Rechargeable batteries and electronic devices

Abstract

To provide a positive electrode active material with a large charge / discharge capacity. Or to provide a positive electrode active material with a high charge / discharge voltage. Or to provide an energy storage device with minimal degradation. Or to provide an energy storage device with high safety. Or to provide a novel energy storage device. [Solution] A positive electrode active material comprising lithium, multiple transition metals, oxygen, and impurity elements. The positive electrode active material has a first region including a surface layer and a second region provided internally, with different concentrations of transition metals in the first region and the second region. It also has an impurity layer between the first region and the second region.

Description

[Technical Field]

[0001] This invention relates to a secondary battery using a positive electrode active material and a method for manufacturing the same, or to a portable information terminal, vehicle, etc., that has a secondary battery.

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

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

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

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

[0006] Therefore, improvements to the positive electrode active material are being considered to improve the cycle characteristics and increase the capacity of lithium-ion secondary batteries (for example, Patent Document 1).

[0007] Furthermore, the characteristics required of energy storage devices include safety in various operating environments and improved long-term reliability. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2019-21456 [Overview of the project] [Problems that the invention aims to solve]

[0009] One aspect of the present invention aims to provide a positive electrode active material with a large charge / discharge capacity. Alternatively, it aims to provide a positive electrode active material with a high charge / discharge voltage. Alternatively, it aims to provide a positive electrode active material with minimal degradation. Alternatively, it aims to provide a novel positive electrode active material. Alternatively, it aims to provide a secondary battery with a large charge / discharge capacity. Alternatively, it aims to provide a secondary battery with a high charge / discharge voltage. Alternatively, it aims to provide a secondary battery that is safe and reliable. Alternatively, it aims to provide a secondary battery with minimal degradation. Alternatively, it aims to provide a secondary battery with a long lifespan. Alternatively, it aims to provide a novel secondary battery.

[0010] Furthermore, one aspect of the present invention aims to provide novel materials, active materials, energy storage devices, or methods for producing them.

[0011] 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.

[0012] Another objective is to provide a vehicle equipped with a secondary battery according to one embodiment of the present invention that has a long driving range, specifically a driving range on a single charge (driving range on a single charge) of 300 km or more, preferably 500 km or more. The driving range on a single charge refers to the distance the vehicle actually travels from the time the onboard secondary battery is charged using an external power source such as a charging station until it is charged again using an external power source. In other words, the driving range on a single charge corresponds to the maximum distance that can be traveled from a state where the secondary battery has been fully charged once using an external power source, and can be said to be the driving distance per charge. [Means for solving the problem]

[0013] One aspect of the present invention is a secondary battery having a positive electrode active material, wherein the positive electrode active material comprises a first region and a second region located inside the first region, and each of the first region and the second region contains lithium, oxygen, and one or more selected from a first transition metal, a second transition metal, and a third transition metal, and the concentration of at least one of the first transition metal, the second transition metal, and the third transition metal differs between the first region and the second region.

[0014] In the above, the positive electrode active material preferably has an impurity layer containing impurity elements, and the impurity layer is preferably provided between the first region and the second region.

[0015] In the above, it is preferable that the impurity layer has the function of suppressing the interdiffusion of elements between the first region and the second region.

[0016] In the above, it is preferable that the impurity element is at least one of titanium, fluorine, magnesium, aluminum, zirconium, calcium, gallium, niobium, phosphorus, boron, and silicon.

[0017] Another aspect of the present invention is a secondary battery having a positive electrode active material, wherein the positive electrode active material comprises a first region, a second region located inside the first region, a first impurity layer located outside the first region, and a second impurity layer located between the first and second regions, and the first region and the second region each contain lithium, oxygen, and one or more selected from a first transition metal, a second transition metal, and a third transition metal, and the concentration of at least one of the first transition metal, the second transition metal, and the third transition metal differs between the first region and the second region, and the impurity elements present in the first and second impurity layers are at least one of titanium, fluorine, magnesium, aluminum, zirconium, calcium, gallium, niobium, phosphorus, boron, and silicon.

[0018] Furthermore, it is preferable that the impurity layer has the function of suppressing the interdiffusion of elements between the first region and the second region.

[0019] Furthermore, in the above, the first transition metal is nickel, the second transition metal is cobalt, and the third transition metal is manganese. Preferably, the concentration of cobalt is higher in the first region than in the second region, and the concentrations of nickel and manganese are lower in the first region than in the second region. Since cobalt is a limited resource, reducing the amount of cobalt used can reduce the material cost of the positive electrode active material. Nickel is more abundant than cobalt and is an environmentally friendly transition metal. When manufacturing low-cost secondary batteries, it is preferable to use more nickel than cobalt.

[0020] Furthermore, in the above, it is preferable that the first region promotes the diffusion of lithium during charging and discharging, thereby contributing to the stabilization of the positive electrode active material.

[0021] Furthermore, in the above, the secondary battery contains a carbon material, and it is preferable that the carbon material is at least one of fibrous carbon, graphene, or particulate carbon. These carbon materials are used as conductive materials (also called conductive imparters or conductive additives). By attaching the conductive material between multiple active materials, the multiple active materials are electrically connected to each other, and conductivity is increased. Note that "attachment" does not only refer to the physical close contact between the active material 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 part of the surface of the active material, the conductive material fits into the surface irregularities of the active material, or where they are electrically connected even if they are not in contact with each other. Note that fibrous carbon refers to carbon nanotubes (also called CNTs), etc. Because graphene is in a thin, planar form, it can form efficient conduction paths with a smaller amount than other carbon materials, and the proportion of active material can be increased, thus improving the capacity per unit volume of the electrode. This makes it possible to miniaturize and increase the capacity of secondary batteries. In addition, using graphene can suppress capacity degradation during rapid charging and discharging. In this specification, graphene includes not only single-layer graphene but also multi-layer graphene and multi-layer graphene. Multi-layer graphene refers to, for example, a material having 2 to 100 layers of carbon sheets. Particulate carbon refers to carbon black (furnace black, acetylene black (also called AB), graphite, etc.). A configuration including graphene is preferred as the conductive material. By using graphene as the conductive material, it may be possible to suppress the degradation of the positive electrode active material associated with charging and discharging. For example, during charging and discharging, degradation may occur from the surface layer of the positive electrode active material due to the effects of cation mixing. In this case, it may be possible to suppress such degradation by using a configuration that includes graphene as the conductive material.

[0022] Another aspect of the present invention is an electronic device having the secondary battery described above.

[0023] Another aspect of the present invention is a vehicle having the secondary battery described above. The use of the above-described positive electrode active material is preferable for next-generation clean energy vehicles equipped with a large battery containing multiple secondary batteries, such as hybrid vehicles, electric vehicles, and plug-in hybrid vehicles, because it enables the realization of a secondary battery with high energy density and high safety and reliability. [Effects of the Invention]

[0024] According to one aspect of the present invention, it is possible to provide a positive electrode active material that has high energy density and large charge / discharge capacity. Alternatively, it is possible to provide a positive electrode active material that has high energy density and high charge / discharge voltage. Alternatively, it is possible to provide a positive electrode active material that exhibits little degradation. Alternatively, it is possible to provide a novel positive electrode active material. Alternatively, it is possible to provide a secondary battery with large charge / discharge capacity. Alternatively, it is possible to provide a secondary battery with high charge / discharge voltage. Alternatively, it is possible to provide a secondary battery that is safe or highly reliable. Alternatively, it is possible to provide a secondary battery that exhibits little degradation. Alternatively, it is possible to provide a secondary battery with a long lifespan. Alternatively, it is possible to provide a novel secondary battery.

[0025] In order to increase the driving range on a single charge, increasing the number of secondary batteries and thus the capacity can increase the total weight of the vehicle, which increases the energy required to move the vehicle and may shorten the driving range on a single charge. By using the high-energy-density secondary battery disclosed in one aspect of the present invention, it is possible to extend the driving range on a single charge without significantly changing the total weight of a vehicle equipped with the same weight of secondary batteries.

[0026] Therefore, according to one aspect of the present invention, a vehicle equipped with a novel energy storage device can be provided.

[0027] Furthermore, according to one aspect of the present invention, novel materials, active materials, energy storage devices, or methods for producing them can be provided.

[0028] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0029] [Figure 1] Figures 1A to 1C show examples of cross-sectional views of positive electrode active materials. [Figure 2] Figures 2A to 2C show examples of cross-sectional views of positive electrode active material. [Figure 3] Figures 3A and 3B are examples of cross-sectional views of positive electrode active material. [Figure 4] Figures 4A1, 4B1, 4C1, 4D1, and 4E1 are examples of perspective views of the positive electrode active material. Figures 4A2, 4B2, 4C2, 4D2, and 4E2 are examples of cross-sectional views of the positive electrode active material. [Figure 5] Figures 5A and 5B illustrate an example of a method for preparing a positive electrode active material. [Figure 6] Figure 6 illustrates the charge depth and crystal structure of the positive electrode active material. [Figure 7] Figure 7 illustrates the charging depth and crystal structure of the positive electrode active material. [Figure 8] Figures 8A to 8D are cross-sectional views illustrating examples of the positive electrode of a secondary battery. [Figure 9] Figures 9A and 9B illustrate examples of secondary batteries. [Figure 10] Figures 10A to 10C illustrate examples of secondary batteries. [Figure 11] Figures 11A and 11B illustrate an example of a secondary battery. [Figure 12] Figures 12A to 12C illustrate a coin-type rechargeable battery. [Figure 13] Figure 13A is a top view illustrating a secondary battery, and Figure 13B is a cross-sectional view illustrating a secondary battery. [Figure 14] Figures 14A to 14C illustrate a secondary battery. [Figure 15] Figures 15A to 15C illustrate a secondary battery. [Figure 16] Figure 16A is a perspective view of a battery pack showing one embodiment of the present invention, Figure 16B is a block diagram of the battery pack, and Figure 16C is a block diagram of a vehicle having a motor. [Figure 17] Figures 17A and 17B illustrate an energy storage device according to one aspect of the present invention. [Figure 18] Figures 18A and 18B illustrate an example of electronic equipment, while Figures 18C through 18F illustrate an example of a transport vehicle. [Figure 19] Figure 19A shows an electric bicycle, Figure 19B shows the secondary battery of an electric bicycle, and Figure 19C illustrates an electric motorcycle. [Figure 20] Figure 20A shows an example of a wearable device, Figure 20B shows a perspective view of a wristwatch-type device, Figure 20C is a side view of a wristwatch-type device, and Figure 20D is a perspective view illustrating a head-mounted display. [Figure 21] Figure 21 is a graph showing the ratio of the radii of region 191 to the radius of particle 190 (where the radius of particle 190 is set to 1), and the ratio of the volumes of region 191 and region 193. [Figure 22] Figure 22A is a graph of the radius of region 191 and the discharge capacity per unit weight when NCM811 is used in region 191 and LiCoO2 is used in region 193, and Figure 22B is a graph of the radius of region 191 and the discharge capacity per unit weight when LiCoO2 is used in region 191 and NCM811 is used in region 193. [Modes for carrying out the invention]

[0030] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and its form and details can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the embodiments described below.

[0031] Furthermore, in this specification, crystal planes and directions are indicated by Miller indices. In crystallography, crystal planes and directions are indicated by a superscript bar above the number, but in this specification, due to limitations in patent application notation, a minus sign (-) may be placed before the number instead of a bar above it. In addition, individual orientations indicating directions within a crystal are indicated by [ ], collective orientations indicating all equivalent directions are indicated by < >, individual planes indicating crystal planes are indicated by ( ), and collective planes having equivalent symmetry are indicated by {}.

[0032] In this specification, segregation refers to the phenomenon in which a certain element (e.g., B) is spatially non-uniformly distributed in a solid composed of multiple elements (e.g., A, B, C).

[0033] In this specification, the surface layer of particles such as active material refers to, for example, the region within 50 nm from the surface, more preferably within 35 nm, even more preferably within 20 nm, and most preferably within 10 nm. Surfaces formed by cracks or fissures may also be considered the surface. The region deeper than the surface layer is referred to as the interior. Furthermore, in this specification, particles are not limited to spherical shapes (circular cross-sections), but the cross-sectional shapes of individual particles can be elliptical, rectangular, trapezoidal, conical, square with rounded corners, asymmetrical shapes, etc., and individual particles may also be irregular in shape.

[0034] In this specification, the layered rock salt crystal structure of a composite oxide containing lithium and a transition metal refers to a crystal structure having a rock salt-type ionic arrangement in which cations and anions are arranged alternately, and in which the transition metal and lithium are regularly arranged to form a two-dimensional plane, thereby enabling two-dimensional diffusion of lithium. Defects such as vacancies in cations or anions may be present. Furthermore, strictly speaking, a layered rock salt crystal structure may have a distorted lattice structure of the rock salt crystal.

[0035] In this specification, a rock salt-type crystal structure refers to a structure in which cations and anions are arranged alternately. However, vacancies in cations or anions are acceptable.

[0036] Furthermore, in this specification, the O3' type crystal structure of a composite oxide containing lithium and a transition metal is assigned to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen 6-coordinate positions. The symmetry of the CoO2 layer in this structure is the same as that of the O3 type. Therefore, this structure is referred to as the O3' type crystal structure in this specification. Note that in the O3' type crystal structure, light elements such as lithium may occupy the oxygen 4-coordinate positions.

[0037] Furthermore, the O3' type crystal structure can be said to be similar to the CdCl2 type crystal structure, although it has lithium randomly placed between the layers. This crystal structure similar to the CdCl2 type is observed when lithium nickelate is charged to a depth of charge of 0.94 (Li 0.06 Although its crystal structure is similar to that of NiO2, it is known that simple, pure lithium cobaltate, or layered rock salt-type cathode active materials containing a large amount of cobalt, do not usually adopt this crystal structure.

[0038] Layered rock salt crystals and the anions in rock salt crystals adopt a cubic close-packed structure (face-centered cubic lattice structure). It is also presumed that the anions in O3' type crystals adopt a cubic close-packed structure. In this specification, if the anions are arranged in a structure where three layers are stacked with a slight offset from each other, such as ABCABC, it will be referred to as cubic close-packed. Therefore, the anions do not have to be strictly cubic. At the same time, since real crystals always have defects, the analytical results do not necessarily conform to theory. For example, in FFT (Fast Fourier Transform) of electron diffraction or TEM images, spots may appear at positions slightly different from the theoretical positions. For example, if the orientation from the theoretical position is 5 degrees or less, or 2.5 degrees or less, it can be said that it adopts a cubic close-packed structure.

[0039] When layered rock salt crystals and rock salt crystals are in contact, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned. Alternatively, the above phenomenon can also be explained as follows: The anions in the (111) plane of the cubic crystal structure have a triangular arrangement. The layered rock salt crystal has a space group R-3m and a rhombohedral structure, but to facilitate understanding of the structure, it is generally represented by a composite hexagonal lattice, and the (000l) plane of the layered rock salt crystal has a hexagonal lattice. The triangular lattice of the cubic (111) plane has a similar atomic arrangement to the hexagonal lattice of the (000l) plane of the layered rock salt crystal. The consistency between the two lattices can be described as the orientation of the cubic close-packed structure being aligned. However, the space group of layered rock salt crystals and O3'-type crystals is R-3m, which is different from the space group Fm-3m (the space group of typical rock salt crystals) and Fd-3m of rock salt crystals. Therefore, the Miller indices of crystal planes that satisfy the above conditions are different for layered rock salt crystals and O3'-type crystals compared to rock salt crystals. In this specification, it is sometimes said that the crystal orientations are approximately the same when the orientations of the cubic close-packed structure composed of anions are aligned in layered rock salt crystals, O3'-type crystals, and rock salt crystals.

