Lithium-ion rechargeable battery

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, wherein the first region has a higher concentration of transition metals than the second region. Furthermore, there is an impurity region between the first region and the second region.

Description

Technical Field

[0001] The present invention relates to a secondary battery using a positive electrode active material and a method for manufacturing the same. Or, it relates to an electronic device, a vehicle, etc. having a secondary battery.

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

[0003] In this specification, an electronic device generally refers to all devices having a power storage device, and an electro-optical device having a power storage device, an information terminal device having a power storage device, etc. are all electronic devices.

[0004] In this specification, a power storage device generally refers to an element and all devices having a power storage function. For example, it includes power storage devices (also referred to as secondary batteries) such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors.

Background Art

[0005] In recent years, various power storage devices such as lithium ion secondary batteries, lithium ion capacitors, and air batteries have been actively developed. In particular, lithium ion secondary batteries with high output and high energy density are rapidly expanding in demand along with the development of the semiconductor industry, for portable information terminals such as mobile phones, smartphones, or notebook computers, portable music players, digital cameras, medical devices, or next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV), and have become indispensable in modern information society as a source of repeatedly rechargeable energy.

[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, Non-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 [Non-patent literature]

[0009] [Non-Patent Document 1] Yang-Kook Sun et.al., High-energy cathode material for long-life and safe lithium batteries, NATURE MATERIALS VOL 8 APRIL 2009 [Overview of the project] [Problems that the invention aims to solve]

[0010] 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.

[0011] Furthermore, one aspect of the present invention aims to provide novel materials, active materials, energy storage devices, or methods for producing them.

[0012] 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.

[0013] 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.

[0014] Another objective is to provide a vehicle with a battery module weight of 300 kg or less by incorporating a secondary battery according to one embodiment of the present invention and increasing its density. Preferably, another objective is to realize a vehicle with a battery module weight of 300 kg or less and a driving range of 300 km or more, preferably 500 km or more, on a single charge. [Means for solving the problem]

[0015] 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 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, wherein the first transition metal is nickel, the second transition metal is cobalt, and the third transition metal is manganese, and the concentration of nickel is higher in the first region than in the second region.

[0016] In the above, it is preferable that the manganese concentration is higher in the first region than in the second region.

[0017] In the above, the positive electrode active material has an impurity region containing an impurity element, and it is preferable that the impurity region is located between the first region and the second region.

[0018] In the above, it is preferable that the impurity region has the function of suppressing the interdiffusion of elements between the first region and the second region. The impurity region may function as a separation layer to prevent the materials from mixing.

[0019] 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.

[0020] Furthermore, in the above, it is preferable that the impurity region has the function of suppressing the interdiffusion of elements between the first region and the second region.

[0021] Furthermore, the embodiments of the present invention are not limited to a double structure, but may also be a triple or higher multilayer structure. For example, in the case of a triple structure, it can be called a region including the central part, an intermediate layer surrounding the region, and a surface layer surrounding the intermediate layer. In the case of a multilayer structure (n or more layers), it can be said that the intermediate layer is increased by (n-2) layers. Another embodiment of the present invention is a secondary battery having a positive electrode active material, wherein the positive electrode active material has a multilayer structure and comprises a first region, a second region provided inside the first region, and a third region provided inside the second region, and each of the first, second, and third regions contains lithium, oxygen, and one or more selected from a first transition metal, a second transition metal, and a third transition metal, the first transition metal being nickel, the second transition metal being cobalt, and the third transition metal being manganese, and the concentration of nickel is higher in the second region than in the third region, in this secondary battery.

[0022] In the above, it is preferable that the nickel concentration is higher in the second region than in the first region.

[0023] In the triple structure described above, the positive electrode active material has an impurity region containing impurity elements, and it is preferable that the impurity region is located between the second region and the third region.

[0024] In the triple structure described above, it is preferable that the impurity region has the function of suppressing the interdiffusion of elements between the second and third regions.

[0025] Furthermore, in the triple structure described above, a second impurity region may be included between the first and second regions. These impurity regions may function as separation layers to prevent the materials from mixing.

[0026] Since cobalt is a limited resource, reducing its use can lower the cost of the active material. Nickel is more abundant than cobalt and is an environmentally friendly transition metal; therefore, when manufacturing low-cost secondary batteries, it is preferable to use more nickel than cobalt.

[0027] Furthermore, in each of the above configurations, the first region is preferably one that promotes the diffusion of lithium during charging and discharging and contributes to the stabilization of the positive electrode active material. Whether it is a double-layer structure, a triple-layer structure, or any other multilayer structure, the first region is a region that is in contact with at least a portion of one or more of the electrolyte, conductive additive, or binder. In some cases, the film thickness of the first region may be thinner than that of other regions, or the second region may be exposed for some reason.

[0028] 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 additives (also called conductive imparters or conductive materials). By attaching the conductive additive 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 additive, but also includes cases where covalent bonds are formed, bonds are formed by van der Waals forces, the conductive additive covers a part of the surface of the active material, the conductive additive 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. Furthermore, 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.). It is preferable to use a configuration that includes graphene as a conductive additive. Using graphene as a conductive additive may 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 is possible to suppress such degradation by using a configuration that includes graphene as a conductive additive. Various combinations can be used as conductive additives. Typical combinations used as conductive additives include a configuration that combines graphene with particulate carbon (e.g., acetylene black), and a configuration that combines fibrous carbon (e.g., carbon nanotubes) with particulate carbon (e.g., acetylene black). Alternatively, the materials used to form the graphene may be mixed with the graphene itself.For example, particles used as a catalyst in forming graphene may be mixed together. Examples of catalysts for forming graphene include silicon dioxide (SiO2, SiO2). x Examples of particles include those having (x<2), aluminum oxide, iron, nickel, ruthenium, iridium, platinum, copper, germanium, etc. Preferably, the average particle size (D50) of these particles is 1 μm or less, and more preferably 100 nm or less.

[0029] Another aspect of the present invention is an electronic device having the secondary battery described above.

[0030] 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]

[0031] 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.

[0032] 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.

[0033] Therefore, according to one aspect of the present invention, a vehicle equipped with a novel energy storage device can be provided.

[0034] Furthermore, according to one aspect of the present invention, novel materials, active materials, energy storage devices, or methods for producing them can be provided.

[0035] 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]

[0036] [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 charge depth and crystal structure of the positive electrode active material. [Figure 8] Figures 8A, 8B, 8C, and 8D are cross-sectional views illustrating an example of the positive electrode of a secondary battery. [Figure 9] Figures 9A and 9B illustrate examples of secondary batteries. [Figure 10] Figures 10A, 10B, and 10C illustrate examples of secondary batteries. [Figure 11] Figures 11A and 11B illustrate an example of a secondary battery. [Figure 12] Figures 12A, 12B, and 12C illustrate coin-type rechargeable batteries. [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 aspect 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 21A shows the calculation model, and Figure 21B 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]

[0037] 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.

[0038] In this specification, crystal planes and crystal directions are expressed using Miller indices. In crystallography, crystal planes, crystal directions, and space groups are expressed by superscripting numbers; however, due to formatting constraints in this specification, a minus sign (-) may be placed before the number instead of a superscript. Individual orientations indicating directions within a crystal are represented by [ ], collective orientations indicating all equivalent directions are represented by < >, individual crystal planes are represented by ( ), and collective planes with equivalent symmetry are represented by {}. Furthermore, for ease of understanding the structure, trigonal crystals represented by the space group R-3m are generally represented as a composite hexagonal lattice of hexagonal crystals, and (hkil) may be used as Miller indices in addition to (hkl). Here, i is -(h+k).

