used in battery cells solidify at around -20°C, making it difficult to manufacture batteries that can be charged and discharged at -40°C. The electrolyte described above, as an organic solvent for low-temperature electrolytes, has a freezing point of -40°C or lower, thus enabling the creation of battery cells that can be charged and discharged even in extremely low-temperature environments of -40°C.

[0191] Furthermore, the lithium salt to be dissolved in an organic solvent suitable for low temperatures can be selected from the lithium salts mentioned above.

[0192] Furthermore, additives in organic solvents suitable for low-temperature applications can be selected from the additives mentioned above.

[0193] [Separator] When the electrolyte contains an electrolyte solution, a separator is placed between the positive electrode and the negative electrode. As a separator, for example, materials such as paper and other cellulose fibers, nonwoven fabrics, glass fibers, ceramics, or porous films made of nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, polyimide, or polyurethane can be used. It is preferable that the separator be processed into a bag shape and placed so as to enclose either the positive electrode or the negative electrode.

[0194] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0195] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and improving the reliability of secondary batteries. Coating with fluorine-based materials facilitates better adhesion between the separator and electrodes, improving output characteristics. Coating with polyamide materials, particularly aramid, improves heat resistance, thereby enhancing the safety of secondary batteries.

[0196] 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.

[0197] 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.

[0198] [Outer Covering] The outer covering of a battery can be made of metal materials such as aluminum, stainless steel, or titanium, or resin materials. A film-like outer covering can also be used. As a film, for example, a three-layer film can be used, in which a highly flexible metal thin film or metal foil made of aluminum, stainless steel, titanium, copper, nickel, etc. is placed on a film made of polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film such as a polyamide resin or polyester resin is placed on the metal thin film as the outer surface of the outer covering. Such a multilayer film can be called a laminate film. In this case, the name of the material of the metal layer in the laminate film may be used to refer to it, such as aluminum laminate film, stainless steel laminate film, titanium laminate film, copper laminate film, nickel laminate film, etc.

[0199] The material or thickness of the metal layer in the laminate film can affect the flexibility of the battery. For batteries where flexibility or weight reduction is important, it is preferable to use an aluminum laminate film having a polypropylene layer, an aluminum layer, and a nylon layer as the outer casing. Here, the thickness of the aluminum layer is preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, and more preferably 20 μm or less. If the aluminum layer is thinner than 10 μm, there is a concern that the gas barrier properties will decrease due to pinholes in the aluminum layer, so it is desirable that the thickness of the aluminum layer be 10 μm or more.

[0200] For batteries where physical strength or safety is important, it is preferable to use a stainless laminate film having a polypropylene layer, a stainless steel layer, and a nylon layer as an outer casing. Furthermore, a polyethylene terephthalate layer may be provided on the nylon layer. Here, the thickness of the stainless steel layer is preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, and more preferably 20 μm or less. If the stainless steel layer is thinner than 10 μm, there is a concern that the gas barrier properties will decrease due to pinholes in the stainless steel layer, so it is desirable that the thickness of the stainless steel layer be 10 μm or more. In this specification, stainless steel refers to steel (an alloy of iron and carbon) containing about 12% or more chromium, and can be broadly classified into martensitic, ferritic, or austenitic types in terms of composition. It also includes stainless steel to which one or more elements selected from Ti, Nb, Mo, Cu, Ni, or Si have been added.

[0201] Alternatively, for example, it is preferable to use a titanium laminate film having a polypropylene layer, a titanium layer, and a nylon layer. Furthermore, a polyethylene terephthalate layer may be provided on the nylon layer. Here, the thickness of the titanium layer is preferably 50 μm or less, more preferably 40 μm or less, more preferably 30 μm or less, and more preferably 20 μm or less. If the titanium layer is thinner than 10 μm, there is a concern that the gas barrier properties will decrease due to pinholes in the titanium layer, so it is desirable that the thickness of the titanium layer be 10 μm or more.

[0202] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0203] (Embodiment 4) In this embodiment, an example of the shape of a secondary battery having a positive electrode manufactured by the manufacturing method described in the previous embodiment will be explained.

[0204] [Coin-type rechargeable battery] An example of a coin-type rechargeable battery is described below. Figure 6A is an exploded perspective view of a coin-type (single-layer flat type) rechargeable battery, Figure 6B is an external view, and Figure 6C is a cross-sectional view thereof. Coin-type rechargeable batteries are mainly used in small electronic devices.

[0205] Note that Figure 6A is a schematic diagram to show the overlapping of components (up / down relationship and positional relationship) for clarity. Therefore, Figures 6A and 6B are not perfectly identical corresponding diagrams.