[0040] The approximate agreement of crystal orientation in two regions can be determined from TEM (Transmission Electron Microscope) images, STEM (Scanning Transmission Electron Microscope) images, HAADF-STEM (High-angle Annular Dark Field Scanning TEM) images, ABF-STEM (Annular Bright-Field Scanning Transmission Electron Microscopy) images, etc. XRD (X-ray Diffraction), electron diffraction, neutron diffraction, etc. can also be used as a basis for determination. In TEM images, etc., the arrangement of cations and anions can be observed as a repetition of bright and dark lines. When the orientation of the cubic close-packed structure is aligned in layered rock salt crystals and rock salt crystals, it can be observed that the angle between the repetition of bright and dark lines between crystals is 5 degrees or less, more preferably 2.5 degrees or less. In some cases, light elements such as oxygen and fluorine may not be clearly visible in TEM images, but in such cases, the alignment of the metallic elements can be determined by their arrangement.

[0041] Furthermore, in this specification, the theoretical capacity of the positive electrode active material refers to the amount of electricity when all of the insertable and detachable lithium present in the positive electrode active material has been detached. For example, the theoretical capacity of LiCoO2 is 274 mAh / g, the theoretical capacity of LiNiO2 is 274 mAh / g, and the theoretical capacity of LiMn2O4 is 148 mAh / g.

[0042] Furthermore, in this specification, the charging depth when all insertable and detachable lithium is inserted is defined as 0, and the charging depth when all insertable and detachable lithium in the positive electrode active material has been detached is defined as 1.

[0043] In this specification, charging refers to the movement of lithium ions from the positive electrode to the negative electrode within the battery, and the movement of electrons from the positive electrode to the negative electrode in the external circuit. For positive electrode active material, the release of lithium ions is referred to as charging. Furthermore, positive electrode active material with a charging depth of 0.7 to 0.9 may be referred to as positive electrode active material charged with high voltage.

[0044] Similarly, discharge refers to the movement of lithium ions from the negative electrode to the positive electrode within the battery, and the movement of electrons from the negative electrode to the positive electrode in the external circuit. For positive electrode active materials, the insertion of lithium ions is called discharge. Furthermore, a positive electrode active material with a charge depth of 0.06 or less, or a positive electrode active material that has been discharged to 90% or more of its charge capacity from a state where it was charged at a high voltage, is considered a sufficiently discharged positive electrode active material.

[0045] Furthermore, in this specification, a non-equilibrium phase change refers to a phenomenon that causes a nonlinear change in a physical quantity. For example, a non-equilibrium phase change is thought to occur around the peak in the dQ / dV curve obtained by differentiating capacitance (Q) with respect to voltage (V) (dQ / dV), indicating a significant change in the crystal structure.

[0046] A secondary battery has, for example, a positive electrode and a negative electrode. The positive electrode is composed of a positive electrode active material. The positive electrode active material is, for example, a substance that performs a reaction that contributes to the charge and discharge capacity. However, the positive electrode active material may also contain a portion of substances that do not contribute to the charge and discharge capacity.

[0047] In this specification, the positive electrode active material of one aspect of the present invention may be expressed as a positive electrode material, a positive electrode material for secondary batteries, etc. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a compound. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composition. In this specification, it is preferable that the positive electrode active material of one aspect of the present invention has a composite.

[0048] The discharge rate is the relative ratio of the discharge current to the battery capacity, and is expressed in units of C. For a battery with a rated capacity of X (Ah), the current equivalent to 1C is X (A). If the battery is discharged with a current of 2X (A), it is said to have been discharged at 2C, and if it is discharged with a current of X / 5 (A), it is said to have been discharged at 0.2C. Similarly, the charge rate is also expressed in the same way: if the battery is charged with a current of 2X (A), it is said to have been charged at 2C, and if it is charged with a current of X / 5 (A), it is said to have been charged at 0.2C.

[0049] Constant current charging refers to a method of charging while maintaining a constant charging rate. Constant voltage charging refers to a method of charging while maintaining a constant voltage once the upper voltage limit is reached. Constant current discharging refers to a method of discharging while maintaining a constant discharge rate.

[0050] Furthermore, in this specification, a value in the vicinity of a given numerical value A refers to a value between 0.9A and 1.1A.

[0051] (Embodiment 1) Particles according to one aspect of the present invention can be used as an electrode material for a secondary battery. Furthermore, particles according to one aspect of the present invention function as an active material. An active material is, for example, a substance that undergoes a reaction that contributes to the charge-discharge capacity. The active material may also contain a portion of a substance that does not contribute to the charge-discharge capacity.

[0052] Furthermore, the particles according to one embodiment of the present invention can be used in particular as a positive electrode material for a secondary battery. Also, the particles according to one embodiment of the present invention can function in particular as a positive electrode active material. A positive electrode active material is, for example, a substance that undergoes a reaction that contributes to the charge-discharge capacity and is used as a positive electrode material. Note that the positive electrode active material may include, in part, a substance that does not contribute to the charge-discharge capacity. Particles, active material, positive electrode material, or positive electrode active material having at least lithium, a transition metal, and oxygen may be called a composite oxide.

[0053] Figure 1A shows an example of a cross-section of a particle 190 according to one embodiment of the present invention. The particle 190 shown in Figure 1A has regions 191, 192, and 193.

[0054] Region 191 is located inside region 193. Region 192 is located between region 191 and region 193.

[0055] Region 193 is the region that includes the surface layer of particle 190. Region 192 is the region located inside region 193. Region 191 is the region located inside region 192. Region 191 is the interior of particle 190, and for example, it is the region that includes the center of the particle. The center of the particle refers to the center of gravity of the particle, and its position can be determined using an electron microscope or similar device. For example, when a particle is cut and its cross-section is observed, it refers to the center of the circle when the circumscribed circle with the smallest cross-sectional area is drawn for the cross-section with the largest cross-sectional area, or for a cross-section with a cross-sectional area of ​​90% or more of that maximum cross-sectional area.

[0056] Region 192 is, for example, a region located between region 191 and region 193.

[0057] Region 191 is sometimes referred to as the "core," and region 193 as the "shell."

[0058] Alternatively, regions 191 and 192 may be collectively referred to as the "core," and region 193 as the "shell." In such cases, region 192 may be described as the surface layer of the "core." Region 192 may also be described as the impurity layer.

[0059] It is sometimes said that particle 190 has a core-shell structure (also called a core-shell type structure).

[0060] The average particle size (median diameter, also called D50) of particle 190 is preferably 0.1 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less.

[0061] Region 191 has a particulate shape. Region 191 occupies an area ratio S of the cross-section of particle 190. 191 / S 190is preferably 0.04% or more and 96.0% or less, more preferably 30% or more and 90% or less, and even more preferably 64% or more and 90% or less. As shown in FIG. 2A, the area of region 191 is S 191 , the area of region 192 is S 192 , the area of region 193 is S 193 , the cross-sectional area of particle 190 is S 190 (S 190 = S 191 + S 192 + S 193 ). Here, the distance from the center O of particle 190 to the surface is R 190 . The distance from the center O of particle 190 to the surface of the particulate shape of region 191 is R 191 .

[0062] Region 192 preferably contacts at least a part of the surface of the particulate shape that region 191 has. Alternatively, it is preferably provided so as to cover at least a part of the surface of the particulate shape that region 191 has. Region 192 is preferably arranged at least in part at a position farther from the center O of particle 190 than region 191.

[0063] Region 192 is preferably provided between region 191 and region 193. It is preferably a layer that covers at least a part of the surface of the particulate shape that region 191 has. Region 192 is preferably, for example, a layer having a thickness of 0.5 nm or more and 100 nm or less, and more preferably a layer having a thickness of 1 nm or more and 30 nm or less. Note that the thickness of region 192 does not necessarily have to be uniform.

[0064] Region 192 preferably has a function of suppressing the mutual diffusion during the synthesis of the elements that region 191 and region 193 have. Also, it preferably has a function of not inhibiting the mutual diffusion of lithium during charge and discharge or promoting the mutual diffusion of lithium.

[0065] It is preferable that at least a portion of region 193 is located at a position farther from the center O of particle 190 than regions 191 and 192. It is preferable that region 193 overlaps with at least one of regions 191 and 192. It is preferable that region 193 is layered. Alternatively, it is preferable that the area ratio of region 193 to the cross-section of particle 190 is 4% or more and 99.96%, more preferably 10% or more and 70%, and even more preferably 10% or more and 36%. The thickness of region 193 does not necessarily have to be uniform.

[0066] Region 193 preferably has the function of promoting the diffusion of lithium during charging and discharging, thereby contributing to the stabilization of the positive electrode active material. Furthermore, region 193 preferably has the function of suppressing the degradation of the positive electrode active material during charging and discharging. For example, during charging and discharging, degradation may occur from the surface layer of the positive electrode active material due to the effects of cation mixing. In this case, region 193 should be configured to be less affected by the effects of such cation mixing. In addition, region 193 is not limited to one region, but may have two or more regions. For example, region 193 may have two or more regions, with region 193b provided on the inside and region 193a provided outside of region 193b.

[0067] Furthermore, as shown in Figure 1B, particle 190 may have a region 194. Region 194 is located outside region 193. In this case, region 193 and region 194 together may be called the "shell". Region 194 may also be described as including the surface layer of the "shell", the surface layer of particle 190, or the surface of particle 190. Region 194 may also be described as an impurity layer or impurity region. Furthermore, as shown in Figure 2B, the area of ​​region 194 is S 194 If region 194 is present, the area of ​​particle 190 is S 190 (S 190 =S 191 +S 192 +S 193 +S 194 )

[0068] Furthermore, it is preferable that at least a portion of region 194 is located at a position farther from the center O of particle 190 than region 193. It is preferable that region 194 overlaps with at least one of regions 191, 192, and 193. Also, at least a portion of region 194 overlaps with region 193. Region 194 is preferably a layer with a thickness of 0.5 nm to 100 nm, and more preferably a layer with a thickness of 1 nm to 30 nm. The thickness of region 194 does not necessarily have to be uniform.

[0069] It is preferable that region 194 also be configured to be less susceptible to the effects of cation mixing. When region 194 is present, since it is the outermost region of particle 190, suppressing cation mixing in region 194 and preventing the collapse of the crystal structure may have a particularly high effect in suppressing deterioration of charge-discharge characteristics, etc.

[0070] The particle size can be evaluated, for example, by a particle size distribution analyzer. The area ratio in the cross-section of region 191 or region 193 can be evaluated by cross-sectional observation and various line and surface analyses after the cross-section of the particle 190 is exposed by processing. When evaluating the area ratio, it is preferable to use a cross-section that sufficiently reflects the internal structure of the particle 190. For example, it is preferable to use a cross-section in which the maximum width of the cross-section is 80% or more of the average particle size (D50).

[0071] Similarly, the thickness of each region can be evaluated by cross-sectional observation after the cross-section is exposed through processing, as well as by various line analyses, surface analyses, etc.

[0072] <Complex Oxides> Regions 191 and 193 can be made of materials that allow lithium ions to be inserted into and removed from them. If the carrier ion is an alkali metal ion or alkaline earth metal ion other than lithium, an alkali metal (e.g., sodium or potassium) or alkaline earth metal (e.g., calcium, strontium, barium, beryllium, magnesium) may be used instead of lithium. When regions 191 and 193 are positive electrode active materials, it is preferable to use compounds having, for example, an olivine-type crystal structure, a layered rock salt-type crystal structure, or a spinel-type crystal structure. Compounds having a layered rock salt-type crystal structure include so-called lithium-rich compounds, where the atomic ratio of lithium to the transition metal is greater than 1. In particular, it is preferable to use a composite oxide having a layered rock salt-type crystal structure and belonging to space group R-3m. However, this is not limited to the functions desired for regions 191 and 193.

[0073] Regions 191 and 193 preferably contain a transition metal. Specifically, it is preferable that they contain one or more of cobalt, nickel, and manganese.

[0074] Furthermore, it is preferable that the concentration of at least one of the transition metals present in regions 191 and 193 differs between regions 191 and 193.

[0075] Furthermore, when using two or more transition metals, two types may be used: cobalt and manganese, cobalt and nickel, or nickel and manganese. Alternatively, three types may be used as transition metals: cobalt, manganese, and nickel. In other words, regions 191 and 193 can each contain composite oxides containing lithium and transition metals, such as lithium cobalt oxide, lithium nickel oxide, lithium cobalt oxide in which part of the cobalt is substituted with manganese, lithium cobalt oxide in which part of the cobalt is substituted with nickel, and nickel-manganese-lithium cobalt oxide.

[0076] <Example of a particle 1> As a specific example of the particle 190, an example in which LCNO (lithium cobalt oxide with a part of cobalt replaced by nickel) is used for the core and LCO (lithium cobalt oxide) is used for the shell is shown, that is, as the region 191, a Li-Co-Ni oxide using two transition metals, cobalt as the first transition metal and nickel as the second transition metal, is used, and as the region 193, an example using a Li-Co oxide is shown.

[0077] In the Li-Co-Ni oxide (LCNO) used as the region 191, when the molar ratio of each metal element is Li:Co:Ni = 1:1 - x:x, x is preferably 0 < x < 1, more preferably 0.3 < x < 0.75, and still more preferably 0.4 ≦ x ≦ 0.6.

[0078] As the Li-Co oxide (LCO) used as the region 193, for example, LiCo y O z It is preferable to use a composite oxide represented by (z = 2 or a value in the vicinity thereof, and 0.8 < y < 1.2).

[0079] Examples of the composite oxide that can be used in the region 192 can refer to the descriptions of the regions 191 and 193. Examples of the composite oxide that can be used in the region 194 can refer to the description of the region 193.

[0080] <Example 2 of the particle> As a specific example of the particle 190, an example in which the first LCNO is used for the core and the second LCNO is used for the shell is shown, that is, as the region 191, a Li-Co-Ni oxide using two transition metals, cobalt as the first transition metal and nickel as the second transition metal, is used, and as the region 193, a Li-Co-Ni oxide using two transition metals, cobalt as the first transition metal and nickel as the second transition metal, is used.

[0081] In the first Li-Co-Ni oxide used as region 191, the molar ratio of each metal element is Li:Co:Ni = 1:1-x:x, and in the second Li-Co oxide used as region 193, the molar ratio of each metal element is Li:Co:Ni = 1:1-w:w. In this case, it is preferable that x and w satisfy 0 < x < 1, 0 < w < 1, and w < x. More preferably, x and w satisfy 0.3 < x < 0.75 and w < x. Even more preferably, x and w satisfy 0.3 < x < 0.75 and w ≤ 0.3. Even more preferably, x and w satisfy 0.4 ≤ x ≤ 0.6 and w < x. Even more preferably, x and w satisfy 0.4 ≤ x ≤ 0.6 and w < 0.4. When within these ranges, it is possible to obtain a secondary battery with good cycle characteristics at high temperatures (for example, 45°C or higher), which is preferable.

[0082] In a composite oxide having a layered rock salt-type crystal structure, when the amount of lithium desorption accompanying charging is large, oxygen desorption and cation mixing are likely to occur, and the crystal structure tends to collapse easily. However, in the particles 190 with such a configuration, since there is a large amount of cobalt in the shell region 193 and the average discharge voltage is high, lithium tends to remain in region 193. Therefore, the collapse of the crystal structure in region 193 and the entire particle 190 can be suppressed. Therefore, even when charge and discharge are repeated, a phase in which lithium is difficult to insert into the surface layer (for example, a NiO domain having a rock salt-type crystal structure generated by cation mixing, etc.) is unlikely to occur. Therefore, a decrease in discharge capacity and discharge voltage can be suppressed.

[0083] For the composite oxide used in region 192, reference can be made to the descriptions of region 191 and region 193. For the composite oxide used in region 194, reference can be made to the description of region 193.