[0039] In this specification, "uneven distribution" 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).

[0040] 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.

[0041] 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.

[0042] In this specification, a rock salt-type crystal structure refers to a structure in which cations and anions are arranged alternately. However, deficiencies in cations or anions are acceptable.

[0043] Furthermore, in this specification, the O3' type (also called pseudo-spinel 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. In both the O3 type and O3' type crystal structures, it is preferable that magnesium is present dilutely between the CoO2 layers, i.e., at the lithium sites. It is also preferable that fluorine is present randomly and dilutely at the oxygen sites.

[0044] Furthermore, the O3' type crystal structure can be said to be similar to the CdCl2 type crystal structure, although it has Li randomly 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 pure lithium cobaltate or layered rock salt-type cathode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0045] 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.

[0046] In this specification, a structure in which anions are stacked in three layers with a slight offset from each other, such as ABCABC, will be referred to as cubic close-packed. Therefore, the anions do not need to be strictly cubic in shape. At the same time, since real crystals always have defects, the analytical results do not necessarily have to match the theory. For example, in FFT (Fast Fourier Transform) such as 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.

[0047] When layered rock salt crystals are in contact with other rock salt crystals, there exists a crystal plane in which the orientation of the cubic close-packed structure composed of anions is aligned.

[0048] Alternatively, the above phenomenon can be explained as follows: In the cubic crystal structure, anions in the (111) plane have a triangular arrangement. The layered rock salt type 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 type 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 type. The consistency between the two lattices can be described as the orientation of the cubic close-packed structure being aligned.

[0049] 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.

[0050] 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, electron diffraction, FFT of TEM images, etc. XRD (X-ray Diffraction) and neutron diffraction can also be used as criteria for determination.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] (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.

[0062] 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.

[0063] 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.

[0064] Region 191 is located inside region 193.

[0065] 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 (it can also be called the center). 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 smallest circumscribed circle 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 that of the largest cross-sectional area.

[0066] Region 192 is, for example, a region located between region 191 and region 193.

[0067] Region 191 is sometimes called the "core," and region 193 is sometimes called the "shell." The "shell" can also be called the surrounding tissue or outer shell. Note that "core" does not mean the nucleus of the entire particle, but is used to indicate the positional relationship between the center of the particle and the outer shell. The "core" can also be called the core material.

[0068] 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 region.

[0069] It is sometimes said that particle 190 has a core-shell structure (also called a core-shell type structure).

[0070] 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.

[0071] Region 191 has a particulate shape. Region 191 occupies an area ratio S of the cross-section of particle 190.191 / S 190 is 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 , and the cross-sectional area of particle 190 is S 190 (S 190 =S 191 +S 192 +S 193 ).

[0072] 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 of particle 190 than region 191.

[0073] 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.

[0074] Region 192 preferably has a function of suppressing the mutual diffusion during the synthesis of the elements that regions 191 and 193 have. Further, it preferably has a function of not inhibiting the mutual diffusion of lithium during charge and discharge or promoting the mutual diffusion of lithium.

[0075] It is preferable that at least a portion of region 193 is located at a position farther from the center 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.

[0076] 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, as shown in Figure 1C, region 193 can have two or more regions, with region 193b provided on the inside and region 193a provided outside of region 193b.

[0077] 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 the 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 )

[0078] Furthermore, it is preferable that at least a portion of region 194 is positioned at a distance from the center of particle 190 that is greater than that of 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.

[0079] 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.

[0080] 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).

[0081] 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.

[0082] <Complex Oxides> Regions 191 and 193 can be made of materials that allow for the insertion and removal of lithium ions. If the carrier ion is an alkali metal ion other than lithium, or an alkaline earth metal ion, an alkali metal (e.g., sodium or potassium) or an alkaline earth metal (e.g., calcium, strontium, barium, beryllium, magnesium) may be used instead of lithium. When regions 191 and 193 are composed of materials that function as 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 the space group R-3m. However, this is not limited to the functions desired for regions 191 and 193.

[0083] Regions 191 and 193 preferably contain a transition metal. Specifically, it is preferable that they contain one or more of cobalt, nickel, and manganese.

[0084] 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.

[0085] 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.

[0086] <Example of a particle 1> As a specific example of the particle 190, an example of using LCO for the core and NCM for the shell, that is, an example of using a lithium composite oxide in which Li-Co oxide is used as the region 191, cobalt as the first transition metal in the region 193, nickel as the second transition metal, and manganese as the third transition metal is shown. In the case of a configuration using LCO for the core and NCM for the shell, since it is possible to reduce the cobalt content as the entire positive electrode active material, the price of the entire positive electrode active material can be made lower than that of the positive electrode active material of LCO alone. Also, 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 + ).

[0087] As the lithium composite oxide using cobalt, nickel and manganese, for example, LiNi x Co y Mn z O2 (x > 0, y > 0, 0.8 < x + y + z < 1.2) (also referred to as NCM) can be used. Specifically, for example, it is preferable to satisfy 0.1x < y < 8x and 0.1x < z < 8x. As an example, it is preferable that x, y and z satisfy x:y:z = 1:1:1 or values in the vicinity thereof. Or as an example, it is preferable that x, y and z satisfy x:y:z = 5:2:3 or values in the vicinity thereof. Or as an example, it is preferable that x, y and z satisfy x:y:z = 8:1:1 or values in the vicinity thereof. Or as an example, it is preferable that x, y and z satisfy x:y:z = 9:0.5:0.5 or values in the vicinity thereof. Or as an example, it is preferable that x, y and z satisfy x:y:z = 6:2:2 or values in the vicinity thereof. Or as an example, it is preferable that x, y and z satisfy x:y:z = 1:4:1 or values in the vicinity thereof.

[0088] As the materials constituting the regions 192 and 194, reference can be made to the above description.

[0089] 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.

[0090] 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.

[0091] Alternatively, in region 193a, x, y, and z may satisfy x:y:z=8:1:1 or its neighbors, and in region 193b, x, y, and z may satisfy x:y:z=1:1:1 or its neighbors. Alternatively, in region 193a, x, y, and z may satisfy x:y:z=9:0.5:0.5 or its neighbors, and in region 193b, x, y, and z may satisfy x:y:z=1:1:1 or its neighbors.

[0092] 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.

[0093] <Example of a particle 2> As a specific example of particle 190, we show an example in which LCO is used for the core and LFP for 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.

[0094] 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 framework composed of phosphorus and oxygen remains stable even after 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.

[0095] <Example of a particle 3> 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.

[0096] 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 z O2 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.

[0097] The materials constituting regions 192 and 194 can be found by referring to the above description.

[0098] 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.

[0099] 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.