[0206] In Figure 6A, the positive electrode 704, separator 710, negative electrode 707, spacer 722, and washer 712 are stacked. These are sealed with a gasket between the negative electrode can 702 and the positive electrode can 701. Note that the gasket for sealing is not shown in Figure 6A. The spacer 722 and washer 712 are used to protect the inside or fix the position within the can when the positive electrode can 701 and the negative electrode can 702 are pressed together. The spacer 722 and washer 712 are made of stainless steel or an insulating material.

[0207] The positive electrode 704 is a laminated structure in which a positive electrode active material layer 706 is formed on a positive electrode current collector 705.

[0208] Figure 6B is a perspective view of the completed coin-type rechargeable battery.

[0209] The coin-type secondary battery 700 has a positive electrode casing 701, which also serves as the positive electrode terminal, and a negative electrode casing 702, which also serves as the negative electrode terminal, both insulated and sealed by a gasket 703 made of polypropylene or the like. The positive electrode 704 is formed by a positive electrode current collector 705 and a positive electrode active material layer 706 provided in contact with it. The negative electrode 707 is formed by a negative electrode current collector 708 and a negative electrode active material layer 709 provided in contact with it. Furthermore, the negative electrode 707 is not limited to a laminated structure, and may use lithium metal foil or a lithium-aluminum alloy foil.

[0210] Furthermore, for the positive electrode 704 and negative electrode 707 used in the coin-type secondary battery 700, the active material layer only needs to be formed on one side.

[0211] The positive electrode can 701 and the negative electrode can 702 can be made of metals such as nickel, aluminum, or titanium, or alloys thereof, or alloys of these with other metals (e.g., stainless steel), which are corrosion-resistant to the electrolyte. Furthermore, it is preferable to coat them with nickel or aluminum to prevent corrosion caused by the electrolyte. The positive electrode can 701 is electrically connected to the positive electrode 704, and the negative electrode can 702 is electrically connected to the negative electrode 707.

[0212] The negative electrode 707, positive electrode 704, and separator 710 are immersed in an electrolyte solution, and as shown in Figure 6C, the positive electrode 704, separator 710, negative electrode 707, and negative electrode 702 are stacked in this order with the positive electrode can 701 at the bottom, and the positive electrode can 701 and negative electrode can 702 are pressed together via a gasket 703 to manufacture a coin-type secondary battery 700.

[0213] By having the above configuration, a coin-type secondary battery 700 can be made that has a high discharge capacity and excellent cycle characteristics.

[0214] [Cylindrical Secondary Battery] An example of a cylindrical secondary battery will be explained with reference to Figure 7A. As shown in Figure 7A, the cylindrical secondary battery 616 has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap 601 and the battery casing (outer casing) 602 are insulated by a gasket (insulating packing) 610.

[0215] Figure 7B is a schematic diagram showing a cross-section of a cylindrical secondary battery. The cylindrical secondary battery shown in Figure 7B has a positive electrode cap (battery cover) 601 on the top surface and a battery casing (outer casing) 602 on the sides and bottom. The positive electrode cap and the battery casing (outer casing) 602 are insulated from each other by a gasket (insulating packing) 610.

[0216] 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 central axis. The battery can 602 is closed at one end and open at the other. The battery can 602 can be made of a metal that is corrosion-resistant to the electrolyte, such as nickel, aluminum, or titanium, or an alloy thereof, or an alloy of these with other metals (for example, stainless steel). Furthermore, it is preferable to coat the battery can 602 with nickel and aluminum, etc., 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. In addition, a non-aqueous electrolyte (not shown) is injected into the inside of the battery can 602 in which the battery element is provided. The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries.

[0217] 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.

[0218] 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 rise in the internal pressure of the battery exceeds 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. PTC elements include barium titanate (BaTiO ３ ) semiconductor ceramics and the like can be used.

[0219] Figure 7C shows an example of an energy storage system 615. The energy storage system 615 has multiple 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, or a protection circuit that prevents overcharging and / or over-discharging.

[0220] Figure 7D 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 the 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.

[0221] Multiple secondary batteries 616 may be connected in parallel and then further connected in series.

[0222] Furthermore, 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.

[0223] Furthermore, in Figure 7D, 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.

[0224] [Other structural examples of secondary batteries] Structural examples of secondary batteries will be explained using Figures 8A to 9C.

[0225] The secondary battery 913 shown in Figure 8A has a wound body 950 with terminals 951 and 952 provided 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 8A, 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.

[0226] Furthermore, as shown in Figure 8B, the housing 930 shown in Figure 8A may be formed from multiple materials. For example, in the secondary battery 913 shown in Figure 8B, 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.

[0227] For the housing 930a, an insulating material such as an organic resin can be used. In particular, by using a material such as an 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 the housing 930a is small, the antenna may be provided inside the housing 930a. For the housing 930b, for example, a metal material can be used.