[0084] <Example 3 of particles> As a specific example of the particle 190, an example in which NCM (lithium nickel manganese cobalt oxide) is used for the core and LCO is used for the shell is shown. That is, as the region 191, a lithium composite oxide using three transition metals, cobalt as the first transition metal, nickel as the second transition metal, and manganese as the third transition metal, is used, and an example in which Li-Co oxide is used as the region 193 is shown. In the case of a configuration in which NCM is used for the core and LCO is used for the shell, the content of expensive cobalt in the entire positive electrode active material can be reduced, so that the price of the entire positive electrode active material can be made lower than that of the positive electrode active material of LCO alone. Further, in the case of a configuration in which NCM is used for the core and LCO is used for the shell, a sufficient discharge capacity can be ensured with respect to a charging voltage in the range of 4.2 V or more and less than 4.6 V (vs. Li / Li + ). Further, by using NCM for the core, the stability when charging and discharging are repeated or when used for a long period can be enhanced as compared with the positive electrode active material of LCO alone.

[0085] As the lithium composite oxide using cobalt, nickel and manganese, for example, a NiCoMn system represented by LiNi x Co y Mn z O2 (x > 0, y > 0, z > 0, 0.8 < x + y + z < 1.2) can be used. Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, x, y and z preferably satisfy x:y:z = 1:1:1 or values in the vicinity thereof. Or as an example, x, y and z preferably satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Or as an example, x, y and z preferably satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Or as an example, x, y and z preferably satisfy x:y:z = 9:0.5:0.5 or values in the vicinity thereof. Or as an example, x, y and z preferably satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Or as an example, x, y and z preferably satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0086] As the composite oxide used in region 192, reference can be made to the descriptions in regions 191 and 193. As the composite oxide used in region 194, reference can be made to the description in region 193.

[0087] <Example 4 of particles> As a specific example of particle 190, an example of using LCO for the core and NCM for the shell, that is, an example of using a lithium cobalt oxide as region 191 and a lithium composite oxide using three transition metals of cobalt as the first transition metal, nickel as the second transition metal, and manganese as the third transition metal as region 193 is shown. In the case of a configuration using LCO for the core and NCM for the shell, since the configuration enables reduction of the cobalt content in the entire positive electrode active material, the price of the entire positive electrode active material can be reduced compared to the positive electrode active material of LCO alone. Further, in the case of a configuration using LCO for the core and NCM for the shell, a sufficient discharge capacity can be ensured for a charging voltage in the range of 4.5 V or more and less than 4.8 V (vs. Li / Li + ).

[0088] As the lithium composite oxide using cobalt, nickel, and manganese, for example, a NiCoMn system (also referred to as NCM) represented by LiNi x Co y Mn z O2 (x > 0, y > 0, z > 0, 0.8 < x + y + z < 1.2) can be used. Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, x, y, and z preferably satisfy x:y:z = 1:1:1 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 9:0.5:0.5 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Or as an example, x, y, and z preferably satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0089] For composite oxides used in region 192, refer to the descriptions in regions 191 and 193. For composite oxides used in region 194, refer to the description in region 193.

[0090] Region 193 may also have multiple other regions. For example, as shown in Figure 1C, it may have regions 193a and 193b. In this case, it is preferable that the concentration of at least one transition metal differs between region 193a and region 193b.

[0091] For example, it is preferable that in region 193a, x, y, and z satisfy x:y:z=1:1:1 or values ​​in their vicinity, and in region 193b, x, y, and z satisfy x:y:z=8:1:1 or values ​​in their vicinity. Alternatively, it is preferable that in region 193a, x, y, and z satisfy x:y:z=1:1:1 or values ​​in their vicinity, and in region 193b, x, y, and z satisfy x:y:z=9:0.5:0.5 or values ​​in their vicinity.

[0092] Alternatively, it is more preferable that in region 193a, x, y, and z satisfy x:y:z=8:1:1 or values ​​in their vicinity, and in region 193b, x, y, and z satisfy x:y:z=1:1:1 or values ​​in their vicinity. Alternatively, it is more preferable that in region 193a, x, y, and z satisfy x:y:z=9:0.5:0.5 or values ​​in their vicinity, and in region 193b, x, y, and z satisfy x:y:z=1:1:1 or values ​​in their vicinity.

[0093] At this time, as shown in Figure 2C, the area of ​​region 193a is S 193a Assuming that the area of ​​region 193b is S 193b S 193 =S 193a +S 193b Let's assume that.

[0094] <Example of a particle 5> As a specific example of particle 190, we show an example in which LCO is used as the core and LFP (lithium iron phosphate) as the shell, that is, an example in which Li-Co oxide is used as region 191 and Li-iron phosphate (LiFePO4) is used as region 193.

[0095] Furthermore, region 193 may be a cathode material having an olivine-type crystal structure other than LiFePO4. The olivine-type crystal structure is less prone to collapse because the polyanionic skeleton consisting of phosphorus and oxygen remains stable even when all lithium has been released. For this reason, composite oxides having an olivine-type crystal structure are suitable for region 193, which is the shell. However, when composite oxides with different crystal structures are applied to region 191 and region 193, it is preferable that region 192 functions as a buffer layer and promotes the diffusion of lithium at grain boundaries. Alternatively, it is preferable that region 192 has the function of strengthening the physical bonding between region 191 and region 193. For composite oxides to be used in region 192, refer to the descriptions of region 191 and region 193. For composite oxides to be used in region 194, refer to the description of region 193.

[0096] <Example of a particle 6> As specific examples of particle 190, an example is shown in which a first NCM is used for the core and a second NCM for the shell, i.e., region 191, which uses a lithium composite oxide with three transition metals: cobalt as the first transition metal, nickel as the second transition metal, and manganese as the third transition metal. Region 193 is also shown as an example in which a lithium composite oxide with three transition metals: cobalt as the first transition metal, nickel as the second transition metal, and manganese as the third transition metal.

[0097] As the first NCM, LiNi is represented by x:y:z=8:1:1 or x:y:z=9:0.5:0.5. x Co y Mn z Using an O2 composite oxide, the second NCM is LiNi represented by x:y:z=1:1:1. x Co y Mn zO2 composite oxides can be used. The atomic ratio of the second NCM is not limited to the above. For example, reducing the nickel ratio compared to the first NCM may produce a similar effect to the above atomic ratio.

[0098] For composite oxides used in region 192, refer to the descriptions in regions 191 and 193. For composite oxides used in region 194, refer to the description in region 193.

[0099] <Example of a particle 7> As specific examples of particle 190, we show an example using a lithium-rich cathode material as region 191 and a Li-Co oxide as region 193.

[0100] Examples of lithium-rich materials include Li2MnO2, Li2MnO3, Li4Mn2O5, Li5FeO4, Li3NbO4, Li 1.2 Ni 0.2 Mn 0.6 O2, Li 1.16 Ni 0.15 Co 0.19 Mn 0.50 O2 or solid solutions thereof can be used. These lithium-rich materials are preferred because they have a high discharge capacity per unit of transition metal and per unit weight. However, when these materials are charged at high voltage or to a deep charge, there is a concern that oxygen release, transition metal elution, or cation mixing may occur. Therefore, it is more preferable to use a shell material that suppresses the collapse of the crystal structure even when charged at high voltage.

[0101] For composite oxides used in region 192, refer to the descriptions in regions 191 and 193. For composite oxides used in region 194, refer to the description in region 193.

[0102] Furthermore, it is preferable that the crystal orientations of regions 191 and 192 are approximately the same. Similarly, it is preferable that the crystal orientations of regions 192 and 193 are approximately the same. Similarly, if region 194 is present, it is preferable that the crystal orientations of regions 193 and 194 are approximately the same. Similarly, if regions 193a and 193b are present, it is preferable that the crystal orientations of regions 193a and 193b are approximately the same.

[0103] When the crystal orientations are roughly aligned, a good lithium diffusion path is ensured, which is preferable for a secondary battery with good rate characteristics or charge / discharge characteristics. If there is a slight difference in ionic radius between the composite oxide regions 191 and 193, it is preferable that region 192 functions as a buffer layer.

[0104] Here, charging refers to the transfer of electrons from the positive electrode to the negative electrode in an external circuit. In other words, lithium ions are released from the positive electrode active material when it is charged. Positive electrode active materials having a layered crystal structure, such as the composite oxide containing lithium and transition metals mentioned above, can sometimes realize secondary batteries with a high lithium content per unit volume and high capacity per unit volume. In such positive electrode active materials, the amount of lithium released per unit volume during charging is also large, and stabilization of the crystal structure after release is required for stable charging and discharging. Furthermore, the breakdown of the crystal structure during charging and discharging may hinder fast charging and fast discharging. In addition, the breakdown of the crystal structure may reduce the area in which lithium can be inserted and removed normally, which may lead to a decrease in charging capacity and discharging capacity.

[0105] The presence of nickel in addition to cobalt as a transition metal can suppress the shifting of the layered structure consisting of octahedra of cobalt and oxygen. Therefore, the crystal structure may become more stable, especially in the charged state at high temperatures, which is preferable.

[0106] In cases where nickel is present in addition to cobalt as a transition metal, increasing the nickel concentration can sometimes suppress the shifting of the layered structure associated with lithium desorption. Therefore, even with the desorption of more lithium, stable charging and discharging can be repeatedly performed. In other words, the capacity can be increased.

[0107] On the other hand, when nickel is present in addition to cobalt as a transition metal, increasing the nickel concentration can easily lead to the collapse of the crystal structure at high charging voltages. This is because the ionic radii of lithium ions and nickel ions are close, making cation mixing, where nickel moves to lithium sites, more likely to occur. In other words, to perform charging at high voltages, it is preferable not to increase the nickel concentration too much.

[0108] <Region containing element X and halogen> Regions 192 and 194 are preferably regions containing element X and halogens. Element X and halogens may be referred to as impurity elements. Element X is one or more selected from titanium, magnesium, aluminum, zirconium, vanadium, iron, chromium, niobium, cobalt, arsenic, zinc, silicon, sulfur, phosphorus, boron, calcium, gallium, and silicon. Furthermore, element X is preferably one or more elements including magnesium. The halogen is preferably one or more of fluorine and chlorine, and particularly preferably fluorine.

[0109] As the region containing element X and halogen, a region in which element X and halogen are added to a composite oxide represented by LiMO2 can be used. Here, the composite oxide only needs to have the crystal structure of the composite oxide represented by LiMO2, and its composition is not strictly limited to Li:M:O=1:1:2.

[0110] The presence of element X and halogens in composite oxides represented by LiMO2 can sometimes further stabilize the crystal structure.

[0111] Furthermore, magnesium is particularly preferred as element X. Furthermore, fluorine is particularly preferred as the halogen. The region containing element X and halogen may include lithium cobaltate with magnesium and fluorine, lithium cobaltate with magnesium, fluorine and titanium, lithium nickel-cobaltate with magnesium and fluorine, lithium cobalt-aluminate with magnesium and fluorine, lithium nickel-cobalt-aluminate with magnesium and fluorine, lithium nickel-manganese-cobaltate with magnesium and fluorine, etc. In this specification, the terms "additive" may be replaced with "mixture," "part of the raw material," "impurity," etc.

[0112] Furthermore, the region containing element X and halogen may, for example, be a region containing a bond between oxygen and element X. The bond between oxygen and element X can be analyzed, for example, by XPS analysis. In addition, the region containing element X and halogen may also contain magnesium oxide.

[0113] The region containing element X and halogen may include multiple of the regions exemplified above. Furthermore, region 192 and region 194 may have different elements, different crystal structures, different bonding, etc.

[0114] In particle 190, even if the metal that becomes a carrier ion is removed from the composite oxide due to charging, the layered structure of the composite oxide is not disrupted by the surface region 194, which contains element X and halogen, i.e., the outer periphery of the particle, and the region 192, which is located between the region 191 containing the composite oxide and the region 193 containing the composite oxide.

[0115] Below, we consider the case where the region containing element X and halogen is a composite oxide represented by LiMO2 to which element X and halogen have been added.

[0116] Magnesium, one of the elements X, is divalent and is more stable in lithium sites than in transition metal sites in layered rock salt crystal structures, thus readily occupying lithium sites. The presence of magnesium at appropriate concentrations in lithium sites within regions containing element X and halogens facilitates the maintenance of the layered rock salt crystal structure. Magnesium is preferable at appropriate concentrations as it does not adversely affect lithium insertion and removal during charging and discharging. However, excessive magnesium may adversely affect lithium insertion and removal.

[0117] Aluminum, one of the elements X, is trivalent and has a strong bonding force with oxygen. Therefore, when aluminum is added as an additive, changes in the crystal structure can be suppressed when it enters the lithium site. As a result, it is possible to create particle 190 that is less prone to crystal structure collapse even after repeated charging and discharging.

[0118] Titanium oxide is known to be superhydrophilic. Therefore, having titanium oxide in the region containing element X and halogens may improve wettability with highly polar solvents. When used in a secondary battery, good contact at the interface between particle 190 and the highly polar electrolyte may be achieved, potentially suppressing an increase in internal resistance. In addition, titanium oxide facilitates lithium diffusion and does not easily release oxygen during charging and discharging. For these reasons, titanium is particularly suitable as element X.

[0119] As the charging voltage of a secondary battery increases, the voltage at the positive electrode generally rises. The positive electrode active material according to one aspect of the present invention has a stable crystal structure even at high voltages. The stability of the crystal structure of the positive electrode active material in the charged state suppresses the decrease in charge / discharge capacity that occurs with repeated charging and discharging.

[0120] Furthermore, a short circuit in a secondary battery not only causes malfunctions in the charging and discharging operations of the secondary battery, but can also lead to overheating and ignition. To realize a safe secondary battery, it is preferable that the short-circuit current is suppressed even at high charging voltages. The positive electrode active material of one aspect of the present invention suppresses the short-circuit current even at high charging voltages. Therefore, it is possible to create a secondary battery that achieves both high charge / discharge capacity and safety.

[0121] A secondary battery using a positive electrode active material according to one aspect of the present invention is preferably capable of simultaneously satisfying high charge / discharge capacity, excellent charge / discharge cycle characteristics, and safety.

[0122] <Grain boundaries, etc.> In one aspect of the present invention, the particles (regions 191, 192, and 193) may be polycrystalline in each or one of regions 191, 192, and 193. The element X or halogen present in the particles (regions 191, 192, and 193) of one aspect of the present invention may be randomly and dilutely present in the internal regions, but it is more preferable that they are concentrated at the grain boundaries. In this case, element X is preferably magnesium or titanium.

[0123] In other words, it is preferable that the magnesium concentration at and near the grain boundaries of the crystals in the particles of one embodiment of the present invention is higher than that in other regions of the interior. It is also preferable that the halogen concentration at and near the grain boundaries is higher than that in other regions of the interior.

[0124] Grain boundaries are a type of surface defect. Therefore, like particle surfaces, they tend to be unstable and prone to initiating changes in crystal structure. For this reason, increasing the magnesium concentration at and near the grain boundaries can more effectively suppress changes in crystal structure.

[0125] Furthermore, if the concentrations of element X and halogen are high at and near the grain boundaries, even if cracks occur along the grain boundaries of the particles in one embodiment of the present invention, the concentrations of element X and halogen will be high near the surface created by the cracks. Therefore, the corrosion resistance to hydrofluoric acid can be improved even in the positive electrode active material after crack formation.

[0126] In this specification, the term "near the grain boundary" refers to the region extending approximately 10 nm from the grain boundary.

[0127] Furthermore, the particle 190 may have defects, cracks, irregularities, fissures, etc., in addition to grain boundaries. It may also have portions lacking regions 192, 193, and 194. For example, as shown in region 196a of Figures 3A and 3B, it may have portions where region 193 is absent and region 192 is visible on the surface, or portions where region 194 and region 192 are in contact.