[0100] Here, 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. In other words, when charging occurs, lithium ions detach from the positive electrode active material. Positive electrode active materials with a layered crystal structure, such as composite oxides containing lithium and transition metals, can sometimes realize secondary batteries with a high lithium content per unit volume and high capacity per unit volume. However, with such positive electrode active materials, the amount of lithium detached per unit volume during charging is also large, and stabilization of the crystal structure after detachment is required for stable charging and discharging. Furthermore, the collapse of the crystal structure during charging and discharging may hinder fast charging and fast discharging. In addition, the collapse of the crystal structure may reduce the area in which lithium can be inserted and detached normally, which may lead to a decrease in charging capacity and discharging capacity.

[0101] As in the particle example 3, when nickel is included as a transition metal in addition to cobalt, the shifting of the layered structure consisting of octahedra of cobalt and oxygen can be suppressed. Therefore, the crystal structure may become more stable, especially in the charged state at high temperatures, which is preferable.

[0102] 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.

[0103] 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.

[0104] <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.

[0105] As the region containing element X and halogen, we use the region in which element X and halogen are added to the composite oxide represented by LiMO2. Here, the composite oxide only needs to have the crystal structure of the region in which element X and halogen are added to the composite oxide represented by LiMO2, and its composition is not strictly limited to Li:M:O=1:1:2.

[0106] The presence of element X and halogens in composite oxides represented by LiMO2 can sometimes further stabilize the crystal structure.

[0107] Furthermore, it is particularly preferable to use magnesium as element X. Furthermore, it is particularly preferable to use fluorine 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 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.

[0108] 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.

[0109] The regions containing element X and halogens may have different elements, different crystal structures, different bonding, etc.

[0110] 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 reinforced by regions containing element X and halogens, i.e., region 194 which is the outer periphery of the particle, or region 192 which is located between region 191 containing the composite oxide and region 193 containing the composite oxide.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] Furthermore, a short circuit in a secondary battery can not only cause malfunctions in the charging and discharging operations of the secondary battery, but 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 100 in 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.

[0117] A secondary battery using the positive electrode active material 100 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.

[0118] <Grain boundaries, etc.> In one embodiment of the present invention, the particle 190 (regions 191, 192, and 193) may have polycrystalline regions 191, 192, and 193, or any one of them. The element X or halogen present in the particle 190 (regions 191, 192, and 193) of one embodiment of the present invention may be randomly and dilutely present in the internal regions. In this case, element X is preferably magnesium or titanium.

[0119] Furthermore, when the concentrations of element X and halogen are high at and near the grain boundary 197 shown in Figure 3, even if a crack occurs along the grain boundary of particle 190 in one embodiment of the present invention, the concentrations of element X and halogen will be high near the surface created by the crack. Therefore, the corrosion resistance to hydrofluoric acid can be improved even in the positive electrode active material after the crack has occurred.

[0120] In this specification, the term "near the grain boundary" refers to the region extending approximately 10 nm from the grain boundary.

[0121] 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. Figures 3A and 3B show modified examples of the particle 190 shown in Figures 1 and 2. For example, as shown in region 196a of Figures 3A and 3B, there may be 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.

[0122] 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.

[0123] 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.

[0124] Furthermore, as shown in region 196d in Figures 3A and 3B, region 195 may have a different composition from the others in areas such as defects, cracks, unevenness, fissures, and grain boundaries (grain boundaries between region 195 and region 193). Region 195 is a region having different elements from regions 191 to 194, or a region having a different composition, or a region having a different crystal structure.

[0125] The presence of region 195 can cause excess impurity elements to be concentrated in region 195, while the impurity elements contained in regions 191 to 194 may be kept 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.

[0126] 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.

[0127] 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%.

[0128] <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. It may also be cubic (dice-shaped).

[0129] Furthermore, Figure 4B1 is a perspective view of particle 190, and Figure 4B2 is a cross-sectional view of Figure 4B1. The particle 190 may also be a rectangular parallelepiped.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] <Manufacturing method> Next, an example of a method for producing particles 190 having regions 191 to 193 will be described using Figure 5A.

[0134] First, in step S11, a lithium source and a transition metal source (M 191 Prepare the source and the other.

[0135] Next, in step S12, the lithium source and the transition metal source are mixed and synthesized. One synthesis method is to mix the lithium source and the transition metal source contained in region 191 using a solid-phase method, and then heat the mixture. In this embodiment, cobalt is used as the transition metal source.

[0136] In this way, the composite oxide to be used in region 191 is prepared (step S13). Alternatively, pre-synthesized lithium cobalt oxide may be used. For example, lithium cobalt oxide particles manufactured by Nippon Chemical Industrial Co., Ltd. (product name: Cellseed C-10N) can be used. These particles have an average particle size (D50) of approximately 12 μm.

[0137] Next, as step S21, X source(X 192 Prepare a halogen source and a halogen source. Lithium fluoride (LiF) is used as the halogen source. LiF is preferred because it has cations in common with LiCoO2. LiF is also preferred because it has a relatively low melting point of 848°C and is easily melted in the annealing process described later. In addition to LiF, MgF2 may also be used. Furthermore, the fluoride that can be used in one aspect of the present invention is not limited to LiF or MgF2.

[0138] Next, in step S31, the composite oxide, the X source, and the halogen source are mixed and synthesized. One synthesis method is to mix these using a solid-phase method and then heat the mixture. The heating temperature must be below the decomposition temperature of LiCoO2 (1130°C). Although the decomposition temperature of LiCoO2 is 1130°C, there is a concern that a small amount of LiCoO2 may decompose at temperatures near this temperature. Therefore, the annealing temperature is preferably below 1130°C, and more preferably below 1000°C. Specifically, it can be lowered to a temperature of 735°C to 1000°C. If the average particle size (D50) of the particles in step S13 is about 12 μm, the heating time is preferably 3 hours or more, and more preferably 10 hours or more. On the other hand, if the average particle size (D50) of the particles in step S13 is about 5 μm, the heating time is preferably 1 hour to 10 hours, and more preferably about 2 hours. The cooling time after heating is preferably, for example, 10 hours or more and 50 hours or less.

[0139] In this way, a composite oxide to be used in regions 191 and 192 is prepared (step S32). In this embodiment, region 192 contains fluorine and magnesium as impurities. The presence of magnesium in region 192 can be inferred from the fact that when a portion of the particles in step S32 are measured by EDX, a magnesium peak can be confirmed in the surface layer of the particles. Furthermore, the magnesium concentration in region 192 in step S32 can be considered as the value obtained by elemental analysis of the entire particle using, for example, ICP-MS. When XPS analysis is performed on the particles in step S32, the relative value of the magnesium concentration, with the cobalt concentration set to 1, is preferably 0.4 to 1.5, and more preferably 0.45 to less than 1.00. The relative value of the fluorine concentration is preferably 0.05 to 1.5, and more preferably 0.3 to 1.00.

[0140] Next, in step S41, a lithium source and a transition metal source (M 193 Prepare the source and . In this embodiment, nickel and manganese are used as the transition metal source.

[0141] Next, in step S71, the composite oxide to be used in regions 191 and 192, the lithium source, and the transition metal source in region 193 are synthesized. One synthesis method is to mix these in a solid-phase manner and then heat them.

[0142] In this way, particle 190 is produced (step S72).

[0143] Furthermore, it is preferable that the composite oxide used in region 191 is a material with a higher melting point than the composite oxide used in region 193. Alternatively, it is preferable that the composite oxide used in region 191 is a material with higher thermal stability than the composite oxide contained in region 193. Due to this difference in melting point or thermal stability, for example, the heating in the synthesis in step S71 can be set to a temperature and time that ensures the composite oxide used in region 191 is stable while the composite oxide contained in region 193 sufficiently interdiffuses.