[0228] Furthermore, the structure of the wound body 950 is shown in Figure 8C. 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.

[0229] Alternatively, the secondary battery 913 may have a wound body 950a as shown in Figure 9. The wound body 950a shown in Figure 9A 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.

[0230] 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 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.

[0231] As shown in Figure 9B, the negative electrode 931 is electrically connected to terminal 951 by ultrasonic bonding, welding, or crimping. Terminal 951 is electrically connected to terminal 911a. The positive electrode 932 is electrically connected to terminal 952 by ultrasonic bonding, welding, or crimping. Terminal 952 is electrically connected to terminal 911b.

[0232] As shown in Figure 9C, the coiled body 950a and the electrolyte are covered by the housing 930, forming a secondary battery 913. It is preferable to provide a safety valve, an overcurrent protection element, etc., in the housing 930. The safety valve is a valve that opens the inside of the housing 930 at a predetermined internal pressure in order to prevent the battery from rupturing.

[0233] As shown in Figure 9B, the secondary battery 913 may have multiple windings 950a. By using multiple windings 950a, a secondary battery 913 with a larger discharge capacity can be made. Other elements of the secondary battery 913 shown in Figures 9A and 9B can be referenced from the description of the secondary battery 913 shown in Figures 8A to 8C.

[0234] <Laminated Secondary Battery> Next, an example of an external view of a laminated secondary battery is shown in Figures 10A and 10B. Figures 10A and 10B 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.

[0235] Figure 11A 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. Note that the area or shape of the tab regions of the positive and negative electrodes are not limited to the example shown in Figure 11A.

[0236] <Method for Manufacturing Laminated Secondary Batteries> An example of a method for manufacturing laminated secondary batteries, whose external appearance is shown in Figure 10A, will be explained using Figures 11B and 11C.

[0237] First, the negative electrode 506, separator 507, and positive electrode 503 are stacked. Figure 11B shows the stacked negative electrode 506, separator 507, and positive electrode 503. Here, an example using five sets of negative electrodes and four 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, for example, ultrasonic welding may be used. Similarly, the tab regions of the negative electrode 506 are joined together, and the negative electrode lead electrode 511 is joined to the tab region of the outermost negative electrode.

[0238] Next, the negative electrode 506, separator 507, and positive electrode 503 are placed on the outer casing 509.

[0239] Next, as shown in Figure 11C, the outer casing 509 is bent at the portion indicated by the dashed line. Then, the outer periphery of the outer casing 509 is joined. For joining, for example, heat compression bonding 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 can be added later.

[0240] Next, the electrolyte 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 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is sealed. In this way, a laminate-type secondary battery 500 can be manufactured.

[0241] [Example of a battery pack] An example of a secondary battery pack according to one embodiment of the present invention, which is capable of wireless charging using an antenna, will be explained with reference to Figures 12A to 12C.

[0242] Figure 12A shows the external appearance of the secondary battery pack 531, which has a thin rectangular parallelepiped shape (it can also be called a thick flat plate shape). Figure 12B is a diagram illustrating the configuration of the secondary battery pack 531. The secondary battery pack 531 includes a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. The circuit board 540 is fixed by a seal 515. The secondary battery pack 531 also has an antenna 517.

[0243] The interior of the secondary battery 513 may have a structure with a wound body or a structure with a laminated body.

[0244] In the secondary battery pack 531, for example as shown in Figure 12B, a control circuit 590 is located on a circuit board 540. The circuit board 540 is electrically connected to terminals 514. The circuit board 540 is also electrically connected to the antenna 517, one of the positive and negative leads 551 of the secondary battery 513, and the other of the positive and negative leads 552.

[0245] Alternatively, as shown in Figure 12C, the system may include a circuit system 590a provided on the circuit board 540 and a circuit system 590b electrically connected to the circuit board 540 via terminals 514.

[0246] The antenna 517 is not limited to a coil shape; for example, it may be linear or plate-shaped. Alternatively, antennas such as planar antennas, aperture antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas may be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of the capacitor. This allows for power exchange not only through electromagnetic and magnetic fields, but also through electric fields.

[0247] The secondary battery pack 531 has a layer 519 between the antenna 517 and the secondary battery 513. The layer 519 has the function of shielding, for example, the electromagnetic field from the secondary battery 513. For the layer 519, a magnetic material can be used, for example.

[0248] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0249] (Embodiment 5) This embodiment shows an example of a vehicle having a secondary battery according to one aspect of the present invention.