[0128] Furthermore, as shown in region 196b in Figures 3A and 3B, region 192 may be absent, and there may be a portion where region 191 and region 193 are in contact.

[0129] Furthermore, as shown in region 196c of Figures 3A and 3B, there may be a portion where region 194, region 193, and region 192 are absent, and region 191 is exposed on the surface.

[0130] Furthermore, as shown in region 196d in Figures 3A and 3B, there may be regions 195 with different compositions in defects, cracks, unevenness, fissures, grain boundaries, etc. Region 195 is a region having different elements, a different composition, or a different crystal structure from regions 191 to 194.

[0131] The presence of region 195 can cause excess impurity elements to segregate into region 195, keeping the impurity elements contained in regions 191 to 194 within a favorable range. Therefore, the presence of region 195 can sometimes result in a secondary battery with good rate characteristics or charge / discharge characteristics.

[0132] Each of the aforementioned regions can be determined to be a different region through various analyses or combinations thereof. Examples of analyses include electron microscope images such as TEM, STEM, HAADF-STEM, and ABF-STEM; diffraction images such as SIMS, ToF-SIMS, X-ray diffraction (XRD), electron diffraction, and neutron diffraction; electron microanalyzer (EPMA); and energy-dispersive X-ray analysis (EDX). For example, in cross-sectional TEM and STEM images of particle 190, differences in constituent elements may be observed as differences in image brightness.

[0133] Furthermore, the boundaries between the aforementioned regions may not be clear. There may be a concentration gradient between adjacent regions. The elemental concentrations may also change continuously, or in steps, or they may form a gradient. In such cases, the boundaries between regions could, for example, be defined as the point where the concentration of an element specific to one of the regions reaches 50%.

[0134] <Particle shape> The shape of particle 190 is not limited to the shapes shown in Figures 1 to 3. For example, Figure 4A1 is a perspective view of particle 190, and Figure 4A2 is a cross-sectional view of Figure 4A1. The particle 190 may also be triangular prism-shaped.

[0135] Figure 4B1 is a perspective view of particle 190, and Figure 4B2 is a cross-sectional view of Figure 4B1. Thus, particle 190 may be cubic (dice-shaped) or rectangular.

[0136] Figure 4C1 is a perspective view of particle 190, and Figure 4C2 is a cross-sectional view of Figure 4C1. The particle 190 may also be hexagonal prism-shaped as shown above.

[0137] Figure 4D1 is a perspective view of particle 190, and Figure 4D2 is a cross-sectional view of Figure 4D1. The particle 190 may also be octahedral in shape.

[0138] Figure 4E1 is a perspective view of particle 190, and Figure 4E2 is a cross-sectional view of Figure 4E1. Thus, the outer shape of particle 190 and the shapes of regions 191 and 192 may be different.

[0139] <Manufacturing method> Next, an example of a method for producing particles 190 having regions 191 to 193 will be described using Figure 5A.

[0140] First, in step S11, a lithium source and the transition metal M in region 191 191 Prepare the source and the other.

[0141] Next, in step S12, a lithium source and the transition metal M of region 191 191 The source and the transition metal source are synthesized. One synthesis method involves mixing the lithium source and the transition metal source present in region 191 using a solid-phase method, followed by heating.

[0142] In this way, the composite oxide C that region 191 possesses 191 Create (step S13).

[0143] Next, as step S21, the region 192 has X 192 Prepare the power source and the halogen source located in region 192.

[0144] Next, in step S31, the composite oxide C of region 191 191 And the X that region 192 possesses 192 The source and the halogen source present in region 192 are synthesized. One synthesis method involves mixing them using a solid-phase method and then heating them.

[0145] In this way, the composite oxide C that regions 191 and 192 have 191+192 This is manufactured (step S32).

[0146] Next, in step S41, a lithium source and the transition metal M in region 193 193 Prepare the source and the other.

[0147] Next, in step S71, the composite oxide C having regions 191 and 192 191+192 And, a lithium source and a transition metal source M in region 193 193 and are synthesized. One synthesis method is to mix them using a solid-phase method and then heat the mixture.

[0148] In this way, particle 190 is produced (step S72).

[0149] Furthermore, the composite oxide C possessed in region 191 191 This is the composite oxide C possessed by region 193. 193 It is preferable that the material has a higher melting point than the composite oxide C in region 191. 191 This is the composite oxide C possessed by region 193. 193 It is preferable to use a material with higher thermal stability. Due to this difference in melting point or thermal stability, for example, the heating in the synthesis in step S71 is required for the composite oxide C that region 191 has 191 While being stable, the composite oxide C possessed in region 193 193 The temperature and time can be set to allow sufficient mutual diffusion.

[0150] Furthermore, element X is present in region 192. 192 The ionic radius of the cation is preferably larger than the ionic radius of the cation in region 191. Due to this difference in ionic radius, element X 192 This makes it easier for the elements to be concentrated in region 192. Furthermore, region 192 is more likely to exhibit the function of suppressing the mutual diffusion of elements in regions 191 and 193.

[0151] Particles 190 having regions 191 to 194 can be fabricated, for example, as shown in Figure 5B.

[0152] Steps S11 through S41 can be manufactured in the same manner as shown in Figure 5A.

[0153] Next, as step S51, the composite oxide C having regions 191 and 192 191+192 And, the lithium source and the transition metal M present in region 193 193 The source and are synthesized. One synthesis method is to mix them using a solid-phase method and then heat the mixture.

[0154] In this way, the composite oxide C that regions 191 to 193 have 191+192+193 This is manufactured (step S52).

[0155] Next, as step S61, the region 194 has X 194 Prepare the source and the halogen source located in region 194.

[0156] Next, as step S71, the composite oxide C having regions 191 to 193 191+192+193 And the X that region 194 possesses 194 The source and the halogen source present in region 194 are synthesized. One synthesis method involves mixing them using a solid-phase method and then heating them.

[0157] In this way, particle 190 is produced (step S72).

[0158] Furthermore, element X possessed in region 194 194 The ionic radius of the cation is preferably larger than the ionic radius of the cation in region 193. This difference in ionic radius makes element X more likely to be concentrated in region 194.

[0159] This embodiment can be used in combination with other embodiments.

[0160] (Embodiment 2) In this embodiment, an example of a material used in region 191 (core) or region 193 (shell) shown in Figure 1A is presented. Using a material having a layered rock salt-type crystalline structure, such as lithium cobalt oxide (LiCoO2), as region 191 or region 193 is preferable because it has a high discharge capacity and is excellent as a positive electrode active material for secondary batteries.

[0161] Examples of materials having a layered rock salt crystal structure include composite oxides represented by LiMO2. In this specification, lithium composite oxides represented by LiMO2 only need to have a layered rock salt crystal structure, and their composition is not strictly limited to Li:M:O=1:1:2. Figure 6 describes the case where cobalt is used as the transition metal M in the positive electrode active material.

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

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

[0164] The positive electrode active material shown in Figure 6 is lithium cobalt oxide (LiCoO2) without halogen and magnesium added, prepared using the method described later. The crystal structure of the lithium cobalt oxide shown in Figure 6 changes depending on the depth of charge.

[0165] As shown in Figure 6, lithium cobalt oxide at charge depth 0 (discharge state) has a region with a crystal structure of space group R-3m, and there are three CoO2 layers in the unit cell. For this reason, this crystal structure is sometimes called an O3 type crystal structure. The CoO2 layer refers to a structure in which octahedral structures, in which oxygen atoms are coordinated to cobalt in a 6-coordinate manner, are continuous in a plane with shared edges.

[0166] Furthermore, at a charge depth of 1, it has a crystal structure of space group P-3m1, with one CoO2 layer present in the unit cell. For this reason, this crystal structure is sometimes called an O1 type crystal structure.

[0167] Furthermore, lithium cobalt oxide at a charge depth of approximately 0.88 has a crystal structure with space group R-3m. This structure can be described as a structure in which CoO2 structures such as P-3m1(O1) and LiCoO2 structures such as R-3m(O3) are alternately stacked. For this reason, this crystal structure is sometimes called the H1-3 type crystal structure. In reality, the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell compared to other structures. However, in this specification, including Figure 6, the c-axis of the H1-3 type crystal structure is shown as half the unit cell for easier comparison with other structures.

[0168] As an example, the H1-3 type crystal structure can be represented by the coordinates of cobalt and oxygen in a unit cell as follows: Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are oxygen atoms, respectively. Thus, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygen atoms.

[0169] Here, lithium cobalt oxide (LiCoO2) is shown as an example of a material to be used for the core or shell, but this is just one example and is not particularly limited.

[0170] Furthermore, an example of a material that can be used in regions 193 and 194 shown in Figure 1B is shown. It is preferable that the material used in at least one of regions 191 or 192 shown in Figure 1B contains lithium, cobalt as a transition metal M, oxygen, and magnesium. It is also preferable that regions 192 and 194 contain halogens such as fluorine and chlorine as impurities. It is even more preferable that the material has an O3' type crystal structure during charging.

[0171] When magnesium and fluorine are added to lithium cobalt oxide (LiCoO2), the crystal structure at charge depth 0 (discharge state) is R-3m(O3), but at a fully charged charge depth, it has a crystal structure different from the H1-3 type crystal structure. This structure belongs to the space group R-3m, and ions such as cobalt and magnesium occupy the oxygen 6-coordinate positions. Furthermore, the symmetry of the CoO2 layer in this structure is the same as that of the O3 type. Therefore, this structure is referred to as the O3' type crystal structure in this specification. In both the O3 type crystal structure and the O3' type crystal structure, it is preferable to have dilute magnesium between the CoO2 layers, i.e., at the lithium sites. It is also preferable to have random and dilute fluorine at the oxygen sites.

[0172] The O3' type crystal structure is preferably represented by a unit cell using one cobalt and one oxygen atom. This is because the symmetry between cobalt and oxygen differs between the O3' structure and the H1-3 type crystal structure, indicating that the O3' structure shows less variation from the O3 structure compared to the H1-3 type crystal structure. The choice of which unit cell is more preferable for representing the crystal structure of the positive electrode active material can be made, for example, by selecting the one that results in a smaller GOF (goodness of fit) value in Rietveld analysis using XRD.

[0173] Furthermore, while Figure 7, which shows the crystal structure of the positive electrode active material, depicts lithium present at all lithium sites with equal probability, the structure of O3' is not limited to this. It may be concentrated at some lithium sites. For example, Li belonging to the space group P2 / m 0.5 Similar to CoO2, lithium may be present at some aligned lithium sites. The distribution of lithium can be analyzed, for example, by neutron diffraction.

[0174] The positive electrode active material having the O3' type crystal structure shown in Figure 7 exhibits less change in its crystal structure when charged at high voltage and a large amount of lithium is released compared to the positive electrode active material in Figure 6. For example, as shown by the dotted line in Figure 7, there is almost no displacement of the CoO2 layer in these crystal structures.

[0175] More specifically, the positive electrode active material having the crystal structure shown in Figure 7 exhibits high structural stability even at high charging voltages. For example, in the positive electrode active material of Figure 7, there is a charging voltage range in which the R-3m(O3) crystal structure can be maintained even at a charging voltage that results in an H1-3 type crystal structure, for example, a voltage of about 4.6V relative to the potential of lithium metal. Furthermore, there is a range in which an O3' type crystal structure can be adopted even at higher charging voltages, for example, a voltage of about 4.65V to 4.7V relative to the potential of lithium metal. Only when the charging voltage is increased even further can an H1-3 type crystal be observed. In addition, in the case of a secondary battery, for example, when graphite is used as the negative electrode active material, there is a charging voltage range in which the R-3m(O3) crystal structure can be maintained even when the secondary battery voltage is between 4.3V and 4.5V. Furthermore, there is a range in which an O3' type crystal structure can be adopted even at higher charging voltages, for example, between 4.35V and 4.55V relative to the potential of lithium metal.

[0176] Therefore, the positive electrode active material having the crystal structure shown in Figure 7 is suitable for use as a shell because its crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0177] Furthermore, the O3' type crystal structure can be represented by showing the coordinates of cobalt and oxygen in the unit cell as follows: Co(0,0,0.5), O(0,0,x), within the range of 0.20≦x≦0.25.

[0178] Additives such as magnesium, which are randomly and dilutely present between the CoO2 layers, i.e., at the lithium sites, have the effect of suppressing the displacement of the CoO2 layers when charged at high voltage. Therefore, when magnesium is present between the CoO2 layers, an O3' type crystal structure is more likely to be formed. For this reason, it is preferable that magnesium is distributed throughout the particles of the positive electrode active material having the crystal structure shown in Figure 7. Furthermore, in order to distribute magnesium throughout the particles, it is preferable to perform heat treatment in the manufacturing process of the positive electrode active material.

[0179] However, if the heat treatment temperature is too high, cation mixing will occur, increasing the likelihood that additives, such as magnesium, will enter the cobalt site. Magnesium present in the cobalt site will negate the effect of maintaining the R-3m structure when charged at high voltage. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium.

[0180] Therefore, it is preferable to add a material that functions as a flux to lithium cobalt oxide before the heat treatment to distribute magnesium throughout the particles. This causes a decrease in the melting point. By lowering the melting point, it becomes easier to distribute magnesium throughout the particles at a temperature at which cation mixing is less likely to occur. Furthermore, if the material that functions as a flux contains fluorine, it can be expected that the corrosion resistance to hydrofluoric acid produced by the decomposition of the electrolyte will improve.

[0181] Furthermore, if the magnesium concentration is increased beyond the desired value, the effect on stabilizing the crystal structure may decrease. This is thought to be because magnesium will enter not only the lithium sites but also the cobalt sites. The number of magnesium atoms in the positive electrode active material having the crystal structure shown in Figure 7 is preferably 0.001 times or more and 0.1 times or less the number of transition metal M atoms, more preferably greater than 0.01 and less than 0.04, and even more preferably around 0.02. Alternatively, 0.001 times or more and less than 0.04 is preferred, or 0.01 or more and 0.1 or less is preferred. The magnesium concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, or it may be based on the value of the raw material composition during the process of manufacturing the positive electrode active material.

[0182] Lithium cobalt oxide may be mixed with one or more metals other than cobalt (hereinafter referred to as metal Z), such as nickel, aluminum, manganese, titanium, vanadium, and chromium, with particular preference for the addition of nickel and one or more aluminum. Manganese, titanium, vanadium, and chromium may readily assume a stable tetravalent state and may contribute significantly to structural stability. By adding metal Z, the positive electrode active material having the crystal structure shown in Figure 7 may become more stable in a high-voltage charged state, for example. Here, in the positive electrode active material having the crystal structure shown in Figure 7, it is preferable that metal Z is added at a concentration that does not significantly alter the crystallinity of lithium cobalt oxide. For example, it is preferable that the amount is such that the aforementioned Jahn-Teller effect does not occur.

[0183] As shown in the legend in Figure 7, transition metals such as nickel and manganese, and aluminum are preferably present at the cobalt site, but some may be present at the lithium site. Magnesium is also preferably present at the lithium site. Oxygen may be partially substituted with fluorine.

[0184] As the magnesium concentration of a positive electrode active material having the crystal structure shown in Figure 7 increases, the charge-discharge capacity of the positive electrode active material may decrease. One possible reason for this is that the amount of lithium contributing to charge-discharge may decrease due to the presence of magnesium at the lithium sites. In addition, excess magnesium may generate magnesium compounds that do not contribute to charge-discharge. By including nickel as metal Z in addition to magnesium in a positive electrode active material having the crystal structure shown in Figure 7, the charge-discharge capacity per unit weight and per unit volume may be increased. Furthermore, by including aluminum as metal Z in addition to magnesium in a positive electrode active material having the crystal structure shown in Figure 7, the charge-discharge capacity per unit weight and per unit volume may be increased. Furthermore, by including nickel and aluminum in addition to magnesium in a positive electrode active material having the crystal structure shown in Figure 7, the charge-discharge capacity per unit weight and per unit volume may be increased.