[0144] Furthermore, it is preferable that the ionic radius of the cation of element X used in region 192 is larger than that of the ionic radius of the metal cation used in region 191. This difference in ionic radius makes it easier for element X to be concentrated in region 192. In addition, region 192 is more likely to exhibit the function of suppressing the interdiffusion of elements in regions 191 and 193.

[0145] Particles 190 having regions 191 to 194 can be fabricated, for example, as shown in Figure 5B.

[0146] Steps S11 through S41 can be manufactured in the same manner as shown in Figure 5A.

[0147] Next, in step S51, the composite oxide, lithium source, and transition metal source are mixed and synthesized. One synthesis method is to mix them using a solid-phase method and then heat the mixture.

[0148] In this way, composite oxides to be used in regions 191 to 193 are prepared (step S52).

[0149] Next, as step S61, X source(X 194 Prepare a (source) and a halogen source.

[0150] Next, in step S71, the composite oxide, the X source, and the halogen source are mixed and synthesized. One synthesis method is to mix them using a solid-phase method and then heat the mixture.

[0151] In this way, particle 190 is produced (step S72).

[0152] Furthermore, it is preferable that the ionic radius of the cation of element X used in region 194 is larger than that of the ionic radius of the metal cation used in region 193. This difference in ionic radius makes it easier for element X to be concentrated in region 194.

[0153] This embodiment can be used in combination with other embodiments.

[0154] (Embodiment 2) In this embodiment, an example of a material used in region 191 (core) shown in Figure 1A is presented. As region 191, a material having a layered rock salt type crystalline structure, such as lithium cobalt oxide (LiCoO2), has a high discharge capacity and is excellent as a positive electrode active material for secondary batteries.

[0155] Examples of materials having a layered rock salt crystal structure include composite oxides represented by LiMO2. In this specification, the lithium composite oxide represented by LiMO2 only needs to have a layered rock salt crystal structure; its composition is not strictly limited to Li:M:O=1:1:2. Referring to Figure 6, we will now describe the case where cobalt is used as the transition metal M in the positive electrode active material.

[0156] 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.

[0157] 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.

[0158] The positive electrode active material having the crystal structure shown in Figure 6 is lithium cobalt oxide, i.e., lithium cobalt oxide (LiCoO2) without the addition of halogens and magnesium, which can be produced by the manufacturing method described later. The crystal structure of this lithium cobalt oxide changes depending on the depth of charge.

[0159] 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, where lithium occupies octahedral sites, and there are three CoO2 layers in the unit cell. For this reason, this crystal structure is sometimes called the O3 type crystal structure. The CoO2 layer refers to a structure in which octahedral structures, in which oxygen atoms are 6-coordinated to cobalt, are continuous in a plane with shared edges.

[0160] 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.

[0161] Furthermore, lithium cobalt oxide at a charge depth of approximately 0.8 has a crystal structure with space group R-3m. This structure can be described as a structure in which CoO2 structures such as P-3m1(O1) and LiCoO2 structures such as R-3m(O3) are alternately stacked. For this reason, this crystal structure is sometimes called the H1-3 type crystal structure. In reality, the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell compared to other structures. However, in this specification, including Figure 6, the c-axis of the H1-3 type crystal structure is shown as half the unit cell to facilitate comparison with other crystal structures.

[0162] As an example, in the H1-3 type crystal structure, as described in Non-Patent Literature 2, the coordinates of cobalt and oxygen in the unit cell can be represented as Co(0,0,0.42150±0.00016), O1(0,0,0.27671±0.00045), and O2(0,0,0.11535±0.00045). O1 and O2 are oxygen atoms, respectively. Thus, the H1-3 type crystal structure is represented by a unit cell using one cobalt and two oxygen atoms.

[0163] Furthermore, examples of materials used in regions 193 and 194 shown in Figure 1B are shown below. The material used in at least one of regions 191 or 192 shown in Figure 1B preferably contains lithium, cobalt as a transition metal M, oxygen, and magnesium. In addition, the impurities in regions 192 and 194 preferably contain halogens such as fluorine and chlorine.

[0164] 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.

[0165] The O3' type crystal structure is preferably represented by a unit cell using one cobalt and one oxygen atom. This indicates that the symmetry between cobalt and oxygen differs between the O3' type crystal structure and the H1-3 type crystal structure, and that the O3' type crystal 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 fitness) value in Rietveld analysis using XRD.

[0166] In the O3' type crystal structure, light elements such as lithium may occupy the oxygen 4-coordinate position.

[0167] 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 O3' type crystal structure 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. The crystal structure in Figure 7 has a lattice constant of 2.871 Å along the a-axis and 13.781 Å along the c-axis.

[0168] Furthermore, the O3' type crystal structure can be said to be similar to the CdCl2 type crystal structure, although it has Li randomly 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 pure lithium cobaltate or layered rock salt-type cathode active materials containing a large amount of cobalt do not usually adopt this crystal structure.

[0169] In positive electrode active materials having an O3'-type crystal structure, the change in crystal structure when charged at high voltage and a large amount of lithium is released is suppressed compared to the crystal structure shown 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.

[0170] More specifically, the positive electrode active material having the crystal structure shown in Figure 7 exhibits high crystal structure stability even at high charging voltages. For example, in the positive electrode active material having the crystal structure shown in 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 between 4.65V and 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, even at lower charging voltages (for example, when the charging voltage is between 4.5V and 4.6V relative to the potential of lithium metal), an O3' type crystal structure may be adopted.

[0171] Thus, the positive electrode active material having the crystal structure shown in Figure 7 is suitable for the core because its crystal structure is less likely to collapse even when repeatedly charged and discharged at high voltage.

[0172] Here, lithium cobalt oxide (LiCoO2) is shown as an example of a material used for the core, but this is just one example and is not particularly limited.

[0173] 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.

[0174] 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 a heat treatment in the manufacturing process of the positive electrode active material having the crystal structure shown in Figure 7.

[0175] However, if the heat treatment temperature is too high, cation mixing occurs, increasing the likelihood that additives, such as magnesium, will enter the cobalt site. Magnesium present in the cobalt site does not help maintain the R-3m structure during high-voltage charging. Furthermore, if the heat treatment temperature is too high, there are concerns about adverse effects such as the reduction of cobalt to its divalent state and the evaporation of lithium.

[0176] 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.

[0177] 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.

[0178] 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 its crystal structure, for example, under high-voltage charging conditions. 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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] The positive electrode active material having the above configuration can reduce the displacement of the CoO2 layer during repeated high-voltage charging and discharging. Furthermore, it can reduce volume changes. Therefore, a secondary battery using a positive electrode active material having the crystal structure shown in Figure 7 in at least a part of the core can achieve excellent cycle characteristics. In addition, the positive electrode active material having the crystal structure shown in Figure 7 in the core can adopt a stable crystal structure in a high-voltage charging state. Therefore, a secondary battery using a positive electrode active material having the crystal structure shown in Figure 7 in the core may be less prone to short circuits when a high-voltage charging state is maintained. In such cases, the safety of the secondary battery is further improved, which is preferable.