[0250] As for vehicles, secondary batteries can typically be applied to automobiles. Examples of automobiles include next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), or plug-in hybrid vehicles (PHEVs or PHVs), and secondary batteries can be applied as one of the power sources installed in these vehicles. Vehicles are not limited to automobiles. For example, examples of vehicles include trains, monorails, ships, submersibles (deep-sea exploration vessels, unmanned submersibles), flying objects (helicopters, unmanned aerial vehicles (drones), airplanes, rockets, artificial satellites), electric bicycles, electric motorcycles, etc., and secondary batteries according to one aspect of the present invention can be applied to these vehicles.

[0251] As shown in Figure 13C, electric vehicles are equipped with a first battery 1301a, 1301b as the main secondary battery for driving, and a second battery 1311 that supplies power to the inverter 1312 that starts the motor 1304. The second battery 1311 is also called a cranking battery (or 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, 1301b.

[0252] The internal structure of the first battery 1301a may be a wound type as shown in Figure 8C or Figure 9A, or a stacked type as shown in Figure 10A or Figure 10B. Furthermore, the first battery 1301a may use the all-solid-state battery of Embodiment 6. Using the all-solid-state battery of Embodiment 6 for the first battery 1301a allows for higher capacity, improved safety, and miniaturization and weight reduction.

[0253] 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.

[0254] Furthermore, the vehicle-mounted secondary battery has a service plug or circuit breaker that can cut off high voltage without using tools in order to interrupt power from multiple secondary batteries, and is provided on the first battery 1301a.

[0255] 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. In the case where there is a rear motor 1317 on the rear wheels, the first battery 1301a is used to rotate the rear motor 1317.

[0256] Furthermore, the second battery 1311 supplies power to 14V automotive components (audio system 1313, power windows 1314, lights 1315, etc.) via the DC-DC circuit 1310.

[0257] Next, the first battery 1301a will be explained using Figure 13A.

[0258] Figure 13A shows an example where nine rectangular secondary batteries 1300 are arranged in a single battery pack 1415. In this example, the 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, 1414 and 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.

[0259] 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 BTOS (Battery operating system or Battery oxide semiconductor).

[0260] It is preferable to use a metal oxide that functions as an oxide semiconductor. In this specification, a metal oxide refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also called oxide semiconductors or simply OS), etc. For example, when a metal oxide is used in the semiconductor layer of a transistor, the metal oxide may be referred to as an oxide semiconductor.

[0261] The metal oxide in the channel-forming region preferably contains indium (In). When the metal oxide in the channel-forming region contains indium, the carrier mobility (electron mobility) of the OS transistor increases. For example, indium oxide (InOx) or indium gallium zinc oxide (In-Ga-Zn oxide, also written as "IGZO") can be used in the channel-forming region. Furthermore, the metal oxide in the channel-forming region is preferably an oxide semiconductor containing element M. Element M is preferably at least one of aluminum (Al), gallium (Ga), and tin (Sn). Other elements applicable to element M include boron (B), silicon (Si), titanium (Ti), iron (Fe), nickel (Ni), germanium (Ge), yttrium (Y), zirconium (Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), neodymium (Nd), hafnium (Hf), tantalum (Ta), and tungsten (W). However, in some cases, element M may be a combination of multiple elements as mentioned above. Element M is, for example, an element with a high bond energy with oxygen. For example, an element with a higher bond energy with oxygen than indium. Furthermore, the metal oxide containing the channel-forming region is preferably a metal oxide containing zinc (Zn). Metal oxides containing zinc may be more prone to crystallization.

[0262] The metal oxides present in the channel-forming regions are not limited to indium-containing metal oxides. For example, the metal oxides present in the channel-forming regions may be zinc-tin oxides, gallium-tin oxides, or other metal oxides that do not contain indium but contain zinc, gallium, or tin.

[0263] Furthermore, since it can be used in high-temperature environments, it is preferable that the control circuit section 1320 uses a transistor made of an oxide semiconductor. To simplify the process, the control circuit section 1320 may also be formed using a unipolar transistor. Transistors using an oxide semiconductor in the semiconductor layer have a wider operating ambient temperature range than single-crystal Si transistors, from -40°C to 150°C, and even if the secondary battery overheats, the change in characteristics is smaller compared to single-crystal Si transistors. The off-current of a transistor using an oxide semiconductor is below the lower limit of measurement regardless of temperature, even at 150°C, but the off-current characteristics of a single-crystal Si transistor are highly temperature-dependent. For example, at 150°C, the off-current of a single-crystal Si transistor increases, and the current on / off ratio does not become sufficiently large. The control circuit section 1320 can improve safety.