[0185] The preferred concentrations of elements such as magnesium and metallic Z in a positive electrode active material having the crystal structure shown in Figure 7 are expressed below in terms of atomic numbers.

[0186] The number of nickel atoms in the positive electrode active material having the crystal structure shown in Figure 7 is preferably more than 0% and 7.5% or less of the number of cobalt atoms, more preferably 0.05% to 4%, and even more preferably 0.1% to 2%. Alternatively, it is preferable to have more than 0% and 4% or less. Alternatively, it is preferable to have more than 0% and 2% or less. Alternatively, it is preferable to have more than 0% and 2% or less. Alternatively, it is preferable to have more than 0% and 7.5.1% and 4% or less. The nickel concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using ICP-MS, or it may be based on the value of the raw material composition during the manufacturing process of the positive electrode active material.

[0187] Nickel present at the above concentrations tends to dissolve uniformly throughout the positive electrode active material having the crystal structure shown in Figure 7, thus contributing particularly to the stabilization of the crystal structure of the interior 100b. Furthermore, the presence of divalent nickel in the interior 100b may allow divalent additive elements, such as magnesium, which are randomly and dilutely present at lithium sites nearby, to exist more stably. Therefore, the dissolution of magnesium may be suppressed even after high-voltage charging and discharging. As a result, the charge-discharge cycle characteristics may be improved. Thus, combining the effects of nickel in the interior 100b with the effects of magnesium, aluminum, titanium, fluorine, etc., in the surface layer 100a is extremely effective in stabilizing the crystal structure during high-voltage charging.

[0188] The number of aluminum atoms in the positive electrode active material having the crystal structure shown in Figure 7 is preferably 0.05% to 4% of the number of cobalt atoms, more preferably 0.1% to 2%, and even more preferably 0.3% to 1.5%. Alternatively, 0.05% to 2% is preferred, or 0.1% to 4% is preferred. The aluminum concentration shown here may be, for example, a value obtained by elemental analysis of the entire particle of the positive electrode active material using GD-MS, ICP-MS, etc., or it may be based on the value of the raw material composition during the manufacturing process of the positive electrode active material.

[0189] When the positive electrode active material having the crystal structure shown in Figure 7 contains magnesium in addition to element X, it exhibits extremely high stability in a high-voltage charged state. When element X is phosphorus, the number of phosphorus atoms is preferably 1% to 20% of the number of cobalt atoms, more preferably 2% to 10%, and even more preferably 3% to 8%. Alternatively, 1% to 10% is preferred. Alternatively, 1% to 8% is preferred. Alternatively, 2% to 20% is preferred. Alternatively, 2% to 8% is preferred. Alternatively, 3% to 20% is preferred. Alternatively, 3% to 10% is preferred. In addition, the number of magnesium atoms is preferably 0.1% to 10% of the number of cobalt atoms, more preferably 0.5% to 5%, and even more preferably 0.7% to 4%. Alternatively, 0.1% to 5% is preferred. Alternatively, 0.1% to 4% is preferred. Alternatively, 0.5% to 10% is preferred. Alternatively, 0.5% to 4% is preferred. Alternatively, 0.7% to 10% is preferred. Alternatively, 0.7% to 5% is preferred. The concentrations of phosphorus and magnesium shown herein may be values ​​obtained by elemental analysis of the entire particle of the positive electrode active material using, for example, ICP-MS, or they may be based on the values ​​of the raw material formulation during the manufacturing process of the positive electrode active material.

[0190] During repeated high-voltage charging and discharging, the displacement of the CoO2 layer can be reduced. Furthermore, the change in volume can be minimized. Therefore, by using a shell having at least a portion of the crystal structure shown in Figure 7, excellent cycle characteristics can be achieved. In addition, a shell having the crystal structure shown in Figure 7 can maintain a stable crystal structure in a high-voltage charging state. Therefore, a shell having the crystal structure shown in Figure 7 may be less prone to short circuits when a high-voltage charging state is maintained. In such cases, safety is further improved, making it preferable.

[0191] Assuming the shell has the crystal structure shown in Figure 7, the change in crystal structure and the difference in volume per unit number of transition metal atoms between a fully discharged state and a high-voltage charged state are small.

[0192] Furthermore, the space group of a crystal structure is identified by methods such as XRD, electron diffraction, and neutron diffraction. Therefore, in this specification, "belonging to a certain space group" or "being a certain space group" can be rephrased as "being identified to a certain space group."

[0193] This embodiment can be freely combined with other embodiments.

[0194] (Embodiment 3) To fabricate a secondary battery using the particles 190 described in Embodiment 1, an example of a positive electrode to be fabricated is shown below. A secondary battery has at least an outer casing, a current collector, an active material (positive electrode active material or negative electrode active material), a conductive material, and a binder. It also has an electrolyte solution containing a lithium salt or the like. In the case of a secondary battery using an electrolyte solution, a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are provided.

[0195] First, let's explain the positive electrode. Figure 8A shows an example of a schematic diagram of the cross-section of the positive electrode.

[0196] The current collector 500 is a metal foil, and the positive electrode is formed by applying a slurry to the metal foil and drying it. After drying, pressing may be applied further. The positive electrode is formed by creating an active material layer on the current collector 500.

[0197] A slurry is a liquid material used to form an active material layer on a current collector 500, and it contains at least an active material, a binder, and a solvent, preferably further mixed with a conductive material. The slurry is sometimes called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, a positive electrode slurry is used, and when forming a negative electrode active material layer, it is sometimes called a negative electrode slurry.

[0198] Conductive materials, also called conductivity imparters or conductive materials, 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 part 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.

[0199] A typical example of a carbon material used as a conductive material is carbon black (particulate carbon including furnace black and acetylene black, as well as graphite).

[0200] Figure 8A illustrates acetylene black 503 as the conductive material. Figure 8A also shows an example where a second active material 502, which has a smaller particle size than the particles 190 described in Embodiment 1, is mixed in. By mixing particles of different sizes, a high-density positive electrode can be obtained. Note that the particles 190 described in Embodiment 1 correspond to the active material 501 in Figure 8A.

[0201] As the positive electrode of a secondary battery, a binder (resin) is mixed with the active material to fix it together with the current collector 500, such as metal foil. The binder is also called a binding agent. The binder is a polymer material, and if too much binder is included, the proportion of active material in the positive electrode decreases, reducing the discharge capacity of the secondary battery. Therefore, the amount of binder mixed is kept to a minimum. In Figure 8A, the areas not filled with the active material 501, the second active material 502, and acetylene black 503 represent voids or binder.

[0202] Furthermore, in Figure 8A, the boundary between the core region and the shell region of the active material 501 is shown by a dotted line inside the active material 501. Although Figure 8A shows an example in which the active material 501 is depicted as spherical, it is not particularly limited and may have various shapes. The cross-sectional shape of the active material 501 may be elliptical, rectangular, trapezoidal, conical, a quadrilateral with rounded corners, or asymmetrical.

[0203] Figure 8B illustrates the active material 501 in various shapes. Figure 8B shows examples different from those in Figure 8A.

[0204] Furthermore, in the positive electrode shown in Figure 8B, graphene 504 is used as the carbon material used as the conductive material.

[0205] Graphene is a carbon material that possesses remarkable electrical, mechanical, and chemical properties, making it promising for applications in various fields, such as field-effect transistors and solar cells.

[0206] Figure 8B shows a positive electrode active material layer formed on a current collector 500, comprising an active material 501, graphene 504, and acetylene black 503. The graphene 504 is formed to partially cover or adhere to the surface of a plurality of granular active materials 501, and is therefore in surface contact with each other. It is preferable that the graphene 504 is clinging to at least a portion of the active material 501. It is also preferable that the graphene 504 overlaps at least a portion of the active material 501. Furthermore, it is preferable that the shape of the graphene 504 matches at least a portion of the shape of the active material 501. The shape of the active material refers, for example, to the irregularities of a single active material particle or the irregularities formed by a plurality of active material particles. It is also preferable that the graphene 504 surrounds at least a portion of the active material 501. The graphene 504 may also have holes.

[0207] In the step of mixing graphene 504 and acetylene black 503 to obtain an electrode slurry, it is preferable that the weight of the carbon black mixed is 1.5 to 20 times, preferably 2 to 9.5 times, the weight of the graphene.

[0208] Furthermore, when the mixture of graphene 504 and acetylene black 503 is within the above range, the dispersion stability of acetylene black 503 is excellent during slurry preparation, and aggregation is less likely to occur. Also, when the mixture of graphene 504 and acetylene black 503 is within the above range, a higher electrode density can be achieved than in a positive electrode where only acetylene black 503 is used as the conductive material. By increasing the electrode density, the capacity per unit weight can be increased. Specifically, the density of the positive electrode active material layer measured by weight can be higher than 3.5 g / cc. Moreover, when the particles 190 described in Embodiment 1 are used as the positive electrode, and the mixture of graphene 504 and acetylene black 503 is within the above range, a synergistic effect in achieving a higher capacity secondary battery can be expected, which is preferable.

[0209] Furthermore, although the electrode density is lower compared to a positive electrode using only graphene as the conductive material, by setting the mixture of the first carbon material (graphene) and the second carbon material (acetylene black) within the above range, rapid charging can be achieved. In addition, using the particles 190 described in Embodiment 1 as the positive electrode, and setting the mixture of graphene 504 and acetylene black 503 within the above range, is preferable because a synergistic effect can be expected in that the secondary battery becomes more stable and can support even faster charging.

[0210] These features make it effective as a secondary battery for use in vehicles.

[0211] Increasing the number of rechargeable batteries increases the vehicle's weight, which in turn increases the energy required to move the batteries, thus shortening the driving range. By using high-density rechargeable batteries, the driving range can be maintained without significantly changing the total weight of a vehicle equipped with the same weight of batteries.

[0212] Furthermore, as the capacity of a vehicle's secondary battery increases, more power is required for charging, making it desirable to complete the charging process in a short time. In addition, regenerative charging, which involves temporarily generating electricity when the vehicle brakes are applied and then charging the battery, is performed under high-rate charging conditions, so good rate characteristics are required for vehicle secondary batteries.

[0213] By using the particles 190 described in Embodiment 1 as the positive electrode and optimizing the mixing ratio of acetylene black and graphene, it becomes possible to achieve both high electrode density and the creation of appropriate gaps necessary for ion conduction, thereby obtaining a secondary battery for automotive use with high energy density and good output characteristics.

[0214] Furthermore, this configuration is also effective for mobile information terminals. By using the particles 190 described in Embodiment 1 as the positive electrode and optimizing the mixing ratio of acetylene black and graphene, the secondary battery can be made smaller and have a higher capacity. In addition, optimizing the mixing ratio of acetylene black and graphene enables rapid charging of mobile information terminals.

[0215] Furthermore, in Figure 8B, the boundary between the core region and the shell region of the active material 501 is shown by a dotted line inside the active material 501. Note that in Figure 8B, the areas not filled with the active material 501, graphene 504, and acetylene black 503 represent voids or binders. While voids are necessary for electrolyte permeation, too many voids reduce electrode density, and too few voids prevent electrolyte permeation. If these voids remain after the battery is constructed, efficiency will decrease.

[0216] By using the particles 190 described in Embodiment 1 as the positive electrode and setting the mixing ratio of acetylene black and graphene within an optimal range, it becomes possible to achieve both high electrode density and the creation of appropriate gaps necessary for ion conduction, thereby obtaining a secondary battery with high energy density and good output characteristics.

[0217] Figure 8C illustrates an example of a cathode using carbon nanotube 505 as an example of fibrous carbon instead of graphene. Figure 8C shows a different example from Figure 8B. Using carbon nanotube 505 can prevent aggregation of carbon black such as acetylene black 503 and improve dispersibility.

[0218] In Figure 8C, the areas not filled with active material 501, carbon nanotube 505, and acetylene black 503 represent voids or binders.

[0219] Furthermore, Figure 8D illustrates an example of another cathode. Figure 8C shows an example in which carbon nanotube 505 is used in addition to graphene 504. Using both graphene 504 and carbon nanotube 505 can prevent aggregation of carbon black such as acetylene black 503 and further improve dispersibility.

[0220] In Figure 8D, the areas not filled with active material 501, carbon nanotube 505, graphene 504, and acetylene black 503 represent voids or binders.

[0221] A secondary battery can be manufactured by using one of the positive electrodes shown in Figures 8A, 8B, 8C, and 8D, placing a separator on top of the positive electrode, and placing the resulting laminate on top of the separator, then placing it in a container (such as an outer casing or metal can) and filling the container with electrolyte.

[0222] 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.

[0223] 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, as well as starch. It is even preferable to use these water-soluble polymers in combination with the aforementioned rubber material.

[0224] Alternatively, it is preferable to use materials such as polystyrene, methyl polyacrylate, 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.

[0225] You may use a combination of several of the binders mentioned above.

[0226] For example, a material with particularly excellent viscosity-modifying properties may be used in combination with other materials. For instance, rubber materials, while possessing excellent adhesive and elastic properties, can be difficult to adjust in viscosity when mixed with a solvent. In such cases, it is preferable to mix them with a material with particularly excellent viscosity-modifying properties. Suitable materials with particularly excellent viscosity-modifying properties include, for example, water-soluble polymers. Suitable water-soluble polymers with particularly excellent viscosity-modifying properties include the aforementioned polysaccharides, such as carboxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropylcellulose, and diacetylcellulose, as well as cellulose derivatives such as regenerated cellulose, and starch.

[0227] Furthermore, cellulose derivatives such as carboxymethylcellulose can be made more effective as viscosity modifiers by increasing their solubility, for example, by using salts such as sodium salts or ammonium salts of carboxymethylcellulose. Increased solubility also improves the dispersibility of the active material and other components when preparing electrode slurries. In this specification, cellulose and cellulose derivatives used as electrode binders include their salts.

[0228] Water-soluble polymers stabilize viscosity by dissolving in water and can stably disperse active materials and other materials used as binders, such as styrene-butadiene rubber, in aqueous solutions. Furthermore, because they possess functional groups, they are expected to be easily and stably adsorbed onto the surface of the active material. Additionally, cellulose derivatives such as carboxymethylcellulose often contain functional groups such as hydroxyl groups and carboxyl groups. Because of these functional groups, the polymers interact with each other and are expected to broadly cover the surface of the active material.

[0229] When a binder that covers or contacts the surface of the active material forms a film, it is expected to function as a passivation film and suppress the decomposition of the electrolyte. Here, the passivation film is a film that has no electrical conductivity or 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. Further, it is more desirable that the passivation film suppresses electrical conductivity while allowing lithium ions to conduct.

[0230] In addition, although the above configuration shows an example of a secondary battery using an electrolytic solution, it is not particularly limited.

[0231] For example, a semi-solid battery or an all-solid battery can also be manufactured using the particles 190 described in Embodiment 1.

[0232] In this specification and the like, a semi-solid battery refers to a battery having a semi-solid material in at least one of an electrolyte layer, a positive electrode, and a negative electrode. Here, the semi-solid does not mean that the ratio of the solid material is 50%. The semi-solid means having properties close to those of a liquid such as flexibility while having properties of a solid such as small volume change. If these properties are satisfied, it may be a single material or a plurality of materials. For example, it may be a liquid material infiltrated into a porous solid material.