[0187] The positive electrode active material having the crystal structure shown in Figure 7 exhibits small changes in crystal structure and small differences in volume per unit number of transition metal atoms when comparing a fully discharged state with a high-voltage charged state.

[0188] 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."

[0189] This embodiment can be freely combined with other embodiments.

[0190] (Embodiment 3) This embodiment shows an example of manufacturing a secondary battery using the particles 190 described in Embodiment 1. The particles 190 described in Embodiment 1 are used to manufacture the positive electrode. The 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 additive, and a binder. It also has an electrolyte in which lithium salt or the like is dissolved. In the case of a secondary battery using an electrolyte, a positive electrode, a negative electrode, and a separator between the positive and negative electrodes are provided.

[0191] [Positive electrode] First, let's explain the positive electrode. The positive electrode has a positive electrode active material layer and a current collector. Figure 8A shows an example of a schematic diagram of the cross-section of the positive electrode.

[0192] 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.

[0193] 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 additive. Slurries are sometimes called electrode slurries or active material slurries, and a positive electrode slurry is used when forming a positive electrode active material layer, while a negative electrode slurry is sometimes used when forming a negative electrode active material layer.

[0194] Conductive additives, also called conductivity imparters or conductive materials, are typically made of carbon. By attaching a conductive additive between multiple active materials, the materials become electrically connected to each other, increasing their conductivity. Note that "attachment" does not only refer to physical contact between the active materials and the conductive additive, but also includes cases where covalent bonds are formed, bonds are formed by van der Waals forces, the conductive additive covers part of the surface of the active materials, the conductive additive fits into surface irregularities of the active materials, or where electrical connections are formed even without physical contact.

[0195] A typical example of a carbon material used as a conductive additive is carbon black (furnace black, acetylene black, graphite, etc.).

[0196] Figure 8A illustrates acetylene black 503 as a conductive additive. 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.

[0197] 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.

[0198] 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.

[0199] Figure 8B illustrates the active material 501 in various shapes. Figure 8B shows examples different from those in Figure 8A.

[0200] Furthermore, in the positive electrode shown in Figure 8B, graphene 504 is used as the carbon material used as a conductive additive.

[0201] 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.

[0202] Figure 8B shows a positive electrode active material layer formed on the current collector 500, comprising an active material 501, graphene 504, and acetylene black 503.

[0203] 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.

[0204] 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 a conductive additive. 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.

[0205] Furthermore, although the electrode density is lower compared to a positive electrode using only graphene as a conductive additive, rapid charging can be achieved by setting the mixture of the first carbon material (graphene) and the second carbon material (acetylene black) within the above range. In addition, it is preferable to use the particles 190 described in Embodiment 1 as the positive electrode and set the mixture of graphene 504 and acetylene black 503 within the above range, as this is expected to have a synergistic effect in increasing the stability of the secondary battery and enabling even faster charging.

[0206] These features make it effective as a secondary battery for use in vehicles.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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, leaving voids even after the battery is formed, thus reducing efficiency.

[0212] 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.

[0213] Figure 8C illustrates an example of a cathode using carbon nanotube 505 instead of graphene. Figure 8C shows a different example from Figure 8B. Using carbon nanotube 505 prevents aggregation of carbon black such as acetylene black 503 and improves dispersibility.

[0214] In Figure 8C, the areas not filled with active material 501, carbon nanotube 505, and acetylene black 503 represent voids or binders.

[0215] 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.

[0216] In Figure 8D, the areas not filled with active material 501, carbon nanotube 505, graphene 504, and acetylene black 503 represent voids or binders.

[0217] 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.

[0218] Furthermore, the above configuration is an example of a secondary battery using an electrolyte, but it is not particularly limited.

[0219] For example, semi-solid-state batteries and all-solid-state batteries can be fabricated using the particles 190 described in Embodiment 1.

[0220] In this specification, a semi-solid battery refers to a battery having a semi-solid material in at least one of its components: the electrolyte layer, the positive electrode, or the negative electrode. Here, "semi-solid" does not mean that the solid material makes up 50% of the battery. A semi-solid material possesses solid properties, such as small volume change, while also having some liquid-like properties, such as flexibility. As long as these properties are met, the battery may consist of a single material or multiple materials. For example, a liquid material may be impregnated into a porous solid material.

[0221] Furthermore, in this specification, a polymer electrolyte secondary battery refers to a secondary battery having a polymer in the electrolyte layer between the positive and negative electrodes. Polymer electrolyte secondary batteries include dry (or intrinsic) polymer electrolyte batteries and polymer gel electrolyte batteries. Polymer electrolyte secondary batteries may also be called semi-solid batteries.

[0222] When a semi-solid battery is fabricated using the particles 190 described in Embodiment 1, the semi-solid battery becomes a secondary battery with a large charge / discharge capacity. Furthermore, it can be a semi-solid battery with a high charge / discharge voltage. Alternatively, a safe or highly reliable semi-solid battery can be realized.

[0223] [Negative electrode] The negative electrode comprises a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer may also contain a conductive additive and a binder.

[0224] <Negative electrode active material> For example, alloy materials or carbon-based materials can be used as the negative electrode active material.

[0225] 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 capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh / g. For this reason, it is preferable to use silicon as the negative electrode active material. Compounds containing these elements may also be used. 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.

[0226] In this specification, SiO refers to silicon monoxide, for example. Alternatively, SiO refers to SiO x It can also be expressed as follows. Here, x is preferably 1 or a value in its immediate vicinity. For example, x is preferably between 0.2 and 1.5, and more preferably between 0.3 and 1.2.

[0227] Suitable carbon-based materials include graphite, easily graphitizable carbon (soft carbon), difficult-to-graphitize carbon (hard carbon), carbon nanotubes, graphene, and carbon black.

[0228] 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.

[0229] 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 capacity per unit volume, relatively small volume expansion, low cost, and higher safety compared to lithium metal.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] The conductive additives and binders that can be present in the negative electrode active material layer can be the same materials as those that can be present in the positive electrode active material layer.

[0235] <Negative electrode current collector> The negative electrode current collector can be made of the same material as the positive electrode current collector. However, it is preferable to use a material for the negative electrode current collector that does not alloy with carrier ions such as lithium.

[0236] [Separator] A separator is placed between the positive and negative electrodes. The separator can be made from materials such as cellulose fibers including paper, nonwoven fabrics, glass fibers, ceramics, or synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol-based fiber), polyester, acrylic, polyolefin, or polyurethane. It is preferable that the separator be processed into a bag shape and positioned to enclose either the positive or negative electrode.

[0237] The separator may have a multilayer structure. For example, an organic material film such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof. Examples of ceramic materials include aluminum oxide particles and silicon oxide particles. Examples of fluorine materials include PVDF and polytetrafluoroethylene. Examples of polyamide materials include nylon and aramid (meta-aramid, para-aramid).

[0238] Coating with ceramic materials improves oxidation resistance, suppressing separator degradation during high-voltage charging and discharging, and thus improving the reliability of secondary batteries. Coating with fluorine-based materials improves adhesion between the separator and electrodes, thereby improving output characteristics. Coating with polyamide materials, particularly aramid, improves heat resistance, thus enhancing the safety of secondary batteries.