[0264] The control circuit unit 1320, which uses a memory circuit including an oxide semiconductor transistor, can also function as an automatic control device for secondary batteries to address 10 causes of instability, such as micro-short circuits. Functions to eliminate the 10 causes of instability include overcharge prevention, overcurrent prevention, overheat control during charging, cell balancing in the battery pack, over-discharge prevention, remaining charge indicator, automatic control of charging voltage and current according to temperature, control of charging current according to the degree of degradation, detection of abnormal behavior of micro-short circuits, and prediction of abnormalities related to micro-short circuits. The control circuit unit 1320 has at least one of these functions. Furthermore, it is possible to miniaturize the automatic control device for secondary batteries.

[0265] Furthermore, "micro-short" refers to a tiny short circuit inside a secondary battery. It does not mean that the positive and negative electrodes of the secondary battery are short-circuited, making charging and discharging impossible. Rather, it refers to a phenomenon where a small short-circuit current flows through a tiny short circuit. Because even a relatively short time and small location can cause a large voltage change, the abnormal voltage value may affect subsequent estimations.

[0266] One of the causes of micro-short circuits is said to be that multiple charge-discharge cycles result in an uneven distribution of the positive electrode active material, causing localized current concentration in parts of the positive and negative electrodes, leading to areas where the separator malfunctions, or causing micro-short circuits due to the generation of by-reactants from side reactions.

[0267] Furthermore, in addition to detecting micro-shorts, the control circuit unit 1320 also 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.

[0268] Next, Figure 13B shows an example of a block diagram of the battery pack 1415 shown in Figure 13A.

[0269] 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 has upper and lower voltage limits set for the secondary battery used, and limits the upper limit of external current or the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the voltage range for which use is recommended, and if it goes outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and / or overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch of the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0270] The switch section 1324 can be constructed by combining n-channel or p-channel transistors. The switch section 1324 is not limited to a switch having a Si transistor using single-crystal silicon, but may also be formed using power transistors such as Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOy (gallium oxide: y is a real number greater than 0). 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, a control circuit section 1320 using OS transistors can be stacked on the switch section 1324 and integrated into a single chip. Since the volume occupied by the control circuit unit 1320 can be reduced, miniaturization becomes possible.

[0271] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage HV) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage LV) onboard equipment. Lead-acid batteries are often used for the second battery 1311 due to cost advantages. Lead-acid batteries have the disadvantage of higher self-discharge and are prone to degradation due to a phenomenon called sulfation compared to lithium-ion batteries. Using a lithium-ion 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 malfunctions occurring that are difficult to detect 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 charge state.

[0272] This embodiment shows an example in which lithium-ion batteries are used for both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. For example, the all-solid-state battery of Embodiment 6 may be used. By using the all-solid-state battery of Embodiment 6 for the second battery 1311, high capacity can be achieved, and the device can be made smaller and lighter.

[0273] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 or the battery controller 1302. Alternatively, it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0274] 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.

[0275] Although not shown in the diagram, when an electric vehicle is connected to an external charger, the charger's plug or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some cases, a control circuit is provided in the charger, and the functions of the battery controller 1302 are not 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 control circuit is also provided in the charger's plug or connection cable. 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. Furthermore, the ECU uses either a CPU or a GPU.

[0276] External chargers installed at charging stations and other locations may have a 100V-200V outlet, or a 3-phase 200V and 50kW output. Additionally, it is possible to charge by receiving power from external charging equipment using contactless power supply methods.

[0277] For rapid charging, a rechargeable battery capable of withstanding high-voltage charging is desired to achieve short charging times.

[0278] Furthermore, by using graphene as a conductive material, it is possible to suppress capacity degradation even when the electrode layer is thickened and the load is increased, and maintain high capacity. As a synergistic effect, a secondary battery with significantly improved electrical characteristics can be realized. This is particularly effective for secondary batteries used in vehicles, and it is possible to provide vehicles with a long driving range, specifically a driving range of 500 km or more on a single charge, without increasing the ratio of the weight of the secondary battery to the total weight of the vehicle.

[0279] 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.

[0280] By mounting a secondary battery as shown in any one of Figures 7D, 9C, or 13A onto a vehicle, next-generation clean energy vehicles such as hybrid vehicles (HVs), electric vehicles (EVs), or plug-in hybrid vehicles (PHVs) can be realized. Furthermore, secondary batteries can also be mounted on agricultural machinery, motorized bicycles including electric-assist bicycles, motorcycles, electric wheelchairs, electric carts, ships, submarines, aircraft, rockets, satellites, space probes, planetary probes, or spacecraft. 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.

[0281] Figures 14A to 14D illustrate a transport vehicle using one embodiment of the present invention. The automobile 2001 shown in Figure 14A 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 14A 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 that is electrically connected to the secondary battery module.

[0282] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via a plug-in method or a contactless power supply method to the secondary battery of the automobile 2001. When charging, the charging method or connector specifications may be carried out as appropriate in accordance with the prescribed methods of CHAdeMO (registered trademark) or Combo. The charging facility may be a charging station installed in a commercial facility or a household power supply. For example, the energy storage device mounted on 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 ADC converter.