[0233] Also, in this specification and the like, a polymer electrolyte secondary battery refers to a secondary battery having a polymer in the electrolyte layer between the positive electrode and the negative electrode. The polymer electrolyte secondary battery includes a dry (or true) polymer electrolyte battery and a polymer gel electrolyte battery. Also, the polymer electrolyte secondary battery may be called a semi-solid battery.

[0234] When a semi-solid battery is manufactured using the particles 190 described in Embodiment 1, the semi-solid battery becomes a secondary battery with a large charge-discharge capacity. Also, a semi-solid battery with a high charge-discharge voltage can be obtained. Alternatively, a semi-solid battery with high safety or reliability can be realized.

[0235] This embodiment can be freely combined with other embodiments.

[0236] (Embodiment 4) This embodiment shows an example of fabricating an all-solid-state battery using the particles 190 described in Embodiment 1.

[0237] As shown in Figure 9A, a secondary battery 400 according to one embodiment of the present invention has a positive electrode 410, a solid electrolyte layer 420, and a negative electrode 430.

[0238] The positive electrode 410 has a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 has a positive electrode active material 411 and a solid electrolyte 421. The positive electrode active material 411 uses the particles 190 described in Embodiment 1, and the boundary between the core region and the shell region is indicated by a dotted line. The positive electrode active material layer 414 may also have a conductive material and a binder.

[0239] The solid electrolyte layer 420 has a solid electrolyte 421. The solid electrolyte layer 420 is located between the positive electrode 410 and the negative electrode 430 and is a region that does not contain either the positive electrode active material 411 or the negative electrode active material 431.

[0240] The negative electrode 430 has a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. The negative electrode active material layer 434 may also have a conductive material and a binder.

[0241] For example, alloy materials or carbon-based materials can be used as the negative electrode active material.

[0242] As the negative electrode active material, elements capable of undergoing charge-discharge reactions through alloying and dealloying reactions with lithium can be used. For example, materials 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 charge-discharge capacity compared to 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. Examples include SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, InSb, SbSn, etc. In this context, 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.

[0243] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO refers to SiO x It can also be expressed as follows: Here, it is preferable that x has one neighboring value. For example, x is preferably between 0.2 and 1.5, and more preferably between 0.3 and 1.2. Or preferably between 0.2 and 1.2. Or preferably between 0.3 and 1.5.

[0244] Suitable carbon-based materials include graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0245] 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. Also, it is relatively easy to reduce the surface area of ​​MCMB, which may be preferable. Examples of natural graphite include flake graphite and spheroidized natural graphite.

[0246] When lithium ions are inserted into graphite (during the formation of lithium-graphite intercalation compounds), graphite exhibits a potential as low as that of lithium metal (0.05V to 0.3V vs. Li / Li). + This allows lithium-ion secondary batteries to exhibit a high operating voltage. Furthermore, graphite is preferred because it has advantages such as a relatively high charge / discharge capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0247] Furthermore, titanium dioxide (TiO2) and lithium titanium oxide (Li4Ti5O2) are used as negative electrode active materials. 12 ), lithium-graphite intercalation compound (Li x Oxides such as C6, niobium pentoxide (Nb2O5), tungsten oxide (WO2), and molybdenum oxide (MoO2) can be used.

[0248] Furthermore, as the negative electrode active material, a Li3N type structure is used, which is a lithium and transition metal binitride. 3-x M x N (M = Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 The N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm²). 3 ) indicates a preference.

[0249] Using a lithium-transition metal complex nitride is preferable because it contains lithium ions in the negative electrode active material, allowing it to be combined with lithium-ion-free materials such as V2O5 and Cr3O8 as the positive electrode active material. Even when using a lithium-ion-containing material as the positive electrode active material, the lithium-transition metal complex nitride can be used as the negative electrode active material by pre-desorbing the lithium ions contained in the positive electrode active material.

[0250] 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. Other materials that undergo a conversion reaction include oxides such as Fe2O3, CuO, Cu2O, RuO2, Cr2O3, and CoS 0.89 This can also occur with sulfides such as NiS and CuS, nitrides such as Zn3N2, Cu3N, and Ge3N4, phosphides such as NiP2, FeP2, and CoP3, and fluorides such as FeF3 and BiF3.

[0251] 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.

[0252] Furthermore, by using metallic lithium for the negative electrode 430, it is possible to have a negative electrode 430 without a solid electrolyte 421, as shown in Figure 9B. Using metallic lithium for the negative electrode 430 is preferable because it can improve the energy density of the secondary battery 400.

[0253] As the solid electrolyte 421 in the solid electrolyte layer 420, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halogen-based solid electrolyte, etc., can be used.

[0254] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75S4, etc.), sulfide glasses (70Li2S·30P2S5, 30Li2S·26B2S3·44LiI, 63Li2S·38SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 50Li2S·50GeS2, etc.), sulfide crystallized glasses (Li7P3S 11 、Li 3.25 P 0.95 S4, etc.) are included. Sulfide-based solid electrolytes have advantages such as having materials with high conductivity, being synthesizable at low temperatures, and being relatively soft so that the conductive path is likely to be maintained even after charge and discharge.

[0255] Oxide-based solid electrolytes include materials having a perovskite-type crystal structure (La 2 / 3-x Li 3x TiO3, etc.), materials having a NASICON-type crystal structure (Li 1-Y Al Y Ti 2-Y (PO4)3, etc.), materials having a garnet-type crystal structure (Li7La3Zr2O 12 etc.), materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 etc.), LLZO (Li7La3Zr2O 12 ), oxide glasses (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), oxide crystallized glasses (Li 1.07 Al 0.69 Ti 1.46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc.) are included. Oxide-based solid electrolytes have advantages such as being stable in the atmosphere.

[0256] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, LiI, etc. Also, composite materials in which these halide-based solid electrolytes are filled in the pores of porous aluminum oxide or porous silica can be used as solid electrolytes.

[0257] Also, different solid electrolytes may be mixed and used.

[0258] Among these, Li 1+x Al x Ti 2-x (PO4)3 (0 < x < 1) (hereinafter referred to as LATP) contains aluminum and titanium, which are elements that the positive electrode active material used in the secondary battery 400 of one aspect of the present invention may have. Therefore, a synergistic effect can be expected for improving the cycle characteristics, which is preferable. Also, an improvement in productivity due to the reduction of processes can be expected. In this specification, etc., the NASICON-type crystal structure is a compound represented by M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.), and refers to a structure in which MO6 octahedra and XO4 tetrahedra share vertices and are three-dimensionally arranged.

[0259] 〔Shape of the exterior body and the secondary battery〕 For the exterior body of the secondary battery 400 of one aspect of the present invention, various materials and shapes can be used, but it is preferable to have a function of pressing the positive electrode, the solid electrolyte layer, and the negative electrode.

[0260] For example, FIGS. 10A to 10C are an example of a cell for evaluating the materials of a all-solid-state battery.

[0261] FIG. 10A is a schematic cross-sectional view of the evaluation cell. The evaluation cell has a lower member 761, an upper member 762, and a fixing screw or wing nut 764 for fixing them. By rotating the pressing screw 763, the electrode plate 753 is pressed to fix the evaluation material. An insulator 766 is provided between the lower member 761 and the upper member 762 made of a stainless steel material. Also, an O-ring 765 for sealing is provided between the upper member 762 and the pressing screw 763.

[0262] The evaluation material is placed on the electrode plate 751, surrounded by an insulating tube 752 around it, and is in a state of being pressed by the electrode plate 753 from above. A perspective view of the periphery of this evaluation material enlarged is FIG. 10B.

[0263] As an example of the evaluated material, an example of a stacked structure consisting of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown, and a cross-sectional view is shown in Figure 10C. Note that the same parts are referred to in Figures 10A to 10C.

[0264] The electrode plate 751 and lower member 761, which are electrically connected to the positive electrode 750a, can be considered to correspond to the positive electrode terminal. The electrode plate 753 and upper member 762, which are electrically connected to the negative electrode 750c, can be considered to correspond to the negative electrode terminal. Electrical resistance and other parameters can be measured while applying pressure to the evaluation material via the electrode plates 751 and 753.

[0265] Furthermore, it is preferable to use a package with excellent airtightness for the outer casing of a secondary battery according to one embodiment of the present invention. For example, a ceramic package and / or a resin package can be used. Also, when sealing the outer casing, it is preferable to block out the outside air and perform the sealing in a sealed atmosphere, for example, inside a glove box.

[0266] Figure 11A shows a perspective view of a secondary battery according to one embodiment of the present invention, having a different exterior and shape from those in Figures 10A to 10C. The secondary battery in Figure 11A has external electrodes 771 and 772 and is sealed with an exterior having a plurality of package members.

[0267] Figure 11B shows an example of a cross-section cut by the dashed line in Figure 11A. The laminate having a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is enclosed and sealed by a package member 770a having an electrode layer 773a on a flat plate, a frame-shaped package member 770b, and a package member 770c having an electrode layer 773b on a flat plate. Insulating materials, such as resin materials and / or ceramics, can be used for the package members 770a, 770b, and 770c.

[0268] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a and functions as a positive electrode terminal. The external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b and functions as a negative electrode terminal.

[0269] By using the particles 190 shown in Embodiment 1, an all-solid-state secondary battery with high energy density and good output characteristics can be realized.

[0270] This embodiment can be used in appropriate combination with other embodiments.

[0271] (Embodiment 5) This embodiment describes an example of the shape of a secondary battery having a positive electrode, as described in the previous embodiment. The materials used in the secondary battery described in this embodiment can be referenced to those described in the previous embodiment.

[0272] <Coin-type rechargeable battery> First, let's describe an example of a coin-type rechargeable battery. Figure 12A is an external view of a coin-type (single-layer flat type) rechargeable battery, and Figure 12B is a cross-sectional view thereof.

[0273] The coin-type secondary battery 300 has a positive electrode casing 301, which also serves as the positive electrode terminal, and a negative electrode casing 302, which also serves as the negative electrode terminal, both insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with it. The negative electrode 307 is formed by a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with it.

[0274] Furthermore, for the positive electrode 304 and negative electrode 307 used in the coin-type secondary battery 300, the active material layer only needs to be formed on one side.

[0275] The positive electrode can 301 and the negative electrode can 302 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 and / or aluminum, etc., to prevent corrosion by the electrolyte. The positive electrode can 301 is electrically connected to the positive electrode 304, and the negative electrode can 302 is electrically connected to the negative electrode 307.

[0276] The negative electrode 307, positive electrode 304, and separator 310 are impregnated with an electrolyte, and as shown in Figure 12B, the positive electrode 304, separator 310, negative electrode 307, and negative electrode 302 are stacked in this order with the positive electrode 301 at the bottom, and the positive electrode 301 and negative electrode 302 are pressed together via a gasket 303 to manufacture a coin-type secondary battery 300.

[0277] By using the particles 190 described in Embodiment 1 as the positive electrode 304, a coin-type secondary battery 300 with high charge / discharge capacity and excellent cycle characteristics can be obtained.

[0278] Here, Figure 12C is used to explain the current flow during charging of a secondary battery. When a lithium-ion secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In a lithium-ion secondary battery, the anode and cathode are reversed during charging and discharging, and the oxidation and reduction reactions are reversed. Therefore, the electrode with the higher reaction potential is called the positive electrode, and the electrode with the lower reaction potential is called the negative electrode. Accordingly, in this specification, whether charging or discharging, whether a reverse pulse current is flowing or a charging current is flowing, the positive electrode will be called the "positive electrode" or "+ electrode (positive electrode)," and the negative electrode will be called the "negative electrode" or "- electrode (negative electrode)." Using the terms anode (positive electrode) and cathode (negative electrode) in relation to oxidation and reduction reactions could lead to confusion as they are reversed during charging and discharging. Therefore, the terms anode (positive electrode) and cathode (negative electrode) will not be used in this specification. If the terms anode and cathode are used, it should be specified whether they refer to the charging or discharging phase, and whether they correspond to the positive or negative electrode.

[0279] A charger is connected to the two terminals shown in Figure 12C, and the secondary battery 300 is charged. As the secondary battery 300 charges, the potential difference between the electrodes increases.

[0280] <Stacked rechargeable battery> Furthermore, one embodiment of the present invention may be a secondary battery 700 in which multiple electrodes are stacked, as shown in Figures 13A and 13B. Also, the electrodes and casing are not limited to an L-shape, but may be rectangular.

[0281] The laminate-type secondary battery 700 shown in Figure 13A comprises a positive electrode 703 having an L-shaped positive electrode current collector 701 and a positive electrode active material layer 702, a negative electrode 706 having an L-shaped negative electrode current collector 704 and a negative electrode active material layer 705, an electrolyte layer 707, and an outer casing 709. The electrolyte layer 707 is installed between the positive electrode 703 and the negative electrode 706, which are located within the outer casing 709.

[0282] In the laminate-type secondary battery 700 shown in Figure 13A, the positive electrode current collector 701 and the negative electrode current collector 704 also serve as terminals for obtaining electrical contact with the outside. Therefore, parts of the positive electrode current collector 701 and the negative electrode current collector 704 may be arranged to be exposed to the outside from the outer casing 709. Alternatively, the positive electrode current collector 701 and the negative electrode current collector 704 may not be exposed to the outside from the outer casing 709, and instead, lead electrodes may be ultrasonically bonded to the positive electrode current collector 701 or the negative electrode current collector 704 using lead electrodes, thereby exposing the lead electrodes to the outside.

[0283] In a laminate-type secondary battery, the outer casing 709 can be a laminate film with a three-layer structure, in which a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an insulating synthetic resin film such as a polyamide resin or polyester resin is provided on the metal thin film as the outer surface of the outer casing.

[0284] Furthermore, an example of the cross-sectional structure of a laminate-type secondary battery is shown in Figure 13B. In Figure 13A, one set of electrodes and one electrolyte layer are shown for clarity, but in reality, it is preferable to have a configuration with multiple electrodes and multiple electrolyte layers as shown in Figure 13B.

[0285] Figure 13B shows an example with 16 electrodes. Figure 13B shows a structure with a total of 16 layers: 8 layers of negative electrode current collectors 704 and 8 layers of positive electrode current collectors 701. Figure 13B shows a cross-section of the positive electrode extraction section cut along the dashed line in Figure 13A, where the 8 layers of negative electrode current collectors 704 are ultrasonically bonded. Of course, the number of electrode layers is not limited to 16; it can be more or fewer. By using the particles 190 described in Embodiment 1 as the positive electrode active material layer 702, a secondary battery with high charge / discharge capacity and excellent cycle characteristics can be obtained. If the number of electrode layers is large, a secondary battery with a larger capacity can be made. Also, if the number of electrode layers is small, the battery can be made thinner.

[0286] Figure 14A shows the positive electrode of the secondary battery 700, which has an L-shaped positive electrode current collector 701 and a positive electrode active material layer 702. The positive electrode also has a region where the positive electrode current collector 701 is partially exposed (hereinafter referred to as the tab region). Figure 14B shows the negative electrode of the secondary battery 700, which has an L-shaped negative electrode current collector 704 and a negative electrode active material layer 705. The negative electrode also has a region where the negative electrode current collector 704 is partially exposed, i.e., the tab region.

[0287] Figure 14C shows a perspective view in which four layers of positive electrode 703 and four layers of negative electrode 706 are stacked. In Figure 14C, for simplicity, the electrolyte layer 707 placed between the positive electrode 703 and the negative electrode 706 is shown as a dotted line.