[0239] For example, a polypropylene film may be coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, the side of the polypropylene film in contact with the positive electrode may be coated with a mixture of aluminum oxide and aramid, and the side in contact with the negative electrode may be coated with a fluorine-based material.

[0240] By using a multi-layered separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, thus increasing the capacity per unit volume of the secondary battery.

[0241] [Electrolyte] The electrolyte has a solvent and an electrolyte. As the solvent of the electrolyte, an aprotic organic solvent is preferred. For example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfoxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran, sulfolane, sultone, etc., one kind, or two or more of these can be used in any combination and ratio.

[0242] In addition, by using one or more ionic liquids (room temperature molten salts) which are flame-retardant and hardly volatile as the solvent of the electrolyte, even if the internal temperature rises due to internal short circuit or overcharging of the secondary battery, rupture or ignition of the secondary battery can be prevented. An ionic liquid consists of a cation and an anion, and contains an organic cation and an anion. Examples of the organic cation used in the electrolyte include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations. Examples of the anion used in the electrolyte include monovalent amide-based anions, monovalent methide-based anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, hexafluorophosphate anions, or perfluoroalkylphosphate anions, etc.

[0243] In addition, as the electrolyte dissolved in the above solvent, for example, LiPF6, LiClO4, LiAsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10 、Li2B12 Cl 12 One kind of lithium salts such as LiCF3SO3, LiC4F9SO3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2)2, LiN(C4F9SO2)(CF3SO2), LiN(C2F5SO2)2, etc., or two or more of these can be used in any combination and ratio.

[0244] The electrolyte used in the secondary battery is preferably a highly purified electrolyte with a low content of particulate dust and elements other than the constituent elements of the electrolyte (hereinafter also simply referred to as "impurities"). Specifically, it is preferable that the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.

[0245] In addition, additives such as vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile may be added to the electrolyte. The concentration of the additive may be, for example, 0.1 wt% or more and 5 wt% or less based on the entire solvent.

[0246] In addition, a polymer gel electrolyte obtained by swelling a polymer with an electrolyte may be used.

[0247] By using the polymer gel electrolyte, the safety against liquid leakage and the like is enhanced. Also, the secondary battery can be made thinner and lighter.

[0248] As the polymer to be gelled, silicone gels, acrylic gels, acrylonitrile gels, polyethylene oxide gels, polypropylene oxide gels, fluorine-based polymer gels, etc., can be used. For example, polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, etc., and copolymers containing them can be used. For example, PVDF-HFP, which is a copolymer of PVDF and hexafluoropropylene (HFP), can be used. Furthermore, the polymer formed may have a porous structure.

[0249] Furthermore, instead of an electrolyte, solid electrolytes containing inorganic materials such as sulfides or oxides, or solid electrolytes containing polymer materials such as PEO (polyethylene oxide), can be used. When using a solid electrolyte, the installation of separators and spacers becomes unnecessary. In addition, since the entire battery can be solidified, the risk of leakage is eliminated, dramatically improving safety.

[0250] Therefore, the particles 190 described in Embodiment 1 can also be applied to all-solid-state batteries. By applying the positive electrode slurry or electrode to an all-solid-state battery, an all-solid-state battery with high safety and good characteristics can be obtained.

[0251] This embodiment can be freely combined with other embodiments.

[0252] (Embodiment 4) This embodiment shows an example of fabricating an all-solid-state battery using the particles 190 described in Embodiment 1.

[0253] 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.

[0254] 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 shown by a dotted line. The positive electrode active material layer 414 may also have a conductive additive and a binder.

[0255] 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.

[0256] 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 additive and a binder. When metallic lithium is used for the negative electrode 430, the negative electrode 430 can be made without the 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.

[0257] 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.

[0258] Sulfide-based solid electrolytes include thiosilicon-based (Li 10 GeP2S 12 Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glass (70Li2S·30P2S5, 30Li2S·26B2S3·44LiI, 63Li2S·38SiS2·1Li3PO4, 57Li2S·38SiS2·5Li4SiO4, 50Li2S·50GeS2, etc.), sulfide crystallized glass (Li7P3S 11 Li 3.25 P 0.95It contains S4, etc. Sulfide-based solid electrolytes have advantages such as the availability of materials with high conductivity, the ability to be synthesized at low temperatures, and their relatively soft nature which helps maintain conductive paths even after charging and discharging.

[0259] Oxide-based solid electrolytes include materials having a perovskite-type crystal structure (La 2 / 3-x Li 3x 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 Materials having a LISICON-type crystal structure (Li 14 ZnGe4O 16 etc.), LLZO(Li7La3Zr2O 12 ), oxide glass (Li3PO4-Li4SiO4, 50Li4SiO4·50Li3BO3, etc.), oxide crystallized glass (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 the advantage of being stable in the atmosphere.

[0260] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl, LiBr, and LiI. Furthermore, composite materials in which these halide-based solid electrolytes are packed into the pores of porous aluminum oxide or porous silica can also be used as solid electrolytes.

[0261] Alternatively, different solid electrolytes may be mixed and used.

[0262] In particular, Li has a NASICON-type crystal structure. 1+x Al x Ti 2-x(PO4)3(0〔x〕1) (hereinafter referred to as LATP) contains elements such as aluminum and titanium, which may be contained in the positive electrode active material used in the secondary battery 400 of one aspect of the present invention. Therefore, a synergistic effect can be expected for improving the cycle characteristics, which is preferable. In addition, an improvement in productivity due to reduction of processes can also be expected. In this specification and the like, the NASICON-type crystal structure refers to a compound represented by M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.), and has a structure in which MO6 octahedrons and XO4 tetrahedrons share vertices and are three-dimensionally arranged.

[0263] 〔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.

[0264] For example, FIG. 10 shows an example of a cell for evaluating the materials of a all-solid-state battery.

[0265] 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 fixing screws and wing nuts 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. An O-ring 765 for sealing is provided between the upper member 762 and the pressing screw 763.

[0266] The evaluation material is placed on the electrode plate 751, surrounded by an insulating tube 752 around it, and is being pressed by the electrode plate 753 from above. A perspective view of the periphery of this evaluation material enlarged is FIG. 10B.

[0267] As an example of the evaluation material, a lamination 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 FIG. 10C. The same reference numerals are used for the same parts in FIGS. 10A, 10B, and 10C.

[0268] 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.

[0269] 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 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.

[0270] 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 that of Figure 10. The secondary battery in Figure 11A has external electrodes 771 and 772 and is sealed with an exterior having a plurality of package members.

[0271] Figure 11B shows an example of a cross-section cut along 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 with an electrode layer 773a provided on a flat plate, a frame-shaped package member 770b, and a package member 770c with an electrode layer 773b provided on a flat plate. Insulating materials such as resin or ceramic can be used for the package members 770a, 770b, and 770c.

[0272] 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.

[0273] 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.

[0274] This embodiment can be used in appropriate combination with other embodiments.

[0275] (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.

[0276] <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.

[0277] 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.

[0278] 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.

[0279] The positive electrode can 301 and the negative electrode can 302 can be made of metals such as nickel, aluminum, or titanium, which are corrosion-resistant to the electrolyte, or alloys thereof or alloys of these with other metals (e.g., stainless steel). Furthermore, it is preferable to coat them with nickel, aluminum, or the like 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.

[0280] 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.

[0281] 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.

[0282] 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), which are related 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.