[0283] Although not shown in the diagram, a power receiving device can also be mounted on the vehicle, and power can be supplied contactlessly from a ground-based power transmission device for charging. In this contactless power supply method, by incorporating the power transmission device into the road or exterior wall, charging can be performed not only when the vehicle is stopped but also while it is in motion. Furthermore, this contactless 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 contactless power supply, electromagnetic induction or magnetic resonance methods can be used.

[0284] Figure 14B 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 nominal voltage of 3.0V to 5.0V. The battery pack 2201 has the same functions as Figure 14A, except for differences in the number of secondary batteries constituting the secondary battery module, so the explanation is omitted.

[0285] Figure 14C 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, for example, by connecting more than 100 secondary batteries with a nominal voltage of 3.0V to 5.0V in series. Furthermore, it has the same functions as Figure 14A, except for differences in the number of secondary batteries constituting the secondary battery module of the battery pack 2202, so a detailed explanation is omitted.

[0286] Figure 14D shows an example of an aircraft 2004 having a fuel-burning engine. The aircraft 2004 shown in Figure 14D can be considered a type of transport vehicle because it has wheels for takeoff and landing, and has a battery pack 2203 which includes a secondary battery module formed by connecting multiple secondary batteries and a charging control device.

[0287] 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 functions as Figure 14A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0288] Figure 14E shows an example of a satellite 2005 equipped with a secondary battery 2204. It is preferable that the secondary battery 2204 is mounted inside the satellite 2005, covered with a heat-insulating material.

[0289] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0290] (Embodiment 6) In this embodiment, an example of mounting a secondary battery, which is one aspect of the present invention, in a building will be described with reference to Figures 15A and 15B.

[0291] The house shown in Figure 15A 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. Alternatively, the power storage device 2612 may 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.

[0292] 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.

[0293] Figure 15B shows an example of an energy storage device according to one aspect of the present invention. As shown in Figure 15B, an energy storage device 2791 according to one aspect of the present invention is installed in the underfloor space 2796 of the building 2799.

[0294] A control device 2790 is installed in the energy storage device 2791, and the control device 2790 is electrically connected by wiring to the distribution board 2703, the energy storage controller 2705 (also called the control device), the display unit 2706, and the router 2709.

[0295] Power is supplied from the commercial power supply 2701 to the distribution panel 2703 via the service drop connection section 2710. Power is also supplied to the distribution panel 2703 from the energy storage device 2791 and the commercial power supply 2701, and the distribution panel 2703 supplies the supplied power to the general load 2707 and the energy storage system load 2708 via outlets (not shown).

[0296] The general load 2707 is an electrical device such as a television or personal computer, and the energy storage load 2708 is an electrical device such as a microwave oven, refrigerator, or air conditioner.

[0297] The energy storage controller 2705 includes a measurement unit 2711, a prediction unit 2712, and a planning unit 2713. The measurement unit 2711 has the function of measuring the amount of electricity consumed by the general load 2707 and the energy storage system load 2708 during a day (for example, from 0:00 to 24:00). The measurement unit 2711 may also have the function of measuring the amount of electricity consumed by the energy storage device 2791 and the amount of electricity supplied from the commercial power supply 2701. The prediction unit 2712 has the function of predicting the amount of electricity demanded by the general load 2707 and the energy storage system load 2708 during the next day, based on the amount of electricity consumed by the general load 2707 and the energy storage system load 2708 during the day. The planning unit 2713 has the function of planning the charging and discharging of the energy storage device 2791 based on the amount of electricity demand predicted by the prediction unit 2712.

[0298] The amount of electricity consumed by the general load 2707 and the energy storage system load 2708, as measured by the measurement unit 2711, can be checked on the display unit 2706. It can also be checked via the router 2709 on electrical equipment such as televisions or personal computers. Furthermore, it can be checked via the router 2709 on portable electronic devices such as smartphones or tablets. Additionally, the amount of electricity demand for each time period (or hourly) predicted by the prediction unit 2712 can be checked on the display unit 2706, electrical equipment, and portable electronic devices.

[0299] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0300] (Embodiment 7) In this embodiment, as an example of mounting a secondary battery in a vehicle, an example is shown in which a lithium-ion battery according to one aspect of the present invention is mounted in a motorcycle and a bicycle.

[0301] Figure 16A shows an example of an electric bicycle using a power storage device according to one aspect of the present invention. The power storage device according to one aspect of the present invention can be applied to the electric bicycle 8700 shown in Figure 16A. The power storage device according to one aspect of the present invention includes, for example, a plurality of batteries and a protection circuit.