[0288] <Wound secondary battery> Furthermore, a secondary battery according to one aspect of the present invention may be a secondary battery 950 having a wound body 951 inside an outer casing 960 as shown in Figures 15A to 15C. The wound body 951 shown in Figure 15A has a negative electrode 107, a positive electrode 106, and an electrolyte layer 103. The negative electrode 107 has a negative electrode active material layer 104 and a negative electrode current collector 105. The positive electrode 106 has a positive electrode active material layer 102 and a positive electrode current collector 101. The electrolyte layer 103 has a wider width than the negative electrode active material layer 104 and the positive electrode active material layer 102, and is wound so as to overlap the negative electrode active material layer 104 and the positive electrode active material layer 102. The electrolyte layer 103, which has a lithium-ion conductive polymer and a lithium salt, is flexible, making it possible to wind it in this way. It is preferable from a safety standpoint that the negative electrode active material layer 104 is wider than the positive electrode active material layer 102. Furthermore, a coiled body 951 of this shape is preferable due to its good safety and productivity.

[0289] As shown in Figure 15B, the negative electrode 107 is electrically connected to terminal 961. Terminal 961 is electrically connected to terminal 963. The positive electrode 106 is electrically connected to terminal 962. Terminal 962 is electrically connected to terminal 964.

[0290] As shown in Figure 15B, the secondary battery 950 may have multiple windings 951. By using multiple windings 951, a secondary battery 950 with a larger charge and discharge capacity can be made.

[0291] By using the particles 190 described in Embodiment 1 for the positive electrode 106, a secondary battery 950 with high charge / discharge capacity and excellent cycle characteristics can be obtained.

[0292] This embodiment can be used in combination with other embodiments.

[0293] (Embodiment 6) This embodiment shows an example of applying the secondary battery shown in Figure 15C to an electric vehicle (EV).

[0294] Electric vehicles are equipped with a first battery 1301a and 1301b as the main secondary battery for propulsion, and a second battery 1311 that supplies power to the inverter 1312 that starts the motor 1304. The second battery 1311 is also called the cranking battery (or starter battery). The second battery 1311 only needs to be able to output power, and does not require a large capacity, so its capacity is smaller than that of the first batteries 1301a and 1301b.

[0295] The internal structure of the first battery 1301a may be a wound type as shown in Figure 15A, or a stacked type as shown in Figures 13A, 13B, 14A, 14B, or 14C. Alternatively, the first battery 1301a may use the all-solid-state battery of Embodiment 4. Using the all-solid-state battery of Embodiment 4 for the first battery 1301a allows for higher capacity, improved safety, and miniaturization and weight reduction.

[0296] In this embodiment, an example is shown in which two first batteries 1301a (or first batteries 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.

[0297] Furthermore, the vehicle-mounted secondary battery has a service plug or circuit breaker that can cut off high voltage without using tools in order to interrupt power from multiple secondary batteries, and this is provided in the first battery 1301a.

[0298] Furthermore, the power from the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V onboard components (electric power steering 1307, heater 1308, defogger 1309, etc.) via the DC-DC circuit 1306. If a rear motor 1317 is located on the rear wheels, the first battery 1301a is used to rotate the rear motor 1317.

[0299] Furthermore, the second battery 1311 supplies power to 14V automotive components (audio 1313, power windows 1314, lights 1315, etc.) via the DC-DC circuit 1310.

[0300] Furthermore, the first battery 1301a will be explained using Figure 16A.

[0301] Figure 16A shows an example where nine rectangular secondary batteries 1300 are arranged in a single battery pack 1415. In this example, nine rectangular secondary batteries 1300 are connected in series, with one electrode fixed by an insulating fixing part 1413 and the other electrode fixed by an insulating fixing part 1414. While this embodiment shows an example of fixing with fixing parts 1413 and 1414, the batteries may also be housed in a battery housing box (also called a casing). Since vehicles are expected to be subjected to vibrations or shaking from external sources (such as the road surface), it is preferable to fix multiple secondary batteries using fixing parts 1413 and 1414 or a battery housing box. Furthermore, one electrode is electrically connected to the control circuit unit 1320 by wiring 1421, and the other electrode is electrically connected to the control circuit unit 1320 by wiring 1422.

[0302] Furthermore, the control circuit unit 1320 may also use a memory circuit that includes a transistor made of an oxide semiconductor. A charging control circuit or battery control system having a memory circuit that includes a transistor made of an oxide semiconductor may be referred to as a BTOS (Battery operating system or Battery oxide semiconductor).

[0303] It is preferable to use a metal oxide that functions as an oxide semiconductor. For example, as the oxide, a metal oxide such as In-M-Zn oxide (where element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium, etc.) is preferable. In particular, the In-M-Zn oxide that can be applied as the oxide is preferably CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). Alternatively, In-Ga oxide or In-Zn oxide may be used as the oxide. CAAC-OS is an oxide semiconductor having multiple crystalline regions, the c-axis of which is oriented in a specific direction. The specific direction is the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. Furthermore, a crystalline region is a region in which the atomic arrangement has periodicity. If the atomic arrangement is considered as a lattice arrangement, then a crystalline region is also a region in which the lattice arrangement is aligned. In addition, CAAC-OS has regions in which multiple crystalline regions are connected in the ab-plane direction, and these regions may have distortion. Distortion refers to a point in a region in which multiple crystalline regions are connected where the orientation of the lattice arrangement changes between a region in which the lattice arrangement is aligned and another region in which the lattice arrangement is aligned. In other words, CAAC-OS is an oxide semiconductor that is c-axis oriented and does not have a clear orientation in the ab-plane direction. Furthermore, CAC-OS is a material composition in which, for example, elements constituting a metal oxide are unevenly distributed in sizes of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or close to that size. In the following, in a metal oxide, a state in which one or more metal elements are unevenly distributed, and regions containing these metal elements are mixed in sizes of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or close to that size, is also referred to as a mosaic or patchy state.

[0304] Furthermore, CAC-OS is a composite metal oxide having a mosaic-like structure formed by the separation of the material into a first region and a second region, with the first region distributed within the film (hereinafter also referred to as a cloud-like structure). In other words, CAC-OS is a composite metal oxide having a structure in which the first region and the second region are mixed.

[0305] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in In-Ga-Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS of In-Ga-Zn oxide, the first region is the region where [In] is greater than the [In] in the composition of the CAC-OS film. The second region is the region where [Ga] is greater than the [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is the region where [In] is greater than the [In] in the second region, and [Ga] is smaller than the [Ga] in the second region. The second region is the region where [Ga] is greater than the [Ga] in the first region, and [In] is smaller than the [In] in the first region.

[0306] Specifically, the first region described above is a region whose main components are indium oxide, indium zinc oxide, etc. The second region described above is a region whose main components are gallium oxide, gallium zinc oxide, etc. In other words, the first region can be rephrased as a region whose main component is In. Similarly, the second region can be rephrased as a region whose main component is Ga.

[0307] Furthermore, a clear boundary may not be observed between the first region and the second region described above.

[0308] For example, in the case of CAC-OS in In-Ga-Zn oxide, EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) confirms that it has a structure in which regions mainly composed of In (first region) and regions mainly composed of Ga (second region) are unevenly distributed and mixed.

[0309] When CAC-OS is used in a transistor, the conductivity due to the first region and the insulation due to the second region work complementaryly to give CAC-OS a switching function (on / off function). In other words, CAC-OS has conductive function in part of the material, insulating function in part of the material, and semiconductor function as a whole. By separating the conductive function and the insulating function, both functions can be maximized. Therefore, by using CAC-OS in a transistor, a high on-current (I) can be achieved. on This enables high field-effect mobility (μ) and good switching operation.

[0310] Oxide semiconductors can take on diverse structures, each possessing different properties. One embodiment of the present invention may include two or more of the following: amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, CAC-OS, nc-OS, and CAAC-OS.

[0311] Furthermore, since it can be used in high-temperature environments, it is preferable that the control circuit unit 1320 uses a transistor made of an oxide semiconductor. To simplify the process, the control circuit unit 1320 may be formed using a unipolar transistor. Transistors using an oxide semiconductor in the semiconductor layer have an operating ambient temperature range of -40°C to 150°C, which is wider than that of single-crystal Si, and the change in characteristics is smaller than that of single-crystal Si even when the secondary battery is heated. 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 unit 1320 can improve safety. Furthermore, a synergistic effect on safety can be obtained by combining it with a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode. The secondary battery and control circuit unit 1320 described in Embodiment 1 using the particles 190 as the positive electrode can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0312] 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.

[0313] Furthermore, a 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-circuit in a small area can cause a large voltage change, the abnormal voltage value may affect subsequent estimations.

[0314] 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.

[0315] 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.

[0316] Furthermore, Figure 16B shows an example of a block diagram of the battery pack 1415 shown in Figure 16A.

[0317] 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 is set to an upper and lower voltage limit for the secondary battery being used, and limits the upper limit of external current and the upper limit of output current to the outside. Within the range between the lower voltage limit and the upper voltage limit of the secondary battery, it is within the 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 overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0318] The switch section 1324 can be constructed by combining n-channel transistors and / or p-channel transistors. The switch section 1324 is not limited to switches using Si transistors made of single-crystal silicon, but may also be formed using power transistors made of, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (gallium oxide; x is a real number greater than 0), etc. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. Also, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost. That is, the control circuit section 1320 using OS transistors can be stacked on the switch section 1324 and integrated into a single chip. Since the occupied volume of the control circuit section 1320 can be reduced, miniaturization is possible.

[0319] Figure 16C is a block diagram of a vehicle with a motor. The first batteries 1301a and 1301b mainly supply power to 42V (high-voltage) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage) onboard equipment. Lead-acid batteries are often used for the second battery 1311 because they are cost-effective. Lead-acid batteries have the disadvantage of having a large self-discharge rate and being prone to degradation due to a phenomenon called sulfation compared to lithium-ion secondary batteries. Using a lithium-ion secondary battery for the second battery 1311 has the advantage of being maintenance-free, but after long-term use, for example more than 3 years, there is a risk of abnormalities occurring that could not be detected at the time of manufacture. In particular, if the second battery 1311, which starts the inverter, becomes inoperable, the motor will not be able to start 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, and it is charged to always maintain a fully charged state.

[0320] This embodiment shows an example in which lithium-ion secondary batteries are used for both the first battery 1301a and the second battery 1311. The second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double-layer capacitor. For example, the all-solid-state battery of Embodiment 4 may be used. By using the all-solid-state battery of Embodiment 4 for the second battery 1311, high capacity can be achieved, and the device can be made smaller and lighter.

[0321] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 and battery controller 1302. Alternatively, it is charged the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged 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.

[0322] 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.

[0323] Although not shown in the diagram, when connected to an external charger, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some cases, the charger may have a control circuit and may not use the functions of the battery controller 1302, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the connection cable or the charger's connection cable may also have a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. The ECU also uses a CPU and / or GPU.

[0324] External chargers installed at charging stations and other locations offer various types of power outlets, including 100V outlets, 200V outlets, and 3-phase 200V and 50kW. Additionally, it is possible to charge by receiving power from external charging equipment using contactless power supply methods.

[0325] For rapid charging, a rechargeable battery capable of withstanding high-voltage charging is desired to achieve short charging times.

[0326] Furthermore, the secondary battery of this embodiment described above has a high-density positive electrode by using the particles 190 explained in Embodiment 1. In addition, by using graphene as a conductive material, it is possible to suppress capacity reduction even when the electrode layer is thickened and the amount of support is increased. Furthermore, a synergistic effect is achieved in maintaining high capacity, and 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.

[0327] In particular, the secondary battery of this embodiment described above can achieve a higher operating voltage by using the particles 190 described in Embodiment 1, and the usable capacity can be increased with increasing charging voltage. Furthermore, by using the particles 190 described in Embodiment 1 as the positive electrode, a secondary battery for vehicles with excellent cycle characteristics can be provided.

[0328] This embodiment can be freely combined with other embodiments.

[0329] (Embodiment 7) This embodiment describes an example in which a secondary battery, which is one aspect of the present invention, is mounted in a vehicle, building, mobile device, or electronic device.

[0330] Examples of electronic devices that utilize rechargeable batteries include television equipment (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, personal digital assistants, sound playback devices, and large game machines such as pachinko machines.

[0331] Furthermore, secondary batteries can be applied to mobile devices, typically automobiles. Examples of automobiles include next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHEV or PHV), and secondary batteries can be applied as one of the power sources installed in these vehicles. Mobile devices are not limited to automobiles. For example, examples of mobile devices include trains, monorails, ships, flying vehicles (helicopters, unmanned aerial vehicles (drones), airplanes, rockets), electric bicycles, and electric motorcycles, and secondary batteries according to one embodiment of the present invention can be applied to these mobile devices.

[0332] Furthermore, the secondary battery of this embodiment may be applied to ground-mounted charging devices installed in residences, and to charging stations installed in commercial facilities.

[0333] An example of implementing a secondary battery, which is one aspect of the present invention, in a building will be explained with reference to Figures 17A and 17B.

[0334] The house shown in Figure 17A has a power storage device 2612 having a secondary battery, which is one embodiment of the present invention, and a solar panel 2610. The power storage device 2612 is electrically connected to the solar panel 2610 via wiring 2611, etc. The power storage device 2612 may also be electrically connected to a ground-mounted charging device 2604. The electricity obtained from the solar panel 2610 can be used to charge the power storage device 2612. The electricity stored in the power storage device 2612 can be used to charge the secondary battery of the vehicle 2603 via the charging device 2604. The power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space above the floor can be used effectively. Alternatively, the power storage device 2612 may be installed on the floor.

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

[0336] Figure 17B shows an example of an energy storage device 800 according to one aspect of the present invention. As shown in Figure 17B, an energy storage device 891 according to one aspect of the present invention is installed in the underfloor space 896 of the building 899. Furthermore, the control circuit described in Embodiment 6 may be provided in the energy storage device 891, and a synergistic effect on safety can be obtained by using a secondary battery with the particles 190 described in Embodiment 1 as the positive electrode in the energy storage device 891. The control circuit described in Embodiment 6 and the secondary battery with the particles 190 described in Embodiment 1 as the positive electrode can greatly contribute to eliminating accidents such as fires caused by the energy storage device 891 having a secondary battery.

[0337] The energy storage device 891 is equipped with a control device 890, which is electrically connected by wiring to the distribution board 803, the energy storage controller 805 (also called the control device), the display unit 806, and the router 809.

[0338] Power is supplied from the commercial power supply 801 to the distribution panel 803 via the service drop connection section 810. Power is also supplied to the distribution panel 803 from the energy storage device 891 and the commercial power supply 801, and the distribution panel 803 supplies the supplied power to the general load 807 and the energy storage system load 808 via outlets (not shown).

[0339] The general load 807 is, for example, an electrical device such as a television or a personal computer, and the energy storage load 808 is, for example, an electrical device such as a microwave oven, refrigerator, or air conditioner.

[0340] The energy storage controller 805 includes a measurement unit 811, a prediction unit 812, and a planning unit 813. The measurement unit 811 has the function of measuring the amount of electricity consumed by the general load 807 and the energy storage system load 808 during a day (for example, from 0:00 to 24:00). The measurement unit 811 may also have the function of measuring the amount of electricity consumed by the energy storage device 891 and the amount of electricity supplied from the commercial power supply 801. The prediction unit 812 has the function of predicting the amount of electricity demanded by the general load 807 and the energy storage system load 808 during the next day, based on the amount of electricity consumed by the general load 807 and the energy storage system load 808 during the day. The planning unit 813 has the function of planning the charging and discharging of the energy storage device 891 based on the amount of electricity demand predicted by the prediction unit 812.

[0341] The amount of electricity consumed by the general load 807 and the energy storage system load 808, as measured by the measurement unit 811, can be checked on the display unit 806. It can also be checked via the router 809 on electrical equipment such as televisions or personal computers. Furthermore, it can be checked via the router 809 on portable electronic devices such as smartphones or tablets. Additionally, the amount of electricity demand predicted by the prediction unit 812 for each time period (or hourly) can be checked on the display unit 806, electrical equipment, and portable electronic devices.