[0283] 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.

[0284] <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.

[0285] 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.

[0286] 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.

[0287] 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.

[0288] 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.

[0289] 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.

[0290] 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.

[0291] 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.

[0292] <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.

[0293] 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.

[0294] 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.

[0295] 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.

[0296] This embodiment can be used in combination with other embodiments.

[0297] (Embodiment 6) This embodiment shows an example of applying the secondary battery shown in Figure 14C to an electric vehicle (EV). Figure 16C shows a block diagram of the electric vehicle.

[0298] Electric vehicles are equipped with a first battery 1301a and 1301b, shown in Figure 16C, 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 the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.

[0299] 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.

[0300] In this embodiment, an example is shown in which two first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary. By configuring a battery pack with multiple secondary batteries, a large amount of power can be extracted. Multiple secondary batteries may be connected in parallel, in series, or connected in parallel and then in series. Multiple secondary batteries are also called a battery pack.

[0301] 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.

[0302] 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.

[0303] 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.

[0304] Furthermore, the first battery 1301a will be explained using Figure 16A.

[0305] 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.

[0306] 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).

[0307] 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.

[0308] 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.

[0309] 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.

[0310] 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.

[0311] Furthermore, a clear boundary may not be observed between the first region and the second region described above.

[0312] 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.

[0313] 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.

[0314] 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.

[0315] 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.

[0316] 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.

[0317] 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.

[0318] 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.

[0319] 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.

[0320] Furthermore, Figure 16B shows an example of a block diagram of the battery pack 1415 shown in Figure 16A.

[0321] 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 recommended voltage range for use, and if it falls outside this range, the switch unit 1324 activates and functions as a protection circuit. The control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent over-discharge and overcharge. For example, if the control circuit 1322 detects a voltage that is likely to cause overcharging, it cuts off the current by turning off the switch unit 1324. Furthermore, a PTC element may be provided in the charge / discharge path to provide a function to cut off the current in response to the rise in temperature. Furthermore, the control circuit unit 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).

[0322] The switch section 1324 can be constructed by combining n-channel transistors and p-channel transistors. The switch section 1324 is not limited to switches using Si transistors made of single-crystal Si, but may also be formed using power transistors made of, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (gallium oxide: x is a real number greater than 0), etc. Furthermore, since memory elements using OS transistors can be freely arranged by stacking them on circuits using Si transistors, integration can be easily achieved. Also, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost. That is, by stacking a control circuit section 1320 using OS transistors on the switch section 1324 and integrating them, it is possible to create a single chip. This makes it possible to reduce the occupied volume of the control circuit section 1320, thus enabling miniaturization.

[0323] The first batteries 1301a and 1301b primarily supply power to 42V (high-voltage) onboard equipment, while the second battery 1311 supplies power to 14V (low-voltage) onboard equipment. Lead-acid batteries are often used for the second battery 1311 due to their cost advantages. Lead-acid batteries have the disadvantage of higher self-discharge and are more susceptible to degradation due to a phenomenon called sulfation compared to lithium-ion secondary batteries. Using a lithium-ion secondary battery for the second battery 1311 offers the advantage of being maintenance-free, but after long-term use, for example more than three years, there is a risk of abnormalities occurring that could not be detected at the time of manufacture. In particular, if the second battery 1311, which starts the inverter, becomes inoperable, it will be impossible to start the motor even if the first batteries 1301a and 1301b have remaining capacity. To prevent this, if the second battery 1311 is a lead-acid battery, power is supplied from the first battery to the second battery to keep it constantly charged to a full state.

[0324] This embodiment shows an example in which lithium-ion secondary batteries are used for both the first battery 1301a (or the first battery 1301b) 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.

[0325] Furthermore, the regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305 and charged to the second battery 1311 via the control circuit unit 1321 from the motor controller 1303 and battery controller 1302. Alternatively, it is charged to the first battery 1301a via the control circuit unit 1320 from the battery controller 1302. Alternatively, it is charged to the first battery 1301b via the control circuit unit 1320 from the battery controller 1302. In order to efficiently charge the regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of rapid charging.

[0326] 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.

[0327] Although not shown in the diagram, when an external charger is connected, the charger's outlet or connection cable is electrically connected to the battery controller 1302. Power supplied from the external charger charges the first batteries 1301a and 1301b via the battery controller 1302. In some cases, the charger may have a control circuit and may not use the functions of the battery controller 1302, but it is preferable to charge the first batteries 1301a and 1301b via the control circuit unit 1320 to prevent overcharging. In some cases, the connection cable or the charger's connection cable may also have a control circuit. The control circuit unit 1320 is sometimes called an ECU (Electronic Control Unit). The ECU is connected to a CAN (Controller Area Network) installed in the electric vehicle. CAN is one of the serial communication standards used as an in-vehicle LAN. The ECU also includes a microcomputer. The ECU also uses a CPU and GPU.

[0328] External chargers installed at charging stations and other locations offer various power options, including 100V outlets, 200V outlets, and 3-phase 200V with 50kW output. Additionally, it's possible to charge by receiving power from external charging equipment using contactless power supply methods.

[0329] For rapid charging, a rechargeable battery capable of withstanding high-voltage charging is desired to achieve short charging times.

[0330] 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 additive, 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.

[0331] 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.

[0332] This embodiment can be freely combined with other embodiments.

[0333] (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.

[0334] 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.

[0335] 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.

[0336] Furthermore, the secondary battery of this embodiment may be applied to ground-mounted charging devices installed in residences or to charging stations installed in commercial facilities.

[0337] An example of implementing a secondary battery, which is one aspect of the present invention, in a building will be explained using Figures 17A and 17B.

[0338] 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. Alternatively, the power storage device 2612 may be electrically connected to a ground-mounted charging device 2604. The electricity obtained from the solar panel 2610 can be used to charge the power storage device 2612. The electricity stored in the power storage device 2612 can be used to charge the secondary battery 2602 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.

[0339] 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.

[0340] 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.

[0341] 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.

[0342] 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).

[0343] General load 807 is, for example, electrical equipment such as televisions and personal computers, while energy storage load 808 is, for example, electrical equipment such as microwave ovens, refrigerators, and air conditioners.

[0344] 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.

[0345] 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 on electrical equipment such as televisions and personal computers via the router 809. Furthermore, it can be checked on portable electronic devices such as smartphones and tablets via the router 809. 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.

[0346] 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.

[0347] 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.

[0348] 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.

[0349] 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.

[0350] 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.

[0351] The mobile phone 2100 preferably has sensors. For example, it is preferable that the sensor includes human body sensors such as a fingerprint sensor, pulse sensor, and body temperature sensor, as well as touch sensors, pressure sensors, acceleration sensors, etc.

[0352] 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.

[0353] 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 mounted on the vehicle, one or more examples of the secondary battery shown in Embodiment 5 are installed in one location. 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 in which multiple secondary batteries are connected. Furthermore, it is preferable to have a charging control device electrically connected to the secondary battery module. The weight of the secondary battery module refers to the weight of the battery pack in which multiple secondary batteries are connected, and if a charging control device is built into the battery pack, that charging control device is included.

[0354] Furthermore, the automobile 2001 can be charged by receiving power from an external charging facility via a plug-in method or 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 using a prescribed method such as CHAdeMO (registered trademark) or Combo. The secondary battery may be a charging station installed in a commercial facility or a household power supply. For example, the 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.