[0302] The electric bicycle 8700 is equipped with a power storage device 8702. The power storage device 8702 can supply electricity to a motor that assists the rider. The power storage device 8702 is also portable, and Figure 16B shows it detached from the bicycle. The power storage device 8702 also has multiple storage batteries 8701 built into it, which are part of a power storage device according to one embodiment of the present invention, and the remaining battery level and other information can be displayed on a display unit 8703. The power storage device 8702 also has a control circuit 8704 capable of controlling the charging of the secondary battery or detecting abnormalities, as exemplified in Embodiment 7. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701.

[0303] Figure 16C shows an example of a two-wheeled vehicle using the power storage device of one aspect of the present invention. The scooter 8600 shown in Figure 16C includes a power storage device 8602, a side mirror 8601, and a direction indicator light 8603. The power storage device 8602 can supply electricity to the direction indicator light 8603.

[0304] Further, the scooter 8600 shown in Figure 16C can store the power storage device 8602 in the under-seat storage 8604. The power storage device 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small.

[0305] The content of this embodiment can be freely combined with the content of other embodiments.

[0306] (Embodiment 8) In this embodiment, an example of mounting a secondary battery, which is one aspect of the present invention, on an electronic device will be described. Examples of electronic devices on which the secondary battery is mounted include, for example, television devices (also referred to as TVs or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also referred to as mobile phones or mobile phone devices), portable game machines, portable information terminals, audio playback devices, and large game machines such as pachinko machines. Examples of portable information terminals include notebook personal computers, tablet terminals, electronic book terminals, and mobile phones.

[0307] Figure 17A shows an example of a mobile phone. The mobile phone 2100 includes, in addition to a display unit 2102 incorporated in a housing 2101, operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. Note that the mobile phone 2100 has a secondary battery 2107.

[0308] The mobile phone 2100 can execute various applications such as mobile phone calls, email, text viewing and creation, music playback, Internet communication, and computer games.

[0309] In addition to time setting, the operation button 2103 can have various functions such as power on and off operations, wireless communication on and off operations, execution and cancellation of the manner mode, execution and cancellation of the power saving mode, etc. For example, the functions of the operation button 2103 can also be freely set by the operating system incorporated in the mobile phone 2100.

[0310] Also, the mobile phone 2100 is capable of performing communication-standardized short-range wireless communication. For example, it can also make hands-free calls by communicating with a wireless communication-capable headset.

[0311] Further, the mobile phone 2100 includes an external connection port 2104 and can directly exchange data with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that the charging operation may also be performed by wireless power supply without going through the external connection port 2104.

[0312] Also, the mobile phone 2100 preferably has a sensor. As the sensor, for example, it is preferable to mount a human body sensor such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, or an acceleration sensor.

[0313] FIG. 17B shows an unmanned aerial vehicle 2300 having a plurality of 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 aspects of the present invention. The unmanned aerial vehicle 2300 can be remotely operated via the antenna.

[0314] FIG. 17C shows an example of a robot. The robot 6400 shown in FIG. 17C includes a secondary battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display unit 6405, a lower camera 6406, an obstacle sensor 6,407, a moving mechanism 6408, an arithmetic unit, etc.

[0315] 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.

[0316] 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.

[0317] The upper camera 6403 and the 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, the lower camera 6406 and the obstacle sensor 6407.

[0318] The robot 6400 is equipped with a secondary battery 6409 according to one aspect of the present invention and a semiconductor device or electronic component in its internal region.

[0319] Figure 17D 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.

[0320] 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 may become entangled in the brush 6304, such as wiring, it can stop the rotation of the brush 6304. The cleaning robot 6300 is equipped with a secondary battery 6306 according to one aspect of the present invention and a semiconductor device or electronic component in its internal region.

[0321] Figure 18A shows an example of a wearable device. Wearable devices use rechargeable batteries as a power source. Furthermore, in order to enhance splash resistance, water resistance, or dust resistance when used by users in daily life or outdoors, there is a demand for wearable devices that can be charged wirelessly in addition to wired charging with exposed connectors.

[0322] For example, a secondary battery according to one aspect of the present invention can be mounted in a spectacle-type device 4000 as shown in Figure 18A. The spectacle-type device 4000 has a frame 4000a and a display unit 4000b. By mounting the secondary battery in the temple portion of the curved frame 4000a, a lightweight spectacle-type device 4000 with good weight balance and a long continuous usage time can be made.

[0323] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the headset-type device 4001. The headset-type device 4001 has at least a microphone section 4001a, a flexible pipe 4001b, and an earphone section 4001c. The secondary battery can be provided in the flexible pipe 4001b or in the earphone section 4001c.