[0342] Next, Figures 18A and 18B show examples of a secondary battery according to one embodiment of the present invention being implemented in an electronic device. Figure 18A shows an example of a mobile phone. The mobile phone 2100 includes a display unit 2102 built into the housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like. The mobile phone 2100 also has a secondary battery 2107.

[0343] The mobile phone 2100 can run various applications such as making phone calls, sending emails, reading and creating documents, playing music, communicating on the internet, and playing computer games.

[0344] The operation button 2103 can be assigned various functions, including time setting, power on / off operation, wireless communication on / off operation, silent mode activation / deactivation, and power saving mode activation / deactivation. For example, the function of the operation button 2103 can be freely configured by the operating system built into the mobile phone 2100.

[0345] Furthermore, the 2100 mobile phone is capable of performing standardized short-range wireless communication. For example, it can communicate with a wireless headset to enable hands-free calling.

[0346] Furthermore, the mobile phone 2100 is equipped with an external connection port 2104, which allows for direct data exchange with other information terminals via a connector. It can also be charged via the external connection port 2104. Note that charging may also be performed wirelessly without using the external connection port 2104.

[0347] The mobile phone 2100 preferably has sensors. For example, it is preferable that the sensor includes a human body sensor such as a fingerprint sensor, pulse sensor, or body temperature sensor, as well as a touch sensor, pressure sensor, acceleration sensor, etc.

[0348] Figure 18B shows an unmanned aerial vehicle 2300 having multiple rotors 2302. The unmanned aerial vehicle 2300 is sometimes called a drone. The unmanned aerial vehicle 2300 has a secondary battery 2301, a camera 2303, and an antenna (not shown), which are embodiments of the present invention. The unmanned aerial vehicle 2300 can be remotely controlled via the antenna. The secondary battery using the particles 190 described in Embodiment 1 as the positive electrode has a high energy density and high safety, so it can be used safely for long periods of time over a long period of time and is suitable as a secondary battery to be mounted on the unmanned aerial vehicle 2300.

[0349] Next, an example of a transport vehicle using one aspect of the present invention is shown in Figures 18C to 18F. The automobile 2001 shown in Figure 18C 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 installed in the vehicle, one example of the secondary battery shown in Embodiment 5 is installed in one or more locations. Furthermore, a synergistic effect on safety can be obtained by using a secondary battery that uses the particles 190 described in Embodiment 1 as the positive electrode. The secondary battery that uses the particles 190 described in Embodiment 1 as the positive electrode can greatly contribute to the elimination of accidents such as fires caused by secondary batteries. The automobile 2001 shown in Figure 18C has a battery pack 2200, and the battery pack has a secondary battery module that connects a plurality of secondary batteries. Furthermore, it is preferable to have a charging control device that is electrically connected to the secondary battery module.

[0350] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via a plug-in method and / or a contactless power supply method, etc., for the secondary battery that the automobile 2001 has. When charging, the charging method and connector specifications may be carried out as appropriate in accordance with the prescribed methods such as CHAdeMO (registered trademark) and Combo. The secondary battery may be a charging station installed in a commercial facility or a household power supply. For example, the energy storage device installed in the automobile 2001 can be charged by supplying power from an external source using plug-in technology. Charging can be performed by converting AC power to DC power via a conversion device such as an AC / DC converter.

[0351] Although not shown in the diagram, the vehicle can also be charged by mounting a power receiving device on the vehicle and receiving power wirelessly from a ground-based power transmission device. In this wireless power supply method, charging can be performed not only when the vehicle is stopped but also while it is in motion by incorporating the power transmission device into the road and / or exterior wall. Furthermore, this wireless power supply method can be used to transmit and receive power between two vehicles. In addition, solar panels can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped and / or in motion. For such wireless power supply, electromagnetic induction and / or magnetic resonance methods can be used.

[0352] Figure 18D shows a large transport vehicle 2002 equipped with an electrically controlled motor as an example of a transport vehicle. The secondary battery module of the transport vehicle 2002 has a maximum voltage of 170V, achieved by connecting 48 cells in series, each consisting of four secondary batteries with a voltage of 3.5V to 4.7V. The secondary battery module of the battery pack 2201 has the same functions as Figure 18A, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0353] Figure 18E shows, as an example, a large transport vehicle 2003 equipped with an electrically controlled motor. The secondary battery module of the transport vehicle 2003 has a maximum voltage of 600V, achieved by connecting more than 100 secondary batteries with voltages of 3.5V to 4.7V in series. Therefore, secondary batteries with small characteristic variations are required. By using a secondary battery that uses the particle 190 described in Embodiment 1 as the positive electrode, a highly safe secondary battery can be manufactured, and mass production at low cost is possible from the standpoint of yield. Furthermore, since it has the same functions as Figure 18C except for differences in the number of secondary batteries constituting the secondary battery module of the battery pack 2202, the explanation is omitted.

[0354] Figure 18F shows an aircraft 2004 having a fuel-burning engine as an example. The aircraft 2004 shown in Figure 18F can be considered part of a 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.

[0355] The secondary battery module of aircraft 2004 has a maximum voltage of 32V, for example, by connecting eight 4V secondary batteries in series. The secondary battery module of battery pack 2203 has the same functionality as Figure 18C, except for differences in the number of secondary batteries that make up the module, so the explanation is omitted.

[0356] This embodiment shows an example of mounting an energy storage device according to one aspect of the present invention on a motorcycle or bicycle.

[0357] Next, Figure 19A shows an example of an electric bicycle to which a secondary battery according to one aspect of the present invention is applied. The electric bicycle 8700 shown in Figure 19A can be fitted with a power storage device according to one aspect of the present invention. The power storage device according to one aspect of the present invention includes, for example, a plurality of storage batteries and a protection circuit.

[0358] 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 19B shows it detached from the bicycle. The power storage device 8702 also has multiple storage batteries 8701, which are part of a power storage device according to one embodiment of the present invention, and the remaining battery level can be displayed on a display unit 8703. The power storage device 8702 also has a control circuit 8704 that can control the charging of the secondary battery or detect abnormalities, as exemplified in Embodiment 6. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701. A small solid-state secondary battery, as shown in Figures 11A and 11B, may also be provided in the control circuit 8704. By providing the small solid-state secondary battery shown in Figures 11A and 11B in the control circuit 8704, power can also be supplied to hold data in the memory circuit of the control circuit 8704 for a long period of time. Furthermore, a synergistic effect on safety can be obtained by combining it with a secondary battery that uses the particle 190 described in Embodiment 1 as the positive electrode. The secondary battery and control circuit 8704 that use the particle 190 as the positive electrode as described in Embodiment 1 can greatly contribute to eliminating accidents such as fires caused by secondary batteries.

[0359] Next, Figure 19C shows an example of a motorcycle to which a secondary battery according to one aspect of the present invention is applied. The scooter 8600 shown in Figure 19C is equipped with a power storage device 8602, side mirrors 8601, and turn signals 8603. The power storage device 8602 can supply electricity to the turn signals 8603.

[0360] Furthermore, the scooter 8600 shown in Figure 19C can accommodate the power storage device 8602 in the under-seat storage compartment 8604. The power storage device 8602 can be stored in the under-seat storage compartment 8604 even if the under-seat storage compartment 8604 is small.

[0361] Figure 20A 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.

[0362] For example, a secondary battery according to one embodiment of the present invention can be mounted in a spectacle-type device 4000 as shown in Figure 20A. 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 achieved. Furthermore, by equipping the secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0363] 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. A secondary battery can be provided in the flexible pipe 4001b and / or in the earphone section 4001c. By providing a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0364] Furthermore, a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode can be mounted in the device 4002, which can be directly attached to the body. The secondary battery 4002b can be provided inside the thin housing 4002a of the device 4002. By incorporating a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0365] Furthermore, a secondary battery according to one embodiment 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. By providing a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0366] 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 inside the belt portion 4006a. By equipping the secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0367] Furthermore, the wristwatch-type device 4005 can be equipped with a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode. The wristwatch-type device 4005 has a display unit 4005a and a belt unit 4005b, and the secondary battery can be provided in either the display unit 4005a or the belt unit 4005b. By providing a secondary battery using the particles 190 described in Embodiment 1 as the positive electrode, a high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing can be realized.

[0368] The display unit 4005a can display not only the time, but also various other information such as incoming emails and phone calls.

[0369] 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.

[0370] Figure 20B shows a perspective view of the wristwatch-type device 4005 after it has been removed from the arm.

[0371] A side view is also shown in Figure 20C. Figure 20C shows the internal structure of the secondary battery 700. Although the external shape differs from the secondary battery 700 in Figure 13, the internal structure is the same, and therefore the same reference numerals are used. The secondary battery 700 is located in a position that overlaps with the display unit 4005a, and is small and lightweight.

[0372] Furthermore, the head-mounted display 8300 shown in Figure 20D comprises a housing 8301, a display unit 8302, a band-shaped fixing device 8304, a pair of lenses 8305, and a secondary battery 700. Although the external shape differs from the secondary battery 700 in Figure 13, the internal structure is the same, and therefore the same reference numerals are used. In addition, two rectangular secondary batteries 700 are provided as an example for installation on the fixing device 8304.

[0373] Furthermore, as shown in Figure 20D, it is preferable that the head-mounted display 8300 includes a circuit unit 8306 and an imaging device 8307.

[0374] Image data (hereinafter referred to as image data A1) is provided to the display unit 8302 of the head-mounted display 8300. Image data A1 is composed of image data (hereinafter referred to as image data B1) generated by the circuit unit 8306 of the head-mounted display 8300 and data (hereinafter referred to as data C1) generated by the information processing device. Alternatively, image data B1 may be generated by a circuit outside the head-mounted display 8300. Data C1 is information about the controller and is updated as needed when the user operates the controller.

[0375] By combining image data B1 with continuously updated data C1 to generate image data A1, and displaying it on the display unit 8302 of the head-mounted display 8300, the head-mounted display 8300 can be used as a VR (Virtual Reality) device, an AR (Augmented Reality) device, or an MR (Mixed Reality) device, etc.

[0376] Furthermore, the head-mounted display 8300 may also have an eye-tracking input device. When generating image data A1, the information processing device may use the signal detected by the eye-tracking input device in addition to image data B1 and data C1.

[0377] Eye-tracking devices can detect gaze. Gaze detection can be performed, for example, by detecting the iris or pupil of a person's eye. It can also be performed by capturing the movement of the eyeball and eyelids. Furthermore, gaze can be detected by providing electrodes that come into contact with the user and detecting the current flowing through these electrodes in response to eye movement.

[0378] Image data A1 and audio data can be combined to generate video data. The display unit 8302 has the function of displaying the video data.

[0379] Furthermore, it is preferable that the head-mounted display 8300 has a sensor element that has the function of receiving electromagnetic waves emitted by the light-emitting element. Here, the imaging device 8307 can be used as a configuration that has a sensor element that has the function of receiving electromagnetic waves emitted by the light-emitting element.

[0380] Since the head-mounted display 8300 is required to be small and lightweight, using the particles 190 described in Embodiment 1 as the positive electrode of the secondary battery 700 makes it possible to create a secondary battery 700 that is both high in energy density and compact.

[0381] This embodiment can be used in appropriate combination with other embodiments. [Examples]

[0382] In this example, we will explain the results of calculations regarding the volume, area, and radius ratio of regions 191 and 193 in particle 190, as well as the charge and discharge capacity.

[0383] To simplify the calculations, the particle 190 in one embodiment of the present invention is assumed to be spherical, as shown in Figure 2A. Furthermore, region 192 is excluded from the calculations in this embodiment because it is not directly related to the charge / discharge capacity.

[0384] Figure 21 is a graph showing the ratio of the radii of region 191 to the radii of region 193, with the radius of particle 190 being set to 1, and the ratio of the volumes of region 191 and region 193. As shown in Figure 21, when the radius of region 191 is 0.8, the volumes of region 191 and region 193 are approximately equal.

[0385] Although not shown in the diagram, the ratio of the cross-sectional areas can be found by squaring the ratio of the radii. For example, when the ratio of the radii of region 191 is 0.02, the area of ​​region 191 is S 190This becomes 0.04%. When the ratio of the radii of region 191 is 0.55, the area of ​​region 191 is S 190 This is approximately 30% of the area. When the ratio of the radii of region 191 is 0.8, the area of ​​region 191 is S 190 This is approximately 64% of the area. When the ratio of the radii of region 191 is 0.95, the area of ​​region 191 is S 190 This is approximately 90% of the area. When the ratio of the radii of region 191 is 0.98, the area of ​​region 191 is S 190 This amounts to approximately 96%.

[0386] As described in the embodiments, the cross-sectional area ratio of region 191 or region 193 can be evaluated by cross-sectional observation and various line and surface analyses after the cross-section of the particle 190 is exposed by processing. When evaluating the area ratio, it is preferable to use a cross-section that sufficiently reflects the internal structure of the particle 190. For example, it is preferable to use a cross-section in which the maximum width of the cross-section is 80% or more of the average particle size (D50).

[0387] Figure 22A shows that particle 190 has a radius of 5 μm, and the core region 191 contains NCM811(LiNi x Co y Mn z This graph shows the radius of region 191 and the discharge capacity per unit weight when region 193, which is the shell, is made of LiCoO2 (O2, x:y:z=8:1:1). Calculations were performed for charging voltages of 4.2V, 4.4V, 4.6V, and 4.7V.

[0388] As shown in Figure 22A, at 4.2V to 4.6V, the discharge capacity tended to increase as the radius of the core region 191 increased. In this case, it was shown that a radius of 4 μm or more (0.8 or more of the radius of particle 190) is preferable, and a radius of 4.75 μm or more (0.95 or more of the radius of particle 190) is more preferable.

[0389] Figure 22B shows that particle 190 has a radius of 5 μm, with LiCoO2 in the core region 191 and NCM811(LiNi) in the shell region 193. x Co y Mn zThis graph shows the radius and discharge capacity per unit weight of region 191 when using O2 (x:y:z=8:1:1). Calculations were performed for charging voltages of 4.2V, 4.4V, 4.6V, and 4.7V.

[0390] As shown in Figure 22B, at 4.2V to 4.6V, the discharge capacity tended to increase as the radius of the core region 191 decreased. In this case, it was shown that the radius of region 191 is preferably 3.5 μm or less (0.7 or less of the radius of particle 190), and more preferably 3.0 μm or less (0.6 or less of the radius of particle 190). [Explanation of symbols]

[0391] 100: positive electrode active material, 101: positive electrode current collector, 102: positive electrode active material layer, 103: electrolyte layer, 104: negative electrode active material layer, 105: negative electrode current collector, 106: positive electrode, 107: negative electrode, 190: particles, 191:Area, 192:Area, 193:Area, 193a:Area, 193b:Area, 194:Area, 195:Area, 196a:Area, 196b:Area, 196c:Area, 196d:Area

Claims

1. Having a positive electrode active material, The positive electrode active material is The first area and, A second region is provided inside the first region, It has a third region provided between the first region and the second region, The first region has a lithium composite oxide which is a Li-Co-Ni oxide (where Li:Co:Ni = 1:1-x:x, and 0.4 ≤ x ≤ 0.6), The second region has lithium cobalt oxide, The third region comprises the first element, a halogen, the lithium composite oxide, and the lithium cobaltate, The first element is one or more selected from titanium, magnesium, aluminum, zirconium, vanadium, iron, chromium, niobium, cobalt, arsenic, zinc, silicon, sulfur, phosphorus, boron, calcium, gallium, and silicon. The positive electrode active material has grain boundaries, The first element is unevenly distributed at the grain boundary in a secondary battery.

2. In claim 1, The halogen is fluorine, in this secondary battery.

3. An electronic device having a secondary battery according to claim 1 or claim 2.

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