[0355] 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, by incorporating the power transmission device into the road or exterior wall, charging can be performed not only when the vehicle is stopped but also while it is in motion. Furthermore, this wireless power supply method can be used to transmit and receive power between two vehicles. In addition, solar panels can be installed on the exterior of the vehicle to charge the secondary battery when the vehicle is stopped or in motion. Electromagnetic induction or magnetic resonance methods can be used for this wireless power supply.

[0356] 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.

[0357] 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.

[0358] 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.

[0359] 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.

[0360] This embodiment shows an example of mounting an energy storage device according to one aspect of the present invention on a motorcycle or bicycle.

[0361] 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.

[0362] 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.

[0363] 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.

[0364] 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.

[0365] 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.

[0366] 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.

[0367] 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 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.

[0368] 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.

[0369] 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.

[0370] 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.

[0371] 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.

[0372] The display unit 4005a can display not only the time, but also various other information such as incoming emails and phone calls.

[0373] 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, allowing for health management.

[0374] Figure 20B shows a perspective view of the wristwatch-type device 4005 after it has been removed from the arm.

[0375] 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.

[0376] 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.

[0377] 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.

[0378] 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.

[0379] 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.

[0380] 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.

[0381] 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 or eyelid. 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.

[0382] 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.

[0383] 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.

[0384] 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.

[0385] This embodiment can be used in appropriate combination with other embodiments. [Examples]

[0386] This presentation will explain the results of calculations regarding the ratio of volume, area, and radius of regions 191 and 193 in particle 190, as well as the charging capacity.

[0387] To simplify the calculations, the particle 190 in one embodiment of the present invention is assumed to be spherical, as shown in Figure 21A. Furthermore, region 192 is excluded from the calculations in this embodiment because it is not directly related to the charging capacity.

[0388] Figure 21B 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 z This graph shows the radius of region 191 and the charging capacity per unit weight 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.

[0389] As shown in Figure 21B, 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).

[0390] 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 190 This 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%.

[0391] 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). [Explanation of Symbols]

[0392] 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: Particle, 191: Region, 192: Region, 193: Region, 193a: Region, 193b: Region, 194: Region, 195: Region, 196a: Region, 196b: Region, 196c: Region, 196d: Region, 197: Crystal grain boundary, 300: Secondary battery, 301: Positive electrode can, 302: Negative electrode can, 303: Gasket, 304: Positive electrode, 305: Positive electrode current collector, 306: Positive electrode active material layer, 307: Negative electrode, 308: Negative Electrode current collector, 309: Negative electrode active material layer, 310: Separator, 400: Secondary battery, 410: Positive electrode, 411: Positive electrode active material, 413: Positive electrode current collector, 414: Positive electrode active material layer, 420: Solid electrolyte layer, 421: Solid electrolyte, 430: Negative electrode, 431: Negative electrode active material, 433: Negative electrode current collector, 434: Negative electrode active material layer, 500: Current collector, 501: Active material, 502: Active material, 503: Acetylene black, 504: Graphene, 505: Carbon nanotube, 700: Secondary battery, 701: Positive electrode current collector, 702: Positive electrode active material layer, 703: Positive electrode, 704: Negative electrode current collector, 705: Negative electrode active Material layer, 706: Negative electrode, 707: Electrolyte layer, 709: Outer casing, 750a: Positive electrode, 750b: Solid electrolyte layer, 750c: Negative electrode, 751: Electrode plate, 752: Insulating tube, 753: Electrode plate, 761: Lower component, 762: Upper component, 764: Wing nut, 765: O-ring, 766: Insulator, 770a: Package component, 770b: Package component, 770c: Package component, 771: External electrode, 772: External electrode, 773a: Electrode layer, 773b: Electrode layer, 800: Energy storage device, 801: Commercial power supply, 803: Distribution board, 805: Energy storage controller, 80 6: Display unit, 807: General load, 808: Energy storage system load, 809: Router, 810: Service drop connection section, 811: Measurement section, 812: Prediction section, 813: Planning section, 890: Control device, 891: Energy storage device, 896: Underfloor space section, 899: Building, 950: Secondary battery, 951: Winding body, 960: Outer casing, 961: Terminal, 962: Terminal, 963: Terminal, 964: Terminal, 1300: Rectangular secondary battery, 1301a: Battery, 1301b: Battery, 1302: Battery controller, 1303: Motor controller, 1304: Motor, 1305: Gear, 1306: DC-DC circuit,1307: Electric power steering, 1308: Heater, 1309: Defogger, 1310: DC-DC circuit, 1311: Battery, 1312: Inverter, 1313: Audio, 1314: Power windows, 1315: Lights, 1316: Tires, 1317: Rear motor, 1320: Control circuit section, 1321: Control circuit section, 1322: Control circuit, 1324: Switch section, 1325: External terminals, 1326: External terminals, 1413: Fixing section, 1414: Fixing section, 1415: Battery pack, 1421: Wiring, 14 22: Wiring, 2001: Automobile, 2002: Transport vehicle, 2003: Transport vehicle, 2004: Aircraft, 2100: Mobile phone, 2101: Housing, 2102: Display unit, 2103: Operation buttons, 2104: External connection port, 2105: Speaker, 2106: Microphone, 2107: Rechargeable battery, 2200: Battery pack, 2201: Battery pack, 2202: Battery pack, 2203: Battery pack, 2300: Unmanned aerial vehicle, 2301: Rechargeable battery, 2302: Rotor, 2303: Camera, 2602: Rechargeable battery, 2603: Car Both, 2604: Charging device, 2610: Solar panel, 2611: Wiring, 2612: Energy storage device, 4000: Glasses-type device, 4000a: Frame, 4000b: Display unit, 4001: Headset-type device, 4001a: Microphone unit, 4001b: Flexible pipe, 4001c: Earphone unit, 4002: Device, 4002a: Housing, 4002b: Rechargeable battery, 4003: Device, 4003a: Housing, 4003b: Rechargeable battery, 4005: Wristwatch-type device, 4005a: Display unit, 4005b : Belt section, 4006: Belt-type device, 4006a: Belt section, 4006b: Wireless power supply and receiving section, 8300: Head-mounted display, 8301: Housing, 8302: Display unit, 8304: Fixing device, 8305: Lens, 8306: Circuit section, 8307: Imaging device, 8600: Scooter, 8601: Side mirror, 8602: Power storage device, 8603: Turn signal light, 8604: Under-seat storage, 8700: Electric bicycle, 8701: Battery, 8702: Power storage device, 8703: Display unit, 8704: Control circuit,

Claims

1. A secondary battery having positive electrode active material particles, The positive electrode active material particle has a first region, a second region located inside the first region, a third region located between the first region and the second region, and a fourth region located outside the first region. The first region is LiNi ｘ Co ｙ Mn ｚ O ２ It has a lithium composite oxide represented by (x > 0, y > 0, 0.8 < x + y + z < 1.2), The second region has lithium cobalt oxide, The third region comprises at least fluorine and magnesium, The fourth region is a lithium-ion secondary battery having at least fluorine and magnesium.

2. In claim 1, A lithium-ion secondary battery in which the nickel concentration is higher in the first region than in the second region.

Images