[0324] Furthermore, a secondary battery according to one aspect of the present invention can be mounted on a device 4002 that can be directly attached to the body. The secondary battery 4002b can be provided inside the thin housing 4002a of the device 4002.

[0325] Furthermore, a secondary battery according to one aspect of the present invention can be mounted on the device 4003, which can be attached to clothing. The secondary battery 4003b can be provided inside the thin housing 4003a of the device 4003.

[0326] Furthermore, a secondary battery according to one aspect of the present invention can be mounted on the belt-type device 4006. The belt-type device 4006 has a belt portion 4006a and a wireless power supply and receiving portion 4006b, and a secondary battery can be mounted in the internal region of the belt portion 4006a.

[0327] Furthermore, a secondary battery according to one aspect of the present invention can be mounted in the wristwatch-type device 4005. The wristwatch-type device 4005 has a display unit 4005a and a belt unit 4005b, and a secondary battery can be provided in either the display unit 4005a or the belt unit 4005b.

[0328] The display unit 4005a can display not only the time, but also various other information such as incoming emails or phone calls.

[0329] Furthermore, since the wristwatch-type device 4005 is a wearable device that is worn directly on the wrist, it may be equipped with sensors to measure the user's pulse, blood pressure, etc. It can accumulate data on the user's exercise level and health, and manage their health.

[0330] Figure 18B shows a perspective view of the wristwatch-type device 4005 after it has been removed from the arm.

[0331] A side view is also shown in Figure 18C. Figure 18C shows how the secondary battery 913 is built into the internal region. The secondary battery 913 is the secondary battery shown in Embodiment 4. The secondary battery 913 is located in a position that overlaps with the display unit 4005a.

[0332] The contents of this embodiment can be freely combined with the contents of other embodiments.

[0333] 10: Lithium-ion battery, 11: Positive electrode, 11A: Positive electrode, 11B: Positive electrode, 12: Negative electrode, 13: Separator, 21: Positive electrode current collector, 22: Positive electrode active material layer, 31: Negative electrode current collector, 32: Negative electrode active material layer, 41: Conductive material, 51: Electrolyte, 100: First positive electrode active material, 101: Mixture, 150: Carbon coating layer, 200: Second positive electrode active material, 201: Mixture, 202: Carbon coating composite, 301: Mixture, 302: Mixture, 303: Composite oxide, 304: Mixture, 401: Mixture, 402: Composite oxide, 403: Mixture

Claims

It comprises multiple lithium iron phosphate particles and multiple lithium manganese iron phosphate particles, The median diameter D50 in the particle size distribution of the plurality of lithium iron phosphate particles is 300 nm or more and 3 μm or less. The median diameter D50 in the particle size distribution of the plurality of lithium iron manganese phosphate particles is 30 nm or more and 100 nm or less. A positive electrode in which the total weight of the plurality of lithium iron phosphate particles is 70% or more of the total weight of the plurality of lithium iron phosphate particles and the plurality of manganese iron phosphate particles. 　 It comprises multiple lithium iron phosphate particles and multiple lithium manganese iron phosphate particles, The median diameter D50 in the particle size distribution of the plurality of lithium iron phosphate particles is 300 nm or more and 3 μm or less. The median diameter D50 in the particle size distribution of the plurality of lithium iron manganese phosphate particles is 30 nm or more and 100 nm or less. A positive electrode in which the total weight of the plurality of lithium iron phosphate particles is 70% or more of the total weight of the plurality of lithium iron phosphate particles and the plurality of lithium iron manganese phosphate particles. 　 In claim 1 or claim 2, The aforementioned manganese iron lithium particles are LiMn １−ｘ Fe ｘ PO ４ The positive pole is represented as such, where x is a number greater than 0 and less than 0.

5. In claim 3, The positive electrode comprises a plurality of lithium iron phosphate particles and a plurality of lithium manganese iron phosphate particles, each having a carbon coating layer. 　 In claim 3, A positive electrode having a region in which one of the plurality of lithium iron phosphate particles and one of the plurality of lithium manganese iron phosphate particles are connected by a carbon coating layer. 　 The steps include: mixing lithium iron phosphate, lithium iron manganese phosphate, and a carbon-containing compound to prepare a mixture; The process involves heating the aforementioned mixture at a temperature of 600°C to 700°C for 2 to 20 hours to produce a carbon-coated composite, The steps include mixing the carbon-coated composite, a conductive material, a binder, and a solvent to prepare a slurry, The steps include applying the slurry to aluminum foil, The process includes the step of removing the solvent, Method for manufacturing the positive electrode. 　 In claim 6, The aforementioned lithium iron manganese phosphate is LiMn １−ｘ Fe ｘ PO ４ It is expressed as such, where x is a number greater than 0 and less than 0.

5. Method for manufacturing the positive electrode.

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